A.S.T.M.24, Metallographic and Materialographic Specimen Preparation-2006

Metallographic andMaterialographic SpecimenPreparation, Light Microscopy,Image Analysis and HardnessTesting

Kay GeelsIn collaboration with Daniel B. Fowler,Wolf-Ulrich Kopp, and Michael Rückert

ASTM International100 Barr Harbor DrivePO Box C700West Conshohocken, PA 19428-2959

Printed in U.S.A.ASTM Stock No. MNL46

Library of Congress Cataloging-in-Publication Data

Metallographic and materialographic specimen preparation, light microscopy,image analysis and hardness testing

Kay Geels; in collaboration with Daniel B. Fowler, Wolf-Ulrich Kopp, and MichaelRückert

p. cm.—�Manual; 46�ASTM stock number: MNL 46.Includes bibliographical references.ISBN 978-0-8031-4265-7E-book ISBN 978-0-8031-5691-31. Metallography. 2. Metallographic specimens. I. Title.TN690.G3785 2006669�.95028—dc22 2006103391

Copyright © 2007 ASTM International, West Conshohocken, PA. All rights reserved.This material may not be reproduced or copied, in whole or in part, in any printed,mechanical, electronic, film, or other distribution and storage media, without thewritten consent of the publisher.

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Authorization to photocopy item for internal, personal, oreducational classroom use, or the internal, personal, or educational classroomuse of specific clients, is granted by ASTM International „ASTM… provided thatthe appropriate fee is paid to the Copyright Clearance Center, 222 RosewoodDrive, Danvers, MA 01923; Tel: 978-750-8400; online: http://www.copyright.com/.

The Society is not responsible, as a body, for the statements and opinions expressedin this publication.

ASTM International does not endorse any products represented in this publication.

Printed in City, StateMonth Year

PrefaceThis book is written both for the experienced and unexperienced metallographer �ma-terialographer� who wants specific advice and information. It is also for persons seek-ing a broader knowledge of metallographic/materialographic specimen preparationand the examination methods, light microscopy, image analysis, and hardness testing.Special emphasis has been made on relations between ASTM standards andmetallography/materialography.

The book will be useful for students in courses devoted to practical metallographyand materialography.

The scope of the book is to give relevant information, in an efficient and clear way,covering the daily work in a metallographic/materialographic laboratory.

Metallographic/Materialographic Preparation

Kay Geels and Michael Rückert �Sections 13.5/6�Part I is a description of sectioning, mounting, grinding, polishing, and etching ofspecimens for examination in reflected light, enabling the reader to understand themechanisms of the entire preparation process. This is combined with practical adviceon specimen preparation and an introduction to existing equipment and consumables.

Part II is a “Hands-on” Manual guiding the metallographer/materialographer tothe correct preparation method, based on the material to be prepared and the purposeof examination. More than 150 methods are indicated covering practically all types ofmaterials, describing the preparation process from sectioning to etching. This partalso includes a section on Trouble Shooting, covering all stages in the preparation pro-cess and artifacts developed during the preparation.

Light Microscopy

Wolf-Ulrich KoppPart III is a description of the optical reflected-light microscope with photomicroscopygiving the reader both an introduction to the subject and a manual for the daily work.Also, a short introduction to electron microscopy and scanning probe microscopy canbe found in this part of the book.

Quantitative Metallography/Materialography—AutomaticImage Analysis

Daniel B. FowlerPart IV gives an introduction to quantitative microstructural analysis and automaticimage analysis, both theoretically and practically, with emphasis on the examinationsbased on ASTM standards and other types of commonly used analyses.

iii

Hardness Testing

Wolf-Ulrich KoppPart V gives a description of the hardness testing methods, Brinell, Vickers, Rockwell,microhardness and instrumented �nano� indentation testing based on ASTM stan-dards, both theoretically and as a practical guide.

The Metallographic/Materialographic Laboratory

Kay GeelsPart VI gives directions on how to establish and maintain a modern metallographic/materialographic laboratory. The important rules and regulations covering occupa-tional safety are described and commented on.

The authors of this book, representing more than 100 years’ experience with prac-tical metallography and materialography, have tried to make this book a practical tooland helpful source of information to all who are involved in the noble art/science ofmetallography/materialography—Kay Geels.

Acknowledgments

The authors wish to acknowledge the four reviewers, who brought forward valuableinsight for improvement. Special thanks to R. C. Nester, for his advice and suggestionson extension and shortening of the chapters. Thanks to G. Petzow, F. Mücklich and L.E. Samuels for permission to use a number of illustrations, and to B. Ottesen and W.Taylor for reading the manuscript and giving good advice. A special acknowledgementgoes to fellow-metallographers/materialographers for support and advice through theyears and directly connected to the book. The list includes U. Täffner, S. Glancy, E.Weidmann, A. Z. Jensen and A. Guesnier. A special thanks to L. Bjerregaard for her veryimportant advice on many of the preparation methods, and to H. Hellestad for her in-valuable support in making the illustrations. Also, thanks go to W. Taylor and StruersGmbH for providing important micrographs. The authors acknowledge the followingcompanies for supply of information and illustrations, Buehler Ltd., Carl Zeiss AG,DoAll Company, Emco-Test GmbH, Leica Microsystems AG, Olympus Optical Co. Inc.,and Struers A/S. Particular thanks to G. E. Totten and K. Dernoga at ASTM Interna-tional for establishing and maintaining the project of making this book. Last but notleast, thanks to B. Freiberg and J. Hestehave for support and encouragement duringthe years of making the book.

Abbreviations

AFM Atomic Force MicroscopeBF Bright Field

CBN Cubic Boron NitrideDF Dark Field

DIC Differential Interference Contrast

iv

EBSD Electron Backscatter DiffractionEDS Energy Dispersive Spectroscopy

EPMA Electron Probe MicroanalyzerFIB Focused Ion Beam

MFM Magnetic Force MicroscopePCB Printed Circuit BoardPOL Polarized LightSEM Scanning Electron MicroscopeSPM Scanning Probe MicroscopeSTM Scanning Tunnel Microscope

STEM Scanning Transmission Electron MicroscopeTEM Transmission Electron Microscope

v

ContentsPart I: The Metallographic/Materialographic Preparation Process

1 Introduction1.1 Metallographic/Materialographic Preparation—The True

Microstucture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.1.1 Henry Clifton Sorby �1826–1908�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 The True Microstructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.3 Selection of Preparation Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.3.1 Artifacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.2 Preparation Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.4 The Metallographic/Materialographic Specimen. . . . . . . . . . . . . . . . . . . 71.4.1 “Specimen” or “Sample”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.5 The Preparation Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.5.1 Sectioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.5.2 Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.5.3 Preparation of the Surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.5.4 Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2 Sectioning2.1 Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.1 General Studies or Routine Work. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.2 Study of Failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.3 Research Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.4 Type of Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.5 Reporting of Locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.2 Sectioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.3 Wet Abrasive Cutting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.3.1 The Cut-off Grinding Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.3.2 The Cut-off Wheel—Abrasives and Bond Materials. . . . . . . . . . . . . . . . 162.3.3 Grinding Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.3.4 Mechanical Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.3.5 Thermal Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.3.6 Cut-off Wheel Wear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.3.7 Cutting Fluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.3.8 The Metallographic/Materialographic Cutting Operation. . . . . . . . . . . 292.4 Abrasive Cut-Off Wheels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322.4.1 Consumable Wheels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322.4.2 Slow Consumable Wheels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342.5 Abrasive Cut-off Machines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362.5.1 Design Principles of Wheel—Work Piece Contact. . . . . . . . . . . . . . . . . . 362.5.2 Machine Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392.6 Advice and Hints on Wet Abrasive Cutting. . . . . . . . . . . . . . . . . . . . . . . . 432.6.1 Cut-off Wheel Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442.7 Other Sectioning Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452.7.1 Fracturing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452.7.2 Sectioning by Melting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462.7.3 Shearing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462.7.4 Sawing—Table 2.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472.7.5 Wire Cutting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3 Mounting3.1 Purpose and Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.1.1 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.1.2 Criteria for a Good Mount. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

vii

3.1.3 Surface Flatness—Edge Retention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.2 Mounting Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573.2.1 Clamping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573.2.2 Hot Compression Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.2.3 Cold �Castable� Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.3 Hot Compression Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.3.1 Advantages of Hot Compression Mounting. . . . . . . . . . . . . . . . . . . . . . . 593.3.2 Disadvantages of Hot Compression Mounting. . . . . . . . . . . . . . . . . . . . . 593.3.3 MSDS �Material Safety Data Sheets�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593.4 Hot Mounting Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.4.1 Thermoplastic Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.4.2 Thermosetting Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613.5 Mounting Presses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.5.1 The Heating/Cooling Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.5.2 The Hydraulic Press. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633.5.3 The Air-operated Press. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653.6 Advice and Hints on Hot Compression Mounting. . . . . . . . . . . . . . . . . . 653.6.1 Selection of Resins for Hot Compression Mounting. . . . . . . . . . . . . . . . 663.7 Cold �Castable� Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673.7.1 Advantages of Cold �Castable� Mounting. . . . . . . . . . . . . . . . . . . . . . . . . 683.7.2 Disadvantages of Cold �Castable� Mounting. . . . . . . . . . . . . . . . . . . . . . . 683.7.3 MSDS �Material Safety Data Sheets�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683.8 Cold Mounting Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683.8.1 Acrylics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683.8.2 Polyesters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693.8.3 Epoxies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693.9 Accessories for Cold �Castable� Mounting. . . . . . . . . . . . . . . . . . . . . . . . . 703.9.1 Mounting Molds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703.9.2 Clips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713.10 Vacuum Impregnation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713.10.1 Dyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723.11 Special Mounting Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723.11.1 Taper Sectioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733.11.2 Edge Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743.11.3 Mounting of Very Small Parts, Foils, and Wires. . . . . . . . . . . . . . . . . . . . 753.11.4 Mounting of Powders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763.11.5 Mounting of PCB Coupons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763.11.6 Conductive Mounts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773.12 Recovery of Mounted Specimen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773.13 Advice and Hints on Cold Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783.13.1 Selection of Cold Mounting Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

4 Marking—Storage—Preservation4.1 Marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.1.1 Marking with Waterproof Ink. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.1.2 Identification Tag. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.1.3 Engraving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.1.4 Stamping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.2 Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814.3 Preservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

viii Metallographic and Materialographic Specimen Preparation

5 Cleaning and Cleanliness5.1 Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825.1.1 Cleaning Before Start of Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825.1.2 Cleaning During and After Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . 825.2 Cleanliness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

6 Mechanical Surface Preparation—Grinding6.1 Grinding—A Basic Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856.1.1 Plane Grinding �PG�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856.1.2 Fine Grinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866.2 Material Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866.2.1 Rake Angle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876.2.2 Grain Shape—Contacting Points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 886.2.3 Grain Penetration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896.2.4 Force on Specimens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896.2.5 Grinding/Polishing Fluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896.3 Deformation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896.3.1 Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896.3.2 Brittle Materials—Ceramics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 926.4 Grinding Abrasives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936.4.1 Aluminum Oxide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936.4.2 Silicon Carbide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936.4.3 Diamond—Diamond Products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946.4.4 Cubic Boron Nitride �CBN�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.4.5 Boron Carbide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.4.6 Hardness of Abrasives and Materials—Table 6.1. . . . . . . . . . . . . . . . . . . 976.5 Grinding/Polishing Fluids—Lubricants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.5.1 Water-Based Lubricant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.5.2 Alcohol-Based Lubricant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.5.3 Water-oil Based Lubricant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986.5.4 Oil-Based Lubricant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986.6 Traditional Grinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996.6.1 Grinding Stones/Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996.6.2 SiC Wet Grinding Paper—Table 6.2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1006.6.3 Alumina—Zirconia Alumina Wet Grinding Paper. . . . . . . . . . . . . . . . . . 1056.7 Contemporary Grinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1066.7.1 Magnetic Fixation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1066.7.2 Resin-Bonded Diamond Grinding Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . 1076.7.3 Resin-Bonded SiC Grinding Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086.7.4 Metal-Bonded Diamond-Coated Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096.7.5 Diamond Pads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096.7.6 Diamond/CBN/ Al2 O3 /SiC Film. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096.7.7 Rigid Composite Disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096.7.8 Fine Grinding Cloths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1166.8 Grinding/Polishing Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1176.8.1 Plane Grinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1176.8.2 Fine Grinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

7 Mechanical Surface Preparation—Polishing7.1 Polishing: Producing the True Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . 1207.1.1 Rough Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207.1.2 Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

ix

7.2 Material Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207.2.1 Influence of Polishing Abrasive on Removal Rate. . . . . . . . . . . . . . . . . . 1217.2.2 Force on Specimens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217.3 Deformation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1227.3.1 The Beilby Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1227.3.2 Influence of Polishing Abrasive, Cloth, and Fluid on Deformation... 1237.4 Polishing Cloths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1247.4.1 Edge Retention—Relief. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267.4.2 Cloths for Fine Grinding and Rough Polishing. . . . . . . . . . . . . . . . . . . . . 1267.4.3 Cloths for Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1277.5 Polishing Abrasives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297.5.1 Diamond Suspensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297.5.2 Diamond Spray. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297.5.3 Diamond Paste. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1307.5.4 Alumina. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1307.5.5 Silica. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1317.5.6 Other Oxides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327.6 Polishing Lubricants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327.7 The Metallographic/Materialographic Preparation Methods—

Method Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327.7.1 RPM of Grinding/Polishing Disk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337.7.2 RPM of Specimen Holder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337.7.3 Direction of Specimen Holder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347.7.4 Force on Specimens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347.7.5 Process Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347.7.6 Stock Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347.8 Grinding/Polishing Equipment—Manual Preparation. . . . . . . . . . . . . . . 1357.9 Grinding/Polishing Equipment—Automatic Preparation. . . . . . . . . . . . 1357.9.1 Machine Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1357.9.2 Polishing Dynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1397.9.3 Semiautomatic and Fully Automatic Systems. . . . . . . . . . . . . . . . . . . . . . 1407.10 Special Preparation Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1437.10.1 PCB Coupons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1437.10.2 Microelectronic Materials—Nonencapsulated Cross Sections. . . . . . . . 1437.10.3 Microelectronic Packages—Table 7.2—Target Preparation. . . . . . . . . . 1477.10.4 EBSD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1497.11 Field Metallography/Materialography—Nondestructive Mechanical

Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1507.11.1 Portable Grinder/Polishers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1507.11.2 Replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1507.12 Chemical Mechanical Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1517.12.1 Protection—Corrosion at CMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1527.13 Thin Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1527.13.1 Thin Sections of Petrographic/Ceramic Materials. . . . . . . . . . . . . . . . . . . 1527.13.2 Thin Sections of Plastics/Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1537.14 Microtomy—Ultramilling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

8 Electrolytic Polishing/Etching8.1 The Electrolytic Polishing/Etching Process. . . . . . . . . . . . . . . . . . . . . . . . . 1568.1.1 The Polishing Cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578.1.2 Smoothing and Brightening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

x Metallographic and Materialographic Specimen Preparation

8.1.3 Electrolytic Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1598.1.4 Advantages and Disadvantages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1608.2 Electrolytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638.3 Electropolishing in Practice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1648.3.1 Factors Influencing Electrolytic Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . 1648.3.2 Example of Electrolytic Polishing/Etching. . . . . . . . . . . . . . . . . . . . . . . . . . 1658.4 Electrolytic Polishing Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658.4.1 Electropolishers for Laboratory Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658.5 Field Metallography—Nondestructive Electropolishing. . . . . . . . . . . . . 1668.6 Electrolytic Thinning for TEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1678.7 Chemical Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

9 Etching9.1 Microetching—Contrast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1699.2 Contrast Without Surface Modifications—Microscope Techniques... 1699.2.1 Dark-Field Illumination �DF�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1699.2.2 Differential Interference Contrast �DIC�. . . . . . . . . . . . . . . . . . . . . . . . . . . 1699.2.3 Polarized Light �POL�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1699.2.4 Fluorescence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1709.3 Contrast with Surface Modification—Etching. . . . . . . . . . . . . . . . . . . . . . 1709.3.1 Grain Contrast Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1709.3.2 Grain Boundary Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1719.3.3 Reproducibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1719.3.4 Safety Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.4 Classical Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.4.1 Chemical Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.4.2 Precipitation �Color� Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.4.3 Heat Tinting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.5 Electrolytic Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.5.1 Anodic Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1729.5.2 Anodizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.5.3 Potentiostatic Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.6 Physical Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.6.1 Relief Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.6.2 Ion Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.6.3 Thermal Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1749.6.4 Vapor Deposition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1749.6.5 Sputtering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1749.7 Macroetching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

Part II: Metallographic/Materialographic Specimen Preparation—A Hands-OnManual

10 Introduction10.1 Specimen Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17910.2 Purpose of Examination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17910.3 Specimen Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

11 Specimen Material—Table 11.111.1 Classification of Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18111.2 How to Use Table 11.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18111.3 Table 11.1—Materials/Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

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12 Purpose of Examination12.1 Purpose in General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.2 Purpose: ASTM Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.3 Table 12.1: Purpose/ASTM Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.4 ASTM Standards—Metallography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.4.2 ASTM Standards in this Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19012.4.3 ASTM Standards—Document Summaries. . . . . . . . . . . . . . . . . . . . . . . . . . 19312.5 Chemical Microetching—Table 12.2—Table 12.3. . . . . . . . . . . . . . . . . . . 19412.5.1 Etching Practice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19412.5.2 Table 12.2—Numerical List of Etchants. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19512.5.3 Table 12.3—Etchant Names. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

13 Specimen Preparation13.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21813.2 Mechanical Preparation—The “Traditional” and “Contemporary”

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21813.2.1 Material/Preparation Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21813.2.2 Method Tables—Generic Methods—Parameters/Consumables—

Table 13.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21913.2.3 Material/Preparation Tables—Methods C-01/T-01 to C-68/T-68. . . . . . . 22213.2.4 Manual Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45013.3 Electrolytic Polishing and Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45313.3.1 Electropolishers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45413.3.2 Electrolytes—Methods for Electropolishing—Table 13.2. . . . . . . . . . . . 45413.3.3 Table 13.2—Electrolytes for Electropolishing/Etching. . . . . . . . . . . . . . . 45413.3.4 Mechanical Preparation for Electropolishing. . . . . . . . . . . . . . . . . . . . . . 45613.3.5 Electropolishing—Method Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45613.3.6 Electropolishing—Methods El-01 To El-25. . . . . . . . . . . . . . . . . . . . . . . . . 45613.4 Field Metallography/Materialography—Nondestructive

Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47513.4.1 Mechanical Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47513.4.2 Electrolytic Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47513.4.3 Replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47513.5 Trouble Shooting—How to Improve Preparation Results. . . . . . . . . . . 47613.5.1 Sectioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47713.5.2 Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47913.5.3 Mechanical Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48213.5.4 Electrolytic Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48313.5.5 General Rules—“The Metallographer’s Rule of Thumb”. . . . . . . . . . . . 48313.6 Trouble Shooting—How to Overcome Preparation Artifacts. . . . . . . . 48413.6.1 Preparation Artifacts—Flow Charts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48413.6.2 Sectioning—General Problems—Flow Charts. . . . . . . . . . . . . . . . . . . . . . 48513.6.3 Mounting—General Problems—Artifacts. . . . . . . . . . . . . . . . . . . . . . . . . . 49513.6.4 Grinding and Mechanical Polishing—Flow Charts. . . . . . . . . . . . . . . . . . 49813.6.5 Electropolishing—General Problems—Artifacts. . . . . . . . . . . . . . . . . . . . 521

Part III: Light Microscopy

14 Introduction14.1 Visible Light–Table 14.1–Table 14.2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52514.2 The Human Eye. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526

xii Metallographic and Materialographic Specimen Preparation

14.3 Magnifying Lens and Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52714.4 Magnification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527

15 The Optical Reflected Light Microscope15.1 The Path of Light Rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52815.2 The Objective. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52815.2.1 Numerical Aperture—Resolution-Magnification–Table 15.1–Table

15.2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52815.2.2 Aberrations in Image-Formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53215.2.3 Available Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53315.3 Eyepieces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53515.4 Illumination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53615.4.1 Koehler’s Illumination System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53615.5 Microscope Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53715.6 The Reflected-Light Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53815.6.1 Upright Type of Reflected-Light Microscope. . . . . . . . . . . . . . . . . . . . . . . 53815.6.2 Inverted Type of Reflected-Light Microscope. . . . . . . . . . . . . . . . . . . . . . 53815.7 Optical Examination Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54015.7.1 Bright-Field �BF� Illumination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54115.7.2 Dark-Field �DF� Illumination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54115.7.3 Polarization Contrasting �POL�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54215.7.4 Differential Interference Contrasting �DIC�. . . . . . . . . . . . . . . . . . . . . . . . 54415.7.5 Fluorescence in Reflected Light. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54515.8 Practical Use of the Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54615.8.1 Setting up the Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54615.8.2 Working with the Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54715.8.3 Correct Adjustment of the Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . 54815.8.4 Focusing and Practical Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54815.8.5 Measurements of Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54915.8.6 Measurements of Height Differences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55015.8.7 Maintenance of the Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55015.9 Documentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55015.10 The Confocal Laser Scan Microscope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55215.10.1 Function of Confocal Laser Scan Microscope. . . . . . . . . . . . . . . . . . . . . . 55215.10.2 Applications of Confocal Laser Scan Microscope. . . . . . . . . . . . . . . . . . . 55415.11 Stereo Microscopy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

16 Electron Microscopy—Scanning Probe Microscopy16.1 The Transmission Electron Microscope �TEM�. . . . . . . . . . . . . . . . . . . . . . 55816.1.1 The Scanning Transmission Electron Microscope �STEM�. . . . . . . . . . . . 55816.2 The Scanning Electron Microscope �SEM�. . . . . . . . . . . . . . . . . . . . . . . . . . 55816.2.1 Energy Dispersive Spectroscopy �EDS�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55916.2.2 Electron Backscatter Diffraction �EBSD�. . . . . . . . . . . . . . . . . . . . . . . . . . . 55916.2.3 The Electron Probe Microanalyzer �EPMA�. . . . . . . . . . . . . . . . . . . . . . . . 56016.3 Focused Ion Beam �FIB�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56016.4 Scanning Probe Microscopes �SPM�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

Part IV: Quantitative Metallography/Materialography— Automatic Image Analysis

17 Quantitative Metallography/Materialography—An Introduction17.1 Quantitative Metallography/Materialography. . . . . . . . . . . . . . . . . . . . . 56517.1.1 Stereology–Table 17.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

xiii

17.1.2 Specimen Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56717.1.3 Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56817.1.4 Field Selection—Bias. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56817.2 Volume Fraction—Point Count. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56917.2.1 ASTM Test Method for Determining Volume Fraction by

Systematic Manual Point Count �E 562�. . . . . . . . . . . . . . . . . . . . . . . . . . . 56917.3 Inclusion Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57017.3.1 ASTM Standard Test Method For Determining the Inclusion

Content of Steel �E 45�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57017.3.2 ASTM Practice for Obtaining JK Inclusion Ratings Using Automatic

Image Analysis �E 1122� �withdrawn 2006, replaced by E 45�. . . . . . . 57017.3.3 ASTM Practice for Determining the Inclusion or Second-Phase

Constituent Content of Metals by Automatic Image Analysis�E 1245�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570

17.4 Grain Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57117.4.1 ASTM Test Methods for Determining Average Grain Size �E 112�. . . 57117.4.2 ASTM Test Methods for Estimating the Largest Grain Observed in

a Metallographic Section �ALA Grain Size� �E 930�. . . . . . . . . . . . . . . . . 57317.4.3 ASTM Test Methods for Characterizing Duplex Grain Sizes �E 1181�.. 57317.4.4 ASTM Test Methods for Determining Average Grain Size Using

Semiautomatic and Automatic Image Analysis �E 1382�. . . . . . . . . . . . 57317.5 Banding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57417.5.1 ASTM Practice for Assessing the Degree of Banding or Orientation

of Microstructures �E 1268�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57417.6 Porosity in Thermal Spray Coatings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57417.6.1 ASTM Test Methods for Determining Area Percentage Porosity in

Thermal Sprayed Coatings �E 2109�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57417.7 Decarburization—Case Depth—Coatings. . . . . . . . . . . . . . . . . . . . . . . . . . 57517.7.1 Specimen Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57517.7.2 ASTM Test Methods for Estimating the Depth of Decarburization

of Steel Specimens �E 1077�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57517.7.3 Case Depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57517.7.4 ASTM Test Method for Measurement of Metal and Oxide Coating

Thickness by Microscopical Examination of a Cross Section �B 487�.. 57617.7.5 ASTM Test Methods for Thickness of Diffusion Coating �C 664�. . . . . 57617.8 Other ASTM Standards for Quantitative Materialography. . . . . . . . . . 576

18 Automatic Image Analysis18.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57718.2 Qualitative and Quantitative Metallography/Materialography. . . . . . 57718.2.1 The Transition to Quantitative Standards. . . . . . . . . . . . . . . . . . . . . . . . . 57718.2.2 Structure, Stereology, and Statistics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57818.3 Principles of Digital Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57918.3.1 What is Digital Image Analysis?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57918.3.2 Image Acquisition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57918.3.3 Image Digitization—Gray Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58018.3.4 The Histogram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58118.3.5 The Effects of Brightness and Contrast on Illumination

Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58118.3.6 Image Processing and True Microstructure. . . . . . . . . . . . . . . . . . . . . . . . 58618.3.7 Image Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595

xiv Metallographic and Materialographic Specimen Preparation

18.4 Image Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59818.4.1 Manual Measurements �Operator Defines Points, Lines, or Areas�... 59918.4.2 Automatic Measurements �Objects Defined by Image

Segmentation�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60018.5 Digital Imaging Applied to Quantitative Materialography. . . . . . . . . . 60218.5.1 Percent Area �Volume Fraction�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60218.5.2 Inclusion Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60318.5.3 Grain Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60618.5.4 Degree of Banding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60818.5.5 Depth or Thickness Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60818.5.6 Graphite in Iron Castings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61018.6 Digital Imaging Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61318.6.1 Hardware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61318.6.2 Software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61618.7 Digital Imaging System Implementation. . . . . . . . . . . . . . . . . . . . . . . . . . 617

19 Digital Image Management „Archiving…Part V: Hardness Testing

20 Introduction20.1 Indentation Hardness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62320.2 ASTM Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

21 Static Hardness Testing Procedures21.1 Brinell Hardness Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62621.1.1 Calculations and Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62621.1.2 Brinell Hardness Testers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62821.2 Vickers Hardness Testers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62821.2.1 Calculations and Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62821.2.2 Vickers Hardness Tester. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63221.3 Knoop Hardness Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63321.3.1 Calculations and Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63321.4 Rockwell Hardness Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63421.4.1 Calculations and Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63421.4.2 Rockwell Hardness Testers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63621.5 Microindentation Hardness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63621.5.1 Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63621.5.2 Specimen Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63721.5.3 Taking the Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63821.5.4 Microindentation Hardness Testers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63921.5.5 Examples of Indentations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63921.6 Universal Hardness—Martens Hardness—Instrumented Indentation

Testing—Nano Indentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63921.6.1 Instrumented Indentation Testing—Nano Indentation. . . . . . . . . . . . . 64121.7 Precision of Hardness Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64221.8 Conversion of Hardness Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

22 Dynamic Hardness Testing Procedures

23 Special Methods for Hardness Testing

xv

Part VI: The Metallographic/Materialographic Laboratory

24 Introduction24.1 Establishing a Metallographic/Materialographic Laboratory. . . . . . . . 64924.2 Running a Metallographic/Materialographic Laboratory. . . . . . . . . . . . 64924.3 Occupational Safety and Health. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

25 How to Build a Metallographic/Materialographic Laboratory25.1 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65025.1.1 Quality Control �QC�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65025.1.2 Research and Education. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65125.1.3 Testing and Inspection Laboratories—Failure Analysis. . . . . . . . . . . . . . 65125.2 Rationalization and Automation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65125.2.1 Reproducibility—Standards—Occupational Safety. . . . . . . . . . . . . . . . . . 65225.2.2 Productivity—Cost Per Specimen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65325.3 Planning the Metallographic/Materialographic Laboratory. . . . . . . . . 65425.3.1 Basic Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65425.3.2 Detailed Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65525.4 Equipment and Laboratory Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65625.4.1 Equipment—Table 25.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65625.4.2 Layout—Furniture—Installations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66025.5 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66225.5.1 Organizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66225.5.2 Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66225.5.3 Servicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663

26 Occupational Safety and Health in the Metallographic/Materialographic Laboratory

26.1 Dangers in the Metallographic/Materialographic Laboratory. . . . . . . 66426.1.1 Sectioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66426.1.2 Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66426.1.3 Mechanical Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66526.1.4 Electrolytic Polishing/Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66526.1.5 Etching—Etchants—Electrolytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66526.1.6 Dust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66726.1.7 Cold �Castable� Mounting Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66726.1.8 Standard Guide on Metallographic Laboratory Safety �E 2014�. . . . . 66826.2 Safety Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66826.2.1 Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66826.2.2 Material Safety Data Sheet �MSDS�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67026.2.3 Standard Operating Procedure �SOP�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67226.2.4 Job Safety Analysis �JSA�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67226.3 Disposal of Chemicals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67226.4 Occupational Safety in General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67326.4.1 Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67326.4.2 Training. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67326.4.3 Maintenance and Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67326.5 Standards and Regulations—Organizations. . . . . . . . . . . . . . . . . . . . . . . 67326.5.1 Designations and Abbreviations Used to Describe a Chemical

Substance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67326.5.2 ASTM Standard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67426.5.3 OSHA—OSHA Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674

xvi Metallographic and Materialographic Specimen Preparation

26.5.4 National Institute for Occupational Safety and Health �NIOSH�. . . . . 68126.5.5 International Chemical Safety Cards �ICSCS�. . . . . . . . . . . . . . . . . . . . . . . 68226.5.6 Environmental Protection Agency �EPA�. . . . . . . . . . . . . . . . . . . . . . . . . . 68326.5.7 National Technical Information Service �NTIS�. . . . . . . . . . . . . . . . . . . . . 68326.5.8 American Conference of Government Industrial Hygienists

�ACGIH�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68326.5.9 National Toxicology Program �NTP�. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68326.5.10 Agency for Toxic Substance and Disease Registry �ATSDR�. . . . . . . . . . 68326.5.11 National Fire Protection Association �NFPA�. . . . . . . . . . . . . . . . . . . . . . . 68426.5.12 National Paint and Coatings Association �NPCA�—HMIS. . . . . . . . . . . . 68426.5.13 BSI—ISO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68426.5.14 EU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68426.6 Literature on Laboratory Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684

27 Literature27.1 Books. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68527.2 Periodicals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686

Appendixes

Appendix I: Other Standards on Metallography/Materialography . . . . . . . . . . . . . 686

Appendix II: Other Standards on Hardness Testing . . . . . . . . . . . . . . . . . . . . . . . . . . 691

Appendix III: Hardness Conversion Tables for Metals �E140� . . . . . . . . . . . . . . . . . . 694

Appendix IV: SI Quick Reference Guide: International System of Units �SI� . . . . 694

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 727

xvii

Part I:The Metallographic/MaterialographicPreparation Process

1Introduction“METALLOGRAPHY” or “MATERIALOGRAPHY”? IN MODERN TECHNOL-ogy and Materials Science we are examining the microstructure of all solid materials;therefore, materialography seems to be the correct word instead of the traditional met-allography. In 1968, Crowther and Spanholtz1 suggested this and it now seems appro-priate to use the word “materialography” to cover the examination of the infinite num-ber of existing and future materials. Also, the term “metallographer” should bechanged to “materialographer.” Changes of this kind, however, take time, and thereforethe terms “metallography” and “metallographer” are used in this book, except in con-texts where materials other than metals are discussed.

G. Petzow2 defines Materialography �metallography� as “an investigative methodof materials science. It encompasses the optical examination of microstructures, andits goal is a qualitative and quantitative description of the microstructure.”

The term materialography includes ceramography �ceramics�, metallography�metals�, plastography �polymers�, and mineralogy �minerals�, in this way covering themicrostructural examination of most materials.

Metallography/materialography includes a wide field in material investigation; itbridges the gap between science in new and existing materials and engineering usingthe materials in modern technology. Figure 1.13 shows how materialography coversthe examination of parts from the centimetre and metre �in and ft� range to atomicdimensions in the nm and sub nm range.

The microstructure is characterized through size, shape, arrangement, amount,type, and orientation of the phases and the defects of these phases, as schematically

Fig. 1.1—Metallography/materialography can be described as a bridge between engineeringand science, covering the examination of the part in cm and m to the examination of thesingle atom in Å.

3

shown in Fig. 1.23. Each material contains many millions of microstructural featuresper cubic centimetre and these features strongly influence many of the properties ofthe material. As seen in Fig. 1.1, the microstructural features can exist in sizes of atleast ten orders of magnitude. There are many instruments today that visualize nearlyall of the features across this range.

The image we see in the typical microscope is two-dimensional, but we should notlose sight of the fact that the constituents in a material are three dimensionally ar-ranged.

A photomontage shows the prepared surface of a silicon nitride alloy superim-posed on a pile of silicon nitride crystals �see Fig. 1.3�.3 It shows that the true size of thecrystals cannot be deduced directly from the microstructure. A statistical extrapola-tion of the two-dimensional surface shows that approximately 80 % of the crystals arerelatively short and have an equiaxial shape. Stereological calculations, however, showa much higher variation in crystal length. The average crystal length is larger, corre-sponding to the three-dimensional characteristics shown in Fig. 1.3.

It can be concluded that the analysis of the microstructure plays an important rolein modern materials science and engineering, and consequently, the metallographic/materialographic preparation. It is important to secure the true microstructure be-cause without this the best examinations and inspired interpretations will be of noavail.

As stated in the Preface, this book concentrates on metallographic/materialographic preparation and the most commonly used examination methods.For a comprehensive, in-depth coverage of metallurgy and microstructures, includinginterpretation of the microstructures, ASM Handbook, Volume 9, Metallography andMicrostructures,4 is recommended.

This part of the book concentrates on the preparation of the specimen surface forexamination in the reflected-light optical microscope. This preparation can also beused frequently for the scanning electron microscope �SEM�. The mechanical removal

Fig. 1.2—The constituents of a microstructure and the factors affecting them.

4 METALLOGRAPHIC AND MATERIALOGRAPHIC SPECIMEN

of material will be described and discussed rather intensively because it is the centralprocess in abrasive cutting, sawing, plane/fine grinding, and polishing, as will the prob-lems involved in obtaining the true microstructure. The machines and consumablesavailable will also be described and discussed.

Etching, often performed after the specimen preparation process to obtain a con-trast to highlight or clearly reveal certain features, will be described in theory and prac-tice.

1.1 Metallographic/Materialographic Preparation—The TrueMicrostructure

The goal of the metallographic/materialographic preparation is to obtain the true mi-crostructure or “The True Structure,” meaning an undisturbed material surface, whichcan be analyzed in an optical �light� microscope or an SEM.

The basic problem for a metallographer preparing a specimen is that the prepara-tion process itself modifies the specimen surface and, theoretically, a “true structure”completely without artifacts can never be obtained. Consequently, a preparation pro-cess should be used that creates the smallest amount of artifacts, making it possible, inpractice, to analyze a microstructure in a satisfactory way.

1.1.1 Henry Clifton Sorby „1826–1908…In the 1860s, because he understood that to obtain a “true structure” he had to removethe irregularities of the material surface, H. C. Sorby was able to produce what is con-

Fig. 1.3—Photomontage of a microsection of silicon nitride alloy superimposed upon a pile ofsilicon nitride crystallites.

Chapter 1 Introduction 5

sidered the first true microstructure. In 1863 he prepared a specimen of Bessemer steelby using a preparation method with several steps, a method similar to the mechanicalpreparation used today. Figure 1.45 shows the microstructure, which was prepared inseveral steps, a rough polishing step and a fine polishing step.

1.2 The True Microstructure

Based on studies by Vilella and Samuels,6–8 the true structure can be defined as:No deformation—The plastically deformed layer created by the preparation should

be removed or be negligible.No scratches—Scratches normally indicate a surface that is not yet sufficiently pre-

pared, but small scratches might be allowed if they do not disturb the examination.No pull-outs—Especially in brittle materials, particles can be pulled out of the sur-

face leaving cavities that can be taken for porosity.No introduction of foreign elements—During the preparation process, abrasive

grains can be embedded in the surface.No smearing—With certain materials, the matrix or one of the phases might smear

�flow�, resulting in a false structure or covering of structure details, or both.No relief or rounding of edges—Relief can develop between different constituents of

the surface, caused by different hardness or other condition. Edge retention is impor-tant if the edge has to be examined.

1.3 Selection of Preparation Method

The preparation process will always influence the prepared surface, creating artifacts.Artifacts are defined as false structural details introduced during the preparation.

Fig. 1.4—Original specimen prepared by H. C. Sorby, 1863, Bessemer steel 0.2 % carbon. BF,450:1. Preparation Method—Rough grinding: Emery paper from coarse to fine. Fine grinding:“Fine grained” water-of-Ayr stone. Rough polishing: “Finest grained” crocus �Fe2O3 used forindustrial polishing�. Polishing: “Very best and finest washed” rouge �Fe2O3, jeweler’s rouge�.


The choice of preparation is usually between using mechanical or electrolytic pol-ishing, but chemical and chemical-mechanical polishing are also used.

1.3.1 ArtifactsA number of artifacts are already stated above under the true structure, but a few morecan be added. Microcracks, comet tails, pitting, contamination, and lapping tracks areall caused by the preparation process. Artifacts can also be introduced during chemicaletching of the surface. Most of these artifacts can be readily observed under the micro-scope. In some cases, artifacts can be accepted and the metallographer can decidewhether, for example, a scratch is acceptable as it does not disturb the structural analy-sis, or whether the specimen surface should be reprepared.

In some cases it can be very difficult to establish the true structure, e.g., a smearedlayer can cover pores. It is important that the metallographer pay attention to this pos-sibility when analyzing a structure �see Section 13.5�.

Artifacts of Mechanical PolishingWith mechanical polishing, it is possible to obtain an approximate true structure whenthe correct procedures are followed, even with very heterogeneous materials. Figure1.5 shows the following most common artifacts: relief between phases caused by differ-ence in hardness; embedded abrasive grain; inclusion protruding �it could also bemissing�; pull-out looking like a pore; rounding of the edge; and deformation of thematrix.

Artifacts of Electrolytic PolishingWith electrolytic polishing, the electrolysis might create problems if more than onephase is present in the structure. Figure 1.6 shows the most common artifacts. Reliefbetween phases caused by a difference in electrochemical potential: in some cases onephase will be removed much faster than another phase, in other cases a phase mightnot be electrically conductive and, as such, will not take part in the polishing process.Inclusions might react in the same way; they will often be dug out during the process.Pitting might develop if the electrolytic process is not controlled correctly. Also, a pro-nounced rounding of the edge will take place because the current density is alwaysstronger at the edge.

1.3.2 Preparation MethodsBecause most materials are heterogeneous �or even nonconductive�, the conclusionmust be that mechanical polishing is by far the most commonly used method. For cer-tain materials, however, electrolytic polishing gives very good results.

Alternatives to the above-mentioned methods are chemical polishing andchemical-mechanical polishing. Chemical polishing is not used much, although reci-pes for polishing of a number of materials are developed. Chemical mechanical polish-ing or attack polishing can be seen as an extension of mechanical polishing and, whenrelevant, recipes will be stated in connection with the specific material.

For recipes on chemical and chemical mechanical polishing, see Refs. 2, 4, and 9.

1.4 The Metallographic/Materialographic Specimen

In practice, the total work piece normally cannot be prepared and examined. For thisreason, a small part of the work piece, the sample �specimen� must be extracted. For


both specimen preparation and examination, using an optical microscope or an SEM,the ideal specimen size is 12–40 mm �0.5–1.5 in� square or cylindrical, with a height of12–30 mm �0.5–1.2 in�. There are, of course, exceptions like welds, where larger speci-mens have to be prepared.

With the specimen being only a small part of the material to be examined, if theinterpretation is to be valuable, it is very important that the specimen be representativeof the material to be studied. This usually happens by cutting out the specimen from acorrect location and in the correct direction �see Section 2.1�. Most ASTM standardscovering examination of a metallographic/materialographic specimen offer guidancein selection and sectioning of specimens �see Section 12.4�. The preparation can be per-formed once the specimen is established.

1.4.1 “Specimen” or “Sample”The two words are often used indiscriminately, describing the object prepared and ex-amined. The “sample” can be defined as the piece of material in its “raw” state, as taken

Fig. 1.5—Mechanical polishing: the most common artifacts shown schematically.


from the original material �work piece�. As soon as the “sample” is treated �prepared�and described, it turns into a “specimen,” and for this reason only the word “specimen”is used in this book, except in a few cases where “sample” is the correct description.

1.5 The Preparation Process

As mentioned above, several polishing methods are available, but in the diagram, Fig.1.7, only the two methods used for almost all preparation, mechanical and electrolytic,are shown. The diagram gives an overview of the total process, of which each step willbe discussed further in this part of the book.

Fig. 1.6—Electrolytic polishing: the most common artifacts shown schematically.


1.5.1 SectioningTo obtain a specimen, some kind of sectioning from the basic material �work piece� isnecessary. If this sectioning could take place without disturbing the specimen surface,the specimen could be examined without further work, but unfortunately all theknown sectioning methods will leave some kind of irregularities on the surface. Abra-sive wet cutting using a precision cut-off machine is considered as a sectioning methodgiving a low deformation of the specimen surface. Figure 1.8 shows a surface from aspecimen cut on a precision cutter and measured with an atomic force microscope�AFM�, and the irregularities of the surface are evident.

Abrasive wet cutting is the most frequently used sectioning method, but other

Fig. 1.7—Diagram showing the total preparation process based on mechanical and electrolyticpreparation.


methods, such as shearing, sawing, and punching are used as well �see Section 2.7�.

1.5.2 MountingIn some cases, the sample taken from the base material can be handled and treateddirectly as a specimen, but often a mount must be made to secure the handling and asatisfactory preparation. The mounting can be made by clamping the specimen be-tween two pieces of a material compatible to the specimen material. This way ofmounting has a number of drawbacks �see Section 3.2.1�; therefore mounting mainlytakes place as hot compression or cold �castable� mounting in a mounting plastic�resin�. Figure 1.9�a� shows three mounts made with hot mounting, giving mounts withvery precise dimensions. Figure 1.9�b� shows three mounts made with cold mounting;these mounts, made in molds, are less exact than the hot mounts.

1.5.3 Preparation of the SurfaceThe goal of the preparation is to obtain the true microstructure or at least a microstruc-ture in a condition that makes a satisfactory examination possible. This means that thenumber of irregularities �artifacts� in the surface must be kept at a minimum.

The preparation is done through a number of steps, either mechanical or electro-lytical �see Fig. 1.7�.

Fig. 1.8—Surface cut with a precision cut-off machine in a very careful way to avoidirregularities in the cut surface. Measurements with an atomic force microscope �AFM� give thepeak-to-valley value of irregularities: higher than 1000 nm �1 �m�. This shows that even withthe most gentle sectioning technique, the cut surface will have deformations which have to beremoved in the following preparation steps.


A mechanical preparation method will normally contain a plane grinding step, oneor more fine grinding steps, and one or more polishing steps.

Electrolytic polishing usually takes place as one electrolytic step, performed on amechanically ground or polished surface.

Fig. 1.9—Mounts made with hot compression mounting �a� and cold �castable� mounting �b�.


1.5.4 EtchingThe prepared surface often reacts as a mirror when examined in the microscope, notshowing all phases of the microstructure. For this purpose, the surface can be etchedchemically or electrolytically or treated in other ways to discriminate between phases,grains, grain boundaries, and other details. Figure 1.10 shows a copper specimen �a� inan unetched condition, giving very little information; and �b� one that is etched, show-ing the microstructure.

Fig. 1.10—Copper unetched �a� showing a bright, reflecting surface and color etched withKlemm III45 �b�, revealing the microstructure.


2Sectioning

2.1 Selection

IT IS VERY IMPORTANT THAT THE SPECIMEN IS SELECTED CORRECTLY SOthat the specimen material is representative of the material to be studied. The intent orpurpose of the examination will usually dictate the location of the specimen.

With respect to the purpose of the study, metallographic examination may be di-vided into three classifications, as stated in ASTM Practice for Preparation of Metallo-graphic Specimens �E 3� �see Section 12.4�.

2.1.1 General Studies or Routine WorkSpecimens should be chosen from locations that are most likely to show the maximumvarieties within the material being studied. For example, specimens should be takenfrom a casting in the zones wherein maximum segregation should occur, as well asspecimens from sections where segregation should be at a minimum. In the examina-tion of strip or wire, test specimens should be taken from each end of the coils.

2.1.2 Study of FailuresSpecimens should be taken as closely as possible to the fracture or to the initiation ofthe failure. Before taking the specimens, study of the fracture surface should be com-plete, or, at the very least, the fracture surface should be documented. In many cases,specimens should be taken from a sound area for a comparison of structures andproperties.

2.1.3 Research StudiesThe nature of the study will dictate the specimen location, orientation, etc. Samplingusually will be more extensive than in routine examinations.

2.1.4 Type of SectionAfter establishing the location of the specimen to be studied, the type of section to beexamined must be decided. For a casting, a section cut perpendicular to the surfacewill show the variations in structure form the outside to the interior of the casting. Inhot-worked or cold-worked metals, both transverse and longitudinal sections shouldbe studied. Special investigations may at times require specimens with surfaces pre-pared parallel to the original surface of the product. In the case of wire and smallrounds, a longitudinal section through the center of the specimen proves advantageouswhen studied in conjunction with the transverse section.

Cross sections or transverse sections taken perpendicular to the main axis of thematerial are more suitable for revealing the following information:• Variations in structure from center to surface• Distribution of nonmetallic impurities across the section.• Decarburization at the surface of a ferrous material, see ASTM Test Methods for

14

Estimating the Depth of Decarburization of Steel Specimens �E 1077�, Section12.4.

• Depth of surface imperfections.• Depth of corrosion.• Thickness of protective coatings and structure of protective coating.

Longitudinal sections taken parallel to the main axis of the material are more suit-able for revealing the following information:

• Inclusion content of steel, see ASTM Test Methods for Determining the InclusionContent of Steel �E 45� and other ASTM standards, Sections 12.4 and 17.2.

• Degree of plastic deformation, as shown by grain distortion.• Presence or absence of banding in the structure, see ASTM Practice for Assessing

the Degree of Banding or Orientation of Microstructures �E 1268�, Sections 12.4and 17.5.

• The quality attained with any heat treatment.

2.1.5 Reporting of LocationsThe locations of surfaces examined should always be given when reporting results andin any illustrative micrographs. A suitable method of indicating surface locations is tomake a sketch of the work piece with an indication of the location.

2.2 Sectioning

The goal is to extract the specimen to be prepared from the material to be studied �workpiece�. This should be done so that the specimen is representative of the work piecematerial and it should be done with a minimum amount of damage to the surface thatis to be prepared.

In principle, all methods, including sawing with a hacksaw, shearing, flame cut-ting, fracturing, etc., can be used to separate a specimen from the work piece. It is,however, important that the surface being prepared is only influenced mechanically orby heat to a degree that is suitable for a rational preparation that follows. This limitsthe sectioning methods to wet abrasive cutting and a few other methods that will bedescribed in the following sections.

2.3 Wet Abrasive Cutting

Abrasive cutting is a cut-off grinding process.

2.3.1 The Cut-off Grinding ProcessThe cut-off grinding �abrasive cutting� is a special operation following the general prin-ciples of the machining process, grinding.

Within the spectrum of machining processes, the uniqueness of grinding is foundin its cutting tool. Grinding wheels are generally composed of two materials: abrasiveparticles called grains that do the cutting and a softer bonding agent to hold the count-less abrasive grains together in a solid mass.

During most grinding processes the surface of the work piece is treated to obtain agiven accuracy or surface finish. In cut-off grinding, a very thin grinding wheel �nor-mally the thickness of the wheel is 1/100 of the wheel diameter, or less� grinds its waythrough a work piece. In metallographic/materialographic cutting, this is to separate a

Chapter 2 Sectioning 15

sample suited for further preparation from the work piece. Although there isn’t a de-mand for high accuracy, the surface quality concerning mechanical damage, thermaldamage, and planeness is important.

Cut-off wheels are made by cementing together abrasive grains with a suitablebonding material. Each grain is a potential microscopic cutting tool. The grinding pro-cess uses thousands of abrasive points simultaneously and millions continually.

By choosing a cut-off wheel with the correct abrasive and bond and using it on asuitable machine, both the mechanical and thermal damage and the planeness can bekept inside narrow limits. This will shorten and facilitate the following preparationprocess.

Figure 2.1 shows the surface roughness of mild steel after cutting, after grit P220SiC grinding paper, and after P320 grinding paper. It can be seen that the irregularscratches from the cut-off are removed by the grinding papers, and for most materials agrinding with grit P220 after cutting will give a satisfactory surface for further prepara-tion; this will be discussed further below. For certain materials P320 paper can be usedas the first step after cut-off, omitting plane grinding with grit P220.

2.3.2 The Cut-off Wheel—Abrasives and Bond MaterialsThe cut-off wheels belong to the category of “bonded abrasive tools.” Such tools consistof hard abrasive grains held in a weaker bonding matrix. Depending on the particulartype of bond, the space between the abrasive particles may only be partially filled, leav-ing voids and porosity, resulting in an open bond. A dense bond is the result of com-pletely filled spaces between the grains. Aside from abrasive and bond material, fillersand grinding-aid material may also be added. The correct combination of abrasive andbond is important to ensure the right cut-off process.

Every abrasive particle has a number of cutting points with each removing a tinychip from the work piece. Eventually the cutting edge becomes blunt and it must bear alarger force in order to remove the chip from the work piece. The force rises until itcauses the grain to fracture and present a new, sharp edge to the work piece. In this waythe grain reduces its size until finally the cutting force �see Section 2.3.3� causes it to becompletely torn out of the wheel, exposing new grains. This “self-sharpening” processis highly controlled by the combination of abrasive material and bond material �seeFig. 2.2� that schematically shows the abrasive grains in the bond with voids �pores� inbetween.

Depending on how the wheel is breaking down, the wheels are defined as either“Consumable Wheels” or “Slow Consumable Wheels” �see Section 2.4�.

Cut-off Wheel SpecificationsThe basic specification of a consumable cut-off wheel defines the following param-eters:1. The type of abrasive, expressed with a number and a letter �aluminum oxide: A,

silicon carbide: S�.2. The size of abrasive grains, expressed with grit number �see Section 6.6.2�.3. The grade �hard/soft� of wheel bond expressed with a letter.4. The wheel’s structure expressed with numbers.5. The bond material expressed with a letter.6. A code in numbers to express the maker’s details of manufacture.

In the following sections parameters 1–5 will be described in detail.


Fig. 2.1—�a� Steel after wet abrasive cutting. An abrasive grain �arrow�, embedded in thesurface during the cutting, can be seen, �b� after grinding with grit P220 SiC paper, and �c�after grinding with P320 grinding paper.


Type of AbrasiveFor cut-off wheels four types of synthetic abrasives, aluminum oxide �Al2O3�, siliconcarbide �SiC�, cubic boron nitride �CBN�, and diamond are used �see Table 6.1 and alsoSection 6.4�.

Al2O3—Although this is the softest of the abrasive materials, it is the abrasive usedin most cut-off wheels. This is due to the fact that Al2O3 is best suited for ferrous mate-rials, from mild steel to high-strength materials, i.e., alloy steels. Al2O3 is not suited forcast iron �see SiC below�.

Al2O3 is made synthetically in different types with varying hardness and friability,and is used for cutting of different materials. It is used in consumable cut-off wheels.

SiC—This synthetic material is harder and tougher than Al2O3, but dulls andglazes rapidly when used with steels. It is well suited for cutting of softer materials likenonferrous metals, and it is also suited for cast iron. SiC is made in two varieties, blackand green; normally the black type is used in cut-off wheels. It is used in consumablewheels.

CBN—This very hard, synthetic abrasive �superabrasive� is used for cutting ofhard materials that are not to be cut with Al2O3 and SiC. CBN is rather expensive; theprice is comparable to the price of diamond, but CBN has the advantage that it cutsferrous materials that cannot be cut with diamond. CBN has a very high thermal stabil-ity and will work for a very long time before getting dull and needs little dressing �seeSection 2.3.6�. It is used in slow consumable wheels where the wheel consists of a metalbody, and CBN is only part of the rim in a very stable bond �see Section 2.4�. CBN grainstend to be blocky shaped with sharp edges and smooth faces, which makes bondingdifficult. Therefore CBN, as diamond, normally is coated before being used in a resinbonded cut-off wheel.

Diamond—Diamond is the hardest abrasive �see Table 6.1� and is used for cuttingof the hardest materials. In spite of its extreme hardness, diamond has been found to beunsuitable for cutting ferrous materials. This is due to graphitization and carbon diffu-sion into the iron causing excessive diamond wear.10 Diamond is found as natural dia-monds, but mostly synthetic diamonds are used in cut-off wheels. The diamond grains

Fig. 2.2—Schematic drawing of cut-off wheel showing abrasive grains and bond material withvoids �pores�.


are normally coated to improve the fixation of the grain in the bond. Diamond is onlyused in slow consumable wheels as described under CBN above �see Section 2.4�.

Grain SizeThe grain size is expressed as a grit number �#�. This number refers to the number ofopenings per linear inch in a mesh screen through which the grain is just able to pass.The grit sizes are standardized by ANSI �American� and FEPA �European� �see Table6.2 and Section 6.6�. For cut-off wheels, grit sizes between 50 �336 �m� and 120�125 �m� are normally used.

Generally speaking, large grains will have a higher material removal rate, but arougher finish.

Large grains also allow for a more open bond structure because the pores �voids�between the grains can be relatively large �see Fig. 2.2 and Structure below�. An openbond structure allows room for the chips created during the cutting process so thatthey can be removed without disturbing the process. For this reason cut-off wheelswith large grains, which enable an open structure with large pores, are suited for cut-ting of large work pieces. This creates a large contact area �arc of contact� between cut-off wheel and work piece �see l in Fig. 2.3�. In the long contact area, chips and bondparticles will be accumulated before they are removed from the wheel outside the workpiece, and this accumulation takes place in the large pores. If not accumulated in thepores, the chips and particles will take room in the interface between wheel and workpiece, reducing the cutting action and creating heat.

Fine grains have a lower removal rate, but a better surface finish. Fine grains willgive a relatively dense bond structure �small pores�, and therefore a fine-grained cut-offwheel is most suited for brittle materials �very small chips� and smaller work pieces

Fig. 2.3—Schematic drawing of the cut-off process. The rotating cut-off wheel is cutting intothe fixed work piece.


with a short arc of contact.

GradeThe grade expresses the degree of retaining grip exerted on each grain by the bondingmaterial that corresponds to the cutting force needed to dislodge the grain Figure 2.2shows the grains bonded together with voids �pores� in between. When the cuttingforce has increased to a certain point, the grain will be dislodged from the bond.

Wheel grades are expressed with letters from E �very soft� to X �very hard�. Cut-offwheels are mostly in the range K to R.

A soft grade of bond has a weak hold in the abrasive grain Blunt grains will be tornaway easily, thus the self-sharpening action will be pronounced. This is desirable whencutting hard materials expressed in the rule: Hard Material—Soft Wheel.

A relatively soft wheel is used if the arc of contact is very large because the long arcwill normally reduce the force per grain �see Sections 2.3.3 and 2.3.8�.

If the wheel is too soft for a given material it will in most cases cut very well, but thewheel wear will be excessive causing a bad economy. In principle, the hardest possiblewheel for a given material should be used to secure the most economical sectioning.

A hard grade has a stronger hold in the abrasive grain, making it suited for softermaterials expressed in the rule: Soft Material—Hard Wheel.

A hard wheel is also used with a short arc of contact �see Section 2.3.6�.A hard bond gives a longer wheel life, but if it is too hard the blunt grains may be

retained for too long, leading to a condition called glazing of the edge of the wheel. Inthis condition the wheel might stop cutting completely and will only generate heat.

A wheel may be made to act harder or softer by varying the forces acting on thegrains. Decreasing the wheel speed or raising the feed speed will increase the cuttingforces. This will cause the wheel to shed grains and wear quicker so it will appear to beacting as a softer grade of wheel. Increasing the wheel speed or reducing the feed speedwill decrease the cutting forces and the wheel will act as a harder wheel.

This can be used in cut-off machines with variable speeds �see Sections 2.3.3 and2.3.8�.

StructureThe structure is a measure of the relationship between the grain size and porosity of thebond. Wheels can be manufactured to give specific structures ranging from very denseto very open. Structure is expressed as a numerical value between 1 and 15, 1 being verydense and 15 very open.

The porosity, the voids deliberately built into the wheel �see Fig. 2.2�, are designedto take the chips away, to avoid clogging the wheel edge �glazing�, and to allow grains tocut efficiently.

A dense structure has closely spaced, relatively small grains and small pores sothat only a small amount of material is removed. An open structure with larger grainsand larger pores can cope with higher rates of material removal as described in GrainSize above.

Bond MaterialThe bond material keeps the abrasive grains together. In general, the bond must bestrong enough to withstand grinding forces, high temperatures, and centrifugal force.

Consumable �abradable� cut-off wheels most often have a phenolic �bakelite�


bond. It is produced by mixing abrasive grains with phenolic thermosetting resin andplasticizers, molding to shape and baking �curing� at 150–200°C �300–400°F�. Thebond hardness and porosity are varied by controlling the amount of plasticizer and byadding fillers.

Phenolics are also used for cut-off wheels of the slow consumable type, using CBNand diamond. These wheels are soft compared to the metal bonded wheels �see below�and will give a smooth cut on very hard materials, but the wheel wear will be relativelyhigh.

Bakelite wheels are sensitive to prolonged exposure to cutting fluids. The fluid low-ers the strength of the wheel so that it wears quicker; therefore cut-off wheels must bekept out of the fluid when not in use and stored in a dry place.

Rubber bonds consist of vulcanized natural or synthetic rubber. They are strongerthan phenolics and are often used for extra thin cut-off wheels. Bakelite rubber bond isa mixture giving a stronger bond than pure bakelite that allows for a thinner wheel. Thedisadvantage with rubber as part of the bond is a strong smell, even with an efficientcooling during the cutting process.

Metal bonds are used for CBN and diamond wheels. The most common metalbond is sintered bronze that is produced by powder metallurgy methods. Other metalbonds that are generally stronger include iron and nickel. A low-cost diamond wheel ismade with the diamond grains fixed through an electroplating process. Metal bondsand electroplating are used for slow consumable wheels �see Section 2.4.2�.

2.3.3 Grinding MechanicsAbrasive cutting is a grinding process where the material removal takes place when theabrasive grains interact with the work piece. The mechanics of the process highly influ-ence the result and the economy of the cut-off process; the most important parameterswill be discussed below.

Grinding forces, power, and specific energy forces are developed between thewheel and the work piece �see Fig. 2.3�. The total force against the wheel, F, can be sepa-rated into a tangential component Ft and a normal �radial� component Fn.10–12

The grinding power P associated with the force components in Fig. 2.3 can be writ-ten as:

P = Ft · v �1�

whereFt is the tangential force andv is thewheel velocity.An important parameter is the energy per unit volume of material removal �spe-

cific energy�, u.

u = P/d · l · b �2�

where d is down feed rate (feed speed), l is length of cut (arc of contact), and b is width ofcut (widthofwheel).

The mean force per grain Ft� is another important parameter since it determinesthe tendency to cause grain fracture and therefore plays a major role in relation towheel wear �self sharpening�.

Ft� = u · d · l · b/v · l · b · C = �d/v�u/C �3�

where C is the number of active cutting points per square mm/in of the wheel surface.


It can be seen from Eq �3� that the ratio �d/v�, feed speed, and wheel velocity plays amajor role. At a higher force per grain, Ft� a given wheel should wear faster. It can beexpected that Ft� in a given cut-off operation will increase until the grain fracturestrength is reached, then the worn grain will either be sharpened �fractured� or forcedfrom the wheel �see Section 2.3.6�.

Chips, Sliding, and PlowingSome of the energy used in the grinding process is used for creating chips. These verysmall chips are comparable to chips made by other cutting processes such as turningand milling. The grinding chips are irregular, probably because of the variation in abra-sive grains and the negative rake angles �see below and Section 6.2.1�.

Part of the energy is expended by mechanisms other than chip formation. Onesuch mechanism could be flattened parts of the abrasive grain sliding against the workpiece surface without removing any material, as shown in Fig. 2.4. Another part of theenergy will be used for plowing, only displacing the material without cutting �see Fig.6.3, Section 6.2�.

The high energy used for grinding compared to other cutting processes can be ex-plained with the energy used for sliding and plowing. The specific energy used forgrinding is virtually the same as the melting energy of the removed material.10

2.3.4 Mechanical DamageAbrasive cutting generates a surface with scratches that are produced by interaction ofabrasive cutting points with the work piece, as shown in Figs. 2.4 and 2.5. Both figuresshow chips being removed from the surface of the work piece. Both the making of chipsand the plowing will create deformation in the specimen surface �see Section 6.3� andthe depth of the deformed layer will depend on the material, cut-off wheel, feed speed,and other factors.

According to the literature7,13–17 the general deformation depth at wet abrasivecutting will be so that it is easily removed by plane grinding with grit 220 SiC grindingpaper. For annealed polycrystalline 70:30, brass, the damage depth has been measuredto 700 �m �maximum depth Dd, see Section 6.3� and significant deformation depth to16 �m.7 For carbon steel the damage depth has been measured to 125 �m and for elec-trolytic copper 250 �m.14 In case of precision cutting with very thin wheels, a low forceon the wheel and lower cutting speeds, the damage is lower, in the range of 50 �m.14

For annealed steel �AISI/SAE 4130� deformation of below 10 �m has been measured atconventional wet cutting and less than 2 �m at precision cutting.16

Very often the unplaneness of the cut surface will be in the range of 300–500 �m

Fig. 2.4—Schematic drawing of an abrasive grain producing a chip from a metal work piece.


�see below�, which means that at least the same amount of material should be removedto obtain a plane surface. The damaged layer will be removed during this process formost materials.

Waviness—Unplane SurfaceIt is important to avoid waviness during the cut. Overloading the cut-off wheel so that itdoes not cut straight can cause waviness. This is due to the flexibility of the wheel thatallows for cutting without breaking even if the wheel body is curved because of an ex-cessive force �Fn in Fig. 2.3�. The wheel also might cut in a curve if the point of attackbetween wheel and work piece is not straight �perpendicular�, forcing the wheel out ofthe line of movement between wheel and work piece. The same effect can develop if thecooling fluid is unevenly distributed to the wheel, causing a chisel-shaped edge of thewheel �see Sections 2.6 and 13.5.1�. Correct clamping is also important �see Section2.3.5�.

In a normal routine-cut specimen, the surface might be unplane with variations upto several hundred �m.17 The variation is strongest at the entry and the exit of the cut-off wheel; therefore, the feed speed should be regulated often at the start and the finishof the cut �see Section 2.6�.

2.3.5 Thermal DamageAs described in Section 2.3.3 the total grinding energy input includes chip formation,sliding, and plowing. Peak “flash” temperatures approach the melting point of the ma-terial being ground. These very high temperatures, however, are of extremely short du-ration and highly localized on the shear planes of the microscopic grinding chips. Justbeneath the surface the work piece feels nearly continuous heating. This heating, atcut-off grinding, will mainly take place in the material under the wheel �see below�.

Specimen burn can take place if the cut-off conditions are not correct. Visibleburns with steels are characterized by bluish temper colors �see Fig. 2.6� and might

Fig. 2.5—Schematic drawing of fractures taking place in the abrasive grains and the bond ofthe cut-off wheel during cutting.


cause a metallurgical transformation in the heat-affected zone �see Section 13.6.2�.The models developed for heat transfer at cut-off are for dry cutting used for indus-

trial purposes, but materialographic cutting with cooling should follow the same pat-terns, but with lower temperatures. The heat is developed in the arc of contact and itwill move downwards in the material under the wheel. This means that the heated ma-terial is continuously removed and only a relatively small part of the heat is transferredto the cut surfaces of work piece and specimen. This process, however, will take place atthe end of the cut when the wheel is about to break through since no work piece mate-rial remains to conduct the heat downwards. To avoid this it is recommended bymanual cutting to decrease the feed speed a moment before the wheel is through thework piece. At automatic cutting a suitable low feed speed should be chosen for thetotal cutting process.

Heat is also developed through friction between the sides of the wheel and thework piece/specimen surfaces because of thermal expansion of the material under thewheel not yet cut. The cutting parameters should be kept so that this expansion is re-duced to a minimum �see Section 2.3.8�. Also, a correct clamping can reduce the fric-tion between wheel and work piece �see below�.

ClampingIt is important that the forces developed by clamping do not influence the microstruc-ture of the clamped work piece. This is mostly not the case when using a standard vice

Fig. 2.6—Macro photograph of a steel specimen cut with thermal damage. “Blue burn” can beseen.


for parts with a stiff cross section, but in the case of sensitive materials, bending anddeformation of the work piece should be avoided.

Clamping is often made by using two vices and clamping both the work piece andthe specimen, which-avoids a burr. When the wheel is completing the cut, and there islittle stock beneath the wheel, the temperature rises rapidly and the uncut material ex-pands thermally. This forces the already cut surfaces against the sides of the wheel andappreciable additional torque is involved. This, combined with internal stresses in thework piece might cause the “disk brake effect” in which the two sides of material clampthe wheel so hard that the rotation stops and most often the wheel breaks �see Section2.6�.

Wet CuttingDuring materialographic cutting it is important to keep the temperature low. For thisreason the process takes place with a strong supply of a grinding fluid, usually waterwith an additive �see Section 2.3.7�.

2.3.6 Cut-off Wheel WearThe cut-off wheel wear is decisive for the efficiency of the wheel. If the wear is too lowthe cutting edge will grow dull causing glazing and the cutting will stop. If the wear istoo high, the economy of the process is not correct and the quality of the cut might begood, but the number of cuts made with one wheel is too low.

The wheel wear involves three parameters: attritious wear, grain fracture, andbond fracture �see Fig. 2.5�.10 Attritious wear involves dulling of abrasive grains and thegrowth of wear flats by rubbing against the work piece �see Fig. 2.4�. Grain fracturerefers to the removal of abrasive fragments by fracture within the grain, and bond frac-ture occurs by dislodging the abrasive from the binder �see Fig. 2.2�.

Both attritious wear and the two types of fracture depend on the tangential force,Ft �Fig. 2.3�. If the force is too low, the process will stop and the grains will be blunt,resulting in glazing and overheating of the cut. A Ft that is too high might cause anincrease in the temperature in the cut which leads to an excessive bond fracture.

Wheel wear is measured by the total weight of abrasive worn away during the pro-cess. Experiments show that attritious wear is very little, grain fracture is only a smallpart of the total wear, and bond fracture is the dominant part. Attritious wear, alto-gether negligible, is probably the most important type of wear because it controls thegrinding forces and thus governs the probability of bond fracture and the overall rate ofwheel wear.

The grinding ratio �G� is a convenient measure of wheel wear and is expressed asfollows:

G = Volume ground away �Qw�/Volume of wheel consumed �Qs�

TheG-rationeeds tobeashighaspossible to secureagoodeconomyof a cut.The best G-ratio is obtained when the cut-off wheel and process parameters are

chosen correctly in relation to the material and shape of the work piece. Experiments12

have shown that the arc of contact �l in Fig. 2.3� is important to obtain a high G-ratio. If lis too high the longer cuts give chip interference, the space �pores� between the grainsin the cut are not able to accommodate the chips that causes larger lumps to be brokenfrom the wheel edge, resulting in a lower G-ratio. It seems that the ideal length of l isaround 12–20 mm �0.5–0.75 in�. If l is smaller, the G-ratio also drops, probably due toa very high load on the wheel edge due to the very short arc of contact. In practical


work, l can be up to around 15–20 % of the wheel diameter without problems, depend-ing on the material11 �see Section 2.3.8�.

Another important factor regarding the G-ratio is the down feed rate �feed speed� din Fig. 2.3.12 It seems that at a too low d, excessive heat is generated, probably becauseof the lack of sufficient chips to take the heat away that causes the wheel to wear too fastbecause of the high temperature in the bond. At a certain optimum value of d the tem-perature drops and the G-ratio increases. If the feed speed is further increased theG-ratio drops because there no longer will be sufficient chip clearance to handle thechips, the temperature increases, and the wheel edge breaks down, as described above.

In practical work the G-ratio is in the range 0.5 to 1.5 depending on the hardness ofthe cut-off wheel and the material to be cut. For a material like medium-carbon steel�40 mm �1.50 in� diameter� cut with a medium hard wheel �250 mm �10 in� diameter�,this gives around 40 to 50 sectioned specimens.

Truing and DressingTruing and dressing are both connected to wheel wear. Truing is a process to be per-formed when the grinding wheel is shaped incorrectly because wheel surface is worn.Cut-off truing is done to an unround wheel, making it run concentrically. This is doneautomatically with consumable wheels during the process, but truing might be neces-sary at slow consumable wheels.

In metallographic/materialographic preparation using grinding disks having aplane surface, truing is done to make the disk plane, and it implies that an amount ofthe disk is removed to establish the original flatness of the disk surface.

Dressing is a process to reinstate the cutting ability of the grains. If the grains areglazed or the edge/surface of the wheel/disk is clogged, the surface is opened by remov-ing a small amount of bond material with a dressing stick, normally a piece of ceramicbonded aluminum oxide or silicon carbide. Dressing should be limited because itcauses wheel/disk wear.

In cut-off, dressing is only done on CBN and diamond wheels �see Section 2.4.2�.

2.3.7 Cutting FluidsMaterialographic cutting is always performed as wet grinding, using a grinding fluid orcoolant. The fluid has the following simultaneous functions: cooling the work piece/cut-off wheel interface; lubrication; flushing away the chips; protecting against corro-sion of work piece and machine; and preventing development of bacteria and fungi.Because water is a very good cooling medium, it is used as the main ingredient. How-ever, an additive that contains a number of components is needed to obtain the men-tioned functions.

Lubrication and CoolingAs described in Sections 2.3.3 and 2.3.5, heat is developed during the grinding opera-tion due to chip formation and friction forces in the cut. For these reasons it is impor-tant that a relatively high lubrication takes place, reducing the power required to re-move a given volume of material and thereby keeping the heat generation as low aspossible, and at the same time cool the work piece to avoid a heat buildup.

Synthetic Grinding Fluids—Oil-Based FluidsThe so-called synthetic or chemical fluids used as additives to water are used for cut-offgrinding. These fluids, generally defined as grinding fluids contain no mineral oil andare typically clear, but may be dyed.


The simplest fluid only contains some inorganic chemicals that protect againstcorrosion and bacterial attack. This fluid can be described as “water that doesn’t makerust,” producing a very good cooling, but no lubrication.

The most frequently used type of synthetic fluid has surface active components�for better wetting of the surfaces� and other components that improve the lubrication,cooling, and corrosion inhibition. The synthetic fluid is mixed as an additive in ratios of1:30 to 1:50 with water.

Semisynthetic fluids have 3–30 % oil and give a stronger lubricating action thanthe synthetic fluid. It can be used instead of emulsions for band sawing and other pro-cesses with high friction.

Emulsions, emulsifiable oil in water and typically milky white are not normallyused for cut-off grinding, but are suited for other cutting processes, such as band saw-ing, hacksawing, etc.

Oil-based fluids are, however, often used for cutting with precision cutters usingdiamond cut-off wheels. This fluid can be used without mixing. Water-soluble �emulsi-fiable� oils, that mix with water in ratios of 1:5 to 1:20 are also available.

Grinding fluids normally have a high pH and can cause skin problems �see Chapter26� and skin contact should be kept to a minimum �see below�.

Application of Grinding FluidIt is very important that the fluid is taken as close as possible to the area of contactbetween work piece and wheel. Caused by the rotation of the wheel, a layer of air ismoving along with the sides of the wheel. It is important that the cooling fluid pene-trates this layer and gets in contact with the sides of the wheel so that a laminar streamof fluid is established along the sides of the wheel. In this way the centrifugal force ofthe wheel takes the fluid into the wheel/work piece contact area. On most cut-off ma-chines there are two nozzles positioned, one on each side of the wheel, that directs thefluid under a certain pressure towards the wheel sides. In some cases other nozzles willlead fluid to the work piece for extra cooling. Systems with the work piece totally sub-merged in fluid have also been used. These systems should, however, only be used as asupplement to the nozzles previously described because the coolant covering the workpiece will not be able to get in contact with the wheel sides due to lack of pressure.

The Cooling SystemThe most important parts of the cooling system are the pump and tank. The pumpshould have a sufficient capacity to supply the fluid, normally from 10–15 L/min�2.6–4 gal/min� for tabletop machines with 200–250 mm �8–10 in� cut-off wheels and20–25 L/min �5.3–6.6 gal/min� for larger machines with 300–500 mm �12–20 in�cut-off wheels. The tank should have a sufficient size, containing 25–30 L�6.6–7.9 gal�, and 80–150 L �21.2–39.7 gal�, respectively. If the tank is too small thefluid might heat up during use, and the tank will fill up too fast with ground-off mate-rial. The tank should have a number of weirs and baffles so that the swarf and grit settleon the bottom of the tank and are not circulated in the system. Very long chips may befloating on the surface of the fluid and may eventually clog the pump. Often a simplefilter positioned near the outlet of the machine will collect these chips. This filtershould be cleaned relatively often. Larger filters and filter conveyor swarf removal sys-tems, originally developed for industrial machine tools, can be used.


Maintenance of Cooling System and Grinding FluidConsidering the importance of a sufficient cooling, both the cooling system and thefluid should be maintained regularly. The flow to the cut-off wheel should be checkeddaily to assure that the flow is uniform on both sides of the wheel. Depending on the useof the machine, the tank should be emptied and cleaned in regular intervals, at leastyearly. The tank should be emptied regularly for sludge to prolong the lifetime of thegrinding fluid. Often the content cannot be taken directly to the sewer because localenvironmental restrictions will forbid this �see below and Chapter 26�. The machine,cutting chamber, and piping should also be cleaned regularly with a detergent cleanerto prevent development of bacterial attack �see below�.

Water QualityThe quality of the water is important to the performance of aqueous grinding fluids.The hardness of the water �content of carbonates� affects the fluid very often and theamount of additive should be adjusted accordingly based on the advice of the additivesupplier. Water with a high calcium or magnesium content, or both, above 7.0 gpg�120 ppm�, is considered to be hard and precautions should be taken. Either a higherpercentage of additive can be used or the water can be softened. Hard water also in-creases the bacteria/fungi growth �see below�. Very soft water might cause develop-ment of foam that often can be suppressed by reducing the amount of additive in thecoolant. Other minerals, such as metal salts also may be present in the water, disturb-ing the action of certain components in the additive.

Concentration of Grinding FluidDuring use, water evaporates and the concentration of additive and minerals will in-crease �see below�. This can be checked by measuring the pH and using a refractometerfor exact measurements. According to the advice of the supplier, additive or water, orboth, should be added. Generally straight water should not be added, but always mixedwith additive in a higher or lower concentration so that the correct values are rein-stated. A rule of thumb is to add water with half of the normal concentration to com-pensate for evaporation. The concentration of the minerals originating from the wateralso will rise to maybe three to four times that of the original water during use. There-fore, the more pure the water used for mixing with the additive and added during use,the longer the fluid can be used before problems might develop.

Bacteria and FungiBacterial growth in the cooling system often develops if a machine has not been usedfor a period of time or the cleaning has not been done for quite a while. Two types ofbacteria are found in the fluid: aerobic, which grow in the presence of oxygen, andanaerobic, which grow in the absence of oxygen. The anaerobic bacteria that mightdevelop in the sludge in the bottom of the tank, produce hydrogen sulfide that cancause dark staining of the work piece and machine and has a strong, unpleasant odor.

The growth of fungus �mold� in the fluid can be a larger problem than bacteria,depending upon the type of fluids used for cut-off. The presence of fungi can be seen inthe form of slimy, semisolid deposits that cling to the walls of the tank and the machine.Development of fungi can be avoided by regular maintenance of the system as men-tioned above. In case of serious attacks the supplier of the additive should be contacted.

In case of strong development of microorganisms, a biocide can be added to the


fluid, or in severe cases, the system must be emptied, completely cleaned, and treatedwith a biocide �germicide� before it is filled up with new grinding fluid. The choice ofbiocide should be done according to information from the supplier of the original addi-tive because the biocide added should not be antagonistic to the biocide already in theformulation.

Disposal of Grinding FluidsA number of components in a used grinding fluid might be dangerous to the environ-ment and therefore should be treated with special care. These can be: components inthe original fluid �additive�, bactericides, and fungicides used for cleaning, sludge con-sisting of metal particles, and particles from cut-off wheels. It is very important that allthese substances are listed and checked with the local authorities regarding their dis-posal. Since disposal is often very troublesome and expensive, the advantage of goodmaintenance is evident; by constantly removing sludge and keeping the fluid clean, thedisposal of the fluid can be done relatively seldom.

Health and Safety Aspects of Grinding FluidsThe operator working with wet abrasive cutting can be affected in one or more of thefollowing ways: skin contact, oral ingestion, inhalation, and eye contact. The fluidsused mostly for cutting are of the water-miscible synthetic �chemical� type having ahigh pH �8.5–9.5� and a low surface tension. If skin is exposed to this fluid for a longperiod of time it loses its protective oily layer and, in seldom but some cases, dermatitiscan develop. This can be avoided by careful prevention and the operator should notcome in contact with the fluid by using gloves, barrier creams, etc., and by maintainingthe fluid so that it is clean and the concentration is correct.

Inhalation of mist and fumes can be avoided by having the cutting chamber con-nected to a ventilation system. The operator should use protective glasses to avoid eyecontact.

ASTM StandardsA number of ASTM standards are related to grinding fluids, the most important are:• Standard Practice for Selecting Antimicrobial Pesticides for Use in Miscible Metal-

working Fluids �E 2169�• Standard Method for Evaluation of Antimicrobial Agents in Aqueous Metal Work-

ing Fluids �E 686�• Standard Test Method for Evaluating the Bacteria Resistance of Water-Dilutable

Metalworking Fluids �D 3946�• Standard Practice for Safe Use of Water-Miscible Metal Removal Fluids �E 1497�

2.3.8 The Metallographic/Materialographic Cutting OperationThe metallographic/materialographic cutting operation has the following goals:1. Produce a specimen surface with lowest possible deformations and scratches.2. The surface should be without any thermal damage.3. The surface should be flat without waviness and without a burr.4. The cut-off should be done with lowest possible costs, meaning lowest possible

wheel wear �high G-ratio� and in the shortest period of time.


The ParametersThe following parameters are available for the operator when cutting with a normalcut-off machine �see Section 2.5 and Figs. 2.3 and 2.7�:

Cut-off Wheel rpmThis is normally in the range of 2000–3000, depending on the diameter of the wheel�see below and Section 2.4.1�.

Wheel VelocityBased on the rpm, the velocity �v� can be calculated. This should be in the range of30 to 50 m/s �6000–10 000 fpm�. On most cut-off machines the rpm, and conse-quently, the velocity, is a fixed value that the operator will not be able to change. Thevelocity will decrease with the decrease of the wheel diameter caused by wear.

On some newer models of cut-off machines the rpm is made variable, making avariation in wheel velocity possible. This changes the forces on the wheel �see Section2.3.3� and therefore also strongly influences the wheel wear, meaning that a “hard”wheel can be changed to a “soft” wheel by reducing the rpm and vice versa.

ForceThe force �F� is an important parameter relating to wheel grade �hard/soft�, work piecematerial, and length of cut �arc of contact�. Normally the force is not used as a control-ling parameter, but made available to accommodate the selected feed speed, even atlong arcs of contact �see Section 2.3.6�.

Feed SpeedThe feed �d� will vary according to material, length of cut, etc. It is usually in the rangeof 0.005–5 mm/s �0.0002 to 0.2 in/s�. This parameter can be controlled by the opera-

Fig. 2.7—Schematic drawing of wet abrasive cutting process. The cut-off wheel is fed into thework piece. The work piece being with a circular cross section, the arc of contact betweenwheel and work piece, l, will vary from a “point” when the wheel touches the work piece tothe total diameter of the work piece, when the wheel is half way through.


tor and is very important to obtain a correct cut �see below�.

PowerThe electric motors available in the cut-off machines range from 15 W to 10 kW. Thepower consumption expresses the tangential force, Ft in Fig. 2.3. The operator will of-ten be able to observe the power consumption on an amp meter, and, if necessary, ad-just the feed speed up for a higher power consumption and down for a lowerconsumption.

Arc of ContactThe contact area �l� between work piece and wheel plays an important role in the pro-cess. Preferably the arc should be in the range of 12–50 mm �0.5–2 in�, but it is oftenlonger. As a general rule, the work piece should always be placed so that the arc is theshortest possible �see Fig. 2.8�. When cutting large work pieces, it is helpful to use anoscillating movement of the wheel or work piece, or to rotate the work piece �see Sec-tion 2.5.1�.

Free CuttingBased on the relations discussed earlier in this chapter, the expression “Free Cutting”can be used as a “Rule of Thumb.” Free cutting is achieved when the correct balance isobtained between force �wheel against work piece�, feed speed, and power consump-tion, giving a correct cut with the highest G-ratio. The balance is reached at a feedspeed corresponding to the optimum chip removal. If the feed speed and force are toolow, the wheel edge gets blunt and heats up the work piece, stopping the process. On anautomatic machine, if the feed speed is set to a certain value, and a lower feed or no feedis obtained, the same will happen because the wheel is too hard for the given material.If the force is increased without a corresponding increase in feed speed, the cut be-comes too hot, causing the bond to fracture, and the wheel will start to break down at arapid rate or bend.

Fig. 2.8—The work piece should be placed correctly to obtain the shortest area of contactbetween cut-off wheel and work piece. �a� This position will give a short area of contact; �b�this position will give a longer area of contact and should be avoided.


Free Cutting by HandWhen cutting a work piece by hand, first a notch is made in the work piece with lowforce to secure a straight cut. Then the force is increased until the feed speed is con-stant, being the free cutting state. Free cutting is when an increase in force does notincrease the feed speed. If a reasonable feed speed is not obtained, even with a rela-tively strong force, the wheel is too hard for the given material. If a relatively high feedspeed can be obtained without a reasonable force, the wheel is probably too soft.

Free Cutting—AutomaticCut-off machines often have a hydropneumatic or electric �electronic� feed system, en-abling the operator to establish an automatic feed �see Section 2.5�. To obtain a “freecutting,” feed speed and power consumption are compared, the consumption express-ing the force in the cut. The feed speed is increased, and as long this increase has acorresponding increase in power consumption, the situation is correct and free cuttingis made, provided that a sufficient force is available. When adjusting to a higher feedspeed, no increase can be observed but the power consumption goes up, the feed speedshould be reduced because the force in the cut is too high. The wheel will start to breakdown at a too high rate or bend. The operation described is assuming that a sufficientforce between wheel and work piece is available. If the force is not adequate for a givenarc of contact, the feed will, of course, stop or be too low �see Section 2.5.1�.

2.4 Abrasive Cut-Off Wheels

Two types of wheels are used for metallographic/materialographic cutting: consum-able wheels and slow consumable wheels. Consumable wheels are based on inexpen-sive abrasives, whereas slow consumable wheels are made with diamond or CBN.

2.4.1 Consumable WheelsWith consumable cut-off wheels, the whole wheel is made from a resin �bond�, bakeliteor rubber, or a combination of these, with mixed-in abrasive grains, either aluminumoxide �Al2O3� or silicon carbide �SiC� �see Fig. 2.9 and Section 2.3.2�.

The consumable wheel functions by wearing down during the cut-off process, thewear being related to the wheel grade. The wheel grade goes from soft to hard, allowingcutting of hard materials �up to HV 700–800� with a soft wheel and soft materials with ahard wheel. Al2O3 is used for cutting of most ferrous materials and SiC for nonferrousand cast iron.

There are normally six to seven different grades available based on either Al2O3 orSiC. Typically the grades are specified according to material type and hardness, span-ning from soft nonferrous materials to very hard ferrous materials. When cuttinglarger work pieces with a long arc of contact, a wheel with a relatively coarse abrasiveshould be used and a soft grade might be needed �see Section 2.3.2�.

Wheel VelocityThe consumable wheels, being rather brittle, are not to be used with wheel velocitieshigher than stated on the wheel, normally a maximum of 50 m/s �9800 fpm� or 60 m/s�11 800 fpm�.

The wheel velocity depends on the rpm of the wheel and the wheel diameter. Thevelocity can be calculated from:


Velocity =rpm · � · Diameter of wheel �mm�

60 · 1000m/s

or

Velocity =rpm · � · Diameter of wheel �in�

12fpm

The velocity for consumable wheels is typically 35–50 m/s �6900–9800 fpm�.Most cut-off machines for general use have a fixed rpm �except precision cut-off

machines �see Section 2.5�, setting the wheel velocity. Because the wheel velocity, evenwith consumable wheels for general use, has an important impact on the cut-off pro-cess, newer machines can be made with variable rpm �see Section 2.5�.

Wheel DimensionsThe consumable wheels are normally available in diameters: 100 mm �4 in�, 125 mm�5 in�, 150 mm �6 in�, 175 mm �7 in�, 200 mm �8 in�, 235 mm �9 in�, 250 mm �10 in�,300 mm �12 in�, 350 mm �14 in�, 400 mm �16 in�, 432 mm �17 in�, 450 mm �18 in�.

Thickness of the wheels varies from 0.5 mm �0.02 in� at the smallest diameters to3.0 mm �0.12 in� at the largest.

Arbor �shaft� diameter is normally 32 mm �1.25 in�. For small wheels for precisioncutting: 12.7 mm �0.5 in�.

StoringConsumable wheels should be stored in a dry atmosphere and laid flat on a stiff flatsurface to prevent bending of the wheel. To safeguard the wheels it is useful to have a

Fig. 2.9—Consumable cut-off wheel. The entire wheel is made of a resin bond with an abrasive�Al2O3 or SiC� and will be totally worn down during the process.


vertical shaft protruding from the holes in the wheels and a weight may be placed onthe top. Bakelite wheels especially will deteriorate when stored in a humidenvironment.

2.4.2 Slow Consumable WheelsAs indicated in the designation, these cut-off wheels are worn during the process, butnot to the same degree as consumable wheels. The abrasives used in consumablewheels are the super abrasives, diamond and CBN �see Section 2.3.2�. The single grainis worn very slowly and therefore a very stable bond is used, either metal or resin�bakelite�. This secures that the abrasive stays in place and is not torn away from thewheel, as is the case with consumable wheels.

The slow consumable wheels are usually made with a metal body and the abrasivewith the bond is placed around the periphery of the body �see Fig. 2.10�. The abrasive/bond layer can be a continuous layer around the periphery �continuous rim� or in seg-ments. The metal body allows for very thin wheels, down to 0.15 mm �0.006 in� suitedfor precision cutting.

In cutting wheels with electroplated abrasives, the abrasives are placed in a bandalong the periphery of a metal body and covered with a metal layer. These wheels onlyhave a thin layer of abrasive; they are less expensive than the wheels described aboveand their lifetime is shorter.

Truing and DressingBecause the slow consumable wheels have a very stable bond, the abrasive grain doesnot readily break away even when very worn. Also, the edge of the wheel may clog up

Fig. 2.10—Slow consumable cut-off wheel, continuous rim. The body of the wheel is metal andthe rim is a bond �metal or bakelite� with diamond or CBN. The wear is very low, caused bycutting and dressing.


with abraded material that stops the cutting action. Therefore, truing or dressing mustbe done. With truing, the shape of the wheel is corrected �see Section 2.3.6� and this isnormally not necessary for a slow consumable cut-off wheel. Dressing is important,because it exposes new abrasive grains in the edge by removing bond material and to acertain degree removes worn down grains. Dressing is done with a dressing stick madefrom hard materials such as sintered Al2O3 and SiC that is held against the edge of thewheel for 5–10 s.

Attention: Dressing should not be overdone because it wears down the relativelyexpensive wheel.

UseSlow consumable wheels are used frequently when consumable wheels are not suit-able.

Cut-off in general: For cutting of ferrous metals with hardness higher than ap-proximately HV 500–700 and up to HV 1400, CBN wheels are used. For sintered car-bides, ceramics, and other very hard materials, diamond wheels are used. Tough �duc-tile� materials like sintered carbides are cut with a bakelite bond and most hard andbrittle materials with a metal bond.

Precision Cut-offThis operation, done on precision cut-off machines �see Section 2.5� often calls for verythin wheels below a thickness of 0.5 mm �0.02 in�; therefore, slow consumable wheelsare used. Normally, when cutting hard materials and composites, metal bond is usedwith either high or low diamond concentration. High concentrations are used for thesofter materials and low concentrations for the hardest materials like ceramics. At lowconcentrations the cutting action is high because of the fewer abrasive grains, creatinga higher force on each grain �see Section 2.3.3�. If possible, ductile materials, like mostmetals, should not be cut with slow consumable wheels. The ductile metal will con-stantly clog up the edge of the wheel, the cutting action will be very low, and the wheelwill “wear” its way through the work piece. When cutting most metals on a precisioncut-off machine, a thin resin bonded consumable wheel should be used if a thickness of0.5 mm �0.02 in� can be allowed.

Wheel VelocityThe wheel speed should be approximately 25 m/s �4900 fpm�. This can be establishedwith most precision machines �see Section 2.5�, but often the heavier machines for gen-eral cutting will not be able to accommodate this relatively low wheel velocity. At low-speed cutting with small precision cutters, very low wheel speeds in the range of 2 m/s�395 fpm� are used �see Section 2.5.2�.

Wheel DimensionsSlow consumable wheels for general use are available in diameters from 200–400 mm�8–16 in�. Thickness from 1–2.2 mm �0.04–0.09 in�. Shaft diameter �arbor� is nor-mally 32 mm �1.25 in�.

Wheels for precision cutting �wafering� are available in diameters from75–200 mm �3–8 in�. Thickness varies from 0.15–0.9 mm �0.006–0.035 in�. Shaft �ar-bor� is normally 12.7 or 22 mm �0.5 or 0.87 in�.


StoringSlow consumable wheels should be stored laid flat on a stiff, flat surface. Especiallythin wheels should be treated with utmost care because of the risk of bending thewheel. The boxes in which the wheels were supplied should be used for storage.

2.5 Abrasive Cut-off Machines

Metallographic/materialographic cut-off machines are made for wet abrasive cuttingof a work piece to obtain a sample �specimen�. The machine is normally built for a cer-tain size of the cut-off wheel, deciding the power of the electric motor driving thewheel.

It is important that the cut-off wheel and work piece are sealed off from the opera-tor during the cutting to avoid damage to persons in case of wheel breakage.

The machine has a system for moving either work piece or wheel to establish a feedmovement �see below�. It also has a system for adding cooling/lubricating fluid to thecutting area. The work piece is normally placed on a table to allow for fixing the workpiece before cutting. The spindle carrying the wheel should be without play and themachine design should be stable to avoid vibration.

During the cutting, mist and fumes are developed, and the machine should have anoutlet for an exhaust system.

2.5.1 Design Principles of Wheel—Work Piece ContactAs described in Sections 2.3.3 and 2.3.8, the arc of contact �or contact area� betweenwork piece and cut-off wheel should be kept around ideally 12–50 mm �0.5–2.00 in�,and preferably kept constant during the whole operation. This is often not possible at“direct” or “chop” cutting where the contact area will vary strongly with the shape andthe size of the work piece �see below�. To avoid this, a number of designs have beendeveloped to keep the contact area constant.

Direct CuttingThe wheel and work piece contact is dependent on the shape of the work piece asshown in Fig. 2.7 and 2.12�a�. If a 50 mm �2 in� shaft is cut, the length of the contactarea will vary from a “point” when the wheel first touches the work piece to more than50 mm when the diameter of the work piece is reached. This means that the force be-tween cut-off wheel and work piece can be very low at the beginning but has to increaseto ensure a sufficient force on the abrasive grains at the long arc of contact �see Section2.3.6�. This is normally solved by operating with a sufficiently high force and control-ling the feed speed, keeping it constant through the whole cut. With the correct cut-offwheels and machine data, a direct cut can be made on almost all materials, even up tolarge sections. A rule of thumb would be that a dimension up to 15–20 % of the wheeldiameter can be cut directly, depending on the material and the type of wheel.

Oscillating CuttingDuring oscillating cutting, the feed movement between the work piece and the wheel iscombined with a relative movement between the two. This means that the arc of con-tact is kept low and dependent of the length of the total cut only to a certain degree sothe cutting force can be kept at an optimum value. For metallographic/material-


ographic cutting the oscillating movement also has the advantage of making room forthe cooling fluid, improving the cooling in the cut.

Oscillating cutting can be made with an oscillating wheel or an oscillating workpiece as shown in Figs. 2.11 and 2.12�b�. In most cases, the arbor �spindle� carrying thewheel is moved in a circle �ellipse� or a horizontal �lateral� movement in the same planeas the wheel, in this way creating a movement relative to the work piece, as shown inFig. 2.12�b�. Only a small amplitude, 1–2 mm �0.04–0.08 in�, a in Fig. 2.11, is neces-sary to limit the arc of contact.

When oscillating the work piece, the table with work piece is moved in a tilting orreciprocating movement. Figure 2.12�b�, shows an oscillating wheel but it can easily beimagined that the work piece has a movement giving the same effect.

Oscillating cutting makes it possible to cut very large work pieces even from diffi-cult to cut materials. The short arc also makes it possible to work with harder wheels,thus reducing the costs.

Fig. 2.12—Comparison between direct cutting �a� and oscillating cutting �b�. At oscillatingcutting the cut-off wheel can be moved relative to the work piece, as shown, or the table withthe work piece can have a tilting or reciprocating movement, not shown.

Fig. 2.11—Principle of oscillating cutting; the cut-off wheel moves relative to the work piece.


Step CuttingAnother way of avoiding the long arc of contact is step cutting �Fig. 2.13�. In this prin-ciple the wheel is moved in increments into the work piece, or vice versa, while movingthe wheel back and forth, performing the process in steps. The depth of each step �in-crement� dictates the contact arc and this depth can be selected according to the hard-ness of the work piece material and the hardness of the wheel. The advantage of stepcutting is that very long work pieces can be cut independently of the size of the wheeland very hard and tough materials can be cut.

Fig. 2.13—Schematic drawing of step cutting. The cut-off wheel is fed into the work piece in astep of 1–5 mm �0.04–0.2 in� and moved along the work piece to the end where a new step ismade.


Rotating Work PieceIn the case of a rotating work piece, the arc of contact is only a point where work pieceand cut-off wheel are touching each other �see Fig. 2.14�. In some cases this is the onlyway to cut very hard materials like sapphire, and by cutting of coatings, the coating issupported all the way around, avoiding peel-off. This way of cutting also will givedouble cutting depth because the cut-off wheel will only reach halfway through thework piece. Complementary rotation should be preferred �see Fig. 2.14�. The figureshows a work piece with a circular cross section, but other shapes can be rotated andcut. However, this usually causes some cutting in air because the wheel will first touchthe corners of the work piece.

A rotating work piece is mostly used at precision cutting but special rotatingchucks are also available for general use machines.

2.5.2 Machine DesignsCut-off machines can be designed according to different principles regarding move-ment of work piece/wheel �see Fig. 2.15�.18 The wheel is either moved towards the work

Fig. 2.14—Schematic drawing of a rotating work piece showing complementary �� andcontra �� rotation. With a rotating work piece, the cut-off wheel and work piece only touchin a “point,” and the specimen will be cut off when the wheel reaches the center of the workpiece; this will double the cutting capacity of the machine.

Fig. 2.15—Design principles for the metallographic/materialographic cut-off machines. At a, b,and c, the cut-off wheel is fed into the work piece. At d, e, and f, the work piece is fed into thecut-off wheel.


piece, a, b, c, or the work piece is moved towards the wheel d, e, f. In the case of theradial in-feed shown in a, c, d, and f, the depth of the cut is limited to the part of thewheel outside the flange. At b and e, the work piece is attacked tangentially, and a largerwork piece can be cut if the movement of the cut-off wheel b or the work piece e allowsfor it.

Most modern machines are built according to c, where the cut-off wheel is movedinto the work piece that is fixed on a stationary table, or e, where the work piece, fixed toa movable table, is moved into the stationary cut-off wheel which in most cases isplaced on the motor shaft. In some machines the two principles are combined, givingmore flexibility.

Cut-off Machines for General UseSmaller machines for wheels of 200–250-mm �8–10-in� diameter are mostly table topmodels with an external recirculation system for the cooling fluid. Most of thesesmaller machines are hand-operated, and the cut is a direct cut �see Section 2.5.1�. Themotor power for these machines is in the range of 1–4 kW. An example of a hand-operated table-top machine is shown in Fig. 2.16.

Machines for wheels of 300 mm �12 in� and larger are mostly floor models withrecirculation systems included in the machine, with motor power ranging from4–10 kW. These machines are usually automatic, meaning that the feed speed is con-trolled by hydropneumatics or by electric means. In the case of electrically driven feed,this can be controlled by a microprocessor, allowing for adaptive control so that theoptimum feed speed in relation to motor power is found �see Section 2.3.8�. An ex-ample of an automatic, floor-based machine is shown in Fig. 2.17.

Fig. 2.16—Standard manual laboratory cut-off machine for chop cutting with dual vices toclamp samples on both sides of the cut-off wheel. A 3 kW motor and 254 mm �10 in� cut-offwheels with cut capacity 76 mm �3 in� in diameter.19


Most machines have tables with T-slots for flexible positioning of the work piece,often with quick clamping devices. The cutting compartment should be closed accord-ing to the rules of safety. It shall not be possible for the operator to open into the com-partment before the wheel has stopped. The compartment should be easy to clean,without too many components and corners. It is also an advantage if electrical parts,such as the motor, are not placed in the cutting compartment.

An efficient cooling system is important, taking the grinding fluid effectively intothe cut, with easy access to cleaning.

Large machines should have a system for reducing the arc of contact betweenwheel and work piece �see Section 2.5.1�.

Precision Cut-off MachinesPrecision cut-off machines are defined as machines being able to cut with relativelyhigh precision, the work piece being placed in a fixture, moved with a micrometrescrew or automatically. Where machines for general use are mostly used for metals, theprecision machines are often used for other �hard� materials such as ceramics and elec-tronic parts to be cut with diamond cut-off wheels. Most of these cutters have variablespeed, from very low �50 rpm� to 5000 rpm. The wheels are from 75 to 200 mm

Fig. 2.17—Automatic cut-off machine with oscillating cutting and step cutting for obtainingthe minimum contact area. A 10.5 kW motor and 432 mm �17 in� cut-off wheels with cutcapacity 160 mm �6.3 in� diameter, cutting length 450 mm.20


�3 to 8 in� in diameter and often very thin, securing a very low loss of material �kerfloss� which can be important when cutting materials of high value. On most modernmachines both consumable and slow consumable wheels can be used. The workpieces, electronic parts, optical parts, and other parts where a precision cut is needed,are normally of a size up to 50–75 mm �2–3 in�.

Fig. 2.18—Low speed precision saw for low volume applications. A 15 W motor, 0–300 rpmand up to 125 mm �5 in� diamond wheels, 32 mm �1.25 in� cutting capacity.19

Fig. 2.19—Precison cut-off machine for automatic precision cutting of larger specimens.Adjustable vertical position of the cut-off wheel makes use of small wheels, 75 mm �3 in�, andlarge wheels, 200 mm �8 in�, easier to work with. Automatic feed speed adjustment and 5 �mspecimen positioning. An 800 W motor, up to 5000 rpm. Cutting capacity 60 mm �2.3 in�,cutting length 190 mm �7.5 in�.20


Precision machines are built according to the same principles as the general pur-pose machines �see Fig. 2.15�. The smallest machines are built according to f in Fig.2.15, with the work piece being fed into the wheel by a weight �constant force�. Thesemachines are made for use with slow consumable wheels �diamond� because consum-able wheels cannot be used with the very simple feed system without getting unround.The speed is low, in the range corresponding to 300 to 600 rpm, and the motor power isvery low, 15–100 W. An example of a low-speed cutting machine is shown in Fig. 2.18.

The larger machines typically have a table with the fixed work piece moving linearinto the rotating cut-off wheel, Fig. 2.15, d and e. The motor power is in the range of500–1000 W.

The feed, “y-movement,” can be hand-operated or automatically controlled by amicroprocessor. The fixture, placed on a table carrying the work piece, can be with amicrometre or with automatic control of the “x-movement,” positioning the workpiece. An example of an automatic precision cutter is shown in Fig. 2.19. All machineshave a system for cooling fluid to be taken into the cut. With machines running morethan approximately 300 r/min, the cutting compartment is protected by a hood and itshould be secured that the wheel is stopped if the hood is opened.

2.6 Advice and Hints on Wet Abrasive Cutting

When working with cut-off, it is possible to routinely make a number of precautions tosecure a good cut and, therefore, a good specimen.• Fix the work piece securely before cutting. Take care that the cut-off piece �the

specimen� is not squeezed against the wheel during the cutting. Preferably thespecimen should be lightly clamped to avoid a burr.

• When clamping sensitive work pieces, place some soft material, such as plastic,between the work piece and the clamp to avoid damage.

• When introducing the wheel into the work piece at manual cutting, do it slowly andstop the feed for 2-–3 s to allow a notch �kerf� to be formed. This secures a straightcut. This is especially important at tapered or rounded work pieces. If the wheel isnot cutting straight from the beginning it will cut sideways and ultimately break.

• Pay attention at manual cutting when the cut-off wheel is almost through the workpiece. Lower the feed speed to avoid overheating of the edge of the specimen orpinching of the wheel.

• Check the edge of the cut-off wheel. It should be flat �square� when cutting mediumthick sections, flat with rounded corners �large sections�, or concave �thin sec-tions�, indicating that the proper cut-off wheel is used and normally giving a burr-free cut. If the edge is strongly rounded �convex� or pointed, the wheel is probablytoo hard for the material and a softer wheel should be used. A glazed edge indicatesa wheel that is too hard, which requires a too high force and therefore developsexcessive heat. If the edge is chisel shaped, the flow of cooling fluid to the wheel isuneven, giving a crooked cut possibly causing wheel breakage �see Section 13.6.2�.

• Disk brake effect: In some materials having internal stresses the work piece willtend to pinch the wheel, very often when the cut is almost finished. This can cause abreakage of the wheel because the pressure between the two parts of the work pieceis so high that the rotation stops. This effect might be avoided when working with avery low feed speed, 0.5 mm/s �0.02 in/s� or lower, and preferably oscillating/stepmovement, minimizing the development of heat.


• When cutting a material for the first time, check that the feed speed and power con-sumption �force in the cut� are in reasonable balance. If yes, the wheel is “free-cutting” �see Section 2.3.8�. If the force on the wheel increases, shown by an in-crease in power consumption, without a visible increase in feed speed, the settingof the feed speed is probably too high and it should be reduced. If the force is al-lowed to mount, the wheel might bend and a straight cut �plane surface� is not ob-tained, or the wheel might break.

• Cutting of a work piece with a coating: Take care that the cut-off wheel is movingthrough the section of the coating to be examined and into the base material. Inthis way the coating is preserved, because it is in compression and not torn awayfrom the base material.

• Mounting before cutting: In some cases it is an advantage to mount the specimenbefore sectioning to be able to establish a correct cutting plane or avoid breakage.This can be failure analysis with cracks/corrosion, electronic parts, small speci-mens of plastic, or very brittle specimens. The mounting is done mostly with a coldmounting resin, preferable epoxy �see Section 3.8�. To avoid clogging of the edgesee electronic parts below.

• Cutting of electronic parts: Often these parts contain soft �copper� and very hard�brittle� materials �ceramics�. Use an electroplated diamond wheel �precision cut-ting�; this wheel has diamonds on both the edge and the sides, and it will cutthrough ductile and brittle materials without clogging �see Dressing below�.

• When the wheel is too hard �glazing�, and a softer wheel is not available, try a worn-down wheel which causes a lower cutting speed and thereby a softer acting wheel,or use a thinner wheel. In the case of hand cutting, “pulse cutting,” by beating thewheel into the work piece will create a wheel wear and the wheel will start cutting;only the lifetime of the wheel is reduced. Another possibility is to make incisions inthe periphery of the wheel, using a pair of pliers to break out small pieces with50–75 mm �2–3 in� in distance. This also increases wheel wear.

• Cutting may cause harmful gases derived from the phenolic bond and a rubberbond will normally develop a strong smell. Therefore, the cut-off machine shouldbe connected to an exhaust system.

• The hood of the cutting machine should be left open after use so that the machineand cut-off wheel can dry out, reducing corrosion of the machine and prolongingthe lifetime of the wheel.

• Dressing: Diamond and CBN wheels can have a material build-up on the edge ofthe wheel �clogging�, reducing the cutting ability. The edge is dressed, “cleaned,”using a dressing stick of Al2O3, for about 5–10 s.For Trouble Shooting, see Section 13.5.

2.6.1 Cut-off Wheel SelectionRule of thumb: Use a soft wheel for a hard material or a large work piece and a hardwheel for a soft material or a small work piece.

Both hardness and ductility of the material must be evaluated. A soft material willnot wear out the abrasive very fast, therefore a hard wheel can be used. A ductile mate-rial might clog the wheel rim so that a softer wheel must be used. On the other hand, aductile material might pull out the grains, causing excessive wear. A hard material willwear out the grains fast, therefore the wheel should break down, releasing new grains.


General UseNonferrous metals—These are relatively soft �up to HV 350�. Use a hard bakelite

�phenolic resin� wheel with SiC.Soft ferrous metals—�Up to HV 350�. Use a hard bakelite or rubber-resin wheel

with Al2O3.Medium hard ferrous metals—�Up to HV 550�. Use a medium hard bakelite or

rubber-resin wheel with Al2O3.Hard ferrous metals—�Up to HV 950�. Use a soft bakelite or rubber-resin wheel

with Al2O3.Very hard ferrous metals—�Harder than HV 950�. Use a slow consumable CBN

wheel with bakelite bond.Sintered carbides/hard ceramics „relatively ductile…—Use a slow consumable

diamond wheel with bakelite bond.Ceramics/minerals „relatively brittle…—Use a slow consumable diamond wheel

with metal bond.

Precision CuttingSoft and medium hard materials—Use a medium hard bakelite wheel with

Al2O3.Medium hard and hard materials, hard, ferrous metals—Use a medium soft

bakelite wheel with Al2O3.Very hard ferrous metals—Use a slow consumable CBN wheel with high concen-

tration, metal bond.Extremely hard ferrous metals—Use a slow consumable CBN wheel with high

concentration, bakelite bond.Ceramics, minerals, very hard materials, general use—Use a slow consumable

diamond wheel with high concentration, metal bond.Brittle materials „ceramics, minerals�—Use a slow consumable diamond wheel

with low concentration, soft metal bond.Electronic parts, hard tough materials, medium to soft ceramics, structural

ceramics—Use a slow consumable diamond wheel with low concentration, metalbond.

Polymers and other soft materials—Use a slow consumable diamond wheelwith high concentration and metal bond, or a toothed saw blade.

Soft and ductile nonferrous metals—Use a medium hard bakelite wheel withSiC.

2.7 Other Sectioning Methods

As described earlier, wet abrasive cutting is the dominating cut-off method formaterialographic specimens. Other methods, however, are used either because theyare simple and effective like fracturing, shearing, punching, and sawing, or becausethey give a gentler treatment of the cut surface, like wire cutting, than can be obtainedwith wet abrasive cutting.

2.7.1 FracturingFracturing can be done on brittle materials like hardened tool steels, ceramics, etc. Of-ten a notch is made to control the fracture. Less brittle steels and cast iron can becooled in liquid nitrogen before fracturing.


2.7.2 Sectioning by MeltingCutting using methods based on melting the material to be cut is not recommended formetallographic specimens. The melting process always develops zones affected by heatand changes the material, often far from the cut surface.16,21 As some of these methodsare used in spite of the drawbacks, the most important methods should be mentioned.

Oxyacetylene TorchingThis method should only be used when no other method is available and it should onlybe used for obtaining a relatively large work piece for further cutting in the laboratorywith other means. When cutting-off steel specimens it should be considered that a zoneof at least 25 mm �1 in� has been affected by heat during the torch cutting,21 but oftenthe affected zone is wider �see Fig. 13.1�.

Plasma TorchingThis method also creates a heat-affected zone with material changes andmicrocracks,16 and should only be used for cutting a work piece for further cutting.

Laser CuttingDuring laser cutting the heat-affected zone is the range of 0.5 mm �0.02 in� for an an-nealed steel �AISI/SAE 4130�,16 and care should be taken to remove enough material atthe grinding stage if laser cutting is used for the specimen.

Electric Discharge MachiningElectric discharge machining �EDM�, or spark machining, is a process that uses sparksin a controlled manner to remove material from a conducting work piece in a liquiddielectric.22 The sparks melt the specimen material creating craters in the surface and aheat-affected zone below the surface. With certain materials that have been melted andthen solidified, the molten material may absorb extraneous alloying elements from thesurroundings.7 A layer containing cracks also may develop immediately beneath thesurface. Both the craters and the heat-affected zone can be several hundred �m deep,and care should be taken, especially in heat-sensitive materials, so that the damagedlayer is removed during the grinding process.

2.7.3 ShearingA shear can be used for cutting of sheets and other flat products of not very hard materi-als. The edge of the produced specimen will be heavily damaged by cold work and aburr often develops. The cold work will alter the microstructure in a layer of the speci-men in most cases, and it is important that this material is removed during the planegrinding and fine grinding process. For this reason, shearing is not recommended formaterials that are sensitive to mechanical twin deformation.9

A hand shear can be used for cutting work pieces up to 4–6 mm �0.15–0.25 in�,depending on the type of material. For shearing of stock up to 13 mm �0.5 in� a powershear is needed. The power shear is built with a table for placing the work piece and alower blade integrated in the table and an upper blade moved mechanically or by hy-draulics. The work piece is fixed during the shearing process by a hold down foot veryclose to the lower blade. The upper blade is not attacking the work piece in its fulllength, but the blade has a slope called the rake. The rake is given by the design of theshear. The load required to shear the work piece material depends on the thickness and


type of material and the rake. In normal shearing a portion of the material is shearedand the rest is broken through due to the shearing action. As an example, in mild steelup to 6 mm �0.25 in�, one-half will be sheared and the rest will break. The shearing loadincreases strongly with the thickness of the work piece, although mild steel of 9.5 mm�0.38 in� is only approximately 50 % thicker than 6 mm �0.25 in�; the load needed is225 % higher. For this reason, a shear should not be used for cutting of metallographicmaterial thicker than the rated capacity, even in narrow pieces. On most power shearsthe upper blade will move in a plane 0.5–1° away from vertical, allowing the upperblade to contact the work piece immediately above the edge of the lower blade. Whenthe upper blade moves downwards and edge contact is obtained, the correct clearanceis developed and this clearance will increase when the blades overlap. In principle, theblades should be adjusted according to the thickness of the work piece, but at mostmodern shears the blades can be set for a wide range of thicknesses. If shearing of boththin and thick products are made, the shear should be adjusted to minimum clearanceto avoid thin stock wedging between the blades. It is very important that the clearancesetting is correct and accurate grinding of the blades is maintained. If the edges of theblades are rounded by wear, or the clearance is too high, the burr mentioned above willincrease.

The shear is a safe tool to use as long the operator follows the given rules.The shear is a precision machine tool and should be kept in good working order

according to the instructions of the supplier.

PunchingPunching is shearing using a die and a punch and it is used for foils and thin plates tomake circular or rectangular specimens. An example of a circular specimen is thepunching of samples for electrolytic thinning �see Section 8.6�. Rectangular specimensare used for printed circuit boards �PCBs� �see Section 7.10.1�. Rectangular specimensalso are used for steel sheet because the long edge of the specimen can be aligned to therolling direction of the sheet.

As with shearing �see above�, cold work and a burr will be developed in the processand this should be removed during the grinding stage of the preparation.

2.7.4 Sawing—Table 2.1Sawing is a machining process using a circular blade or a straight band having a seriesof small teeth for cutting of most materials. By sawing, material is removed from thework piece in chips as described in Section 6.2 and shown in Figs. 6.1 and 6.2. Whensawing, the rake angle �see Fig. 6.2� is always neutral �0°� or positive, up to 10° forpower hacksawing and bandsawing and 18° for circular sawing. The distance betweenadjacent teeth on the saw blade is called the pitch, normally expressed in number of

TABLE 2.1—Recommended Band Pitches for Sawing of Work Pieces of Different Thickness.

Work Piece Thickness Band Pitch

Less than 25 mm �1 in� 10 or 14

25–75 mm �1–3 in� 6–8

75–150 mm �3–6 in� 4–6

150–300 mm �6–12 in� 2 or 3

Over 300 mm �12 in�1

1

2to 3


teeth per inch, and it depends primarily on the cross section area of the work piece to becut and to a lesser degree on the type of material. As a rule, two or three teeth should beengaged with the work piece at all times during sawing. Under Bandsawing, below, thetooth geometry, pitch, etc., are further discussed. Sawing should be performed with acutting fluid �see Section 2.3.7�.

The surfaces created by sawing normally are rather rough, but if correctly treatedin the following specimen preparation, sawing can be used for sectioning ofmetallographic/materialographic specimens.

HacksawingThe hand-held hacksaw often can be used for cutting of a work piece from a large part,maybe placed outside the materialographic laboratory, the work piece later to be sec-tioned by wet abrasive cutting to produce a specimen. If the hacksaw is used for cuttinga specimen from a work piece, the surface should be carefully prepared, often with anextended plane-grinding step to remove cold work and deformation �see Fig. 13.2�.

Power HacksawingPower hacksawing is characterized by the reciprocating action of a relatively short,straight-toothed blade that is drawn back and forth over the work piece in much thesame manner as a hand hacksaw.

Hacksawing machines consist of a supported reciprocating frame and saw blademounted to a base for supporting the work piece. The machines are made as both hori-zontal and vertical designs, horizontal machines being the most popular. The blade isfed into the work piece with a feed mechanism and a flow of cutting fluid is led to thecutting area. Because of the limited possibilities for clamping the work piece, powerhacksawing is well suited for cutting of stock material, tubing, etc., but less suited forcutting of more complicated parts. The surfaces produced with power hacksawing arevery rough and the problems mentioned above with cold work and deep deformationare evident. Therefore, this cutting method should only be used for cutting of a workpiece from a larger part, the specimen to be cut later from the work piece by wet abra-sive cutting.

Circular SawingCircular sawing is a process using a rotating, continuous cutting blade with teeth on itsperiphery to cut most materials under a flow of cutting fluid. A circular saw producesbetter surfaces than power hacksawing, but the limitations regarding cutting of otherwork pieces than stock material and tubes, etc., are the same.

BandsawingBandsawing uses a long, endless band traveling over two or more wheels in one direc-tion. The band, with only a portion exposed, produces a continuous and uniform cut-ting action using a cutting fluid to improve the cutting, cool the work piece, and in-crease band life.

In bandsawing the cutting takes place as a continuous, single-direction cutting,and this, combined with blade guiding and tensioning, gives the possibility of follow-ing a free cutting path, making contour cutting possible. In this way a specimen can becut out from a work piece of odd form, a great advantage compared to other types ofsawing mentioned above.


A number of saw blade types are available for bandsawing, but only two of themare suited for cutting of metallographic/materialographic specimens. These types are“conventional sawing” with a bandsaw blade with teeth, used primarily for cut-off andcontour cutting of most materials, and “saw-grinding” with a blade with continuous/segmented edge for the cutting of very hard materials and composites �see below�.

The quality of the cut is generally better than hacksawing, but still a relativelystrong deformation caused by cold work is developed.16,21 At conventional properlyperformed bandsawing, the heat developed will not create an altered microstructurebut this could happen if the cooling has not been efficient or the feeding pressure hasbeen too high. Care should be taken so that cold work and heat-affected zones are to-tally removed during the grinding steps of the preparation process.

Safety at BandsawingThe dangerous area when bandsawing is the point of operation where the saw bandtraverses to process the work piece. It is very important that the operator is careful tokeep his hands out of the immediate sawing area whenever the band is moving. Thework piece should always be guided into the band with some kind of distance piece sothat the hands will not be close to the band, even when the band has cut totally throughthe work piece.

Bandsaw BladesIt is important to select the correct saw band �blade� for the given work piece to becut.23 Important factors are:• Type and hardness of the work piece material that determine the tooth form and

composition of the band.• The size and variation in cross section of the work piece that determine the pitch of

the teeth of the band.• Type of cut, is it straight, contoured or both? If cutting in small radii, the width of

the band should be limited.• Type and condition of the machine to be used.• Whether a cutting fluid will be used.

Different bandsaw blades with different width, thickness, and tooth geometriesare available for cutting of different materials, ranging from relatively soft carbon steelbands for cutting of mild steel, cast iron, copper, and other relatively soft materials, tobi-metal and tungsten carbide-tipped blades for hard, very hard, and tough materialslike work-hardening alloys, high temperature alloys, hastalloy, and titanium. Bandsawblades with a grit edge are available with a tungsten grit for cutting hardened tool steel,titanium, nickel- and iron-based superalloys, glass fiber optics, low density ceramics,and composites. The more expensive diamond edge blades are used for very hard,brittle materials, such as minerals and ceramics.

Figure 2.20 shows the terminology commonly used for saw bands. The cutting ac-tion of the band depends on the tooth geometry. There are three main types of toothforms: precision, claw, and buttress, as shown in Fig. 2.21. The precision form nor-mally has a 0° rake angle, but a positive rake angle is also available. It has a full-roundedgullet with a smooth radius; the gullet is taking up the chip as long as the tooth is incontact with the work piece. Bands with precision-form teeth are the most versatile,have a smooth finish, and are recommended for cutting of most metallographic/materialographic specimens. The claw form has the same form as the precision except


the gullet is more shallow with less chip capacity but greater backing strength and a 10°rake angle that requires less feed force. The claw form is recommended for the toughestmaterials that demand heavy feed and yield small chips. The buttress form also has amore shallow gullet and neutral rake angle and is a stronger, less aggressive variant ofthe claw form for cutting of wood and plastics.

The band width should be as high as possible for the given cutting operation �seeFig. 2.20�. The wider the band, the greater its beam strength and the more accurate thecut. For straight cuts the widest band that the machine can accommodate should beused. Narrower bands should be used only for contour cutting.

The band thickness is important for the strength of the band, especially if the bandwidth is small.

The tooth set is the distance between the outer corners of oppositely set teeth, de-termining the kerf �width of the cut�. The teeth are set by bending the single tooth toone side of the band. At straight set the bending alternates all teeth left and right. Rakerset includes one unset tooth �raker� in each sequence of 3, 5, or 7 teeth. The raker set isrecommended for materialographic cutting of ferrous materials.

Fig. 2.20—The terminology commonly used for bandsaw blades.

Fig. 2.21—The three main types of bandsaw blades.


The band pitch, the number of teeth per inch of length �see Fig. 2.21� is primarilydetermined by the thickness of the work piece to be cut. A thin work piece requiresbands with a finer pitch �more teeth per inch�, thick stock a coarser pitch �see Table2.1�. The work piece material and the surface finish required also must be consideredwhen selecting the optimum pitch. It should, however, be assured that at least two teethare in contact with the work piece at all times during sawing.

Definitions, tooth form and set, pitch sizes, etc., regarding bandsaw blades are dis-cussed in ASME Standard B94.51M, “Specifications for Band and Saw Blades �MetalCutting�.”

Bandsawing MachinesBandsawing machines are built as vertical machines and horizontal machines. Thevertical type23 having a vertical band and a horizontal table on which the work piece ismoved into the band is the most versatile and typically used for cutting ofmetallographic/materialographic specimens �see Fig. 2.22�. The table often can betilted to allow for cutting under an angle to the work piece, and the maximum workheight is in the range of 300–400 mm �12–16 in�. Most machines have variable bandspeed in the range from 0.2–28 m/s �39–5500 fpm�, but most cutting takes place atspeeds in the range of 0.6–5 m/s �118–985 fpm�, the speed varying with the hardness/ductility of the work piece material and the cross section to be cut �see below�. Mostmetals are cut with speeds in the range of 0.4–2 m/s �847–394 fpm� for a cross sectionof 25 mm �1 in� reducing the speed to half or less at sections above 150 mm �6 in�. Forsoft materials like copper the speed can go up to 5 m/s �985 fpm�.

Cutting FluidsFor cutting fluids, semisynthetic or emulsion type fluids are used because a relativelyhigh mechanical lubricity is needed to prevent the chips from bonding to the toothfaces. A good cooling is also important to keep the teeth cool when they are in the cut,and the viscosity may also be important depending on the application �see Section2.3.7�.

Advice and Hints on Bandsawing• For a higher cutting rate, increase the blade velocity or use a band with a coarser

pitch. A higher feeding pressure also will give a higher cutting rate.• To increase the life of the blade, the blade velocity should be reduced or a band with

a finer pitch should be used. Be careful that the feeding rate �feeding pressure� isnot too high.

• To improve the finish of the cut, precision bands �0° rake angle� should be used�preferably with a fine pitch�. The band velocity may be increased and the feedingrate �feeding pressure� may be reduced.

• To improve accuracy of the cut, the band velocity may be increased and the feedingrate may be reduced.

• A bandsaw is a relatively dangerous machine, and all precautions should be takento avoid accidents when the work piece is guided towards the moving band, seeabove.For Trouble Shooting, see Section 13.6.2.


2.7.5 Wire CuttingWhen sectioning very sensitive materials with relatively small dimensions, wet abra-sive cutting might be too rough; therefore, other methods have been developed.

Among these, electro-erosive, chemical, and mechanical principles have beenused, but only the mechanical sectioning, based on a wire with embedded diamondgrains, has gained ground and is commercially available.

Wire cutting uses a metal wire with diamond particles pressed into the metal, inthis way anchored so that they can remove material from a work piece when the wire isdrawn against the work piece under a certain force. The wire, the length up to 10–20 m�30–60 ft�, is rolled on two drums moving in two directions, the wire being rolled fromone drum to the other. This gives a strong wire �no welding� which can be highly tight-

Fig. 2.22—General purpose contour bandsaw machines, Model 2013-V3 and Model 3613-1.Model 2013-V3 is designed for contour sawing, band filing and band polishing; it cuts metal,wood, plastics and other materials. It has a 660�660 mm �26�26 in� table that tilts 45° right,and 10° left and a 330 mm �13 in� work height. The band speed can be varied through a two-speed transmission from 17–97 or 292–1585 m/min �55–300 or 960–5200 fpm�. The bandwidth capacity is 1.5–27 mm �1/16–1 in� and the motor capacity is 2.25 hp.23


ened, securing a good precision of the cut. The force in the cut, creating the feed move-ment, is achieved using a weight. The wire is 0.2–0.5 mm �0.008–0.02 in� thick andmoves with up to 2.5 m/s �493 fpm�. The process runs without cooling because the re-moval rate is very low. A fluid is used only for cleaning the wire, keeping the diamondsfree from swarf.

Work pieces up to 50 mm �2 in� can be cut.The advantages are a very low deformation of the cut surface and a low material

loss �kerf loss�. The disadvantage is the long cutting time.


3MountingMOUNTING IS A PROCESS IN WHICH THE SPECIMEN, IN ONE WAY OR AN-other, is encapsulated to facilitate and often improve the following preparation. Themounting normally takes place after sectioning �for mounting before sectioning, seeSection 2.6� and several methods are available.

3.1 Purpose and Criteria

3.1.1 PurposeMounting is needed for a number of reasons:• The specimen is small and is difficult to handle.• The specimen has an awkward shape and mounting is necessary to secure the

preparation of the correct surface.• Edge retention and flatness of the specimen is important for a correct examination.• The specimen is brittle or has cracks or pores, and the mounting �impregnation�

will stabilize the surface. Also the specimen could be a powder material or in ashape not fit for preparation.

• A standard specimen size is required when using semiautomatic or automaticpreparation equipment.

3.1.2 Criteria for a Good MountIf mounting is done only for handling a small, awkwardly shaped specimen, and thedemands for the quality of the prepared surface are relatively low, a simple mounting,such as clamping, can be used �see Fig. 3.4�. In most cases, however, a mounting inplastic is performed �see Fig. 1.9�. This is to ensure a certain quality of the mount toavoid problems when cleaning the specimen �see Fig. 3.1�. The problem shown in Fig.3.1 is due to a gap between the specimen and the mounting material, letting fluids�etchants� or abrasives, or both, from the preparation leak onto the prepared surfaceafter drying of the specimen. In case of an etchant, the objective of the microscopemight be damaged. The gap develops because the shrinkage of the mounting materialis too high or with a clamped specimen, a gap exists between the specimen and theclamp material. This gap also spoils the edge retention of the specimen which is one ofthe common advantages at mounting.

To obtain a good mount the following criteria should be fulfilled:• No gap between specimen and mount material.• Rate of removal �wear resistance� of mounting material should correspond to that

of the specimen material.• No air bubbles in the mounting material or along the edge of the specimen.• The mounting material should be resistant to common etchants.• The mounting material should not pick up abrasive grains during the preparation.

3.1.3 Surface Flatness—Edge RetentionTo obtain a satisfactory examination in a light microscope the specimen surface has tobe relatively flat. This is due to the depth of field of the microscope, the distance along

54

the optical axis over which details of the specimen surface can be observed with ad-equate sharpness. The depth of field decreases with increasing magnification, at 100,250, and 500� the distance is 20, 3, and 1 �m, respectively. This means that if a speci-men should be examined at 250� or higher, special care should be taken to obtain aplane specimen surface. This can be obtained by mounting as described below for edgeretention, but another important factor is the use of the correct preparation process�see Sections 6.6 and 6.7�.

When examining surface layers, a very good edge retention is definitely needed,even for low magnifications. However, also in other cases, a flat specimen surface with-out edge rounding is wanted. Figure 3.2 shows a specimen with �a� a rounded edge dueto a gap between mounting material and specimen. In �b� there is contact betweenmounting material and specimen, which provides a good edge retention.

To support the edge of the specimen, the mounting material must be in contactwith the specimen, and ideally, the surface of the mounting material should be in thesame level as the specimen �no relief�. To obtain this the mounting material shouldhave the lowest possible shrinkage, good adhesion, and a removal rate �wear resis-tance� corresponding to the specimen material.

Plating the edges of the specimen, mostly with electroless nickel, is used also, butwith modern preparation methods this relatively laborious process can be avoided.

Attention: Although the edge retention to a high degree depends on a good supportof the edge, the correct preparation process is even more important, using the rightgrinding/polishing surfaces �see Chapters 6 and 7�.

Shrinkage and AdhesionAll mounting materials typically have a higher shrinkage than the specimen material.In case of hot mounting materials, using powder of polymers �see Section 3.4�, theshrinkage is due to the thermal expansion of the polymer during heating and the con-traction during cooling. This means that hot mounting resins that usually have ahigher thermal expansion than the specimen material will have a stronger contractionthan the specimen. Therefore, they will “squeeze” the specimen, making a good con-tact. This means, however, that a gap will develop in a hole or cavity in the specimen.

Fig. 3.1—Fluid leaking from a gap between mounting material and specimen onto theprepared surface.

Chapter 3 Mounting 55

To ensure a good contact, hot compression mounting materials should always becooled under pressure �see Section 3.3�.

In cold �castable� mounting resins, the shrinkage takes place during the polymer-ization of the components �see Section 3.7� and a gap will develop if the shrinkage ishigh. The shrinkage of cold mounting resins can be reduced by mixing a mineral pow-der in the resin If the polymerization process is accelerated by heating, then the shrink-age is usually increased. High adhesion between the resin and the specimen materialensures the contact, but only epoxy has a strong adhesion.

Material Removal Rate—Wear ResistanceDuring the preparation process, the specimen material and the mounting material areremoved from the surface, expressed in the material removal rate �see Sections 6.2 and7.2�. Ideally the removal rate should be equal for both materials. In most cases, how-

Fig. 3.2—Edge retention: �a� In case of a gap between mounting material and specimen, arounding of the specimen edge is developed; �b� with contact between specimen andmounting material, edge retention is obtained.


ever, the mounting material �resin�, being relatively soft, has a much higher removalrate than the specimen. This could be critical because a positive relief is developed �Fig.3.3�a��, and the edge of the specimen is not protected. In some cases, if the specimenmaterial has a higher removal rate than the resin, a negative relief develops, with thespecimen material being in a lower level than the resin �Fig. 3.3�b��.

The removal rate of the resin, as it pertains to “wear resistance,” depends to a highdegree on the hardness of the resin Tests have shown that when grinding on a P240 SiCgrinding paper, the removal �abrasion� rate of an acrylic or phenolic mounting materialis 10 to 15 times as high as for soft metals like copper and brass. At rough polishing on acloth with 4–6 �m diamond, however, the removal �polishing� rate is only 2–3 timeshigher.7 It seems that not only the hardness of the mounting material plays a role, butalso the machinability, meaning that at rough polishing the mounting material to a cer-tain degree will be removed with the same speed as the sample material.

Wear resistance can be regulated by adding hard fillers to the resin, and this type ofresin should be used if a good edge retention is wanted �see Sections 3.4 and 3.7�.

See also Sections 3.6.1 and 3.13.1 with indications of the material removal rate forthe single mounting material.

If the wear resistance of a resin is very high, as known from hot mounting epoxywith filler, it will influence the preparation process and probably a negative relief willdevelop, as mentioned above. The resin will behave like a hard material and if SiCgrinding papers are used, these will wear out the same way as by hard materials. Thisalso means that if a standard preparation time for a given specimen, mounted in nor-mal phenolic resin, is 2 to 3 min, it might be doubled if the specimen is mounted in theepoxy resin with filler.

3.2 Mounting Methods

3.2.1 ClampingBy clamping, the specimen is fixed mechanically without using a mounting material.For automatic preparation, the specimens can be clamped in a holder �see Fig. 3.4�a�and Fig. 3.5�a� for flat specimens and Fig. 3.5�b� for circular specimens�.

In Fig. 3.4�b� a clamp, normally used for hand preparation, is shown. It has two flatpieces of soft steel or stainless steel which are kept together with two screws and the

Fig. 3.3—Relief at mounting: �a� In case of a mounting material that is too soft, a positive reliefis developed, and the edge of the specimen is rounded. �b� With a mounting material that istoo hard, a negative relief is developed.


specimen �often pieces of sheet metal� placed between the two pieces that should haverounded outer edges to avoid excessive wear of the polishing cloth. If possible, theclamp material and the specimen material should be compatible.

Common for all clamping: it is difficult to avoid rounding, and often, when clamp-ing several sheets, gaps will retain abrasives or fluids, creating problems during theexamination.

3.2.2 Hot Compression MountingHot compression mounting or hot mounting indicates that the specimen is placed withan amount of resin in a cylinder in a mounting press and heated under pressure for aspecified period of time. The resin polymerizes around the specimen, and after cooling,a mount can be ejected from the press �see Section 3.3�.

3.2.3 Cold „Castable… MountingCold mounting typically takes place at room temperature but often the temperatureduring the curing will reach 30–130°C �82–265°F� �peak temperature�.

During cold mounting, the specimen is normally placed in a mold �mounting cup�and a mixture of a resin and a hardener is poured into the mold. After 5 min to 20 h theplastic will cure, and a mount can be taken from the mold �see Section 3.7�.

3.3 Hot Compression Mounting

Hot compression mounting is based on the fact that certain plastics, such as powder, inthe following called resins, can be formed to a given shape, usually cylindrical, whenheated and cooled under pressure in a metallographic/materialographic mountingpress.

Fig. 3.4—Clamping of specimens. �a� Specimen holder for clamping of flat specimens forautomatic preparation; �b� six pieces of sheet metal clamped between two flat pieces of steelfor manual preparation.


3.3.1 Advantages of Hot Compression Mounting• The quality and wear resistance �hardness� is generally superior to cold mounting.• Fast method for making one single mount.• A choice of diameters from 25 mm �1 in�–50 mm �2 in�.• The diameter of the mount is very exact.

3.3.2 Disadvantages of Hot Compression Mounting• High initial cost for mounting press.• Fragile and brittle specimens can be damaged by the pressure in the cylinder that is

from 20–30 MPa �2.900–4.350 psi�.• Heat sensitive materials can be damaged. The temperature is normally 120–200°C

�250–400°F� in the mounting cylinder.• If mounting large series of specimens, hot mounting is slow because usually only a

limited number of mounting presses will be available.

3.3.3 MSDS „Material Safety Data Sheets…Hot mounting resins are generally not hazardous, but the MSDS should always be ob-tained from the supplier and studied before use. Vapors from the heated materialmight be irritating; especially vapors from phenolics that might contain formaldehydeshould be avoided. Prolonged skin contact with phenolic and epoxy materials may irri-tate the skin and cause a skin rash �dermatitis�, and, of course, all skin contact to veryhot mounts should be avoided.

Fig. 3.5—Clamping in specimen holders without mounting: �a� specimens of a flat shape; �b�specimens of cylindrical shape.


3.4 Hot Mounting Resins

The resins for metallographic/materialographic mounting are used as powders andcan be classified into two groups: thermoplastic and thermosetting.

A thermoplastic resin is a polymeric material that can be formed on application ofheat and pressure and is solidified by cooling.

A thermosetting resin is a polymeric material that can be formed and cured by theapplication of heat and pressure but cannot be reformed on further heat and pressure.

For selection of the correct hot mounting resin for a given purpose, see Section3.6.1.

3.4.1 Thermoplastic ResinsThermoplastic materials undergo no permanent change on heating. They flow andmay be molded into a shape which they retain on cooling. The material will flow againwhen reheated and can be remolded. Thermoplastic polymers contain linear mol-ecules that are not cross linked; these are shown schematically in Fig. 3.6.

AcrylicsA number of well-known plastics are thermoplastics. For metallography/material-ography, acrylics �polymethylmethacrylate �PMMA�� are used. Acrylics are known assheets used instead of glass for many purposes. This transparency often is an advan-tage for mounting. Acrylics have to be heated to 150–180°C �300–360°F� to flow �melt�and cooled to obtain its shape. The pressure is in the range of 30 MPa �4350 psi� likemost other hot mounting resins. The pressure can be omitted or kept very low during apreheating period, and this can be of advantage when mounting porous specimenswhen the resin penetrates into the pores. Cooling under pressure should be performeddown to 40°C �104°F�, preferably room temperature, before the mount is removedfrom the press. The total time for heating and cooling is 14–24 min depending uponthe diameter of the mount.

Acrylics are resistant to water, alcohol �when properly cured�, solutions of mostsalts, diluted alkalies, hydrochloric acid, and sulfuric acid, but soluble in nitric andacetic acids, some ketones, and esters. Acrylics are notch-sensitive and cracks may de-velop if stress is too high �see Section 13.6.3�.

The shrinkage is relatively high, hardness is medium, compared to other mount-ing resins, and wear resistance is low �see Section 3.1.3�.

Acrylics with FillersAcrylics can be made electrically conductive by adding a metal powder, usually Fe orCu, and the mount loses its transparency. This is done to create a conductive mount forelectrolytic polishing. This type of conductive mounting material cannot be recom-mended for use with SEM because the metal powder �Fe or Cu� can contaminate the

Fig. 3.6—Schematic drawing of thermoplastic polymer, not cross-linked.


specimen surface leading to false results. For SEM, a resin with graphite should beused �see Section 3.4.2�.

3.4.2 Thermosetting ResinsThermosetting resins for hot mounting are capable of a high degree of cross-linkingshown schematically in Fig. 3.7. They are generally molded in a practically polymer-ized state so that they can flow by the application of heat and pressure. During themolding process further polymerization occurs, and the plastic becomes highly cross-linked and can no longer flow or be changed on further application of heat and pres-sure.

The following three types of thermosetting resins are available for hot mounting:phenolics �bakelite�, diallyl phthalate, and epoxy.

PhenolicsThe phenolic resin is made from phenol and formaldehyde and a filler. Formaldehyde,being a critical solvent, should only be present in very low amounts �below 1 %� in thefinished resin The filler is important to obtain the right properties of the mount. Gener-ally wood flour is used as a filler giving brown mounts. Added colors provide phenolicresins with a number of colors. The temperature for a correct polymerization is150–180°C �300–360°F�, and although the thermosetting resin need not be cooled forcuring, the mount should be cooled under pressure to approximately 60°C �140°F� toreduce shrinkage. The pressure in the cylinder should be approximately 30 MPa�4350 psi� and the total time for heating and cooling is in the range of 8–13 min. Phe-nolics have a number of drawbacks, but being the most inexpensive of the mountingresins, they are used for routine examinations.

Phenolics are resistant to weak acids, organic solvents, hydrocarbons, detergents,and cleaning fluids, but attacked by strong alkalis, oxidizing acids, and hot �boiling�etchants.

Phenolics have good mechanical properties. The shrinkage is relatively high, thehardness is low, and the wear resistance is low �see Section 3.1.3�.

Phenolics with Conductive FillerGraphite can be added as a filler, making the resin electrically conductive. This resin isused for mounts to be examined in an SEM.

Phenolics in Tablet FormTablets or premounts are made by pressing phenolic powder to form a “mount,” withdimensions slightly smaller than the diameter wanted. It is used for mounting of solidspecimens, which are not influenced by the pressure, when the tablet is pressed on thespecimen. The advantage is that working with a powder resin is avoided.

Fig. 3.7—Schematic drawing of thermosetting polymer with a high degree of cross-linking.


Diallyl PhthalateThe diallyl phthalate �DAP� resin is a polyester with a filler. The filler strongly influencesthe strength of the resin, and for materialographic mounting, mineral and glass fiber�short� are used with glass fiber-filled resin, the most all-round material. The tempera-ture for a correct polymerization is 150–180°C �300–360°F� and the pressure in thecylinder 25–30 MPa �3650–4350 psi�. The total time for heating and cooling is8–13 min.

Compared to phenolics, DAP has a number of advantages but it is more expensivethan phenolics.

DAP is resistant to most chemicals and the mechanical properties are excellent.The shrinkage is much lower than in phenolics, and the filler causes a relatively highhardness and a high wear resistance, securing a good edge retention �see Section 3.1.3�.

EpoxyEpoxy resin for hot mounting is made as a powder with a filler. Epoxy has a number ofproperties very suitable for mounting. The filler is a mineral like calcium carbonateground to a very fine powder which to a high degree reduces the removal rate and con-sequently improves the wear resistance of the resin �see Section 3.1.3�. The tempera-ture for a correct polymerization is 150–180°C �300–360°F�, and the pressure in thecylinder is approximately 10 MPa �1450 psi�, considerably less than for other resins.The total time for heating and cooling is 9–15 min.

The resistance to all chemicals, even to hot etchants, is very high. The mechanicalproperties are excellent and the strong adhesion to the specimen and an extremely lowshrinkage make epoxy resin the best resin for retention of edges. The strong adhesioncan cause problems with adhesion to rams and cylinder walls in the mounting cylinder.These parts need to be treated with a release agent �see Section 3.6�.

3.5 Mounting Presses

Heating, pressure, and cooling are needed when making a mount from a hot mountingresin

The temperature should be in the range of 100–200°C �210–400°F� and coolingshould take place from the maximum temperature to approximately 60°C �140°F� in areasonable time. Cooling is necessary for thermoplastics, but even thermosetting res-ins should be cooled to around 60°C �140°F� under pressure to secure the lowest pos-sible shrinkage. The force between the lower and upper ram during the process shouldbe in the range of 1–50 kN �225–11.235 lbf� making it possible to establish a pressureof 10–30 MPa �1450–4350 psi� in the mounting cylinder at diameters from 25–50 mm�1–2 in�.

3.5.1 The Heating/Cooling UnitThe heart of the press is the heating/cooling unit consisting of mounting cylinder�mold�, lower ram, upper ram, top closure, heating coil, controlled by a thermostat,and cooling coil �water cooling� �see a schematic drawing in Fig. 3.8�. The cylinder canbe typically supplied in diameters of 25 mm �1 in�, 30 mm �1.18 in�, 31.75 mm�1.25 in�, 38.1 mm �1.5 in�, 40 mm �1.57 in�, and 50 mm �1.97 in�.

The lower ram is moved up and down in the mounting cylinder by hydraulics �orby air�. Before the sample is placed in the cylinder, the lower ram is normally placed in


the top to secure the right position of the sample. After moving down the lower ram, anamount of resin is put into the cylinder. This amount should cover the sample so thatthe upper ram should not be damaged when the resin is put under pressure, and there-fore has a volume reduction. The upper ram with top closure is placed and secured, andthe lower ram is moved upwards, building up pressure. Heating is switched on for afew minutes, followed by cooling, usually water cooling as shown in Fig. 3.8, but alsoair cooling with cooling blocks is used. After about 9–24 min, depending on the resinand the diameter, the mount can be pushed out of the top after removing the upperram.

Considering that both pressure and heating should be continuously adjusted dur-ing the process, an automatization is a great advantage for the operator �see below�.

The heating/cooling unit is typically exchangeable so that one press can be used fora number of different mount diameters, or the cylinder can be exchanged in theheating/cooling unit.

If the cylinder has enough space, two mounts can be made at the same time, usingan intermediate ram �piston� separating the two mounts.

On modern units, the heating and water-cooling coils are totally integrated withthe mounting cylinder, Fig. 3.8. This secures the best heat transfer, saving energy, water,and time.

3.5.2 The Hydraulic PressHydraulic presses are the most frequently used way of obtaining the relatively highpressure needed. The first presses were car jacks operating inside a frame, the jack put-ting a pressure on the lower ram and the frame holding the cylinder and upper ram inplace. Heating was done with a jacket containing a heating element with a thermostatplaced around the cylinder and exchanged with a cooling block �air cooling� or a jacketwith water.

From this simple setup, the hand-operated presses were developed, the pressureestablished through a hand pump, and the heating/cooling unit as part of the press �see

Fig. 3.8—Schematic drawing of heating/cooling unit. The heating and cooling coils can be seenaround the mounting cylinder with upper and lower ram.


Fig. 3.9 which shows a hand-operated mounting press for mold sizes from 25–38 mm�1–1.5 in��.

Heating is switched on and off manually and the temperature is controlled by abuilt-in thermostat. Water cooling is controlled by a water tap, and the operator has tobe careful that the pressure in the mounting cylinder is maintained during the process.To avoid the requirement for an operator to be present during the whole process, auto-matic presses are available.

The simplest automatic press uses a motorized hydraulic pump which automati-cally keeps the pressure controlled by an adjustable pressostat. The operator switchesthe heating and cooling on and off.

With more advanced presses, all parameters, pressure, temperature, cooling �cool-ing rate�, and time, are microprocessor-controlled. In some cases, a number of meth-ods for different mounting materials and mount sizes can be programmed and stored.Figure 3.10 shows an electrohydraulic, automatic, programmable press with twoheating/cooling units with mold diameters from 25–50 mm �1–2 in�.

Fig. 3.9—Hand-operated mounting press for mold sizes from 25–38 mm �1–1.5 in�. Thestandard model is with air cooling, and water cooling is optional.19


3.5.3 The Air-operated PressCompressed air has been used for establishing the pressure during hot mounting. Anair-operated press could be made at a lower cost than a hydraulic press. The drawbackis the compressibility of the air which makes the ejection of the finished mount difficultto control. The air presses seem to have vanished from the market.

3.6 Advice and Hints on Hot Compression Mounting• Check that the specimen to be mounted is not too brittle, has brittle layers �spray

coatings might change the porosity under pressure�, or is not suited for compres-sion mounting or in other ways. If in doubt, use cold mounting.

• Check that the specimen material can be treated at minimum 150°C �300°F�.• Take care that the specimen is clean and dry, without grease or other residues.• Keep the mounting cylinder and rams �upper/lower� clean.• Mold release agent: Treat the upper and lower ram with a thin layer of agent. This is

especially important for resins, like epoxy, sticking to metal surfaces.• Process time depends upon the amount of resin; therefore, keep the amount low.

On the other hand, the distance from the specimen to the cylinder wall should benot less than 3 mm �0.12 in�, and the resin should effectively cover the top of thespecimen so that the upper ram will not touch the specimen.

• Save expensive resin: Only use the expensive resin in a thin layer around the speci-men and fill up with a less expensive “back-up” resin

• Pressure: At phenolics and other thermosetting resins, apply the pressure at thesame time as the heating. At acrylics and other thermoplastic resins, the pressuremay be applied after a preheating period �see below�. Never use excessive pressure.

• Phenolic mounts: Cool the mount under pressure down to approximately 60°C�140°F�. Do not take out a very hot mount and cool it directly in water; the mount-ing material might crack or a gap along the specimen will develop, or both.

• Specimens with layers requiring a superior edge retention: Use an epoxy resin• Porous specimens: Use a thermoplastic resin �acrylics�; if possible preheat the

resin or use cold mounting.• Small specimens: These can be supported during the process by using a clip �see

below�.• Electrolytic polishing: Use a conductive resin but apply a thin layer of nonconduc-

Fig. 3.10—Electrohydraulic, automatic, programmable press with two heating/cooling unitswith mold diameters from 25–50 mm �1–2 in�.20


tive resin around the specimen to avoid an electrolytic reaction in the resinFor Trouble Shooting see Sections 13.5/6.

3.6.1 Selection of Resins for Hot Compression Mounting

PurposeSpecificProperty

MountingResin

Temp.,°C �°F�Force

KN �lbf�

Heat./Cool.Time�min�

PriceRange

Glass clear mountsPorous specimens�low pressure�Nonconductivesurface forelectropolishing

ThermoplasticTransparentLow initialpressure,slow cureMediumshrinkageLow hardnessHigh removal rateat grinding,medium atpolishingLow chemicalresistanceTendency todefects

Acrylics,transparentwithoutfillers

150–180�300–360�15–50�3375–11250�

6/8 at25 mm�1 in�to 12/12at 50mm�2 in�

Medium

RoutineexaminationBack-up resinColor markingSerial mountingof uncomplicatedshapes Resin intablet form

ThermosettingFast cycleMedium shrinkageMedium hardnessHigh removal rateat grinding,medium atpolishingMediumchemicalresistance

Phenolics�Bakelite�as powderwith woodflour filler,with orwithoutcolorPhenolics�Bakelite�in tabletform

150–180�300–360�15–50�3375–11 250�

6/3 at25 mm�1 in�to 11/4at 50mm �2in�

Low

Low

Good edge retention�Thermal spraycoatings�High planenessChemical resistance

ThermosettingLow shrinkageHigh hardnessLow removal rateMedium/highchemicalresistance

Diallylphthatalatewith glassfiberor mineralfiller

150–180�300–360�15–50�3375–11 250�

5/3 at25 mm�1 in�to 9/4 at50 mm�2 in�

High


PurposeSpecificProperty

MountingResin

Temp.,°C �°F�Force

KN �lbf�

Heat./Cool.Time�min�

PriceRange

Very good edgeretention�Thermal spraycoatings,plated layers�Very high planeness

ThermosettingVery lowshrinkageGood adhesionHigh hardnessVery lowremoval rateMedium/highchemicalresistance

Epoxy withmineralfiller

150–180�300–360�5–50�1125–11 250�

6/3 at25 mm�1 in�to 11/4at50 mm�2 in�

Medium

Electroyticpolishing,to be used with anonconductiveresin as surfaceagainst electrolyteExamination inSEM

Thermoplastics orthermosettingElectricallyconductiveLow shrinkage

Acrylics orphenolicswith metalor carbonfillerPhenolicswithcarbonfiller

150–180�300–360�15–50�3375–11 250�

6/3 at25 mm�1 in�to 11/4at 50mm�2 in�

High

High

3.7 Cold „Castable… Mounting

Cold mounting, or castable mounting, is used parallel to hot compression mounting.Normally cold mounting is not “cold” �room temperature�; often temperatures willreach 30–150°C �82–265°F�.

In most cases with cold mounting, two components, either two liquids or a powderand liquid, are mixed. The components, resin and hardener, are measured either byweight or by volume with a relatively high precision. In the case of very small quanti-ties, measurement by weight is recommended. The mixing of the components shouldbe very careful to secure a total distribution of the hardener. The time after mixing untilthe curing starts, the pot life varies for the different resins, but as a rule the mixed resinshould be used immediately, securing the lowest possible viscosity of the mixture. Themixture is preferably done in disposable paper cups which can be discarded after use.

Normally the clean, grease-free specimen is placed in a mounting mold �see be-low�, and the mixture is poured carefully into the mold, avoiding entrapment of air,when the mold is filled. The low viscosity ensures that the resin flows into all irregulari-ties of the specimen and air bubbles, if any, will be able to move to the top of the mount.To improve the penetration of the resin into the specimen, vacuum impregnation canbe used �see Section 3.10�. A pressure chamber that creates a pressure with a smallcompressor, 0.2–0.28 MPa �30 to 40 psi�, will help to avoid bubbles and improve theinfiltration of the resin into the specimen.

During the curing, the temperature increases to the peak temperature, dependingon the type of resin Up to 130°C �265°F� is measured. The temperature can be kept


down if good heat conduction is established. The different resins have different peaktemperatures �see Section 3.13.1�.

3.7.1 Advantages of Cold „Castable… Mounting• Low initial cost.• Brittle and fragile specimens are not damaged.• Specimens with cracks and pores, or both, can be impregnated.• Large series can be made simultaneously, using inexpensive mounting molds.

3.7.2 Disadvantages of Cold „Castable… Mounting• Some of the resins have a relatively high shrinkage.• Some of the resins are relatively soft with a low wear resistance �high removal rate�.• The shape �diameter� is not very exact.• Risk of bubbles and cracks around the specimen.• Hazardous vapors and risk if skin is in contact with chemicals.

3.7.3 MSDS „Material Safety Data Sheets…Some cold mounting resins can be hazardous and special care should be taken duringuse. MSDS should be obtained from the supplier and studied carefully. Special precau-tions to be taken for the different resins are mentioned below.

3.8 Cold Mounting Resins

Similar to hot mounting resins, cold mounting materials can be both thermoplasticand thermosetting �see Section 3.4�.

3.8.1 AcrylicsAcrylics are thermoplastic and are supplied as a resin, a powder �polyamized methylmethacrylate �MMA�� with an initiator, and a fluid, the hardener �MMA monomer�,with a promoter.

The size of the single particles �beads� of the resin has a specific importance. Theyvary from 5–50 �m. Figure 3.11 shows the beads and the grains of a filler. With smallbeads, the flow of the mixed resin is more viscous, and better able to penetrate intomicrocracks and pores. The peak temperature is 90–110°C �194–240°F� and curingtime 5–15 min �see also Section 3.13.1�.

The acrylics �without filler� are translucent and will cure in down to 5–10 minwhich makes it the fastest curing resin If the system is expanded with a filler, the shrink-age can be reduced considerably �see below�.

Acrylics being thermoplastic have a tendency to melt during grinding, clogging upthe cut-off wheel and grinding paper if not efficiently cooled.

Acrylic cold mounting materials are not as chemical resistant as the hot mountingmaterials �see Section 3.4.1�.

The shrinkage is relatively high and this material should not be used if a very goodedge retention is wanted. The wear resistance is relatively low but both this and theshrinkage can be modified with fillers �see below�.

Attention: Fumes from methyl methacrylates are considered hazardous and skincontact should be avoided so work should be done with gloves and under a fume hood.


Acrylics with FillersWith hot mounting materials, the fillers usually are established during the manufactur-ing process, the filler being integrated into the polymer. With acrylics used for coldmounting, fillers like fine ground calcium carbonate are mixed into the powder and thegrains of the filler will be integrated in the finished mount �as shown in Fig. 3.11�. Acryl-ics with fillers are opaque.

Combinations of acrylics �MMA� with styrene �see below� have been developedhaving two liquid components and a powder component consisting mainly of filler ma-terial. This resin has a very low shrinkage and good edge retention.

Attention: Grains from the filler can be released from the surface during prepara-tion and cause scratches in the finished specimen.

3.8.2 PolyestersPolyester is a thermosetting resin that is supplied as two liquids: an unsaturated poly-ester resin and styrene acting as an accelerator with peroxide as the initiator. A polyes-ter mount is transparent.

The amount of accelerator is very small compared to the amount of resin, makingthe measurement of the two components relatively difficult, when small amountsshould be used. The peak temperature is 50–110°C �122–240°F� and curing time isfrom 45 min to 6–8 h �see also Section 3.13.1�.

The shrinkage is high, and polyester should only be used for mounting of speci-mens with no need for edge retention. The price is relatively low, however, and the resinis often used for routine mounts.

Attention: Styrene is considered a dangerous material and all work with measure-ment and mixing should take place under a fume hood using gloves. Polyester has alimited shelf life �6 to 12 months�; therefore, the container should be marked with thedate of receipt to secure that the oldest material is used first.

