ENGINEERING PROPERTIES OF NICKEL AND NICKEL ALLOYS

ENGINEERING PROPERTIES OF NICKEL AND NICKEL AllOYS

by John l. Everhart,P. E.

Metallurgical Engineer Westfield, New Jersey

9? PLENUM PRESS • NEW YORK - LONDON • 1971

Library of Congress Catalog Card Number 74-141242

ISBN-13: 978-1-4684-1886-6 e-ISBN-13: 978-1-4684-1884-2 001: 10.1007/978-1-4684-1884-2

© 1971 Plenum Press, New York Softcover reprint of the hardcover 1st edition 1971

A Division of Plenum Publishing Corporation 227 West 17th Street, New York, N.Y. 10011

United Kingdom edition published by Plenum Press, London A Division of Plenum Publishing Company, Ltd.

Davis House (4th Floor), 8 Scrubs Lane, Harlesden, NW10 6SE, England All rights reserved

No part of this publication may be reproduced in any form without written permission from the publisher

Preface

Nickel is probably the most versatile of the metallic elements. Among alloys containing nickel are some having high corrosion resistance and others that retain excellent strength and ductility from temperatures approaching ab­solute zero to those near 2000 F. Some nickel alloys are strongly magnetic, others are virtually nonmagnetic; some have low rates of thermal expansion, others have high rates; some have high electrical resistivities; some have practically constant moduli of elasticity; one has an "elastic" memory. In addition, nickel is magnetostrictive.

With this wide range of characteristics, it is not surprising that there are several thousand alloys containing nickel. It is impossible to consider all of these compositions in this publication and, therefore, several alloys in each of a number of categories have been selected to indicate the properties to be expected of the group. Low-alloy and constructional nickel-containing steels have been excluded on two grounds. To do them justice would require excessive space and, in addition, their applications differ generally from these of the materials under discussion. On the other hand, nickel-containing stainkss steels have been included because many of their applications fall into the same areas as those of a number of the high-nickel alloys.

Many of the compositions discussed are proprietary alloys and they are protected by trademarks. A list of the trademarks and their owners is in­cluded in the appendix.

Data are presented in the form of tables and graphs. All of the graphs . have been drawn especially for this publication, in a number of instances to permit combining data from several sources to point out some characteristic of the group under discussion. To simplify the graphs, some symbols have been used on the curves and, although the meaning is usually self-evident, a list of these symbols is included in the appendix.

v

vi Preface

The international System of Units (the SI System) is being advocated both here and abroad, but it seems premature to use these units in place of those which are conventional. However, Kelvin temperatures are given on the graphs in addition to Fahrenheit temperatures, and a brief discussion of the SI System is included in the appendix, which also contains conversion factors for the more common units used in this publication.

Sources of the data are acknowledged in the text, and it is a pleasure to take this opportunity to thank the members of the staff of the Engineering Societies Library (New York) for their courteous and efficient assistance in my search of the literature.

Finally, this book could not have been completed without the assistance of my wife, Helen, who prepared all of the graphs and assisted in proof­reading.

Contents

Chapter 1. The Nickel Situation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Occurrence .................................................... 1 Sulfide Ores .................................................. 2 Nickel Silicates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 Lateritic Ores ................................................ 2

Reserves ...................................................... 3 Expansion of Production Facilities ................................ 4 Future Developments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Recovery of Nickel.. .. .............................. ............ 5 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7

Chapter 2. Nickel.............................................. 8

Effect of Impurities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 Physical Properties .............................................. 9

Thermal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 Electrical Properties .......................................... 11 Magnetic Properties .......................................... 11 Elastic Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12 Miscellaneous Physical Properties ............. . . . . . . . . . . . . . . . .. 13

Mechanical Properties .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 Room-Temperature Properties .................................. 13

Tensile Properties .......................................... 13 Hardness .................................................. 16 Fatigue Properties Impact Properties

.......................................... 18 18

vii

viii Contents

Neutron Irradiation ............ . . . . . . . . . . . . . . . . . . . . . . . . .. 19 Elevated-Temperature Properties ................................ 19 Low-Temperature Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23

Cast Nickel .................................................... 24 Physical Properties ............................................ 25 Mechanical Properties ........................................ 25

