CHARACTERISATION OF STAINLESS STEEL 316L AND PALM …eprints.utm.my/id/eprint/51426/25/MurniFarahinMFKM2014.pdf · me a chance to use material engineering department’s laboratory

CHARACTERISATION OF STAINLESS STEEL 316L AND PALM STEARIN

BASED BINDER BY USING METAL INJECTION MOLDING (MIM) PROCESS

MURNI FARAHIN BT MUSA ZAINAL ABIDIN

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Materials Engineering)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

JUNE 2014

iii

Thank you Allah and a special thanks is dedicated to my beloved parents for

supporting me through my master program in UTM. Without their bless and support,

I could not have smooth and ease in all my way through here. Zillion thanks to my

supervisor for guiding me through this project. Without her guidance and

supervision, I will not finish this project on track. I also will not manage to succeed

here without moral support and bunch of help from my dear friends. They are very

helpful when I really need help. Thank you for all the supports that you have shown.

I really appreciate all the helps.

iv

ACKNOWLEDGEMENT

In preparing this thesis, I was in contact with many people, researchers and

academicians. They have give huge contribution towards my understanding of this

project and machines’ that I should use. In particular, I wish to express my sincere

appreciation to my main thesis supervisor, Dr. Norhayati bt Ahmad, for

encouragement, guidance, advices, motivation, critics and friendship. I am also very

thankful to Dr. Khairur Rijal for letting me use his machines, Metal Injection

Molding machine and Vacuum Furnace which available at UTM Jalan Semarak, KL.

He also helps me in understanding the Metal Injection Molding process and defects.

Without his approval and support, this project could not finished and presented in the

same way as I presented here.

I am also want to thank Universiti Kebangsaan Malaysia (UKM) for giving

me a chance to use material engineering department’s laboratory. They deserve a

special thanks for the support and cooperation that we had went through. I am very

grateful to all my family members as well for their endless moral and physical

support towards me here.

My fellow postgraduate students should also be recognized for their support.

My sincere appreciation also extends to all my colleagues and others who have

provided assistance at various situations. Their thoughts and recommendation are

very useful indeed. Unfortunately, I am not possible to list down all of their names

here due to limited space.

iv

ABSTRAK

Polisterin telah menjadi isu degradasi sekian lama kerana ia tidak boleh

terurai secara semulajadi. Dalam projek ini. Polisterin (PS) yang telah dikitar semula

telah dijadikan sebagai pengikat utama dalam pengacuan suntikan logam (MIM).

Objektif projek ini ialah untuk menyiasat parameter suntikan optimum untuk keluli

tahan karat 316L dengan pengikat polimer (PS, PE, stearin sawit dan gliserol) dan

kajian ciri kekerasan dan keliangan juga mikrostruktur selepas acuan suntikan. Bahan

suapan 63wt%, 64wt% dan 65wt% dihasilkan daripada proses pencampuran.

Kesemua sebuk mentah disuntik dengan parameter suntikan yang telah dimanipulasi

bagi suhu acuan dan tekanan untuk mencari parameter yang optimum yang boleh

menghasilkan bentuk ‘dumb bell’ yang sempurna. Parameter suntikan ( suhu acuan:

110 hingga 115 o

C dan tekanan : 7 hingga 8kPa) boleh menghasilkan bentuk ‘dumb

bell’ yang sempurna diteruskan dengan proses penyahikatan, proses pensinteran,

ujian mekanikal dan analisa. Daripada kajian, bahan suapan 63wt% menunjukkan

pengaliran dan pembentukan yang bagus serta tahap ketahanan tinggi (388Hv) selain

tahap keliangan yang rendah (89%) apabila menggunakan 110oC sebagai suhu acuan

dan tekanan sebanyak 7kPa.

v

ABSTRACT

Polystyrene (PS) has been a nature’s degradable issue as it cannot

biodegradable. In this project, recycle polystyrene (PS) is used as main binder in

Metal Injection Molding (MIM). The research aims are to investigate the optimum

injection parameter for stainless steel 316L with polymeric binder (PS,PE, palm

stearin and glycerol) and study its hardness and porosity also microstructure after

injection molding. 63wt%, 64wt% and 65wt% of powder loading of feedstock were

prepared in mixing process. All prepared feedstock were injected under manipulated

injection parameter for mold temperature and pressure to find the optimum parameter

which can inject full dumb bell shape. The injection parameter (mold temperature:

110 to 115oC and pressure: 7 to 8kPa) which able to produce full dumb bell shape is

continued for debinding process, thermal pyrolisis process, sintering process,

mechanical testing and analysis. From the studies, 63wt% of powder loading shows

good flowability and moldability with high hardness (388Hv) and low porosity

(89%) when using 110oC as mold temperature and 7kPa of pressure.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES

LIST OF APPENDICES

xii

xiv

1 INTRODUCTION 1

1.1 Significant And Benefits Of Research 2

1.2 Objectives 3

1.3 Problem Statement 3

1.4 Scope Of Work 4

2 LITERATURE REVIEW 5

2.1 Precision Manufacturing of Medical Device 5

2.2 Metal Injection Molding (MIM) 9

2.2.1 Mixing 13

2.2.2 Injection

2.2.3 Binder Removal or Debinding Process

14

15

viii

2.2.4 Sintering Process 15

2.3 Stainless Steel as Powder Material

2.3.1 Stainless Steel as Orthopedic Implant

2.3.2 Corrosion of Stainless Steel 316L in Human Body

2.4 Polystyrene as Binder

2.5 Polyethylene

2.6 Palm Stearin

2.7 Research of Metal Injection Molding

2.8 MPIF Standard 35

17

17

19

20

21

21

23

25

3 RESEARCH METHODOLOGY 28

3.1 Mixing Process 28

3.2 Injection Molding Process 32

3.3 Debinding Process 35

3.4 Sintering Process 37

3.5 Mechanical Testing

3.5.1 Hardness Test

38

38

3.6 Microstructure Study

3.7 Fourier Transform Infrared Analysis (FTIR)

41

43

4 RESULTS AND ANALYSIS

4.0 Introduction 46

4.1 Fourier Transform Infra Red (FTIR) Spectroscopy

Analysis.

46

4.2 Hardness Test 51

4.3 Porosity Test 63

5

CONCLUSION AND RECOMMENDATION 65

5.1 Conclusion 65

5.2 Future Work 66

ix

REFERENCES

APPENDICES

67

69

x

LIST OF TABLE

TABLE NO. TITLE PAGE

Table 2.1 Comparison between Metal Injection Molding (MIM)

and Powder Compaction. 10

Table 2.2 Major biomedical metals and alloys and their

applications. 18

Table 2.3 Content of palm stearin with its melting point. 21

Table 2.4 Chemical composition of MIM materials. 24

Table 2.5 Mechanical properties of stainless steel in MIM materials

properties. 27

Table 3.1 Injection parameters which are manipulated in this

research at all stages of each series of experiments. 32

Table 3.2 Injection molding parameters which are maintained for

63%, 64% and 65wt% powder loading. 34

Table 4.1 Preliminary result of Metal Injection Molding (MIM) for

63, 64, 65wt% powder loading. 39

Table 4.2 Result for sintered sample of MIM after hardness testing. 53

Table 4.3 Result of mechanical testing for sintered sample using

pressure of 8kPa in MIM parameter. 55

Table 4.4 Result of brown part when it is injected using 115

oC for

mold temperature and 7kPa in pressure for MIM

parameter.

57

xi

LIST OF FIGURE

FIGURE NO. TITLE PAGE

Figure 2.1 Gear and screw produce with MIM. 10

Figure 2.2 Fasteners made from MIM. 11

Figure 2.3 MIM components with no geometric shape restriction. 12

Figure 2.4 Picture of part after sintering on left side and right side

is product before sintering and after debinding process. 16

Figure 2.5 Knee and hip implant from metal alloy. 18

Figure 2.6 Products made from palm stearin. 22

Figure 3.1 Brabender machine for mixing process. 30

Figure 3.2 Mixing process is done at this part of Brabender

machine. 30

Figure 3.3 Mixing chamber. 31

Figure 3.4 Crushing machine. 31

Figure 3.5 Crushing process is done at this chamber. 32

Figure 3.6 Micro Injection Molding (MIM) machine. 32

Figure 3.7 Injection barrier where feedstock is inserted and melted

in it. 34

Figure 3.8 Injection molding apparatus to clean the barrier and

removed mould from injection molding machine. 35

Figure 3.9 Venticell Furnace. 36

Figure 3.10 Example of green specimen immersed in n-heptane

solution. 36

Figure 3.11 Green specimen is placed inside the furnace for

debinding process. 37

xii

Figure 3.12 Low Vacuum Furnace. 38

Figure 3.13 Shimadzu Micro Hardness. 39

Figure 3.14 Schematic diagram about diamond indenter touches on

the surface of a specimen. 40

Figure 3.15 Formula for hardness test using Viskers Hardness

Tester. 40

Figure 3.16 Scanning Electron Microscope (SEM) which is

available at Universiti Teknologi Malaysia (UTM). 42

Figure 3.17 Tabletop SEM available at FBME. Images were taken

here when SEM at FKM was broken. 43

Figure 3.18 Diagram of how FTIR works to produce wavelength. 44

Figure 3.19 FTIR Spectrometer machine which is available at

Faculty of Chemical Engineering is used to identify

polymeric binder.