3.8.3 EpoxiesEpoxy is a thermosetting resin supplied as two liquids, a “resin” and a hardener. Epoxyis the cold mounting resin with the lowest shrinkage and the best grinding and polish-

Fig. 3.11—Acrylic-mounting material with filler. The small gray particles between the beads ofthe polymer are the filler.


ing properties. Epoxy adheres strongly to the specimen, and if the curing time is rea-sonably long, more than 6–8 h, the shrinkage is extremely low. If curing time is short-ened, either by adding accelerator to the hardener �30–45 min� or by introduction ofheat �2–4 h�, the shrinkage will be higher. By introduction of heat, the negative effectcan be reduced by letting the epoxy cure in 1 h after mixing at room temperature andthen complete the curing at 60–70°C �140–158°F�.

Epoxies are supplied with a very low viscosity and a high boiling point, securing anefficient impregnation of porous specimens �see below�.

Epoxies are transparent and cure through an exothermic reaction. The peak tem-perature varies with the curing time. Curing for periods from 6 to 20 h gives a peaktemperature 40–60°C �104–140°F�, while curing for 45 min results in peak tempera-tures from 85–100°C �185–220°F�. The peak temperature can be kept low by placingthe mold in a fridge. To avoid very high temperatures at mounts larger than the normalsize, cooling with air using a fan is recommended. Epoxies for cold mounting are nor-mally not supplied with fillers for metallographic/materialographic purposes, but fill-ers can be mixed in by the user �see Section 3.11.2�.

The two parts, resin and hardener, should be measured in a precise manner be-cause even a small variation can cause problems after curing �see Section 3.13�.

The good adhesion properties of epoxy can result in problems with removal of thefinished mount from the mounting mold. The mold should be made of a plastic mate-rial with low adhesion and certain flexibility, like POM �see Section 3.9�.

Epoxies are not attacked by weak acids, weak alcohols, and organic solvents.Strong acids and strong alcohols give a slight attack. Resistance to heat: 90–250°C�200–500°F�.

Epoxy has good mechanical properties and it is the strongest, most durable of thecold mounting resins. The shrinkage, as mentioned previously, is very low if the curingprocess is not shortened down. The hardness is relatively high and the wear resistanceis relatively high �see Section 3.1.3�.

Attention: Epoxies can cause allergies and all work should be done with correctgloves under a fume hood.

3.9 Accessories for Cold „Castable… Mounting

In most cases it is important to have a relatively exact shape of the finished mount andtherefore a mounting mold �cup� is normally used. Clips are other accessories that sup-port the specimen during the curing.

3.9.1 Mounting MoldsIn most cases these are cylindrical molds, made of a flexible plastic like POM or of sili-cone rubber �see Fig. 3.12�. The specimen is placed on the bottom of the mold and theliquid mounting resin is poured into the mold. Some molds have a removable bottomto allow the mount to be pushed out after curing. Molds made of silicone rubber arenormally in one piece, the high flexibility of the silicone rubber allowing the mount tobe removed from the mold. To secure the removal of the mount, the mold can besmeared with a silicone compound before the resin �epoxy� is introduced. Reusablemolds of a square or rectangular shape are also available.

Disposable ring forms often made of phenolics remain as an integrated part of themount after curing. The ring is placed on an adhesive film so that the resin will not leak


during the curing. The specimen is placed inside the ring and, after curing, the ringwith resin and specimen is taken for preparation.

Another type of disposable mounting mold is an aluminum cup used for packagingof foods, etc. This is especially useful for large specimens of odd shapes.

3.9.2 ClipsIf specimens are small and flat, it helps to support the specimen during the curing. Plas-tic and metal clips that squeeze the specimen are available, being an integrated part ofthe mount �see Fig. 3.12�. The clips can be used for both hot and cold mounting.

3.10 Vacuum Impregnation

Specimens like sintered materials and ceramics having pores, cracks, etc., are difficultto prepare without an impregnation �infiltration� of the surface. If not impregnated thepores will increase in size and cause pullouts, resulting in a microstructure that is notshowing the correct conditions of the material. Also, electronic parts or other parts of acomplicated structure that should be kept in place during the preparation may be en-capsulated using vacuum impregnation.

Impregnation in depth can only take place in a material with open pores. In thecase of closed pores, only the pores on the surface will be infiltrated. Normally the im-pregnation takes place after cutting, but to certain, very brittle materials, impregnationshould be done before cutting. In the case of closed or very narrow pores, the impreg-nation should take place both after cutting and after plain grinding or even fine grind-ing.

Impregnation is done in vacuum �80–120 mbar� using an epoxy resin with a lowviscosity and a boiling point high enough to avoid boiling in the vacuum chamber.

The impregnation takes place in a vacuum chamber which can be a normal labora-

Fig. 3.12—Mounting molds consisting of two parts, a bottom and a cylinder. The specimens aresupported by clips.


tory bell jar or an apparatus made for the purpose �see Fig. 3.13�. The specimen, care-fully cleaned and degreased, is placed in a mold in the vacuum chamber and a vacuumis established for an appropriate time from a couple of minutes for not very porousspecimens up to half an hour for very porous specimens. The impregnation is done bysucking the mixed epoxy into the mold through a tube until the specimen is covered.�For best results, only a small amount of resin is taken into the mold, just covering thearea of interest and then slowly returning the chamber to atmospheric pressure. Theback pressure will further the penetration of the resin into the specimen. Repeat theevacuation of the chamber and let in epoxy to completely cover the specimen.� Now themold can be removed for curing, or curing can take place in the vacuum chamber with-out vacuum.

A simpler method, which can be used for materials with less pores, is to place thespecimen in a mold with epoxy and immediately after pouring in the epoxy, the mold isplaced in the vacuum chamber and vacuum is established. To obtain the best result, thefirst method should be preferred.

Cold mounting can also be done under a low pressure �see Section 3.7�.

3.10.1 DyesDyes can be used in connection with vacuum impregnation of porous materials, thedye being mixed into a low viscous cold mounting epoxy resin By using a dye it is pos-sible to contrast the voids into which the resin has penetrated against the surroundingstructure. The contrast is created through fluorescence. Figure 3.14�a� shows a micro-structure in bright field where the pores cannot be identified. In Fig. 3.14�b�, the samestructure in fluorescent light is shown and the pores filled with epoxy can be clearlyidentified. To obtain the fluorescence, a so-called short-pass filter in the microscope isneeded to excite the areas with dye, and a long pass filter is needed to see the fluorescentlight �see Section 15.7.5�. Dyes are commercially available.

3.11 Special Mounting Techniques

For some materials special mounting techniques are necessary, i.e., examination ofvery thin layers, powders, wires, etc.

Fig. 3.13—Apparatus for impregnation; the mounting molds are placed in a vacuum chamberand the epoxy is sucked into the chamber through a tube.


3.11.1 Taper SectioningThis technique allows the examination of very thin layers and was highly developed byL. E. Samuels in his work with surface deformation at metallographic/material-ographic preparation �see Section 6.3�.7

TABLE 3.1—Taper Sectioning: Enlargement Factor, f, with the Corresponding Taper Angle, �.

f � f �

100:1 0° 30� 10:1 5°40�50:1 1° 20� 5:1 11°30�25:1 2° 20� 3:1 19°30�20:1 2° 50� 2:1 30°

15:1 3° 50� 1.5:1 41°50�1:1 90°

Fig. 3.14—Use of impregnation with epoxy and dye. �a� Microstructure in bright field; �b� andthe same structure in fluorescent light revealing the pores filled with epoxy.


The specimen is placed under an angle to the plane of examination, in this wayenlarging the width of the layer, when examined in an optical microscope �see Fig.3.15�.

If measured as a normal cross section in an optical microscope, the lower limit of alayer thickness is approximately 2 �m because below this the measurement uncer-tainty is too big, the limit of the optical microscope being 0.5 �m. Very thin layers canbe examined or measured using taper sectioning because, depending on the taperangle, an enlargement of 1.5� to 100� can be obtained. Table 3.1 shows the enlarge-ment factor, f, and the corresponding taper angle, �.

If only the layer or the diffusion zone, or both, should be analyzed without mea-surement of layer thickness, a suitable angle can be established with a spacer, the anglenot being exact.

In case of measurement of the layer thickness, the taper angle should be knownand exact, or the dimension of the specimen should be known. The angle can be estab-lished with a wedge. If the angle is known, the layer thickness A=B sin �, as shown inFig. 3.15.

If the dimensions X and Y are known, A=X B/Y, as shown in Fig. 3.16.

3.11.2 Edge ProtectionWhen examining layers, it is absolutely necessary to have a good edge retention. Theedge retention depends very much on the type of preparation performed; it can to avery high degree be obtained by using the modern grinding and polishing methods andautomatic polishing �see Section 6.7�.

In some cases, especially if preparation has to take place with SiC grinding paper,some precautions can be taken to preserve the edge.

Section 3.1.3 describes the use of the correct mounting resin to protect the edgeand often this will be sufficient.

Fig. 3.15—Taper section with taper angle, �. The thin layer with thickness A can be analyzedand measured, B.

Fig. 3.16—Taper section with known dimensions X and Y.


If further edge protection is needed there a number of methods available.

PlatingDuring plating a thin layer of metal is deposited on the surface to be analyzed. The ideais that the edge rounding takes place on the plated layer, leaving the original layerplane.

Plating can be done electrolytically, placing the specimen as cathode in a bath con-taining a Cu, Ni, or Fe salt. Electrolytic plating is laborious and the result is not oftensatisfactory for metallographic/materialographic examination.

Electroless plating gives better results and is easier to perform. Electroless nickelis the most commonly used metal for metallographic/materialographic specimens.Most metals can be plated. Only bismuth, cadmium, tin, lead, and zinc cannot beplated.9

Other materials such as plastics, wood, glass, carbide, silicon, and porcelain canbe plated.

An example of a formula for electroless nickel:45 g nickel chloride11 g sodium hypophosphite100 g sodium citrate50 g ammonia chloride1000 mL distilled waterpH 8.5–9Use the mixture at 90–100°C �194–212°F�. The plating rate will be in the range of

0.015 mm/h.Instead of mixing the solutions yourself, different solutions for electroless plating

are commercially available.

FillersMany mounting resins are supplied with integrated fillers, in this way improving theedge protection �see Sections 3.4 and 3.8�. Fillers can be mounted together with thespecimen, placed in the surface of the mount close to the edge to be protected, andpreferably adjusted to correspond to the hardness of the specimen.

The preferred filler is alumina used together with epoxy cold mounting resin toavoid shrinkage and increase hardness. The alumina should be made preferably as hol-low nodules to secure the stability of the alumina grain in the resin If grains fall outduring the final steps of the preparation this might create scratches in the specimensurface.

Fillers are commercially available.

Back-up MaterialsA relatively simple way of securing the edge is to mount a piece of material similar tothe specimen material close to the edge of the specimen.

A metal foil can be wrapped around a cylindrical specimen, which, in the case ofhot mounting, is pressed close to the specimen because of the high pressure in themounting cylinder.

3.11.3 Mounting of Very Small Parts, Foils, and WiresVery small parts and foils can be difficult to place correctly for mounting. A solutionwould be to mount several at a time placed in a piece of tube.


It can be advantageous to use a fast curing glue �cyano acrylate� to fix the parts tothe bottom of a mounting mold before the resin is poured into the mold. Clips for stabi-lizing the parts are commercially available �see Section 3.9�.

Wires can be examined as cross sections or longitudinal sections. Longitudinalsections can be done, as mentioned above, but cross sections, especially at thin wires,can be difficult. If hot mounting is possible, Nelson24 recommends drilling holes in amount made of thermoplastic resin without a specimen. The wires are put into theholes, the holes are filled with resin and some resin is placed over the top of the mountto avoid damage of the upper ram. Then the mount is reprocessed. Transparent mountsare to be preferred when working with small parts and wires, making it possible to ob-serve the position of the specimen.

3.11.4 Mounting of PowdersThe most common method for mounting of powder is mixing the powder with epoxyresin The problem can be the settling of the particles because they either settle aroundthe periphery of the mounting cup or, if the powder has a lower gravity, the setting isnot efficient, the powder being suspended in the liquid epoxy.

Metal powder will settle, but often irregularly, and Glancy25 suggests a method offilling a small plastic vial or plastic tube with powder. The vial is placed in a vacuumimpregnation apparatus �see Section 3.10� under vacuum and epoxy is added, the sameas at a normal impregnation. Once the epoxy has cured, the plastic vial is cut length-wise using a razor knife. Now the slug is mounted by hot or cold mounting. Care shouldbe taken at cold mounting that the slug does not float.

For powder with particles sizes under 2 �m, Petzow2 suggests the following: Thepowder is placed in a test tube in a low vacuum �like at impregnation, see Section 3.10�.It is then impregnated with a mixture of methacrylic acid methyl ester and 1 % �wt %�of benzole peroxide. This mixture cures in 12 h at 50°C �122°F� with the test tubeclosed. The test tube is then broken and the content is mounted as usual.

3.11.5 Mounting of PCB CouponsA test coupon, normally around 10 by 20 mm �0.4 by 0.75 in� with two reference holesof 2 mm �0.079 in� is needed if a PCB board should be inspected metallographically/materialographically with an automatic system. In some cases the coupon is producedtogether with the board and it can be removed from the board and taken directly formounting.

Very often, the coupon has to be made from the finished board, in this way destroy-ing the board. For hand preparation, the reference holes are not needed.

Test CouponAccording to the American standard IPC-TM-650, the plated-through holes �inspectionholes� of a PCB board should be inspected metallographically. For this purpose a testcoupon is produced and prepared so that the exact center of the plated holes can beinspected in a microscope. To obtain the exact position of the coupon during automaticpreparation, two positioning �reference� holes must be made in an exact distance fromthe inspection holes �see Fig. 3.17�.

Often the coupon is produced through punching the board, risking deformationsin the areas of the coupon later to be examined. If a router is used, this deformation isavoided and the two reference holes are made in the same operation.


Mounting for Automatic PreparationA preparation system, made according to IPC-TM-650, Method 2.1.1.2, is typicallyused. As mentioned earlier, this means that two reference holes are drilled in the cou-pon. Two or more coupons are placed on two precision pins so that the pins are in agiven distance from the holes to be measured. Now the coupons with pins aremounted, allowing the ends of the pins to be used as contact surface in a special speci-men holder. Generally acrylics are used for mounting of PCB coupons but polyesterand epoxy can be used also. It is important that the mounting resin is able to flow intothe holes to be measured. When using acrylics, the coupon can be dipped in the mono-mere component ensuring a good penetration into the very small inspection holes, of-ten down to 50 �m �for preparation, see Section 7.10�.

3.11.6 Conductive MountsConductive mounts can be necessary for electropolishing and for observation in anSEM. The simplest way of mounting is using a conductive resin, either thermoplasticor thermosetting �see Section 3.13.1�.

The conductive resin should only be used to establish conductivity to the top of themount. Around the specimen surface contacting the electrolyte, a nonconductive resinshould be used.

If the specimen should be cold mounted, the simplest way is letting the specimenprotrude at the top of the mount. This is only possible if the specimen has a certainheight.

Another effective way is to drill a hole in the cold mount and insert a piece of metalor a screw to make contact to the specimen. Also, a wire can be soldered to the speci-men before mounting and the wire taken outside the top of the mount.

3.12 Recovery of Mounted Specimen

In some cases, the specimen cannot be etched or examined, or both, when mounted ina mounting resin The resin can be removed mechanically, chemically, or by heating. It

Fig. 3.17—PCB test coupon. It can be seen that the distance from the upper edge of theprecision pins, placed in the positioning holes, to the center of the plated �inspection� holes is5 mm.


is important that the prepared surface is not damaged. First, as much resin as possibleis removed mechanically by sawing, grinding, and breaking the resin away from thespecimen. When only a small amount of resin is left on the surface of the specimen,possibly impregnated in the surface, this can be removed chemically or by heating.M-Pyrol �N-Methyl-2-Pyrrolidone� is a resin solvent, classified as a combustible liquid,which is less hazardous than other solvents used for removal of resin The strippeddown specimen is placed in M-Pyrol at room temperature for 24 h and in most casesthe remaining resin is dissolved or can be removed.

An alternative is boiling N,N-Dimethyl-formamide �approximately 150°C�300°F�� or in a laboratory furnace at 500–600°C �900–1100°F�. Epoxy can be dis-solved by submerging the mount in methylene chloride. Methylene chloride is a strong,hazardous solvent and is carcinogenic. The mount can also be dipped in boiling glycer-ine for 1 or 2 h, which will soften the epoxy so that the specimen can be removed.

All work should be done under a fume hood and with suitable protection. The rele-vant MSDSs should be studied carefully before commencing the work.

3.13 Advice and Hints on Cold Mounting

Check that the specimen material is not being influenced by the mounting material, ifthe material is at all sensitive to heat, use epoxy curing in 6–20 h.• Ensure that the specimen is clean and dry without grease.• If using a mounting mold, take care that the material of the mold is suited for the

mounting material. Relatively flexible molds should be used when using epoxy.• Be careful when mixing that the exact amount of each component �by volume or by

weight� is measured out. Stir for the time stated in the directions for use. It is veryimportant that the components are totally mixed.

• Specimens with layers requiring a perfect edge retention: Use an epoxy resin• In case of epoxy mounts larger than 50 mm �2 in�, the heat developed can acceler-

ate the process causing shrinking. To avoid this the amount of hardener can be re-duced or the mount can be cooled in a refrigerator for the first period of time, orboth.

• If using a filler mixed into the mounting material, this mixture need only be in athin layer around the specimen. When this layer is partly cured, fill up with normalresin

• Always use special gloves when handling epoxy.• Always use a fume hood for all cold mounting resins.• Cold mounting materials, especially polyester have a limited shelf life; take care to

mark the containers upon receipt to ensure that the oldest material is used first.For long-term storage, use a refrigerator.For Trouble Shooting see Sections 13.5/6.


3.13.1 Selection of Cold Mounting Materials

PurposeSpecificProperties

MountingMaterial

Approxi-mateCuringTime at 20°C �68°F�

PeakTemp.°C�°F�

PriceRange

Serial mountingRoutingexaminationFast curingTranslucent�Printed circuitboards�

ThermoplasticTranslucentMediumshrinkageLow hardnessHigh removal rateMedium chemicalresistance

Acrylics, resin�powder�with onehardenerWithout filler

6–15 min 90–110�194–220�

Medium

Good edgeretentionSerial mountingFast curing

ThermoplasticLow shrinkageHigh/mediumhardnessLow removal rateMedium chemicalresistance

Acrylics, resin�powder� withone hardenerand withmineral filler

8–15 min 90�194�

Medium/high

RoutineexaminationSerial mounting

ThermosettingTransparentHigh shrinkageMedium hardnessHigh removal rateLow chemicalresistance

Polyester, resinand hardener,both liquids

45 min to6– 8 h

50–110�122–240�

Low

Very good edgeretentionTransparentmountsPorousspecimensImpregnation�Plated layers,thermalspray coatings�Mineralogy

ThermosettingTransparentLow shrinkageMediumhardnessMedium removalrateLow viscosity

Epoxy, resinand hardener,both liquids

6–20 h 30–60�86–140�

Medium

Serial mountingRoutineexaminationTransparentmounts

ThermosettingTransparentMedium shrinkageLow hardnessMedium removalrate

Epoxy, resinandhardener, bothliquids

30–45 min 85–100�185–220�

High


4Marking—Storage—Preservation

4.1 Marking

MARKING OF METALLOGRAPHIC/MATERIALOGRAPHIC SPECIMENS ISvery important because a proper identification of the specimen is the only thing thatensures that the result of the analysis is correctly used. This is true for both qualitycontrol and research, and it can be said that the specimen must be marked in all caseswhere a metallographic/materialographic analysis should be reported.

The marking should not in any way influence the microstructure of the surface tobe examined; therefore, this risk should be considered before marking is done. Itshould also be considered that the marking is placed where it is not disturbed or re-moved during the preparation process.

The backside of the specimen/mount is usually used for marking. Considering thelimited space, a code expressing job number, material treatment, etc., is used most of-ten.

If the final marking is done on the mount, special care should be taken that thespecimen is identified at the stage after sectioning, before mounting, so that correctmarking of the mount is assured.

A number of methods for marking are available.

4.1.1 Marking with Waterproof InkThis cannot be recommended because the treatment of the specimen/mount will inmost cases remove the ink. Marking ink or pencil can be used as an intermediate.

4.1.2 Identification TagThis works well if the tag �carton or metal� is placed on the backside of the specimenand mounted in a reasonably transparent resin, the resin protecting the tag. A tagplaced on the outside of the specimen/mount, however, might be removed duringcleaning in water and alcohol.

4.1.3 EngravingOne of the most widely used methods of marking is vibration engraving. A very hardvibrating needle induces a visible deformation of the surface of the mount/specimen.This method will stress the material layer below the surface and it should not be usedfor thin specimens like foils.

Electro engraving gives less damage to the surface, but can only be used on electri-cally conducting materials. The engraving, on a clean and smooth surface, is donethrough the melting/evaporation of metal, caused by a high temperature spark.

Hand engraving, using a hard needle, is also possible in most, not too hard,materials.

4.1.4 StampingStamping a number or code in the specimen is possible but because of the very strongdeformation below the stamped surface this method should only be used in caseswhere it will not disturb the material to be examined.

80

4.2 Storage

It is important that the prepared surface of a specimen is not disturbed by attack fromthe atmosphere. Therefore, the prepared specimen is placed very often in a dessicatorwith moisture-absorbing material. Airtight cabinets are also commercially available.For long-term storage, often the specimen should be stored for several years, a directpreservation of the surface is recommended �see below�.

4.3 Preservation

To absolutely protect the prepared surface a lacquer usually from a spray can is used.The microstructure can be examined through the lacquer, or the lacquer can be re-moved easily with acetone and the specimen resprayed after examination.

Chapter 4 Marking—Storage 81

5Cleaning and CleanlinessTO AVOID ARTIFACTS IT IS VERY IMPORTANT, ESPECIALLY IN THE POLISH-ing stage, that the specimen/specimen holder is carefully cleaned between each step. Itis also important that the room in which the process takes place and the operator’shands are clean to avoid contamination of the polishing cloths.

Cross contamination: Considering that the preparation process often includesabrasives with grain sizes spanning from grit 180 �82 �m� grinding paper to 1 �m dia-mond suspension, it is evident that cross contamination, larger grains from an earlierstep, cannot be tolerated. Cross contamination can be caused by an inadequate clean-ing of the specimen, specimen holder, or by the operator’s hands.

The polishing disk may become contaminated from airborne particles or excessivedebris in the machine.

5.1 Cleaning

5.1.1 Cleaning Before Start of PreparationAll greases, oils, and other residues on the specimen should be removed by water with adetergent or a suitable organic solvent. Failure to clean thoroughly can prevent cold�castable� and hot compression mounting resins from adhering to the specimen sur-face. Also oxidation, etc., should be removed �unless these products are to be exam-ined�. As some of the more rough cleaning methods, like shot blasting and wire brush-ing might damage the surface, it should be considered whether this might influence thefinal result of the preparation. In special cases, where normal procedures are unsuc-cessful, electrolytic or chemical cleaning can be used �see ASTM Standard Practice forPreparation of Metallographic Specimens �E 3�, Section 12.4�.

5.1.2 Cleaning During and After PreparationIn principle, the specimen and the specimen holder �fixed specimens� should becleaned between every step in the grinding and polishing process, but at wet grindingon SiC paper, using a constant flow of water, a careful cleaning can be limited to afterthe last grinding step. When grinding on other media, like rigid composite disks and atpolishing, a cleaning between each step is absolutely necessary.

There are, however, some materials or some constituents in materials that will bepreferentially attacked by water �zinc coatings on steel, lead inclusions in machiningsteels, etc.�, therefore, water must be avoided completely in the latter preparationsteps.

Cleaning by HandFor cleaning of most metals and other materials without pores, cracks, etc., manualcleaning is the most effective method.

The specimen or specimen holder is held under running lukewarm water andrinsed with a soft brush or cotton ball dipped in water with a detergent. In cases of softmaterials and after the last polishing step, a cotton ball is used to clean the prepared

82

surface. The cleaning is finished with the spraying of ethylene alcohol from a spraybottle on the prepared surface and possibly wiping the surface before it is taken fordrying. Ethanol containing a denaturation additive can be used as long as the additivedoes not leave a film on the specimen. In case of specimens with pores, cracks, etc., andmounts with a gap between mounting material and specimen, ultrasonic cleaning isrecommended, except for fragile materials.

In case the standard cleaning methods are inadequate, the cleaning solutionsstated in ASTM Standard Practice for Preparation of Metallographic Specimens �E 3�,TABLE X1.1, can be used.

EthanolAlthough ethanol �ethyl alcohol� is taken by many persons in different forms, the etha-nol used in a laboratory has the following Hazards Identification, Human Health: “Or-ganic solvents may be absorbed into the body by inhalation and ingestion and causepermanent damage to the nervous system, including the brain. The liquid may irritatethe skin, the eyes and the respiratory tract.”

Ultrasonic CleaningUltrasonic cleaning is efficient and relatively fast, removing dirt from pores, gaps,cracks, etc.

The specimen or specimen holder is placed in a tank with a liquid, water with adetergent, alcohol, or an organic solvent like acetone. In cases of dirt difficult to re-move, weak acids and basic solutions can be used.

A transducer vibrates under the bottom of the tank, with 20–40 kHz creating gasbubbles �cavitation� in the liquid. These bubbles implode and a rubbing effect occurswhich removes the dirt. The dirt contaminates the liquid and therefore a specimenmust be rinsed, as mentioned above, before drying. Ultrasound penetrates glass so it ispossible to place one or more beakers in the tank with water with a detergent aroundthe beakers. When the specimens are only placed in the beakers, in a suitable liquid,this liquid can easily be exchanged when contaminated. Cleaning usually takes0.5–1 min. Some soft, very porous and brittle materials should not be cleaned ultra-sonically or only for 10–30 s. Using specimen holders, the whole holder can be placedin the tank.

Ultrasonic ApparatusUltrasonic apparatuses are supplied with tanks of different size from 1.5–10 L�0.4–2.6 gal �U.S.�� and with capacities from 80 W to 470 W. The ultrasound is pro-duced mostly from a piezoelectric transducer but magnetostrictive transducers canalso be used with large units. The frequency is 20–50 kHz.

DryingDrying should take place in a stream of mild air. It is important that the layer of alcoholis not dried on the prepared surface but is blown away and evaporates from the sides ofthe specimen/mount. Air can be supplied from a fixed hair dryer type apparatus allow-ing both hands to be free to clean the specimen with soft cotton wool and alcohol. Com-pressed air can be used as well, in which case a clean, dry, oil free air must be secured. Ahair dryer is recommended for the finished specimen to avoid possible oil drops fromthe compressed air.

Chapter 5 Cleaning and Cleanliness 83

Cleaning of Grinding Disks and Polishing ClothsGrinding disks based on diamond usually are used with water as a lubricant and clean-ing shouldn’t be necessary. Rigid composite disks �RCD�, lubricated by a special lubri-cant, will be covered with swarf after use. This typically will not disturb the function,but if the swarf has dried and therefore filled up the openings between the segments ofthe disk, the disk should be cleaned. This is done with a brush, detergent, and luke-warm water. A cloth that has been contaminated can be cleaned in the same way butdifferent brushes should be used for the grinding disks and the cloths because of thedifferent grain sizes.

5.2 Cleanliness

It has already been mentioned above that a high level of cleanliness is needed whenpreparing metallographic/materialographic specimens. The operator should be awarethat no contamination takes place through transfer of debris from the hands of the op-erator. The room in which polishing takes place should be clean and should not containdust in the air. The room for preparation, when possible, should not be part of a pro-duction environment.

It is advisable that cutting does not take place in the same room as grinding andpolishing, as the cutting produces large amounts of debris.

The grinding/polishing machines should be kept clean according to a weeklyschedule, securing that no contamination can take place from the sides of the machine,splash ring, etc. This also prolongs the lifetime of the equipment.


6Mechanical SurfacePreparation—Grinding

6.1 Grinding—A Basic Process

AFTER SECTIONING AND POSSIBLY MOUNTING, THE METALLOGRAPHIC/materialographic specimen is now to be prepared to obtain the true microstructure ora structure, which, in spite of certain defects �artifacts�, will give a true examinationresult. For a thorough description of artifacts and how to avoid them, see Sections13.5/6.

The true structure has been defined in Section 1.2, indicating a surface with no orfew artifacts. In practice only two ways are open to obtain this, either mechanicalpreparation, grinding and polishing, or grinding, followed by electrolytic polishing�see Fig. 1.7 to get an overview�. In some cases a chemical attack can be included in themechanical polishing, creating chemical mechanical polishing, and, more seldom,chemical polishing is used �see Sections 7.12 and 8.7�, but in all cases one or severalgrinding steps are performed before the polishing takes place.

In this book, grinding is defined as an abrasive machining process with a fixedabrasive. The abrasive grain might be fixed from the start of the process, either by abond �ceramic, metal, resinoid� or placed on a flexible backing covered by a coating,like at SiC grinding paper, or covered by a thin layer of metal on a backing of metalplate. Also the abrasive grain, normally suspended in a liquid, can be added to the abra-sive machining process taking place on a plane, prepared disk. In this case some of thegrains will be forced into the disk surface, be fixed in the moment of cutting, and grind-ing takes place. In case the abrasive grain is not fixed but staying loose and rolling be-tween the work piece and the disk surface a lapping process takes place. Consequentlyin this book, a disk to be used with loose abrasive grains is called a “grinding disk,” ifthe majority of the grains are fixed when the material removal takes place, producing a“ground surface,” and a disk where the majority of the grains are loose, producing a“lapped surface,” is called a “lapping disk” �see also Section 6.7.7�.

6.1.1 Plane Grinding „PG…Plane grinding, also called planar grinding, may be necessary for three reasons:�1� To plane the surface after sectioning, depending on the sectioning method, the sec-

tioned surface might not be plane.�2� To remove the deformation caused by the sectioning and establish a known “start

surface” of the specimen to secure a reproducible further preparation.�3� When a number of specimens are fixed in a specimen holder, the specimen sur-

faces are not in the same plane, and material has to be removed to obtain this.Plane grinding is usually performed with relatively coarse abrasive grains and will

be described further under the different grinding methods mentioned below �see alsoFig. 13.14�.

85

6.1.2 Fine GrindingFine grinding is the process used for establishing a specimen surface suited for the firstpolishing step. This means that the relatively rough surface from sectioning or planegrinding, through one or several steps with finer and finer grain sizes, is changed into asurface that can be treated by polishing. The fine grinding step�s� are needed becausethe material removal is relatively high, opposite to the polishing steps with a low mate-rial removal �see below�.

Fine grinding is further described under the different grinding methods men-tioned below �see also Fig. 13.15�.

Grinding plays a major role in the preparation process and, therefore, it will bediscussed in depth in the following. The mechanics of the grinding process, being a“cutting” process producing chips are the same as in wet abrasive cutting �see Chapter2�, and they are basically the same in mechanical polishing.

In mechanical grinding/polishing, the following two features should beconsidered.

Material RemovalMaterial is removed from the specimen surface during the process. The amount of ma-terial removed can be expressed by the removal rate, often measured as �m per minuteor �m per a certain travel in m �metres� of the specimen on the preparation surface.

The preparation process is controlled mostly by time, assuming that a certainamount of material is removed from the specimen per time unit. This assumption isoften not correct because a number of parameters that are not totally controlled, suchas preparation surface, abrasive, and lubrication, influence the removal rate. By thedevice, “stock removal,” sometimes used on grinding machines, the process is not con-trolled by time but through a constant measurement of the actual removed amount ofmaterial. In this way the process can be stopped when the amount of material plannedfor is removed �see Section 7.7.6�.

DeformationDeformation can be defined as the nature and depth of the plastically deformed layerthat is produced in the specimen surface during material removal.

In general, the removal rate should be as high as possible and the deformation aslow as possible. This depends on the interaction between the abrasive grain and thespecimen surface as described in the following.

6.2 Material Removal

Grinding is defined as a process with fixed abrasive grains, acting like machine tools.Figure 6.1 shows a schematic drawing of a tool removing a chip from a work piece. Theabrasive grains will remove chips from the specimen surface in the same way.

Using a normal machine tool like a lathe for the cutting process, macroscopicchips in the form of ribbons or particles having a thickness of from about0.025 to 2.5 mm �0.001–0.1 in� are produced. In grinding, the chips produced aremuch smaller, ranging in thickness from 0.0025 to 0.25 mm �0.0001–0.01 in�. Thereason for this is the shape and size of the abrasive grains, acting very differently as“tools.”

During the cutting process the tool and work piece are forced against each other


and a compressive force is set up which causes the metal to deform in front of the toolpoint.

The deformation will take place in a zone along the shear plane �see Fig. 6.1� andthe metal is forced to slide over the tool surface. In doing this, the stress will cause thematerial to separate as a chip, if the rake angle is correct �see below�. The cutting pro-cess is very complex, influenced by cutting speed, tool geometry, and feed rate.

A mathematical model has been developed for abrasive machining of a work piecemoving in a linear path across a planar abrasive device like grinding paper under aconstant normal load �L�.7 In this model the material removal rate can be expressed as:

m = f�DL/�Hm� �1�

wherem is themassofmaterial removed, f is the fractionof the contactingpoints that cut achip, � is the density of thework piecematerial, D is the distance traveled, L is the load,H isthe indentation value of the surface layers of the work piece material and m is a formfactor expressing the shape of the contacting points. The most interesting aspect from ametallographic/materialographic viewpoint is that thematerial removal increaseswith in-creasing load and decreases with increasing hardness of the work piecematerial. This lat-ter assumption, however, only covers hardmetals where the removal rate can be expectedto be relatively small, but the relative removal rates for metals of low and intermediatehardnesses are virtuallyunpredictable.7

6.2.1 Rake AngleThe rake angle � is the angle between the top face of the tool and a plane perpendicularto the work piece, as schematically shown in Fig. 6.2.

Rake angles may be classed as positive, negative, or neutral �tool face perpendicu-lar to the work piece�, as shown in Fig. 6.3.

To create a chip, the rake angle has to be positive, neutral, or to a certain degreenegative. With a positive rake angle, the area under shear decreases, leaving less defor-mation in the surface of the work piece, and the friction �heating� is lower than with aneutral or negative angle.

At a certain negative angle, the critical rake angle, the chip is not produced any-more and a “plowing” takes place as shown in Fig. 6.3.7

When plowing, the rake angle is so negative that only a groove is made in the workpiece surface. A standing wave bulge forms in front of the tool, and material is dis-

Fig. 6.1—Basic model of cutting process indicating shear zone.

Chapter 6 Mechanical Surface 87

placed into a ridge on each side of the groove. The material removal approaches zeroand the deformation of the surface increases.

6.2.2 Grain Shape—Contacting PointsIn cutting, using a machine tool like a lathe, the shape of the cutting tool is given with afixed geometry. In grinding, using the abrasive grains as cutting tools, the shape of thegrain and the number of edges and points vary extremely. Figure 6.13 shows the grainsof a grit 220 SiC grinding paper. The most effective shape of the grain is a V-form creat-ing an efficient chip provided that the rake angle is correct. If the grain is flat, the crosssection of the chip is reduced and in the case of flat grains of a certain size the specificpressure between grain and surface will decrease and no cutting will take place, result-ing in plowing or no action at all.

It is very important that a high number of contacting points are available to obtainan efficient grinding. Only a small number of the visible contacting points make con-tact with the specimen surface. At coarser SiC papers like grit 220 only approximately 1in 10 points make contact and at finer papers like grit 600 only 1 in 20.7

Fig. 6.2—Basic model of cutting process indicating rake angle.

Fig. 6.3—Schematic drawing of possible rake angles with abrasive grains in different positions.Cutting is shown with a chip being removed from the work piece and plowing is indicated as agroove with ridges.7


6.2.3 Grain PenetrationThe depth of penetration at the contacting points of an abrasive grain into the workpiece is only a small percentage of its size. At grinding, the maximum value is in therange of 5 %, meaning that a grit 220 grain with an average size of 68 �m using a pres-sure of 40 kPa �6 psi� will penetrate less than 3–4 �m into the specimen surface. Inpractice, at grit 220 SiC grinding paper the penetration �scratch depth� at an annealed30 % Zn brass will be up to 5 �m in the first seconds and drop to 2–2.5 �m.7

6.2.4 Force on SpecimensIn principle, the material removal increases linearly with the increase in specific pres-sure between specimen surface and grinding surface. This means that a certain force isneeded to obtain a satisfactory high removal rate. It is, however, a problem with SiCpaper that a too high specific pressure might cause stronger deformation in the speci-men. This is especially important during the first few seconds when the paper has a fewlarge grains causing a very aggressive attack �see Section 6.6�.

At grinding, the force should correspond to a specific pressure from 30–100 kPa�4.35–14.5 psi� depending on the material to be ground. In theory the specific pressureshould be kept regardless of specimen size, but experience has shown that the force onthe single specimen should not exceed 50 N �11 lbf�, and as compensation, to obtainthe necessary material removal the preparation time is extended. A too high pressuremight cause the grinding paper, in most cases held only by a water layer �see Section13.2.4� to be dragged off the support disk and the more expensive paper with adhesivebacking or a double adhesive foil must be used. If a polishing cloth is used for “grind-ing” the cloth may overheat.

6.2.5 Grinding/Polishing FluidsThe fluids used for metallographic/materialographic grinding/polishing has no lubri-cating effect regarding the actual cutting process taking place between the abrasivegrain and the work piece �specimen� material, creating chips.7 The fluid has a strongcooling effect and especially in case of grinding, the fluid, usually water, will remove theswarf. If the debris is not removed the grinding surface becomes clogged and it willcreate deformation in the specimen surface.

At polishing the fluid, also called lubricant, is lubricating the surface of the polish-ing cloth, reducing the friction and heat developed between cloth and specimen, at thesame time removing swarf from the cloth surface. For more details on fluids and lubri-cants see Sections 2.3.7 and 6.5.

6.3 Deformation

6.3.1 MetalsIn metals, being ductile materials, the separation of a chip during machining opera-tions induces complex systems of plastic deformation in both the separating chip andthe specimen material. An inevitable consequence is that a layer, plastically deformedduring machining, is left in the new surface that is produced. In general terms, thestrains in this layer are very large at the surface and decrease more or less exponentiallywith depth. See also Figs. 13.3–13.6 and Figs. 13.19–13.22.

This deformed layer becomes important in metallography when the plastic defor-mation changes the microstructure of the specimen in a way that can be detected in themicroscopic examination that is to be performed. The layer is then an important poten-


tial source of false structures, or preparation artifacts, the avoidance of which is one ofthe primary objectives of a metallographic preparation sequence.

As mentioned above, the abrasive grains act as machine tools set at different rakeangles. When a chip is separated from the surface, the shear strains are concentrated inthe so-called shear zone in front of the tool. A region adjacent to this shear zone, andextending into the specimen in advance of the tool is also plastically deformed thoughto a lesser degree, as shown in Fig. 6.4.

Samuels7 has done an exhaustive study of the deformation created in the specimensurface of metals, by using taper sections �see Section 3.11�.

A taper section of annealed polycrystalline 30 % Zn brass ground on a 220 grit SiCpaper, etched with different etchants shows the surface of the specimen with scratchesand the deformation in Fig. 6.5.

Samuels7 splits up the layers into two levels of deformation, the shear-band layerat the surface that has been subjected to large strains, and the deformed layer beneaththe shear-band layer. The shear-band layer typically extends preferentially beneath in-dividual polishing scratches for approximately twice the depth of the scratch withwhich it associates. In the deformed layer the material has been strained by simplecompression, and the magnitude of the strains decreases with depth until a level isreached where the material is only elastically strained. This elastic-plastic boundarydefines the lower limit of the deformed layer. An important difference between theshear-band layer and the deformed layer is that the presence of shear-band layer mate-rial is always apparent after etching with any etchant suited for the material, whereasthe presence of the less deformed material becomes apparent in light microscopy only

Fig. 6.4—Section of a chip cut in 70:30 brass by an orthogonal tool with a highly negative rakeangle.7


in a rather limited number of materials, and then, perhaps, only after etching by spe-cific methods.

Samuels splits the deformed layer into two depths, the total deformed layer Dd andthe significant deformation Ds. This gives the following three levels of deformation inan abraded materialographic specimen:

Depth of shear-band layer �Dsb�: The maximum depth beneath the root of the sur-face scratches of the shear-band layer.

Depth of deformation �Dd�: The maximum depth beneath the root of the surfacescratches to the elastic-plastic boundary.

Depth of significant deformation �Ds�: The maximum depth beneath the root of thesurface scratches of the deformation that would noticeably affect the observations tobe made on the finished surface.

The value of Ds is the most important one regarding metallographic preparation. Itvaries with materials and the etchant used and the level of the finished specimen sur-face should always be beyond Ds.

Example: Annealed Polycrystalline 30 % Zn Brass7

SiC grinding paper, 220 grit, with water, hand abrasionDsb �scratches�: 2 �mDd: 77 �mDs: 7.5 �m

Fig. 6.5—Taper section of the surface of annealed polycrystalline 30 % Zn brass that has beenground on grit P220 SiC paper. The section has been etched by several methods that havedifferent threshold strains for revealing deformation as follows. �a� Ferric chloride reagent�threshold strain: 5 % compression�. �b� Cupric ammonium chloride reagent �threshold strain:0.1 % compression�. �c� Low sensitivity thiosulfate etch �threshold strain: 0.1 % compression�.�d� High-sensitivity thiosulfate etch �threshold strain: elastic limit�. In each case, the base of thelayer, in which the manifestations of deformation have been developed, is indicated by anarrow. Taper ratio 8.2, 250:1.7


6.3.2 Brittle Materials—CeramicsThe above description covers ductile materials like metals, which when stressed, willplastically deform a significant amount before fracture occurs. This is not the case withbrittle materials like most ceramics, which deform only elastically prior to fracture bypropagation of a crack. To understand the effect often taking place at grinding of brittlematerials, it can be seen how the indentation of a sharp point and a spherical pointaffects the surface of a specimen. When a sharp point, �a� in Fig. 6.6, is pressed into thesurface, a pseudo-plastic zone �1� of irreversible deformation is produced beneath theindentation. This impression stays in the surface, and by increasing force a so-calledmedian vent crack in vertical direction �2� develops, and by further increase of the forcelateral vent cracks develop �b� �3�. When this lateral vent crack develops to the surface,a relatively large volume of material is removed which can be called a fracture chip,considerably larger than the chips earlier described under metals.7 If an indentation ismade with a spherical point, �c� in Fig. 6.6, first a pseudo-plastic zone �1� develops, atincreasing force followed by a cone �ring� crack �2� and by further increase of the forcealso a median vent crack develops �3�. The circular symmetry of the ring crack will belost if the indenter is drawn across the surface as by grinding/polishing, and the crackmight follow grain boundaries and cause pull-outs of whole grains or parts of grains,�d� in Fig. 6.6. The same might happen with the crack formation shown in �a�, Fig. 6.6.As mentioned above the material removal in brittle materials to a high degree takesplace with fracture chips, leaving cavities in the surface �e� in Fig. 6.6, but according toSamuels7 this is mainly the case at the larger abrasive grain sizes, whereas below gritP1200 �approximately 15 �m� it seems that chip cutting without fracturing takes over.

It can be seen in Fig. 6.6 that beneath the fracture cavities and pull-outs, a crack-

Fig. 6.6—Schematic drawing of surface damage to ceramic material. Because of the brittlenessof the material, micro cracks and pull-outs �surface fractures� are developed in the surfaceduring the grinding. When a sharp point �a� is pressed into the surface, a pseudo-plastic zone�1� of irreversible deformation is produced beneath the indentation. A median vent crack �2� invertical direction may develop. By increasing force �b� lateral vent cracks �3� may develop. If anindentation is made with a spherical point, �c� first a pseudo-plastic zone �1� develops, atincreasing force followed by a cone �ring� crack �2� and by further increase of the force also amedian vent crack �3� may develop. Pull-outs of whole grains or parts of grains, �d� and smallerpull-outs �e�. Crack following grain boundary �f�.


containing layer develops, �f�, which extends to considerable depth. This layer must beremoved during the preparation.

A normal preparation procedure for ceramics and other hard and brittle materialsis grinding with a bonded diamond grinding disk followed by grinding on rigid com-posite disks or very hard polishing cloths with diamond and a final polishing on a me-dium hard cloth with silica. The most serious problem is the development of pull-outsand cavities developed during the first grinding step�s� with bonded diamond disks.These artifacts, which as a mistake can be considered to be pores belonging to the truestructure, must be effectively removed during the grinding on the rigid composite disks�see Sections 3.10, 6.6.1, 6.7.7, and 13.5/6�.

Preparation of ceramics is stated in Material/Preparation Tables 02–06 in Section13.2.3. For in-depth information on ceramics and preparation of ceramics, see Refs. 26and 27.

6.4 Grinding Abrasives

The abrasives already described in Section 2.3 for abrasive cutting are also used forgrinding, but below a further description related to grinding/polishing is given.

6.4.1 Aluminum OxideHardness: 2500 HV

Although Al2O3, alumina, has certain advantages, especially for grinding of steel, itis not used much for metallographic/materialographic grinding except in ceramicgrinding stones and in connection with zirconia in wet grinding paper for plane grind-ing.

Very fine alumina is used for polishing �see Section 7.5�.Aluminum oxide was the first grinding medium found in nature, typically emery

�about 50 % Al2O3 with other oxides, principally iron oxide� and corundum. Around1900 a process was found to turn bauxite into Al2O3 and today it is the most used abra-sive. Al2O3 is available in different crystals with the � particles mostly used for grind-ing. Al2O3 easily forms substitutional solid solutions like the combination Al2O3 andZrO2 mentioned above.

Being made in many different types, Al2O3 also has very different surface struc-ture. The types with relatively smooth surfaces are used for rough grinding operations.Types with a surface with sharp facets are used for finer grinding.

6.4.2 Silicon CarbideHardness: 2700 HV

SiC plays an important role in metallographic/materialographic grinding with SiCgrinding paper being used for both plane grinding and fine grinding �see Section 6.6.2�.

SiC is the first synthetic abrasive, made in the 1890s. There are two grades of SiC.The green type is relatively friable and has fewer impurities; the black type has thesame hardness as the green type but is less friable. Most of the SiC used for grinding isof the black type. Silicon carbide is the second most widely used type of abrasive.

The surface structure of an SiC grain is rather irregular, resembling fracturedglass. This is an advantage when coated on an SiC grinding paper because the grain willbe fixed firmly in the coating cement but the irregular surface combined with an irregu-lar shape will give an increased deformation of the specimen surface �see Section6.6.2�.


6.4.3 Diamond—Diamond ProductsHardness: 8000 HV

Diamond plays an increasing role in metallographic/materialographic prepara-tion. A number of products based on diamond are developed using diamond grains asfixed or loose abrasive for both grinding and polishing �see below�.

Diamond, together with cubic boron nitride �CBN�, belongs to the superabrasives.Since the 1940s, natural diamonds have been used for grinding purposes. After manyyears of research, methods to make synthetic diamonds were developed in the 1950s–60s and today almost all diamonds used for grinding and polishing are synthetic. Dia-monds are made with two crystal structures: polycrystalline and monocrystalline.

The polycrystalline grain, having many sharp edges, is relatively friable and willbreak down during use, giving a self-sharpening effect, as shown in Fig. 6.7. Polycrys-talline diamonds are considered the most effective for materialographic preparationbecause of a higher removal rate than monocrystalline diamonds in most materials.7

Monocrystalline grains are stronger, having a blocky form with relatively few cut-ting edges and will not easily break down. If they break down, it takes place alongstraight lines, as shown in Fig. 6.8, not creating many new cutting edges.

Fig. 6.7—Schematic drawing of polycrystalline diamond grain before and after grain fracturecreating many new cutting edges.

Fig. 6.8—Schematic drawing of monocrystalline diamond grain before and after grain fracturecreating only a few new cutting edges.


Diamond Products with Fixed GrainsDiamond is used in a number of products, all having the diamond grains fixed in somekind of bond. These materials are used for grinding of metallographic/material-ographic specimens, ranging from plane grinding with relatively coarse grits to ex-tremely fine grits used in the diamond �lapping� films �see below�.

Diamond Grinding Disks—The diamond grains are placed in a metal or bakelitebond. Primarily used for “traditional” grinding of very hard materials �see Section6.6.1�.

Resin-Bonded Diamond Grinding Disks—The diamonds are placed in a thin layerin a resin bond �not bakelite�. This type of disk is used for “contemporary” grinding ofall materials harder than 150 HV �see Section 6.7�.

Metal-Bonded Diamond Disks—The diamonds are placed in a thin layer fixed by anickel coating �see Section 6.7.4�.

Diamond Pads—The diamonds are placed in a bond of metal or resin in a dot ma-trix on a self-adhesive backing. Used for plane and fine grinding of hard materials �seeSection 6.7.5�.

Diamond Film—The diamonds are coated to a very thin film �lapping film�. Thisproduct is used for grinding/polishing of electronic devices, wafers, etc. �see Section6.7.6�.

Diamond Products with Loose „Free… GrainsA number of products are available with the diamond grains mixed with a carrier, en-abling grinding or polishing with free grains on the surface of the grinding/polishingdisk �see below�.

Grain SizeIt is very important that the grains for a given grain size are selected with a narrowtolerance. If the grains are relatively uniform, as shown in Fig. 6.9 �a� a very high part ofthe grains are active, securing a high removal rate; Fig. 6.9 �b� shows diamond grainswith a large difference in grain size and it can be seen that a high number of grains arepresent only as “filler” and with only a few acting grains. This causes the specific pres-sure on each grain to be high, possibly causing deeper scratches in the specimensurface.

Fig. 6.9—Diamond grains �2�, uniform size �a� and nonuniform size �b�, between grinding/polishing disk �3� and specimen �1�. The smallest grains �b� are not active.


Diamond SuspensionsThe use of diamond suspensions �slurries� is increasing because applying the abrasivein small quantities during the process is an advantage, giving a more constant removalrate than other types of diamond products.28

Suspensions are suited for being applied from a dosing unit, in this way makingthe charging of the grinding disk/polishing cloth, automatic. The automatic dosing canbe performed as spray, creating aerosols, which are considered dangerous to health, orby pumps, supplying the suspensions in drops. Also the suspension can be conve-niently applied by hand from a pump �spray� bottle.

Diamond suspensions can be based on water, alcohol, oil, or other hydrocarbons.Water-based suspensions are to be preferred, because of the nontoxic nature of water.To the suspension should be added an ingredient that stabilizes the diamond grains sothat they do not sediment or only sediment very slowly. In case sedimentation takesplace, the bottle with suspension can be placed on a stirring apparatus or in other waysbe stirred during the process.

In certain cases, when the material to be prepared is sensitive to water, a water-freesuspension based on oil or preferably on alcohol, should be used. Diamond suspen-sions are available with both polycrystalline and monocrystalline diamonds in therange 45 �m to 0.05 �m. The grain sizes most used are 9 and 6 �m for fine grinding/rough polishing and 3, 1, 0.25, 0.1, and 0.05 �m for polishing and final polishing.

The polycrystalline suspension is preferred if the highest removal rate and bestfinish is wanted. This is due to the fact that the polycrystalline grains break down dur-ing the process and in this way creates new cutting edges. Monocrystalline suspensionsare normally less expensive than polycrystalline, and the removal rate is considered tobe lower.

Normally the suspension is used in combination with a lubricant �see Section 6.5�.In this way the adding of new grains and the establishment of a lubricating film areseparated, making it possible for a more exact dosing of both. Diamond suspensions,also acting as lubricants, however, are available. Using these, only one product is addedto the grinding/polishing disk, establishing both a sufficient number of active grainsand a lubricating film.

Diamond SpraysBoth polycrystalline and monocrystalline diamonds are available in spray cans. Theadvantage of using spray is the very small amount of “other material” introduced to theprocess that are opposite of suspensions and pastes which contain a high amount ofcarrier. Diamond sprays are available in the grain sizes 45, 25, 15, 9, and 6 �m for finegrinding/rough polishing and 3, 1, and 0.25 �m for polishing.

Diamond PastesThis is the original way of distributing the diamond, by rubbing a small amount of dia-mond paste into the polishing cloth. For this reason diamond cannot be added duringthe process and in certain cases, like working with a rigid composite disk �RCD�, thepaste will disturb the process.

A variation of paste is the stick, where the diamonds are placed in a harder wax;this is easier to apply than paste. Pastes are available with both polycrystalline andmonocrystalline diamonds. The grain sizes available are 15, 9, and 6 �m for finegrinding/rough polishing and 3, 1, and 0.25 �m for polishing


6.4.4 Cubic Boron Nitride „CBN…Hardness: 4500 HV

CBN is made along the same lines as diamond, with high pressures and high tem-peratures. The main reason why CBN is of interest as an abrasive is that it is muchmore chemically stable than diamond in the presence of hot iron �see Section 2.3�.

CBN crystals are relatively smooth which makes bonding difficult. Therefore, thegrains are often coated with metal, suck as nickel.

CBN can be used in grinding disks in a metal or bakelite bond for very hard ferrousmetals.

6.4.5 Boron CarbideHardness: 2800 HV

Boron carbide �B4C� was developed for grinding purposes, but for different rea-sons the use is limited. It is used as a suspension for lapping purposes, the grain havinga porous structure with many sharp edges. B4C is seldom used in metallographic/materialographic grinding and polishing.

6.4.6 Hardness of Abrasives and Materials—Table 6.1Table 6.1 gives a comparison between the Vickers hardness of a number of materials tobe prepared and the abrasive materials used in the preparation process.

6.5 Grinding/Polishing Fluids—Lubricants

The most commonly used fluid for “traditional grinding” �see Section 6.6�, with grind-ing stones and SiC wet grinding paper, is water with or without an additive. If the wateris recirculated, an additive should be used to prevent corrosion and reduce bacterialgrowth in the water �see Section 2.3.7�.

For “contemporary grinding” �see Section 6.7�, using grinding disks with fixedgrains, water is also used, but in the case of fine grinding on rigid composite disks�RCDs�, lubricants, also called extenders �normally used for polishing�, are used. Theyare described below.

6.5.1 Water-Based LubricantThis lubricant is to be used if possible because it has no environmental effects. It issuited for polishing of most materials using polishing cloths. In case of fine grinding onrigid composite disks, the water-based lubricant should be dosed in small amounts toavoid “aqua planing” where the specimen is planing on the fluid layer, not getting intocontact with the surface of the disk. For polishing of certain soft, ductile materials, awater-oil based lubricant should be used �see below�.

6.5.2 Alcohol-Based LubricantThis type of lubricant gives a high removal rate and a good cooling due to the fastevaporation of the alcohol. For this reason this lubricant can be used as an alternativefor a water-based lubricant for work on rigid composite disks, which shall work “dry”to secure that the specimen is in direct contact with the disk surface. An alcohol-basedlubricant should be used for materials that are sensitive to water.

Alcohol �ethanol� is considered dangerous to health by inhalation and ingestionand for this reason this lubricant should be avoided if possible.


6.5.3 Water-oil Based LubricantThis type of lubricant, water with an in-mixed oil forming an emulsion, will give a lessaggressive action between cloth/abrasive and specimen surface than the water- andalcohol-based types. An oil film will act as a membrane between the polishing cloth andspecimen. The lubricant is used for polishing of soft, ductile materials. Because of theoil, which might cause skin problems, the use should be as limited as possible.

6.5.4 Oil-Based LubricantThis lubricant is a “lapping oil” based on mineral oil �heavy petroleum distillate�. Likewith the water-oil based lubricant mentioned above, it is used for soft, ductile materials

TABLE 6.1—Hardness of Abrasives and Materials.


to reduce the formation of deformations. Mineral oil may cause irritation by repeatedskin contact and by inhalation of vapors or aerosols, or both. For these reasons the useshould be limited or avoided, if possible.

6.6 Traditional Grinding

The expression “traditional grinding” covers the grinding methods used for a very longtime in metallographic/materialographic preparation: Grinding stones/disks with ce-ramic or bakelite bonds and silicon carbide �SiC�, alumina �Al2O3�, and zirconium-alumina wet grinding paper.

6.6.1 Grinding Stones/Disks

Grinding Stones for Plane Grinding of MetalsGrinding stones with aluminum oxide as abrasive and a ceramic bond are used mainlyfor plane grinding when a relatively large amount of material shall be removed. Thewheel normally is of the recessed type �see Fig. 6.10�, the specimen holder beingpressed against the top surface of the stone.

The grinding stones change during the process, the main problems being unevenwear and clogging of the surface. The stone has to be trued regularly to keep the surfaceplane and dressed to remove material clogging the surface �see Section 2.3.6�. This isusually done with a diamond truing device placed on the grinding machine.

Diamond Disks for Grinding of Very Hard MaterialsCeramics and other very hard materials have to be ground with diamond. This can begrinding disks with a metal bond or a bakelite bond. The metal bond gives a relativelyrough surface of the specimen and the wear is relatively low. Bakelite bond produces aspecimen surface with less deformation but the wear is higher than by the metal bond.Both types of diamond grinding disks are very expensive and only used for grinding ofsintered carbides, ceramics, and other very hard materials. In the past few years, a newtype of diamond disk with resin bonded fixed grains has been developed. These disksare considerably less expensive and suited for a wide scale of materials �see Section6.7�.

Fig. 6.10—Grinding stone for plane grinding, the grinding takes place on the top surface ofthe stone.


6.6.2 SiC Wet Grinding Paper—Table 6.2SiC paper is the traditional grinding medium, used since the 1950s, both for planegrinding and fine grinding. SiC grinding paper is made of a waterproof paper backingwith a layer of SiC abrasive grains. As shown in Fig. 6.11, an adhesive layer called themake coat is first applied to the backing before the abrasive grains are applied. As thebacking material passes through a strong electrostatic field the particles are orientedwith their longest dimension in the vertical direction. This provides good grain reten-tion and also orients the particles with their sharpest edges upwards. A second layer ofadhesive, called the size coat, is then applied over the entire assembly.

TABLE 6.2—Comparison between Grit Numbers according toANSI Standard B74.18 and FEPA “P” Standard 43-GB.

FEPA“P”Standard43-GB-1984 R1993

Approx. Average GrainDiameter

FEPA Pμm

ANSIμm

ANSIB74.18-2006

P60 269 268 60P80 201 192 80P100 162 141 100P120 125 116 120P150 100 93 150P180 82 80 180P220 68 67 220P240 59P280 52 52 240P320 46P360 41 42 280P400 35 34 320P500 30P600 26 27 360P800 22 22 400P1000 18 16 500P1200 15 13 600P1500 13P2000 10P2500 (P2400) 8.4 6.5 (800)(P4000) 5 5 (1200)

Fig. 6.11—Schematic drawing of cross section of SiC grinding paper.


The paper backing can be of A-type, relatively thin, and C-type, which is somewhatthicker. Type C is normally used for metallographic/materialographic grinding. The pa-per is supplied as disks in the diameters 200 mm �8 in�, 230 mm �9 in�, 250 mm�10 in�, and 300 mm �12 in�.

The SiC abrasive is classified according to standards established by ANSI �Ameri-can National Standard Institute� and FEPA �Federation of European Abrasive Produc-ers�. The grit sizes are split into two categories: macrogrits and microgrits.

Macrogrits ranging from grit 12 to grit 220 are determined by sieving, the gritnumber indicating the number of openings per square inch. Macrogrits are the same inthe ANSI standard and the FEPA standard, the FEPA designation having a P before thenumber.

Microgrits ranging from grit 240 to grit 4000 are determined by sedimentation,and the grit numbers covering a specific grain size are not the same in the two stan-dards �see Table 6.2�.

Comparison Between Standard Grits—Table 6.2In practical preparation a selection of grits is used. The suppliers of consumables formetallographic/materialographic preparation supply both according to the Americanand European Standards. In Table 6.2, the most commonly used grits are shown forcomparison �P2400 and P4000 are not FEPA designations, 800 and 1200 are not ANSIdesignations�.

Plane GrindingFor plane grinding the grits 120 �P120�, 180 �P180�, 220 �P220�, or 240 �P280� normallyare used. As mentioned above, the finest possible grit should be chosen to limit the de-formation of specimen surface �see below�. When using SiC paper, the last plane-grinding step should be grit 220 or 240 �P220 or P280� to be sure of the correct result�reproducibility� of the following preparation method. Considering that each sheet ofpaper is only grinding efficiently in 20–60 s, depending on the material to be ground,often several sheets must be used to secure a totally plane specimen surface co-planarto the grinding surface.

Fine GrindingFor fine grinding, three to four steps based on the following grits are used typically: 280�P320�, 320 �P360�, 360 �P500�, 400 �P600�, 500 �P1000�, 600 �P1200�, 800 �P2400/P2500�, 1200 �P4000�. A normal fine grinding sequence could be 320–400–600 usingANSI-designated paper or P320, P500, P1200 using FEPA designated paper.

In the case of soft ductile materials, one or two fine steps can be added, 800, 1200�ANSI� or P2400/P2500, P4000 �FEPA�.

Material RemovalThe material removal rate for SiC paper is relatively high as long as the paper is notworn down. This is due to the abrasive grains being rather exposed and having a goodspace in between, allowing for the chips to be produced and taken away by the waterflow. This is opposite to dry grinding on emery paper, which will very soon have aclogged surface causing deformations and material flow in the specimen surface.

Because of the brittleness of the SiC and the relatively high load on the grains, theybreak down caused by fractioning and wear. In Fig. 6.12 this is shown schematically,the SiC grains with different rake angles are broken and worn, creating new, negative


rake angles resulting in a loss of cutting action.29 This develops in 20–60 s or longer,depending on the material to be ground, hard materials strongly reducing the time.According to tests made by Samuels7 the removal rate when grinding some metals likecopper and copper alloys, aluminum and aluminum alloys, silver and titanium staysconstant over a long period of time, and for some metals like nickel-chromium austen-itic steels, nickel and nickel alloys, titanium alloys, chromium and gold, a deteriorationin removal rate occurs in the first minutes and is followed by a period of relatively highmaterial removal. These tests were based on a single specimen at a time, whereas inmodern preparation three to six specimens often are ground at the same time, conse-quently reducing the lifetime of the paper.

In Fig. 6.13, an SEM micrograph shows the single grains of a 220 grit SiC paperwith the different shapes and sizes. Also the large variation in contacting points andrake angles can be seen. At 220 grit, the median grain size is 63 �m and the largestallowed grain size is 74 �m. Because of this large variation in shape and size, onlyaround 5–10 % of the many visible contacting points of the grinding paper actually getin contact with the specimen surface. Only a fraction of these points are able to removematerial from the surface. Samuels7 estimates that less than 1 in 1000 of the grainsvisible can be expected to actually remove material. During the process when the SiCgrains break down, the cutting effect will change into plowing, shown in Figs. 6.3 and6.14. At certain soft, ductile materials, grains or parts of fractured grains can be embed-ded in the specimen surface �see Fig. 2.1 and Section 13.6.4�.

DeformationAs shown in Section 6.3, a 220 grit SiC paper will induce a relatively strong deforma-tion of the specimen surface. This is mostly because of the single large SiC grains beingvery aggressive in the first seconds of the grinding process. Figure 6.14 shows a com-parison between an SiC grinding paper and a grinding disk with diamond abrasivegrains in a resin bond. The situation after 2–5 s, �a� Fig. 6.14 shows the introduction of

Fig. 6.12—Schematic drawing of grains on a SiC paper with different rake angles, as new andafter 30–60 s use, the gray parts are worn away or fractured.


the deep deformations by the paper, whereas the grinding disk with grains embeddedin a bond gives more moderate deformation.

Edge Retention—ReliefIn Section 3.1.3 edge retention is discussed, concentrating on mounting. Another im-portant aspect is the resilience of the substrate, the surface, used for the grinding/polishing. To totally avoid a rounding of edges, a hard substrate without resiliencemust be used. SiC paper has some resilience because the paper backing has a certainflexibility, but in most cases a sufficient planeness can be obtained for most materials.In more extreme cases, however, where edge rounding or relief, or both, must be abso-lutely avoided, SiC paper might have too much resilience. In Figs. 6.15 and 6.16 grit 220SiC paper is compared to a diamond grinding disk with the same grain size, havingalmost no resilience. In Fig. 6.15, two unmounted, similar specimens are compared.The specimen on the SiC paper was rounded due to resilience of the paper backing; thespecimen on the diamond disk is not rounded due to the very low resilience of the disk.Even with mounted specimens, SiC paper in certain extreme cases will create a round-

Fig. 6.13—SEM micrograph of a P220 SiC paper. The irregular shapes of the grains and thevariety in grain size can be seen.


ing of the specimen or a relief of the specimen surface. In Fig. 6.16 a drawing of a me-dium hard, nitrided steel, mounted in epoxy resin, is shown. When prepared on SiCpaper, the SiC particles grind away the surface irregularly due to the high differences inhardness between the nitrided layer and the core steel. Because of the limited differ-ence in hardness between the nitrided layer and the SiC particles and the resilience of

Fig. 6.14—Comparison of surface deformation using SiC paper and a resin bonded diamonddisk. After 2–5 s �a� single large grains of the SiC paper give deep deformations, after 30 s �b�the SiC grains are wearing down, and after 60 s �c� the SiC grains are worn down creatingplowing, causing deformation, see Section 6.2.1. The diamond grinding disk gives lessdeformation and remains almost constant during the process.


the paper backing, the layer protrudes above the surface of the specimen due to therelatively low rate of material removal. The diamond disk cuts all parts of the surfaceuniformly due to the extreme hardness of the diamond particles and the lack ofresilience.

Environment—EconomyAs mentioned above the efficient grinding time to a high degree depends on the speci-men material and the number of specimens prepared at the same time. At soft and me-dium hard materials the total plane and fine grinding might be performed with onlyfour sheets of paper, but at hard materials, especially with several specimens in aholder, several sheets of each grain size must be used. In case of a high production ofspecimens this is relatively costly and it will cause a relatively high amount of waste. Asa waste substance, the SiC paper is neutral.

6.6.3 Alumina—Zirconia Alumina Wet Grinding PaperUsing alumina or zirconia alumina instead of SiC as the abrasive, a longer efficientgrinding time is obtained. The alumina grinding paper is available in grit 120 and thezirconia alumina papers are available in the grits 60 �P60�, 80 �P80�, 120 �P120�, and180 �P180�, and consequently they are only for plane grinding. Due to the longer effi-cient grinding time they are especially suited for automatic preparation using speci-men holders with many specimens.

The influence on the specimen surface is as described under SiC paper.

Fig. 6.15—Comparison between SiC grinding paper and a resin bonded diamond disk. The SiCpaper has a relatively high resilience, and an edge rounding is introduced on an unmountedspecimen. The diamond disk has no resilience and gives no rounding.


6.7 Contemporary Grinding

“Traditional” grinding described in the previous section has a number of drawbacks,especially when used for semiautomatic and fully automatic preparation. For this rea-son “contemporary” grinding has been developed, in this way eliminating or reducingthe drawbacks:• Quality of specimen surface: Better edge retention, less deformation.• Constant removal rate: Fewer steps and higher reproducibility.• Less handling: By using fewer steps, and using automatic preparation systems,

handling is reduced to a minimum and operation time is saved.• Less waste: By using longer lasting consumables, the amount of waste is reduced.

In short it can be said that with contemporary grinding it is possible to preparespecimens with extreme hardness differences as a routine process. These specimenscould only be prepared with great difficulty using the traditional methods. The grind-ing media used for contemporary grinding are almost all based on diamond as theabrasive, either as fixed �bonded� in the surface of a rigid grinding disk, or added duringthe process on a rigid composite grinding disk �rigid composite disk �RCD��. The prod-ucts are supplied as disks in the diameters 200 mm �8 in�, 250 mm �10 in�, 300 mm�12 in�, and 350 mm �14 in�.

6.7.1 Magnetic FixationAs part of the development of the products for advanced preparation, it was importantalso to avoid the relatively troublesome handling of grinding papers and polishingcloths with adhesive back. For this purpose magnetic systems were developed using a

Fig. 6.16—Comparison of edge rounding and relief with a mounted specimen with a hardsurface layer prepared on SiC paper and a resin bonded diamond disk. At the SiC paper a reliefdevelops between the hard layer and the mounting material/basic material.


supporting disk with a permanent magnet foil on which the substrate, a grinding diskor polishing cloth, made with a ferromagnetic backing, is fixed �see Fig. 6.17�. The hold-ing power is very high in the direction parallel to the supporting disk, in this way keep-ing the substrate on the disk, but vertically the holding power is low enabling the opera-tor to easily remove the substrate. A further advantage is the use of only one supportingdisk for all grinding/polishing steps instead of changing the supporting disk for eachstep. Normally the magnetic supporting disk is made especially for that purpose, but itis possible to convert a normal metal grinding/polishing disk by placing a magnetic foilwith adhesive back on the disk. The drawbacks are an increase in the disk thickness,and after some time, the foil might loosen due to attack from liquids during the prepa-ration process.

6.7.2 Resin-Bonded Diamond Grinding DisksSection 6.6.1 describes conventional diamond disks. These have either a metal orbakelite bond and because of the high price and careful maintenance �truing is impor-tant to keep the surface plane�, they are only used for very hard materials, harder than600 HV �55 HRC�, where SiC and Al2O3 are not hard enough. Diamond as an abrasive,however, would be ideal for grinding of softer materials.

In the past five to ten years, a new type of diamond grinding disk has been devel-oped, taking advantage of the hard diamond, but supplied at a reasonable price, whichmatches the SiC grinding paper. The disk is suitable for materials harder than HV 150.The cost is kept low because the diamonds are fixed only in a thin layer in a resin bondand placed in segments on the surface of the disk as shown in Fig. 6.17

The figure shows how the disk is fixed to the supporting disk by a permanent mag-net, as described above, but the disk can also be fixed by a double adhesive foil placedon a normal grinding/polishing disk.

The bond keeping the diamond grains, Fig. 6.18, is made so that it allows the grainsto leave the surface when the grain is worn. The disk is used with water like SiC paper.Using only a thin layer of bond with diamonds, the disk needs not to be trued, when thelayer is worn away at the center of the disk the disk is discarded, see Section 6.7.7 for amore extensive description of this wear. Only a dressing of the surface with a dressingstick is needed if the surface is clogged.

Plane GrindingThe disks are used for plane grinding, using the same grain sizes as for SiC paper, grit80 �P80� to 220 �P220�. Because of the constant removal rate �see below� the wholegrinding sequence can take place in one operation, even when much material shall beremoved and the material has a high hardness.

Fig. 6.17—Resin bonded diamond disk for magnetic fixation on a support disk with apermanent magnet.


Fine GrindingThe disks can also be used for fine grinding in the grit sizes 360 �P600� and 600 �P1200�.

Material RemovalThe disks have a relatively high, constant removal rate securing that the grinding pro-cess can be finished without interruptions. This is due to the high hardness of the dia-monds and the ability of the bond to break down, releasing fresh abrasive grains.

DeformationThe diamond grains, being of a more regular shape and with a closer tolerance of thegrain size than SiC grains, will produce less deformation than SiC paper, as shown inFig. 6.14. Also the position of the grains, placed in a bond �see Fig. 6.18� gives less im-pact when touching the specimen surface, creating less deformation. The segmentedsurface, with grooves to lead away the swarf, is important to avoid smearing of thespecimen surface.

Edge Retention—ReliefEdge retention, to a high degree depending on the resilience of the disk, is very good.The resin bond is relatively hard and unflexible �see Figs. 6.15 and 6.16� and the veryhard diamonds are able to remove material even from very hard phases in the speci-men surface, avoiding relief

Environment—EconomyThe diamond disk as described above has very little environmental impact when dis-carded. It only consists of a thin, tinned steel plate �as used for canned food� and a verythin layer of synthetic resin

Depending on the material to be prepared, one disk is equivalent to 100 sheets ofSiC paper or more, making the cost comparable to the cost of SiC paper.

6.7.3 Resin-Bonded SiC Grinding DisksThe diamond disks described above are only suited for materials harder than HV 150.Therefore, disks have been developed with SiC as an abrasive suited for softer materi-als. In general, the above description of the diamond grinding disks also covers the SiCgrinding disks.

Fig. 6.18—Resin bonded diamond disk. Diamond grains placed in a bond.


6.7.4 Metal-Bonded Diamond-Coated DisksThese types of disks are different from the conventional metal-bonded disks. The dia-mond abrasive is placed in a very thin layer on a metal surface and bonded �coated�with a layer of nickel.

These disks can be used for the softest to the hardest materials, but they are notused much because the cost per prepared specimen is high.

6.7.5 Diamond PadsThis product, originally developed for grinding/polishing of glass, uses the diamond ina metal or bakelite bond in a dot matrix covering the surface of the pad.

The metal bond is only suited for plane grinding of ceramics, sintered carbides,and other very hard materials. The grain size varies from 250 �m in steps down to20 �m. The bakelite bond can be used for fine grinding of hard materials, being avail-able in grain sizes 30, 10, and 2 �m.

Dressing: It is important that the diamond pads are dressed regularly with a dress-ing stick, normally Al2O3 or SiC in a ceramic bond. This is to open the surface of thedisk when clogging has taken place �see Section 2.3.6�.

6.7.6 Diamond/CBN/Al2O3 /SiC FilmIn the case of preparation of microelectronic devices, wafers, optical fibers, and certainceramics where extreme flatness and very low deformation is needed, films �lappingfilms� coated with diamond, CBN, Al2O3, or SiC can be used.

The very accurately graded abrasive is coated on a thin polyester film either forgluing �PSA� or for adhering only using water �plain back�. The films are used wet or dryand they are available both with a continuous layer of abrasive and with the abrasive asdots allowing the swarf to flow away. The film with dots �ceramic beads� gives a highermaterial removal, a longer life, and a coarser finish, compared to films with a continu-ous layer.

The films are available in steps from 30 �m down to 0.05 �m.

6.7.7 Rigid Composite DisksSince the 1970s, the rigid composite disk �RCD� has been available for materialo-graphic preparation. The RCD has the advantage of making very flat specimens with aconstant removal rate and relatively little deformation, and this makes the RCD verywell suited for fine grinding of most materials. During the process on an RCD, a dia-mond suspension is continuously added. This is known from lapping, a very commonabrasive machining process used in the industry to produce flat surfaces. Normal lap-ping takes place on cast iron disks and the surface obtained is not suited formetallography/materialography �see below�. The surface of an RCD consists of a resinwith mixed-in metal powder in different grain sizes, and it seems to be the effect of thissurface which changes the process taking place on an RCD, from lapping to grinding.To explain the mechanisms of an RCD, a comparison was made between lapping �loosegrains� on a glass disk, grinding on a diamond film �fixed grains�, and grinding on twoRCDs of different hardness.30

Experiment: Lapping Versus GrindingThe scratch pattern of the specimen surface created with an RCD is similar to a surfacemade with grinding paper, apparently ground, with grinding defined as a process with


fixed abrasive grains, each grain acting as a machine tool producing a chip. This seemsstrange because when using an RCD, the abrasive, mostly diamond with a grain size of6–9 �m, is added during the process. Normally these loose grains should create a lap-ping, defined as a process with loose abrasive grains, rolling and flowing in nearly asingle layer between specimen surface and disk, and not a grinding. At lapping, thecorner of the rolling grain digs into the specimen surface, the grain tumbles onto anedge, and then another corner contacts the specimen, and so on. Lapping is consideredless appropriate for metallographic/materialographic preparation because the re-moval rate is low, and the specimen surface is rather strongly deformed.

A steel specimen with a high finish was used for all parts of the experiment. Grind-ing took place on a diamond film, 9 �m, to secure a perfect grinding. For the lapping afloated glass disk with an alcohol/water diamond suspension was used with 9 �m ofthe same type of diamonds used on the film, added during the process. The RCD pro-cess was performed on two RCDs, RCD 1 and 2, both of the disposable type �see below�with the composite placed in segments on the disk surface �see Fig. 6.27 below�. RCD 1was with metal powder composite �relatively hard and aggressive�, and RCD 2 was witha composite without metal powder, which is relatively soft and with less aggressive ma-terial removal. For both RCDs the diamond suspension mentioned above was used.

All the resulting surfaces were analyzed in an SEM.The results showed that the specimen ground on the film showed a typical grind-

ing pattern with scratches in all directions �Fig. 6.19�. To the naked eye the surface wasrelatively bright.

The specimen lapped on the glass plate showed a typical lapping pattern with twodistinct features �Fig. 6.20�. The freely moving �rolling� diamond grains have made arelief with cavities in the surface, and a few very large scratches have been produced,probably due to single grains fixed in the surface of the glass disk. It can be seen that thelapped surface is considerably rougher than the ground surface �Fig. 6.19�. To the na-ked eye the surface was dull.

The specimen prepared on RCD 1 �Fig. 6.21� has scratches very similar to the

Fig. 6.19—Pattern of scratches and deformations after grinding on a diamond film. SEM.


scratches initiated by grinding �Fig. 6.19�, only a little larger. The surface is reasonablyplane between the scratches. To the naked eye the surface was relatively bright.

The specimen prepared on RCD 2 �Fig. 6.22� has almost the same scratch patternas at grinding �Fig. 6.19�. It is finer than the RCD 1 pattern due to the fact that RCD 1 is amore aggressive RCD. This also can be seen from the removal rates �see below and Fig.6.23�. To the naked eye the surface was relatively bright.

The conclusion of the SEM analysis is that according to the scratch pattern, thesame process takes place when grinding on a film with fixed diamond grains and on anRCD surface with loose grains added during the process.

The removal rate was also measured, defined as material removal in �m per 300 m�movement of specimen on the grinding/lapping surface� �see Fig. 6.23�. It can be seenthat the diamond film is very active during the first approximately 50 m and wears outafter approximately 250 m. The glass disk has a relatively constant removal rate duringthe whole distance and the same is the case with the two RCDs. This is because theabrasive is added during the whole process. The aggressive RCD 1 shows a higher re-moval rate than the other three surfaces.

Based on the above experiment, a suggestion for the mechanisms taking place dur-ing the processes was made and a model proposed.

Lapping on a hard, homogenous disk: It is beyond doubt that the process with roll-ing grains makes indentations in the specimen material, in this way breaking particlesout of the surface �Figs. 6.20 and 6.24�. A fractured, indented, dull surface can be seenonly with a few scratches. A few grains will penetrate into the surface of the disk andproduce a scratch like grain �b� in Fig. 6.24.

Process on an RCD: On an RCD the surface is very much softer than the samplematerial. This means that the abrasive grain is pressed into the disk surface so that arolling is prevented and a process, creating chips like at grinding, takes place. Only avery small number of grains are rolling �see Fig. 6.25�. According to Samuels7 it seemsthat the abrasive grains embed in the upper regions of the edge faces of the segmentswhere they can contact the specimen surface.

Fig. 6.20—Pattern of scratches and deformations after lapping on a glass plate. SEM.


At RCD 1, the surface consists to a high degree of metal powder �Fig. 6.25�. Thisgives a variation in surface hardness, and the abrasive will penetrate differently intothe surface, less in the metal particles. This means that the grain is able to make a largerchip, counting for the higher removal rate of RCD 1. In the case of RCD 2 with a consid-erably softer surface, the abrasive grains penetrate deeper into the disk resulting in asmaller effective diamond size, and the abrasive is held more firmly, which is importantwhen grinding ductile materials.

Rigid Composite Disks „RCD… for Longtime UseThe original RCDs were made as solid disks with a thick layer of composite material,consisting of a synthetic resin with mixed-in metal powder �iron, copper�, or a mineralpowder like Al2O3. The surface can be with segments of different composites and withgrooves of different types to remove the swarf during the process.

The disks can be used for plane grinding with 30–45 �m, but they are mostly usedfor fine grinding with 6 to 9 �m diamond suspension added during the process. Theprocess has to run relatively dry, with a minimum of lubricant added during the pro-cess. As the disk surface texture turns smooth during use, a dressing is necessary withintervals to regain a rough surface and thereby secure the removal rate.

The disks are difficult to use for hand preparation and are normally used with asemiautomatic specimen mover �see Section 6.8�. Most specimen movers work withthe specimen holder placed eccentrically on the grinding disk �see Polishing Dynamics�Section 7.9.2�. This eccentricity causes a wear concentrated around the center of thedisk, making it concave �Fig. 6.26�. This unevenness will, when exceeding100–200 �m, cause an unevenness of the specimens and the effect of the disk will bereduced. The concave surface must be trued to regain the planeness and this is mostlydone with a truing tool using diamond. Due to this rather laborious truing, many RCDswere not used and the use of SiC paper was preferred.

The development of the thin, disposable RCD changed this situation.

Fig. 6.21—Pattern of scratches and deformations after grinding on a hard rigid composite disk�RCD�. SEM.


Rigid Composite Disk, DisposableTaking into consideration the advantages of the RCD, it was evident that an RCD with-out the drawbacks mentioned above, and even compatible with SiC paper, should bedeveloped.

This was done with the disposable RCD, consisting of a tinned steel foil or a steelplate with segments of composite material. This is fixed magnetically to a supportingdisk with a permanent magnet �Fig. 6.27�. The disposable RCD is made in two versions,one relatively aggressive for materials harder than 150–200 HV and a softer one forsofter materials in the 40–250 HV range and for composite materials.

Plane GrindingThe disposable RCD is normally not suited for plane grinding because it should not beused with diamond grain sizes larger than 15 �m. In some cases, however, when work-

Fig. 6.22—Pattern of scratches and deformations after grinding on a soft rigid composite disk�RCD�. SEM.

Fig. 6.23—Comparison of removal rates of specimens after grinding on a diamond film,lapping on a glass plate and grinding on a hard and a soft RCD.


ing with “single-specimen preparation,” �see Section 7.9.1� the amount of material toremove at this stage is so low that grinding with a hard RCD using 9-�m diamond sus-pension can be considered a “plane grinding.”

Fine GrindingThe disposable RCD is made for fine grinding with diamond suspension 9, 6, or 3 �m.The total fine grinding stage can be performed usually in only one step in 2–4 min andthe specimen is ready for the first polishing step.

Material RemovalThe removal rate is considerably higher than at a conventional RCD. This is mostlybecause the disposable RCD works at a higher specific pressure and the removed mate-rial �swarf� is efficiently removed through the channels between the segments. Also, it

Fig. 6.24—Schematic drawing of a lapping process. The abrasive grains are loose and rollsbetween the specimen and the lapping disk. A corner of the grain digs into the specimensurface, and the grain tumbles onto an edge. A track of angular indentations �cavities� isproduced in the specimen surface.

Fig. 6.25—Schematic drawing of a material removal process on a rigid composite disk �RCD�.The majority of the abrasive grains are fixed in the surface of the disk �grinding�; only a smallamount is moving �lapping�.


shall not be dressed during use, but keeps its surface texture during the whole lifetime,securing a constant removal rate. The material removal varies with material type andtype of RCD. The hard, more aggressive type has the highest removal rate �see Fig.6.23�.

DeformationUsing diamonds �9–6 �m� with a narrow tolerance on the relatively flexible RCD sur-face, the grain, momentarily fixed in the surface, will not have the same damaging im-pact on the specimen surface as with fixed grains �SiC paper�. Also, by varying theamount of metal in the composite, the aggressiveness of the surface can be minimizedwhich is very important with soft materials.

Edge Retention—ReliefThe composite material, although “microflexible,” will be rigid and plane as a total sur-face. This, together with the high cutting capacity of the diamond grains, will give avery good edge retention and practically no relief.

WearAs described earlier, an RCD turns concave during use �see Fig. 6.26�. To avoid thetroublesome truing of the surface, the disposable RCD is discarded when the segmentsaround the center of the disk are worn away, showing the user that the difference inplaneness between periphery and center is so high that uneven specimens will beproduced.

Fig. 6.26—Wear pattern of grinding/polishing disk. Due to the geometry of disk and specimenholder, the wear around the center of the disk is stronger than at the periphery, causing aconcave disk surface, after a certain preparation time.


Environment—EconomyThe disposable RCD can be compared with a piece of tin plate or a thin stainless steelplate with a layer of paint, and it can be disposed of like a normal tin can or metal piece.

The price per specimen using the RCD depends on the material to be prepared, butat normal use more than 100 specimen holders can be prepared on one RCD.

6.7.8 Fine Grinding ClothsWhen using very hard cloths, absolutely without nap, like nonwoven chemo textilesand nylon, with diamond suspension or spray/paste of a grain size of 9 �m or larger,the process can be defined as “fine grinding” if the pressure on the specimen is high.

Polishing can be defined as grinding producing very small chips and is explainedfurther in Chapter 7. In the above-mentioned case, however, a material removal similarto grinding can be obtained.

The materials used for the fine grinding cloths are stainless steel mesh, wovenpolyester, woven silk, woven nylon, and nonwoven synthetics. These are all withoutnap and used with 15, 9, 6, or 3 �m diamond suspension or spray �see Section 7.4�.

With the introduction of rigid composite disks �RCDs� for soft materials �see Sec-tion 6.7.7�, the use of these cloths has been reduced.

Material RemovalThe removal rate is not as high as with an RCD, but higher than at a normal polishingstep.

DeformationThe deformation is much lower than at grinding on a disk with fixed abrasives. It iscomparable to the deformation created by an RCD �see Section 6.7.7�.

Edge Retention—ReliefDue to the relatively high resilience of the cloths, except the steel mesh, a certain edgerounding and relief might develop.

Environment—EconomyAll materials mentioned above can be discarded as normal waste; the cost per speci-men is comparable to SiC paper.

6.8 Grinding/Polishing Equipment

Mechanical grinding and polishing are normally performed on the same type of ma-chines.

Fig. 6.27—Disposable rigid composite grinding disc �RCD� magnetically fixed to a support discwith a permanent magnet.


Only in a few cases machines only for grinding �mostly plane grinding� are sup-plied. For this reason only equipment that can be described as “grinders” are includedin this section. The grinders/polishers are described in Sections 7.8 and 7.9.

6.8.1 Plane Grinding

Manual GrindingPlane grinding using grit 220 �240� or coarser can be done by hand on a rotating disk ofa 200-250-300 mm �8-10-12 in� diameter disk with a grinding paper. The paper canbe placed with a plain back in a water-filled disk, and the paper is sucked to the diskwhen rotating due to the centrifugal force, which moves the water to the outside of thepaper. The paper may also have a self-adhesive backing or a double-adhesive foil can beused.

For the technique of manual �hand� grinding see Section 13.2.4.

Fig. 6.28—Polisher/grinder with two disks �200/250 mm �4/6 in� diameter� and 300 rpm formanual preparation.20

Fig. 6.29—Belt grinder with two workstations for coarse grinding. Adjustable water flow andsink.19


Machines with one or two disks are available and used for both grinding and pol-ishing; two disks can be of advantage when using four steps for grinding with SiC pa-per. Figure 6.28 shows a two-disk grinder/polisher �250 mm �10 in� disk diameter� witha single speed, 300 rpm, for hand grinding on SiC grinding paper.

For a more effective grinding by hand, a belt grinder can be used, built with one ortwo work stations. The belt grinder works with a belt moving on two rolls and with aflow of water; it can be used for both plane and fine grinding. Figure 6.29 shows a beltgrinder with two work stations, water flow system and sink.

Automatic GrindingPlane grinding of specimen holders with six or more specimens can be done on mostautomatic systems, which are described in Section 7.9.

At very large holders with large specimens, it can be an advantage to plane grind on

Fig. 6.30—Semiautomatic grinding machine �grinding stone� for plane grinding with specimenholders. Diameter of grinding stone 356 mm �14 in�, 1450 rpm.20


a grinding stone with a relatively high speed �1450 rpm� and a diameter of 356 mm�14 in�. The machine, shown in Fig. 6.30, is only for plane grinding and fine grinding/polishing must take place on another automatic grinder/polisher.

6.8.2 Fine Grinding

Manual GrindingFine grinding by hand takes place on equipment spanning from simple apparatus withfour strips of grinding paper �Fig. 6.31�, to rotating grinder/polisher as mentioned un-der plane grinding �Fig. 6.28�. Figure 6.31 shows a four stage hand-grinding apparatuswith four strips of SiC grinding paper supplied from rolls for plane and fine grinding.

Automatic GrindingFine grinding of specimen holders either with a number of fixed specimens �centralforce� or individually loaded �single force� takes place on semi- or full-automaticgrinders/polishers described in Section 7.9

Automatic grinding/polishing systems have gained ground because they reducethe work load on the metallographer and produce an overall better specimen quality.Also, the reproducibility is improved, securing that if a certain method is followed, theresult always is consistent.

Fig. 6.31—Four stage hand-grinder for wet grinding on four strips of grinding paper in rolls.19


7Mechanical SurfacePreparation—Polishing

7.1 Polishing: Producing the True Structure

AFTER PLANE GRINDING AND FINE GRINDING THE SPECIMEN SURFACEmust be polished to obtain the true microstructure or a structure, which is satisfactoryfor a given analysis. In principle, the surface always will have a certain deformation�artifacts�, but if not too deep this can often be removed through the etching of the sur-face �see Chapter 9�. For a thorough description of artifacts and how to avoid them, seeSection 13.5/6.

This chapter covers mechanical polishing and chemical mechanical polishing�CMP�. Electrolytical and chemical polishing are described in Chapter 8.

Mechanical polishing is defined as a material removing process with loose abra-sive grains placed on a substrate like a polishing cloth. The abrasive can be added be-fore or during the process and normally lubricant is applied during the process for lu-brication and cooling.

CMP can be defined as a material removal process where the material removaltakes place chemically and mechanically at the same time �see Section 7.12�.

Mechanical polishing is by far the most used process, and depending on the type ofmaterial and the nature of the preceding fine grinding step, one or several polishingsteps are needed �see Fig. 1.7�.

7.1.1 Rough PolishingThis step immediately follows the last fine grinding step and is usually done on a hard,napless cloth with 9 or 6 �m diamond. This step can be compared to the last step of finegrinding done on a hard, napless cloth �see Section 6.7.8�. The rough polishing step isvery important because most of the material, damaged by the grinding, is removed inthis step �see Table 7.1�.

7.1.2 PolishingThe polishing is done in one to three steps with hard, medium hard, or soft cloths withdiamond 3–0.25 �m or finer polishing media, such as silica and alumina, 0.1–0.05 �m�see Section 7.5�, depending on the material to be polished.

7.2 Material Removal

The process of material removal during polishing, micromachining, is considered tobe the same as it is during grinding �see Section 6.2�. According to Samuels7 it seemsthat another mechanism, delamination, takes place when polishing with diamondabrasives below 3 �m. Delamination does not produce the elongated chips that resultfrom micromachining, but small, plate-shaped equiaxed particles are produced. No ex-

120

planations have been advanced for the mechanism by which delamination occurs dur-ing the polishing with the smallest grain sizes.

At micromachining, the abrasive grain is able to produce a chip, implying that thegrain is, at least momentarily, fixed in the polishing cloth, as shown schematically inFig. 7.1. The diamond grain wedges between the cloth fibers with a rake angle sufficientto be able to cut a chip from the specimen surface. To obtain a high removal rate atrough polishing, hard cloths are used, creating a higher load on the grain, giving alarger chip. Using softer, more resilient cloths for the final steps, the load on the grain isreduced, causing smaller scratches and less deformation of the specimen surface.

7.2.1 Influence of Polishing Abrasive on Removal RateFor grinding, the hardness of the abrasive is important. Therefore, diamond is used forboth rough polishing and polishing. For final polishing, alumina �Al2O3�, colloidalsilica �SiO2�, and magnesia �MgO� are also used.

Likewise, the shape of the grain plays a role. Polycrystalline diamonds give ahigher removal rate than monocrystalline diamonds,7 probably because the individualpolycrystalline grain contains more angular points of the size needed to provide cut-ting points than those of monocrystalline.

7.2.2 Force on SpecimensIn principle, the removal rate increases linearly with the increase in specific pressurebetween specimen surface and the polishing surface once a certain low threshold valuehas been exceeded. Using a high force causing a high specific pressure might create arounding of the specimen, and often the lubrication will not be satisfactory and heatmight develop. Also, an increased wear of the polishing cloth will take place. For nap-less, hard cloths the specific pressure should be in the range of 30 to 100 kPa�4.35 to 14.5 psi�; for softer cloths the pressure should be 15 to 50 kPa �2.2 to 7.25

Fig. 7.1—Schematic drawing of an abrasive grain fixed in a fiber of a polishing cloth.

Chapter 7 Mechanical Surface Preparation 121

psi�. Experience has shown that in specimens from 40 mm �1.5 in� diameter and up,the force per specimen should not exceed 50 N �11.5 lbf� to avoid overheating of thecloth and excessive wear. To compensate, the polishing time may be extended1 to 4 min.

7.3 Deformation

Polishing, as mentioned earlier, in principle being the same process as grinding, willproduce shallower deformed layers. With hard cloths with a low resilience, a strongerdeformation will develop than with softer cloths. The depth of the deformed layers isan order of magnitude smaller than that on surfaces ground with SiC paper, as shownby Samuels7 �see Table 7.1�. This shows the importance of the rough polishing step�6 �m diamond�.

For explanations of Dsb, Ds, and Dd see Section 6.3.1.In theory, even the finest abrasive will create a deformed layer. It is, however, pos-

sible to obtain a surface very close to the true structure with the use of very fine abra-sives like alumina �Al2O3� and silica �SiO2� for the final polishing step. Silica, having acarrier liquid with a pH in the range of 8.5 to 11 �see Section 7.5.5� and a grain size of afraction of a micron, will create a combined mechanical and chemical material re-moval �see Section 7.12�.

Deformation in the form of smearing can take place with soft metals, the materialbeing smeared across the surface. For this and other types of deformation, see Section13.6.

In the literature, the very thin deformed layer left by the last polishing step is oftencalled the Beilby Layer. The existence of such a layer is not supported by recent re-search and the use of this term should be avoided; however, to give an impression of themechanisms taking place, a short description of the theories by Beilby31 and Samuels7

will be given in the following section.

7.3.1 The Beilby LayerAt the beginning of the 20th century, Sir George Beilby established the theory of theso-called Beilby layer. This layer was proposed to be of an amorphous nature created bya smeared layer that had passed through the liquid state �Fig. 7.2�.31

The layer would fill out the existing scratches and give the surface its mirror-likecharacter. The layer was thought to have developed due to the very high temperatures

TABLE 7.1—Depth of the Plastically Deformed Layer. Annealed Polycrystalline 30 % Zn Brass by ManualGrinding/Polishing.

Abrasive Grade μm/GritScratches/Dsb, μm Ds, μm Dd, μm

SiC paper 220 2.0/- 7.5 77

SiC paper 400 1.5/- 6.5 43

SiC paper 600 0.8/- 5.0 22

Diamond 6 0.08/0.17 ¯ 1.0

Diamond 1 0.05/0.1 0.7

Alumina, �-type 0–1 ¯ ¯ 2.5

Alumina, -type 0–0.1 0.03/- ¯ 0.7


attained at the points where an abrasive grain touches the specimen surface. This hightemperature, being close to the melting point, would cause the material to melt or be-come very plastic.

According to Samuels7 the layer, which Beilby considered amorphous and couldbe removed by etching, a phenomenon known to most metallographers, is simply de-formed material still remaining on the surface �see Fig. 7.3�. When the original scratchand most of the deformation below the scratch is removed, the polished surface looksperfect. After etching, the deformed material is etched preferentially and the originalscratch seems to reappear. This was supposed by Beilby, but what reappears is not thescratch, but an artifact created by the scratch. It could be called a scratch trace.

7.3.2 Influence of Polishing Abrasive, Cloth, and Fluid on DeformationDeformation will decrease with a lower abrasive grain size as shown in Table 7.1. Thetype of abrasive will play a role, diamond grains, especially on soft materials, will givemore scratches than -type alumina and silica; therefore, the small grain sizes of dia-mond �1, 0, 25 �m� are not used for the final polishing of softer materials.

Hard polishing cloths, without nap, will normally create more deformation thannapped cloths; however, napped cloths might create other artifacts like relief androunding of phases and edges.

The polishing fluid is very important for lubrication, cooling, and removal ofswarf. The lubrication is necessary to obtain a reduced friction between the cloth and

Fig. 7.2—Beilby layer, diagrammatic section of a calcite plate across the line of flow. Theflowed material has completely filled up even the deepest scratches.31

Fig. 7.3—Schematic drawing of Beilby Theory and Local Deformation Theory.7


the specimen surface. The type of lubricant gives different lubricating effects, the oil-based lubricants giving the strongest effect, recommended for softer materials. Thewater-based type gives a medium effect suited for general purpose use, and the alcoholtype gives a low effect suited for brittle materials. The oil-based lubricants also give athin surface film on the cloth that minimizes the damaging effect from the cloth, im-portant for soft materials. The cooling effect of the lubricant is important when manyspecimens at a time under a relatively high pressure are polished. The alcohol- andwater-based lubricants cool most efficiently; the water-based type is preferred. In ex-treme cases, with many specimens with high pressure and a large disk diameter, a spe-cial disk cooling, usually with water, might be necessary to keep the temperature lowenough. When using rigid composite disks �RCD� it is important to have an efficientremoval of swarf to prevent it from damaging the specimen surface. To a lesser degree,this is the case with hard cloths and even less on soft cloths.

7.4 Polishing Cloths

Polishing cloths can be defined as substrates upon which a polishing medium is ap-plied to perform a polishing process. The polishing cloth is supported by a rigid polish-ing disk made of metal or a polymer. As described in Section 7.2, the abrasive grainshould, at least momentarily, be fixed by the cloth, making material removal possible.The fixing of the abrasive can be done in several ways, depending on the structure of thecloth. For hard cloths, the abrasive grains will be placed on the surface of the cloth,placed in hard fibers, securing a more aggressive attack, whereas on a soft cloth, thegrains will penetrate into the nap of the cloth, and a less aggressive material removalwill take place. Consequently, the cloth is a very important factor regarding materialremoval, but also the deformation developed during the process and the edge retentionand relief are strongly influenced by the cloth.

The term pad is often used for certain polishing cloths made of nonwoven material�see below�, but in the following cloth is used as the general term.

A polishing cloth can be characterized through the following:• Material: All kinds of flexible materials can be used. The most used are: Chemotex-

tiles, nonwoven materials, woven nylon, woven acrylates �satin�, woven silk, wovenwool, a backing �often cotton� with synthetic flocked nap.

• Surface Structure: The material can be smooth, porous, perforated, woven, orflocked �nap�. The flocked cloths always have a nap, but other types also might havea napped surface. The nap normally will give the cloth a high resilience �see below�,but with certain cloths a high nap will lay down during use and create a compact,smooth surface with a relatively low resilience. The surface structure mightstrongly influence the polished surface �see below�.

• Resilience: The resilience, the elasticity of the cloth in the vertical direction, dic-tates whether a cloth is hard or soft. All cloths can be compressed when subject topressure from the specimen. A cloth having a low resilience is hard and a cloth witha high resilience is soft. A hard cloth, which can only be slightly compressed, willusually give a high material removal and create deep scratches and more damageto the specimen than a soft cloth. Two cloths, however, with the same low resiliencecan perform differently caused by the surface structure of the cloth. Figure 7.4shows an aluminum/silicon specimen polished on a very hard cloth with an un-smooth, woven surface, shown in Fig. 7.6; the deformations in the Al/Si surface are


strong. Figure 7.5 shows the same specimen polished on a cloth with the same re-silience, but with a relatively smooth, woven surface, shown in Fig. 7.8, the defor-mations are considerably reduced. A soft cloth with nap will normally have a rela-tively low material removal and create little deformation and small scratches. Thenap will make an edge rounding. Also, because of the brushing effect �the fibers ofthe nap brushing the specimen surface�, a relief might develop if the specimen sur-face has phases of different hardness; the softer phase being preferably removed.Polishing cloths are fixed to the supporting grinding/polishing disk with a self-

adhesive backing �PSA� or through magnetism established by a steel foil integrated inthe cloth �see Section 6.7.1�. Cloths can also be fixed by using a retaining ring thatstretches the cloth over the disk. This often causes wrinkles of the cloth and should beavoided.

Polishing cloths are supplied in the following diameters: 73 mm �2.9 in�, 102 mm�4 in�, 200 mm �8 in�, 250 mm �10 in�, 300 mm �12 in�, 350 mm �14 in�, and 400 mm�16 in�. For a table of available polishing cloths, see Section 13.2.2, Table 13.1.

Fig. 7.4—AlSi material after polishing with 3 �m diamond suspension on a very hard cloth witha very irregular surface structure. The surface has deep scratches and strong deformation. Thecloth is shown in Fig. 7.6. BF.

Fig. 7.5—The same material as in Fig. 7.4 after polishing with 3 �m diamond suspension on ahard cloth with a smooth surface structure. The surface has considerably less scratches anddeformation although the abrasive is the same. The cloth is shown in Fig. 7.8. BF.


7.4.1 Edge Retention—ReliefAs described in Section 3.1.3 and Sections 6.6.2/6.7.7, edge retention is often very im-portant and development of a relief should be avoided. The sections mentioned earlierand Figs. 6.15 and 6.16 describe how the resilience, the vertical flexibility of the prepa-ration substrate, is decisive for the development of edge rounding and relief. It is evi-dent that when using a cloth with a relatively high resilience as substrate, the risk ofedge rounding and relief will increase strongly. This means that a good fine grinding,either on SiC grinding paper or on rigid composite disks, might be spoiled if the polish-ing cloths used for the following steps have a too high resilience or the polishing timesare too long, or both. It is important that cloths with the lowest possible resilience toobtain a satisfactory result are used and the times are kept at a minimum. The charac-teristics regarding edge retention and relief will be discussed further for the singlecloths below.

7.4.2 Cloths for Fine Grinding and Rough PolishingThese cloths are all hard with very low to medium resilience. Although primarily usedfor fine grinding and rough polishing, some of the cloths can also be used for final pol-ishing of medium hard and hard materials. They are typically used with diamondsfrom 15–1 �m.

Fig. 7.6—Napless, very hard, woven, coated polyester cloth for fine grinding/rough polishing.SEM.

Fig. 7.7—Napless, hard, non woven, synthetic cloth for fine grinding/rough polishing. SEM.


Edge Retention—ReliefAll cloths for fine grinding and rough polishing, except the woven steel cloth, will have alow, often very low, resilience, which theoretically will cause an edge rounding of thespecimen. In practice, however, if the preparation time is kept inside reasonable limits,the edge retention is high with these hard cloths, which, used with diamond as an abra-sive, give a good flatness without relief.

ClothsWoven Steel: This is a cloth made of stainless steel wire mesh. The resilience is close tozero and consequently the edge rounding is very low. The cloth is used for fine grindingwith 15–6 �m diamond for hard metals, ceramics, and composites.

Woven Coated Polyester �Fig. 7.6�: A napless, very hard, coated polyester cloth foruse with 15–3 �m diamond for fine grinding/rough polishing of metals, composites,ceramics, and hard metals. The resilience is very low giving very little edge rounding.

Nonwoven Textile �Fig. 7.7�: A napless perforated/not perforated nonwoven clothfor use with 15–3 �m diamond for fine grinding/rough polishing of harder materialsand softer materials depending on the resilience of the cloth. On cloths with a certainresilience, an edge rounding may take place after prolonged polishing.

Woven Nylon �Fig. 7.8�: A napless cloth for use with 9–1 �m diamond. Mediumhard and suited for rough polishing and polishing of ferrous materials and cast irons toretain inclusions/graphite and maximize flatness. The very low resilience gives verylittle edge rounding.

Woven Silk �Fig. 7.8�: A napless cloth for use with 9–1 �m diamond. Hard andsuited for fine grinding/rough polishing and polishing of most metals, coatings, andplastics. The low resilience gives good flatness and very little edge rounding.

Woven Synthetic Silk �Acetate� �Fig. 7.8�: A napless cloth for use with 3–1 �m dia-mond. Hard and suited for rough polishing of most metals to maximize flatness withvery little edge rounding and retention of hard phases.

7.4.3 Cloths for PolishingThese cloths have medium to high resilience and are used for one or more polishingsteps, an intermediate step or a final step. They are used with diamond in the6–0.25 �m, mostly from 3–1 �m. Also, some can be used for oxide polishing �see Sec-tion 7.5� for the final step. Some of these cloths are napless; some have naps of differentheight and structure.

Fig. 7.8—Napless, hard, woven nylon, silk or acetate cloth for fine grinding/polishing. SEM.


Edge Retention—ReliefThe polishing cloths, having medium to high resilience and often a nap, will cause anedge rounding of the specimen, depending on the preparation time and force on thespecimen. As a rule the polishing time should be kept as short as possible, with mosttime used on a napless cloth, which gives less rounding, and less time used on a nappedcloth, often only for a short final polishing. The force on the specimen should be kept aslow as possible, especially on napped cloths. In general, the napless polishing clothswill not develop a relief, but the napped cloth might develop relief if phases of differenthardness are present in the specimen surface.

ClothsWoven Wool �Fig. 7.9�: A napless, soft cloth with medium resilience for use with6–1 �m diamond. It is suited for polishing and fine polishing of minerals, glass, met-als, composites, coatings, and polymers. An edge rounding might develop, but it willusually be acceptable. No relief will develop except in extreme cases.

Synthetic Nap on Woven Backing �Fig. 7.10�: A cloth with a medium nap of flockedfibers on a �cotton� backing for use with 6–0.25 �m diamond, alumina, and silica �seeSection 7.5�. This cloth is for general usage for final polishing. The nap and backinggive a very high resilience that will cause rounding of the edges of the specimen surfaceand often create a relief because of the brushing effect �see Section 7.4�. For these rea-

Fig. 7.9—Napless, medium hard, woven wool cloth for polishing. SEM.

Fig. 7.10—Medium napped, soft, with synthetic fibers flocked on a backing, cloth for polishing.SEM.


sons the cloth should only be used for a short time to establish the final specimen sur-face.

Synthetic Nap on Nonwoven Backing: A soft cloth with a dense nap with high resil-ience to be used with 3–1 �m diamond. It is suited for one-step or final polishing of softto hard ferrous and nonferrous metals. The dense nap gives relatively good edge reten-tion in spite of the high resilience and no relief.

Synthetic Porous Material �Fig. 7.11�: A soft, napless cloth with high resilience.The synthetic material �neoprene� is chemically resistant and will take up the very finealumina and silica suspension in the pores, and it is used with oxide suspensions0.02–0.05 �m �see Section 7.5�. The cloth is suited for the final step for most materials.The time should be short to avoid edge rounding. The risk for a relief is very little, but acertain relief might develop because of a chemical mechanical attack from the polish-ing medium.

Woven Felt: A soft, napless cloth with very high resilience used for 9–1 �m dia-mond, alumina, and silica �see Section 7.5�. It is suited for rough and final polishing ofhard metals, cast iron, and mild steels, preserving inclusions. The high resilience willcause edge rounding and possibly relief.

7.5 Polishing Abrasives

The polishing abrasives are used in connection with a polishing cloth for the steps fromrough polishing �fine grinding� to the final polishing step. In general, diamond is usedfor all steps except the last step �final polishing step�. In case of harder materials, dia-monds, down to 0.1 �m also cover the final step, but often, especially with softer mate-rials and composites, a final cleaning step is made with an oxide, normally silica �SiO2�or alumina �Al2O3�.

7.5.1 Diamond SuspensionsDiamond suspensions are described in Section 6.4.

7.5.2 Diamond SprayDiamond spray is described in Section 6.4.

Fig. 7.11—Napless, soft, porous synthetic cloth for polishing with silica and alumina and forchemical mechanical polishing. SEM.


7.5.3 Diamond PasteDiamond paste is described in Section 6.4.

7.5.4 AluminaAlumina �Al2O3� has been the classic polishing medium in metallographic/material-ographic preparation. Earlier it was used for all polishing steps, often causing bad re-sults, because the removal rate is very low. In modern preparation, alumina shouldonly be used for the final polishing steps in grain sizes 1–0.05 �m.

Alumina is available as suspensions and powders with two crystal types, alpha andgamma. The alpha crystal has relatively sharp edges giving the highest removal rates,whereas gamma is more rounded, causing a very small removal rate suited for the lastpolishing step.

Both powder and suspension can be supplied in agglomerated and deagglomer-ated condition. In agglomerated alumina the particles will form agglomerates �Fig.7.12� because of the electric forces between the particles. These agglomerates will givea higher removal rate and might cause scratches in the specimen surface, althoughthey are normally broken down during the polishing. In the deagglomerated aluminathe material is treated to avoid the agglomerates so that only the single particles will beactive �Fig. 7.13�, ensuring an ultrafine specimen surface.

Alumina is available in grain sizes from 5–0.05 �m.

Fig. 7.12—Alumina, agglomerated, the large agglomerates can be seen.

Fig. 7.13—Alumina, deagglomerated.


SuspensionsThese are ready for use either in diluted or undiluted condition. In some cases the sus-pension is stabilized so that the alumina does not come out of suspension when notused. This is an advantage if used in automatic dispensing systems �see Section 7.9.3�.

Alumina can be mixed with silica �see below� to form special polishingsuspensions.

PowdersPowders have to be mixed with distilled or demineralized water to form a suitable sus-pension. In special cases, if water is not allowed for the preparation, the powder can bemixed with other fluids like glycerine or alcohol.

7.5.5 SilicaOriginally developed for the preparation of silicon wafers, colloidal silica �SiO2 in asuspension� has gained ground in metallographic/materialographic preparation. Thegrain size is very small, 0.1–0.02 �m, and the grains are almost spherical and softerthan alumina, causing a very low mechanical material removal making SiO2 very wellsuited for the final polishing step. By comparing the microstructures of an aluminum-silicon alloy �Figs. 7.14 and 7.15�, the effect of silica can be recognized. The strong de-formations from the 3 �m diamond polishing as shown in Fig. 7.14 are removed andboth matrix and silicon are perfectly polished, see Fig. 7.15.

For wafers and many other materials, the colloidal silica suspension works ac-cording to a chemical mechanical polishing �CMP� process. The suspension, having apH between 8.5 and 11, plays an important role in the material removal mechanism inCMP.32

The CMP gives SiO2 suspensions and suspensions based on SiO2 and other oxides,like iron oxide, an increased removal rate on ceramic materials and metal/ceramiccomposites and a number of metals �see Section 7.12�.

A CMP can be established also when mild chemicals like hydrogen peroxide�H2O2� and an ammonia �NH3� solution are mixed into the suspension; this will be de-scribed under each material in the Material/Preparation Tables, Section 13.2.3. In thisway, very soft and ductile materials can be mechanically polished to a deformation-free

Fig. 7.14—AlSi surface after polish with 3 �m diamond suspension, strong deformations inboth matrix and silicon phase. BF.


finish, avoiding electropolishing. Colloidal silica is available only as suspensions with apH 8.5–11 and grain sizes from 1–0.02 �m.

Attention: A colloidal silica suspension should not be allowed to dry on the polish-ing cloth, because it will then be unusable. The polishing cloth shall be carefullycleaned after use to avoid dried-in crystals which will cause scratching of the specimensurface. It can be of advantage to finish the polishing process by running up to 10 s onlywith water to clean the cloth and the specimen; otherwise the chemical attack mightcontinue, resulting in etching of the specimen surface.

7.5.6 Other OxidesMagnesium oxide �MgO�, iron oxide �Fe2O3� �jeweler’s rouge�, chromium oxide �CrO�,and cerium oxide �CeO� are all polishing media which now are used very seldom. Al2O3and SiO2 will in most cases do the same job and are much easier to work with.

7.6 Polishing Lubricants

Polishing lubricants are described in Section 6.5.

7.7 The Metallographic/Materialographic PreparationMethods—Method Parameters

As described above under sectioning, grinding, and polishing, a deformed or otherwisedamaged layer inevitably is formed during the machining processes. The depth of thislayer decreases with decreasing grain size of the used abrasive, and for this reason thespecimen, in the preparation process, goes through a number of steps with each stepremoving the deformations from the previous step. The diagram in Fig. 1.7 shows theprocesses of both mechanical preparation and electropolishing. Figure 13.18 shows atypical process consisting of three stages, sectioning �cutting�, grinding, and polishing.The grinding stage and polishing stage both have two steps, plane grinding/fine grind-ing and rough polishing �Polishing 1� and fine polishing �Polishing 2�. It can be seenthat the deformations from the previous step are removed and the last step ends withvery little or no deformation. The most critical steps are between cutting and plane

Fig. 7.15—The same material as in Fig. 7.14 but polished with colloidal silica after 3 �mdiamond. The deformations are removed and the true structure can be seen. BF.


grinding and between the last grinding step and rough polishing; this is especially thecase when using SiC grinding paper for the last fine grinding step.

It is important that the method is adapted to the specific material being prepared.For an overview of available methods refer to the 67 Traditional and ContemporaryMethods covering most materials that is stated in Section 13.2.3.

The following contains a brief description of the basic methods for most metals�methods used for ceramics and other very hard materials are described in Section6.3.2�.

The grinding stage: As described in Sections 6.6 and 6.7 this book discriminatesbetween “Traditional” grinding based on SiC grinding paper and “Contemporary”grinding based on rigid composite disks �RCDs�. This gives two types of preparationprocedures: The Traditional Methods �T-Methods� based on grit P220 SiC paper forplane grinding and grits P320, P500, �P1000� for fine grinding, and the ContemporaryMethods �C-Methods� based on SiC paper grit P220 for plane grinding, and one or twoRCDs with 9 or 6 �m diamond abrasive for fine grinding.

The polishing stage: At the T-Method the rough polishing step normally is on ahard, napless cloth with 6 �m diamond, a very important step for removal of thescratches and deformations from the grinding. In the C-Method the rough polishingstep is often on a hard, napless cloth with 3 �m diamond for removal of the scratchesand deformations from the RCD. For the T-Method, the rough polishing step is fol-lowed by a 3 �m diamond step on a hard, napless cloth followed by a final step on asoft, napped cloth with 1 �m diamond or on a soft, napless, porous cloth with aluminaor silica. In the C-Method, the rough polishing step is followed by a final polishing asmentioned for the T-Method.

The end result is to a high degree influenced by the consumables used in the prepa-ration, as described earlier in this chapter, but also the parameters of the process playan important role.

In the case of automatic polishing with the use of a specimen mover on a grinding/polishing machine, all parameters, not associated with consumables, are controlled bythe machine �see Section 7.9�. For manual �hand� polishing, only the rpm of the polish-ing disk is a machine parameter.

7.7.1 RPM of Grinding/Polishing DiskThis is typically in the range of 50–600 rpm, but for certain machines with continu-ously variable speed, the rpm can be varied from close to 0 up to 1200 rpm.

The rpm of the disk will, to a high degree, influence the relative velocity betweenspecimen and grinding/polishing substrate. In principle this should be high to secure ahigh removal rate, but experiments have shown �see Section 7.9.2� that at polishing,certain limits shall be observed, and for automatic polishing, 150 rpm is recom-mended. At grinding, however, higher velocities can be allowed corresponding to300 rpm or more.

7.7.2 RPM of Specimen HolderTo obtain the best results, the rpm of the specimen holder should be approximately thesame as the rpm of the disk �see Section 7.9.2�. The direction, whether it rotatescomplementary to or contra to the direction of the disk is important �see below�. Mostmachines have rpm in the range from 3–300 rpm.


7.7.3 Direction of Specimen HolderMost modern grinder/polishers work with the specimen mover rotating in the samedirection as the grinding/polishing disk, complementary �comp�. This makes synchro-nous polishing possible �see Section 7.9.2� securing the best polishing action, avoidingcertain artifacts. If contra rotation �counter rotation� is used, the removal rate is higher,the specimen mover and the disk rotating in opposite directions, but this can only berecommended for grinding, not polishing. Contra rotation is also used to keep the ox-ide suspension on the polishing cloth because then the specimen mover pulls the sus-pension towards the center of the polishing cloth, but according to polishing dynamics,as described in Section 7.9.2, the contra rotation has certain drawbacks, as mentionedabove.

7.7.4 Force on SpecimensThe force �load� on the specimens is important to obtain a satisfactory removal rate. Atgrinding the specific pressure shall be relatively high, in the range of 3 to 10 N/cm2

�4.35 to 14.5 psi� �30 to 100 kPa�, corresponding to a force of 20 to 70 N �4.5 to 15.8lbf� for a 30-mm �1.25-in� specimen.

The pressure will in certain cases influence the degree of deformation, especiallyfor soft, ductile materials. Therefore, the pressure on the specimens shall be lower atpolishing than at grinding, in the range of 14 to 40 kPa, corresponding to a force of10 to 30 N �2.3 to 7 lbf� for a 30-mm �1.25-in� specimen. In principle, the specific pres-sure shall be the same for large specimens, but experience has shown that a maximumforce of 50 N should be established on specimens of 40 mm �1.5 in� in diameter andlarger. This is to avoid an overheating and excessive wear of the polishing cloth. Tocompensate for the loss of material removal, the time can be extended from 1 to 4 min.

7.7.5 Process TimeThe duration of each step basically depends on the amount of material removed fromthe specimen surface �stock removal�. This, however, cannot normally be measured onmost machines, and therefore the process time is used as an indicator. When grinding,the amount of material removed is so high that measurement is possible �see below�,but the removal rate at polishing is so low that measurement on a polisher is not pos-sible. Only by measuring the time can a reproducible process be established. It should,however, be recognized that a specific preparation time does not guarantee that thenecessary material is removed from the surface; this is only the case if the consumablesused react like the consumables when the process was established. Also, parameterssuch as force should be correct to ensure reproducibility.

7.7.6 Stock RemovalThe whole preparation process is based on removal of material from step to step. Theideal way of working would be to measure the material �stock� removed and stop theprocess when the preselected amount, corresponding to the deformations from theprevious step, is removed. This is possible at the grinding steps, removing stock from40 to 50 �m to several hundred micrometres per step. Grinder/polishers with mea-surement of stock removal are available in the market. At polishing, the stock removalis so low �for example, 3 to 6 �m per 5 min� that it cannot be measured without highprecision instruments, which are not usually available on grinder/polishers.


7.8 Grinding/Polishing Equipment—Manual Preparation

The basic polishing machine has a rotating turntable on which an interchangeabledisk, covered with a polishing cloth, is placed. Normally the polishing process will con-sist of two to four steps, including rough polishing, polishing, and final polishing. Insome cases, when the fine grinding has been done with the contemporary method �seeSection 6.7� only one polishing step might be sufficient.

As described in Section 6.8, plane grinding, fine grinding, and polishing can takeplace on the same grinder/polisher only by changing the disk/disk surface used for eachstep. See Section 13.2.4 for the technique of manual �hand� polishing.

The grinder/polisher is a standard piece of equipment that is available in manymodels and sizes. Most models have one turntable for 200 mm �8 in�, 230 mm �9 in��for SiC paper�, 250 mm �10 in�, or 300 mm �12 in� disks, one/two speeds or continu-ously variable speed, a water supply and a drain Figure 7.16 shows a grinder/polisherwith mineral casting base. It will work with 200 and 254 mm �8 and 10 in� disks �plat-ens� and is available in different models with one or two wheels �turntables�. Onemodel has 150 and 300 rpm; another model has 30 to 600 rpm. A grinder/polisher withtwo turntables is also shown in Fig. 6.28.

Very often the grinder/polisher is prepared for retrofitting of a semiautomaticspecimen mover.

7.9 Grinding/Polishing Equipment—Automatic Preparation

If we look at the typical specimen mover system for “automatic polishing,” the correctterm would be “automatic preparation” because polishing is only part of the process.Also the word “automatic” needs explanation, taking into consideration that in mostcases it expresses semi- or part-automation, meaning that only the basic process ineach step is mechanized, all handling of specimen holders, change of disk, cleaning,etc., is done by hand. In some cases, however, the whole process is automated �“fullyautomatic”� as described below. In the following the word “automatic” refers only tothe basic process involving manual work. If the system is “fully automatic,” this will bedescribed.

The reason for using automatic equipment is that hand grinding/polishing is hardand, in the long run, overloads the hand and arm of the metallographer. Automaticpreparation also ensures a better quality of the specimen through a uniform processthat is reproducible. The dependence on the skill of the operator is reduced as well.

7.9.1 Machine DesignThe Englishman I. E. Stead, who continued the work done by H. C. Sorby, already in-vented a rotating specimen holder in 1900 for four specimens mounted on a movablearm so that the holder would sweep the rotating polishing disk.

Many other principles have been suggested over the years, but the “specimenmover” with a number of specimens placed eccentrically on the grinding/polishingdisk is dominating today. A supplement is vibratory polishing �see below�.

The standard specimen mover system is a grinding/polishing machine with a ro-tating disk and a rotating specimen holder placed eccentrically on the disk �see Fig.7.17�. The specimen holder or the individual specimens are pressed against the disksurface to obtain a grinding/polishing action.


Fig. 7.16—Grinder/polisher, with mineral casting base for manual preparation and, as shown,with a specimen mover for semiautomatic preparation, 200/250 mm �8/10 in� disks,150–300 rpm or 30–600 rpm.19


For a specimen holder with several fixed specimens, these are fixed in suitableholes �see Fig. 7.18� and during the operation, a central force is established pressing allthe fixed specimens against the disk surface. The advantage of this system is a goodflatness of the specimens, with the whole holder acting as a large “specimen” thatavoids the angling of the holder in comparison to the disk surface �see below�. The dis-advantage is the work �fixing� involved, and the need for at least three specimens in theholder to keep the balance. In the event that only one specimen is to be prepared, “blindspecimens” must be used. Also, the plane grinding may be prolonged to obtain that allspecimens are in the same plane. The microscopic inspection of the specimens duringthe preparation process is rather tedious, having to put the whole holder on the micro-scope.

The alternative is that specimens are placed in a holder plate and individuallyloaded and called “single specimen preparation” �Fig. 7.19�. The advantage is easy han-dling and being able to take out a specimen after every step of the preparation for in-spection. The disadvantage is a tendency to “angling,” the specimen being only at-tacked in one direction, or “penciling,” the specimen being attacked along theperiphery, especially when grinding on SiC paper �see Fig. 7.20�. In the first moments ofthe grinding the SiC grains will create a very strong pull in the specimen surface causedby the grains removing very much material in the first seconds �see Section 6.6�. Thetendency will be to remove most material at the edge where the grains move into thespecimen. As soon as an unevenness has been made, the specimen might start rotating

Fig. 7.17—Specimen holder placed eccentrically on the grinding/polishing disk.

Fig. 7.18—Specimen holder with fixed specimens and central load.


around its own axis and penciling will take place, or it might stay without rotation cre-ating angling. Penciling and angling can be suppressed by working with as low speci-mens as possible and establish the smallest possible distance, d in Fig. 7.20, betweenholder plate and disk surface. Also, an exact guidance of the specimen in the holderplate will suppress the angling.

The force on the specimens can be established through compressed air or by me-chanical means. With central pressure the force is transferred through the center of thespecimen holder. By individual load, a pressure foot will be lowered against each speci-men �see Section 7.7.4�.

A number of parameters should be controlled during the process �see Section 7.7�.On simpler systems, the operator sets the rpm of the disk and the force. The rpm of theholder is mostly fixed, and in some cases the direction, complementary or contra, canbe set. The operator will stop the machine after a certain period of time.

On more advanced systems all parameters are controlled through a microproces-sor and programmed before the start of the process. This makes storing of programs�methods� possible so that a method, once developed, can be reused whenever neces-sary. The microprocessor also may control other parameters such as dosing of abrasivesuspension and lubricant �see Section 7.9.3�.

The fully automatic systems are based on the above; only several preparation stepsincluding cleaning and drying are programmed as a process. This means either thedisks are changed automatically during the process or a certain number of disks areavailable in the machine �see Section 7.9.3�.

Fig. 7.19—Specimen holder plate with specimens placed in holes without fixation andindividually loaded �single specimens�.

Fig. 7.20—Schematic drawing of a single specimen placed in the holder plate on a grinding/polishing disk. If the distance d is too long, angling or penciling will take place at grinding onsurfaces with fixed abrasives.


7.9.2 Polishing DynamicsAs described above, the most common way of automatic polishing is placing the speci-mens in a specimen holder which rotates eccentrically on a polishing disk �Fig. 7.21�.As the dynamics between grinding/polishing disk and specimen holder have a certaininfluence on the preparation result, these dynamics shall be briefly described. It is evi-dent that the relative velocity between the surface of the polishing disk and the surfaceof the specimen will depend on three factors: rpm of the disk, rpm of the holder anddirection of rotation.

Two systems that are quite common can be compared.

�1� Polishing disk: 150 rpmSpecimen holder: 30 rpmComplementary �comp� rotation

�2� Polishing disk: 150 rpmSpecimen holder: 149 rpmComplementary �comp� rotation

Comparing the velocity vectors in Fig. 7.21, we see that for system �1� the velocityvectors are one-sided, causing a nonuniform material removal. This phenomenon iseven more pronounced during contrarotation.

In system �2� the vectors cover all directions causing a uniform removal.This means that certain conditions, the optimum dynamic conditions �ODC� can

be defined.33 ODC will be when the relative velocity is constant during a full revolutionof the specimen holder �synchronous polishing�, as can be seen in �2� �Fig. 7.21�. If therpm of the grinding/polishing disk is higher than the specimen holder, ODC is not ful-filled and the preparation might result in having artifacts like comet tails �see Section13.6�.

Fig. 7.21—Polishing dynamics for a specimen holder eccentrically placed on a grinding/polishing disk. Velocity vectors for two specimen holders, 30 rpm and 149 rpm are shown.


7.9.3 Semiautomatic and Fully Automatic SystemsConsidering that automatic preparation is useful, even with an output of very fewspecimens, semiautomatic and fully automatic systems can be considered very impor-tant. They are supplied in different sizes, catering from one to six specimens or more ata time.

The tendency is to include as many parameters as possible in the automatic pro-cess, still maintaining the manual change of the disk and handling �cleaning� of thespecimen holder with the semiautomatic systems.

With the microprocessor a programming of all parameters is possible.

Small Semiautomatic SystemsThe small systems will handle one to three specimens at a time on a 200 or 150 mm �8or 10 in� disk. The load is mostly supplied by a spring or a weight. In some cases a timercontrolling the process is available.

Figure 7.22 shows a grinder/polisher for low volume semiautomatic preparation,preparing one specimen at a time. Figure 7.23 shows a specimen mover for low volume

Fig. 7.22—Automatic grinding/polishing system for one specimen at a time.19


semiautomatic preparation mounted on a grinder/polisher, preparing up to threespecimens at a time. Specimens with very low deformations especially suited for EBDS�see Section 7.10� can be produced.

Medium to Large Semiautomatic SystemsThese systems carry the work load in most laboratories. They work with 250, 300, 350,400 mm �10, 12, 14, 16 in� disks and specimen holders for six specimens or more, andmostly rpm, force, and process time can be controlled and preset �see Section 7.7�.

A dispensing system �see below� may also be included in the controls so that thetotal preparation sequence including dosing of abrasive and lubricant can be pro-grammed. The possibility of a permanent storage of programs for different materialsmight be included as well, and newer systems allow for connection to a local net �LAN�and for establishment of databases with preparation methods. It is even possible todownload preparation methods from the Internet and use them directly.

Figure 7.24 shows a semiautomatic system consisting of a number of grinder/polishers, specimen movers and a dosing unit. The system is microprocessor con-trolled allowing for connection to a local network �LAN�, sharing preparation methodswith other users.

Dispensing ApparatusDispensing �dosing� of abrasive and lubricant is part of the preparation process. Basi-cally, the operator can perform this before and during the process, but especially add-ing lubricant during the process that ties the metallographer to the machine is againstthe idea of automatic preparation. Therefore, most semiautomatic systems have alubricant-dispensing �dosing� unit connected to the system, in this way adding smallamounts �adjustable� in regular intervals �adjustable� to the disk surface during theprocess.

To obtain a constant removal rate it is an advantage to apply the abrasive, prefer-ably as a diamond suspension, during the process. This can be done with dispensing

Fig. 7.23—Specimen mover for one to three specimens, 8 rpm and force 2–20 N.20


�dosing� units available for one or several bottles of suspension/lubricants. An oxidepolishing suspension can also be part of the suspensions to be applied, but this needs awater cleaning system as part of the dispensing unit.

The more advanced semiautomatic preparation systems include the control of adispensing unit.

Stock RemovalStock removal �controlled material removal� is sometimes included in the control sys-tems covering the grinding steps �see Section 7.7�.

Fully Automatic SystemsThese systems include all tasks of the preparation process. All parameters for the pro-cess are programmed and stored permanently before the start, and the automatic pro-cess includes: grinding, dispensing of abrasive and lubricant, cleaning and drying ofspecimen holder after every step, change of grinding/polishing surface, and polishingin several steps. In some cases stock removal can also be programmed. The goal is tosupply a specimen ready for the microscope.

In some cases the specimen holder with specimens is plane ground on another ma-chine before going into the automatic system. In other systems, the plane grinding ispart of the automated process.

Figure 7.25 shows a fully automatic system that combines the function of a semi-

Fig. 7.24—Modular preparation system with single and central pressure, available in threedifferent disk sizes, 200-, 250-, and 300-mm diameter. Equipped with an automatic dosing unitand programmable with preparation methods.20


automatic grinder/polisher, a dispensing system, an ultrasonic cleaner, and specimendryer in one compact unit to be placed on a tabletop. It has single and central pressure,and it is programmable with permanent storage of methods.

Vibratory Polishing SystemsVibratory polishing is an alternative to the specimen mover described previously. Itwas originally developed for use in the hot cells preparing radioactive materials. Thereason was the very simple design without rotating parts, cutting maintenance down toa minimum.

Vibratory polishing is based on the principle of a vibrating plate in the shape of abowl. A number of specimens, typically up to twelve, are mounted in weights andplaced face down on the polishing cloth, covering the plate. The bowl shape takes carethat a suspension, mostly Al2O3 or SiO2, stays on the cloth. The vibration has both avertical and horizontal movement, normally established with an electromagnet. Thismeans that the single specimen, caused by the inertia, moves slowly along the periph-ery of the bowl, in this way being polished through the movement between cloth andspecimen. By adjusting the amplitude of the vibratory movement, the speed around thebowl can be controlled and set according to sample size and weight. The polishing ac-tion is very low, suited for sensitive materials making a scratch-free surface possiblewith very low deformation. Due to the low removal rate, a normal final polishing stepwill take several hours in which the apparatus can be left unattended.

Figure 7.26 shows a heavy duty vibratory polisher with variable settings.

7.10 Special Preparation Techniques

7.10.1 PCB CouponsPrinted circuit boards �PCB� are often metallographically/materialographically in-spected to ensure the quality of the metal layer in the holes of the board. For this pur-pose a so-called coupon is made �see Fig. 3.17�.

PCB coupons to be tested according to the American standard IPC-TM-650 shouldbe prepared so that the prepared surface is exactly through the middle �diameter� of theholes to be inspected. This is usually done by mounting several coupons on two preci-sion pins using two reference holes �see Section 3.11.5 and Fig. 3.17�. The two precisionpins can be used as contact surface in a special specimen holder so that the coupons areplaced exactly in relation to the holder. In this way the target �the middle of the inspec-tion holes� can be reached by using a number of adjustable stops on the holder. Thestops are calibrated according to the surface on which the pins are resting, in this waysecuring that the process stops before the target is reached. Normally a rough SiCgrinding paper is used for the first step, the grinding being stopped 100 to 200 �mfrom the target. By readjusting the holder the next step with a finer SiC paper will stopvery close to the target. According to the type of PCB, the grinding steps shall be fol-lowed by one or more polishing steps. These steps are made without stops because thematerial removal at polishing is very low, minimizing the risk of removing too muchmaterial from the PCB. For a preparation process, see Method T-27 in Section 13.2.3.

7.10.2 Microelectronic Materials—Nonencapsulated Cross SectionsMicroelectronic materials are cross-sectioned to a specific point �target� for both lightmicroscopy and scanning electron microscope �SEM� examination.


Cross sections serve two main functions:34

• Cuts through representative structures within an IC show relationships of layersand features, such as step coverage, interfaces between layers, and possibly em-bedded defects or voids.

• Precision cross sections through specific defects often lead to the process step ormechanism that produced the defect.

When applicable, nonencapsulated cross-sectioning is simpler and faster than the classi-cal encapsulated method. Results of nonencapsulated cross-sectioning are more suitablefor viewing ina scanningelectronmicroscope.

The passivation layer of the IC provides sufficient encapsulation of malleable met-allization to prevent smearing. Rounding of the front edge is avoided by using hard, flatgrinding and polishing surfaces.

Tripod Fixture—The ProcessCross sections can be prepared with the relatively simple tripod fixture where the speci-men is the third leg on a fixture �see Fig. 7.27�. Cross sections can also be prepared on

Fig. 7.25—Fully-automatic, microprocessor controlled grinding/polishing system, with built-indispenser, ultrasonic cleaner, and specimen dryer. Programmable, with permanent storage ofmethods.19


semiautomatic systems and fully automatic systems; both are commercially available.In the following only the use of the tripod fixture will be described �see also

Material/Preparation Tables 22, Section 13.2.3�.SiC paper �600 grit� was used originally to grind to within 20 to 30 �m of the tar-

get. Polishing from that point was accomplished solely and slowly on a glass disk.34,35

However, the need for faster throughput and the introduction of hard tungsten plugsnecessitated new polishing media and techniques.

The procedure described below using a hand-held tripod fixture is basic, simple,and fast. It produces excellent results that can be imaged on either standard or fieldemission SEMs.

The grinding procedure described involves several short steps with Al2O3 and dia-mond lapping film starting with relatively coarse grits. Satisfactory results can be ob-tained by grinding longer with fewer steps, but the procedure will be tedious if the over-all grinding time is increased by using fine grain sizes to remove material slowly.Additionally, if the grinding time is excessive, the material removal rate may decreaseas grinding/polishing media wear and it is difficult to judge whether enough materialhas been removed.

Cross sections wider than the 5 by 5 mm �0.20 by 0.20 in� in width will requiresignificantly longer grinding and polishing times. The use of worn out grinding mediashould be avoided; fresh, finer grain size grinding/polishing media may have a fasterremoval rate than coarser, worn media.

Even if a cleaved edge is close to the desired final line such that no grinding is re-quired, a brief grinding on grit P4000 �US grit 1200� is recommended to make a flatsurface. Grind only as necessary to create a flat surface, even if a part of the surfaceremains untouched. Jagged edges on a cleaved sample, if not removed, will scratchaway the Al2O3 or diamond from the film.

Equipment and ConsumablesA tripod fixture with the specimen mounted on a sample mount �paddle� �see Fig. 7.27�is used by hand on the rotating grinding/polishing disk of a grinder/polisher with a200 mm �8 in� disk and variable speed, preferably 10 to 150 rpm �see Section 7.9�.

Fig. 7.26—Heavy duty vibratory polisher, horizontal vibratory movement, with variablesettings.19


A stereomicroscope and a metallurgical microscope with measuring abilities arerequired to check the progress of the preparation process.

Sample mounts are used for carrying the sample �specimen� during the prepara-tion steps and for the analysis in SEM. The process involves grinding paper and lappingfilms, Al2O3 and diamond, and for polishing diamond suspension and a polishingcloth. Dry nitrogen �or a supply of aerosol cans� is required to blow the specimens dry.

Preparation, See also Method C-22, Section 13.2.3Sectioning can be done on a precision cut-off machine with a diamond wheel �see Sec-tion 2.5�. The desired cross section target should be within 50 �m of one edge. The sili-con piece is then attached to a sample mount such that the edge containing the target isparallel to and extending over the edge of the sample mount �cantilever fashion�, plac-ing the specimen on a hot sample mount �125°C �250°F�� using wax, as shown in Fig.7.28.

Grinding takes place in three to four steps. The purpose of grinding is to rapidlyachieve a surface, 1 �m away from and parallel to the desired cross section line �tar-get�.

The surface left by grinding, later to be polished, should be flat and scratchesshould be no greater than those caused by 1 �m Al2O3 or diamond particles onAl2O3/diamond films. The grinding procedure typically requires less than 15 min in-cluding inspection time.

In Method C-22 the total preparation process is described. It is important that thespecimen is adjusted so that the ground surface is parallel to the cross section line �tar-get�. The time in minutes is not stated at the grinding steps, but the distance remainingto the target. This is to ensure that all deformation from the previous step is removedand to ensure that the target is not reached in a too early step.

Polishing is used when a very fine finish is wanted. Microelectronics with metalsystems of Al �no tungsten� or gold �no tungsten� are polished using a 0.05 �m Al2O3lapping film or a soft, napped or napless, porous cloth using colloidal silica as the abra-sive. In case of metal systems with Al/W and Au/W, polishing is done with a napless,hard, woven synthetic cloth and 0.1 �m diamond suspension or a napless, soft, porouscloth with 0.1 �m diamond suspension mixed in a 50:50 solution with colloidal silica.

Fig. 7.27—Tripod fixture, the specimen is placed as one of three “legs” of the handheld-holder.


7.10.3 Microelectronic Packages—Table 7.2—Target PreparationElectronic and microelectronic assemblies are complex material composites. The ma-terials used are dissimilar in their chemical composition, their crystal structure, andtheir microstructure. Of technical importance for the qualification of the componentsare interfaces, grain boundaries and phase boundaries as well as heterogeneous pre-cipitations. Imaging and analysis of the microstructure is a prerequisite for estimatingthe quality of a component. Further criteria for qualification, from the materialo-graphic point of view, are inclusions, contaminations, pores, cracks, holes, as well asthe evaluation of contours, e.g., the wetting angle of a soft solder connection.36

Due to the close packaging of electronic and microelectronic devices with manyvarious materials within a small volume, microstructural examination is faced withthe problem of simultaneously imaging different materials that have very differentproperties. Specimen preparation therefore involves the simultaneous processing ofhard, often brittle materials and soft materials exhibiting plastic deformation. The ma-terials most used in advanced integrated circuit packaging and interconnection tech-nology, their use and hardness �HU, see Section 21.5� are listed in Table 7.2.37

Each of the materials stated in Table 7.2 has its specific properties and, as can beseen, the hardness is very different and often the materials are brittle. This must betaken into consideration during the materialographic preparation; each individualstep from cutting through grinding to the final polishing step is of significance. Mis-takes made in the first stages of preparation can only be corrected during the subse-quent steps with considerable difficulty or not at all. For each step the rate of materialremoval and the deformation layer which remains are important factors. The prepara-tion parameters used �grinding surface, type of abrasive, grain size, lubricant� must becarefully selected on the basis of the physical properties. The general rules for thepreparation of solid materials are that soft and medium-hard materials should beplane ground using SiC grinding papers, whereas hard materials require resin-bonded

Fig. 7.28—Microelectronic specimen mounted on a sample mount for a tripod fixture.


disks with fixed diamond grains or rigid composite disks �RCDs� with added diamonds.Very often for the devices described herein, both extremely hard and very soft materialsmust be prepared at the same time, and in such cases the preparation must be based ona compromise. The goal of the preparation is to obtain a flat specimen without reliefbetween the different constituents and good edge retention, while at the same timeavoiding deformation and other artifacts of the soft and brittle constituents. If only SiCgrinding papers are used for grinding of hard materials, then edge rounding and reliefwill set in at an early stage. Plane grinding and the first steps of fine grinding should bedone with the hardest possible abrasive suited for the hardest materials in the speci-men and always using the finest grain size possible. Often SiC paper should not be usedwith a grit coarser than P500 to avoid damage to the brittle materials in the specimen,and during both grinding and polishing the pressure should be kept low to avoiddamage.36

In the Material/Preparation Tables 19–26, Section 13.2.3, eight methods are indi-cated covering the preparation of different electronic components. To be able to selectthe method best suited for a given component, it shall be analyzed before the prepara-tion starts to be able to decide on the best method and how the preparation shall beperformed.

Inspection and Location of Fail Site—Target PreparationBefore the preparation starts, the structure of the assembly should be studied by visualmacroscopic methods to decide on the materials involved and to locate critical sitesand the locations of both obvious and possible defects to be marked. Typical fail sites�targets� include: poor solder joints, cracks in components, or defects in the circuitboard material. These faults are then investigated more closely using other techniques

TABLE 7.2—Materials Used in Electronic and Microelectronic Devices and Interconnections.

Material

Common Applications inMounting and Connection

Technology Universal Hardness (HU)

Al2O3 ceramic Carriers (hybrid technology),body of components

17000

Silicon Semiconductors, transistors, ICs 9300

Nickel-phosphorus (NiP) Resist layer, metallization 4000

Kovar (FeNiCo) Lead frames, circuit board core 1900

Invar (FeNi) Lead frames, lead wires 1800

Aluminum (Al) Housing, heat sinks, capacitorfoils

1300

Copper-silver (CuAg)solder

Solder (brazing) 1100

Gold (Au) Surface finishing layers,(connectors, solder, adhesive andwire bond contacts)

500

Tin-silver (SnAg) solder Soft solder 300

Copper (Cu) Metallization on circuit boards,lead frames

300

Epoxy-fiberglass sheet Circuit board material 280

Tin-lead (SnPb) solder Soft solder 230


like radiography, ultrasonic imaging, fine and gross leak testing, and die penetration.The orientation of the plane of preparation will depend upon the orientation or thefeatures to be imaged and is often marked on the assembly plan. If the fail site �target�has been located then this will determine the plane of preparation, often starting withthe sectioning close to this plane. Special apparatus for target preparation is availablein the market.

Sectioning and Mounting „Encapsulation…Sectioning must be done so that the site of interest is not damaged by deformation orinput of heat. Therefore, very often the device is mounted �encapsulated� before thesectioning takes place. Encapsulation shall be accomplished with only a low develop-ment of heat and the resin shall be able to fill out all cavities without shrinkage. Thismeans that an epoxy with a low viscosity should be used, preferably under vacuum sothat an impregnation takes place �see Section 3.10�. It is very important that the speci-men is cleaned very effectively in acetone, preferably using ultrasonics before the en-capsulation. After cleaning, the specimen should only be handled with a pair of twee-zers and dried with N2 or absolutely clean air, not normal compressed air.

Sectioning and mounting are described in detail in the Material/PreparationTables 19 to 26.

7.10.4 EBSDElectron backscatter diffraction �EBSD� has gained ground in recent years as an acces-sory to a scanning electron microscope �SEM�. The main advantage of EBSD is thepossibility to link morphology �grain size and shape� with crystallographic features�phase, orientation, disorientation� on the microscopic scale, but still in a representa-tive specimen area.38 The preparation is much simpler than for thin foils for TEM �seeSection 8.6�, but more demanding than that for normal SEM.

The information depth of EBSD is very low, in the range of 20–370 nm dependingon material, SEM, etc. This means that the surface of the specimen shall be without thethin distorted layer that normally exists after a mechanical polishing �see Section 7.3�.This can be obtained by etching, but etching should often be avoided for EBSD. Forcertain materials electrolytic polishing can give a deformation-free surface, but formany materials like ceramics, heterogeneous materials, etc., mechanical preparationis the only possibility to obtain a flat and distortion-free surface.

For this reason the standard grinding/polishing process shall be adjusted, espe-cially with regard to the last polishing step. In principle, the normal method used for aspecific material can be used with special attention to the last polishing step usingsilica, which often is prolonged. A long preparation time using silica as an abrasivemight give an unwanted relief, and therefore polishing cloths must be chosen verycarefully.

Specimen Mover SystemsThe most used specimen mover �standard system� for normal metallographic/mate-rialographic preparation has a specimen holder rotating eccentrically on the grinding/polishing disk �see Section 7.9�.

The preparation methods described in Section 13.2.3 are based on the use of thisstandard specimen mover, normally operating with 150 rpm �grinding/polishing diskand specimen holder� and a force per specimen not lower than 5 N �1.1 lbf�. This sys-tem will give acceptable results for EBSD for very hard materials like ceramics, possi-


bly using chemical mechanical polishing �CMP� �see Section 7.12�.For most materials, however, it is not possible to obtain a distortion-free surface

after the last step, and this step either has to be prepared on a special slow movingspecimen mover or by vibratory polishing.

Specimen movers with very low rotation and force per specimen are commerciallyavailable. The rpm of both the disk and specimen holder can be adjusted to a relativevelocity close to zero �see Section 7.9.2� and the force on the specimen down to close tozero. This means that all metals can be prepared for EBSD in a reasonable time, oftenusing CMP, see under the specific materials in Section 13.2.3. CMP is also needed forhard materials like certain ceramics. For specific preparation data for a high number ofmaterials see Ref. 38.

Vibratory SystemsVibratory polishing normally gives good results for EBSD; the main drawback beingthe very long preparation times, although the vibratory polisher can work unattended.

If vibratory polishing is used for all steps including grinding, a high surface wavi-ness can be observed and due to the long polishing times a relief can develop. There-fore, vibratory polishing should be limited to the last step, having done the previoussteps on the standard specimen mover or the slow specimen mover described above.38

7.11 Field Metallography/Materialography—NondestructiveMechanical Preparation

Field metallography is, as the term indicates, used in the field, often called in situ or onthe spot. It is based on the grinding and polishing processes described above; portableapparatus is available that is able to prepare a small area nondestructively. Field metal-lography is used on large parts, steam pipes, etc., to be able to check the microstructurewithout destructing the work piece. Very often it is not possible to analyze the preparedspot and a replica is taken �see below�. The preparation methods and etching proce-dures to be used can be seen from Table 11.1 and Section 13.2.3.

Many materials like steel, aluminum, and titanium are very well suited for electro-lytic polishing using a portable electropolisher �see Section 8.5�.

7.11.1 Portable Grinder/PolishersThese are available with a hand piece with a flexible rotating disk upon which a smallpiece of grinding paper or polishing cloth is placed. This apparatus can be suppliedfrom the mains or battery operated. The normal preparation process in a number ofsteps is employed and normally, after etching, the prepared spot is analyzed with a por-table microscope to ensure that the microstructure is acceptable for further examina-tion. Following this, a replica is made. This replica is taken to the laboratory for exami-nation.

Often the grinder/polisher is used for the preparation of a spot that is finallyelectropolished/etched to obtain the microstructure �see Section 8.5�.

7.11.2 ReplicationReplication is a very important part of nondestructive preparation. Replication is anondestructive procedure that records and preserves the topography of a materialo-graphically prepared surface as a negative relief on a plastic film or other medium �rep-


lica�. See also the ASTM Standard Practice for Production and Evaluation of Field Met-allographic Replicas �E 1351� �Section 12.4�.

The replica material shall have a number of characteristics:• All features present on the surface that was replicated shall be accurately repro-

duced.• Simple and reproducible handling.• High stability and strength.• Flexibility so that replica can be made on curved surfaces.

Replicas should be made either using a piece of plastic �acetate� film or a fast cur-ing silicone rubber-based material.

Plastic FilmThe film or foil is 12 by 18 mm �0.5 by 0.75 in� in size. Two methods can be followedwhich are described in Section 13.4.3.

Silicone RubberThe silicone rubber-based material used is a two-component silicone rubber that isavailable in different types according to the specific purpose.

The compound is supplied in cartridges that are mixed and dispensed on the pre-pared surface using a special hand-operated gun. The silicone rubber is very flexible,suited for curved surfaces, inside tubes, etc. The material is also very suitable for engi-neering inspection applications like microcracks, wear marks, corrosion marks, etc.For use of silicon rubber, see Section 13.4.3.

7.12 Chemical Mechanical Polishing

Chemical mechanical polishing �CMP� has been highly developed for the preparationof silicon wafers, but CMP is also used with advantage for other materials.

In CMP, also called etch polishing or attack polishing, the specimen surface is at-tacked both mechanically �by an abrasive� and chemically at the same time.32 Nor-mally an abrasive suspension with an in-mixed chemical substance is used. Materialremoval occurs as a consequence of a combination of the chemical reaction of thechemical with the specimen surface material and the continuous removal of the reac-tion materials by the abrasive. Because of the removal of the reaction products, evenchemical solutions that typically would not attack a given material will have an effectbecause the passivating layer is constantly removed. CMP is established either by usingsuspensions of silica �SiO2� often with a pH between 8.5 and 11 or alumina �Al2O3�,with a pH between 3 and 7, or by mixing a chemical solution, often an etchant, with theoxide suspension.

CMP, using a very fine abrasive like silica with a grain size of 0.02/0.05 �m, and arelatively weak chemical attack, will create surfaces almost without deformation andscratches. This means that CMP is very well suited for the final polishing step for mostmaterials, creating a clean surface. Especially in soft and ductile materials this is anadvantage. The polishing will take place on a relatively soft, porous polishing cloth, andtherefore the time shall be limited to 0.5 to 1.5 min.

Aluminum, refractory metals, Ti, and other metals can be polished with silica withor without an added chemical. Also, ceramics and other materials with high abrasion


resistance are suited for CMP; both acidic alumina suspensions and basic silica can beused.

For some materials like Ti and most Cu alloys, the final polishing step can be madeusing a silica suspension with the addition of hydrogen peroxide and ammonia solu-tion. Ferrous metals and Ni-based alloys can be polished with acidic alumina. If the pHshould be lowered, oxalic acid can be added, and if the pH shall be raised a chemicallike potassium hydroxide can be added.

For solutions used for the specific materials, see the Material/Preparation Tables,Section 13.2.3.

With the modern advanced methods of preparation, CMP is mostly limited to thesuspensions and solutions mentioned earlier. CMP, however, can be performed with avery high number of chemical solutions, mostly etchants.2,9

7.12.1 Protection—Corrosion at CMPWhen using the chemical solutions recommended in this book �see Section 13.2.3� thecorrosive attack on equipment and accessories is minimal. In the case of suspensionsmixed with stronger chemicals �acids�, care should be taken to protect equipment andpersons working with the mixture. Also, only synthetic polishing cloths made for CMPshould be used.

7.13 Thin Sections

For certain materials such as minerals, ores, ceramics, and plastics, the use of reflectedlight for microscopic examination is not always satisfactory. By using thin sectionswith a thickness of 20–35 �m �down to 7–10 �m at plastics and polymers� it is pos-sible to examine the specimen in transmitted light, and if the thin section is polished,also in reflected light.

To make a thin section a high amount of material must be removed by cutting,lapping/grinding, and polishing. The process is time consuming and extreme careshould be taken not to make changes in the material of the thin section.

Below follows a short description of thin section preparation for petrographic/ceramic materials and for plastics/polymers.

7.13.1 Thin Sections of Petrographic/Ceramic MaterialsThe preparation of thin sections can be done on machines and consumables availablein the market. In the following a method as shown in Fig. 7.29 is described. Often im-pregnation of the material is needed before the cutting or the preparation, or both, cantake place. For this and for a further description of the cutting, lapping, and polishingsee Material/Preparation Tables �M/P T� 39 and 40 for petrographic/mineralogical ma-terials and M/P T 02–06 for ceramics.1. The specimen to be sectioned is selected often from a larger piece.2. The specimen is sectioned normally with wet abrasive cutting using a diamond

metal bond cut-off wheel. The size of the specimen depends on the size of the glassslide used �see below�.

3. For minerals, one side of the specimen is lapped in two steps with SiC powder, gritP220 and P1000, on a cast iron disk to obtain a plane surface; normally this is donein a special specimen holder plate on a semiautomatic grinder/polisher. For ce-ramics, grinding and polishing of one side are made as described in M/P T 02–06.


4/5. A glass slide 27 by 46 mm, 28 by 48 mm or 30 by 45 mm is ground to a giventhickness, e.g., 1.164 mm on a special machine with a diamond grinding wheelor lapped in a holder as described in No. 9 below.

6. The specimen, with the prepared side towards the glass, is glued to the glass slideunder vacuum using epoxy.

7. The surplus material of the specimen is removed by cutting with a diamond cut-offwheel to a thickness of about 0.5 mm �0.02 in�.

8. The mineralogical thin section is ground down to 80–100 �m on a special ma-chine with a diamond grinding wheel, or only lapped as described under No. 9.Ceramics are ground according to M/P T 02–06 to a thickness of approximately80 �m.

9. Mineralogical materials are lapped with SiC powder on a cast iron disk in a specialholder on a semiautomatic grinder/polisher so that the finished section has athickness, including the resin layer, of e.g., 30 �m. The holder has built-in sticks ofboron carbide or diamond so that the process stops when the section has the thick-ness that is wanted. If the thin section has been ground down to 80–100 �m on aspecial machine, lapping only with grit P1000 SiC powder is needed. If all materialshall be removed by lapping, two steps are used, grit P220 and grit P1000. Ceram-ics are fine ground and polished down to 5–30 �m depending on the ceramic. Thepreparation procedure follows M/P T 02–06.

10. If the thin section is to be polished, this is done in a special holder so that the finalthickness is in the range of 20–25 �m.The finished thin section can now be examined in reflected light. For examination

in transmitted light, a cover glass shall be placed on the polished surface.