Nickel Powder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26 Carbonyl Nickel .............................................. 26 Chemically Reduced Nickel Powder ............................ 28 Physical Properties ............................................ 29 Mechanical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30

Chapter 3. Nickel-Base Corrosion- and Heat-Resistant Alloys-I .. .... 32

Nickel-Copper Alloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 Physical Properties ............................................ 34 Mechanical Properties ........................................ 35

Room-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35 Tensile Properties ........................................ 35 Hardness ................................................ 37 Fatigue Properties ........................................ 38 Impact Properties ........................................ 38

Elevated-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 Low-Temperature Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41

Cast Nickel-Copper Alloys ...................................... 44 Physical Properties ............................................ 44 Mechanical Properties ........................................ 45

Nickel-Molybdenum Alloys ...................................... 46 Physical Properties ............................................ 47 Mechanical Properties ........................................ 48

Tensile Properties ........................................ 49 Impact Properties ........................................ 49

Elevated-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50 Low-Temperature Properties .................................. 51

Cast Nickel-Molybdenum and Nickel-Chromium-Molybdenum Alloys.. 53 Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54 Mechanical Properties ........................................ 54

Nickel-Silicon Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56 Physical Properties ............................................ 56 Mechanical Properties ........................................ 57

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57

Contents ix

Chapter 4. Nickel-Base Corrosion- and Heat-Resistant AIloys-ll .... 58

Nickel-Chromium Alloys ........................................ 58 Physical Properties ............................................ 61 Mechanical Properties ........................................ 61

Room-Temperature Properties ................................ 61 Tensile Properties ........................................ 61 Hardness ................................................ 64 Fatigue Properties ........................................ 64 Impact Properties ........................................ 65

Elevated-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 66 Low-Temperature Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70

Cast Nickel-Chromium Alloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 71 Physical Properties ............................................ 71 Mechanical Properties ........................................ 73

Nickel-Iron-Chromium Alloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73 Physical Properties ............................................ 74 Mechanical Properties ........................................ 75

Room-Temperature Properties ......... '" .................... 75 Tensile Properties ........................................ 75 Hardness ................................................ 76 Fatigue Properties ........................................ 76 Impact Properties ........................................ 77

Elevated-Temperature Properties .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 77 Low-Temperature Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 79

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 80

Chapter 5. Nickel-Base SuperaIIoys .............................. 82

Wrought Alloys ................................................ 84 Physical Properties ............................................ 85 Mechanical Properties ........................................ 88

Room-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 88 Elevated-Temperature Properties .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89 Low-Temperature Properties .................................. 91

Cast Alloys .................................................... 94 Physical Properties ............................................ 94 Mechanical Properties ........................................ 96

Room-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 96 Elevated-Temperature Properties .... . . . . . . . . . . . . . . . . . . . . . . . . .. 98

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 99

x Contents

Chapter 6. Copper-Base Nickel Alloys ............................ 100

Copper-Nickel Alloys ............................................ 100 Physical Properties ............................................ 101 Mechanical Properties ........................................ 102

Room-Temperature Properties ................................ 102 Tensile Properties ........................................ 102 Hardness ................................................ 103 Fatigue Properties ........................................ 105 Impact Properties ........................................ 106

Elevated-Temperature Properties ............... " ............. 106 Low-Temperature Properties .................................. 109

Cast Copper-Nickel Alloys ...................................... 111 Physical Properties ............................................ 112 Mechanical Properties ........................................ 114

Nickel Silvers (Copper-Nickel-Zinc Alloys) ........................ 114 Physical Properties ............................................ 115 Mechanical Properties .......................................... 117

Room-Temperature Properties ................................ 117 Tensile Properties ........................................ 117 Hardness ................................................ 117 Fatigue Properties ........................................ 117

Elevated-Temperature Properties .............................. 120 Low-Temperature Properties .................................. 121

Cast Nickel Silvers .............................................. 122 Physical Properties ............................................ 123 Mechanical Properties .......................................... 123

Nickel Silver Powder ............................................ 125 Properties .................................................... 127

References ...................................................... 127

Chapter 7. Nickel-Containing Stainless Steels ...................... 129

Wrought Stainless Steels ............. '" .. " ...................... 129 Physical Properties ............................................ 133 Mechanical Properties ........................................ 133