44

Figure 4.1 FTIR of palm oil and sesame oil. FTIR or palm oil is a

reference for this research. 47

Figure 4.2 FTIR spectrum for polystyrene. 48

Figure 4.3 FTIR spectrum for polyethylene. 48

Figure 4.4 FTIR spectrum for glycerol. 49

Figure 4.5 FTIR spectroscopy analysis of palm oil (PO),

polystyrene (PS), polyethylene (PE) and glycerol (glc). 50

Figure 4.6 FTIR spectroscopy shown above is taken for sintered

sample. From FTIR analysis, glycerol (glc) and palm oil

(PO) are present in the analysis.

51

Figure 4.7 Metal content in white colour images from EDX result

obtained 54

Figure 4.8 Microstructure of 63wt% under 110°C for mold

temperature, 180°C for melt temperature and 7kPa in

pressure.

55



pressure.

55

xiii



pressure.

56



pressure.

57



pressure.

58



pressure.

58



pressure.

60



pressure.

60



pressure.

61

Figure 4.17 Hardness obtained from experiment using 110

oC and

115oC mold temperature and 7kPa pressure in MIM

parameter.

61

Figure 4.18 Comparison of hardness value using 7kPa and 8kPa in

pressure and 110oC for mold temperature.

62

Figure 4.19 Percentage of porosity in sintered part of 110

oC and

115oC in mold temperature using 7kPa pressure were

compared.

63

Figure 4.20 Percentage of porosity for sintered part after injected

with 7kPa and 8kPa in pressure. 64

xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Gant Chart I 64

B Gant Chart II 65

CHAPTER 1

1.0 Introduction

Metalworking industries has been growing up since then and metalworkers

started to learn and implemented better quality product from metal alloys such as

wrought iron, cast iron and steels. From this implementation, people started to

develop more products form iron and metal alloys and trigger Industry Revolution

where boilers, steam engines and railways can be made from mass production.

As for today, many products are being made in metal from advance metal

alloy. The techniques of fabricating the metals are also facing a revolution. The

revolution in technique of fabricating metal has introduced Metal Injection Molding

(MIM). By using this technique precise and intricate product from big to nano-scale

size product can be made. This technique often used in electronic industry. This

process is similarly like baking a cake.

MIM is a process of manufacturing where combination of metal powder and

binder can produce a very precise, optimum mechanical properties and intricate

shape product. Binders used in this process can be organic and inorganic product. For

an instance, recycle polymer product can be implemented and use as binder since it is

hard to degrade naturally in earth besides it creates hazardous gas when polymer

degrades naturally with other items. The resource of recycle polymer can be found in

mineral water bottle, beads of pillow, shampoo bottle and even toys (Rashid,2011).

When metal powder and binders are mixed in mixing machine, it creates a

mixture of feedstock (Rashid and Amalina,2011) . Feedstock has to be transformed

into granulate shape in order to melt it in injection molding for shaping into desired

2

shape product. At this stage, feedstock is heated and melted at polymer melting point

then injected in the mould. After injection process, the desired part is allowed to cool

to a solid form. In order to obtain the metal part, part which also known as green part

has to undergo debinding process. In this process, low melting point binder is

removed and the remaining part is sintered to ensure binder is completely removed

from metal part in sintering process. Low melting point binder in this binder system

is palm stearin. Palm stearin will be removed from the specimen through debinding

process. Other binders are removed via sintering process which requires more heat.

1.1 Significant and Benefits of Research

MIM process is a new approach in Malaysia. By applying MIM in Malaysia,

many profits can be gained and new gadgets can be produced without dependency on

import product. Malaysia has high potential in MIM industry as the material for

binder and powder metal can be obtained in Malaysia. Binder for MIM can adapt a

wide range of materials because MIM can be used for high temperature in melting

temperature. Local binder of MIM is beneficial to industry and has become a great

concern in research. Binder system of MIM has been varied and attempted in

research in order to find the most cost reduction and can shorten production process.

Polystyrene has been used for food container in 1990s. Polystyrene has

become a favorable food container among the businessman especially in food

industry because of hygiene factor where the food is resisted from bacteria growth

and water from entering the food. Polystyrene has been made for other various

products such as solid spoons and folks, polystyrene cups and plates and disposable

polystyrene razor. Polystyrene has attracted many industries as its light weight,

economical and sturdy which against moisture but at the same time maintain its

original shape.

Polystyrene has become a critical issue in Malaysia where it can be

biodegradable. Polystyrene can only degrade after 500 years in earth and resistance

3

to photolysis as reported by Amruta (2013). Polystyrene has been introduced as

potential main binder in MIM. The character of can be burnt and vanished in air has

captured researchers to try polystyrene as binder in MIM.