7.13.2 Thin Sections of Plastics/PolymersThin sections are made when plastics and polymers are required to be examined bytransmitted light or contain hard inclusions. Most often unfilled plastics and polymerscan be examined in the form of thin microtome slices �see below�. If carefully prepared,the thin sections made by grounding/polishing will be less damaged than a thin micro-tome section so it is to a high degree the purpose of the examination that decides whichmethod to use. In the following a method for preparing thin sections39–41 is describedthat is based on the methods stated in Material/Preparation Tables 64 and 65, Section13.2.3.1. A specimen with good edge retention is made.2. A thin slice is cut from the prepared side of the specimen. See Material/

Preparation Tables 64 and 65.3. The prepared side of the slice is glued to a glass slide with an adhesive while not

disturbing the specimen material and without air bubbles.4. Grind down manually or in a holder to about 20 �m from the required thickness.5. Fine grind to about 5 �m from the required thickness.6. Polish with 3 �m diamond and finish with alumina, step P 3 in Method C-64 to a

thickness of 10–15 �m.For examination in transmitted light, a cover glass is placed on the polished sur-

face; this is not needed for reflected light.As mentioned above, thin sliced specimens of plastic and polymers can be made

with a microtome, where the slice is cut in a thickness of 3–30 �m, generally around10 �m. For further information, see Refs. 40, 41 and Section 7.14.


Fig. 7.29—Method for preparation of petrographic/ceramic thin sections. 1. Sampling. 2.Cutting of a specimen. 3. Lapping of the specimen. 4./5. Grinding/lapping of glass slide. 6.Cementing of specimen to glass slide using epoxy under vacuum. 7. Cutting of surplus material.8. Grinding on a special machine of thin section, or lapping as shown in 9 down to 80 �m 9.Lapping of thin section in a special holder down to e.g., 30 �m �section and resin layer�. 10.Polishing in a special holder down to approximately 25 �m. 11. The finished thin section.


7.14 Microtomy—Ultramilling

Both microtomy and ultramilling are mechanical preparation processes comparableto grinding and polishing, and made on relatively sophisticated equipment. In mostcases the specimen, soft metal, or other soft materials can be examined without furtherpreparation.

Microtomy is developed for preparation of biological specimens for transmittedlight. In this case the thin section is made by moving the specimen with a controlledfeed into a fixed tool �knife�. In this way a section of a thickness of 0.5 to 60 �m can bemade, suited for examination in transmitted light. This method can be used for prepa-ration of plastics as described in Section 7.13.2 and for preparation of bone, teeth, andother organic materials.

When used for metals the microtome produces a surface comparable to a planegrinding or polishing for examination in reflected light. To justify the use of a micro-tome and ultramilling �see below� the finished surface should be of a high quality, readyfor the microscope. Soft, nonferrous metals up to a hardness of 150 HV can be pre-pared on very stable microtomes using special knives with hard metal or diamondedge.

Microtomes are commercially available.In ultramilling the specimen surface is prepared not with a knife but with a rotat-

ing milling tool.The specimen is placed on a sledge traveling underneath the milling head consist-

ing of a vertical, rotating spindle equipped with a diamond cutting tool. The rotationalspeed of the spindle is adjustable between 500 and 3000 rpm. The feed between speci-men and milling tool can be adjusted in steps from 1 �m, securing a very fine surface.Also the speed of the sledge can be adjusted according to the properties of the specimenmaterial. The process is done in two steps, pre-milling with a special cutter, where thedeformations from sectioning, etc., are removed, and the finishing step using a millingtool which leaves a very smooth surface ready for investigation.

Ultramilling equipment is commercially available.


8Electrolytic Polishing/EtchingELECTROLYTIC POLISHING OR ELECTROPOLISHING „ANODIC POLISHING…is a polishing method whereby the specimen is placed as an anode in an electrolytic celland the electrolysis establishes a surface suitable for metallographic analysis.

In principle, electropolishing is the ideal polishing method because no deforma-tions are added to the surface during the process, and most or all deformations intro-duced before the polishing are removed. Also, the process is done in a very short time,usually in 5 to 20 s.

The electrolysis has some effects that unfortunately limit the use. Most pure met-als and a vast number of alloys can be electropolished, with special advantage to metalsthat are relatively difficult to polish mechanically, such as aluminum/aluminum alloysand copper/copper alloys. But as soon as the material has several phases with a certaindifference in potential, the results are not satisfying. To limit the negative influence ofthe electrolysis by shortening the process time, the specimen is usually mechanicallyground and sometimes polished before the electropolishing.

An advantage with electropolishing is the possibility of electrolytic etching of thespecimen as part of the process.

8.1 The Electrolytic Polishing/Etching Process

Electrolytic polishing is the anodic dissolution of the specimen surface in an electro-lytic cell �see Fig. 8.1�.42 An electrolytic cell is used very often for depositing a coatingon a work piece, the cathode, removing the material from the anode; in this case a pol-ishing of the anode barely takes place. It is, however, possible to control the conditionsin the cell so that a “smoothing”, removal of all large-scale irregularities �above 1 �m�,takes place. This is followed by a “brightening” which is a removal of all submicro-scopic irregularities down to approximately 0.01 �m, establishing a surface of the an-ode without irregularities that is suited for microscopical examination. The amount of

Fig. 8.1—Schematic drawing of an electrolytic cell, showing the anode, cathode andelectrolyte.

156

material removed is so small that the metal ions stay in the electrolyte without beingdeposited on the cathode.

A number of factors play a role for obtaining the right conditions for polishing:• Shape of polishing chamber, position of anode and cathode.• Voltage.• Anode current density.• Electrolyte composition and temperature.• Flow of electrolyte.• Condition and area of the specimen surface.• Polishing time.

The process, especially the brightening, is not fully understood, but the supposedprocess is described in the following.

8.1.1 The Polishing CellThe specimen surface normally has been ground on SiC grinding paper or on a dia-mond disk, �grit P500 or finer�, before electropolishing �see Chapter 6�. In some cases,however, it is possible to go straight to electropolishing from the cut-off, but in mostcases a fine grinding, as mentioned, and even a rough polishing is needed. The surfacebefore electropolishing will in all cases have “hills” and “valleys” as shown in Fig. 8.2.This figure shows the development of the process from the rough ground surface to thefinished surface �see further explanation below�.

The specimen is placed in an electrolytic cell �Fig. 8.3� shown schematically withthe specimen as anode, a thermometer for temperature control, a stirrer to obtain anelectrolyte flow, and a cooling vessel around the cell to keep the temperature constant.The dc voltage is controlled by a potentiometer, the voltage and amperage can be mea-sured on meters, and a timer will control the process time.

8.1.2 Smoothing and BrighteningTo explain the theory behind the process, an ideal polishing sequence based on an elec-trolytic cell using a potentiostat is used. The resulting current-density curve is shown inFig. 8.4 with the developments on the specimen surface as shown in Fig. 8.2.

When starting the process in the cell shown in Fig. 8.3, by increasing the voltagefrom 0 V towards Point B �Fig. 8.4�, at first a direct anodic dissolution takes place. AtPoint B, a viscous film is developed and an electroetching of the specimen surface takesplace, removing very little material �see Section 9.5�. When the voltage/current densityreaches the level of Point B an unstable condition develops until Point C, where a stableplateau is established with increasing voltage. At this plateau the previously developedviscous film, having a passivating effect, reaches equilibrium, enabling a smoothing ofthe specimen surface �see Fig. 8.2�. The material removal by diffusion through the vis-cous layer will be higher at the tops of the hills, the current being higher, because thediffusion path is shorter than at the valleys. This creates a smoothing of the surface.The best polishing takes place between C and D on the curve. With increasing currentdensity, D towards E, oxygen bubbles develop and make openings in the viscous layer,creating pitting in the specimen surface. Close to D the gas development is still rela-tively low and polishing may take place, but at E the amount of bubbles will totallydestroy the film and polishing is not possible.

The presence of the viscous layer, however, cannot explain the brightening of thesubmicroscopic irregularities. On many examinations it has been proven that a thinsolid film will arise on the surface of the anode, which will play an important part dur-

Chapter 8 Electrolytic Polishing 157

ing the polishing. This film is considered to have a thickness of a few atom layers and isvery difficult to identify with regard to its composition. Some scientists think the filmconsists of metal oxide, but a final proof of that has not been obtained. The presence ofthe film, however, must be taken for granted. The very thin film follows very exactly thesurface of the anode �specimen� and the decrease of metal ions will be the same every-where. This will cause a removal of the quite small irregularities.43

The voltage/current density curve at a cell without potentiostat will not show thesame distinct plateau. Figure 8.5 shows a curve taken from polishing of mild steel on acommercial electropolisher.

Fig. 8.2—Schematic drawing showing the surface of the specimen during the different stepsdeveloped during the electrolytic polishing and etching. The letters A to E refer to the curve inFig. 8.4.


8.1.3 Electrolytic EtchingFor many materials, the etching process can take place as a continuation of the polish-ing but at a lower voltage. The low voltage, usually around one-tenth of the polishingvoltage between A and B on the curve �Fig. 8.4� creates a weak attack on the specimen

Fig. 8.3—Schematic drawing of an apparatus for electrolytic polishing/etching.

Fig. 8.4—Theoretical curve showing current density versus voltage during the process ofelectrolytic polishing/etching.


surface, preferably attacking the grain boundaries �see Fig. 8.2�. In some cases, likewith stainless steel, the polishing electrolyte cannot be used for etching, and etchingmust be performed with another electrolyte outside the polishing chamber �see Sec-tion 9.5�.

8.1.4 Advantages and DisadvantagesAt the time when specimen preparation to a high degree was based on manual polish-ing with alumina, with long polishing times, the quality of the achieved preparationresult was relatively low. Therefore, when electrolytic polishing was commercially de-veloped around 1950, it gained ground for many years because the quality was higherthan with alumina polishing. A number of artifacts developed during electropolishing,problems with edge retention, etc., were accepted as “necessary evils.” With the devel-opment of diamond polishing, rigid composite grinding disks and better polishingcloths, the quality of mechanical polishing has increased considerably, and the weakpoints of electropolishing can hardly be accepted for a number of materials, even whenmechanical polishing normally takes more time than electrolytic polishing. With softermaterials, relatively difficult to polish mechanically, the electropolishing still has anadvantage.

Electropolishing should be performed on commercially available polishers, spe-cifically developed for that purpose. In principle, electropolishing can be performed inany electrolytic cell, but because of the risk of fire, explosion, spill, etc., the commer-cially developed apparatus provides better safety and good, reproducible results �seeSection 8.4�. The following descriptions relate to the use of a commercialelectropolisher.

Advantages• Etching included: For most materials it is possible to include the etching as the last

step in the process.• No deformation: The process leaves a clean, undistorted surface, not adding defor-

mation to the specimen surface. This is an important feature when doing researchwork which is surface-related, or for preparing surfaces for micro hardness test-ing, X-ray studies and electron microscopy.

• Fast: The method is very fast. The polishing, which takes place after mechanicalgrinding and in some cases rough polishing, only takes 5 to 15 s for the polishingand 2 to 10 s for etching �if possible�. This can be very important in quality control.

• Reproducible: When all parameters of a procedure are established, the process canbe exactly repeated giving reproducible results.

Fig. 8.5—Current density/voltage curve at electropolishing of mild steel.


• Automatic: The modern electropolishers are totally automated so that all param-eters are programmed before the process starts. This secures that the operation istotally independent of the operator. Also, a number of different methods can besaved in the database of the apparatus.

Disadvantages• Nonuniform material removal: The different phases in the specimen surface will

have a different electrochemical potential. This means that the material removalwill be different from phase to phase �preferential attack�, the more anodic phasehaving the biggest removal rate. An example is gray cast iron, where the graphitewill stand in relief relative to the matrix. Also, at inclusions a problem exists. SeeFig. 8.6 showing mild steel polished mechanically �a� with visible inclusions, andelectropolished �b� with inclusions partly removed. This takes place because the

Fig. 8.6—Mild steel mechanically polished with the inclusions clearly visible �a�, and elec-trolytically polished with the inclusions partly removed by the polishing process �b�.


current density will increase around the inclusion so that material from the matrixis preferably removed which causes a relief or even a dropout of the inclusion �seealso Fig. 1.6�.

• Low removal rate: The removal rate is relatively low, so in case of deep deformationin the specimen surface, the polishing time must be long, causing different arti-facts to develop �see below�. Caused by the low removal rate, the deformationsfrom the grinding scratches are not removed and they are visible in the surface, asshown in Fig. 8.7. This can be avoided if the grinding is done with a finer grit up toP4000, or even a rough polishing with 9 or 6 �m is performed.

• Bad edge retention: Even when the edge of the specimen is protected with a lacqueror mounted, the edge will be preferentially attacked and rounded �see Fig. 8.8�.

• Limited polished area: Depending on the available amperage restricting the cur-rent density, the polished area is limited. Short time polishing performed on com-

Fig. 8.7—Surface with deformations from grinding still visible after electrolytic polishing.

Fig. 8.8—Edge rounding after electrolytic polishing.


mercial electropolishers takes place at 1 to 2 A/cm2 �0.16 A/in2�. In most cases apolisher is made for a maximum amperage of 10 A �see below�.

• Artifacts—Unplane Surface: Due to the different potentials mentioned above, allvariations in the specimen material tend to cause artifacts like increasing the sizeof pores, preferential attack of differently oriented grains and pitting �see Fig. 1.6�.The surface is often not plane but wavy, which causes problems at high magnifica-tions. See also Sections 13.5.4 and 13.6.5.

8.2 Electrolytes

The electrolyte is an important factor in the electropolishing process. A good electro-lyte should have a number of characteristics to support a good polishing and etching.When choosing an electrolyte for polishing a metal, certain basic principles must betaken into consideration. The electrolyte must have a low viscosity since the viscositydetermines the quality of the viscous layer that forms on the specimen surface. It mustbe a good solvent for the anodic material under the prevailing electrolytic conditions.The formation of any insoluble reaction products that deposits on the specimen sur-face interferes with the polishing operation. The electrolyte should, preferably, not at-tack the metal in the absence of the current, but it is not always possible. Similarly,preference will be given to an electrolyte that can be used at room temperature, and islittle affected by changes in temperature, because in practice it is difficult to controland maintain an exact electrolyte temperature during the polishing operation. Lastly,the electrolyte must be stable and safe to handle.

The most used electrolytes are based on perchloric, phosphoric, hydrochloric, orsulfuric acids mixed with ionizing solutions like acetic acid, alcohol, or water. Perchlo-ric acid �HClO4� is by far the most universal acid suited for polishing of a great numberof metals. Unfortunately HClO4 is a very dangerous substance that can cause explo-sions, especially when mixed with acetic anhydride ��CH3CO�2O�. It is safe, however, touse perchloric acid if the correct recommended recipes are used and the necessary pre-cautions are taken �see Section 13.3.2, Table 13.2�. Nevertheless, use of perchloric acidis not permitted in some laboratories. If possible, an electrolyte that is mixed with per-chloric acid and acetic acid �glacial� should be avoided. The temperature of a perchlo-ric acid electrolyte should not exceed 30 to 35°C �90 to 100°F�.

It is practical to limit the number of electrolytes used in a laboratory from one tothree, covering most materials. With a general purpose electrolyte based on perchloricacid covering aluminum/Al alloys, steel, stainless steel, zinc, lead, magnesium, tita-nium, and other metals, supplemented with an electrolyte based on phosphoric acidcovering copper and copper alloys, most needs should be covered.

These two electrolytes are:No. 1-1 �Table 13.2� 78 mL perchloric acid �60 %�, 90 mL distilled water, 730 mL

ethanol �96 %�, 100 mL butylcellosolve �ethylene glycol monobutyl ether�.The perchoric acid which must be shipped and stored separately, should be added

to the mixture of ethanol, butylcellosolve, and water immediately before use.This electrolyte has a lifetime of around two months according to use.Attention: With this and other perchloric acid electrolytes, they should never be

allowed to become more concentrated by evaporation of one or more of the compo-nents �water/ethanol� during storage or use.

No. 3-2 �Table 13.2� 250 mL phosphoric acid, 500 mL distilled water, 250 mL etha-


nol �96 %�, 50 mL propanol �n-propanol, 100 %�, 5 g urea �carbamide�.Water, ethanol, and propanol are mixed and the acid is added under constant stir-

ring.For more electrolytes see Table 13.2, ASTM Standard Guide for Electrolytic Pol-

ishing of Metallographic Specimens �E 1558� and Refs. 2,4, and 9.For Safety Precautions, see Section 26.2.

8.3 Electropolishing in Practice

As already mentioned above electrolytic polishing has some limitations, but also has anumber of advantages. Before deciding on the use of electropolishing for a given mate-rial a number of factors should be evaluated that are given below. See also Section13.5.4 and 13.6.5.

8.3.1 Factors Influencing Electrolytic Polishing

MaterialThe material must be electrically conductive and, if mounted, a good electrical connec-tion should be secured. At the same time, the mounting material around the specimenshould not be conductive �see Section 3.2.2�.

ElectrolyteThe right electrolyte composition for a given material should be selected.

The Area to be PolishedWhen using a commercially available electropolisher �see below�, the specimen isplaced on a mask, defining the area to be polished. The area should be in relation to thevoltage/amperage �current� available. The smaller the area, the better, giving the bestpolishing conditions and the lowest development of heat. Typically an area of1 to 2 cm2 �0.16 to 0.32 in2� is polished.

Voltage/CurrentThe voltage depends on the type of material and electrolyte. Usually the voltage creat-ing the necessary amperage �current� to establish the correct current density is set.

The Flow of the ElectrolyteIt is important that the reaction products established on the specimen surface duringthe process are removed continuously and the temperature in the polishing chamber iskept low. This is done by circulating the electrolyte through the chamber. At the sametime it is important not to create any air bubbles that are caused by a flow rate that istoo high.

The Temperature of the ElectrolyteThe temperature should be kept as close to room temperature as possible. This givesthe best polish with high reproducibility. If the electrolyte is heated to temperaturesabove 30 to 35°C �90 to 100°F�, the process deteriorates and with electrolytes withperchloric acid and ethanol, the risk of fire and explosion will increase. Therefore, if


more than a few polishings are done in a short period of time, the electrolyte must becooled.

TimeThe polishing time should be as short as possible to avoid the negative effects of theelectrolysis. For this reason it is important to prepare the specimen before theelectropolishing.

8.3.2 Example of Electrolytic Polishing/EtchingSee Method E 1-01, Section 13.3.6 stating a much used method for steel.

8.4 Electrolytic Polishing Equipment

Electropolishers have been commercially available for many years, both for normalpolishing in the laboratory and as portable polishers for polishing on the spot. Also,apparatus for electrolytic thinning of specimens for TEM is available �see Section 8.6�.Only electropolishers for normal polishing for laboratory use will be described below.

8.4.1 Electropolishers for Laboratory UseThese are usually built in two parts: a polishing table, the cell where the actual polish-ing is done, and an operating unit containing electronics and software.

The Polishing TableThe main components �see Fig. 8.9� are: the polishing chamber with cathode and maskupon which the specimen is placed, the electrolyte container with a pump circulatingthe electrolyte, driven from outside the electrolyte container with a magnet, coolingcoil, and a contact beam making anodic contact to the specimen.

The specimen is placed with the surface to be polished against the exchangeablemask. The mask has a hole of 0.5 to 5.0 cm2 �0.08 to 0.8 in2�, allowing contact betweenthe electrolyte and the specimen. The cathode of stainless steel is placed in the bottomof the polishing chamber and during the polishing/etching the pump circulates the

Fig. 8.9—Schematic drawing of a polishing table for electrolytic polishing.


electrolyte through the chamber in a laminar flow. This flow can be adjusted. Often thepump is driven magnetically as shown to avoid corrosion of metal parts. A cooling coilof stainless, acid resistant steel is placed around the pump, through which cooling wa-ter can be circulated to keep the electrolyte temperature constant, normally between20 to 30°C �70 to 90°F�. In certain cases a cooled liquid is circulated making polishingat sub 0°C �32°F� temperatures possible. The container is exchangeable, and in thisway the electrolyte can be stored covered with a lid when not in use. This allows for theleast possible handling of the electrolytes.

The Operating UnitThe operating unit has controls for all process parameters and a power supply. Using amicroprocessor, storing of polishing methods is possible that saves time when differentmaterials are to be polished.

ElectropolishersElectropolishers are only made by a few suppliers; an example is shown in Fig. 8.10. Ithas electrolyte temperature control and a load simulation mode for preselection ofpolishing/etching voltages. Input to power source is 1 kVA.

8.5 Field Metallography—Nondestructive Electropolishing

One of the very first commercially available electropolishers in the 1940s was made fornondestructive polishing. Only a spot of 1 mm �0.04 in� in diameter was made, allow-ing the tested product to be sold as “new.” This was done in the laboratory or at themanufacturer, but today nondestructive polishing is mostly “in the field,” “on the spot”�in situ�, used for inspection of work pieces such as steam pipes still in function.

For the right type of materials �see earlier in this chapter� electropolishing is wellsuited for nondestructive on the spot polishing because the polishing time is short.Normally the same electrolytes and data are used as for normal electrolytic polishingdepending on the type of polisher used �see Section 13.3.6�. In most cases the spot to beexamined is first treated mechanically �see Section 7.11� to secure a deformation-free

Fig. 8.10—Electrolytic polisher/etcher with electrolyte temperature control and a loadsimulation mode for pre-selection of polishing/etching voltages. Input to power source is1 kVA.19


surface after electropolishing/etching. Often a replica is taken after polishing and etch-ing �see Sections 7.11.2 and 13.4�.

Portable polishers consisting of a “pencil” with a polishing chamber to be pressedagainst the work piece and a unit supplying electrolyte and an electric current are com-mercially available.

8.6 Electrolytic Thinning for TEM

In a transmission electron microscope �TEM�, normally a 3-mm �0.118 in� diameterspecimen is used. This specimen must be very thin to allow for the TEM analysis, andelectropolishing is suited for thinning of conductive metal specimens. By electrolyticthinning a hole is made in the specimen, and the edge of this normally is very thin, asshown in Fig. 8.11.

The specimen is normally thinned first by grinding so that a 3-mm �0.118-in� diam-eter disk with a thickness of 0.5 to 0.1 mm �0.02 to 0.004 in� can be thinned. The thin-ning is a normal electrolytic polishing as described above, except the thinning, in mostcases, takes place on both sides at the same time. This can actually be done in a glassbeaker, positioning the specimen as anode, with a lacquer to cover the edges so thatonly the center is polished. This “window” technique is stopped when a hole is estab-lished in the specimen, and it is quickly taken under water to avoid further attack. Thismethod is relatively laborious, giving less reproducible results; therefore, the commer-cial jet thinners have been developed. See Fig. 8.12 which shows a cross section of thepolishing chamber. The specimen is placed in the middle in a movable holder. On eachside of the specimen holder a nozzle holder is placed with a nozzle leading the electro-lyte flow toward the sides of the specimen. A cathode is placed at each nozzle. The pro-cess is observed from one side either by watching or with a photocell reacting to thelight which breaks through the hole in the specimen created by the polishing process.The light comes from a light source placed behind the specimen, and when the photo-cell is “hit” the process stops automatically, ensuring a very small hole in the specimen.

Electrolytes and data from normal electrolytic polishing can often be used, but in

Fig. 8.11—Specimen of bronze for TEM. Electropolished with jets from two sides, 87 mA, 7.4 V,5 min and 50 sec, electrolyte No. 3-2 �Table 13.2�, electrolyte temperature 5°C �41°F�.


certain cases special electrolytes and temperatures, considerably below room tem-perature, are needed to be able to effectively control the process. See the literature onelectrolytic thinning.44

8.7 Chemical Polishing

Chemical polishing is a relatively simple method, comparable to electrolytic polishing,only without an electric current. It is a process based on the electrolytic action thattakes place when a chemical solution gets into contact with the metal surface �see alsoSection 9.4.1�. The chemical polishing solutions are developed so that material is re-moved from the surface of the specimen in much the same way as in electrolytic polish-ing. This means that chemical polishing has the same disadvantages as mentionedabove under electropolishing. The polishing is made by immersing the specimen intothe polishing solution often combined with a rubbing to remove reaction products.

Due to the disadvantages of the method and the trouble/danger with handling ofchemicals, chemical polishing is not used much. With certain sensitive materials, how-ever, like cadmium, lead, zinc, tin, and zirconium, chemical polishing might be usefulwhen mechanical polishing or electropolishing are unsuccessful. See the literature,Refs. 2 and 9 for further information and for chemical polishing solutions.

Fig. 8.12—Schematic drawing of a polishing cell for electrolytic jet polishing for TEM. Thespecimen placed in a holder for quick removal, is attacked from both sides simultaneously,having two cathodes and the electrolyte in two jets conducted towards the specimen. Using aphotocell instead of an eye, the process can be switched-off immediately when the lightbreaks through the specimen, assuring a very small hole in the specimen.


9Etching

9.1 Microetching—Contrast

MICROETCHING IS ETCHING OF MICROSTRUCTURES TO BE OBSERVED BYmagnification higher than 25� �50� in Europe�. For macroetching, see Section 9.7.

In the bright field illumination �BF� of the light microscope, a preparedmetallographic/materialographic specimen will only show certain features like inclu-sions, nonmetallic phases �graphite�, pores, cracks, etc. It is usually not possible to seethe microstructure because the light is reflected equally from the bright surface.

Figure 9.1 shows a steel specimen, unetched �a�, and chemically etched �b�, theetched surface revealing the grains of the microstructure �see also Fig. 1.10�. To obtainan image with the structure details, a contrast between the elements in the microstruc-ture has to be established. The contrast can be caused by a number of methods �see thediagram Fig. 9.2�. The most important of these methods will be further discussed in thefollowing sections. Chemical microetching of metals is covered by ASTM StandardPractice for Microetching Metals and Alloys �E 407�, see also Section 12.5. For furtherstudy see the literature, Refs. 2, 4, 9, 21, 26, 27, 45–49.

9.2 Contrast Without Surface Modifications—MicroscopeTechniques

In the bright field illumination �BF� of the light microscope only structure details thatdiffer in reflectivity from one another can be distinguished from each other. For thisreason special microscope techniques have been developed, making it possible to ob-serve certain details that cannot be observed in BF. See also Part III of this book.

9.2.1 Dark-Field Illumination „DF…In dark-field illumination, the light beam is angled to the specimen surface, making itpossible to observe details like inclusions and scratches that stand in relief to the sur-rounding structure. This can be of advantage when observing some features, such aslightly etched grain boundaries and light scratches �see Fig. 15.10�.

9.2.2 Differential Interference Contrast „DIC…This illumination technique uses a beam splitter to direct two beams towards the speci-men surface. This makes even very small differences in height �relief� visible, and DICcan be used with great advantage using relief polishing �see below�, in this way avoid-ing an additional “etching” process �see Fig. 15.14�.

9.2.3 Polarized Light „POL…Using polarized light the microstructure of anisotropic metals such as zirconium andtitanium can be observed without any treatment of the prepared surface. For isotropic�cubic� metals, polarized light can be used when an anisotropic surface film is estab-

169

lished on the specimen surface. In some cases a chemically etched surface can also beobserved on an anisotropic material �see Fig. 15.12�.

9.2.4 FluorescenceSome materials emit radiation when illuminated by certain types of light. Fluores-cence can be used to distinguish pores and other surface details �see Section 3.10 andFig. 3.14�.

9.3 Contrast with Surface Modification—Etching

To obtain the necessary contrast so that a surface can be observed in bright field in areflected light microscope, a treatment, often called “etching” must take place. Themost used method is “chemical etching” based on an electrochemical attack of the sur-face, but “electrolytic etching” and other methods such as “physical etching” are alsoused �see Fig. 9.2�.

9.3.1 Grain Contrast EtchingTo obtain grain contrast etching, certain grains in the specimen surface are influenced.Figure 9.318 shows �1� a grain in relief caused by relief polishing �which could also beestablished by ion etching �see below�; �2� grains which are differently attacked by the

Fig. 9.1—Unetched steel specimen. �a� Only the inclusions can be seen. �b� Etched in 3 % Nital�100 mL ethanol 96 %, 3 mL nitric acid 65 %� revealing the grains.


etchant; �3� a grain covered by an interference layer �film� that is selectively deposited;�4� a layer deposited independently of the grains; and �5� the film deposited accordingto the orientation of the grains.

9.3.2 Grain Boundary EtchingIn this type of etching the grain boundaries only are attacked �see Fig. 9.3�. Figure 9.3shows: �6� a grain boundary attacked by chemical etching; and �7� a grain boundaryafter treatment under heat and vacuum.

9.3.3 ReproducibilityDuring the preparation of the specimen, the process of making a contrast shall be re-producible. It is important that the “etching process” does not introduce artifacts, but

Fig. 9.2—Diagram showing the methods to create surface contrast.

Fig. 9.3—Schematic drawing of grain contrast “etching.” �1� Relief polishing, �2� grainsdifferently attacked, �3� grain covered with interference layer, �4� layer depositedindependently of the grains, �5� film deposited according to the orientation of the grains, �6�grain boundary etch, �7� grain boundary treated under vacuum and heat.

Chapter 9 Etching 171

ensures that the true structure is revealed. This is particularly important when imageanalysis is to be performed on the specimen in question �see Part IV�.

Typical artifacts developed during etching are stains if the specimen surface wasnot properly cleaned after the last polishing step. Also pitting and other artifacts can bedeveloped at over-etching.

9.3.4 Safety PrecautionsEspecially in chemical etching it is important to take necessary safety precations. Be-fore using or mixing any chemical, all product labels and pertinent Material SafetyData Sheets �MSDS� should be read and undertood concerning all of the hazards andsafey precautions to be observed �see Section 26.2�.

9.4 Classical Etching

9.4.1 Chemical EtchingThe most commonly used method for creating the necessary contrast in the specimensurface is chemical etching, also called dissolution etching.2,4,9,21,26,45–47

Chemical etching is a process based on the electrolytic action that takes placewhen a chemical solution �etchant� is in contact with a metal surface. The etchant, nor-mally having a “reduction” component that is usually an acid, an “oxidizer” compo-nent, and a “modifier” component, causes an electric potential between differently ori-ented grains, different phases, grains and boundaries, inclusions, and matrix, etc. Thedifference in attack, which is the amount of material removed from the single details,reveals the structure. For electrolytic etching, where the specimen is placed as an an-ode in an electrolytic cell, the applied current acts as the oxide component.

A number of etchants for chemical etching are stated in Table 12.2.

9.4.2 Precipitation „Color… EtchingThis etching method, also called color etching or tint etching, uses a chemical etchantthat reacts with the specimen surface and deposits a very thin insoluble film. The filmacts as an interference layer producing colors in bright field illumination and polarizedlight. Variations in the grains influence the observed colors. Precipitation etching re-quires a high quality of the prepared specimen; even small scratches or deformationswill be visible when the film is established.46,47

9.4.3 Heat TintingOxidizing will take place on the surface of metal specimens that are heated to tempera-tures in the range 250 to 700°C �500 to 1300°F� in air. The oxidized film will vary inthickness according to the variations in the specimen material. If the layer is thickerthan 30 nm, interference colors can be seen in the bright field of the microscope. Heattinting is not suited for carbon steels and low-alloy steels, but works well with high-alloy steels, tool steels, stainless steels, titanium, and other metals.

9.5 Electrolytic Etching

9.5.1 Anodic EtchingAnodic etching, also known as electrolytic etching, is in principle the same as chemicaletching, except in this case the specimen is placed as an anode in a galvanic cell. This


means that material is removed from the specimen surface, causing an etching and nota polishing as with electrolytic polishing �see Fig. 8.1�. The etching takes place becausethe voltage and current density are low �see Fig. 8.4�.

Frequently, electrolytic etching can be performed as the second step of thepolishing-etching process, using a voltage of approximately 1/10 that used as the pol-ishing voltage. In many cases, however, the electrolyte suited for polishing cannot beused for etching. In this case, electrolytic etching often takes place using a stainlesssteel vessel connected as a cathode containing the etchant. The specimen is handledwith a pair of tongs, connected as an anode, and a suitable low direct current is estab-lished between the cathode and anode. An example is etching of stainless steel that canbe electrolytically etched in an electrolyte �etchant� of 10 g oxalic acid in 100 mL water,using a voltage of 6 V in 10 to 15 s. A number of etchants for electrolytic etching arestated in Table 12.2.

9.5.2 AnodizingDuring this process that is closely related to electrolytic etching/polishing, a layer, oftenan oxide film, is established on the surface of the specimen �see Fig. 9.3�3–5��. This in-terference layer will produce a colored image in bright field illumination and with po-larized light. The layers can be related to the layers created at precipitation etching,heat tinting, and vapor deposition.

9.5.3 Potentiostatic EtchingA reproducible, selectively working electrolytic etching is made with an electronic po-tentiostat and a reference electrode. With the potentionstat it is possible to establish aconstant potential at the specimen surface �anode�.

Because of the controlled etching process, potentiostatic etching is very wellsuited for selective etching of desired microstructural constituents with high repro-ducibility.

9.6 Physical Etching

9.6.1 Relief PolishingIn some cases it is possible to establish a contrast by relief polishing that creates a smallrelief between the grains or the grain boundaries, or both �see 1� in Fig. 9.3�.

Relief polishing is often done with a relatively resilient cloth �see Section 7.4� and avery fine polishing medium like colloidal silica or alumina �see Section 7.5�. Relief canalso be established through chemical mechanical polishing �see Section 7.12�.

Relief polishing should only establish a very small relief between the single grainsor other constituents, not to disturb the microstructure; therefore, often DIC is usedwhen examining relief polished surfaces �see Section 9.2.2�.

9.6.2 Ion EtchingThis method, also called ion beam etching, uses an ion bombardment of the specimento remove material from the single grains, depending on orientation and phase compo-sition. Ion beam etching can be used for thinning of specimens for transmission elec-tron microscopy �TEM� as an alternative to electropolishing �see Section 8.6�. It is,however, also suited for etching microstructures, especially of nonconductive materi-als for materialographic examination.48 The ions, often argon, are supplied in a strong


vacuum �10–4 mbar� by an ion gun towards the specimen which is often placed so thatthe surface is bombarded under an angle.

9.6.3 Thermal EtchingThermal etching takes place at high temperatures in an oven with an inert atmosphereor vacuum. Both metals and ceramics can be thermally etched. During the processgrooves are formed in the grain boundaries/phase boundaries and grain surfaces arecurved. The method can be used at high-temperature microscopy for metals, but ther-mal etching is mostly used for etching of ceramics taking place at temperatures be-tween 1000 and 1400°C �1800 and 2500°F�.26

9.6.4 Vapor DepositionInterference films can be established on the specimen surface by vacuum deposition ofa suitable material. This method �Pepperhof� will enhance the irregularities in the pol-ished surface and the structure will be visible through the interference between thelight reflected from the top of the film and the specimen surface. The film materialsshall have a high refractive index; ZnS, ZnTe, ZnSe, and TiO2 are often used. The pro-cess takes place in a chamber with a vacuum of about 10–5 mbar.49

9.6.5 Sputtering

Sputtering—Cathodic DischargeInterference layers �films� can be produced by sputtering. In sputtering, materials likecarbon, gold, or gold-palladium alloys are atomized by bombarding a surface �target�with high energy particles. Positively charged gas ions produced by electrical discharge�1 to 5kV dc� are accelerated by a potential difference between the anode �specimen�and cathode �target� so that they bombard the cathode, thereby dislodging atoms thatleave the surface in all directions. These atoms settle on the specimen surface wherethey form the desired layer. If undesirable reactions with the target material shall beavoided, the process shall take place at 0.03 to 0.05 mbar in an inert gas like argon.49

Reactive SputteringAt reactive sputtering, not an inert gas, but an atmosphere of oxygen is used. Thismeans that the atomized target material is oxidized, forming oxidic layers on thespecimen.49

9.7 Macroetching

Macroetching can be defined as revealing the macrostructure for examination with thenaked eye or at a magnifications up to 10�, either direct or by using sulfur prints �Bau-mann prints�.

Macroetching is considered outside the scope of this book.Macroetching is described in great detail in the three following ASTM standards

�see also Section 12.4�.Standard Test Method for Macroetching Metals and Alloys �E 340�. This standard

is very comprehensive covering a wide range of materials.Standard Methods for Macrotech Testing Steel Bars, Billets, Blooms, and Forging

�E 381�


Standard Practice for Preparing Sulfur Prints for Macrostructural Examination�E 1180�

References „Part I…�1� Crowther, D. S. and Spanholtz, R. B., “ANew Name for Metallography? Try ‘Materialogra-

phy’,” Metal Progress, September 1968, p. 21.

�2� Petzow, G., Metallographic Etching, ASM International, Materials Park, Ohio, USA, 1999.

�3� Petzow, G. and Mücklich, F., “Microstructure-FascinatingVariety in Stringent Rules,” Practi-

cal Metallography, Vol. 33, 1996, pp. 64–82.

�4� ASM Handbook, Metallography and Microstructures, Volume 9, ASM International, Materi-

als Park, Ohio, USA, 2004.

�5� Edyvean, R. G. I. and Hammond, C., Journal of Historical Metallurgy, October 1998.

�6� Vilella, J. R., Metallographic Technique for Steel, American Society for Metals, Cleveland,

Ohio, USA, 1938.

�7� Samuels, L. E., Metallographic Polishing by Mechanical Methods, ASM International, Materi-

als Park, Ohio, USA, 2003.

�8� Bjerregaard, L., Geels, K., Ottesen, B., and Rückert, M., Metalog Guide, Struers A/S, Copen-

hagen, Denmark, 2000.

�9� Vander Voort, G. V., Metallography Principles and Practice, ASM International, Materials

Park, Ohio, USA, 1999.

�10� Malkin, S., Grinding Technology, Ellis Horwood Ltd., Chichester, UK, 1989.

�11� Shaw, M. C., Principles of Abrasive Processing, Clarendon Press, UK, 1996.

�12� Shaw, M. C., Farmer, D. A., and Nakayama, K., “Mechanics of the Abrasive Cut-Off Opera-tion,” Journal of Engineering for Industry, August 1967.

�13� Nelson, J. A. and Westricht, R. M., “Abrasive Cutting in Metallography,” Metallographic

Specimen Preparation, Plenum Press, Plenum Publishing.

�14� Wellner, P., “Investigations on the Effect of the Cutting Operation on the Surface DeformationofDifferentMaterials,” Practical Metallography, Vol. 17, 1980, p. 525.

�15� Geels, K., Andersen, A. T., and Damgaard, M., “An Analysis of Two Principles of AbrasiveCutting inMaterialographic Cut-Off Machines,” Proceedings, MC95 International Metal-

lography Conference, ASM International, Materials Park, Ohio, 1996, p. 251.

�16� Cloeren, H. H., “Thermische und mechanische Probenentnahme und deren Einfluss auf daswahre Gefüge,” Fortschritte in der Metallographie, Vol. 33, Werkstoff-

Informationsgesellschaft mbH, Frankfurt, Germany, 2002, p. 309.

�17� Geels, K., Müller, G., and Sorensen, J. I., “Oberflächenphenomene beimmaterialographischenNasstrennschleifen,” Fortschritte in der Metallographie, Vol. 34, Werkstoff-

Informationsgesellschaft mbH, Frankfurt, Germany, 2003, p. 93.

�18� Waschull, H., Präparative Metallographie, Wiley-VCH Verlag, Weinheim, Germany, 1993.

�19� Courtesy of Buehler, Ltd.

�20� Courtesy of Struers A/S.

�21� Bramfitt, B. L. and Benscoter, A. O., Metallographer’s Guide, Practices and Procedures for Iron

and Steels, ASM International, Materials Park, Ohio, USA, 2002.

�22� Barrett, J., “Electric Discharge Machining,” Metallographic Specimen Preparation, Ple-

num Press, Plenum Publishing Corporation, New York, USA, 1974, p. 69.

�23� Technical documents from DoALL Company, Des Plains, Illinois, USA, 2004.


�24� Nelson, J. A. and Slepian, R. M., Practical Metallography, Vol. 7, 1970, p. 510.�25� Glancy, S., Structure, Vol. 22, 1990, p. 14.�26� Carle, V., Schäfer, U., Täffner, U., Predel, F., Telle, R., and Petzow, G., “Ceramography of High

Performance Ceramics: Description of the Materials, Preparation, Etching Techniques, andDescription of the Microstructure,” Practical Metallography, Part I, Ceramographic Etch-ing, Vol. 28, 1991, pp. 359–377; Part II, Silicon Carbide, Vol. 28, 1991, pp. 420–434; Part III,Zirconium Oxide, Vol. 28, 1991, pp. 468–483; Part IV, Aluminum Nitride, Vol. 28, 1991, pp.542–552; Part V, Silicon Nitride, Vol. 28, 1991, pp. 592–610; Part VI, High-Temperature Su-perconductor YBa2Cu3O7, Vol. 28, 1991, pp. 633–648; Part VII, Boron Carbide, Vol. 31, 1994,pp. 218–233; Part VIII, Aluminum Oxide, Vol. 32, 1995, pp. 54–76.

�27� Elssner, G., Hoven, H., Kiessler, G., and Wellner, P., Ceramics and Ceramic Composites: Mate-rialographic Preparation, Elsevier Science Inc., New York, USA, 1999.

�28� Exner, E. and Kuhn, K., Practical Metallography, Vol. 8, 1972, pp. 453–469.�29� Bousfield, B., Surface Preparation and Microscopy of Materials, John Wiley & Sons, Chi-

chester, UK, 1992.�30� Damgaard, M. J., Bjerregaard, L., and Geels, K., Practical Metallography, Vol. 8, 2001, pp.

466–476.�31� Beilby, G., Aggregation and Flow of Solids, MacMillan and Co. Ltd., London, UK, 1921.�32� Luo, J. and Dornfeld, D. A., “Material Removal Mechanism in Chemical Mechanical Polish-

ing: Theory and Modeling,” IEEE Transactions on Semiconductor Manufacturing,2000.

�33� Geels, K. and Gillesberg, B., Practical Metallography, Vol. 37, 2000, pp. 150–159.�34� Burgess, D. and Blanchard, R. A., Wafer Failure Analysis for Yield Enhancement, Accelerated

Analysis, Half Moon Bay, California, USA, 2001.�35� Ross, Boit, and Staab, Eds., Microelectronics Failure Analysis, ASM International, Materials

Park, Ohio, USA, 1999.�36� Wulff, F. W. and Arens, T., Structure, Vol. 32, 1998, p. 9.�37� Reiter, K., Reiter, M., and Arens, T., Structure, Vol. 34, 1999, p. 12.�38� Katrakova, D., Damgaard, M., and Mücklich, F., Structure, Vol. 38, 2002, p. 19.�39� Kopp, W.-U. and Linke, U., Practical Metallography, Vol. 17, 1980.�40� Trempler, J., Practical Metallography, Vol. 5, 2001, pp. 231–269.�41� Trempler, J., Practical Metallography, Vol. 10, 2003, pp. 481–531.�42� McG. Tegart, W. J., The Electrolytic and Chemical Polishing of Metals in Research and Industry,

Pergamon Press Ltd., London, 1956.�43� Knuth-Winterfeld, E., Korttidsmetoder til metallografisk elektropolering ved stuetemperatur,

C. A. Reitzel, Copenhagen, Denmark, 1952.�44� Thompson-Russell, K. C., and Edington, J. W., Monograph Five, Electron Microscope Speci-

men Preparation Techniques in Materials Science, N. V. Philip’s Gloeilampenfabrieken, Eind-hoven, Holland, 1977.

�45� Beckert, M. and Klemm, H., Handbuch der metallographischen Âtzverfahren, Deutscher Ver-lag für Grundstoffindustrie, Leipzig, Germany, 1984.

�46� Beraha, E. and Shipgler, B., Color Metallography, American Society for Materials, MaterialsPark, Ohio, USA, 1977.

�47� Weck, E. and Leistner, E., “Metallographic Instructions for Colour Etching by Immersion, PartI �1982�, II �1983� and II �1986�,” Deutscher Verlag für Schweisstechnik GmbH, Düsseldorf,Germany.

�48� Gräff, I., Practical Metallography, Vol. 36, 1999, pp. 669–684.�49� Bühler, H. E. and Hougardy, H. P., Atlas of Interference Layer Metallography, Deutsche Gesell-

schaft für Materialkunde, Oberursel, Germany, 1980.


Part II:Metallographic/MaterialographicSpecimen Preparation—A Hands-OnManual

10IntroductionTHE GOAL FOR ANY METALLOGRAPHIC/MATERIALOGRAPHIC PREPARA-tion is a true microstructure, or at least a structure that makes a correct analysis of astructure detail possible. It should be stressed that an examination with a subsequentinterpretation, using a light microscope or other method, is of no use if the preparedmicrostructure is not correct.

This part of the book is made to guide the reader directly towards the correctpreparation of the microstructure for most materials and material groups. To obtainmore information on the true structure, a more detailed description of the total prepa-ration process and the theories behind it, see Part I of this book.

Before starting a preparation process, two facts must be considered: SpecimenMaterial and Purpose of Examination.

10.1 Specimen Material

The specimen material, in the following material, is decisive for the choice of a prepara-tion process. It is evident that soft, hard, ductile, brittle, homogenous, heterogeneous,etc., materials cannot be treated the same way to obtain a correct result.

To find the correct preparation method for a given material, the reader shall reviewTable 11.1 and find the material or group of materials corresponding to the given mate-rial �see below�.

10.2 Purpose of Examination

Before a preparation method is selected, the purpose of examination, in the followingthe purpose, should be considered. A given material can be prepared often electrolyti-cally in a relatively short time for one purpose, and for another purpose, a longer me-chanical preparation sequence should be performed. An example is medium carbonsteel. If the purpose of examination is the study of grain size, the electrolytic polishingmethod El-01, Section 13.3.6, can be used, having a total preparation time of approxi-mately 3 min, including grinding �less than 3 min� and polishing/etching �10–12 s�. Ifthe purpose is examination of inclusions, the mechanical methods, C-28 and T-28, Sec-tion 13.2.3, are recommended with a total preparation time of 10–12 min.

Based on the purpose, the user will select the correct process/method stated in theMaterial/Preparation Tables. Other information connected to the purpose, such asetchants, will be stated also.

10.3 Specimen Preparation

Modern specimen preparation is based on a systematic approach, and in this way se-curing the reproducibility that is a must in both research and quality control. In theMaterial/Preparation Tables, Section 13.2.3, the total preparation process is stated, in-

179

cluding sectioning, mounting, grinding/polishing methods �mechanical and electro-lytical�, and etching. Mechanical polishing can be done by hand and is also described inthis part of the book, but for the indicated methods, a semiautomatic grinder/polisheris recommended.

A section covering “trouble shooting” of all stages of the preparation process, andhow to analyze the used preparation method to avoid or overcome artifacts is also in-cluded in Part II.


11Specimen Material—Table 11.1THE SPECIMEN MATERIAL, COMBINED WITH THE PURPOSE OF EXAMINA-tion, is decisive for the choice of preparation process/method. Two physical properties,hardness and ductility, are important in selecting a specific preparation method, butconditions such as coatings or composites also play an important role.

In Table 11.1, Section 11.3, most materials and the most common material combi-nations are indicated to guide the reader to a preparation process/method best suitedfor a specific material stated in the Material/Preparation Tables, Section 13.2.3.

11.1 Classification of Materials

A classification of all available materials is needed to guide the reader to a specific ma-terial in an efficient way. This is done by defining twelve main groups partly based onmaterial composition, such as “ceramics,” “ferrous metals,” etc., and on other impor-tant features like “coatings,” “electronic components,” etc. The twelve main groups arestated alphabetically �see below�.

The main groups are split into a number of subgroups. An example is the maingroup Ceramics, which has five subgroups: Carbides, Nitrides, Oxides, Traditional Ce-ramics, and Other Ceramics.

These subgroups lead to the specific material or material group, e.g., under Ceram-ics, Oxides: Al2O3, BaTiO3, CaO, CeO2, Cr2O3, MgO, SiO, ZnO, ZrO2, and Other Oxides.

The twelve main groups �alphabetic�:• Ceramics• Coatings• Composites and Reinforced Materials• Electronic Components• Ferrous Metals• Mineralogical Materials• Nonferrous Metals• Organic Materials• Polymers• Powder Metals• Sintered Carbides

11.2 How to Use Table 11.1

When a given material or material group should be found in the table, the main groupmost likely will be evident such as Ceramics, Coatings, Ferrous Metals, Polymers, etc.If in doubt, a look at the subgroups will often lead the way to the material or materialgroup. In the case of an alloy, the material should be found according to the componentwith the highest content. Example: The superalloy: 48 % Ni, 25 % Co, 19 % Cr, 7.5 % Fe,0.5 % Ti, is classified under the main group Nonferrous Metals, subgroup Nickel andNickel Alloys.

181

When the material �material group� is found, two or more Methods with MethodNumbers are indicated in the same row. Now go to Section 13.2.3 and find the Material/Preparation Tables with the same number. A number of purposes with correspondingpreparation methods are indicated here �see Chapter 12�, and the method correspond-ing to the correct purpose is selected.

11.3 Table 11.1—Materials/Methods

TABLE11.1—Materials/Methods.

MaterialGroup/Material (Alphabetical)Method(SeeSection13.2.3/3.6)

Ceramics Bioceramics Hydroxyapatite Coating T-01, C-01

Bioceramics, Others T-05, C-05, T-06, C-06

Carbides B4C T-02, C-02

CrC T-03, C-03

SiC T-02, C-02

TaC T-03, C-03

TiC T-03, C-03

WC T-03, C-03

Nitrides CBN T-03, C-03

Si3N4 T-04, C-04

TiN T-03, C-03

Other Ceramics T-03, C-03

Oxides Al2O3 T-05, C-05

BaTiO3 T-06, C-06

CaO T-06, C-06

CeO2 T-06, C-06

Cr2O3 T-05, C-05

MgO T-06, C-06

SiO T-06, C-06

UO2 T-68, C-68

ZnO T-06, C-06

ZrO2 T-06, C-06

Oxides, Others T-05, C-05, T-06, C-06

Borides T-06, C-06

Traditional Glasses, Optical Fibers T-07, C-07

Ceramics Porcelain T-06, C-06

Slag T-06, C-06

Tile T-06, C-06

Other Traditional Ceramics T-06, C-06

Coatings Electrolytically Anodized Coatings T-08, C-08

Deposited Galvanization—Plated Coatings T-09, C-09

Other Electrolytically Deposited T-09, C-09

Other Coatings CVD T-08, C-08

Diffusion Coatings T-09, C-09

Hot Dip Zn-Coating T-10, C-10

Other Zn-based Coatings T-10, C-10

PVD T-08, C-08


TABLE11.1—(Continued.)


Paint Layers T-11, C-11

Other Coatings T-09, C-09

Thermal Spray Flame T-12, C-12

Coatings HVOF (High Velocity OxygenFuel)

T-12, C-12

Plasma Spray Coatings—Metallic Layers

T-13, C-13

Plasma Spray Coatings—Ceramic Layers

T-14, C-14

Plasma Spray Coatings—Composite Layers

T-15, C15

Other Thermal Spray Coatings T-12, C-12

Composites SiC Fibers in Ti Matrix T-16, C-16

and Glassfiber Reinforced Plastic T-17, C-17

Reinforced Other Composite Materials T-18, C-18

Electronic Ceramic Capacitors T-19, C-19

Components Components Resistors T-19, C-19

Diodes T-19, C-19

YBCO Ceramic SuperConductors

T-20, C-20

Metallic Germanium, Silicon, Si Wafers T-21, C-21

Components Microelectronic Material C-22

(Semiconductor Device)

Resistors T-23, C-23

Solderballs T-24, C-24

Other Metal Components T-23, C-23

Polymer Capacitors, Other Electronic T-25, C-25

Components Components

Microelectronic Packages,Integrated

T-24, C-24

Circuits, Transistors T-26, C-26

PCB Coupon T-27, C-27

Other Microelectronic Devices T-26, C-26

Ferrous Carbon Steels High Carbon Steels T-28, C-28, E1-01

Metals Low Carbon Steels T-29, C-29, El-02

Medium Carbon Steels T-28, C-28, El-01

Cast Irons Gray Cast Iron, T-30, C-30, El-03

Lamellar

Cast Iron, T-30, C-30, El-03

Malleable

Cast Iron, T-31, C-31, El-03

Nodular

Cast Iron, White T-32, C-32, E1-03

Cast Iron, others T-28, C-28, El-03

Heat Treated Heat Treated, High-Alloy Steels T-33, C-33, El-04

Chapter 11 Specimen Material 183



Steels Heat Treated, Low-Alloy Steels T-33, C-33, El-04

High-Alloy Stainless Steels T-34, C-34, El-05

Steels Super Alloys, Fe-Based T-35, C-35, El-06

Other High-Alloy Steels T-33, C-33, El-05

Low-Alloy High Strength Low-Alloy Steels T-36, C-36, El-04

Steels Other Low-Alloy Steels T-34, C-34, E1-04

Other Ferrous T-33, C-33, E1-02

Metals

Pure Iron T-34, C-34, El-07

Surface Treated Carbonitrided Steels T-37, C-37

Steels Carburized Steels T-37, C-37

Nitrided Steels T-37, C-37

Other Surface Treated Steels T-37, C-37

Tool Steels High Speed Steels T-38, C-38, El-08

Low-Alloyed Tool Steels T-38, C-38, El-09

Tool Steels, Others T-38, C-38, El-09

Mineralogical Constructed Portland Cement Clinker,Concrete

T-39, C-39

Materials Materials

Natural Minerals T-40, C-40

Ores T-40, C-40

Nonferrous Aluminum and Pure Aluminum T-41, C-41, El-10

Metals Al Alloys Cast Aluminum Alloys T-41, C-41

Wrought Aluminum Alloys T-43, C-43, El-10

Other Aluminum Alloys T-42, C-42, El-10

Americium See Material/Preparation

Tables 68

Antimony and Pure Antimony T-44, C-44, El-10

Sb Alloys Antimony Bearing Alloys T–44, C-44, El-10

Other Sb Alloys T-44, C-44, El-10

Beryllium and T-45, C-45, El-10

Be Alloys

Bismuth and Bi T-44, C-44, El-10

Alloys

Cadmium See Material/Preparation

Tables 68

Chromium and T-46, C-46, E1-11

Cr Alloys

Cobalt and Co Pure Cobalt, Cobalt Alloys T-47, C-47, El-12

Alloys Super Alloys, Cobalt-Based T-48, C-48, El-12

Copper and Cu Pure Copper T-50, C-50, El-13

Alloys Brass T-49, C-49, El-13

Bronze T-49, C-49, El-14




Copper Bearings Alloys T-50, C-50, El-14

Other Copper Alloys T-49, C-49, E1-13

Germanium T-21, C-21

Gold and Au T-51, C-51

Alloys

Hafnium andHf Alloys

T-62, C-62, El-11

Indium See Material/Preparation

Tables 68

Iridium and Ir T-57, C-57

Alloys

Lead and Pb T-52, C-52, E1-15

Alloys

Magnesiumand

T-53, C-53, E-16

Mg Alloys

Manganese and T-54, C-54, El-01

Mn Alloys

Mercury andAmalgams

See Material/Preparation

Tables 68

Molybdenumand Mo Alloys

T-55, C-55, E1-01

Neptunium See Material/Preparation

Tables 68

Nickel, Ni T-56, C-56, El-17

Alloys and Ni-

Based Super

Alloys

Niobium and T-55, C-55

Nb Alloys

Osmium andOs Alloys

T-57, C-57

Palladium and T-57, C-57

Pd Alloys

Platinum andPt Alloys

T-57, C-57

Plutonium See Material/Preparation

Tables 68

Rare EarthMetals

See Material/Preparation

Tables 68

Rhenium and T-55, C-55




Re Alloys

Rhodium and T-57, C-57

Rh Alloys

Ruthenium and T-57, C-57

Ru Alloys

Selenium See Material/Preparation

Tables 68

Silicon T-21, C-21

Silver and Ag T-58, C-58, E1-18

Alloys

Tantalum and T-55, C-55

Ta Alloys

Tellurium See Material/Preparation

Tables 68

Thallium See Material/Preparation

Tables 68

Thorium See Material/Preparation

Tables 68

Tin, SnBearing

T-59, C-59, E1-19

Alloys and

Other SnAlloys

Titanium andTi Alloys

T-60, C-60, E1-20

Tungsten andW Alloys

T-55, C-55, E1-21

Uranium and T-68, C-68

UraniumDioxide

Vanadium andV Alloys

T-55, C-55, E1-22

Zinc and Zn T-61, C-61, E1-23

Alloys

Zirconium and T-62, C-62, E1-24

Zr Alloys

Zircalloy

Organic Biological T-63, C-63

Materials MaterialsBoneTeeth

Tissue




Carbon, Coal, T-63, C-63

Graphite

Paper, T-63, C-63

Wood

Other Organic T-63, C-63

Materials

Polymers Elastomers Elastomers, Others T-64, C-64

EPDM Polymers T-64, C-64

Silicone T-64, C-64

Thermoplastics Acrylic (CS) T-64, C-64

Acrylonitril Butadicne Styrene T-65, C-65

(ABS)

Polyamid (PA) T-64, C-64

Polycarbonate (PC) T-65, C-65

Polyester, Saturated T-65, C-65

Polyethylene (PE) T-64, C-64

Polymethylmethacrylate(PMMA)

T-65, C-65

Polyoxymethylene (POM) T-65, C-65

Polypropylene (PP) T-64, C-64

Polystyrene (PS) T-64, C-64

Polyvinylchloride (PVC) T-64, C-64

Thermoplastics, Others T-64, C-64

Thermosetting Epoxy T-65, C-65

Plastics Phenolic Resins (PF) T-65, C-65

Polyester, Unsaturated T-65, C-65

Polyurethane (PUR) T-65, C-65

Other Thermosetting Plastics T-65, C-65

PowderMetals

Ferrous PowderMetals

Nonferrous T-66, C-66

Powder Metals

Sintered Cemented T-67, C-67, E1-25

Carbides Carbides,

(CementedCarbides)

(Hard metals),CoatedSintered

Carbides and

Other Sintered

Carbides


12Purpose of Examination

12.1 Purpose in General

FOR A GIVEN MATERIAL SEVERAL PREPARATION METHODS WILL USU-ally be available, however, the correct method should be chosen based on the purposeof examination. For this reason, a number of relevant purposes are stated with eachmaterial/method in the Material/Preparation Tables, �see Section 13.2.3�.

Table 12.1 shows a number of the most common “purposes of examination.” It isexpressed in the following text and in the table as “purpose.” Most of these purposes arecovered by one or more ASTM standards and, in this case, the standard�s� is indicated.

For a given material also microetching is performed in accordance with the pur-pose of the examination, and therefore also chemical microetching with a list ofetchants �Table 12.2� is stated in this chapter.

12.2 Purpose: ASTM Standards

A preparation is made very often to be able to make an examination according to anASTM standard. Section 12.4 lists all ASTM standards commonly used in metallogra-phy and materialography and a Document Summary of each standard is indicated in aCD-ROM included with this manual.

Other relevant standards �ISO, BSI, DIN, etc.� are stated in Appendixes I and II. InTable 12.1, the ASTM standards are shown relating to purpose.

12.3 Table 12.1: Purpose/ASTM Standards

Table 12.1indicates a number of common purposes of examination with the most im-portant ASTM standards, if any. Not all applicable standards are listed in this table,only some of the more pertinent ones.

As part of each Material/Preparation Tables �Section 13.2.3�, a similar table will bestated, but only the purposes and the ASTM standards, relevant for the material de-scribed in the Material/Preparation Tables, will be indicated.

12.4 ASTM Standards—Metallography

12.4.1 IntroductionThe metallographic field is covered by ASTM with a number of documents of the fol-lowing types:

Guide—a compendium of information or series of options that doesn’t recom-mend a specific course of action.

Practice—a definitive set of instructions for performing one or more specific op-erations or functions that does not produce a test result.

188

Specification—an explicit set of requirements to be satisfied by a material, prod-uct, system, or service.

Terminology—a document comprising definitions of terms—explanation of sym-bols, abbreviations, or acronyms.

Test Method—a definitive procedure that produces a test result.Most of the standards covering metallography and materialography are published

in the Annual Book of ASTM Standards, Volume 03.01, Metals—Mechanical Testing;Elevated and Low-Temperature Tests; Metallography �ASTM Stock Number:S030100�.

The standards covering metallography, including Microindentation HardnessTesting, are under the jurisdiction of ASTM Committee E4. Those covering other typesof hardness testing are under ASTM Committee E28.

DesignationEach standard has a serial designation prefixed to the following title, the number fol-lowing the dash indicates the year of original adoption as a standard or, in the case ofrevision, the year of the last revision. Thus, standards adopted or revised during theyear 2003 have as their final number, 03. A letter following this number indicates morethan one revision during that year, that is, 03a indicates the second revision in 2003,03b, the third revision, etc. Standards that have been reapproved without change areindicated by the year of last reapproval in parentheses as part of the designation num-ber, for example, �2003�. A superscript epsilon indicates an editorial change since thelast revision or reapproval-�1 for the first change, �2 for the second change, etc.

TABLE 12.1—Purpose/ASTM Standards.

Purpose (alphabetic): ASTM Standard (See Section 12.4)

Case or coating thickness/hardness B 487, B 578, B 748, B 931, B 933, B 934, C 664,

Surface layers E 1077

Perfect edge retention

Graphite in cast iron A 247

Grain size, grain boundaries B 390, E 112, E 930, E 1181, E 1382

Heat-influenced zone E 1077

Heat treatment

Image analysis, rating of inclusion content E 45, E 562, E 768, E 1077, E 1181,

High planeness E 1245, E 1268, E 1382, E 2109

Inclusions in steel B 796, E 45, E 768, E 1245

Microhardness, hardness B 578, C 730, C 849, C 1326, C 1327, E 10,

E 18, E 92, E 103, E 110, E 140, E 384, E 448

Microstructure A 247, A 892, B 657, B 665, E 3, E 45, E 112, E

407, E 562, E 768, E 883, E 930, E 1077, E 1122, E

1181, E 1245, E 1268, E 1351, E 1382, E 1558, E

1920, E 2015, E 2109, E 2283

Phase identification A 247, B 657

Porosity B 276, E 2109, F 1854

Structure changes (forging)

Thermal sprayed coatings: Distribution, porosity,unmelted particles

E 1920, E 2109

Chapter 12 Purpose of Examination 189

In this manual, only the serial designations are indicated because the followingnumbers are continuously changed.

12.4.2 ASTM Standards in this BookAll ASTM standards mentioned under METALLOGRAPHY in Volume 03.01 and oth-ers, relating to the subjects covered by this book, are listed below. Most of these will bestated as DOCUMENT SUMMARY in Section 12.4.3. The listed standards should notbe considered as a complete list of standards covering the subject of metallography/materialography and related subjects. Also, a few specifications covering materials areshown as examples.

The standards listed are based on the situation as per October 2006, and this situa-tion will change due to the development of new standards and the revision or deletionof old standards.

ASTM Standards Listed by Subject „Alphabetically…Coatings

Test Methods for:B 487 Measurement of Metal and Oxide Coating Thickness by Microscopical Ex-

amination of a Cross SectionB 578 Microhardness of Electroplated CoatingsB 588 Measurement of Thickness of Transparent or Opaque Coatings by Double-

Beam Interference Microscope TechniqueB 748 Measurement of the Thickness of Metallic Coatings by Measurement of

Cross Section with a Scanning Electron MicroscopeC 664 Thickness of Diffusion Coating

Criteria for Metallographic Laboratory Evaluation, Safety, andManagementGuide for:

E 1578 Laboratory Information Management Systems �LIMS�E 2014 Metallographic Laboratory Safety

Grain SizeTest Methods for:

E 1181 Characterizing Duplex Grain SizesE 112 Determining Average Grain SizeE 930 Estimating the Largest Grain Observed in a Metallographic Section �ALA

Grain Size�Practice for:

B 390 Evaluating Apparent Grain Size and Distribution of Cemented TungstenCarbidesGuides for:

E 1951 Calibrating Reticles and Light Microscope Magnifications

InclusionsTest Methods for:

B 795 Determining the Percentage of Alloyed or Unalloyed Iron ContaminationPresent in Powder Forges �P/F� Steel Parts


B 796 Nonmetallic Inclusion Content of Powders Intended for Powder Forging�P/F� Applications

E 45 Determining the Inclusion Content of Steel

Indentation Hardness TestingSpecifications for:

E 140 Hardness Conversion Tables for Metals. Relationship Among Brinell Hard-ness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness,and Scleroscope Hardness. Please refer to ASTM E 140 in the CD-ROM included withthis manual.Test Methods for:

C 730 Knoop Indentation Hardness of GlassC 849 Knoop Indentation Hardness of Ceramic WhitewaresC 1326 Knoop Indentation Hardness of Advanced CeramicsC 1327 Vickers Indentation Hardness of Advanced CeramicsD 785 Rockwell Hardness of Plastics and Electrical Insulating MaterialsD 1415 Rubber Property-International HardnessD 2240 Rubber Property-Durometer HardnessE 10 Brinell Hardness of Metallic MaterialsE 110 Indentation Hardness of Metallic Materials by Portable Hardness TestersE 103 Rapid Indentation Hardness Testing of Metallic MaterialsE 18 Rockwell Hardness and Rockwell Superficial Hardness of Metallic MaterialsE 92 Vickers Hardness of Metallic MaterialsPractice for:E 448 Scleroscope Hardness Testing of Metallic Materials

Microindentation Hardness TestingTest Methods for:

B 578 Microhardness of Electroplated CoatingsB 931 Metallographically Estimating the Observed Case Depth of Ferrons PowderMetallurgy �P/M� PartsB 933 Microindentation Hardness of Poweder Metallurgy �P/M� MaterialsB 934 Effective Case Depth of Ferrous Poweder Metallurgy �P/M� Parts Using Mi-croindentation Hardness MeasurementsE 384 Microindentation Hardness of Materials

Practice for:WK 382 Instrumented Indentation Testing

PorosityTest Method for:

B 276 Apparent Porosity in Cemented CarbidesSee also under Quantitative Metallography

Quantitative MetallographyTest Methods for:

D 629 Quantitative Analysis of TextilesD 1030 Fiber Analysis of Paper and Paperboard


D 2798 Microscopical Determination of the Reflectance of Vitrinite in a PolishedSpecimen of CoalE 562 Determining Volume Fraction by Systematic Manual Point CountE 1382 Determining the Average Grain Size Using Semiautomatic and AutomaticImage AnalysisE 1077 Estimating the Depth of Decarburization of Steel SpecimensE 2109 Determining Area Percentage Porosity in Thermal Sprayed CoatingsF 1854 Stereological Evaluation of Porous Coatings on Medical Implants

Practices for:C-856 Petrographic Examination of Hardened ConcreteE 1268 Assessing the Degree of Banding or Orientation of MicrostructuresE 1245 Determining the Inclusion or Second-Phase Constituent Content of Metalsby Automatic Image AnalysisE 2283 Extreme Value Analysis of Nonmetallic Inclusions in Steel and Other Mi-crostructural Features

Sampling, Specimen Preparation and PhotographyTest Methods for:

A 247 Evaluating the Microstructure of Graphite in Iron CastingsB 328 Density, Oil Content, and Interconnected Porosity of Sintered Metal Struc-tural Parts and Oil-Impregnated BearingsB 657 Metallographic Determination of Microstructure in Cemented TungstenCarbidesE 381 Macroetch Testing Steel Bars, Billets, Blooms, and ForgingsE 340 Macroetching Metals and AlloysE 3 Preparation of Metallographic Specimens

Practices for:B 665 Metallographic Sample Preparation of Cemented Tungsten CarbidesE 122 Calculating Sample Size to Estimate, with a Specified Tolerable Error, the

Average for Characteristic of a Lot or ProcessE 178 Dealing with Outlying ObservationsE 407 Microtching Metals and AlloysE 1180 Preparing Sulfur Prints for Macrostructural ExaminationE 768 Preparing and Evaluating Specimens for Automatic Inclusion Assessmentof SteelE 1351 Production and Evaluation of Field Metallographic Replicas

Guides for:A 892 Defining and Rating the Microstructure of High Carbon Bearing SteelsE 1558 Electrolytic Polishing of Metallographic SpecimensE 1920 Metallographic Preparation of Thermal Sprayed CoatingsE 2015 Preparation of Plastics and Polymeric Specimens for Microstructural Ex-aminationE 883 Reflected-Light Photomicrography


TerminologyTerminology for:

E 7 Metallography

X-Ray and Electron Metallography „This subject is not included in thisBook.…Test Methods for:

E 82 Determining the Orientation of a Metal CrystalE 2142 Rating and Classifying Inclusions in Steel Using the Scanning Electron Mi-croscope

Practices for:E 766 Calibrating the Magnification of a Scanning Electron MicroscopeE 963 Electrolytic Extraction of Phases from Ni and Ni-Fe Base Superalloys Usinga Hydrochloric-Methanol ElectrolyteE 81 Preparing Quantitative Pole FiguresE 986 Scanning Electron Microscope Beam Size Characterization PerformanceCharacterizationE 975 X-Ray Determination of Retained Austenite in Steel with Near RandomCrystallographic Orientation

Guides for:E 1508 Quantitative Analysis by Energy-Dispersive Spectroscopy

ASTM Specifications—ExamplesStandard Specification for:

A 1 Carbon Steel Tee RailsA 3 Steel Joint Bars, Low, Medium, and High Carbon �Non-Heat-Treated�A 36 Carbon Structural SteelA 47 Ferritic Malleable Iron CastingsA 48 Gray Iron CastingsA 126 Gray Iron Castings for Valves, Flanges, and Pipe FittingsA 159 Automotive Gray Iron CastingsA 197 Cupola Malleable IronA 220 Pearlitic Malleable IronA 242 High-Strength Low-Alloy Structural SteelA 338 Malleable Iron Flanges, Pipe Fittings, and Valve Parts for Railroad, Marine,and Other Heavy Duty Service at Temperatures Up to 650°F �345°C�A 377 Ductile-Iron Pressure PipeA 439 Austenitic Ductile Iron CastingsA 532 Abrasion-Resistant Cast IronsA 536 Ductile Iron CastingsA 572 High-Strength Low-Alloy Colombium-Vanadium Structural SteelA 602 Automotive Malleable Iron CastingsA 656 Hot-Rolled Structural Steel, High-Strength Low-Alloy Plate with ImprovedFormability

12.4.3 ASTM Standards—Document SummariesFor Document Summaries on the above mentioned standards please refer to the CD-ROM included with this manual.


12.5 Chemical Microetching—Table 12.2—Table 12.3

The prepared specimen surface typically must be etched to reveal the microstructuredepending on the purpose of examination. Mostly this is done with chemical solutions,etchants, developed for a specific material and often for a specific purpose.

In ASTM Practice for Microetching Metals and Alloys �E 407� �see Section 12.4.3� alarge number of etchants for metals are stated with the purposes �uses�. Based on Table1 of the newest version of this practice �ASTM E 407–99� and other sources, Refs. 2, 4,and 9, Part I, etchants are stated according to their purpose on each Material/Preparation Tables, Section 13.2.3. The etchant is identified with a number. This num-ber is taken to Table 12.2, which states the composition and procedure for the etchingprocess. Table 12.2 is based on Table 2 of ASTM E 407–99 covering metals �etchants1–226� with additions �etchants 901–950�, mainly covering ceramics and plastics,taken from Petzow, Ref. 2, �Part I�, ASM Handbook, Vol. 9, Ref. 4, �Part I�, and VanderVoort, Ref. 9, �Part I�.

Attention: The ASTM Practice E 407 mentioned above is updated at different timeintervals and the reader should consult with the latest published version of the stan-dard which can be found in Annual Book of Standards, Volume 03.01 �see Section12.4.1�.

For etchants not mentioned in this book, see references in Section 9.1, and Litera-ture, Chapter 27.

Etchant Names: Some etchants have special names, like “Beraha.” These namesare stated in Table 12.3, indicating the etchant number so that the composition can befound in Table 12.2. Table 12.3 is based on Table 3 of ASTM E 407.

Theory of Microetching: For chemical etching theory, different types of etchingand literature on etching see Chapter 9.

12.5.1 Etching PracticeChemical etching is a straightforward, reasonably simple process. In most cases a rela-tive small quantity of the etchant is placed in a shallow beaker, and the carefullycleaned and dried specimen is immersed into the reagent. The specimen should alwaysbe held with a pair of tongs, and preferably with the surface turning upwards to be ableto see the progress of the process. The specimen is moved gently to remove reactionproducts on the surface. In some cases a swabbing with a saturated piece of cotton canbe recommended, but the cotton might scratch the surface and care should be takenthat the cotton is regularly recharged with reagent.

Safety Precautions: See Sections 9.3.4 and 26.2 and ASTM Guide for Metallo-graphic Laboratory Safety �E 2014�. Please refer to E 2014 in the CD-ROM includedwith this manual.


12.5.2 Table 12.2—Numerical List of Etchants

TABLE12.2—Numerical list of etchants. (This table contains etchants mentioned in the Material/Preparation Tablesandother etchants, seeASTME407.)

Etchant Composition Procedure

1 1 mL HF200 mL water

(a) Swab with cotton for 15 s.(b) Alternately immerse and polish severalminutes.(c) Immerse 3–5 s.(d) Immerse 10–120 s.


(a) Swab 10 s to reveal general structure.(b) Immerse 15 min, wash 10 min in water to formfilm with hatchingwhich varies with grain orientation.

3 2 mL HF3 mL HCl

5 mL HNO3

190 mL water

(a) Immerse 10–20 s. Wash in stream of warmwater. Reveals general structure.(b) Dilute with 4 parts water-colors constituents—mix fresh.

4 24 mL H3PO4

50 mL Carbitol (diethylene glycolmonoethyl ether)

4 g boric acid2 g oxalic acid

10 mL HF32 mL water

Electrolytic: Use carbon cathode raising d-cvoltage from 0–30 V in 30 s. Totaletching time 3 min with agitation. Wash and cool.Repeat if necessary.

5 5 g HBF4

200 mL waterElectrolytic: Use Al, Pb, or stainless steel cathode.Anodize 1–3 min,20–45 V d-c. At30 V, etch for 1 min.

6 25 mL HNO3

75 mL waterImmerse 40 s at 70°C �160°F�. Rinse in coldwater.

7 10–20 mL H2SO4

80 mL waterImmerse 30 s at 70°C �160°F�. Rinse in coldwater.

8 10 mL H3PO4 (a) Immerse 1–3 min at 50°C �120°F�.90 mL water (b) Electrolytic at 1–8 V for 5–10 s.

9 3–4 9 sulfamic acid5 drops HF

100 mL water

Use just prior to the last polishing operation.It is not intended as a final etchant.The specimen is examined as polished even underpolarized light.

10 10 mL HF90 mL methanol (90 %)

Immerse 10–30 s.


Immerse or swab few seconds to a minute.

12 20 mL HNO3

60 mL HClUse hood. Do not store. Immerse or swab 5–60 s.

13 10 g oxalic acid100 mL water

Electrolytic at 6 V:(a) 10–15 s.(b) 1 min.(c) 2–3 s.

Use stainless steel cathode and platinum orNichrome connection to specimen.


TABLE12.2—Numerical list of etchants. (This table contains etchants mentioned in the Material/Preparation Tablesandother etchants, seeASTME407.)(Continued.)


14 10 mL HNO3

90 mL methanol (95 %)Immerse few seconds to a minute.

15 15 mL HNO3

15 mL acetic acid60 mL HCl

15 mL water

Age before use. Immerse 5–30 s. May be usedelectrolytically.

16 5–10 mL HCl100 mL water

Electrolytic at 3 V for 2–10 s.

17 5 mL HCl10 g FeCl3

100 mL water

Electrolytic at 6 V for few seconds.

18 2–10 g CrO3

100 mL waterElectrolytic at 3 V for 2–10 s.

19 A8 g NaOH

100 mL waterB

Saturated aqueous solution of KMnO4

Immerse in freshly mixed Solutions A+B (1:1) for5–10 s.If surface activation is necessary, first use Etch#18, then rinse in water.While still wet, immerse in Solutions A+B (1:1).Mixture of solutions A+B has 15 min useful life.

20 5 mL H2O2 (30 %)100 mL HCl

Use hood. Mix fresh. Immerse polished face up forfew seconds.

21 1 g CrO3

140 mL HClUse hood. To mix, add the HCl to CrO3.Electrolytic at 3 V for 2–10 s.

22 100 mL HCl0.5 mL H2O2 (30 %)

Use hood. Do not store.(a) Immerse or swab 1/2–3 min. Add H2O2

dropwise to maintain action.(b) Electrolytic, 4 V, 3–5 s.

23 5 mL HCl95 mL ethanol (95 %) or methanol

(95 %)


24 5 mL HNO3

200 mL HCl65 g FeCl3

Use hood. Immerse few seconds.

25 10 g CuSO4

50 mL HCl50 mL water

Immerse or swab 5–60 s. Made more active byadding few drops of H2SO4 just before use.

26 5 g FeCl3

10 mL HCl50 mL glycerol

30 mL water

Swab 16–60 s. Activity may be decreased bysubstituting glycerol for water.

27 1 g KOH20 mL H2O2 (3 %)

50 mL NH4OH30 mL water

Dissolve KOH in water, then slowly add NH4OHto solution. Add 3 % H2O2 last. Usefresh—immerse few seconds to a minute.

28 1 g FeNO3

100 mL waterSwab or immerse few seconds to a minute.




29 1 g K2Cr2O7

4 mL H2SO4

50 mL water

Add 2 drops of HCl just before using. Swab fewseconds to a minute.

30 25 mL NH4OH25 mL water

50 mL H2O2 (3 %)

Mix NH4OH and water before adding H2O2. Mustbe used fresh. Swab 5–45 s.

31 10 g ammonium persulfate100 mL water

(a) Swab or immerse to 5 s.(b) Immerse to 2 min to darken matrix to revealcarbides and phosphides.(c) Electrolytic at 6 V for few seconds to a minute.(d) Immerse 3–60 s. Can be heated to increaseactivity.

32 60 g CrO3

100 mL waterSaturated solution.Immerse or swab 5–30 s.

33 10 g CrO3

2–4 drops HCl100 mL water

Add HCl just before use. Immerse 3–30 s. Phasescan be colored by Nos. 35, 36, 37.

34 5 g FeCl3


(a) Immerse or swab few seconds to few minutes.Small additions of HNO3

activate solution and minimize pitting.(b) Immerse or swab few seconds at a time. Repeatas necessary.

35 20 g FeCl35 mL HCl1 g CrO3

100 mL water

Immerse or swab few seconds at a time untildesired results are obtained.

36 25 g FeCl3



37 1 g FeCl3


Immerse or swab few seconds at a time untildesired results are obtained

38 8 g FeCl3


Swab 5–30 s.

39 5 g FeCl3

10 mL HCl1 g CuCl2

0.1 g SnCl2

100 mL water


40 5 gFeCl3 16 ML HCl 60 mLethanol (95 %) or methanol

(95 %)

Immerse or swab few seconds to few minutes.

41 2 g K2Cr2O7

8 mL H2SO4

4 drops HCl100 mL water

Add the HCl just before using. Immerse 3–60 s.




42 10 g cupric ammonium chloride100 mL water

NH4OH

Add NH4OH to solution until neutral or slightlyalkaline. Immerse 5–60 s.

43 20 mL NH4OH1 g ammonium persulfate

Immerse 5–30 s.

44 50 mL NH4OH20–50 mL H2O2 (3 %)

0–50 mL water

Use fresh. Peroxide content varies directly withcopper content of alloy to be etched.Immerse or swab to 1 min. Film on etchedaluminum bronze removed by No. 82.

45 1 g CrO3

100 mL waterElectrolytic at 6 V for 3–6 s. Use aluminumcathode.

46 15 mL NH4OH15 mL H2O2 (3 %)

15 mL water4 pellets NaOH

When mixing, add NaOH pellets last.For best results use before pellets have dissolved.

47 5 g NaCN or KCN5 g �NH4�2S2O2

100 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide.Precaution—Also poisonous by ingestion as wellas contact.

48 10 g NaCN100 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide.Precaution—Also poisonous by ingestion as wellas contact. Electrolytic at 6 V:(a) 5 s for sigma.(b) 30 s for ferrite and general structure.(c) to 5 min for carbides.

49 3 g FeSO4

0.4 g NaOH10 mL H2SO4

190 mL water

Electrolytic at 8–10 V �0.1 A� for 5–15 s.

50 5 mL acetic acid10 mL HNO3

85 mL water

Use hood. Do not store. Electrolytic at 1.5 V for20 to 60 s. Use platinum wires.

51 2 g FeCl3

5 mL HCl30 mL water

60 mL ethanol or methanol

Immerse few minutes.

52 1 g sodium dichromate1 g NaCl

4 mL H2SO4

250 mL water

Swab few seconds.

53 1–5 mL NH4OH100 mL water

Immerse 5–60 s.

54 1 g ammonium acetate3 g sodium thiosulfate

7 mL NH4OH1300 mL water

Electrolytic at 0.3 A/cm2 for 5–30 s.




55 1 mL H2SO4

15 mL HNO3

10 mL acetic acid5 mL H3PO4

20 mL lactic acid

Swab gently 10–15 s. Rinse with methanol andblow dry. Helps to chemically polish.If final etch is too even mild, follow with No. 98.

56 30 mL HNO3

10 mL H3PO4

20 mL acetic acid10 mL lactic acid

Swab gently 5–15 s. Rinse with ethanol ormethanol and blow dry.

57 75 mL acetic acid25 mL H2O2 (30 %)

Immerse 6–15 s.

58 25 mL HF25 mL HNO3

5 mL water

Swab 3–20 s.

59 2 g AgNO3

40 mL water40 mL HF

20 mL HNO3

Mix AgNO3 and water, then add HF and HNO3.Swab 1/2–2 min.

60 25 mL HNO3

15 mL acetic acid15 mL HF

5–7 drops bromine

Use hood. Let stand 1/2 h before using. Swab3–20 s.

61 60 mL HCl40 mL HNO3

Use hood. Immerse few seconds to a minute.

62 1–5 g CrO3

100 mL HClVary composition of reagent and aging of reagentafter mixing to suit alloy.Swab or immerse few seconds to a minute.

63 0.1 g CrO3

10 mL HNO3

100 mL HCl

Swab few seconds to a minute.

64 5 mL HNO3


(a) Immerse 1–5 min.(b) Use hot. Will form chloride film on gold alloysif much silver is present.Ammonia will remove film.

65 A10 g ammonium persulfate

100 mL waterB

10 g KCN100 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide.Precaution—Also poisonous by ingestion as wellas contact. Mix 1+1 mixture of Solutions A and Bjust before use. (A mixture of 5 drops of each willcover the surface of a 1 in. dia. mount.)Immerse 1/2–2 min.


30 mL HCl

Swab 3–10 s or immerse to 2 min.

67 10 mL perchloric acid10 mL 2-butoxyethanol70 mL ethanol (95 %)

10 mL water

Precaution—Keep cool when mixing and use.Electrolytic at 30–65 V for 10–60 s.




68 3 mL perchloric acid35 mL 2-butoxyethanol

60 mL methanol (absolute)


69 5 mL perchloric acid80 mL acetic acid

Precaution—Keep cool when mixing and use.Electrolytic at 20–60 V for 1–5 min.

70 5 mL HF2 mL AgNO3 (5 %)

200 mL water

Swab for 5–60 s.


Add 5–10 drops of this solution on the finalpolishing wheel which has been chargedwith the polishing solution. The specimen ispolished on this wheel until the surfaceturns black. Distilled water is then slowly added tothe wheel and polishing continueduntil the surface is bright. At this time thespecimen should be ready for examinationvia polarized light.

Note—Use inert substance between cloth andwheel to prevent attack of the wheel.Wear gloves.


45 mL water

Swab for 5–20 s.

73 20 mL HCl25 g NaCl

65 mL water

Electrolytic etch—use carbon cathode andplatinum wire connection to specimen.(a) 6 V ac for 1 min.(b) 5 V–20 V ac for 1–2 min.(c) 20 V ac for 1–2 min.For etch-polishing, use shorter times. After etching,water rinse, alcohol rinse, and dry.

74 1–5 mL HNO3

100 mL ethanol (95 %) or methanol(95 %)

Etching rate is increased, sensitivity decreased withincreased percentage of HNO3.(a) Immerse few seconds to a minute.

(b) Immerse 5–40 s in 5 % HNO3 solution. Toremove stain, immerse 25 s in 10 %HCl-methanol solution.(c) For Inconels and Nimonics, use 5 mL HNO3

solution—electrolytic at 5–10 V for 5–20 s.(d) Swab or immerse several minutes.(e) Swab 5–60 s. HNO3 may be increased to30 mL in methanol only depending onalloy. (Ethanol is unstable with over 5 % HNO3).Do not store.




75 5 g picric acid8 g CuCl2

20 mL HCl200 mL ethanol (95 %) or methanol

(95 %)

Immerse 1–2 s at a time and immediately rinsewith methanol. Repeat as often asnecessary. (Long immersion times will result incopper deposition on surface.)

76 4 g picric acid100 mL ethanol (95 %) or methanol

(95 %)

Composition given will saturate with picric acid.Immerse few seconds to a minute ormore. Adding a wetting agent such as zepherinchloride will increase response.

77 10 g picric acid5 drops HCl


Composition given will saturate the solution withpicric acid. Immerse few seconds toa minute or more.

78 10 g potassium metabisulfite100 mL water

Immerse 1–15 s. Better results are sometimesobtained by first etching lightly withNo. 76 or 74.

79 40 mL HCl5 g CuCl2

30 mL water25 mL ethanol (95 %) or methanol

(95 %)

Swab few seconds to a minute.

80 5 mL HCl1 g picric acid


Immerse or swab few seconds to 15 min. Reactionmay be accelerated by adding afew drops of 3 % H2O2. Optional (for prioraustenite grain boundaries)—temperspecimen at 600–900°F prior to preparation.

81 2 g picric acid1 g sodium tridecylbenzene sulfonate

100 mL water

Composition given will saturate the should withpicric acid.(a) Immerse few seconds to a minute.(b) Immerse to 15 min with occasional swabbingfor heavy grain boundary attack.

82 5 g FeCl35 drops HCl

100 mL water

Immerse 5–10 s.

83 10 g CrO3

100 mL water(a) Electrolytic at 6 V for 5–60 s. Attackscarbides.(b) Electrolytic at 6 V for 3–5 s.

84 10 mL H2SO4

10 mL HNO3

80 mL water

Precaution—Add H2SO4 slowly to water and cool,then add HNO3. Immerse 30 s.Swab in running water. Repeat three times andrepolish lightly.

85 2 g picric acid25 g NaOH

100 mL water

Immerse in boiling solution for 5 min. Precaution—Do not boil dry—anhydrous picricacid is unstable and highly explosive. Alternative:Electrolytic at 6 V for 40 s (roomtemperature). Use stainless steel cathode.




86 3 g oxalic acid4 mL H2O2 (30 %)

100 mL water

Solution should be freshly prepared. Immerse15–25 min when specimens or partscannot be given usual metallographic polish.Multiple etching may be required.

87 10 mL HNO3

20–50 mL HCl30 mL glycerol

Use hood—Can give off nitrogen dioxide gas.Precaution—Mix HCl and glycerolthoroughly before adding HNO3. Do not store.Discard before solution attains a darkorange color. Immerse or swab few seconds to fewminutes. Higher percentage ofHCl minimizes pitting. A hot water rinse just priorto etching may be used to activatethe reaction. Sometimes a few passes on the finalpolishing wheel is also necessaryto remove a passive surface.

88 10 mL HNO3


Use hood—Can give off nitrogen dioxide gas.Precaution—Discard before solutionattains a dark orange color. Immerse few secondsto a minute. Much stronger reactionthan No. 87.

89 10 mL HNO3

10 mL acetic acid15 mL HCl

2–5 drops glycerol

Use hood. Do not store. Immerse or swab fewseconds to few minutes.

90 10 mL HNO3

20 mL HF20–40 mL glycerol

Immerse 2–10 s.

91 5 mL HNO3

5 mL HCl1 g picric acid


This etchant is equivalent to a 1+1 mixture of No.80 and No. 74 (5 % HNO3). Swabfor 30 s or longer.


(95 %)

Immerse 5–30 min or electrolytic at 6 V for3–5 s.

93 concentrated HNO3 Use hood. Electrolytic at 0.2 A/cm2 for fewseconds.

94 2 g CuCl2

40 mL HCl40–80 mL ethanol (95 %) or methanol

(95 %)

Submerged swabbing for few seconds to severalminutes. Attacks ferrite more readilythan austenite.

95 2 g CuCl2

40 mL HCl40–80 mL ethanol (95 %) or methanol

(95 %)40 mL water

Immerse or swab few seconds to few minutes.

96 85 g NaOH50 mL water





97 45 g KOH60 mL water

Composition of solution is approximately 10 N.Electrolytic at 2.5 V for few seconds.Stains sigma and chi yellow to red brown, ferritegray to blue gray, carbides barelytouched, austenite not touched.

98 10 g Fe�CN�4

10 g KOH or NaOH100 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide. Precaution—Alsopoisonous by ingestion as well as contact. Usefresh.

(a) Immerse or swab 15–60 s. Stains carbides andsigma. (To differentiate, No. 31electrolytic at 4 V will attack sigma, but notcarbides. If pitting occurs, reduce voltage.)

(b) Immerse in fresh, hot solution 2–20 min.Stains carbides dark, ferrite yellow,sigma blue. Austenite turns brown on overetching.

(c) Swab 5–60 s. (Immersion will produce a stainetch.)Follow with water rinse, alcohol rinse, dry.

99 25 mL HCl3 g ammonium bifluoride

125 mL waterfew grains potassium metabisulfite

Mix fresh. (For stock solution, mix first three items.Add potassium metabisulfite justbefore use.) Immerse few seconds to a fewminutes.

100 10 g FeCl3

90 mL waterImmerse few seconds.

101 2 g CrO3


Immerse 5–60 s. (CrO3 may be increased up to20 g for difficult alloys. Staining andpitting increase as CrO3 increased.)

102 concentrated NH4OH Use hood. Electrolytic at 6 V for 30–60 s. Attackscarbides only.

103 20 mL HNO3

4 mL HCl20 mL methanol (99 %)

Immerse 10–60 s.

104 5 mL HNO3


Immerse 10 min or longer.

105 5 mL H2SO4

3 mL HNO3

90 mL HCl

Use hood. Precaution—add H2SO4 slowly to HClwith stirring, cool; then add HNO3.Discard when dark orange color. Swab 10–30 s.

106 7 mL HNO3

25 mL HCl10 mL methanol (99 %)

Use fresh to avoid pitting. Immerse or swab10–60 s.




107 10 mL H3PO4

50 mL H2SO4

40 mL HNO3

Use hood. Precaution—Mix H3PO4 and HNO3

thoroughly, then add H2SO4 slowlywith stirring. Use fresh, but allow to cool.Electrolytic at 6 V for few seconds. Browndiscoloration will form at edges of specimen. Toslow reaction, add water (to 100 mL)very carefully with stirring. Attacks bakelitemounts.

108 3–10 mL H2SO4

100 mL waterElectyrolytic at 6 V for 5–10 s. Tends to pit withlonger times.


1 g CuCl2

150 mL water

Make fresh but allow to stand 30 min to avoidplating out copper. Immerse fewseconds to a few minutes.



Immerse to several minutes until deeply etched.Follow with light repolish.

111 5 mL H2SO4

8 g CrO3

85 mL H3PO4

Electrolytic at 10 V �0.2 A/cm2� for 5–30 s.Reveals Ti- and Cb-rich areas at a fasterrate than grain boundaries.


Immerse 8–15 s.


60 mL glycerol

Do not store. Use fresh solution at 80°C �176°F�.


80 mL water

Use fresh solution at 40–42°C �104–108°F�.Immerse 4–30 min depending on depth ofworked metal layer. Clean with cotton in runningwater.


Immerse 10–30 min depending on depth ofworked metal layer. Clean in HNO3 ifnecessary.

116 5–10 g AgNO3 90 mL water Swab.

117 10 mL HCl90 mL water

(a) Immerse for 1 /2–5 min. Follow withelectrolytic etch at low current density in samesolution. If specimen has considerable surface flow,immerse in concentrated HCl fora few seconds, then follow above procedure.(b) Immerse for 1 /2–2 min.

118 1 mL HNO3

75 mL diethylene glycol25 mL water

Swab 3–5 s for F and T6, 1–2 min for T4 and Otemper.

119 1 mL HNO3

20 mL acetic acid60 mL diethylene glycol

20 mL water

Swab 1–3 s for F and T6, 10 s for T4 and Otemper.





Immerse with gentle agitation 3–30 s.

121 0.7 mL H3PO4

4 g picric acid100 mL ethanol (95 %) or methanol

(95 %)

Composition critical.(a) Immerse with gentle agitation 10–30 s.(b) To increase staining immerse and withdrawwith a meniscus layer. Lightly applyetchant over surface until dark stain develops.


Swab.

123 60 mL H3PO4

100 mL ethanol (95 %)Electrolytic: Use stainless steel cathode. Spaceelectrodes 2 cm apart. Start at 3 V dc.After 30 s maintain at 11/2 V.

124 5 mL acetic acid10 mL water


(95 %)


125 10 mL acetic acid6 g picric acid





(95 %)




(95 %)



200 mL water



60 mL lactic acid

Swab 10–20 s. Vary HF to increase or decreaseactivity.

130 25 mL HCl75 mL methanol

Caution—Keep below 24°C �75°F�. Electrolyticat 30 V for 30 s.

131 5 mL H2SO4

1 mL HF100 mL methanol (95 %)

Electrolytic at 50–60 V for 10–20 s.


50 mL lactic acid

Use fresh.(a) Swab with heavy pressure for 5–10 s. Waterrinse, alcohol rinse, dry, then etchwith No. 98c.(b) Swab for 5–30 s.




133 50 mL HNO3

50 mL acetic acidUse hood. Do not store. Mix fresh. Immerse orswab 5 to 30 s. Will chemically polishwith longer times. Sulfidized grain boundariesetched before normal grain boundaries.

134 70 mL H3PO4

30 mL waterElectrolytic 5–10 V for 5–60 s. (Polishes at highcurrents.)

135 80 mL HNO3

3 mL HFUse hood. Warm specimen in boiling water prior toimmersion for 10 to 120 s.

136 20 mL H3PO4

80 mL waterElectrolytic at 10–20 V for 10–15 s.

137 10 g NaNO3

100 mL waterElectrolytic, 0.2 A/cm2, 1 min.

138 5 g FeCl3

2 mL HCl100 mL ethanol (95 %) or

methanol (95 %)

Swab 10–60 s.

139 5 g (95 %) KCN100 mL water

0.5 mL H2O2 (3 %)

Use hood—Can give off extremely poisonoushydrogen cyanide. Precaution—Alsopoisonous by ingestion as well as contact. Immerse10–100 s.


50 mL acetone

Use hood. Do not store. Decomposes with possibleexplosion on standing. Immerse10–30 s.

141 3 g NH4Cl3 g CrO3

10 mL HNO3

90 mL water

Swab 5–30 s. Do not store.

142 5 mL HF10 mL glycerol

85 mL water

Electrolytic at 2–3 V for 2–10 s.

144 A10 g sodium thiosulfate

100 mL waterB


Electrolytic in Solution A: specimen is cathode,10 V, 5–10 s. Then electrolytic inSolution B: specimen is anode, 10 V, 5–10 s.

145 2 mL H2SO4

100 mL waterElectrolytic at 3–10 V for 5–15 s. Use platinumwires. H2SO4 may be increased to 20mL for deeper attack.

146 10 mL HF100 mL HNO3

Immerse 30 s-3 min.

147 20 mL HNO3

80 mL HClImmerse 5–30 s.

148 5 mL HNO3

100 mL waterImmerse 10–30 s.

149 50 mL HCl2 mL H2O2 (30 %)

50 mL water

Immerse 10–30 s. Do not store.





40 mL glycerol

Use hood. Do not store. Swab few seconds to aminute. Discard when solution turnsdark yellow.


150 mL water

Swab 5–30 s.

152 85 mL NH4OH15 mL H2O2 (30 %)

Immerse 5–15 s. Do not store—Decomposes.

153 10 mL HNO3

50 mL HCl60 mL glycerol

Use hood. Do not store. Add HNO3 last. Discardwhen dark yellow. Immerse 10–60 s.Preheating specimen in boiling water hastensreaction.


(95 %)

Immerse 10–100 s.

155 3 mL selenic acid10 mL HCl

100 mL ethanol (95 %)or methanol(95 %)

Immerse 1–15 min. (Up to 30 mL of HCl may beused for more vigorous action.) Stablefor 3–90 days, depending on HCl concentrations.

158 1 g thiourea1 mL H3PO4

1000 mL water

Electrolytic, 0.005–0.01 A/cm2, 1–2 min.

157 25 g CrO3


Immerse 5–20 s.


20 mL glycerol

Swab 5–15 s.


50 mL acetic acid

Swab 10–30 s.

160 20 mL HF15 mL H2SO4

5 mL HNO3

50 mL water

Immerse to 5 min.

161 25 mL HNO3

5 mL HFImmerse 5–120 s.

162 A50 mL lactic acid

30 mL HNO3

2 mL HFB

30 mL lactic acid10 mL HNO3

10 mL HF

Swab 1–3 min in Solution A (acts as etch polish).To etch, swab with Solution B for 5 s.Repeat if necessary. The HF may be varied to givemore or less etching.




163 30 mL H2SO4

30 mL HF3–5 drop H2O2 (30 %)

30 mL water

Immerse 5–60 s. Use this solution for alternateetch and polishing.

164 50 mL HNO3

30 g ammonium bifluoride20 mL water

Use hood. Swab 3–10 s.

165 10 mL HCl90 mL ethanol

(a) Electrolytic at 10 V for 30 s. Use carboncathode and platinum wire connection tospecimen. For etch-polishing, use shorter time.(b) Electrolytic at 6 V for 10 s. Use stainless steelcathode and platinum or Nichromewire contact to specimen.


90 mL waterB

20 g KCN90 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide. Precaution—Alsopoisonous by ingestion as well as contact. Mix 1+1 ratio of Solution A and B justbefore use. (A mixture of 5 drops of each willcover the surface of the 1 in. dia mount.)Immerse to several minutes.

167 5 g NaCN100 mL water

Use hood—Can give of extremely poisonoushydrogen cyanide. Precaution—Alsopoisonous by ingestion as well as contact.Electrolytic at 1–5 V ac for 1–2 min. Useplatinum cathode.

168 20 mL HCl35 g NaCl

80 mL water

Composition given will saturate the solution withNaCl. Electrolytic at 11/2 V ac for 1min.

169 5 mL HNO3

50 mL ethylene glycol20 mL ethanol (95 %) or methanol

(95 %)

Electrolytic at 0.05 A/cm2 for 2 min. Use stainlesssteel cathode.


(a) Swab 5–30 s. Follow with water rinse, alcoholrinse, dry.

30 mL lactic acid (b) Swab for 10 s intervals. Increase HF toexaggerate grain boundaries.

171 concentrated HCl Use hood. Electrolytic at 5 V ac for 1–2 min. Foretch-polishing, use shorter times.Follow with water rinse, alcohol rinse, and dry.


10 mL waterB

5 g KCN100 mL water

Use hood—Can give off extremely poisonoushydrogen cyanide. Precaution—Alsopoisonous by ingestion as well as contact. Prepare1+1 mixture of Solutions A and B just before use.(A mixture of 5 drops of each will cover thesurface of a 1 in. diamount.) Immerse 1–2 min.

173 50 mL NH4OH10–30 mL H2O2 (50 %)

Immerse few seconds to a minute.




174 A25 mL HNO3

1 g K2Cr2O71000 mL water

B40 g CrO33 g Na2SO4

200 mL water

Prepare 1+1 mixture of Solutions A and B. Applywith camel’s hair brush.Nonadherent film of silver chromate should form.If film adheres, add more of solutionA, if none forms, add Solution B.

175 1 g CrO3

1 mL H2SO4

100 mL water

Immerse to 1 min.

176 2 g FeCl3

100 mL waterImmerse 5–30 s.


Swab or immerse 5–15 s.


60 mL lactic acid

Swab for 5–20 s.

179 A10 mL HF

10 mL HNO3

30 mL lactic acidB

10 mL HF10 mL HF

90 mL H2SO4

Use hood—Mix Solution B very slowly. SolutionA is used as a chemical polish, thoughsome etching will occur. Swab 2 or more minutesfor desired surface. If surface isinsufficiently etched use Solution B electrolyticallyat 1 /2–1 V/ in.2 of specimen. Usecarbon cathode and platinum wire connection tospecimen. Discard Solution B after 1h.

180 10 mL HNO3

30 mL acetic acid50 mL glycerol

Immerse for 1 /2–10 min at 38 to 42°C�100–108°F�.


(95 %)

Swab for 1–3 min.

182 10 mL HNO3

10 mL acetic acid80 mL glycerol

Immerse for 1 /2–10 min at 38 to 42°C�100–108°F�

183 2 drops HF1 drop HNO3

25 mL glycerol

Immerse for 1 min.

184 10 g FeCl3


Immerse for1

2–5 min.


Swab for few seconds.


Swab 3–2 s.

85 mL water





50 mL water

Swab 3–20 s.


50 mL H2O2 (30 %)50 mL water

Swab until stain is removed.


45 mL glycerol20 mL water

Swab 3–20 s.

190 8 g KOH10 mL H2O2 (30 %)

60 mL water

Swab 3–20 s.

191 25 mL HF18 g benzalkonium chloride

35 mL methanol (95 %)40 mL glycerol

Swab 3–20 s.

192 1–3 mL HF2–6 mL HNO3

100 mL water

Swab 3–10 s or immerse 10–30 s. (HF attacksand HNO3 brightens the surface oftitanium. Make concentration changes on thisbasis.)

193 2 drops HF1 drop HNO3

3 mL HCl25 glycerol

Swab 3–20 s.


60 mL glycerol

Immerse 5–30 s.

195 30 mL H3PO4

30 mL ethylene glycol50 mL ethanol (95 %)

Electrolytic at 18–20 V �0.03 A/cm2� for5–15 min.

196 18 g CrO3

75 mL acetic acid20 mL water

Dissolve CrO3 in hot water and cool before addingacetic acid. Keep solution below2°C �35°F� during use. Electrolytic at 80 V for5–30 min. Do not store.




30 mL glycerol

Swab for 60 s.

199 2 mL HF5 g AgNO3

100 mL water

Swab for 5 s




200 A40 g CrO3

3 g Na2SO4

200 mL waterB

40 g CrO3

200 mL water

Immerse in Solution A with gentle agitation forseveral seconds. Rinse in Solution B.

201 A40 g CrO3

1.5 g Na2SO4

200 mL waterB

40 g CrO3

200 mL water

Immerse in Solution A with gentle agitation forseveral seconds. Rinse in Solution B.

202 A10 g CrO3

1 g Na2SO4

200 mL water

Immerse in Solution A for 2–5 s. Rinse inSolution B.

B40 g CrO3

200 mL water

203 20 g CrO3

100 mL waterElectrolytic at 0.2 A/cm2 for 5 s.

204 10 mL perchloric acid10 mL glycerol

70 mL ethanol (95 %)10 mL water


205 5 mL HF2 mL AgNO3 (5 %)

100 mL water

Swab vigorously for 10–60 s. Wet cottonfrequently.


10 mL glycerol

Precaution—Discard after use. Solutiondecomposes on standing. Electrolytic at 9–12V for 1–10 min.

207 30 mL HNO3

30 mL acetic acid30 mL water

Swab for 5–30 s.

208 1 mL NH4OH3 g ammonium persulfate

10 mL water

Immerse or swab few seconds to a minute.

209 15 mL HNO3

3 mL HF80 mL water

Immerse 5–60 s.




210 50 mL water (cold) saturated withsodium

thiosulfate1 g potassium metabisulfite

First ingredient in stock solution. Add potassiummetabisulfite before use. Solutiongood for several days, or longer. Immerse face up,gently agitate until colorationbegins, allow to settle. Stop etch when surface isred-violet. Etch time varies withmaterial. Colors matrix phases.

211 3 g potassium metabisulfite10 g sodium thiosulfate

100 mL water

Use fresh solution. Immerse specimen face up,gently agitate solution until colorationbegins, allow to settle. Stop etch when surface isred-violet. Etch time varies withmaterial. Colors matrix phases.

212 10–50 % HCl in water0.5–1.0 g potassium metabisulfite per

100 mL of aqueous HCl solutionOptional: 1 g CuCl2

1–3 g FeCl3

2–10 g ammonium bifluoride

For more corrosion resistant alloys. Increase theHCl and potassium metabisulfitecontents. Use optional ingredients to improvecoloration, if needed. Colors matrixphases. Use by immersion only.

213 2–10 mL HCl0.5–3 mL selenic acid

100 mL ethyl alcohol (95 %)

For more corrosion resistant alloys, increase theHCl and selenic acid content. For highlycorrosion-resistant alloy, use 20–30 mL HCl.Colors second phaseconstituents. Use by immersion only.

214 1 g sodium molybdate100 mL water

Add nitric acid to lower the pH to 2.5–3. Add0.1–0.5 g ammonium bifluoride for cartonsteels. Use by immersion only. Colors carbides.Immerse about 15 s.

215 240 g sodium thiosulfate30 g citric acid

24 g lead acetate1000 mL water

Mix in order given. Store in a dark bottle at least24 h before use at 20°C. Lightly pre-etch specimen before use. Use small portion ofstock solution for 4 h max. Pre-etchsteel specimens with nital before tinting the MnS(add 0.2 g sodium nitrite to 100 mLof etch) white. Colors phosphides in cast iron.Colors matrix of Cu alloys.

216 8–15 g sodium metabisulfite100 mL water

Do not store. Mix fresh. Immerse specimen faceup. Agitate solution gently untilcoloration begins, allow to settle. Stop whensurface is dark. use crossed polarizedlight and sensitive tint to improve coloration.

217 5 g ammonium bifluoride100 mL water

Mix fresh, use plastic coated tongs andpolyethylene beaker. Immerse until surface iscolored.

218 3 g ammonium bifluoride4 mL HCl

100 mL water

Mix fresh, use plastic coated tongs andpolyethylene beaker. Immerse until surface iscolored. Works best with attack-polishedspecimens.




219 60 mL HNO3

40 mL waterElectrolytic etch, does not reveal twins in

stainless steel. Excellent grain boundaryetch for ferritic stainless steels. Use at 1 V dc,120 s, with stainless cathode; 0.6 V dcwith platinum cathode.


Electrolytic etch, colors �-ferrite in stainless steel.Use at 2–20 V dc, 5–20 s,stainless steel cathode. If � is not colored, increaseNaOH to 40 g.

221 50 mL water50 mL ethyl alcohol

Use by immersion. Will not attack sulfides instainless steels.

50 mL methyl alcohol50 mL HCl1 g CuCl2

2.5 g FeCl3

2.5 mL HNO3

222 8 g Na2SO4

100 mL water(a) Few seconds to 1 minute.(b) Pre-etch 2 s in No. 74, rinse, and etch 20 s.

223 A8 g oxalic acid5 mL H2SO4

100 mL waterB

H2O2 (30 %)

Mix equal volumes of Solutions A and B justbefore use. Etch 2–3 s; 3 s pre-etch inNo. 74 may be needed.

224 10 mL H2O2 (30 %)20 mL 10 % aqueous NaOH

Immerse 10 s at 20°C �68°F�.

225 4 g NaOH100 mL saturated aqueous KMnO4

Immerse 10 s at 20°C �68°F�.

226 15 mL HCl10 mL acetic acid

5 mL HNO3

2 drops glycerol

Use hood—Can give off nitrogen dioxide gas.Precaution—Mix HCl and glycerolthoroughly before adding HNO3. Do not store.Discard before solution attains a darkorange color. Use fresh or age up to 1 min.Immerse or swab few seconds to fewminutes. Can increase HNO3 to increase strength.Sometimes a few passes on thefinal polishing wheel is also necessary to remove apassive surface.

901 1 g KOH100 mL water

Electrolytic: Use stainless steel cathode. 40 VDC at 3 A/cm2 in 30–60 s

902 Plasma etching with CF4 gas and O2

gas (1:1)3–5 min, 60–80 W

903 See etchant 98 (Murakami’s reagent) Use hot, 30–40 min for SiC with 1 % B4C orboiling for B-doped SiC

904 30 g K3Fe�CN�6

3 g NaOH60 mL water

Immerse 5–30 min at 110°C �230°F�




905 10 g K3Fe�CN�6

10 g NaOH20 mL water

Immerse 5–10 min

906 10 g K3Fe�CN�6

10 g NaOH80 mL water

Immerse 10–20 min

907 10 mL HNO3 (65 %)10 g K3Fe�CN�6

100 mL water

Immerse 30–40 min at 60°C �140°F�

908 30 g K3Fe�CN�6

3 g NaOH60 mL water

Immerse 8–15 min. Use boiling

909 10 mL HNO3 (65 %)10 mL HF (40 %)

10 mL water

Immerse seconds to min

910 10 mL HF (40 %)50 mL lactic acid

30 mL HNO3 (65 %)

911 10 mL HF (40 %)30 mL HNO3 (65 %)

Immerse 2 min

912 10 mL HCl (32 %)10 mL H2O2 (30 %)

Immerse seconds to min

913 Plasma etchingCF4 gas and O2 gas (2:1)

1–5 min, 60–80 W

914 H3PO4 (85 %) Use boiling up to 15 min

915 Molten NaOH (free of water) 20 s to 3 min at 300–350°C �570–660°F�, 2–3samples per melt

916 10 mL 10 % aqueous NaH solution10 mL 10 % aqeous potassium

ferricyanide solution50 mL water

(Modified Murakami, see etchant 98)

Immerse 30 min at 100°C �212°F�)

917 Thermal etch in air 1100–1500°C 15–20 min at 1300–1400°C �2370–2550°F�(Etch temperature is approximately 150°C�300°F� below sintering temperature

918 H3PO4 (85 %) 5 s to 3 min at 250°C �480°F�919 HCl (32 %) Immerse 3–6 min

920 Sat. aq. Na2S Immerse up to 1 min

921 20 mL HNO3 (65 %)10 mL HF (40 %)

20 mL water

Immerse up to 15 min

922 45 mL HNO3 (65 %)5 mL HF (40 %)

50 mL water

Immerse up to 15 min agitate

923 KHSO4, molten Immerse 15–20 s at 300°C

924 15 mL HNO3 (65 %)100 mL water

Immerse 3–5 min at 25–60°C �77–140°F�




925 10 g NaOH10 g K3Fe�CN�6

100 mL water

Immerse seconds to minutes

926 Thermal etch in air Minutes to 1 h at 1300–1400°C �2370–2550°F�(according to sintering temperature)

927 H3PO4 (85 %) Immerse 3 s to 2 min at 250°C �480°F�928 Thermal etch in air 30–60 min at 1200°C �2190°F� 5 s to 2 min

929 3 mL HCl (32 %)2 mL HF (40 %)

95 mL water

Immerse 5 s to 2 min

930 2 mL HF (32 %)98 mL water

Immerse 10–15 min

931 5 mL HNO3 (65 %)5 mL HF (40 %)

90 mL water

Immerse, up to 20 s

932 10 mL HNO3 (65 %)10 mL HF (40 %)

Immerse up to a few min

933 50–100 g NaOH100 mL water


934 15 mL HCl (32 %)10 mL HF (40 %)

90 mL water


935 30 mL HCl (32 %)5 mL H2O2 (32 %)

70 mL water


936 30 mL CH3COOH (glacial acetic acid)10 mL H2O2 (30 %)


937 30 mL HCl (32 %)2 g FeCl3

100 mL water


938 25 mL HCl (32 %)8 g FeCl3

100 mL water

939 15 mL HCl (32 %)50 mL aq. sodium thiosulfate (16 %)

3 mL aq. CrO3 (10 %)30 mL water

Add CrO3 just before use

940 50 mL HCl (32 %)50 mL water

Immerse 1–10 min

941 25 down to 9 mLHNO3 (65 %)

25 down to 9 mL CH3COOH (glacialacetic acid)

100 mL glycerol (87%)

Immerse s to min

942 200 mL acetyl acetone1–2 mL nitric acid (65 %)

Immerse 2–18 min in ultrasonic bath to break upthe oxide layer




943 100 mL HNO3 (65 %)100 mL H2SO4+CrO3

(chromosulfuric acid)(Variable concentration)

Immerse in 2 min at 70°C, time varies

944 60 g CrO3 (chromium (VI)oxide)100 mL water

Immerse several hours at 70°C

945 HNO3 (65 %) Polyethylene (PE): Immerse in seconds tominutesPolyoxymethylene (POM) and polypropylene(PP): Immerse in 10 min

946 C6H4�CH3�2 (xylol) (99.8 %) Polyethylene, polypropylene: Immerse 3 days at70°CPolyamid, polyethylene: 70°Cfor 60 s. Nylon 6: 65–70°C for 2–3 min. Nylon6,6: 75°C for 3–4 min

947 C6H15N (triethylamine (99 %) Immerse seconds to minutes

948 30 mL HCl (32 %)100 mL distilled water

Immerse 20 s

949ASTM

StandardB 657,Etching

Technique1

A: Freshly prepared mixture of equalquantities of 10 % (mass/mass)

aqueous solutions of K3Fe �CN�6 (III)(potassium ferricyanide and

potassium or sodium hydroxide)

Etch in mixture A at approx. 20°C for 2–10 s.Flush the test-piece section with waterimmediately, without removing the oxide layer.Dry the surface carefully with acetone or alcoholwithout wiping

950ASTM


Technique2

A: same as A (949)B: A mixture of equal volumes of

concentrated hydrochloric acid andwater

Etch at approx. 20°C in mixture A for 3–4 min..then wash in water and etch in mixture B forapprox. 10 s. Next wash in water, then in alcoholand dry the test-piece section. Finally, etch inmixture A for approx. 20 s

951ASTM


Technique3

A: same as A (949) Etch in mixture A at approx. 20°C for 3–6 min


12.5.3 Table 12.3—Etchant Names

TABLE12.3—Etchantnames. (This tablewas taken fromASTME407.)

CommonName No. CommonName No.

Acetic glyceregia 89, 226 Groesbeck’s 19

Alkaline Sodium Picrate 85 Hatch 2

Aqua regia 12 Howarth’s 84

Barker’s 5 Kalling’s 1 95

Beraha’s 99, 155, 211–215 Kalling’s 2 94

Carapella 138 Keller’s 3

Chrome regia 101 Klemm’s 210

Contrast 141 Kroll’s 192, 187

CP 4 60 Marble’s 25

El-1R 107 Marshall’s 223

Flat 133 Murakami’s 98

Flouregia 90, 158 Nital 74

Frank’s 104 Palmerton 200

Fry’s 79 Phoschromic 111

G 107 Picral 76

Glyceregia 87 Ralph’s 221

Gorsuch 75 Super Picral 77

Grard’s No. 135 Vilella’s 80

Green contrast 94 92-5-3 105


13Specimen Preparation

13.1 Introduction

THIS CHAPTER COVERS THE PRACTICAL PREPARATION OF THE MATER-ials stated in Table 11.1 for each material two different methods of the mechanicalpreparation process are stated in 68 Material/Preparation Tables. These tables alsocontain specific information on ASTM standards and etching described in Chapter 12.

Electropolishing is covered by 25 methods.At the end of the chapter, Section 13.5 covers Trouble Shooting regarding the pro-

cess and the results.The background for the preparation process, including general advice and hints

for wet abrasive cutting and mounting can be found in Part I. Advice and hints for thetotal preparation process covering specific materials will be stated on each Material/Preparation Table and in Section 13.5.

13.2 Mechanical Preparation—The “Traditional” and“Contemporary” Methods

As described in Part I, two basic methods are available for the metallographer, one isbased on SiC grinding paper or other “traditional” grinding media, referred to as the“traditional” method with a T-number, and another method, based on rigid compositedisks �RCDs�, referred to as the “contemporary” method, with a C-number.

Both methods will be stated side-by-side in the Material/Preparation Tables, Sec-tion 13.2.3.

13.2.1 Material/Preparation TablesEach sheet of Material/Preparation Tables has a number starting with 1–68. The twoMethod Tables, one for the C-Method and one for the T-Method are part of the Material/Preparation Tables and have the same number as the sheet, for example, C-01 and T-01.Each sheet with tables can be from three to six pages, depending on the amount of text.The tables include as far as possible all relevant information for the preparation pro-cess of the given material or material group.

The text is in the following order:Material or Material Group, see Section 11.2 and Table 11.1.Material Properties: For most materials, four basic properties are stated: Crystal

Structure, Density in g/cm3, Melting Point in °C �°F�, and Hardness, �for nonferrousmetals the figures for hardness are taken from ASM Handbook, Vol. 02, Properties andSelection: Nonferrous Alloys and Special-Purpose Materials, ASM International, Materi-als Park, Ohio, USA, 1990. The hardness can be in HB, HK, HRC, HV, and Moh �in somecases, no hardness is indicated�.

Comments on Material: Basic information on the material and the preparationof the material.

General Comments on:

218

SectioningMountingGrindingPolishingEtchingPurpose: A table indicating relevant methods relating to the purpose of examina-

tion and ASTM standards �see Section 12 and Table 12.1�.Preparation Process:Sectioning: Specific indications.Mounting: Specific indications. Attention: In most cases several types of mount-

ing materials can be used. In these cases only examples, “bakelite” �hot mounting� and“acrylics” �cold mounting� are stated.

Grinding: Specific indications.Polishing: Specific indications.Contemporary Method: Method Table.Traditional Method: Method Table.Etchants: Table with relevant etchants.

13.2.2 Method Tables—Generic Methods—Parameters/Consumables—Table 13.1

Generic MethodsThe Method Tables covering the C- and T-methods contain a number of parametersand consumables. The methods should be considered “generic,” and state a basic pro-cedure for a given material, using a standard semiautomatic grinder/polisher with ex-changeable grinding/polishing disks. The specimens are either “single specimens” or“fixed specimens” in a holder on a 300 mm �12 in� grinding/polishing disk. If materialor equipment/consumables vary, the data must be changed accordingly �see below un-der “Force per Specimen” and “Time”�.

The time stated for each step can in some cases be shortened with the stated timesbeing to the “safe side.” This is because the preparation time normally is the only indi-cation we have of “material removal.” During the preparation a certain amount of ma-terial should be removed. The best would be a direct measurement, but in normal prac-tice only the process time can be measured, giving an indication of material removalbased on experience. Variation in polishing cloths, abrasives, etc., justifies the rela-tively long times indicated to secure a sufficient material removal, but often the metal-lographer with experience will be able to shorten these times.

StepsThe method is divided into a number of steps:

PG �plane grinding�. This is the first step and is usually performed with one or sev-eral sheets of 220 grit SiC grinding paper. In the row, Time �see below� normally “Untilplane” is stated, indicating that a sufficiently prepared surface, coplanar to the surfaceof the paper and with a regular “220” scratch pattern covering the whole specimen sur-face is obtained.

In some cases a coarser grain like grit 180 can be used before grit 220, but 220should always be used as the last paper for PG. This ensures the reproducibility of themethod.

For some materials �very hard or soft�, grit 220 grinding paper is not stated for PG;

Chapter 13 Specimen Preparation 219

in these cases, PG, possibly made in several steps, shall end with the Disk/Cloth statedin the Method Table.

See also Time below.FG �fine grinding�. This can be in several steps indicated with a number, e.g., FG 1.P �polishing�. This can be in several steps, indicated with a number, e.g., P 1. In

most methods, the last step indicated is with silica/alumina. Often this step can beomitted, depending on the purpose of the preparation.

ParametersEach step contains a number of parameters:

Disk/Cloth: The surface covering the rotating disk of the grinding/polishing ma-chine.

Abrasive Type: The abrasive used for grinding and polishing.Grit/Grain Size: Grit, indicated with a P- number corresponding to the FEPA stan-

TABLE 13.1—Comparison Between Surfaces for Grinding and Polishing from a Number of Suppliers withAbbreviations Used in Method Tables.

Suppliers Buehler Struers Leco

AlliedHighTech

MarkV

Lap-master

Abbreviations inMethod Tables

Dia, pad, bak ormet

Ultra-Prep DiamondPad

DiamondSpotPattern

BondedDiamondDisk

FlexDiamondDisk

Dia, disk, fixed,res

Apex DGD MD-Piano CameoPlatinum

RCD, hard ApexHerculesH MD-Allegro

CameoSilver

RCD, soft ApexHercules S MD-Largo CameoGold

Cloth, napless,v. hard, wov,syn

Ultra-Pad DP/MD-Plan

PlanCloth

Cloth, napless,hard, nonwovsyn

Texmet 2000Texmet 1000

DP/MD-Pan

Leco PolPan-W

KempadPan-B

Met-X Pan-W

Cloth, napless,hard, wov, silk

Ultra-Pol DP/MD-Dur

Silk Silk Silk Silk

Cloth, napless,hard, wov, syn

TridentNylon

DP/MD-Dac

GoldTechnotronNylon

GoldLabelNylon

RAMNylon

ASRNylon

Cloth, napless,med hard, wov,wool

DP/MD-Mol

Broadcloth

MicroLP

Cloth, med nap,soft, syn

Microcloth DP/MD-Nap

Lecloth Spec-Cloth

AlphaA

NTR

Cloth, napless,soft, porous, syn

Chemomet OP/MD-Chem

BlackTechnotron

Chem-Pol Supreme


dard �see Table 6.2 for comparison to American standard�. In case of diamond or an-other abrasive, the grain size is indicated in �m.

Lubricant Type: The type of medium used for lubrication during the process.Rotation Disk/Holder, Comp/Contra: rpm of grinding/polishing disk and speci-

men holder. “Comp” means complementary: The disk and holder rotates in the samedirection. “Contra” means counter rotation: The disk and the holder rotates in oppositedirections.

Force per Specimen: The force in N and lb per specimen. Attention: The force isbased on a 30 mm �1.25 in� mounted specimen with the specimen totaling approxi-mately 50 % of the mount. At 25 mm �1 in� specimens the force should be reduced withthe factor 0.7. At 40 mm �1.50 in� only increase the force up to a maximum of 50 N�11 lb� and as compensation, to obtain the necessary material removal, extend thepreparation time with 1–4 min. This is to avoid a possible overheating of the polishingcloth that can take place at a force on each specimen of more than 50 N �11 lb�. WithSiC grinding paper, a very high force might create heavy damage to the specimen �seeSection 6.6� and the paper, if not glued to the disk, might be torn away.

Be aware that the values indicated are for a single specimen. When using a holderwith say six fixed specimens, the value should be increased with a factor 6.

Time: The number of minutes the specimens are in contact with the disk. Atten-tion: For specimens larger than 30 mm �1.25 in� the time should be extended �seeForce per Specimen above�. Also, if the grinding/polishing disk is smaller than300 mm �12 in�, the time should be extended. At PG, until plane indicates that thespecimen surface should be uniformly covered with a regular scratch pattern. The timeused depends on the quality of the sectioning and the alignment of the specimens if aspecimen holder with several fixed specimens is used.

Consumables—Abbreviations—Table 13.1The methods are based on the use of a number of consumables which are described inthe Method Tables with abbreviations. These consumables have different names fromthe different suppliers. For this reason a description is given below for each type ofconsumable. Based on this, the user should be able to choose the correct consumablefrom any supplier.

The surfaces used for grinding and polishing can be difficult to describe. For thisreason, a list of surfaces from a number of suppliers is stated in Table 13.1.

The descriptions are given according to the abbreviations used in the MethodTables, stated alphabetically.

For a more detailed description of consumables see Part I.

Abbreviations Used in Method Tables—Description of ConsumablesAlco: Alcohol-based lubricant. This lubricant should be phased out if possible and re-placed with water-based lubricant because ethyl alcohol �ethanol� is considered a dan-ger to health in certain countries.

Alumina: Al2O3 suspension as abrasive.Bak: The abrasive is fixed in a bakelite bond.Cloth: A surface made of a textile or other flexible material fixed to the polishing

disk with adhesive backing or magnetically.Disk: A surface for grinding/polishing made of a material with a “rigid” surface

normally fixed to the polishing disk like a cloth, or in some cases a solid disk taking theplace of the polishing disk.


Dia: Diamond as abrasive. This is followed by spr or susp, or both �see below�.Diamond: Diamond as abrasive.Fixed: The abrasive is fixed in the surface of the disk.Hard: A hard rigid composite disk �RCD� or polishing cloth with a relatively hard,

aggressive surface. A hard cloth could be satin woven, very thin or compact �see “V.hard”� without nap and with a very low resilience.

Low nap: Polishing cloth with a very short nap could be synthetic material. Lowresilience.

Med„ium… hard: Polishing cloth, napless, with a low resilience.Med„ium… nap: Polishing cloth with a medium nap could be a flocked cloth with

relatively high resilience.Met: The abrasive is fixed in a metal bond.Napless: Polishing cloth without nap �see Hard above�.Nonwov: Polishing cloth made of a nonwoven material.Oil: Oil-based suspension or lubricant. This type should be avoided because oil-

based products are considered dangerous to health in certain countries. Oil-based dia-mond suspensions are only stated in the T-methods. Lubricants based on oil emulgatedwith water �see below�.

Pad: Diamond pad �disk� with either metal or bakelite bond.Porous: Polishing cloth with a porous surface mostly used for oxide polishing.RCD: Rigid Composite Disk.Res: The abrasive is fixed in a resin bond like epoxy, different from bakelite.SiC paper: SiC wet grinding paper, normally with a C weight backing, and nor-

mally used with plain backing �see Section 13.2.4�. In certain cases it is an advantage touse paper with an adhesive back for “heavy” automatic grinding.

Silica: Colloidal silica �SiO2� as abrasive.Silk: Polishing cloth made of silk.Soft: A soft RCD or cloth with a relatively soft, less aggressive surface. For a cloth,

soft indicates a certain relative resilience, and can be with “Nap” or “Napless.”Spr: Diamond spray.Susp: Diamond suspension.Syn: Polishing cloth made of synthetic material.V.hard: A very hard cloth with an aggressive surface mostly used for “fine grind-

ing” �see “Hard” above�.Wat: Water-based suspension or lubricant. This type should be preferred because

alcohol- and oil-based products are considered dangerous to health in certain coun-tries.

Water: Normal tap water or recirculated water, with or without an additive.Wat-oil: Lubricant based on water with an in-mixed oil forming an emulsion.Wool: Polishing cloth made of wool.Wov: Polishing cloth made of a woven material.

13.2.3 Material/Preparation Tables—Methods C-01/T-01 to C-68/T-68This section contains 68 numbered sheets with Material/Preparation Tables �M/PT�that include material/process information and two Method Tables.

To find the correct M/PT use Table 11.1Using these tables should guide the user to obtaining a satisfactory preparation

result based on the material and the examination purpose.The data stated in the Method Tables are based on a specimen of 30 mm �1.25 in�


diameter, clamped in a specimen holder on a 300 mm �12 in� grinding/polishing disk.Using a smaller disk diameter might prolong the preparation time. The specimen areashould be approximately 50 % of the mount.

The force indicated is per specimen and should be multiplied with the number offixed specimens in the holder.

The dosing levels for lubricant and abrasives are to be adjusted individually be-cause temperature, humidity, etc., has a significant influence on the preparation pro-cess. Take care that the surface of the polishing cloth/RCD is just “moist” when touchedwith a fingertip, not “wet.”

For manual preparation see Section 13.2.4; often the data indicated in theT-methods and some of the C-methods are suited for preparation by hand.

For electrolytic polishing see Section 13.4.2.

Material/Preparation Tables 01Material: Hydroxyapatite „HA… coating

Material Properties: HA: Ca10�PO4�6�OH�2

Comments on Material: Ceramic materials that are specially developed for use asmedical and dental implants are called bioceramics. They include alumina andzirconia, bioactive glasses, glass-ceramics, coatings and composites,hydroxyapatite �HA�, tricalcium phosphate �TCP� and other calcium phosphatesand radiotherapy glasses. The most used bioceramics are calcium phosphatecompounds, especially HA and TCP. This is because they have almost the samecompositions as the skeleton �69 % of bone is HA� and they have excellentbiocompatibility. When these ceramics are implanted into the living body �in vivo�for a range of time, it is found that they have a strong chemical bond with bonetissue and finally become a firm attachment. Ceramics are brittle and they are lesssuited for load-bearing applications. Therefore, a calcium phosphate like HA isused as a coating on materials such as titanium alloys or stainless steel where itcan contribute its bioactive properties, while the metallic component bears theload. Also the coating gives a relatively rough surface that increases themechanical fixation of the component. The accepted method of applying HAcoatings to metallic implants is plasma spraying. The coatings with HA and TCPare made with a controlled porosity. This porosity and other features like thecontact between base material �substrate� and coating should bematerialographically examined.For preparation of other bioceramics see Material/Preparation Tables �M/PT� 05and 06, and for other ceramic coatings see M/PT 14.


Sectioning: HA/TCP are very sensitive materials and should be kept free ofcontamination during the cutting. This can be done by masking the areas ofconcern using plastic film and tape. It is important that the specimen is mountedand vacuum impregnated before sectioning takes place to avoid damaging thebrittle ceramic layer �see below�. The sectioning should be done on a precisioncutter with a cut-off wheel suited for the base material �substrate�. The specimenshould be oriented so that the coating is compressed into the substrate during thecutting �see also M/PT 08�. The thinnest possible cut-off wheel should be used andthe feed speed should be low.Mounting: Before sectioning a careful vacuum infiltration of the specimen shouldtake place �see M/PT 02 and Section 3.10�. It is important that all open pores arefilled with epoxy so that the coating cannot be contaminated or damaged duringthe following preparation. The sectioned specimen should possibly be vacuumimpregnated after the sectioning and carefully mounted in epoxy to secure a goodedge retention.Grinding: In Methods C-01 and T-01 it is an assumption that the base materialcan be ground with SiC grinding paper. For grinding surfaces for the harderceramics see M/PT 02–06.Grinding times should be kept at a minimum.Polishing: Also, polishing times should be as short as possible to secure a goodedge retention.Etching: Normally the HA/TCP layer is not etched, but relief polishing, creating a“physical etching” can be used �see Section 9.6�. For other ceramics see M/PT 02to 06.

Purpose ASTM Standard �See Section 12.4� MethodCase or coating thickness/hardness,surface layers

C-01

Perfect edge retentionGrain size, grain boundaries E 562, E 1245,

E 1268, E 1382C-01

Image analysis, rating of inclusioncontent

E 562, E 1245,E 1268, E 1382

C-01

High planenessMicrohardness, hardness C 730, C 849, C 1326,

C 1327, E 384C-01,T-01

Microstructure E 3, E 562, E 883,E 1245, E 1268, E 1382

C-01,T-01

Phase identification C-01,T-01

Porosity C-01Thermal spray coatings: Distribution,porosity, unmelted particles

C-01


Preparation Process 01

Sectioning

Cut-Off Wheel Al2O3 or SiC, backlite bond or diamond, metal bond

Mounting

HotCompressionMounting

Resin Cold Mounting Resin EpoxyTimeMinutes

TimeMinutes/Hours

6–12 h

Grinding

Attention: In C-methods when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-01: In some cases a step with a napless, hard, wov, silk cloth and 1 �mdiamond, other parameters like step P 2 in method T-01, can be added as P 1,making the shown P 1 to P 2.

Contemporary Method C-01 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/Polishing

PG FG 1 FG 2 P 1

Disk/Cloth SiC paper SiC paper RCD,soft

Cloth, naplesssoft, porous, syn

Abrasive Type SiC SiC Dia, spror susp

Silica

Grit of GrainSize �m

320 500 9 0.04

Lubricant Type Water Water Alco/watRotationDisk/Holder

300/150 300/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp ContraForce perSpecimenN �lb�

30 �7� 30 �7� 40 �9� 15 �3.3�

TimeMinutes

Until plane 1 5–6 2–4


Traditional Method T-01 �For definitions of parameters and consumbles seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

PaperSiCPaper

SiCPaper

SiCPaper

Cloth,napless,hard, wov,silk

Cloth,napless,hard,wov,syn

Cloth,napless,soft,porous,syn

AbrasiveType

SiC SiC SiC SiC Dia, spr orsusp

Dia, spror susp

Silica

Grit orGrainSize ��m�

P220 P320 P500 P1000 6 3 0.04/0.05

LubricantType

Water Water Water Water Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comporcontra

Comporcontra

Comp Comp Contra

Force perSpecimenN �lb�

20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 6 3 1–2


Material/Preparation Tables 02Material: Boron carbide, B4C. Silicon carbide, SiC. Other carbides

Material Properties: B4C: Rhombohedral, 2.52 g/cm3, 2450°C �4442°F�, HV3400–3800SiC: Hexagonal/cubic, 3.21 g/cm3, 2300°C �4172°F�, HV 2800–3600Comments on Material: High-performance ceramics can roughly be characterizedby structure and function. They can be divided roughly into two categories,structural and functional ceramics. For those structural ceramics like siliconnitride, silicon carbide, some types of zirconium dioxide, and a number of mixedceramics based on Al2O3, the properties are directed towards mechanical strengthand other mechanical properties. For those functional ceramics like bariumtitanate, zinc oxide, and titanate the properties are directed towards electric,magnetic, dielectric, and optical properties. Some ceramics like aluminum oxide�the most important high-performance ceramic� and zirconium dioxide can beoptimized towards either structural or functional properties. For in-depthinformation on ceramics and preparation of ceramics see Carle et al. Ref. 26, �PartI� and Elsner et al. Ref. 27, �Part I�.In contrast to metals, the evaluation of ceramic materials with light microscopycan be carried out both by reflected light and �with some exceptions� on thinsections by transmitted light. For economic reasons, however, the more simplepreparation of specimens for reflected light is preferred for routine examination.For preparation of thin sections see Section 7.13.1.Compared to metals, ceramics have a high to very high hardness, a low ductility,and a high brittleness. The high hardness influences the preparation to a highdegree, but other factors like porosity and brittleness also makes the preparationdifficult.Brittleness: This might cause pull-outs during cutting and grinding, the ceramicgrains being removed by the abrasive. Pull-outs are especially critical in materialswith a vitreous �amorphous� phase between the grains. Also cracks and surfacestress can develop during sectioning and grinding �see Sections 6.3.2 and 13.6�.Porosity: Often the following should be determined: Total porosity, pore type,shape, size, and pore size distribution. Pull-outs are often made during the firststages of the preparation. These pull-outs can be observed as pores and often willdisturb the analysis of grains, etc. Also, the edges of the original pores will bedamaged and rounded after grinding and fine grinding. In case of differences inhardness between phases, material can be smeared into the original pores �see alsoSection 13.6�.Preparation methods: Due to the large variations in ceramic materials, five Material/Preparation Tables, 02–06, with ten methods, are stated in the following.Preparation times: A wide variation in time is provided in the method tables. Thisis due to the large variations in ceramic materials which in some cases call forlong times, especially in the case of a high porosity.


Sectioning: The bond of the diamond cut-off wheel, its thickness and also thetype, size, and concentration of the abrasive grains are mainly responsible for thequality of the cut surface. Both metal bond �bronze� and bakelite bond can beused. Bakelite bond will give the least damage to the surface and should be usedon brittle/porous materials. Depending on the material properties, feed rate androtational speed of the cut-off wheel should be adjusted. The higher porosity andrisk of pull-outs of a material, the slower the feed rate. The rotational speedshould not exceed 2000 rpm and often a lower speed should be used. The surfacequality can normally be improved by using a cut-off wheel with small grain size,giving a drawback when cutting large specimens as the cutting time is prolonged.The concentration of diamonds in the bond should not be too high, causing thewheel to “press” and “pinch,” which will create pull-outs and micro andmacrocracks �see Section 2.4.2�. The same types of material damage develop witha very hard bond. As a rule the cutting should be made with a thinnest possiblewheel with a grain size around 94 �m. Special care should be taken whenclamping specimens. Pressure spots induce high stress which might fracture thematerial prior to cutting. In case of very brittle and porous materials, animpregnation before cutting can be necessary �see below and also Section 13.6�.Mounting: Vacuum impregnation: If the porosity is higher than 5 % it is advisableto impregnate under vacuum in a special apparatus using epoxy of low viscosityand possibly a dye �see Section 3.10�. Impregnation should often be repeated aftergrinding to close pores that have been opened.Mounting: Dense ceramic specimens with porosity under 5 % can be preparedunmounted, clamped in a holder, if the shape permits. Ceramics with a porosityover 5 % should be impregnated as described above and mounted in a coldmounting material, preferably epoxy having an addition of hard filler to increasethe hardness of the mounting material. For very stable ceramics that will not bedamaged by the pressure, hot compression mounting in a mineral filled epoxy ispreferred because it provides a mount with a hardness matching the ceramic. Incertain cases hot mounting can be made with acrylic that can be used virtuallywithout pressure �see Section 3.4�.Grinding: Plane grinding �PG� is normally done with grinding disks with diamond�see Sections 6.6.1 and 6.7.2�. PG is causing relatively heavy damage to thespecimen surface; for this reason the finest possible grain size should be chosen. Ifusing diamond pads, the metallic bond will be the most aggressive, giving shorttimes but with strong damage. For sensitive ceramics the less aggressive bakelitebond should be used. If the ceramic is not too hard �functional ceramics�, SiCgrinding paper might be used.Fine grinding �FG� normally takes place using diamond but in relatively soft,brittle materials, sensitive to pull-outs, SiC paper can be used down to P4000.Fine grinding �FG� can be done on different surfaces stated in the Method Tables.In case of brittle materials the pressure when using RCDs should be kept at 25 N�5.7 lb�. On materials with many pores the swarf from the RCD might be forcedinto the pores, making examination very difficult. In this case a napless very hard,woven, synthetic cloth is used for FG.


Polishing: The 6 �m and 3 �m diamond steps are very important for mostceramics, removing the heavy deformations from grinding. In the case of pores a1 �m diamond step can be useful to establish the edges of the pores. Oxidepolishing gives chemical mechanical action on ceramics. The effect can often beincreased by adding small quantities of H2O2 �32 %� and ammonia solution �25 %�to the colloidal silica. This polishing can be used for relief polishing �see Section9.6�.

Etching: Ceramic materials may often be difficult to examine under themicroscope since reflection differences in the structure are very slight. Variousetching and contrast methods can be used. Oxide materials are often contrasted bythermal etching in air, vacuum, or various gases. The temperature range is usuallybetween 1200 and 1650°C �2200 and 3000°F� �Approximately 150°C �300°F�below sintering temperature in air.� Etching time can be from 15 minutes toseveral hours. Chemical etching mostly takes place only with hot �boiling� acidmixtures or molten metal salts. All etching shall take place under a fume hoodwith extreme care. Often optical etching like dark field and DIC can be used on thespecimen surface taken directly from the preparation �relief polishing�. Alsoplasma etching and ion etching are used �see Chapter 9�.

Purpose ASTM Standard �See Section 12.4� MethodsCase or coating thickness/hardness,surface layers

C-02


E 1181, E 1382C-02, T-02


E 562, E 1245,E 1268, E 1382

C-02


C 1327, E 384C-02, T-02

Microstructure E 3, E 562, E 883, E 1245,E 1268, E 1382

C-02, T-02

Phase identification C-02, T-02Porosity C-02


Sectioning

Cut-Off Wheel Diamond, metal bond, or bakelite bond


Mounting

Hot CompressionMounting

Resin Epoxy withMineral Filler

Cold Mounting Resin Epoxy

Time Minutes 9 TimeMinutes/Hours

6–8 h

Grinding

C-02: Often the FG2 step can be omitted.T-02: Often the PG step can be omitted.T-02: PG and FG1: Often both steps or only FG1 should be changed tobakelite bond. Also, conventional diamond disks, preferably with bakelite bondcan be used �see Section 6.6.1�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-02: Often P 2 can be changed to a napless, hard, silk cloth or be omitted.C-02, T-02: Final polishing step: Chemical mechanical polishing can be used byadding small quantities of H2O2 �32 %� and ammonia solution �25 %� to thecolloidal silica.

Etching

Etchants for oxides see Material/Preparation Tables 05/06.

Contemporary Method C-02 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth Dia. disk,

fixed, resDia. diskfixed, res

RCD,soft

Cloth,napless,hard,wov, syn

Cloth, mednap, syn

Cloth,napless,soft,porous

Abrasive Type Diamond Diamond Dia.spror susp

Dia.spror susp

Dia.spror susp

Silica

Grit or GrainSize �m

P220 P1200 9 3 1 0.04/0.05

Lubricant Type Water Water Alco orwat

Alco orwat

Alco orwat


RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp or

contraComp Comp Comp Comp Contra


25 �6� 25 �6� 30 �7� 30 �7� 25 �6� 15 �3.4�

TimeMinutes

Untilplane

2 8–15 10–120 2–10 1–6

Traditional Method T-02 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth Dia

pad,met

Diapad,met

Cloth,napless,v. hard,nonwov/wov,syn

Cloth,napless,v. hard,nonwov/wov,syn

Cloth,napless,hard,nonwov,syn

Cloth,napless,hardwov,silk


AbrasiveType

Diamond Diamond Dia,spr orsusp

Dia,spr orsusp

Dia,spror susp

Dia,spror susp

Silica

Grit orGrainSize �m

125 40 15 9 6 3 0.04/0.05

LubricantType

Water Water Alco/wat Alco/wat Alco/wat Alco/wat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp Comp Comp Comp Comp Comp Contra


30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

2–10 6–15 6–15 5–30 10–60 1–10


Etchants

Material Etchants �see Table 12.2� UsesB4C 901 General structureSiC with 5–15 %oxide additions

902 Secondary phaseremain

SiC with 1 % B4C 903 Grain boundariesSSiC 904 Alpha/alpha �� /��

grain boundariesAlpha/beta �� / �phase boundaries

SSiC dopedwith B

905 Grain boundaries

SSiC dopedwith Al

906 Grain boundaries

SiC with B4C 907 Grain boundariesSiSiC 908 Grain boundaries

Material/Preparation Tables 03Material: Chromium carbide, CrC. Titanium carbide, TiC.Titanium nitride, Tin Cubic boron nitride, CBN. Tungstencarbide, WC. Other ceramics

Material Properties:TiC: Face-centered cubic, 4.93 g/cm3, 3140°C �5684°F�, HV 2800–3500TiN: Face-centered cubic, 5.4 g/cm3, 2950°C �5342°F�, HV 2450CBN: Face-centered cubic, 3.48 g/cm3, 1700°C �3092°F�, HV 4500WC: Hexagonal, 15.7 g/cm3, 2780°C �5036°F�, HV 2400Comments on Material: See Material/Preparation Tables 02.Preparation times: A wide variation in time is provided in the Method Tables. Thisis due to the large variations in ceramic materials which in some cases call forlong times, especially in the case of high porosity.Sectioning: See Material/Preparation Tables 02.Mounting: See Material/Preparation Tables 02.Grinding: See Material/Preparation Tables 02, and directions for specific materialsbelow.Polishing: See Material/Preparation Tables 02, and directions for specific materialsbelow.Etching: See below and Material/Preparation Tables 02.


C-03



Grain size, grain boundaries E 112, E 930,E 1181, E 1382

C-03,T-03

Image analysis, rating ofinclusion content

E 562, E 1245,E 1268, E 1382

C-03


C 1327, E 384C-03,T-03


C-03,T-03


Porosity C-03


Sectioning

Cut-Off Wheel Diamond, metal bond, or bakelite bond

Mounting


Resin Epoxy withMineral Filler


TimeMinutes

9 TimeMinutes/Hours

6–8 h

Grinding

C-03: PG: If the surface is very rough, start with Dia, disk, fixed res, P120.T-03: The PG step can often be omitted.T-03: PG and FG 1: Often both steps or only FG 1 should be changed to bakelitebond. Also conventional diamond disks, preferably with bakelite bond can beused �see Section 6.6.1�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

Tungsten carbide: C-03: FG 2 can be omitted, P 1 can be changed to a napless,hard, wov silk cloth and a P 2 step from Method C-02 can be included before thefinal step �see also Method C-67�.


Contemporary Method C-03 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth Dia, disk,

fixed, resRCD, hard RCD,

softCloth,napless,hard,wov, syn


Abrasive Type Diamond Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp

Silica


P220 9 3 3 0.04/0.05

Lubricant Type Water Alco or wat Alco or wat Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150


contraComp Comp Comp Contra

Force perSpecimen N �lb�

35 �8� 35 �8� 35 �8� 25 �5.5� 10 �2.2�

TimeMinutes

Until plane 5–6 10–15 8–10 2

Traditional Method T-03 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ FG 3 P 1 P 2 P 3Polishing PG FG 1 FG 2Disk/Cloth Dia,

pad,met

Dia,pad,met

Cloth,napless,v. hard,wov,syn

Cloth,napless,v. hard,wov,syn


Cloth,napless,hard,wov,silk


AbrasiveType

Diamond Diamond Dia,spr/susp

Dia,spr/susp

Dia,spr/susp

Dia,spr/susp

Silica


125 40 15 9 6 3 0.04/0.05

LubricantType

Water Water Alco Alco Alco Alco

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpm


Comp/Contra

Comp orcontra

Comp orcontra

Comp Comp Comp Comp Contra


30 �7� 30 �7� 40 �9� 40 �9� 40 �9� 25 �5.5� 10 �2.2�

TimeMinutes

Untilplane

2 6–8 6–8 5–6 5–6 2

EtchantsMaterial Etchants �see Table 12.2� UsesCrC, HfC, TiC, VC 909 General structureTaC 910, 911 General structureWC 912 General structure

Material/Preparation Tables 04Material: Silicon nitride, Si3N4

Material Properties: Si3N4: Hexagonal, 3.18 g/cm3, 1900°C �3452°F�, HV 800–1900Comments on Material: See Material/Preparation Tables 02.Preparation times: A wide variation in time is provided in the Method Tables. Thisis due to the large variations in ceramic materials which in some cases call forlong times, especially in the case of high porosity.Sectioning: See Material/Preparation Tables 02.Mounting: See Material/Preparation Tables 02.Grinding: See Material/Preparation Tables 02.Polishing: See Material/Preparation Tables 02.Etching: See below and Material/Preparation Tables 02.

Purpose ASTM Standard �See Section 12.4� MethodsCase or coatingthickness/hardness,surface layers

C-04

Perfect edge retentionGrain size,grain boundaries

E 112, E 930,E 1181, E 1382

C-04, T-04


E 562, E 1245,E 1268, E 1382

C-04


C 1327, E 384C-04, T-04


C-04, T-04

Phase identification C-04, T-04


Porosity C-04


Sectioning

Cut-Off Wheel Diamond, metal bond

Mounting


Resin Epoxywith Filler


TimeMinutes

9 TimeMinutes/Hours

6–8 h

Grinding

C-04: PG: If the surface is very rough, start with Dia, disk, fixed, res, P120.T-04: PG with 125 �m diamond can often be omitted.T-04: PG and FG 1: Often both steps or only FG 1 should be changed to bakelitebond. Also conventional diamond disks, preferably with bakelite bond can beused �see Section 6.6.1�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-04: P 1 can often be omitted so that FG 3 is the last step. In some cases alsoFG 3 can be omitted.

Contemporary Method C-04 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1PolishingDisk/Cloth Dia, disk,

fixed, resRCD, soft RCD, soft RCD, soft Cloth,

napless,soft, porous,syn


Dia, spr orsusp

Dia, spr orsusp

Silica

Grit/GrainSize �m

P220 9 3 0.25 0.04/0.05

Lubricant Type Water Alco or wat Alco or wat Alco or wat


RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150




35 �8� 50 �11� 40 �9� 25 �5.5� 10 �2.2�

TimeMinutes

Untilplane

7–8 7–8 6–8 1

Traditional Method T-04 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth Dia, pad,

metDia, pad,met

Cloth,napless,v. hard,non wov,syn



Cloth,napless.soft,porous,syn

Abrasive Type Diamond Diamond Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp

Silica


125 30 9 6 3 0.04/0.05

LubricantType

Water Water Alco orwat

Alco or wat Alco orwat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 40 �9� 40 �9� 30 �7� 15 �3.4�

TimeMinutes

Untilplane

4 8–10 5–6 5–6 2

EtchantsMaterial Etchants �see Table 12.2� UsesSi3N4 913 General structureSi3N4 914 Grain boundariesSi3N4 915 Grain boundariesAlN-Al2O3 916 Grain boundaries


Material/Preparation Tables 05Material: Aluminum oxide, Al2O3. Chromium oxide, Cr2O3

Material Properties: Al2O3: Trigonal �rhombohedral�, 4.0 g/cm3, 2050°C�3722°F�, HV 2500–2800Cr2O3: Hexagonal, 5.12 g/cm3, 2340°C �4244°F�, HV 2900Comments on Material: See Material/Preparation Tables 02.Preparation times: A wide variation in time is provided in the Method Tables. Thisis due to the large variations in ceramic materials which in some cases call forlong times, especially in the case of high porosity.Sectioning: See Material/Preparation Tables 02.Mounting: See Material/Preparation Tables 02.Grinding: See Material/Preparation Tables 02 and directions for specific materialsbelow.Polishing: See Material/Preparation Tables 02 and directions for specific materialsbelow.Etching: See below and Material/Preparation Tables 02.


C-05


E 1181, E 1382C-05, T-05


E 562, E 1245,E 1268, E 1382

C-05


C 1327, E 384C-05, T-05


C-05, T-05



Sectioning



Mounting


Resin Epoxy with Filler Cold Mounting Resin EpoxyTimeMinutes

9 TimeMinutes/Hours

6–8 h

Grinding

T-05: The PG step with 125 �m diamond and FG 2 can often be omitted.T-05: PG and FG 1: Often both steps or only FG 1 should be changed to bakelitebond. Also conventional diamond disks, preferably with bakelite bond can beused �see Section 6.6.1�.Very hard oxides: Use C-03.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-05: Cr2O3: The steps FG 1 and P 2 can be omitted.

Contemporary Method C-05 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth Dia, disk,

fixed, resDia, disk,fixed, res

RCD,soft


Cloth, mednap,soft,syn


Abrasive Type Diamond Diamond Dia, spror susp

Dia, spror susp

Dia, spror sup

Silica

Grit orGrain Size �m

P220 P1200 9 6 1 0.04/0.05

Lubricant Type Water Water Alcoor wat

Alcoor wat

Alcoor wat

RotationDisk/Holder

150/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp Comp Comp Contra


35 �8� 35 �8� 35 �8� 30 �6.6� 25 �5.5� 25 �5.5�


TimeMinutes

Untilplane

1 9–10 8 2–3 1–2

Traditional Method T-05 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth Dia

pad,met

Diapad,met

Cloth,napless,v. hardwov,syn

Cloth,nap-less,v. hard,wov, syn




AbrasiveType

Diamond Diamond Dia, spr/susp

Dia, sprorsusp

Dia, spror susp

Dia, spror susp

Silica


125 40 15 9 6 3 0.04/0.05

LubricantType


Alco orwat

Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra



30 �7� 30 �7� 40 �9� 40 �9� 40 �9� 20 �4.7� 15 �3.4�

TimeMinutes

Untilplane

2 6–7 6–7 5–6 5–6 2

EtchantsMaterial Etchants �see Tables 12.2� UsesAl2O3 917 Grain boundaries

and small grainsAl2O3 918 Grain boundariesCr2O3 923 General structure


Material/Preparation Tables 06Material: Barium titanate, BaTiO3. Calcium oxide, CaO. Ceriumoxide, CeO2. Magnesium oxide, MgO. Silicon oxide, SiO2.Zirconium dioxide, ZrO2. Zinc oxide, ZnO. Other oxides. Borides.Porcelain Tile. Slag. Other traditional ceramics

Material Properties:CeO2: Cubic, 7.28 g/cm3

MgO: Cubic, 3.5 g/cm3, 2800°C �5072°F�, HV 1130SiO2: Hexagonal, 2,2-2,65 g/cm3, 1710°C �3100°F�, HV 1000—1250ZrO2: Monoclinic, 5.7–6 g/cm3, 2690°C �4874 °F�, HV 1500–1900Comments on Material: See Material/Preparation Tables 02.Preparation times: A wide variation in time is provided in the Method Tables. Thisis due to the large variations in ceramic materials which in some cases call forlong times, especially in the case of high porosity.Sectioning: See Material/Preparation Tables 02.Mounting: See Material/Preparation Tables 02.Grinding: See Material/Preparation Tables 02 and directions for the specificmaterials below.Polishing: See below and Material/Preparation Tables 02 and directions for thespecific materials below.Etching: See below and Material/Preparation Tables 02.