Room-Temperature Properties ................................ 133 Tensile Properties ........................................ 133 Hardness ................................................ 135 Fatigue Properties ........................................ 137 Impact Properties ........................................ 138

Elevated-Temperature Properties .............................. 138 Low-Temperature Properties .................................. 141

Contents xi

Precipitation Hardenable Stainless Steels .......................... 143 Physical Properties ............................................ 146 Mechanical Properties ........................................ 146

Room-Temperature Properties ................................ 146 Tensile Properties ........................................ 146 Hardness ................................................ 148 Impact Properties .......................................... 148

Elevated-Temperature Properties .............................. 148 Low-Temperature Properties .................. , ............ " .150

Cast Stainless Steels ............................................ 151 Physical Properties ............................................ 152 Mechanical Properties ........................................ 153

Room-Temperature Properties .....................•.......... 153 Tensile Properties ........................................ 153 Hardness ................................................ 153 Impact Properties ........................................ 153

Elevated-Temperature Properties .............................. 153 Low-Temperature Properties .................. , ............... 155

Stainless Steel PjM Parts ........................................ 156 Properties .................................................... 157

References ...................................................... 158

Chapter 8. Electrical Resistance and Thermocouple Alloys ............ 159

Electrical Resistance Alloys ...................................... 159 Physical Properties ............................................ 161 Mechanical Properties ........................................ 165

Room-Temperature Properties ................................ 165 Tensile Properties ........................................ 165 Hardness ................................................ 165 Fatigue Properties ........................................ 165

Elevated-Temperature Properties .............................. 166 Low-Temperature Properties .................................. 168

Thermocouple Alloys ........................ , ................... 169 Physical Properties ............................................ 171 Mechanical Properties ........................................ 173

References ...................................................... 173

Chapter 9. Controlled-Expansion and Controlled-Modulus Alloys ...... 175

Low-Expansion Alloys .......................................... 175 Physical Properties ............................................ 176

xii Contents

Mechanical Properties ........................................ 179 Room-Temperature Properties ................................ 179

Tensile Properties ........................................ 179 Hardness ................................................ 180 Other Properties .......................................... 180

Elevated-Temperature Properties .............................. 181 Low-Temperature Properties .................................. 182

High-Expansion Alloys .......................................... 183 Physical Properties ............................................ 184 Mechanical Properties ........................................ 184

Constant-Modulus Alloys ........................................ 185 Physical Properties ............................................ 186 Mechanical Properties ........................................ 188

Room-Temperature Properties ................................ 188 Tensile Properties ........................................ 188 Hardness ................................................ 189 Fatigue Properties ........................................ 190 Other Properties .......................................... 190

Elevated-Temperature Properties .............................. 190 Low-Temperature Properties .................................. 191

References ...................................................... 191

Chapter 10. Magnetic Materials . ................................. 192

Soft Magnetic Materials .......................................... 193 Physical Properties ............................................ 194 Mechanical Properties ........................................ 195

Permanent Magnet Materials .................................... 196 Physical Properties ............................................ 199 Mechanical Properties ........................................ 201

References ...................................................... 202

Chapter 11. Other Nickel Alloys . ................................. 203

Age-Hardenable Nickel Alloys .................................... 203 Physical Properties ............................................ 204 Mechanical Properties ........................................ 205

Room-Temperature Properties ................................ 205 Tensile Properties ........................................ 205 Hardness .......... , ..................................... 206 Fatigue Properties ........................................ 208

Elevated-Temperature Properties .............................. 208

Contents xiii

Low-Temperature Properties .................................. 210 Cast Beryllium-Nickel Alloys .................................... 211

Physical Properties ............................................ 212 Mechanical Properties ........................................ 213

Nitinol ........................................................ 213 Physical Properties ............................................ 214 Mechanical Properties ........................................ 214

Tungsten-Nickel PjM Products .................................. 217 Physical Properties ............................................ 217 Mechanical Properties ........................................ 218

References ...................................................... 218

Appendix I. Trademarks ........................................ 221

Appendix II. Conversion Factors and Symbols ...................... 223

Index .......................................................... 225

Chapter 1

The Nickel Situation

The discussion of the properties of nickel alloys, which is the major subject of this book, would be rather pointless if there were to be a continued shortage of nickel. Therefore, it seems desirable to discuss the nickel situa­tion briefly.