Palm oil has become one of the largest exports in Malaysia. In 2007, palm oil

industry has obtained RM 31.8 billion. Fractions of palm oil are majority of palm

stearin and palm olein as reported by Siew Lin (2007). As in palm stearin, there are

many fatty acids which can be used as lubricant and surfactant in MIM’s binder

system. One of fatty acids in palm stearin is stearic acid which is commonly used in

MIM binder system as lubricant. Besides its high melting point which is in range of

44 to 56 ºC higher than room temperature, palm stearin is categorized as potential

lubricant and surfactant for MIM’s binder system. Palm stearin is also economical in

price and easy to obtain in Malaysia rather than other foreign country. The most

unique characteristic of palm stearin is that chemistry composition of palm stearin

can be modified to meet the requirement of MIM.

1.2 Objective of Research

The main objective in this research is to investigate the optimum metal

injection parameter for the prepared feedstock which are 63wt%, 64wt% and 65wt%

of powder loading. Another objective is to study the sintered specimen in hardness

and porosity in order to find the best injection parameter.

1.3 Problem Statement

Polystyrene (PS) and polyethylene (PE) have environmental problem in

biodegradable. PS and PE are introduced as binder in MIM in order to overcome this

problem as these polymers are classified as thermoplastic. PS and PE can be burnt

and vanished in the air.

4

1. No study in optimum metal injection molding parameter (mold temperature,

injection holding time, melting temperature and injection pressure) has been

done for stainless steel 316L for particle size of 7.157µm.

2. Optimum powder loading composition of 63wt%, 64wt% and 65wt%. is not

found yet for stainless steel 316L with powder particle of 7.157µm and

powder loading of 63% and 64%.

1.4 Scope of Work

The scope of this research is to investigate the optimum powder loading and

binder composition for stainless steel 316L by using MIM process.

1. Preparation of feedstock with different solid loading (63wt%, 64wt% and

65wt%) mixed with polymeric binder by using Metal Injection Molding

(MIM).

2. The green part was injected with different injection molding parameter to find

optimum MIM parameter for each powder loading. The manipulated injection

parameters were mold temperature (110 to 115ºC) and injection pressure (7 to

8 bar). Optimum parameter value of mold temperature and injection pressure

will inject full dumb bell part with good mechanical properties.

3. The sintered part was injected with manipulated injection molding parameter

was related with its hardness property.

62

REFERENCE

Amalina Amir, March 2011, Development of Metal Injection Molding (MIM)

Binder Formulation of 17-4PH Stainless Steel Powder, Master, UiTM

Amruta Deshpande, 2013, Polystyrene Properties, Unpublished Note, Buzzle

Bertazzo, S.; Gentleman, E.; Cloyd, K. L.; Chester, A. H.; Yacoub, M. H.

Stevens, M. M., 2013, Nano-Analytical Electron Microscopy Reveals

Fundamental Insights Into Human Cardiovascular Tissue Calcification,12 (6):

576–583, Nature Materials.

Douglas C. Hansen, 2008, Metal Corrotion In Human Body : The Ultimate Bio-

Corrosion Scenario, Vol. 17 No.2, The Electrochemical Society Interface.

Dr Frank Petzoldt, 2007, Metal Injection Molding in Europe, Vol.1 No. 2, pages

23-28, PIM International Inovar Communications Ltd.

Fei Ling Pua et. el, 2013, Solvolytic Liquefaction of Oil Palm Empty Fruit Bunch

(EFB) Fibres: Analysis of Product Fractions Using FTIR and Pyrolysis-

GCMS,42(6)(2013): 793–799, Sains Malaysiana.

Hj Nor Rashid Ismail, 2010, The Green Choice Changing The Buying Habit of

Malaysian Consumer, SIRIM Link Driving Innovation Through Technology, PP

10002/05/2010(024916), Page 10-14.

Jmazunder, 2014, White Paper Title: Precision Additive Manufacturing of

Medical Device, The Pom Group, Inc.

Juan M Adames, December 2007, Characterization Of Polymeric Binders For

Metal Injection Molding (MIM) Process, Doctor of Philosophy, University of

Akron.

M. A. Omar, I. Subuki, N. S. Abdullah, N. Mohd Zainon and N. Roslani, 2012,

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Processes, Vol. 8, 1–13.

MPIF Standard 35, 2007, Materials Standard for Metal Injection Molded Parts,

New Jersey, USA, Metal Powder Industries Federation

63

National Institute of Standard and Technology (NIST), 2011, Glycerin, U.S,

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Ahmad, Mohd Halim Irwan Ibrahim, Murtadhahadi, Khairur Rijal Jamaludin,

2008, Pengacuan Suntikan Logam (MIM) Bagi Serbuk Titanium Dengan Sistem

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Malaysia, Page 1-9.

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CHARACTERISATION OF STAINLESS STEEL 316L AND PALM …eprints.utm.my/id/eprint/51426/25/MurniFarahinMFKM2014.pdf · me a chance to use material engineering department’s laboratory