Purpose ASTM Standard �See Section 12.4� MethodsCase or coating thickness/hardness,surface layersPerfect edge retention

C-06

Grain size, grain boundaries E 112, E 930,E 1181, E 1382

C-06, T-06

Image analysis, rating ofinclusion contentHigh planeness

E 562, E 1245,E 1268, E 1382

C-06

Microhardness, hardness C 730, C 849, C 1326,C 1327, E 384

C-06, T-06


C-06, T-06



Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond


Mounting



9 TimeMinutes/Hours

6–8 h

Grinding

Borides: T-06: FG 4 can be changed to grit 4000 SiC paper and P 1 can bechanged to FG 3 in C-06.Calcium oxide: C-06: PG can be done with SiC paper grit 500, FG 1 and FG 3can be omitted by changing FG 2 to 9 �m diamond.Zirconium dioxide: The methods C-02 and C-05 can also be used. Often the stepP 3 in C-05 can be omitted.Porcelain and traditional ceramics: The step FG 2 can be omitted and FG 3can be prolonged to 10 minTile, slag: Method C-02 can be used with SiC paper grit 220 for PG and FG 1and P 3 omitted.T-06: FG 3 and FG 4 can be omitted if a 6 �m step is performed �see below�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

T-06: In some cases a P 1 step with 6 �m diamond and a napless, hard, wov, silkcloth should be added with further data like P 1 indicated below. In this case FG3 and FG 4 may be omitted.T-06: Often the step P 2 can be omitted.

Contemporary Method C-06 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2PolishingDisk/Cloth Dia, disk,

fixed, resRCD,hard

RCD,soft

RCD, soft Cloth,napless,hard,wov,syn


AbrasiveType

Diamond Dia, spr orsusp

Dia, spr orsusp

Dia, spror susp

Dia, spr orsusp

Alumina

Grit orGrainsize �m

P220 9 6 3 3 0.02/0.05


LubricantType

Water Alco orwat

Alco orwat

Alco orwat

Oil-wat

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra


Force perSpecimenN�lb�

30 �7� 40 �9� 35 �8� 35 �8� 20 �4.4� 15 �3.4�

TimeMinutes

Untilplane

5–6 5–6 5–6 5–6 3–5

Traditional Method T-06 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType

SiC SiC SiC SiC SiC Dia,sprorsusp

Dia,sprorsusp

Silica


P220 P320 P500 P1200 P2400 3 1 0.04/0.05

LubricantType

Water Water Water Water Water Alcoor wat

Alcoor wat

RotationDisk/Holder

100/150 300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5� 25 �5.5� 25 �5.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 5–8 5–15 3–5


EtchantsMaterial Etchants �see Table 12.2� UsesCaO 919, 920, 921, 922, 923 General structureMgO 919, 924 General structurePorcelain 930 General structureZnO 925 Grain boundariesZrO2 926, 927 Grain boundariesBa TiO3 928, 929 Grain boundaries

Material/Preparation Tables 07Material: Glasses. Optical fibers

Comments on Material: There are many different types of glass with differentchemical and physical properties. Glass can be defined as an amorphous solid. Amaterial is amorphous when it has no long-range order, that is, when there in noregularity in the arrangement of its molecular constituents on a scale larger than afew times the size of these groups. For example, the average distance betweensilicon atoms in vitreous silica �SiO2� is about 3.6 Å, and there is no order betweenthese atoms at distances above about 10 Å. A solid is a rigid material that does notflow when it is subjected to moderate forces. This definition is not totally agreedupon. In the ASTM standard for glass, the material is described as “glass is aninorganic product of fusion which has been cooled to a rigid condition withoutcrystallization.” This description is based on the fact that most glass is made bycooling a liquid in such a way that it does not crystallize. The difficulty with thisview is that glasses can be prepared without cooling from the liquid state. Glasscoatings are deposited from the vapor or liquid solution, sometimes with chemicalreactions. Sodium-silicate glass made by evaporation and baking isindistinguishable from sodium-silicate glass made by cooling from the liquid.The main types of glass and their used are: Soda lime �containers, windows, lampbulbs�, pyrex borosilicate �headlamps, cookware, laboratory ware� vitreous silica�semiconductor crucibles, lamps, optical components, optical fibers�, alkali lead�lamp tubing, sealing�, “E” lime aluminosilicate �fibers�, lime magnesiaaluminosilicate �high temperatures, cookware�.Optical fibers are coated strands of optically pure glass with a thickness of9–62.5 �m that carry digital information over long distances. They are also usedin medical imaging and mechanical engineering inspection.Preparation of glass is not difficult; if planeness is important, the use of MethodC-07 should be preferred. Glass being a very brittle material can be prepared bylapping �see Section 6.7.7� and Method T-39. As the surface of glass is softened bywater, this liquid should be used to carry the lapping abrasive to obtain the highestremoval rate. Also at polishing a hydrated layer is formed by chemical reactionand the process can be described as chemical mechanical polishing �CMP�, thepolishing abrasive only removing the soft reaction layer �see Section 7.12�.


Sectioning: Wet abrasive cutting with a diamond metal bond cut-off wheelpreferably on a precision cut-off machine. Because of the brittleness of the glass,the feed rate should be low and the use of a thin cut-off wheel should bepreferred. In the case of examination of a coating, the area to be examined shouldbe under compression when the cut-off wheel enters the work piece �see alsoMaterial/Preparation Tables 08–10�.Mounting: In general, hot compression mounting cannot be recommended due tothe risk of cracking because of the pressure and thermal cycle in the mountingpress. If considered possible, the hot compression mounting should be with epoxywith a filler to obtain a high hardness of the mounting material. Cold mountingcan be with acrylics �with a filler�, epoxy, and polyester.Grinding: Most glasses can be ground with SiC grinding paper. As an alternative,diamond disks with fixed abrasives in a resin bond should be used combined withan RCD �see Method C-07� if a very plane surface is needed. Also lapping �seeMethod T-39� and diamond lapping film can be used �see Section 6.7.6�.Polishing: Polishing can be done with diamond, silica, and alumina. The methodsmentioned below may be extended as indicated. To increase the CMP, an acidicsuspension can be used for the final polishing step by adding a few drops of nitricacid.Etching: Normally glasses are not etched.

Purpose �alphabetic�: ASTM Standard �See Section 12.4� MethodsCase or coatingthickness/hardness,surface layersPerfect edge retention

C-07


C-07

Microhardness, hardness C 730 C-07, T-07Microstructure C-07, T-07Phase identification C-07, T-07Porosity C-07


Sectioning


Mounting


Resin Cold Mounting Resin Acrylics/EpoxyTimeMinutes

TimeMinutes/Hours

6–10 min/6–8 h


Grinding

C-07: FG 1 can be omitted and FG 2 changed to 9 �m diamond. In this case twopolishing steps are added �see below�.Medium hard materials: C-07: PG can be changed to SiC paper grit 500followed by the three steps mentioned above and below.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-07: A polishing step like P 1 in Method T-07 can be added. If FG 1 is omittedand FG 2 is changed as mentioned above, two polishing steps, P 1 from C-06 andP 1 from T-07 are added.T-07: A step like P 2 in Method T-06 can be used between FG 4 and P 1 to securea good edge retention. A few drops of HNO3 can be added to the final polishingstep �see above�.

Contemporary Method C-07 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2PolishingDisk/Cloth Dia, disk,

fixed, resDia, diskfixed, res

RCD, soft

Abrasive Type Diamond Diamond Dia, spr, or suspGrit or Grain size �m P220 P1200 1Lubricant Type Water Water WatRotation Disk/Holder 150/150 150/150 150/150rpm/rpmComp/Contra Comp Comp CompForce per Specimen N �lb� 30 �7� 30 �7� 35 �8�TimeMinutes

Until plane 3–5 7

Traditional Method T-07 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1PolishingDisk/Cloth SiC paper SiC paper SiC paper SiC paper SiC paper Cloth,

napless,soft,poroussyn

Abrasive Type SiC SiC SiC SiC SiC Silica


Grit orGrain Size�m

P320 P400 P800 P1000 P4000 0.04/0.05

LubricantType

Water Water Water Water Water

RotationDisk/Holder

300/150 300/150 300/150 300/150 300/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Comp ContraForce perSpecimen N�lb�

20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 2

Material/Preparation Tables 08Material: Anodized coatings. CVD coatings. PVD Coatings

Material Properties: See below.Comments on Material: Anodizing is used for surface treatment of aluminumproducts. The work piece is placed as an anode in an electrolytic bath, and analuminum oxide layer is developed. It consists of a solid layer of typically0.005–0.04 �m towards the work piece and further a layer with pores 5–25 �mthick.Solid aluminum oxide has a hardness in the range of 2000 HV, the hardness of theporous layer is normally higher than 1000 HV. Hard anodizing is performed at lowtemperatures around 5°C �41°F� and gives a coating with few small pores andthickness up to 50–100 �m. Anodizing is mainly used for decorative finishing andprotection against wear and corrosion. Metallographic/materialographicexamination is mainly made for measurement of the thickness, microhardness,and the quality of the coating.Chemical vapor deposition �CVD� is a method of forming dense structural parts orcoatings using the decomposition of relatively high vapor pressure gases. Coatings,which are the most common application of CVD, generally fall into one of twocategories, electronic materials or protective coatings, and are applied either asconversion coatings or as deposited coatings. Conversion coatings involve thesurface formation of a compound where one of the elemental components isalready present on the surface. At deposited coatings all the elemental constituentsof the coating comes from the vapor phase Protective coatings are deposited ontoa work piece �substrate� to provide wear, corrosion or erosion protection, or both.A high number of materials, metals, and ceramics can be used for coatings.Metallographic/materialographic examination includes the purposes mentionedabove and the adhesion between coating and work piece �substrate�.


Physical vapor deposition �PVD� is a method of depositing a coating using avacuum chamber and an electric current between the material source and thework piece. The material source can consist of any electrically conductive metal.The coating has a thickness of 3–5 �m and the hardness can go up to 5000 HVusing AlTiN as the coating material. Used coating materials are Cr, CrN, Ni, Ag, Ti,TiAlCN, TiCN, AlTiN, TiO, TiN, and ZrN. The coatings are made for corrosiveprotection, decoration, high hardness, improved wear resistance, and reducedfriction.The metallographic/materialographic examination includes the purposesmentioned above.Sectioning: It is important that the cutting takes place perpendicular to thesurface to be prepared. If the plane of the cross section is not perpendicular to theplane of the coating, the measured thickness will be greater than the truethickness. For example, an inclination of 10° will contribute a 1.5 % error.The cutting should preferably take place on a precision cut-off machine using thethinnest possible cut-off wheel with a bakelite bond, the wheel suited for the workpiece material, not the coating material. The wheel speed should be in the range of25 m/s �82 ft/s�. Diamond cut-off wheels should only be used for very hard workpiece materials like ceramics. It is very important that the cut-off wheel is enteringthe work piece through the coating at the area later to be examined so that thecoating is compressed into the work piece. This reduces the risk that the truecondition of the coating �adherence to substrate material� is disturbed. For thisreason also the feed speed should be low.If shearing is used for sectioning of plate material, the grinding time should beprolonged to remove damaged material and possible cracks between base materialand coating caused by the shearing �see Section 2.7.3�Mounting: It is very important that edge rounding and gaps between sample andmounting material are avoided. Therefore, a mounting material without shrinkageshould be used, preferably epoxy. On very hard coatings hot mounting with epoxywith a filler should be preferred if heat and pressure can be tolerated.Also a phenolic resin with carbon fibers can be of advantage. In hot mounting aspecial application can be made to secure the edge: Tightly wrap up the specimenin Al-foil �household type�. This gives a good separation between mountingmaterial and coating. Choose a mounting material with hardness as close aspossible to the hardness of the coating. As an alternative cold mounting withepoxy can be used, and in case of porosity, vacuum impregnation can be anadvantage �see Section 3.10�.Grinding: The preparation process should secure the highest possible edgeretention. This means that all grinding, either on SiC grinding paper or rigidcomposite disks �RCDs�, should be as short as possible.Polishing: Also the polishing steps should be kept as short as possible.Etching: For most examinations no etching is needed.


Purpose ASTM Standard �See Section 12.4� MethodCase or coatingthickness/hardness,surface layers

B 487, B 578, B 681, B 748 C-08

Perfect edge retentionGrain size, grain boundaries B 390, E 112, E 930,

E 1181, E 1382C-08, T-08

Heat influenced zone C-08, T-08Image analysis, ratingof inclusioncontent

E 562E 1245, E 1268, E 1382

C-08

High planenessMicrohardness, hardness B 578, C 730, C 849,

C 1326, C 1327, E 10,E 18, E 92, E 103,E 110, E 140, E 384,E 448

C-08, T-08

Microstructure E 3, E 407, E 883 C-08, T-08Phase identification C-08, T-08Porosity C-08, T-08


Sectioning

Cut-Off Wheel Bakelite, Al2O3 or SiC depending on the work piece�substrate� material 0.5 mm �0.019 in� thickness

Mounting



9 TimeMinutes/Hours

6–8 h

Grinding

C-08, T-08: If possible make PG step with SiC paper grit 500.C-08: FG 1 and FG 3: Often these two steps can be omitted.C-08: For CVD coating and PVD coatings on a hard substrate change PG and FG1 to PG from Method C-09.C-08: For preparation of CVD and PVD coatings, use shortest times stated.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

C-08: For preparation of anodized coatings, the P 1 step can be changed to anapless, hard, wov, silk cloth.

Contemporary Method C-08 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2PolishingDisk/Cloth SiC paper Sic paper RCD, soft RCD, soft Cloth,

napless,hard,wov, syn


Abrasive Type SiC SiC Dia, spr orsusp

Dia, spror susp

Dia, spror susp

Silica

Grit/GrainSize �m

P320 P500 9 3 3 0.04/0.05


Alco orwat

Wat-oil

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 25 �4.5� 20 �4.5� 10 �2.3�

TimeMinutes

Untilplane

0.5–1 3–8 3–7 1.5–5 0.5–1

Traditional Method T-08 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType

SiC SiC SiC SiC Dia,sprorsusp

Dia,sprorsusp

Silica



P220 P320 P500 1200 6 3 0.04/0.05

LubricantType


Alco orwat

RotationDisk/Holderr/min/r/min

300/150 300/150 300/150 150/150 150/150 150/150 150/150

Comp/Contra

Comporcontra

Comporcontra

Comporcontra



25�5.7�

25�5.7�

25�5.7�

25�5.7�

20 �4.3� 20 �4.3� 10 �2.3�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 3–5 2–5 0.5–1

Material/Preparation Tables 09Material: Electrolytically deposited coatings: Galvanization,plated coatings, other coatings. Diffusion coatings. Othercoatings

Material Properties: See below.Comments on Material: Electrolytically deposited coatings are produced byelectrolysis, the work piece �substrate� placed as a cathode in an electrolyte withan anode of the coating material. In galvanization, zinc is used as the coatingmaterial and in electroplating �plating� other metals like chrome may be used. ForZn coatings also see Material/Preparation Tables 10.Diffusion coating is a process in which the work piece is either coated withanother material and heated to a sufficient temperature in a suitable environmentor exposed to a gaseous or liquid medium containing the other material, causingdiffusion of the coating material into the work piece surface resulting in a changeof the composition and properties of the surface �see also Material/PreparationTables 37�.An example of other coatings is electroless plating in which metal ions in a diluteaqueous solution are plated out on the work piece by means of an autocatalyticchemical reduction.Typical examples of metallographic/materialographic examination of coatings arethe layer thickness, porosity of coating, cracks, adherence to base material, andthe diffusion zone between substrate �work piece� and coating.Sectioning: See Material/Preparation Tables 08.Mounting: See Material/Preparation Tables 08. As an alternative to epoxy for coldmounting, acrylics with a filler can be used.Grinding: See Material/Preparation Tables 08.


Polishing: See Material/Preparation Tables 08. For zinc coatings, see Material/Preparation Tables 10.Etching: For most examinations, etching is not needed, but an etchant for Sncoating on steel is stated below and etchants for Zn coatings are stated in Material/Preparation Tables 10.

Purpose ASTM Standard �See Section 12.4� MethodCase or coatingthickness/hardnesssurface layers

B 487, B 587, B 748, B 931, B 933, B 934 C-09

Perfect edge retentionGrain size, grain boundaries B 390, E 112, E 930, E 1181, E 1382 C-09, T-09Heat influenced zone C-09, T-09Image analysis, ratingof inclusioncontent

E 562, E 1245, E 1268, E 1382 C-09

High planenessMicohardness, hardness B 578, C 730, C 849, C 1326,

C 1327, E 10, E 18, E 92, E 103,E 110, E 140, E 384, E 448

C-09, T-09



Sectioning

Cut-Off Wheel Al2O3 or SiC according to base material, bakelitebond, 0.5 mm �0.019 in� thickness

Mounting


Resin Epoxy Cold Mounting Resin EpoxyTimeMinutes

8–10 TimeMinutes/Hours

6–8 h

Grinding

Plated coatings: C-09: Use SiC paper grit 500 for PG.Diffusion coatings: C-09: FG 1: RCD, soft can be changed to a napless v. hard,wov, syn cloth.C-09: PG: SiC paper grit 220 or grit 320 can be used instead of a diamond disk.C-09: For some Zn coatings where water sensitivity is suspected, diamond sprayand alcohol-based lubricants are preferred at the step FG 1 and P 1. If silica in P2 is too alkaline use alumina, pH 7-7.5.


C-09: P 2: For sensitive layers this step can be changed to a napless, hard, wov,silk cloth with 1 �m diamond spray and alcohol-based lubricant.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �mbetween the center and the periphery, the disk is either discarded or trued.

Polishing

C-09: A step like P 3 in Method T-17 can be added before the final step.

Contemporary Method C-09 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2PolishingDisk/Cloth Dia, disk,

fixed, resRCD,soft



Abrasive Type Diamond Dia, spror susp

Dia, spror susp

Silica

Grit/Grain Size �m P220 9 3 0.04/0.05Lubricant Type Water Alco or wat Alco or watRotation Disk/Holder 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or

contraComp Comp Contra

Force per Specimen N �lb� 25 �5.7� 25 �5.7� 25 �5.7� 15 �3.4�TimeMinutes

Until plane 3–5 3–5 0.5–1

Traditional Method T-09 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 Fg 2 FG 3 P 1 P 2PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper



Abrasive Type SiC SiC SiC SiC Dia, sprorsusp

Silica

Grit or Grain Size �m P220 P320 P500 P1200 3 0.04/0.05Lubricant Type Water Water Water Water Wat-oil


Rotation Disk/Holderrpm/rpm

300/150 300/150 300/150 150/150 150/150 150/150

Comp/Contra Comporcontra

Comporcontra

Comporcontra

Comp Comp Contra

Force per SpecimenN �lb�

30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 2–3 1

EtchantsMaterial Etchants �see Table

12.2�Uses

Sn coating on steel 183 General structureZn coatings, see M/PT-10

Material/Preparation Tables 10Material: Hot dip zinc coatings. Other Zn coatings

Material Properties: See below.Comments on Material: In hot dipped zinc coating the work piece is dipped intomolten zinc. This is a very efficient way to apply a sufficient thickness of zinc toobtain a very good corrosion protection.Other Zn coatings include electrolytically deposited coatings mentioned in Material/Preparation Tables 09, and the below stated methods should be seen asalternatives to Methods C/T-09.The metallographic/materialographic examination of Zn coatings includesthickness measurement of the coating, adhesion of coating to base material,microstructure of base material, and coating and failure analysis like cracks in thecoating.Sectioning: See Material/Preparation Tables 08.Mounting: See Material/Preparation Tables 08. It is very important that mountingis done without gaps between sample and mounting material because the watersensitive zinc is strongly influenced by water bleeding from the gap. Degrease thespecimen in acetone before mounting. Place the specimen in clips to keep itupright. Use epoxy for cold mounting or bakelite with a carbon filler for hotmounting. In case of having many pieces of coated sheets in the same mount,gluing the sheets together with instant glue and hot mounting give good resultswithout bleeding of liquid from the gaps between the sheets.


Grinding: Pure zinc is very soft and sensitive to water. The purer the zinc of thecoating is, the softer and the more water-sensitive it becomes. Therefore, plain, hotdipped, and electrolytically deposited coatings are soft and prone to mechanicaldeformation and they cannot be cleaned with water. Ethanol or isopropanolshould be used for cleaning. It is important that the grinding steps are properlyperformed to avoid excessive damage that is very difficult to remove during thepolishing.Polishing: Water-free suspensions and lubricants should be used for polishing ofzinc coatings. The polishing can be finished with a cleaning step �see below�.Etching: Etching times should be short and concentration of etchant low to avoidover-etching �see below�.


B 487, B 578, B 748 C-10

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-10, T-10Heat influenced zone C-10, T-10Image analysis,rating of inclusioncontent

E 562, E 1245, E 1268, E 1382 C-10

High planenessMicrohardness, hardness B 578, C 730, C 849, C 1326,

C 1327, E 10, E 18, E 92,E 103, E 110, E 140, E 384,E 448

C-10, T-10



Sectioning

Cut-Off Wheel Al2O3 or SiC according to base material, bakelitebond, 0.5 mm �0.019 in� thickness

Mounting


Resin Bakelite withCarbon Filler


TimeMinutes


6–8 h


Grinding

Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-10: P 1 can be changed to a hard silk cloth as used in P 2 and P 3 can beomitted.C-10 and T-10: The polishing can be finished with a cleaning step �see P 3 inMethod C-10�. This is to avoid contact with water to the finished surface. For allother cleaning alcohol should be used.In the case of very sensitive Zn coatings, water free suspensions and lubricantsshould be used with Method C-10.


PG FG 1 P 1 P 2 P 3

Disk/Cloth SiC paper RCD, soft Clothnapless,hard,wov, syn



Abrasive Type SiC Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp

Seeabove

Grit/Grain Size �m P320 9 3 1RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150


contraComp Comp Comp Comp


30 �7� 30 �7� 25 �5.7� 20 �4.5� 10 �2.2�

TimeMinutes

Until plane 4 4–6 4–6 15–20 s


Traditional Method T-10 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 Fg 2 FG 3 P 1 P 2PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper


Cloth,napless,medhard,wov,wool

Abrasive Type SiC SiC SiC SiC Dia, spr orsusp

Dia,spr orsusp


P220 P320 P500 P1200 3 1

LubricantType

Water Water Water Water Alco Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp


20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–6 1–2

EtchantsMaterial Etchants �see Tables 12.2� UsesZn-Fe 74a Structure of galvanized sheet

Material/Preparation Tables 11Material: Paint layers

Comments on Material: Paint layers can be very different, either charged directlyon the base material of the work piece or on a coating.The metallographic/materialographic examination includes measurement of layerthickness, adhesion to work piece surface, and failures in the paint.Sectioning: Sectioning shall take place as mentioned for coatings, see Material/Preparation Tables 08.Mounting: See Material/Preparation Tables 08.Grinding: See Material/Preparationn Tables 08.


Polishing: See Material/Preparation Tables 08. The paint coat normally is very softcompared to the base material. This increases the risk of edge rounding and thepolishing times should be kept to a minimum, depending on the base material.Etching: For etching, an etchant suited for the base material should be used.


B 487, B 578, B 748 C-11


E 1181, E 1382C-11, T-11

Heat influenced zone C-11, T-11Image analysis, ratingof inclusion content

E 562, E 1245,E 1268, E 1382

C-11


C 1326, C1327, E 10,E 18, E 92, E 103,E 110, E 140, E 384,E 448

C-11, T-11



Sectioning

Cut-Off Wheel Al2O3 or SiC, bakelite bond, 0.5 mm �0.019 in�thickness

Mounting


Resin Bakelite or Epoxywith Filler


TimeMinutes


6–8 h

Grinding

T-11: FG 1: This step with grit 320 is only needed at hand preparation.Attention: In C-methods, when using RCD: The disk concave during use. Whenthe diffenence is more than 100–150 �m between the center and the periphery,the disk is either discarded or trued.


Polishing

C-11: P 2 can changed to step P 2 in Method T-11.T-11: P 2 can be changed to P 2 in Method C-11.

Contemporary Method C-11 �For definitions of parameters and consumable seeSection 13.2.2.�Grinding/Polishing

PG FG 1 FG 2 P 1 P 2

Disk/Cloth SiC paper SiC paper RCD, soft Cloth,napless,hard,wov, silk

Cloth,napless,soft, porous,syn


Dia, spror susp

Silica


220 500 9 3 0.04/0.05


Alco or wat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150




35 �8� 35 �8� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 4–6 2–6 1

Traditional Method T-11 �For definition of parameters and consumables seeSection 13.2.2.�Grinding/Polishing

PG FG 1 FG 2 FG 3 P 1 P 2

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

SiCpaper



Abrisive Type SiC SiC SiC SiC Dia, spror susp

Dia, spror susp

Grit or Grain Size �m P320 P500 P1200 P4000 3 1LubricantType

Water Water Water Water Alco orWat

Wat-oil

Rotation Disk/Holder 300/150 300/150 300/150 300/150 150/150 150/150


rpm/rpmComp/Contra Comp

orcontra

Comp Comp Comp Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 2–5 1–3

Material/Preparation Tables 12Material: Thermal spray coatings: Flame, HVOF „High VelocityOxygen Fuel… and other coatings

Material Properties: See below.Comments on Material: Thermal spraying is a group of processes in which finelydivided metallic or nonmetallic surface materials are deposited in a molten orsemimolten condition on a substrate to form a spray deposit. The surfacingmaterial may be in the form of powder, rod, cord, or wire. A common feature ofall thermal spray coatings is their lenticular grain structure resulting from therapid solidification of small globules, flattened from striking a cold surface at highvelocities.Flame spraying or the combustion wire thermal spray process is basically thespraying of molten metal �ceramics and cements can be used in rod or compositeform� onto a surface to provide a coating.Material in wire form is melted in a flame and atomized using compressed air toform a fine spray. This flame spray process is called a “cold process” �relative tothe work piece material being coated�, as the substrate �work piece� temperaturecan be kept low during the processing, avoiding damage, metallurgical changes,and distortion to the substrate material. Flame spraying is used for improvementof wear resistance, etc., at machine elements and for anticorrosion coatings.HVOF/HVAF �high velocity oxygen fuel/high velocity air fuel� and LVOF �lowvelocity oxygen fuel� are spraying processes using material in powder form whichis melted in a flame to form a fine spray. In HVOF the spray velocity is extremelyhigh and the coatings are very dense, strong, and show low residual tensile stressor in some cases compressive stress. This enables very much thicker coatings to beapplied than possible with other spray processes.Metallography/materialography is used for examination of a number of features,decisive for the quality of the coating, described below.Bond: The bonding at the thermal spray coating/substrate interface and betweenthe particles in the spray coating should be such that both mechanical interlockingand diffusion bonding occur. A number of factors like cleanliness, temperature,time, velocity, and physical/chemical properties influence the bonding.


Microstructure: The coatings show lamellar or flattened grains appearing to flowparallel to the substrate. The structure is heterogeneous that is due to thevariations in the condition of the individual particle on impact. An importantfeature is the presence of unmelted particles and also whether the coating containssome porosity.Porosity: This is present in most thermally sprayed coatings due to a lack of fusionbetween sprayed particles or the expansion of gases generated during the sprayingprocess. A porosity of 1 to 25 % is normal but can be influenced by changes inprocess and materials.Linear detachment: Cooling and solidification of most materials is accompanied bycontraction or shrinkage. This generates a tensile stress within the particle and acompressive stress within the surface of the substrate. As the coating is built up,so are the tensile stresses in the coating. At a certain point the thickness will bereached while the tensile stresses will exceed that of the bond strength or cohesivestrength and linear detachment will occur.Oxides: Most metallic coatings suffer oxidation during normal thermal spraying inair. The products of oxidation are usually included in the coating. Oxides aregenerally much harder than the coating metal. Oxides in coatings can bedetrimental towards corrosion, strength, and machinability. During metallographic/materialographic examination it is important to be able to discriminate betweenoxides and pores �voids�. Other features to be examined are coating thickness,hardness, and microhardness.Metallographic/materialographic preparation: Preparation of thermal spraycoatings is more difficult than the average specimen. This is due to the differencein coating material and substrate �work piece� material, the complicated nature ofthe coating, etc. All stages in the preparation process should be carefully executedto obtain a sufficient result; a special problem is to reveal the true porosity �seeSection 13.6.4, “Pull-Outs—False Porosity”�. As the preparation process has thisvery important influence on the microstructure, it is important that a systematicand reproducible process is maintained. The preparation process is describedbelow, and two ASTM standards cover specifically the preparation andexamination of thermal sprayed coatings:Standard Guide for Metallographic Preparation of Thermal Sprayed Coatings �E1920� and Test Method for Determining Area Percentage Porosity in ThermalSprayed Coatings �E 2109�.


Sectioning: Care must be exercised to avoid affecting the soundness of the coatingand the interface between the coating and the substrate. Friable, porous, or brittlecoatings may be vacuum impregnated with epoxy before sectioning to protect thespecimen �see Section 3.10�. Specimens should always be sectioned such that thecoating is compressed into the substrate. If the coating or interface is placed undertension, it may cause the coating to be pulled away from the substrate or result indelamination of the coating. If a part of the specimen has been under stress, thispart should not be included in the examination of the specimen. Sectioningmethods creating strong damage to the specimen, even wet cutting with a normalcut-off wheel, should be avoided. Preferably precision cutting should be used withthe thinnest possible cut-off wheel, using Al2O3 or SiC in a bakelite bondaccording to the substrate material. Only in case of very thick ceramic layers adiamond wheel should be used. The cut-off wheel speed should be in the range of25 m/s �82 ft/s� and the feed speed should be low to minimize the damage.

Mounting: It is very important that edge rounding and gaps between sample andmounting material are avoided. Therefore, a mounting material without shrinkageshould be used, preferably epoxy. At very hard coatings hot mounting with epoxywith a filler should be preferred if heat and pressure can be tolerated. Also, aphenolic resin with carbon fibers can be an advantage. However, only coldmounting with epoxy should be used in the initial determination of the truecharacteristics of a coating before considering the use of any other mountingmaterial because hot mounting might influence the microstructure. As a rule hotmounting should only be used for mounting of dense, nonfriable coatings withsubstrates a minimum of 1.5 mm �0.06 in� thick. Choose a mounting material withhardness as close as possible to the hardness of the coating. In case of porosity,vacuum impregnation can be required �see Section 3.10� and often the use of a dyecan be of advantage �see Section 3.10.1�.Grinding: Grinding may have a strong influence on the edge retention and anumber of artifacts like false porosity and smearing �see below�. Due to the manydifferent types of thermal coatings and substrate materials, the grinding sequencewill vary, but it should be possible to find a useable method among the methodsdescribed in the Material/Preparation Tables 12–15.Polishing: It is very important to evaluate the type of coating and substrate beforethe start of the preparation because of the high variety of coatings and substratematerials. Two important features are whether one or more of the components inthe microstructure are brittle or ductile. In case of a brittle component, oftenpull-outs will take place during the grinding, causing a “false porosity” that canonly be removed with a prolonged polishing. In case of a ductile component thismight be smeared into the existing pores �voids� and a too dense microstructuremight appear. To avoid this the use of SiC grinding paper should be reduced andgrinding on rigid composite disks �RCDs� or very hard cloths followed by at leasttwo polishing steps should be used. See Section 13.6.4, “Pull-Outs—False Porosity,”where a number of thermal spray coatings are shown.Etching: The thermally sprayed coating is usually not etched, but etchants for thesubstrate material can be used, mentioned under this material.



B 487, B 748 C-12

Perfect edge retentionGrain size, grainboundaries

E 112, E 930, E 1181 C-12, T-12

Heat influenced zone C-12, T-12Image analysis, ratingof inclusioncontent

E 45, E 562, E 768,E 1245, E 1382, E 2109

C-12

High planenessMicrohardness,hardness

B 578, C 730, C 849,C 1326, C 1327, E 10,E 18, E 92, E 103,E 110, E 140, E 384, B 448

C-12, T-12

Microstructure E 3, E 45, E 407, E 562,E 768, E 883, E 1245,E1920

C-12, T-12

Phase identification C-12, T-12Porosity E 2109 C-12Thermal spray coatings:Distribution, porosity,unmelted particles

E 1920, E 2109 C-12, T-12


Sectioning


Mounting


Resin Epoxy or Bakelitewith Filler


TimeMinutes


6–8 h

Grinding



Polishing

C-12: At certain thermal spray coatings where longer polishing times are needed,the P 1 step can be changed to diamond with grain size 6 �m and the P 1 and P2 steps shown will be “P 2” and “P 3.”



RCD,soft

Cloth,napless,hard, wov,syn



Dia, spr orsusp

Alumina

Grit/Grain Size �m P220 P1200 9 3 0.02/0.05Lubricant Type Water Water Alco or wat Alco or watRotation Disk/Holder 300/150 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or



25 �5.7� 30 �7� 30 �7� 25 �5.7� 10 �2.2�

TimeMinutes

Until plane 2 5–7 4–6 1

Traditional Method T-12 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper

SiCpaper


Cloth,med.nap,soft,syn

AbrasiveType

SiC SiC SiC SiC SiC Dia, spror susp

Dia, spror susp


P220 P320 P500 P1200 P2400 3 1

LubricantType

Water Water Water Water Water Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5� 20 �4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 3 0.5–1

Material/Preparation Tables 13Material: Plasma spray coatings: Metallic layers

Material Properties: See below.Comments on Material: Plasma spraying is a thermal spraying process in which anontransferred arc is utilized as the source of heat that ionizes a gas that meltsand propels the coating material to the work piece �substrate�. Compared tocombustion �flame� spraying the plasma spraying provides rapid heating, lowparticle flight time, more inert flame and higher velocity, resulting in a finer,denser microstructure with less oxide inclusions. For further information seeMaterial/Preparation Tables 12.Sectioning: See Material/Preparation Tables 12.Mounting: See Material/Preparation Tables 12.Grinding: See Material/Preparation Tables 12.Polishing: See Material/Preparation Tables 12.Etching: See Material/Preparation Tables 12.


B 487, B 748 C-13

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181 C-13, T-13Heat influenced zone C-13, T-13Image analysis,rating of inclusioncontent

E 45, E 562, E 768, E 1245,E 1382, E 2109

C-13


B 578, C 730, C 849, C 1326,C 1327, E 10, E 18, E 92,E 103, E 110, E 140, E 384, E 448

C-13, T-13

Microstructure E 3, E 45, E 407, E 562,E 768, E 883, E 1245,E 1920

C-13, T-13

Phase identification C-13, T-13Porosity E 2109 C-13


Thermal spray coatings:Distribution, porosity,unmelted particles

E 1920, E 2109 C-13, T-13


Sectioning


Mounting




TimeMinutes


6–8 h

Grinding

C-13: PG: Grit 320 should be used if possible.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-13: P 2: Can be changed to P 2 from Method T-12.

Contemporary Method C-13 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth SiC paper RCD, soft RCD,

softCloth,napless,hard,wov,silk


Abrasive Type SiC Dia,spr orsusp

Dia,spr orsusp

Dia,spr orsusp

Silica

Grit/GrainSize �m

P220 9 3 3 0.04/0.05

LubricantType

Water Alco or wat Alco or wat Alco or wat


RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150



Force perSpecimen N�lb�

25 �5.7� 25 �5.5� 25 �5.5� 25 �5.5� 10 �2.3�

TimeMinutes

Untilplane

4–6 5–7 3–4 0.5–1


paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



AbrasiveType


Alumina


P220 P320 P550 P1200 P4000 3 0.02/0.05

LubricantType


RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra



25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 15 �3.4� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 3–4 0.5–1


Material/Preparation Tables 14Material: Plasma spray coatings: Ceramic layers

Material Properties: See below.Comments on Material: See Material/Preparation Tables 12 and 13.Sectioning: Depending on the substrate an Al2O3 or SiC, bakelite bond, ordiamond metal bond, 0.5 mm �0.019 in� thickness cut-off wheel should be used. Incase of very brittle coatings a diamond wheel with bakelite bond should be used,see Material/Preparation Tables 12.Mounting: See Material/Preparation Tables 12.Grinding: Remove at least 500 �m during the PG step to ensure that all damagefrom the cutting is removed. Pull-outs will be developed during the grinding,resembling pores �see below�.See also Material/Preparation Tables 12.Polishing: Polishing must be performed until the pull-outs made during thegrinding are removed. Check the porosity and go on polishing with the P 1 stepuntil the porosity level is constant.See also Material/Preparation Tables 12.Etching: See Material/Preparation Tables 12.


B 487, B 748 C-14

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181 C-14, T-14Heat influenced zone C-14, T-14Image analysis, ratingof inclusioncontent

E 45, E 562, E 768,E 1245, E 1382, E 2109

C-14


C 1326, C 1327, E 10,E 18, E 92, E 103,E 110, E 140, E 384,E 448

C-14, T-14


C-14, T-14

Phase identification C-14, T-14Porosity E 2109 C-14Thermal spray coatings:Distribution,porosity, unmelted particles

E 1920, E 2109 C-14, T-14



Sectioning

Cut-Off Wheel Al2O3 or SiC, bakelite bond, or diamond metal orbakelite bond, 0.5 mm �0.019 in� thickness

Mounting


Resin Epoxy orBakelitewith Filler

Cold Mounting Resin Epoxy �vacuumimpregnation�

TimeMinutes


6–8 h

Grinding

The PG step is very important �see above�.C-14, T-14: PG: At thin or brittle layers, or both, change to PG from MethodsT-13.C-14: FG 1: For very hard ceramic layers, the disk should be changed to RCD,hard.


Polishing

C-14, T-14: The time for the step, P 1 depends on the porosity level �see M/PT 12�.


fixed, resRCD,soft

RCD,soft




Dia, spr orsusp

Dia, spr orsusp

Silica

Grit/Grain Size �m P220 9 3 3 0.04/0.05Lubricant Type Water Alco or wat Alco or wat Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150





30 �7� 40 �9� 35 �8� 35 �8� 15 �3.4�

TimeMinutes

Untilplane

4–5 3 3–4 1

Traditional Method T-14 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 3PolishingDisk/Cloth Dia, pad, met Cloth, napless,

v. hard, nonwov/wov, syn

Cloth, napless,hard,non-wov, syn


Abrasive Type Diamond Dia, spr or susp Dia, spr or susp AluminaGrit or Grain Size �m 40 9 3 0.02/0.05Lubricant Type Water Alco or wat Alco or watRotation Disk/Holder 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or



25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5�

TimeMinutes

Until plane 6–7 3–4 1–2

Material/Preparation Tables 15Material: Plasma spray coatings: Composite layers

Material Properties: See Material/Preparation Tables 12 and 13.Comments on Material: See Material/Preparation Tables 12 and 13.Sectioning: See Material/Preparation Tables 12 and 14.Mounting: See Material/Preparation Tables 12.Grinding: See Material/Preparation Tables 12 and 14.Polishing: See Material/Preparation Tables 12 and 14.Etching: See Material/Preparation Tables 12.


B 487, B 748 C-15



Grain size, grainboundaries

E 112, E 930, E 1181 C-15,T-15

Heat influenced zone C-15,T-15

Image analysis,ratingof inclusioncontent

E 45, E 562, E 768, E 1245,E 1382, E 2109

C-15


B 578, C 730, C 849, C 1326,C 1327, E 10E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-15,T-15


C-15,T-15


Porosity E 2109 C-15Thermal spraycoatings:Distribution,porosity, unmeltedparticles

E 1920, E 2109 C-15,T-15


Sectioning

Cut-Off Wheel Al2O3 or SiC, bakelite bond, or diamond metal bond,0.5 mm �0.019 in� thickness

Mounting




TimeMinutes


6–8 h

Grinding

C-15: PG: For softer composites this can be changed to PG or FG 1 in MethodT-15C-15: FG 2 and FG 3: It is important that the true level of pores is obtained atthese steps.


C-15: FG 1: If the composite layer is very hard �ceramic�, the disk can bechanged to RCD, hard. During the FG 2 step the level of porosities should beevaluated, and FG 2 shall go on until the level stays constant.T-15: If the composite layer contains hard ceramics ��800 HV�, SiC papershould be changed to diamond pads. PG: 40 �m, met, FG 1: Diamond pad10 �m, bak. See also Method T-14.


Polishing

C-15 and T-15: The last step can be changed to P 2 from Method T-12.T-15: P 1 and P 2: It is important that the true level of pores is obtained at thesesteps. During the P 2 step the level porosities should be evaluated, and P 2 shallgo on until the level stays constant.

Contemporary Method C-15 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth Dia, disk

fixed, resRCD, soft RCD,

softCloth,napless,hard, wov,silk



Dia, spr orsusp

Dia, spr orsusp

Silica

Grit/GrainSize �m

P220 9 3 3 0.04/0.05


300/150 150/150 150/150 150/150 150/150




30 �7� 35 �8� 35 �8� 25 �5.7� 10 �2.3�

TimeMinutes

Until plane 5–6 5–7 3–4 1

Traditional Method T-15 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3Polishing


Disk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

Cloth,napless,v.hard,nonwov/wov,syn



AbrasiveType

SiC SiC SiC SiC Dia,spr,orsusp

Dia,sprorsusp

Silica


P220 P320 P500 P1000 6 3 0.04/0.05

LubricantType

Water Water Water Water Alcoorwat

Alcoorwat

RotationDisk/Holder

300/150

300/150 300/150 150/150 150/150

150/150

150/150

rpm/rpmComp/Contra

Comporcontra

Comp Comp Comp Comp Comp Contra


30 �7� 25 �4.5� 25 �4.5� 25 �4.5� 20�4.5�

20�4.5�

10�2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 15–20 10 0.5–1

Material/Preparation Tables 16Material: Composites: SiC fibers in Ti matrix

Material Properties: See below.Comments on Material: A composite material is characterized as consisting oftwo or more different components. Depending on the bonding component used, adistinction is made between metal matrix composites, ceramic matrix composites,and plastic matrix composites. The intention behind a composite material is tocombine the favorable properties of various materials and, at the same time,compensate for less favorable properties. The required combination of propertiesdetermines the choice of materials. Another vital factor in achieving a materialwith favorable properties is whether the various components “work together.” Forexample, good bonding between the components is important and nounintentional component alterations may occur during the production process. Inthe area of metal matrix composites, cermets, the high hardness of ceramicparticles or the extreme strength of ceramic fibers, will typically be combined withthe toughness of the metal.


Metallographic/materialographic examination includes separation betweencomponents, porosity, and transitions between components. Due to the very widevariety of composite materials it is only possible to indicate six basic methods inthe Material/Preparation Tables 16 to 18, and these should be changed accordingto the given material following the comments stated for each stage/step in thepreparation process.The most common problems with the preparation of composites are related torelief and unplaneness between the different components, often combined withsmearing of material from a soft component covering pores, etc., of the othercomponents.Sectioning: Depending on the hardness of the components of the composite,sectioning should be made as wet abrasive cutting with an Al2O3/SiC, bakelitebond cut-off wheel or a diamond wheel. If the bond between the components inthe composite is sufficiently high, a diamond wheel with metal bond can be used.If the bond is not adequate or one of the components is very hard and brittle, orboth, bakelite bond should be used. The sectioning should be performed withgreat care, and often it is an advantage to use a precision cutting machine for thecutting using thin wheels �see Material/Preparation Tables 12�. A band saw shouldonly be used for cutting of a large piece, later to be cut with a cut-off wheel.Mounting: As composite materials often have very high differences in hardness,mounting in a relatively hard mounting material is of advantage. In the case ofporosity in one or more of the components, vacuum impregnation may be needed�see Section 3.10�.Grinding: In case of very high differences in hardness, SiC grinding paper may beless suited for grinding, removing too much material from the soft componentcreating relief. In case of ceramic components, diamond disks should be used forgrinding.Polishing: As a general rule, both grinding and polishing times should be kept asshort as possible to secure the planeness. It is important, however, that the hardestcomponent is correctly ground/polished at each step before going on to the nextfiner step.Etching: Etching is performed according to the components of the composite.


C-16

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181 C-16, T-16Image analysis, ratingof inclusion content

E 562, E 1245, E 1382 C-16


C 1326, C 1327, E 10,E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-16, T-16



C-16, T-16



Sectioning


Mounting




TimeMinutes


6–8 h

Grinding

The material is relatively difficult to prepare because of the very hard SiC andthe relatively soft and tough Ti. It is important that the SiC phase is “finished” ineach step, before going to the next finer step.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

Ti may be chemically-mechanically polished: C-16: P 2 and T-16: P 3: Use thesolution: 96 mL silica, 2 mL H2O2 �30 %�, 2 mL NH3 solution �25 %�.

Contemporary Method C-16 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2PolishingDisk/Cloth Dia, disk


RCD,soft

RCD,soft



Abrasive Type Diamond Diamond Dia, sprorsusp

Dia, spror susp

Dia, sprorsusp

SilicaSee note

Grit/GrainSize �m

P220 P600 9 3 1 0.04/0.05


LubricantType


Alco orwat

Alco orwat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 20 �4.5� 20 �4.5� 10 �2.3�

TimeMinutes

Untilplane

2 4 5 3 1

Traditional Method T-16 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth Dia,

pad,met

Dia,pad,bak

Cloth,napless,v. hard,nonwov/wov, syn



Abrasive Type Diamon Diamond Dia, spr orsusp

Dia, spr orsusp

SilicaSee note


40 10 6 1 0.04/0.05

Lubricant Type Water Water Alco or wat Alco or watRotationDisk/Holder

300/150 300/150 150/150 150/150 150/150




30 �7� 25 �4.5� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Until plane 3 5 3 1–2

Material/Preparation Tables 17Material: Composites: Glass fiber reinforced plastic

Material Properties: See below.Comments of Material: See Material/Preparation Tables 16. No “contemporary”method is developed for this kind of material, instead, Method C-17 describes amethod using SiC grinding paper. See also the Material/Preparation Tables 64 and65 covering polymers.


Sectioning: See Material/Preparation Tables 16.Mounting: See Material/Preparation Tables 16.Grinding: See Material/Preparation Tables 16.Polishing: See Material/Preparation Tables 16.Etching: See Material/Preparation Tables 16.


C-17, T-17

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181 C-17, T-17Image analysis, ratingof inclusioncontent

E 45, E 562, E 768,E 1245, E 1382

C-17, T-17

High planenessMicrohardness, hardness B 578, C 730, C849, C 1326,

C 1327, E 10, E 18, E 92,E 103, E 110, E 140, E 384,E 448

C-17, T-17

Microstructure E 3, E 45, E 407, E 562, E 768,E 883, E 1245

C-17, T-17

Phase identification C-17, T-17Porosity C-17, T-17


Sectioning

Cut-Off Wheel Al2O3 or SiC, bakelite bond or diamond, metal bondor bakelite bond

Mounting



TimeMinutes/Hours

6–8 h

Contemporary Method C-17 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3Polishing


Disk/Cloth SiCpaper

SiCpaper


Cloth,napless,mediumhard,wov, wool


Abrasive Type SiC SiC Dia, sprorsusp

Dia, sprorsusp

Silica

Grit/GrainSize �m

P220 P1200 3 1 0.04/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 3–5 3 1

Traditional Method T-17 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3 P 4PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

Cloth,napless,hard,wov, silk




Abrasive Type SiC SiC SiC Dia, spror susp

Dia, spror susp

Dia, spror susp

Silica


P220 P320 P500 9 3 1 0.04/0.05

LubricantType

Water Water Water Alco orwat

Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp Comp Comp Comp Comp Contra


30 �7� 25 �4.5� 25 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 10 �2.2�


TimeMinutes

Untilplane

0.5–1 0.5–1 4 4 4 2–3

Material/Preparation Tables 18Material: Composites. Other composite materials

Comments on Material: See Material/Preparation Tables 16.Sectioning: See Material/Preparation Tables 16.Mounting: See Material/Preparation Tables 16.Grinding: See Material/Preparation Tables 16.Polishing: See Material/Preparation Tables 16.Etching: See Material/Preparation Tables 16.


C-18


E 112, E 930, E 1181 C-18, T-18

Image analysis, ratingof inclusioncontent

E 45, E 562, E 768,E 1245, E 1382

C-18

High planenessMicrohardness, hardness B 578, C 730, C 849, C 1326,

C 1327, E 10, E 18, E 92,E 103, E 110, E 140, E 384,E 448

C-18, T-18

Microstructure E 3, E 45, E 407, E 562, E 768,E 883, E 1245

C-18, T-18



Sectioning

Cut-Off Wheel Al2O3 or SiC, bakelite bond or diamond, metal bondor bakelite bond


Mounting




TimeMinutes


6–8 h

Grinding

T-18: At composites with ceramics, SiC grinding paper may not be used; usediamond for grinding �see Method T-16 or use Method C-18�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C/T-18: Polishing step with silica: Depending on the matrix of the material,alumina is used instead of silica. See under the actual material. Also the silicastep can be changed to P 2 from Method T-12.T-18: P 2: Can be changed to step P 2 from Method T-12 as final step.


PG FG 1 P 1 P 2

Disk/Cloth Dia, disk,fixed, res

RCD,soft

Cloth,napless, hard,wov, syn



Dia, spr orsusp

Silica

Grit/Grain Size �m P220 9 3 0.04/0.05Lubricant Type Water Alco or wat Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp Comp Contra

Force per Specimen N �lb� 30 �7� 40 �9� 40 �9� 10 �2.2�TimeMinutes

Until plane 4–6 3–5 1

Traditional Method T-18 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3


PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia,sprorsusp

Silica


P220 P320 P500 P1200 3 1 0.04/0.05

LubricantType


Alcoorwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra



30 �7� 25 �5.5� 25 �5.5� 25 �5.5� 20�4.5�

20�4.5�

10�2.3�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–5 3 0.5–1

Material/Preparation Tables 19Material: Ceramic capacitors. Ceramic resistors. Diodes

Comments on Material: In ceramic capacitors, ceramic resistors, and diodes wehave the hard, brittle ceramic or glass phases combined with softer materials likesilicon and metals. Delamination, voidage, and cracks are typical processingdefects which can be assessed by materialography/metallography. Alsomaterialography/metallography can be used for dimension analysis.The monolithic ceramic capacitor consists of ceramic plates, often bariumtitanate, coated with layers of a silver-palladium alloy and with terminations insilver. The barium titanate being very brittle and sensitive to mechanical stressmust be prepared very carefully with Method T-19 below; only the two grindingsteps PG and FG 1 should be omitted so that the preparation starts with grit P500grinding paper.Ceramic resistors are normally made with a less brittle and harder ceramic�alumina� and Method C-19 can be recommended.Glass and silicon of the diodes are very brittle materials and very carefulpreparation is necessary. Method T-19 is considered the most suitable.


A number of artifacts can be developed during the preparation, like pull-outs,cracks, delaminations, and relief �see Section 13.5�. The correct mounting�encapsulation� is important; uncorrect mounting may create voids and gapsbetween mounting material and the single constituents, leaving the constituentunsupported causing rounding and possibly cracking.Methods C-19 and T-19 may also be used for preparation of other electronic/microelectronic devices like integrated circuits �see also Material/PreparationTables 26�.Sectioning: Wet abrasive cutting with a diamond metal bond cut-off wheel as thinas possible. This should preferably take place on a precision cut-off machine, bothto obtain the smallest possible stress to the specimen and to be able to cutreasonably precise in the correct distance from the site �target� to be investigated.This distance should be so that neither the damages from the cutting and from therough grinding steps will influence the surface at the site of interest �target�.In case the part �capacitor� is relatively small, the part can be encapsulated�mounted� �see below� and a sectioning is not necessary; the inspection plane�target� can be reached by grinding.Mounting: The lowest possible heating of the specimen should take place duringmounting, so hot mounting should be avoided. Cold mounting in epoxy isrecommended because of the low viscosity, the low peak temperature, and thepossibility of vacuum impregnation �see Section 3.10�.Grinding: It is important that the very brittle materials are not damaged too muchby the rough grinding papers and often, as mentioned above, the grinding shouldstart with the grits P320 or P500. If a relief between areas with a high differencein hardness should be avoided, Method C-19 should be used if possible.Polishing: Polishing times should be kept as short as possible to avoid relief, butoften long times are needed to remove deformation and other artifacts developedduring the grinding. Often a water-oil based lubricant should be used for the finaldiamond steps.Etching: Normally no chemical etching takes place, but physical etching, likerelief polishing can be used �see Section 9.6�.

Purpose ASTM Standard �See Section 12.4� MethodCase or coating thickness/hardness,surface layersPerfect edge retention

C-19

Grain size, grain boundaries E 112, E 1382 C-19, T-19Image analysis, rating of inclusioncontentHigh planeness

E 562, E 1245, E 1382 C-19, T-19

Microhardness, hardness E 92, E 384 C-19, T-19Microstructure E 3, E 407, E 562, E 883,

1245, E 1382C-19, T-19




Sectioning

Cut-Off wheel Diamond, metal bond, 0.5 mm �0.019 in� thickness

Mounting

Hot Compression Mounting Resin Cold Mounting Resin EpoxyTimeMinutes

TimeMinutes/Hours

12–24 h

Grinding

C-19 and T-19: For very sensitive materials it is recommended not to use the PGstep with grit P220 grinding paper, but start with grit P320 or P500.Diodes: C-19: It is recommended to use SiC paper grit P220 for PG and gritP500 for FG 1 so that FG 1 �RCD, soft� is changed toFG 2.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-19: P 2: At materials with less tendency for relief, the cloth can be changed tomed nap, soft, syn.Diodes: C-19: The cloth for the step P 1 is changed to napless, hard, wov, syn,and the cloth for P 2 is changed to med nap, soft, syn.C-19: In case of sensitive materials like constituents of soft metals �diodes�, thelubricant for 3 �m and 1 �m diamond-polishing steps should be water-oil based.T-19: Often the step P 1 can be omitted.


PG FG 1 P 1 P 2 P 3

Disk/Cloth Dia, disk,res

RCD,soft




Abrasive Type Diamond Dia,spr orsusp

Dia,spr orsusp

Dia,spr orsusp

Silica

Grit/GrainSize �m

P220 9 3 1 0.04/0.05


Lubricant Type Water Alco orwat

Alco or wat Alco or wat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



30 �7� 30 �7� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Until plane 4–6 1–2 1–2 0.5–1

Traditional Method T-19 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3 P 4PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

Cloth,nap-less,hard,wov,silk



Cloth,nap-less,soft,porous

AbrasiveType


Dia,sprorsusp

Dia,sprorsusp

Silica

Grit orGrainsize �m

P220 P320 P500 P1200 9 6 1 0.04/0.05

LubricantType

Water Water Water Water Alcoor wat

Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp Comp Comp Comp Comp Comp Comp Contra

ForceperSpecimenN �lb�

15 �3.4� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 10–15 5–10 2 0.5–1


Material/Preparation Tables 20Material: YBCO ceramic super conductors

Comments on Material: A superconductor is an element, intermetallic, orcompound that will conduct electricity without resistance below a certaintemperature, Tc. However, this applies only to direct current �dc� electricity and tofinite amounts of current. All known superconductors are solids, and all requireextreme cold to enter a superconductive state. Once set in motion, current willflow forever in a closed loop of superconducting material—making it the closestthing to perpetual motion in nature. Tc is the critical transition temperature belowwhich a material begins to superconduct, and research is going on to find thematerial with the highest Tc. Superconductors are categorized in Type 1 and Type2. Type 1 category is mainly comprised of metals and metalloids that requireextremely low temperatures, Tc, up to a few K, to become superconductive. TheType 2 category is comprised of metallic compounds and alloys, of which the“perovskites,” metal-oxide ceramics like the so-called YBCO compounds composedof yttrium, barium, copper, and oxygen, are important because they have a Tchigher than 90 K.In general, YBCO materials are very brittle and porous, so pull-outs andmicrocracks can be introduced during the sectioning and grinding stages. TheMethod T-20 is developed for YBa2Cu3O7+, and in case of materials too hard forSiC grinding paper, or an extremely plane specimen is wanted, Method C-20 canbe used.Sectioning: Sectioning should take place with utmost care because of the brittleand porous material. Wet abrasive cutting can be done with a thin diamond cut-offwheel, metal bond, or, if damage should be reduced, with bakelite bond on aprecision cut-off machine. The cut-off wheel should be as thin as possible and forsome softer materials, a thin SiC bakelite bond wheel, 0.5 mm �0.02 in� can beused. The feed rate should be low and the wheel speed in the range of 1000 rpm.If the porosity is high, it can be recommended to vacuum impregnate thespecimen before cutting �see below�. The clamping of the specimen during cuttingshould be so that pressure spots are avoided, as these can cause fractures in thematerial. Very sensitive materials can be glued to a piece of nonmetallic basematerial which is then clamped in the machine.When water is used for cutting, place the cut specimen in alcohol for one hour ifthe material is water sensitive.Mounting: If the porosity is above 5 % it is advisable to vacuum impregnate thesectioned specimen with epoxy possibly using a dye �see Section 3.10�. Thematerial should not be hot mounted, but mounting after impregnation should bewith a slow curing epoxy. To balance the hardness of the epoxy a filler can beadded �see Section 3.11.2�.Grinding: As grinding with rough grinding papers causes pull-outs andmicrocracks, the PG step with grit P220 grinding paper may be changed to gritP320 if the surface after cutting seems relatively little damaged. Water should beavoided for water sensitive materials �see below�.Polishing: To remove pull-outs and microcracks polishing may be carried out atlow pressure over relatively long times �see methods below�.


Etching: No etchants are stated below, but contrast can be developed as indicated.

Purpose ASTM Standard �See Section 12.4� MethodsCase or coatingthickness/hardness,surface layersPerfect edge retention

C-20

Grain size, grain boundaries E 112, E 930, E 1181, E 1382 C-20, T-20Image analysis, ratingof inclusion contentHigh planeness

E 562, E 1245, E 1268, E 1382 C-20

Microhardness, hardness E 384 C-20, T-20Microstructure E 3, E 562, E 883, E 1245,

E 1268, E 1382C-20, T-20



Sectioning

Cut-Off Wheel Diamond, metal bond �bakelite bond�, or SiC bakelitebond, 0.5 mm �0.019 in� thickness

Mounting


Resin Cold Mounting Resin Epoxy �with filler�TimeMinutes

TimeMinutes/Hours

12–24 h

Grinding

C-20: FG 1 and FG 2: If material is highly sensitive to water use a water-freediamond suspension.T-20: If the material is not water sensitive, water should be used as a coolingfluid for the steps PG and FG 1 to FG 4.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-20: P 1: If the material is water sensitive, use P 1 and P 2 from T-20.


T-21: If material is water sensitive, use water-free diamond suspension or sprayfor P 1 and P 2 as indicated.

Contemporary Method C-20 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1PolishingDisk/Cloth SiC paper RCD, soft RCD, soft Cloth,

napless,soft,porous,syn

Abrasive Type SiC Dia, spror susp

Dia, spror susp

Silica

Grit or Grain Size �m P220 9 3 0.04/0.05Lubricant Type Water/dry Alco, water-free Alco, water-freeRotation Disk/Holder 150/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp Comp Comp ContraForce per Specimen N �lb� 15 �3.4� 25 �5.7� 25 �5.7� 20 �4.5�TimeMinutes



paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



Abrasive Type SiC SiC SiC SiC SiC Dia, spror susp

Dia, spror susp

Grit andGrain Size�m

P220 P500 P1200 P2400 P4000 1 0.25

Lubricant Type Dry Dry Dry Dry Dry Alco,waterfree

Alco,water-free

RotationDisk/Holderrpm/rpm

150/150 150/150 150/150 150/150 150/150 150/150 150/150

Comp/Contra Comp Comp Comp Comp Comp Comp CompForce perSpecimenN �lb�

15 �3.4� 15 �3.4� 15 �3.4� 15 �3.4� 15 �3.4� 10–15�2.–3.4�

10–15�2.3–3.4�


TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4–20 5–15

EtchantMaterial Etchants �see Table 3.2� UsesYiBa2Ca3O7+ Contrast can be made by:

a� vapor depositing of interference layer �e.g., iron oxide�b� Observation of the polished specimen in polarized light

Material/Preparation Tables 21Material: Germanium. Silicon. Si wafers. Other semiconductors

Material Properties: Germanium: Face-centered cubic, 5.3 g/cm3, 937.4°C�1719°F�.Silicon: Face-centered cubic, 2.42 g/cm3, 1420°C �2588°F�.Comments on Material: Germanium and silicon are metalloids and belong to thegroup of materials, semiconductors. Silicon is the most commonly used materialand is often prepared as a chip �see Material/Preparation Tables 22 and 26� or as awafer/solid piece, which is discussed here. It is, however, only the preparation formetallographic/materialographic examination, the polishing �thinning�, which ispart of the production process, is outside the scope of this book. Thesemiconductors are brittle materials that fracture easily, and especially as thinwafers, the specimens should be handled with great care.Sectioning: Wet abrasive cutting with a diamond metal bond cut-off wheel,0.5 mm �0.02 in� thick or thinner. The cutting should be done on a precisioncut-off machine to obtain the most controlled cutting with a low feed speed. Theclamping should not be directly on the specimen, but with elastic material asspacers. Often it can be of advantage to encapsulate the specimen before cutting.Sectioning for production of wafers is outside the scope of this book.Mounting: For preparation of the flat side of a wafer, the wafer or a piece of thewafer is temporarily glued with wax to a support disk which can be placed in thespecimen holder. In the case of a cross section of the wafer, the specimen is coldmounted and placed in the mounting mold supported by clips to hold it in anupright position �see Section 3.9�. Due to the brittle nature of the semiconductorsthese should not be hot mounted, but cold mounted, preferably with epoxy.Grinding: The rough grits of SiC grinding papers will damage silicon and othersemiconductors rather strongly, and therefore the grits P220 and P320 should onlybe used if relatively much material should be removed. If the cut surface is of agood quality, the plane grinding should be done with a grit P500 grinding paper ifpossible. To avoid SiC grinding paper for fine grinding, use Method C-21. As analternative to SiC grinding papers, Al2O3/diamond lapping films can be used �seeSection 6.7.6 and Material/Preparation Tables 22�.Polishing: Polishing times should be as short as possible to avoid edge rounding.The semiconductor materials respond very well to chemical mechanical polishingwith colloidal silica, but also here the time should be as short as possible.Etching: See Etchants below.


Purpose ASTM Standard �See Section 12.4� MethodsCase or coating thickness/hardness,surface layersPerfect edge retention

C-21

Grain size,grain boundaries

E 112, E 930, E 1382 C-21, T-21

Image analysis, ratingof inclusion contentHigh planeness

E 562, E 1245, E 1382 C-21

Microhardness, hardness E 384 C-21, T-21Microstructure E 3, E 562, E 883, E 1245,

E 1382C-21, T-21



Sectioning

Cut-Off Wheel Diamond, metal bond, 0.5 mm �0.02 in� or thinner

Mounting



TimeMinutes/Hours

12–24 h

Grinding

C-21 and T-21: Plane grinding with grit P220 or P320, or both, should beavoided if possible.C-21: PG: Grit P500 SiC paper can be used.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-21 and T-21: Polishing times should be kept as short as possible.C-21 and T-21: P 1: This step can be changed to step P 2 in Method T-21.

Contemporary Method C-21 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2Polishing



RCD, soft RCD, soft Cloth,napless,hard, wov,syn

Cloth, nap-less, soft,porous, syn

AbrasiveType


Dia, spr orsusp

Dia, spr orsusp

Silica


P500 9 3 3 0.04/0.05

LubricantType


RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra



15 �3.4� 20 �4.5� 20 �4.5� 20 �4.5� 10 �2.3�

TimeMinutes



paperSiCpaper

SiCpaper

SiCpaper




Abrasive Type SiC SiC SiC SiC Dia, spror susp

Dia, spror susp

Silica


P500 P1000 P2400 P4000 3 1 0.04/0.05

Lubricant Type Water Water Water Water Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Comp Comp ContraForce perSpecimenN �lb�

15–25�3.4–5.7�

20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 10–15�2.2–3.4�


TimeMinutes

Untilplane

1.5–2 1.5–2 1.5–2 4 3 1–3

EtchantsMaterial Etchants �see Table

12.2�Uses

Si, Si alloys 931 General structureSi, Si alloys 932 General structureSi 933 General structureSi 934 To reveal SiO2

Material/Preparation Tables 22Material: Microelectronic material „semiconductor device…

Preparation of cross section of a semiconductor device using a tripod fixture forhand preparation on a grinder/polisher with a 200 mm �8 in� polishing disk andvariable speed 0–150 r/min.Comments on Material: Nonencapsulated cross sections through microelectronicmaterial �semiconductor devices� serve two main functions. Cuts throughrepresentative structures within an IC show relationships of layers and features,such as step coverage, interfaces between layers, and possibly embedded defects orvoids. Precision cross sections through specific defects often lead to the processstep or mechanism which produced the defect �see Section 7.10.2�.The preparation of a nonencapsulated cross section of microelectronic material isdescribed below. The method is considered a “C-Method,” using a combination ofSiC grinding papers and Al2O3/diamond lapping films �see Section 6.7.6�, and no“T-Method” is stated.Sectioning: The specimen should be a piece of silicon roughly 5 mm �0.20 in�square. The desired cross section target should be within 50 �m from the edge.The specimen can be cut out with a thin diamond cut-off wheel on a precisioncut-off machine medium speed or cleaved. Determine the desired cross section line�target�. If suitable landmarks do not exist, create visible marks with a laser ormechanical probe.Mounting: Heat up a sample mount to approximately 125°C �250°F�. Apply a dotof wax and mount the specimen in cantilever fashion on the sample mount. Thetarget cross section line must extend beyond the end of the sample mount �seeSection 7.10.2�. Place the sample mount with specimen in the tripod fixture.Grinding: The purpose of grinding is to rapidly achieve a surface 1 �m away fromand parallel to the desired cross section line. If more than 40 �m of materialshould be removed to reach the final cross section line, begin grinding with SiCpaper grit P1200 �see step PG below�. If the distance to line is 20 �m or less, startwith step FG 1 below.FG 3 and FG 4 uses Al2O3 and diamond lapping film plane back, placed withwater as a “glue” on a plane, smooth surface �glass/metal plate� on the polishingdisk.


Diamond lapping film can be used as an alternative to SiC paper, and Al2O3lapping film in the steps PG and FG 1, 2, 3, and 4; this is stated in the MethodTable below. Step FG 5 shall always be with diamond lapping film. Attention:Always let the grinding/polishing disk rotate into the edge containing the target,except at the last polishing step �reverse position�.Polishing: The completed cross section should be exactly centered on the contact,via, or other feature in the target. Polishing will only remove very little material �2 �m or less� and cannot remove deep scratches or damage created by grindingtoo close to the desired finish with coarse abrasives. Polishing is most importantwhen the cross section is to be viewed in a high-resolution field emission SEM.Type of “polishing” depends on the composition of the specimen: Si, SiO2, and Alwith/without thin barrier layers: Repeat step FG 4 after step FG 5, only with0.05 �m Al2O3 lapping film in 0.5 min or longer until the diamond scratches areremoved. Finish with 0.5 min holding the fixture in reverse position �see Section7.10.2�.Si, SiO2, and metallization including tungsten plugs or layers: Use step P 1 below,holding the fixture in reverse position �see Section 7.10.2�.Etching: Normally no etching is used.


Sectioning

Cut-Off Wheel Diamond wheel metal bond 0.5 mm �0.019 in�thickness or by cleaving

Mounting


Resin See above Cold Mounting Resin See aboveTimeMinutes

TimeMinutes/Hours

Contemporary Method C-22 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 FG 5 P 1PolishingDisk/Cloth SiC

paperordiamondlappingfilm

SiCpaperordiamondlappingfilm

SiCpaperordiamondlappingfilm

Al2O3ordiamondlappingfilm

Al2O3ordiamondlappingfilm

Diamondlappingfilm


AbrasiveType

SiC ordiamond

SiC ordiamond

SiC ordiamond

Al-oxide

Al-oxide Diamond Dia, susp

Grit/GrainSize �m

P1200or 15

P2400 or8

P4000 or3

1 0.3 0.1 0.1


LubricantType

Water Water Water Water Water Water Alco

RotationDisk/Holder

60/100 60/100 60/100 60/100 30 30 70/100

rpm/rpmComp/ContraForce perSpecimenN �lb�

Weightoffixture

Weightoffixture

Weightoffixture

Weightoffixture

Weightoffixture

Weightof fixture

Weightof fixture

TimeMinutes

Untilwithin22 �mfromtargetline

Untilwithin12�mfromtargetline

Untilwithin 7�mfromtargetline



Untilwithin 1-1.5 �mfromtargetline

0.5–1,untiltarget

Material/Preparation Tables 23Material: Resistors. Other electronic metal components

Comments on Material: Metal film resistors and other metal-based electroniccomponents often consist of several very different types of material that rangefrom a very soft metal to a very hard ceramic. The methods stated below shouldbe considered as supplement to the methods stated in Material/Preparation Tables19 and 26.Sectioning: See Material/Preparation Tables 19 and 26.Mounting: See Material/Preparation Tables 19 and 26.Grinding: See Material/Preparation Tables 19 and 26.Polishing: See Material/Preparation Tables 19 and 26.Etching: See Material/Preparation Tables 19.


C-23

Perfect edge retentionGrain size, grain boundaries E 112, E 1382 C-23, T-23Image analysis, rating of inclusioncontent

E 562, E 1382 C-23, T-23

High planenessMicrohardness, hardness E 92, E 384 C-23, T-23



C-23, T-23


Preparation Process 23Sectioning

Cut-Off Wheel Diamond wheel metal bond or SiC bakelite bond,0.5 mm �0.019 in� thickness.

Mounting


Resin Cold Mounting Resin Acrylics with aFiller/Epoxy

TimeMinutes

TimeMinutes/Hours

6–15 min/12–24 h

Grinding

C-23: In the case of a high amount of ceramics in the specimen, PG may bechanged to a diamond pad, 30 �m, bakelite bond. See also Methods C/T-19.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

T-23: The step P 1 can be followed by a step like P 1 in Method C-23.

Contemporary Method C-23 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1PolishingDisk/Cloth SiC paper RCD, soft RCD, soft Cloth, nap-

less, soft,porous, syn


Dia, spror susp

Silica

Grit or Grain Size �m 320 9 3 0.04/0.05Lubricant Type Water Alco or wat Alco or watRotation Disk/Holder 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or


Force per Specimen N �lb� 35 �8� 35 �8� 35 �8� 20 �4.5�


TimeMinutes

Untilplane

3–4 3 0.5–1

Traditional Method T-23 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1PolishingDisk/Cloth SiC paper SiC paper SiC paper SiC paper Cloth,


Abrasive Type SiC SiC SiC SiC Dia,spr orsusp


P220 P320 P500 P1200 3

Lubricant Type Water Water Water Water Alcoor wat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150


ContraComp orContra

Comp orContra

Comp Comp


30 �7� 30 �7� 30 �7� 30 �7� 30 �7�

TimeMinutes

Until plane 0.5–1 0.5–1 0.5–1 3

Material/Preparation Tables 24Material: Solder balls. Microelectronic packages

Comments on Material: The tin-lead solders used for solder balls often have to beprepared together with other components like printed circuit boards �PCBs�,ceramics, plastics, etc. �see Section 7.10.3�. This means that the ideal preparationof the soft solder is not possible if the other components also should be preparedin an acceptable way. For soft solders the main problem is embedding of abrasivegrains and particles from the preparation process �see below and Section 13.5/6�.In case of soldered joints, cracks may develop after the preparation due to stress,and for this reason the specimen should be examined and documentedimmediately after preparation. For preparation of PCBs see Material/PreparationTables 27. For microelectronic packages see also Material/Preparation Tables 19and 26.


Sectioning: Sectioning often involves cutting through components of verydifferent hardness. Wet abrasive cutting should be done with a diamond metalbond cut-off wheel if the sectioning involves ceramics, and a SiC bakelite wheel ifcutting involves only softer materials �see also Material/Preparation Tables 26�.Cutting should be done on a precision cut-off machine to secure a precise cut andmake the use of a thin wheel, 0.5 mm �0.02 in� or thinner, possible. In case ofcomponent-mounted boards, take care that all specimens are properly identifiedbefore they are sectioned from the PCB. The cut should be in a certain distancefrom the level of investigation so that damage from the cutting can be removed atgrinding and polishing.Often the section to be investigated should be encapsulated �mounted� in epoxyprior to cutting to ensure the integrity of delicate joints/components.Mounting: The specimen should be carefully cleaned in acetone and preferablyultrasonics before mounting. Hot mounting cannot be recommended. Coldmounting with epoxy and vacuum impregnation is recommended so that all voidsare filled with epoxy �see Section 3.10�.Grinding: For specimens containing ceramics the Method C-24 should be usedwith Method C-19 as an alternative.Polishing: In case of embedded abrasive grains, the use of diamond paste can betried out for the 3 and 1 �m steps; also the use of only small amounts of lubricantmay prevent embedding of particles.Etching: Normally no etching is made, but in case of etching, see Material/Preparation Tables 52.


C-24

Perfect edge retentionGrain size, grain boundaries C-24, T-24Image analysis, ratingof inclusion content

C-24, T-24

High planenessMicrohardness, hardness E 92, E 384 C-24, T-24Microstructure E 3, E 407, E 883 C-23, T-23Phase identification C-23, T-23


Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond, thinnestpossible


Mounting


TimeMinutes/Hours

12–24 h

Grinding

C-24: FG 1 and T-24: FG 3: Grind until solder balls are visible, being close totarget.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-24, T-24: In case of embedded diamonds, diamond paste may be used insteadof spray/suspension for the 3 �m and 1 �m steps.

Contemporary Method C-24 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth SiC paper SiC paper RCD, soft Cloth, nap-

less, mediumhard,wov, wool



Dia, spr orsusp

Silica


220 320 9 3 0.04/0.05

Lubricant Type Water Water Alco or wat Wat-oilRotation Disk/Holder 300/150 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or

contraComp orcontra

Comp Comp Contra


20 �4.5� 15 �3.4� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Until plane To target 2 1–2 1



paperSiC

paperSiC

paperSiC

paperCloth,

napless,hard,

nonwov,syn

Cloth,napless,

hard,wov, silk

Cloth,nap-

less, softporous,

synAbrasiveType

SiC SiC SiC SiC Dia, spror susp

Dia, spror susp

Silica


P220 P320 P500 P1200 3 1 0.04/0.05

LubricantType

Water Water Water Water Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra



30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4 2 0.5–1

Material/Preparation Tables 25Material: Capacitors. Other polymer electronic components

Comments on Material: Film capacitors often incorporate two layers of dielectricfilm that have each been metallized on one side; these strips are stacked androlled. The assembly may be packaged in a polymeric conformal coating or in amolded polymeric housing.Sectioning: See Material/Preparation Tables 19.Mounting: See Material/Preparation Tables 19.Grinding: If the specimen contains phases of very different hardness, Method C-25should be preferred.Polishing: Polishing times should be kept as short as possible to avoid relief.Etching: Normally no etching is done.


C-25



Grain size, grain boundaries E 112, E 1382 C-25,T-25


E 562, E 1245, E 1382 C-25,T-25

High planenessMicrohardness, hardness E 92, E 384 C-25,

T-25Microstructure E 3, E 407, E 562, E 883,

E 1245, E 1382C-25,T-25


Porosity C-25,T-25


Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond, 0.5 mm�0.02 in� thick

Mounting



TimeMinutes/Hours

6–10 min/8–12 h

Grinding

C-25: PG step: In the case of little or no ceramic material, SiC paper can beused.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Contemporary Method C-25 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth Dia, disk,

resRCD, soft Cloth, nap-

less, hard,wov, silk




Dia, spr orsusp

Dia, spr orsusp

Silica


Grit orGrain Size �m

P220 9 6 1 0.04/0.05

LubricantType

Water Alco or wat Wat-oil Wat-oil

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150


contraComp Comp Comp


25 �5.7� 25 �5.7� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Until plane 5 1–2 0.5–1 0.5


paperSiCpaper

SiCpaper

SiCpaper

Cloth,napless,v. hard,wov, syn


Cloth,napless,softporous,syn


Dia, spror susp

Silica


P320 P500 P800 P1200 6 3 0.04/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 3 2 0.5–1


Material/Preparation Table 26Material: Microelectronic packages. Integrated circuits.Transistors. Other microelectronic devices

Comments on Material: As an introduction to preparation of microelectronicpackages Section 7.10.3 should be studied to get an impression of the problemsinvolved.Electronic and microelectronic devices and packages are complex materialcomposites. Imaging and analysis of the various material microstructures, layeredstructures, and interfaces are necessary for a number of reasons, includingpackage qualification, monitoring of the manufacturing process, incoming qualitycontrol, and failure analysis. The dimensions of the individual features range fromfractions of a micron to several cm �fraction of an in�. Due to the close packing ofthe various materials within a small volume, all materials having very differentproperties; materialographic preparation faces the problem of making all thematerials suited for proper analysis. It is essential to have a general understandingof the physical properties of all materials used in the construction of the package�see Table 7.1�. As a rule the preparation is tailored to the predominant componentmaterial to be analyzed, but often all materials must be considered to obtain asatisfactory result. Ignoring the unique interfaces that are present in amicroelectronic package will likely result in artifacts induced during thepreparation process. Such artifacts may be edge rounding, relief, embedding ofabrasive grains, smearing and fracturing, and introduction of microcracks. Severalof these artifacts could be misinterpreted as defects in the package developedduring the production or in other ways.Making a cross section of a microelectronic package is a destructive test; it isimportant that as much information as possible about the device is gatheredbefore the preparation starts. Such information is important to decide on thetarget of the preparation and may be important to be able to decide whether adefect was pre-existing or induced during the preparation. Also, this information isimportant in case of failure analysis. The information can be obtained through anumber of analysis techniques like radiography, ultrasonic imaging, andmacrophotography. Based on the available information, thepreparation process is decided upon as either one of the two methods indicatedbelow or other methods stated in Material/Preparation Tables 19, 22, 23, and 25,with the Methods C-19 and T-19 as the first choice.Sectioning: Wet abrasive cutting with a diamond metal bond cut-off wheel,0.5 to 1 mm �0.02 to 0.04 in� thick on a precision cut-off machine with1500 to 2000 rpm. Often an electroplated diamond wheel can be used withadvantage, and in the case of very hard components a diamond wheel withbakelite bond should be used. In certain cases depending on the materials, SiCbakelite bond cut-off wheel can be used.Cutting before encapsulation: In some cases the package should be opened to beable to make the encapsulation �mounting�. This can be done with wet abrasivecutting as mentioned or with grinding away the material or by other means. It isimportant that this process takes place at a safe distance to the site to beinvestigated.


Cutting after encapsulation: Wet abrasive cutting as stated above is recommended.It is important that the specimen is oriented, with respect to wheel rotation, suchthat the brittle material in the specimen, like silicon, is cut in compression. Doingthis will minimize delamination or fracturing, or both, of the brittle componentmaterial. Also the specimen should be positioned so that the wheel cuts into thesmallest dimension of the critical parts in the package. To shorten the followingpreparation process, the cutting should be done in a plane relatively close to thesite of investigation with this under the condition that the damage caused by thecutting is “under control.”Mounting: Microelectronic packages cannot be subjected to pressure and heat, soonly cold mounting, most often as an encapsulation in epoxy under vacuum, isrecommended.Encapsulation: It is very important that the package is carefully cleaned to securea complete adhesion by the epoxy during the encapsulation. This can be done inacetone, preferably in a beaker in an ultrasonic bath. Drying should be done withN2 gas or absolutely pure compressed air; normal compressed air shouldbe avoided. The cleaned part should be handled with a pair of tweezers and driedin an oven at 50°C �122°F�. The package is placed in the mounting mold so thatthe plane of interest will ultimately be parallel to the cutting wheel. If needed, thespecimen is supported with clips or by other means. It is important that themounting material adheres to all constituents and that all topographical featuresof the package is filled with mounting material. This can best be provided with anepoxy with a low viscosity and impregnation under vacuum �see Section 3.10�.Also a pressure vessel can be used for securing a good encapsulation �see Section3.7�.Grinding: Considering the often very brittle materials in the specimen, planegrinding with rough SiC grinding papers should be avoided. In the methods statedbelow plane grinding is with grit P320 grinding paper, but this paper should onlybe used if the plane grinding is in a plane relatively far from the site of interest�target�. If possible, depending on the surface established by the sectioning, theplane grinding should be done with an RCD stated in Method C-26, step FG 2,below. In case of packages with many soft, ductile materials, Method T-26 belowmay have the best grinding steps.Polishing: It is very important that the deformation and other damage developedduring the grinding is removed during the rough polishing step. Often step P 2 inMethod T-26 can be omitted. For packages containing predominantly softmaterials �plastics�, it can be of advantage to use a mixture of 50 % colloidal silicaand 50 % deagglomerated alumina �0.05 �m� for the final polishing step.Etching: Normally no chemical etching takes place, but physical etching, likerelief polishing and methods like deposition of layers can be used �see Section 9.6�.



C-26

Perfect edge retentionGrain size, grain boundaries E 112, E 1382 C-26, T-26Image analysis, rating of inclusioncontent

E 562, E 1245, E 1382 C-26, T-26

High planenessMicrohardness, hardness E 92, E 384 C-26, T-26Microstructure E 3, E 407, E 562, E 883,

E 1245, E 1382C-26, T-26



Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond,0 to 1 mm �0.02 to 0.04 in� thick, see also above.

Mounting


TimeMinutes/Hours

12–24 h

Grinding

C-26, T-26: Only use rough grits of SiC grinding paper, when not close to target.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

T-26: Often the step P 2 can be omitted.C-26: P 2: Often the cloth can be changed to a med nap, soft, syn, if thedifference in hardness of the components materials is not high.C-26 and T-26: For predominantly soft materials use a mixture of 50 % colloidalsilica and 50 % deagglomerated alumina �0.05 �m� for the final polishing step.C-26 and T-26: For the steps with 6, 3, and 1 �m diamond, colloidal silica canbe used as lubricant.


Contemporary Method C-26 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth SiC paper SiC paper RCD, soft Cloth, nap-

less, hard,wov, syn



AbrasiveType

SiC SiC Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp

Silica


220 320 9 3 1 0.04/0.05

LubricantType


Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra



25 �5.7� 25 �5.7� 20 �4.5� 20 �4.5� 20 �4.5� 10–15�2.2–3.4�

TimeMinutes

Untilplane

0.5–1 2–15�Close totarget�

1–5 1–4 0.5–1

Traditional Method T-26 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ FG 3 P 1 P 2 P 3 P 4Polishing PG FG 1 FG 2Disk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper


Cloth,nap-less,hard,wov,syn


Cloth,nap-less,soft,por-ous,syn

AbrasiveType


Dia,sprorsusp

Dia,sprorsusp

Silica


P320 P500 P800 P1200 6 3 1 0.04/0.05

LubricantType

Water Water Water Water Wat-oil Wat-oil Wat-oil


RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra



30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5� 20 �4.5� 20 �4.5� 10–15�2.2–3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5 –1�Closetotarget�

5–15 1–2 1–4 0.5–1

Material/Preparation Tables 27Material: PCB coupon

Comments on Material: For a description of PCB coupons with reference holesand their preparation, see Section 7.10.1.A “contemporary” method is not developed for this type of preparation; therefore,Method C-27 is a “traditional” method using SiC grinding paper.Sectioning: The coupon is normally cut out with a router or punched out. Aprecision cut-off machine with a diamond cut-off wheel, metal bond, can also beused.Mounting: Two to six coupons are mounted with a cold mounting material likeacrylics in a special mounting mold to be placed in a special holder, with referencepins, to obtain a controlled material removal.Grinding: Grinding is done in two steps against adjustable stops mounted on thespecimen holder to stop material removal before the center of the holes to beinspected.Polishing: The polishing steps P 3 and even P 2 in Methods C-27 and T-27 may beomitted according to the type of PCB and the purpose of examination.Etching: If an etching is wanted this can be done in the polishing step P 3: Use96 mL colloidal silica, 2 mL H2O2 �30 %� and 2 mL ammonia solution �25 %�.


Sectioning

Cut-Off Wheel Diamond, metal bond, if not routed or punched, seeabove.


Mounting

Hot Compression Mounting Resin Cold Mounting Resin AcrylicsTimeMinutes

TimeMinutes/Hours

8–10 min

Grinding

C-27, T-27: Grinding is performed against adjustable stops �see above�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-27, T-27: Etching can be done through chemical mechanical polishing with96 mL colloidal silica, 2 mL H2O2 �30 %� and 2 mL ammonia solution �25 %�.

Contemporary Method C-27 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth SiC paper SiC paper Cloth,


Cloth,napless,hard, wov,wool



Dia, spr orsusp

Silica

Grit or Grain Size �m P220 P1200 3 1 0.04/0.05Lubricant Type Water Water Water WaterRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150



Force per Specimen N �lb� 20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4� 10 �2.2�TimeMinutes

See above See above 2 2 0.5

Traditional Method T-27 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3Polishing


Disk/Cloth SiC paper SiC paper Cloth,napless,hard,wov, syn




Dia, spr orsusp

Silica


P220 P1200 6 1 0.04/0.05

Lubricant Type Water Water Water WaterRotationDisk/Holder

300/150 300/150 150/150 150/150 150/150




20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4� 10 �2.2�

TimeMinutes

See above See above 2 2 0.5

Material/Preparation Tables 28Material: High carbon steels. Medium carbon steels

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Low carbon steel: �0.2 % C, medium carbon steel: 0.2–0.5 % C, high carbon steel:�0.5 % C �weight %�.Comments on Material: The plain carbon steels are characterized by theircomposition, having only carbon as the important alloying element. A typicalmedium carbon steel �SAE-AESI 1042� has the composition: 0.4–0.47 % carbon,0.60–0.90 % manganese, maximum 0.040 % phosphorus, maximum 0.05 % sulfur.The plain carbon steels and other steels are classified according to theircomposition by the American Iron and Steel Institute �AISI� and the Society ofAutomotive Engineers �SAE�. ASTM also has a classification system built on thesteel product and its application. The ASTM standards are specifications forspecific products; a few examples are: A 1, A 3, A 36 �see Section 12.4.2�. Themicrostructure of plain carbon steels is a mixture of ferrite and pearlite, with anincrease in pearlite corresponding to the increase in carbon content. At 0.8 %carbon, only pearlite is present and above 0.8 % carbon, cementite will develop.Medium and high carbon steels are relatively easy to prepare. The problem is toobtain a true ferrite without deformation. At higher carbon contents with smallamounts of ferrite, the preparation can be cut down to three or four steps forroutine examination �see below�. These materials are well suited for electrolyticpolishing.


Sectioning: The correct selection of the specimen is important, especially onrolled material �see Section 2.1�. In wet abrasive cutting an Al2O3 cut-off wheelshould be used. Overheating should be avoided because martensite can bedeveloped. Cutting pressure should be moderate and cooling should be efficient onboth sides of the cut-off wheel. If shearing or band sawing is used, the increase indeformation should be taken into consideration, prolonging the plane grindingstep, or possibly use of a rougher grinding paper before grit 220.Mounting: For routine examination bakelite as powder or tablets is sufficient. Inthe case of examination of coatings, other mounting materials should be used �seeMaterial/Preparation Tables 08–15�. For mounting for electrolytic polishing, seeSection 3.11.6.Grinding: Grinding normally will give no problems with these materials. Careshould be taken that the deformations from plane grinding are effectively removedbefore the polishing. If not, the deformed ferrite can be seen after etching, and theprocess must be repeated from FG 1. In the case of water sensitive inclusions,mineral spirits or kerosene can be used for grinding with SiC grinding paper �seealso Material/Preparation Tables 36�.Polishing: The problem can be to obtain a perfect ferrite phase as mentionedabove. In the case of only small deformations, prolong the 3 �m step for 1–2 min.For medium carbon steels the final step could be with diamond �see below�.A common test on steels is nonmetallic inclusion identification; often SEM andEDAX analysis is used. As Si may be contained in the indigenous inclusions, silica�SiO2� should be avoided for the last polishing step. Therefore this step should bechanged to diamond �see below�.Electrolytic polishing can be recommended.Etching: A high number of etchants are available for steels. In most cases arelative small selection will cover the need in a given laboratory �see below�.Electrolytic etching is possible.


B 487, E 1077 C-28

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-28, T-28,

El-01Heat influenced zone E 1077 C-28Heat treatment C-28, T-28,

El-01Image analysis, ratingof inclusion contentHigh planeness

E 45, E 562, E 768, E 1077,E 1245, E 1268, E 1382, E 2283

C-28

Inclusions in steel E 45, E 768, E 1245 C-28, T-28Microhardness, hardness E 10, E 18, E 92, E 103, E 110,

E 140, E 384, E 448C-28, T-28


Microstructure A 892, E 3, E 45, E 407, E 562, E768,E 883, E 1077,E 1181, E 1245, E 1268,E 1351, E 1382, E 1558

C-28, T-28,El-01

Phase identification C-28, T-28,El-01

Structure changes �forging� C-28, T-28,El-01


Sectioning

Cut-Off Wheel Al2O3, bakelite bond

Mounting


Resin Bakelite Cold Mounting Resin AcrylicsTimeMinutes


6–10 min

Grinding

T-28: In some cases, at high C content, FG 1 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-28 and T-28: In case of SEM and EDAX analysis of inclusions, the finalpolishing step is changed to diamond 1 �m, see step P 2 in Method C-29. Also,0.25 �m diamond can be used as a step after 1 �m diamond, using the samecloth and same data.C-28: P 1: The cloth can be changed to napless, hard, wov, silk.C-28: P 2: This step can be changed to diamond 1 �m, see P 2 in C-29, and thesilica step will be P 3 or it may be omitted.T-28: P 3: Often the alumina suspension can be diluted with water 1:1. In somecases this step can be omitted.



fixed, resRCD, hard Cloth,

napless,hard, wov,syn

Cloth,napless,soft, porous, syn


Dia, spror susp

Silica

Grit or Grain Size �m P220 9 3 0.02/0.05Lubricant Type Water Alco or wat Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150




30 �7� 25 �5.5� 20 �4.5� 10 �2.2�

TimeMinutes

Until plane 4–6 3 1–4

Traditional Method T-28 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper



Cloth,napless,porous,syn

AbrasiveType

SiC SiC SiC Dia, spr orsusp

Dia, spr orsusp

Alumina


P220 P320 P500 6 3 0.02/0.05

LubricantType

Water Water Water Alco or wat Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150




40 �9� 40 �9� 40 �9� 30 �7� 20 �4.5� 10 �2.2�


TimeMinutes

Untilplane

0.5–1 0.5–1 3 3 1–4

EtchantsMaterial Etchants �see Table 12.2� UsesFe+C and 76, 74a, 77, 78, 79 General structureFe+ �1 C 74a, 77, 31a, 223 Ferrite grain boundaries+�4% additions 80, 81, 82 Prior austenitic grain boundaries in

martensitic and bainitic steels78, 222a Untempered martensite31b, 78 Carbides and phosphides �matrix

darkened carbides and phosphidesremain bright�

83 Cementite attacked rapidly, susteniteless, ferrite and iron phosphide least

84 Overheating and burning stainscarbides

85 Stains carbides86 Chemical polish-etch210, 211 Colors ferrite213, 214 Colors carbides216222b

Color latch martensite in low carbonhigh-alloy grades for dual phase steels;reveals pearlite, darkens martensiteand outlines austenite

Material/Preparation Tables 29Material: Low carbon steels

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Low carbon steel: �0.2% C, medium carbon steel: 0.2–0.5 % C, high carbon steel:�0.5%C �weight %�Comments on Material: Low carbon steels are relatively easy to prepare. Theproblem is to obtain a true ferrite without deformation. This depends on thecarbon content and often, at higher carbon contents, a fine grinding step can beomitted for routine examination �see Material/Process Tables 28�.Sectioning: See Material/Preparation Tables 28.Mounting: See Material/Preparation Tables 28.Grinding: See Material/Preparation Tables 28.Polishing: See Material/Preparation Tables 28.Etching: See Material/Preparation Tables 28.



B 487, E 1077 C-29


E 112, E 930, E 1181, E 1382 C-29, T-29,El-02

Heat influencedzone

E 1077 C-29

Heat treatment C-29, T-29,El-02


E 45, E 562, E 768, E 1077,E 1245, E 1268, E 1382, E 2283

C-29

Inclusions in steel E 45, E 768, E 1245 C-29, T-29Microhardness,hardness

E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-29, T-29

Microstructure A 892, E 3, E 45, E 407, E 768, E 883,E 1077, E 1181, E 1245,E 1268, E 1351, E 1382, E 1558

C-29, T-29,El-02


Structure changes�forging�

C-29, T-29,El-02


Sectioning


Mounting

Resin Bakelite Resin AcrylicsCold Mounting Time

Minutes8–9 Time

Minutes/Hours8–10 min

Grinding

C-29: P 2: This step can be changed to SiC paper grit P220/320.T-29: In some cases, at a relatively high carbon content, FG 1 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

C-29 and T-29: In case of SEM and EDAX analysis of inclusions, the finalpolishing step is changed to diamond 1 �m, see step P 2 in Method C-29 andstep P 3 in T-29. Also 0.25 �m diamond can be used as a step after 1 �mdiamond, using the same cloth and same data.C-29: P 2: For certain materials �cast iron� this step can be omitted or P 3 can beomitted.C-29 and T-29: Silica can be used instead of alumina.T-29: A fine polishing step, P 3, from C-29 can be added.

Contemporary Method C-29 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth Dia, disk

fixed, resRCD, soft Cloth,


Cloth,med. nap, soft,syn

Cloth, napless, soft,porous, syn

AbrasiveType

Diamond Dia,spr orsusp

Dia, sprorsusp

Dia, sprorsusp

Alumina


P220 9 3 1 0.02/0.05

LubricantType

Water Alcoor wat

Alcoor wat

Alcoor wat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150




25 �5.5� 30 �6.6� 25 �5.5� 25 �5.5� 10 �2.2�

TimeMinutes

Until plane 4–6 4–5 1 1



paperSiCpaper

SiCpaper

SiCpaper



Cloth,mednap,soft,syn

AbrasiveType


Dia, spror susp

Dia, spror susp


P220 P320 P500 P1200 6 3 1

LubricantType


Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150


contraComp Comp Comp Comp Comp Comp


40 �9� 40 �9� 40 �9� 40 �9� 40 �9� 35 �8� 35 �8�

TimeMinutes

Unitplane

0.5–1 0.5–1 0.5–1 3–4 3–4 1

EtchantsSee Material/Preparation Tables 28.


Material/Preparation Tables 30Material: Gray cast iron, lamellar. Malleable cast iron

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Gray cast iron: Carbon 2.5–4.0 %, silicon: 0.5–3.5 %, manganese: 0.2–1.3 %,phosphorus 0.002–1.0 %, sulfur: 0.2–0.15 % �weight %�.Comments on Material: Gray cast iron is by far the most used cast iron. Themicrostructure consists of ferrite or pearlite with graphite in flakes �lamellar�, orboth, or in other shapes. The name refers to the color of a fresh fractured surface,which is grayish because of the graphite. Gray cast iron has a relatively highsilicon content because silicon promotes the formation of graphite duringsolidifidation. The microstructure of lamellar cast iron contains 5–10 volume % ofgraphite, and the lamellar size and distribution are important for the strength ofthe cast iron, but in general lamellar cast iron has a relatively low strengthbecause of the graphite. The type, size, and distribution are standardized in theASTM Standard Test Method for Evaluating the Microstructure of Graphite in IronCastings �A 247�. Also, a number of other specifications are described in ASTMstandards; some examples covering gray cast iron and malleable cast iron are: A47, A 48, A 126, A 159, A 197, A 220, A 338, and A 602 �see Sections 12.4.2�.Malleable cast iron, also called TG �temper graphite� iron, is made by heattreatment of white cast iron. During this treatment, up to 20 h, the carbides of thewhite cast iron are changed into graphite which will be separated into irregularlyshaped nodules in a ferritic or ferritic/pearlitic matrix. This condition makesmalleable cast iron comparable to steel regarding strength, but the importance ofthis material has been reduced because of the development of nodular cast iron�ductile cast iron� �see Material/Preparation Tables 31�.As the microstructure strongly influences the mechanical properties of cast iron,metallographic/materialographic examination is important. The examination issupported by standard reference comparison charts or image analysis techniques,or both, to determine the morphology, size, and distribution of the graphite on anunetched specimen.During the metallographic/materialographic preparation, the retention of the freegraphite in a ferrite/pearlite matrix causes a problem. The difference in hardnessbetween the two phases and the relative brittleness of the graphite may causepull-outs of the graphite and development of a relief between the phases. To obtaina correct result of a running analysis, it is important that the same high number ofgraphite lamellars/nodules are satisfactorily present in the structure withoutmissing parts of the graphite. The pull-outs to a high degree take place during therougher steps of the grinding and therefore it is important that the graphite isre-established during the fine grinding and polishing steps.SiC paper may cause a pull-out of graphite even at the fine grain sizes. In that caseMethod C-30 should be used.In the case of a matrix containing much ferrite this may cause problems withdeformations �see Material/Preparation Tables 28�. For certain cast irons,electrolytic polishing can be used.Method C-29 and T-29 can also be used for cast iron.


Sectioning: These materials are normally sectioned with wet abrasive cuttingwithout problems using an Al2O3, bakelite bond cut-off wheel. If band sawing isused, the increase in deformation should be taken into consideration, prolongingthe plane grinding step, or possibly use of a rougher grinding paper before grit220. Standards test bars are to be preferred, reducing the amount of sectioning,only it should be considered, whether the microstructures of the test bar trulyrepresent the structure of the casting.Mounting: Normally a mounting is not needed except for establishing a suitableshape for automatic preparation. Often the preparation and examination shall takeplace as part of a production process and the time for preparation is very short. Inthat case the shape of the test bar coming from the production should be so that itfits into a specimen holder or specimen holder plate without mounting.If graphite close to the edge shall be examined, mounting in a suitable mountingmaterial with a hardness corresponding to the cast iron is recommended.Grinding: In Method T-30 the high number of grinding papers is due to thedevelopment of the correct graphite at the finest papers. In case of problems withretaining of graphite, the steps FG 3 and FG 4 may be used without water. Oftenthe number of steps can be reduced �see also Method T-31�. Always use freshpaper, as worn down paper may create pull-out of the graphite.Polishing: In case of routine examination without image analysis, polishing maystop after the P 1 step for Method C-30 and after the P 2 step in Method T-30.Electrolytic polishing cannot be recommended, but it may be used for routineexamination of certain materials.Etching: See Material/Preparation Tables 28.


C-30

Perfect edge retentionGraphite in cast iron A 247 C-30, T-30Grain size, grain boundaries E 112, E 930, E 1181, E 1382 C-30, T-30,

El-03Heat treatment C-30, T-30Image analysis, ratingof inclusioncontent

E 562, E 1077, E 1245, E 1382 C-30

High planenessMicrohardness, hardness E 10, E 18, E 92, E 103, E 110,

E 140, E 384, E 448C-30

Microstructure A 247, E 3, E 407, E 562, E 883,E 1245, E 1351, E 1382, E 1558

C-30, T-30,El-03



Sectioning


Mounting




8–10 min

Grinding


Polishing

C-30: A P 3 step from T-30 can be added.

Contemporary Method C-30 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2PolishingDisk/Cloth SiC paper RCD, soft Cloth,

napless,hard, wov, syn

Cloth, shortnap,soft, syn

Abrasive Type SiC Dia, spr or susp Dia, spr orsusp

Dia, spr or susp


P220 9 3 1


300/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 25 �5.7�

TimeMinutes



Traditional Method T-30 �For definitions of parameters and consumables seeSection 13.2.2.�

Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper

Cloth,napless,hard,wov,silk ornonwov,syn



AbrasiveType


Dia,sprorsusp

Silica


P220 P320 P500 P1200 P2400 6 1 0.04/0.05

LubricantType

Water Water Water Water Water Alcoorwat

Alcoorwat

RotationDisk/Holder

300/150 100/150 300/150 300/150 300/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



40 �9� 30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 25�5.7�

10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4–5 2–3 1



Material/Preparation Tables 31Material: Nodular cast iron „ductile iron…

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Nodular cast iron: Carbon 3.0–4.0 %, silicon: 1.8–2.8 %, manganese: 0.1–1.0 %,phosphorus: 0.01–0.1 %, sulfur: 0.01–0.03 % �weight %�.Comments on Material: Nodular cast iron, also called ductile iron and spheroidalgraphite �SG� cast iron, is a cast iron with the graphite in the form of nodules orspheres. Unlike malleable cast iron �see Material/Preparation Tables 30�, thenodules are developed during the solidification due to small additions ofmagnesium and cerium. The advantage of nodular cast iron is the considerableincrease in toughness, caused by the spheroidal graphite, which makes itcomparable to steel for many purposes. The type, size, and distribution arestandardized in the ASTM Standard Test Method for Evaluating theMicrostructure of Graphite in Iron Castings �A 247�. Also a number of otherspecifications are described in ASTM standards; some examples are: A 377, A 439,A 536, and A 439 �see Sections 12.4.2�.The metallographic/materialographic examination of the microstructure is asdescribed in the Material/Preparation Tables 30. Also Methods C-30 and T-30 canbe used for nodular cast iron.Sectioning: See Material/Preparation Tables 30.Mounting: See Material/Preparation Tables 30.Grinding: Fine grinding with the finer grades of SiC paper in Method T-31 isimportant to re-establish the graphite after pull-outs with the coarser grades.Polishing: At routine examinations, not using image analysis, the specimensurface after the 3 �m polishing step might be satisfactory. Electrolytic polishingcannot be recommended, but it may be used for routine examination of certainmaterials.Etching: See Material/Preparation Tables 28.


C-31

Perfect edge retentionGraphite in cast iron A 247 C-31, T-31Grain size, grain boundaries E 112, E 930, E 1181, E 1382 C-31, T-31Heat treatment C-31, T-31Image analysis, ratingof inclusioncontent

E 562, E 768, E 1245, E 1382 C-31


E 140, E 384, E 448C-31, T-31


Microstructure A 247, E 3, E 407, E 562, E 883,E 1245, E 1351, E 1382, E 1558

C-31,T-31,El-03




8–10 min


Sectioning


Mounting




8–10 min

Grinding

C-31: SiC grinding paper P220 can be used for PG.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference ismore than 100–150 �m between the center and the periphery, the disk is eitherdiscarded or trued.

Polishing

C-31 and T-31 Both methods can be finished with a fine polishing step withsilica �see Method T-30step P 3�.

Contemporary Method C-31 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1PolishingDisk/Cloth Dia, disk,

fixed, resRCD, soft Cloth, napless,

hard,nonwov, syn

Cloth, nap-less, hard, wov,syn


Dia, spror susp

Dia, spror susp



P220 9 3 1


300/150 150/150 150/150 150/150




25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5�

TimeMinutes



paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

Dia,sprorsusp


P220 P320 P500 P1000 6 3 1

LubricantType


Alco orwat

Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp Comp


30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 25 �5.7� 20 �4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 5 3–4 3–4



Material/Preparation Tables 32Material: White cast iron

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.White cast iron: Carbon 1.8–3.6 %, silicon: 0.5–1.9 %, manganese: 0.25–0.8 %,phosphorus: 0.006–0.2 %, sulfur: 0.06–0.2 % �weight %�.Comments on Material: If the liquid iron-carbon is solidified relatively fast, thecarbide is not formed as graphite like in gray cast iron, but as cementite in anetwork. This makes the white cast iron very hard and wear resistant, and thecementite gives the fractured surface the white appearance. If white cast iron isheated over a period of time, the cementite will break down to form graphite �seeMaterial/Preparation Tables 30�. White cast iron is often alloyed with nickel,chromium, or molybdenum or combinations thereof, to improve the wearresistance. The different types of white cast irons are standardized in the ASTMSpecification for Abrasion-Resistant Cast Irons �A 532� �see Sections 12.4.2�.Materialographic preparation of white cast iron is relatively easy because of thevery hard cementite.Sectioning: Wet abrasive cut-off should be done with a soft Al2O3, bakelite bondcut-off wheel. White cast iron may be difficult to cut because of internal stressesand the feed speed should be low. For very hard materials a CBN wheel resin bondmay be needed �see Section 2.4.2�.Mounting: Normally mounting is not needed except in the case of examination ofsurface layers �see Material/Preparation Tables 08–15�, or in the case of obtaining ashape of the specimen suited for automatic preparation. If possible, the specimenshould be sectioned so that it can be placed in a specimen holder withoutmounting.Grinding: Because of the high hardness, the SiC grinding papers will be worn veryfast, and especially at the PG step several sheets may be needed.Polishing: The polishing step with silica may be omitted for routine examinations�see below�.Etching: See below and Material/Preparation Tables 28, 33, and, 34.


C-32

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-32, T-32Image analysis, ratingof inclusioncontent

E 562, E 768, E 1245, E 1382 C-32

High planeness


Microhardness,hardness

E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-32, T-32

Microstructure E 3, E 407, E 562, E 883, E 1245,E 1351, E 1382, E 1558

C-32, T-32


Sectioning

Cut-Off Wheel Al2O3, bakelite bond. For very hard materials ��HV500–700� a CBN wheel resin bond may beneeded �see Section 2.4.2.�.

Mounting


Resin Epoxy with Filler ColdMounting

Resin Acrylicswith Filler

TimeMinutes


6–15 min

Grinding

C-32 and T-32: The PG step may start with SiC grinding paper grit P120 orP180, if a high material removal is needed.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-32: P 3. This step can often be omitted.T-32: A step like P 2 in Method C-32 can be added.



napless,hard, wov,silk

Cloth, mednap, soft,syn



Dia, spr orsusp

Dia, spr orsusp

Silica


P220 9 3 1 0.04/0.05



300/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 25 �5.7� 15 �3.4�

TimeMinutes

Untilplane

4 4 3 1


paperSiCpaper

SiCpaper

Cloth,v. hard,wov, syn

Cloth,napless,hardnonwov,syn


Abrasive Type SiC SiC SiC Dia, spr orsusp

Dia, spr orsusp

Dia,spr orsusp


P220 P320 P500 9 6 3

Lubricant Type Water Water Water Alco orwat

Alco orwat

Alcoor wat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp


40 �9� 40 �9� 40 �9� 40 �9� 35 �8� 30 �7�

TimeMinutes

Untilplane

0.5 0.5 4 4 3

Etchants

Material Etchants �see Table 12.2� UsesWhite cast iron 210 General structure

See also Material/Preparation Tables 28, 33,and 34


Material/Preparation Tables 33Material: High-alloy steels. Heat-treated, low-alloy steels. Heat-treated, High-alloy steels. Other ferrous metals

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite� face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.High-alloy steels: �8 % total alloying elements �weight %�.Comments on Material: High-alloy steels have been developed to obtain specialcharacteristics like resistance to corrosion, heat, and wear. The corrosion resistantsteels, stainless steels, are described in Material/Preparation Tables 34. The heatresistant steels can be low- or high-alloyed depending on the temperature range.The high-alloyed steels may contain chromium, molybdenum, nickel, cobalt, andtitanium to obtain highest heat resistance. For iron-based super alloys, seeMaterial/Preparation Tables 35. The wear resistant high-alloy steels, tools steels,may contain a high percentage of chromium and manganese, molybdenum, andvanadium �see Material/Preparation Tables 38�.High-alloy steels can be difficult to prepare because of the often relatively softmatrix. It can be difficult to conserve all inclusions and carbides, especially if thespecimen should be examined by image analysis. Also hardened alloy steels can bedifficult to prepare; they often have different hardness within the microstructureand contain a high amount of very hard and brittle carbides. For problems withsmearing, loss of inclusions, etc., see Section 13.6. Often electrolytic polishing canbe used.Sectioning: Wet abrasive cutting with an alumina, bakelite bond cut-off wheelwith an effective cooling should be without problems. For very hard materials aCBN wheel resin bond may be needed �see Section 2.4.2�. Cutting with a band sawmay give deformations and possible work hardening in steels with an austeniticstructure that should be removed at a prolonged plane grinding, or only used forinitial cutting followed by wet abrasive cutting.Mounting: Normally mounting is not needed except in case of examination ofsurface layers �see Material/Preparation Tables 08–15� or in case of obtaining ashape of the specimen suited for automatic preparation. If possible the specimenshould be sectioned so that it can be placed in a specimen holder withoutmounting.Grinding: In case of water-sensitive inclusions or carbides Method C-33 should bepreferred without the final polishing step.Polishing: Electrolytic polishing can be recommended for steels not having a tooheterogenous microstructure.Etching: For observation of certain phases, like carbides, in the microstructure, aminimal relief can be developed during the last polishing step so that these can beseen in the microscope without chemical etching �see Section 9.6�. A number ofetchants are stated below �see also Material/Preparation Tables 34�.

Purpose ASTM Standard �See Section 12.4� MethodCase of coating thickness/hardness, surface layers

E 1077 C-33




E 112, E 930, E 1181, E 2283 C-33,T–33,El-04

Heat influenced zone E 1077 C-33Heat treatment C-33,

T-33Image analysis, rating ofinclusion content

E 45, E 562, E 768, E 1077,E 1122, E 1245, E 1268, E 1382,E 2283

C-33

High planenessInclusion in steel E 45, E 768, E 1122, E 1245 C-33,

T-33Microhardness, hardness E 10, E 18, E 92, E 103, E 110,

E 140, E 384, E 448C-33,T-33

Microstructure A 892, E 3, E 45, E 407, E 562,E 768, E 883, E 1077, E 1181,E 1245, E 1268, E 1351,E 1382, E 1558

C-33,T-33,El-04

Phase identification C-33,T-33,El-04

Structure changes �forging� C-33,T-33,El-04


Sectioning

Cut-Off Wheel Al2O3, bakelite bond. For very hard materials ��HV500–700� a CBN wheel resin bond may beneeded �see Section 2.4.2.�.

Mounting




6–10

Grinding

C-33: PG: For low-alloyed steels SiC paper grit P220 should be used.C-33: FG 1: For low-alloyed steels an RCD soft can be used.






Cloth, med.nap, soft, syn


Dia, spr orsusp

Dia, spr orsusp

Grit/Grain Size �m P220 9 6 1Lubricant Type Water Alco or wat Alco or

suspAlco or wat

Rotation Disk/Holder 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or



30 �7� 30 �7� 35 �8� 25 �5.7�

TimeMinutes

Until plane 4–5 4–5 2–3 1


paperSiCpaper

SiCpaper

SiCpaper

Cloth,nap-less,hard,wov, silk

Cloth,nap-less,hard,wov, syn

Cloth,nap-less,soft,porous,syn


Dia, spror susp

Alumina


P220 P320 P500 P1200 6 3 0.02/0.05

Lubricant Type Water Water Water Water Alco orwat

Alco orwat

Rotation Disk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 25 �5.7� 10 �2.2�

TimeMinutes

Untilplane

0.5 0.5 0.5 3–4 3 1

EtchantsMaterial Etchants �see Table 12.2� UsesFe+4−12 Cr 80, 87, 88, 89, 90, 91, 79, 210 General structureFe+12−30 Cr+ �6Ni�400 Series�

80, 87, 88, 89, 34, 40, 92, 93,94, 95, 91, 226

General structure

96, 97, 98 Sigma phase31c Carbides86 Chemical polish etch219 Grain boundary220 Darkens delta ferrite

High temperature 89, 25, 105, 106, 97, 212, 221 General structure107, 108, 213, 86 precipipate chemical

polish etchNonstainless maragingsteels

109, 89, 99, 100, 221 General structure

Nonstainless maragingsteels

83b, 86 Grain boundaries,chemicalpolish etch

Material/Preparation Tables 34Material: Stainless steels. Pure iron

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Austenitic stainless steels: 15–24 % chromium, 3–22 % nickel.Ferritic stainless steels: 10.5–27 % chromium.Martensitic stainless steels: 11.5–18 % chromium.Duplex stainless steels: 23–28 % chromium, 2.5–5.0 % nickel, 1.0–2.0 %molybdenum.Precipitation-hardening stainless steels: 12.25–18 % chromium, 7.5–8.5 % nickel�weight %�.


Comments on Material: The stainless steels are corrosion resistant steelsclassified according to the type of microstructure, austenitic, ferritic,austenitic-ferritic, martensitic, duplex, and precipitation-hardening. The austeniticstainless steels have a microstructure of austenite at room temperature because ofa high nickel content, and they are nonmagnetic. The steels are chromium-nickelsteels, and a typical alloy is the steel 18 % chromium, 8 % nickel. The ferriticstainless steels are basically chromium steels without nickel, therefore, the ferriticmicrostructure. Martensitic stainless steels are chromium steels with a highercarbon content than other stainless steels making hardening possible. Duplexstainless steels have a mixed microstructure of ferrite and austenite.Precipitation-hardening stainless steels are alloyed with elements as copper andaluminum to establish the precipitation hardening. They can have either a ferriticor martensitic microstructure.Pure iron �Fe� has a ferritic microstructure.Most stainless steels having an austenitic or ferritic microstructure give difficultiesin metallographic/materialographic preparation because these structures arerelatively soft and ductile. Austenite may work harden during cutting and grinding.It can be difficult to remove all deformation and scratches and obtain a truestructure preserving all inclusions, often brittle carbides and oxides. Themartensitic microstructure is easier to prepare, but in case of brittle carbides,these can easily be damaged. For advice on smearing, inclusions, etc., see Section13.6.The ferrite of pure iron may give problems with deformations �see Material/Preparation Tables 28�.Sectioning: Wet cut-off cutting with a correct Al2O3, bakelite bond cut-off wheelwill be without problems. Cutting with a band saw and shearing may givedeformations and cold work that should be removed at a prolonged planegrinding. For deformation sensitive austenitic steels these methods should beavoided.Mounting: Normally mounting is not needed except in the case of examination ofsurface layers �see Material/Preparation Tables 08 to 15� or in case of obtaining ashape of the specimen suited for automatic preparation. If possible, the specimenshould be sectioned so that it can be placed in a specimen holder withoutmounting.Grinding: Due to deep deformations and possible cold work in the austenite, it isimportant that the fine grinding steps are carefully performed to secure that alldeformations and cold work from the sectioning and plane grinding are removed.Using new SiC grinding paper there is a risk that retained austenite is transformedinto martensite due to mechanical deformation. Also very rough papers and highgrinding forces should be avoided, as deep deformation, introduced in the firstgrinding steps may not be removed by the fine grinding.Polishing: It can be a problem to obtain a perfect ferrite phase as mentionedabove. In the case of only small deformations, prolong the 3 �m step for 1–2 min.Often electrolytic polishing can give very good results �see Section 13.3�.


Etching: For stainless steels, observation of inclusions can normally be donewithout etching. Chemical etching is relatively difficult, often electrolytic etchinggives good results. A much used electrolytic etching is with 10 g oxalic acid,100 mL water, using 6–8 volts for 20–30 s, in a stainless steel beaker, using thebeaker as cathode �see Section 9.5�. For etchants, see below and Material/Preparation Tables 33.Etchants for pure iron, see Material/Preparation Tables 28.


E 1077 C-34

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-34, T-34

El-05Heat influenced zone E 1077 C-34Heat treatment C-34, T-34Image analysis, ratingof inclusion content

E 45, E 562, E 768, E 1077E 1245, E 1268, E 1382, E 2283

C-34

High planenessInclusions in steel E 45, E 768, E 1245 C-34, T-34Microhardness, hardness E 10, E 18, E 92, E 103, E 110,

E 140, E 384, E 448C-34, T-34

Microstructure A 892, E 3, E 45, E 407, E 562,E 768, E 883, E 1077,E 1181, E 1245, E 1268, E 1351,E 1382, E 1558

C-34, T-34,El-05


Structure changes �forging� C-34, T-34,El-05


Sectioning


Mounting




6–10 min


Grinding

C-34: PG: Use SiC paper grit P320 for pure iron.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

T-34: P 1: This step can be changed to an FG 4 step with SiC paper grit P4000,same data as FG 3.C-34 and T-34: The final step can be done with alumina 0.02/0.05 �m.


napless,hard, wov, syn

Cloth,napless,soft, porous, syn


Silica

Grit/GrainSize �m

P220 9 3 0.04/0.05

Lubricant Type Water Alco or wat Alco or watRotationDisk/Holderrpm/rpm

300/150 150/150 150/150 150/150

Comp/Contra Comp orcontra

Comp Comp Contra


25 �5.5� 30 �7� 25 �5.5� 15 �3.3�

TimeMinutes


Traditional Method T-34 �For definitions of parameters and consumable seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper





AbrasiveType


Dia, spror susp

Silica


P220 P320 P500 P1200 6 3 0.04/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



20�4.4�

20�4.4�

20�4.4�

20�4.4�

30 �7� 25 �5.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4 3–5 1–2

EtchantsMaterial Etchants �see Table 3.2� UsesFe+12−20 Cr+4−10 Ni+ �7 % 80, 31c, 89, 99, 100, 91 Generalother elements structure�controlledtransformation,precipitationhardening,stainlessmaragingalloys�

31c Carbides86 Chemical polish-

etch220 Darkness delta

ferriteFe+15−30 Cr+6−40Ni+ �5%other elements �300series�

13b, 89, 87, 88,83a, 80, 94, 95,91, 101, 212, 221,226

General structure

13 a, 102, 31 c,48 c, 213

Carbides andsensitiza-tion

Fe+16-25 Cr+3−6

Ni+5−10

48, 96, 97, 98 Stains sigma phase


Mn �200 series� 103, 104,98

Delineates sigmaphase and weldsof dissimilarmetals

86 Chemicalpolish-etch

219 Grain boundaryetch �notwins�

220 Darkens deltaferrite

Pure iron 74a Grain boundaries75 Substruc-

ture210 Colors ferrite

grains

Material/Preparation Tables 35Material: Super alloys, iron based

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Super alloys �Fe based�: 26 to 55 % nickel, 13 to 23 % chromium, 1 to 2.5 %titanium, 1 to 9 % molybdenum �weight %�.Comments on Material: The Fe based super alloys are closely related to the highalloy steels described in Material/Preparation Tables 33.Sectioning: See Material/Preparation Tables 33.Mounting: See Material/Preparation Tables 33.Grinding: See Material/Preparation Tables 33.Polishing: See Material/Preparation Tables 33.Etching: See below and Material/Preparation Tables 33 and 34.

Purpose ASTM Standard �See Section 12.4� MethodCase or coatingthickness/hardness,surface layersPerfect edge retention

C-35

Grain size.grain boundaries

E 112, E 930, E 1382 C-35, T-35,E1-06

Heat influences zone C-35Heat treatment C-35, T-35Image analysis,rating of inclusioncontentHigh planeness

E 45, E 562, E 768, E 1245, E 1382, E 2283 C-35


Inclusions in steel E 45, E 768, E 1245 C-35, T-35Microhardness,hardness

E 10, E 18, E 92, E 103, E 110,E 140, E 384

C-35, T-35

E 448Microstructure A 892, E 3, E 45, E 407, E 562,

E 768, E 883E 1245, E 1351, E 1382, E 1558

C-35, T-35,E1-06

Phase identification C-35, T-35,E1-06


Cut-off Wheel Al2O3, bakelite bond

Mounting




6–10 min

Grinding

C-35: PG: SiC paper grit P220 can be used.C-35: FG 1: Very often this step can be omitted. In that case the step FG 2 �RCD,soft� is prolonged to seven minutes.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100—150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-35: P 2: Often this step can be omitted.C-35: P 3: Alumina �0.02/0.05� can be used.

Contemporary Method C-35 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P3PolishingDisk/Cloth Dia, disk,

fixed, resRCD,hard

RCD,soft

Cloth,napless,

hard,wov,silk

Cloth, shortnap,

soft, syn

Cloth,napless,

soft,porous,

synAbrasive Type Diamond Dia, spr

or suspDia, spror susp

Dia, spror susp

Dia, spror susp

Silica


Grit/Grain size�m

220 9 9 6 1 0.04/0.05

LubricantType

Water Alco orwat

Alco orwat

Alco orwat

Alco orwat

Rotation Disk/Holder

300/150 150/150 150/150 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 30 �7� 25 �5.7� 15 �3.4�

TimeMinutes

Untilplane

3 3 4 3 1–2

Traditional Method T-35 �For definitions of parameters and consumable seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiC

paperSiC

paperSiC

paperCloth,

napless,hard,

wov, silk

Cloth,napless,

hard,wov, syn


AbrasiveType

SiC SiC SiC SiC Dia,spr

or susp

Dia,spr

or susp

Dia,spr

or suspGrit or GrainSize �m

P220 P320 P500 P1000 6 3 1

LubricantType


Alco orwat

Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp Comp


30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 20 �4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–5 4 1–2

EtchantsMaterial Etchants �see Table 12.2� UsesSuper alloys�Fe based�

86, 87, 94, 221, 226 General etch


111 General structure111 � depletion

Material/Preparation Tables 36Material: High strength low-alloy steels

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.High strength low-alloy steels: Low and medium carbon steels with small amountsof alloying elements, vanadium, niobium, titanium.Comments on Material: High strength low-alloy �HSLA� steels are a group of low-and medium-carbon steels with small amounts of alloying elements to improve theyield strength. The steels are classified by SAE according to yield strength and byASTM according to composition, mechanical property requirements, andapplication. Examples of the ASTM specifications are: A 242, A 572, and A 656 �seeSection 12.4.2�.The microstructure of HSLA steels is a mixture of ferrite, pearlite, bainite, andmartensite, and the problems regarding preparation are the same as with medium-and low-carbon steels �see Material/Preparation Methods 28 and 29�. In somecases, water sensitive inclusions should be examined; for this reason the polishingsteps in Methods C-36 and T-36 are stated with water-free lubricants.Sectioning: At wet abrasive cutting with an Al2O3 cut-off wheel, overheatingshould be avoided because martensite can be developed. Cutting pressure shouldbe moderate and cooling should be efficient on both sides of the cut-off wheel. Ifshearing or band sawing is used, the plane grinding should be prolonged toremove possible deformation or a rougher grinding paper should be used beforegrit P220.Mounting: For routine examination bakelite as powder or tablets is sufficient. Inthe case of examination of coatings, other mounting materials should be used �seeMaterial/Preparation Tables 08–15�. For mounting for electrolytic polishing, seeSection 3.11.6.Grinding: Grinding normally will give no problems with these materials. Careshould be taken that the deformations from plane grinding are effectively removedbefore the polishing. If not, the deformed ferrite can be seen after etching and theprocess must be repeated from FG 1.Polishing: The problem can be to obtain a perfect ferrite phase as mentionedabove. In the case of only small deformations, prolong the 3 �m step for 1–2 min.Electrolytic polishing can be recommended for certain alloys.Etching: A high number of etchants are available for steels. In most cases arelative small selection will cover the need in a given laboratory �see Material/Preparation Tables 28 and 33�.

Purpose ASTM Standard �See Section 12.4� MethodCase or coating thickness/hardness,surface layers Perfect edge retention

B 487, E 1077 C-36


Grain size, grain boundaries E 112, E 930, E 1181,E 1382

E-36,T-36El-04

Heat influenced zone E 1077 C-36Heat treatment C-36,

T-36,El-04

Image analysis, rating of inclusioncontentHigh planeness

E 45, E 562, E 768,E 1077, E 1245,E 1268, E 1382, E 2283

C-36

Inclusion in steel E 45, E 768, E 1245 C-36,T-36

Microhardness, hardness E 10, E 18, E 92, E 103, E 110,E 110, E 140, E 384, E 448

C-36,T-36

Microstructure A 892, E 3, E 45, E 407, E 562,E 768, E 883, E 1077, E 1122,E 1181, E 1245, E 1268, E 1351,E 1382, E 1558

C-36,T-36,El-04

Phase identification C-36,T-36,El-04

Structure changes �forging� C-36,T-36,El-04


Sectioning

Cut-Off-Wheel Al2O3, bakelite bond

Mounting




6–10 min

Grinding

C-36: PG: SiC paper grit P220 can be used.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

C-36 and T-36: Steps P 1 and P 2 are stated with water-free diamondsuspensions. These can be changed to normal water-based suspensions.C-36: P 2: This step can be followed by a final step with silica like step P 3 inMethod C-35.


fixed, resRCD, soft Cloth, napless,

hard, wov, synCloth, med. nap,

soft, synAbrasive Type Diamond Dia, spr or susp Dia, spr or

susp, water-freeDia, spr or

susp, water-freeGrit or GrainSize �m

P220 9 3 1

Lubricant Type Water Alco or wat Alco or oil,water-free

Alco or oil,water-free

RotationDisk/Holder

300/150 150/150 150/150 150/150



Force perpecimen N �lb�

25 �5.5� 30 �6.6� 25 �5.7� 15 �3.4�

TimeMinutes


Traditional Method T-36 �For definitions parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper


Cloth,naplesss,hard,wov,syn


AbrasiveType


Dia,sprorsusp

Alumina


P220 P320 P500 P1200 6 3 0.02/0.05


LubricantType

Water Water Water Water Alco oroil,water-free

Alco oroil,water-free

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



35 �8� 35 �8� 35 �8� 25�5.7�

25 �5.7� 25 �5.7� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 3 3 1–2

EtchantsSee Material/Preparation Tables 28 and 33.

Material/Preparation Tables 37Material: Carbonitrided steels. Carburized steels. Nitrided steels.Other surface treated steels

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Comments on Material: Case hardening is a term that covers the process ofchanging the surface layer of steel by absorption of carbon or nitrogen, or both.The process can be done in different ways as carbonitriding, carburizing,cyaniding, nitriding, and nitrocarburizing. With or without further heat treatmenta hard surface layer is created.Mostly low carbon steels are used for carburization, often a case with a carboncontent of 0.7–1 %, and a hardness of approximately 60 HRC �HV 700�. The casedepth varies from 0.3 to 3 mm depending on processing time and temperature.For nitriding low carbon steels and steels alloyed with Al, Cr, and V are used. Thehardness of the diffusion layer may be up to 70 HRC �HV 1000� and the thickness0.01–0.5 mm depending on process time and temperature.The metallographic/materialographic examination normally covers layer thickness,diffusion zone, and defects in the layer. For this reason it is very important toobtain the highest degree of edge retention �see also the Material/PreparationTables 08–15�.


Sectioning: Cutting, often of a test piece treated along with the work piece, shouldbe wet abrasive cutting with an Al2O3, bakelite bond cut-off wheel. It is importantthat excessive heat and deformation is avoided. When cutting nitrided layers thatare very hard, a relatively soft wheel is used and cooling should be very effective.If shearing or band sawing is used, the plane-grinding step should be prolonged toremove possible deep deformation. It is important that the cutting takes placeperpendicular to the surface to be prepared. If the plane of the cross section is notperpendicular to the plane of the surface layer, the measured thickness will begreater than the true thickness. For example, an inclination of 10° will contributea 1.5 % error.Mounting: It is very important that edge rounding and gaps between sample andmounting material are avoided. Therefore, a mounting material without shrinkageshould be used, preferably epoxy. For very hard coatings hot mounting with epoxywith a filler should be preferred. Also, a phenolic resin with carbon fibers can beof advantage. For hot mounting a special application can be made to secure theedge: Tightly wrap up the specimen in Al foil �household type�. This gives a goodseparation between mounting material and surface layer. Also, a copper foil can beused on nitrided and carburized layers giving an excellent edge definition andcontrast. Choose a mounting material with hardness as close as possible to thehardness of the coating. As a less ideal alternative, cold mounting with epoxy oran acrylic material with filler can be used.Grinding: The preparation process should secure the highest possible edgeretention. This means that all grinding, either on SiC grinding paper, diamondpads, or rigid composite disks �RCDs�, should be as short as possible.In Method T-37 the grinding is suggested with diamond pads, considered for veryhard surface layers. In case of softer layers these pads can be changed to SiCgrinding paper, as stated in Method T-32 �see below�.It has been found that the use of fixed diamonds for plane grinding of certainnitrided and carburized layers may introduce fine cracks in the hard layer,therefore, SiC paper should be used �see below�.Polishing: Also the polishing steps should be kept as short as possible.Etching: See Material/Preparation Tables 28, 33, and 34.


C-37, T-37

Prefect edge retentionGrain size, grain boundaries E 112, E 1382 C-37, T-37Heat influenced zone C-37, T-37Heat treatment C-37, T-37Image analysis, ratingof inclusion contentHigh planeness

E 45, E 562, E 768, E 1077E 1245, E 1268,E 1382, E 2283

C-37, T-37

Inclusions in steel E 45, E 768, E 1245 C-37, T-37Microhardness, hardness E 10, E 18, E 92, E 103,

E 140, E 684, E 448C-37, T-37


Microstructure A 892, E 3, E 45, E 407, E 562, E768,E 883, E 1077, E 1245, E 1268,E 1351, E 1382, E 1558



Sectioning


Mounting


Resin Expoxywith Filler

Cold Mounting Resin Epoxywith filler

TimeMinutes

9 TimeMinutes/Hours

6–8 h

Grinding

C-37 and T-37: PG: For certain nitrocarburized/nitrided layers, disks/pads withfixed diamonds should be avoided �see above�. SiC paper grit P220 should beused. Also FG 1 in Method T-37 shall be changed to SiC paper grit P320/P500�see Method T-32�.C-37: Very often FG 1 can be changed to RCD, soft and FG 2 can be omitted.T-37: In case of relatively soft surface layers, the diamond pads in PG and FG 1can be changed to SiC grinding paper �see Method T-32�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

T-37: To improve edge retention, the step P 2 can be changed to P 2 fromMethod C-37.

Contemporary Method C-37 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth Dia, disk

fixed, resRCD, hard RCD, soft Cloth,


Cloth, mednap, soft, syn


AbrasiveType


Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp


220 9 3 3 1

LubricantType

Water Alco or wat Alco or wat Alco or wat Alco or wat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp Comp Comp Comp


35 �8� 25 �5.5� 25 �5.5� 40 �9� 25 �5.5�

TimeMinutes

Untilplane

5 4–5 4–5 1–2

Traditional Method T-37 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth Dia, pad

metDia, pad met Cloth nap-

less, v. hardnonwov orwov, syn


Cloth,napless,soft,porous, syn


Dia, spr orsusp

Silica


125 40 9 3 0.04/0.05

Lubricant Type Water Water Alco or wat Alco or wat Alco or watRotationDisk/Holder

300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp Comp Contra


35 �8� 35 �8� 40 �9� 40 �9� 15 �3.4�

TimeMinutes

Until plane 2 4–5 4–6 1

EtchantsSee Material/Preparation Tables 28, 33, and 34.


Material/Preparation Tables 38Material: High-speed steels. Low-alloyed tool steels. Other toolsteels

Material Properties: Alpha iron �ferrite�: Body-centered cubic, gamma iron�austenite�: Face-centered cubic, 7.85 g/cm3, 1528°C �2782°F�, HV 70 �ferrite�.Comments on Material: The tool steels cover a wide range from the highlyalloyed high-speed steels to low-alloy steels with small amounts of a few alloyingelements. Most tool steels contain molybdenum or tungsten, or both. Often otherelements like vanadium, cobalt, nickel, and chrome are added. The tool steels areclassified by the American Iron and Steel Institute �AISI� using a letter to representeach class of steel. Tool steels are metallographically/materialographicallyexamined for inclusion content, decarburization, degree of spheroidization, grainsize, hardness, etc., and they are often difficult to prepare because of the hardnessand the brittle carbides. For advice on artifacts developed during the preparation,see Section 13.6.Sectioning: In the case of nontempered tool steels, it is important that thesectioning takes place without excessive heat because this will introduce localizedtempering effects. Cutting should take place as wet, abrasive cutting with anefficient cooling, preferably using a thin cut-off wheel, or a relatively soft wheel, orboth. The feed speed should be low with a low force in the cut. For high-hardness,high-alloy steels, precision cutting with a thin CBN cut-off wheel may be ofadvantage, producing a cut surface with very little damage. Steels with a hardnessbelow 35 HRC may be cut using a band saw, but in this case, because of theconsiderable deformation, the plane grinding should start with SiC grinding paperrougher than grit 220. In case of as-quenched high-alloy steels, the specimen maybe sectioned by fracture.Mounting: For routine examination bakelite as powder or tablets is sufficient ifheat degredation is not anticipated. In the case of examination of coatings, othermounting materials should be used �see Material/Preparation Table 08–15�. Formounting for electrolytic polishing, see Section 3.11.6.Grinding: The often very hard material will wear out the SiC grinding papers in avery short time, and often several sheets of each grain size should be used. In caseof pull-outs of carbides at high-alloy steels, Method C-38 should be preferred.Polishing: For routine examination, the number of steps may be reduced �seebelow�.Etching: A number of etchants are stated below.


B 748, C 664 C-38

Perfect edge retentionGrain size, grain boundaries E 112, E 1382 C-38, T-38Heat influenced zone C-38, T-38Heat treatment C-38, T-38


Image analysis,rating of inclusioncontent

E 45, E 562, E 768, E 1077E 1245, E 1268, E 1382, E 2283

C-38, T-38

High planenessInclusions in steel E 45, E 768, E 1245 C-38Microhardness,hardness

E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-38, T-38

Microstructure A 892, E 3, E 45, E 407, E 562, E768,E 883, E 1077, E 1245, E 1268, E1351, E 1382, E 1558



Sectioning


Mounting




6–10 min

Grinding

C-38: For certain tool steels, the step P 1 can be changed to an RCD, soft.T-38: For routine examination the step FG 3 may be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-38: For certain tool steels, the step P 2 can be changed to P 3 from MethodT-38 or P 3 �Method T-38� can be added.T-38: In case of routine examinations, the step P 2 can be changed to step P 1from Method C-38, as the last step.

Contemporary Method C-38 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG P 1 P 2Polishing



RCD, hard Cloth,napless,hard, wov,syn

Cloth, med.nap,soft, syn


Dia, spr orsusp

Dia, spr orsusp

Grit or Grain Size�m

P220 9 3 1

Lubricant Type Water Alco or wat Alco or wat Alco or watRotation Disk/Holder

300/150 150/150 150/150 150/150




35 �8� 35 �8� 35 �8� 40 �9�

TimeMinutes



paperSiCpaper

SiCpaper

SiCpaper



Cloth,naplesssoftporous,syn


Dia, spror susp

Alumina


P220 P320 P550 P1200 6 3 0.02/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp Comp


40 �9� 40 �9� 40 �9� 40 �9� 40 �9� 30 �7� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 5 4 1–2


EtchantsMaterial Etchants �see Table 12.2� UsesTool steels 74a, 80, 14 General structure

110 Grain boundaries in tempered tool steel210, 211 Colors ferrite, lower alloy grades214 Colors cementite224, 225 Carbides attacked and colored

Material/Preparation Tables 39Material: Cement clinker. Concrete

Material Properties: Portland cement clinker, mineralogical composition: Alite�C3S� 35–75 %, Belite �C2S� 0–40 %, Aluminate �C3A� 1–10 %, Ferrite �C4AF� 2–15%, Periclase �MgO� 0–3 %, Free lime �CaO� 0–5 %, Arcanite �K2SO4� 0–3 %,Ca-Langbeinite �2CaSO4� 0–3 %.Comments on Material: Portland cement clinker is a raw material for cementproduction consisting of several mineral phases with different physical properties,as mentioned above.Hardened concrete consists of cement paste mixed with aggregates like sand andstone.Cement clinker and concrete can be examined in reflected light and in transmittedlight. The preparation of cross sections for reflected light is stated below. Thinsections for transmitted light is described in Section 7.13.Both cement clinker and concrete often are very sensitive to water used during thepreparation and, consequently, this should be avoided, especially during the laststeps of the preparation.Sectioning: The material being brittle should be treated carefully to avoiddamage. Often it can be of advantage to impregnate the specimen before cutting�see below�. Cutting is preferably done with a precision cut-off machine with athin cut-off wheel, diamond, metal bond or SiC, bakelite bond and with awater-free coolant.Mounting: Very often the specimen is porous so that impregnation with epoxy isneeded to stabilize the material. Also, often the examination, especially atconcrete, is done to determine pores �air voids� and microcracks, and therefore itcan be recommended to add fluorescent dye to the epoxy �see Section 3.10�.Grinding: The traditional method, T-39, stated below is based on lapping on castiron disks, as known from preparation of mineralogical materials. Often thelapping can be changed to the use of SiC grinding paper, as indicated underPreparation Process 39 below.Polishing: The two methods stated below have a 3 �m step as the last polishingstep. If needed, this step can be followed by finer steps, as indicated underPreparation Process 39 below.Etching: Normally these materials are not etched.


Purpose ASTM Standard �See Section 12.4� MethodCase or coatingthickness/hardness,surface layerPerfect edge retention

Cement clinkers and concrete are coveredby a number of ASTM standards. These arenot stated here, as it is considered outsidethe scope of this book.

C-39


C-39, T-39

Image analysis, ratingof inclusion content

C-39


C-39, T-39

Microstructure C-39, T-39Phase identification C-39, T-39Porosity C-39


Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond, 0.5 mm�0.019 in� thickness

Mounting


TimeMinutes/Hours

8–12 h

Grinding

C-39: PG, if material is very water sensitive use alcohol or glycerol instead ofwater.C-39: PG and FG: For clinker, lower force on specimens to 15 N.C-39: In some cases �clinker� FG 1 can be omitted.T-39: In some cases the lapping on cast iron disks can be changed to SiC paper,P220, P320, P500 and P1000 using glycerol as cooling fluid.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

C-39: P 1: For clinker, lower force per specimen to 10 N.C-39 and T-39: If needed, P 1 can be followed with one or two steps, seeP 2 in Method C-38 with water-free lubricant, followed by P 2 in Method T-37.

Contemporary Method C-39 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P1PolishingDisk/Cloth Dia, disk, fixed,

resDia, disk, fixed,res

RCD, soft Cloth, napless,hard, wov, syn

Abrasive Type Diamond Diamond Dia, spr or susp,water-free

Dia, spr orsusp,water-free


P220 P1200 9 3

Lubricant Type Water/glycerol

Water/glycerol Alco,water-free

Alco, water-free

RotationDisk/Holder

300/150 300/150 300/150 150/150

rpm/rpmComp/Contra Comp or contra Comp Comp CompForce perSpecimen N /lb

35 �8� 35 �8� 35 �8� 20 �4.5�

TimeMinutes

Until plane 5 5 5

Traditional Method T-39 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1PolishingDisk/Cloth Cast iron

diskCast irondisk

Cast irondisk

Cast irondisk


Abrasive Type SiC powder SiC powder SiC powder SiC powder Dia, spr orsusp, water-free


P220 P400 P800 P1200 3

Lubricant Type Glycerol Glycerol Glycerol Glyecerol Alco or oil,water-free

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150

rpm/rpm


Comp/Contra Contra Contra Contra Contra CompForce perSpecimen N�lb�

5 �1.1� 5 �1.1� 5 �1.1� 5 �1.1� 20 �4.5�

TimeMinutes

2–3 2–3 2–3 2–3 5

Material/Preparation Tables 40Material: Minerals. Ores

Comments on Material: Minerals, ores, and rocks cover a wide field of materialswith a high variety of phases. Most often minerals are brittle and hard, but oftenwith a very different hardness of the different phases. This makes preparation ofminerals relatively difficult, both because of the risk of deformation, thebrittleness, pores, and cracks, creating the risk of pull-outs, and the tendency forrelief between the phases.Minerals are prepared as polished sections for reflected light examination and asthin sections for transmitted light examination. Below the preparation of polishedsections is described; thin sections are described in detail in Section 7.13 �see alsoMaterial/Preparation Tables 39�.Sectioning: It is important that the often very hard and brittle material is notdamaged too much during the sectioning. Often the cutting of an intermediatepiece is cut with a large machine specially built for cutting of minerals, using adiamond cut-off wheel, metal bond. For the actual specimen, wet abrasive cuttingis often done with a thin diamond, metal bond cut-off wheel on a precision cut-offmachine to ensure a good surface. In case of very brittle materials, with pores andcracks, an impregnation before the cutting is recommended �see below�. For softerminerals an SiC bakelite bond cut-off wheel can be used.Mounting: Often the specimen, being brittle and with pores and cracks, should beimpregnated under vacuum with an epoxy �see Section 3.10�. To easily distinguishpores and cracks, the epoxy resin can be added as a dye �see Section 3.10�. Also,an impregnetion with a dye makes it possible to distinguish between original poresand “pores,” pull-outs, caused by the preparation process �see Section 13.6�.Grinding: The “traditional” grinding of minerals is made as a lapping with loosegrains �see Section 6.7.7�. This method is stated in Method T-39, however, below,the two methods stated are with fixed grains considered the most useful forpolished sections. Some phases in minerals are very sensitive to deformation likecertain soft and ductile metals. For this reason the fine grinding step with 9 �mdiamond in Method C-40 and the steps with 9 �m and 6 �m in Method T-40 arevery important to create a deformation free surface, and these steps should beprolonged if the deformation is not reduced to a satisfactory level that can beremoved by the 3 �m step.Polishing: In the case of phases with very different hardness, the polishing timeshould be kept as short as possible and the force as low as possible to reducerelief.


Etching: Etching of minerals can be done for identification of the single phases ina mineral based on the reaction of a specimen material to a standard set ofreagents. Another approach is to use the reagents for revealing the microstructuraldetails, as it is known from etching of metals. Both approaches are relativelycomplicated and fall outside the scope of this book.

Purpose ASTM Standard �See Section 12.4� MethodCase or coatingthickness/hardness,surface layers Perfect edgeretention

ASTM standards coveringminerals and ores arenot stated here, as it isconsidered outside thescope of this book.

C-40

Grain size, grain boundaries C-40, T-40Image analysis, rating of inclusioncontent

C-40

High planenessMicrohardness, hardness C-40, T-40Microstructure C-40, T-40Phase identification C-40, T-40Porosity C-40


Sectioning

Cut-Off Wheel Diamond, metal bond or SiC, bakelite bond, 0.05 mm�0.019 in� thickness

Mounting



TimeMinutes/Hours

8–12 h

Grinding

C-40: For soft/brittle materials, SiC paper grit P320 can be used.C-40: FG: For hard materials a step like FG 1 in Method C-39 can be added.Attention: In C-methods, when using RCD: the disk turns concave during use.When the difference is more than 100–50 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-40: P 1 and P 2: For hard materials a step like P 2 in Method C-38 can be usedbetween the steps P 1 and P 2.


T-40: P 1 can be followed by a P 2 step like in Method C-40

Contemporary Method C-40 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2PolishingDisk/Cloth Dia, disk



Clothnapless,soft,porous, syn

Abrasive Type Diamond Dia, spr, or susp Dia, spr orsusp

Silica


P220 9 3 0.04/0.05

Lubricant Type Water Alco or wat Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150




20 �4.5� 20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes


Traditional Method T-40 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ FG 3 P 1Polishing PG FG 1 FG 2Disk/Cloth Dia, pad

bakCloth,napless,v. hard,nonwov/wov

Cloth, napless,v. hardnonwov/wov

Cloth,napless,v. hardnonwov/wov



Dia, spror susp

Dia, spror susp

Dia, spror susp


30 9 6 3 1

Lubricant Type Water Alcoor wat

Alcoor wat

Alcoor wat

Alcoor wat

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp CompForce perSpecimen N �lb�

25 �5.7� 30 �7� 30–40 �7–9� 30–40 �7–9� 10–30 �2.3–7�


TimeMinutes

Untilplane

5 5 5 2

Material/Preparation Tables 41Material: Pure aluminum. Cast aluminum alloys

Material Properties: Aluminum: Face-centered cubic, 2.699 g/cm3, 660.2°C�1220°F�, HV 150.Cast alloy: Aluminum-silicon: 12.5 % Si �eutectic composition�. Other cast alloys:Aluminum-silicon-magnesium, aluminum-silicon copper, aluminumsilicon-copper-magnesium, aluminum-magnesium, aluminum-zinc-magnesium,aluminum-copper-titanium-magnesium �weight %�.Comments on Material: Commercially pure aluminum has an aluminum contenthigher than 99 % for wrought alloys and 99.5 % for cast alloys. Cast alloys can bealloyed with a number of elements as mentioned above. Aluminum and its alloysare classified through a number of systems, the most important is the systemestablished by the Aluminum Association �see below�. Another important systemuses the chemical symbols of the most important alloying elements combined witha number stating the content in weight %. AlMg3MnCr describes an alloy with 3 %magnesium and amounts of manganese and chromium, normally �but not always�below 1 % each. Less important alloying elements are not mentioned.Aluminum Association has developed a system for wrought and cast alloysconsisting of four numbers followed by a — with a letter and a number. Forwrought alloys the four numbers are like: nnnn, at cast alloys the numbers have adot: nnn.n. For wrought alloys the first number expresses:1nnn Commercially pure aluminum ��99 % �2nnn Copper as most important alloying element3nnn Manganese4nnn Silicon5nnn Magnesium6nnn Magnesium and silicon.7nnn Zinc8nnn Other alloying elements9nnn Is not usedFor cast alloys the first number expresses:1nn.n Commercially pure aluminum ��99.5% �2nn.n Copper3nn.n Silicon with copper or magnesium4nn.n Silicon5nn.n Magnesium6nn.n Is not used7nn.n Zinc8nn.n Tin9nn.n Other alloying elements


The letter following the — expresses heat treatment and the number will expressfurther specification of the alloy.ASTM has specified a high number of aluminum alloys and a number of testmethods for aluminum.Pure aluminum is a very soft and ductile metal that can be difficult to preparemechanically. It is important that deformations developed during sectioning andgrinding are removed through the polishing steps. Also, there is a risk ofembedded grains �see Section 13.6.4�. Electrolytic polishing can be done with aperchloric acid electrolyte and often gives very good results. Cast aluminum alloysand wrought alloys are easier to polish mechanically and they are normally notsuited for electropolishing.Sectioning: Wet abrasive cutting with an SiC bakelite bond cut-off wheel shouldbe recommended. To avoid solid state transformation in certain materials, anefficient cooling is important. If shearing or band sawing are used, it is importantthat the induced heavy deformation is removed during the plane grinding step.Mounting: Both hot and cold mounting materials can be used. In the case ofheat-sensitive alloys cold mounting is recommended. For examination of pores�castings�, vacuum impregnation may be of advantage �see Section 3.10�.Preferably the mounting material should be a little harder than the hardestconstituent in the specimen material. In the case of examination of thin layers itcan be recommended that the specimen is tightly wrapped in thin metal foil �e.g.,household aluminum foil or nickel foil� and then hot mounted. In this way thesurface layer can be easily distinguished from the mounting material.Grinding: It is important that the deformation from sectioning and the roughgrinding steps are removed. If the grinding steps give too high deformation, theforce per specimen should be reduced.Polishing: The rough polishing steps with 6 and 3 �m are important. If strongdeformation can be seen after 3 �m, the process should be repeated from FG 1.With only small deformation the time can be prolonged or the force increased, orboth. If relief develops between matrix and a second phase, Method C-41 shouldbe used.Electrolytic polishing can be used for pure aluminum and for not tooheterogenous alloys.Etching: It can be difficult to etch the surface of aluminum due to a thin oxidefilm. Also, it is difficult to etch the matrix and several intermetallic phases andprecipitates with the same etchant, making the use of several ecthants necessary. Itis, however, possible to avoid this for a number of alloys by using a color etchantbased on potassium permanganate �Weck, see Ref. 47, Part I�: 100 mL distilledwater +4 g potassium permanganate, after dissolving: +1 g sodium hydroxide.Immersion in 15 s at room temperature with a freshly prepared solution. Thedrawback with this etchant is that the specimen surface must be absolutely freefrom deformation. This can be obtained by pre-etching the surface with 100 mLdistilled water +2 g sodium hydroxide. Immersion in 30 to 60 s at roomtemperature. For other etchants, see below, and Material/Preparation Tables 42/43.



B 487 C-41


E 112, E 930, E 1181, E 1382 C-41, T-41El-10 �pureAl�

Heat treatment C-41, T-41Image analysis,rating of inclusioncontent

E 562, E 1245, E 1382 C-41, T-41

High planenessMicrohardness, hardness E 10, E 18, E 92, E 103,

E 110, E 140, E 384,E 448

C-41, T-41

Microstructure E 3, E 407, E 562, E 883,E 1181, E 1245, E1351, E 1382, E 1558

C-41,T-41,El-10 �pureAl�



Sectioning

Cut-Off Wheel SiC, bakelite bond

Mounting




6–10 min

Grinding

C-41: PG: If possible use SiC paper grit P320.T-41: Very often FG 4 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-41: P 2: This step can often be omitted.Pure Al: Electrolytic polishing will give good results.


Contemporary Method C-41 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth SiC paper RCD, soft Cloth,

napless,med hard,wov, wool

Cloth, mednap, soft, syn



Dia, spr orsusp

Dia, spr orsusp

Silica


P220 9 3 1 0.04/0.05

Lubricant Type Water Water Wat-oil Wat-oilRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp ContraForce perSpecimen N �lb�

25 �5.7� 30 �7� 25 �5.7� 20 �4.5� 15 �3.3�

TimeMinutes

Until plane 5 5 1–2 1–2

Traditional Method T-41 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper

SiCpaper


Cloth,nap-less,medhard,wov,wool


AbrasiveType


Dia,sprorsusp

Silica


P220 P320 P500 P1200 P2400 6 3 0.04/0.05

LubricantType


Wat-oil


300/150 300/150 300/150 300/150 150/150 150/150 150/150 150/150


Comp/Contra

Comporcontra

Comporcontra

Comporcontra

Comporcontra



25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4 3–4 1–2

Etchants

Material Etchants see �Table 12.2� UsesPure aluminum 1a, 2, 3 General structureCast aluminum �2000 series� 3, 2, 1a General structure

8a, 6, 7 Phase identificationsCast aluminum �4000 series� 3, 1a General structure

Material/Preparation Tables 42Material: Other aluminum alloys

Material Properties: Aluminum: Face-centered cubic, 2.699 g/cm3, 660.2 °C�500°F�, HV 150.Comments on Material: See Material/Preparation Tables 41.Sectioning: See Material/Preparation Tables 41.Mounting: See Material/Preparation Tables 41.Grinding: See Material/Preparation Tables 41.Polishing: See Material/Preparation Tables 41.Etching: See Material/Preparation Tables 41/43 and below.


B 487 C-42

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-42, T-42

El-10Heat treatment C-42, T-42Image analysis, rating of inclusioncontent

E 562, E 1245, E 1382 C-42, T-42


E 110, E 140, E 384, E 448C-42, T-42

Microstructure E 3, E 407, E 562, E 883,E 1181, E 1245, E 1351,E 1382, E 1558

C-42, T-42,El-10




Sectioning


Mounting




6–10 min

Grinding

C-42: PG: If possible use SiC paper grit P320.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-42: P 1: For harder alloys this step can be changed to a napless, hard, wov, silkcloth.C-42: For softer alloys the step P 1 from Method T-42 can be added, between FG1 and P 1.T-42: P 3 can be followed by a step with silica, see C-42. Also at harder alloys thestep P 3 can be omitted.Often electrolytic polishing can be recommended for the examination of themicrostructure.


napless, medhard, wov,wool

Cloth, napless,soft, porous, syn


Silica


P220 9 3 0.04/0.05

Lubricant Type Water Water Wat-oilRotationDisk/Holder

300/150 150/150 150/150 150/150

rpm/rpm



Comp Comp Contra


25 �5.7� 30 �7� 25 �5.7� 15 �3.3�

TimeMinutes

Untilplane

5 3 1–2


paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

Dia, spror susp


P220 P320 P500 P1200 6 3 1

LubricantType


Alco orwat

Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Comp Comp


25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4 4 1

EtchantsMaterial Etchants �see Table 12.2� UsesAl alloys 3, 1a, 2 General structure�7000 series� 4, 5 Grain structure under polarized light

3b, 6 Phase identification


Material/Preparation Tables 43Material: Wrought aluminum alloys

Material Properties: Aluminum: Face-centered cubic, 2.699 g/cm3, 660.2°C�500°F�, HV 150. Wrought aluminum alloys: Manganese. Magnesium.Magnesium-manganese-chrome. Magnesium-silicon. Copper. Copper-manganeseand copper-silicon-manganese. Zinc-magnesium. Zinc-magnesium-copper.Lithium-copper-magnesium.Comments on Material: See Material/Preparation Tables 41.Sectioning: See Material/Preparation Tables 41.Mounting: See Material/Preparation Tables 41.Grinding: See Material/Preparation Tables 41.Polishing: Alloys containing magnesium may be sensitive to water and should bepolished with water-free lubricants �see also Material/Preparation Tables 41�.Etching: See Material/Preparation Tables 41/42 and below.