For several years, there has been an imbalance between the supply and the demand for nickel, with the demand exceeding the supply by a sufficient amount to cause a significant shortage. This has led in the United States to allocation of available supplies by the Government and by industry, to a price increase which in black market operations reached six to seven times the nominal price, and to attempts to find substitutes for nickel. However, it has also been instrumental in stimulating production. The major producers, of whom there are very few, are expanding their facilities and opening new ones, and a number of new organizations are entering the nickel mining and recovery fields.

There is no shortage of nickel ore. The difficulty in maintaining an adequate supply lies in the unexpected sharp increase in demand which has overtaxed the facilities and in the problems of winning nickel from the ore after it is mined.

Progress is being made in the expansion of mining and in the develop­ment of more efficient recovery methods and it requires no clairvoyance to predict that, within a few years, supply will equal demand even though the demand continues to increase.

OCCURRENCE

According to Ware, 1 there are three major types of nickel deposits: nickel-copper sulfides, nickel silicates, and nickel laterites and serpentines.

2 Chapter 1

They are found in different areas of the earth and vary considerably in the ease of handling to win the nickel they contain.

Sulfide Ores

The commonest of the sulfide ores of nickel is pentlandite. It is a nickel­iron sulfide, (NiFe)9Ss, brass or bronze in color, and is almost invariably found in association with pyrrhotite, Fe7Ss, and chalcopyrite, CuFeS 2 •

The major known reserves of sulfide ore lie in the northern regions of the earth. Most of the nickel produced at present comes from Canadian sulfide deposits in the Sudbury district of Ontario and in Manitoba.

In the United States, nickel sulfide ores have been found in Alaska and Minnesota and are being explored. Other sources of ores of this type are Northwestern Siberia, an area near the Finnish border in the USSR, and Finland. Nickel is being produced in the USSR and in Finland from these deposits; the output in Finland is small, that in the USSR has not been publicized.

Nickel Silicates

The largest known deposits of nickel silicate ores occur in New Cale­donia, and two varieties are mined there. The richer is a green hydrous nickel-magnesium silicate of variable composition, H 2(NiMg)Si04 ·nH20, known as garnierite. The intensity of the green color of this mineral is directly proportional to the nickel content. The second variety ranges from greenish yellow to chocolate brown in color and has a higher iron and lower magnesium content than garnierite.

From 1875 to 1905, New Caledonia was the world's largest producer of nickel; since that time Canada has moved into the lead. In 1965, about one-eighth of the world's supply of nickel came from New Caledonia.!

The only source of nickel in the United States is a garnierite deposit in Oregon. Specimens of ore from that deposit range from 2.3 to 37 % nickel and from yellowish to green in color. Commercially significant nickel silicate deposits occur also in South American and Indonesia.

Lateritic Ores

According to Ware, nickeliferous lateritic mantles are formed by the weathering of ultra basic rocks, notably serpentine. The content of mineral decreases with depth down to unweathered rock and there is no line of de­marcation between laterites and the serpentine. Therefore the deposits are

The Nickel Situation 3

referred to as laterite and serpentine. However, they are also called nickeli­ferous iron ores, lateritic ores, or simply oxide ores. A typical composition of the mantles is about 49 % iron, 1 % nickel, 2 % chromium oxide, and 0.05 % cobalt.

Lateritic ores are abundant in a wide belt of tropical and semitropical countries around the world. The reason for this distribution is that the type of weathering that dissolves the metallic elements is most active in tropical climates where there is plenty of rainfall and abundant decaying vegetation to supply organic acids and carbon dioxide to the ground water.

Nickel-bearing lateritic ores occur in Cuba, Puerto Rico, the Dominican Republic, Brazil, Venezuela, Greece, Pakistan, India, the Republic of the Philippines, the Malagase Republic, the Republic of Indonesia, New Cale­donia, and probably in other locations. The prospects of discovering addi­tional deposits is excellent because many areas in the tropics have not been explored.

RESERVES

The largest know potential reserve of nickel in the world is in the nickel-bearing lateritic ores of Cuba. The Nicaro deposits were the first in Cuba to be mined on a large scale. Later development was undertaken in the Moa Bay area. It is estimated that there are at least 17,000,000 tons of nickel content in the Cuban ores.