B 487 C-43


El-10Heat treatment C-43, T-43Image analysis, ratingof inclusion content

E 562, E 1245, E 1382 C-43, T-43


E 140, E 384, E 448C-43, T-43

Microstructure E 3, E 407, E 562, E 883, E 1181,E 1245, E 1351, E 1382, E 1558

C-43, T-43,El-10



Sectioning


Mounting




6–10 min


Grinding

C-43: PG: If possible use SiC paper grit P320.C-43: FG 2: Very often this step can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Contemporary Method C-43 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth SiC paper RCD, soft RCD, soft Cloth,


Cloth, nap-less, soft,porous,syn


Dia, spr orsusp

Dia, spr orsusp

Silica

Grit or Grainize �m

P220 9 3 3 0.04/0.05

Lubricant Type Water Alco or wat Alco or wat Wat-oilRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp ContraForce perSpecimenN �lb�

20 �4.4� 30 �6.6� 25 �5.7� 15 �3.4� 15 �3.4�

TimeMinutes

Until plane 5–7 5 5 1


paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



AbrasiveType


Alumina


P220 P320 P500 P1200 P2400 3 0.02/0.05


LubricantType

Water Water Water Water Water Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150


orcontra

Comporcontra

Comporcontra

Comporcontra

Comp Comp Contra


25�5.7�

25�5.7�

25�5.7�

25�5.7�

25�5.7�

20 �4.5� 15 �3, 4�

TimeMinutes

Unitplane

0.5–1 0.5–1 0.5–1 0.05–1 3–4 1–2

EtchantsMaterial Etchants �see Table 12.2� Uses1000 series 1a, 2, 3, General structure

4, 5 Grain structure underpolarized light

6, 7 Phase identifications3000 series 3, 1a General structure


8a, 6, 7 Phase identifications5000 series 3, 1a, 2, 6, 8a General structure


6000 series 3, 1a, 2, 6, 8a, 222 General structure4, 5 Grain structure under

polarized light1a, 2, 7, 6, 8a Phase identifications

Material/Preparation Tables 44Material: Pure antimony. Sb alloys, and Sb bearing alloys. Purebismuth. Bi alloys

Material Properties: Antimony: Hexagonal, 6.691 g/cm3, 630.5°C �1167°F�.Bismuth: Hexagonal, 9.78 g/cm3, 271.3°C �520°F�, HB 70.Comments on Material: Both antimony and bismuth are seldomly used as puremetals, but mostly used as alloying elements. Antimony is used for bearing alloys.Pure antimony is relatively hard and pure bismuth is soft. Both metals are verybrittle.Sectioning: Care should be taken that the brittle materials are not damaged toomuch during the cutting. At wet abrasive cutting, a thin SiC cut-off wheel bakelitebond should be used. To avoid cracking during cutting it may be useful to mountthe specimen in epoxy before cutting.


Mounting: Both hot and cold mounting can be used. Be careful that the highpressure during hot mounting doesn’t damage the brittle specimen.Grinding: During grinding with SiC grinding paper, the paper may be loaded withthe material because this is not taken away by the water flow. A loaded papershould not be used as it will give stronger damage to the specimen. The water flowshould be strong and the aggressiveness of the paper can be dampened by addinga small amount of hard wax to the paper surface before use, or the new paper canbe “run-in” with a hard material in a few seconds.Polishing: It is important that all deformations from the grinding are removedafter the rough polishing step P 1. For polishing of pure antimony and purebismuth, a solution of 3 % nitric acid in glycerol can be added to the silica usedfor the last step. At polishing of Sb alloys containing lead, the last polishing stepcan be with a 0.3 alumina suspension with added ammonium tartrate, 1 g per 1 Ldistilled water. At polishing of Bi, the 6 �m step can be omitted �see below�.Both pure antimony and bismuth are well suited for electrolytic polishing.Etching: See below.


B 487 C-44


E 112, E 930, E 1181, E 1382 C-44, T-44El-10


E 562, E 1245, E 1382 C-44, T-44


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-44, T-44


C-44, T-44,El-10



Sectioning


Mounting


Resin Bakelite Cold Mounting Resin Acrylics/EpoxyTimeMinutes


6–10 min/6–8 h


Grinding

T-44: For harder alloys, FG 4 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-44 and T-44: P 1: At polishing of bismuth and Bi alloys this step can beomitted.C-44: P 3: At polishing of bismuth and Bi alloys the time may be increased toseveral minutes.For the final step chemical mechanical polishing can be recommended �seeabove�.

Contemporary Method C-44 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth SiC paper SiC paper RCD, soft Cloth,

napless,hard,wov, silk




Dia, spror susp

Dia, spror susp

Silica


P220 P320 9 6 3 0.04/0.05


Wat-oil

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



25 �5.7� 25 �5.7� 30 �7� 25 �5.5� 25 �5.7� 15 �3.3�

TimeMinutes

Untilplane

0.5–1 5 4 3 1


Traditional Method T-44 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper


Cloth,nap-less,med.hard,wov,wool


AbrasiveType


Dia, spror susp

Silica


P220 P320 P500 P1200 P2400 6 3 0.04/0.05

LubricantType

Water Water Water Water Water Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4–5 3 1

EtchantsMaterial Etchants �see Table 12.2� UsesSb, lean,Sb alloys

935 General structure

Sb 938 Grain contrastSb, Sb alloys 936, 937, 940 General structureSb-Pb alloys 938, 941 General structureBi, Bi alloys 937, 940 General structureBi-Sn alloys, Bi-Ca alloys 938 General structure


Material/Preparation Tables 45Material: Pure beryllium. Be alloys

Material Properties: Beryllium: Hexagonal close-packed, 1.8 g/cm3, 1350°C�2462°F�, HRB 80.Comments on Material: Beryllium is a light metal which is mostly used as analloying element, improving the strength of the alloy. Pure beryllium is toxic toinhale which means that the preparation process, when dust is developed, musttake place in a glove box or under an efficient fume hood, or both.Pure beryllium resembles magnesium �see Material/Preparation Tables 53� itdeforms and fractures easily and preparation must be done with great care.Sectioning: For wet abrasive cutting a thin SiC bakelite bond cut-off wheel shouldbe used. For alloys based on copper, a medium hard wheel is recommended. Fornickel-based alloys a softer wheel should be used. The cooling should be efficientto avoid thermal damage. When cutting pure beryllium and alloys with a high Becontent, it is important that the sludge, metal dust, and particles from the wheelare correctly disposed of because of the toxicity.Mounting: Both hot mounting and cold mounting can be used.Grinding: When wet grinding pure beryllium and alloys with a high Be contentthe dust is bound by the water, but care must be taken to have the correct disposalof the sludge. For pure beryllium the force on the specimen should be reduced andoften it can be of advantage to make the grinding on a stationary paper in onedirection.Polishing: For pure beryllium and certain alloys electrolytic polishing isrecommended. Also a chemical mechanical polishing can be used �see below�.Etching: Pure beryllium can be examined in polarized light. For etchants, seebelow.

Purpose ASTM Standard �See Section 12.4.� MethodCase or coatingthickness/hardness,surface layers

B 487 C-45


El-10Image analysis, ratingof inclusion content

E 562, E 1245, E 1382 C-45, T-45


E 110, E 140, E 384,E 448

C-45, T-45

Microstructure E 3, E 407, E 562, E 883, E 1181, E 1245,E 1351, E 1382, E 1558

C-45, T-45,El-10




Sectioning


Mounting




6–10 min

Grinding

C-45: PG: If possible use SiC paper grit P320.T-45: Pure Be is relatively brittle and grinding should be performed with MethodT-45, but with lower force than indicated.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-45, T-45: For the last step with silica, one part of hydrogen peroxide �30 %�can be added to five parts of silica suspension.

Contemporary Method C-45 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding PG FG 1 P 1 P 2PolishingDisk/Cloth Dia, disk,


napless,hard,wov, silk



Dia, spr orsusp

Silica


P220 9 3 0.04/0.05

Lubricant Type Water Water WaterRotation Disk/Holder 300/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp or contra Comp Comp ContraForce per SpecimenN �lb�

20 �4.4� 30 �6.6� 25 �5.5� 15 �3.4�

TimeMinutes



Traditional Method T-45 �For definitions of parameters and consumablessee Section 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

Silica


P220 P320 P500 P1200 6 3 0.04/0.05

LubricantType

Water Water Water Water Alco-wat Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comp orcontra



25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–5 3–4 1–2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Be 9, 10 General structure via polarized lightBe alloys 11 General structure

Material/Preparation Tables 46Material: Pure chromium. Cr alloys

Material Properties: Chromium: Body-centred cubic, 7.17 g/cm3, 1875°C�3407°F�, HB 125.Comments on Material: Chromium belongs to the refractory metals and purechromium is soft and ductile. The alloys, which are commercially available, oftenused for plating, are hard and relatively brittle.The machinability of chromium is low and cold working is easy which makeschromium relatively difficult to prepare mechanically.


Sectioning: Wet abrasive cutting can be made with an SiC bakelite bond cut-offwheel. Due to the poor machinability a relatively soft wheel, as thin as possible,should be used.Mounting: Both hot and cold mounting can be used.Grinding: Because of the poor machinability the grinding papers should only beused as long as they are cutting efficiently, if not, cold work and deformation willdevelop.Polishing: It is important that the deformations from grinding are removed duringthe rough polishing step. It can be difficult to remove all deformation bymechanical polishing and often chemical mechanical polishing can be anadvantage �see below�. Also electrolytic polishing can be recommended.Etching: Chromium is difficult to etch, two etchants are stated below.

Purpose ASTM Standard�See Section 12.4�

Method

Case or coatingthickness/hardness,surface layers

B 487 C-46


E 112, E 930, E 1181, E 1382 C-46, T-46,El-11


E 562, E 1245, E 1382 C-46, T-46


E 10, E 18, E 92, E 103, E 110, E 140,E 384, E 448

C-46, T-46,El-11


C-46, T-46,El-11




Mounting




6–10 min

Grinding

T-46: Very often FG 3 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

C-46 and T-46: The last polishing step can be with alumina �0.02–0.05 �m� indistilled water �100 mL� with sodium hydroxide �5 g�, or alumina �300 mL� withhydrogen peroxide �H2O2� �20 mL� �30 %�.C-46: If needed the step P 1 from T-46 can be used between FG 1 and P 1expanding the method with one step.C-46: P 2: This step can often be omitted.

Contemporary Method C-46 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth Dia, disk,



Cloth, med.nap, soft, syn


AbrasiveType


Dia, spr orsusp

Dia, spr orsusp

Silica


P220 9 3 1 0.04/0.05


300/150 150/150 150/150 150/150 150/150


30 �7� 30 �7� 30 �7� 25 �5.7� 15 �3.39�

TimeMinutes



paperSiCpaper

SiCpaper

SiCpaper





AbrasiveType


Dia,sprorsusp

Alumina


P220 P320 P500 P1200 6 3 0.02/0.05

LubricantType


Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra



15�3.4�

15�3.4�

15�3.4�

15�3.4�

30 �7� 20 �4.5� 10 �2.3�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–5 3 1

EtchantsMaterial Etchants �see Table 12.2� UsesCr 12, 13c General structure

Material/Preparation Tables 47Material: Pure Cobalt. Co Alloys

Material Properties: Cobalt: Above 417°C �783°F�: Face-centred cubic. Below417°C �783°F�: Hexagonal close packed, 8.8 g/cm3, 1495°C �2723°F�.Comments on Material: Cobalt is a metal with characteristics close to iron andnickel; it is tough and the machinability is relatively low. Cobalt is very magneticand used for magnets and for alloying element to improve strength. For superalloys based on cobalt, see Material/Preparation Tables 48. For cobalt in cementedcarbides, see Material/Preparation Tables 67.Pure cobalt being tough and with a tendency to cold work and deformation isrelatively difficult to prepare. Cobalt alloys are less difficult. Preparation is similarto the refractory metals �see Material/Preparation Tables 55�.Sectioning: Wet abrasive cutting is done with an SiC bakelite bond cut-off wheel.A thin and relatively soft wheel is recommended to secure a cut with the lowestdeformation possible.Mounting: Hot mounting and cold mounting can be used.Grinding: Due to the toughness of cobalt the SiC grinding papers shall not beused for too long of a time to avoid smeared layers.


Polishing: It is important that the rough polishing step has removed thedeformation from the grinding. If this cannot be obtained with the 3 �m step, a6 �m step is used �see below�. Electrolytic polishing can be recommended.Etching: See below.

Purpose ASTM Standard �See Section 12.4� MethodCase or coating thickness/hardness, surface layers

B 487 C-47


E 112, E 930, E 1181, E 1382 C-47, T-47,El-12


E 562, E 1245, E 1382 C-47, T-47


E 10, E 18, E 92, E 103,E 110, E 140, E 384,E 448

C-47, T-47,El-12


C-47, T-47,El-12




Mounting




6–10 min

Grinding


Polishing

C-47: The step P 1 from Method T-47 can be used between the FG 1 step and theP 1 step �see above�.C-47: P 2: Often this step can be omitted.T-47: The method can be expanded with P 3 from C-47.





Cloth, mednap, soft,syn



Dia, spror susp

Dia, spror susp

Alumina


P220 9 3 1 0.02/0.05

LubricantType

Water Alco orwat

Alco orwat

Alco or wat

Rotation Disk/Holder 150/150 150/150 150/150 150/150 150/150rpm/rpmComp/Contra Comp Comp Comp Comp ContraForce perSpecimen N �lb�

25 �5.7� 30 �7� 30 �7� 30 �7� 10 �2.2�

TimeMinutes

Untilplane

5–6 4 2


paperSiCpaper

SiCpaper

SiCpaper



Clothmed.nap,soft,syn

AbrasiveType


Dia, spror susp

Dia, spror susp


P220 P320 P500 P1200 6 3 1

LubricantType


Alcoorwat

Alcoorwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comp orcontra

Comp Comp Comp Comp



20 �4.5� 20 �4.5� 20 �4.5� 15 �3.4� 25 �5.7� 30 �7� 30 �7�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4–5 4 2

EtchantsMaterial Etchants �see Tables 12.2� UsesPure Co 14, 15, 17 General structureHard-facing and tool metals 18, 19, 20 General structureHigh temperature alloys 20, 18, 16, 21, 22b, 24, 25 General structure

19 Phase identification

Material/Preparation Tables 48Material: Cobalt-based super alloys

Material Properties: Cobalt: Above 417°C �783°F�: Face-centered cubic. Below417°C �783°F�: Hexagonal close packed, 8.8 g/cm3, 1495°C �2723°F�.Super alloys �Co based�: Heat-resistant casting alloys: 20–32 % chromium, 7–13 %tungsten, 1–11 % nickel and molybdenum, niobium, zirconium, titanium,aluminum, tantalum, boron, silicon and manganese.Wrought heat-resistant alloys: 1–15 % iron, 3–35 % nickel, 20–30 % chrome, 7–10% molybdenum, carbon, manganese, tungsten, niobium �weight %�.Comments on Material: The cobalt-based super alloys are high-temperatureresistant materials. They are hard and tough, relatively easy to prepare. Stellite is aspecial cobalt-based alloy with 45–65 % Co, 25–35 % Cr, and 5–20 % W. This alloyis very wear resistant used only as casting alloy. It is hard and brittle. Cobalt isalso used in cemented carbides �see Material/Preparation Tables 67�.Sectioning: Wet abrasive cutting is done with an SiC bakelite bond cut-off wheel.Very often shearing or other more rough sectioning methods should be avoided, asserious distortions and cold work could be introduced. Use only these methods forsectioning of large pieces, later to be sectioned by wet cutting.Mounting: Both hot mounting and cold mounting can be used. In case of edgeretention a hot mounting material like bakelite or epoxy with a filler should beused.Grinding: For the harder alloys, like stellite, Method C-48 should be preferred.Polishing: For the final step with alumina, the pH should be lowered to around 4.Electrolytic polishing is recommended.Etching: See Material/Preparation Tables 47.


B 487 C-48




E 112, E 930, E 1181, E 1382 C-48,T-48E-12


E 562, E 1245, E 1382 C-48,T-48


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-48,T-48El-12


C-48,T-48El-12



Sectioning


Mounting


Resin Bakelite/Epoxy

Cold Mounting Resin Acrylics

TimeMinutes


6–10 min

Grinding

C-48: FG: Very often FG 1 can be changed to RCD, soft, and FG 2 and FG 3 canbe omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-48 and T-48: The P 3 step: Use alumina with a pH around 4.


Contemporary Method C-48 �for definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 3PolishingDisk/Cloth Dia, disk

fixed, resRCD, hard RCD, soft RCD, soft Cloth, nap-

less, hard,wov, syn


AbrashiveType

Diamond Dia, spror susp

Dia, spror susp

Dia, spror susp

Dia, spror susp

Alumina


P220 9 6 3 3 0.02/0.05

LubricantType

Water Alcoor wat

Alcoor wat

Alcoor wat

Alcoor wat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



30 �7� 30 �7� 30 �7� 25 �5.7� 30 �7� 15 �3.4�

TimeMinutes

Untilplane

4–5 4 5 2–4 1–2

Traditional Method T-48 �For definitions parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper

Clothnapless,hard,wov, silk

Clothnapless,hard,wov,syn

Clothnapless,soft,porous,syn

AbrasiveType


Dia, spror susp

Alumina


P220 P320 P500 P1200 6 3 0.02/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra




30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 30 �7� 10 �2.3�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 5 2–3 1


Material/Preparation Tables 49Material: Copper and copper alloys. Brass. Bronze. Other copperalloys

Material Properties: Copper: Face-centered cubic, 8.93 g/cm3, 1083°C �1981°F�,HRB 37.�-brass: Body-centered cubic, up to 38 % zinc.�- -brass: Body-centered cubic, 38 to 47 % zinc.Bronze: Up to 30 % tinComments on Material: Copper makes alloys with a high number of othermetals. In alloys improving the characteristics of pure copper, small amounts ofalloying elements like silver, cadmium, sulfur, tellurium, chromium, beryllium, andcobalt are used. The alloys with zinc, brasses, are numerous, often with lead as afurther alloying element. In special brasses further elements like aluminum, tin�1–2 %� manganese nickel and iron are used. Brass can be obtained as wroughtand cast alloys. The alloys with tin, bronzes are supplied as wrought bronzes withup to 6 % tin and cast bronzes with up to 30 % tin Often zinc is added up to 2 %and other elements like phosphorous and lead. Aluminum bronze is a group ofbronzes with 5–11 % aluminum, up to 6 % nickel, 6 % iron, and 2 % manganese.Manganese bronze contains 5–15 % manganese. Copper-nickel alloys have a nickelcontent of 4.5–45 % nickel with small amounts of iron and manganese.Copper and copper alloys are specified in a number of systems by a number oforganizations. The most important are:UNS System, Standard Designations for Copper and Copper Alloys, by CopperDevelopment Association �CDA�.AMS System, Aerospace Material Specifications, by Society of AutomotiveEngineers �SAE�.ASME System, by American Society of Mechanical Engineers �ASME�.ASTM System by ASTM.AWS System by American Welding Society �AWS�.Ingot No System by Brass and Bronze Ingot Manufacturers.Federal System and Military System.SAE System by American Society of Mechanical Engineers �ASME�.Metallographic examination is often used for the determination of grain size,evaluation of the distribution of second phase, and control of heat treatment.


Copper alloys are soft and ductile, making them difficult to prepare withoutdeformation. Care should be taken to keep the deformation low at sectioning andgrinding and to remove deformation from previous steps. See also the Material/Preparation Tables 50 covering the preparation of pure copper and copper bearingalloys.Sectioning: Wet abrasive cutting with an SiC bakelite bond cut-off wheel. Use anefficient cooling to avoid recrystallization of cold-worked lean alloys. When usingshearing or band sawing, care should be taken that the strong deformationdeveloped is removed during the plane grinding.Mounting: Hot and cold mounting can be used.Grinding: Sectioning and the rough grinding steps introduce deep deformation soit is important to remove this during the finer grinding steps.Polishing: It can be very difficult to remove the last deformation and obtain ascratch-free surface with mechanical polishing. Using chemical mechanicalpolishing at the last polishing step is an efficient way to obtain a correct surface�see below�. Electrolytic polishing gives very good results with a number of brassesand bronzes.Etching: See below.


B 487 C-49


E 112, E 930,E 1181, E 1382

C-49, T 49,El-13�Brass�, El-14 �Bronze�


E 562, E 1245,E 1382

C-49, T-49

High planenessMicrohardness, hardness E 10, E 18, E 92, E 103, E 110, E 140,

E 384, E 448C-49, T-49


C-49, T-49,El-13�Brass�, El14 �Bronze�




Sectioning


Mounting




6–10 min

Grinding

Attention: In C-method, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-49 and T-49: For Cu and Cu-alloys a chemical mechanical polishing can beobtained in the last polishing step by mixing 98 �96� mL colloidal silica with1 mL �2 mL� H2O2 �30 %� and 1 mL �2 mL� ammonia solution �25 %�.Electrolytic polishing: Brass: El-13. Bronze: El-14





Dia, spror susp

SilicaSee note


P220 9 3 0.04/0.05

Lubricant Type Water Alco or wat Wat-oilRotationDisk/Holder

300/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp or Contra Comp Comp ContraForce perSpecimen N �lb�

25 �5.7� 30 �7� 25 �5.5� 15 �3.3�


TimeMinutes

Until plane 4 4 2–3

Traditional Method T-49 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 FG 5 P 1 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper


Clothnap-less,soft,por-ous,syn

AbrasiveType

SiC SiC SiC SiC SiC SiC Dia,sprorsusp

SilicaSeenote


P220 P320 P500 P1200 P2400 P4000 3 0.04/0.05

LubricantType

Water Water Water Water Water Water Wat-oil

RotationDisk/Holder

300/150

300/150

300/150

150/150

150/150

150/150

150/150

150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 20 �4.5� 25�55.7�

10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 0.5–1 3 1

EtchantsMaterial Etchants �see Table 12.2� UsesCu-Al �aluminum,bronze�

44, 31d, 34 b, 35, 36,37, 38, 39, 40, 45, 215

General structure

Cu-Be 46, 41, 45 General structureCu-Cr 41 General structureCu-Mn 41 General structureCu-Ni 34, 47, 48, 40, 49, 50 General structureCu-Si 41 General structure


Cu-Sn �tinbronze�

51, 52 General structure

Admirality metal 8b General structureGilding metal,cartridge metal,freecutting brass,nickel silver

31d, 32, 33, 41, 42, 49 General structure

Cu alloys 26, 27, 28, 29, 30, 44,41, 31d, 32,33, 34b, 35, 36, 37, 38,39, 210, 215

General structure

53, 43, 28, 49 Chemical polishand etch

42, 49, 210 Darkens beta inalpha-beta brass

54 Etching of coldworked brass

Material/Preparation Tables 50Material: Pure copper. Copper-bearing alloys

Material Properties: Copper: Face-centered cubic, 8.93 g/cm3, 1083°C �1981°F�,HRB 37.Copper bearing alloys: 3.5–25 % lead, 3.5–11 % tin, 0.5–4 % zinc, small additionsof antimony, nickel and iron �weight %�.Comments on Material: Commercially pure copper, 99.9–99.99 %, can beobtained as oxygen-free electronic copper and as tough pitch copper containingvery small amounts of oxide. Copper bearing alloys have high contents of lead andtin, as mentioned above.Pure copper is very ductile and soft making the preparation difficult. Copperbearing materials, having the very soft phases of lead and tin is difficult to preparewithout smearing of these phases. The methods described in Material/PreparationTables 49 can also be used for pure copper. For further information see Material/Preparation Tables 49.Sectioning: Wet abrasive cutting with an SiC bakelite bond cut-off wheel. Whenusing shearing or band sawing, care should be taken that the strong deformationdeveloped is removed during the plane grinding.Mounting: Hot and cold mounting can be used.Grinding: Sectioning and the rough grinding steps introduce deep deformation soit is important to remove this during the finer grinding steps.


Polishing: It is important that the deformation developed during the grinding isremoved after the step with 9 �m or 6 �m. For pure copper it can be very difficultto remove the last deformation and obtain a scratch- free surface with mechanicalpolishing. Using chemical mechanical polishing at the last polishing step is anefficient way to obtain a correct surface �see below�. Electrolytic polishing givesgood results with pure copper using Method El-13. Electrolytic polishing ofbearing alloys can be done with Method El-14 if the amount of phases is not toohigh.Etching: Etching can take place between preparation steps to remove deformation�see below�. See etchants below.


B 487 C-50

Perfect edgeretentionGrain size,grain boundaries

E 112, E 930,E 1181, E 1382

C-50, T-50,El-13 �Purecopper�, El-14�Bearingalloys�


E 562, E 1245, E 1382 C-50, T-50


E 140, E 384, E 448C-50, T-50


C-50, T-50,El-13 �Purecopper�, El-14�Bearingalloys�


Sectioning



Mounting




6–10 min

Grinding

T-50: FG 4: This step can often be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-50 and T-50: To remove deformation after the last FG step etch with 100 mLwater mixed with 100 mL ethanol and 10 g iron �III� nitrate before the P 1 step.C-50 and T-50: For Cu and Cu alloys a chemical mechanical polishing can beobtained in the last polishing step by mixing 98 �96� mL colloidal silica with1 mL �2 mL� H2O2 �30 %� and 1 mL �2 mL� ammonia solution �25 %�. Analternative is adding a few drops of the nitrate etchant mentioned above to thecolloidal silica during the polishing.Electrolytic polishing: Pure copper: El-13. Copper bearing alloys: El-14.

Contemporary Method C-50 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2PolishingDisk/Cloth SiC paper SiC paper RCD, soft Cloth,


Cloth, nap-less, soft,porous,syn


Dia, spr orsusp

SilicaSee note


P220 P320 9 3 0.04/0.05

Lubricant Type Water Water Alco or wat Wat-oilRotationDisk/Holder

300/150 300/150 150/150 150/150 150/150




20 �4.4� 20 �4.4� 30 �7� 2.5 �5.7� 15 �3.3�

TimeMinutes

Until plane 0.5–1 3–4 5 1–2


Traditional Method T-50 �For definitions of parameters and consumables �seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

SilicaSeenote


P220 P320 P500 P1200 P2400 6 3 0.04/0.05

LubricantType


RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra

Comporcontra

Comporcontra



20�4.5�

20�4.5�

20�4.5�

20�4.5�

20�4.5�

25�5.7�

25�5.7�

15�3.3�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 3–4 3–4 1

EtchantsMaterial Etchants

�see Table 12.2�Uses

Pure Cu 26, 27, 28, 29,30, 31d, 32, 33,34b, 35, 36, 37,38, 39, 40, 41,42, 8b, 210, 215

General structure

43, 28 Chemical polish and etch


Material/Preparation Tables 51Material: Pure gold. Au alloys

Material Properties: Body-centered cubic, 19.3 g/cm3, 1063°C �1945°F�Comments on Material: Gold belongs to the precious metals which include theplatinum-group metals �see Material/Preparation Tables 57�, gold and silver, Puregold, 99.99 % is seldomly used, most often gold is alloyed with silver, copper,nickel, or the platin-metals. Gold is the most ductile metal; it can be rolled to athickness of 1/12 000 mm. Gold is used for jewelry and has a number of industrialapplications. Often gold is used as a coating on other materials, and for electronicparts gold is used as coatings for certain components �see Section 7.10.3 andMaterial/Preparation Tables 22 and 26�. Pure gold, being very soft and ductile, isvery difficult to prepare; deformation and smearing are difficult to avoid. Also,there is a risk of embedded abrasive grains in the specimen surface. Some alloysare harder and therefore easier to prepare.Sectioning: Because of the high price of gold, the wet abrasive cutting should bewith a thin cut-off wheel to reduce the kerf loss. Cutting is best done on aprecision cut-off machine using SiC bakelite bond cut-off wheels 0.5 mm �0.02 in�thick and with an efficient cooling. In the case of examinations of coatings, thecutting should be done correctly �see Material/Preparation Tables 08–10�. Also, itcan be of advantage to mount the specimen in epoxy before cutting to stabilize thecoating �see below�. If using shearing, the strong deformation of the edge shouldbe taken care of when plane grinding the specimen.Mounting: Hot and cold mounting can be used. Very often coatings should beexamined and the correct hot mounting material, with a filler, should be used.Also, cold mounting with epoxy may be satisfactory �see Sections 3.1.3 and 3.11�.Grinding: If following a proper cutting, grit P220 grinding paper should beavoided, starting with grit P320. To reduce the induction of deformation in thematerial, the grinding paper can be covered with a thin layer of wax, or the papercan be “worn-in” with a hard specimen for a few seconds. It is important that alldeformation from the previous step is removed. In the case of embedded SiCgrains in the specimen surface, use Method C-51. To avoid embedded abrasivegrains �see Section 13.6.4�, a softer grinding/polishing surface should be used. Inthe case of embedded grains the FG 2 step of Method C-51 can be changed to ahard, nonwoven, synthetic cloth. Also diamond paste, fixing the grains in the cloth,can be used. As an alternative to C-51, Method C-58 for silver can be used. For thesoftest materials, Method C-51 should be used.Polishing: For pure gold and alloys with a high gold content chemical mechanicalpolishing can be used for the last polishing step �see below�.Etching: See etchants below.


B 487 C51




E 112, E 930, E 1181, E 1382 C-51,T-51


E 562, E 1245, E 1382 C-51,T-51


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-51,T-51


C-51,T-51



Sectioning

Cut-Off Wheel SiC, bakelite bond, 0.5 mm �0.02 in� thick

Mounting


Resin Bakelite/Bakelitewith a Filler

ColdMounting

Resin Acrylics/Epoxy

TimeMinutes


6–10 min/6–8 h

Grinding

C-51: The step FG 2 can be changed to a hard, nonwoven, synthetic cloth ifembedded abrasive grains are a problem using the RCD.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-51 and T-51: Both methods can be finished with chemical mechanicalpolishing: Step P 3 in C-51 with alumina �0.05 �m� added a few drops of etchant62: 1–5 g CrO3, 100 mL HCl �see Etchants below�.C-51: For certain alloys the step P 1 can be changed to 3 �m diamond, followedby P 2 from Method T- 51 for 2–8 min so that P 2 and P 3 are omitted.T-51: Can be finished with P 3 from C-51.T-51: Steps FG 3 and FG 4 can be changed to P 1 from C-51. In some cases P 1can be omitted, and P 2 changed to 1 �m diamond.


Contemporary Method C-51 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth SiC paper SiC paper RCD,

softCloth,napless,hard,wov, silk

Cloth, nap-less, medsoft,wov, wool


AbrasiveType

SiC SiC Dia,spr orsusp

Dia,spr orsusp

Dia,spr orsusp

Alumina�see note�


P220 P320 9 6 3 0.02/0.05

LubricantType


Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Comp ContraForce perSpecimenN �lb�

20 �4.5� 20 �4.5� 25 �5.7� 20 �4.5� 20 �4.5� 10 �2.3�

TimeMinutes

Untilplane

0.5–1 5 5 3 1


paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



AbrasiveType


Dia,sprorsusp


320 500 1000 2400 4000 3 0.25

LubricantType


Wat-oil


RotationDisk/Holder

300/150 300/150 300/150 300/150 300/150 150/150 150/150


orcontra

Comp Comp Comp Comp Comp Comp


20�4.5�

20�4.5�

20�4.5�

20�4.5�

20�4.5�

20 �4.5� 15�3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 1 4 2–8

EtchantsMaterial Etchants �see Table 12.2� UsesPure Au 61, 62 General structure

63 Chemical polish and etchAu alloys 64b, 62 General structure

63 Chemical polish and etch�90 % noble metals 61 General structure�90 % noble metals 65 General structure

Material/Preparation Tables 52Material: Pure lead. Pb alloys. Pb bearing alloys

Material Properties: Lead: Face-centered cubic, 11.34 g/cm3, 327°C �621°F�, HV25–40.Lead bearing alloys: 0.9–11.0 % tin, 3–16 % antimony, 0.1–0.7 % copper, arsenic,bismuth, zinc, aluminum, cadmium �weight %�.Comments on Material: Lead is a very soft and ductile metal with a low meltingpoint and a recrystallization temperature around 20°C �68°F�. Lead and most leadalloys are toxic both when inhaled and ingested. Pure lead is difficult to prepare,whereas bearing alloys are less difficult. After cold working lead rapidlyrecrystallizes. The cold work developed during sectioning and grinding should bekept at a minimum to avoid development of a pseudostructure throughrecrystallization. Also, abrasive grains are easily embedded in the specimensurface.No “contemporary” �C�-method for lead is available. C-52 describes a methodbased on etching between steps. T-52 is a “normal” “traditional” method. MethodC-52 with etching between steps is recommended for pure lead.Sectioning: Abrasive wet cutting of pure lead and lead alloys can be done with athin SiC bakelite cut-off wheel, preferably on a precision cutting machine. Also, atoothed cut-off wheel can be used. Pure lead also can be cut by using a sharp knifeor a band saw or hand saw with fine teeth. If a microtome is available, very goodsurfaces can be obtained so that grinding is not needed �see Section 2.7.6�. In thecase of examination of corrosion products �batteries�, the specimen should beimpregnated before sectioning �see Section 3.10�.


Mounting: As a rule pure lead and lead alloys should not be hot compressionmounted, both because of the low recrystallization temperature and because ofvoids and pores in the alloys that possibly may collapse under the high pressure ofhot mounting. To obtain the lowest possible temperature during cold mounting,epoxy should be used �see Section 3.8.3�.Grinding: To minimize the risk of embedded SiC grains in the specimen surface,the grinding paper can be treated with wax and a low pressure is used. Alsoparaffin can be used instead of water. In both cases an abundant flow of liquidshould be used to secure the removal of loose grains. In Method C-52 thespecimen is etched after the last grinding step �FG 2� to remove deformation fromgrinding �see below�.Polishing: It is important that the deformation from the grinding is removedduring the rough polishing step. For pure lead chemical mechanical polishing isrecommended for the last polishing step �see Method C-52 below�. Lead and somelead alloys are suited for electrolytical polishing.Etching: See below.


B 487 C-52, T-52

Perfect edge retentionGrain size, grain boundaries E 112, E 930, E 1181, E 1382 C-52, T-52, El-15Image analysis,rating of inclusioncontent

E 562, E 1245, E 1382 C-52, T-52


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-52, T-52


C-52, T-52,El-15



Sectioning

Cut-Off Wheel SiC bakelite bond cut-off wheel, 0.5 mm �0.02 in�thick, low speed, very careful, see also above.


Mounting


Resin Cold Mounting Resin Acrylics/epoxy w.lowest possiblepeak temp.

TimeMinutes

TimeMinutes/Hours

6–8 min/12–24 h

Grinding

T-52: PG, FG 1 and FG 2: Charge SiC papers with wax or use paraffin instead ofwater.C-52: Instead of water, paraffin is used for SiC steps.C-52: After FG 2 the specimen is etched in Solution 1: 15 mL acetic acid, 15 mLnitric acid �65 %�, 60 mL glycerol. Do not store, use fresh solution at 80°C�176°F�. The solution is etchant 113 below.See also alternative below.C-52: As an alternative to Solution 1, Solution 2 can be used: 100 mL hydrogenperoxide �30 %� mixed with 139 mL ammonia �25 %�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-52 and T-52: For pure lead use chemical mechanical polishing with last step,P 3: Solution 3: 84 mL glycerol, 8 mL acetic acid �96 %�, 8 mL ammonia �25 %�.10 mL of Solution 3 is added to 90 mL colloidal silica. Also a mixture of 90 mLsilica and 10 mL hydrogen peroxide �30 %� can be used. A third possibility isadding a few drops of ammonium tartrate to the silica.T-52: P 2: This step can often be omitted.

Contemporary Method C-52 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper





Dia, spror susp

Silica,see note


P320 P500 P1200 P2400 3 1 0.04/0.05


LubricantType

Paraffin Paraffin Paraffin Paraffin Wat-oil Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 300/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Comp Comp ContraForce perSpecimenN�lb�

15�3.4�

15�3.4�

15�3.4�

15�3.4�

20 �4.5� 15 �3.4� 10 �2.2�

TimeMinutes

0.5–1 0.5–1 0.5–1 0.5–1 3–4 3 1–2


paperSiCpaper

SiCpaper


Cloth,napless,med hard,wov, wool


Abrasive Type SiC SiC SiC Dia,spr orsusp

Dia,spr orsusp

Silica


320 500 1200 9 3 0.04/0.05

LubricantType

Water Water Water Alco or wat Wat-oil

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Comp ContraForce perSpecimenN �lb�

10–20�2.2–4.5�

10–20�2.2–4.5�

10–20�2.2–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

10�2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 4–5 3 2



Pure Pb 57, 112 General structurePure Pb, Pb+ �2Sb, Pb+ �2Sb,Pb+Ca

113 For alternate polishingand etching

Pb+ �2Sb 114, 115, 57, 74b General structurePb+ �2Sb 114, 57, 74b General structure


Pb+Ca 112 General structurePb alloys 116, 117b General structureBabbitt 74b General structure

Material/Preparation Tables 53Material: Pure magnesium and Mg alloys

Material Properties: Magnesium: Hexagonal close-packed, 1.74 g/cm3, 650°C�1202°F�, HB�B� 35.Magnesium alloys: 1.2–10 % aluminum, 0.15–1.5 % manganese, 0.2–3.0 % rareearths, 1.8–3.0 % thorium, 0.5–5.7 % zinc, 0.6–0.7 % zirconium �weight %�.Comments on Material: Magnesium is the light metal with the lowest specificgravity in practical use. Pure magnesium is rarely used because of the lowstrength, but in form of alloys based on the five alloying elements mentionedabove. Magnesium alloys are normally available as low-pressure casting alloys,high-pressure casting alloys, and wrought alloys. Magnesium alloys are notuniversally classified, but in ASTM “Practice for Temper Designation ofMagnesium Alloys, Cast and Wrought” �B 296� a designation is stated.Magnesium is soft and will easily cold-work making it difficult to prepare. As thedust from grinding may ignite, all sectioning and grinding should be with acooling fluid. Pure magnesium and many alloys are sensitive to water.The preparation of Mg cast and wrought alloys vary considerably, and therefore anumber of suggestions are stated below. For harder alloys use Method C-53.Sectioning: At examination of die castings it should be recognized that themicrostructure varies strongly through the casting. This should be consideredwhen selecting the sample. Wet abrasive cutting with an SiC cut-off wheel. Careshould be taken to avoid excessive deformation of the cut surface and the fixing ofthe work piece should be as gentle as possible. As mentioned above themagnesium swarf/dust may ignite and even development of hydrogen may takeplace at the contact with water, and special precautions should be made. If cuttingwith a shear or a band saw, at least 1 mm of the cut surface should be removedduring the plane-grinding step.Mounting: The pressure that is needed for hot mounting may cause cold-work inthe specimen, and cold mounting should be preferred. In case of heat-sensitivealloys only epoxy should be used for cold mounting, keeping the peak temperaturelow �see Section 3.8.3�.Grinding: The plane grinding should be performed with the finest possible grit. Ifthe sectioned surface is not very rough, the first grinding step can be with gritP320 or P500 as deep deformations are very difficult to remove at the later steps.For water-sensitive materials use a mixture of glycerol and ethanol, 1:3, instead ofwater, or pure ethanol for the finer grits. In case of embedded SiC particles in thespecimen surface, charge the surface of the grinding paper with wax.


Polishing: For most materials water should be totally avoided for polishing.Ultrasonic cleaning in ethanol between polishing steps is recommended. Duringthe polishing a relief may develop between the matrix and hard particles; to avoidthis use Method C-53. Also this method should give the smallest amount ofembedded abrasive grains in the specimen surface. By the final cleaning, watershould be avoided for most alloys. Use soap and ethanol, and avoid using cottonafter the last polishing step because new scratches may be introduced.Pure magnesium and most alloys can be electrolytically polished.Etching: Magnesium having a hexagonal close-packed crystal structure can beexamined in polarized light. For enchants, see below.


B 487 C-53


E 112, E 930, E 1181, E 1382 C-53, T-53,El-16

Image analysis,rating of inclusion content

E 562, E 1245, E 1382 C-53, T-53


E 140, E 384, E 448C-53, T-53


C-53, T-53,El-16



Sectioning


Mounting


Resin Cold Mounting Resin AcrylicsTimeMinutes

TimeMinutes/Hours

6/10 min

Grinding

C-53 and T-53: If the material is very water sensitive use ethanol or a mixture1:3 of glycerol and ethanol instead of water.C-53: FG 1: For water-sensitive materials use water-free lubricant.



Polishing

Cleaning: For most alloys cleaning between polishing steps should be donewithout water.C-53 and T-53: If the specimen material is sensitive to water use water-freepolishing media and lubricants.C-53 and T-53: The final cleaning can be done on a rotating polishing cloth, mednap, soft, syn, only with ethanol.C-53: P 3: This step can be changed to step P 2 in Method T-53, only with 1 �mdiamond in 2 min.C-53: Polishing step, P 3: Mix silica 1:1 with ethanol.T-53: P 1: This step can be changed to a step like FG 3 with SiC paper grit 2400.T-53: P 2: The cloth can be changed to napless, med hard, wov, wool.T-53: P 3: For pure Mg: Use same data as P 2 except grain size: 1 �m.

Contemporary Method C-53 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperRCD,soft


Cloth,napless,med hard,wov, wool

Cloth,napless, soft,porous, syn

AbrasiveType

SiC Dia, spr orsusp

Dia, spr orsusp

Dia, spr orsusp

Silica, seeabove


P500 9 6 3 0.04/0.05

LubricantType

Water Alco or wat Alco or wat Wat-oil

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150


20–30 �4.5–7� 20–30�4.5– 7�

30 �7� 15 �3.3� 10 �2.2�

TimeMinutes

Until plane 5–8 4 3–5 1–2



paperSiCpaper

SiCpaper

SiCpaper


Cloth,med.napsoft, syn



Dia, spror susp

Silica

Grit orGrain Size

220 320 500 1200 15 3 0.04/0.05

LubricantType

Water Water Water Water Alco oroil

Alco oroil

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150 150/150


20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

10–20�2.3–4.5�

30 �7� 25 �5.7� 15 �3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 1–2 3–4 3–4 0.5–1

EtchantsMaterial Etchants �see Table 12.2� UsesPure Mg 118, 119, 74a,

120, 121, 122General structure

123 Stainfree polish-etchMg-Mn 119, 74a, 124, 122 General structureMg-Al, Mg-Al-Zn�Al+Zn�5 % �

118, 119, 74a, 125,124, 123, 122

General structure

120, 125, 126, 127 Phase identification124, 126, 127 Grain structure

Mg-Al, Mg-Al-Zn�Al+Zn�5 % �

118, 119, 74a, 125,124, 121, 122

General structure

120, 125, 126, 127 Phase identificationMg-Zn-Zr and Mg-Zn-Th-Zr 118, 119, 74a, 1d, 128,

124, 126, 127, 121, 122General structure

120, 121 Phase identificationMg-Th-Zr 118, 119, 74a, 1d, 124,

127, 121, 122General structure

Mg-rare earth-Zr 120, 121 Phase identification


Material/Preparation Tables 54Material: Pure manganese. Mn alloys

Material Properties: Manganese: Body-centered cubic or body-centeredtetragonal, 7.2 g/cm3, 1260°C �2300°F�, HRC 35.Comments on Material: Manganese is a metal resembling iron, but it is harderand very brittle. It is primarily used as an alloying element, examples are withsteel, where 0.2–2 % manganese is used, brass with up to 3 % and bronze with5–15 % Mn.Pure manganese and alloys with high manganese content are not difficult toprepare. In the case of most alloys, the Material/Preparation Tables covering thebase metal should be followed.Sectioning: Wet abrasive cutting with an Al2O3 bakelite bond cut-off wheel.Mounting: Hot and cold mounting can be used.Grinding: No special precautions are needed.Polishing: Pure manganese and some alloys can be electrolytically polished.Etching: See below.


B 487 C-54


E 112, E 930, E 1181, E 1382 C-54, T-54,El-01


E 562, E 1245, E 1382 C-54, T-54


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-54, T-54

Microstructure E 3, E 407, E 562, E 883,E 1181, E 1245, E 1351,1382, E 1558

C-54, T-54,El-01



Sectioning



Mounting




6–10 min

Grinding

C-54: PG: For pure Mn use SiC paper grit P220.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


fixed, resRCD, hard Cloth, napless,

hard, wov, synCloth, napless,soft, porous, syn

Abrasive Type Diamond Dia, spr or susp Dia, spr orsusp

Alumina


P220 6 3 0.02/0.05


300/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp or contra Comp Comp ContraForce perSpecimenN �lb�

30 �7� 40 �9� 30 �7� 15 �3.4�

TimeMinutes

Until plane 4 4 2


Traditional Method T-54 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2PolishingDisk/Cloth SiC paper SiC paper SiC paper SiC paper Cloth,



Abrasive Type SiC SiC SiC SiC Dia, spr orsusp

Alumina


P220 P320 P500 P1200 3 0.02/0.05

Lubricant Type Water Water Water Water Alco or watRotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Contra


35 �8� 35 �8� 35 �8� 35 �8� 35 �8� 15 �3.7�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4 1–2

EtchantsMaterial Etchants �see Table 12.2� UsesMn-Fe, Mn-Ni,Mn Cu, Mn alloys


Pure Mn, Mn-Cu,and small additionsof Ni, Cu, Fe, Ge



Material/Preparation Tables 55Material: Pure molybdenum. Mo alloys. Pureniobium„Columbium…. Nb „Cb… alloys. Pure rhenium. Re alloys.Pure tantalum. Ta alloys. Pure tungsten. W alloys. Purevanadium. V alloys

Material Properties: Molybdenum: Body-centered cubic, 10.2 g/cm3, 2620°C�4748°F�, HV 200.Niobium �Columbium�: Rhombohedral, 8.4 g/cm3, 1950°C �3542°F�.Rhenium: Hexagonal close packed, 20.53 g/cm3, 3000 °C �5432°F�, HK 200.Tantalum: Body-centered cubic, 16.6 g/cm3, 2996°C �5425°F�, HV 110.Tungsten: Body-centered cubic, 19.3 g/cm3, 3410°C �6170°F�, HV 350.Vanadium: Body-centered cubic, 5.96 g/cm3, 1710 °C �3110°F�, HB 72.Comments on Material: Molybdenum, niobium, rhenium, tantalum, tungsten,and vanadium all having high melting points belong to the refractory metals. Theyare seldomly used pure but mostly as alloying elements. Pure niobium, rhenium,tantalum, and vanadium are soft and ductile, difficult to prepare. Puremolybdenum and tungsten are harder and more brittle. All metals have a lowmachinability and this combined with development of deformation and cold-workmakes it difficult to obtain a true microstructure by mechanical polishing; often itmust be combined with chemical mechanical polishing.Sectioning: Wet abrasive cutting can be made with a SiC bakelite bond cut-offwheel. Due to the poor machinability and to minimize the deformation, arelatively soft wheel, as thin as possible, should be used.Mounting: Both hot and cold mounting can be used. In case of examination ofporosity, a vacuum impregnation with epoxy may be useful �see Section 3.10�. Formounting of wires, see Section 3.12. Foils and wire samples should preferably becold mounted to avoid induction of deformation at hot compression mounting.Grinding: Because of the poor machinability the SiC grinding papers should onlybe used as long they are cutting efficiently; if not, cold work and deformation willdevelop. In case of alloys with hard nonmetallic precipitates, it may be ofadvantage to use Method C-55 to avoid relief and pull-outs. Variation regardingspecific materials, see below.Polishing: It is important that the deformations from grinding are removed duringthe rough polishing step, and if needed this step must be prolonged. It can bedifficult to remove all deformation by mechanical polishing and often chemicalmechanical polishing can be an advantage �see below�. Also electrolytic polishingcan be recommended �see below for methods covering the different metals�.Etching: See etchants below. Molybdenum may be electrolytically etched �seeMethod El-01�.



B 487 C-55


E 112, E 930,E 1181, E 1382

C-55, T-55,El-methods,see below

Image analysis, ratingof inclusioncontentHigh planeness

E 562, E 1245,E 1382

C-55, T-55

Microhardness, hardness E 10, E 18, E 92, E 103,E 110, E 140, E 384,E 448

C-55, T-55


C-55, T-55El-methods,see below



Sectioning

Cut-Off Wheel SiC, bakelite bond, a thin wheel

Mounting




6–10 min

Grinding

Niobium: T-55: An extra step with P4000 SiC paper can be added after FG 4.Rhenium: Method C-55 can be recommended.Tantalum and other very soft metals: C-55: A grinding step with P320 SiCpaper can be used between PG and FG 1 steps.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.


Polishing

Tungsten: C-55, T-55: The polishing step P 1 may be prolonged.Molybdenum: C-55 and T-55: To remove deformed layers, the P 2 step can beused with 0.05 �m alumina dispersed in a small amount of a 30 % K3Fe �CN�6aqueous solution.Molybdenum, niobium, tantalum, tungsten: C-55, T-55: To remove deformedlayers, the P 2 step can be used with colloidal silica �95 mL� added 5 mL of a 20% aqueous solution of chromium �VI� oxide �20 g CrO3 in 100 mL distilledwater�.Molybdenum: C-55 and T-55: For last step mix 96 mL of colloidal silica with2 mL of ammonia �25 %� and 2 mL of hydrogen peroxide �30 %�.Niobium, pure vanadium: C-55, T-55: The last polishing step can be done aschemical mechanical polishing: Mix 80 mL of colloidal silica with 20 mL ofhydrogen peroxide �30 %�.Tungsten, vanadium: C-55 and T-55: For last step mix 95 mL of colloidal silicawith 5 mL of hydrogen peroxide �30 %�.Rhenium: C-55, T-55: The last polishing step can be done as chemicalmechanical polishing: 15 g potassium ferricyanide �K3Fe�CN�6, 2 g sodiumhydroxide �NaOH�, 100 mL distilled water and equal part of silica.Electropolishing: Molybdenum: El-01, Vanadium: El-22, Tungsten: El-21






Dia, spror susp

Silica,see above


P220 9 3 0.04/0.05


300/150 150/150 150/150 150/150


ContraComp Comp Contra


20–30�4.5–7�

20–30�4.5–7�

30 �7� 10–15�2.3–3.4�

TimeMinutes




paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



AbrasiveType


Silica,seeabove


P220 P320 P500 P1200 P2400 3 0.04/0.05

LubricantType


RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/contra Comp or

contraComp orcontra

Comp orcontra



20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20 �4.5� 20 �4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 3–5 2–5

EtchantsMaterial Etchants �see Table 12.2� UsesMo base 98c, 129, 130, 131 General structureAs cast 132 a Chemical polish prior to etchingNb and Nballoys

129, 66, 158, 159, 160, 161,162, 163

General structure

164, 129, 160 Grain boundariesRe base 13b, 98c, 132b, 170a General structurePure Ta 177 General structureTa alloys 159, 66, 178, 163, 161, 179 General structure

164 Grain boundaries and inclusions158 Grain boundaries—retains carbide

precipitatePure W 98c, 131 General structureAs cast 132a Chemical polish prior to etchingW-Th 209 General structurePure V 170b, 165b General structure

197, 198 Grain boundariesV alloys 199, 198 General structure


Material/Preparation Tables 56Material: Pure nickel. Ni alloys. Ni Based super-alloys

Material Properties: Nickel: Face-centered cubic, 8.89 g/cm3, 1452°C �2646°F�.Nickel-copper alloys: 28–34 % copper, 1 % manganese, 1 % iron, carbon,aluminum.Nickel-iron alloys: 0.1 % carbon, 0.2 % manganese, 0.2 % iron.Super alloys �nickel based�: Heat resistant casting alloys: 8–15 % chromium, 2–28% molybdenum 0.5–2 % niobium, 0.8–4.7 % titanium, 0.5–6 % aluminum, 1–18.5% iron, 0.1–10 % tungsten, 0.3–1 % tantalum, 2.5–18.5 % cobalt, carbon,zirconium, boron.Wrought heat resistant alloys: 1–8 % iron, 2–19 % cobalt, 5–50 % chromium, 0.4–5% titanium, 3–25 % molybdenum, carbon, tungsten, niobium, aluminum,zirconium, boron, tantalum �weight %�.Comments on Material: Pure nickel and nickel-copper alloys are mostly used forthe good resistance to corrosion, also for this purpose nickel is used for coatings.Nickel being somewhat magnetic, it makes special magnetic alloys with iron. Thesuperalloys are very heat resistant.Nickel is a metal with characteristics close to iron and cobalt; it is tough and themachinability is relatively low. Pure nickel being tough and with a tendency tocold-work and deformation is relatively difficult to prepare. Nickel alloys are lessdifficult.Sectioning: Wet abrasive cutting is done with an SiC bakelite bond cut-off wheelwith an efficient cooling. A thin and relatively soft wheel is recommended tosecure a cut with the lowest deformation possible. Very often shearing or othermore rough sectioning methods should be avoided, as serious distortions andcold-work could be introduced. Use only these methods for sectioning of largepieces later to be sectioned by wet cutting.Mounting: Hot mounting and cold mounting can be used. In the case ofexamination of nickel coatings, see Material/Preparation Tables 08–10.Grinding: Due to the toughness of nickel the SiC grinding papers shall not beused for a too long time, to avoid smeared layers.Polishing: It is important that the rough polishing step has removed thedeformation from the grinding. In case of pure nickel and soft alloys, it may benecessary to add a silica step to the methods �see below�. Electrolytic polishing canbe recommended. Often a very short electrolytic polishing after mechanicalpolishing will remove smeared material �see Method El-17�.Etching: Nickel is relatively difficult to attack, strong solutions are needed �seeetchants below�.

Purpose ASTM Standard �See Section 12.4� MethodCase of coatingthickness/hardness,surface layersPerfect edge retention

B 487 C-56


E 112, E 930, E 1181, E 1382 C-56, T-56,El-17


Image analysis,rating of inclusioncontentHigh planeness

E 562, E 1245, E 1382 C-56, T-56


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-56, T-56,El-17

Microstructure E 3, E 407, E 562, E 883,E 1181, E 1245, E 1351, E 1382,E 1558

C-56, T-56,El-17



Sectioning


Mounting




6–10 min

Grinding

C-56: PG: For pure nickel and the most ductile alloys SiC paper grit P220/320should be used.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

Pure Ni and Ni-Cu alloys: T-56: P 3 can be followed by or replaced by a stepwith silica, see P 2 in Method C-56.C-56: P 2: Alumina 0.02/0.05 �m can be used instead of silica.T-56: In some cases FG 3 can be omitted.




Cloth,napless, soft,porous,syn



Dia, spr orsusp

Silica


P220 9 3 0.04/0.05


300/300 150/150 150/150 150/150




30 �7� 30 �7� 30 �7� 15 �3.3�

TimeMinutes


Traditional Method T-56 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType

SiC SiC SiC SiC SiC Dia,spr orsusp

Dia,spr orsusp

Dia,sprorsusp


P220 P320 P500 P1000 P1200 6 3 1

LubricantType

Water Water Water Water Water Alcoor wat

Alcoor wat

Alcoor wat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp Comp Comp Comp Comp Comp Comp Comp


25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 25 �5.7� 30 �7� 30 �7� 20 �4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4 3 1–2


EtchantsMaterial Etchants �see Table 12.2� UsesPure Ni andhigh Ni alloys

133, 134, 47, 135, 136, 25, 108, 31c General structure

137 Grain boundary sulfidationNi-Ag 38, 138, 50, 139 General structureNi-Al 50, 140, 141, 142, 89, 143 General structureNi-Cr 144, 50, 83, 134, 145,

98, 146, 147, 13aGeneral structure

Ni-Cu 38, 138, 50, 133, 140, 25,134, 47, 48b, 94, 108, 34

General structure

Ni-Fe 50, 140, 141, 83, 134, 148, 40,107, 149

General structure

74e, 25, 150 Orientation pittingNi-Mn 74e General structureNi-Mo 143 General structureNi-Ti 143, 151, 50, 133 General structureNi-Zn 152 General structureSuperalloys 94, 105, 138, 153, 12, 87, 89, 212,

226, 25, 94General structureGrain size

107, 111, 13a Reveals microstructuralinhomogneity

133 Grain boundary sulfidation154 Fine precipitation structure19b, 155, 156 Differential matrix and

nonmetallic staining22a For passive alloys �for

example, UNS Alloy N06625�157 Specific for UNS Alloys

N10004107 Submicroscopic structure in

aged super alloys particularlyfor electron microscopyStains the matrix when �precipitates are present

154 � banding18 Pre-etch activation for passive

specimens �electrolytic etchant�213 Colors carbide and �


Material/Preparation Tables 57Material: Pure palladium. Pd alloys. Pure platinum. Pt alloys.Pure iridium. Ir alloys. Pure osmium. Os alloys. Pure rhodium. Rhalloys. Pure ruthenium. Ru alloys

Material Properties: Palladium: Face-centered cubic, 12.16 g/cm3, 1553°C�2827°F�.Platinum: Face-centered cubic, 21.37 g/cm3, 1773.5°C �3224°F�.Iridium: Face-centered cubic, 22.42 g/cm3, 2350°C �4262°F�, HV 220.Osmium: Hexagonal, 22.48 g/cm3; 2700°C �4892°F�.Rhodium: Face-centered cubic, 12.5 g/cm3, 1985°C �3605 °F�, HV 122.Ruthenium: Hexagonal, 12.2 g/cm3, 2450°C �4442°F�.Comments on Material: The above-mentioned metals belong to the so-calledplatinum metals that belong to the precious metals with gold and silver. Platinumis used as base metal in a number of alloys used for jewelry and technicalpurposes. The other metals are to a high degree used as pure or as alloyingelements in materials for the electronics, medical, and other industries.Palladium and platinum are soft ductile metals, difficult to prepare because ofdeformation and smearing. Iridium and rhodium, and especially the hexagonalclose-packed ruthenium and osmium are harder and less difficult to prepare.Because of the high ductility, embedded abrasive grains in the specimen surface isa risk �see below�.No “contemporary” method is available for these metals, and C-57 is a variation ofT-57. In case of harder alloys the C-methods, C-51 �se also Grinding below� andC-58 may be used.Sectioning: Because of the high price of the platinum metals, the wet abrasivecutting should be with a thin cut-off wheel to reduce the kerf loss. Cutting is bestdone on a precision cut-off machine using SiC bakelite bond cut-off wheels0.5 mm �0.02 in� thick with efficient cooling. In the case of examinations ofcoatings, the cutting should be done correctly �see Material/Preparation Tables08–10�. Also, it can be of advantage to mount the specimen in epoxy before cuttingto stabilize the coating �see below�. If using shearing, the strong deformation ofthe edge should be taken care of when plane grinding the specimen.Mounting: Hot and cold mounting can be used. If coatings should be examinedthe correct hot mounting material, with a filler, should be used. Also coldmounting with epoxy may be satisfactory �see Sections 3.1.3 and 3.11�.Grinding: If following a proper cutting, grit P220 grinding paper should beavoided, starting with grit P320. It is important that all deformation from theprevious step is removed. Wax can be used to reduce the aggressiveness of the SiCpaper, or the paper can be “dulled” by grinding a hard material in 1–5 s beforeuse. In the case of embedded SiC grains in the specimen surface, use Method C-51or C-58 to reduce the use of SiC grinding paper. To avoid embedded abrasivegrains �see Section 13.6.4�, a softer grinding/polishing surface should be used. Inthe case of embedded grains the FG 2 step of Method C-51 or the FG 3 step ofC-58 can be changed to a hard, nonwoven, synthetic cloth. Also diamond paste canbe used to improve the fixation of the diamond grains.


Polishing: Methods C-57 and T-57 both use diamond for the last polishing step.For use of silica for the last step see Methods C-51 and C-58.For chemical mechanical polishing �etch-polishing� of ruthenium and osmiumalloys see Etchants below.Etching: See below.


B 487 C-57


E 112, E 930, E 1181, E 1382 C-57, T-57


E 562, E 1245, E 1382 C-57, T-57


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-57, T-57


C-57, T-57



Sectioning


Mounting


Resin Bakelite ColdMounting

Resin Acrylics/epoxyTimeMinutes


6–10 min/6–8 h

Grinding

See above.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-57: For pure metals use wat-oil lubricant in P 1 and P 2.T-57: P 2: This step can be changed to P 3 in C-57.



PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3

Disk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia,sprorsusp

Dia,sprorsusp


P220 P320 P500 P1200 P2400 6 1 0.25

LubricantType


Alco orwat

Wat-oil

RotationDisk/Holder

300/150

300/150

300/150

150/150

150/150

150/150

150/150

150/150

rpm/rpmComp/Contra

Comporcontra

Conmporcontra



15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15 �3.4–4.5�

10–15�2.3–3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4 2 1–2

Traditional Method T-57 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/Polishing

PG FG 1 FG 2 FG 3 FG 4 P 1 P 2

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper

Cloth,napless,med hard,wov,wool

Cloth,mednap,soft, syn


Dia, spror susp


P320 P500 P1000 P2400 P4000 3 1

Lubricant Type Water Water Water Water Water Wat-oil Wat-oil


RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


orcontra



15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

10–15�2.3–3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4 2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Pd 61, 166, 62, 165a General structurePd alloys 166, 64a, 62, 165a General structure�90% noble metals 61 General structure�90 % noble metals 65 General structurePure Pt 64a, 73a General structure

167 Electrolytic polish and etchPt alloys 64b, 73a General structure�90 % noble metals 61 General structure�90 % noble metals 65 General structurePt-10 % Rh 168 General structureOs base 165a General structure

165a Etch-polish for viewing grainsfor polarized light

Rh base 171 General structureRu base 73b General structure

73b Etch-polish for viewing grainsfor polarized light

Material/Preparation Tables 58Material: Silver. Ag alloys

Material Properties: Silver: Face-centered cubic, 10.5 g/cm3, 961°C �1762°F�, HV25.Comments on Material: Silver is used for jewelry and in the electronics andchemical industries. Pure silver, like the other precious metals �see Material/Preparation Tables 51 and 52�, is soft and ductile and therefore has a strongtendency to deformation and smearing during the preparation. Also, abrasivegrains can be embedded in the specimen surface �see Section 13.6.4�. Silver alloys,like Ag-Cu, Ag-Pd, and Ag solders are harder and therefore easier to prepare. Oftensilver is used as a coating and if this coating should be examined the methodsstated in Material/Preparation Tables 08–10 may be used.


Sectioning: Because of the relatively high price of silver, the wet abrasive cuttingshould be with a thin cut-off wheel to reduce the kerf loss. Cutting is best done ona precision cut-off machine using SiC bakelite bond cut-off wheels 0.5 mm�0.02 in� thick with an effective cooling. In the case of examination of coatings, thecutting should be done correctly �see Material/Preparation Tables 08–10�. Also, itcan be of advantage to mount the specimen in epoxy before cutting to stabilize thecoating �see below�. If using shearing, the strong deformation of the edge shouldbe taken care of when plane grinding the specimen.Mounting: Hot and cold mounting can be used. If coatings should be examined,the correct hot mounting material,with a filler, should be used. Also, coldmounting with epoxy may be satisfactory �see Sections 3.1.3 and 3.11�.Grinding: If following a proper cutting, grit P220 grinding paper should beavoided, starting with grit P320. Wax can be used to reduce the aggressiveness ofthe SiC paper, or the paper can be “dulled” by grinding a hard material in 1–5 sbefore use. It is important that all deformation from the previous step is removed.In the case of embedded SiC grains in the specimen surface, use Method C-58. Toavoid embedded abrasive grains �see Section 13.6.4�, a softer grinding/polishing-surface should be used. For this reason the FG 3 step of Method C-58can be changed to a hard, nonwoven, synthetic cloth and possibly the FG 2 stepcan be omitted. Also diamond paste, fixing the grains in the cloth, can be used. Asan alternative to C-58, Method C-51 for gold can be used.Polishing: For pure silver and alloys with a high content of silver, chemicalmechanical polishing can be used for the last polishing step �see below�.Electrolytic polishing can be used for pure silver and certain alloys.Etching: See Etchants below.


B 487 C-58


E 112, E 930, E 1181, E 1382 C-58, T-58,El-18

Image analysis, ratingof inclusioncontent

E 562, E 1245, E 1382 C-58, T-58


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-58, T-58

Microstructure E 3, E 407, E 562, E 883,E 1181, E 1245, E 1351, E 1382, E 1558

C-58, T-58,El-18




Sectioning


Mounting


Resin Bakelite orbakelite w. filler

ColdMounting


TimeMinutes


6–10 min/6–8 h

Grinding

See above.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-58: P 2: Chemical mechanical polishing of silver alloys can be done by addinga solution of 25 mL distilled water, 25 mL ammonia solution �32 %� and10–20 mL hydrogen peroxide �30 %� to 1000 mL of colloidal silica.C-58: P 2: This step can be changed to P 2 from Method T-58.


PG FG 1 FG 2 FG 3 P 1 P 2

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

RCD,soft



Abrasive Type SiC SiC SiC Dia, spror susp

Dia, spror susp

Silica, seenote above

Grit/GrainSize �m

P220 P320 P500 9 3 0.04/0.05


Wat-oil

Rotation Disk/Holder 300/150 300/150 150/150 150/150 150/150 150/150rpm/rpm


Comp/Contra

Comporcontra



20 �4.5� 20 �4.5� 20 �4.5� 25 �5.7� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 5 5 1


PG FG 1 FG 2 FG 3 FG 4 P 1 P 2

Disk/Cloth SiCpaper

SiCpaper

SiC paper SiCpaper

SiCpaper

Cloth,napless,med hard,wov,wool


AbrasiveType


Dia,sprorsusp


320 500 1000 2400 4000 3 0.25

LubricantType


RotationDisk/Holder

300/150 300/150 300/150 300/150 300/150 150/150 150/150

rpm/rpmComp/Contra

Comporcontra



15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

15–20�3.4–4.5�

10–15�2.3–3.4�

TimeMinutes

Untilplane

0.5 0.5 0.5 1 4 2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Ag 172 173, 62 General structureAg alloys 65, 61, 174, 175, 62 General structureAg-Cu alloys 130 General structureAg-Pd alloys 173 General structure


Ag solders 173, 176 General structure

Material/Preparation Tables 59Material: Tin, Sn bearing alloys and other Sn alloys

Material Properties: Body-centered tetragonal ��13.2°C �56°F��, 7.29 g/cm3,232°C �450°F�, �HV 25.Tin bearing alloys: 7 to 8 % antimony, 0.5 % lead, 3 to 4 % copper, iron, arsenic,bismuth, zinc, aluminum.Other tin alloys: Tin-lead, tin-copper, tin-zinc �weight %�.Comments on Material: Pure tin is a soft metal, with a recrystallizationtemperature close to room temperature. Pure tin is often used for coating toobtain a reduced corrosion �tinned steel plate� and on electric parts to makesoldering easier. Tin-lead alloys are used for solders and tin-antimony alloys forbearing materials.Tin and tin alloys being soft and having a low recrystallization temperature makesthe preparation very difficult, and all steps in the preparation process must beperformed with great care. For the softest alloys use Method T-59.Sectioning: Abrasive wet cutting of pure tin and tin alloys can be done with a thinSiC bakelite cut-off wheel, preferably on a precision cutting machine with anefficient cooling. Pure tin also can be cut by using a sharp knife or with a bandsaw or hand saw with fine teeth. In the case of sawing the very deformed zonemust be carefully removed during grinding. For cutting of tinned steel plate, seeMaterial/Preparation Tables 08.Mounting: As a rule pure tin and tin alloys should not be hot mounted, bothbecause of the low recrystallization temperature and because of voids and pores inthe alloys which possibly may collapse under the high pressure of hot mounting.To obtain the lowest possible temperature during cold mounting, epoxy with a lowpeak temperature should be used �see Section 3.8.3�. In the case of examination ofthin coatings see Material/Preparation Tables 08–10.Grinding: To minimize the risk of embedded SiC grains in the specimen surface,the grinding paper can be treated with wax and a low pressure is used. For watersensitive alloys paraffin �kerosene� can be used instead of water.Polishing: It is important that the deformation from the grinding is removedduring the rough polishing step. Chemical mechanical polishing can be used at thelast step �see below�. For pure tin and certain alloys, the specimen surface can be“cleaned” by electrolytic “shock-polishing,” using Method El-19 in only 1–2 s. Tinand some tin alloys are suited for electrolytical polishing.Water sensitive alloys: use water-free lubricants and clean between steps withoutwater �see below�.Etching: See Etchants below.



B 487 C-59


E 112, E 930, E 1181, E 1382 C-59, T-59,El-19


E 562, E 1245, E 1382 C-59, T-59


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-59, T-59


C-59, T-59,El-19



Sectioning

Cut-Off Wheel SiC bakelite bond cut-off wheel, 0.5 mm �0.02 in�thick, low speed, very careful �see also above�

Mounting


Resin Cold Mounting Resin Epoxy, lowestpossible peaktemp.

TimeMinutes

TimeMinutes/Hours

12–24 h

Grinding

T-59: The cutting action of SiC papers P1000 and P1200 can be reduced by usingwax before grinding, or making the paper “dull” by first grinding a hard materialin 10 s.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-59 and T-59: P 3: Mix 96 mL of colloidal silica with 2 mL ammonia �25 %�and 2 mL of hydrogen peroxide �30 %�.


T-59: P 1: This step can be changed to a step like FG 4, only with SiC paper gritP4000.C-59 and T-59: To remove deformed layers and scratches, electrolytic polishingin a short time, 1–2 s �shock-polishing�, can be recommended to follow the P 3step �see Method El-19�.Water sensitive alloys: C-59: The step P 1 can be omitted and the step P 3 ischanged to a diamond step like P 2 in Method T-57 using a water-free lubricant.


PG FG 1 P 1 P 2 P 3

Disk/Cloth SiCpaper

RCD,soft


Cloth, nap-less, medhard, wov,wool

Cloth, napless,soft, porous,syn

AbrasiveType

SiC Dia, spror susp

Dia, spror susp

Dia, spror susp

Silica


320 9 6 3 0.04/0.05

LubricantType

Water Alco or wat Alco orwat

Wat-oil

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150


20 �4.5� 25 �5.5� 25 �5.5� 25 �5.5� 10–15�2.3–3.3�

TimeMinutes



PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia,sprorsusp

Silica



P220 P320 P500 P1000 P1200 6 3 0.04/0.05

LubricantType

Water Water Water Water Water Alcoorwat

Wat-oil

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra



20�4.5�

20�4.5�

20�4.5�

20�4.5�

20�4.5�

20�4.5�

25�5.5�

15–20�3.3–4.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 5 5 1–2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Sn 74d, 180, 151 General structure

181 Grain boundariesSn-Cd 74d General structureSn-Fe 74d, 177a General structureSn-Pb 182, 183, 74b General structure

116 Darkens Pb in Sn Pbeutectic

Sn coatings on steel 183 General structureBabbitts 184 General structureSn-Sb-Cu 74b General structure

Material/Preparation Tables 60Material: Titanium and Ti alloys

Material Properties:Titanium: �allotropic: more than one crystallographic form�: �-titanium:Close-packed hexagonal, -titanium: Body-centered cubic, 4.5 g/cm3, 1670°C�3038°F�, HB 70.Titanium alloys: � alloys: Alloying elements: Aluminum, gallium, germanium,carbon, oxygen, and nitrogen. alloys: Alloying elements: �Isomorphous group�:Molybdenum, vanadium, tantalum, and niobium. �Group forming eutectoidsystems�: Manganese, iron, chromium, cobalt, nickel, copper, and silicon.


Comments on Material: Titanium is a relatively new metal that is expensive toproduce, but nevertheless is gaining ground for applications in the aerospacechemical, and medico-technical industries. Titanium has a high strength to weightratio, and it has a self-healing oxide layer that provides an effective barrier againstincipient corrosion. Commercial titanium grades and alloys are divided into fourgroups: 1� commercially pure titanium, 2� � and near � alloys such asTi-6Al-2Sn-4Zr-2Mo, 3� �- alloys like Ti-6Al-4V, and 4� alloys that have a highcontent of vanadium, chromium, and molybdenum.Commercially pure titanium and most of the alloys are soft and ductile with a lowmachinability, difficult to prepare because of development of a deformed layer.Also, titanium can be sensitive to hydrogen and high temperatures during thepreparation. Heat-treated alloys are harder and consequently easier to prepare.Sectioning: Due to the high ductility and toughness of titanium it has lowmachinability. Consequently it can be very difficult to cut with wet abrasive cuttingusing the standard cut-off wheels because the edge will clog-up with abradedmaterial.Titanium should be cut with a special SiC, bakelite bond wheel with a strong flowof cooling fluid to obtain a cool and burr-free cut. Sectioning with a shear or witha band saw cannot be recommended, but if they are used, care should be takenwith prolonged plane grinding to remove the heavy deformation �cold work�developed during cutting.Mounting: Generally hot and cold mounting can be used. Because of the lowmachinability of titanium a mounting material with a high wear resistance shouldbe used �see Section 3.1.3�. Still it can be experienced that the mounting materialis removed at a much higher rate than the sample. This can be dampened byplacing two or more samples in the same mount, not only one in the center of themount.If the specimen should be etched with a strong etchant, a mounting material witha high chemical resistance should be used. In the case of examination of surfacelayers, special mounting materials should be used �see Material/Preparation Tables08–10�. If the examination involves the hydride phase, it may be of advantage toleave the specimen unmounted or use an epoxy which cures slowly at atemperature not much above room temperature.Grinding: As rough SiC papers will leave deep deformation in the specimen, theplane grinding should be performed with the finest grinding paper possible. Plentyof water should be used. In the two methods below grit 220 is stated for planegrinding, but if the sectioned surface is not very rough, grit 320 should bepreferred. New papers should be used. Often the paper can only be used in20–25 s to avoid smearing and development of cold work.Polishing: Using finer and finer diamond grades as is normally done developsdeformed layers in titanium, very difficult to remove. Therefore, the deformationfrom the grinding is removed by chemical mechanical polishing �see below�.Both pure titanium and a number of alloys can be electrolytically polished.Etching: A microstructure of titanium can be examined in polarized light withoutetching. For Etchants, see below.



B 487 C-60


E 112, E 930, E 1181, E 1382 C-60, T-60,El-20

Heat treatment C-60, T-60Image analysis,rating of inclusioncontentHigh planeness

E 562, E 1245, E 1382 C-60


E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-60, T-60


C-60, T-60,El-20



Sectioning

Cut-Off Wheel SiC, bakelite bond, specially developed for titanium

Mounting


Resin Bakelite/Epoxywith Filler

ColdMounting

Resin Epoxy

TimeMinutes


8–24 h

Grinding

C-60 and T-60: Use a grit 320 grinding paper for the PG step if possible, for puretitanium and soft alloys.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-60: For the step P 1 use one of the following solutions: 90 mL silica with10 mL hydrogen peroxide �30 %� or 96 mL silica, 2 mL hydrogen peroxide �30 %�and 2 mL ammonia solution �25 %�.


T-60: For the steps P 1, P 2, and P 3 use the solution: 260 mL silica, 40 mLhydrogen peroxide �30 %�, 1 mL nitric acid �65 %� and 0.5 mL hydrofluoric acid�40 %�.

Contemporary Method C-60 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1PolishingDisk/Cloth SiC paper RCD, soft Cloth, napless,

soft,porous,syn

Abrasive Type SiC Dia, spr or susp Silica,see note above


220 9 0.04/0.05

Lubricant Type Water Alco or watRotationDisk/Holder

300/150 150/150 150/150

rpm/rpmComp/Contra Comp or Contra Comp ContraForce perSpecimenN �lb�

25 �5.7� 30 �7� 20–30 �5.7–6.6�

TimeMinutes

Until plane 5 8–10


paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType

SiC SiC SiC SiC Silica,seenoteabove

Silica,seenoteabove

Silica,seenoteabove


P220 P320 P500 P1200 0.04/0.05 0.04/0.05 0.04/0.05

LubricantType

Water Water Water Water


RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


orcontra

Comporcontra

Comporcontra

Comp Contra Contra Contra


20�4.5�

20�4.5�

20�4.5�

20�4.5�

35 �8� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.25–1 0.25–1 0.25–1 10 2 2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Ti 186, 187, 67, 68, 69, 217 General structure

188 Removes stain72 Chemical polish and etch

Ti-5Al-2.5Sn 189 Reveals hydridesTi-6Al-6V-2Sn 190 Stains alpha and transformed

beta, retained beta remainswhite

Ti-Al-Zr 191 General structureTi-8Mn 192 General structureTi-13V-11Cr-3Al �aged� 192 General structureTi Si 193 General structureTi alloys 186, 187, 192, 194, 158,

132b, 1c, 67, 68, 69, 3a, 218General structure

11, 1c Reveals alpha case72, 192, 178 Chemical polish and etch170a Outlines and darkens hydrides

in some alloys188 Removes stain

Material/Preparation Tables 61Material: Zinc and Zn alloys

Material Properties: Zinc: Close-packed hexagonal, 7.14 g/cm3, 419°C �786°F�.Zinc alloys: Zn is mainly alloyed with aluminum, 1 to 15 % and copper up to 4 %.Other alloying elements are lead, cadmium, iron, titanium, magnesium, and tin�weight %�.Comments on Material: Zinc is to a high degree used for die-casting and forcoating of steel sheet �see Material/Preparation Tables 08–10�.Zinc is very difficult to prepare because of the tendency to form layers of plasticdeformation with smearing and twins when being ground and polished. Also,embedding of abrasive grains during grinding and polishing is a risk.


Sectioning: Abrasive wet cutting of pure zinc and zinc alloys can be done with athin SiC bakelite cut-off wheel, preferably on a precision cutting machine with anefficient cooling. Zinc also can be cut by shearing or with a band saw or hand sawwith fine teeth. In the case of shearing and sawing the very deformed zone mustbe carefully removed during grinding. For cutting of zinc coated steel sheet, seeMaterial/Preparation Tables 08–10.Mounting: Cold mounting should be preferred because hot compression mountingmay cause deformation and recrystallization in the material. In the case ofmounting of zinc coated steel sheet, see Material/Preparation Tables 08–10.Grinding: If the sectioned surface is not very rough, plane grinding should bedone with grit 320 SiC grinding paper. To minimize the risk of embedded SiCgrains in the specimen surface, the grinding paper can be treated with wax and alow pressure is used. Also, paraffin can be used instead of water. For pure zinc itcan be of advantage to extend the time for the last FG steps to ensure thatdeformation from earlier steps is removed.Polishing: Only use a polishing cloth for zinc, do not mix with copper or lead. Itis important that the deformation from the grinding is removed during the P 1polishing step. Pure zinc and some zinc alloys are suited for electrolytic polishing.Cleaning: Avoid water for cleaning between the polishing steps; use alcohol forcleaning and finish the polishing with a very brief polish with pure alcoholfollowed by rinsing and drying.Etching: A microstructure of zinc can be examined in polarized light withoutetching. For Etchants, see below.


B 487 C-61

Grain size, grain boundaries E 112, E 930, E 1181, E 1382 C-61, T-61,El-23

Heat treatment C-61, T-61Image analysis, rating ofinclusion content

E 562, E 1245, E 1382 C-61


E 110, E 140, E 384,E 448

C-61, T-61

Microstructure E 3, E 407, E 562, E 883,E 1183, E 1245, E1351, E 1382, E 1558

C-61, T-61,El-23




Cut-Off Wheel SiC bakelite bond, thin wheel

Mounting




6–10 min

Grinding

T-61: Cutting action of SiC papers can be dampened with wax. If possible, usegrit P320 for the PG step.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-61: In some cases P 2 can be omitted. Also, the cloth in P 2 can be changed toa medium nap, soft, synthetic.T-61: A step like P 2 in Method T-57 can be added between steps P 1 and P 2.Cleaning: Avoid water for cleaning between polishing steps, use alcohol forcleaning and finish the polishing with a very brief polish with pure alcoholfollowed by rinsing and drying.

Contemporary Method C-61 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperRCD,soft





Dia, spror susp

Dia, spror susp

Silica

Grit/GrainSize �m

P320 9 3 1 0.04/0.05

Lubricant Type Water Alco or wat Wat-oil Alco or watRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra Comp Comp Comp Comp Contra



25 �5.7� 30 �7� 25 �5.7� 20 �4.5� 10–15�2.2–3.3�

TimeMinutes

Untilplane

4 4–6 3–5 1–2

Traditional Method T-61 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2Polishing

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

SiCpaper

Cloth,napless,medhard,wov, wool



Silica


P220 P320 P500 P1200 3 0.04/0.05

Lubricant Type Water Water Water Water Wat-oilRotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra

Comp Comp Contra


20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 1–2 1–2 4–6 1–2

EtchantsMaterial Etchants �see Table 12.2� UsesPure Zn 200a General structureZn-Co 177 General structureZn-Cu 201 General structure

203 Distinguishes gamma ��and epsilon ��

Zn-Fe 74a Structure of galvanized sheetDie castings 202 General structure


Material/Preparation Tables 62Material: Zirconium. Zr alloys. Zircalloy. Hafnium. Hf alloys

Material Properties: Zirconium: Close-packed hexagonal, 7.14 g/cm3, 1490°C�2714°F�.Hafnium: Close-packed hexagonal, 13.3 g/cm3, 1700°C �3092°F�. Zircalloy:Zirconium with tin, oxide, iron, chromium, and nickel.Comments on Material: Pure zirconium and zircalloy are mainly used forcladding of uranium fuel elements for nuclear power plants. Hafnium also is usedin the nuclear reactors. Both pure zirconium and hafnium are soft and ductile,difficult to prepare, they deform easily and mechanical twinning may develop. Alsothe machineability is low.Sectioning: Sectioning should take place with great care to avoid excessivedeformation. Wet abrasive cutting can be done with an SiC bakelite bond cut-offwheel. Preferably the cutting should take place with a precision cut-off machineusing a thin wheel �0.5 mm �0.02 in��. It is important that the cooling is veryefficient so that over-heating is avoided. If shearing or band sawing is used, planegrinding should be extended to remove the strong deformation caused by thesecutting methods.Mounting: Hot mounting and cold mounting can be used. If the specimen is to bestudied for hydrogen content, or in the case of a risk for mechanical twinning bythe pressure at hot mounting, cold mounting should be preferred. As the specimenmay be attacked by rather strong acids for chemical mechanical polishing andetching, a mounting material with good chemical resistance, like epoxy, should beused �see Sections 3.6.1 and 3.13.1�.Grinding: To avoid excessive deformation, the plane grinding should preferably bedone with a grit P320 grinding paper. The grinding should always be wet becauseZr and Hf dust may generate fire. The cutting action of the finer grinding papersmay be dampened with wax.Polishing: To obtain a surface free from deformation, the final mechanicalpolishing step can be turned into chemical mechanical polishing. The chemicalsolutions contain strong acids and precautions should be taken to avoid attack ofthe grinding/polishing disk and the machine �see below�. In the case of hardparticles in the specimen surface, use Method C-62 to avoid relief. For pure metalsuse Method T-62 because SiC paper has a better cutting action than diamond.Etching: Both zirconium and hafnium can be examined in polarized light. ForEtchants, see below.



B 487 C-62

Perfect edge retentionGrain size,grainboundaries

E 112, E 930,E 1181, E 1382

C-62, T-62,El-24�Zirconium�,El-11�Hafnium�

Heattreatment

C-62, T-62


E 562, E 1245,E 1382

C-62

HighplanenessMicro-hardness,hardness

E 10, E 18, E 92, E 103,E 110, E 140, E 384, E 448

C-62, T-62

Micro-structure

E 3, E 407,E 562, E 883,E 1181, E 1245, E 1351,E 1382, E 1558

C-62, T-62,El-24�Zirconium�,El-11�Hafnium�

Phaseidentification

C-62, T-62,El-24�Zirconium�El-11�Hafnium�

Preparation Process

Sectioning

Cut-Off Wheel SiC bakelite bond, a thin wheel

Mounting


Resin Bakelite/Epoxy ColdMounting


TimeMinutes


6–10 min/6–8 h


Grinding

C-62 and T-62: Avoid grit P220 if possible for PG.T-62: The cutting action of the SiC papers can be damped with wax.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-62 and T-62: The step P 2: A chemical mechanical polishing can be obtainedby using 96 mL colloidal silica with 2 mL hydrogen peroxide �30 %� and 2 mLammonia solution �25 %� or 95 mL colloidal silica with 5 mL chromium trioxidesolution �20 g CrO3 to 100 mL distilled water�. Another solution is 75 mLdistilled water, 10 g oxalic acid, 5 mL acetic acid �glacial�, 6 mL nitric acid �70%� and 2 mL hydrofluoric acid �48–52 %� �Caution!�. One part of the solution ismixed with four parts of silica for the purer zirconium materials and 1 to 1 forzircalloys and hafnium materials.Also, a mixture of 90 mL colloidal silica and 10 mL of hydrogen peroxide �30 %�can be used. Zirconium can be electropolished with Method El-24 and hafniumwith El-11.

Contemporary Method C-62 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 P 1 P 2PolishingDisk/Cloth SiC paper RCD,

softCloth, napless,hard, wov, syn

Cloth, naplesssoft, porous, syn

AbrasiveType

SiC Dia, spr or susp Dia, spr orsusp

Silica, see noteabove

Grit/GrainSize �m

P320 9 3 0.04/0.05


300/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp or contra Comp Comp Contra


20 �4.5� 30 �7� 25 �5.5� 15 �3.3�

TimeMinutes



Traditional Method T-62 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiC paper Cloth,napless,hard,wov, silk


AbrasiveType


Silicasee noteabove


P320 P500 P1200 P2400 P4000 3 0.04/0.05

LubricantType


RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 20 �4.3� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4–6 3–10

EtchantsMaterial Etchants �see Table 12.2� UsesZr base 66, 67, 204, 68, 69, 205 General structure

206 Electrolytic polish and etch71 Grain structure under polarized light72 Chemical polish and etch

Material/Preparation Tables 63Material: Bones. Carbon. Coal. Graphite. Paper. Teeth. Tissue.Wood. Other organic materials

Comments on Material: Common to the preparation of organic materials is thegrinding steps on SiC grinding paper to the finest grit. For this reason no“contemporary” method is developed, and both Methods C-63 and T-63 statedbelow are “ traditional” methods. Often organic materials, having pores, cracks,and voids should be impregnated to obtain a surface that can be satisfactorilyprepared �see below�.


Sectioning: Many organic materials like paper and wood can be cut with a scissoror a fine toothed saw. Other materials like teeth, bones, and coal should be cut ona precision cut-off machine with a thin cut-off wheel, either with SiC bakelitebond, diamond in a metal bond, or with fine teeth. In some cases the materialshould be impregnated before cutting �see below�. For some materials like coal,the selected sample is crushed and the particles are mounted in a transparentmounting material �see Section 3.11.4�.Mounting: Often the material contains pores, cracks, and cavities, or it is verybrittle. In this case a vacuum impregnation with epoxy should be done �seeSection 3.10�. An example of an organic material, difficult to prepare withoutimpregnation is paper. It is important that the paper fibers are totally wetted. Thisis done with an epoxy with a low viscosity, which, to obtain the best wetting, isthinned with acetone or another thinner. A method is to briefly soak the paperspecimen in acetone to wet it, soak the specimen in a 50 % acetone/epoxy mixturefor several minutes with abundant stirring. Then transfer the specimen to a 10 %acetone/90 % epoxy mixture for several minutes, followed by transfer to a bathwith 100 % epoxy for several minutes and finally transfer to a second bath of 100% epoxy in the mounting cup in which the specimen should be hardened. Severalspecimens can be mounted in the same mounting cup, using clips to keep thespecimens upright and separated.Grinding: In the two methods stated below grinding to P4000 is stated. For somematerials the steps FG 3 and FG 4 can be omitted.Polishing: Diamond polishing generally is not suited for organic materials;therefore, diamond is only used for one polishing step in Method T-63. Thepolishing step, with silica in Method C-63 can vary considerably in time,depending on the material being prepared.Etching: Normally no etching is done.


C-63, T-63


C-63, T-63


C-63, T-63

High planenessMicrohardness, hardness E 384 C-63, T-63Microstructure E 883 C-63, T-63Phase identification C-63, T-63



Sectioning

Cut-Off Wheel Thin wheel, SiC bakelite bond or diamond with metalbond or with fine teeth

Mounting


Resin Cold Mounting Resin Epoxy/AcrylicsTimeMinutes

TimeMinutes/Hours

6–12 h/6–10 min

Grinding

C-63, T-63: Carbon and similar materials: Step FG 3 and FG 4 can be omitted,when followed by a step with 3 �m diamond �see below�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded trued.

Polishing

Carbon and similar materials and paper: C-63 and T-63: Establish a P 1 stepwith a napless, hard cloth with 3 �m diamond, see step P 1 in Method C-62,followed by P 1 in C-63 or T-63. To improve planeness a napless, hard, wov, silkcloth can be used in P 1 of T-63, possibly followed by P 1 in C-63.Bones and teeth: T-63: The step P 1 from Method C-64 can be added as finalstep.Paper: C-63: The step FG 4 can be changed to the step P 1 in Method C-62 usingwat-oil lubricant.

Contemporary Method C-63 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper

SiCpaper


Abrasive Type SiC SiC SiC SiC SiC SilicaGrit or GrainSize �m

P320 P500 P1200 P2400 P4000 0.04/0.05

Lubricant Type Water Water Water Water WaterRotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150





30 �7� 30 �7� 30 �7� 20 �4.3� 20 �4.3� 10 �2.2�

TimeMinutes

Untilplane

2 2 2 1–2 1–10

Traditional Method T-63 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1PolishingDisk/Cloth SiC paper SiC paper SiC paper SiC paper SiC paper Cloth,

med nap,soft, syn



P320 P500 P1200 P2400 P4000 1

Lubricant Type Water Water Water Water Water Wat-oilRotationalDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150


contraComp Comp Comp Comp Comp


30 �7� 30 �7� 30 �7� 20 �4.3� 20 �4.3� 15 �3.4�

TimeMinutes

Untilplane

2 2 2 1–2 1–6

Material/Preparation Tables 64Material: EPDM polymers. Silicone. Other elastomers.Polypropylene „PP…. Polystyrene „PS…. Polyvinylchloride „PVC….Other thermoplastics

Comments on Material: Plastics and polymers cover a very wide range ofmaterials with different characteristics, rigid, semi-rigid, and nonrigid. The plasticsand polymers are classified in ASTM Classification System for Specifying PlasticMaterials �D 4000�.


A basic reason for making materialographic examinations of plastics and polymersis to gain a more complete understanding of the relationships between themanufacturing processes, the microstructure and texture of the material, and theproduct’s performance. The microstructures of plastics and polymers visible in thelight microscope are affected to a considerably greater extent by their chemicalcomposition and method of production than is the case with metals.Plastics and polymers can be examined in different ways, as cross sections�polished� in reflected light, or as thin sections and microtome sections intransmitted light �see Section 7.13�. The cross sections can be prepared bygrinding and polishing and by ultramilling; only the preparation by grinding andpolishing is described below.Plastics and polymers are normally soft and very often the material is sensitive toheat and possibly also to the type of cooling fluid used during the preparation. It isimportant that the correct fluid is used in sufficient amounts both at sectioning,grinding, and polishing to avoid thermal damage. Heat developed may cause asoftening of the material resulting in embedding of abrasive grains in thespecimen surface. It can be advised to test the cooling fluids �water, alcohol, etc.�and mounting material �acrylics, etc.� on the specimen material before thepreparation to check the resistance of the material.The preparation of plastics and polymers is described in the ASTM StandardGuide for Preparation of Plastics and Polymeric Specimens for MicrostructuralExamination �E 2015�.No “contemporary method” is developed for these materials, so Method C-64below is a variant of the “traditional method,” T-64 by Trempler, Ref. 40, �Part I�.Also, Methods C-65 and T-65 can be used for these materials. For furtherinformation on preparation of plastics and polymers see Refs. 40 and 41, �Part I�.Sectioning: Selection: The selection of the test specimen is extremely importantand dependent upon the purpose of the examination, the material, and themicroscopical technique to be used. It should be decided whether the specimenshould be taken as a cross section, longitudinal, or inclined. The selection criteriamust include the following considerations: The size and scale of homogeneity/heterogeneity of all structures, textures, and other features within the work piecebeing studied, the size or scale and distribution of the structures to be studied,and the need for control/reference specimens. In general, sectioning shouldproduce a flat, relatively damage-free surface near to the region of interest.Depending on the type of material, the sectioning can be made by cutting with asharp knife, a pair of scissors or a scalpel. This technique will introduce a strain�typically dominated by ductile deformation� in the region near the cut face. Thewidth of the strain region can be minimized by properly securing the specimenduring cutting, using a sharp instrument, making the cut with uniform speed andforce, and making the cut at the appropriate temperature �often below roomtemperature�. The cut face from a �cryogenically� microtomed specimen is oftenready for microstructural examination with minimal final polishing or withoutadditional preparation. Sawing either manually or by precision cut-off machinecan be done with a sharp, fine short-toothed saw blade with an efficient cooling.The surface after sawing is rather rough and the region with nonuniform strainmust be removed by the following grinding and polishing. Also, wet abrasivecutting with a precision cut-off machine using a wheel with electroplated


diamonds or an abrasive wheel with SiC in a bakelite bond may be used. Abrasivewheels tend to clog when cutting certain materials and a diamond wheel should bepreferred, using a low feed rate. The cutting should take place with an efficientcooling using a cooling fluid which is nonreactive with the specimen material.Often small specimens or parts, or both, with the plane of interest not parallel to aflat surface may require mounting prior to sectioning to facilitate sectioning of thespecimen parallel to the desired plane to be polished. Also, laminated, friable, orvery ductile materials may be mounted prior to sectioning to minimize damageduring the process.Mounting: The specimen can be clamped between plates of the same or similartype of material as the specimen. Also, the specimen can be cold mounted using amounting material that does not react with the specimen material, and generallywith a peak temperature sufficiently below the softening temperature of thespecimen material. The softening temperature being in the range from70 to 125°C �158 to 257°F� for most plastics and polymers limits the use of coldmounting materials to acrylics having a peak temperature of 90°C �194°F� andslow curing epoxy with a peak temperature of 30 to 60°C �86 to 140°F�. It can berecommended to work with a temperature not above 40°C �104°F�. This limits thecold mounting material to a slow curing epoxy that also can be used for vacuumimpregnation in case of porous or cracked specimen materials �see Section 3.10�.To discriminate between the mounting material and the specimen material, theepoxy should be added to a dye. To slow down the curing to keep the temperaturelow, the smallest amount of mounting material should be used, and curing cantake place in a refrigerator. Also, cooling can be obtained by placing metal heatsinks into or around the mount. In the case of the mounting of small parts,powder or particles, see Section 3.11. In the case of a very sensitive specimenmaterial, the specimen can be sputter coated with a 20 to 60 nm thick metal filmof gold or gold/palladium to form a barrier towards the mounting material. Also, a�100 nm film will make a good contrast between the specimen-mounting material.In the case of examination of materials with hard fibers an acrylic mountingmaterial with a filler should be used.Hot mounting cannot be recommended for plastics and polymers because of thehigh temperatures and high pressure.

Grinding: In Methods C-64 and T-64 four grinding steps are indicated, but oftenthe step FG 4 and in fewer cases both FG 3 and FG 4 can be omitted. The force onthe specimens should be low and the rotational speed of the grinding/polishingwheel should not be higher than indicated in the methods. The specimen surfaceshould be inspected after every 15 to 30 s of grinding to ensure that materialremoval does not go beyond the area of interest; this is especially important atmounted and impregnated specimens. Water is normally used as cooling fluid andthe cooling must be effective. In case the specimen material reacts with water,another fluid must be chosen.Perfluorinated liquids, such as those used as diffusion pump oil or as coolingliquids for active electronic circuits, are often appropriate for use withwater-soluble plastics and polymers. In the case of embedded SiC grains, use morecooling fluid, lower the force on the specimen and briefly move a blind specimenacross the new grinding paper before it is used for the specimens.


Polishing: When using the grinding papers grit P2400 and P4000 as indicated inMethods C-64 and T-64, the rough polishing, step P 1, can be done with 3 �mdiamond. It is important to ensure a good cooling during the polishing. Use water,or in special cases glycerol, as lubricant. Care must be taken not to embed theabrasive in the specimen which can easily occur with softer plastics and polymers.The use of a lubricant that contains a surfactant or wetting agent can minimizethe embedding of the abrasive. Also, a polish only with distilled water in a fewminutes may remove embedded grains. If after the step P 1, only a few finescratches are visible, then proceeding to the final polish, as indicated in MethodT-64, is appropriate. If numerous scratches are visible, then repeat the step P 1 orfollow Method C-64, going to a step with 1 �m diamond.Cleaning: Cleaning is very important when preparing plastics and polymers. Thespecimen should be cleaned between each step in an aqueous solution of dish soapif the material is not water sensitive. The use of ultrasonic baths cleaning isusually an acceptable practice. However, materials such as partially cured resinsmay be damaged by excessive cavitation in ultrasonic cleaning. When drying,avoid hot air.Etching: Relief polishing may be sufficient to establish a good examination of thespecimen in dark field illumination �DF� or in differential interference contrast�DIC� �see Section 9.2�. For Etchants, see below.


C-64, T-64

Perfect edge retentionGrain size, grain boundaries C-64, T-64Image analysis,rating of inclusion content

C-64, T64

High planenessMicrohardness, hardness D 785, D 1415, D 2240, E 384 C-64, T-64Microstructure E 3, E 2015, E 883 C-64, T-64Phase identification C-64, T-64


Sectioning

Cut-Off Wheel SiC bakelite bond, thin, a thin electroplated diamondwheel or a fine toothed saw blade


Mounting



TimeMinutes/Hours

6–15 min/12–24 h

Grinding

C-64, T-64: For some materials the steps FG 4 and even FG 3 can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-64, T-64: Check that the specimen material is not damaged by the lubricant.For water sensitive materials use glycerol. Clean in distilled water.C-64 and T-64: Colloidal silica can be used instead of alumina.T-64: Often the step P 1 can be omitted.

Contemporary Method C-64 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 FG 4 P 1 P 2 P 3PolishingDisk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia,sprorsusp

Alumina


P320 P500 P1200 P2400 P4000 3 1 0.02/0.05

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150 150/150 150/150

rpm/rpm


Comp/Contra



10–20�2.2–4.5�

10–20�2.2–4.5�

10–20�2.2–4.5�

10–15�2.2–3.4�

10–15�2.2–3.4�

20 �4.5� 20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 4–5 3 Up to10


paperSiCpaper

SiCpaper

SiCpaper

SiCpaper



Abrasive Type SiC SiC SiC SiC SiC Dia,spr orsusp

Alumina

Grain orGrainSize �m

P320 P500 P1200 P2400 P4000 3 0.02/0.05

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150 150/150


10–20�2.2–4.5�

10–20�2.2–4.5�

10–20�2.2–4.5�

10–15�2.2–3.4�

10–15�2.2–3.4�

20 �4.5� 10 �2.2�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 0.5–1 5 Up to 10


EtchantsMaterial Etchants �see Table 12.2� UsesPolypropylene �PP� 943, 942, 945, 946 General structurePolyethylene �PE� 945 Reveals lamellar structure

946 Reveals spherolitesPolyamid �PA� 946, 947 General structure

Material/Preparation Tables 65Material: Acrylics. Acrylonitrile butadiene styrene „ABS….Polyamid „PA…. Polycarbonate „PC…. Polyethylene „PE….Polymethyl methacrylate „PMMA…. Polyester „saturated….Polyoxymethylene „POM…. Epoxy „EP…. Phenolics. Polyester „unsaturated…. Polyurethane „PUR…. Other thermosetting plastics

Comments on Material: See Material/Preparation Tables 64. Also Methods C-64and T-64 can be used for these materials.Sectioning: See Material/Preparation Tables 64.Mounting: ASTM E 2015 recommends: For polyurethanes �PUR�: Sputter coatwith 40 nm of gold, and encapsulate in a moderately soft epoxy �70 to 75 Shore Dhardness� under vacuum and cure at room temperature for 24 h. Forpolycarbonates: Sputter as for PUR and encapsulate in acrylic or hard epoxy �80Shore D hardness or greater� under vacuum; cure acrylic at less than roomtemperature; cure epoxy at room temperature for 24 h. For polymethylmethacrylate �PMMA� the same procedure as for polycarbonates is recommendedonly a hard setting epoxy resin should be used since PMMA may react with acrylicmounting resin For polyester thick films and sheets: Sputter as for PUR andencapsulate in moderately hard �75 to 80 Shore D hardness� epoxy under vacuum�for contrast�, and cure epoxy at room temperature for 24 h.Grinding: ASTM E 2015 recommends: For grinding of PMMA and polycarbonates:The FG 3 step in Methods C-65 and T-65 are changed to a rough polishing stepwith 6 �m diamond or to 9 �m diamond for polyester thick films and sheets �seebelow�.For preparation of soft and ductile materials, use T-65.Polishing: ASTM E 2015 recommends: For final polishing of urethanes, PMMAand polycarbonates: The P 3 step in Methods C-65 and T-65 are changed to0.05 �m gamma alumina �see below�.Etching: See etchants below and Material/Preparation Tables 64.


B 487 C-65, T-65

Grain size, grain boundaries C-65, T-65



C-65, T-65

Microhardness, hardness D 785, D 1415, D 2240, E 384 C-65, T-65Microstructure E 3, E 2015 C-65, T-65Phase identification C-65, T65


Sectioning

Cut-Off Wheel SiC bakelite bond, thin wheel or wheel with fine teethor a thin electroplated diamond wheel

Mounting



TimeMinutes/Hours

6–15 min/12–24 h

Grinding

C-65 and T-65: For PMMA and polycarbonates: Change the step FG 3 to a roughpolishing step with a soft napless nonwoven synthetic cloth, 6 �m diamond,lapping oil, 150/150 r/min, Comp, 18–27 �4–6� N �lb�, 30 s, repeat as needed. Forpolyester thick film and sheets: Change the step FG 3 to a rough polishing stepwith a perforated hard nonwoven chemitextile pad, 9 �m diamond, distilledwater, 120/120 r/min, Comp, 13 �3� N �lb�, 30 s, repeat as needed.C-65: Often a step with SiC paper grit P2400 should be added between FG 2 andFG 3.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-65 and T-65: For urethanes, PMMA and polycarbonates: Use 0.05 �m aluminafor final polishing, step P 3, instead of the stated silica. For polyester thick filmand sheets: Use 0.05 �m alumina mixed with colloidal silica in high pH aqueoussuspension for step P 3.C-65: Often the steps P 1 and P 2 can be omitted.


Contemporary Method C-65 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 FG 3 P 1 P 2 P 3PolishingDisk/Cloth SiC

paperSiCpaper

SiCpaper

SiCpaper


Cloth,med nap,soft, syn


Abrasive Type SiC SiC SiC SiC Dia,sprorsusp

Dia,sprorsusp

Silica

Grit orGrianSize �m

P320 P500 P1200 P4000 3 1 0.04/0.05

LubricantType

Water Water Water Water Wat-oil Wat-oil

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150 150/150


orContra



20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

30 �7� 20–30�4.5–7�

10–20�2.2–4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 3–4 2–3 0.5–1


paperSiCpaper

SiCpaper

SiCpaper





Dia, spror susp

Silica


P320 P500 P1200 P2400 3 1 0.04/0.05

Lubricant Type Water Water Water Water Wat-oil Wat-oil


RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150 150/150 150/150


orcontra



20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

30 �7� 20–30�4.5–7�

10–20�2.2–4.5�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 3–4 2–3 0.5–1



Polyoxymethylene �POM� 945 Reveals spherolite spherolitecores and growth direction

948 General structurePolycarbonate of styrene 947 General structure

Material/Preparation Tables 66Material: Powder Metals. Ferrous. Nonferrous

Material Properties: Iron-graphite mixtures: Up to 0.8 % carbon. Iron-copper: 2to 20 % copper. Iron- copper-carbon: 2.0 to 5.0 % copper, 0.8 % carbon.Iron-phosphorous: Phosphorous less than 1 %. Iron- nickel: 2 to 4 % nickel, 0.4 to0.8 % carbon, up to 2.0 % copper.Stainless steels: Compositions that approximate AISI designations 303, 304, 316,for austenitic stainless steels and 410 for martensitic stainless steels.Copper-base: Bronzes with 10.0 % tin Brasses with 10, 20, and 30 % zinc. Nickelsilver with 18 % zinc and 18 % nickel. Some alloys may contain 2.0 % lead.Titanium-based: 6.0 % aluminum, 4.0 % vanadium.Aluminum-based: 0.25 to 4.4 % copper, 0.6 to 0.8 % silicon, 0.4 to 1.0 %magnesium �weight %�.Comments on Material: Powder metal is one of the four major methods offorming metals �casting, machining, and plastic forming�. It is the process ofproducing metal shapes from metallic powders. The metal powder is blended,pressed �compacted� into shape, and sintered to temperatures just below themelting point. The process offers a wide variety of alloys and material properties.The main production of powder metal parts is small to medium sized parts for theauto and manufacturing industry. The advantage is that the parts have a goodsurface finish with close dimensional tolerances so that machining is reduced oravoided. Other alloys are made for cutting tools with tungsten carbide and othercarbides �see Material/Preparation Tables 67�. Powder metals are classified with aprefix and a code, an example is: CNZ—1816–13, where C means copper �base


element�, N means nickel �minor element #1�, Z means zinc �minor element #2�, 18means percentage of minor element #1, 16 means percentage of minor element #2,and 13 means minimum yield strength.During the sintering, recrystallization and grain growth occur between theparticles in a contact area, and a grain and lattice structure such as known fromsolid metals is developed. Voids and pores between the particles are still present,depending on the amount of compression and the time of sintering. When doingmetallographic/materialographic examination, the major difference between solidmetals and powder metals is the amount of porosity. Sintered materials generallyexhibit 0 to 50 % porosity which affects mechanical properties and stronglyinterferes with the preparation and interpretation of the microstructure. Carefulpreparation is important because the shape of the porosity is as important as theamount in judging sintered strength and the degree of sintering. The mainproblem during the preparation is the smearing of the pores during grinding andrough polishing that may occur even when the pores are filled with a resin �seebelow�.For mounting of uncompacted powder, see Section 3.12.4. Preparation of mountedspecimens with uncompacted powder is in principle done as for the base material,but often the preparation times should be reduced to avoid over-polishing of thepowder particles embedded in the epoxy.Sectioning: Selection: As the density and other features can vary considerably, itis important that the specimens are selected from the surface and interior of thepart and from top and bottom. Wet abrasive cutting with an SiC or Al2O3 bakelitebond cut-off wheel, depending on the base material of the powder metal.Preferably a precision cut-off machine with an effective cooling and a thin wheel�0.5 mm �0.02 in�� should be used to reduce material damage.In the case of band sawing, the relatively large deformed layer of the cut surfaceshould be removed through a careful plane grinding.Mounting: Before mounting it may be necessary to remove fluids absorbed in thepores of the material during the manufacture and cutting. If the specimen can beheated, the fluids �water and oil� can be removed by heating the specimen in ashort time on a hot plate under a fume hood. If the specimen material cannot beheated an extractor-condenser like the Soxhlet apparatus may be used. Theapparatus consists of a flask, a siphon cup, and a condensing-coil unit that fits onthe top of the flask. A solvent, such as toluene or acetone, is placed in the flask,and the specimen to be cleaned is placed in the siphon cup. Six cycles, requiring atotal of 1 h, will usually ensure removal of the oil. The method is described inASTM Standard Test Method for Density, Oil Content, and Interconnected Porosityof Sintered Metal Structure Parts and Oil-Impregnated Bearings �B 328�. Also,ultrasonic cleaning under a fume hood for one h in 1-1-1 trichloroethane and ahot ultrasonic bath has been recommended. The residual entrapped solvent shouldbe evaporated from the specimen.Mounting of specimens, which should be examined for porosity, should be donewith a low viscosity epoxy, ensuring an effective vacuum impregnation �see Section3.10�. If edge retention is important, the epoxy should be mixed with a filler �seeSection 3.11.2�. Other specimens can be hot mounted or cold mounted withacrylics.


Grinding: For materials with high porosity and which are relatively soft andductile it may be of advantage to extend Method T-66 with a step using grit 2400grinding paper �see below�.

Polishing: It is important that the porosity is “clean,” all pores must be opened,after the 3 �m diamond step. If this is not the case, the step should be prolonged.For the final polishing step a chemical mechanical polishing may be of advantage�see under the Material/Preparation Tables covering the base material�.Etching: Often the specimen is examined in unetched condition to evaluate thenumber and distribution of the particle boundaries.Etchants used for the base metal may be used; these can be found under therelevant Material/Preparation Tables.


B 487 C-66


E 112, E 930, E 1181, E 1382 C-66, T-66


E 562, E 1245, E 1382 C-66, T-66

Microhardness, hardness B 931, B 932, B 933,E 10, E 18, E 92, E 103, E 110,E 140, E 384, E 448

C-66, T-66

Microstructure B 328, E 3, E 407, E 562, E 883, E 1181,E 1245, E 1382, E 1558

C-66, T-66



Sectioning

Cut-Off Wheel SiC or Al2O3, bakelite bond, thin wheel

Mounting


Resin Bakelite ColdMounting

Resin Epoxy/AcrylicsTimeMinutes


6–12 h/6–10 min


Grinding

T-66: In case of soft, ductile materials a grinding step, FG 4, with grit P2400grinding paper can be added.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-66 and T-66: For final polishing chemical mechanical polishing may be used�see the relevant Material/Preparation Tables for the base material�.C-66: Often the step P 2 can be omitted.

Contemporary Method C-66 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 2PolishingDisk/Cloth SiC

paperSiCpaper

RCD,soft




AbrasiveType

SiC SiC Dia,sprorsusp

Dia,sprorsusp

Dia,sprorsusp

Alumina

Grit/GrainSize �m

P220 P500 9 3 1 0.02/0.05

LubricantType

Water Water Alco or wat Alco or wat Alco or wat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra

Comp orcontra



20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

10–15�2.2–3.4�

TimeMinutes

Until plane 1 5 4 3 1



paperSiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

Alumina


P220 P320 P500 P1200 6 3 0.02/0.05

LubricantType


Alco orwat

RotationDisk/Holder

300/150 300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra

Comp orcontra



20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

20–30�4.5–7�

10–15�2.2–3.4�

TimeMinutes

Untilplane

0.5–1 0.5–1 0.5–1 4 3 1–2

EtchantsSee under the relevant Material/Preparation Tables covering the base material of

the powder metal.

Material/Preparation Tables 67Material: Sintered „cemented… tungsten carbides. Hard metals.Other coated sintered carbides

Comments on Material: Cemented carbides �sintered carbides, hard metals� aresintered materials consisting of tungsten carbide or a mixture of tungsten carbide,titanium, or tantalum carbide in powder form, sintered in a matrix of cobalt ornickel. Cemented carbides, being very hard and tough with a high wear resistance,are suited for cutting tools, metal forming tools, rock drilling, and other purposeswhere a high wear resistance is needed. To improve the wear resistance of thecutting tool, often the cemented carbide insert is coated by chemical vapordeposition �CVD� with one or more hard materials like titanium carbide, titaniumnitride, titanium carbonitride, and aluminum oxide, the coating being0.2 to 10 �m thick.


Cemented carbides are covered by a number of ASTM standards regardingspecimen preparation �B 665�, determination of microstructure �B 657�, apparentgrain size �B 390�, and apparent porosity �B 276� �see below and Section 12.4�.The high hardness of cemented carbides makes only metallographic/materialographic preparation with diamond possible. The relatively soft cobalt canbe smeared over the carbides and lack of adequate pressure on the specimenduring polishing may result in pull-outs �material being torn from the surface ofthe specimen�. This condition may erroneously be interpreted as porosity �seeSection 13.6.4�.Sectioning: The carbides, being very hard, the wet abrasive cutting should bedone with a diamond metal bond cut-off wheel preferably on a precision cut-offmachine so that a thin wheel can be used, reducing the damage to the cut surface.The cutting, with an efficient cooling, should be performed with a suitable lowfeed speed to avoid fracturing of the relatively brittle material, especially at theend of the cut.Mounting: Due to the high hardness, cemented carbides should always bemounted in a mounting material with a filler. For hot mounting, epoxy with a filleris recommended and for cold mounting acrylics with a filler or epoxy with anin-mixed filler may be used �see Sections 3.1.3 and 3.11.2�. In the case ofexamination of coatings, an epoxy mounting material should be used �see alsoMaterial/Preparation Tables 08–15�.Grinding: If the sectioning has been without excessive deformation, the PG step inMethod T-67 can be omitted.Polishing: It is important that all deformation from the previous steps areremoved after the 3 �m diamond step, P 1 in Method C-67 and P 2 in T-67. Oftenthe surface after this step is satisfactory for routine examination. Alumina shouldnot be used for cemented carbides with cobalt matrix because the surface maycorrode. Also, the cleaning should be with alcohol only because water may corrodethe cobalt matrix.Etching: See etchants below. A physical etching by relief polishing can be made ifa napped cloth is used for the final polishing step, a relief between carbides andmatrix will develop �see below� Also, vapor deposition of interference layers maygive good results �see Section 9.6�.

Purpose ASTM Standard �See Section 12.4� MethodCase of coating thickness/hardness, surfacelayersPerfect edge retention

B 487 C-67

Grain size, grain boundaries B 390, E 1382 C-67, T-67Image analysis, ratingof inclusion contentHigh planeness

E 562, E 1245 C-67, T-67

Microhardness, hardness E 10, E 18, E 92, E 140, E 384 C-67, T-67Microstructure B 657, B 665, E 3, E 562,

E 1245C-67, T-67



Porosity B 276 C-67, T-67


Sectioning


Mounting


Resin Epoxywith Filler

ColdMounting

Resin Epoxy with Filler/Acrylics with Filler

TimeMinutes

TimeMinutes/Hours

6–12 h/6–10 min

Grinding

C-67: Very often the FG 2 step can be omitted.T-67: Very often the PG step can be omitted.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-67: In case of pull-outs developed during the grinding, the time of step P 1should be prolonged.T-67: In case of pull-outs developed during the grinding, the time of step P 2should be prolonged.C-67 and T-67: The final polishing step can be changed to 1 �m diamond on amedium napped cloth�see Method T-65, step P 2�.


fixed, resRCD, hard RCD,

softCloth,napless,hard, wov,syn



Dia, spr orsusp

Dia, spr orsusp

Silica


P120 9 3 3 0.04/0.05


LubricantType


RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150




40 �9� 35 �8� 35 �8� 30 �6.6� 15 �3.4�

TimeMinutes

Untilplane

5 5–10 5–8 1–2

Traditional Method T-67 �For definitions of parameters and consumables seeSection 13.2.2.�Grinding/ PG FG 1 FG 2 P 1 P 2 P 3PolishingDisk/Cloth Dia

pad, metDia pad,bak

Cloth,napless,v. hardwov, syn

Cloth,napless,hard,non-wov, syn




Dia, spr orsusp

Dia, spr orsusp

Silica


125 30 15 6 3 0.04/0.05

LubricantType


Alco or wat Alco orwat

RotationDisk/Holder

300/150 300/150 150/150 150/150 150/150 150/150


contraComp orcontra



30 �7� 30 �7� 40 �9� 40 �9� 30 �7� 15 �3.4�

TimeMinutes

Untilplane

3–5 6 5 5 2

EtchantsMaterial Etchants �see Table 12.2� UsesCemented tungstencarbides according toASTM Standard B 657�Etching Technique 1�

951 Identificationof � phase


Cemented tungstencarbides according toASTM Standard B 657�Etching Technique 2�

949 in combination with950

Identificationof phase

Cemented tungstencarbides according toASTM Standard B 657�Etching Technique 3�

951 Identificationof � phase

Material/Preparation Tables 68Material: Uranium and Uranium dioxide. Americium. Cadmium.Indium. Mercury and amalgams. Neptunium. Plutonium. Rareearth metals. Selenium. Tellurium. Thallium. Thorium

Material Properties: Uranium: Body-centered cubic, 238.07 g/cm3, 1689°C�3010°F�, HV 190. For all other materials mentioned above, see below.Comments on Uranium: Uranium �U� belongs to the rare earth metals radioactivegroup. It is the most important of the rare earth metals �see below� because it hasbeen used as a metallic fuel in producing atomic energy. The metallic fuels havebeen superceded by oxide fuels, and the information below covers preparation ofuranium dioxide �UO2�. Uranium dioxide is normally used in the form of pelletsthat are made through a process where the raw material in powder form issintered at a high temperature. In this state the uranium dioxide can beconsidered a ceramic material of cubic crystal structure with a very high meltingpoint.U and UO2 are radioactive materials and a health hazard so that all handling shalltake place in hot cells or glove boxes through manipulators so that human contactwith the radioactive material is avoided.The metallographic/materialographic preparation process follows the same lines asnormal preparation, only as mentioned in a shielded environment and with specialprecautions regarding the disposal of the used consumables. The preparationprocess stated below is for uranium dioxide, and two methods, a “C-method” anda “T-method” are indicated.Comments on Other Materials:Americium �Am�, neptunium �Np�, plutonium �Pu�, and thorium �Th� areradioactive metals and will not be discussed further.Cadmium �Cd�, indium �In�, and thallium �Tl� are very soft metals that are seldomused. Cd and Tl are toxic. These metals will not be discussed further.Mercury �Hg� and amalgams: Amalgams are mercury alloys consisting of Hgmixed with powders of silver, tin, copper, and zinc. Only amalgams can bemetallographically prepared, and these alloys will not be discussed further.Rare earth metals: This group of 15 metals are very rarely prepared and will notbe discussed further. For yttrium �Y� see Material/Preparation Table 20.Selenium �Se� and tellurium �Te� are semiconductors and very toxic and will notbe discussed further. For preparation of the semiconductors silicon andgermanium see Material/Preparation Tables 21.


Sectioning: The uranium dioxide, in pellet form, is normally encapsulated inepoxy �mounted� prior to cutting. This is to minimize fragmentation of thematerial and thereby reduce the waste and contamination issues. The cutting isdone on a special cutting machine made for the special conditions in a hotcell/glove box, using a diamond wheel with resin or metal bond. A wheel withelectroplated diamonds may also be used, especially when cutting encapsulatedmaterial. When working with radioactive material the volume of liquid in any hotcell/glove box is strictly controlled to a minimum. Consequently, cutting is carriedout with a low rotational wheel speed, controllable feed rate, and wheel cooling bydip transfer of the coolant to the wheel so that splashing is avoided and theconsumption of coolant is kept very low.Mounting: Cold mounting with epoxy is used. Vacuum impregnation is used onsome applications �see Section 3.10�.Grinding: Grinding and polishing are carried out on special semiautomaticmachines, often with modifications of standard machines so that all handling cantake place through manipulators.When using SiC grinding paper, as indicated in Method T-68 below, a largeamount of low level contaminated waste is generated which involves costlydisposal.Polishing: For the final step both alumina and colloidal silica can be used, oftenwith addition of hydrogen peroxide �see below�.Etching: See below.

Purpose ASTM Standard �See Section 12.4� MethodsCase or coatingthickness/hardness,surface layersPerfect edge retention

C-68


E 112, E 930, E 1181, E 1382 C-68, T-68


E 562, E 1245, E 1268, E 1382 C-68


C 730, C 849, C 1326, C 1327,E 384

C-68, T-68


C-68, T-68



Sectioning

Cut-Off Wheel Diamond, metal/resin or electroplated,see above.


Mounting



TimeMinutes/Hours

6–8 h

Grinding

C-68 and T-68: When using water for cooling this shall be only as drops toreduce contaminated waste �see above�.Attention: In C-methods, when using RCD: The disk turns concave during use.When the difference is more than 100–150 �m between the center and theperiphery, the disk is either discarded or trued.

Polishing

C-68 and T-68: P 3: Mix 90 mL of alumina or colloidal silica with 10 mL ofhydrogen peroxide �30 %�.


PG FG 1 P 1 P 2 P 3


RCD,hard




AbrasiveType

Diamond Dia,spr orsusp

Dia,spr orsusp

Dia,spr orsusp

Silica�seenote�

Grit/GrainSize �m

P220 6 6 3 0.04/0.05

LubricantType

Water�drip�

Wat�drip�

Wat�drip�

Alcoor wat

RotationDisk/Holder

300/150 150/150 150/150 150/150 150/150



Force per Specimen N �lb� 30 �6.6� 30 �6.6� 35 �8� 30 �6.6� 30 �6.6�TimeMinutes

2 5 5 4 1.5



PG FG 1 FG 2 FG 3 P 1 P 2 P3

Disk/Cloth

SiCpaper

SiCpaper

SiCpaper

SiCpaper




AbrasiveType


Dia, spror susp

Alumina�seenote�


P220 P320 P500 P1000 6 3 0.02/0.05

LubricantType

Water�drip�

Water�drip�

Water�drip�

Water�drip�

Alco Alco

RotationDisk/Holder

150/150 150/150 150/150 150/150 150/150 150/150 150/150

rpm/rpmComp/Contra



25 �5.5� 25 �5.5� 25 �5.5� 25 �5.5� 20 �4.4� 20 �4.4� 20 �4.4�

TimeMinutes

3�1 min 4�1 min 6�1 min 10�1 min 8 6 5

EtchantsMaterial Etchants �see Table 12.2� UsesUO2 924 General

structure

13.2.4 Manual PreparationThe methods stated in Section 13.2.3 are based on semiautomatic preparation. It ispossible, however, to use the data stated in the Method Tables for manual �hand� prepa-ration also.

The T-methods are most suited for preparation by hand, both the methods basedon SiC grinding paper, and the methods based on diamond disks/pads, but also theC-methods, often using resin bonded diamond disks and rigid composite disks �RCDs�for grinding, can in some cases be transferred to manual �hand� preparation �see be-low�.

As manual �hand� preparation is less uniform, to a high degree depending on theoperator, the times indicated in the Method Tables should only be taken as guidelines�see below�.


Manual grinding/polishing should preferably be done on two machines, a grinderwith one or two disks especially designed for SiC paper �see below�, rotating with300 rpm, and a polisher �150 and 300 rpm� with one or two interchangeable disks formounting of several polishing cloths or one magnetic disk �see Section 6.7.1�. Formanual grinding and polishing, disks for 230 mm �9 in� grinding paper and for200 mm �8 in� polishing cloths should be preferred. Separating the grinding and pol-ishing on two machines reduces the risk of contamination, but both processes can alsobe done on the same machine.

Before starting on manual preparation, it is recommended to read relevant sec-tions in Chapters 6 and 7.

Grinding

SiC Grinding PaperIn the Method Tables, P220 grit is usually stated as the first step. If the original surfaceof the specimen is very rough it might be necessary to start with P120 or P180 grit be-fore grinding with a P220 grit. In general, paper with plain back should be used, thepaper being fixed by a thin layer of water between the paper and the disk. For this pur-pose the disk has a raised edge, allowing water to stay on the disk when not rotating,and water is added to the disk before the sheet of paper is placed. A ring is often used tokeep down the edge of the paper, but this ring is not fixing the paper, the fixation takesplace through the suction between disk surface and sheet, because most of the water isslung away by the centrifugal force when the disk starts rotating. The paper should notbe stored in water between uses because this weakens the bond of the paper. Paper withadhesive back can also be used, but generally the force on the paper at manual grindingis so low that a plain backed paper can be used. Also, paper with adhesive back is con-siderably more expensive than plain backed paper. As a “middle solution” a double ad-hesive foil can be placed between disk and paper and the foil can be used for manysheets. Water should be supplied in a constant flow to the center of the rotating disksecuring that all debris is washed away.

When grinding, hold the specimen in a firm grip, with a relatively strong pressure,both hands can be used, and move it from periphery to center of the paper surface andback in a slow movement. Be careful that the specimen is held so that the scratches arein the same direction on a given paper. Also, be careful that the specimen is not tilting,making facets on the surface. When going to next finer grit paper, turn the specimen 90°so that the new scratch pattern can be seen perpendicular to the scratches from theprevious step. Continue grinding until all scratches from the previous step are re-moved, and as a rule go on for at least the same period of time to remove possible defor-mation. This rule covers harder materials with limited deformations introduced, butfor softer, more sensitive materials grinding shall go on for a longer period of time. Insome cases it might be necessary to use several sheets of the same grit. Do not use thepaper for too long, depending on the hardness of the material, the paper is worn after20–120 s. If the paper is worn out it is not removing material but creating deformationin the specimen surface �see Chapter 6�. The specimen surface ground correctly is dullwith parallel scratches. If the surface is bright, the paper has been worn and new papershould be used.

All grinding steps can be done without cleaning in between, but after the last �fin-est� step the specimen should be cleaned and dried �see below�.


Diamond Disks—Diamond PadsDiamond disks with fixed diamond grains are in the form of diamond in a metal/bakelite bond on a solid disk, as diamond pads or as resin �epoxy� bonded diamonds,both on a thin backing, to be fixed by adhesion or magnetically to a grinding/polishingdisk. They are all used with a flow of water and in the same way as SiC paper.

Rigid Composite Disks „RCD…A disposable RCD is placed on a disk magnetically as described for polishing clothsbelow, or a solid disk is used �see Section 6.7.7�. Also, the diamond is charged as statedbelow, only spray and suspension can be used. The disk shall rotate with 150 rpm.

It can be difficult to use an RCD for hand preparation because the RCD normallyworks with relatively little lubrication to avoid “aqua planing.” This process dragsstrongly in the specimen and it might be difficult to hold it by hand. The effect is notvery strong on less aggressive �soft� RCDs, and hand preparation can easily be per-formed. The specimen is rotated around the disk, as described below under polishing;take care that the whole surface of the disk is used to avoid an unplane surface.

A firm pressure is applied during grinding with RCD; both hands are often used,like for SiC paper.

The disk should be cleaned regularly to avoid swarf closing the openings betweenthe segments on the surface.

Diamond PolishingIf using polishing cloths with adhesive back, take care that a number of disks, corre-sponding to the number of polishing steps, including the step with silica or alumina, isavailable. In this way, the cloths charged with different grain sizes can easily bechanged during the process and should only be removed from the disk when worn out,securing the highest degree of cleanliness and avoiding contamination from disk todisk. If cloths with magnetic backing are used, the cloth can be removed easily from themagnetic disk which can stay in the machine, and only one disk is needed.

In the case of a new cloth, charge the cloth with a reasonable amount of diamond,at paste, use approximately 1 g for a 200 mm disk and recharge regularly with 0.5 g. Atdiamond spray, spray one round on the cloth for a start and respray every 2–3 minduring the process. At suspension, charge the new cloth with a reasonable amount andrecharge during the process every 2–3 min from a spray bottle. If a product with “dia-mond and lubricant in one” is used, it is added as stated below for lubricant. Accordingto Samuels Ref. 7, �Part I�, diamond paste should give the highest removal rate atmanual polishing.

In the case of a used cloth, take care that the cloth can be used for the material inquestion. Normally a cloth should only be used for the same group of materials; thisgives three sets of disks with cloths in an all-round laboratory: for ferrous metals, non-ferrous metals, and for ceramics.

Starting with a dry cloth, the cloth is wetted with a reasonable amount of lubricantso that the total surface is moist, but not “swimming,” �see below�. It is preferable to usea water-based lubricant because alcohol- and oil-based lubricants may be dangerous tohealth.

The polishing disk should rotate with 150 r/min and the specimen is rotatedslowly in a circle against the direction of the disk. The specimen is moved slowly fromthe periphery to the center of the disk and back to secure a uniform wear of the polish-ing cloth. By rotating the specimen, all phases in the specimen surface are uniformly


treated, ensuring a minimum of artifacts in the surface. Charge the cloth �RCD� withsmall amounts of lubricant at the center of the disk in short intervals so that the surfaceis just “moist” when touched with a fingertip, not “wet.”

The pressure during polishing is firm at the rough steps and lower at the final steps.Also, at all steps, the pressure is reduced during the last approximately 30 s.

Important: The times indicated in the Method Tables are based on semiautomaticpreparation, therefore the times for manual preparation could be longer. Until experi-ence with a given material is developed, take care that deformations and scratchesfrom the previous step are removed by looking at the specimen surface in the micro-scope �see the “Metallographer’s Rule of Thumb” and Trouble Shooting �Section 13.5��.

Silica and Alumina PolishingBe careful, especially with silica �SiO2� polishing, that the cloth is absolutely clean be-fore starting the process, not having dried-in particles from previous polishing; theseparticles might scratch the specimen surface. Circulate the specimen as describedabove, adding the polishing medium to the center of the cloth from a spray bottle insmall amounts at short intervals.

When finished, clean the specimen and the cloth by further “polishing” in approxi-mately 10 s with plenty of water added to the center of the cloth. Silica can be especiallydifficult to remove and at certain, not too sensitive materials, the specimen surface canbe rubbed with a wad of cotton. To clean a porous cloth use the edge of a piece of plasticas a scraper on the rotating cloth to remove remaining polishing media to avoid par-ticles that will later dry-in on the cloth.

Cleanliness and CleaningIt is important that a step is not contaminated with abrasive grains from the previousstep. The specimen should be washed and cleaned with cotton in lukewarm water andfinally rinsed with ethanol and dried in a stream of warm air or cleaned �dry� com-pressed air �see also Chapter 5�. The hands of the operator should also be washed.

13.3 Electrolytic Polishing and Etching

In electrolytic polishing, or electropolishing, the specimen is placed as an anode in anelectrolytic cell. Material is removed from the specimen surface through the electroly-sis, and because of this, the prepared surface often has a number of artifacts �see Chap-ter 8�. If the specimen has two or more phases, with different potential, like cast ironand contains nonmetallic �nonconductive� inclusions, or both, the prepared surfacewill not usually show a true or acceptable microstructure.

Electropolishing has, however, a number of advantages. The surface created isusually scratch-free and without deformation, an advantage for soft metals, difficult topolish mechanically. Also electropolishing is very effective for routine polishing, thepolishing time is very short, and often the etching can take place as part of the process.

In certain cases like in stainless steel, the etching cannot be done with the electro-lyte used for polishing, and “external etching” can take place using a low voltage and aspecial electrolyte �see Section 9.5�.

Trial and Error: To develop a new method, start with a relatively low voltage andincrease with 5 V for each trial until the correct voltage �current density� is found.Grind with relatively fine SiC paper between trials to remove traces from the previous


electropolishing. Newer electropolishers �see below� have a built-in scan function thatindicates the correct voltage/current level for a given material.

Trouble Shooting: See Section 13.6.5.Electrolytic polishing is described in the ASTM Guide for Electrolytic Polishing of

Metallographic Specimens �E 1558� �see Section 12.4�.

13.3.1 ElectropolishersThe methods stated in this book are based on the use of an apparatus in which thespecimen is placed as an anode on top of a polishing chamber with a mask defining aspecific area to be polished, the chamber containing a cathode and a flow of electrolyte.The area is usually from 0.5–5 cm2 �0.08–0.8 in2�. A number of parameters, voltage,polishing/etching current �amperage�, flow rate of electrolyte, polishing/etching time,and electrolyte temperature, are controlled by the apparatus �see Chapter 8�.

13.3.2 Electrolytes—Methods for Electropolishing—Table 13.2A number of electrolytes have been developed for most metals, mainly based on per-chloric, perchloric/acetic, phosphoric, and sulfuric acids. The composition of a num-ber of electrolytes covering most materials is stated in Table 13.2. To obtain the formu-las of a very high number of electrolytes, see Table 2 in the ASTM Standard E 1558 �seeSection 12.4�.

To find the correct electrolyte for a specific material, go to Table 11.1 and find theElectropolishing Method �El-Method� number. These methods are stated in Section13.3.5. The El-Method numbers are also stated in the Material/Preparation Table, Sec-tion 13.2.3. In the El-Method, the Electrolyte number is stated. This number is taken toTable 13.2, and the composition is found.

When mixed, the electrolytes often have a relatively short shelf life, around twomonths for the most used perchloric acid type. Life also depends on the number of pol-ishings performed. Often an electrolyte only works best after a few polishings when anumber of metal ions are established.

Attention: Perchloric acid is very dangerous �explosion� when in contact with or-ganic material at high concentrations. For this reason, only “authorized” electrolytescontaining perchloric acid should be used, and care should be taken that the concen-tration of perchloric acid is not increased by evaporation of other ingredients in theelectrolyte, like ethanol.

General Safety Precautions: Work with acids and other chemicals is potentiallydangerous. Before using or mixing any chemicals, all product labels and pertinent Ma-terial Safety Data Sheets �MSDS� should be read and understood. All general precau-tions should be taken regarding protection of persons. For specific information on han-dling electrolytes, see Chapter 26.

13.3.3 Table 13.2—Electrolytes for Electropolishing/Etching

Comments to Table 13.2:The electrolytes are split into five groups. The group number is the first digit in the Elec-trolyte Number.

Group 1: Perchloric Acid and Alcohol With and Without Organic AdditionsGroup 2: Perchloric Acid and Glacial Acetic Acid in Varying ProportionsGroup 3: Phosphoric Acid in Water or Organic SolventGroup 4: Mixed Acids or Salts in Water or Organic SolventGroup 5: Alkaline Solutions


TABLE 13.2—Electrolytes for Electropolishing/Etching.

ElectrolyteNumber Use Formula Remarks

1-1 Steel, cast iron, Al, Alalloys, Ni, Sn, Ag, Be,Ti, Zr, U, heat resistingalloys

Ethanol (95 %) 700 mL2-butoxy ethanol 100 mLPerchloric acid (30 %) 200 mL

One of the best formulas foruniversal use.Add the perchloric acid to themixture of the other twocomponents.

1–2 Iron and steel ingeneral, stainless steel,Al, Al alloys, Ni, Sn,Ag, Mo, Ti, Zr, Pb, Pb-Sa, Zn, Zn-Al-Cn, Mgand high Mg alloys

Ethanol (95 %) 730 mLDistilled water 90 mLButylcellosolve 100 mLPerchloric acid (60 %) 78 mL

Universal use.Add the perchloric acid to themixture of the other threecomponents. Shelf life aroundtwo months.

1–3 Carbon, steels, alloyedsteels, stainless, steels,martensite, high temp.alloys, Pb, Al-Cualloys, Mn, Mo, Sn, Ti,Ti-alloys, Zr, V

Methanol (100 %) 600 mLPerchloric acid (60 %) 60 mLButylcellosolve 360 mLVogel’s Sparbeize 2 mL

Vogel’s Sparbeize is an inhibitorused in industrial electrolyticpolishing. The electrolyte canbe used without this.Attention: Methanol is a poison,use fume hood.

1–4 Cast iron, low alloyedC-steels, stainlesssteels, Be, Mg, Ni

Ethanol (95 %) 800 mLPropanol (100 %) 100 mLPerchloric acid (60 %) 15 mLSodium thiocyanate dihydrate

Mix in the following way:Propanol and ethanol are mixedand hydroxychinolin is dissolved.After dissolution the sodium

60 gCitric acid 75 gHydroxychinolin ortho 10 g

thiocyanate is added and afterdissolution the citric acid. Whenthe citric acid is added, the liquidturns muddy, but turns clear whenall is dissolved and the perchloricacid is added.

2-1 Austenitic steels, Cr,Hf, Ni, Pb, Th, Ti

Acetic acid (glacial) 950 mLPerchloric acid (60 %) 50 mL

Alternative to Group 1 electrolytesfor certain materials.

3-1 Alpha, alpha+betabrass, Cu-Fe, Cu-Co,Co, Cd

Distilled water600 mLOrtho phosphoric acid (84 %)400 mL

Alternative to electrolyte No. 3-2for Cu alloys.

3-2 Cu, brass, Au Distilled waterEthanol (95 %) 250 mLPropanol (100 %) 50 mLOrtho phosphoric acid (84 %)250 mLUrea 5 gVogel’s Sparbeize 2 mL

Vogel’s Sparbeize is an inhibitorused in industrial electrolyticbaths; this or another similarinhibitor improves the electrolyte,but can be omitted.

4-1 Cd, Mg, Zn, Pb Ethanol (95 %) 800 mLButylcellosolve 80 mLDistilled water 20 mLSodium thiocyanate dihydrate160 g

The sodium thiocyanate isdissolved in the mixture of waterand ethanol. When in solution thebutylcellosolve is added.

4-2 Bronzes, brasses,examination ofinclusions, materialswith strongly varyingstructural elements,steels with inclusions

Methanol (100 %) 900 mLPropanol (10 %) 140 mLButylcellosolve 200 mLAcetic acid (glacial) 120 mLCobalt nitrate (II) 400 gIron (III) nitrate 40 gTartaric acid 140 gUrea 4 g

Methanol and propanol aremixed and tartaric acid isdissolved in the mixture, thenthe cobalt nitrate, the iron nitrateand the urea is dissolved. Atlast the acetic acid and butylcellosolveare added.Attention Methanol is a poison,use fume hood.

5-1 W Distilled water 1000 mLSodium hydroxide 20 g

The NaOH content can beincreased to 100 g


13.3.4 Mechanical Preparation for ElectropolishingTo shorten the polishing time and thereby improve the quality of the electropolishedsurface, the specimen is normally ground on a number of SiC grinding papers beforepolishing. In the Method Tables �Section 13.3.6� only three grinding steps are stated. Ifonly fine grinding �FG� is indicated, often a plane-grinding step should be performedbefore the FG steps. If the polishing time should be reduced, it is recommended to usefiner grits of SiC paper, a rigid composite disk, or a hard polishing cloth both with dia-mond for fine grinding and rough polishing �see the Method Tables for the given mate-rial in Section 13.2.3�.

Short Time „Shock… PolishingIn case of materials difficult to electropolish, the polishing time can be reduced to1–2 s, in some cases repeated two to three times, when a mechanical preparation, in-cluding the 3 �m and even 1 �m diamond steps are performed. In this way only anelectrolytical “cleaning” of the surface takes place.

13.3.5 Electropolishing—Method TablesIn Section 13.3.6 a number of Method Tables are stated, containing the parameters forelectropolishing of a number of metals. The methods are called El-01 to El-25.

The user will find the method for a specific material by using Table 11.1. The meth-ods are also stated in the Material/Preparation Tables �Section 13.2.3�.

ParametersPreparation before the electrolytic polishing is stated with a number of parameters �ab-breviations� similar to the Method Tables of mechanical preparation �see Section13.2.2�.

The electrolytic polishing and etching is stated with the following parameters:Electrolyte. An “electrolyte number” will be stated. This number is taken to Table 13.2,which indicates the formula of the electrolyte.Area. The polished area in cm2, always 1 cm2 �0.16 in2�. The current stated corre-sponds to this area.Temp. The electrolyte temperature during the process in °C �°F�. The temperatureshould not increase more than 10°C above room temperature during the polishingprocess. If polishing large areas or many specimens with short intervals, the electrolytemust be cooled �see Chapter 8�.Voltage. Voltage between specimen �anode� and cathode in V �see Area above�. Twovalues are indicated: polishing and etching.Current. Current �amperage� in A passing between the cathode and the specimen. Theprocess depends on the correct “current density,” A per cm2�in2�.Flow Rate. The flow of electrolyte through the polishing chamber. The rate is indicatedas low, medium, and high.Time. Polishing and etching time in seconds, indicating the period of time the voltageis on.

13.3.6 Electropolishing—Methods El-01 To El-25This section contains 25 Method Tables for electrolytic preparation. The tables includethe data regarding preparation before the electropolishing, and the data for electropol-ishing and etching.


The data for electropolishing are based on the use of a commercial available elec-tropolisher �see Section 8.6� that is able to control the stated data. The values indicatedrefer to an area of 1 cm2 �0.16 in2�. In the case of mounted specimens, the mountingresin in the surface of the mount should not be conductive �see Section 3.11.6�.

Attention: A mixed electrolyte will often have a limited shelf life, the most used per-chloric acid based electrolyte �No. 1–2� only approximately two months.

Trouble Shooting: See Section 13.6.5.

Method Table—Electrolytic Polishing Method El-01Material: High carbon steels. Medium carbon steels. Manganeseand Mn alloys. Molybdenum and Mo alloys

Method El-01

Grinding/Polishing

FG 1 FG 2 FG 3 Electropolishing/Etching

ElectrolyticPolishing

ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

Electrolyte No.�Table 13.2�

1–3 1–3

AbrasiveType

SiC SiC SiC Area cm2 1 1

Grit/GrainSize �m

P220 P320 P500 Temperature°C �°F�

20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 40 2–3

RotationDisk/Holder

300/150 300/150

300/150

Current A 1.8–2 0.2–0.3

rpm/rpmComp/Contra

Comp orcontra

Comp Comp

Force perSpecimenN �Ib�

30 �7� 30 �7� 30 �7� Flow Rate Medium Medium/high

Time Minutes 0.5–1 0.5–1 0.5–1 Time s 6–8 2–5

CommentsElectrolytes: 1–2 or 1–1 can be used as alternatives. In case of inclusions, use elec-

trolyte 4–2.

Method Table—Electrolytic Polishing Method El-02Matherial: Low carbon steels

Method El-02Grinding/Polishing



ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2 1–2


AbrasiveType


Gri/GrainSize �m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 35–40 1,5

RotationDisk/Holder

300/150

300/150

300/150

Current A 1.8–2 0.2–0.3

rpm/rpmComp/Contra

Comporcontra

Comp Comp

Force perSpecimenN �Ib�

30�7�

30�7�

30�7�

Flow Rate Medium Medium/high

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 8 5

CommentsSteels with very low carbon content could be fine ground with P1000 SiC paper.Electrolyte: In case of inclusions, use 4-2.


Method Table—Electrolytic Polishing Method El-03Material: Gray cast iron. Malleable cast iron. Nodular cast iron


FG 1 FG 2 FG 3 Electro-polishing/Etching


Electro-lyticEtching

Disk/Cloth SiCpaper

SiCpaper



1–4

AbrasiveType

SiC SiC Dia,spr orsusp

Area cm2 1

Grit/GrainSize �m

P500 P1200 6 Temperature°C �°F�

20–30�68–86�

LubricantType


Voltage V 80

RotationDisk/Holder

300/150 150/150

150/150

Current A 1.8–2

rpm/rpmComp/Contra

Comp orcontra

Comp Comp


30 �7� 20 �4.5� 30 �7� Flow Rate Low/medium

Time Minutes 0.5–1 0.5–1 4–5 Time s 4–6

CommentsIn general, cast iron is not suited for electrolytic polishing.If performed, the process should be short and etching should be chemical with

etchant No. 74 �Nital� �Table 12.2�.The result can be improved by introducing a polishing step before the electropol-

ish, see step P 2 in Method T-30, and cut down the electrolytic polishing to 3–4 s.

Method Table—Electrolytic Polishing Method El-04Material: Heat treated steels



Electro-lyticPolishing


Disk/Cloth SiCpaper

SiCpaper

SiCpaper

ElectrolyteNo.�Table 13.2�

1–3 1–3

Abrasive Type SiC SiC SiC Area cm2 1 1


Grit/GrainSize�m


20–30�68–86�

20–30�68–86�

LubricantType

300/150

300/150

Alcoorwater

Voltage V 80

RotationDisk/Holder

300/150 150/150 150/150 Current A 2 0.2–0.3

rpm/rpmComp/Contra

Comporcontra

ComporContra

Comp


30�7�

30�7�

30 �7� Flow Rate Medium Medium

Time Minutes 0.5–1 0.5–1 0.5–1 Time s 10 2–10

CommentsElectrolyte: 1-2 or 1-1 can be used as alternatives.Steels with a high Cr–Ni content might not be electrolytically etched as part of the

process �see Method El-05�.

Method Table—Electrolytic Polishing Method El-05Material: Stainless steels. High alloy steels





Disk/Cloth SiCpaper

SiCpaper

SiCpaper

ElectrolyteNo. �Table 13.2�

1–2 1–2,see below

AbrasiveType

SiC SiC SiC Area cm2 1

Grit/GrainSize�m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 40–50 15–20

RotationDisk/Holder

300/150 300/150 300/150 Current A 1.9 0.2–0.3

rpm/rpmComp/Contra

Comp orcontra

Comp Comp


30 �7� 30 �7� 30 �7� Flow Rate Low/medium High


TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 12 up to 120

CommentsEtching: For stainless steels external electrolytic etching in oxalic acid �10 %� at

6 V in 10–15 s, can be recommended.Electrolytes: 1–3 can be used as an alternative. 2-1 is suited for austenitic steels.In some cases FG can be reduced to grit P500 SiC paper.

Method Table—Electrolytic Polishing Method El-06Material: Super alloys, Fe based




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCaper

SiCpaper


1–1 1–1

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 40–50

RoationDisk/Holder

300/150 300/150 300/150 Current A 1.5–2 0.2–0.3

rpm/rpmComp/Contra

Comp orcontra

Comp Comp


30 �7� 30 �7� 30 �7� FlowRate

Medium High

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10–12 5–10

CommentsElectrolyte: 1–2 and 1–3 can be used as alternatives.


Method Table—Electrolytic Polishing Method El-07Material: Iron, pure





Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–1 1–1

AbrasiveType


Grit/GrainSize


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 30–35 1.5

RotationDisk/Holder

300/300 150/300 150/150 Current A 1.5–2 0.2

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comp


30 �7� 30 �7� 20 �4.5� Flow Rate Medium Medium/high

Time Minutes 0.5–1 0.5–1 0.5–1 Time s 8–10 5

CommentsElectrolyte: 1–2 and 1–3 can be used as alternatives. In case of inclusions, use 4-2.

Method Table—Electrolytic Polishing Method El-08Material: High-speed steels





Disk/Cloth

SiC paper SiC paper SiCpaper

Electro-lyte No.�Table. 13.2�

1–2 Seebelow

AbrasiveType


Grit/GrainSize �m

P220 P320 P500 Temper-ature°C �°F�

20–30�68–86�

LubricantType



RotationDisk/Holder

300/150 300/150 150/150 Current A 2

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comp


30 �7� 30 �7� 30 �7� Flow Rate Medium

Timesinutes

0.5–1 0.5–1 0.5–1 Time s 6–10

CommentsEtching: External electrolytic etching with oxalic acid �10 %� at 5–10 V in 10–15 s.Electrolytes: 1-1 and 1–3 can be used as alternatives.

Method Table—Electrolytic Polishing Method El-09Material: Low-alloyed tool steels





Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2 1–2

Abrasive Type SiC SiC SiC Area cm2 1 1Grit/GrainSize �m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 30–40 3

RotationDisk/ Holder

300/150 300/150 300/150 Current A 1.8–2 0.3

rpm/rpmComp/Contra

Comp orcontra

Comp orcontra

Comp


30 �7� 30 �7� 30 �7� Flow Rate Medium Medium/high

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 6–10 5–10

CommentsElectrolytes: 1-1 and 1–3 can be used as alternatives.


Method Table—Electrolytic Polishing Method El-10Material: Aluminum and Al alloys. Antimony and Sb alloys.Beryllium and Be aloys. Bismuth and Bi alloys





Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2 1–2

AbrasiveType


Grit/GrainSize �m

P500 P1200 P2400 Tempera-ture°C �°F�

20–30�68–86�

20–30�68–86�

LubricantType


RotationDisk/Holder

300/150 150/150 150/150 Current A 1.5–2 0.2–0.4

rpm/rpmComp/Contra

Comp orcontra

Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� Flow Rate Low/medium High

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 5–15 10–20

CommentsCast Al with Si is not suited for electrolytic polishing. Al alloys with a low Si con-

tent can often be polished as Al alloys.Electrolytes: 1–1 and 1–3 can be used as alternatives.Al-Cu alloy should be polished with the electrolyte 1–3.Etching: Often electrolytic etching is not satisfactory, chemical etching is recom-

mended �see the Material/Preparation Tables, Section 13.2.3�.Fine grinding: By introducing grit P4000 SiC paper before electropolishing the

polishing time can be shortened and a possible relief reduced.Antimony: The electrolyte 2–1 can be an alternative.Beryllium: The electrolytes 1–1 and 1–4 can be alternatives.

Method Table—Electrolytic Polishing Method El-11Material: Chromium and Cr alloys






Disk/Cloth

SiCpaper

SiCpaper

SiCpaper

ElectrolyteNo.�Table.13.2�

2–1

AbrasiveType


Grit/GrainSize�m


20–30�68–86�

LubricantType


RotationDisk/Holder

300/150 150/150 150/150 CurrentA

1.8–2.2

rpm/rpmComp/Contra

Comporcontra

Comp

ForceperSpecimenN �lb�

20�4.5�

20�4.5�

20�4.5�

FlowRate

Medium

TimeMinutes

0.5–1

0.5–1

0.5–1 Time s 10–15 5–10

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 46�.Fine grinding: By introducing grit 4000 SiC paper and a rough polishing step �see

Method T-46, step P 1�, the polishing time can be shortened or deformations in the elec-tropolished surface can be avoided.

Method Table—Electrolytic Polishing Method El-12Material: Cobalt and Co alloys





Disk/Cloth SiCpaper

SiCpaper

SiCpaper

Electrolyte No.�Table. 13.2�

3–1 3–1

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 15–30 3–4


RotationDisk/Holder

150/150 150/150 150/150 Current A 1.8–2.5 0.1–0.2

rpm/rpmComp/Contra

Comp Comp Comp


15�3.4�

15�3.4�

15 �3.4� Flow Rate Medium Medium/high

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10–15 5–10

CommentsElectrolyte: As an alternative use phosphoric acid �85 %�.

Method Table—Electrolytic Polishing Method El-13Material: Brass. Copper alloys. Pure Cu





Disk/Cloth SiCpaper

SiCpaper

SiCpaper


3–2 3–2

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

20–30�68–86�

Lubricant Type Water Water Water Voltage V 15–30 3–4RotationDisk/Holder

300/150 150/150 150/150 Current A 1.8–2.5 0.1–0.2

rpm/rpmComp/Contra

Comporcontra

Comp Comp


20 �4.5� 20 �4.5� 20�4.5�

Flow Rate Medium Medium/high

Time Minutes 0.5–1 0.5–1 0.5–1 Time s 10–5 5–10

Comments brass: Having more than one phase, further fine grinding with SiC paper grit

4000 is recommended to shorten the electropolishing time. Also a mechanical polish-ing step with 3 �m diamond can be recommended �see Method T-49�.

Copper alloys: See also El-14.Copper with oxides: See brass above.


Method Table—Electrolytic Polishing Method El-14Material: Bronze. Copper bearing alloys





Disk/Cloth SiCpaper

SiCpaper

SiCpaper


4–2 4–2

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

20–80�68–86�

LubricantType


RotationalDisk/Holderrpm/rpm

300/150 150/150 150/150 Current A 1.5–2 0.1–0.2


Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� Flow Rate Medium High

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10–15 10–15

CommentsBronze and other alloys with several phases see Method El-13 regarding prepara-

tion before electropolishing.

Method Table–Electrolytic Polishing Method El-15Material: Lead and Pb alloys

Methods: El-15Grinding/Polishing

FG 1 FG 2 FG 3 Electro-polishingEtching


ElectroyticEtching

Disk/Cloth SiCpaper

SiCpaper

Cloth,napless,hardwov,sil


1–1

AbrasiveType

SiC SiC Dia sprorsusp

Area cm2 1

Grit/GrainSize �m

P500 P1200 6 Temperature°C �°F�

20–30�68–86�


LubricantType

Water Water Wat-oil Voltage V 40–60


150/150150/150 150/150 Current A 1.5–2

Comp/Contra

Comp Comp Comp


20�4.5�

20�4.5�

20�4.5�

Flow Rate Low

Timeinutes

0.5–1 0.5–1 5 Time s 3–5

CommentsEtching: Chemical etching �see Material/Preparation Tables 52�.Electrolytes: 1–2, 2–1, and 4–1 can be used as alternatives.Electrolytic polishing of Pb should only be last step in a mechanical preparation

process �see Method T-52�.

Method Table–Electrolytic Polishing Method El-16Material: Magnesium and Mg alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


4–1

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 Current A 1.5–2

rpm/rpmComp/Contra

Comp Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� Flow Rate Low

TimeMinutes

0.5–1 0.5–1 5 Time s 10–15

Comments


Etching: Often the surface is etched by the electrolyte. Chemical etching is recom-mended �see Material/Preparation Table 53�.

Electrolytes: 1–2 and 1–4 can be used as an alternative.

Method Table—Electrolytic Polishing Method El-17Material: Nickel and Ni alloys. Ni-based super alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 Current A 2–2.5

rpm/rpmComp/Contra

Comp Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� Flow Rate Low

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 56�.Electrolyte: 2–1 can be used as an alternative.Preparation before electropolishing: See Method El-13 and T-56.Short time �shock� polishing: Often a specimen, prepared according to M/PT 56

can be “cleaned” by electrolytic polishing in 1–2 s.

Method Table—Electrolytic Polishing Method El-18Material: Silver and Ag alloys


FG 1 FG 2 FG3 ElectropolishingEtching


ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2 1–2


AbrasiveType


Grit/GrainSize �m


20–30�68–86�

20–30�68–86�

LubricantType

Water Water Water Voltage V 20 15

RotationDisk/Holder

300/150

150/150

150/150 Current A 1.7

rpm/rpmComp/Contra

Comporcontra

Comp Comp


10�2.3�

10�2.3�

10�2.3�

Flow Rate Medium Medium

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10 5–10

CommentsElectrolyte: 1–1 can be used an alternative.

Method Table—Electrolytic Polishing Method El-19Material: Tin and Sn alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType

Water Water Water Voltage V 60

RotationDisk/Holder

300/150 150/150 150/150 Current A 1.5–2

rpm/rpmComp/Contra

Comp orcontra

Comp Comp


20 �4.5� 20 �4.5� 20 �4.5� Flow Rate Medium


TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10

CommentsEtching: Use chemical etching �see Material/Preparation Tables 59�.Electrolytes: 1–1 and 1–3 can be used as alternatives.Preparation before electropolishing: To avoid deformation, a rough polishing step

can be performed before electropolishing �see Method T-59�.See also Method El-10 for antimony alloys.

Method Table—Electrolytic Polishing Method El-20Material: Titanium and Ti alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–2

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

300/150 150/150 150/150 Current A 2

rpm/rpmComp/Contra

Comporcontra

Comp Comp


25 �5.7� 25 �5.7� 25�5.7�

Flow Rate Medium

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 20–30

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 60�.Electrolytes: 1-1, 1–2, and 2–1 can be used as alternatives.


Method Table—Electrolytic Polishing Method El-21Material: Tungsten and W alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper

Area cm2 1

AbrassiveType

SiC SiC SiC

Grit/GrainSize �m


20–30�68–86�

LubricantType

Water Water Water Voltage V 50

RotationDisk/Holder

150/150 150/150 150/150 Current A 2–2.5

rpm/rpmComp/Contra

Comp Comp Comp


20�4.5�

20�4.5�

20�4.5�

Flow Rate Low

Time Minutes 0.5–1 0.5–1 0.5–1 Time s 15–20

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 55�.

Method Table—Electrolytic Polishing Method El-22Material: Vanadium and V Alloys

Method El-22Grinding/ FG 1 FG 2 FG 3 Electropolishing/ Electrolytic ElectrolyticPolishing Etching Polishing EtchingDisk/Cloth SiC

paperSiCpaper

SiCpaper

Electrolyte No.�Tables 13.2�

1–3

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 Current A 2–2.5

rpm/rpm


Comp/Contra

Comp Comp Comp


15 �3.4� 15 �3.4� 15 �3.4� Flow Rate Medium

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 55�.Fine grinding: See Method El-11.

Method Table—Electrolytic Polishing Method El-23Material: Zinc and Zn alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


4–1

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 Current A 2–2.5

rpm/rpmComp/Contra

Comp Comp Comp


15 �3.4� 15 �3.4� 15 �3.4� Flow Rate Medium

Timeminutes

0.5–1 0.5–1 0.5–1 Time s 20–25

CommentsEtching: Chemical etching can be recommended �see Material/Preparation Tables

61�.Preparation before electropolishing: A rough polishing step can be performed to

avoid deformation �see Method T-61�.Electrolytes: 1–2 can be used as alternative.


Method Table—Electrolytic Polishing Method El-24Material: Zirconium and Zr alloys




ElectrolyticEtching

Disk/Cloth SiCpaper

SiCpaper

SiCpaper


1–3

AbrasiveType


Grit/GrainSize �m


20–30�68–86�

LubricantType


RotationDisk/Holder

150/150 150/150 150/150 Current A

rpm/rpmComp/Contra

Comp Comp Comp


15 �3.4� 15 �3.4� 15 �3.4� Flow Rate Medium

TimeMinutes

0.5–1 0.5–1 0.5–1 Time s 10

CommentsEtching: Chemical etching is recommended �see Material/Preparation Tables 62�.Electrolytes: 1–1 and 1–2 can be used as alternatives.For preparation before electropolishing: See Method T-62.

Method Table—Electrolytic Polishing Method El-25Material: Hard metals. Sintered carbides

Method El-25Grinding/ FG 1 FG 2 FG 3 Electropolishing/ Electrolytic ElectrolyticPolishing Etching Polishing EtchingDisk/Cloth See

belowSeebelow

Seebelow


5–1

Abrasive Type Area cm2 1Grit/GrainSize �m

Temperature°C �°F�

20–30�68–86�

Lubricant Type Voltage V 15–24RotationDisk/Holderrpm/rpm


Comp/ContraForce perSpecimenN �lb�

Flow Rate Medium

Time Minutes Time s 1

CommentsElectropolishing can only be done as a shock polishing. The specimen is prepared

according to Material/Preparation Tables 67 except for the last step, which is done aselectropolishing, shown above.

13.4 Field Metallography/Materialography—NondestructivePreparation

Nondestructive preparation is used for metallographic/materialographic examinationin the field on steam pipes, boilers, etc., and for inspection of large structures like dropforgings, weldings, etc. The preparation of the surface is along the same lines as for anormal specimen; both mechanical and electrolytic preparation can be used. Portableapparatus are available for mechanical grinding/polishing and electropolishing, eithercable- or battery-driven. A portable microscope is needed to check the prepared sur-face before, in most cases, a replica is made so that the microstructure can be examinedin the laboratory. The process, apparatus, and consumables are described in Part I.

13.4.1 Mechanical PreparationThe same grinding and polishing media are used as stated in the T-methods �see Sec-tion 13.2.3�. A surface of approximately 25 mm �1 in� diameter is prepared to be surethat a replica of 12 by 18 mm �0.5 by 0.75 in� can be made. The prepared surface isnormally chemically etched before the replica is made. The preparation should bedone very carefully and the prepared area cleaned between polishing steps and beforereplication �see also Manual Preparation, Section 13.2.4�.

Trouble Shooting: See Section 13.5/6.

13.4.2 Electrolytic PolishingNormally grinding before electropolishing is made mechanically by hand or with a por-table grinder. Often also a rough mechanical polishing is performed to shorten downthe electropolishing time and thereby improving the result. For electropolishing, thedata stated in Section 13.3.6 are used only the polished area and correspondingvoltage/current should be calculated. Etching can often be done electrolytically as partof the polishing process.

Trouble Shooting: See Sections 13.5.4 and 13.6.5.

13.4.3 ReplicationThe prepared surface is controlled with a portable microscope to ensure that the sur-face expresses a microstructure that can be accepted for further examination.

The replica can be made either with a piece of plastic �acetate� film or with anamount of silicon rubber-based material positioned on the prepared spot �see Section7.11.2�.


Plastic FilmThe plastic film, 12 by 18 mm �0.5 by 0.75 in�, normally made of methyl acetate, can beused in two ways. It can be wetted on one side with a suitable solvent such as monomethyl acetate and after a moment �5–10 s� to dissolve the surface, pressed against theprepared spot, or the spot can be wetted with the solvent, and the film pressed againstthe spot. It should be held against the work piece with stable, high pressure with a fin-ger, and it should be placed very carefully to avoid a movement parallel to the workpiece surface. It is important that the film adheres to the work piece before it is re-moved; usually a time of 10–20 s is needed.

In case the plastic film is transparent, it may be difficult to distinguish the details ofthe microstructure. This can be improved by coating the backside with black paint ortape. Another more complicated, but better type of enhancement is to place the replicain a sputtering device producing an interference layer on the replica �see Section 9.6.5�.

Silicone RubberThe silicone rubber material is dispensed with a hand-operated dispensing gun di-rectly on the prepared spot. The material will cure in 5–15 min and can be used at tem-peratures from −10°C �15°F� to 180°C �350°F�.

When the replica is made it is placed on a glass slide with double adhesive tape toimprove the handling both for microscopy and for filing together with the report.

See also Section 7.11 and ASTM Practice for Production and Evaluation of FieldMetallographic Replicas �E 1351� in Section 12.4.

13.5 Trouble Shooting—How to Improve Preparation Results

The goal of metallographic/materialographic specimen preparation is to produce aspecimen that gives a true picture of the microstructure, reflecting the influence of theprevious manufacturing process or any other process intended to influence or changethe properties of the material.

If the material has in any way been treated with an influence on the microstructureas a result, either thermally, mechanically, or chemically, this change has to be visibleso it may be classified or graded. In many cases the purpose of the metallographic/

Fig. 13.1—Part after torching, heavy thermal damage.


materialographic examination is the validation of the quality of the involved process.Therefore, it is of utmost importance that the finished specimen, after metallographic/materialographic preparation, displays the changes introduced during the manufac-turing, no more and no less.

The preparation must in no way change the structure which means it must not addany characteristics that have not been there before and, as important, it must not re-move any of the characteristics that have been introduced during manufacturing. Oth-erwise the metallographer may misinterpret the result shown in the microscope thatmight result in either faulty parts being classified as being satisfactory, or good parts asbeing scrap.

To illustrate the above here are a couple of examples: If a specimen is coated with athin layer of a soft material this coating can be smeared over the base material, indicat-ing a thicker layer than actually exists. Thus the layer can be measured and acceptedeven if the actual layer thickness is insufficient.

More often it will happen that correctly manufactured parts are rejected becauseof incorrect specimen preparation. If hardened materials are cut using insufficientcooling the reached temperature might anneal the material, resulting in a lower hard-ness. Thus, a complete batch of correctly treated parts might be scrapped only becauseof faulty specimen preparation.

The first case, accepting faulty parts as correct ones, might be the most critical, butthe other, scrapping good parts, can also be very costly.

Therefore it is essential that the prepared specimen shows what can be describedas the “True Structure.”

As shown previously, the entire preparation process can be divided into a series ofpreparation steps, from cutting over mounting to grinding and polishing. All thesesteps can introduce preparation artifacts if they are not carried out correctly.

In the following the individual preparation steps are listed and possible failuresthat can occur during these steps are explained. Afterwards these preparation artifactsand how to avoid or overcome them are discussed in detail.

13.5.1 SectioningThere are several possible reasons for sectioning:• To reduce the size of the work piece and turn it into a manageable sample.

Fig. 13.2—Part after sawing, heavy mechanical damage.


• To be able to measure or examine layers, coatings, hardened zones, or welds.• To be able to examine a part in different orientations or angles.

In all cases it is important to ensure that a representative part of the work piece istaken out for further examination. Especially important when sectioning a part with asurface treatment or some sort of layer is the correct angle of the cut. If the cut is notcarried out in an angle of 90° to the surface, the layer, coating, or hardened zone will beenlarged, and the result is a kind of taper section, something used quite often on pur-pose when mounting samples for easier measurement of layer thickness �see Section3.11.1�.

Apart from that, the most important consideration to take when sectioning is toavoid any mechanical or thermal influence that could alter the structure. As previouslydescribed, wet abrasive cutting is the most appropriate way of sectioning when alsotime and economy are considered.

Most of the other sectioning techniques introduce either heavy thermal damagesuch as after torching as shown in Fig. 13.1, or mechanical damage as is the case afterhacksawing to be seen in Fig. 13.2. In case of bandsawing, however, an acceptable re-sult often can be obtained when the correct machine, saw blade, speed, pressure, andcutting fluid are used.

For this reason the following examples are concentrating on wet abrasive cuttingand bandsawing. However, also with these two methods, thermal or mechanical, dam-age can occur if care is not taken.

Thermal DamageThermal damage is a result of excessive heat generated in the cut. Either because ofinsufficient cooling due to an insufficient amount of cutting fluid in the actual cut orbecause the feed speed is too high and thus too much heat is introduced �see Section2.3�. Thermal damage can change the structure of the material to be examined whichespecially is critical with heat treated parts where these structural changes can result inwrong readings in the following microhardness tests. To avoid thermal damage makesure that there always is plenty of cooling fluid in the cut and that the feed speed is setcorrectly, i.e., not too high �see Figs. 13.7 and 13.8�.

In wet abrasive cutting, also the selection of cut-off wheels is important. Wheelswith a hard bond release abrasive grains slower. That makes them more economicalbut also less suited for cutting of harder materials, as blunt abrasive particles will notcut properly, but instead introduce heat and result in thermal damage �see also Section2.3.5�. At bandsawing, the type of saw blade is important �see Section 2.7.4�.

Mechanical Damage

Wet Abrasive CuttingMechanical damage mostly occurs when cutting brittle materials or materials withbrittle or fragile coatings. In many cases damage first occurs when the cut-off wheel isexiting the part to be sectioned. If the force or the selected feed speed is too high, thesample fractures easily. If it is not possible to use a low pre-set constant feed-speed andthus avoid the damage, it usually helps to support the sample with some similar mate-rial or bond it onto another material using wax.

When cutting coated materials it is very important to cut through the layer or coat-ing into the base material as this then acts as a support. Otherwise the layer might bepushed away from the base material resulting in cracks or delamination. During the


final examination in the microscope it can be impossible to tell if this kind of fault is areal fault from production or if it has been introduced during cutting. Cylindrical,coated samples can, if possible, be rotated during cutting, thus securing support of thecoating over the entire circumference.

BandsawingBandsawing, as a rule, always leaves more mechanical damage than wet abrasive cut-ting. For most materials this damage, if all sawing parameters are correct, can be re-moved through an effective plane grinding, but in case of a too low band velocity or atoo coarse pitch of the band, or both, an unacceptable mechanical damage can be de-veloped. Also, feed speed that is too high or a cutting fluid that is not enough or is wrongmay give a very rough surface with deep mechanical damage.

13.5.2 MountingThere are several reasons for mounting samples. The most common reason is simply toget specimens with uniform size and shape to facilitate future preparation. In this case,requirements to the mounting techniques are limited. However, a few matters shouldbe considered.

If the sample to be mounted is sensitive to heat, cold mounting should be preferredto hot mounting, because the temperature during hot mounting can get as high as180–200°C �350–400°F�. Cold mounting is not really “cold” but temperatures seldomexceed 100°C �210°F� for a normal-sized mount of 30 mm �1.25 in� diameter.

If the temperature is really critical then only slow curing epoxy resins can be used.To keep temperatures as low as possible epoxy resins can sometimes even be cured in arefrigerator. That takes a longer time but the temperature of the mount does not exceedroom temperature.

Some materials and fragile samples are sensitive to pressure. In this case, hotmounting cannot be used and cold mounting must be utilized instead.

ImpregnationPorous materials are usually impregnated under vacuum and here epoxy resins areused; most of the other resins will start boiling when exposed to a pressure below theatmospheric pressure. Vacuum impregnation has several advantages:• Vacuum impregnation acts as a reinforcement of the sample because the resin

works as a bonding agent in the pores. This facilitates the following specimenpreparation as pull-out of material is eliminated or at least reduced. Pull-out of par-ticles during the final polishing steps is very often the cause of deep scratches re-sulting in lengthy reruns of the preparation method.

• Colored dyes can be added to the epoxy resin to help distinguish between porosityand pull-out. Very often fluorescent dyes are used as these show up more brightlythan normal colors. This dye is added to the epoxy resin before impregnation. Dur-ing impregnation all pores connected to the surface are filled with the dyed epoxyresin and after the preparation is finished all the filled pores can be identified easily.Areas that are not filled can then be either unfilled pores or pull-outs. The trainedmetallographer can often determine pull-outs from pores by looking at the circum-ference of the “hole.” Pull-outs leave a more jagged edge than real pores �see alsoSection 3.10�.


ShrinkageA general rule when cold mounting is that the faster a resin cures or the higher thecaring temperature gets, the higher the shrinkage. Shrinkage of the resin can result in avariety of preparation artifacts �see also Section 3.1�.

StainingWater, cleaning agents, alcohol, and etchants are trapped in the gap between specimenand resin Cleaning is almost impossible and the different liquids will continue seepingout of the gap and staining the specimen. This can produce problems both when exam-ining the specimen, but also when etching the specimen, as some other liquid mightcover part of the surface, which then will not be attacked correctly �see Fig. 3.1�. Whenhydrofluoric acid is used for etching, this can even ruin the objective of the microscopebecause the acid seeping out of the gap during examination of the specimen might etchthe glass.

Fig. 13.3—Deformation after grinding on SiC grinding stone, grit 150.

Fig. 13.4—Deformation after grinding on ZrO2/Al2O3 paper, grit 120.


ScratchingIf the gap is large enough, coarse abrasive grains from an earlier preparation step canbe transferred to one of the final steps, ruining the preparation result and contaminat-ing the polishing cloth.

Edge RoundingGaps can also result in edge rounding of the sample, as the resin cannot support theedge of the sample. However, when using modern preparation methods, this risk isquite limited since the consumables used today provide very good edge retention.

DelaminationWhen resins with relatively high shrinkage are used for mounting of samples with po-rous coatings, the coating can be pulled away from the substrate during the polymer-ization of the resin This is quite rare and not explained in the section: How to OvercomePreparation Artifacts.

Fig. 13.5—Deformation after grinding on SiC paper, grit P1000.

Fig. 13.6—Deformation after grinding on rigid composite disk �RCD� using 6 �m diamonds.


13.5.3 Mechanical PreparationAs cutting or mounting, or both, not always are necessary operations the “real” speci-men preparation process usually is defined as grinding and polishing.

Preparation time should be kept as short as possible. In production control, time isimportant and the faster the specimens are finished the earlier production can con-tinue. The second important point is that shorter preparation times usually also reducecosts for consumables and labor.

The first preparation step is grinding.

GrindingThere are two considerations when the grinding process is started.• How is the surface finish from the previous cutting?• Are the specimens prepared as single specimens or are they clamped in a specimen

holder?If cutting has been carried out correctly the surface finish is in many cases suffi-

cient for immediate fine grinding. However, if the specimens are clamped together in aholder, plane grinding has to be carried out first to level all specimens in the specimenholder at the same height.

In this case the correct grit/grain size of abrasive has to be selected to have a re-moval rate high enough to achieve short grinding times, but on the other hand, not toocoarse to avoid unnecessary deformation which then must be removed in the followingsteps. Figures 13.3 and 13.4 show the deformation after plane grinding with a grindingstone, 150 grit and a ZrO2/Al2O3 grinding paper, grit 120, respectively, and the heavydeformation is evident. Figures 13.5 and 13.6 show the much smaller deformation atSiC grinding paper grit P1000 and a rigid composite disk �RCD� using 6 �m diamonds.

Especially with soft materials, very coarse grit sizes should be avoided. The defor-mation introduced can be very deep and might take a very long time to be removed inthe following steps. It can even happen that fractured abrasive grains become embed-ded into the soft material during the preparation and may disturb future preparation.

Like with cutting, sufficient cooling is required to avoid thermal damage of thespecimens. Water is in most cases sufficient but for water-sensitive materials other flu-ids like water-free oil can be used to avoid attack of the sensitive phases. Recirculationcooling systems are advantageous in these cases because the fluid is reused continu-ously. However, in many cases even water-sensitive materials can be ground using wa-ter as a lubricant during the first step since plenty of material still is removed after-wards and material is removed beyond the damaged area.

PolishingAfter grinding to a sufficiently fine finish the preparation is continued with polishing.During polishing the last deformation is removed and a reflective surface is produced.A reflective surface is necessary for examination in an optical microscope. Addition-ally, the surface should be plane without height differences between different phases orrounded edges. Otherwise a correct evaluation of the specimen might be difficult oreven impossible. Especially when working with very thin coatings, edge rounding can-not be tolerated.

There are several ways to avoid edge rounding and unplaneness. Using the correctmounting technique was already mentioned, but also the choice of polishing cloths is


very important for the result. Soft cloths usually give a better reflectivity but can easilygenerate unplane samples and rounded edges.

During polishing, a lubricant must be used to avoid any thermal damage. Espe-cially during the final stages of the preparation, water-free products must be used if thematerial to be prepared is water sensitive. Otherwise certain phases might be attackedor even dissolved and a correct assessment is no longer possible.

13.5.4 Electrolytic PolishingAs described in Section 8.3, electrolytic polishing is well suited for the preparation ofhomogeneous materials whereas it is difficult, in most cases impossible, to get accept-able results with heterogeneous materials. The most common artifacts are relief, miss-ing inclusions �see Fig. 8.6� and edge rounding �see Fig. 8.8�.

In any case, like with mechanical preparation, it is important that the consum-ables used are in perfect condition. Take care that the correct electrolyte for the givenmaterial is available �see Section 13.3�. The electrolyte must not be too old since impu-rities in the electrolyte may cause phenomena that might lead to a wrong interpreta-tion of the prepared specimen. Used electrolytes may be heavily loaded with metal ionsfrom the specimens. These ions can act as catalysts and reduce the lifetime of the elec-trolyte which in turn will have a negative influence on the following preparation.Therefore the electrolytes must be discarded in due time.

13.5.5 General Rules—“The Metallographer’s Rule of Thumb”Before the actual preparation process is started it is important to define the purpose ofthe specimen preparation: “Why am I going to prepare this specimen; what do I want toevaluate?”

If you are working with the inspection of incoming materials and have to check acertain type of steel for a certain heat treatment, e.g., normalized, a short preparationof an unmounted sample will in most cases be sufficient. A slight rounding of the edgeor a few scratches will not influence the examination. In this case it is important to get aresult in a very short time and in many cases also at low cost. Therefore a short prepara-tion method with few steps is selected.

However, specimens with very specific characteristics, such as a very thin coatingthat has to be measured accurately, must be treated in a completely different way. Al-ready during cutting great care has to be taken to avoid damage of the coating. Thesample should be mounted in a resin with low shrinkage to prevent any edge roundingand also the preparation method has to be selected carefully with regards to planenessand edge retention. The entire preparation process will take longer, as in the previousexample, and the cost will be higher, but it is the only way to ensure that the correctresult is obtained.

When the purpose is established, use the “Metallographer’s Rule of Thumb,” whena new preparation procedure shall be developed:

Put Up a Goal for Each Preparation StepWhen following this rule, the result of every step is checked in the microscope. This isto avoid that one of the early steps are not correctly made, a fact that often is not real-ized before the final polishing step, causing a repetition of the whole process.

The above also means that you request as much information as possible if you areasked to prepare a new material or a different kind of sample. Without having sufficientinformation about the type of material, mechanical, chemical, or thermal treatment,


service history and request to the final examination, it is very difficult to choose thecorrect preparation method and to put up acceptable goals for the preparation process.

13.6 Trouble Shooting—How to Overcome Preparation Artifacts

In the following sections the most important preparation artifacts are described insome detail and solutions on how to avoid or overcome them are presented.• Whenever a new method is established for a specific material, the specimens

should be checked under the microscope after every step to ensure that thescratches, deformation, and other possible damage from the previous step havebeen removed before continuing with the next step.

• The preparation times should be kept as short as possible without sacrificing thequality of the preparation. This usually results in specimens with better planenessand edge retention and saves time and consumables.

• When utilizing “fresh” consumables like RCDs or polishing cloths where abrasivehas to be added, they have to be used for a while before they reach maximum per-formance. Allow for a slightly longer preparation time in the beginning.The first part of the preparation process, sectioning, does by and large not cause

very high requirements to the equipment used. But generally it can be said that at wetabrasive cutting the more automatic cut-off machines can produce better or at leastmore repeatable results than manual equipment.

Mounting depends much more on the correct choice of consumables than on theequipment used, especially with cold mounting where no equipment except maybe avacuum chamber for the impregnation is employed.

With the grinding and polishing procedures it is a completely different situation.To be able to achieve the best possible preparation results and to use the guidelinesstated in the following sections, the specimen preparation has to be carried out on ei-ther semiautomatic or automatic equipment. Otherwise it is not possible to controlforce, time, dosing levels, polishing dynamics and other preparation parameters andconsistent results can only be accomplished with great difficulty.

13.6.1 Preparation Artifacts—Flow ChartsThe following artifacts are described both in words and pictures, and a flow chart isused to show ways to improve the quality of the prepared specimen and avoid theartifacts.

SectioningThermal damageMechanical damageCracksDelamination

MountingStainingScratchingEdge rounding


Grinding and PolishingScratchingLapping tracksDeformationSmearingPull-outs—False porosityEmbedded abrasiveDestroyed inclusions—Pull-outsEdge rounding and reliefComet tails

Flow Chart SymbolsThe symbols used in the flow chart indicate the following:

13.6.2 Sectioning—General Problems—Flow Charts

Wet Abrasive Cutting

General ProblemsAs an introduction to the flow charts for the specific artifacts connected to wet abrasivecutting, a number of general problems with suggested solutions are indicated in thetable below.

Problem Cause Solution

Wheel does not cutor stops cuttingafter some time

Incorrect wheel, theabrasive hasbecome blunt, or therim of the wheelhas been clogged

Use a softer wheel,or in case ofvery hard materialuse diamond orCBN as abrasive

Arc of contact too large Increase the force,if possible

Use oscillating cutting

Wheel wears very fast Wheel is too soft Use a harder wheel

Wheel wobbles orvibrates

Wheel is not straight Change wheel

Wheel is not clampedcorrectly

Clamp the wheelcorrectly

Wheel is too hard Use a softer wheelor reduce thespeed of the wheel

Bearings of machine are defect Have machine repaired

Wheel breaks Feed speed too high Reduce the feed speed


Problem Cause Solution

Work piece has moved Clamp the work piececorrectly

Wheel bends while cutting Did the wheel attack atilting surface? Take carethat a notch is madebefore the cutting starts

Check fixation of workpiece

“Disk brake effect,”the wheel ispinched in cut

Internal stress in workpiece, lower feed speedor preferable useoscillating/step cutting,clamp sample downwards on both sides

Wheel does notcut straight

Wheel bond varies Change wheel

Work piece not clampedcorrectly

Realign and clamp workpiece

Attack of wheel notperpendicular

Change position of workpiece ortake care that the wheelmakes a notch before thecutting starts

Feed speed too high Reduce feed speed

Signs of overheatingof specimen surface

Wheel is too hard ortoo thick

Use a softer wheel ora thinner wheel

Feed speed too low Increase feed speed

Wheel is clogged Used a softer wheel

Feed speed too high Reduce feed speed

Arc of contact too large Change position ofwork piece oruse a softer wheel

Cooling not efficient Check the cooling system, thelevel of the cooling liquid and thepositioning of the nozzles

Foam and smell from thecooling liquid, or both

Additive to coolingliquid is not active,bacteria might havedeveloped

Check that the cooling liquid hasthe correct additive content orclean system using bacterial killer, or both.

Wet Abrasive Cutting—Flow Charts

Thermal DamageThere can be different reasons for thermal damage of the sample during cutting.Mostly thermal damage is directly visible as discoloration on the cut surface, as shownin Fig. 13.7. A cross section through the discolored area shows how deep the thermaldamage extends, see Fig. 13.8. A correctly cut sample does not display any discolora-tion and is free from any thermal damage, as shown in Fig. 13.9. The most commonreason is the lack of cooling fluid during cutting. A relatively large amount of coolingfluid is needed to remove the heat generated during cutting. Therefore the


recirculation-cooling unit has to be monitored and the level of cooling liquid checkedregularly and refilled if necessary.

Another reason might be the wrong selection of the cut-off wheel. As described inSection 2.6.1, different cut-off wheels are available for different materials. If a wheel isused which is too “hard” for the material to be cut, “free cutting” cannot be obtained,the specific pressure in the cut rises and overheating will take place. To avoid overheat-

Fig. 13.7—Thermal damage after cutting with insufficient cooling.

Fig. 13.8—Cross section of part shown in Fig. 13.7, deep thermal damage can be seen.


ing a softer wheel must be used. A softer wheel will break down faster, releasing moreabrasive grains and consequently cut more efficiently through hard materials.

The same behavior can be achieved by reducing the speed of the cut-off wheel. If itis possible to adjust the spindle speed on the cut-off machine the “hardness” of thewheel can be modified. Lower speed makes the wheel act softer and higher speed pro-duces harder wheels �see Section 2.3.8�. Instead of changing wheels when different ma-terials have to be cut, an adjustment of the wheel speed can simply compensate for thevariation in hardness of the different materials.

The third reason for thermal damage is very often a too high feed speed. Materialfrom the sample cannot be removed as fast as the wheel is moved into the cut. “Freecutting” is not achieved and overheating is taking place �see Sections 2.3.5 and 2.3.8�.Often the reason for using high feed speed is to save time. This is usually not a goodidea, since the time saved during cutting has to be used again in the grinding process toremove the thermal damage. In many cases more time has to be spent than was savedin the first place. Therefore it cannot be recommended to go too fast during cutting; itusually prolongs the total preparation time instead of reducing it.

Thermal damage during cutting can usually be avoided if these three guidelinesare followed:• Check and maintain the correct cooling fluid in the recirculation-cooling unit. Di-

rect the cooling fluid into the cut.• Select the correct cut-off wheel for the material to be cut. If a variable wheel speed

is available it can be used instead of changing the cut-off wheel.• Adjust the feed speed depending on sample material and size.

Fig. 13.9—No thermal damage after cutting.


Abrasive Wet Cutting, Thermal Damage

Mechanical DamageWhen cutting correctly, the total amount of applied energy can be transformed intoremoval of material. If the feed speed is too high more energy is applied than can betransformed. The excess energy has to be consumed somehow, and where it often istransformed into heat resulting in thermal damage with metallic materials, it can re-sult in the initiation of cracks in brittle materials as shown in Figs. 13.10 and 13.11.

Fig. 13.10—Plasma sprayed coating with crack.


With solid materials we very often get cracks extending from the surface into the mate-rial whereas we often see delamination, the separation of layers, with coated materials.Therefore special care has to be taken with ceramics and other brittle materials andwith coated materials. In Fig. 13.12 a delamination is seen; the coating is not in contactwith the base material.

In many cases thermal damage is restricted to the area around the cut, whereascracks propagate deep into the material.

Often materials are examined to see whether cracks or delamination have beenintroduced during the manufacturing process. This means that cracks or delaminationthat have been introduced during cutting might cause the entire series to be scrappedor at least lead to a lot of extra work, because the production process will be suspectedto be faulty. This can be avoided by impregnation of the specimen before cutting usingan epoxy with a fluorescent dye. In Fig. 13.11 a specimen is shown that has beenvacuum impregnated before grinding and polishing so when examined in the micro-

Fig. 13.11—Prior to grinding and polishing, the sample was vacuum impregnated using anepoxy resin with a fluorescent dye �showing up green when examined using fluorescent light�.As the crack is completely filled with resin it was there before the grinding and polishing werestarted. Whether it was there before cutting or created during cutting cannot be said.

Fig. 13.12—Delamination between coating and base material.


scope it can be seen whether a crack existed before the preparation. The same type ofimpregnation can be done before cutting.

To reduce the risk of introducing cracks during cutting a few simple rules shouldbe followed.• Always use moderate feed speed.• Use the correct cut-off wheel for the material to be cut. In the case of coatings the

cut-off wheel should be selected to suit the majority of the material, e.g., a thin ce-ramic coating on a steel bar should be cut using an abrasive Al2O3 wheel suitablefor the steel bar instead of using a diamond cut-off wheel that would suit the ce-ramic coating only.

• Thin cut-off wheels should be preferred to thicker wheels because they remove lessmaterial and thus introduce less energy.

• With very brittle and fragile materials, vacuum impregnation prior to the cut canreinforce the samples and prevent cracking.

• With coatings: always cut through the coating into the base material. Thus thecoating is supported all the time and the risk of cracking is reduced.


Abrasive Wet Cutting, Mechanical Damage

Bandsawing

General ProblemsWhen working with a vertical bandsaw a number of problems can be experienced, andbelow the most important of these are listed with suggested solutions �see also Section2.7.4�.


Problem SolutionPremature dulling of teeth Decrease band velocity.

Use band with finer pitch.Apply proper cutting fluid when cutting ferrousand nonferrous materials.Keep teeth engaged. Do not allow the teeth toidle through cut.Increase feeding pressure.Apply cutting fluid at point of cut, saturating theteeth evenly when cutting ferrous andnonferrous alloys.Be sure that band is running with teeth pointingdown.

Band vibrating in the cut Increase or decrease band velocity.Increase band tension.Use band with finer pitch.Increase feeding pressure.Hold work piece firmly.

Band teeth ripping out Use fine-pitch bands on thin work piecesections.Eliminate vibration by holding work piecefirmly while it is fed into the band.Use cutting fluid on ductile materials.If gullets are loading, use heavier duty cuttingfluid.Reduce feed pressure.

Surface of finished cut toorough

Increase band velocity.Use band with finer pitch.Use slower feeding rate.Apply correct amount of proper cutting fluid.

Premature band breakage Change to band with gage that is not too heavyfor diameter of wheels and speed of themachine.Decrease band velocity.Check periphery of wheels for defects.Cracking at weld. Try longer annealing period,decrease unit load by using finer pitch.Decrease feeding pressure.Decrease band tension.Properly adjust band tool guides.Apply cutting fluid.

Band making belly-shaped cut Increase band tension.Adjust guides close to work piece.Use band with coarser pitch.Decrease feeding pressure.


Gullets loading Use band with coarser pitch.Apply cutting fluid.Lower band velocity.

Band not running true againstsaw guide backup bearing

If clicking against saw guide backup bearing,remove burr on back of band where joined.If hunting back and forth against saw guidebackup bearing, re-weld with back of band intrue alignment.Check alignment of band carrier wheels.Check saw guide backup bearing, if worn orunbalanced, replace same.

Negative camber developing inband

Band riding too heavy on saw guide backupbearing. Adjust band for alignment on top andbottom wheels.

Cutting rate too slow Increase band velocity.Use band with coarser pitch.Increase feeding pressure.Apply cutting fluid.

Band leading in cut Unbalanced set or partial dullness caused bystriking hard inclusion in material being cut.Apply cutting fluid.Saw guides out of adjustment. Carefully readjustguide inserts or rollers. If worn, replace same.In the case of brush-equipped cut-off machines,make sure brushes are properly adjusted, ifworn, replace with new.Reduce feeding pressure.

Premature loss of set Band too wide for radii being cut.Decrease band velocity.Apply cutting fluid.

Positive camber developing inband

Reduce feeding pressure.Use band with coarser pitch to permit greatertooth penetration.Saw guides too far apart, adjust closer to workpiece.

Band developing twist Band binding in cut, decrease feeding pressure.Side inserts or rollers of saw guides adjusted tooclose to band.Wrong width of band for radii.Decrease band tension.


13.6.3 Mounting—General Problems—Artifacts

General Problems—Hot MountingIn the following overview some of the general problems that can arise during hotmounting are shown and both cause and the possible solution are described �see alsoSection 3.6�.

General Problems—Cold MountingIn the subsequent overview some of the problems that can arise during cold mountingare shown and both cause and the possible solution are described �see also Section3.13�.


Problem Cause/SolutionThe surface of the mount issticky after normal curing time.

The components are not mixed in the correctquantities, the mixing has not been correct orthe room temperature has been too low.Mix carefully with the exact portions of eachcomponent and check that the roomtemperature is approx. 20–22°C �68–72°F�.Also cover the mounting cup so as to preventany reaction between the surface of the mountand the air.

The mount is brown aftercuring, too rapid curing.

The temperature during curing has been toohigh.Mix carefully with the exact portions of eachcomponent and check that the roomtemperature is approx. 20–22°C �68–72°F�.When using large amounts of resin make surethat the mount is cooled during curing. Useeither a stream of cool air, a water bath or arefrigerator.

It is very difficult to remove themount from the mounting mold.

The mounting resin �epoxy� has very littleshrinkage and good adhesion to all materials.Use a more flexible mounting mold or coat theinner surface with a thin layer of silicone moldrelease agent.

The mount is soft after curing,not cured completely.

The components are not mixed in the correctquantities or one of the components is too old.Check the expiry date of the components andmake sure to measure the correct quantities ofeach component. The mount can maybe besaved by placing it in an oven at 40–50°C�100–120°F�.

Specimen moves, turns, falls orfloats in the mounting mold.

The specimen is very light.Coat the bottom of the mounting mold withspray lacquer and position the specimen beforethe lacquer is dry or use double adhesive tapeto secure the specimen.

StainingStaining is the discoloration of the specimen surface through residues of liquids usedduring preparation, cleaning, or etching of the specimen.

Sometimes staining is used to purposely contrast the specimen surface in order toidentify different phases, but here we are only talking about unintended discoloration.

Staining usually occurs when the sample is not mounted correctly and there is agap between the sample and the mounting material. This gap is often filled with lubri-cant that is accumulated there during polishing or with cleaning liquid or etchant thathas been used during the preparation process. Very often the gap is rather narrow, butthe capillary action fills the gap easily with liquid. Figure 3.1 �Section 3.1.2� shows a


specimen surface with staining caused by a gap, and in Fig. 3.2�b� a correct mount isseen without gap and consequently without staining.

To avoid staining the subsequent rules can be followed:• Always clean and degrease the samples prior to mounting; this will provide a better

adhesion of the resin to the sample.• Select a resin with very low shrinkage; these usually are hot mounting resins con-

taining a filler material or epoxy resins for cold mounting. The epoxy resins providethe best result, especially with vacuum impregnation; however, the long curingtime often prohibits their use.

• Clean the specimen carefully after each step, possibly using ultrasonic cleaning.• Dry the specimen very thoroughly to avoid bleeding out of liquids during examina-

tion with the microscope.• Use a piece of soft tissue together with a hair dryer to make sure that all liquid is

removed from the gap. �Be careful with soft materials that the tissue does notscratch the material.�

• After etching the specimen make sure that all etchant is removed from the speci-men or the gap in the specimen, otherwise the specimen might start “bleeding” onthe microscope. This can destroy the specimen, or, if hydrofluoric acid was used,even the objective of the microscope.

ScratchingScratching is usually not related to mounting; however, under certain circumstances apoor quality of the mount might result in scratching of the specimen surface.

As with the previous example, incorrect mounting can result in a gap between thesample and the mounting material. During preparation some of the abrasive particlescan be trapped in the gap and carried on to the following preparation stage, as shown inFig. 13.13. If the particles are falling out of the gap and stay on the polishing cloth theywill result in few but distinct scratches.

To avoid scratching because of poor mounting quality, follow these rules:

Fig. 13.13—Abrasive grains in the gap between sample and mounting resin When these fallout during preparation they will result in scratching.


• Always clean and degrease the samples prior to mounting; this will provide a betteradhesion of the resin to the sample.

• Select a resin with very low shrinkage; these usually are hot mounting resins con-taining a filler material or epoxy resins for cold mounting. The epoxy resins providethe best result, especially with vacuum impregnation; however, the long curingtime often prohibits their use.

• Clean the specimen carefully after each step, possibly using ultrasonic cleaning.If abrasive particles are carried from one preparation step to a following step, it

will not only damage the specimen and require at least part of the preparation methodto be repeated, it will also require the contaminated polishing cloth to be exchanged.The result is both longer preparation time and increased cost �see also Section 13.6.4�.

Edge RoundingMounting is often carried out to protect the edges of the sample, especially when thesample is coated with very thin layers of another material. To be able to measure thethickness of these layers accurately it is crucial that they are absolutely plane withoutany rounding. The same is valid when microhardness testing has to be carried out veryclose to the edge; also here perfect planeness of the sample is required.

Today’s selection of consumables for grinding and polishing has made the prepa-ration easier and faster as previously stated. Still, when the maximum edge retention isrequired it is usually not possible to avoid mounting the samples. The correct mount-ing resin has to be selected carefully to avoid a gap between sample and mounting ma-terial, and usually there are not so many choices. The best option when mountingsamples with porous or fragile coatings is epoxy resin because this can be used undervacuum and will provide both a reinforcement of the coating and a mount without anygap. For mounting of samples with very hard coatings or the mounting of surface hard-ened materials it can be advantageous to use hot mounting. In this case resins withdifferent filler materials are available. This makes it possible to select a mounting resinthat has similar wear characteristics as the material to be prepared. Thus a uniformremoval of material across the entire specimen surface is obtained and perfect plane-ness and edge retention will be the result �see Section 3.1.3.� Figure 3.2�a� shows amount with a mounting material not in contact with the sample, causing edge round-ing. In Fig. 3.2�b� the correct mounting material adhering to the sample is used.

13.6.4 Grinding and Mechanical Polishing—Flow Charts

ScratchingThe mechanical removal of material from the surface is carried out step-by-step usingcontinuously finer grain sizes of abrasive. The abrasive particles act as machiningtools, removing small chips of material. As a result, the surface is covered with unidi-rectional grinding scratches getting smaller after every step of the preparation, disap-pearing totally at the end, or at least being so small that they are no longer visible in anoptical microscope. The unidirectional pattern is achieved when the specimen is pre-pared using some kind of automatic or semiautomatic preparation equipment as de-scribed in Section 7.9. To avoid scratches on the finished sample, the specimen has tobe examined after every preparation step to ensure that all scratches from the previousstep have been removed completely before continuing to the following step. Otherwisesteps from one of the early grinding steps might still be visible after final polishing. It iscrucial that the specimen is checked carefully after every step because the removal rate


of smaller abrasives is much less than that of larger abrasives causing the polishingtimes needed to be extremely long if a final polishing step should remove scratchesfrom an initial grinding step. Figure 13.14 shows the very rough scratch pattern withheavy deformations after plane grinding, in contrast to the pattern developed duringthe fine grinding shown in Fig. 13.15.

It is also very important to clean the specimens carefully after every step as con-tamination of a polishing cloth quite easily can occur. �Scratching because of mountinggaps has been described in Section 13.6.3.�

Fig. 13.14—Scratched and deformed surface after plane grinding.

Fig. 13.15—Uniform scratching after fine grinding.


Scratching

Lapping TracksDuring mechanical preparation the abrasive particles should act as small cutting tools,machining chips from the surface of the specimen. This requires the abrasive grain tobe held firmly on the polishing cloth while the specimen is passing over it as the abra-sive grain otherwise will start rolling.

Since we use loose abrasives that are added during preparation, this presents achallenge to the polishing cloth used. The polishing cloth must be selected carefullydepending on the grain size of abrasive it is going to be used with and especially inrelation to the hardness of the material to be prepared. If the polishing cloth is too softthe abrasive will disappear into the fabric and will not remove any material. If the pol-


ishing cloth is too hard the abrasive cannot be pressed deep enough into the cloth andthe abrasive may start rolling, resulting in lapping tracks. If the cloth is even harder, ora rigid fine grinding disk with too high of a hardness is used, the abrasive might even bepressed into the sample material and become firmly embedded �see the section belowon embedded abrasives�.

Lapping on softer materials does not remove any material, it only introduces deepdeformation. The lapping tracks are easy to identify, they follow a straight line, like agrinding scratch; however, it is interrupted as the abrasive grain is tumbling across thesurface, as shown in Figs. 13.16 and 13.17 in bright field �BF� and differential interfer-ence contrast �DIC�, respectively.

For information on polishing cloths see Section 7.4.

Fig. 13.16—Specimen with lapping tracks, BF.

Fig. 13.17—Specimen with lapping tracks, DIC.


Lapping Tracks

DeformationThe entire mechanical preparation process is based on the removal of material throughgrinding and polishing as described earlier. Any mechanical treatment will result in acertain amount of plastic deformation of the surface of the specimen. It is the purposeof metallographic/materialographic specimen preparation to remove the deformationfrom the surface to allow for the examination of the true structure. Therefore,metallographic/materialographic specimen preparation is carried out in steps togradually remove the deformation from the previous steps; see Fig. 13.18 that showsthe preparation process schematically from the surface left after cutting through planegrinding, fine grinding, and polishing to a surface to be examined on the microscope�see also Section 7.7�. However, very often some residual deformation is left after thepreparation is finished and that can lead to wrong conclusions; see Fig. 13.19 thatshows the remaining deformation from an earlier grinding step. Therefore, it is


Fig. 13.18—The preparation process. Deformation is removed step-by-step.

Fig. 13.19—Remaining deformation from preparation, following early grinding scratches.


important to follow certain preparation routines and to check the specimens fre-quently during preparation.

Generally each step has to remove the material deformed during the previous step,while at the same time only introducing a limited amount of new deformation. Withtoday’s modern consumables the preparation of most materials can be reduced toabout four steps resulting in a deformation free sample surface. If these steps are notcarried out correctly deformation may be visible after preparation. Very often the de-formation is first visible after etching. Especially color etching will reveal even thesmallest amount of remaining deformation as shown in Fig. 13.20.

Fig. 13.20—Color etched specimen, remaining deformation can clearly be seen.

Fig. 13.21—Smearing on a soft type of steel.


Deformation

SmearingSmearing is not as common as many of the other artifacts; however, it is important tobe aware of the possibility and the influence smearing can have on the final result.Smearing usually happens with very soft materials, as shown in Fig. 13.21, and oftenwhen soft materials are contained in layers. Instead of being cut cleanly the material ispushed across the surface. Especially when the thickness of layers has to be measured,e.g., copper and solder layers on a PCB, the correct thickness must be obtained, other-wise the part might be not acceptable. As can be seen in Fig. 13.22 the soft solder mate-rial has been deformed and dragged across the copper layer following a coarse grind-ing scratch. The exact measurement of the different layers in this case is not possible.Therefore, smearing is not acceptable and has to be avoided. Also, smeared materialmay hide the pores in the surface �see Pull-Outs—False Porosity, below�.

Mostly the occurrence of smearing is due to one of the following reasons:• Wrong type of abrasive used. Abrasives that are too blunt cannot cut properly and

may result in smearing. Therefore diamond is the best choice of abrasive for thefirst, relatively coarse polishing steps. Diamond is the hardest known abrasive andconsequently will produce a clean cut over a long period of time. Polycrystallinediamonds are superior for specimen preparation.


• Insufficient lubricant level during polishing. When the amount of lubricant addedto the polishing cloth is too low, the lubricant film between specimen and cloth canbe imperfect and thus smearing can occur. The lubricant level should be main-tained on a stable level throughout the entire preparation step in a way that thepolishing cloth is moist but not wet.

• Polishing cloths that are too soft. With soft polishing cloths the abrasive can bepressed too deep into the textile and thus not create any cutting action. Change to aharder polishing cloth or increase the abrasive grain size �see below�.

• Abrasive grain size that is too small. This is similar to the above reason; small abra-sive grains can also be pressed so deep into the fabric of the cloth that their cuttingaction is nonexistent. Either increase the size of the abrasive used or change to aharder polishing cloth to avoid the condition that the abrasive is pressed too deepinto the fabric.

Fig. 13.22—Smearing on a PCB. The solder material is smeared over the copper layer, followinga grinding scratch.


Smearing

Pull-Outs—False PorosityAs stated earlier, the goal of metallographic/materialographic preparation is to showthe true structure. For most solid materials that is a relatively easy task, but porousmaterials quite often produce a challenge, even to experienced metallographers. De-pending on the type of material, the preparation process can produce either a too highporosity level or a too low level.

Porous, brittle materials usually display a higher porosity level than what is actu-ally in the material due to fracturing of the material during cutting and plane grinding.This fracturing creates pull-outs, cavities in the surface, and cracks �see Section 6.3.2,see also pull-outs in connection with inclusions in the following section�.


Ductile materials often display a too low porosity since the softer metallic materialcan be smeared into the pores during plane grinding, covering these up.

The following examples are taken from the same type of application, thermalspray coatings, using two different types of materials where the above can be seen veryclearly. To reach the correct result, displaying the accurate porosity level with the sameroutine can be used with both types of material. When preparing such a specimen forthe first time it is important to monitor the porosity level throughout the entire prepa-ration and first continue to the following preparation step when the porosity level staysconstant. With brittle materials it will get smaller and smaller until it reaches the cor-rect level as shown in Figs. 13.23–13.26. At ductile materials the porosity level will in-crease with finer and finer preparation steps until the final, correct level is reached, asshown in Figs. 13.27–13.32.

In both sections on false porosity the use of an RCD is recommended. Experienceshows that the constant supply of abrasive during preparation on an RCD gives themost constant removal of material and thus is best suited for fine grinding of both softand hard porous materials when the correct porosity level has to be obtained. If the useof an RCD is not possible the correct type of abrasive for the material in questionshould be selected.

On hard, brittle materials diamond grinding disks or diamond pads in successivelyfiner grain sizes should be used to remove the damage from plane grinding.

For soft materials fine grained SiC paper can be selected; however, it is importantto change the paper frequently to allow fresh, still sharp grains to remove material andthus avoid smearing.

Fig. 13.23—Ceramic plasma sprayed coating after plane grinding, the porosity level is very highdue to many pull-outs.


Fig. 13.24—Same specimen as in Fig. 13.23 after fine grinding, pull-outs are reduced.

Fig. 13.25—Same specimen as in Fig. 13.23 after diamond polishing, pull-outs are furtherreduced.

Fig. 13.26—Same specimen as in Fig. 13.23 after final polishing, correct porosity level.


Fig. 13.27—WC/Co plasma sprayed coating after plane grinding. The surface is completelysmeared and the pores are not visible.

Fig. 13.28—Same specimen as Fig. 13.27 after fine grinding. Most of the pores are still smearedover.

Fig. 13.29—Same specimen as Fig. 13.27 after 6 �m polishing. Pores start to open up.


Fig. 13.30—Same specimen as Fig. 13.27 after 3 �m polishing. More pores are opening up.

Fig. 13.31—Same specimen as Fig. 13.27 after 1 �m polishing.

Fig. 13.32—Same specimen as Fig. 13.27 after final polishing on colloidal silica. Correct porositylevel.


Pull-Outs, False Porosity, Hard, Brittle Materials


False Porosity, Soft, Ductile Materials

Destroyed InclusionsMany materials contain different types of nonmetallic inclusions. They are naturallycontained in the material or added to improve machinability. These inclusions havedifferent mechanical behavior than the base material; they can be harder or softer andoften they have other thermal expansion values resulting in relatively bad adhesion ofthe inclusions to the base material.

During metallographic/materialographic preparation these inclusions can becrushed if they are very brittle �see Fig. 13.33�, or removed by a long napped polishingcloth if they are soft, but the result is the same, partly or completely missing inclusionsin the base material. Apart from misleading results in the following microscopic ex-amination, these inclusion particles, pulled out during the preparation can also resultin other preparation artifacts such as scratching.

There is, however, another important group of inclusions, the water-sensitive in-clusions. If not treated correctly, the result after preparation will be the same with theseinclusions as with those described above; they will simply be missing when examiningthe specimen �see Fig. 13.34�. This takes place if the polishing consumables used, espe-cially during the last steps of the preparation, contain water.


Fig. 13.33—Brittle inclusion, removed during polishing.

Fig. 13.34—Missing water-sensitive inclusions.


Destroyed Inclusions

Embedded AbrasivesContrary to pull-outs, no material is removed from the specimen, but during prepara-tion, abrasive grains are embedded into the specimen surface. Also, this is unwanted


because the foreign matter will make interpretation much more difficult or even im-possible. Embedded abrasives are only seen with relatively soft materials, and mostlybecause they are prepared on preparation disks that are quite hard; this can be rigidcomposite disks �RCDs� or hard polishing cloths, but even from SiC grinding papergrains can be embedded in the specimen material.

This can pose a problem with certain composite materials. If they consist of bothhard and soft phases, RCDs and hard polishing cloths are recommended to keep thespecimens plane and avoid edge rounding. Therefore, a way has to be found to fulfillboth requirements at the same time, plane specimens without embedded abrasivegrains. Figure 13.35 shows embedded abrasive particles after 3 �m diamond polishingin a PbSn solder, and Fig. 13.36 shows the same specimen in SEM.

To resolve the problem with embedded abrasive it is essential to know when theabrasive particles became embedded. Therefore, the specimens have to be checked af-ter every preparation step to be certain

Fig. 13.35—Embedded abrasive �3 �m diamonds� in PbSn solder.

Fig. 13.36—Same specimen as Fig. 13.35, SEM image of diamonds in the solder phase.


Embedded Abrasive

Edge Rounding and ReliefThe goal of specimen preparation is to produce specimens showing the true structure.This usually requires perfect edge retention and absolutely plane specimens. Withcomposite materials containing phases of very different hardness or materials withthin, sometimes multiple coatings, this can present a serious challenge to the metallog-rapher. Figures 13.37 and 13.38 show a composite material with relief and without re-lief, respectively. Figures 13.39 and 13.40 show a coated material with rounded edgeand with perfect edge retention, respectively.


Fig. 13.37—Composite material with relief between fibers and matrix.

Fig. 13.38—Same specimen as Fig. 13.37 after correct preparation, perfect planeness.

Fig. 13.39—Coated material with rounded edge.


Edge rounding has already been touched upon in connection with mounting inSection 3.1.3; however, it is not always possible to mount the sample and in the follow-ing some tips are provided to get good edge retention without mounting. Basically thesame rules are valid to avoid relief between the different phases in the specimen.• Use rigid composite disks �RCDs� for fine grinding and relatively hard cloths for

polishing to keep the specimen flat.• Use diamond as the abrasive because it can cut equally through all phases.• Use polishing times as short as possible.• Use as few polishing steps as necessary, e.g., go directly from 6 to 1 �m polishing,

omit the 3 �m step.• Use a lubricant with higher viscosity for the finer polishing steps.

Fig. 13.40—Same specimen as Fig. 13.39 after correct preparation, perfect edge retention.

Fig. 13.41—Specimen after unidirectional polishing with comet tails around the inclusions.


Edge Rounding and Relief

Comet TailsComet tails owe their name to their characteristic shape. They are found adjacent toinclusions or pores and are the result of unidirectional polishing �see Fig. 13.41�. Byadjusting the polishing dynamics, comet tails can be avoided easily �see Section 7.9.2�.

As with the other artifacts we also assume here that the preparation process is car-ried out on some kind of semiautomatic or automatic equipment. To achieve an accept-able polishing result it is necessary that the specimen is moved across the entire surfaceof the polishing disk and that the specimen holder at the same time is rotated around itscenter. This is difficult to carry out manually, but most modern machines are designed


to utilize the entire preparation surface and to rotate the specimens at the same time.One reason to move the specimen across the entire preparation surface is to wear

the polishing cloth symmetrically, thus increase the lifetime and as result reduce thecost of specimen preparation. But more important is that the specimen is subjected toa unidirectional influence from the polishing cloth. This is important as differentphases or constituents in the specimen react differently to metallographic/material-ographic specimen preparation. If we are polishing a material with hard inclusions,the inclusions will be polished slower than the rest of the material, and after a while theinclusions will stick slightly out of the base material. As a result, less of the base mate-rial will be removed in the “shadow” of the inclusion. When examined in the micro-scope this characteristic feature will look like a comet tail. Apart from disturbing theexamination it will also make, for instance, correct automatic inclusion rating usingimage analysis impossible, since the inclusions will seem larger than they actually are.

To avoid comet tails it is important that the speed of the polishing disk and thespeed of the specimen holder or specimen mover disk in which the specimens are lo-cated are almost the same. They must not be identical because the specimens other-wise would run in exactly the same track over and over again, but they should be simi-lar. As a rule of thumb the speed of the specimen holder should not differ more than±5–10 % from the speed of the preparation disk.

This is only relevant during polishing where the removal rate is limited and therelative softness of the cloths contributes to uneven removal between softer and harderphases. Grinding is carried out on hard supporting disks and the removal rate is muchhigher. Here comet tails will not occur and therefore the speed of the grinding disk canbe much higher than the speed of the specimen holder to achieve a higher removal rateand thus a shorter preparation time.

13.6.5 Electropolishing—General Problems—ArtifactsIn the following overview some of the problems and artifacts that can be observed dur-ing electrolytic preparation are indicated and both cause and the possible solution aredisplayed.


General Problems and Artifacts

Problem Cause SolutionSurface not polishedor only partlypolished

Current density insufficientElectrolyte too oldInsufficient quantityof electrolyte

Adjust the voltageRenew electrolyteAdd electrolyteReduce the flow rate

Spots that have notbeen polished

Gas bubbles Adjust flow rateCheck the electrolytetemperatureDecrease the voltage

Etching of thepolished surface

Chemical attack ofgrain boundariesafter switching offthe current

Remove the specimenimmediately when thecurrent is switched offChoose a less corrosiveelectrolyte

Phases in relief Polishing film isinadequate

Increase the voltageImprove the mechanicalpreparationof the specimen

Polishing time too long Reduce the polishing timePitting Polishing time too long Improve the mechanical

preparationDecrease the time

Voltage too high Lower the voltageInsufficient anodic layer Reduce flow rate

Use a different electrolyteAttack at the edgeof the specimen

Film too viscous or too thin Decrease the voltageIncrease flow rate

The center of thespecimen isdeeply attacked or notpolished at all

Polishing film did not formin the center of thespecimen

Increase the voltageReduce the flow rateAdd more electrolyte

Deposits on thesurface

Insoluble reaction products Renew electrolyte or try adifferent oneIncrease the voltage

Wavy surface orresidualdeformation

Polishing time too shortFlow rate too high or toolowRough surface aftergrinding

Increase the timeChange the flow rateImprove the preparationprior to electrolyticpolishing

Electrolyte too old Renew electrolyteSelective polishing becauseof potential differences insurface�heterogeneous material�

Other electrolyte withother polishing data or usemechanicalpreparation instead


Part III: Light Microscopy

14IntroductionMETALLOGRAPHY/MATERIALOGRAPHY COMPRISES THE OPTICAL EXAMI-nation of a material for the purpose of giving a qualitative and quantitative descriptionof that material’s structure. The structure is characterized by size, shape, distribution,density, orientation, and type of phases, as well as microstructural defects �see Fig. 1.2�.

In this context, the light microscope is an important tool. In the following chapter,the basic physical principles of reflected light microscopy and the most importantmethods of microscopic examination will be described in more detail. In Chapter 16 ashort introduction to electron-microscopy and scanning probe microscopy is given.

The optical effect of enlargement that occurs when one looks through the roundedglass of a convex lens �magnifying lens or loupe� was known to the ancient Egyptians,Greeks, and Romans. Today, a convex lens still serves as a magnifying glass for observ-ing small objects, the useful magnification is limited to 10–15�.

The first microscope, consisting of two lenses, was probably built by either Hansand Zacharias Jansen in about 1590 in the Netherlands or by Cornelius Drebbel around1600. In connection with the growing significance of the natural sciences in the 19thcentury, microscopic observations in the fields of medicine, biology, and geology be-came ever more important.

H. C. Sorby in England �1864� and A. Martens in Germany �1878� were the first toprepare metallographic polished sections of steel and cast iron, examine them by mi-croscope, and sketch or photograph their visible structure.

Microscopes used today are still built according to the old principle of a system oflenses placed together. Their essential elements are source of light, lens, eyepiece �orocular�, prism, mirror, and shutter and filtering systems.

14.1 Visible Light–Table 14.1–Table 14.2

Light that can be seen by the human eye is an electromagnetic light wave with wave-lengths of between 350 and 780 nm. Depending on the wavelength, the human eye seesdifferent colors �see Table 14.1�.

White light consists of a mixture of all the colors in the spectrum. Light of an evenwavelength is monochromatic.

When wavelengths of a particular range are missing from a beam of polychro-matic light, we see a mixed color �Table 14.2�.

TABLE 14.1—Range of Wavelength of Visible Light and Color.

Range of Wavelength, nm Color

360–440 violet

440–495 blue

495–580 green

580–640 yellow/orange

640–780 red

525

14.2 The Human Eye

The construction of the human eye is similar to that of a camera �Fig. 14.1�. Thanks tothe muscles in our eyes, the focal distance of their flexible lenses �1� can be varied toenable us to focus on any object at a distance between approximately 20 cm and infin-ity. The inner diameter of the iris �3� can be varied to change the amount of light fallinginto it. This variation produces a sharp image on the retina �2�, the gray values of whichare received by receptor-rods, and the color values of which are received by the conesand transformed into electrical impulses. These impulses are in turn transmitted viathe optical nerve �4� to the brain where they are then processed.

For example, let us look at a 160 m ��490 ft� high tower from a distance of about300 m ��915 ft�. If we imagine two lines that extend from the middle of our eye, one tothe foot of the tower and one to the top, we get what is called the visual angle. In thisexample, the visual angle � is about 30 degrees. We are not able to recognize the faces ofpeople on the tower because the visual angle is too small for our eye to process. But ifwe go closer to the tower, then we can better recognize the details of the building andthe people. This means that the closer we bring an object to our eye, however, therebyincreasing the visual angle, the more details we are able to discern.

Normally, we are able to read the text on a page of a book from a distance of 25 cm��10 in�. This distance is called the conventional visual range, or visual range of refer-ence. It enables us to compare the magnification data of different optical systems.

To make out the details of the individual letters on that page of text, we must de-crease the visual angle. If we bring the text closer to our eyes, in order to increase the

TABLE 14.2—Spectral Color Filtered Out and Visible Mixed Color.

Spectral Color Filtered Out Mixed Color

Violet Green-yellow

Ice blue Orange

Yellow Ultramarine blue

Red Blue-green

Fig. 14.1—Light path of the human eye, with lens, cornea �1�, retina �2�, iris �3�, optical nerve�4�.1


visual angle further, the text begins to blur because the ability of our lenses to adjust tothe visual angle is limited.

14.3 Magnifying Lens and Microscope

Magnifying glasses and microscopes are optical devices that enable us to increase thevisual angle between the eye and objects that are small and near so that details thatcannot be seen with the unaided eye now become visible.

If we place a convex lens �magnifying glass� between our eyes and the page of text,the visual angle is increased and the details of individual letters as well as the surfacestructure of the paper become visible.

A magnifying glass produces an enlargement by means of a single imaging step.The object lies in the center of focus and the eye is accommodated ad infinitum. Thesmaller the focal point of the magnifying lens, the greater the magnification. Practi-cally speaking, a magnification of the object of 10 up to a maximum of 15 times itsactual size remains in the useful range.

By using several lenses arranged one after the other, the magnification effect canbe increased considerably.

The construction of the classical microscope consists of a two-lens system. Themagnification takes place in two image-forming steps. First, an enlarged image of theobject is projected by the objective in the intermediate image plane. This image is thenmagnified by the ocular, or eyepiece.

14.4 Magnification

Magnification, M, as the function of an optical instrument is defined as:

M =Visual angle with optical instrument �1

Visual angle without optical instrument �2�1�

or

M = tan �1/tan �2 �2�

Magnification by a compoundmicroscope results as a product of themagnification of theobjective and themagnificationof the eyepiece

M = Mobjective � Meyepiece �3�


15The Optical Reflected LightMicroscope

15.1 The Path of Light Rays

FIGURE 15.1 SHOWS THE COURSE OF LIGHT RAYS IN A MODERN THREE-lens transmitted light microscope with “infinity optics” �the ICS principle, whichmeans “Infinity Color-corrected System”�. Let us follow the light rays that emanatefrom an object �1�. From these rays the objective �2� projects an image to infinity. Theintermediate lens �3� that also intervenes in the progress of the light rays creates a mag-nified intermediate image �4� from the rays that are now running parallel. This inter-mediate image is further magnified by the eyepiece �5�. As the illustration shows, thevisual angle �1 that results when this optical system is used is considerably greater thanit is when the object is viewed by the naked eye at the same distance of 25 cm ��10 in�,visual angle �2.

15.2 The Objective

The objective consists of a combination of lenses, both converging and diverging, thatare precisely adjusted to one another. This makes a correction of any part of the image-forming process possible whereby something has been lost, e.g., missing color, and aflat intermediate image is projected.

The angle of opening 2�, the aperture of the objective lens system, is crucial for thequality of a microscopic system �Fig. 15.2�. An effective aperture is one that is as largeas possible so that as many diffraction spectrum maxima as possible of the rays re-flected by the object can be captured and an image rich in detail consequently ren-dered.

If, with regard to the illumination, one uses a condenser lens system �Fig. 15.2� thatconcentrates the initially parallel rays into a cone, the objective can then catch rays thatare even more diffracted. This means a greater optical resolving power and, conse-quently, more detail.

For technical reasons, the angle at which a ray of light can enter into the objectiveis maximally �=72°.

15.2.1 Numerical Aperture—Resolution-Magnification–Table 15.1–Table15.2The numerical aperture, by means of which a comparison can be made between twoobjectives, is defined as follows:

NA = n � sin � �1�

In this equation,� is half of theaperture angleof theobjective.If air is present between the objective and the object, the refractive index, n�1 �see

Table 15.1�.

528

Under comparable conditions, maximum achievable image brightness is propor-tional to NA2.

The greater the aperture of the objective and the shorter the light wavelength ��the better one can distinguish two adjacent image points from one another. The short-est distance �do� is a measure of the resolving power of the microscope. This is shownschematically in Fig. 15.3.

According to the laws of wave optics, one has achieved this distance �do� when amaximum degree of refraction is emitted from each of two image points that are sepa-rated from one another by a minimum of refraction.

Ernst Abbe has defined this relationship mathematically with the following equa-tion:

Fig. 15.1—Optical path A in a three-lens transmitted light microscope with infinity optics withthe visual angle �1 compared to the visual angle �2, when the object is viewed by the nakedeye in beam path B. With object A and B �1�, objective �2�, tube lens �3�, magnifiedintermediate image �4�, eyepiece �5�, eye �6�.1

Chapter 15 The Optical Reflected 529

do =�

NAObjective + NACondensor�

�

2NA�2�

Example: If we assume that the aperture of the objective and the condenser is 1.25and a wavelength �� in the middle range of 0.5 �m, respectively, we receive, as thesmallest distance possible between two object points that can just be distinguished, ado value of 0.2 �m.

TABLE 15.1—Immersions Agents, Their Refractive Index, and the Possible Numerical Aperture.

Medium Refractive Index (n) Numerical Aperture NA

Air 1 to 0.95

Water 1.333

Immersion oil 1.515 to 1.4

Monobromonaphtalene 1.66

Methylene iodide 1.740

Fig. 15.2—Optical path of a condenser lens system with object in transmitted light �1�, lightbeam �2�, objective �3�, condenser �4�.1


The resolving power can be improved by using light of shorter wavelength and alarger aperture in the objective. With the use of white light, if one takes a medium wave-length � of 0,56 �m and an immersion objective with an aperture of 1.4 and with k=0.61, a resolving power of 0.25 �m results. For blue light with a wavelength of �=0,49 �m, one gets a resolving power, under otherwise identical conditions, of about0.2 �m. Table 15.2 shows some values of resolutions that are theoretically possible forvarious objectives and for a wavelength of 0,55 �m. Here, do is the distance betweentwo points on the object and Do is the point distance on the intermediate image.

In actual practice, the attainable resolution is usually less than the theoretical val-ues stated in Table 15.2. It is dependent on the quality of the objective, the optimal set-ting of the aperture diaphragm, use of the right immersion oil and, naturally, the speci-men. One gets the best results with dust-free microscope systems and clean objectivesand well prepared specimens.

The overall magnification of a microscope is the product of the scale magnificationof the objective multiplied by the ocular magnification.

The magnification number indicates how many times larger the intermediate im-age produced by the objective is than the object itself.

M = Mobjective � Meyepiece �3�

With a 50� objective and a 10� eyepiece the overall magnification of the micro-scope is 500�.

Commonly used are 5�, 10�, 20�, 50�, and 100�-objectives.Additional magnifications gained through the use of between-lenses or zoom-

devices are to be borne in mind.

M = Mobjective � Meyepiece � Mbetween-lens or zoom-device �4�

Fig. 15.3—The shortest distance �d0� between two adjacent image points. The shortest distanceis a measure of the resolving power of the microscope.


The magnifications achieved individually by the objective, the intermediate lens,and the eyepiece must be attuned to one another. One obtains optimal image qualitywith an objective of a high scale number in combination with an eyepiece of low mag-nification. For example, the combination 50�-objective and 5�-eyepiece is preferableto the combination 10�-objective with 25�-eyepiece.

The total magnification of a microscope should be from 500 to a maximum of 1000times the aperture of the objective. This is the maximum useful magnification that al-lows the objective to reproduce tiny details in which the intermediate image can thenbe magnified further by the eyepiece.

The numerical aperture of an objective increases with the objective magnification,while the depth of field decreases. It is possible to increase the depth of focus, withinlimits, by lowering the aperture diaphragm. But this is done at the cost of resolution.Setting the aperture diaphragm too low results in empty enlargements and blurred im-ages inasmuch as one thereby leaves the range of useful magnification.

In the case of dry objectives, there is air between the front lens and the object. Amaximum aperture of 0.95 is possible. In the case of immersion objectives, use of cer-tain immersion agents with a higher refraction index between the front lens and theobject makes possible an increase of the numerical aperture to 1.7. This is shown inFig. 15.4.

Table 15.1 shows some values of immersions agents, their refractive index and thepossible numerical aperture.

The numerical aperture �NA� is of essential significance for:• Maximum image brightness• Resolving power• Useful total magnification• Depth of focus

15.2.2 Aberrations in Image-FormationGeometric and chromatic aberrations in image-formation are possible with uncor-rected optical systems.

Geometric aberrations in the imaging process can occur even with monochro-matic light. These include:

Aperture errors: With light beams on a plane parallel to the axis, the convergenceon the image side occurs not in the ideal image plane but rather either in front of it �inthe case of converging lens� or behind it �in the case of dispersing lens�.

Coma: Off-axis point objects appear as asymmetrical areas with a comet-like tail.Astigmatism: Point objects appear not as point images but rather as line images.Curvature of field: The image points of a larger object do not lie on a plane but

TABLE 15.2—Values of Resolutions that are Possible for Various Objectives and for a Wavelength of 0 ,55 μm.

Objective NA do /μm Do /μm

5� 0.15 2.2 11.2

10� 0.30 1.1 11.2

40� 0.75 0.45 17.9

40� 1.3 oil 0.26 10.3

63� 1.4 oil 0.24 15.1

100� 1.3 oil 0.26 25.8


instead on a curved surface. With uncorrected optical systems one can therefore focussharply either on the center of the image or else on peripheral zones.

Distortion: The image scale is dependent on the distance of the image point fromthe optical axis. Increasing that scale leads to a pillow-shaped distortion. Decreasingthe scale results in barrel-shaped distortions.

With the polychromatic light used in microscopy, chromatic aberration can alsooccur.

Since the refractive index decreases with an increase in wavelength, the focallength of a lens for these light rays increases. The image of an object point, produced byshort-wave light �violet� lies in front of the image produced with long-wave light �red�.Undesirable color fringes are the result.

The chromatic difference of spherical aberration manifests itself in blue and yel-low fringes.

With an appropriate combination of converging and dispersing lenses made of op-tical glass with varying dispersive and refractory properties, these aberrations can becorrected and objectives with varying optical properties can be produced.

15.2.3 Available ObjectivesDepending on the purpose for which they are used and the quality that is required ofthe microscopic image, various corrected objective lens systems are available for selec-tion.

The objectives most often used are achromats. They are inexpensive because theyconsist of relatively few lenses. Spherically they are corrected for one wavelength andchromatically for only two wavelengths, usually red and green. This may lead to redand blue color fringes around the object, but this can be avoided to a large extentthrough the use of a green filter. Because the flatness of field is limited, they are appro-priate for visual fields of up to approximately 18 mm in diameter. These objectives canbe used for routine tasks, including those as in polarized light. They are less useful for

Fig. 15.4—Improved resolution by use of an immersion liquid �6� between object, over slip �5�and objective �3�.1


microscopy in darkfield and for color photography, especially when there is a high de-gree of magnification.

With fluorite or semiapochromatic objectives, spherical and chromatic aberrationis more strongly corrected. Flatness of field is also improved. For these reasons suchobjectives can be used for fields of vision of up to 23 mm in diameter and are appropri-ate for color microphotography in reflected light and transmitted light as well as fordark field and DIC.

With apochromats, spherical aberration is corrected for two colors and chromaticaberration for three colors. Because of their even further improved flatness of field,these objectives can be used for fields of vision of up to 25 mm in diameter. And be-cause color fringes hardly ever occur, these high-quality objectives are well suited forcolor photography and for microscoping in dark field. Because of the better image cor-rection, higher numerical apertures are possible and consequently a better resolution.These objectives are therefore appropriate for the upper range of magnification to dif-ferentiate the finest details �precipitations, grain boundaries� and capture them in theirtrue colors. This means, however, less depth of field and a smaller working distancebetween objective and object in comparison with achromats.

Plan apochromats and epiplan apochromats exhibit an outstanding flatness offield and can therefore be used for large fields of view. Furthermore, since they possesscolor correction for four wavelengths, the color rendering is optimal. The high numeri-cal aperture makes a maximum of resolution power possible. These objectives in theupper price range satisfy the highest demands in research and technology.

Objectives are usually marked with color rings corresponding to their magnifica-tions: red-5�, yellow-10�, green-20�, blue-50�, white-100�.

The most important technical data are also inscribed on the barrel of the objective.For example,

Epiplan-Neofluar10� /0 ,30 HD DIC� /0

provides the following information:“Epiplan” means that this is an objective for a reflected light microscope that ren-

ders a flattened intermediate image. “Fluar” refers to the fluorite glass with which theobjective has been constructed.

The indicated scale number “10�” means that the intermediate image is 10 timeslarger than the object.

“0.30” is the numerical aperture of the objective.Using a light with an assumed wavelength of �=500 nm, a resolving power of

1 �m can be calculated.“HD DIC” means that this objective can be used for bright-field �BF� illumination,

dark-field illumination �DF�, and differential interference contrast �DIC� illumination.On most microscopes, objectives of varying scale number are exchangeable with

the rotatory nosepiece. To keep the focus essentially unchanged, the distance betweenthe screw-on surface of the objective and the eyepiece head is an important mechanicaldimension. It is called the mechanical tube length and is engraved on the objective.

If “�” is indicated there, this means that the object is imaged to infinity by the ob-jective and that an additional tube lens produces a real intermediate image.

With a transmitted light microscope, objects are placed on a glass stage and pro-tected by a cover glass. Consequently, transmitted light objectives are calculated andcorrected for a cover glass thickness of 0.17 mm.


In our example we are looking at an objective for reflected light microscopy. Be-cause one usually examines uncovered specimens, the cover glass thickness is repre-sented as a “ 0.”

15.3 Eyepieces

The simplest eyepieces consist of a convergent lens that acts as a magnifying glass.Good eyepieces are equipped with a corrected lens system including an eye lens �above�and a field lens �below�. Figure 15.5 shows a schematic cross section of an eyepiecewith the position of the intermediate image plane �1�, the boundaries of the visible fieldof vision �2�, the eyepiece optical system �3�, the pupil of the observer’s eye �4�, and thefocusing ring for the diopter adjustment �5�.

Although eyepieces magnify the intermediate image that is produced by the objec-tive, they do not bring about any further improvement in resolving power. But since theangle of vision is now larger, the human eye is able to discern more detail.

If aberrations are still present in the intermediate image, they can be correctedwith the appropriate eyepieces.

Many eyepieces are designed for people who wear eyeglasses. They are usuallyequipped with eyecups. The eyecups can be attached or they can be folded up to get theright visual distance if the individual wants to use the microscope without eyeglasses.

The area of the intermediate image that can be examined, the field of view, is re-stricted by the field lens and the aperture diaphragm. The value S is the measure of thefield of vision and is indicated on every eyepiece.

The diameter of the field of vision can be calculated from the field of vision value ofthe objective together with the objective’s scale number:

Field of vision value S/M �objective�An example: If M �objective�=40 and S �eyepiece�=18 mm, the result is a viewing

field of 0.45-mm diameter.Wide-field eyepieces should be used only in combination with corrected plane ob-

jectives that produce a well flattened intermediate image.Micrometer eyepieces have a glass plate with a scale situated on the plane surface

of the diaphragm. After the system has been calibrated, linear measurements as well as

Fig. 15.5—Schematic cross section of an eyepiece, with the position of the intermediate imageplane �1�, the boundaries of the visible field of vision �2�, the eyepiece optical system �3�, thepupil of the observer’s eye �4� and the focusing ring for the diopter adjustment �5�.1


measurement of angles �goniometric eyepiece� can be made. The corresponding stan-dard guides for calibrating are cited.

A tip: The eyepiece can also be used as a magnifying glass. Simply turn the eye-piece, train the eye lens on the object, and look through the field �condensing� lens.

15.4 Illumination

Illumination source and light path are important elements of a microscope.Halogen lamps are often used, as are xenon high-pressure lamps.Halogen lamps of between 25 and 100 watts emit light with a color temperature of

about 3000 K. This must be kept in mind when colored photographs are being takenand conversion filters must be used for correction.

Xenon high-pressure lamps that produce between 100 and 500 watts are available,and they produce a light that is more like natural light. Spectral response of the radi-ated light and color temperature are about 5000 K.

A microscope’s illumination should• Be adapted to the illuminated object field.• Illuminate completely and evenly the object field to be observed.• Be such that the illuminated object field is adapted to the field of vision of the mi-

croscope.• Be adjustable according to the aperture angle.

15.4.1 Koehler’s Illumination SystemThe illumination system proposed by August Koehler in 1893 is still used today withmany optical systems using transmitted- and reflected-light microscopy.

The Koehler’s illumination method produces images that are illuminated withevenly distributed light using three lenses placed between the light source �1� in Fig.15.6 and the reflector �2�. This type of illumination also contributes to the enhance-ment of the resolution power. On reflected-light microscopes used for metallography/materialography the Koehler illumination system is adjusted by the microscope fac-tory and should not be changed by the user, for transmitted light, the system shall beadjusted regularly. The three lenses of the Koehler system are part of the illuminationelements �A� in Fig. 15.6. As the first lens in front of the light source �1�, the collectorlens forms an image of the light source at the second lens, the first condenser lens. Thethird lens, the second condenser lens, reproduces the image of the light source in theback focal plane of the objective �3� after passing the reflector �2�. In this way the sur-face of the specimen is uniformly illuminated.

In the path of the illuminating light rays there are two important diaphragms.The centering radiant field diaphragm makes it possible to adjust the illuminated

object field to the microscope’s actual field of view. This diaphragm is correctly setwhen the image of the edges of the diaphragm disappear behind the border of the fieldof vision. Stray light is avoided and contrast is heightened. With reflected-light micro-scopes a one-time setting of the field diaphragm is sufficient; it does not have to be read-justed each time the objective is changed.

By means of the aperture diaphragm, the cone of light is adjusted to the aperture ofthe objective. It has an optimal setting when that part of the light rays that is not dia-phragmed out covers about two-thirds of the objective’s entrance pupil. This dia-phragm must be reset whenever the objective is changed to meet the requirements of


the desired image. This means that a compromise must be made between resolution,contrast, and depth of focal field.

15.5 Microscope Options

The optical elements of a microscope, i.e., the objective, tube lens, eyepiece or projec-tive, illuminators with light source, aperture and light field diaphragm—are assembledin a mechanical device, the microscope body.

Depending on the expandability and capability of the built-in optical and me-chanical assembly parts, one differentiates between student microscopes, laboratorymicroscopes, and research microscopes.

Student microscopes are the most simply built and therefore the most limited intheir uses. The interchangeability of the individual optical elements is limited. Becauseof their ease of use these microscopes are appropriate for the beginner or are used forthe preselection of specimens.

Laboratory �or working� microscopes are equipped in such a way that they can be

Fig. 15.6—Bright field �BF� illumination in reflected light and components in the optical pathfor establishing contrast: Light source �1�, beamsplitter, color neutral �2�, objective �3�, object�4�, lens �5� and contrast components on the side of the lamp �A�, on the side of the eyepiece�B� and components for both light paths �C�.1


used without problem for many routine tasks. The stage can be rotated or can be ad-justed in an x-y-direction, or both, and the focusing of the objective occurs through acoarse and fine focusing mechanism.

As an illumination source, a halogen bulb is mostly used. Koehler illumination aswell as interchangeable objectives and filters make it possible to perform all the usualexamination procedures. Attachment possibilities for further fixtures, as for exampleanalogue or digital cameras, are present.

Research microscopes belong to the top class of instruments. With these micro-scopes all the essential parts, such as lamp-housing, condenser turret, object holdingstage, objective rotator, and tubes are interchangeable and can be adapted to specialtasks. Specimens can be viewed in either reflected or transmitted light. All knownmethods of microscopic examination are possible.

The motorized variants are especially convenient because they make it possible forchange of objective, focusing, and movement of the mechanical stage to occur auto-matically. Moreover, with the appropriate software all the important data such as ob-jective, illumination, magnification, coordinates of the object, and the digital photo-graphing of the image can be saved and later retrieved.

In a metallographic/materialographic laboratory, reflected-light microscopes ofeither the upright or inverted type are used. If other materials are also examined, forexample, ceramic, stone, glass, or synthetics, a microscope with reflected-light as wellas transmitted-light beam projection is necessary.

15.6 The Reflected-Light Microscope

In metallography/materialography, ground and polished surfaces of materials are themain objects that are examined with reflected �incident� light.

The essential parts of a reflected-light microscope are: light source, condenser,aperture- and radiant-field diaphragm, filter holder, reflector, rotating nosepiece withreflected-light objective, stage, intermediate optic, body tube, and eyepiece.

15.6.1 Upright Type of Reflected-Light MicroscopeWith the reflected-light microscope of the upright type that is customarily used in ma-terials research, the top surface of the specimen is illuminated from above through theobjective. Here the light rays are reflected or scattered. These rays are collected by theobjective. The tube lens projects an enlarged intermediate image that is caught by theeyepiece and further magnified.

Figure 15.7 shows a modern upright type, reflected-light microscope, for routinepurposes.

The specimen lies on a movable stage. Direct observation of the fully lit position ispossible.

For the area being examined to be positioned absolutely perpendicular to the opti-cal axis, the specimen must be correspondingly orientated with a leveling device. Thethickness of the specimen is limited by the working distance between objective andstage.

15.6.2 Inverted Type of Reflected-Light MicroscopeIn the field of metallography/materialography, reflected light microscopes of the in-verted type are also used often. Following the suggestion of Le Chatellier, the specimen


is placed on a movable specimen stage with a hole above the microscope column andthe objective.

Figure 15.8 shows a modern research microscope, inverted type, reflected-light.The inverted type has the following advantages: �1� The specimen is simply placed

with the prepared surface facing down on the stage and over the hole; �2� There is noneed for cumbersome manipulation of a leveling device in order to get the preparedsurface of the specimen perpendicular to the light path; �3� Larger, irregularly shapedspecimens can be easily examined microscopically as well, inasmuch as the workingdistance object-objective is not affected by the size of the specimen. One disadvantageis that the prepared surface can become scratched when it is placed on the stage. Fur-thermore, one may not be able to see the illuminated area very clearly.

The objective of a reflected-light microscope differs from that of a transmitted-light microscope. Optical calculations must take into account the fact that surfaces likepolished specimens are examined without a cover glass. In addition, reflected-light ob-jectives are especially well dereflected so that no disruptive “false flashes” are superim-posed on the image of the specimen.

With both systems, all the necessary construction elements are integrated in themicroscope. With a rotating nosepiece, different objectives can be inserted into thebeam path and the magnification thereby changed. Exchangeable slide-in componentspermit quick and simple change to other types of illumination or filters.

Fig. 15.7—Upright type reflected-light microscope.2


A camera connection makes documentation of the magnified image of the objectpossible.

15.7 Optical Examination Methods

The prepared specimen normally has a plane surface. The ground and polished metal-lic surface reflects light very well, therefore, usually shine brightly. The surface is eithersilver or slightly colored, depending on the composition of the material. However, wecan differentiate individual portions of structural constituents only when they showdifferent contrast. If the reflection difference between two structural constituents isgreater than 10 %, they can be distinguished from each other. If that difference is lessthan 10 %, contrast must be heightened using methods suited to that purpose.

Before contrasting, either by chemical or physical means, can be undertaken on aground and polished specimen, the specimen should first be observed in a polishedcondition. To this end it is advisable to begin with the lowest degree of magnificationand then proceed to greater magnification. This enables one to check the quality of thespecimen preparation. Moreover, fissures, shrinkage and pores, inclusions, impurities,corroded areas, thin oxide films, peripheral layers, and their adhesion to the base mate-rial can already be detected. If the contrast between individual structural constituentsis sufficiently high, they can be distinguished as well.

With most metallographically/materialographically prepared specimens, how-ever, the reflection differences between the individual structural constituents or phasesare so small that the contrast must be heightened by using carefully selected methods.

One process used to effect a change in the specimen surface, and which is con-nected with contrast-heightening, is the electrochemical etching method. This processincludes the classical chemical as well as electrolytic etching.

In addition, physical contrasting methods, including thermal etching, ionic etch-ing, and the application of interference coating are used to bring about a change in the

Fig. 15.8—Inverted type reflected-light microscope for research.3


surface of the specimen �see Figs. 9.1 and 9.2�. These methods are described in moredetail in Chapter 9.

Our task here is to consider in greater detail various optical methods of producingcontrast that do not cause any change in the specimen surface.

The four main optical contrast methods used for the purpose of examining the tex-tures and structures of metallographically/materialographically prepared specimenswith a microscope are the following: bright-field illumination, dark-field illumination,polarization contrast, and differential interference contrast.

15.7.1 Bright-Field „BF… IlluminationReflected light bright-field illumination is the most important method used inreflected-light microscopy. In this process, the light that is reflected into the light pathof the microscope passes through the objective directly onto the specimen surface. Fig-ure 15.6 shows the light path when bright-field illumination is used. An integrated ver-tical illuminator �1� emits a light that travels through the reflected-light aperture dia-phragm and the radiant-field diaphragm. The light beam is then reflected by a colorneutral beam splitter �2�, which is set at 45° to the optic axis, and through the objective�3� the beam strikes the surface of the specimen �4�. There, the reflected or scatteredbeams again pass through the objective �3� and traverse the beam splitter �2�. The tubelens �5� then projects the intermediate image. The image is further enlarged by the eye-piece. Half-translucent mirrors may be used as beam splitters, but a higher light yield isobtained by using prism illuminators.

Figure 15.6 also shows the location of all possible contrasting components ar-ranged in a small area above the objective withA: Contrasting element of the illumination side,B: Contrasting element of the observation side, andC: Space for components for both light paths.

The reflecting capacity of the individual structural constituents depends on theirrefraction number n. More important, however, is the varying absorption power of in-dividual phases and diffuse reflections. Differences in absorption of individual phasesand the presence of diffuse reflections create contrasts. If this contrast is sufficient, thedifferences can be visible to the eye.

Accordingly, the polished specimen of a single-phase gold alloy, as well as those ofmany multiphase metal alloys, show hardly any contrasts. If the material has constitu-ent parts of widely varying reflection power, e.g., cast iron with laminated graphite,steel with slag inclusion or sulfides, those individual constituent parts are already mi-croscopically detectable immediately after the material has been polished.

Diffuse reflection occurs when there are rough surfaces, grain boundaries, andscratches. But the presence of these things may also give some indication, in individualcases, of the material’s structure.

For microstructures in bright field �BF�, see Figs. 7.15 and 15.10�a�.In other methods of achieving optical contrast, the light rays emanating from the

light source are diverted or else altered. Various reflectors that are built into the reflec-tor slide of the microscope are used for this purpose. To gain a particular kind of micro-scopic illumination or to observe the specimen in a particular way, one simply insertsthe reflector in the corresponding position.

15.7.2 Dark-Field „DF… IlluminationIn the case of reflected-light dark-field illumination �Fig. 15.9�, the light that is emittedby the reflected-light illuminator �1� does not fall directly on the specimen surface. By


means of a reflector “staircase” �2 and 3�, the light is conducted around the actual ob-jective and into a second housing case �4� where it strikes a ring-shaped concave reflec-tor. This device reflects the rays at a very flat angle of illumination onto the specimensurface �5�. Only scattered light returns for observation in the microscopic beam path.For this reason, the flat surface of a well-polished specimen appears dark.

Reflected-light dark-field illumination is well suited to show the quality of a pol-ished surface inasmuch as the oblique light rays allow lapping tracks, scratches, andfine cracks to show up bright. Unevenness and rough surfaces are easily detected aswell. Hard phases that stand out, deeper-lying soft phases, as well as contraction cavi-ties and pores display bright edge seams �relief�. Half-opaque phases may show theirinherent color.

Figure 15.10 shows a carbon steel in bright field �a� and dark-field �b�. The struc-ture and texture as well as surface details can be clearly seen with dark-fieldillumination.

15.7.3 Polarization Contrasting „POL…When contrast is achieved using polarization, a polarizer �P� is inserted into the illumi-nation beam pathway and an analyzer �A� into the observation beam pathway �Fig.

Fig. 15.9—Dark field �DF� illumination in reflected light, with light source �1�, mirror stepassembly �2�, mirror with an oval hole �3�, light, directed in a second housing case towards theobjective �4�, sample surface �5�.1


15.11�. The direction of transmission of the analyzer �6, A� is at a right angle to the po-larizer �2, P�. Only the depolarized portions of the rays can reach the tube lens �7�. Inthis polarized light a lambda plate �6a, �� changes the gray contrast into color contrast.

Interference reflection can be prevented by using a rotating � /4-plate �antiflex-plate� between the object and the objective.

In the case of substances that are optically isotropic, e.g., cubic or amorphous, thespecimen always appears dark because reflection from these materials does not lead toa change in the state of polarization. The polarized light is, consequently, not letthrough by the analyzer.

Structural constituents that are optically anisotropic, as for example zinc, tita-nium, spheroidal graphite, some nonmetallic inclusions or minerals on the other hand,do change the polarization state of a ray of light when reflected. Then the depolarizedportions of the light can penetrate the analyzer.

Fig. 15.10—Microstructure of carbon steel in bright field �a� and dark field �b�.


Observation of a metallographic/materialographic polished specimen in polarizedlight is therefore useful for differentiating between isotropic �cubic� and anisotropic�noncubic� phases. Ferromagnetic phases can be identified as well inasmuch as theplane of polarization, affected by the magnetization, is turned. For this reason, the do-main boundaries of the magnetic zones appear in varying degrees of brightness.

The gray contrasts that occur in anisotropic phases can be transformed into colorcontrasts through the use of a lambda plate �6a� in the observation beam pathway. Iso-tropic phases can likewise be contrasted in polarized light by applying an optically an-isotropic layer. For example, an oxide layer applied by anodization to aluminum pro-duces color contrasts. With slag, minerals, ceramic, and glass that show half-opaquebehavior, the use of polarized light results in less scattered light. This makes a bettercontrast possible and the structural constituents can be delineated better one from an-other.

The microstructure in Fig. 15.12 shows titanium with deformed areas made vis-ible with polarization contrast �POL�.

15.7.4 Differential Interference Contrasting „DIC…When Nomarski’s differential interference contrast method is used, the polarized rayof light is split into two beams of different oscillation directions �Fig. 15.13� by a doubly

Fig. 15.11—Polarization contrast �POL� in reflected light, with polarizer �2 P�, analyzer �6 A�,lambda plate �6a ��.1


refracting prism �4�. These two rays are out of phase with each other when they strikethe specimen �6�. If the specimen surface is not completely flat, path differences are theresult. In a reverse direction, the reflected or scattered beams, or both, now traverse theDIC-prism �4� and the analyzer �7�, thereby acquiring the same oscillation directionand now capable of interfering with the intermediate image. The path differences thatare caused by the specimen surface are converted to gray values. Unevenness becomesvisible as relief. With a lambda plate, color contrasts can be obtained.

Figure 15.14 shows a microstructure of a soldering in bright field �BF� �a� and indifferential interference contrast �DIC� �b�. In BF the solder can only be seen as a grayphase in the lighter matrix, but in DIC the solder can be clearly discriminated from thematrix.

15.7.5 Fluorescence in Reflected LightSpecific areas of a microstructure can be marked with a fluorescence dye �see Section3.10.1�. These areas will absorb light of a specific wavelength in a short period of time,and then emit the light. The wavelength of the emitted light is always around20–50 nm longer than the incoming light. If blue light is absorbed, green light is emit-ted, from UV-light visible light is emitted.

Especially at the examination of medical and biological samples, fluorescence isoften used, as specific dyes are suited for specific phases in the sample. In this way anexact microscopic examination can be performed.

In metallography/materialography the use of a dye can give important informa-tion on size and distribution of pores, cracks, gaps between basic material and surfacelayers, etc. �see Section 3.10.1�.

At the reflected fluorescence microscopy �Fig. 15.15� a short pass filter �A� is placedin the light path, only allowing light of a narrow wavelength to pass to the specimen. Inbetween is placed a beam splitter �B�, which reflects the short waved reflected light andonly let through the long waved emitted light. The reflected light that is not absorbed bythe specimen surface is stopped by a long pass filter �C�; this filter only lets the longwaved fluorescence light pass.

Lamps with a high degree of red or infrared light are less suited for fluorescence

Fig. 15.12—Microstructure of titanium in polarized light. Cold work is visible.


microscopy; mercury vapor lamps with a line type spectrum are to be preferred.For a microstructure impregnated with a dye and examined with fluorescence see

Fig. 3.14.

15.8 Practical Use of the Microscope

15.8.1 Setting up the MicroscopeIf possible, the microscope should be set up in a room of its own on a stable worktable.There should be sufficient space to the right and to the left of the apparatus for thedepositing of specimens and supplemental equipment. If no separate room is availablefor microscopic or measurement work, the instrument should be located in a place re-moved from all sectioning, grinding, and polishing equipment to avoid any transfer-ence of vibrations or abrasion particles. Moisture, especially alkaline and acid vaporsfrom electrolytic polishing or chemical etching, can also damage important parts ofthe microscope after just a short time. Such chemical procedures should be performedunder a fume hood in a separate room.

Fig. 15.13—Differential interference contrast �DIC� in reflected light, with doubly refractingprism �4�, objective �5�, specimen �6� and analyzer �7�.1


15.8.2 Working with the MicroscopeIn this section and the following two sections, a number of points are stated that shouldbe followed when working with the microscope.• Adjust the height of your chair in such a way that you are sitting erect but comfort-

ably as you look into the eyepiece and can reach all the operating parts of the in-strument effortlessly.

• Turn on the source of light.• Place a specimen on the microscope stage �focus plane�.• Look into the distance, then, without changing the focus of your eyes, look into the

eyepiece.• Adjust the distance between the eyepieces according to the distance between your

eyes.• If you do not wear glasses, put rubber eyecups on the eyepieces to get the right eye

distance to the eyepiece.

Fig. 15.14—Microstructure of a soldering in bright field �BF� �a� and differential interferencecontrast �DIC� �b�.


If you do wear glasses, check to see whether the eyepieces are designed accord-ingly. If you have done everything right you will have a clear view of everything in thewhole field of vision.

15.8.3 Correct Adjustment of the Microscope• Begin by using an objective of a low scale number and bring the specimen into fo-

cus.• Open the field diaphragm and center this and the condenser in such a way that the

viewing field is illuminated evenly.• Close the field diaphragm and, through centering, bring the little fuzzy fleck of light

that is still present into the middle of the viewing field.• This fleck of light can be brought into sharp focus by vertically adjusting the con-

denser.• Open the centered field diaphragm in such a way that the diaphragm leaves extend

out over the field of vision.• Open the aperture diaphragm and close it again carefully until the image has be-

come dark enough to show sufficient contrast.With transmitted-light microscopes, a change of objective requires each time a re-

adjustment to accommodate the settings of the field and aperture diaphragms. Suchreadjustments are not necessary with reflected-light microscopes. With the latter it issufficient to adjust the aperture diaphragm to the object and the objective.

15.8.4 Focusing and Practical Use• The task of getting a sharp focus on shiny polished specimens of metal can be facili-

tated by partially closing the radiant-field diaphragm. After that, focus sharply onthe image of the radiant-field diaphragm. Because this diaphragm is imaged in the

Fig. 15.15—Fluorescence: Short pass filter �A�, beamsplitter �B� and long pass filter �C�.1


object plane, it is easy to find the image of the specimen surface.• As an alternative move the field of view to the edge of the sample. The contrast be-

tween the sample and the mounting material or air allows for a simple focus.• In focusing the microscope, use at first an objective of weak magnification and look

for the area of interest. Then change to objectives with a higher magnification, asnecessary.With unfamiliar specimens it is advisable to experiment with all the different illu-

mination possibilities �optical contrasting methods�. Often structural details can beidentified better in this way and distinguished from one another.

If an oil immersion objective is used on an upright type microscope, the area of theobject that is of interest is first of all located with an objective of a low magnification �10� �. Then one focuses with the oil immersion objective �e.g., 100��. After that, using theobjective revolver, this objective is turned to the side and the one with the lower magni-fication is again swung into position. Now one applies a drop of immersion oil to theilluminated area on the object, trains the objective with the higher magnification onthe specimen, and refocuses with fine focusing. Proceeding in this way can avoiddampening other objectives with oil. In case of an inverted microscope, first focus withthe oil immersion objective without oil. The specimen is removed then from the micro-scope, and a very small drop of immersion oil is placed on the center of the objective.Now the specimen is replaced and a fine focusing is done.

After work with the microscope is finished, the oil on the objective and on thespecimen is removed immediately and carefully with fine tissue paper and thencleaned with ethanol.

15.8.5 Measurements of LengthThe microscopic image can be measured with eyepiece crosses on which there arescales, squared grids, or reference samples. This can be in the form of a reticle, which isa system of lines, circles, dots, cross hairs, or wires, or some other pattern, placed in theeyepiece or at an intermediate plane on the optic axis which is used as a measuringreference, focusing target, or to define a camera field of view. Also a graticule, which is ascale on glass or other transparent material placed in the eyepiece or at an intermediateplane on the optic axis can be used. The scale of the reticle or the graticule serves as areference gage. The distance between gradation marks on this scale is very precise, e.g.,0.1 mm.

Let us suppose that we want to measure the length of an integral part of a micro-structure that we are examining with an objective with a scale number of 100. If itsapparent length amounts to 1.2 mm in the intermediate image of the eyepiece, its truelength can be determined by dividing by the scale number on the objective. The lengthis 1.2 mm divided by 100, i.e., 12 �m. It is not necessary to take the magnification of theeyepiece into consideration.

A calculated magnification, using the manufacturer’s supplied ratings, as men-tioned earlier, is only an approximation of the true magnification, since individual opti-cal components may vary from their marked magnification. For a precise determina-tion of the magnification �calibration� observed through an eyepiece, a stage micro-metre is used. This is a graduated scale, placed like a specimen on the stage of a micro-scope and used for calibration.

It is very important that the measuring devices used are precise, and it is recom-mended that these should be traceable to the National Institute of Standards and Tech-nology �NIST� or a similar organization.


Measurements should be performed according to ASTM Standard Guide for Cali-brating Reticles and Light Microscope Magnifications �E 1951�. This guide coversmethods for calculating and calibrating microscope magnifications, photographicmagnifications, video monitor magnifications, grain size comparison reticles, andother measuring reticles.

15.8.6 Measurements of Height DifferencesOccasionally it is of interest to measure height differences of layers of differing hard-ness or the depth of scratches. To do this, an objective of a high numerical aperture isused because its depth of focus is very slight. One narrows the field diaphragm to asmall circle and focuses on the highest plane. On the fine-focusing knob scale a valuecan be read. Then one focuses on the deepest place and again reads off the appropriatevalue. If one knows the level difference �obtained from the instruction manual� thatcorresponds to the distance between two scale-marks on the fine focus mechanism,one can easily calculate the measurement. Use of a dial gage that is connected to themicroscope stage or of an electric position encoder is more convenient.

15.8.7 Maintenance of the MicroscopeMicroscopes are precision instruments that should serve their purpose for many years.For this reason they should be handled with care.

Dust particles or smoke are especially a problem. Always cover your microscopewith a protective dust cover after you have finished working and turned it off. The frontlenses of the objective are especially sensitive. Avoid letting the objective come intocontact with the specimen or the stage when you are focusing. The most minutescratches that can occur when these touch one another can cause blurred areas in theimage.

Etched specimens should be thoroughly cleaned and dried before they are used inthe microscope. Acids and residual moisture can not only leave flecks on the specimenbut also have an adverse effect chemically on the front lenses of the objective, as forexample can happen with hydrofluoric acid.

If you must remove dust from the objective, eyepiece, or filter, blow them off with arubber dust blower. Fingerprints, traces of grease, and residues of immersion oil can beremoved with a cotton ball dipped in grease-free benzene if necessary.

It is a good idea to have the service department of the manufacturer check the de-vice at least once a year and make any adjustments or calibrations that may be neces-sary. Leave repair work to the service department of the manufacturer also.

15.9 Documentation

The documentation of microscopic images can be done in different ways. In the earlydays of microscopy, the viewer sketched the image details that interested him.

Today either reflex cameras for photos in various formats or video or digital cam-eras, or both, are used.

Modern microscopes are equipped accordingly. They have their own photograph/television connection. One can change over to this connection from the ordinary bin-ocular tube via a beam splitter.

Figure 15.16 shows the light path. Through a photo-ocular �3�, the intermediateimage �2�, coming from the tube lens �1�, is magnified and projected to infinity. The


photo-objective produces from this an intermediate image on the film plane in thecamera �6� if the central shutter �4� is opened for exposure. The size of this intermediateimage must be adjusted to the format of the film. With microphotography film, for ex-ample, a magnification with the factor 2.5� must be effected when the original inter-mediate image has a diameter of 20 mm. This means that the entire image cannot becaptured on film of microphotography format.

The housing of a reflex camera can be joined to the photo/TV connection by meansof an adapter with a built-in objective. The reflex camera should be equipped with anelectric motor for film transport and a remote control switch. One disadvantage is thatthe flipping up of the mirror at the moment of exposure may cause both the microscopeand the camera to vibrate, resulting in blurred images.

For professional documentation, microscope cameras are to be preferred. All theimportant camera settings can be regulated electronically from a control desk. Thecamera itself works with a vibration-free shutter. Depending on the model, the film cas-sette may be exchangeable.

For several years now, video cameras and digital cameras have been increasinglyused for image documentation. Because semiconductor sensors can be used with themodern CCD-cameras that have very small active surface areas, the enlarged interme-diate image in the microscope must be reduced again. For this purpose, TV-adapterswith special optics and a fixed reduction factor are necessary. With a TV-zoom-adapter,the reduction factor and consequently the area of image detail can be changed. In thisway, the size of the image can be made to fit the format of the camera or video printer.

Fig. 15.16—Optical path for photomicrography, with tube lens �1�, intermediate image �2�,photo eyepiece �3�, central shutter �4�, camera lens �5� and image in the film plane �6�.1


This can be of advantage in connection with the required standard magnifications.Such linear standard magnifications are 25, 50, 75, 100, 200, 250, 400, 500, 750, 800,and 1000�.

The picture taken by the camera can be shown on a monitor, printed out by a videoprinter, or processed and stored in digitalized form on a PC.

In this process, the overall magnification, Mtotal, can be calculated from the opticalmagnification, Moptical, and the electronic magnification Melectronic.

Moptical = Mobjective � Madapter �5�

whereMobjective is the magnification of the objective, andMadapter is the magnification oftheadapter.

Melectronic = Dmonitor/Dsensor �6�

whereDmonitor is the diagonal length of the image of the monitor andDsensor is the diago-nal of theactive surfaceof thepicture sensor.

So the overall magnification is

Mtotal = Moptical � Melectronic �7�

In addition to the conventional CCD-cameras that shoot from 25–30 images perminute, “Slow-Scan” CCD-cameras are also being used in even greater numbers. Thesecameras take fewer images per second but with higher resolution and with less noise.

In combination with a PC, digitalized images can be processed and archived.Thanks to the many highly efficient software programs, they can also be qualitativelyimproved, marked, and labeled. Program modules that analyze structure make pos-sible the quantitative measurement of the structural parameters and a description ofthe measurement results in the appropriate form, the numerical values in the form oftables or clarifying diagrams �see Part IV of this book�.

15.10 The Confocal Laser Scan Microscope

Depth of focal field is a fundamental problem in light microscopy. It is also the reasonwhy we produce surfaces that are as plane possible when preparing metallographic/materialographic specimens and why we arrange them perpendicularly to the micro-scope’s light ray. This is the only way to achieve a sharp image over a larger area.

The greater a microscope’s magnification, the smaller the field of view, and theshallower the depth of focal field.

This system-determined limitation on the light microscope can be circumvented,and the possibilities for its use significantly broadened with the help of modern laserand computer technologies. The specimen surface can be scanned in a line-by-linemanner with a focused laser ray. Confocal reproduction conditions, the recording,storage, and processing of the signals in a PC, make a three-dimensional representa-tion of the specimen surface possible. The laser scan microscope �LSM� thus combinesthe advantages of the light microscope with those of the scanning microscope and theprofilometer.

15.10.1 Function of Confocal Laser Scan MicroscopeFigure 15.17 shows the path of light rays and the operational mechanism for the de-vice. The laser ray is focused onto the specimen through the objective lens. Light that is


reflected there is focused onto a variable pinhole aperture by an additional lens. Onlylight coming from the objective’s focal plane can reach the detector unimpeded. Lightcoming from other optical planes is suppressed by the confocal spatial filter that con-sists of lens and aperture. The specimen surface, with the light ray falling onto it, can bescanned point-by-point, line by line, by means of the dichroic mirror. The light signalsreceived by the detector are converted into electronic impulses and digitally processed.

We, therefore, obtain a reproduction of the level specimen surface on a monitor.Because of the low depth of focal field, we obtain an “optical section” in x, y coordinateswhen the surface is irregular.

By successively changing the arrangement of the object along a series of definedsteps in direction z, we can record several sections and compile these images into athree-dimensional stacked image, process them digitally and draw qualitative as wellas quantitative conclusions about the topography of the specimen surface.

Lasers with varying excitation wavelengths in the ultraviolet through infraredspectral range are used. As lasers of wavelengths 488 and 514 nm �25 mW� and HeNelasers of wavelengths 543 nm �1 mW� and 633 nm �5 mW� are usually used inmetallography/materialography.

At 0.2, the laser scan microscope’s lateral resolution capability is somewhat betterthan that of the conventional light microscope.

Depth resolution depends on the wavelength of the laser light, the numerical aper-ture �NA� of the objective and the diameter of the aperture, which is a determining fac-tor for the quality of the confocal spatial filter.

Assuming that the aperture’s diameter in front of the detector approaches zero, thefollowing holds true for reflective surfaces:

Fig. 15.17—Path of light rays and the operational mechanism for a confocal laser scanmicroscope.1


dz = n � 0.89 � �/�NA�2 �8�

where dz is the axial half-width of an intensity curve of light reflected by the object, deter-mined by the height of the object stage; � is the laser's wavelength and n is the refractionindex.

In practice, values between 20 and 50 nm turn out to correlate with a useful depthof focal field, depending on objective type and the medium that is between the objectiveand the object.

15.10.2 Applications of Confocal Laser Scan MicroscopePossible types of lighting for LSM are bright-field, differential interference contrast,and fluorescence. If lasers that emit polarized light are used, polarization microscopycan also be used. Figure 15.18 shows a confocal laser scan research microscope set upwith a motorized fine focusing stage and monitor.

In the area of material research and testing, confocal light microscopy is suitablefor the investigation of the surfaces of metallic materials, ceramics, plastics, and repli-cas as well as of semitransparent and transparent layers such as glass, polymer foils,coatings, or varnishes.

In addition to the representation of compounds, surface profiles can be recordedand the microroughness of very small areas such as tears, pores, and hollow spaces can

Fig. 15.18—Confocal laser scan microscope.1


be three-dimensionally ascertained. The arrangement and thickness of single and mul-tiple layers can also be represented and quantitatively analyzed.

Figure 15.19 shows a fractured steel plate, the single grains can be seen three-dimensionally.

15.11 Stereo Microscopy

For the purpose of a three-dimensional evaluation of fractured surfaces, the size andshape of those fractures, as well as the three-dimensional shape and configuration ofconstituent elements, it is advantageous to use a stereomicroscope. With a stereomi-croscope the same spot on a specimen can be viewed from two places at a short dis-tance from one another, similar to the distance between the two eyes of a human being.

Modern stereomicroscopes may use two different principles for the light raypaths.

Following the Greenough principle, two light ray systems are directed onto thespecimen through two identical objectives that are tilted toward one another at the ste-reo angle. This yields two images that produce a single three-dimensional image whenobserved through the two eyepieces.

Following the telescope principle, two parallel but not axially aligned light beamsare directed through an objective. The beams are deflected by the objective and strikethe specimen at the stereo angle. With this method of operation, an expansion of theoperational possibilities becomes relatively easy because supplementary optical mod-ules can be installed either above or below the body of the microscope.

For stereomicroscopes, a number of exchangeable objectives are obtained withthe magnifications from 5� to 100� and eyepieces from 5� to 20�.

Fig. 15.19—Confocal image of a fractured steel plate.4


Apochromatic objectives are well suited for three-dimensional observations. Forflat objects like prepared specimens, wafers and foils, plan achromats are better suited.For the finest structures with very low contrast, the apochromats can be used with ad-vantage.

The magnification can be changed by zoom when a special system of lenses isused. According to design and manufacturer the variation in magnification may be be-tween 3:1 or 12:1.

The observation of details depends to a high degree on the illumination that shallbe adapted to the object and the purpose of examination. Therefore, different illumina-tion systems can be obtained like halogen-incandescent lamp for incident light or co-axial illumination, optical fiber for vertical illumination, and other light sourcesfor highest light intensity and for homogeneous illumination. Metallographic/materialographic specimens or other flat, strongly reflecting objects like LCDs, wafers,and integrated circuits may be examined most effectively with coaxial illumination.Three-dimensional objects may be illuminated from two sides or with ring-illumination. Using illumination under an angle will give an improved observation of

Fig. 15.20—Stereo microscope with digital camera.3


high differences in the surface. Vertical illumination is best suited for exposing of cavi-tations and open pores. Fluorescence modules make examination of fluorescence sub-stances possible.

The advantages of stereomicroscope systems are: Ample working distances, largeobject fields, and the three-dimensional viewing of nonreversal images.

Stereomicroscopes can produce meaningful overall magnifications of up to about250 times the original.

Figure 15.20 shows a modern stereomicroscope.


16Electron Microscopy—ScanningProbe MicroscopyAN IN-DEPTH DESCRIPTION OF ELECTRON MICROSCOPY AND SCANNINGprobe microscopy falls outside the scope of this book, but in this chapter a short intro-duction is given to the transmission electron microscope �TEM�, the scanning electronmicroscope �SEM�, the focused ion beam techniques �FIB�, and a number of scanningprobe microscopes �SPM�.

16.1 The Transmission Electron Microscope „TEM…Electron beams penetrate thin layers and, in doing so, are diffracted at the crystal lat-tice and interferences arise. One can make these visible, after amplification with elec-tromagnetic lenses and electronic processing, as bright-dark effects. With an accelera-tion voltage of up to 1 million volts, magnifications of up to 106 with a resolution below1 nm can be attained. Disruptions in the crystal lattice, such as dislocations, elimina-tions, grain boundaries, and other lattice defects, are detectable; they appear mostlydark.

Specimens for the TEM examinations must be thin enough for the electrons topass through and thick enough for their structural features to remain verifiable. Vari-ous methods can be used for the preparation.

With metallic materials and ceramic basic materials, thinning procedures are pre-ferred. Using this method, the specimen �diameter 3 mm� is made sufficiently thin,through either ion bombardment �see Section 16.3� or electrolytically, that a hole isproduced in the middle. Areas next to the hole are sufficiently thin to be suitable forTEM examination �see Section 8.5�.

For purposes of imaging the surfaces, carbon or lacquer is used to take a replica ofthe specimen. The peeled-off layer of lacquer is then vapor-coated in a vacuum cham-ber with carbon or metal �Au, Pt� to bring out the contrast. After the layer of lacquer hasbeen removed, the metal foil or carbon foil can be transluminated.

Fine powder, dust, or smoke particles are applied directly to a backing film �car-bon, lacquer�. With extraction replicas, individual particles of a specimen, their size,and distribution can be identified.

With the use of ultramicrotomes one can produce thin sections from embeddedpowders or synthetics. Synthetic materials that tend to smudge must be worked with atlow temperatures �cryomicrotomy�.

16.1.1 The Scanning Transmission Electron Microscope „STEM…This microscope is a combination of a TEM and a SEM �see below� and gives the advan-tages of both microscope types. A STEM is a very high cost investment and primarilyused for research.

16.2 The Scanning Electron Microscope „SEM…In the scanning electron microscope, the surface of the specimen is linearly scannedwith the electron beam �ca. 0.01 �m�. Secondary electrons are emitted and captured by

558

an electron detector. The spatial distribution of these secondary electrons can be madevisible, after electronic amplification, on a monitor. Depending on the accelerationvoltage of the primary electrons, magnifications of up to 200 000� are possible. Withmagnification of 1000� the depth of field is about 35 �m; the resolution poweramounts up to 0.01 �m. Differences in levels on the surface of the specimen result indifferences in contrast. Moreover, shadow formations can arise as a result of the slantwith which the electron beams fall on the specimen. As a result, an image of high reso-lution and great depth of field is obtained.

The SEM is used preferably for the examination of rough surfaces and investiga-tions of damage or loss, e.g., fractured surfaces.

Preparation of the specimen for SEM examinations is simple: the specimen mustbe free of volatile elements like water, oil, or grease. Loose particles must also be re-moved. If the specimen does not consist of electricity-conducting material, the surfacemust be coated with a layer of electro-conductive material �C, Pt, Au� to prevent charg-ing.

In case of mounting, care should be taken that metal powder, like copper, con-tained in the mounting material, is not contaminating the specimen.

16.2.1 Energy Dispersive Spectroscopy „EDS…An SEM can be equipped with additional equipment like EDS and EBSD �see below�.

Besides the electrons emitted from the specimen mentioned above, also X-rays areemitted. As high-energy electrons produced with an SEM interact with the atomswithin the top few micrometres of a specimen surface, X-rays are generated with anenergy characteristic of the atom that produced them. The intensity of these X-rays isproportional to the mass fraction of that element in the specimen. In EDS, X-rays fromthe specimen are detected by a solid-state spectrometer that converts them to electricalpulses proportional to the characteristic X-ray-energies. If the X-ray intensity of eachelement is compared to that of a standard of known composition and suitably cor-rected for the effects of other elements present, then the mass fraction of each elementcan be calculated.

16.2.2 Electron Backscatter Diffraction „EBSD…Electron Backscatter Diffraction �EBSD� has become popular among materials scien-tists since the first commercial automatic systems were available in 1994. The mainadvantage of this method is the possibility to link morphology �grain size and shape�with crystallographic features �phase, orientation, disorientation� on the microscopicscale, but still in a representative specimen area. During the examination, an electronicbackscatter pattern �EBSP� is produced, an image consisting of relatively intensebands �Kikuchi bands� intersecting one another and overlying the normal distributionof backscattered electrons, as a result of Bragg diffraction of electrons by atomicplanes in the crystal lattice. The results can be compared to TEM, but the specimenpreparation is much simpler than the preparation of thin foils. The specimens, how-ever, are considerably more difficult to prepare than for normal imaging in SEM, be-cause of the very low information depth of the EBSD signal based on channeling ef-fects. This means that the very thin deformed layer, often left on the specimen aftermechanical preparation, cannot be tolerated to obtain a good pattern quality, andtherefore the specimen preparation shall be improved. In general, classic etching is notneeded for EBSD because the contrast is defined through the orientation differences.Etching should even be avoided, as the induced surface roughening is disturbing due to

Chapter 16 Electron Microscopy 559

the high specimen tilt �70°� during the examination process. The specimen preparationfor EBSD is discussed in Section 7.10.4.

16.2.3 The Electron Probe Microanalyzer „EPMA…This instrument, also called the microprobe is closely related to the SEM, only theX-ray detectors are not analyzing only the energy as in EDS mentioned above, but thewavelength of the X-rays generated from the interaction of the primary and backscat-tered electrons and the specimen. This is called wavelength dispersive spectroscopy�WDS� and compared to EDS, WDS gives much more accurate quantitative data for thesingle components in the specimen surface.

16.3 Focused Ion Beam „FIB…A focused ion beam system �FIB� is in principle built like an SEM. In the SEM an elec-tron beam is used for scanning, but in the FIB a beam from a liquid metal ion source�mostly gallium, Ga+� is used. This beam is focused so that it can be scanned like anelectron beam. This allows for sputtering material from the sample or for depositingmaterial on the sample if gases are used �see Section 9.6.5�. Also, imaging is possible byion-induced secondary electrons, as it is known from the SEM. As the FIB can removematerial with a very high precision, it is used for preparation of samples for TEM. Thiscovers both samples of electronic devices and samples for material research.

The TEM samples can be made either by using a pre-prepared sample in the formof a thin strip of material, which then is further thinned by the FIB, or by the newerlift-out technique. With this technique no mechanical preparation is needed, the ionbeam cuts into the base material and the sample is lifted out using a special manipula-tor.

The great advantage of using FIB for preparation of samples for TEM is the shortertimes compared to conventional methods �see Section 8.6�, and the very high rate ofsuccess.

16.4 Scanning Probe Microscopes „SPM…In addition to the methods of optical metallography/materialography already men-tioned �LM, TEM, SEM�, we will briefly discuss scanning probe microscopy. In the pastfew years it has gained increasingly greater significance in the area of metallography/materialography.

All scanning probe microscopes work according to the following principle: the sur-face of the specimen is scanned with the sharp tip of a needle that is mounted on aflexible cantilever. The interactive force that is present between the tip and the surfaceserves as a measurement signal and can be evaluated. Through the use of piezoelectri-cal actuators, movements of the measuring tip in the magnitude of atomic diameterscan be initiated, with a resolution of less than 1 nm. Scanning probe microscopes areused in biology, physics, and materials science to characterize surfaces.

The first device of this kind, the Scanning Tunneling Microscope �STM�, was devel-oped by Binnig and Rohrer and used for the first time in 1981. It makes use of thequantum-mechanical tunneling effect for measurement of distance. For this purpose,voltage is applied between the tip and the specimen. If one brings the tip closer to thesurface without actually touching it �noncontact mode�, a current begins to flow. Inas-


much as the amplitude of this current depends exponentially on the distance it can beused to regulate the distance. With STM the surface topographies of conductivesamples and images in the atomic range can be shown.

With the Atomic Force Microscope �AFM�, the tip is positioned at the free end of acantilever. The interaction between tip and surface, e.g., a repulsive force, is registeredthrough the vibration of the cantilever. Its detection occurs in accordance with the lightconducting principle: a laser beam focused on the backside of the flexible cantilever isreflected and registered by a photo diode. The measured values in the nanometre rangecan be used to guide piezoelectric actuators in the x-, y-, z-direction of the tip. In thismanner one can obtain a three-dimensional image of the surface on the computer.

AFM is suited for electrical-conductive and nonconductive materials such as met-als, ceramics, glasses, and synthetics. Samples, either unprocessed or processed, canbe examined in air, in a gaseous environment, or in liquids.

The field to which ATM is applied is constantly growing and now this technique isalso used for measuring of nano hardness and elastic modulus �Young’s modulus� �seeSection 21.6.1�.

If the specimen is to be prepared metallographically/materialographically, onemust take care that it has been polished with as little resulting deformation as possible�electrolytic polishing may be an advantage�, and that through chemical etching only aminimal level contrast in the nanometre range arises between the individual phases.Very small structural elements, e.g., the very finest precipitates, can then be identifiedthat can no longer be seen with a light microscope because of its limited resolutionpower. Nevertheless, other local interactive forces can be detected with the AFM proce-dure.

With magnetic force microscopy �MFM�, the surface of the sample is scanned witha nickel or iron tip in noncontact mode. One obtains an image of the local magneticcharacteristics with a resolution in the nanometre range.

Adhesion force microscopy conveys perceptions with regard to the local structure-specific adhesive force between measuring tip and specimen surface.

With friction force microscopy, the local frictional forces can be measured and im-aged. This is performed in contact mode by letting the tip move across the surface ofthe specimen and measuring the deflection of the cantilever. Good contrasts can be ob-tained especially with synthetics.

References „Part III…�1� Courtesy of Carl Zeiss, Germany.

�2� Courtesy of Olympus, Germany.

�3� Courtesy of Leica Microsystems, Germany.

�4� Courtesy of E. Bischoff, Max-Planck-Institut für Metallforschung, Stuttgart, Germany.

Chapter 16 Electron Microscopy 561

Part IV: QuantitativeMetallography/Materialography—Automatic Image Analysis

17Quantitative Metallography/Materialography—An IntroductionWHEN MAKING A QUALITATIVE EXAMINATION OF A MICROSTRUCTURE,the interpretation of the structure is to a high degree based on the knowledge and expe-rience of the observer. In quantitative metallography/materialography the constituentsin the microstructure are measured to provide more reliable data for materials engi-neering and quality control purposes. Typical microstructural measurements includethe length, width, and area of features or the relative amount of a structure or phase.The application of stereological principles enables two-dimensional measurementdata extracted from metallographic/materialographic specimens to provide accurateinformation about three-dimensional structures increasing the usefulness and impor-tance of quantitative microstructural analysis. It can be tedious to implement quanti-tative methods. Digital image analysis equipment and software have been developed astools to automate the collection and reporting of quantitative data.

In this chapter, the most important uses of quantitative metallography/material-ography and corresponding ASTM standards are discussed briefly. Automatic imageanalysis is described in Chapter 18. Both chapters should be considered as introduc-tions to quantitative metallography/materialography and image analysis �see the Ref-erences and Literature List for further study of these subjects�.

17.1 Quantitative Metallography/Materialography

In short, quantitative metallography/materialography can be defined as the measure-ment of microstructural parameters. This may be linear measurements when examin-ing layer thickness, case depth, etc., or measurements of area, when analysis of volumefraction or grain size is required.

Both manual quantitative methods, including measurements using point count-ing screens or templates, and automatic image analysis are defined in a number ofstandards.

17.1.1 Stereology–Table 17.1Stereological methods are procedures used to characterize three-dimensional micro-structural features based on measurements made on two-dimensional sectioningplanes.1

For the stereological calculations, the International Society for Stereology recom-mends a number of symbols and notations. The most important are stated in Table17.1.1,2

Basic MeasurementsA number of the above-mentioned parameters are simple counting measurements thatare relatively easy to measure and are used in a number of equations �see below�.

565

PP is the ratio P� /PT, where P� is the number of points that fall in the �-phase andPT is the total number of test points �see also below�.

PL is the number of points of intersections generated per unit length of test line. Anintersection count is the number of boundaries between the matrix phase and thephase or constituent of interest that are crossed by the lines of a test grid. For isolatedparticles in a matrix, the number of feature intersections will equal twice the numberof feature interceptions. The total length of the test line is determined in advance tofacilitate calculations.

NL is the number of interceptions of features divided by total test line length. Thepart of the test line superimposed on the feature constitutes the intercept. The numberof interceptions equals the number of particles �or clusters of particles� of a phase or

TABLE 17.1—Principal Symbol and Combined Notations for Quantitative Metallography/Materialography.

Symbol Units Description Common Name

P ¯ Number of point elements or test points ¯PP ¯ Point fraction (number of point elements per total number

of test points).Point Count

L mm Length of linear elements or test line length ¯PL mm−1 Number of point intersections per unit length of test line ¯LL mm/mm Sum of linear intercept lengths divided by total test line

lengthLineal fraction

A mm2 Planar area of intercepted features or test area ¯S mm2 Surface area or interface area, generally reserved for

curved surfaces¯

V mm3 Volume of three-dimensional structure elements or testvolume

¯AA mm2/

mm2Sum of areas of intercepted features divided by total testarea

Area fraction

SV mm2/mm3

Surface or interface area divided by total test volume(surface-to-volume ratio)

¯VV mm3/

mm3Sum of volumes of structural features divided by total testvolume

Volume fraction

N ¯ Number of features ¯NL mm−1 Number of interceptions of features divided by total test

line lengthLineal density

PA mm−2 Number of point features divided by total test area ¯LA mm/

mm2Sum of lengths of linear features divided by total test area Perimeter (total)

NA mm−2 Number of interceptions of features divided by total testarea

Area density

PV mm−3 Number of points per test volume ¯LV mm/

mm3Length of feature per test volume ¯

NV mm−3 Number of features per test volume Volumetricdensity

L mm Mean linear interception distance, LL/NL ¯A mm2 Mean area intercept, AA/NA ¯S mm2 Mean particle surface area, SV/NV ¯V mm3 Mean particle volume, VV/NV ¯


constituent of interest that are crossed by the lines of a test grid. For all microstructureswith more than a single phase, PL=2 NL and for a single phase, PL=NL.

PA is the number of point features, such as grain boundary junctions, inside a givenarea, divided by this area.

NA is the number of interceptions of features, such as grains or graphite nodules,inside a given area, divided by this area.

See also ASTM Standard Terminology Relating to Metallography �E 7� for stan-dard stereological terminology definitions.

To obtain a true measurement, the instrument used must be calibrated �see Sec-tion 17.1.3�.

Basic EquationsBased on the measurements mentioned above, a number of equations are developedfor covering the calculation of points, lines, areas, and volumes used for metall-ographic/materialographic analysis. The most important measurements such as vol-ume fraction, inclusion rating, etc., with the covering ASTM standards are described inshort below, and the relevant equations will be stated there.

Use of Comparison Charts and GridsComparison charts were developed for the evaluation of a given microstructure. Anexample is the so-called JK charts �developed by the Swedish Jernkontoret� depicting aseries of typical inclusion configurations �size, type, and number� to be used for directcomparison with the microscopical field in view. Comparison charts can be used alsofor determination of volume fraction and grain sizes, but a grid is used normally �seethe relevant standards below�.

17.1.2 Specimen Preparation

Selection of SpecimensThe selection of specimens, sampling, for quantitative analysis is very important be-cause if the measured results are to be of value, the specimens must be representativeof the material that is being analyzed.

The number of specimens and the selection depends on the type of examination tobe performed. As described in ASTM Standard Practice for Calculating Sample Size toEstimate, with a Specified Tolerable Error, the Average for Characteristic of a Lot orProcess �E 122� �see Section 12.4�, random sampling should be performed.

As an example, the sampling procedure for the ASTM Test Method for Determin-ing the Inclusion Content of Steel �E 45�, should be described in short: To obtain a rea-sonable estimate of inclusion variations within a lot, at least six locations, chosen to beas representative of the lot as possible, should be examined. For cases in which a defi-nite location within a heat, ingot, or other unit lot is unknown, statistical random sam-pling with a greater number of specimens should be employed. Very often the geometryof the work piece plays a role; in examination of inclusions, the polished surface mustbe parallel to the longitudinal axis of the product. In case of rolled or other hot workedmaterial, the microstructure to be measured will vary strongly according to the planeof the prepared surface �see also Section 2.1�.

Chapter 17 Quantitative 567

ReproducibilityIt is very important that the specimen surfaces examined in quantitative metallo-graphy/materialography are prepared with the highest degree of reproducibility; onlythen can the measured results be compared. In case of manual image analysis, the op-erator might be able to compensate for minor artifacts in the prepared microstructure,but when using digital imaging equipment to delineate structures with image segmen-tation, artifacts may be included in the measurements producing inaccurate results�see below�.

Preparation of the Specimen SurfaceAs a general rule the goal of specimen preparation is to consistently show the “TrueStructure,” free of all artifacts. A specimen for automatic image analysis should also beplane, without relief and edge rounding. All phases should be visible without smearingor other artifacts; in inclusion rating even small scratches can disturb the measuring�see Section 13.6�.

Preparation of specimens suitable for quantitative analysis is described in Section13.2.3 and in every quantitative standard under the jurisdiction of the ASTM Commit-tee E-4 �see Section 12.4�.

EtchingFor a number of quantitative examinations, such as inclusion rating, etching shouldnot be used; the contrast developed obscures the features to be measured.

In other cases, etching has to be performed to obtain the contrast necessary toshow the structures of interest such as in steel grain size and banding measurements.

Reproducibility of the etching is very important in automatic image analysis sothat a uniform contrast can be developed. Variable and inconsistent etching will pro-duce contrast irregularities which influence the measurements.

17.1.3 CalibrationBefore making any measurement, it is essential to create calibrations for each instru-ment �microscope, video system, etc.� used to deliver an image. Calibration is the pro-cess of establishing the graphical or mathematical relationship relating the desiredproperty �expressed in a standard unit of measure such as �m� to the instrument out-put �instrument units such as filar divisions or pixels�.

Although the operational requirements for equipment calibration differ widely,the ASTM Standard Guide for Calibrating Reticles and Light Microscope Magnifica-tions �E 1951� provides an overview of calibration concepts and generalized calibrationprocedures.

17.1.4 Field Selection—BiasQuantitative measurement of a specimen surface will take place in microscopic fieldsonly representing a small part of the surface. To obtain a specific measurement accu-racy, a number of fields must be examined. This number depends on the homogeneityof the microstructure and the magnification. The higher the magnification observedand the lower the homogeneity of the specimen, the higher the number of fields thatwill be needed to accurately evaluate the microstructure, because at higher magnifica-tion the area covered by the field is smaller and with a heterogeneous microstructurethe variations of the surface are higher. The number of fields is stated very often in the


specific standards. If not, the number should be calculated to obtain a reasonable rela-tive accuracy.

As a rule, the fields should be placed randomly on the specimen surface. This canbe performed easily on an upright microscope, the specimen surface being visible �seeSection 15.6�. It is important that the operator does not look at the image when theplacement of the fields is decided on. This is the only way bias can be avoided.

17.2 Volume Fraction—Point Count

The volume fraction of a given phase or constituent in an alloy is one of the most impor-tant and most common measurements in quantitative metallography/materialo-graphy. This is because the amount of a second phase can have a strong influence onthe properties of the material.

The amount of a specific constituent �second phase� is quantified by the volumefraction. The volume fraction of a component � is designated by VV, and is the ratio ofthe volume of this component V� referred to the test volume VT �total volume of thespecimen�. This can be expressed:

VV = V�/VT �1�

VV corresponds to the area fraction of the structural component � that is visiblein the polished specimen surface and can be determined by planimetry. Because ofthe valid relationship in the range of statistical scatter, AA �area fraction�=LL�lineal fraction�=PP �point count�, the volume fraction can also be determined from LL.This is done by measurement of the fraction L� of a straight line LT that falls within thecomponent, or from the point fraction PP by counting the points P� of a point grid withthe point count PT that fall on the component. This can be expressed:

VV = V�/VT = A�/AT = L�/LT = P�/PT �2�

In ASTM Test Method for Determining Volume Fraction by Systematic ManualPoint Count �E 562� �see below�, an efficient way for statistically estimating the volumefraction of an identifiable constituent or phase from sections through the microstruc-ture by means of a point grid, is described.

17.2.1 ASTM Test Method for Determining Volume Fraction by SystematicManual Point Count „E 562…The test method may be used for all opaque materials �see Section 12.4.3�. The testmethod is based on the stereological principle that a clear plastic test grid with a num-ber of regularly arrayed points, when systematically placed over an image of a two-dimensional section through the microstructure, can provide, after a representativenumber of placements on different fields, an unbiased statistical estimation of the vol-ume fraction of an identifiable component or phase. A grid of lines or curves is super-imposed on a magnified image of a metallographic/materialographic specimen, andthe number of points falling within the microstructural component of interest iscounted and averaged for a selected number of fields. These points divided by the totalpoints in the grid is the point fraction PP �see above�. Based on PP the volume fractionVV can be calculated.


17.3 Inclusion Rating

Inclusions can significantly influence the properties of a material. For this reason in-clusion rating, especially of steel, is a very important quantitative method.

Inclusions can be exogenous like slag particles or indigenous, oxides, sulfides, sili-cates, etc., developed in the material during the manufacturing process. Normally onlythe indigenous inclusions, sulfides and oxides, are measured, quantifying the amount,size, shape, and distribution. In a number of standards, ASTM E 45 �see below�, SAEJ422a, and the German standard SEP 1570 �DIN 50602�, the inclusions are determinedby using manual comparison chart methods based on volume fraction and pointcounting. Since this involves a vast amount of counting time, image analyzers are oftenused for inclusion rating �see below�.

17.3.1 ASTM Standard Test Method For Determining the Inclusion Contentof Steel „E 45…ASTM E 45 covers a number of recognized methods for determining the nonmetallicinclusion content of wrought steel.

The methods are both macroscopical and microscopical; only the latter shall beshortly described here.

Comparison charts, mostly based on JK charts, as described above in this chapter,are used. The inclusions are separated into four categories, A, B, C, and D and aregraded by calculating a severity level based on width and length �for D types the count�of inclusions in 0.50 mm2 fields within a 160 mm2 specimen surface area. In Method A�Worst Field� the inclusions are assessed qualitatively, seeking out and reporting onlythe field with the highest severity rating. In Method D the length or count and the widthof inclusions are examined and the severity level of each inclusion type for each field ofview is determined and reported for a 160 mm2 specimen surface area. The Methods Band C require that a specimen area be surveyed and inclusions greater than a certainlength and those of the maximum length be reported.

Manual performance of E 45 �especially Method D� involves much work to obtainan acceptable measurement accuracy; therefore, the use of digital image analysisequipment has become more common �see Section 18.5.2�.

17.3.2 ASTM Practice for Obtaining JK Inclusion Ratings Using AutomaticImage Analysis „E 1122… „withdrawn 2006, replaced by E 45…This practice covers procedures to perform JK-type inclusion ratings using automaticimage analysis in accordance with microscopical methods A and D of E 45.

E 1122 is further described in Section 18.5.2.

17.3.3 ASTM Practice for Determining the Inclusion or Second-PhaseConstituent Content of Metals by Automatic Image Analysis „E 1245…The practice describes a procedure for obtaining stereological measurements thatquantify basic characteristics of the morphology of indigenous inclusions in steels andother metals using image analysis. The practice can be applied to provide such data forany discrete second-phase constituent in any material.

ASTM E 1245 is further described in Section 18.5.2.


17.4 Grain Size

A very high number of metallographic/materialographic examinations are performedto determine the grain size of the material; this parameter to a high degree influencesthe material properties.

Three procedures for determining grain size are described in ASTM E 112 �see be-low�, the comparison procedure does not require counting of either grains, intercepts,or intersections but only involves comparison of the grain structure to a series ofgraded images. The planimetric procedure involves an actual point count of the num-ber of grains within a known area, NA. NA is used to determine the ASTM grain sizenumber, G �see below�. The intercept procedure involves an actual count of the numberof grains intercepted by a test line or the number of grain boundary intersections with atest line, per unit length of line, used to calculate the mean lineal intercept length, l. l isused to determine the ASTM grain size number, G �see below�.

17.4.1 ASTM Test Methods for Determining Average Grain Size „E 112…ASTM E 112 includes the comparison procedure, the planimetric procedure, and theintercept procedures. The methods apply chiefly to single-phase grain structures inmetallic materials, but they can be applied to determine the average grain, crystal, orcell size in nonmetallic materials like ceramics.

ASTM E 112 is a very comprehensive standard covering the earlier mentioned pro-cedures, a description of the ASTM Grain Size Number, and a number of annexes de-scribing how to establish the grain size for a number of materials.

ASTM Grain Size NumberThis number, the G number, is defined as:

NAE = 2G−1 �3�

whereNAE is the number of grains per square inch at 100�magnification. To obtain thenumber per squaremmat 1�,NA,NAE is multiplied by 15.50. The International StandardOrganization (ISO) and in several national standards, themetric grain size number,GM, isbasedon thenumberof grainspermm2, at1�, and this gives the equation:

NA = 8�2GM� �4�

The metric grain size number, GM, is a little lower than the ASTM grain size num-ber, G, for the same microstructure:

G = GM + 0.046 �5�

Comparison ProcedureThe comparison procedure, as mentioned above, does not require counting of grains,intercepts, or intersections, but involves comparison of the grain structure to a series ofgraded images, either in the form of a wall chart, clear plastic overlays, or an eyepiecereticle. Experience has shown that unless the standard image reasonably well ap-proaches that of the specimen, errors may occur. To minimize such errors, the com-parison charts are presented in four categories: Plate I—Untwinned grains �flat etch�includes grain size numbers 00, 0, 1

2 , 1, 1 12 , 2, 2 1

2 , 3, 3 12 , 4, 4 1

2 , 5, 5 12 , 6, 6 1

2 , 7, 7 12 , 8, 8 1

2 , 9,9 1

2 , 10, at 100�. Plate II—Twinned grains �flat etch� includes grain size numbers 1, 2, 3,


4, 5, 6, 7, 8, at 100�. Plate III—Twinned grains �contrast etch� includes nominal graindiameters of 0.200, 0.150, 0.120, 0.090, 0.070, 0.060, 0.050, 0.045, 0.035, 0.025, 0.020,0.015, 0.010, 0.005 mm at 75�. Plate IV—Austenite grains in steel �McQuaid-Ehn� in-cludes grains size numbers 1, 2, 3, 4, 5, 6, 7, 8, at 100�. As an example, Plate III is usedfor twinned copper and brass with a contrast etch.

Repeatability and reproducibility of comparison chart ratings are generally ±1grain size number.

Planimetric ProcedureAs mentioned above, the planimetric procedure, also called Jeffries’ procedure, in-volves an actual count of the number of grains within a known area �circle or rect-angle�. The number of grains per unit area, NA, is used to determine the ASTM grainsize number, G. The precision of the method is a function of the number of grainscounted, and a magnification shall be selected which gives at least 50 grains in the fieldto be counted �a minimum of three fields�. When the counting is done, the figure is mul-tiplied by Jeffries’ multiplier, f, that is a factor relating to the magnification used, M.The number of grains per square mm at 1�, NA is calculated from:

NA = f�NInside + NIntercepted/2� �6�

where f is the Jeffries' multiplier taken from a table in the standard,NInside is the numberof grains completely inside the test circle andNIntercepted is the number of grains that inter-cept the test circle.

A precision of ±0.25-grain size units can be attained with a reasonable amount ofeffort. Results are free of bias and repeatability and reproducibility are less than±0.5-grain size units. An accurate count does require marking off the grains as they arecounted.

Intercept ProcedureThe intercept procedure, also called Heyn’s procedure, is more convenient to use thanthe planimetric procedure. With the intercept method an accurate estimate of the grainsize can be obtained in a fraction of the time used with the planimetric method. Asmentioned above, the intercept method involves an actual count �at least 50 intercepts�of the number of grains intercepted by a test line or the number of grain boundary in-tersections with a test line, per unit length of test line, used to calculate the mean linealintercept length, l−. l− is used to determine the ASTM grain size number, G.

The precision of the method is a function of the number of intercepts and intersec-tions counted. An intercept is a segment of test line overlaying one grain. An intersec-tion is a point where a test line is cut by a grain boundary. Experiments have shown thata test pattern consisting of three concentric and equally spaced circles having a totalcircumference of 500 mm gives satisfactory results. Based on the calculation of thenumber of intercepts, NL and the number of intersections, PL, the mean lineal interceptvalue for each field, l can be calculated:

l = l/NL = 1/PL �7�

A precision of better than ±0.25-grain size units can be attained with a reasonableamount of effort. Results are free of bias; repeatability and reproducibility are less than±0.5-grain size units. Because an accurate count can be made without the need of


marking off intercepts and intersections, the intercept method is, as mentioned, fasterthan the planimetric method for the same level of precision.

ASTM E 1382 describes determining average grain size using semiautomatic andautomatic image analysis �see below�.

17.4.2 ASTM Test Methods for Estimating the Largest Grain Observed in aMetallographic Section „ALA Grain Size… „E 930…Commercial material specifications sometimes include, in size limits for grain struc-tures, the need for identification of the largest grain observed in a sample, often ex-pressed in ALA �as large as� grain size. ASTM E 930 is used when the number of largegrains is too few for measurement with ASTM E 112.

The test methods are simple manual procedures, using comparison and measur-ing. The measuring procedure is recommended for greater accuracy.

17.4.3 ASTM Test Methods for Characterizing Duplex Grain Sizes „E 1181…The above-mentioned test methods for determination of average grain size covers ma-terials assumed to contain a single log-normal distribution of grain sizes. ASTM E 1181is set forth to characterize grain size in products with any other distributions of grainsize. The term “duplex grain size” is chosen to describe any of these other distributionsof grain size, because of its common usage and familiarity. However, the use of thatterm does not imply that only two-grain size distributions exist.

Duplex grain size may occur in some metals and alloys as a result of their thermo-mechanical processing history, and these methods are made for these materials, butthey can also be used for other materials with a similar microstructure. Duplex grainstructures �for example, multiphase alloys� are not necessarily duplex in grain size, andas such not covered by these methods.

The test methods use a comparison procedure, a point count procedure based onASTM E 562 �see above�, a planimetric procedure, and a direct measurement pro-cedure.

17.4.4 ASTM Test Methods for Determining Average Grain Size UsingSemiautomatic and Automatic Image Analysis „E 1382…These test methods may be used to determine the mean grain size, or the distribution ofgrain intercept lengths, or areas in metallic and nonmetallic polycrystalline materials.The methods may be applied to specimens with equiaxed or elongated grain structureswith either uniform or duplex grain distribution. Either semiautomatic or automaticimage analysis devices may be utilized to perform the measurements.

The semiautomatic procedure is based on a digitizing tablet with a measurementresolution of at least 0.1 mm. A variety of approaches can be employed: The simplest isto fix a photograph to the tablet surface and place a suitable grid over the photograph,tape down the corners of the grid, and use the cursor, fitted, with fine cross hairs, tomeasure the appropriate features. Alternatively, the grid can be placed on an eyepiecereticle. The cursor is moved over the table surface and the microscopist can see theilluminated cross hairs in the cursor through the eyepieces over the field of view andgrid pattern. A third approach is to transfer the microstructural image, the test gridimage, and cursor image to a television monitor. The microscopist moves the cursoracross the tablet surface while watching the monitor to make the appropriate measure-ments.

The automatic procedure is described in Section 18.5.3.


17.5 Banding

A banded microstructure is caused by segregation that occurs during the dendritic so-lidification of metals and alloys and is aligned by subsequent deformation. Solid-statetransformations may be influenced by the resulting microsegregation pattern leadingto development of a layered or banded microstructure. The most common example ofbanding is the layered ferrite-pearlite structure of wrought low-carbon and low-carbonalloy steels. Other examples of banding include carbide banding in hypereutectoid toolsteels and martensite banding in heat-treated alloy steels.

Microstructural banding influences the uniformity of mechanical properties ofthe material, and ASTM E 1268 describes a number of procedures for testing of bandedmicrostructures.

17.5.1 ASTM Practice for Assessing the Degree of Banding or Orientationof Microstructures „E 1268…This practice describes a procedure to qualitatively describe the nature of banded mi-crostructures and stereological procedures for quantitative measurement of the degreeof microstructural banding or orientation. The practice also includes a procedure us-ing microindentation hardness testing. Only the stereological procedure will be dis-cussed here.

The stereological measurements are made on an etched specimen by superimpos-ing a test grid �consisting of closely spaced parallel lines of known length� on the pro-jected image of the microstructure or on a photomicrograph. Measurements are madewith the test lines parallel and perpendicular to the deformation direction.

The stereological measurements may be made using a semiautomatic tracing typeimage analyzer. The test grid is placed over the image projected onto the digitizing tab-let and a cursor is used for counting. For certain microstructures where the contrastbetween the banded or oriented constituents is adequate, an automatic image analyzermay be used for counting �see Section 18.5.4�.

17.6 Porosity in Thermal Spray Coatings

Thermal spray coatings are susceptible to the formation of porosity due to a lack offusion between sprayed particles or the expansion of gases generated during the sprayprocess. The determination of area percent porosity is important to monitor the effectof variable spray parameters and the suitability of a coating for its intended purpose.Depending on application, some or none of this porosity may be tolerable. In TestMethods for Determining Area Percentage Porosity in Thermal Sprayed Coatings �E2109�, two methods are indicated for the determination of the porosity �see below�.

17.6.1 ASTM Test Methods for Determining Area Percentage Porosity inThermal Sprayed Coatings „E 2109…These test methods cover the determination of the area percentage porosity of thermalsprayed coatings. Method A is a manual, direct comparison method using seven stan-dard images shown on figures in the standard. These figures depict typical distribu-tions of porosity in thermal spray coatings. Method B is an automated technique re-quiring the use of a computerized image analyzer �see Section 18.5.1�. The methodsquantify area percentage porosity only on the basis of light reflectivity from a metallo-


graphically polished cross section. In ASTM Guide E 1920 �see Section 12.4.3�, a num-ber of preparation procedures are recommended �see also Material/Preparation Tables12–15�.

17.7 Decarburization—Case Depth—Coatings

The measurement of thickness �depth� of surface phenomena like decarburization,carburizing, nitriding, and coatings �surface layers� is a common metallographic/materialographic procedure. Normally a specimen is prepared and examined in an op-tical microscope using an ocular micrometre reticle or other measuring instrument�see below�. The automatic image systems are also able to measure these surface phe-nomena �see Section 18.5.5�.

17.7.1 Specimen PreparationFor all measurements on layers, etc., mentioned above, the quality of the preparedspecimen is of utmost importance. The plane of the cross section must be perpendicu-lar to the plane of the surface phenomenon to secure measurement of the true thick-ness. The preparation must be performed so that the specimen surface is flat withoutedge rounding and the surface shall be without artifacts such as smearing of a softercoating. For correct preparation see Table 11.1 and Section 13.5/6.

17.7.2 ASTM Test Methods for Estimating the Depth of Decarburization ofSteel Specimens „E 1077…These test methods cover procedures for estimating the depth of decarburization ofsteels irrespective of the composition, matrix microstructure, or section shape. The fol-lowing basic procedures may be used: Screening methods, microscopical methods, mi-croindentation hardness methods, and chemical analysis methods. Only the micro-scopical methods will be discussed here.

Microscopical methods are most suitable for measuring the depth of decarburiza-tion of as-hot rolled, as-forged, annealed, or normalized specimens. These methodscan also be applied to heat-treated specimens, although with less certainty in deter-mining the maximum affected depth. Spheroidized-annealed or cold-worked speci-mens can also be evaluated, but detection of structural variations due to decarburiza-tion is more difficult than with hot-worked or fully annealed structures. Measurementis done on an etched specimen and based on evaluation of the variation in the micro-structure at the surface due to change in carbon content.

Measurements are made on a microscope using an ocular reticle, a screw �Filar�micrometre ocular, or with a scale placed against a ground glass projection screen.

For use of automatic image analysis see Section 18.5.5.

17.7.3 Case DepthThe measurement of the often very thin zone developed by carburizing, nitriding, etc.,is done in much the same way as decarburization and coatings �see below�. The speci-men preparation can be difficult because the often very hard zone will create problemswith the planeness of the specimen �see above�. For very low depths, taper sectioningmay be used �see Section 3.11.1�.

For the use of automatic image analysis see Section 18.5.5.


17.7.4 ASTM Test Method for Measurement of Metal and Oxide CoatingThickness by Microscopical Examination of a Cross Section „B 487…This test method covers measurement of the local thickness of metal and oxide coat-ings by the microscopical examination of cross sections using an optical microscope.Under good conditions, when using an optical microscope, the method is capable ofgiving an absolute measuring accuracy of 0.8 �m.

A carefully prepared specimen �cross section� is used �see above�. A special prob-lem when preparing specimens with soft coatings is embedded abrasives �see Section13.5/6�.

The measuring device may be a screw �Filar� micrometre ocular or a micrometreeyepiece. An image splitting eyepiece is advantageous for thin coatings on rough sub-strate layers. The measuring device shall be calibrated at least once before and onceafter the measurement using a stage micrometre. The magnification should be chosenso that the field of view is between 1.5 and 3� the coating thickness.


17.7.5 ASTM Test Methods for Thickness of Diffusion Coating „C 664…These test methods cover two procedures for measuring the thickness of diffusioncoatings.

Method A is the determination of the difference in the thickness of the part beforeand after coating.

Method B is the determination of total coating thickness, defined as the distancebetween the observably unaffected substrate and the exterior surface of the coating.The total coating thickness is determined by cross-sectioning the coating, preparing ametallographic/materialographic specimen, and microscopically measuring the coat-ing thickness.


17.8 Other ASTM Standards for Quantitative Materialography

Below follows the designations of a number of ASTM standards relating to quantitativemetallography/materialography. For further information see the Document Summa-ries in Section 12.4 �the CD-ROM included with this manual�.

For other standards �ISO, DIN, BSI, etc.� see Appendix I.ASTM Practice for Petrographic Examination of Hardened Concrete �C 856�ASTM Test Method for Quantitative Analysis of Textiles �D 629�ASTM Test Method for Fiber Analysis of Paper and Paperboard �D 1030�ASTM Test Method for Microscopical Determination of the Reflectance of Vitrin-

ite in a Polished Specimen of Coal �D 2798�ASTM Practice for Calculating Sample Size to Estimate, with a Specified Tolerable

Error, the Average for Characteristic of a Lot or Process �E 122�


18Automatic Image Analysis

18.1 Introduction

THE NEED TO CONSIDER DIGITAL IMAGING SYSTEMS IS PREDICATED ONrecognition of stereological principles and quantitative metallography/materialo-graphy as essential concepts in materials science. The application of quantitativemetallography/materialography in materials science requires the measurement of mi-crostructures. It may be argued that the study of materials cannot be termed a “sci-ence” if it does not use quantitative methods.

Equipment using digital imaging technology is not essential to the implementa-tion of quantitative metallographic/materialographic methods. Quantitative metallo-graphy/materialography can be practiced using nondigital methods �see Chapter 17�.

Digital imaging technology is applied to materials science to expeditiously pro-duce the structural measurements required by quantitative metallographic/materialo-graphic standards. Performing image analysis is not a goal; rather it is a means ofachieving a goal. To hear a laboratory technician or manager discuss the need to “doimage analysis” is disturbing. What actually needs to be performed in a materials sci-ence laboratory is the measurement of microstructures, i.e., quantitative metallo-graphy/materialography. The required products of quantitative metallography/materialography are the measured dimensions of microstructural features, numericalvalues that describe the physical extent of the structures. The goals of quantitativemetallography/materialography can be more easily achieved through the use of digitalimage measurement technologies to simplify and maximize control of the measure-ment process. In the most basic sense an image analysis system is nothing more than agage; principally no different than a micrometre, scale, or other device used to extractphysical dimensions from any object. An image analysis system is nothing more than atool designed to deliver digital images, extract the structural measurement data re-quired by quantitative metallography/materialography and, as a bonus, process andmanage the data. Primarily, such a system offers the possibility of making accurate andreproducible measurements of microstructural features. The availability of relativelyinexpensive digital imaging equipment greatly facilitates the extraction of data frommicrostructural images as well as producing data that are immediately ready to bestored and analyzed using a wide variety of common information management tools.

18.2 Qualitative and Quantitative Metallography/Materialography

18.2.1 The Transition to Quantitative StandardsThe barriers to implementing quantitative methods are primarily the continued exis-tence of qualitative standards; lack of cost effective and efficient instrumentation; andperhaps most significantly, the existence of procedural obstacles. Bringing rigorousquantitative methods to metallography/materialography necessitates the existence ofspecifications and standards requiring these methods, the equipment and operational

577

procedures to produce the results specified in the standards, and, finally, the organiza-tional desire to institute these methods.

Nearly all of the more recent standard test methods produced by ASTM Interna-tional, as well as other standards organizations and private industry, are quantitative innature and require the actual measurement of structural features rather than the tradi-tional chart comparison or other subjective methods. New standards generally tend toeliminate the use of chart comparison and rating or indexing schemes. Instead theyreport the actual measured values for length, width, area, etc., as well as appropriatestatistical values. In many cases, the quantitative standard actually simplifies the testmethod.

The equipment necessary to perform the operations required by quantitativemethods is readily available. In addition to a microscope, the components needed toassemble an image analysis system generally include: computer with monitor, camera,and printer. Early implementations of image analysis systems required specialized andrelatively expensive hardware components. Fortunately, the exponential rise in con-sumer use of computers and digital cameras has benefited the use of image analysis inmaterials science. Many of the technologies used in consumer imaging products aredirectly transferable to microstructural image analysis systems. For example, theavailability of mass-produced personal computer components and image sensor chipshave resulted in dramatically lower system hardware costs.

A certain symbiosis exists between the advancement of digital imaging componenttechnology and the propagation of quantitative standards. Technological develop-ments and component cost reductions have facilitated the adoption of more quantita-tive standards by virtue of easing the efforts and costs of implementing the standards.Conversely, the increased number of quantitative standards has expanded industry de-mand for more efficient and cost-effective systems to perform the measurements incor-porated in these standards.

Perhaps the most significant remaining barrier to the use of quantitative methodsis organizational �procedural� in nature. While the imprecision and the shortcomingsof nonquantitative methods are widely recognized, there remains in many metallo-graphic/materialographic laboratories a strong inertia slowing the adoption of newstandards. The advancement of quantitative materials science often suffers from a bur-densome process of new standards approval. In many organizations the effort requiredto secure organizational approval of new standards is difficult, tedious, and presents aformidable barrier to what is technically and logically obvious. None the less, quantita-tive methods and standards are gradually replacing qualitative procedures, driven bythe issuance by industry leaders, both public and private, of quantitative standards andthe constantly improving price/performance ratio of the equipment necessary to con-veniently implement the standards.

18.2.2 Structure, Stereology, and StatisticsWhat structural parameters should be quantified? Physical metallurgy and the study ofmicrostructure property relationships provide the answers. An obvious problem is thatthe preparation of materials for microscopic observation and quantification yields aplanar, two-dimensional surface on which three-dimensional phase and structural fea-tures are displayed in some cross-sectional views. The solution lies in the body of ste-reological principles that provide a scientific basis extrapolating planar measurementdata to yield valid volumetric material structure information.1 The physical extent ofmicrostructures as shown by metallographic preparation including feature number,


length, width, and area, are the primary structural dimensions of importance. Nearlyall standards for the measurement of materials microstructures call for the determina-tion of some or all of these parameters. Several other measurements are sometimesrequired including perimeter as well as calculated data such as percent area, density,distance from a surface, aspect ratio, and shape factor. For most quantitative standardsthe data extraction requirements are very basic. Commonly, in the implementation ofquantitative standards using image analysis software, far more effort is required in theprocessing of the measurement data to provide reporting in the format required by thestandard. This situation is particularly encountered when translating the older qualita-tive standards �for example, ASTM Standard Test Method for Determining the Inclu-sion Content of Steel �E 45�� that rely on rating or other manipulations to produce re-sults expressed as an index or relative value rather than as stereological data.