The second largest known reserve is in New Caledonia with an estimated nickel content of 16,000,000 tons. Reserves of proven and indicated nickel in sulfide ore deposits of the Sudbury district in Ontario and in Manitoba, Canada, total about 6,000,000 tons of nickel content.

As of early 1964, reserves of proven and indicated nickel-bearing material in the United States were placed at about 500,000 tons of nickel content. Of this material, about 360,000 tons were in silicate and nickeliferous iron ores and 140,000 tons in sulfide ores, about one-half of the latter in Alaska.

Lateritic deposits are also being exploited in the Ural region of the USSR.

In addition to the reserves mentioned above, there are large nickel­bearing lateritic ore deposits throughout the world in tropic regions. Puerto Rico has nickeliferous iron deposits estimated at lOO,OOO,OOO tons of ore with an average nickel content of less than 1 %. It is estimated that there is a similar deposit in the Philippines of about 120,000,000 tons and a vast tonnage of lower grade ore, estimated at more than a billion tons. Other nickel resources with potential value for large-scale production are in Central America, South America, Indonesia, and Africa.

4 Chapter 1

EXPANSION OF PRODUCTION FACILITIES

Most of the nickel produced in the free world is furnished by the fol­lowing organizations: The International Nickel Company of Canada, Ltd., Falconbridge Nickel Mines Ltd., Societe Le Nickel, and Sherritt Gordon Mines Ltd. In the United States nickel is mined and smelted only by the Hanna Nickel Smelting Company. All of these organizations are engaged in expanding their facilities or in planning such expansion.

In Canada, International Nickel is developing six new mines in Ontario and three in Manitoba and a new refinery is being built in Copper Cliff, Ontario. These new facilities and expansion of older ones will bring the company's Canadian production capacity to 300,000 tons per year by the end of 1971.2

Also in Canada, Falconbridge started production in a new facility in 1968 and broke ground for a new iron ore concentrator that will handle nickeliferous pyrrhotite to produce 300,000 tons per year of iron-nickel pellets containing approximately 90 % iron and 1.5 % nickel. Delivery was to start in 1969.2

Societe Le Nickel is doubling its production capacity in New Caledonia to produce 72,000 tons per year by 1972 and expects to expand further to reach 200,000 tons per year by 1980.2

In 1967, Australia joined the nickel-producing countries of the world. By the end of that year, Western Mining Corporation was producing at the rate of 100,000 tons of ore per year. Its reserves were reported to be about 14.3 million tons with a nickel content of 3.4 %. The company has taken a license to use the Sherritt Gordon ammonia leach process in a refinery being built in Western Australia which is expected to start operations in 1970 with an annual capacity of 20,000 tons.2

Also in Western Australia, Metals Exploration Ltd. began trucking ore from its mine to a mill operated by Western Mining Corporation in late 1969 at the rate of 120 tons per day. 3

Falconbridge is developing a mining and metallurgical complex in the Dominican Republic which will have an annual capacity of 31,000 tons of nickel contained in ferronickeI. Operations are scheduled to begin in 1972. 3

FUTURE DEVELOPMENTS

Extensive exploration in Australia has led to the discovery of new depo­sits with two additional producers scheduled to begin operations in 1969-70. In addition, at least half a dozen other organizations have been formed to seek for and exploit nickel deposits in Australia. 2

The Nickel Situation 5

In New Caledonia, Le Nickel plans to erect a new smelter for the treat­ment of low grade silicate ores to be supplied by several New Caledonian mining enterprises, with an annual capacity of 40,000 metric tons of nickel contained in ferronickel. 4

In August 1969, a new organization entered the nickel industry in New Caledonia. American Metal Climax, Inc. and a French associate signed an agreement with the government for the development of nickel deposits with production of 50,000 tons per year scheduled to begin in 1975. 5

Japanese interests have signed agreements with the Indonesian Govern­ment for exploration and exploitation of lateritic deposits and similar con­tracts were signed previously by International Nickel and a consortium of United States, Dutch, and Canadian companies. 6, 7