An extremely important aspect of quantitative standards is the role of statisticalconcepts. Not only is the validity of stereological principles predicated on meeting cer-tain statistical conditions, but the results to be calculated also consist almost entirely ofstatistical parameters, such as mean standard deviation and confidence interval. It isvital that the laboratory personnel who are engaged in the performance and use ofquantitative methods have a basic understanding of statistical concepts in order to ob-tain accurate results.

This chapter will cover the basic elements of image analysis systems and theirpractical application to several of the most common quantitative standards. The sec-tions below present an overview of image analysis functions that are frequently foundto be useful in quantitative metallography/materialography. This overview is not de-signed to be a detailed examination of the vast array of image processing functions. Fora thorough discussion of many of these processing functions see the work of John C.Russ.3

18.3 Principles of Digital Imaging

18.3.1 What is Digital Image Analysis?Because the terminology used in describing digital imaging equipment and systems isconfusing, often ambiguous, and because of rapid changes in technology, prone toshort-term obsolescence the discussion that follows minimizes reference to specificcomponents.

How is digital image analysis applied to materials science? Image analysis is a setof software functions that can be used to extract quantitative data from microstruc-tural images. Digital imaging technology integrated into a “system” is used as a tool toprovide the measurement of microstructures as required by quantitative methods.Employing the power of digital imaging technology, the extraction of data is accom-plished in a more timely and efficient manner.

18.3.2 Image AcquisitionGenerally an image of materials microstructure consists of a rectangular or squarearea showing physical structure �voids or grain boundaries� or material phases embed-ded in a matrix. In most cases the objective of quantitative analysis is to measure thephysical extent of the structure or phase, most commonly length, width, or area. Indoing so it is necessary to remove the matrix portion of the image from consideration.For this reason all of image processing is essentially a data reduction problem. Even for

Chapter 18 Automatic Image Analysis 579

a standard NTSC format camera the number of pixels in an image is 307 200. Everystep in the image acquisition and processing is performed with the objective of remov-ing pixels representing matrix material information from consideration. Ironicallythe large format digital cameras capable of delivering images having more than1 000 000 pixels �one mega pixel� provide an even greater amount of data that must beeliminated to produce the quantitative information required. The argument can bemade that more pixels are not always a benefit in the extraction of measurements frommaterials microstructure. Very little work has been done on identifying the level onimaging digitization that is optimal for the data extraction job at hand. The assump-tion that more pixels are better is not a universal truth, i.e., it should not be applied toall analysis situations. Rather, the minimum number of pixels needed to quantify thestructure, based on the requirements of the standard should be taken into accountwhen selecting a camera. The more image data captured beyond that required to pro-vide the measurement tolerances required by the standard, the more elaborate and,therefore, more exposed to error the image processing �data reduction� will be.

18.3.3 Image Digitization—Gray ScaleDigitization is the process of converting a continuous scene �microscopic field of view�into a block of numerical values �a number of horizontal rows and a number of verticalcolumns�. Individual units in the rows and columns are picture elements �pixels�. Pix-els are the basic unit of digital images. Pixels have a location within the image. X is thehorizontal position and Y is the vertical position. Each pixel also has a brightness, illu-mination intensity, or color value. These numerical values associated with each pixelconstitute a digital image. After a structural field of view has been digitized, all imageprocessing and measurement is based on the quantitative values of each pixel. A dis-cussion of the details of image digitization can easily fill a volume, but an in-depthknowledge of the technology is not necessary. See the excellent work of Inoue andSpring for a detailed discussion of image digitization.4

The X, Y positional information associated with a pixel is straightforward. Thepixels into which the image is divided form an array or grid. The relative position ofeach pixel within the overall grid �image� can be expressed as a coordinate location.Once a calibration has been established the position of each pixel can be expressed as areal distance from the coordinate system origin or from any other point �pixel� in thearray. The least common denominator for an image pixel array as produced from anNTSC standard video camera has dimensions of 640 pixels in each horizontal row and480 pixels in each vertical column. A so-called mega pixel image has upwards of 1000horizontal by 1000 vertical pixels.

The third value possessed by every pixel is a measure of its illumination level. Thisvalue is a quantification of the relative amount of light found at that location of theimage. The range of values possibly varies and is dependent on technical specificationsof the camera and digitizing components used to perform digitizing. In digitizing thetotal range of illumination from no light �pure black� to the maximum amount of light�pure white� is divided into an equal number of levels. Commonly, an image from amonochrome camera is digitized into 256 distinct levels, beginning with 0 for no lightup to a maximum of 255 for the maximum amount of light. In this scheme every level ofillumination has a value from 0–255. This range of digital illumination values is calledthe gray scale. A gray scale having a range of from 0–255 is an 8-bit gray scale, since adigital computer represents numbers as “bits” and to count to 255 requires 8 bits. Im-age illumination may be digitized into ranges other than 0–255. The wider the range of


digital illumination levels, the more bits are required to count them. The number ofbits used in digitizing illumination is called the bit depth. To digitize a true color imagerequires at least 24 bits and produces a total of 16.7 million possible illumination �orcolor� levels.

18.3.4 The HistogramDigitization of the illumination levels within a microstructural field of view is in fact ameasurement of the illumination. Taken together, the pixel illumination measure-ments show a pattern of variation representing the various phases and structureswithin the image. By counting the number of pixels at each illumination value in a digi-tized image, an illumination frequency distribution can be produced. The frequency orquantitative distribution is a basic statistical method for summarizing data. Once amicrostructural field of view has been digitized its distribution of illumination valuescan be viewed graphically by constructing a histogram.5 The typical image illumina-tion histogram uses the gray scale range as the horizontal, X axis, and the count of pix-els falling into each of the gray scale levels as the vertical, Y axis. In fact, the frequencydistribution of illumination presents the raw image data upon which all image process-ing is based and from which all materials structure measurements are extracted. If thestructural features to be measured are not represented in the initial raw data of theillumination quantitative distribution, then measurement of those features will not bepossible. The shape and position of the illumination histogram provides important in-formation about the brightness, contrast, and measurability of the image.

18.3.5 The Effects of Brightness and Contrast on Illumination DistributionThe effects of different illumination �brightness� levels on quantitative distribution canbe seen as measurability by considering the example of an image of a thermallysprayed coating structure digitized to a depth of 8 bits, having a possible range of mea-sured illumination values of 0–255 �displayed in Fig. 18.1�a��.

A histogram of the pixel brightness distribution of this field of view is shown at theright in Fig. 18.1�b�. Digitized pixel brightness values are shown on the horizontal Xaxis beginning with a value of 0 at the left end of the axis. The vertical Y axis shows thenumber of pixels at each gray scale value. An inspection of the distribution reveals sev-eral things. First, notice that this distribution is approximately normal; it has the shapeof the classic “bell” curve of a normal distribution. There is also a small but prominent

Fig. 18.1a—Base line image.


“spike” or relatively high number of pixels at the 0 or black gray scale level. Addition-ally, the majority of the brightness measurements are clustered somewhat to the right,or bright end of the distribution, at around the 180 level. To show the effects of a changein illumination levels on the resultant distribution, the brightness level was decreasedby 15 % for the same field of view. The image and its associated histogram are shown inFig. 18.2.

Notice that the distribution is basically the same shape but it has shifted to the leftor darker end of the scale and that the most frequent illumination value is now approxi-mately 140. Also, the number of pixels at the 0 illumination level has increased nearlythree times.

Next the image brightness level was increased by 15 %. The average brightnesslevel of the resultant image is approximately 213 and the brightest areas within the im-age have been set to 255, the highest possible level �saturation�. Note in Fig. 18.3 thatthe distribution is shifted so far to right end of scale that a portion of the distributionhas been clipped. This means that at the higher illumination levels some data repre-senting the brightest structural features have been lost. In most cases the loss of rawimage illumination data due to excessive or insufficient image brightness should beavoided.

Fig. 18.1b—Base image illumination.

Fig. 18.2a—Brightness decreased.


Now let us examine the effects on the image illumination distribution of changesto the field of view contrast. Contrast is a measure of the range of illumination values

Fig. 18.2b—Histogram shifted left.

Fig. 18.3a—Brightness increased.

Fig. 18.3b—Histogram shifted right.


between the darkest and lightest areas within the field of view. Again, referring to thedistribution shown in Fig. 18.1�a�, the range of brightness values extends across theentire 0–255 gray scale range. The result of decreasing the contrast by 10 % is displayedin Fig. 18.4�a�.

Notice in Fig. 18.4�b� that the range of illumination values has been reduced andthe distribution no longer fills the gray scale with the lowest value somewhat above 0and the highest values somewhat below the 255 maximum. A decrease in contrast hasthe effect of compressing the illumination distribution. Increasing the contrast by 10 %produces the image and distribution displayed in Fig. 18.5.

In this case, the distribution range has been expanded or stretched. Note the gapsin the bars plotted in Fig. 18.5�a�, indicating that after increasing contrast some illumi-nation levels are not present in the image. See more on “stretching” in the Image Pro-cessing section of this chapter. Based on these examples, several generalizations can bemade about the optimal illumination conditions for extracting measurement datafrom digital images. First, the illumination �brightness� level selected for the imageshould provide the broadest possible range of values in the distribution histogramwhile avoiding clipping at either end of the gray scale. Also the contrast level should beselected to maximize the range of illumination values present in the gray scale distribu-

Fig. 18.4a—Contrast decreased.

Fig. 18.4b—Distribution decreased.


tion. The reason for seeking these conditions is simply to create an image that providesthe maximum amount of raw data to be used to define and measure the material micro-structure.

Controlling illumination is essential. And while image processing software in-cludes many powerful methods for altering digital image brightness and contrast,these mathematical techniques must be considered as secondary tools. The primaryand most powerful control for controlling microstructure illumination is the micro-scope or metallograph used to obtain the images. No software alteration of image illu-mination characteristics should be undertaken prior to a thoughtful use of microscopeillumination controls including illumination level, aperture, filtering, etc., to producean image possessing the illumination conditions optimal for the intended use of theimage. During the process of setting illumination conditions with the microscope theoperator may quickly digitize candidate images and use the imaging software to dis-play a distribution histogram. A series of microscope illumination adjustments shouldbe made and checked by viewing the histogram until the illumination distribution isoptimized. Only after such a process should additional software illumination adjust-ment be undertaken if necessary.

The state of the image illumination distribution along with the intended uses of

Fig. 18.5a—Contrast increased.

Fig. 18.5b—Distribution stretched.


the digitized image determines what, if any, image processing can or should beperformed.

18.3.6 Image Processing and True MicrostructureThe phrase image processing describes a wide range of operations, implemented bysoftware programs and designed to transform a digital image into another image byperforming one or more mathematical calculations upon the image pixel data. There isonly one goal in applying any image processing function and that is to produce an im-age that more clearly represents the microstructure of interest. To achieve this singleresult, image processing functions are commonly used in microstructural images forthe removal of artifacts that obscure the image structures of interest and to enhance orexaggerate image structures so as to maximize the possibility of uniquely delineating�and therefore more accurately measuring� the structures.

The goals of image processing should be identical to those of materialography, thatis, to produce a visible microstructure with no artifacts that is the truest possible depic-tion of the material structure for the intended purpose. The application of modern con-trolled metallographic/materialographic processes results in observable microstruc-tures that optimally reveal the material structural or phase constituents, or both.Consequently, materialography or metallography is actually the most powerful imageprocessing tool available, in that the mechanical or chemical processes employed aredesigned to physically produce “true microstructure,” whereas software-based imageprocessing relies on mathematical calculations performed upon an image to produce anew image displaying a structure which in fact does not exist physically.

All applications of image processing will alter the image illumination distribution.Therefore, any image that exists as the result of image processing is not “true micro-structure.” Such an image is not necessarily bad. But recognizing this simple truthleads to the inescapable conclusion that in all cases electronic image processing shouldbe strictly limited to only those operations without which the original image wouldremain unmeasureable or for purposes of human visualization to enhance the struc-ture visibility. In regard to quantitative materials science, image processing operationsshould be applied only in so far as they render the image more measurable or moreviewable. So the application of image processing processes is determined by the stateof the real world image and the use to which the digital image is to be put. In furtheringthe purpose of materialography or metallography, that is to reveal microstructure forsubsequent measurement or examination, digital image manipulation is nothing morethan another process for materials specimen preparation. Digital �image� preparationshould be used as a secondary class of techniques to be applied only if the primary class�physical metallographic/materialographic methods� has failed to provide the requiredstructural visibility.

There are a very large number of image processing functions available in most im-age analysis software products. Of the many possible image processing operations arelatively few provide useful results in preparation of materials microstructure images.Presented here is a short list of several image processing functions that are frequentlyapplied to improving microstructural images. For an extensive discussion of manymore image processing techniques see Russ.3

Background CorrectionA common artifact resulting from poor microscope illumination alignment is observ-able as bright or dark areas within the image. Background correction is an image pro-


cessing program that is used to reduce uneven image illumination due to misalignmentof microscope lighting. Microscope illumination alignment must always be centered.All possible physical positioning and optical path alignment adjustments must bemade to the microscope or metallograph prior to performing software-based back-ground correction. A common method of software background correction performs asubtraction of a poorly illuminated image with a second copy of the same image show-ing only the background. The background-only image can be produced by digitizing animage of a uniform white surface or by defocusing the optics to obliterate all imagefeatures. A background correction operation yields a resultant image that has been cor-rected. The images in Fig. 18.6 illustrate this process.

Figure 18.6�c� clearly shows that the dark edge seen in Fig. 18.6�a� has been re-moved by the background correction. Also note that several dust particles presentwithin the lenses of the microscope or camera used to capture the image are visible inboth Fig. 18.6�a� and 18.6�b� and have been removed by the correction software. A sideeffect or artifact of the background correction process is that the right edge of the im-age is now slightly brighter than the balance of the image. It is a near universal truththat the application of image processing functions seldom provides results that arewholly without artifacts. The existence of some degree of nonuniform image illumina-

Fig. 18.6a—Unevenly illuminated image.

Fig. 18.6b—Background only copy of Fig. ???


tion may be acceptable provided it does not interfere with the measurement of thestructures of interest.

Contrast StretchingOnce digitized the image brightness and contrast may be altered using image process-ing software. Again, it is important to use the illumination controls found on the imag-ing system microscope being able to optimize image brightness and contrast beforeresorting to software processing functions. Adjustments to brightness and contrastshould always be performed to increase the amount of illumination data available. SeeSection 18.3 for examples of brightness and contrast changes to the amount and rangeof data in the digitized image.

Stretching techniques increase image contrast by expanding the brightness valuesfound in the original image into a wider range of values. Stretching is generally appliedto images that display a narrow range of illumination levels in their initial digitizedstate. One approach to stretching determines the minimum and maximum illumina-tion levels within the image and mathematically extrapolates these values to cover themaximum possible range, 256 values in an 8-bit gray scale image, as seen in Fig. 18.7.

Notice that there are no 0 or 255 brightness level pixels within the image �extremeleft and right ends of the distribution in Fig. 18.7�a��. Figure 18.7�b� displays the sameimage after applying a contrast-stretching program to radically expand the illumina-tion range �contrast�. In addition to increasing contrast across the entire image illumi-nation range, it is possible to increase the contrast within a specific part of the illumina-tion range. Stretching of this type may be helpful if several material phases have nearlycontiguous or slightly overlapping illumination ranges. This enhancement is per-formed by dividing the histogram into three sections: brightness values that have avalue below a dark-end threshold �some value greater than the minimum illuminationvalues in the image�; brightness values above a bright-end threshold �some illumina-tion level less than the maximum�; and brightness values lying between the dark andbright thresholds. brightness values that lie below the dark threshold are assigned anew value of 0. Similarly, values that lie above the bright threshold are assigned a valueof 255. The remaining values between the dark and bright threshold are assigned newbrightness levels between 0 and 255, according to a linear mathematical extrapolationand are thereby stretched slightly to provide a calculated set of structural brightnesslevels. The histograms in Fig. 18.8 display the effects of this type of stretching.

Fig. 18.6c—Resultant image after applying background correction.


This form of histogram stretching eliminates low and high pixel brightness valuesthat do not represent the structures of interest by setting them to 0 or 255. Notice thehigh pixel counts at the extreme ends of the distribution.

Fig. 18.7a—Narrow illumination range.

Fig. 18.7b—Entire range stretched.

Fig. 18.8a—Original image.


Watershed FilterThe watershed filter is a mathematical function that transforms an image containingindividual particles that are touching or fused together into a new image wherein thetouching or fused objects have been separated. This is a very useful tool because severalquantitative metallography/materialography standards require the measurement ofindividual objects. In material microstructure analysis the watershed filter can be ap-plied to grain size measurement as well as to other structures where it is desirable tomeasure individual particles within the unprocessed image that are touching. ASTMStandard Test Methods for Determining Average Grain Size Using Semiautomatic andAutomatic Image Analysis �E 1382� for grain size measurement by image analysis de-scribe procedures incorporating individual grain area measurement. To achieve maxi-mum accuracy each grain must be separated.

Figure 18.9�a� shows a steel grain boundary structure. Notice that the dark lineargrain boundaries are broken and do not completely delineate the individual grains.Frequently the condition of uneven and incomplete grain boundary definition is pro-

Fig. 18.8b—Middle values expanded.

Fig. 18.9a—Gray scale image showing incomplete grain boundaries.


duced when revealing grain boundaries by chemical etching. The watershed filter canbe applied to such images and ideally will produce an image such as seen in Fig.18.9�b�, which shows all the grain boundaries completed. Such an image can be easilymeasured using automated methods �see Section 18.5.3 for additional discussion ofgrain size measurement�.

Another example will illustrate risks of applying image processing functions aswell as demonstrate another function that occasionally is useful in materials measure-ment. In Fig. 18.10�a� below, a materials image showing darker second phase particleswithin a light gray matrix has been digitized. To accurately count or measure the indi-vidual particles a watershed separation processes has been performed. The resultantbinary image with particles assigned to white and the matrix to black is shown in Fig.18.10�b�.

The separation function has been fairly successful, having split many of the previ-ously touching particles by constructing a black line between them. Note that the con-

Fig. 18.9b—Binary version of Fig. ??? after watershed separation operation to fill in missingboundaries.

Fig. 18.10a—Touching particles.


structed separations tend to give angular and geometric rather than smoothly curvingedges to the particles. This type of mathematical artifact is typical of many image pro-cessing operations and while the results are less than perfect, the slight distortion inparticle boundaries is more than offset by the overall improvement in particle measur-ability. However, the separation has produced two relatively serious errors. In one in-stance, near the upper center part of the image, a small triangular “particle” has beencreated in the separation process that clearly does not exist in reality. Also, near thelower right corner of the image a small particle has been incorrectly cracked in half.Close examination of the Fig. 18.10�a� image reveals that small bright dots are foundwithin the particles at the site of the incorrect separations. In fact, just as in materialswhere small voids or impurities can produce structural weaknesses that act as originsites for failures, these bright spots within the image have served as nuclei for the fail-ure of the separation process. Caution should be used in the application of the separa-tion function since the manufactured boundaries may result in the separated particleshaving slightly altered dimensions. As discussed below, applying additional image pro-cessing operations prior to running the separation program can minimize the occur-rence of these errors.

Smoothing

There are a large number of processing operations designed to alter individual pixelbrightness values based upon the values of surrounding pixels. Such spatial filteringoperations exist for increasing or decreasing illumination changes within pixel neigh-borhoods. When separating touching particles, a prior filtering operation that reducesor smoothes illumination variability can eliminate bright spots that may lead to errors.Applying such a filter results in the image shown in Fig. 18.10�c�. Compare Fig. 18.10�c�with Fig. 18.10�a�, nothing that the smoothing filter has remove the bright spots. Apply-ing the watershed separation operation to the image in Fig. 18.10�c� yields the imageshown in Fig. 18.10�d�.

Figure 18.10�d� displays a very good separation of the particles with no grossly in-accurate particle shapes. This example has demonstrated the ability of image process-ing programs to both reduce as well as increase artifacts present within an image as

Fig. 18.10b—After separation.


well as the potential benefits of performing a series of image processing operations toachieve an optimal result. Developing a multi-stage image processing procedure ismuch like developing a metallographic/materialographic specimen preparation proce-dure. It is extremely important to note, however, that since the outcome of any givenimage processing operation is directly dependent upon the level of illumination in theoriginal image, any change to the illumination level may result in an entirely differentresult.

SharpeningSharpening is an image processing operation that is designed to accentuate the edgesof objects within the image. It can be thought of as a way to bring an object into sharperfocus. The figures below illustrate the visual as well as quantitative effects of sharpen-ing. Figure 18.11�a� shows a portion of a micron scale. Figure 18.11�b� is a plot of thepixel brightness levels measured along the horizontal section line drawn in Fig.18.11�a�. Note that the brighter scale lines result in spikes on the illumination valueplot.

Fig. 18.10c—Smoothed image.

Fig. 18.10d—More accurate separation.


A typical sharpening function has been applied to the same image and the resultsare displayed in Figs. 18.11 and 18.11�c� and 18.11�d�.

Visually the scale lines in Fig. 18.11�c� are more prominent and show more con-trast between the lines and the gray matrix areas. The plot in Fig. 18.11�d� shows a dis-tinct dip at the base of the spikes indicating a greater illumination difference in thepixels at the boundary where the scale lines and the matrix meet. These visual andquantitative changes are characteristic of the image sharpening process. By blowingup a section of the image the effects of sharpening can be seen in detail.

Note the exaggerated black to white illumination transition along the edges of thesharpened image scale line in Fig. 18.11�f�. Also notice the visible pixel brightness arti-facts created in the matrix area immediately above the scale line in the sharpened im-age. Exaggerating minor image brightness variations may cause difficulties dependingon the ultimate goals of the analysis. Sharpening filters can be valuable in enhancingimages for human viewing and can be helpful in reducing the so-called halo effectwhen performing automatic detection of objects for measurement �see ASTM Stan-dard Practice for Obtaining JK Inclusion Ratings Using Automatic Image Analysis �E1122��.

Fig. 18.11a—Scale with section line.

Fig. 18.11b—Plot of illumination along section line.


Many other image processing functions including filters and morphological op-erations exist and are commonly found in commercially available image processingsoftware. For a thorough discussion of many of these processing functions see thework of John C. Russ.2

18.3.7 Image CalibrationTo measure the physical extent of structural features within a digital image, it is neces-sary to create a spatial calibration. The process of calibration is the method by whichactual measurements may be extracted from any object displayed within an image. Acalibration is a numerical ratio that defines the relationship between a pixel and a realworld measurement unit such as a millimetre. Recall that a pixel is the unit buildingblock from which the entire digital image is formed. Spatial calibration provides aheight and width dimension for the image pixel. Within any digital image, all pixels areidentical in horizontal and vertical dimension. By assigning horizontal and verticalpixel dimensions, structural features can be measured by counting the number of pix-els within the feature and multiplying by the appropriate spatial calibration factors.Pixel calibration factors are generally created for each of the magnification options

Fig. 18.11c—Sharpened image.

Fig. 18.11d—Exaggerated illumination at edges.


available through the microscope or other device that is used to acquire images foranalysis. A calibration must be associated with an image prior to performing any mea-surements within the image. A notable exception to this requirement is the case of per-cent area or other relative measurements wherein the desired data are expressed as aratio and can be calculated by pixel counting.

The general process of creating a calibration involves the digitization of an imageof a scale or other object for which a dimensional distance is known. In microscopy thisis usually a slide micrometre having an etched scale in inches, millimetres, or microns,or a geometric shape such as a circle or square with a known dimension. Figures18.12�a�, 18.12�b�, 18.12�c�, and 18.12�d� illustrate the calibration process. First a slidemicrometre is placed on the microscope stage, aligned, and the image is digitized.

After the scale image is digitized the operator initiates a series of steps that include

Fig. 18.11e—Unsharpened blowup.

Fig. 18.11f—Sharpened blowup.


drawing a calibration line on the image across some distinct distance on the scale asseen in Fig. 18.12�b�.

Next the software prompts the operator to enter the length of the calibration line inreal world units, such as millimetres, as shown in Fig. 18.12�c�.

The image analysis system software uses this information to calculate the calibra-tion factor. Figure 18.12�d� shows a typical software control where the resultant cali-bration factor is displayed as a ratio of pixels per unit measurement.

Note that in the example a calibration factor is shown for both the X �horizontal�and Y �vertical� pixel dimensions. If the image pixels are square and have an aspect�height to width� ratio of 1 then the X and Y calibration factors are the same. The pixelaspect ratio is a function of the camera and digitizing hardware. It is very important to

Fig. 18.12a—Image of portion of slide micrometre scale.

Fig. 18.12b—Scale with calibration line overlay.

Fig. 18.12c—Operator input of calibration line distance.


determine the pixel aspect ratio and if it is not 1 then the X and Y calibration factorsmust be calculated independently. Another feature on the calibration display panel ofimportance is the name of the calibration. This name could include information abouthow the calibration is configured, including optics, measurement units, etc. An addi-tional essential item of information displayed and adjustable from this control is theorigin of the XY coordinate grid of pixels into which the image is divided.

Although not specifically written for use with digital imaging systems, ASTM Stan-dard Guide for Calibrating Reticles and Light Microscope Magnifications �E 1951�,provides relevant information on the calibration process �see Section 12.4�.

18.4 Image Measurement

Once calibration has been established it becomes possible to extract data from an im-age. It is at this point that digital image analysis becomes a tool to implement quantita-tive metallography/materialography. Assuming that the metallographic/materialo-graphic specimen preparation and digitization processes have yielded an image thatdisplays the microstructure clearly, the next task to be performed is the delineation ofthe features to be measured. A typical materials image is composed of a relatively largearea of matrix or background material within which one or more structural featureshaving one or more individual occurrences are distributed. To extract measurements itis necessary to separate the pixels that represent the features of interest from the pixelsthat represent the matrix or background material. This is a data reduction operation toseparate pixel data that are associated with the microstructure of interest from allother pixel data.

It is interesting to note that from this point forward what is taking place is dataprocessing—not image processing.

There are two basic approaches to defining and separating the features within the

Fig. 18.12d—Typical operator for control for creating spatial calibration.


image to be measured. In the more basic method the equipment operator interactivelydelineates the points, lines, or areas to be measured.

18.4.1 Manual Measurements „Operator Defines Points, Lines, or Areas…Manually indicating what is to be measured by operator interaction is a simple yet use-ful method of extracting measurements from microstructural images. In general thereare three possible forms to be delineated by direct operator interaction, points, lines,and areas. Figure 18.13�a� shows an image of a grain boundary structure. Exercisingthe line feature creation tool available with nearly all image measurement software theoperator can use the computer system mouse to position the cursor on a grain bound-ary, then click the mouse button and drag the cursor to another point on the grainboundary. Another mouse click and the image measurement software immediatelycounts the number of pixels in the line, calculates the length of the line, and notes thedistance on the image.

A slightly different implementation of the same techniques allows the operator totrace an outline of a complete grain boundary and the measurement software can im-mediately calculate the grain area as shown in Fig. 18.13�b�.

While manual measurement techniques are basic and require operator input, theyshould not be overlooked as a viable means for accurately extracting measurementdata from materials structure.

Fig. 18.13a—Grain diameters measured.

Fig. 18.13b—Grain boundaries traced and grain areas measured.


18.4.2 Automatic Measurements „Objects Defined by ImageSegmentation…Of all the many advantages of digital image analysis, possibly the single most powerfulis the process of delineating and measuring structural features over multiple fields ofview without the necessity of operator interaction. The ability to measure dozens, hun-dreds, and even thousands of individual occurrences of structural features withoutconstant operator involvement is a strong incentive for the implementation of imageanalysis for quantitative metallography/materialography. Such automation of extract-ing data from materials images based upon the concept of image segmentation. Seg-mentation provides a means whereby, after initial operator setup, features can be de-lineated and thus measured without additional operator input. In segmentation theimage is divided into the structural features of interest and the matrix or image back-ground based upon the pixel illumination values. The division is based on the histo-gram showing the distribution of image pixel illumination values. The process of seg-mentation produces a range of values having a lower limit and an upper limit withinthe overall image illumination distribution. The segmentation range is set to match asclosely as possible the pixel illumination values of the structure to be measured. Thesuccess of this process is directly dependent upon the degree to which the structures tobe measured are represented by an exclusive set of pixel brightness values. Ideally thestructure to be measured is represented within the image by a distinct range of the pixelillumination values different from the pixel illumination values of the matrix. All imageanalysis software provides a control mechanism to allow the operator to interactivelyadjust the segmentation levels to detect the features of interest. Commonly, the controlwill display a histogram showing the image illumination distribution with the upperand lower segmentation range limits superimposed as a pair of vertical lines. The im-age itself may also be shown with a color overlay corresponding to the current segmen-tation range settings. In effect, the color will show exactly what part of the image isbeing detected. Figure 18.14�a� shows a portion of a typical segmentation control panelprovided with image analysis software.

In this example the histogram of an image digitized to 8 bits �0=black to 255=white� is displayed. Notice also the bar along the top of the control; the size and posi-tion of this bar relative to the distribution histogram is a visual indicator of the currentsegmentation range setting. The 0–255 setting shown is actually detecting the entireimage and is simply the starting point for segmentation adjustment. The operator, us-ing a combination of cursor positioning and mouse clicks, must move either or both ofthe segmentation limits set to achieve detection of the features of interest. Figure 18.14�b� shows the image under analysis.

The darker gray objects are to be detected for measurement. Since the objects are

Fig. 18.14a—Segmentation control showing distribution of image illumination.


relatively darker than the surrounding matrix material, the upper segmentation limitmust be adjusted to a lower level to exclude the brighter pixels representing the matrix.Using the software control the upper segmentation limit can be reduced. As the limit ismoved lower, the pixels falling within the range are indicated by the bar and with acolor overlay on the actual image. This color-coding method allows the operator toclearly see the results of segmentation at each possible level. The segmentation limitmust be lowered until the best possible delineation of the objects is achieved. Figures18.14�c� and 18.14�d� show the final segmentation setting on the distribution plot andthe image with the red overlay indicating objects detected for measurement.

It is important to note two items regarding the setting of segmentation levels. First,while automatic software-controlled segmentation can be performed by virtually allimage analysis software, the accuracy of the segmentation operation and therefore allsubsequent measurements, are primarily the responsibility of the operator and in mostcases are based upon a subjective judgment concerning the optimal limit settings. Sec-ondly, if a relatively clear distinction between object feature illumination levels andmatrix illumination levels does not exist, the process of segmentation may be difficultand in some cases it may be impossible to set with adequate accuracy to produce mean-ingful measurement results. If the structures to be measured cannot be cleanly delin-eated by segmentation further metallographic/materialographic specimen prepara-tion or additional image processing must be considered. It is possible that micro-structures of certain materials, regardless of preparation and processing, do not lendthemselves to the use of segmentation to delineate features for measurement. In such

Fig. 18.14b—Segmentation control showing the image under analysis.

Fig. 18.14c—Illumination distribution with segmentation range set.


cases extraction of measurements must be accomplished interactively.Once structural objects have been defined by segmentation, the extraction of mea-

surement data are almost trivial. All image analysis software includes a variety of mea-surements that may be extracted from defined objects. In most cases the variety of mea-surements possible greatly exceeds the requirements of common quantitative metallo-graphic/materialographic standards. Structure area, diameter, length, width, perim-eter, and many other measurement types can be made. In the next section the applica-tion of these measurement methods to several of the most commonly employed quanti-tative standards will be discussed.

18.5 Digital Imaging Applied to Quantitative Materialography

This section is composed of a series of detailed discussions of several of the most com-monly practiced quantitative materials standards. The Annual Book of ASTM Stan-dards, Volume 03.01—Standards Relating to Metals-Mechanical Testing; Elevated andLow-Temperature Tests; Metallography �see Part II, Section 12.4� contains the major-ity of standards written by this body that are applied to quantitative materials micro-structural analysis. Other standards not found in this volume but applicable to micro-structural measurements include: ASTM Standard Test Method for Evaluating theMicrostructure of Graphite in Iron Castings �A 247� and ASTM Standard Specificationfor Compacted Graphite Iron Castings �A 842�. One or two other quantitative methodsfor which specific standards do not exist are included based upon their widespread use.

18.5.1 Percent Area „Volume Fraction…One of the simplest and most widely used forms of quantitative metallography/materialography is area, or volume fraction. To perform percent area measurementsrequires image digitization but does not require calibration, since the required out-come is a ratio. The manual standard for implementing this quantitative method isASTM Standard Test Method for Determining Volume Fraction by Systematic ManualPoint Count �E 562�. This standard relies upon the use of a grid consisting of “equallyspaced points formed by the intersection of fine lines.” This, of course, is a method of

Fig. 18.14d—Image showing detected objects with red overlay.


digitizing the microstructure. Interestingly, ASTM E 562 references ASTM Practice forInclusion or Second-Phase Constituent Content of Metals by Automatic Image Analy-sis �E 1245� for the “use of automatic image analysis to determine the volume fraction.”Another standard, ASTM Test Methods for Determining Area Percentage Porosity inThermally Sprayed Coatings �E 2109�, describes the use of digital imaging to measurepercent area of a specific structural feature. Performed either manually or by com-puter, the point counting technique is the essence of percent area or volume fractionmeasurement. By definition a digitized image is composed of a number of pixels thatare, in fact, a grid of equally spaced points. All that is necessary is to count the pixels�grid points� that fall within the structure of interest and divide that value by the totalnumber of pixels in the entire field of view. In order for the software to calculate thepercentages, the operator must use the system segmentation control to detect thephase �or phases� to be measured. The detection operation is the key step in the proce-dure and all concerns relative to segmentation discussed in Section 18.3.6 apply. Inevi-tably, microstructures will be encountered in which the pixel illumination values of thestructure to be measured and the matrix have some overlap with no distinct boundary.In these cases setting the segmentation range necessarily requires a subjective judg-ment on the part of the operator. The reliability of the calculated volume fraction maybe improved by employing a technique of setting several segmentation ranges to detectthe same structure. Since most imaging systems have the capability of measuring morethan one segmented range simultaneously, it is a simple matter to set several ranges forthe same structure and take the statistical average for the reported result. This ap-proach of taking a larger sample of data is consistent with statistical thinking and theadditional measurements and calculations necessary are easily performed by analysissoftware. There are other advantages to using digital image measurement software forpercent area �volume fraction� as well as other measurements. The possibility of apply-ing a color overlay to the image to highlight the measured phases provides an excellentvisual aid to the operator and yields highly informative images for inclusion in the re-sults report.

Another advantage is the capability of the image measurement software to pro-duce data that may be exported directly to external analysis and reporting softwaresuch as database, statistical process control, and spreadsheet programs.

18.5.2 Inclusion RatingInclusions are occurrences of precipitates or other products of indigenous processesthat result in random distributions of observable particles in the matrix material. Be-cause of the significance of inclusions in influencing material properties, methods ofclassifying and determining the level of inclusions present in materials have been de-veloped and widely used, primarily in steel, as a major determining factor of quality.

A number of published standards employing manual comparison as well as quan-titative methods for determining the content of inclusions exist. ASTM Volume 03.01includes three standards, ASTM Standard Test Methods for Determining the InclusionContent of Steel �E 45�, ASTM Standard Practice for Obtaining JK Inclusion RatingUsing Automatic Image Analysis �E 1122� �withdrawn 2006, replaced by E 45� andASTM Standard Practice for Determining the Inclusion or Second Phase ConstituentContent of Metals by Automatic Image Analysis �E 1245� for determining inclusioncontent.

ASTM E 45 is the original manual comparison method. Of the several methodsfound in this standard by more widely practiced microscopic methods are Method A


and Method D. The heart of these methods involves classifying inclusions into fourtypes �A, B, C, and D� based upon inclusion morphology, separating each type into athin and heavy series based upon inclusion width and assigning each type a SeverityLevel �1/2 to 5� based upon the total length or number of inclusions in a field of view.The Method A requires the reporting of the inclusion rating for the field of view with themost severe rating for each inclusion type. The compilation of these four ratings is the“worst field.” In Method D a specimen surface area of 160 mm2 must be covered usingindividual fields of view of 0.05 mm2. This results in the requirement to cover 320 fieldsof view, each to be rated for the severity level of all types. ASTM E 45 includes a series ofdrawings showing the amount of inclusions at each severity level for each inclusiontype and requires that the operator judge the best comparison and record the observa-tions.

Obviously this manual approach is quite labor intensive and has the potential togenerate subjective results particularly in the Method D rating of 320 fields. ASTM E 45is one of the best examples of a standard that has been significantly improved by con-verting to more quantitative and automatable methods. While incorporating the meth-ods of E 45, ASTM E 1122 defines inclusion typing and rating in a sufficiently quantita-tive way so as to enable these classifications to be performed by image analysissoftware. Although eliminating the reliance on chart comparison, ASTM E 1122 pre-serves the traditional severity level-rating scheme rather than requiring a more statisti-cally robust results report. In recognition of this short-coming ASTM E 1245 has beenpublished and provides a thoroughly quantitative method with statistically relevant re-porting of results.

Following the ASTM E 45/E 1122 standard to perform the severity level rating ofinclusions using digital imaging software requires first the separation of the inclusionsfrom the matrix by the process of segmentation. The matrix of the steel microstructureafter specimen preparation has a very high illumination level nearly white. The type Asulfide inclusions are generally quite high in illumination levels and appear in a grayscale digital image as light gray. A-type inclusions may be close to the matrix in illumi-nation level and therefore the requirements for specimen preparation and lighting op-timization are critical. Background correction may be required to ensure that the Atypes can be successfully segmented without detection of bits of the matrix. Inclusiontypes B, C, and D are the oxide types and generally appear as black objects in the ma-trix. The B types are sometimes described as broken stringers and occur as a series ofthree or more particles strung out in a line; C types are single particles called stringershaving an elongated form with an aspect ratio of greater than designated in the stan-dard. The D types are globular oxides and are circular with aspect �length to width�ratios of less than designated in the standard. The B, C, and D oxide type inclusionsmust also be separated from the matrix by segmentation. Normally segmentation toseparate the B, C, and D types is not difficult due to their high contrast with the brightmatrix.

Separation of the sulfide A type inclusions from the B, C, and D oxide types is gen-erally straightforward since the A types appear as brighter objects than the darker ox-ide types. Once segmentation is established the measurement of length and width of allinclusion types and counting of the D types must be performed. These data are thenused to calculate the severity levels for each inclusion type. For many image analysissystems, the specimens must be oriented on the microscope stage such that the elon-gated inclusions are aligned horizontally or parallel to the X axis of stage movement.Several difficulties can be encountered when implementing this standard. To begin


with, inclusion ratings must be made for a specific field area �0.05 mm2�. If this areacannot be displayed in a single digitized image, it is necessary to digitize and measure asequence of images until the 0.50 mm2 area has been achieved before a rating can becalculated. The need to measure and accumulate data over multiple images requiresmore complex software and will be more time consuming. To improve efficiency anattempt should be made to choose a combination of camera lens and microscope ob-jective magnification to yield a digitized image area of 0.50 mm2. Another difficultymay be encountered because of the standard requirement that inclusions as thin as2 �m be measured. Such small objects can be difficult to distinguish from commonlyoccurring artifacts that possess illumination levels similar to the inclusion types. Anyscratches visible on the specimen surface after materialographic preparation may bedetected as an elongated A or C type inclusion, although generally imaging software isdesigned to eliminate such artifacts due to their orientation. A more common problemis the misdetection of small circular artifacts as D type inclusions. It is nearly impos-sible to separate with software filtering legitimate D types from artifacts of this classand therefore it is absolutely essential to perform inclusion measurement only onspecimens that are freshly prepared in order to minimize the occurrence of corrosion,oxidation, or staining. Another issue arises from the requirement to measure a rela-tively large specimen area, 160 mm2.

As mentioned earlier 320 images are needed to cover this area at 0.50 mm2 perimage. Obtaining such a large number of images can obviously take a significantamount of time and has naturally led to the use of motorized microscope stages thatcan be programmed to move the necessary number of fields without the need formanual operator interaction. While without question an improvement, the use of mo-torized stage movement along with motorized focusing procedures to eliminate opera-tor interaction during the inclusion measurement process can also lead to problems. Itis inevitable that an unattended, fully motorized, and automatic inclusion rating pro-cess will produce some field ratings that are incorrect. Two types of errors are com-monly encountered. Excessively high severity levels can be calculated because imageartifacts �scratches, dust, oxidation spots, stains, etc.� have been measured as inclu-sions. Also slightly out-of-focus images can be digitized to display inclusions with exag-gerated dimensions that produce results higher than actual severity levels. More rarely,the focus is so far off so as to cause complete failure to detect any inclusions present inthe image. Falsely high field measurements can be flagged and the images stored sepa-rately so at the conclusion of specimen measurement the operator may check the list ofsuspect rating data and review the associated images. Any images displaying obviousartifacts may then be removed from the rating database. Incorrectly under rated im-ages are impossible to discover, short of an operator examination of every image rated.This of course is impractical and completely defeats the desire to eliminate direct op-erator involvement in the measurement process. Several additional error sources canbe identified including misclassification of inclusion type by the software. In contrastto ASTM E 45 and ASTM E 1122 the ASTM E 1245 provides another approach to inclu-sion rating.

ASTM E 1245 is a primary example of a stereologically and statistically robustquantitative microstructural quality standard. The Procedures Section of E 1245 liststhe Measurement of Stereological Parameters including volume fraction of the inclu-sions, the number of inclusions per field, and the number of interceptions of the inclu-sions per unit length of test line. Additional individual inclusion feature measurementsmay be made. From these basic measurements, statistical parameters such as aver-


ages, standard deviations, 95 % confidence interval, and percent relative accuracy areto be calculated for each type of inclusion detected. An important aspect of this stan-dard that is significantly different from its predecessors is the elimination of separatinginclusion types into thin and heavy and calculation of severity levels.

The stereological and statistical procedures embodied in the ASTM E 1245 stan-dard make it an important addition to the traditional severity rating level methods.

18.5.3 Grain SizeGrain size is a key determiner of materials properties. Several standards, both qualita-tive and quantitative exist that describe methods for determining grain sizes �see Sec-tion 17.3�. ASTM Standard Test Methods for Determining Average Grain Size UsingSemiautomatic and Automatic Image Analysis �E 1382� is a quantitative standard writ-ten for implementation via digital image analysis that is based on many of the samemeasurement parameters described in the quantitative methods of the ASTM Stan-dard Test Methods for Determining Average Grain Size �E 112�. The several variationsin methods described in both of these standards are derived from measurement of ei-ther grain interior areas, grain boundary lengths, or the interceptions of these featureswith some pattern of test lines. The chief difficulty in applying digital image analysis tograin size determination arises from the problem of grain boundary delineation. Toshow the grain boundaries in most materials requires some form of chemical etching.Acidic etch compounds may erode the material at the structurally weaker boundarybetween grains producing a slight “groove” that has a lower illumination level whenviewed with a microscope �see Part II, Chapter 13�. Some acidic etchants, such as Nital,when applied to steel, chemically dissolve grains at different rates based on each grain’scrystal orientation. This difference in attack creates differences in elevations at theboundaries between adjacent grains resulting in what appears to be, in bright-field illu-mination, black lines at the boundaries between grains. In practice the precise and uni-form application of etchants is difficult to achieve and along with naturally occurringvariations in material etching rates, results in grain boundary visibility and appear-ance that is highly variable. Even within a single microscopic field of view it is commonto observe strongly etched boundaries immediately adjacent to areas that displayfaintly or incomplete boundary delineation. In fact, the preparation of microstructuralspecimens with 100 % grain boundary delineation is uncommon. The boundary delin-eation issue is so significant that the ASTM E 1382 standard prefaces all discussion ofdigital image measurement methods with the statement “The precision … of grain sizemeasurements using automatic image analysis is highly dependent on the quality ofthe etch delineation of the grain boundaries. The grain boundaries should be fully anduniformly delineated.” If the boundary between adjacent grains is incomplete whenusing a grain area method, the separate grain areas will be measured as one, resultingin erroneously high grain area data. Similarly, missing boundaries will produce an in-accurately low measurement when employing a grain boundary length method ofgrain size determination.

In nearly every case the application of a watershed type digital image filter must beapplied to improve grain boundary delineation before measuring grain features withdigital imaging systems. This process is commonly referred to as grain boundary re-construction; see Section 18.3.6 for a discussion of the watershed filter. It is importantto note that the watershed filter can be too aggressive in defining boundaries; the filtertypically connects truncated grain boundaries but also tends to connect any dots ap-


pearing in the grain interiors to form boundary networks. This action can result in avirtual “fracturing” of grains into small pieces.

Minimization of this effect can be achieved by careful operator adjustment of thesegmentation levels. Most implementations of this filter require that the operator setthe segmentation levels to select the grain interiors. In practice it may be advantageousto set the segmentation range to over detect the grains, i.e., include some of the lighterboundaries �and grain interior artifacts� along with the grain interiors. Observing theresults of boundary reconstruction at several different segmentation levels and select-ing the most accurate level should be a part of the standard analysis procedure. It mayalso be necessary to run one or more digital image processing functions designed toeliminate grain interior artifacts that can serve as sites for nonexistent boundary con-struction. Ultimately, it may be necessary for the operator to manually insert, via a soft-ware drawing function, missing boundary sections. This operation obviously lacks effi-ciency and should be avoided. In reality, boundaries have no dimensions, but in anygraphical representation they will have some width. Depending on the magnification,the grain size and the width of the boundaries, an area reduction introduced by theboundary delineation could be significant, thus the boundary thickness should be keptto a minimum.

After performing the appropriate image processing steps to “reveal” the completegrain boundary network in a specific image, the image processing software can pro-duce a binary, or black and white image with only the boundaries shown. An imagecomposed of only test lines in any orientation and density, linear or circular �or virtu-ally any other configuration� can be constructed by software. This test line image canbe mathematically combined with the grain boundary image using a class of imageprocessing functions commonly termed “image arithmetic.” The imaging software canproduce a resultant image showing just the points where the test lines intercept theboundaries. This is accomplished by checking pixels at exactly the same coordinatelocation in both images and if the location is occupied by a boundary and by a test lineit is counted. Alternatively other image arithmetic functions may be performed to yieldan image showing just the lengths of the test lines falling within the grain interiors. Thegrain intercept lengths displayed in these images can be measured to provide the meanlineal intercept length, a method of grain measurement described in ASTM E 1382 aswell as in ASTM Standard Test Methods for Characterizing Duplex Grain Sizes�E 1181�.

In reality, perfect grain boundary delineation is not necessary. It is perfectly ac-ceptable that over any given number of fields measured there will be some over andsome under-measured grain areas or boundary lengths. Since the statistical reportingrequirements of the quantitative standards provide methods for determining measure-ment accuracy based on statistical parameters such as confidence interval and percentrelative accuracy, if, after measuring a specimen area, appropriate statistical signifi-cance levels are not produced, then it is necessary to measure more grains in more im-ages. Typically, imaging system software accumulates the grain feature measurements,as they are collected over multiple images. Based on these raw measurements the re-quired statistical parameters are calculated. One advantage in delineating and collect-ing individual grain areas for average grain size determination is that in the samedataset the largest grain area and clusters of grains can be found. The largest grain areacan be used to satisfy the requirements of ASTM Standard Test Methods for Estimatingthe Largest Grain Observed in a Metallographic Section �ALA Grain Size� �E 930�. EvenTable 1 of ASTM E 930 listing the relationship of the ALA grain area to the grain size


number can be created easily in software such that the grain size number can be auto-matically reported, further streamlining the performance of ALA grain size analysis.Grain area cluster data can be useful in characterizing duplex grain sizes as describedin ASTM E 1181.

18.5.4 Degree of BandingThe nature and importance of quantifying banding in microstructures is discussed inSection 17.5. ASTM Standard Practice for Assessing the Degree of Banding or Orienta-tion of Microstructures �E 1268� provides quantitative as well as qualitative methodsfor assessing the degree of banding. The standard requires the measurements of vol-ume fraction and count of feature interior interceptions or feature boundary intersec-tions with superimposed test grid lines. Both of these operations have been discussed�see Sections 18.5.1 and 18.5.3�; they can be performed using digital imaging tech-niques providing the banded structures exhibit a sufficiently high degree of illumina-tion contrast to enable successful segmentation. Application flexibility is increased andsegmentation requirements relaxed if the imaging software provides the option for di-rect operator insertion or deletion of the test line-feature interceptions or intersec-tions. The only other condition to be satisfied for banding measurements is to orientthe image so that the deformation axis seen in the structure is aligned horizontally orvertically in the digitized image. While image rotation can be performed by software toavoid introduction of image processing artifacts, it is preferable to achieve the requiredstructure alignment by physically rotating the material specimen on the microscopestage.

18.5.5 Depth or Thickness MeasurementsSeveral standards exist that address the linear measurement of depth or thickness ofstructures, zones, and layers. These include ASTM Standard Test Methods for Estimat-ing the Depth of Decarburization of Steel Specimens �E 1077� and ASTM Standard TestMethod for Measurement of Metal or Oxide Coating Thickness by Microscopical Ex-amination of a Cross Section �B 487�. These standards rely primarily on the use of eye-piece reticles or filar micrometres to perform the necessary measurements. Digital im-aging offers several approaches to emulate the nondigital quantitative procedures.When measuring the depth or thickness of structures that exhibit a strong contrastwith surrounding or adjacent material the “segment and combine” techniques de-scribed in Section 18.5.3 may be used. Briefly, an image of the segmented layer to bemeasured is mathematically combined with an image of a set of section lines. A result-ant image is produced that displays only that portion of each section line that lies onthe segmented layer and these lines are measured. While section lines may be discon-tinuous, the image analysis software calculates the overall length of each horizontalrow of line segments no matter how many segments into which the line is broken. Theactual thickness measurement is made starting from the left end point of the left-mostsegment in each row and finishes at the right end point of the right-most segment in therow. Figures 18.15�a–e� depict this process.

For structures lacking the contrast to use the segmentation approach the measure-ments can be made using operator interactive methods to construct point-to-point dis-tances or parallel lines that are measured by the software. These methods are the digi-tal equivalents of positioning filars for thickness measurement, with the operator usingthe computer mouse to position filar lines on the digital image as displayed in Figs.18.16�a� and 18.16�b�.


Fig. 18.15b—Binary �segmented�

Fig. 18.15a—Image of coating.

Fig. 18.15c—Binary section line image.


One of the additional advantages in using digital imaging systems for thickness-type measurements is that annotations showing measurement lines as well as the mea-sured distances can be added to the image automatically by the software.

18.5.6 Graphite in Iron CastingsASTM Standard Test Method for Evaluating the Microstructure of Graphite in IronCastings �A 247� is essentially a qualitative chart comparison standard, applied to duc-tile, gray and malleable irons. For nodular �ductile� and flake �gray� iron particles a size�maximum diameter or length� classification chart is given. Much could be done to im-prove this standard by introducing additional quantitative procedures. The highly con-trasted nature of microscopically observed graphite in prepared cast iron specimensmake the use of segmentation-based digital image measurement of these structuresquite straightforward. Well prepared specimens that do not exhibit graphite smearingseldom require extensive image processing since the dark �nearly black� graphiteshapes are strongly contrasted with the bright white of the cast iron ferrite matrix.

One problem that may hinder automatic measurement is the possibility, particu-larly in gray iron, of touching graphite particles. The application of a separation filter

Fig. 18.15d—Combined 18.15b and c.

Fig. 18.15e—Section lines over coating.


may reduce these occurrences and as a final solution manual editing of the image maybe undertaken to separate massively touching particles.

Ductile Cast IronAlthough not incorporated into any ASTM standard, an important factor in determin-ing ductile or nodular iron product acceptability is the percentage of graphite particlesthat are nodular. Digital imaging systems provide outstanding capabilities for calculat-ing the percent nodularity. The classic function used to calculate particle roundness�nodularity� is the shape factor. While several equations exist for calculating shape fac-tor the most commonly used is:

Shape Factor = 4*Pi* Particle Area/Particle Perimeter2

To calculate nodule shape factor the area and perimeter of each graphite particle is

Fig. 18.16a—Vertical filar.

Fig. 18.16b—Horizontal point-to-point.


measured. These values are entered into the equation and the shape factor number isproduced. Possible shape factor values range from 1.0 for a perfectly circular particledownward towards 0 for increasingly “uncircular” shapes. Some shape factor levelmust be chosen as a lower limit to define the most “uncircular” shape to be considerednodular. This value is often set to 0.6, so that graphite particles have a shape factorequal to 0.6 or greater are nodules, and those with shape factors less than 0.6 are not.Percent nodularity can then be easily calculated by dividing the total count of nodulesby a count of all graphite particles. The precision with which the imaging software de-fines the particle perimeter length has a significant effect on the outcome of the calcula-tions. In particular, the measuring of small undulations in perimeter can significantlyalter the percent nodularity since the perimeter is squared in the calculation of shapefactor. Figure 18.17�a� shows a nodule in an enlarged portion of a digital image. In thisview the imaging software was adjusted to measure the graphite perimeter using justeight line segments seen as dark lines around the perimeter.

In Fig. 18.17�b� the software was readjusted to use 128 line segments to define theobject perimeter. The 8-line delineation yields a perimeter of 0.47953 mm while the

Fig. 18.17a—8-line perimeter.

Fig. 18.17b—128-line perimeter.


128-line perimeter is 0.51311 mm in length. The shape factor of Fig. 18.17�a� is 0.929while the shape factor of Fig. 18.17�b� is 0.869, a significant difference. This exampleillustrates the importance of the software algorithms used to define objects and extractmeasurements. The algorithms are in fact critical functions in the process of data pro-duction. As such their contribution to the end result must be understood and con-trolled if reproducible structure measurements are to be achieved. Attention to suchinternal software methods is especially important when results produced by severalseparate digital imaging systems are to be compared.

Gray Cast IronThe length of graphite flakes in gray iron can normally be readily measured from digi-tal images. The lengths can be input to calculations of the percentage of the flakes fall-ing in each of the size classes listed in ASTM A 247. However, the task of digitally classi-fying the “Graphite Distribution Patterns” as types of graphite flakes described in thestandard is beyond the capability of common image analysis techniques.

Compacted GraphiteCompacted graphite cast iron contains graphite particles in shapes that are intermedi-ate between flake and spheroid shapes. This type is defined by the ASTM StandardSpecification for Compacted Graphite Iron Castings �A 842� as “The acceptable graph-ite formation in the microstructure shall contain 80 % minimum Type IV graphite asdepicted in ASTM A 247 which may be arrived at by using…automatic image analysismethods.” Also, this type is “described as cast iron with the graphite in compacted �ver-miform� shapes and essentially free of flake graphite.” Based upon these guidelines it ispossible to produce imaging software to calculate the percentage of graphite that is notspheroid �calculate shape factor as in ductile cast iron except the percent particles thatare not spherical is found�. Also, to ensure that there is no flake graphite present, theaspect �length to width� ratio may be calculated. In this case since the standard doesnot provide a quantitative value to separate compacted from flake graphite, a reason-able value must be assumed and used in the software to calculate the presence of anyflake graphite.

18.6 Digital Imaging Technology

18.6.1 HardwareSeveral distinct hardware components are required to perform image digitization, pro-cessing, and analysis. Microscopes and other optical devices are not discussed here.The basic imaging system hardware components are: computer, camera, and printer.Recently all hardware components needed for image digitization have become avail-able as “off-the-shelf” items and the need for specialized hardware components for allcommon materials structure measurements is nonexistent. A general philosophy con-cerning selection of digital imaging systems should be based upon using the most stan-dard components available. It is no longer necessary or even desirable to purchase pro-prietary, single purpose, single source, and fully integrated systems. Such systemsinevitably have limited shelf life, provide functionality that is behind the curve of hard-ware capabilities available on the open market, and provide very limited �and expen-sive� upgrade possibilities. With the possible exception of image measurement soft-


ware there is no component necessary for assembling a state-of-the-art digital imagingsystem that is not widely available commercially.

Because the same technologies developed and priced for mass-marketed con-sumer cameras, computers, and printers are used in industrial grade digital imagingsystems, the cost of the hardware components needed to provide image digitizing func-tions continues to decline while the capabilities of the components continue toimprove.

ComputerToday, computers designed for normal business �or even home� use have more thanadequate power and information processing capabilities to run even the most sophisti-cated materials analysis software. It is not necessary or even desirable to procure cus-tom designed or nonstandard computers to power digital imaging systems. All of thecomputer peripherals present in a typical home computer system designed for Internetaccess and game playing should in most cases be present on a system for image mea-surement. Several specific components can be briefly commented upon. For viewingimages �especially those delivered by large format digital cameras�, relatively largemonitors are helpful. Monitors of 19 in. or larger display size and to save laboratorybench space �albeit at a premium price� flat, active matrix LCD monitors should beconsidered. Efficient management of digital images does require relatively large capac-ity computer memory, high processing speed, and extensive file storage space. Fortu-nately, computer processors, memory chips, and disk drive components are among themost cost effective of all equipment needed for digital imaging. Rapid technologicaldevelopment and a long history of downward trending prices in these devices are pri-mary reasons to avoid imaging systems based upon private label and custom designedhardware that cannot be readily upgraded or enhanced with standard components.

CamerasNo other single component required to perform digital imaging is more widely avail-able than the camera. There are literally hundreds of camera models available. Of thisvast array there are two basic types: analog and digital. The analog camera outputs ananalog electronic signal that is essentially a television signal; it is not in digital formand requires that image digitization be performed by a video digitizing or frame grab-ber circuit board installed in the computer.4 Digital cameras are designed to digitizethe image signal internally and output a digital format data stream to the computer.The key element in cameras is the sensor that converts light into an electronic signal. Atthis time the predominant sensor technology is the charged coupled device or CCD sili-con chip. Another type of image sensor becoming increasingly available is the Comple-mentary Metal Oxide Semiconductor or CMOS. Among the specifications that differ-entiate cameras, the physical size of the chip is one of the more significant. Chip sizesgenerally range from 1

4, 13 , 1

2 , 23 , up to 1 in. or more. Chip size is important because all

other components remaining equal, the size of the chip is directly proportional to thesize of the digital image field of view. A system equipped with a camera featuring one ofthe smaller chip sizes �1

4 or 13 in.� may not be capable of delivering the required field of

view area.Obviously the quality of the image produced by the camera is important. But other

factors such as image size, ease of operation, cost, and most importantly, how the im-


ages are to be used should be considered.

Analog CamerasAnalog cameras output a video signal that can be displayed in real time, that is, theimage signal is output fast enough to refresh the monitor display at approximately 30times a second. For viewing images on a monitor at a display rate that produces nonoticeable delay or jerky movement when the field of view is moved or the image focusis adjusted, in general an analog camera performs better than a digital camera. Sinceanalog cameras contain a minimal amount of circuitry the physical size of the cameracan be relatively small. In general, the more digitizing and signal processing that isdone within the camera, the larger the camera body.

To digitize an image the analog camera must be connected to a digitizing circuitboard mounted inside the computer. Digitizing boards can display a live signal fromthe camera along with digitizing the image for storage, processing, and measurement�see Inoue and Spring for a detailed discussion of digitizing boards4�. There are a widevariety of digitizing boards available. When selecting a digitizing board it is importantto match the board input and digitizing capabilities with the signal output of the ana-log camera. Many digitizing boards are available with the capability of being con-nected to multiple cameras. This feature is useful in laboratories requiring cameras tobe mounted on a microscope, a stereoscope, a microhardness tester, and more.

Digitizing boards are supplied with software for adjusting the board to accept vari-ous camera signal formats, for capturing images, and perhaps for image file manage-ment. Digitizing board products may also include software programs called driversthat are designed to enable the board to work directly with specific digital imaging soft-ware. There is an industry standard digitizer-to-imaging software driver called TWAIN.Digitizing boards and imaging software products providing the TWAIN interface canwork together and do not require any additional special software drivers. Analogcamera/digitizing board combinations provide a fast and efficient means for digitizingimages. For most material microstructure digitizing applications high-resolution ana-log camera/digitizing board combinations are the best all around choice.

Digital CamerasDigital cameras digitize the image signal output from the image sensor chip before itenters the computer. Digital cameras connect to the computer using a variety of com-puter ports or circuit boards, some standard and some custom designed. Digital cam-eras are available with large format image sensor chips and can digitize images into avery large number of pixels. With their high pixel counts digital cameras can provideexcellent quality images and are generally capable of displaying fine structural detailsmore sharply than an analog camera/board combination. As with digitizing boards,digital cameras will be supplied with software for image acquisition and the availabil-ity of TWAIN software is equally important. While providing high quality images, itshould be noted that many digital cameras are slower to capture images than analogcameras.

The real time image display rate is 30 times a second for analog output while digi-tal cameras may require up to several seconds to display a full image. In general, thegreater the number of pixels the digital camera offers, the longer the image capturetime. Delays in refreshing the computer image display are particularly noticeable dur-ing focusing of the image. Additionally, digital cameras may be more complex to oper-


ate than analog systems. Digital cameras should be considered when the primary usefor the digitized images is viewing, particularly when the images are to be printed. Ofcourse, the quality of printed images is also a function of the printer used and printersare briefly discussed in this section.

Black and White or ColorFor extracting structural measurements from most materials a gray scale �8 bit or 256levels of pixel illumination� is adequate. In a few materials segmentation to separate astructure for automatic delineation may require the use of a 24 bit �16.7 million levels�true color image. Due to the increased difficulty in setting color segmentation levelsand inefficiencies attendant to managing color images, the use of color images for ex-tracting measurements is only recommended if the measurements are not possiblewith gray scale images. Color images are recommended when the primary use of theimage is for publication and human viewing.

PrintersAs with cameras, a very large number of computer printers are available for use withdigital imaging systems. The growth in consumer digital photography has impactedthe quality of prints and the price of image printers very positively. Inkjet type printersthat can produce “photographic quality” images continue to become less expensive.The primary printer specification used to judge the potential quality of printed imagesis the number of ink dots per inch the printer is capable of putting on the paper. A countof 2400 by 1200 dots per inch is dense enough to produce high quality prints. For thehighest quality images coated photographic type paper must be used. Another type ofprinter technology known as thermal dye diffusion can produce a continuous-toneprint with resolution of 300 pixels-per-inch. The quality of these prints is termed “pro-fessional grade” and these printers have prices in the range of one order of magnitudehigher than ink jet printers. Specifications and pricing level aside, it is recommendedthat actual prints of material microstructures be viewed prior to making a decision onprinter acquisition.

18.6.2 SoftwareThere is an enormous variety of digital imaging software available. A recent search ofthe Internet yielded the following results:

Search Phrase: digital imaging software Web Page Matches over 50 000Search Phrase: image acquisition software Web Page Matches over 2400Search Phrase: imaging editing software Web Page Matches over 400Search Phrase: image archiving software Web Page Matches over 400Search Phrase: image measurement software Web Page Matches over 300Although not designed specifically for materialographic structure imaging, the

number of “image software” product sources is significant. Many of the products, con-cepts, techniques, and software modules developed for other digital imaging applica-tions can be used in metallographic/materialographic systems. This results in the avail-ability of constantly improving software functionality at competitive prices. Of course,several software systems have been designed particularly for materials science applica-tions. These should provide minimum basic image processing functions as well as themodules to perform one or more of the metallographic/materialographic test methodsdescribed in Section 18.5, depending on the requirements of the individual laboratory.


It is a near certainty that most imaging software packages will provide far more pro-cessing and measurement capabilities than are normally needed in all but the mostdiverse research and development environments. One of the challenges in selectingsoftware for materials analysis uses is in identifying products that provide the func-tions needed to perform structural imaging tasks without the presence of extraneoussoftware capabilities that may complicate operation and inflate costs. A few generalguidelines can be suggested.

Obviously the most important consideration is that the software is capable of per-forming the required tasks. What may not be so apparent is what those tasks are �seeSection 18.7 for additional comments concerning software selection�. The same gen-eral criteria used in selecting any type of software are applicable. Avoid software thatcan only be used with a specific computer or other hardware components. The soft-ware should provide an open architecture that permits exchange of data and interac-tion with other software products such as database, spreadsheet, and statistical pro-cess control programs. The software must also follow industry standards for data andimage file formats, user interface control designs, and device connectivity. In mostcases it is advisable to avoid proprietary designs that create a “sole source” supplierdependency.

Open Source/Public Domain SoftwareIt is possible to obtain open source/public domain software like NIH Image from Na-tional Institutes of Health for image processing/analysis. However, it should be notedthat the basic philosophy of open source software requires a strong commitment tomaintain and support the software on the part of the user. Often the typicalmetallographic/materialographic laboratory is not able or willing to perform suchtasks.

18.7 Digital Imaging System Implementation

The selection of software should always be based on a thorough and realistic study ofcurrent organizational tasks, established laboratory procedures and a realistic ap-praisal of future requirements. A digital imaging system is not a stand-alone device; itis a tool to facilitate the operation of a quantitative microstructural quality control pro-gram. The same care and attention to detail should be accorded the selection of a digi-tal imaging system as to other organizational information management or quality con-trol systems. An imaging system is part of a bigger organizational structure.

In a well designed system implementation project three distinct phases can beidentified. The purpose of Phase 1 is to produce a master plan based on an analysis ofexisting metallographic/materialographic operations and a definition of objectives.Part of this phase is actually a traditional systems analysis study, undertaken to definein some detailed and formal manner the procedures and work flow of the existingmetallographic/materialographic operations. This information can serve as a base linefor integration of new equipment. A clear understanding of the standards to be fol-lowed, the type of measurements necessary, and the volume of current as well as pro-jected work are among the many questions to be answered. It is also essential to consultwith engineers, information technology personnel, and others within the organizationwho will be in any way impacted by the new system. A very important factor in thesuccessful implementation of a digital imaging system is the skill level required by thesystem operator. Efficient operation of the imaging system may require a more techni-


cal background than general lab work; in particular a firm understanding of basic com-puter operation techniques is essential. Since quantitative metallography/materialo-graphy is based on stereological and statistical principles the system operators mustalso possess an understanding of these subjects. If an evaluation of potential systemoperators reveals a deficiency in these areas, suitable training programs should be re-quired. The system suppliers should provide training in the operation of specific imag-ing systems and software. However, general computer and quantitative methodsknowledge are a prerequisite and remedial instruction in these topics, if necessary, isnot the responsibility of equipment vendors. One important result of the initial phaseshould be the generation of a set of expectations or specifications that define the func-tions required of the imaging system.

The purpose of Phase 2 is to use the requirements, priorities, and specificationsgenerated in Phase 1 to determine which of the many commercially available systemswill best meet the current and future requirements of the company. This phase mayinclude identification of potential suppliers, compilation of a list of products available,demonstrations, circulation of a Request for Quotation, and of course, final system se-lection.

Phase 3, the last step of the process, is actually placing the system into operation.The process of converting to digital imaging from qualitative or manual quantitativemethods should have been defined in Phase 1. Implementation of new technology willalmost certainly necessitate changes in the procedures used to employ that technology.Common procedural points that may need changing include:1. Specific orientation and positioning of specimen may be required by standards or

by equipment.2. Selection of microscope objective magnification may be significant, i.e., field of

view area required by standard.3. Upgrading of preparation standards to eliminate artifacts that defeat automatic

imaging.Often results obtained from image analysis equipment will not match historical

results based on qualitative estimates or chart comparison methods. In these cases itmay become necessary to devise a strategy to correlate pre-and post-digital imagingresults. Ideally, major issues arising during implementation will have been identified,and the new system will be placed into operation in an efficient and cost-effective man-ner. Even with flawless planning it is to be expected that the full use of the system atmaximum efficiency will require a “learning” period.

ASTM Standard Guide for Laboratory Information Management Systems �LIMS��E 1578�, offers many insightful guides for the selection of a Laboratory InformationManagement System. Many of these concepts may be adapted for use in selecting asystem for digital imaging and an examination of ASTM E 1578 is suggested. A particu-larly useful idea found in ASTM E 1578 is the need to focus on functions, not technol-ogy. Additionally, see ASTM E 2066-00 Standard Guide for Validation of LaboratoryInformation Management Systems.

In conclusion, the objective of this chapter was to highlight some of the digital im-aging functions that are commonly applied to materials structure images and to pro-vide an overview of the use of image measurement techniques to implement selectedstandard test methods. It is also hoped that these comments have initiated an aware-ness of the necessity of quantitative metallography/materialography and also that digi-tal imaging systems are but a part of an overall program for the improvement of prod-uct quality.


19Digital Image Management„Archiving…A DIGITAL IMAGE ARCHIVING SYSTEM MAY INCLUDE ALL OF THE FEA-tures and components of a full image measurement system, the difference being thatthe primary purpose of archiving is to provide efficient and convenient yet powerfulmethods for capturing, identifying, storing, and retrieving digital images and associ-ated information rather than to extract structure measurement data. Such a systemmay include sophisticated database software or simple filing schemes for identifyingimages by a range of user definable classifications and keyword associations. As withdigital image measurement systems the selection of archiving must be based upon anevaluation of existing and projected needs.

A broader view of laboratory digital imaging possibilities must include consider-ation of the ASTM Standard Guide for Laboratory Information Management Systems�LIMS� �E 1578� �see Sections 12.4.2/3�. ASTM E 1578 provides a detailed discussion ofLIMS concepts. Laboratory information management systems are designed to providetotal data management from initial material sample receipt through logging of allspecimen preparation procedures, recording of image acquisition parameters such asmicroscope magnification brightness, contrast, segmentation levels, calibration, andany image processing functions performed along with the original, intermediate, andfinal images as well as final structural measurements data and many others. In short,these systems aspire to compile a complete record of all possible information related tothe processing of the specimen within the laboratory along with the ability to search,retrieve, and report selected views or dynamic combinations of the information fromthese records. These systems represent the most ambitious and sophisticated level ofdigital system possible in the laboratory. The demands of design and implementationof digital systems are increased by levels of magnitude when considering a LIMS. Atthe most advanced implementation level, the LIMS must provide electronic integra-tion of the technologies of many diverse instruments, requires the use of local as well aswide area networking, and employs sophisticated database technologies. And becausethey provide the several functional LIMS components as defined in ASTM E 1578 suchas data/information capture, data analysis, and reporting, systems for digital image ar-chiving and structural measurement may be considered components or subsystems ofa LIMS.

References „Part IV…�1� Underwood, E. E., Quantitative Stereology, Addison-Wesley Publishing Company, Reading,

MA, USA, 1970.

�2� Friel, J. J., et al., Practical Guide to Image Analysis, ASM International, Materials Park, OH,

USA, 2000.

�3� Russ, J. C., The Image Processing Handbook, 3rd ed., CRC Press, Boca Raton, FL, USA, 1998.

�4� Inoue, S. and Spring, K. R., Video Microscopy, Plenum Press, New York, NY, USA, 1997.

�5� Freund, J. E., Statistics: A First Course, 2nd ed., Prentice Hall Inc., Englewood Cliffs, New

Jersey, USA, 1970.

619

Part V: Hardness Testing

20IntroductionHARDNESS IS AN IMPORTANT PROPERTY WHEN JUDGING THE QUALITYand possible applications of a material. It can also give indications concerning the ten-sile strength, ductility, or wearing quality of the material.

Beginning in approximately 1822, quantitative evaluation of hardness was carriedout based on the hardness scale developed by F. Mohs. He ordered known minerals sothat the harder mineral scratched the one preceding it.

It must be noted that the differences in hardness between the individual steps ofthe scale are not equal. For example, the difference between steps 9 and 10 is substan-tially greater than that between 1 and 9.

Around 1900, further testing procedures were developed for technical purposes. Inthese procedures, hardness is not determined by scratching, but rather by indentingthe material to be tested with very hard objects of a specified size and shape. TheBrinell, Rockwell, Vickers, and Knoop hardness testing procedures are the best knownof these techniques.

Already in 1900, Martens suggested the following definition of hardness for techni-cal purposes:

Hardness is the resistance of a material to penetration by another �harder� mate-rial.

This simple conceptualization remains the basis of our understanding of hardnesseven today.

20.1 Indentation Hardness

Figure 20.1 schematically shows the significant elements of indentation hardness test-ing. A particular indenter �1�, attached to the lower end of a press, is pressed into the

TABLE 20.1—Mohs Hardness Scale.

Mohs ScaleMohs Standard

MineralEquivalent KnoopHardness Number

1 Talc 2

2 Gypsum 32

3 Calcite 120

4 Fluorite 150

5 Apatite 400

6 Feldspar 560

7 Quartz 700

8 Topaz 1300

9 Corundum 1800

10 Diamond 6000

623

specimen surface �2� with a particular test force �in N or kgf� and then pulled back. Theindentation that is created can then be measured.

The shape and size of the indenter are decisive for indentation resistance. Withball-shaped indenters, the specimen material is pushed away sideways and down-wards through plastic and elastic deformation. Angular or needle-shaped indenterscan, in addition to the deformation, cause separation processes like cracks, especiallyin brittle materials �ceramics�.

Depending on the characteristics of the material being tested, various mostly non-homogeneous deformation processes with multiple axes and varying degrees of elas-ticity and plasticity occur with penetration.

The speed of penetration also influences the behavior of the material being tested.For these reasons, the guidelines for the hardness testing procedures, including equip-ment construction, indenter, penetration speed, optical system, and evaluation are ofparticular importance.

Hardness is a distinguishing feature of a material. It is usually measured quantita-tively according to the following general relationship:

Hardness value = Test force/indentation size �1�

Beginning in 1940, hardness testing procedures in which the penetration depth ismeasured during application of a test force and then used to determine hardness weredeveloped. These procedures quickly gained in importance.

We differentiate among:Hardness testing procedures with static load action.Hardness testing procedures with dynamic load action.Special hardness testing procedures.

Fig. 20.1—Schematic drawing of hardness tester indicating force, indenter �1� specimen �2� andsupport �3�.


The most important of these will be shortly described below.

20.2 ASTM Standards

To be able to compare hardness values, the equipment, testing procedures, testingmethod, and evaluation must correspond to particular standards. The following ASTMstandards describe the various hardness testing procedures. See Section 12.4.2 formore standards on hardness.

Standard Practices for Force Verification of Testing Machines �E 4�Standard Test Method for Brinell Hardness of Metallic Materials �E 10�Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness

of Metallic Materials �E 18�Standard Test Method for Rapid Indentation Hardness Testing of Metallic Materi-

als �E 103�Standard Test Method for Indentation Hardness of Metallic Materials by Portable

Hardness Testers �E 110�Hardness Conversion Tables for Metals �Relationship Between Brinell Hardness,

Vickers Hardness, Rockwell Hardness, Rockwell Superficial Hardness, Knoop Hard-ness and Scleroscope Hardness� �E 140�

Standard Practice for Scleroscope Hardness Testing of Metallic Materials �E 448�Standard Test Method for Microindentation Hardness of Materials �E 384�Standard Test Method for Vickers Hardness of Metallic Materials �E 92�


21Static Hardness Testing Procedures

21.1 Brinell Hardness Testing

THE FIRST STATIC HARDNESS TESTING METHOD WAS INTRODUCED BY J.A. Brinell, a Swedish researcher, at the 1900 Paris World Exposition. A hardened steelball or tungsten carbide ball with a diameter �D� of 1, 2, 2.5, 5, or 10 mm was used asindenter. This was pressed into the smooth, clean specimen surface with a test force�F�. Figure 21.1 shows the principle of test with test force F �N�, D the diameter of theball �mm�, d the mean diameter of the indentation �mm�, and h the depth of the inden-tation �mm�. It is important that the specimen rests on a rigid support, and that theindenter contacts the specimen without being shaken or jolted. The test force is thenincreased to the predetermined maximum value within 2–10 s and held for 10–15 s. Ifthe duration of load application falls outside of this range, this must be indicated. Forexample, for nonferrous materials, the duration may be as long as 180 s.

Depending on the elastic-plastic behavior of the material, the indentation mayvary. Figure 21.2 shows an ideal indentation, �a�, an indentation with sink-in due to ahigh degree of elasticity �b� and an indentation with pile-up due to a high degree ofplasticity �c�.

21.1.1 Calculations and ProceduresThe spherically shaped indentation that is created is measured. The Brinell hardness iscalculated from the mean indentation diameter according to the following equation:

HBS or HBW = 0.102F

A= 0.102 �

2F

�D�D − �D2 − d2��1�

whereHBS=Brinell hardness with steel ball as indenterHBW=Brinell hardness with tungsten carbide ball as indenterF=test force in NA=indentation surface in mm2

Fig. 21.1—Brinell hardness testing, test principle. Force, kgf �F�, diameter of ball, mm �D�, meandiameter of indentation, mm �d�, depth of indentation, mm �h� �ASTM Standard E 10�.

626

D=ball diameter in mmd=arithmetical mean value of two measured indentation diameters in mmThe test force F is multiplied by 0.102 ��1/9.80665=1/g� to get the calculated

hardness as a unitless numerical value.Specimen thickness should be at least ten times the expected indentation depth. If

the expected hardness of a material can be estimated, then the minimum specimenthickness can also be estimated.

For the indentation depth, it can be assumed that

A = D�h �2�

The minimum thickness S of the specimen is then

S = 8�0.102F/�DHB .. . � �3�

Steel balls can be recommended as indenters for Brinell hardness values of up to350. They are permitted up to HBS=450. When testing harder materials, elastic defor-mations of the ball must be expected. These lead to increased indentation diametersand thus to erroneously elevated measured values. Tungsten carbide balls may be usedup to HBW 650.

Test results are given as follows:Duration of test load application �25�Test force identifying value 0.102 F �3000�Ball diameter in mm �10�Identifying marking of indenter �in this case tungsten carbide��W�Abbreviation for Brinell hardness �HB�Determined Brinell hardness value �410�

The relatively large indentations are an advantage of the Brinell hardness testingmethod. They ensure representative hardness values even when heterogeneous materi-als are tested.

Fig. 21.2—Ball-shaped indentation shapes. Ideal indentation �a�, indentation with sink-in �b�and indentation with pile-up �c�.

Chapter 21 Static Hardness Testing 627

It is important that the ball creates an easily measurable indentation. For that rea-son, it is stipulated that the indentation diameter lies between 0.24 D and 0.6 D. If dif-ferent ball diameters are used on the same material, the measured values can only becompared when the indentations are geometrically similar. Accordingly, the test forceF must be appropriate for the ball diameter D. For comparison of hardness values, theoptimum stress level 0.102F /D must therefore be closely adhered to. Table 21.1 showsthe relationship between stress level and measured hardness range for various mate-rial categories.

If the material to be tested, and therefore the load ratio and the diameter D of thetest ball selected �10, 5, 2.5, or 1.25 mm�, are known, then the test force F can be set onthe testing apparatus.

The minimum distance from the middle of an indentation to the edge of the speci-men should be at least 2.5 d for steel, gray cast iron, copper, and copper alloys. Thedistance between adjacent indentations must be �4 d.

For light alloys, Pb, Zn, and their alloys, the respective distances should be �3 d�specimen edge� and �6 d �adjacent indentations�.

21.1.2 Brinell Hardness TestersFigure 21.3 schematically shows the construction of a Brinell hardness testing ma-chine with hand wheel �1�, support �2�, specimen �3�, objective �4�, indenter �5�, loadingsystem �7�, and screen for measuring the projected Brinell indentation �6�.

Figure 21.4 shows a modern Universal Hardness Tester for Vickers, Knoop,Brinell, and Rockwell. It has unattended testing and analysis cycle via fully automatedimage analysis for Brinell/Vickers and automatic focusing. The test load ranges are9.81 N to 2450 N or 49 N to 7350 N.

Testing procedure details can be found in the directions for use of the equipmentand in the procedural and material-specific norms, for example, the ASTM TestMethod for Brinell Hardness of Metallic Materials �E 10�. Internal company proce-dural guidelines should also be observed.

21.2 Vickers Hardness

21.2.1 Calculations and ProceduresSmith and Sandland developed the Vickers method �named for the English companyVickers� in 1925. The reason for this development was the fact that Brinell hardnessonly provided usable results up to HBS=450, because higher test forces cause defor-mation of the steel ball to begin to occur.

In Vickers Hardness Testing, the indenter is a regular four-sided diamond pyramid

TABLE 21.1—Stress Level and Recorded Hardness Range for Various Materials.

Stress Level Hardness Range, HB Material

30 70–600 Steel, Iron �140 HB

10 22–315 Ti, Ni-, Co, Cu-Alloys �200 HB

5 11–158 Nonferrous metals and their

alloys

2.5 6–78 Bearing metals

1.25 3–39 Lead, tin


with an interfacial angle, �, of 136°. The geometry of this Vickers pyramid produces agood correlation between the Vickers values HV and the Brinell hardness values HBSbetween 350 and 400.

The Vickers pyramid is pressed vertically into the specimen with a test force P �kgf��2� shown schematically in Fig. 21.5. � �1� is the face angle of the diamond �136°�, d1 andd2 �3� are the diagonals of the impression �mm�. The mean diagonal diameter d of theindentation is used to calculate the Vickers hardness.

HV = 0.9272P

A=

2P sin�136 ° /2�d2 � 1.8544

P

d2 �4�

whereHV=Vickers hardnessP=test force in kgf

Fig. 21.3—Schematic drawing of Brinell hardness testing machine with hand wheel �1�, support�2�, specimen �3�, objective �4�, disengaged indenter �5�, screen for projection of theindentation �6�, and loading system �7�.1


A=indentation surface in mm2

d=arithmetical mean value of the measured indentation diagonals in mmFor Vickers Hardness, given in GPa units, we find that

HV = 0.0018544 � P2/d22 �5�

with forceP2 inN and themean lengthof indentationdiagonals inmm.Because of the pyramidal geometry, the relationship between the indentation

depth and the indentation diagonals is h=d /7.0006.For Vickers macrohardness testing, the test load must normally also be selected

such that the indentation diagonals are relatively large in comparison to the phasecomponents. The diagonal d should be a maximum of 2/3 of the specimen thickness,and the penetration depth thus 1/10 of the specimen thickness, to exclude influencefrom the specimen support. This is important when testing thin sheets or layers �seebelow�.

Fig. 21.4—Universal hardness tester for all standard testing processes such as Vickers, Knoop,Brinell, and Rockwell. Unattended testing and analysis cycle via fully automated image analysisfor Brinell and Vickers. Automatic focusing. Test load ranges: 9.81 N to 2450 N or 49 N to7350 N.2


Test results are given as follows:Duration of test load application in s �25�Test load identifying value �100�Abbreviation for Vickers hardness �HV�Measured Vickers hardness value �780�

Figure 21.6 shows the ideal indentation �a� and possible undesirable indentationswith sink-in �b�, pile-up �c� formation and “kite” shape �d�.

For high-test forces, determination of Vickers hardness is independent of the testforce. However, for test forces P�5N the calculated Vickers hardness becomes testforce dependent. This phenomenon is known as Indentation Size Effect �ISE�. Its influ-ence is particularly disruptive in microhardness testing, where HV values that havebeen measured for the same specimen with differing test forces are no longer compa-rable. The cause can be tension induced when the Vickers pyramid is imposed or sur-faces that have stabilized dissimilarly during metallographic/materialographic prepa-ration.

For this reason, hardness value classification is divided into test ranges.Following the ASTM Standard Test Method for Vickers Hardness of Metallic Mate-

rials �E 92�, Vickers Hardness Tests are performed with test forces of from 1 to 120 kgf.The ASTM Standard Test Method for Microindentation Hardness of Materials �E

384� specifies a test force range of 1–1000 gf for microindentation hardness testing withVickers indenters �see Section 21.5�.

At Vickers hardness testing �E 92� the distance between the center of the indenta-tion and the specimen edge and between the center of two indentations should be�2.5d. When laminated material is tested, a bond surface shall be considered as anedge for spacing of indentation calculations.

In hardness testing of small parts, thin sheets, layers or foils, low-test forces shouldbe used to avoid the so-called anvil effect. The anvil effect is caused by use of a test force

Fig. 21.5—Vickers hardness testing, test principle �ASTM Standard E 92�.


that is too high when testing a thin specimen, resulting in a bulge or shiny spot on theunderside of the specimen. Also a force that is too high may cause edge effects, a plasticdeformation in the direction towards the edge. For this reason an indentation shall bein a certain distance to the edge as mentioned above. The use of low-test forces alsoapplies to the determination of hardness of individual structural constituents.

As the test force or indentation size, or both, decrease, the influence of the speci-men surface increases. A carefully smoothed and cleaned surface is sufficient whenmacro testing, but when micro testing, the specimen must be metallographically/materialographically prepared to remove any disruptive roughness or solidified sur-face layers. If smoothing and polishing are insufficient, the surface can be electrolyti-cally or chemically treated to have access to mechanically undisrupted areas. Ifindividual structural constituents are to be tested, additional phase contrasting, for ex-ample by means of etching, is necessary.

21.2.2 Vickers Hardness TesterThe hardness tester shown in Fig. 21.4 can easily be converted for use in Vickers macro-hardness measurements. The indenter is exchanged and the appropriate test force in-crements selected. Measurement takes place on the screen or automatically.

Depending on the producer, the machines differ in various ways. For example, thetest force may be produced mechanically or hydraulically in different increments, thetest method may be more or less automated and special testing needs may be met bymeans of additional equipment.

Fig. 21.6—Vickers indentation shapes. Ideal indentation �a�, indentation with sink-in �b�,indentation with pile-up �c�, and kite-shaped indentation �d�.


21.3 Knoop Hardness Testing

21.3.1 Calculations and ProceduresSpecial machines were developed for low load, microindentation hardness, and ultra-microindentation hardness testing in order to further decrease potentially disruptivedevice-related influences and better measure very small indentations. Essentially, how-ever, the testing procedure corresponds to that of macrohardness testing.

In 1932, Knoop, Emerson, and Peters introduced a method developed specificallyfor low load and microindentation hardness testing. In Knoop hardness testing, arhombic-based pyramidal-shaped diamond indenter with edge angles of 172° 30� ��A�and 130° ��B� is used. In Fig. 21.7, the pyramidal-shaped diamond is shown with thetwo angles and the long diagonal, d ��m�. As in the Vickers method, this pyramid ispressed vertically into the specimen surface. Knoop hardness in kgf/mm2 is calculatedby means of the long indentation diagonal d in �m, which is 7.114 times longer thanthe short diagonal of the Knoop indentation.

The following equation applies:

HK = 14.229P1/d12 �6�

whereHK=Knoop hardness in kgf/mm2

P1=test force in kgfd1=long indentation diagonal in mmKnoop hardness in GPa units is determined as follows:

HK = 0.014229 � P2/d22 �7�

whereP2=test force in Nd2=long indentation diagonal in mmTest results are given as follows:650 HK 0.5/30

Fig. 21.7—Knoop diamond pyramid and indentation �ASTM Standard E 384�.


Duration of test force application in seconds; not recorded ifbetween 10 and 15 s �30�

Test force identifying value: 0.102F �F in N� �0,5�Abbreviation for Knoop hardness �HK�Measured Knoop hardness value �650�

Knoop hardness measurements are primarily taken using hardness testers devel-oped for low load and microindentation hardness testing. In such machines, the loadsystem is changed accordingly and adjusted for small test forces. The screen ontowhich the indentation is projected is exchanged for a measuring ocular.

Due to the measurement length that is greater than that of a comparable Vickersindentation, measurement error is smaller in the Knoop method. Therefore, even verythin layers or foils can be tested better. The Knoop method is also advantageous withbrittle materials, as cracks form more easily around a Vickers indentation.

The Knoop indenter does not produce a geometrically similar indentation as afunction of test force. Consequently, the Knoop hardness will vary with test force.

Due to the elongated shape of the Knoop diamond, any anisotropy that may existin individual structural constituents can be ascertained. When this is the case, differentmeasurements of the crystallite are taken and the specimen is appropriately rotatedbefore every new measurement.

Knoop hardness testing is described in ASTM Standard Test Method E 384 �seeSection 21.5�.

21.4 Rockwell Hardness Testing

21.4.1 Calculations and ProceduresDue to a number of disadvantages of the Brinell hardness test and the limitations re-garding testing of steels with high hardness, Stanley P. Rockwell developed a hardnesstesting method in 1919. In this method, the hardness of a material is determined bymeans of measured indentation depth. A diamond indenter is used for Rockwell C �seeFig. 21.8� or a tungsten carbide/steel ball is used for Rockwell B. In Fig. 21.8 the follow-ing symbols and designations are used:

1: Angle of the top of the diamond indenter �120°�; 2: Radius of the curvature at thetip of the cone �0.200 mm�; 3: P0, Preliminary test force; 4: P1, Additional force; 5: P,Total test force �P0+P1�; 6: Depth of penetration under preliminary test force; 7: In-crease in depth under additional force; 8: e, Permanent increase in depth of penetrationunder preliminary test force after removal of additional force, the increase being ex-pressed in units of 0.002 mm; 9: xxHRC, Rockwell C hardness=100−e.

It can be seen that the indenter is first pressed a small distance into the material; inthis way the influence of the specimen surface can be excluded.

Rockwell hardness value is calculated by means of a process internal to the ma-chine with the help of a scale division factor S and a numerical value N.

The simple equation for determining Rockwell hardness is:

HR = N − e/S �8�

whereHR=Rockwell hardnessN=Numerical value tied to Se=Remaining indentation depth in mm


S=Scale division in mmThe standard indenters are a diamond cone with 120° apical angles and tungsten

carbide balls with diameters of 1.588, 3.175, 6.350, and 12.70 mm.The preliminary test force for the Rockwell Standard Method is 98 N �10 kgf�; the

possible total force is 589 N �60 kgf�, 981 N �100 kgf�, 1471 N �150 kgf�.For the Rockwell Superficial Hardness test, the preliminary force is 29 N �3 kgf�

and the possible total force is 147 N �15 kgf�, 294 N �30 kgf� and 441 N �45 kgf�.Corresponding scales are available for different application purposes and material

groups �see Table 21.2�.Lower test forces are used in Rockwell Superficial Hardness Testing. The prelimi-

nary test force is 29 N and the total test force can be 147 N, 294 N, and 441 N.Rockwell scales B �for the steel ball of 1.588 mm diameter� and C �for the diamond

cone� are the most frequently used. As in Brinell hardness testing, however, it must benoted that deformation of the ball can occur in very hard materials with HRB. There-fore, use of the B steel ball for materials harder than 100 HRB is not recommended.

The test object should lie solidly on the support table �anvil� so that it cannot slipduring the test method. Care must be taken to select the correct indenter and forcewhen working with thin specimens so that the hardness value of the specimen is notfalsified due to the influence of the support table, the so-called anvil effect. Specimenthickness should be �15 times the depth of indentation when using a ball indenter and�10 times the depth of indentation with a diamond cone. As a rule, no deformationshould be visible on the back of the work piece after the test.

Indentations should be made at a distance of at least 2.5 times the indentation di-ameter from the specimen edge. The distance between adjacent indentations should bethree times the indentation diameter.

The preliminary test force F should be produced within 3 s. The usual duration ofstress by the additional force is 1–8 s.

Further information about the method can be found in ASTM Standard TestMethod E 18.

Fig. 21.8—Rockwell C hardness test with diamond indenter, test principle, see text �ASTMStandard E 18�.


Designation of Rockwell hardness is made by supplying the hardness value fol-lowed by the abbreviation HR �for Rockwell hardness� and the scale symbol. This givesinformation about the indenter and the force. For example, 80 HRC means a Rockwellhardness value of 80 on the C scale using the diamond cone as indenter.

21.4.2 Rockwell Hardness TestersFigure 21.9 shows a basic Rockwell hardness testing machine. The testing procedurediffers in two significant ways from the Brinell and Vickers methods described previ-ously. First, with the help of a hand wheel, the specimen is pressed against the indenteruntil the meter indicates the desired preliminary force F0. Then, the additional force F1is applied for the specified length of time. A further difference lies in the fact that theRockwell hardness value HR can be read from the meter immediately after withdraw-ing the major force.

The significant advantages of Rockwell hardness testing compared to the Vickersand Brinell procedures include the simpler machine construction without optical mea-suring equipment, the direct readability of the hardness values, and the less stringentquality requirements for the specimen surface.

For these reasons, the Rockwell method was quickly adopted and is used primarilyfor simple and fast quality control in production.

21.5 Microindentation Hardness

21.5.1 MethodsMeasuring methods and machines must be appropriately adapted to perform hardnessmeasurements on very small objects, thin layers, surface-treated materials, or indi-vidual structural constituents.

TABLE 21.2—Rockwell Scales and Test Conditions for Various Groups of Materials.

Scale Symbol Indenter (Diam.) Total Test Force kgf Application Example

B Steel �1.588 mm� 100 Moderately hard, soft steels; brass, bronze, Alalloys

C Diamond 150 Hardened, tempered steel; hard casting,materials harder than HRB 100

A Diamond 60 Sintered carbides as well as HRC with lowspecimen thickness

D Diamond 100 Thin steel sheets, case-hardened layers

E Steel �3.175 mm� 100 Cast iron, Al and Mg alloys, bearing metals

F Steel �1.588 mm� 60 Thin, soft steel sheets, annealed copper alloys

G Steel �1.588 mm� 150 Copper-nickel-zinc, hard bronzes

H Steel �3.175 mm� 60 Aluminum, zinc, lead

K Steel �3.175 mm� 150

L Steel �6.350 mm� 60

M Steel �6.350 mm� 100 Soft bearing metals and thin specimens, verysmall balls and heaviest load that does notgive an anvil effect

P Steel �6.350 mm� 150

R Steel �12.70 mm� 60

S Steel �12.70 mm� 100

V Steel �12.70 mm� 150


Microindentation hardness, also often called microhardness, means the determi-nation of hardness values with low test forces. Compared to the macrohardness testingmethods described previously, the test force range in microhardness testing is verysmall. Following the ASTM Standard Test Method for Microindentation Hardness ofMaterials �E 384� the range is between 1 and 1000 gf �9.8�10−3 and 9.8 N�, and theindentations are correspondingly small.

In practice, the geometric forms of the Vickers and Knoop diamond indenters haveproved successful. In addition, the Berkovich diamond indenter must be mentioned.This is a regular three-sided pyramid with an angle of 142° between the lateral edge andthe opposite lateral face. The indentation surface is an equilateral triangle; the lengthsof its sides are measured.

The hardness value that has already been described, is in any case ascertained bydividing the test force by the remaining indentation surface.

It is especially important to monitor the loading system regularly, since the hard-ness error percentage is directly proportional to force error. The total force should beapplied within 10 s, while the duration of the force can range from 10 to 15 s. Forsteels, 10 s are sufficient. If longer load times are necessary for softer materials, thismust be indicated in the test protocol.

Vibrations and shaking of the machine must be avoided during measurement.

21.5.2 Specimen PreparationTo achieve precise measurement values, the polished and cleaned specimen surfaceshould be set up perpendicularly to the direction of indentation. This is the only way toachieve clearly defined indentations that can be evaluated to a microscopically exactdegree. The smaller the test force and the indentation, the greater the influence ofspecimen preparation. For example, excessive polishing can cause cold work of the sur-face material �see Part II, Section 13.16�. Whenever possible, the surface should not be

Fig. 21.9—Rockwell hardness tester.2


etched since the indentation otherwise becomes uneven due to the attacked surfaceand may be difficult to measure.

See Part II, Table 11.1 and Chapter 13.2.3 for information regarding suitable speci-men preparation. Small unevenly shaped specimens must be mounted or fastened intospecimen holders. It is important to ensure that the specimen cannot move under theeffects of the force.

21.5.3 Taking the MeasurementsThe microindentation hardness measurement method takes place in the followingway:

Turn on lighting system and the calibrated hardness testerSelect, carefully clean and apply an indenterSet or fasten specimen material on table surfaceFocus a low-enlargement lens on the specimen surfaceSelect indentation area, adjust contrast and resolution to optimal valuesRemove lens from and move indenter into the operating positionSelect forceActivate test, adhere to specified force timesAfter withdrawing the force, disengage indenter and move lens into measuring

modeCheck indentation for desired position and symmetryEvaluateNonsymmetrical indentations can be caused by the following:Indenter does not penetrate specimen surface perpendicularlySpecimen surface is not levelMaterial is texturedAnisotropy of structural constituentsBecause microindentation hardness values are strongly influenced by different

components and their size and distribution in the material, it is advisable, dependingon the task at hand, to make several indentations under otherwise identical conditions.The distance between two Knoop indentations shall lengthwise be �1.5 d �length ofKnoop diagonal�, side by side be �4 w �width of Knoop diagonal� and the distance tothe edge of the specimen shall be �3w. The distance between the center of two Vickersindentations shall be �4 d �length of Vickers diagonal�, and the distance to the edge ofthe specimen shall be �2d.

In ceramics or other brittle substances, the indentation can cause cracks. TheASTM Test Method for Knoop Hardness for Advanced Ceramics �C 1326� and theASTM Test Method for Vickers Hardness for Advanced Ceramics �C 1327� addressmore closely the consideration of such special circumstances.

When test forces and indentations are so small, high demands are placed on theindenter in terms of precision, particularly where the four faces meet. For the Knoopindenter the line of junction between opposite faces �offset� shall be not more than1 �m in length for indentations greater than 20 �m in length, as shown in Fig. 21.7.For Vickers indenters the offset shall be not more than 0.5 �m. Formation of an offsetbetween the faces cannot occur with the Berkovich indenter, as it has only three faces.

Indenters should be examined periodically and replaced if they become worn,dulled, chipped, cracked, or separated from the mounting material.


21.5.4 Microindentation Hardness TestersFigure 21.10 shows a modern microhardness tester. With this machine, Vickers,Knoop, Berkovich, and Brinell testing procedures can be carried out with adherence tothe most recent ISO and ASTM standards. Machines of this kind operate completelyautomatically with motorized lens carousel and autofocus �motorized z-axis�. The loadproduction and the load changes among nine increments �from 98.07 mN to 19.61 N�take place automatically when the duration of load application is between 5 and 999 s.With the help of a video camera and appropriate measuring and controlling software,the image of the indentation surface can be transferred to a PC and evaluated there.Serial measurements are possible in addition to individual tests. Measurement valuescan be statistically evaluated �maximum, minimum, mean values, standard deviation,histogram�. Conversion of hardness values �HR, HB, MPa, etc.� occurs automatically.

21.5.5 Examples of IndentationsFigure 21.11 gives four examples of indentations. In Fig. 21.11 �a� shows three indenta-tions in differential interference contrast �DIC�; �b� shows Vickers indentations in steel,indicating the softer ferrite and the harder pearlite; �c� shows the hardness progressionin case hardened steel; and �d� the indentation is in a ceramic material, Si3N4. Thebrittle material causes cracks at the corners of the indentation.

21.6 Universal Hardness—Martens Hardness—InstrumentedIndentation Testing—Nano Indentation

The extent of elastic and plastic deformation varies greatly among technical materials.In rubber, for example, elasticity predominates, and the indentation regresses almostcompletely when the load is removed, whereas in materials like lead the hardness in-dentation is retained. The hardness values of the two materials can therefore not becompared to each other.

Comparison is possible when the Universal hardness, HU, is calculated. In thisprocedure that has been known since 1940, the Vickers hardness is measured underforce. The Universal hardness is calculated from the maximal test force Pmax and theindentation depth hmax. Universal hardness is now known as Martens hardness, HM�see below�.

Fig. 21.10—Microhardness testing machine.3


By means of this procedure, hardness values from all material types can be com-pared on one scale, which is a great advantage, particularly for industrial purposes.The Vickers procedure’s visual evaluation of the indentation, along with its possibilityof error, is hereby eliminated. The indentation depth is recorded by measuring tech-niques that make possible the automation of the procedure.

Additional valuable quantitative information about a material’s elastic and plasticbehavior can be extracted from load-indentation depth curves, Fig. 21.12, that are aschematic representation of the test force �indentation-load�, F, versus depth of inden-tation �displacement�, h. The diagram shows that the depth of indentation �displace-ment� increases with increasing load. At unloading only the elastic portion of the dis-placement is recovered, which allows for separation of the elastic properties of thematerial from the plastic properties. Based on the maximum depth, hmax and the maxi-mum load, Fmax, the Martens hardness, HM, previously Universal hardness, can be de-fined �see below�. It is also possible from Fig. 21.12 to calculate the elastic modulus�Young’s modulus� based on the slope of the unloading curve.

Fig. 21.11—Examples of Vickers and Knoop indentations. Three Vickers indentations in DIC,220X �a�, indentations in steel indicating ferrite and pearlite, BF 500X �b�, progression ofhardness in a case hardened steel, BF, 100X �c�, and a Vickers indentation in silicon nitride withcracks at the corners, DIC, 200X �d�.


21.6.1 Instrumented Indentation Testing—Nano IndentationIn classical light-optical microhardness testing, even when using automatic machineswith high-grade optical measurement systems, a Vickers or Knoop diagonal length isrecordable to at most 2–3 �m. This is due to the limited resolution capability. Whenworking with microcrystalline materials and extremely thin layers, however, hardnessindentations of substantially smaller indentation size are required. This is achieved byusing the testing principle, Instrumented Indentation Testing �IIT�, also called nanoindentation. IIT is used for determination of Martens hardness, HM, Indentation hard-ness, HIT, and Indentation modulus, EIT. The indentation depth �h� is measured andused to calculate the hardness value. In this way, indentation depths to 0.1 nm can berecorded and evaluated in adherence to international standards �see below�.

Martens Hardness Scale: The Martens hardness value is calculated by dividing thetest force F by the surface area of the indenter penetrating beyond the original surfaceof the test piece As�h�.

For Vickers indenter:

HM = F/As�h� = F/26.43h2 �9�

For Berkovich indenter:

HM = F/As�h� = F/26.44h2 �10�

Indentation Hardness Scale: The indentation hardness HIT is calculated from thetest force, F, divided by the projected area of the indenter in contact with the test pieceat maximum load:

HIT = F/A�hc� �11�

where the projected contact area A�hc� is calculated from knowledge of the geometry ofthe indenter and the stiffness of the contact.

During the indentation the force-trajectory progression can be recorded that givessignificantly more information about elastic-plastic behavior than does a classical in-dentation for which the size is evaluated. In this way, hardness, elasticity, or viscoelas-

Fig. 21.12—Schematic representation of indentation force—depth of indentation �displace-ment� data during one complete cycle of loading and unloading.


tic properties of paint, varnish, or synthetic layers, galvanized layers, carbide layers ofTiN or TiC, diamond and anodized layers as well as fibers and foils can be determinedand compared. Also, the hardness and elastic modulus of a single grain in a microstruc-ture can be measured. Fully automated measurement and evaluation ensure high re-producibility and prevent subjective error.

Instruments for IIT work with test forces down to 1 nN and indentation depths�displacement� down to 0.1 nm. HM can be measured with Vickers and Berkovich in-denters. For measurements in the nano range the Berkovich indenter, having onlythree faces �see Section 21.5.3� is preferred, but other geometries like sphero-conicalindenters are also used.

Instrumented Indentation Testing is described in ASTM Work Item, Practice forInstrumented Indentation Testing �WK 382� and in the Standard ISO 14577.

21.7 Precision of Hardness Values

The hardness testing procedure takes place in two steps: The production of the hard-ness indentation and its measurement. The measurement value that is obtained in thepresence of known standard testing machine and specimen conditions is influenced bythe geometric precision of the indentation specimen and by penetration direction, testforce, test time, penetration speed, and temperature. This can lead to constant or vari-able errors.

For this reason the testing machine shall be verified. The direct verification of thehardness tester includes the inspection of the force application, the indenters, and themeasuring device at regular intervals. If the test force or the indenter is changed, a newverification must be performed.

Indirect verification takes place by making a series of at least five test impressionson a standardized hardness test block. The closer the mean values of the test impres-sions are to the hardness of the test block, the more exact the hardness tester functions.The difference in hardness values around a mean value may be an indication of theprecision of the hardness tester: The less difference the higher precision.

A verification report often should be worked out after the verification. The test re-port should contain the following information: Reference to the ASTM test method.Method of verification. Identification of the hardness testing machine. Means of verifi-cation. Type of indenter and test force. The result obtained. Date of verification andreference to the calibration institution. Identity of the person performing the verifica-tion.

For specification regarding the single hardness testing method, see the relevantASTM standard stated in Section 20.2.

21.8 Conversion of Hardness Values

The conversion back and forth among Brinell, Vickers, or Rockwell hardness values ispossible with the help of conversion tables �see below�. The conversion values are solelyempirical in nature.

In certain cases the following equations can be used; these should be considered asrules of thumb, not as exact as the equations stated in the conversion tables mentionedbelow.

Simple Hardness Conversion Equations:


From HB to HV: HB�0.95 HVFrom HRB to HB: HRB�176–1165/�HBFrom HRC to HV: HRC�116–1500/�HVFrom HV to HK: HV�HK �in low load range�Procedural information can be found in the ASTM Standard Hardness Conversion

Tables for Metals �Relationship between Brinell Hardness, Vickers Hardness, RockwellHardness, Rockwell Superficial Hardness, Knoop Hardness, and Scleroscope Hard-ness �E 140�. Please refer to ASTM E 140 in the CD-ROM included with this manual.

Values that have been estimated using the equations given above or taken from theconversion tables should be indicated, stating the original hardness value.


22Dynamic Hardness TestingProceduresIN DYNAMIC HARDNESS TESTING PROCEDURES, THE INDENTER HITSthe specimen surface with impact. The specimen material can thereby be elasticallyand unelastically deformed. Deformation that arises due to the kinetic energy of theindenter and remains can be measured. In such dynamic-plastic procedures, the hard-ness value is the quotient of the test force and the indentation size. We distinguish be-tween fall hardness testing and impact hardness testing �see Fig. 22.1�.

In the fall hardness testing method �a�, an object of defined mass falls freely ontothe specimen along with the indenter �ball� and creates an indentation. In the impacthardness testing method �b�, the ball rests on the specimen surface. Triggered by ahammer blow or by spring force, an object of known mass is thrust onto the indenter,which then penetrates the specimen.

One such instrument is the Poldi impact hardness tester, Poldi hammer for short.The indenter is pressed, by means of a hammer blow, simultaneously into the specimenand into a comparison rod of known Brinell hardness. The HBP hardness can then bedetermined by comparison.

With the Baumann hammer, the indenter is driven into the specimen surface bymeans of spring force. The indentation is measured and assigned a correspondingBrinell hardness value.

Fig. 22.1—Principles of dynamic hardness testing procedures, schematic. Rebound with drop�a�, and rebound with spring loaded hammer and ball placed on the work piece �b�.

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In dynamic-elastic hardness test procedures, the rebound height, or reboundangle is measured �see Fig. 22.2�. In materials with low deformation potential, such astungsten carbide or rubber, the indenter, which hits the specimen surface at a definedvelocity, springs back. We can infer a hardness value from the rebound height that isproportional to the rebound energy. Such dynamic-elastic procedures also include theShore hardness testing method and the Equotip method.

The Scleroscope functions according to the drop hammer principle. The indenteris either a rounded diamond point of a particular size and shape or a steel ball that restson a drop hammer. This falls through a pipe vertically onto the specimen and reboundsagain up to a particular height �Fig. 22.2�a��. This rebound height is a measure of hard-ness that is given in Shore hardness values. In the Model C Scleroscope, a high-precision, low-friction glass pipe is used. The rebound height can be recorded on ascale of 0–140, and the hardness can be read in HSc. In the Model D Scleroscope, thehammer is automatically detained after reaching the rebound height, and height andhardness are then recorded using technical measuring instruments. Since the hammeris larger and heavier compared to the one used for the Model C, the fall height can bereduced without changing the impact energy. The hardness values are given in HSd.Depending on the machine model, application, and test material, various indentersand scales are used. More exact guidelines are found in the ASTM Standard Practice E448.

The Equotip tester functions according to the drop hammer principle. A carbideball 3 mm in diameter is used as indenter. After the release of a preloaded spring, theindenter is thrust against the test specimen. Impact and rebound velocity of the ball areelectronically measured at a distance of 1 mm above the test surface. From the rela-tionship between these two velocities we can ascertain an L hardness value �namedafter D. Leeb, the machine’s inventor�. Hardness measurements of up to approximately1200 HV can be calculated with this method.

The advantages of the portable machines described above include their suitabilityfor use on slanted surfaces and the short duration �only a few seconds� of the test proce-dure. The disadvantage is that these methods do not supply the hardness values withthe same high precision as the static hardness testers.

Fig. 22.2—Types of rebound hardness testers, schematic. Hardness value based on height ofrebound �a�, and hardness value based on rebound angle �b�.

Chapter 22 Dynamic Hardness 645

23Special Methods for HardnessTestingSPECIAL HARDNESS TESTING PROCEDURES INCLUDE THE MARTENSscratch hardness determination as well as the Mohs scratch hardness. In the Martensprocedure, a specimen surface under a specified test force is scratched by a diamondcone with a 90-deg apical angle. The test force F is varied until a scratch width of 10 �mis microscopically measured. In this way, a particular scratch hardness value can beattributed to the specimen.

There are continuous test procedures that allow us to record hardness progressioncurves for case-hardened or nitrided steels. In these, the width of the scratch that ap-pears is evaluated, at a constant test force, in light of the scratch length. Or, the forcetrajectory-dependent indentation process may be recorded by means of technical mea-surement instruments, much as is done in instrumented indentation testing �see Sec-tion 21.6.1�.

References „Part V…�1� Courtesy of Deutscher Verlag für Grundstoffindustrie.

�2� Courtesy of Emco-Test Prüfmaschinen GmbH.

�3� Courtesy of Struers A/S.

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Part VI:The Metallographic/MaterialographicLaboratory

24Introduction

24.1 Establishing a Metallographic/Materialographic Laboratory

WHEN ESTABLISHING A METALLOGRAPHIC/MATERIALOGRAPHIC LABO-ratory, many conditions have to be taken into consideration. The two main conditionsare: �1�What is the purpose of the metallographic/materialographic examination? Is itquality control, research, education, etc.?; �2� What is the specimen volume; few ormany specimens per day?

Another important condition is the degree of automation of the preparation pro-cess. This really depends on the volume of specimens to be prepared and the size of thespecimens, as well as the specimen quality �reproducibility�. The occupational situa-tion for the persons performing the preparation should also be taken into consider-ation.

Chapter 25 discusses the above-mentioned conditions and other important mat-ters connected to planning for and establishing a metallographic/materialographiclab, and suggestions for a number of laboratories suited for different purposes and ca-pacities will be given.

24.2 Running a Metallographic/Materialographic Laboratory

The metallographic/materialographic laboratory should be considered a productionunit, producing specimens of the desired quality at the lowest price. This means thatcorrect planning must be made, covering both the day-to-day operation and preventivemaintenance.

24.3 Occupational Safety and Health

The work in the laboratory involving machines, chemicals, etc., makes it imperativethat all relevant rules and regulations covering occupational safety are followed. Thissubject is described in Chapter 26.

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25How to Build a Metallographic/Materialographic LaboratoryA LABORATORY IS SELDOM BUILT FROM SCRATCH. AN EXISTING LABORA-tory should usually be changed, possibly moved to other locations, etc. In all thesecases it is very useful to analyze a number of factors regarding the laboratory so thatthe right changes, gradually, can be made.

25.1 Purpose

The purpose of the laboratory as part of a larger organization should be considered.The purpose may be quality inspection of parts from a running production, meaningthat the preparation with examination result should be finished in a short time, or aresearch lab with large test series that can be prepared at a steady speed with ampletime available.

Three purposes together with the capacity, number of specimens to prepare perweek, should be discussed here.

25.1.1 Quality Control „QC…The laboratory performing quality inspection ranges from the relatively small sub-supplier, who prepares a few specimens per week, to the large lab with several hundredspecimens per week.

In both cases, the specimen size and the materials to be prepared are known andoften of a limited number. This means that fixed documented procedures can be estab-lished. This ensures the reproducibility that is very important if the analysis over a pe-riod of time shall provide a true picture of the product quality.

Although a smaller lab with few specimens per week could prepare the specimensby hand and still be rational, the preparation should be performed with a small semiau-tomatic grinder/polisher to secure the reproducibility. This also makes it possible touse a rather untrained person for the preparation, which can be of advantage, when thespecimen volume is low, and it is not possible to have a full-time person on the job.

A lab with higher volume will use semiautomatic or fully automatic equipment tohave rational specimen production, at the same time securing reproducibility and aprogrammed process.

The “cost per specimen” is important �see Section 25.2.2�.If preparation time is important, electrolytic polishing should be considered if the

materials are suited for this �see Chapter 8�.A QC lab often will have the advantage of digital imaging connected to a system for

registration, connecting the metallographic/materialographic analysis with other testslike hardness, etc. �see Chapter 19�.

If a QC lab also makes failure analysis, this might indicate other types of equip-ment �see below�.

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25.1.2 Research and Education

ResearchLike the QC lab, the research lab needs a high reproducibility to secure correct inter-pretation of the materials being developed. For this reason, semiautomatic equipmentshould be used. This equipment should have a reasonable capacity, but the productionof specimens can usually be planned for and “high-production” equipment is notneeded.

For research, typically a wide spectrum of materials should be prepared and theequipment should preferably be for mechanical preparation. Electrolytic polishingand thinning �TEM� could be interesting also, electrolytic polishing resulting in“deformation-free” specimens �see Chapter 8�.

EducationAs part of education in physical metallurgy, the students often have to prepare one ormore materials, both to experience the metallographic/materialographic process andto be able to see a prepared microstructure in a microscope with their own eyes.

A group of students usually works with specimen preparation at the same time,and this can be done on a number of small grinder/polishers, either by hand or with asimple semiautomatic specimen mover.

Education is often connected to a research lab, but equipment used for researchshould not be used by the students for educational purposes.

25.1.3 Testing and Inspection Laboratories—Failure AnalysisLaboratories established for preparation of specimens for customers should be able toprepare “all materials” for a wide number of examinations. The job may be just onespecimen representing a failure, a special case �archaeology, forensic�, or a series ofspecimens. For this reason, equipment for both mechanical preparation and electro-lytic polishing should be available, “high productivity” playing a minor role, with thepossibility of preparing all difficult materials playing a major role. Preparation ofspecimens for failure analysis is often difficult because the specimen is not “regular,”but has to be taken from a work piece at a special location, and the area to be preparedis often difficult to establish. In certain cases hand preparation is preferred, but in mostcases the specimen can be mounted so that a semiautomatic grinder/polisher can beused. Therefore, even large laboratories with advanced automatic equipment, some-times engaged in failure analysis, need a small semiautomatic machine for singlespecimens.

25.2 Rationalization and Automation

The demand for more cost-efficient processes and procedures has been increasing inall parts of the society for a long time. In the metallographic/materialographic lab, thefocus is on “cost per specimen,” including all the costs covering manpower, equipment,consumables, locations, administration, energy consumption, etc.

Examples are changes in the production, the organization, or the requirements todocumentation. As a result, the lab has to produce more specimens without increasingthe personnel, or the quality of the specimens should be improved because an auto-

Chapter 25 How to Build 651

matic image analyzer has been installed. Improvements in quality have to be made veryoften without a similar increase to the budget.

The demand for a higher specimen quality and a better reproducibility is also in-creasing because of quality standards like ISO 9000 and IS 9000.

Rationalization can often be made in all steps from the work piece/specimen arriv-ing in the lab to the finished report leaving the lab. This can be in specimen handling,choice of equipment, preparation procedures, and administrative routines, includingwriting of reports and filing the micrographs. At the same time the occupational safetycan very often be improved.

Automation according to the “state-of-the-art” is limited to the preparation pro-cess from plane grinding to the finished specimen and to the automatic printing of mi-crophotographs through digital systems �see below�. In case of image analysis, this canalso be automatic �see Part IV�.

25.2.1 Reproducibility—Standards—Occupational SafetyBasically the only assurance that a microstructure is “true” depends on the evaluationdone by the person who is interpreting the structure. In most technical matters, theresult can be measured and the correctness be verified, but this is not possible with amicrostructure. A high element of subjectivity is present when it should be decidedwhether a microstructure is “true.” It is very possible, of course, to measure the struc-ture using image analysis, but whether the microstructure being measured is the truestructure representing the work piece material, or not, is based on the evaluation of anexperienced person.

For this reason, it is very important that methods are developed, documented, andfollowed when making a preparation. A proven method “guaranteeing” the true struc-ture, executed on a machine with constant parameters and uniform consumables,makes it possible �with a high certainty� to say that a running production of specimensis correct. As soon as human treatment is involved, the risk of an incorrect result willincrease.

In modern quality control �QC�, according to standards like ISO 9000 and IS 9000,the correct measurement of all results is very important. Therefore, in the case ofmetallography/materialography, the microscope should be calibrated regularly to en-sure that the analysis is correct. It is very difficult, however, to give correct “measuringdata” for the preparation process, securing a correct preparation, as mentioned above.Therefore, the responsibility of the correct structure is transferred to the skilled personevaluating the microstructure, and to support this, a documented procedure usingsemiautomatic or automatic preparation equipment should be worked out.

In a number of ASTM standards, such as Standard Test Methods for DeterminingAverage Grain Size Using Semiautomatic and Automatic Image Analysis �E 1382�, thepreparation is part of the standard, spelling out that the “true structure” must be avail-able at a high reproducibility. In most cases, however, the methods for a given materialmust be worked out in the laboratory �see Section 13.2.3�.

Occupational safety and health play an increasing role, both regarding the physi-cal work done by the operator and the total laboratory environment �see Chapter 26�.Using semiautomatic or fully automatic equipment for cutting-off, mounting, andpreparation will reduce the amount of physical power needed and, when possible, theequipment can be connected to an exhaust system to avoid contaminating the air.


25.2.2 Productivity—Cost Per SpecimenEssentially the preparation of a specimen can be seen as a “production” as any otheritem made in a production facility. This means that preparation should be constantlyanalyzed according to the following demands:• Increased productivity• Improved quality• Cost reduction

The increase in productivity can be obtained by analyzing the whole preparationprocess and calculating the cost per specimen �see below�.

Improved quality can often be achieved by using semiautomatic or automaticequipment. This also usually provides increased productivity. Cost reduction can oftenbe obtained by reducing the cost per specimen, but other factors should also be ana-lyzed to give the most cost-efficient function of the total metallographic/material-ographic lab.

The following should be taken into consideration:Development of the correct application for each material: It is very important that

the optimum process is found for a given material. One or more preparation steps canoften be omitted or times can be reduced.

Training of Personnel: The persons responsible for the preparation should betrained to optimize the use of equipment and consumables.

Service: The equipment should be serviced regularly �preventive servicing� toavoid breakdowns. If breakdowns happen, a service support should be available fromthe supplier, keeping the downtime short.

Cost per SpecimenA cost-savings analysis must be made to decide on the present cost per specimen and apossible lower cost per specimen.

The analysis is supposed to show all costs involved in making a specimen.• Operator costs• Consumable costs• Depreciation of equipment

The first step in the analysis is to decide on the actual costs.Operator costs are calculated for the total operator time used per specimen from

receiving the work piece �specimen� through to a prepared specimen that is ready forthe microscope. Consumable costs are calculated by listing all consumables used foreach preparation step and calculating the amount used per step.

For the equipment, the service costs and depreciation costs are calculated, the lat-ter based on the total investment in equipment, time of depreciation, and the interestrate.

The cost per specimen will usually be lower when using more automatic prepara-tion equipment, and often depends on the number of specimens made per day. In Fig.25.1, two curves are shown indicating the cost per specimen for a highly automatedmachine �Equipment 1� and a relatively simple piece of equipment �Equipment 2�. Itcan be seen that around 55 specimens per day, the price per specimen is lower using theexpensive machinery.

The Payback Time is interesting too. This indicates the time for how long the newequipment should operate before the savings are so high that the investment is “paidback.” Figure 25.2 shows an example of Equipment 1 mentioned earlier. The Payback


Time shows that the expensive �automatic� equipment �Equipment 1� is paid back inone year when approximately 38 specimens are prepared per day.

Additionally, the advantage of having a higher certainty for correctly preparedspecimens should be taken into consideration also, supporting the procurement of au-tomatic equipment.

25.3 Planning the Metallographic/Materialographic Laboratory

25.3.1 Basic PlanningThe metallographic/materialographic lab, like all other investments, should be subjectto a total cost-benefit analysis. It is, however, not as easy to calculate as the morestraightforward processes like a production facility. The lab is a mixture of production�specimen preparation�, analysis, reporting, and other administrative work, often witha high variation in the work load.

The metallographic/materialographic lab is established like any other lab, but anumber of specific features should be evaluated.

The lab should be split into several rooms, the basic parts including a room forcutting, a room for preparation, and a microscope room.

Fig. 25.1—Cost per specimen. Comparison between preparation with a highly automatedmachine �Equipment 1� and a relatively simple piece of equipment �Equipment 2�.

Fig. 25.2—Payback time. Payback time in years in relation to number of specimens per day forEquipment 1 in Fig. 25.1.


A good workflow should be secured. Considering the number of apparatus, the in-stallation of electric power �both 1-phase and 3-phase�, compressed air, water drains,and ventilation should be made flexible and easy to maintain The floor load should alsobe taken into consideration.

Because of the relatively large machines used in materialographic preparation, thepassages and doors need to be wide enough so that machines up to 1.3 m �4.3 ft� canpass through.

A person’s workplace in the lab should have the best possible lighting �daylight�,low noise level, and correctly placed fume hoods.

A 20–25 % spare area should be designed, if possible, to make room for future ex-pansion.

It is important to consider all demands regarding safety �cupboard for first aid,etc.� �see Chapter 26�.

With both basic and detailed planning it is important that the personnel alreadyusing the lab, or intending to work in the new lab, participate in the planning work.This ensures that a lot of problems are solved in the planning stage and the most effi-cient function is obtained.

25.3.2 Detailed PlanningFactors like type of specimen material, number of specimens to prepare, etc., will influ-ence the details in the lab.

Specimen MaterialThe specimen material influences the type of equipment used. If only one type of mate-rial is to be prepared, relatively simple machinery may be used. In the case of a vastspectrum of materials, more machinery may be needed because of the different prepa-ration methods needed.

Number of SpecimensThe average number of specimens per day will vary very much from lab to lab. A QC labmight have a hundred or more specimens per day, maybe in working shifts. In this case,a very rational preparation can take place �see Section 25.2�. In a research lab perhapsonly ten specimens per day are made on average, but the materials span widely so thatseveral types of preparation processes are available.

In some cases with very few specimens, the preparation might be performed in the“Chemical Lab” or “Materials Testing Lab.”

The Specimen Size and ShapeIn some cases the lab receives the specimens cut to the right size. In other cases largework pieces, machine parts, or stock material are received and the lab should take careof cutting out the specimen. This may require a special room for cutting, often withlarge machines.

The mounting of the specimen will vary. In mounting a large number of speci-mens, a special room for hot mounting presses should be considered. In the case ofcold mounting, fume hoods must be available.

Type of ExaminationFor labs working with QC or other types of inspection, the lab might be under timepressure, being required to deliver an analysis result in a given period of time. This


influences how the lab is organized, securing fast results and reporting, effective com-munication, etc. In some cases, the metallographic/materialographic analysis is com-bined with other examinations, like hardness testing, and care should be taken thatthese other instruments are integrated in the best possible way in the lab. In some labo-ratories, the specimens, before or after preparation, have to be treated in other labora-tories and a rational cooperation must be secured. Using a digital camera, the imagesoften necessary for reporting can easily be communicated, avoiding the more tediousphotographic work.

PersonnelPersons with different educational background and training are needed in themetallographic/materialographic lab. Cutting, mounting, and preparation work canbe done by persons with little or no metallographic/materialographic background. Forpersons without knowledge of metallography/materialography, they should be trainedthoroughly before starting the work because lack of knowledge may jeopardize thepreparation result.

Interpreting the microstructure, working out reports, etc., should be performed bypersons with the necessary education in metallography/materialography. In spite ofthe increasing use of semiautomatic equipment, it should be emphasized that the per-sonnel should be well trained and be allowed to develop experience over a long periodof time.

25.4 Equipment and Laboratory Layout

A large selection of equipment for preparation, examination, and reporting �IT� isavailable in the market. The tendency goes towards automation both regarding prepa-ration and analyzing, where the result will now be electronically communicated in ITnetworks.

It is important to select the right equipment, both to secure a high quality, cost-efficient production of specimens and to secure a certain flexibility �increase� in thenumber of specimens to be prepared and analyzed. Table 25.1 gives an overview of theequipment needed for a metallographic/materialographic lab, and in the following sec-tions examples for different labs are given.

The layout of the lab with several rooms and the correct installations, etc., alsoplays an important role to ensure an efficient specimen production. This will be dis-cussed below.

25.4.1 Equipment—Table 25.1The basic equipment is stated in Table 25.1, but in each category several models areavailable, e.g., a grinder/polisher can be hand-operated or automatic �see Chapter 7�.

In the following sections some examples are given for different sizes of labs, indi-cating the types of machines.

Small LaboratoryA laboratory with only one to ten specimens per day can be defined as a small lab. Thistype of lab can be at a sub-supplier to a large company, where a metallographic/materialographic examination is part of the specifications for the supplied product.

The following equipment should be available:


TABLE 25.1—Equipment, Accessories, and Consumables for a Metallographic/Materialographic Laboratory.

Preparation Stage Process EquipmentAccessory/Consumable

Sectioning Wet abrasive cuttingPrecision cutting

Cut-off machinePrecision cutter

Cut-off wheels,additive for coolingfluid

Shearing Shear

Sawing Hacksaw Saw blades

Bandsaw Saw bands, cutting fluid

Wire cutting Wire cutter Wire

Mounting Hot compression Hot mounting press Hot mounting resins

mounting

Cold (castable) Mounting molds Cold mounting resins

mounting

Heating of epoxy Small oven Cold mounting epoxy

Clamping (sheets) Clamp

Impregnation Vacuum impregnationapparatus

Resins with low viscosity

Vacuum pump Dye

Marking Engraving Engraver Engraving needless

Surface preparation—mechanical

Grinding Plane grinder withgrinding stone

Grinding stones,additive for cooling fluid

Grinder/Polisher/sample mover

Disks (platens),rigid composite disks(RCD),wet grinding papers,diamond disks

Belt grinder Grinding belts

Mechanical polishing Grinder/polisher/samplemover

Disks (platens),polishing cloths,

Vibratory polisher diamond consumables,lubricants,oxide consumable(Al2O3, SiO2)

Dispensing of diamondsuspension

Dosing unit Diamond suspension

Surface preparation—electrolytic

Electrolytic polishing Electropolisher ElectrolytesElectrolyte containers

Thinning for TEM Electrolytic polishing Jet-thinning apparatus Electrolytes

Cleaning Ultrasonic cleaning Ultrasonic apparatus Cleaning liquidsEthanol, cotton

Drying Drying apparatus(hair dryer)

Conservation Desiccator Desiccants

Special cupboard Protective media

Etching Chemical etching Plastic container, pair oftongs

Etchants

Electrolytic etching DC-power supply withpair of tongs

Etchants


Sectioning: Cut-off machine, table top, hand operated, cut-off wheel diameter200–250 mm �8–10 in�. For an examination of sheet products, a hand shear should beavailable. A vertical band saw might be useful also.

Mounting: Cold mounting materials with mounting cups or a hot mounting press,or both, if the investment is justified. In the case of sheet specimens, a clamp can beused for manual preparation.

Plane grinding/Fine grinding/Polishing: Rotating grinder/polisher �2 speeds�, 200or 250 mm �8 or 10 in� disk diameter. This is sufficient for manual preparation, but toensure highest reproducibility and avoid tedious work, a small specimen mover forthree or six specimens should be mounted on the grinder/polisher. This also ensures arelatively high quality of the specimens, even with a relatively unskilled operator. Adosing unit, adding diamond suspension and lubricant in an optimal way, will also im-prove quality and economy.

Microscope/Documentation: A small or medium-sized light microscope withbright field/dark field and differential interference contrast �DIC� is recommended �see

TABLE 25.1—(Continued.)

Preparation Stage Process EquipmentAccessory/Consumable

Potentiostatic etching Potentiostat

Thermal etching Oven

Vapor depositionSputtering

Vacuum chamber

Ion etching

Examination Optical microscopy Magnifying glass,Light microscope, small,medium, largeStereomicroscopeImage analysis system

ObjectivesEyepieces

Electron microscopy SEM Sample mounts

EPMA

TEM

STEM Sample mounts

Documentation Microscopy Macro camera Films, paper

Micro camera

Polaroid camera

Digital camera

PC with monitor

Video equipment

Printer

Cutter

Refrigerator

Indentation hardnesstesting

Vickers/Knoopmicroindentationhardness

Microhardness tester Indenters

Brinell/Vickers hardness Universal hardness tester Indenters

Rockwell hardness Rockwell hardnesstester

Indenters


Part III�. For making images for reporting, a Polaroid �4 in�5 in� or digital camerashould be used, the latter in connection to a PC and a printer.

Medium-Sized LaboratoryA medium-sized lab will prepare three to fifty specimens a day, mounted or unmounted�see Table 25.1�.

The following equipment can be recommended:Sectioning: Cut-off machine, table top or floor model, automatic feed, cut-off

wheel diameter 250–350 mm �10–14 in�. For large work pieces, larger automatic ma-chines with a wheel diameter up to 600 mm �24 in� are needed �see Section 2.5�. If pre-cision cutting or cutting with lowest possible deformation of the cut surface is needed,a precision cutter should be available. A bandsaw can also be useful, and a hand shearcan be used for sheet products.

Mounting: One or two hot mounting presses and consumables for cold mounting.A vacuum impregnation apparatus and a small oven for accelerating the curing of ep-oxy cold mounting resins might be included.

Plane grinding: With large specimens and a relatively high production with thespecimens fixed in holders, a special plane grinding machine is recommended using agrinding stone. In most cases, however, the plane grinding can take place on the samemachine as for fine grinding/polishing.

Fine grinding/polishing: This is preferably done on a table model, semiautomaticsystem, consisting of a grinder/polisher with a 250 or 300 mm �10 or 12 in� disk andspecimen mover with specimen holders for fixed or single specimens, or both, whichcan prepare up to six to eight specimens at a time. To obtain the highest reproducibilitya semiautomatic, programmable system with a dosing unit included is recommended.In case of a relatively high production of larger specimens, a floor-based, program-mable grinder/polisher, using specimens fixed in a holder is recommended.

To save manpower and increase the reproducibility, a fully automatic preparationsystem could be used. A fully automatic system might show a favorable cost/benefit�see Section 25.2�, especially for difficult to prepare materials.

An electropolisher could be of advantage as a supplement to the mechanicalpreparation equipment, depending on the type of material to be prepared �see Chapter8�.

Etching: Chemical etching is typically used and needs only a very low investment�see Table 25.1�. If other contrasting methods should be used, like thermal etching orinterference layers, special equipment must be procured �see Table 25.1 and Chapter9�.

Microscopy/Documentation: A good quality light microscope with good opticsshould be available. This shall have bright field/dark field, polarized light, differentialinterference contrast �DIC�, and fluorescence.

For documentation one or more of the following cameras should be available:A normal, single lens reflex camera �35 mm�, a Polaroid camera �4 in�5 in�, or a

digital camera. For all types, an automatic control unit should be connected to the mi-croscope. For a digital camera, a PC with monitor should be available and a printer.

For macro work, a stereomicroscope with camera connection should be available.A camera for macrophotography should be available also.


Large-Sized LaboratoryThe large laboratory has from 10–100/200 specimens per day, and the specimens pro-duced are very often for quality control relating to a production. Therefore, the mainconcern is to have a fast, efficient flow of prepared specimens.

The following equipment can be recommended:Sectioning: The conditions are the same as mentioned above under the Medium-

Sized Laboratory.Mounting: The conditions here are also close to the medium-sized lab, only a

larger number of mounting presses may be needed.Plane grinding: With a large number of specimens and using specimen holders

with fixed specimens, plane grinding can be a bottleneck; therefore, a special planegrinding machine is recommended, using a grinding stone. In some cases, the planegrinding will be part of a fully automatic system �see below�.

Fine Grinding/Polishing: With a large number of specimens, handling, manualcleaning, etc., should be avoided to save time. Therefore, fully automatic systems witha high number of preparation programs and built-in dosing and cleaning are recom-mended. These systems can be used for both “normal” specimen sizes and for large,unmounted specimens. The only manual handling is placing the specimens in a holderand removing the finished specimen ready for etching/microscopy from the holder.

An alternative is one or more of the systems described above under Medium-SizedLabs. Electropolishing may be useful also, as mentioned above.

Etching/Microscopy/Documentation: This is the same as mentioned underMedium-Sized Labs.

25.4.2 Layout—Furniture—InstallationsThe layout of a metallographic/materialographic lab should include several rooms,making it possible to keep the different activities separated. The furniture should beappropriate and the installations specifically made to ensure an effective working pro-cedure.

The space between tables and machines should be so that several persons canwork and move around in the lab without disturbing each other. During planning,space should also be reserved for extension considering a period of three to five years,often, a relatively new lab gets crammed after a few years.

RoomsA metallographic/materialographic lab should have at least three rooms, each con-nected with a door for easy passage from room to room. A lab for quality control pur-poses could have three rooms, and a research lab, covering a wide material field andmany different processes might have four rooms.

Room 1: This is the room for “dirty” processes, sectioning, and mounting. If coldmounting is performed in this room, a fume hood should be installed. Plane grindingalso may be done in this room if a special machine is available for plane grinding. Asink should be installed in this room, and the idea is that a specimen, leaving the room,is clean and ready for the proper preparation in Room 2.

Room 2: This is the main area of the lab, containing a preparation area and possi-bly an area for the personnel for working out preparation reports, etc. �see below�. Ma-chines for preparation should be placed so that persons passing by do not disturb theoperator. Table space around a machine should be 80–100 cm �3–4 ft� to ensure an


efficient working order and make room for possible service work on the machine.At least one or two sinks should be placed very close to the grinder/polisher. It must

be understood that cleaning is a very important part of the preparation process, and theoperator should be able to clean the specimens when only moving a few steps.

Another sink is placed under a fume hood to be used for chemical etching. Thesame hood, if large enough, can be used for electrolytic polishing, with the polishingtable being placed under the hood.

A small, low cost, upright or inverted microscope, placed near the preparation ma-chines, is also useful to examine the specimens between the preparation steps. Otherinstruments like hardness testers are also placed in this room. Space should be avail-able for desks with PCs for the personnel, preferably separated from the machine area,if these are not placed in connection with Room 3 together with the microscopes.

Room 3: This is the microscope room with a large microscope and possibly astereomicroscope and other examining instruments. The working places for the per-sonnel can be placed in this room also, separated from the microscopes, preferably as aseparate “office.” In the ideal microscope room, an air conditioning system keeps aconstant temperature. Specimens can also be stored in this room in a desiccator �onefor each metallographer� or a special cupboard.

Room 4: In certain cases, a fourth room may be recommended. This room will takeover the “etching functions” of Room 2. The room will have one or two fume hoods foretching, electro polishing, and other processes that must be kept under strict control.

Darkroom: For photographic work, one or two darkrooms will be necessary, butthis won’t be necessary if only digital photography is used.

FurnitureLaboratory furniture is available from many suppliers, but it should be taken into con-sideration that this furniture is made typically for chemical labs, not metallographic/materialographic labs. The most important points to observe are the following: Themetallographic/materialographic machine has a certain height, and the working areaof the machine is often too high for convenient work if the table is a normal lab table.The surfaces of tables, etc., should be resistant to acids, alcohol, etc. Drawers for thegrinding/polishing disks should be available, preferably placed under the tabletopsvery close to the machines. Shelves for consumables like cut-off wheels, grinding pa-per, etc., and storing space for other consumables, specimen holders, etc., should beclose to the machines, and correctly made storage space for chemicals, glass articles,etc., should be close to fume hoods. Channels for taking pipes, tubes, and cables to themachines should be made in the tables.

Other furniture is solid tables for microscopes, special cupboards for storing ofspecimens, cupboards for archiving, etc., shelves for a small library, and a refrigeratorfor storing of polaroid films, etc.

InstallationsThe metallographic/materialographic lab should have the following installations:

Hot/cold water at all sinks and compressed air preferably at all sinks and at alltables and places to be used for equipment. The compressed air should be clean, pass-ing a water/oil separator and a particle filter. Adequate three-phase and one-phase elec-tricity should be taken to all tables and places to be used for equipment, especially cut-off machines require a high amperage.

Drainage should be installed in all tables and places to be used for equipment. The


drainage should be made according to the regulations of the local authorities, takinginto consideration that acid and other chemicals together with debris from the prepa-ration process will flow in the drainage system.

For installations regarding protection of personnel see Chapter 26.

25.5 Maintenance

The most obvious reason for maintaining the laboratory in good working order iseconomy. A badly organized laboratory that cannot carry out its work properly andtimely can cause unnecessary additional lab expenses and costs due to delayed produc-tion.

Another important reason to focus on quality inspection and competitiveness isthat the laboratory is a showcase for the company. Any manufacturing company thatwants to attract customers and convince them of the quality of its goods needs a wellequipped and presentable laboratory. A well run metallographic/materialographiclaboratory with a good working atmosphere will reflect positively on the company’simage.

The maintenance can be split into organizing, cleaning, and servicing.

25.5.1 OrganizingAccessories and consumables for machines should be in easy reach of the operators.Special lab furniture or wall shelves help to keep grinding paper, cut-off wheels, polish-ing cloths, and disks out of the way but still accessible. In a metallographic/materialo-graphic lab a large variety of small items are needed in everyday operation. Small toolor tackle boxes help to keep screws, tweezers, springs, rings, “dummy” samples in or-der. Wire racks over the sink are essential for storing wet glassware.

It is always important to have enough consumables available to guarantee uninter-rupted work.

Large quantities of consumables should not be stocked in the laboratory, but in themain storeroom because they take up too much of the valuable space in the lab.

25.5.2 CleaningKeeping the machines and work area clean is one of the most important matters in ametallographic/materialographic laboratory. Every machine should be wiped cleanwith a wet cloth before the staff leaves in the afternoon. This should also be done beforeshift change, so that the incoming operators start with clean machines. If this routine isnot possible, a specific day or time should be set aside each week for cleaning the ma-chines.

Recirculation cooling units have to be cleaned and refilled at regular intervals, atleast once a month depending on the workload. The spray nozzles of certain automaticdiamond dispensing systems must be cleaned occasionally to avoid drying of the dia-mond suspensions inside the nozzles.

As a rule, rigid composite disks �RCDs� and polishing cloths should not be cleanedregularly. However, they can be cleaned with water/soap or ethanol, or both, if toomuch debris has built up on the surface and stops them from grinding/polishing prop-erly, or if they are contaminated.


25.5.3 ServicingRegular service checks ensure that the equipment is always in a correct working condi-tion. This is crucial because correct maintenance is the basis of reliability, avoidingirritating stops, and reproducibility, and securing the correct preparation result, evenover a long period of time.


26Occupational Safety and Health inthe Metallographic/Materialographic LaboratoryOCCUPATIONAL SAFETY AND HEALTH ARE IMPORTANT IN A METALLO-graphic/materialographic labs considering the use of machines, chemicals, plastics,etc.

The dangers in the metallographic/materialographic laboratory will be discussed,and a special section will describe dangerous and hazardous materials. In Section26.1.8 the ASTM Guide for Metallographic Laboratory Safety �E 2014� will be shortlydescribed, the only standard specifically covering the safety in the metallographic/materialographic lab. The standard is stated in full in the CD-ROM included in thismanual.

At the end of this chapter, the most important rules and regulations for safety andhealth covering the metallographic/materialographic lab will be stated.

26.1 Dangers in the Metallographic/MaterialographicLaboratory

The laboratory having functions like cut-off, specimen preparation, and etching in-volves a number of potential dangers. In the following the most important precautionsregarding safety and health are mentioned, not claiming that all potential dangers andnecessary safety and health measures are mentioned.

26.1.1 SectioningEye protection and gloves should be used when working with machines and tools forsectioning. Abrasive cut-off machines will have a hood �shield� protecting the operatoragainst cooling fluid, pieces from a broken cutting wheel, etc. According to safety regu-lations, the machine can only be started when the hood is closed. When cutting withbakelite or rubber wheels, fumes develop, and at larger machines the cutting chambershould be connected to an exhaust system.

For bandsaws, the operator will guide the work piece into the band, and it is veryimportant that this is done indirectly using a distance piece or a special holder for thework piece.

A Standard Operating Procedure �SOP�, including a Job Safety Analysis �JSA� �seeSection 26.2.3/4� should be completed for each piece of equipment being used forsectioning.

26.1.2 MountingWith hot compression mounting, the main danger is the high temperatures used in themounting presses. Gloves should be used for handling of the hot mounts, and when

664

filling mounting material such as bakelite powder into the press, inhalation of dustshould be avoided.

A SOP, including a JSA, should be completed for each piece of equipment.At cold �castable� mounting there are several potential dangers. The cold mount-

ing resins are potentially dangerous to health �see Section 26.1.7�, and therefore allhandling should be done with rubber �latex� gloves to avoid skin contact and the mixingand hardening shall take place under a fume hood. When using an oven for accelerat-ing the hardening of epoxy, gloves should be used.

MSDS information should be available for all mounting resins �see Section26.2.2�.

26.1.3 Mechanical PreparationThe semiautomatic preparation machines are basically safe to use. If a specimen isslung away from the specimen holder during rotation, the specimen will usually bekept inside the machine, and the speeds of the disks and holders are relatively low. Toavoid dirty hands, especially when using rigid composite disks that create a very finesludge that is difficult to remove from the skin, rubber or plastic gloves should be used.For large machines using a flammable alcohol-based lubricant, the alcohol fumes canbe rather strong, and the machine should be placed in connection to a fume exhaustsystem. A better solution might be to change the lubricant to a water-based type.

When working with semiautomatic machines, a laboratory coat should be used toavoid that ties or other pieces of clothing get into contact with the rotating specimenholder.

Fully automatic systems are totally enclosed and will not operate if the protectiveshields are not closed.

At manual grinding/polishing, care should be taken that a specimen released bythe operator and flying from the grinding/polishing disk will not injure other persons.

A SOP, including a JSA, should be completed for all mechanical and polishingequipment.

26.1.4 Electrolytic Polishing/EtchingThe most serious potential danger at electrolytic polishing and etching is the mixing,handling, use, and storing of electrolytes �see Section 26.1.5�. During the polishing pro-cess, care should be taken to avoid heating of the electrolyte that may cause a fire oreven an explosion. It is important to keep a correct level of electrolyte in the electrolytecontainer because too little electrolyte might give air pockets in the polishing chambercausing a spark between anode and cathode, which might ignite the alcohol in the elec-trolyte.

A SOP, including a JSA, should be completed for each electropolisher.

26.1.5 Etching—Etchants—ElectrolytesThe etching procedure should be performed using gloves and eye protection under afume hood. The most serious potential dangers are connected to the mixing, handling,and storing of the chemicals used for etchants, and the same is the case for electrolytes.The user should have sufficient information on all the chemicals used from trainingand MSDSs, which should be available in the laboratory �see Section 26.2�. Etchants/electrolytes are mostly solution mixtures of different materials mixed in the laboratory.During the mixing, very dangerous reactions can be established like fire, explosion, anddissolution, creating dangerous substances. The etchants are generally more danger-

Chapter 26 Occupational Safety and Health 665

ous than the electrolytes because they contain very oxidizing substances.As a rule, the mixing should always start with the water �alcohol� and then mix the

other ingredients into this. A special procedure, however, should often be followed toobtain the necessary safety, and certain combinations of chemicals are known to bedangerous. Information on this must be available in the laboratory. A number of themost hazardous materials are mentioned below, and further information can be ob-tained in the Standard Guide on Metallographic Laboratory Safety �E 2014� in Section26.1.8 of this book.

Acetic Acid: Extreme care should be taken when mixing with other acids like per-chloric acid and nitric acid. Mixtures of acetic acid and perchloric acid should beavoided.

Chromic Acid: Very strong oxidation substance, very strong reaction with organicor easy to oxidize material and it cannot be safely mixed with acetic acid and most or-ganic liquids, such as alcohols or glycerol. Poisonous.

Nitric Acid: Strong oxidizing acid, creating gases with many organic materials andmetals. Do not store solutions of more than 3 % nitric acid in ethanol.

Perchloric Acid: Very aggressive acid that can cause serious explosions at higherconcentrations. Very dangerous at contact with metals that oxidize easily, such as bis-muth. Contact to organic material should also be avoided; if absorbed in organic mate-rial the material must be placed in water. Organic material should never be used towipe up perchloric acid.

Picric Acid: Aggressive oxidizer and should always be stored in wet condition. Indry condition the risk of explosion is high. Storage should be cool and fire safe.

Toxic SubstancesToxic materials are substances that, when inhaled or taken in by the mouth or by theskin, can lead to death or serious damage to the health. These substances are listed byofficial organizations like the National Institute for Occupational Safety and Health�NIOSH� �see Section 26.5�, and rules are defined for their use, storing, handling anddisposal. Also, for many substances the permissible exposure through air and skin isstated �see Section 26.5�.

A number of toxic substances with CAS Nos. �see Section 26.5.1� often used in ametallographic/materialographic laboratory are mentioned below.

Chemicals based on the metals Be, Pb, Cr, Cu, Ag, U, Sn, Zn �not ZnO2�: Poisonousas liquids or as vapor.

Chlorinated Carbohydrates: These solvents are very dangerous to inhale.Cyanides �CAS No. 460-19-5�: These react strongly with acids, even the CO2 con-

tent in humid atmospheric air gives a reaction. Very poisonous.Hydrofluoric Acid, Anhydrous �CAS No. 7647-01-0�: In concentration higher than

0.5 % the acid is very dangerous, making very serious damage to tissue. Attacks almostall metals and glass. Very dangerous.

Mercury �CAS No. 7439-97-6�: Chemicals bond on mercury and mercury vapor arepoisonous.

Methanol �CAS No. 67-56-1�: Poisonous.Oxalic Acid �CAS No. 144-62-7 �Anhydrous�� CAS No. 6153-56-6 �Dihydrate��: In

concentrations higher than 5 % oxalic acid is poisonous.Phosgen �Carbonyl Chloride� �CAS No. 75-44-5�: Very dangerous to the respiratory

system.


Flammable LiquidsFlammable liquids are used in metallographic/materialographic preparation for elec-trolytic polishing, lubrication, etching, and cleaning.

OSHA �see Section 26.5� defines flammable liquids. “Class I liquids” as any liquidhaving a flashpoint below 100°F �37.8°C�, except any mixture having componentswith flashpoints of 100°F �37.8°C� or higher, the total of which make up 99 % or moreof the total volume of the mixture.

Liquids, which are somewhat harder to ignite, with a flash point above 100°F�37.8°C� are called combustible liquids, “Class II liquids.” These are defined by OSHAas liquids with flashpoints at or above 100°F �37.8°C� and below 140°F �60°C�, exceptany mixture having components with flashpoints of 200°F �93.3°C� or higher, the vol-ume of which make up 99 % or more of the total volume of the mixture.

“Class III liquids” are even harder to ignite and are defined by OSHA as “liquids.”Class IIIA liquids include those with flashpoints 140°F �60°C� or above and below

200°F �93.3°C�, except any mixture having components with flashpoints of 200°F�93.3°C�, or higher, the total volume of which make up 99 % or more of the total volumeof the mixture.

Class IIIB liquids include those with flashpoints at or above 200°F �93.3°C�.When a combustible liquid is heated for use to within 30°F �16.7°C� of its flash-

point, it should be handled in accordance with the requirements for the next lowerclass of liquids.

All containers with flammable liquids should be marked �see Section 26.5.3�.The number of flammable liquids stored in the lab should be kept at a minimum

and carefully protected against heat and against possible ignition.All rules and regulations should be followed carefully when handling flammable

liquids. Heating in open containers should be done with special care, using a fumehood and special electric heating plates.

The flammable liquids are also very often dangerous to health and precautionsshould be taken according to the MSDS for the liquid �see Section 26.2.2�.

Disposal can be a problem and should be done according to rules and regulationsby local authorities.

26.1.6 DustDust can be developed from specimen material, abrasives, or powders used for mount-ing. This should be suppressed as much as possible, because even if not toxic, the dustcan give respiratory problems. Dust from metals can be toxic and should be avoided.

26.1.7 Cold „Castable… Mounting ResinsAll the cold �castable� mounting resins described in Section 3.8 are potentially danger-ous to health.

EpoxyThis material, both resin and hardener, can damage the skin, causing allergic reac-tions. The material should never come in contact with skin and the vapors should notbe inhaled. All work with epoxy should take place under a fume hood using personalprotective equipment �PPE� specified in the MSDS. It is recommended that containersand stirring pins are disposed of after mixing.

The epoxy is not dangerous when it has fully hardened.


Acrylics and PolyestersMixing should always take place under a fume hood and gloves should be used whenhandling these materials to avoid inhalation and skin contact.

26.1.8 Standard Guide on Metallographic Laboratory Safety „E 2014…This ASTM guide covers the outline of the basic safety guidelines to be used in ametallographic/materialographic laboratory. Safe working habits are discussed forvarious tasks performed in the laboratory and the guide goes into more details of thework than stated above in this chapter. Please refer to ASTM E 2014 in the CD-ROMincluded with this book.

26.2 Safety Information

It is very important that the user of a chemical substance is informed on all importantfacts regarding the substance. According to the OSHA Standard 29 CFR 1910.1200 �seeSection 26.5.3�, any chemical should be labeled for safe identification and a MaterialSafety Data Sheet �MSDS� should be available on the working place for any chemical.

26.2.1 IdentificationIt is important that the dangerous materials can be identified. Materials that are in oneway or another hazardous should be marked with a label according to a system, asstated in the standards �see Section 26.5�. This label must express a number of factsregarding the substance so that the user is able to evaluate the possible hazard. Thecontainer with the substance is usually labeled by the supplier, but in cases wherechemicals are taken into smaller containers in the lab and in other cases where theoriginal container is not used, a new label must be used.

Below two “official” identification systems, NFPA and EU �EC�, used by suppliersof chemicals and one system, HMIS, developed for use in the laboratory, are described.

NFPA 704 Hazard Identification Ratings SystemThis identification system, developed by the National Fire Protection Association�NFPA� uses the “Hazard Diamond” �see Fig. 26.1� for identification of health, flamma-

Fig. 26.1—The NFPA diamond symbol: 1� Indication of color and type of hazard of the foursmall diamonds. 2� Example of number ratings and symbol.


bility and instability �reactivity� �see also Section 26.5.11�. The diamond is broken intofour smaller diamonds one each blue, red, yellow, and white. The numbers in the threecolored diamonds range from 0 �least severe hazard� to 4 �most severe hazard�. Thefourth �white� diamond is left blank and is used only to devote special fire fightingmeasures/hazards, indicated with special symbols.

Meaning of Colors—Ratings of NumbersRed: FLAMMABILITY �Instability� is the degree of susceptibility to burning.

0 Will not burn.1 Must be preheated to burn. Flash point above 200°F �93.5°C�.2 WARNING: Ignites with moderate heat. Flash point 100°F–200°F �38–93.5°C�.3 HAZARDOUS: Ignites at room temperature. Flash point 73°F–99°F �23–37°C�.4 EXTREMELY DANGEROUS: Highly flammable liquids and explosive gases. Flash

point below 73°F �23°C�.

Yellow: REACTIVITY �Instability� is the degree of susceptibility of materials to re-lease energy.

0 Normally stable at all temperatures. Not reactive with water.1 CAUTION: May become unstable when heated or mixed with water.2 HAZARDOUS: Normally unstable or may have violent chemical change when mixed

with water.3 DANGEROUS: Explodes with exposure to confined heat, shock, or when mixed with

water.4 EXTREMELY DANGEROUS: Explodes at room temperature.

Blue: HEALTH HAZARD is the degree of injury from burning materials.

0 Creates no unusual hazard.1 CAUTION: Causes irritation or minor injury.2 HAZARDOUS: Intense exposure may be harmful.3 EXTREMELY DANGEROUS: Avoid skin contact and inhalation.4 FATAL: Too dangerous to enter without specialized protective equipment.

White: OTHER indicates special warnings.

ACID acidALK alkaliCOR corrosiveOXY oxidizing chemicals�� radiationP subject to polymerization when mixed with waterW— do not use water

EU „EC… Identification SystemThe European Union �EU� has issued a directive, Council Directive 67/548/EEC of 27June 1967, covering classification, packaging, and labeling of dangerous substances.


According to this directive, all dangerous substances sold in the EU, the EuropeanEconomic Area and selected other countries, should be marked with a labeling symboland one or more Risk Phrases and Safety Phrases.

Labeling SymbolsThe symbols indicate the basic serious dangers, expressed in a figure, and a short textexpressing the Category of Danger, Symbol Letter, and Indication of Danger �see Fig.26.2�.

Risk Phrases—Safety PhrasesTo give further information to the user of the substance, one or more Risk Phrases �RPhrases� and Safety Phrases �S Phrases� should be indicated. The phrases are oftencombined �see below�. A high number of R and S phrases are available and a few ex-amples are given below, indicating the number of the phrase.

Examples of R Phrases:

R1 Explosive when dryR10 FlammableR20 Harmful by inhalationR21 Harmful in contact with skinR20/21 Harmful by inhalation and in contact with skinR24 Toxic in contact with skinR25 Toxic if swallowedR24/25 Toxic in contact with skin and if swallowed

Examples of S Phrases:

S1 Keep locked upS15 Keep away from heatS20 Do not eat or drink when usingS24 Avoid contact with the skinS25 Avoid contact with eyesS24/25 Avoid contact with skin and eyesS36 Wear suitable protective clothingS37 Wear suitable gloves

HMIS: Hazardous Materials Identification SystemIn case the user makes the labeling, this can be supported by systems developed for thispurpose.

HMIS® is a complete program that helps employers comply with OSHA’s HazardCommunication Standard �HCS�. The program uses a numerical hazard rating system,labels with colored bars giving information on health, flammability, and reactivity haz-ards. Training material is provided to inform workers of chemical hazards in the work-place �see Section 26.5.12�.

26.2.2 Material Safety Data Sheet „MSDS…A Material Safety Data Sheet �MSDS� is designed to provide both laboratory personneland emergency personnel with the proper procedures for handling or working with a


particular substance. MSDSs include information such as physical data, health effects,first aid, reactivity, storage, disposal, protective equipment, and spill/leak procedures.These are of particular use if a spill or other accidents occur.

MSDSs are made according to the OSHA Standard on Hazard Communication�HCS� or the EC Directive on Safety Data Sheets �see Section 26.5�.

MSDSs are meant for:

Fig. 26.2—EU labeling system. Symbols �pictograms� with words and letters indicatingcategories of danger.


• Employees who may be occupationally exposed to a hazards at work.• Employers who need to know the proper methods for storage, etc.• Emergency responders such as fire fighters, hazardous material crews, emergency

medical technicians, and emergency room personnel.MSDSs are not meant for consumers. An MSDS reflects the hazards of working

with the material in an occupational fashion. For example, an MSDS for a given paintis not highly pertinent to someone who uses a can of paint once a year, but is extremelyimportant to someone who does this in a confined space for 40 hours a week.

The MSDS FormatThe formats of MSDSs tend to vary, but they usually convey the same basic kinds ofinformation.

Supply of MSDSMSDSs should be kept at the workplace. They are usually delivered by the supplier of agiven product. If it is not delivered, ask the supplier for immediate delivery. For com-monly known substances, MSDSs can be obtained from an OSHA office or science li-brary. Many organizations and chemical suppliers, like Cornell University and Sigma-Aldrich have databases with MSDS on the Internet.

26.2.3 Standard Operating Procedure „SOP…Standard Operating Procedures �SOPs� can be made for chemicals or processes andshall contain the operating procedure in relative detail so that an operator can performthe procedure in a satisfactory way without risk. Often at procedures involving hazard-ous materials or other potential risks a Job Safety Analysis �JSA� is included in the SOP�see below�.

26.2.4 Job Safety Analysis „JSA…The Job Safety Analysis �JSA� is a very effective means of helping reduce accidents andinjuries in the workplace. Any job that has hazards or potential hazards is a candidatefor a JSA. Based on the operating procedure �SOP�, the potential hazards for each stepin the working process are identified. It is very important to look at the entire environ-ment to determine every hazard that might exist. Based on the steps in the workingprocess and potential hazards, it is decided what actions are necessary to eliminate,control, or minimize hazards that could lead to accidents, injuries, damage to the envi-ronment, or possible occupational illness.

26.3 Disposal of Chemicals

Disposal of chemicals should follow the local rules and regulations. These can varyvery much from place to place and therefore it is very important to obtain the rulesfrom the local authorities.

As a common rule, the chemicals should be kept separated. Strongly oxidizingchemicals especially should not be mixed with other chemicals. The chemicals for dis-posal should be carefully categorized so that no mistake can take place when the wasteis transported and treated further.

Typical categories could be:�1� Chlorinated hydrocarbons like trichloroethylene


�2� Hydrocarbons containing aromatic solvents like xylene, terpentine, kerosene�3� Hydrocarbons not containing aromatic solvents like acetone, ketones, alcohols�4� Acidic, aqueous solutions containing chromium compounds�5� Acidic, aqueous solutions containing nitric acid, but not hydrofluoric acid�6� Acidic, aqueous solutions containing hydrofluoric acid or HF salts�7� Acidic, aqueous solutions containing hydrochloric acid, sulfuric acid or phos-

phoric acid�8� Basic aqueous solutions containing metal compounds but not cyanide�9� Metal sludge containing chromium, copper, nickel, zinc, lead, cadmium and silver

26.4 Occupational Safety in General

26.4.1 StandardsIn the sections above, the hazards of chemicals and machines have been discussed.

As a rule, the machines and apparatus are designed and manufactured accordingto relevant standards. These are the “technical” standards, “safety” standards, and “oc-cupational” standards. The “occupational” standards, describing the conditions, whenworking in the laboratory concerning machines and chemicals, can be the OSHA stan-dards No. 29 CFR 1910.212, General Requirements for All Machines, No. 29 CFR1910.215, Abrasive Wheel Machinery, No. 29 CFR 1910.95, Occupational Noise Expo-sure, No. 29 CFR 1910.120, General Description and Discussion of the Levels of Protec-tion and Protective Gear, and the important Hazard Communication standard, No. 29CFR 1910.1200 �see Section 26.5�.

26.4.2 TrainingIt is very important that the personnel be trained, both in using the machines and otherequipment, and in health and safety precautions. Not only the training in the practicaluse, but an education in the correct attitudes is also important.

26.4.3 Maintenance and ServiceIt is important that all equipment, building parts, and installations are kept in goodworking order and repair is made immediately in case of failure.

Unauthorized personnel should not perform repair work.

26.5 Standards and Regulations—Organizations

A number of American and International organizations are responsible for issuingstandards and regulations connected to occupational safety and health in themetallographic/materialographic laboratory.

The first section below states a number of abbreviations used in connection withsafety and health.

26.5.1 Designations and Abbreviations Used to Describe a ChemicalSubstanceCa: A substance NIOSH �see below� considers a potential occupational carcinogenCAS Number: Chemical Abstract Service Registry Number. This number identifieseach chemical. The Chemical Abstracts Service is a division of the American ChemicalSociety


IDLH: Immediately Dangerous to Life or Health ConcentrationsPEL: Permissible Exposure LimitPPE: Personal Protective EquipmentREL: Recommended Exposure LimitRTECS: Registry of Toxic Effects of Chemical Substances �see Section 26.5.4�STEL: Short-Term Exposure Limit as designated by “ST” preceding the valueTLV: Threshold Limit Value, issued by ACGIH �see Section 26.5.8�TWA: Time-Weighted Average �used in REL�UN Number: Four digit number to identify hazardous chemicals �transport�.

26.5.2 ASTM StandardThe only standard that directly describes the safety in the metallographic/material-ographic laboratory is issued by ASTM.

Standard Guide on Metallographic Laboratory Safety �E 2014� covers the outlineof the basic safety guidelines to be used in a metallographic/materialographic labora-tory. This standard is stated with its full text in the CD-ROM included with this book�see Section 26.1.8�.

All other standards �see below� are directed towards the problems in general andspecific matters inside and outside the metallographic/materialographic lab. E 2014,being specific regarding metallographic/materialographic labs, makes it an importantdocument that should be followed by all metallographic/materialographic labora-tories.

26.5.3 OSHA—OSHA StandardsIn 1970, the Occupational Safety and Health Act was passed by the U.S. Congress, es-tablishing NIOSH �see below� and OSHA.

Occupational Safety and Health Administration �OSHA� in the U.S. Department ofLabor has issued a number of regulations �standards� covering occupational safety andhealth in laboratories in general, these also covering the metallographic/material-ographic laboratory.

In the following, the most important standards are described in short form, withthe important Hazard Communication Standard in relative detail.

Standard Title: Hazard Communication StandardStandard Number: 29 CFR 1910.1200

The Hazard Communication Standard �HCS�, sometimes called the Right toKnow law or HazCom, is a set of regulations first promulgated in 1988 by the Office ofOccupational Safety and Health Administration �OSHA�. HCS’s purpose is to ensurethat the hazards of workplace chemicals are evaluated, and that information on thehazards is provided to employers and employees. Details of the standard are providedin parts 1910.1200 of the Code of Federal Regulations �CFR� of Chapter XVII of Title 29under the Department of Labor. HCS covers nearly all employers and is applicable tomost work operations where hazardous materials are present.


Contents:In short, the standard requires that every affected employer must establish a pro-

gram to inform the employees of the hazards associated with the materials in theirworkplace. The program must have five main components as follows:• Written Hazard Communication Program documentation• Identifying and keeping an inventory of hazardous chemicals• Obtaining and keeping material safety data sheets �MSDS� on the identified haz-

ards• Ensuring that the hazardous materials are labeled with name and hazard• Training employees on the standard, safety information, labeling, and protective

measures

Hazardous Chemicals/MaterialsThe HCS covers chemicals in all physical forms—liquids, solids, gases, vapors, fumes,and mists—whether they are “contained” or not. The hazardous nature of the chemicaland potential for exposure are the factors that determine whether a chemical is cov-ered. If it is hazardous and there is potential for exposure, the rule applies.

Written ProgramUnder the standard each laboratory �employer� must complete and keep a written Haz-ard Communication Program. The written program describes how the requirementsfor labels and other forms of warning, material safety data sheets �MSDSs�, and em-ployee information and training are implemented in the workplace. It indicates who isresponsible for MSDSs, labels, warning signs, and training, as well as the location ofthe inventory. MSDSs and other information and resources pertaining to hazardouschemicals and safety measures. An inventory list of hazardous chemicals is required tobe maintained as part of the written program.

Chemical InventoryThe person working in the laboratory needs to know about the hazards to be able toprotect oneself. The leader of the laboratory is responsible for establishing an inven-tory of hazardous chemicals.

All potentially hazardous chemicals in containers should be registered and chemi-cals possibly generated in work operations should be included, including vapor, fumes,dust, etc. In the inventory, information based on the labels and the MSDSs made avail-able by the supplier of the chemical is stated.

MSDSThe role of the MSDS is to provide detailed information on each hazardous chemical,including its potential hazardous effects, its physical and chemical characteristics, andrecommendations for appropriate protective measures. This information is useful fordesigning protective programs, as well as informing the chemical user of the hazards.MSDSs must be readily accessible to users when they are in their work areas. Somelaboratories keep the MSDSs in a binder in the individual work area or in a centrallocation in the department.

An MSDS should be available for each hazardous chemical used in the lab. TheMSDS must be in English. The MSDS should be delivered by the supplier, and it shouldinclude all of the information required under the rule. If an MSDS is not supplied auto-


matically it should be requested for. If an MSDS is obviously inadequate an appropri-ately complete one should be requested.

Employees should not use or be exposed to any chemicals for which the safety datahave not been reviewed and appropriate safety measures implemented.

LabelsContainers of hazardous chemicals must be labeled, tagged, or marked with the iden-tity of the material and appropriate hazard warnings. The original label must includethe identity of the material, appropriate hazard warnings, and the manufacturer nameand address. The identity used by the supplier may be a common or trade name, or achemical name. The hazard warning is a brief statement of the hazardous effects of thechemical �“flammable,” “causes lung damage”�. Labels frequently contain other infor-mation, such as precautionary measures �“do not use near open flame”�. Labels mustbe legible and prominent.

Secondary Containers Label and SignsIf materials are transferred from the original container into other containers, thesemust be labeled as well. Depending on the employers written plan, the secondary labelsmay be warning symbols, text, or use a numerical hazard rating system, such as HMISand NFPA �see Section 26.2�.

Large containers or storage units containing hazardous chemicals or mixturesmust also be labeled or have warning signs. It is strongly recommended that otherwarning or caution signs be placed in the work areas to remind individuals of the haz-ards and of the protective equipment that may be necessary in the area.

Employee Information and TrainingAn employee working with hazardous chemicals must receive both information andtraining on the hazard communication.

Information and training may be done either by individual chemical, or by catego-ries of hazards �such as flammability or carcinogenicity�. If there are only a few chemi-cals in the laboratory, each chemical may be discussed individually. Where there arelarge numbers of chemicals, or the chemicals change frequently, training may be basedon the hazard categories �e.g., flammable liquids, corrosive materials, carcinogens�.Employees must have access to the substance-specific information on the labels andMSDSs.

The underlying purpose of the HCS is to reduce the incidence of chemical sourceillnesses and injuries. In general, the most important aspects of training are to ensureemployees are aware that they are exposed to hazardous chemicals, that they knowhow to read and use labels and material safety data sheets, and that, as a consequenceof learning this information, they are following the appropriate protective measures�e.g., personal protective equipment, safe procedures, engineering controls�.

Frequently Asked Questions on HCS „HAZCOM…HCS being an important standard, the answers to a number of questions can be ofinterest.

What are the containers labeling requirements under HCS?Under HCS, the manufacturer, importer, or distributor is required to label each con-tainer of hazardous chemicals. If the hazardous chemicals are transferred into un-


marked containers, these containers must be labeled with the required information,unless the container into which the chemical is transferred is intended for the immedi-ate use of the employee who performed the transfer.

Can MSDSs be stored in a computer to meet the accessibility requirementsof HCS?If the employee’s work area includes the area where the MSDSs can be obtained, thenmaintaining MSDSs on a computer would be in compliance. If the MSDSs can only beaccessed out of the employee’s work area�s�, then the employer would not be in compli-ance with HCS.

When is the supplier required to distribute MSDSs?Hazard information must be transmitted on Material Safety Data Sheets �MSDSs� thatmust be distributed to the customer at the time of first shipment of the product. TheHazard Communication Standard also requires that MSDSs be updated by the chemi-cal manufacturer or importer within three months of learning of “new or significantinformation,” regarding the chemical’s hazard potential.

What is considered proper training under HCS?Employees are to be trained at the time they are assigned to work with a hazardouschemical. The intent of this provision is to have information prior to exposure to pre-vent the occurrence of adverse health effects. This purpose cannot be met if training isdelayed until a later date.

The training provisions of the HCS are not satisfied solely by giving the employeethe data sheets to read. An employer’s training program is to be a forum for explainingto employees not only the hazards of the chemicals in their work area, but also how touse the information generated in the hazard communication program. This can be ac-complished in many ways �audiovisuals, classroom instruction, interactive video�, andshould include an opportunity for employees to ask questions to ensure that they un-derstand the information presented to them.

Training need not be conducted on each specific chemical found in the workplace,but may be conducted by categories of hazard �e.g., carcinogens, acutely toxic agents�that are or may be encountered by an employee during the course of his duties.

Furthermore, the training must be comprehensible. If the employees receive jobinstructions in a language other than English, then the training and information to beconveyed under the HCS will also need to be conducted in a foreign language.

What are the requirements for refresher training or retraining a new hire?Additional training is to be done whenever a new physical or health hazard is intro-duced into the work area, not a new chemical. For example, if a new solvent is broughtinto the workplace, and it has hazards similar to existing chemicals for which traininghas already been conducted, then no new training is required. As with initial training,and in keeping with the intent of the standard, the employer must make employeesspecifically aware which hazard category �i.e., corrosive, irritant, etc.� the solvent fallswithin. The substance-specific data sheet must still be available, and the product mustbe properly labeled. If the newly introduced solvent is a suspect carcinogen, and therehas never been a carcinogenic hazard in the workplace before, then new training for


carcinogenic hazards must be conducted for employees in those work areas where em-ployees will be exposed.

It is not necessary for the employer to retrain each new hire if that employee hasreceived prior training by a past employer, an employee union, or any other entity. Gen-eral information, such as the rudiments of the HCS could be expected to remain withan employee from one position to another. The employer, however, maintains the re-sponsibility to ensure that their employees are adequately trained and are equippedwith the knowledge and information necessary to conduct their jobs safely. It is likelythat additional training will be needed since employees must know the specifics of theirnew employer’s programs such as where the MSDSs are located, details of the employ-er’s in-plant labeling system, and the hazards of new chemicals to which they will beexposed.

Do you need to keep MSDSs for commercial products such as Windex®and “White-out®”?OSHA does not require that MSDSs be provided to purchasers of household consumerproducts when the products are used in the workplace in the same manner that a con-sumer would use them, i.e., where the duration and frequency of use �and thereforeexposure� is not greater than what the typical consumer would experience. This ex-emption in OSHA’s regulation is based, not on the chemical manufacturer’s intendeduse of his product, however, but on how it actually is used in the workplace. Employeeswho are required to work with hazardous chemicals in a manner that results in a dura-tion and frequency of exposure greater than what a normal consumer would experi-ence have a right to know about the properties of those hazardous chemicals.

What are the requirements and limits to use generic MSDSs?The requirements for MSDSs are found in paragraph �g� of the standard. MSDSs mustbe developed for hazardous chemicals used in the workplace, and must list the hazard-ous chemicals that are found in a product in quantities of 1 % or greater, or 0.1 % orgreater if the chemical is a carcinogen. The MSDS does not have to list the amount thatthe hazardous chemical occurs in the product.

Therefore, a single MSDS can be developed for the various combinations of chemi-cals, as long as the hazards of the various mixtures are the same. This “generic” MSDSmust meet all of the minimum requirements found in HCS, including the name, ad-dress, and telephone number of the responsible party preparing or distributing theMSDS who can provide additional information.

What is the application of HCS to an office environment?Office workers who encounter hazardous chemicals only in isolated instances are notcovered by the rule. OSHA considers most office products �such as pens, pencils, adhe-sive tape� to be exempt under the provisions of the rule, either as articles or as con-sumer products. OSHA has previously stated that intermittent or occasional use of acopying machine does not result in coverage under the rule. However, if an employeehandles the chemicals to service the machine, or operates it for long periods of time,then the program would have to be applied.

Is an MSDS required for a nonhazardous chemical?MSDSs that represent nonhazardous chemicals are not covered by the HCS. Para-graph 29 CFR 1910.1200 �g� �8� of the standard requires that “the employer shall main-


tain in the workplace copies of the required MSDSs for each hazardous chemical, andshall ensure that they are readily accessible during each work shift to employees whenthey are in their work area�s�.” OSHA does not require nor encourage employers tomaintain MSDSs for nonhazardous chemicals. Consequently, an employer is free todiscard MSDSs for nonhazardous chemicals.

Standard Title: Occupational Exposure to Hazardous Chemicals inLaboratoriesStandard Number: 29 CFR 1910.1450

Scope and ApplicationThe standard covers all laboratories engaged in the laboratory use of chemicals definedas hazardous by this standard, generally, superseding provisions of all other healthstandards except in specific instances. The obligation to maintain employee exposuresat or below the permissible exposure limits �PELs� specified in the air contaminantsstandard and in substance specific standards is retained.

It does not apply to users of hazardous chemicals, which do not meet the definitionof laboratory use, and in such cases, the employer must comply with the relevant stan-dard even though use occurs in a laboratory.

The standard does not apply for laboratory use of hazardous chemicals that pro-vide no potential for employee exposure such as procedures using chemically impreg-nated test media and commercially prepared test kits.

Employee Exposure DeterminationThe employer must measure the employee’s exposure periodically to any substanceregulated by a standard which requires monitoring if there is reason to believe thatexposure levels for that substance routinely exceed the action level �or in the absence ofan action level, the PEL�. The employer must notify the employee of the results within15 working days after receipt of the monitoring results.

Chemical Hygiene PlanWhere hazardous chemicals are used a laboratory covered by this standard the em-ployer must develop and carry out the provisions of a written Chemical Hygiene Plan�CHP�. The CHP must include the necessary work practices, procedures, and policiesto ensure that employees are protected from all potentially hazardous chemicals in usein their work area. The plan must be available to employees, to employee representa-tives, and to the Assistant Secretary for Occupational Safety and Health.

Employee Training and InformationThe employer must provide employees with information and training to ensure thatthey are aware of the hazards of the chemicals present in their work area. This informa-tion must be provided at the time of an employee’s initial assignment to a work areawhere hazardous chemicals are present and prior to assignments involving new expo-sure situations.

Employees must be informed of:• The contents of this standard and its appendices must be made available to them• The location and availability of the employer’s Chemical Hygiene Plan• The permissible exposure limits for OSHA


• Signs and symptoms associated with exposures to hazardous chemicals used inthe laboratory

• The location and availability of known reference material on the hazards, safe han-dling, storage, and disposal of hazardous chemicals found in the laboratory includ-ing, but not limited to Material Safety Data Sheets �MSDS� received from chemicalsuppliers

Medical Consultation and ExaminationsAll employees who work with hazardous chemicals must be given the opportunity toreceive medical attention, including any follow-up examinations, which the examininglicensed physician determines to be necessary under certain circumstances. Medicalexaminations and consultants must be provided without cost to the employee, withoutloss of pay, and at a reasonable time and place.

The employer must provide certain information to the physician, including theidentity of the hazardous chemicals, a description of the conditions under which theexposure occurred, and a description of the signs and symptoms of exposure that theemployee is experiencing.

Hazard IdentificationLabels on incoming containers of hazardous chemicals must not be removed or de-faced. MSDSs on incoming hazardous chemicals must be retained and made availableto lab employees.

Respirator UseWhere the use of respirators is necessary to maintain exposure below permissible ex-posure limits, the employer must provide, at no cost to the employee, the proper respi-rator equipment.

Record KeepingThe employer must establish and maintain for each employee an accurate record ofany measurements taken to monitor employee exposure and any medical consultationand examination including tests or written opinions.

Standard Title: List of Highly Hazardous Chemicals, Toxics and ReactivesStandard Number: 29 CFR 1910.119 App A

The standard contains a listing of toxic and reactive highly hazardous chemicalsthat present a potential for a catastrophic event at or above the treshold of quantity.Chemical name, CAS number �Chemical Abstract Service Number� and TresholdQuantity in Pounds are stated in the list.

Standard Title: Flammable and Combustible LiquidsStandard Number: 29 CFR 1910.106.

The standard defines “flammable” and “conbustible” �see Section 26.1.5� andstates the rules and regulations regarding safety and health, using flammable liquids ingeneral.

Standard Title: General Description and Discussion of the Levels ofProtection and Protective GearStandard Number: 29 CFR 1910.120 App B


Scope and ApplicationThe standard gives information about personal protective equipment �PPE� protectionlevels, which may be used to assist employers in complying with the PPE requirements.

As required by the standard, PPE must be selected, which will protect employeesfrom the specific hazards, which they are likely to encounter during their work on-site.

Selection of the appropriate PPE is a complex process, which should take into con-sideration a variety of factors. Key factors involved in this process are identification ofthe hazards, or suspected hazards; their routes of potential hazard to employees �inha-lation, skin absorption, ingestion, and eye or skin contact�; and the performance of thePPE materials �and seams� in providing a barrier to these hazards. The amount of pro-tection provided by PPE will protect well against some hazardous substances andpoorly, or not at all, against others.

Standard Title: Availability of NIOSH Registry of Toxic Effects of ChemicalSubstances „RTECS… „non-mandatory….Standard Number: 29 CFR 1910.1020 App. B

The standard applies to all employee exposure and medical records, and analysesthereof, of employees exposed to toxic substances or harmful physical agents �para-graph �b� �2�. The term “toxic substance or harmful physical agent” is defined by para-graph �c� �13� to encompass chemical substances, biological agents, and physicalstresses for which there is evidence of harmful health effects. The regulation uses thelatest printed edition of the National Institute for Occupational Safety and Health�NIOSH� �see below�, Registry of Toxic Effects of Chemical Substances �RTECS� as oneof the chief sources of information as to whether evidence of harmful health effectsexists. If a substance is listed in the latest printed RTECS, the regulation applies to ex-posure and medical records �and analyses of these records� relevant to employees ex-posed to the substance.

It is appropriate to note that the final regulation does not require that employerspurchase a copy of RTECS, and many employers need not consult RTECS to ascertainwhether their employee exposure or medical records are subject to the rule. Employerswho do not currently have the latest printed edition of the NIOSH RTECS, however,may desire to obtain a copy. The RTECS is issued in an annual printed edition as man-dated by section 20 �a� �6� of the Occupational Safety and Health Act �29 U.S.C. 669 �a��6��.

26.5.4 National Institute for Occupational Safety and Health „NIOSH…National Institute for Occupational Safety and Health �NIOSH� is, like OSHA estab-lished according to the Occupational Safety and Health Act of 1970. They are, however,two distinct agencies with separate responsibilities, NIOSH is in the U.S. Departmentof Health and Human Services.

NIOSH is the Federal agency responsible for conducting research and making rec-ommendations for the prevention of work-related disease and injury.

NIOSH works with the Health Hazard Evaluation Program, investigating poten-tially hazardous working conditions and with the NIOSH Publications Office supply-ing information on hazardous materials. NIOSH has a number of other activities.

NIOSH Pocket GuideNIOSH Pocket Guide to Chemical Hazards is a useful book that can be obtained fromNIOSH. It includes the following:


Chemical Names, synonyms, trade names, conversion factors, CAS, RTECS, andDOT Numbers

NIOSH Recommended Exposure Limits �NIOSH, RELS�Permissible Exposure Limits �PELs�NIOSH Immediate Dangerous to Life and Health values �NIOSH IDLHs�.A physical description of the agent with chemical and physical propertiesMeasurement methodsPersonal Protection and Sanitation RecommendationsRespirator RecommendationsInformation on Health Hazards including route, symptoms, first aid, and target

organ information.

RTECS® DatabaseThe Registry of Toxic Effects of Chemical Substances �RTECS®� is a database of toxi-cological information compiled, maintained, and updated by the NIOSH. RTECS®contains over 133 000 chemicals as NIOSH strives to fulfill the mandate to list “allknown toxic substances … and the concentrations at which … toxicity is known to oc-cur.”

RTECS® is a compendium of data extracted from the open scientific literature.The data are recorded in the format developed by the RTECS® staff and arranged inalphabetical order by prime chemical name. No attempt has been made to evaluate thestudies cited in RTECS®. The user has the responsibility of making such assessments.

26.5.5 International Chemical Safety Cards „ICSCS…The International Chemical Safety Cards are worked out by an international group ofexperts under The International Programme on Chemical Safety under the WorldHealth Organization �WHO�.

The ICSCs are based on standard phrases, the criteria for which are given in theCompiler’s Guide. A certain number of Cards are available in 22 languages and theirtranslation into a further eight languages is on-going.

The first edition of the Compiler’s Guide and ten series, representing over 900Cards, have been published as hard copies in English, Spanish, Japanese, Chinese, andPolish, and about 1300 Cards are available in electronic form. Cards in English areavailable on the ILO Web site: www.ilo.org/public/english/protection/safework/cis/products/icsc

An ICSC summarizes essential health and safety information on chemicals fortheir use at the “shop floor” level by workers and employees in factories, agriculture,construction, and other work places.

ICSCs are not legally binding documents, but consist of a series of standardphrases, mainly summarizing health and safety information collected, verified, andpeer reviewed by internationally recognized experts, taking into account advice frommanufacturers and Poison Control Centers.

The identification of the chemicals on the Cards is based on the UN numbers, theChemical Abstracts Service �CAS� number, and the Registry of Toxic Effects of Chemi-cal Substances �RTECS/NIOSH� numbers. It is thought that the use of those three sys-tems assures the most unambiguous method of identifying the chemical substancesconcerned, referring as it does to numbering systems that consider transportationmatters, chemistry, and occupational health.


ICSCs and Material Safety Data SheetsGreat similarities exist between the various headings of the ICSC and the manufactur-ers’ Safety Data Sheet �SDS� or Material Safety Data Sheet �MSDS� of the InternationalCouncil of Chemical Associations. However, MSDSs and the ICSCs are not the same.The MSDS, in many instances, may be very complex technically and too expensive forshop floor use, and secondly it is a management document. The ICSCs, on the otherhand, set out peer-reviewed information about substances in a more concise andsimple manner. Although not a legal document, the ICSC is an authoritative documentemanating from WHO/ILO/UNEP. This is not to say that the ICSC should be a substi-tute for an MSDS, nothing can replace management’s responsibility to communicatewith workers on the exact chemicals, the nature of those chemicals used on the shopfloor and the risk posed in any given work place. Indeed, the ICSC and the MSDS caneven be thought of as complementary. If the two methods for hazard communicationcan be combined, then the amount of knowledge available to the safety representativeor shop floor workers will be more than doubled.

26.5.6 Environmental Protection Agency „EPA…The U.S. Environmental Protection Agency is to protect human health and to safe-guard the natural environment—air, water, and land—which life depends on.

EPA administrates important laws like Occupational Safety and Health Act andToxic Substances Control Act, both important in relation to metallographic/material-ographic laboratories.

26.5.7 National Technical Information Service „NTIS…The National Technical Information Service �NTIS� is the largest, central resource forgovernment-funded scientific, technical, engineering, and business information avail-able in United States.

Toxic Substances Control Act �TSCA� Chemical Substances Inventory—RevisedInventory Synonym and Preferred Name File: This inventory list covers more than65 000 chemicals as defined under TSCA.

26.5.8 American Conference of Government Industrial Hygienists „ACGIH…The American Conference of Governmental Industrial Hygienists, Inc. �ACGIH�, is anorganization open to all practitioners in industrial hygiene, occupational health, envi-ronmental health, or safety.

ACGIH publishes over 400 titles in occupational and environmental health andsafety. They are best known for their Treshold Limit Values publication that lists theTLVs for over 700 chemical substances and physical agents, as well as 50 BiologicalExposure Indices for selected chemicals.

26.5.9 National Toxicology Program „NTP…The National Toxicology Program is an organization under U.S. Department of Healthand Human Services �DHHS� to coordinate toxicological testing programs.

NTP has collected health and safety data on over 2000 chemicals.

26.5.10 Agency for Toxic Substance and Disease Registry „ATSDR…The Agency for Toxic Substances and Disease Registry �ATSDR� is an agency underU.S. Department of Health and Human Services.


The mission is to prevent exposure and advise human health effects associatedwith exposure to hazardous substances.

ATSDR TOX FAQs is a series of summaries about hazardous substances. Each factsheet serves as a quick and easy to understand guide, �www.atsdr.cdc.gov/toxfaq.html�.

26.5.11 National Fire Protection Association „NFPA…The National Fire Protection Association �NFPA� is a nonprofit organization that is re-sponsible for over 300 codes covering basic fire safety, electricity, and other topics.

The NFPA 704 Hazard Identification Ratings System is described in Section 26.2.

26.5.12 National Paint and Coatings Association „NPCA…—HMISThe National Paint and Coatings Association �NPCA� has established a complete pro-gram, HMIS, �Hazardous Materials Identification System� that helps employers com-ply with OSHA’s Hazard Communication Standard �HCS� �see Section 26.2�.

26.5.13 BSI—ISOBritish Standards Institution is the independent national body responsible for prepar-ing British Standards. BSI cooperates with ISO �International Standard Organization�and EU �European Union�.

The British Standard BS 7750 on Environmental Management has been used asthe basis for the standard, BS EN ISO 14001: 1996, Environmental Management Sys-tems. This standard covers all sides of environmental management and connects to thequality standard BS EN ISO 9000: 2000.

The standard BS 8800: 1996, Guide to Occupational Health and Safety Manage-ment Systems, puts emphasis on OHS management. Two standards are establishedbased on this standard:

OHSAS 18001: 1999, Occupational Health and Safety Management SystemsSpecifications.

OHSAS 18002: 2000, Occupational Health and Safety Management Systems.Guidelines for the implementation of OHSAS 18001.

An important factor in OHSAS 18001: 1999 is “Risk Assessment” defined as “Theoverall process of estimating the magnitude of risk and deciding whether or not the riskis tolerable or acceptable.” Risk assessment involves three basic steps: �1� identify haz-ards; �2� estimate the risk from each hazard—the likelihood and severity of harm; �3�decide if the risk is tolerable.

26.5.14 EUThe European Union �EU� �European Community �EC�� has established a number ofdirectives, covering occupational safety.

The directive 67/548/EEC on dangerous substances is described further in Section26.2.

26.6 Literature on Laboratory Safety

Literature can be seen in References of the Standard Guide on Metallographic Labora-tory Safety �E 2014� in the CD-ROM included with this manual �see Section 26.1.8�. Inaddition the books by Petzow and Vander Voort �Refs 2 and 9, Part I� can be recom-mended.


27Literature

27.1 Books

THE BOOKS LISTED BELOW COVER THE FIELD OF METALLOGRAPHIC/materialographic preparation and examination. They are intended as a supplement tothis book and should not be considered as a complete list of books on these subjects.

Amelinckx, S., Van Dyck, D., Van Landuyt, J., and Van Tendeloo, G., Handbook of Microscopy: Applications in

Materials Science, Solid-State Physics, and Chemistry. Wiley-VCH, New York, N.Y., USA, 1997.

Beraha, E. and Shipgler, B., Color Metallography, ASM Materials Park, Ohio, USA, 1977.

Bjerregaard, L., Geels, K., Ottesen, B., and Rückert, M., Metalog Guide, Struers A/S, Copenhagen, Denmark,

2000.

Bousfield, B., Surface Preparation and Microscopy of Materials, John Wiley & Sons, Chichester, UK, 1992.

Bramfitt, B. L. and Benscoter, A. O., Metallographer’s Guide—Practices and Procedures for Iron and Steels, ASM

International, Metals Park, Ohio, USA, 2001.

Burgess, D. and Blanchard, R. A., Wafer Failure Analysis for Yield Enhancement, Accelerated Analysis, Half

Moon Bay, California, USA, 2001.

Bühler, H. E. and Hougardy, H. P., Atlas of Interference Layer Metallography, Deutsche Gesellschaft für Met-

allkunde, Oberursel, Germany, 1980.

Durand-Charre, M., Microstructure of Steels and Cast Irons, Springer-Verlag New York, Inc., New York, NY, USA,

2004.

Durand-Charre, M. and Durand-Charre, M., Microstructure of Superalloys, Taylor & Francis, Inc., Philadelphia,

PA, USA, 1998.

Elssner, G., Hoven, H., Kiessler, G., and Wellner, P., Ceramics and Ceramic Composites: Materialographic Prepara-

tion, Elsevier Science, Inc., New York, NY, USA, 1999.

Freund, J. E., Statistics: a First Course, 2nd ed., Prentice Hall, Englewood Cliffs, New Jersey, USA, 1970.

Friel, J. J., et al., Practical Guide to Image Analysis, ASM International, Materials Park, Ohio, USA, 2000.

Handbook of Thermal Spray Technology, ASM International, Materials Park, Ohio, USA, 2004.

Higginson, R. L. and Sellars, C. M., Worked Examples in Quantitative Metallography, Maney Publishing, Cam-

bridge MA, USA, 2003.

Inoue, S. and Spring, K. R., Video Microscopy, Plenum Press, New York, NY, USA, 1997.

Kapitza, H. G., Microscopy from the Very Beginning, Carl Zeiss, Jena, Germany, 1994.

Metals Handbook, Metallography and Microstructures, Vol. 9, ASM International, Materials Park, Ohio, USA,

2004.

Petzow, G., Metallographic Etching, ASM International, Materials Park, Ohio, USA, 1999.

Ross, Boit, and Staab, �edit.�, Microelectronics Failure Analysis, ASM International, Materials Park, Ohio, USA,

1999.

Rostoker, W. and Dvorak, J. R., Interpretation of Metallographic Structures, Elsevier Science, Inc., New York, NY,

USA, 1990.

Russ, J. C., The Image Processing Handbook, 3rd ed., CRC Press, Boca Raton, FL, USA, 1998.

Samuels, L. E., Metallographic Polishing by Mechanical Methods, ASM International, Materials Park, Ohio, USA,

2003.Schumann, H. and Oettel, H., Metallografie, Wiley-VCH Verlag, Weinheim, Germany, 2004 �In German�.Tegart, Mc.G., The Electrolytic and Chemical Polishing of Metals in Research and Industry, Pergamon Press, Lon-

don, UK, 1959.Tomer, A., Structure of Metals through Optical Microscopy, ASM International, Materials Park, Ohio, USA, 1990.Underwood, E. E., Quantitative Stereology, Addison-Wesley Publishing Company, Reading, MA, USA, 1970.

685

Vander Voort, G. V., Metallography Principles and Practice, ASM International, Materials Park, Ohio, USA, 1999.Waschull, H., Präparative Metallographie, Wiley-VCH Verlag, Weinheim, Germany, 1993 �In German�.Weck, E. and Leistner, E., Metallographic Instructions for Colour Etching by Immersion, Part I �1982�, II �1983�,

III �1986�, Deutscher Verlag für Schweisstechnik GmbH, Düsseldorf, Germany.

27.2 Periodicals

THE PERIODICALS STATED IN THIS LIST COVER THE FIELD OF METALLO-graphic/materialographic preparation and interpretation, but it should not be consid-ered a complete list of all periodicals covering these subjects.

Advanced Functional Materials, English/18 issues yearly,Wiley-VCH, P.O. Box 191161, D-69451,Weinheim,Germany.

Advanced Materials, English/24 issues yearly,Wiley-VCH, P.O. Box 191161, D-69451,Weinheim,Germany.

Advanced Materials and Processes, English/monthly,ASM International,Materials Park, OH44073, USA.

Advanced Engineering Materials, English/monthly,Wiley-VCH, P.O. Box 191161, D-69451,Weinheim,Germany.

Alloy Digest, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Electronic Device Failure Analysis, English/quarterly,ASM International,Materials Park, OH44073, USA.

International Materials Reviews, English/bimonthly,ASM International,Materials Park, OH44073, USA.

JOM, English/monthly, TMS �TheMinerals,Metals andMaterials Society�, 184ThornHill Road,Warrendale, PA15086, USA.

Journal of Electronic Materials, English/monthly, TMS �The Minerals, Metals and Materials Society�, 184 Thorn Hill Road,

Warrendale, PA15086, USA.

Journal of Failure Analysis and Prevention, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Journal of Materials Engineering and Performance, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Journal of Phase Equilibria and Diffusion, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Journal of the American Ceramic Society, English/monthly,American Ceramic Society, P.O. Box 6136,Westerville, OH 43086-

6136, USA.

Journal of Thermal Spray Technology, English/quarterly,ASM International,Materials Park, OH44073, USA.

Materials Characterization, English/10 issues yearly, Elsevier Science Publishing Co. Inc., 655 Avenue of the Americas, New

York, NY10010, USA.

Metallurgical and Materials Transactions A, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Metallurgical and Materials Transactions B, English/bimonthly,ASM International,Materials Park, OH44073, USA.

Praktische Metallographie/Practical Metallography, bilingual, German/English/monthly, Carl Hanser Verlag, Kolbergstrasse

22, 81679München, Germany.

SlipLines, newsletter, English/quarterly, IMS �International Metallographic Society�, ASM International, Materials Park, OH

44073, USA.

Structure, English/German/French editions, twice a year, StruersA/S, Pederstrupvej 84, 2750Ballerup, Denmark.

Welding Journal, English/monthly,AWS �AmericanWelding Society�, 550N.W. LeJeunneRoad,Miami, FL33126, USA.

Appendixes

Appendix I: Other Standards on Metallography/Materialography

A NUMBER OF STANDARDS, OTHER THAN ASTM, COVERING METALLO-graphy/materialography from ISO �International Standard Organization� and a num-ber of important industrial countries are listed below. The list is not complete.

ISO standards/National standards: The national standards, which are local ver-sions of ISO standards, are not indicated below.

CEN �European Committee for Standardization� is involved in European Stan-


dards �EN�, Technical Specifications �CEN TS�, Technical Reports �CEV TR� and CENWork Agreements �CWA�. All documents are supplied by the national members of CEN.

ISO �INTERNATIONAL STANDARD ORGANIZATION�ISO 643 Steels—Micrographic determination of the ferritic or

austenitic grain sizeISO 945 Cast iron—Designation of microstructure of graphiteISO 1083 Spheroidal graphite cast irons—ClassificationISO 1463 Metallic and oxide coatings—Measurements of thickness—

Microscopical methodISO 2064 Metallic and other inorganic coatings—Definitions and

conventions concerning the measurement of thicknessISO 2624 Copper and copper alloys—Estimation of average grain sizeISO 2639 Steel—Determination and verification of the effective depth

of carburized and hardened casesISO 3057 Nondestructive testing—Metallographic replica techniques

of surface examinationISO 3082 Iron ores—Sampling and sample preparation proceduresISO 3085 Iron ores—Experimental methods for checking the

precision of sampling, sample preparation andmeasurement

ISO 3754 Steel—Determination of effective depth of hardening afterflame or induction hardening

ISO 3763 Wrought steels—Macroscopic methods for assessing thecontent of nonmetallic inclusions

ISO 3887 Steels—Determination of depth of decarburizationISO 4499 Hard metals—Metallographic determination of

microstructureISO 4505 Hard metals—Metallographic determination of porosity and

uncombined carbonISO 4524-1 Metallic coatings—Test methods for electrodeposited gold

and gold alloy coatings—Part 1 Determination of coatingthickness

ISO 4967 Steel—Determination of content of nonmetallic inclusions—Micrographic method using standard diagrams

ISO 4968 Steel—Micrographic examination by sulfur prints�Baumann method�

ISO 4969 Steel—Macroscopic examination by etching with strongmineral acids

ISO 4970 Steel—Determination of total or effective thickness of thinsurface-treated layers

ISO 5949 Tool steels and bearing steels—Micrographic method forassessing the distribution of carbides using referencephotomicrographs

ISO 6196 Micrographics—Vocabulary—Part 1: General terms

Chapter 27 Books 687

ISO 8036 Optics and photonics—Microscopes—Immersion liquids forlight microscopy

ISO 9042 Steels—Manual point counting method for staticallyestimating the volume fraction of a constituent with a pointgrid

ISO 9220 Metallic coatings—Measurement of coating thickness—Scanning electron microscope method

ISO 11567 Carbon fibre—Determination of filament diameter andcross-sectional area

ISO 13520 Determination of ferrite content in austenitic stainless steelcastings

ISO 14250 Steel—Metallographic characterization of duplex grain sizeand distribution

ISO/TR 14321 Sintered metal materials, excluding hardmetals—Metallographic preparation and examination

ISO 14703 Fine ceramics �advanced ceramics, advanced technicalceramics�—Sample preparation for the determination ofparticle size distribution of ceramic powders

ISO 14923 Thermal Spraying—Characterization and testing ofthermally sprayed coatings

ISO 16793 Nuclear fuel technology—Guide for ceramographicpreparation of UO2 sintered pellets for microstructureexamination

ISO 17642-2 Destructive tests on welds in metallic materials—Coldcracking tests for weldments—Arc welding processes—Part2: Self-restraint tests

ISO 20160 Implants for surgery—Metallic materials—Classification ofmicrostructures for alpha�beta titanium alloy bars

ISO 21227 Paints and varnishes—Evaluation of defects on coatedsurfaces using optical imaging—Part 1: General guidance

FRANCENF A04-105 Iron and steel. Methods of determination of the

nonmetallic inclusion content of wrought steels. Part 1:Macroscopic methods.

NF A04-106 Iron and steel. Methods of determination of content ofnonmetallic inclusions in wrought steel. Part II:Micrographic method using standards diagrams.

NF A04-107 Iron and steel. Micrographic method of dtermination of thenonmetallic inclusion content of unalloyed wire rod.

NF A04-108 Iron and steel. Characterization of sulfide shapes instructural steels with improved machinability usingstandard diagrams. Micrographic method.

NF A04-110 Iron and steel. Wire rods of non-alloy general purpose steelfor wire drawing. Surface examination.

NF A04-111 Iron and steel. Micrographic determination of the extent ofdecarburization of non-alloy high carbon steel wire rod.


NF A04-112 Iron and steel. Macrographic method of showing anddescribing the chemical heterogeneity of effervescent steelwire rod.

NF A04-113 Iron and steel. High carbon steel wire rod derived fromingots. Macrographic method of showing and describingthe chemical heterogeneity.

NF A04-114 Iron and steel. High carbon continuous cast steel wire rod.Macrographic method of showing and describing thechemical heterogeneity.

A04-115 Iron and steel. Characterization of sulfide shapes infree-cutting steels using standards diagrams. Micrographicmethod.

NF A04-203 Steel products. Determination of the effective hardeningafter flame or induction hardening.

NF A04-204 Steel products. Determination of the total or conventionalthickness of surface hardened thin layers.

NF A04-503 Semi-products made from aluminum, copper, nickel andtheir alloys. Determination of grain size. Aluminium andaluminium alloys.

NF A05-150 Steel products. Techniques of micrographic examination.NF A05-151 Steel products. Macrographic examination by sulfur print

�Baumann method�.NF A05-152 Steel products. Macroscopic examination by etching with

strong mineral acids.NF A05-153 Iron and steel. Macroscopic examination by means of

copper salt etching.NF A05-154 Steel products. Metallographic replica techniques �optical

examination�.NF A05-156 Iron and steel. Macrographic examination by sodium sulfur

print �so-called lead print method�.A05-165 Steel products. Manual point counting method for

statistically estimating the volume fraction of a constituentwith a point grid.

NF A95-342 Powder metallurgy. Sintered materials includinghardmetals. Micrographic examination techniques.

NF EN 1321 Destructive tests on welds in metallic materials.Macroscopic and microscopic examination of welds.

NF EN 12797 Brazing—Destructive tests of brazed joints.NF EN 24499 Hard metals. Metallographic determination of

microstructure.NF EN 24505 Hard metals. Metallographic determination of porosity and

uncombined carbon.XP ENV 10247 Micrographic examination of the nonmetallic inclusion

content of steels using standard pictures.GERMANY


DIN V ENV1071-5

�Pre-standard� Advanced technical ceramics—Methods oftest for ceramic coatings—Part 5: determination of porosity

DIN CEN/TS1071-10

Advanced technical ceramics—Methods of test for ceramiccoatings—Part 10: determination of coating thickness bycross sectioning

DIN EN 1321 Destructive tests of welds in metallic materials—macroscopic and microscopic examination of welds

DIN EN2004-10

Aerospace series—Test methods for aluminium andaluminium alloy products; Part 10: preparation ofmicrographic specimens for aluminium alloys

DIN EN 2007 Aerospace series—Test methods for aluminium andaluminium alloy products—metallographic determinationof cladding thickness and copper diffusion in the claddingfor rolled products

DIN EN 3684 Aerospace series—Test methods—titanium alloy wroughtproducts—determination of beta transus temperature;metallographic method

DIN EN 10247 Micrographic examination of the nonmetallic inclusioncontent of steels using standard pictures

DIN 50192 Determination of the depth of decarburizationDIN 50600 Testing of metallic materials; metallographic micrographs;

picture scales and formatsDIN 50601 Metallographic examination; determination of the ferritic

or austenitic grain sizeDIN 50602 Metallographic examination; microscopic examination of

special steels using standard diagrams to assess the contentof non-metallic inclusions

DIN 54150 Nondestructive Testing Impression Methods for SurfaceExamination

JAPANJIS H 0501 Methods for estimating average grain size of wrought

copper and copper alloysJIS G 0551 Steels—Micrographic determination of the apparent grain

sizeJIS G 0552 Method of ferrite grain size test for steelJIS G 0553 Macrostructure detecting method for steel, Edition 1JIS G 0555 Microscopic testing method for the non-metallic inclusions

in steelJIS Z 6014 Micrographics—Test charts for digitizing image—

Description and use in electronic imageryUNITED KINGDOM

BS M 37 Method for the etch inspection of metallic materials andcomponents

BS EN 1321 Destructive test on welds in metallic materials.Macroscopic and microscopic examination of welds


BS 4490 Methods for micrographic determination of the grain sizeof steel

BS 5710 Macroscopic assessment of the nonmetallic inclusioncontent of wrought steels

BS 6285 Macroscopic assessment of steel by sulfur printBS 6286 Measurement of total or effective thickness of thin

surface-hardness layers in steelBS 6479 Determination and verification of effective depth of

carburized and hardened cases of steelBS 6481 Determination of effective depth of hardening of steel after

flame or induction hardeningBS 6533 Guide to microscopic examination of steel by etching with

strong acidsBS 6617 Determination of decarburization in steel. Methods for

determining decarburization by microscopic andmicrohardness techniques

BS 7590 Method for statistically estimating the volume fraction ofphases and constituents by systematic manual pointcounting with a grid

BS 7590 A Worksheet for the determination of volume fraction bysystematic manual point count

BS 10247 Micrographic examination of the nonmetallic inclusioncontent of steels using standard pictures

BS EN 10328 Iron and steel—determination of the conventional depth ofhardening after surface heating

93/7105316 DC Aerospace series. Test methods for aluminium andaluminium alloy products. Metallographic determination ofcladding thickness and copper diffusion in the cladding forrolled products �prEN 2007�

94/710839 DC Aerospace series. Test methods. Titanium alloy wroughtproducts. Determination of primary � content. The pointcount method and line intercept method �prEN 3683�

94/710840 DC Aerospace series. Test methods. Titanium alloy wroughtproducts. Determination of transus temperature.Metallographic method �prEN 3684�

Appendix II: Other Standards on Hardness Testing

A number of standards, other than ASTM, covering hardness testing from ISO �Inter-national Standard Organization� and a number of important industrial countries arelisted below. The list is not complete.

ISO standards/National standards: The national standards, which are local ver-sions of ISO standards, are not indicated below.

CEN �European Committee for Standardization� is involved in European Stan-dards �EN�, Technical Specifications �CEN TS�, Technical Reports �CEV TR� and CENWork Agreements �CWA�. All documents are supplied by the national members of CEN.


ISO „International Standard Organization…A number of standards covering hardness testing from ISO are listed below. The list isnot complete.

ISO �INTERNATIONAL STANDARD ORGANIZATION�ISO 48 Rubber, vulcanized or thermoplastic—Determination of

hardness �hardness between 10 IRHD and 100 IRHD�ISO 3738-1 Hard metals—Rockwell hardness test �scale A�—Part 1:

Test methodISO 3738-2 Hard metals—Rockwell hardness test �scale A�—Part 2:

Preparation and calibration of standard test blocksISO 3878 Hard metals—Vickers hardness testISO 4384-1 Plain bearings—Hardness testing of bearing metals—Part

1: Compound materialsISO 4384-2 Plain bearings—Hardness testing of bearing metals—Part

2: Solid materialsISO 4498 Sintered metal materials, excluding hardmetals—

Determination of apparent hardness and microhardnessISO 4498-1 Sintered metal materials, excluding hardmetals—

Determination of apparent hardness—Part 1: Materials ofessentially uniform section hardness

ISO 4498-2 Sintered metal materials, excluding hardmetals—Determination of apparent hardness—Part 2:Case-hardened ferrous materials, surface enriched bycarbon or carbon and nitrogen

ISO 4507 Sintered ferrous materials, carburized or carbonitrided—Determination and verification of hardening depth by amicrohardness test

ISO 4516 Metallic and other inorganic coatings—Vickers and Knoopmicrohardness tests

ISO 4545 Metallic materials—Hardness test—Knoop testISO 4546 Metallic materials—Hardness test—Verification of Knoop

hardness testing machinesISO 4547 Metallic materials—Hardness test—Calibration of

standardized blocks to be used for Knoop hardness testingmachines

ISO 6506-1 Metallic materials—Brinell hardness test—Part 1: Testmethod

ISO 6506-2 Metallic materials—Brinell hardness test—Part 2:Verification and calibration of testing machines

ISO 6506-3 Metallic materials—Brinell hardness test—Part 3:Calibration of reference blocks

ISO 6507-1 Metallic materials—Vickers hardness test—Part 1: Testmethod

ISO 6507-2 Metallic materials—Vickers hardness test—Part 2:Verification of testing machines


ISO 6507-3 Metallic materials—Vickers hardness test—Part 3:Calibration of reference blocks

ISO 6508-1 Metallic materials—Rockwell hardness test—Part 1: Testmethod �scales A, B, C, D, E, F, G, H, K, N, T�

ISO 6508-2 Metallic materials—Rockwell hardness test—Part 2:Verification and calibration of testing machines �scales A,B, C, D, E, F, G, H, K, N, T�

ISO 6508-3 Metallic materials—Rockwell hardness test—Part 3:Calibration of reference blocks �scales A, B, C, D, E, F, G,H, K, N, T�

ISO 9015-1 Destructive test on welds in metallic materials—Hardnesstesting—Part 1: Hardness test on arc welded joints

ISO 9015-2 Destructive tests on welds in metallic materials—Hardnesstesting—Part 2: Microhardness testing of welded joints

ISO 9385 Glass and glass-ceramics—Knoop hardness testISO 14271 Vickers hardness testing of resistance spot, projection and

seam welds �low load and microhardness�ISO 14577-1 Metallic materials—Instrumented indentation test for

hardness and materials parameters—Part 1: Test methodISO 14577-2 Metallic materials—Instrumented indentation test for

hardness and materials parameters—Part 2: Verificationand calibration of testing machines

ISO 14577-3 Metallic materials—Instrumented indentation test forhardness and materials parameters—Part 3: Calibration ofreference blocks

ISO 18571 Rubber, vulcanized or thermoplastic—Hardness testing—Introduction and guide

FranceNF A95-329 Powder metallurgy. Sintered metal materials excluding

hardmetals. Measurement of Vickers microhardnessNF A95-348 Powder metallurgy. Sintered ferrous materials, carburized

or carbonitried. Determination of effective case depth bythe Vickers microhardness testing method.

GermanyDIN EN 1043-2 Destructive test on welds in metallic materials—Hardness

test—Part 2: Micro hardness testing on welded jointsDIN CEN/TS1071-7

�Pre-standard� Advanced technical ceramics—Methods oftest for ceramic coatings—Part 7: Determination ofhardness and Young’s modulus by instrumentedindentation testing

DIN CEN/TS1071-8

�Pre-standard� Advanced technical ceramics—Methods oftest for ceramic coatings—Part 8: Rockwell indentationtest for evaluation of adhesion

JapanJIS Z 2255 Method for ultra-low loaded hardness testJIS Z 2255 Method for ultra-low loaded hardness test


JIS R 1623:1995 Testing method for Vickers hardness of fine ceramics atelevated temperatures

JIS B 7724:1999 Brinell hardness test—Verification of testing machinesJIS B 7726 Rockwell hardness test—Verification of testing machinesJIS B7727:2000

Shore hardness test—Verification of testing machines

JIS B 7730 Rockwell hardness test—Calibration of reference blocksUnited Kingdom

BS DD ENV843-4

Advanced technical ceramics—monolithic ceramics—mechanical properties at room temperature—Part 4.Vickers, Knoop and Rockwell superficial hardness tests

BS 1881 P 202 Recommendations for surface hardness testing by reboundhammer

BS 2782 P3METH 3665 C

Determination of Rockwell hardness

BS 3900-E12.1 Methods of test for paints—determination of Knoophardness by measurement of the indentation length usinga microscope

BS 4443 P2 Method 7, indentation hardness testsBS 5411 P6 Vickers and Knoop microhardness testsBS 5600 P4 S4.5 Powder metallurgical materials and products—methods of

testing and chemical analysis of hardmetals—Rockwellhardness test �scale A�

BS 6431 P13 Method for determination of scratch hardness of surfaceaccording to Mohs

BS 6617 Determination of decarburization in steel. Method fordetermining decarburization by microscopic andmicro-hardness techniques

BS 7442 P3 S3.2 Determination of Shore hardnessBS EN 23878 Hardmetals—Vickers hardness testBS EN 24428-1 Sintered metal materials, excluding hardmetals—

determination of apparent hardness—Part 1. Materials ofessentially uniform section hardness

Appendix III: Hardness Conversion Tables for Metals „E 140…�Included on CD-Rom in back of this book.�

Appendix IV: SI Quick Reference Guide: International System ofUnits „SI…�Included on CD-Rom in back of this book.�


Glossary

Abrasion The process of rubbing, grinding, or wearing away by theuse of abrasives; a roughening or scratching of a surface dueto abrasive wear [1].

Abrasive A substance capable of removing material from anothersubstance in machining, abrasion, or polishing that usuallytakes the form of several small, irregular shaped particles ofhard material [1].

Abrasive disk (1) Grinding wheel mounted on a steel plate, with theexposed flat side being used for grinding. (2) Grinding diskwith a layer of abrasive product [1].

Abrasive paper See Grinding paper.Abrasive wet cutting Cutting method for almost all solid materials using

mechanical friction and wear with abrasives bonded in acut-off wheel (similar to grinding) [3].

Achromatic Literally, color-free. A lens or prism is said to be achromaticwhen corrected for two colors. The remaining color seen inan image formed by such a lens is said to be secondarychromatic aberration [2]. See Achromatic objective.

Achromatic objective An objective that is corrected chromatically for two colors,and spherically for one, usually in the yellow-green part ofthe spectrum [2].

Acid A chemical substance that yields hydrogen ions �H+� whendissolved in water gives a pH of less than 7 [1]. See alsoBase.

Age hardening Hardening through aging, usually after rapid cooling or coldworking [1]. See also Precipitation hardening.

Aging A change in the property of certain metals and alloys thatoccurs at room temperature or slightly elevatedtemperatures, after hot working or heat treatment, or aftercold working. The aging is usually due to phase changes(precipitation) [1]. See also Precipitation hardening.

Air-hardening steel A steel containing sufficient carbon and other alloyingelements to harden fully during cooling in air or othergaseous media from a temperature above its transformationrange. Same as self-hardening steel [1].

Alloy A substance having metallic properties and being composedof two or more chemical elements of which at least one is anelemental metal [1].

Alloying element An element added to a metal (and which remains within themetal) to effect changes of properties [1].

Alloy steel Steel containing significant quantities of alloying elements(other than carbon and the commonly accepted amounts ofmanganese, copper, silicon, sulfur, and phosphorus) toimprove the mechanical properties [1].

Alpha brass Solid solution phase of one or more alloying elements incopper and having the same crystal lattice as copper [2].

Alpha iron „Fe… Solid phase of pure iron [2].Amalgam Alloy with mercury and one or more other metals [3].Amorphous Not having a crystal structure; noncrystalline [1].

695

Anisotropy Characterized by having different values of a property indifferent crystallographic directions [1].

Annealing Heating to and holding metals and alloys at a suitabletemperature followed by cooling at a suitable rate, usedprimarily to soften metals, but also to simultaneouslyproduce desired changes in properties or in microstructure[3].

Anode Electrode where electrons leave (current enters) anoperating system (battery, X-ray tube, electrolytic cell) [3].See also Cathode.

Anode corrosion The dissolution of a metal acting as an anode [3].Anodic etching See Electrolytic etching.Anvil effect The effect caused by use of too high a load, or when testing

the hardness of too thin a specimen, resulting in a bulge orshiny spot on the underside of the specimen [2].

Aperture, optical The working diameter of a lens or a mirror [2].Apochromaticobjective

An objective with longitudinal chromatic correction for red,green, and blue, and spherical chromatic correction forgreen and blue. This is the best choice for high resolution orcolor photomicrography [2].

Arc cutting A group of cutting processes that melts the metals to be cutwith the heat of an arc between an electrode and the basematerial [1].

Artifact A false microstructural feature that is not an actualcharacteristic of the specimen; it may be present as a resultof improper or inadequate preparation, handling methods,or optical conditions for viewing [2].

Attack polishing Simultaneous etching and mechanical polishing by adding aweak etching solution to the polishing compound [1]. Seealso Chemical mechanical polishing.

Austenite A face-centered cubic solid solution of carbon or otherelements in gamma iron [2].

Austenitic steel An alloy steel whose structure is austenitic at roomtemperature [1].

Automatic imageanalysis

A device which can be programmed to detect and measurefeatures of interest in an image. It may include accessoriessuch as automatic focus and an automatic traversing stage topermit unattended operation [2].


Bainite—upper,lower, intermediate

Metastable microstructure or microstructures resulting fromthe transformation of austenite at temperatures betweenthose which produce pearlite and martensite. Thesestructures may be formed on continuous (slow) cooling ifthe transformation rate of austenite to pearlite is muchslower than that of austenite to bainite. Ordinarily, thesestructures may be formed isothermally at temperatureswithin the above range by quenching austenite to a desiredtemperature and holding for a period of time necessary fortransformation to occur. If the transformation temperatureis just below that at which the finest pearlite is formed, thebainite (upper bainite) has a feathery appearance. If thetransformation temperature is just above that at whichmartensite is produced, the bainite (lower bainite) isacicular, resembling slightly tempered martensite. At thehigher resolution of the electron microscope, upper bainiteis observed to consist of plates of cementite in a matrix offerrite. These discontinuous carbide plates tend to haveparallel orientation in the direction of the longer dimensionof the bainite areas. Lower bainite consists of ferrite needlescontaining carbide platelets in parallel array cross-striatingeach needle axis at an angle of about 60°. Intermediatebainite resembles upper bainite; however, the carbides aresmaller and more randomly oriented [2].

Banded structure„banding…

Alternate bands parallel with the direction of workingresulting from the elongation of segregated areas [2].

Band saw Mechanical cutting method using an endless steel saw blade.Base A chemical substance that yields hydroxyl ions �OH−�, when

dissolved in water gives a pH of more than 7 [1].Base metal (1) After welding, that part of the metal which was not

melted. (2) A metal that readily oxidizes, or that dissolves toform ions [1]. See also Noble metal.

Beilby layer A layer of amorphous or amorphous-like characterdeveloped on the surface of a specimen during mechanicalpolishing. Theory by G. Beilby, but later research has shownthat the layer does not exist.

Beta structure Structurally analogous body-centered cubic phases (similarto beta brass), or electron compounds, that have ratios of 3valence electrons to 2 atoms [2].

Binder Cementing medium holding together mixtures of particlesor powder [3].

Blow torch Method for cutting metal using an acetylen burner, with thepossibility of adding an extra flow of oxygen, melting, andblowing away the material. Also called oxyacetylen torching.

Bond The material that binds the abrasive in a cut-off wheel and inother abrasive products.

Glossary 697

Brass Alloy consisting of copper (over 50 %) and zinc, to whichsmall amounts of other elements may be added [3].

Brightfieldillumination

For reflected light, the illumination which causes specularlyreflected surfaces normal to the axis of a microscope toappear bright. For transmission electron microscopy, theillumination of an object so that it appears on a brightbackground [2].

Brinell hardnesstesting

Hardness test performed by forcing a hard steel or tungstencarbide ball of specified diameter into a material [3].

Brittleness The tendency of a material to fracture without firstundergoing significant plastic deformation [1]. See alsoDuctility.

Bronze Copper-tin alloy with or without small amounts of otheralloying elements such as phosphorus and zinc [3].

Burningmetallography/materialography…

Can occur in cutting and grinding, when sufficient heat isgenerated on the surface of the work piece to causediscoloration or a change of the microstructure bytempering or hardening [1].

Calibration (1) The act or process of determining the relationshipbetween a set of standard units of measure and the outputof an instrument or test procedure. (2) The graphical ormathematical relationship relating the desired property(expressed in a standard unit of measure such asmicrometres or Kg/mm2) to the instrument output(instrument units such as filar divisions or pixels) [2].

Carbide A compound of carbon with one or more elements, which,in customary formulation, are considered as being morepositive than carbon [2].

Carbide tools Cutting or forming tools, usually made of tungsten, titanium,tantalum, or niobium carbides or a combination of them ina matrix of cobalt, nickel, or other metals. Carbide tools arecharacterized by high hardness and compressive strengthand may be coated to improve wear resistance [1].

Carbon steel Steel containing carbon up to 2 % [3].Carbonitriding A case-hardening process by which a suitable ferrous metal

is heated in a gaseous atmosphere. Through the gas, themetal surface will absorb carbon and nitrogen by diffusionand form a very hard compound layer [1].

Carburizing Absorption and diffusion of carbon into solid ferrous alloysby heating to a temperature usually above Ac3, in contactwith a suitable carbonaceous material. A form of casehardening [1]. See also Case hardening.

Case In a ferrous alloy, the outer portion that has been madeharder than the inner portion as a result of alteredcomposition, or structure, or both, from treatments such ascarburizing, nitriding, and induction hardening [2]. See alsoCore.


Case hardening A generic term covering several processes applicable to steelthat change the chemical composition of the surface layerby absorption of carbon, nitrogen, or a mixture of the twoby diffusion. It is also called carburizing, nitriding,carbonitriding, cyaniding, nitrocarburizing, and quenchhardening [1].

Cast iron Generic term of a large family of cast ferrous alloyscontaining 2.5–4 % carbon and about 1–3 % silicon. Thecarbon content exceeds the solubility of carbon in austenitethat exists at the eutectic temperature, which is usually morethan 2 % [3].

Cast structure The structure, on a macroscopic or microscopic scale, of acasting [2]. See also Dendrites.

Cathode Electrode where the electrons enter (current leaves) anoperating system [3]. See also Anode.

Cemented carbides„sintered carbides…

Material made by pressing and sintering a powder of one ormore metallic carbides with a small amount of metal(cobalt) serving as a binder [1].

Cementite A very hard and brittle compound of iron and carboncorresponding to the empirical formula Fe3C. It iscommonly known as iron carbide and possesses anorthorhombic lattice. In “plain-carbon steels” some of theiron atoms in the cementite lattice are replaced bymanganese, and in “alloy steels” by other elements such aschromium or tungsten. Cementite will often appear asdistinct lamellae or as spheroids or globules of varying sizein hypo-eutectoid steels. Cementite is in metastableequilibrium and has a tendency to decompose into iron andgraphite, although the reaction rate is very slow [2].

Ceramic Inorganic, nonmetallic material with crystalline andnoncrystalline structures (for instance: metal carbides,oxides, nitrides, and borides are ceramics) [3].

Cermets Powder metallurgy product consisting of ceramic particlesbonded with metal [1].

CG iron Same as compacted graphite cast iron [1]. See alsoCompacted cast iron.

Chemical deposition Precipitation of a metal from solutions of its salts throughthe introduction of another metal or reagent to the solution[1].

Chemical etching Develops the microstructure by using an electrochemicalprocess, which takes advantage of the differences in theelectrochemical potentials of the various constituents in thestructure [3].

Chemical polishing Improving the surface luster of a metal by chemicaltreatment [1]. See also Chemical mechanical polishing.

Glossary 699

Chemicalmechanicalpolishing

Using a combination of a chemical solution (usually anetchant) with an oxide suspension on a polishing cloth,resulting in a scratch free surface. Mainly used for very softor ductile metals [3]. See also Oxide polishing.

Chips Pieces of material removed from a work piece by cuttingtools or by an abrasive medium [3].

Clad metal A composite metal containing two or three layers that havebeen bonded together. The bonding may have beenaccomplished by co-rolling, welding, casting, heavy chemicaldeposition, or heavy electroplating [1].

Clay Earthy or stony mineral aggregate, which is plastic whensufficiently pulverized and wetted, rigid and dry, andvitreous when fired at a sufficiently high temperature [3].

Cold etching Reveals the microstructure at room temperature and below[4].

Cold rolled sheet Sheets of metal made by feeding metal through mill rolls atroom temperature [3].

Cold workedstructure

A microstructure resulting from plastic deformation of ametal or alloy below its recrystallization temperature [1].

Combined carbon That part of the total carbon in steel or cast iron that ispresent as other than free carbon [1]. See also Free carbon.

Comet tails Artifact in the form of unidirectional scratches developed bymechanical polishing of a metallographic/materialographicsurface.

Compacted graphitecast iron

Cast iron having a graphite shape intermediate between theflake form typical of gray cast iron and the spherical form offully spherulitic cast iron. Also known as CG iron [1].

Component One of the independently variable substances by means ofwhich the composition of each phase of a system ofheterogeneous equilibrium may be described completely;usually an element, or a compound that remainsundissociated throughout the range of temperature andpressure concerned [2].

Composite material A heterogeneous, solid structural material consisting of twoor more distinct components that are mechanically ormetallurgically bonded together (such as a cermet, or boronwire embedded in a matrix of epoxy resin) [1]. See alsoCermet.

Condenser A term applied to lenses or mirrors designed to collect,control, and concentrate radiation in an illumination system[2].

Constant feed speed In cutting: Cutting principle where the movement of thespecimen or the cut-off wheel is kept constant throughoutthe cutting process. This cutting principle is preferred to theprinciple of Constant force as it will produce the leastdeformation possible while still achieving the shortestcutting times [3]. See also Constant force.


Constant force In cutting: Cutting principle where the force applied is keptconstant throughout the cutting process. Constant force canproduce damage to the sample especially at sample entryand exit [3].

Constituent A phase, or combination of phases, which occurs in acharacteristic configuration in an alloy microstructure [2].

Contamination„metallography/materialography…

(1) Debris from grinding or dust from the lab environmentcontaminating a polishing cloth resulting in scratches of thespecimen surface. (2) Material from a source other than thespecimen itself, which is deposited on the specimen surfaceduring preparation [3].

Continuous phase The phase forming the matrix or background in which otherphases may be dispersed as isolated units [2].

Controlled etching Electrolytic etching with selection of suitable etchant andvoltage, resulting in a balance between current and dissolvedions [4].

Conversion,hardness

The exchange of a hardness number determined by onemethod for an equivalent hardness number of a differentscale [2].

Coolant See Cutting fluid.Core (1) Case hardening—interior portion of unaltered

composition, or microstructure, or both, of a case-hardenedsteel article. (2) Clad products—the central portion of amultilayer composite metallic material [2].

Corrosion Deterioration of a metal by chemical or electrochemicalreaction with its environment [1].

Corrosionembrittlement

The chemical or electrochemical reaction between amaterial, usually a metal, and its environment that producesa deterioration of the material and its properties [1].

Corrosion fatigue Cracking produced by the combined action of repeating andfluctuating stress and a corrosive environment [1].

Coupon A piece of material especially made for testing. Known fromprinted circuit boards, where a coupon is made togetherwith the board.

Creep Time-dependent strain occurring under stress [1].Crystal A solid composed of atoms, ions, or molecules arranged in a

pattern which is periodic in three dimensions [2].Crystallite A crystalline grain not bounded by habit planes [2].Cut-off wheel Abrasive wheel consisting of an abrasive in a bond for

cutting any material or part [3].Cutting„metallography/materialography…

Sectioning of a piece of material to obtain a specimen [3].See also Cut-off wheel.

Cutting fluid Fluid used to cool a work piece, wash chips away, andimprove surface finish and cut-off wheel lifetime [3].

Glossary 701

Cutting speed The linear or peripheral speed of relative motion betweenthe tool and work piece in the principal direction of cutting[1].

Darkfieldillumination

The illumination of an object such that it appearsilluminated with the surrounding field dark. This resultsfrom illuminating the object with rays of sufficient obliquityso that none can enter the objective directly. As applied toelectron microscopy, the image is formed using onlyelectrons scattered by the object [2].

Decarburization Loss of carbon from the surface of a carbon-containing alloydue to a reaction with one or more chemical substances in amedium that contacts the surface. Decarburization may beeither (1) partial. That is, where carbon content is less thanthe unaffected interior but greater than the roomtemperature solubility limit of carbon in ferrite or (2)complete. That is, where carbon content is less than thesolubility limit of carbon in ferrite so that only ferrite ispresent [2].

Deep drawing Forming of deeply recessed parts by means of plastic flow ofthe material [1].

Deep etching Macroetching; etching preliminary to macro-examination,intended to develop gross features such as segregation, grainflow, cracks, or porosity [2]. See also Macroetching.

Deformation„metallography/materialography…

Plastic deformation, which may also be referred to as coldwork, can result in subsurface defects after grinding,lapping, or polishing. Remaining plastic deformation canfirst be seen after etching. Plastic deformation (deformedlayer) is an artifact that has to be removed during samplepreparation [3].

Deformation bands Bands produced within individual grains during coldworking which differ variably in orientation from the matrix[2].

Dendrites Crystals, usually formed during solidification or sublimation,which are characterized by a tree-like pattern composed ofmany branches; pine-tree or fir-tree crystals [2].

Depth of field The depth or thickness of the object space that issimultaneously in acceptable focus [2].

Diamond polishing Polishing using diamond as abrasive. Removes scratchesintroduced during fine grinding. Makes the specimensuitable for microscopic observation [3]. See also Finalpolishing, Polishing.

Diamond wheel A grinding wheel in which crushed and sized industrialdiamonds are held in a resinoid, metal, or vitrified bond [1].

Diaphragm A fixed or adjustable aperture in an optical system.Diaphragms are used to intercept scattered light, to limitfield angles, or to limit image-forming bundles or rays [1].


Differentialinterference contrastillumination „DIC…

A microscopical technique employing a beam-splittingdouble-quartz prism; that is a modified Wollaston prismplaced ahead of the objective with a polarizer and analyzerin the 90° crossed positions. The two light beams are madeto coincide at the focal plane of the objective, thus renderingheight differences visible as variations in color. The prismcan be moved, shifting the interference image through therange of Newtonian colors [2].

Diffraction (1) A modification which radiation undergoes, as in passingby the edge of opaque bodies or through narrow slits, inwhich the rays appear to be deflected. (2) Coherentscattering of X-radiation by the atoms of a crystal whichnecessarily results in beams in characteristic directions.Sometimes called reflection. (3) The scattering of electrons,by any crystalline material, through discrete anglesdepending only on the lattice spacings of the material andthe velocity of the electrons [2].

Diffusion The spontaneous movement of atoms or molecules to newsites within a material [1].

Direct cut„metallography/materialography…

Cutting mode in which the cut-off wheel cuts directlythrough the work piece; also called chop cutting [3].

Dislocation A linear imperfection in a crystalline array of atoms [1].Dislocation etching Reveals exit point of dislocations on the specimen surface

[4].Dissolution etching Reveals the microstructure by surface removal [4].Double etching Two etchants are used sequentially; the second one will

accentuate a particular microstructural feature [4].Drawing Forming recessed parts of metal by pressing them in or

through a die. Reducing cross section of a wire or tube bypulling it through a die [1].

Drop etching Placing a drop of an etchant on a selected area of thespecimen surface to develop the microconstituents [4].

Dry etching Develops the microstructure by gaseous exposure [4].Ductile cast iron A cast iron that has been treated while molten with an

element such as magnesium or cerium to induce theformation of free graphite as nodules or spherulites, whichimparts a measurable degree of ductility to the cast metal.Also known as nodular cast iron, cast iron with spheroidalgraphite and SG iron [1].

Ductility Ability of a material to deform plastically without fracturing,measured by elongation or reduction of area in a tensile test[1]. See also Brittleness.

Duplexmicrostructure

A two-phase structure [2].

Dye penetrant Color spray used in nondestructive testing to find cracks insurface of parts [3].

Glossary 703

Elastic deformation Change of dimensions of a piece of material under stress.Upon release of stress original dimensions are restoredagain (example: elastic band which takes its original shapeafter it has been stretched) [3].

Elasticity Ability of a solid to deform in direct proportion to and inphase with increases or decreases in applied force [3].

Electrical dischargemachining „EDM…

Removal of stock from an electrically conductive material byrapid, repetitive spark discharge through a dielectric fluidflowing between the work piece and a shaped electrode [1].

Electrolyte Liquid, most often a solution, that will conduct an electriccurrent [1].

Electrolytic cell An assembly consisting of a vessel, electrodes (anode andcathode) and an electrolyte in which electrolysis can becarried out [1].

Electrolytic etching Development of microstructure by selective dissolution ofthe polished surface under application of a direct current[1]. Also called anodic etching.

Electrolyticpolishing

A metallographic preparation procedure where metal ispreferentially dissolved from high points on an anodicsurface by passage of an electric current through aconductive bath, to produce a specular reflecting surface.Used as an alternative to mechanical polishing [2].

Electron microscopy The study of materials by means of the electron microscope[2]. See also SEM and TEM.

Embedded abrasives Loose abrasive particles pressed into the surface of aspecimen. This happens mainly with soft or ductilematerials, or both. Abrasives can be embedded when using asmall abrasive particle size, the grinding or polishing clothused has a low resilience or a lubricant with a low viscosityis used or a combination of these conditions takes place [3].

Equiaxed grain A polygonal crystallite, in an aggregate, whose dimensionsare approximately the same in all directions [2].

Equilibrium diagram A graphical representation of the temperature, pressure, andcomposition limits of phase fields in an alloy system, as theyexist under conditions of complete equilibrium [1].

Etchant Chemical substance or mixture used for etching [1].Etch figures Markings formed on a crystal surface by etching or chemical

solution and usually related geometrically to the crystalstructure [2].

Etching Controlled preferential attack on a metal surface for thepurpose of revealing structural details [2].

Eutectic Phase consisting of intermixed solid constituents formed bya eutectic reaction, (pearlite=ferrite end cementite). Thenumber of solids being the same as the number ofcomponents in the system [3].

Eutectic structure The structure resulting when an alloy has passed through aeutectic equilibrium upon freezing [2].


Exogenousinclusions

A nonmetallic constituent produced by entrapment offoreign material in the melt [2]. See also Inclusions,Nonmetallic inclusions.

Eyepiece The lens system used in an optical instrument formagnification of the image formed by the objective [2].

Fatigue Process by which repeated or fluctuating stress, or both,leads to fracture [3].

Feed speed Rate by which a tool or cut-off wheel advances along or intothe surface of a work piece [3].

Ferrite Designation commonly assigned to alpha iron containingalloying elements in solid solution. Increasing carboncontent markedly decreases the high-temperature limit ofequilibrium [2].

FG Fine Grinding. Reduces surface roughness of a specimen toa degree that is suitable for polishing [3].

Field The portion of the object in view [2].Field metallography Metallographic techniques carried out in the field when the

part or component is too large to bring to a metallographiclaboratory or a specimen cannot be removed [1].

Filar An eyepiece equipped with a fiducial line in its focal plane,which is movable by means of a calibrated micrometrescrew, in order to make accurate measurements of length[2].

Filler Material used to increase the bulk of a product withoutadding to its effectiveness in functional performance [3].

Final polishing The final step in a specimen preparation process producinga surface suitable for microscopic examination.

Flame spraying Coating technique in which the coating material is fed aswire or powder into a flame and sprayed in the molten stateagainst the surface to be coated [3].

Flow lines A fiber pattern, frequently observed in wrought metal, whichindicates the manner in which the metal flowed duringdeformation [2].

Fluorescent screen A sheet of material which emits visible light when exposed toinvisible radiation [2].

Foil A thin sheet of a material, usually a metal, not exceeding0.13 mm �0.005 in.� in thickness [2].

Forging Process of plastically deforming metal, usually hot, into adesired shape with compressive force, with or without dies[1].

Formability„workability,drawability…

Relative ease with which a metal can be shaped throughplastic deformation [1].

Fractography Description of fractures with macrographs ��25� � andmicrographs at high magnification ��25� � from the opticalmicroscope and the SEM [3].

Glossary 705

Fracture test Test in which a specimen is broken and its fracture surfaceexamined to determine such factors as composition, grainsize, case depth, or soundness [1].

Free carbon Part of the total carbon in steel or cast iron that is present inelemental form as graphite [1]. See also Combined carbon.

Free machining Machining capabilities of an alloy to which one or moreingredients have been introduced to produce small brokenchips, better surface finish, and longer tool lifetime duringthe machining process [1].

Galvanizing Coating the surface of iron or steel with zinc appliedelectrolytically or by hot dipping [3].

Goniometer An instrument devised for measuring the angle throughwhich a specimen is rotated [1].

Grain An individual crystallite in metals [2].Grain boundary An interface separating two grains, where the orientation of

the lattice changes from that of one grain to that of theother. When the orientation change is very small theboundary is sometimes referred to as a subboundary [2].

Grain boundaryetching

Reveals the intersections of the individual grains. Grainboundaries have a higher dissolution potential than theindividual grains because of their high density of structuraldefects. Accumulation of impurities in grain boundariesincreases this effect [4].

Grain size (1) Measure of the areas or volume of grains in apolycrystalline material, usually expressed as an averagewhen the individual sizes are fairly uniform. In metalscontaining two or more phases, grain size refers to that ofthe matrix unless otherwise specified. Grain size is reportedin terms of number of grains per measuring unit area orvolume, average diameter, or as a grain size derived fromarea measurements. See also ASTM Standard E 112. (2)Dimension of one individual particle of an abrasive,measured in micrometres, �m [1]. See also Grit size.

Grain-contrastetching

Etching the surface of the grains according to their crystalorientation. They become distinct by the different reflectivitycaused by reaction layers or surface roughness [4].

Graphite The polymorph of carbon with a hexagonal crystal structure[1]. See also CG iron, Gray cast iron, Nodular cast iron,Spheroidal cast iron.

Graphitic carbon Free carbon in steel or cast iron [1].Graticule A scale on glass or other transparent material placed in the

eyepiece or at an intermediate plane on the optic axis of alight microscope for the location and measurement ofobjects (a graticule is different than a reticle) [2]. See alsoReticle.


Gray cast iron orgray iron

Cast iron that looks gray on the fractured surface due to thepresence of free graphite. Contains carbon as graphite inform of flakes or nodules [3].

Grinding The removal of material from the surface of a specimen byabrasion through the use of randomly orientedhard-abrasive particles bonded to a suitable substrate, suchas paper or cloth, where the abrasive particle size isgenerally in the range of 60 to 600 grit (approximately150 to 15 �m) but may be finer [2].

Grinding paper Coated abrasive product in which paper is used as a backingmaterial [3].

Grit size Nominal size of abrasive particles in a grinding wheel,corresponding to the number of openings per linear inch ina screen through which the particles can just pass.Sometimes but inadvisably called “grain size” [1]. See Grainsize.

Half moonphenomenon

Appears mainly when using wet grinding disk and coarseSiC-paper for plane and fine grinding of specimens clampedin a specimen holder. This phenomenon is due to the factthat the abrasive grains of the SiC-paper are not gettingworn down at the edge of an SiC-paper as fast as in themiddle, combined with the higher speed at the periphery ofthe disk [3].

Hardening Increasing hardness of a metal with a suitable treatment,usually through heating and fast cooling [1].

Hardness„indentation…

Resistance of a metal to plastic deformation, usually byindentation. However, the term may also refer to resistanceto scratching, abrasion, or cutting. Indentation hardness maybe measured by various hardness testing methods, such asBrinell, Rockwell, Vickers, Knoop, and Scleroscope [3].

Heat-resistant alloy Alloys used for applications for which resistance againsthigh temperature and corrosion, combined with highstresses are required. They are usually high nickel alloys [1].

Heat tinting Coloration of a metal surface through a thin oxide film,formed by heating in oxidizing atmosphere, to reveal detailsof the microstructure [1].

Heat treatment Heating and cooling a solid metal or alloy in such a way thatdesired properties are obtained [1].

Heterogenous Nonuniform in microstructure or composition [2].High alloy steel Contains up to 2.5 % carbon and more than 6 % metallic

alloying elements, mainly chromium (Cr), nickel (Ni),vanadium (V), tungsten (W), and manganese (Mn). Very hardtool steels and ductile stainless steels are high alloy steels[3].

Homogenizing Holding at high temperature to eliminate or decreasechemical segregation by diffusion [1].

Glossary 707

Hot dip coating Metallic coating obtained by dipping the basic metal into amolten metal [1].

Hot etching Development and stabilization of the microstructure atelevated temperature in etching solutions or gases [4].

Identification„selective… etching

Etching for the identification of particular microconstituentswithout attacking any others [4].

Image A representation of an object produced by means ofradiation, usually with a lens or mirror system [2].

Image processing, inimage analysis

The computer modification of a digitized image on apixel-by-pixel basis to emphasize or de-emphasize certainaspects of the image [2]. See also Automatic image analysis.

Immersion etching The specimen is immersed in the etchant with the polishedsurface up and is agitated. This is the most common etchingmethod [4].

Immersion objective An objective in which a medium of high refractive index isused in the object space to increase the numerical apertureand hence the resolving power of the lens [2].

Impact test A test to determine the behavior of materials when subjectedto high rates of loading, usually bending, tension, andtorsion. The quantity measures the energy absorbed inbreaking the specimen by a single blow, as in Charpy andIzod tests [1].

Impregnation„metallography/materialography…

Process of filling voids and cracks under vacuum with asealing medium, for instance, epoxy cold mounting resin [3].

Impression (1) Electron microscopy. The reproduction of the surfacecontours of a specimen formed in a plastic material after theapplication of pressure and heat, or both.(2) Hardness. The imprint or dent made in the specimen bythe indenter of a hardness-measuring device [2].

Impurities Elements or compounds whose presence in a material isundesired [1].

Inclusions Foreign material held mechanically, usually referring tononmetallic particles, such as oxides, sulfides, silicates, etc.[2]. See also Exogenous inclusions, Nonmetallic inclusions.

Indentationhardness

Resistance of a material to indentation. This is the usual typeof hardness test, in which a pointed or rounded indenter ispressed into a surface under a substantially static load [3].See also Hardness.

Indigenous„endogenous…inclusion

A nonmetallic material that precipitates from the melt [2].See Inclusions.

Induction hardening Surface hardening in which only the surface layer of asuitable ferrous work piece is heated by electrical inductionto hardening temperature and then quenched [3].

Ingot Casting of a simple shape suitable for hot working orremelting [1].


Intercrystalline Between crystals, or between grains of a metal, the same asintergranular [1].

Intercrystallinecracks

Cracks or fractures that occur between the grains or crystalsin a polycrystalline aggregate [2].

Interdendriticcorrosion

Corrosive attack that progresses preferentially along aninterdendritic path [1].

Interface Surface that forms the boundary between phases or systems,or both [1].

Intergranullarcorrosion

A preferential attack at the grain boundaries [2].

Intracrystalline Within or across the crystals or grains of a metal, same astranscrystalline and transgranular [1].

Inverted microscope A microscope so arranged that the line of sight is directedupwards through the objective to the object [2].

Ion etching Surface removal by bombardment with accelerated ions in avacuum �1 to 10 kV� [4].

Iron Iron-based metals not falling into the steel category, such aspure iron, gray iron, pig iron, white cast iron, etc. [3].

Isotropy The condition of having the same values of properties in alldirections [2].

Kikuchi lines Light and dark lines superimposed on the background of asingle crystal electron diffraction pattern caused bydiffraction of diffusely scattered electrons within the crystal[2].

Koehler illumination A specular illumination system. In reflected-lightmicroscopy, used directly for the brightfield mode, and as apreliminary setup for all other modes except darkfield. Theimage of the field diaphragm is focused on the specimensurface and the image of an undiffused lamp source isfocused in the plane of the aperture diaphragm [2].

Knoop hardness Microhardness determined from resistance of a metal toindentation using a rhombic-based pyramidal diamondindenter, which makes an impression with one long and oneshort diagonal [3].

Lamellar structure A microstructure consisting of parallel plates of a secondphase [3]. See Pearlite.

Laminate (1) A composite material, usually in the form of sheet or bar,composed of two or more materials bonded to form a solidstructure. (2) Product of two or more bonded metal layers[3].

Lapping The abrasive removal of material using graded abrasiveparticles in a loose form as in a liquid slurry on a platen [2].

Lapping tracks Indentations on the specimen surface made by abrasiveparticles moving freely on a hard surface. These are notscratches from a cutting action, but are the distinct tracks ofparticles tumbling over the surface without removingmaterial [3].

Glossary 709

Light metal Low density metal such as aluminum, magnesium, titanium,beryllium, or their alloys [1].

Light micoscopy See Optical microscope.Long-term etching Etching times of a few minutes to several hours [4].Lubricant Any substance used to reduce friction between surfaces in

contact. Liquid used for cooling and lubricating. Dependingon the type of material and the preparation stage, differenttypes of lubricants can be used for grinding and polishing[3].

Machining Removing surface material in the form of chips, usually witha mechanical tool [3].

Macroetching Controlled etching of the surface of a metallic specimen,intended to reveal a structure which is visible at lowmagnifications (not usually greater than ten times) [2]. Seealso Deep etching.

Macroscopic Observation using the naked eye or magnifications up to10–30 times [3].

Macrostructure Structure of metals as revealed by macroscopic examinationof the etched surface of a polished specimen [1].

Magnetic-particleinspection

A nondestructive method of inspection for determining theexistence and extent of possible defects in ferro-magneticmaterials. On the surface of a magnetized part fine magneticparticles are attracted to areas where the magnetic field isdisplaced or interrupted, such as cracks or pores [1].

Malleability The characteristic of metals that permits plastic deformationin compression without rupture [1].

Malleable cast iron A cast iron made by prolonged annealing of white cast ironin which decarburization or graphitization, or both, takesplace to eliminate some or all of the cementite [1].

Martensite Metastable phase resulting from the diffusionless athermaldecomposition of austenite below a certain temperatureknown as the Ms temperature (martensite starttemperature). It is produced during quenching when thecooling rate of a steel, in the austenitic condition, is suchthat the pearlite and bainite, or both, transformation issuppressed. The composition of the martensite is identicalwith that of the austenite from which it transformed. Hence,martensite is a super-saturated solid solution of carbon inalpha iron (ferrite) having a body-centered tetragonal lattice.It is a magnetic plate-like constituent formed by adiffusionless shear type of transformation. These plates mayappear needle-like or veriform in cross section [2].


Materialography Materialography is defined as an investigative method ofmaterials science. It emcompasses the optical examinationof microstructures, and its goal is a qualitative andquantitative description of the microscopic structuralanalysis of solid materials. Materialography includesmetallography, ceramography, plastography, and mineralogy[4]. See also Metallography.

Matrix The continuous phase [2]. See Continous phase.Mechanicalpolishing

Specimen preparation process using finer and finerabrasives, mostly diamond, to obtain a surface suited formicroscopic examination.

Mechanicalproperties

The properties of a material that reveal its elastic andinelastic behavior when force is applied, by indicating itssuitability for mechanical applications; for example,modulus of elasticity, tensile strength, elongation, hardness,and fatigue limit [1]. Compare with Physical properties.

Mechanical testing Determination of mechanical properties [1].Mechanical twin A twin formed in a crystal by simple shear under external

loading [1]. See also Twin bands.Metallograph An optical instrument for the examination of metallographic/

materialographic specimens. In principle it consists of alight source, a microscope, and a camera.

Metallography That branch of science which relates to the constitution andstructure, and their relation to the properties, of metals andalloys [2]. See also Materialography.

Metallurgy The science and technology of metals and alloys [1].Metastable A state of apparent equilibrium which has a higher free

energy than has the true equilibrium state; usually applied toa phase existing outside its temperature and pressure spanof equilibrium existence, by reason of a greatly delayedtransformation [2].

Microetching Development of microstructure for microscopicobservation.The usual magnification exceeds 25� (50� inEurope) [1].

Micrograph A graphic reproduction of an object as seen through themicroscope or equivalent optical instrument, atmagnifications greater than ten diameters [2].

Micro indentationhardness„microhardness…

Hardness of a material determined by forcing an indenterinto the polished surface of a material under very light loadusing a microhardness tester [3]. See also Micro penetrationhardness.

Micro penetrationhardness

The hardness number obtained by use of a low load testerwhose indentation is usually measured with a high powermicroscope [2]. See also Micro indentation hardness.

Microscopy The science of the interpretive use and applications ofmicroscopes [1].

Glossary 711

Microstructure The structure of a suitably prepared specimen as revealed bya microscope [2].

Mineralogy Scientific study of minerals [3]. See also Petrographicexamination.

Modulus of elasticity„E…

The measure of rigidity or stiffness of a metal; the ratio ofstress, below the proportional limit, to the correspondingstrain. In terms of stress-strain diagram, the modulus ofelasticity is the slope of the stress-strain curve in the range oflinear proportionality of stress to strain. Also known asYoung's modulus [1].

Monochromatic„homogeneous…

Of the same wavelength [2].

Monocrystalline A solid composed of a unique crystal [3].Morphology The shape characteristics of a structure; the form and

orientation of specific phase or constituent [2].Mounting To embed the specimen in resin to facilitate the further

handling during grinding and polishing, and to improve thepreparation result [3].

Multiple etching A specimen is etched sequentially with the specific etchantsto reveal certain constituents [4].

Nitriding Nitriding is a form of surface hardening. By exposing aferrous part at a certain temperature to nitrogenousmaterials, nitrogen will diffuse into the surface of the partand form hard nitrides [3].

Nitrocarburizing Any of several case-hardening processes in which bothnitrogen and carbon are absorbed into the surface layers ofa ferrous material at a certain temperature. Nitrocarburizingimproves fatigue resistance [1].

Noble metal (1) A metal whose potential is highly positive relative to thehydrogen electrode. (2) A metal with marked resistance tochemical reaction, particularly to oxidation and to solutionby inorganic acids. The term as often used is synonymouswith precious metal [1].

Nodular cast iron Also called ductile cast iron; trace amounts of magnesiumare added to the melt to induce formation of free graphitein the form of nodules. See also Spheroidal cast iron.

Nonmetallicinclusions

Particles of impurities (usually oxides, sulfides, silicates, andsuch) that are held mechanically or are formed duringsolidification or by subsequent reaction within the solidmetal [2]. See also Exogenous inclusions, Inclusions.

Nondestructivetesting

Inspection by methods that do not destroy the part in orderto determine its suitability for use [1]. See also Fieldmetallography.

Normalizing Heating a ferrous alloy to a suitable temperature above thetransformation range and then cooling it in air to atemperature substantially below the transformation range[1].


Numerical aperture„NA…

The sine of half the angular aperture of an objective lensmultiplied by the refractive index of the medium betweenthe lens and the sample [2].

Objective The primary magnifying system of a microscope [1].Ocular See Eyepiece.Optical etching Develops the microstructure by using special illumination

techniques (dark field, interference contrast, polarized light,phase contrast) [4].

Optical microscope Instrument containing one or more lenses which usesartificial light to produce an enlarged image of an objectplaced in the focal plane of the lens(es) [3].

Ore A natural mineral that may be mined and treated for theextraction of any of its components, metallic or otherwise[3].

Organic materials For example, wood, bone, tissue, teeth, paper.Orientation The angular position of a crystal described by the angles

which certain crystallographic axes make with the frame ofreference. In hardness measurements, the relationshipbetween the direction of the axes of the indenter of ahardness tester and the direction of nonhomogeneousproperties of the specimen [2].

Overheating (1) In ferrous alloys, heating to an excessively hightemperature such that the properties/structure undergomodification. The resulting structure is very coarse-grained.Unlike burning, it may be possible to restore the originalproperties/structure by further heat treatment or mechanicalworking, or a combination thereof. (2) In aluminum alloys,overheating produces structures that show areas ofresolidified eutectic or other evidence that indicates themetal has been heated within the melting range [2].

Oxide polishing Process used for the final polishing of a specimen with asuspension containing fine abrasive particles of oxides(aluminum oxide, silicon dioxide) with or without chemicalsof different pH. See also Final polishing.

Oxidation (1) A reaction in which there is an increase in valenceresulting from a loss of electrons. (2) A corrosion reaction inwhich the corroded metal forms an oxide; usually applied toreaction with a gas containing elemental oxygen, such as air[1].

P Polishing (mechanical) taking place as the last steps (P1, P2,P3, etc.) of metallographic/materialographic preparation toobtain a surface suited for microscopic examination. Seealso Final polishing, Oxide polishing, Polishing.

Particle size The controlling linear dimension of an individual particle,such as of a powdered metal, as determined by analysis withscreens or other suitable instruments [1].

Glossary 713

Pearlite A metastable microstructure formed when local austeniteareas attain the eutectoid composition in alloys of iron andcarbon containing greater than 0.025 % but less than 6.67 %carbon. The structure is an aggregate consisting of alternatelamellae of ferrite and cementite formed on slow coolingduring the eutectoid reaction. In an alloy of givencomposition, pearlite may be formed isothermally attemperatures below the eutectoid temperature by quenchingaustenite to a desired temperature (generally above 550°C)and holding for a period of time necessary fortransformation to occur. The interlamellar spacing variesdirectly with the transformation temperature; that is, thehigher the temperature the greater the spacing [2].

Petrographicexamination

Methods of examining nonmetallic matter under suitablemicroscopes to determine structural relationships and toidentify the phases or minerals present. With transparentmaterials, the determination of the optical properties, suchas the indices of refraction and the behavior in transmittedpolarized light, serve as means of identification. Withopaque materials, the color, hardness, reflectivity, shape, andetching behavior in polished sections serve as means ofidentification. Metallographic applications includeexamination of particles mechanically or chemicallyseparated from the metal by these methods [2].

PG Plane (planar) grinding. Removes damage introduced bycutting, and levels specimens clamped in a holder forautomatic grinding [3]. See also Planar grinding.

pH The negative logarithm of the hydrogen-ion activity. Itdenotes the degree of acidity or basicity of a solution. At25°C �77°F�, 7.0 is the neutral value. Lower values than 7.0indicate acidity and higher values increasing basicity [1].

Phase A physically homogeneous and distinct portion of a materialsystem [1].

Phase contrastmicroscopy

A special method of controlled illumination, ideally suitedfor observing thin, transparent objects whose structuraldetails vary only slightly in thickness or refractive index. Thiscan also be applied to the examination of opaque materialsto determine surface elevation changes [2].

Photo micrograph See Micrograph.Physical etching Develops the microstructure through removal of surface

atoms, lowering the grain surface potential and depositionof interference layers [4].

Physical properties Properties, other than mechanical properties, that pertain tothe physical nature of a material; for example, density,electrical conductivity, thermal expansion, reflectivitymagnetic susceptibility, and so on [1]. See also Mechanicalproperties.


Physical testing Determination of physical properties [1].Pig Metal casting poured from the melting furnace, used for

remelting [3].Pitting„metallography…

Forming small sharp cavities in a metal surface ifelectrolytic polishing is not performed correctly.

Pixel „pictureelement…

Smallest spatial unit of an image [2].

Planar grinding The first step in a preparation procedure used to bring allspecimens into the same plane of polish. It is unique to semior fully automatic preparation equipment that utilizespecimen holders [2]. See also PG.

Plane grinding See PG.Plasma spraying Coating technique in which the coating material is fed as

powder into an ionized gas atmosphere (plasma) andsprayed in the molten state onto the surface to be coated [3].

Plastic Any of various organic compounds produced bypolymerization, capable of being molded, extruded, cast intovarious shapes and films, or drawn into filaments used astextile fibers [3].

Plastic deformation Deformation that remains or will remain permanent afterrelease of the stress that caused it [1].

Plasticity The capacity of a material to deform nonelastically withoutrupturing [1].

Plating Forming an adherent layer of metal on metal, usuallythrough a galvanic process. Any adherent layer of metal onother material can also be called plating [3].

Plowing In tribology, the formation of grooves by plastic deformationof the softer of two surfaces in relative motion [1].

Polarized lightillumination

A method of illumination in which the incident light is planepolarized before it impinges on the specimen [2].

Polishing A mechanical, chemical, or electrolytic process orcombination thereof used to prepare a smooth reflectivesurface suitable for microstructure examination, free ofartifacts or damage introduced during prior sectioning orgrinding [2]. See also Final polishing, Oxide polishing,Polishing cloth.

Polishing artifact A false structure introduced during a polishing stage of asurface preparation sequence [1]. See also Artifact.

Polishing cloth A substrate, mostly a textile or a nonwoven material, usedfor polishing of specimens with selected abrasives. See alsoFinal polishing, Oxide polishing, Polishing.

Polishing rate The rate of which material is removed from a surface duringpolishing. It is usually expressed in terms of the thicknessremoved per unit of time or distance traversed [1].

Polycrystalline Characteristic of an aggregate composed of more than one,and usually of a large number, of crystals [2].

Glossary 715

Polymers Plastics, for instance polyethylene, epoxy, polyester andpolyacryl, and polyamide (Nylon) [3].

Pores Small voids in the body of a material [1].Porosity Holes in a solid, not necessarily connected [2].Potentiostaticetching

Anodic development of the microstructure at a constantpotential enables a defined etching of singular phases [4].

Powder Particles of a solid characterized by small size, nominallywithin the range from 0.1 to 1000 �m [3].

Powder metallurgy Production and use of metal powders, which are hot pressedand sintered into solid materials and shaped objects [1].

Precious metals Gold, silver, and platinum-group metals [3].Precipitation Separation of a new phase from solid, liquid, or gaseous

solutions, usually with changing conditions of temperatureor pressure, or both [2].

Precipitation etching Develops the microstructure by the formation of reactionproducts at the specimen surface [4].

Precipitationhardening

Hardening caused by precipitation of a constituent from asupersaturated solid solution [1]. See also Age hardening,Aging.

Primary crystals The first type of crystals that separates from a melt oncooling [2].

Primary etching Develops the cast microstructures including coring [4]. Seealso Secondary etching.

Pull-out Void existing on the plane of polish of a metallographicspecimen caused by the dislodging of a particle orconstituent during the grinding or polishing operation [2].

Quantitativemetallography

Determination of specific characteristics of a microstructureby making quantitative measurements on micrographs ormetallographic/materialographic images. Quantities someasured include volume concentration of phases, grainsize, particle size, and surface-area-to-volume ratios ofmicro-constituents, particles, or grains [1]. See alsoAutomatic image analysis.

Quenching Rapid cooling, usually in water [3].Quenching crack A crack formed as a result of thermal stresses produced by

rapid cooling from a high temperature, not to be confusedwith fire crack [2].

Ram Moving part in e.g, the cylinder of a mounting press [3].Rare earth metals One of the group of 15 chemically similar metals with

atomic numbers 57 through 71, commonly referred to as thelanthanides [1].

RCD Rigid composite disk, hard or soft, used for fine grinding.See also Rigid grinding disk.

Recarburize (1) Increase the carbon content of molten cast iron or steelby adding carbonaceous material, high-carbon pig iron or ahigh carbon alloy. (2) Carburize a metal part to returnsurface carbon loss in processing [1].


Recrystallization The formation of a new grain structure through nucleationand growth commonly produced by subjecting a metal, thatmay be strained, to suitable conditions of time andtemperature [3].

Reflected light In the metallographic/materialographic microscope thespecimen is illuminated with reflected (incident) light. Forexamination of mineralogical thin sections and in biologythe transmitted light is used.

Refractory (1) Material of very high melting point with properties thatmake it suitable for furnace linings and kiln construction.(2) Quality of resisting heat [1].

Refractory alloy (1) Heat-resistant alloy. (2) Alloy having an extremely highmelting point. (3) An alloy difficult to work at elevatedtemperatures [1].

Refractory metal Metal with an extremely high melting point, above the rangeof iron, cobalt, and nickel (Mo, V, W, Ta, Nb) [3].

Relief Due to varying hardness or wear rate of a matrix orindividual phases, or both; material is removed at differentrates, and relief is developed [3].

Removal rate The rate at which material is removed from a surface duringgrinding and polishing. See also Polishing rate.

Glossary 717

Replica A reproduction of a surface in a material, for example, aplastic.(1) Atomic. A thin replica devoid of structure on themolecular level, prepared by the vacuum or hydrolyticdeposition of metals or simple compounds of low molecularweight.(2) Cast. A reproduction of a surface in plastic made by theevaporation of the solvent from a solution of the plastic orby polymerization of a monomer on the surface.(3) Collodion. A replica of a surface cast in nitro-cellulose.(4) Formvar. A reproduction of a surface in a plasticFormvar film.(5) Gelatin. A reproduction of a surface prepared in a filmcomposed of gelatin.(6) Impression. A surface replica which is made byimpression. The results of making an impression.(7) Molecular. The reproduction of a surface in a highpolymer such as collodion and other plastics.(8) Negative. That replica which is obtained by the directcontact of the replicating material with the specimen. In it,the contour of the replica surface is reversed with respect tothat of the original.(9) Oxide film. A thin film of an oxide of the specimen to beexamined. The replica is prepared by air, oxygen, chemical,or electrochemical oxidation of the parent metal and issubsequently freed either mechanically or chemically forpurposes of examination.(10) Plastic. A reproduction in plastic of the surface to bestudied, prepared by evaporation of the solvent from asolution of plastic, by polymerization of a monomer, orsolidification of a plastic on the surface.(11) Positive. A replica, the contours of which corresponddirectly to the surface being replicated; that is, elevations onthe surface are elevations on the replica.(12) Preshadowed. A replica formed by the application ofthe shadowing material to a surface to be replicated, beforethe thin replica film is cast or otherwise deposited on thesurface.(13) Pseudo. A replica which has portions of the materialbeing replicated embedded in it.(14) Tape replica method (faxfilm). A method of producing areplica by pressing the softened surface of a tape or sheet ofa plastic material on the surface to be replicated.(15) Vapor deposited—a replica formed of a metal or a saltby the condensation of the vapors of the material onto thesurface to be replicated [2].


Reproducibility The ability to achieve the same result every time. Inspecimen preparation reproducibility is crucial, as specimenpreparation is often employed in quality inspection andfailure analysis. Reproducibility can be ensured by usingconsumables of high standard and uniform quality, and byusing automatic preparation equipment which controlspreparation parameters, e.g., rotational speed, force, dosinglevels, and time [3].

Resolution The fineness of detail in an object which is revealed by anoptical device. Resolution is usually specified as theminimum distance by which two lines or points in the objectmust be separated before they can be revealed as separatelines or points in the image. The theoretical limit ofresolution is determined from the equation:

d = 0.61�/�n sin A.A./2�

where

d = minimum distance between object pointsobserved as distinct points in the image;

� = wavelength of the radiation employed;

n = the minimum refractive index of the mediabetween the object and the objective lens;

A.A. = the angular aperture �2�. See also Resolvingpower.

Resolving power The ability of a given lens system to reveal fine detail inan object �2�. See also Resolution.

Reticle A system of lines, circles, dots, cross hair or wires, orsome other pattern, placed in the eyepiece or anintermediate plane on the optic axis which is used as ameasuring reference, focusing target, or to define acamera field of view �a reticle is different than a graticule��2�. See also Graticule.

Rigid grinding disk A nonfabric support surface, such as a composite ofmetal/ceramic or metal/polymer, charged during use withan abrasive �usually 6 to 15 micrometre diamondparticles� and used for grinding operations in ametallographic preparation �2�. See also RCD.

Rockwell hardnesstest

Indentation hardness test based on the depth ofpenetration of a specified penetrator �cone or ball� into aspecimen under a specified load �3�.

Roughness Relatively finely spaced surface irregularities, the heights,width, and directions of which establish the predominantsurface pattern �1�.

Glossary 719

Rough polishing A polishing process after fine grinding to remove the layerof significant damage caused by the grinding. Roughpolishing is followed by the steps polishing and finalpolishing to finish the specimen preparation. See alsoFinal polishing, Oxide polishing, Polishing.

Scanningmicroscope

An electron microscope in which the image is formed by abeam operating in synchronism with an electron probescanning the object. The intensity of the image formingbeam is proportional to the scattering or secondaryemission of the specimen where the probe strikes it �2�.See also SEM.

Scratches A groove produced in a surface by an abrasive point �1�.Secondary etching Develops the microstructures that differ from primary

structures through transformation and heat treatment inthe solid state �4�. See also Primary etching.

Segregation Concentration of alloying elements in specific regions in ametallic object �2�.

Segregation „coring…etching

Develops segregation �coring� mainly in macrostructuresand microstructures of castings �4�.

SEM Scanning Electron Microscope is a type of electronmicroscope capable of producing high resolution imagesof a specimen surface. Due to the manner in which theimage is created, SEM images have a characteristicthree-dimensional appearance and are useful for judgingthe surface structure of the specimen �3�. See alsoScanning microscope.

SG iron See Ductile cast iron.Shear �1� That type of force that causes or tends to cause two

contiguous parts of the same body to slide relative to eachother in a direction parallel to their plane of contact. �2� Atype of cutting tool with which a material in the form ofwire, sheet, plate, or rod is cut between two opposingblades. �3� The type of cutting action produced by rake sothat the direction of chip flow is other than at right anglesto the cutting edge �1�.

Short-term etching Etching time of seconds to a few minutes �4�.Shrinkage Reduction in volume of a material from beginning to end

of solidification �3�.Shrinkage cavity A void left in cast metals as a result of solidification

shrinkage �1�.Shrinkage gaps Gaps are voids between the mounting resin and sample

material caused by shrinkage of the mounting resin �3�.Single specimen Single specimens can be prepared on preparation systems

using specimen mover plates. The specimens are notclamped and force is applied to each individual specimen�3�.


Sintering Bonding of particles in a mass of metal powder byheating, usually with prior compacting �3�.

Slag Nonmetallic product resulting from the dissolution of fluxand nonmetallic impurities in smelting, refining, andcertain welding operations �1�. See also Inclusions.

Slip Translation of a portion of a crystal relative to theadjacent portion �2�.

Slip lines Traces of slip planes observed at low magnifications onthe polished surface of a crystal which has been deformedafter polishing; since no differences in orientation exist,repolishing will remove the traces. With increasingresolving power and magnification, an individual line maybe revealed as a series of parallel lines. The “line” which isvisible at low magnifications is then described as a slipband �2�.

Smearing Plastic deformation of a soft matrix or soft phases.Instead of being cut, the material is pushed, moved acrossthe surface. Smearing occurs when the abrasive is toosmall or when using the wrong lubricant or polishingcloth, or a combination of these conditions, whichreduces the cutting effect of the abrasive �3�.

Soldering Bonding of metals using filler metals at temperaturesbelow 450°C �3�.

Specimen A test object, often of standard dimensions orconfiguration, or both, which is used for destructive andnondestructive testing. One or more specimens may becut from each unit of a sample �1�.

Specimen holder„metallography/materialography…

A holder in which 3–12 specimens are clamped. Duringspecimen preparation force is applied to the center of theholder �3�.

Spheroidal cast iron„SG…

Same as nodular cast iron or ductile cast iron. See alsoNodular cast iron.

Spheroidite A coarse aggregate of carbide and ferrite usually producedby tempering martensite at temperatures slightly belowthe eutectoid temperature. Generally, any aggregate offerrite and large spheroidal carbide particles no matterhow produced �2�.

Spheroidizing Heating and cooling to produce a spheroidizing orglobular form of carbide in steel �1�.

Stage A device for holding a specimen in the desired position inthe optical path �2�.

Stage micrometre A graduated scale used on the stage of a microscope forcalibration �2�.

Staining Staining is a discoloration of the specimen surface,typically caused by water, alcohol, or etching solutions�3�.

Glossary 721

Stainless steel Any of several steels containing 12 to 30 % chromium asthe principal alloying element �1�.

Steel Malleable iron-base alloy, containing carbon and otheralloying elements. Carbon and low-alloy steels contain amaximum of 2 % carbon, high-alloy steels up to 2.5 %carbon and over 8 % metallic alloying elements �3�.

Stereology The study of mathematical procedures used to derivethree-dimensional parameters describing a structure fromtwo-dimensional measurement �2�.

Stereomicroscope A light optical microscope that permits each eye toexamine the specimen at a slightly different angle, therebyretaining its three-dimensional relationship �2�.

Strain hardening An increase in hardness and strength caused by plasticdeformation at temperatures below the recrystallizationrange �1�.

Stringer A single, high-aspect ratio, elongated inclusion, two ormore elongated inclusions, or a number of smallnondeformable inclusions aligned in a linear pattern dueto deformation �2�. See also Inclusions.

Structure As applied to a crystal, the shape and size of the unit celland the location of all atoms within the unit cell. Asapplied to microstructure, the size, shape, andarrangement of phases �2�. See also True structure,Polishing.

Subgrain A portion of a crystal or grain, with an orientation slightlydifferent from the orientation of neighboring portions ofthe same crystal or grain �1�.

Substrate �Substratum� that which lies under �2�.Superalloy Same as heat-resistant alloy; superalloys are heat and

corrosion resistant and ductile and contain up to 20 %chromium �Cr� �3�. See also Heat-resistant alloy.

Swab etching Wiping the specimen surface with cotton saturated withan etchant. This will simultaneously remove undesiredreaction products �4�.

Swarf Mixture of chips, abrasive material, and lubricatingmedium developing during grinding/polishing.

Technical ceramics Pressed and sintered oxides, carbides, and nitrides. Theyare very dense, insulators, highly wear resistant, andresistant against chemicals: aluminum oxide �Al2O3�,silicon carbide �SiC�, silicon nitride �Si3N4�, tungstencarbide �WC�, titanium carbide �TiC�, boron carbide�B4C�, titanium boride �TiB2�, zirconium oxide �ZrO2��3�.


TEM The Transmission Electron Microscope is an imaginginstrument whereby a beam of electrons is focused onto aspecimen causing an enlarged version to appear on afluorescent screen or layer of photographic film or can bedetected by a CCD camera �3�. See also Thin foil,Transmission microscope.

Tensile testing To determine the strength of a material by pulling asample applying equal and constant stress until it breaks.The elongation of the sample is also measured. Alsoknown as tension testing �3�.

Thermal Any physical process taking place due to heat �3�.Thermal etching Annealing the specimen in a vacuum or inert atmosphere.

This is a preferred technique for high-temperaturemicroscopy and for ceramics �4�.

Thermoplastic resins Mounting resins that soften or melt at elevatedtemperatures and harden during cooling �3�.

Thermosettingresins

Mounting resins that cure under heat and pressure andcannot be melted after curing. They are also calledduroplastics �3�.

Thin foil A very thin specimen prepared for transmissionmicroscopy. See also TEM.

Tool steel Any of a class of carbon and alloy steels commonly usedto make tools. Tool steels are characterized by highhardness and resistance to abrasion, often accompaniedby high toughness and resistance to softening at elevatedtemperature. These attributes are generally attained withmedium carbon and high-alloy contents �1�.

Traditional ceramics Earthenware, brick, clay, porcelain �3�.Transmissionmicroscope

A microscope in which the image forming rays passthrough �are transmitted by� the specimen being observed�2�. See also TEM.

True structure The microstructure representing the material without anyinfluences from the preparation of the specimen. See alsoStructure, Polishing.

Twin bands Bands across a crystal grain, observed on a polished andetched section, the crystallographic orientations of whichhave a mirror image relationship to the orientation of thematrix grain across a composition plane which usually isparallel to the sides of the band. �1� Annealing twins—twin bands which are produced during annealingfollowing cold work. �2� Mechanical twins—twin bandswhich are produced by cold work. �3� Neumann bands—mechanical twins in ferrite �2�.

Ultrasonic cleaning Immersion cleaning aided by ultrasonic waves that causemicroagitation �1�.

Glossary 723

Ultrasonic testing Nondestructive test used on sound conductive materials tolocate cavities, cracks, and structural discontinuities bymeans of ultrasonic impulse �3�.

Vibratory polishing Mechanical polishing process where one or severalspecimens are moved around in a bowl through vibrationof the bottom of the bowl.

Vickers In a more restricted sense, the 136° diamond pyramidindenter used in microindentation hardness tests �2�. Seealso Micro indentation hardness, Micro penetrationhardness, Vickers hardness test.

Vickers hardnesstest

Indentation hardness test using a pyramid-shapeddiamond indenter and variable loads which enables theuse of one hardness scale for all materials from very softlead to tungsten carbide �3�. See also Micro indentationhardness, Micro penetration hardness, Vickers.

Weld Union between materials by welding �3�. See also Welding.Welding Joining two or more pieces of metal by applying heat or

pressure, or both, with or without a filler material, toproduce a localized union through fusion orrecrystallization across the interface �1�.

Weld structure The microstructure of a weld deposit and heat-affectedbase metal �2�. See also Welding.

Wet etching The specimen surface has to be wetted before immersioninto the etching solution. This is important for coloretchants �4�.

Whiskers Metallic or ceramic filaments, mostly microscopic, moreor less evenly distributed in a matrix �3�.

White cast iron Cast iron that shows a white fracture because the carbonis present in the form of iron carbide, Fe3C, which givesit its very high hardness and also brittleness �3�.

White metal A general term covering a group of white-colored metalsand their alloys of relatively low melting points �lead,antimony, tin, cadmium, bismuth, and zinc� and alloysbased on these metals �1�.

Wire cutting A cutting method mainly used for sectioning of smallspecimens of various types of materials. A fine wire isdrawn along the work piece with a controlled force. Theabrasive is either diamond bonded to the wire, or anabrasive slurry that is dripped continuously onto the wireand drawn into the cut �3�.

Workability See Formability.Work hardening A change in the hardness of a material as a result of

plastic deformation �2�.Working distance The distance between the surface of the specimen being

examined and the front surface of the objective lens �2�.


Wrought iron An iron produced by direct reduction or ore or by refiningmolten cast iron under conditions where a pasty mass ofsolid iron with included slag is produced. The iron has alow carbon content �1�.

X-ray testing Using X-ray radiation to check work pieces for cavities,cracks, pores, and overlaps. Especially used for checkingof welds �3�.

Young’s modulus A term used synonymously with modulus of elasticity. Theratio of tensile or compressive stresses to the resultingstrain �1�. See also Modulus of elasticity.

References „Glossary…[1] Benscoter, A. O. and Bramfitt, B. L., Metallographer’s Guide, Practices and

Procedures for Irons and Steels, ASM International, Materials Park, Ohio, USA, 2002.Reprinted with permission of ASM International®. All rights reserved. www.asminternational.org

[2] ASTM Standard, Terminology Relating to Metallography �E 7�, ASTM International,West Conshohocken, Pennsylvania, USA, 2003.

[3] Terms defined by Struers in the on-line training material e-Education and e-Trainingunder www.struers.com.

[4] Petzow, G., Metallographic Etching, ASM International, Materials Park, Ohio, USA,1999.

Glossary 725

Subject IndexA

Abbreviationsoccupational safety and health,

labs, 673–674specimen preparation, 221

Abrasive cut-off machines, 36–43design principles of wheel-work

piece contact, 36–39machine designs, 39–43

Abrasive cut-off wheels, 32–36consumable wheels, 32–34slow consumable wheels, 34–36

Abrasives, 18–19aluminum oxide, 18cubic boron nitride, 18diamond, 18–19polishing, 129–132silicon carbide, 18wet abrasive cutting,

sectioning, 16–21Acrylics

occupational safety and health,labs, 668

specimen preparation, 436–439After preparation cleaning, 82–84Agency for Toxic Substance and

Disease Registry �ATSDR�, 683–684Alcohol-based grinding/polishing

fluids, 97Alumina wet grinding paper, 105–106Aluminum

electrolytic polishing andetching, 464

specimen preparation, 352–356Aluminum alloys, 356–358Aluminum oxide

abrasive types, 18grinding abrasives, 93specimen preparation, 238–240

American Conference of GovernmentIndustrial Hygienists �ACGIH�, 683

Analog cameras, automatic imageanalysis, 614–615

Anodic etching, 172–173Anodized coatings, specimen

preparation, 247–251Anodizing, etching, 173Antimony, specimen preparation,

361–364

Arc of contact, metallographic/materialographic cuttingoperation, 31

Archiving, 619Artifacts of electrolytic polishing,

selection of preparation method, 7ASTM B 487, 576ASTM C 664, 576ASTM E 45, 570ASTM E 112, 571–573ASTM E 562, 569ASTM E 930, 573ASTM E 1077, 575ASTM E 1122, 570ASTM E 1181, 573ASTM E 1245, 570ASTM E 1268, 574ASTM E 1382, 573ASTM E 1578, 619ASTM E 2014, 668, 674ASTM E 2109, 574–575ASTM standards

cutting fluids, wet abrasivecutting, 29hardness, 625metallography, 188–193

Atomic force microscope �AFM�, 561Automatic grinding equipment,

119, 135Automatic image analysis, 577–617

analog cameras, 614–615automatic measurements,

600–602background correction, 586–588banding degree, 608brightness and contrast, 581–586cameras, 614–615compacted graphite, 613computers, 614contrast stretching, 588–589depth measurements, 608–610digital cameras, 615–616digital imaging, 579, 602–613digital imaging technology,

613–616ductile cast iron, 611–613grain size, 606–608graphite in iron castings, 610–611gray cast iron, 613hardware, 613–616

727

histogram, 581image acquisition, 579–580image calibration, 595–598image digitization, 580–581image measurement, 598–602image processing, 586–595implementation, 617–618inclusion rating, 603–606manual measurements, 599–600open source/public domainsoftware, 617percent area, 602–603printers, 616sharpening, 593–595smoothing, 592–593software, 616–617thickness measurements, 608–610volume fraction, 602–603watershed filter, 590–592

Automatic measurements, automaticimage analysis, 600–602

Automatic systems, polishing, 140–143Automation labs, 651–654Availability of NIOSH Registry of Toxic

Effects of Chemical Substances, 681

B

Background correction, automaticimage analysis, 586–588

Bacteria and fungi, cutting fluids, wetabrasive cutting, 28–29

Bakelite bond, 20–21Banding, quantitative metallography/materialography, 574Banding degree, automatic image

analysis, 608Bandsawing, 48–52

blades, 49–51cutting fluids, 51machines, 49–51safety, 49tips, 51–52

Barium titanate, specimenpreparation, 241

Baumann hammer, 644Before preparation start cleaning, 82Beryllium, specimen preparation,

365–367

Bias, quantitative metallography/materialography, 568–569

Blades, bandsawing, 49–51Bond materials

cut-off wheel, 20–21wet abrasive cutting, sectioning,

16–21Bones, specimen preparation, 427–430Boron carbide

grinding abrasives, 97specimen preparation, 227–232

Brass, specimen preparation, 376–380Brightness and contrast, automatic

image analysis, 581–586Brinell hardness testing, 626–628British Standards Institution, 684Brittle materials, grinding, 92–93Bronze

electrolytic polishingand etching, 467specimen preparation, 376–380

Building labs, 649, 650–663

C

Calcium oxide, specimenpreparation, 241

Calibration, quantitativemetallography/materialography, 568

Cameras, automatic imageanalysis, 614–615

Capacitors, specimen preparation,298–300

Carbonitrided steels, specimenpreparation, 339–342

Cement clinker, specimen preparation,346–349

Cemented carbides, 187Ceramic capacitors, specimen

preparation, 281–284Ceramic layers, specimen preparation,

268–270Ceramic resistors, specimen

preparation, 281–284Ceramics

deformation, grinding, 92–93specimen material, 182specimen preparation, 232–235


Cerium oxide, specimenpreparation, 241

Chemical disposals, occupational safetyand health, labs, 672–673

Chemical etching, 172Chemical mechanical polishing �CMP�,

7, 151–152Chemical microetching, examination

purpose, 194–217Chemical polishing, 7

electrolytic polishing/etching, 168Chips, sliding, plowing, grinding

mechanics, 22Chromium

electrolytic polishingand etching, 464–465

specimen preparation, 367–370Chromium carbide, specimen

preparation, 232–235Chromium oxide, specimen

preparation, 238–240Circular sawing, 48Clamping, thermal damage, wet

abrasive cutting, 24–25Classical etching, 172Classification of materials, specimen

material, 181Cleaning, 82–84

after preparation, 82–84drying, 83ethanol, 83grinding disks, 84hand, 82–83polishing cloths, 84before preparation start, 82rubbing effect, 83ultrasonic, 83ultrasonic apparatuses, 83

Cleanliness, 84Cloths, polishing, 124–129Coatings, specimen material, 182–183Cobalt

electrolytic polishingand etching, 465–466

specimen preparation, 370–373Cobalt-based super alloys, specimen

preparation, 373–376Cold mounting resins, occupational

safety and health, labs, 667

Color etching, 172Color ratings system, occupational

safety and health, labs, 669Compacted graphite, automatic image

analysis, 613Comparison procedure, quantitative

metallography/materialography,571–572

Compositesspecimen material, 183specimen preparation, 276–281

Compressed air, cleaning, 83Computers, automatic image

analysis, 614Concrete, specimen preparation,

346–349Confocal laser scan microscope,

552–555Consumable abrasive cut-off wheels

storing, 33–34wheel dimensions, 33wheel velocity, 32–33

Consumables, specimen preparation,221

Contemporary grinding, 106–117diamond film, 109diamond pads, 109fine grinding cloths, 116magnetic fixation, 106–107metal-bonded diamond-coated

disks, 109resin-bonded diamond grinding

disks, 107–108resin-bonded SiC grinding

disks, 108rigid composite disks, 109–116

Contrast stretching, automatic imageanalysis, 588–589

Cooling, cutting fluids, 26Cooling system, cutting fluids, wet

abrasive cutting, 27–28Copper

electrolytic polishingand etching, 466

specimen preparation, 376–380Copper-bearing alloys, specimen

preparation, 380–383Cubic boron nitride, abrasive types, 18

Subject Index 729

Cubic boron nitride �CBN�, grindingabrasives, 97

Cut-off grinding process, wet abrasivecutting, sectioning, 15–16

Cut-off wheelabrasive types, 18–19bond material, 20–21grade, 20grain size, 19–20rpm, 30selection, 44–45specifications, 16–18structure, 20truing and dressing, 26wear, 25–26wet abrasive cutting, sectioning,

16–21Cutting fluids, 26–29

ASTM standards, 29bacteria and fungi, 28–29bandsawing, 51cooling system, 27–28grinding fluid application, 27grinding fluid concentration, 28grinding fluid disposal, 29health and safety aspects, 29lubrication and cooling, 26synthetic grinding fluids-oil-

based, 26–27water quality, 28

CVD coatings, specimen preparation,247–251

D

Dangers, occupational safety andhealth, labs, 664

Dark-field illumination �DF�,etching, 169

Decarburization, quantitativemetallography/materialography,

575–576Deformation, 89–93

brittle materials, 92–93ceramics, 92–93grinding, 86metals, 89–92polishing, 122–124

Depth measurements, automatic imageanalysis, 608–610

Design principles of wheel-workpiece contact

abrasive cut-off machines, 36–39direct cutting, 36oscillating cutting, 36–37rotating work piece, 39step cutting, 38–39

Diamond productsabrasive types, 18–19film, 109fixed grains, 95grinding abrasives, 94–96loose grains, 95–96monocrystalline, 94pads, 109pastes, 96polycrystalline, 94sprays, 96suspensions, 96

Differential interference contrast �DIC�,etching, 169

Diffusion coatings, specimenpreparation, 251–254

Digital cameras, automatic imageanalysis, 615–616

Digital image management, 619Digital imaging, automatic image

analysis, 579, 602–613Digital imaging technology, automatic

image analysis, 613–616Diodes, specimen preparation, 281–284Direct cutting, design principles of

wheel-work piece contact, 36Documentation, optical reflected light

microscope, 550–552Drying, cleaning, 83Ductile cast iron, automatic image

analysis, 611–613Dust, occupational safety and health,

labs, 667Dynamic hardness testing procedures,

644–645

EEconomy, grinding, traditional, 105Edge retention, grinding, traditional,

103–105


Education, labs, 651Electric discharge machining �EDM�,

sectioning by melting, 46Electrolytes, polishing/etching, 163–164Electrolytic polishing and etching,

172–173, 453–475aluminum, 464bronze, 467chromium, 464–465cobalt, 465–466copper, 466gray cast iron, 459hard metals, 474–475heat treated steels, 459–460high carbon steels, 457high-speed steels, 462–463iron, 462lead, 467–468low-alloyed tool steels, 463low carbon steels, 457–458magnesium, 468–469nickel, 469silver, 469–470stainless steels, 460–461super alloys, 461tin, 470–471titanium, 471tungsten, 472vanadium, 472–473zinc, 473zirconium, 474

Electrolytic polishing/etching, 156–168chemical polishing, 168electrolytes, 163–164electrolytic thinning fortransmission electron microscope

�TEM�, 167–168electropolishing in practice,

164–165equipment, 165–166field metallography, 166–167nondestructive electropolishing,

166–167occupational safety and health,

labs, 665process, 156–163

Electrolytic polishing etching,artifacts, 7

Electrolytic thinning for transmission

electron microscope �TEM�, 167–168Electrolytically deposited coatings,

251–254Electron backscatter diffraction

�EBSD�, 559–560polishing, 149–150

Electron microscopy, 558–561atomic force microscope �AFM�,

561electron backscatter diffraction

�EBSD�, 559–560electron probe microanalyzer

�EPMA�, 560energy dispersive spectroscopy

�EDS�, 559focused ion beam �FIB�, 560magnetic force microscopy

�MFM�, 561scanning electron microscope

�SEM�, 558–559scanning probe microscopes

�SPM�, 560–561scanning transmission electron

microscope �STEM�, 558transmission electron microscope

�TEM�, 558Electron probe microanalyzer �EPMA�,

560Electropolishing in practice, 164–165Energy dispersive spectroscopy �EDS�,

559Engraving, marking, 80Environment, grinding, traditional, 105Environmental Protection Agency

�EPA�, 683EPDM polymers, 430–436Epoxy, occupational safety and health,

labs, 667Equipment

electrolytic polishing/etching,165–166

labs, 656–660Equotip tester, 645Etchant names, examination purpose,

217Etching, 169–176

anodic, 172–173anodizing, 173chemical, 172

Subject Index 731

classical, 172color, 172dark-field illumination �DF�, 169differential interference contrast

�DIC�, 169electrolytic, 172–173examination purpose, 194fluorescence, 170grain boundary etching, 171grain contrast etching, 170–171heat tinting, 172ion, 173–174macroetching, 174–175microetching, 169microscope techniques, 169–170occupational safety and health,

labs, 665–666physical, 173–174polarized light �POL�, 169–170potentiostatic, 173precipitation, 172preparation process, 13reactive sputtering, 174relief polishing, 173reproducibility, 171–172sputtering, 174thermal, 174vapor deposition, 174

Ethanol, cleaning, 83European Union �EU�, occupational

safety and health, labs, 669–670, 684Examination purpose, 179, 188

ASTM standards, 188–217chemical microetching, 194–217etchant names, 217etching practice, 194

Eyepieces, optical reflected lightmicroscope, 535–536

F

Failure analysis, labs, 651Feed speed, metallographic/

materialographic cutting operation,30–31

Ferrous metals, specimen material,183–184

Field metallography


polishing, 150–151Field metallography/materialography,

specimen preparation, 475–476Field selection, quantitative


Fine grinding, 86, 119Fine grinding cloths, 116Fixed grains, diamond products, 95Flammable and Combustible Liquids,

680Flammable liquids, occupational safety

and health, labs, 667Fluorescence, etching, 170Focused ion beam �FIB�, 560Force

material removal, grinding, 89metallographic/materialographic

cutting operation, 30Fracturing, sectioning, 45Free cutting, 31–32

automatics, 32hand, 32

G

Galvanization, specimen preparation,251–254

General Description and Discussion ofthe Levels of Protection and

Protective Gear, 680–681General studies or routine work, 14General use, machine designs, abrasive

cut-off, 40–41Generic methods, specimen

preparation, 219Germanium, specimen preparation,

288–291Glasses, specimen preparation,

244–247Gold, specimen preparation, 384–387Grades

cut-off wheel, 20hard, 20soft, 20

Grain boundary etching, 171Grain contrast etching, 170–171


Grain penetration, material removal,grinding, 89

Grain shape, material removal,grinding, 88

Grain sizeautomatic image analysis,

606–608cut-off wheel, 19–20quantitative metallography/materialography, 571–573

Graphite in iron castings, automaticimage analysis, 610–611

Gray cast ironautomatic image analysis, 613electrolytic polishing and etching,

459specimen preparation, 315–318

Grinding, 85–86chips, sliding, plowing, 22contemporary, 106–117deformation, 86, 89–93fine, 86material removal, 86–89plane, 85traditional, 99–106wet abrasive cutting, sectioning,

21–22Grinding, traditional, 99–106

alumina wet grinding paper,105–106

economy, 105edge retention, 103–105environment, 105relief, 103–105SiC wet grinding paper, 100–105stones/disks, 99–100zirconia alumina wet grinding

paper, 105–106Grinding abrasives, 93–97

aluminum oxide, 93boron carbide, 97cubic boron nitride �CBN�, 97diamond, 94–96silicon carbide, 93

Grinding disks cleaning, 84Grinding fluid

application, 27concentration, 28disposal, 29

Grinding/polishing equipment, 117–119automatic grinding, 119fine grinding, 119manual grinding, 117–119plane grinding, 117–119

Grinding/polishing fluids, 89, 97–99alcohol-based, 97oil-based, 98–99water-based, 97water-oil based, 98

Grit number, 19

H

Hacksawing, 48Hand cleaning, 82–83Hard grade, 20Hard metals, electrolytic polishing

and etching, 474–475Hardness, 623–625

ASTM standards, 625indentation, 623–624testing special methods, 646

Hardness valuesconversion, 642–643precision, 642

Hardware, automatic imageanalysis, 613–616

Hazard Communication Standard�HCS�, OSHA standard, 674–679Health and safety aspects, cutting

fluids, 29Heat tinting, etching, 172Heat treated steels, electrolytic

polishing and etching, 459–460High-alloy steels, specimen

preparation, 325–328High carbon steels

electrolytic polishing and etching,457

specimen preparation, 307–311High-speed steels

electrolytic polishing and etching,462–463

specimen preparation, 343–346Histogram, automatic image analysis,

581HMIS, occupational safety and health,

labs, 670

Subject Index 733

Hot dip zinc coatings, specimenpreparation, 254–257

Human eye, light microscopy, 526–527Hydroxyapatite �HA� coating, specimen

preparation, 223–226

I

Identification tag marking, 80Illumination, optical reflected light

microscope, 536–537Image

acquisition, 579–580calibration, 595–598digitization, 580–581measurement, automatic image

analysis, 598–602processing, automatic image

analysis, 586–595Implementation, automatic image

analysis, 617–618Inclusion rating

automatic image analysis,603–606

quantitative metallography/materialography, 570

Indentation hardness, 623–624Instrumented indentation testing,

641–642Integrated circuits. specimen

preparation, 301–305Intercept procedure, quantitative


International Chemical Safety Cards,682–683

Ion etching, 173–174Iron, electrolytic polishing and etching,

462

J

Job Safety Analysis �JSA�, 670–672

K

Knoop hardness testing, 633–634

L

Laboratory information managementsystems �LIMS�, 619

Labs, 649automation, 651–654building, 649, 650–663education, 651equipment, 656–660failure analysis, 651layout, 660–662maintenance, 662–663occupational safety and health,

649, 664–684planning, 654–656purpose, 650quality control, 650rationalization, 651–654research, 651running, 649testing and inspection labs, 651

Laser torching, sectioning bymelting, 46

Layout, labs, 660–662Lead


specimen preparation, 387–391Light microscopy, 525–527

human eye, 526–527magnification, 527magnifying lens and microscope,

527visible light, 525–526

List of Highly Hazardous Chemicals,Toxics and Reactives, OSHA

standards, 680Literature, occupational safety and

health, labs, 684–686Loose grains, diamond products, 95–96Low-alloy steels, specimen preparation,

336–339Low-alloyed steels, electrolytic

polishing and etching, 463Low carbon steels


specimen preparation, 311–314Lubricants, 97–99


cutting fluids, 26

M

Machine designs, 39–43general use, 40–41polishing, 135–139precision, 41–43

Machines, bandsawing, 49–51Macroetching, 174–175Magnesium


specimen preparation, 391–394Magnesium oxide, specimen

preparation, 241Magnetic fixation, contemporary

grinding, 106–107Magnetic force microscopy �MFM�, 561Magnification, light microscopy, 527Magnifying lens and microscope, 527Maintenance, labs, 662–663, 673Malleable cast iron, specimen

preparation, 315–318Manganese, specimen preparation,

395–397Manual grinding equipment,

117–119, 135Manual measurements, automatic

image analysis, 599–600Marking, 80

engraving, 80identification tag, 80stamping, 80with waterproof ink, 80

Martens scratch hardness, 646Material exam, 179Material removal, 86–89

force on specimens, 89grain penetration, 89grain shape, 88grinding, 86grinding/polishing fluids, 89polishing, 120–122rake angle, 87–88

Material Safety Data Sheet �MSDS�,occupational safety and health, labs,

670–672Materialographic specimen, 7–9

specimen or sample, 8–9Materialography, 3Mechanical damage, wet abrasive

cutting, 22–23unplane surface, 23waviness, 23

Mechanical polishing artifacts,selection of preparation method, 7

Mechanical preparation, occupationalsafety and health, labs, 665

Mechanical surface preparation. seegrinding

Medium carbon steels, specimenpreparation, 307–311

Metal-bonded diamond-coated disks,contemporary grinding, 109

Metallographic/materialographiccutting operation

arc of contact, 31cut-off wheel rpm, 30feed speed, 30–31force, 30free cutting, 31–32power, 31wet abrasive cutting,

sectioning, 29–32wheel velocity, 30

Metallographic/materialographicpreparation, 5–6

Metallography, 3Metals, deformation, grinding, 89–92Microelectronic material, specimen

preparation, 291–293Microelectronic materials, polishing,

143–147Microelectronic packages

polishing, 147–149specimen preparation,

295–298, 301–305Microetching, 169Microindentation hardness, 636–639Microscopes

options, 537–538techniques, etching, 169–170

Microtomy, polishing, 155Mineralogical materials, specimen

material, 184Minerals, ores, specimen preparation,

349–352

Subject Index 735

Mohs scratch hardness, 646Molybdenum, specimen preparation,

398–401Monocrystalline, diamond products, 94Mounting

occupational safety and health,labs, 664–665

preparation process, 11

N

National Fire Protection Association�NFPA�, 684

National Paint and CoatingsAssociation, 684

National Technical Information Service�NTIS�, 683

National Toxicology Program �NTP�,683

NFPA 704 Hazard IdentificationRatings System, 668–669

Nickelelectrolytic polishing and etching,


NIOSH standards, 681–682Nodular cast iron, specimen

preparation, 319–321Nondestructive electropolishing,


Nonferrous metals, specimen material,184–186

O

Occupational Exposure to HazardousChemicals in Laboratories, 679–680Occupational Safety and Health

Administration �OSHA� standardsAvailability of NIOSH Registry of

Toxic Effects of ChemicalSubstances, 681

Flammable and CombustibleLiquids, 680

General Description andDiscussion of the Levels of

Protection and Protective Gear,680–681

Hazard Communication Standard�HCS�, 674–679

List of Highly HazardousChemicals, Toxics andReactives, 680

Occupational Exposure to HazardousChemicals in Laboratories, 679–680Occupational safety and health labs,

649, 664–684abbreviations, 673–674acrylics, 668Agency for Toxic Substance and

Disease Registry �ATSDR�,683–684

American Conference ofGovernment IndustrialHygienists �ACGIH�, 683

ASTM E 2014, 668, 674British Standards Institution, 684chemical disposals, 672–673cold mounting resins, 667color ratings system, 669dangers, 664dust, 667electrolytic polishing/etching, 665Environmental Protection Agency

�EPA�, 683epoxy, 667etching, 665–666EU system, 669–670European Union �EU�, 684flammable liquids, 667HMIS, 670International Chemical Safety

Cards, 682–683Job Safety Analysis �JSA�,

670–672literature, 684–686maintenance and service, 673Material Safety Data Sheet

�MSDS�, 670–672mechanical preparation, 665mounting, 664–665National Fire Protection

Association �NFPA�, 684National Paint and Coatings

Association, 684


National Technical InformationService �NTIS�, 683

National Toxicology Program�NTP�, 683

NFPA 704 Hazard IdentificationRatings System, 668–669

NIOSH standards, 681–682OSHA standards, 674–681

polyesters, 668risk phrases, 670safety information, 668–672sectioning, 664Standard Operating Procedure

�SOP�, 670–672standards, 673toxic substances, 666training, 673

Oil-based grinding/polishing fluids,98–99

Open source/public domain software,image analysis, 617

Optical examination methods, reflectedlight microscope, 540–546

Optical fibers, specimen preparation,244–247

Optical reflected light microscope,528–555

confocal laser scan microscope,552–555

documentation, 550–552eyepieces, 535–536illumination, 536–537microscope options, 537–538optical examination methods,

540–546path of light rays, 528practical use of microscope,

546–550reflected-light microscope,

538–540stereo microscopy, 555–557

Ores, specimen preparation, 349–352Organic materials, specimen material,

186–187Oscillating cutting, design principles of

wheel-work piece contact, 36–37Oxyacetylene torching, 46

P

Paint layers, specimen preparation,257–260

Palladium, specimen preparation,406–409

Parameters, specimen preparation,220–221

Pastes, diamond products, 96Path of light rays, optical reflected light

microscope, 528PCB coupon, specimen preparation,

305–307Percent area, automatic image analysis,

602–603Phenolic bond, 20–21Physical etching, 173–174Pitting, 9Plane grinding, 85, 117–119Planimetric procedure, quantitative

metallography/materialography, 572Planning, labs, 654–656Plasma spray coatings, specimen

preparation, 265–267, 270–273Plasma torching, sectioning by

melting, 46Plated coatings, specimen preparation,

251–254Point count, quantitativemetallography/materialography, 569Polarized light �POL�, etching, 169–170Poldi impact hardness tester, 644Polishing, 120–155

abrasives, 129–132automatic grinding/polishingequipment, 135automatic systems, 140–143chemical mechanical polishing

�CMP�, 151–152cloths, 84, 124–129deformation, 122–124dynamics, 139–140electron backscatter diffraction

�EBSD�, 149–150field metallography, 150–151machine design, 135–139manual grinding/polishing

equipment, 135material removal, 120–122

Subject Index 737

microelectronic materials,143–147

microelectronic packages,147–149

microtomy, 155polishing dynamics, 139–140preparation methods, 132–134printed circuit boards �PCB�,

143rough, 120semiautomatic systems, 140–143thin sections, 152–154ultramilling, 155

Polycrystalline diamond products, 94Polyesters, occupational safety and

health, labs, 668Polymers, specimen material, 187Porosity in thermal spray coatings,

574–575Potentiostatic etching, 173Powder metals

specimen material, 187specimen preparation, 439–443

Power, metallographic/materialographic cutting

operation, 31Power hacksawing, 48Practical use of microscope, 546–550Precipitation etching, 172Precision

cut-off, slow consumable wheels,35

machine designs, abrasive, 41–43Preparation methods

polishing, 132–134selection of preparation

method, 7Preparation process, 9–13

etching, 13mounting, 11sectioning, 10–11surface preparation, 11–13

Preservation, 81Printed circuit boards �PCB�,

polishing, 143Printers, automatic image analysis, 616Process, electrolytic polishing/etching,

156–163Punching, shearing, 47

Purpose, labs, 650PVD coatings, specimen preparation,

247–251

Q

Quality control labs, 650Quantitative metallography/

materialography, 565–576ASTM B 487, 576ASTM C 664, 576ASTM E 45, 570ASTM E 112, 571–573ASTM E 562, 569ASTM E 930, 573ASTM E 1077, 575ASTM E 1122, 570ASTM E 1181, 573ASTM E 1245, 570ASTM E 1268, 574ASTM E 1382, 573ASTM E 2109, 574–575banding, 574bias, 568–569calibration, 568comparison procedure, 571–572decarburization, 575–576field selection, 568–569grain size, 571–573inclusion rating, 570intercept procedure, 572–573other standards, 576planimetric procedure, 572point count, 569porosity in thermal spray

coatings, 574–575specimen preparation, 567–568stereology, 565–567volume fraction, 569

R

Rake angle, material removal,grinding, 87–88

Rationalization, labs, 651–654Reactive sputtering, etching, 174Reflected-light microscope, 538–540Relief


grinding, 103–105polishing, 173

Reporting locations, 15Reproducibility, etching, 171–172Research labs, 651Research studies, 14Resin-bonded diamond grinding disks,

107–108Resin-bonded SiC grinding disks, 108Resistors, specimen preparation,

293–295Rigid composite disks, grinding,

109–116Risk phrases, occupational safety

and health, labs, 670Rockwell hardness testing, 634–636Rotating work piece, 39Rough polishing, 120Rubber bonds, 21Rubbing effect, cleaning, 83Running labs, 649

S

Safetybandsawing, 49occupational safety and health,

labs, 668–672Sample, materialographic specimen,

8–9Sawing

bandsawing, 48–52circular sawing, 48hacksawing, 48power hacksawing, 48sectioning, 47–52

Scanning electron microscope �SEM�,558–559

Scanning probe microscopes �SPM�,558–561, 560–561

Scanning transmission electronmicroscope �STEM�, 558

Scleroscope, 645Section type, selection, sectioning,

14–15Sectioning, 14–53, 15

abrasive cut-off machines, 36–43abrasive cut-off wheels, 32–36fracturing, 45

occupational safety and health,labs, 664

other methods, 45–53preparation process, 10–11sawing, 47–52sectioning by melting, 46selection, 14–15shearing, 46–47wet abrasive cutting, 15–32wet abrasive cutting tips, 43–45wire cutting, 52–53

Sectioning by melting, 46electric discharge machining

�EDM�, 46laser torching, 46oxyacetylene torching, 46plasma torching, 46

Selection, sectioning, 14–15general studies or routine

work, 14reporting locations, 15research studies, 14section type, 14–15study of failures, 14

Selection of preparation method, 6–7artifacts of electrolytic

polishing, 7artifacts of mechanical

polishing, 7preparation methods, 7

Semiautomatic systems, polishing,140–143

Semiconductors, specimenpreparation, 288–291

Sharpening, automatic image analysis,593–595

Shearingpunching, 47sectioning, 46–47

Si wafers, specimen preparation,288–291

SiC fibers in Ti matrix, specimenpreparation, 273–276

SiC wet grinding paper, 100–105Silicon, specimen preparation, 288–291Silicon carbide

abrasive types, 18grinding abrasives, 93

Subject Index 739

Silicon nitride, specimen preparation,235–237

Silicon oxide, specimen preparation,241

Silverelectrolytic polishing and etching,

469–470specimen preparation, 409–412

Sintered carbidesspecimen material, 187specimen preparation, 443–447

Slow consumable wheelsprecision cut-off, 35storing, 36truing and dressing, 34–35use, 35wheel dimensions, 35wheel velocity, 35

Smoothing, automatic image analysis,592–593

Soft grade, 20Software, automatic image analysis,

616–617Solder balls, specimen preparation,

295–298Sorby, Henry Clifton, 5–6Special methods hardness testing, 646Specimen material, 179, 181–187

ceramics, 182classification of materials, 181coatings, 182–183composites, 183ferrous metals, 183–184materialographic specimen, 8–9mineralogical materials, 184nonferrous metals, 184–186organic materials, 186–187polymers, 187powder metals, 187sintered carbides, 187

Specimen preparation,179–180, 218–521

abbreviations, 221acrylics, 436–439aluminum, 352–356aluminum alloys, 356–358aluminum oxide, 238–240anodized coatings, 247–251antimony, 361–364

barium titanate, 241beryllium, 365–367bones, 427–430boron carbide, 227–232brass, 376–380bronze, 376–380calcium oxide, 241capacitors, 298–300carbonitrided steels, 339–342cement clinker, 346–349ceramic capacitors, 281–284ceramic layers, 268–270ceramic resistors, 281–284ceramics, 232–235cerium oxide, 241chromium, 367–370chromium carbide, 232–235chromium oxide, 238–240cobalt, 370–373cobalt-based super alloys,

373–376composites, 276–281concrete, 346–349consumables, 221copper, 376–380copper-bearing alloys, 380–383CVD coatings, 247–251diffusion coatings, 251–254diodes, 281–284electrolytic polishing and etching,

453–475electrolytically deposited

coatings, 251–254EPDM polymers, 430–436field metallography/

materialography, 475–476galvanization, 251–254generic methods, 219germanium, 288–291glasses, 244–247gold, 384–387gray cast iron, 315–318high-alloy steels, 325–328high carbon steels, 307–311high-speed steels, 343–346hot dip zinc coatings, 254–257hydroxyapatite �HA� coating,

223–226integrated circuits, 301–305


lead, 387–391low-alloy steels, 336–339low carbon steels, 311–314magnesium, 391–394magnesium oxide, 241malleable cast iron, 315–318manganese, 395–397medium carbon steels, 307–311microelectronic material,

291–293microelectronic packages,

295–298, 301–305minerals, ores, 349–352molybdenum, 398–401nickel, 402–405nodular cast iron, 319–321optical fibers, 244–247paint layers, 257–260palladium, 406–409parameters, 220–221PCB coupon, 305–307plasma spray coatings,

265–267, 270–273plated coatings, 251–254powder metals, 439–443PVD coatings, 247–251quantitative metallography/

materialography, 567–568resistors, 293–295semiconductors, 288–291Si wafers, 288–291SiC fibers in Ti matrix, 273–276silicon, 288–291silicon nitride, 235–237silicon oxide, 241silver, 409–412sintered carbides, 443–447solder balls, 295–298stainless steels, 328–333steps, 219–220super alloys, 333–335teeth, 427–430thermal spray coatings, 260–265tin, 413–416tin cubic boron nitride, 232–235tissue, 427–430titanium, 416–420titanium carbide, 232–235titanium nitride, 232–235

transistors, 301–305trouble shooting, 476–521tungsten carbide, 232–235uranium, 447–450white cast iron, 322–324wrought aluminum alloys,

359–361YBCO ceramic super conductors,

285–288zinc, 420–423zinc oxide, 241zirconium, 424–427zirconium dioxide, 241

Sprays, diamond products, 96Sputtering, etching, 174Stainless steels


specimen preparation, 328–333Stamping, marking, 80Standard Operating Procedure �SOP�,

670–672Standards, occupational safety and

health, labs, 673Static hardness testing, 626–643

Brinell hardness testing, 626–628hardness values conversion,

642–643hardness values precision, 642instrumented indentation

testing, 641–642Knoop hardness testing, 633–634microindentation hardness,

636–639Rockwell hardness testing,

634–636universal hardness, 639–642Vickers hardness testing, 628–632

Step cutting, design principles ofwheel, 38–39

Steps, specimen preparation, 219–220Stereo microscopy, 555–557Stereology, 565–567Stones/disks, grinding, 99–100Storage, 81Storing

consumable abrasive cut-offwheels, 33–34

slow consumable wheels, 36

Subject Index 741

Structure, cut-off wheel, 20Study of failures, selection, sectioning,

14Super alloys


specimen preparation, 333–335Surface preparation, 11–13Suspensions, diamond products, 96Synthetic grinding fluids-oil-based,

26–27

T

Teeth, specimen preparation, 427–430Testing and inspection labs, 651Thermal damage, wet abrasive cutting,

23–25clamping, 24–25wet cutting, 25

Thermal etching, 174Thermal spray coatings, specimen

preparation, 260–265Thickness measurements, automatic

image analysis, 608–610Thin sections, polishing, 152–154Tin


specimen preparation, 413–416Tin cubic boron nitride, specimen

preparation, 232–235Tissue, specimen preparation, 427–430Titanium

electrolytic polishingand etching, 471

specimen preparation, 416–420Titanium carbide, specimen

preparation, 232–235Titanium nitride, specimen

preparation, 232–235Toxic substances, occupational safety

and health, labs, 666Traditional grinding, 99–106Traditional versus contemporary

methods, specimen preparation, 218Training, occupational safety and

health, labs, 673

Transistors, specimen preparation,301–305

Transmission electron microscope�TEM�, 558

Trouble shooting, specimenpreparation, 476–521

True microstructure, 5–6, 6Truing and dressing

cut-off wheel wear, wet abrasivecutting, 26

slow consumable wheels, 34–35Tungsten, electrolytic polishing and

etching, 472Tungsten carbide, specimen


U

Ultramilling, polishing, 155Ultrasonic apparatuses cleaning, 83Ultrasonic cleaning, 83Universal hardness, static hardness

testing, 639–642Unplane surface, mechanical damage,

wet abrasive cutting, 23Uranium, specimen preparation,

447–450Use, slow consumable wheels, 35

V

Vanadium, electrolytic polishing andetching, 472–473

Vapor deposition, etching, 174Vickers hardness testing, 628–632Visible light, light microscopy, 525–526Volume fraction

automatic image analysis,602–603

quantitative metallography/materialography, 569

W

Water-based grinding/polishing fluids,97

Water-oil based grinding/polishingfluids, 98


Water quality, cutting fluids, wetabrasive cutting, 28

Waterproof ink marking, 80Watershed filter, automatic image

analysis, 590–592Waviness, mechanical damage, wet

abrasive cutting, 23Wet abrasive cutting, sectioning, 15–32

abrasives and bond materials,16–21

cut-off grinding process, 15–16cut-off wheel, 16–21cut-off wheel wear, 25–26cutting fluids, 26–29grinding mechanics, 21–22mechanical damage, 22–23metallographic/materialographic

cutting operation, 29–32thermal damage, 23–25tips, 43–45

Wet cutting, thermal damage, 25Wheel dimensions

consumable abrasive cut-offwheels, 33

slow consumable wheels, 35Wheel velocity

consumable abrasive cut-offwheels, 32–33

metallographic/materialographiccutting operation, 30

slow consumable wheels, 35White cast iron, specimen preparation,

322–324Wire cutting, 52–53Wrought aluminum alloys, specimen


Y

YBCO ceramic super conductors,specimen preparation, 285–288

Z

Zincelectrolytic polishing and etching,


Zinc oxide, specimen preparation, 241Zirconia alumina wet grinding paper,

105–106Zirconium


specimen preparation, 424–427Zirconium dioxide, specimen

preparation, 241

Subject Index 743

Documents

A.S.T.M.24, Metallographic and Materialographic Specimen Preparation-2006