Copper-nickel deposits in northeastern Botswana have been found with proven reserves of about 12 million tons of ore containing from 0.6 to 1.5 % nickel and 1.2 to 1.5 % copper and probable reserves of about 14 mil­lion tons of ore with lower nickel content. Plans are underway for exploi­tation by a group consisting of Roan Selection Trust, American Metal Climax, and the Botswana Government. 8

Marinduque Mining and Industrial Corporation is developing lateritic nickel ores in the Philippines. Planned production is 75 million pounds of nickel per year by mid-1973. Of this capacity, 70 million pounds will be pure nickel powder and briquettes, the remainder along with about 3 million pounds of cobalt will be in the form of concentrates. 8

In addition to these developments, active exploration is proceeding in many other parts of the world. Thus, there should be an adequate supply of ore within a few years.

RECOVERY OF NICKEL

There are a number of established processes for nickel recovery and they will be mentioned briefly. Anyone interested in this aspect of the nickel business should consult Boldt and Queneau. 9

According to Ware,l a typical Canadian sulfide ore from the Sudbury district is crushed and a nickel concentrate is separated magnetically. The sulfides of nickel and copper are separated by flotation. Then the concentrate is roasted with a flux and melted into a matte containing three separate phases, nearly pure nickel sulfide, copper sulfide, and a nickel-copper alloy. This matte is ground and the alloy is removed magnetically and refined electrolytically. The nickel and copper sulfides are separated by flotation. The copper sulfide is blown in a converter to black copper and refined electroly­tically. The nickel sulfide is cast directly into anodes for electrolytic refining.

6 Chapter 1

In New Caledonia, Le Nickel produces nickel matte and ferronickel from its ores. The former is produced by blast furnace smelting, the latter in electric furnaces.

In Oregon, Hanna melts the ore in an electric furnace and pours the liquid matte into a reduction ladle where it is treated with ferrosilicon to produce ferronickel.

Sherritt Gordon uses amonia leaching at elevated temperatures and pressures to extract nickel from sulfide ores. The leach solution is boiled to precipitate the copper as a sulfide and recover part of the ammonia. Nickel and cobalt are recovered as pure powders by reduction with hydrogen under pressure. This process can be used for silicate ores if the ore is first given a sulfating roast.

Briefly, these are methods which have been used commercially for years. According to Ware, problems arise more frequently with silicate and lateritic ores than with sulfide ores. He notes that sulfide ores can usually be separated magnetically or by flotation but that no economical method has been developed to produce a physical separation of the other types of ores.

Ware points out that present processes do not make full use of the poten­tial of the silicate and lateritic ores for the recovery of iron, cobalt, and other metal content. As an example, he mentions that the ammonia leach process used by the United States Government plant at Nicaro, Cuba, recovered only 80% of the nickel and less than 10% of the cobalt. The tailings were too high in nickel, chromium, and cobalt to be suitable for use as iron ore.

He notes further that an acid leach process used at Freeport Sulphur's plant at Moa Bay, Cuba, recovered over 95 % of the nickel and cobalt and the 50% iron content of the tailings was also recovered by a direct reduction process. However, the process does not extract the metal values from the serpentine portion of the lateritic ores which may make up a third of the total weight of the ore and be richest in nickel.

Of course, these problems have been known for years and research is in progress to develop methods of increasing the yields. The fact that there is wide variation in the composition of the ores from various localities compli­cates the problem.

The ammonia leach process of Sherritt Gordon seems to have shown the most ·promise for application to a variety of ores, and the company has built a pilot plant for the hydrometallurgical treatment of 25 tons per day of lateritic ore samples from various parts of the world to devise methods for the economical recovery of nickel. 2 Other producers and potential producers are also actively engaged in developing procedures for the recovery of nickel from lateritic ores.

The Nickel Situation 7

REFERENCES

1. Glen C. Ware, "Nickel," Mineral Facts and Problems, Bull. 630, Bureau of Mines (1965), p.607.

2. G. L. DeHuff, "Nickel," 1968 Minerals Yearbook Preprint, Bureau of Mines (1969). 3. "Nickel in January 1970," Mineral Industry Surveys, Bureau of Mines, March 31,1970. 4. "Nickel in October 1969," ibid., December 23, 1969. 5. "Nickel in August 1969," ibid., October 27, 1969. 6. "Nickel in July 1969," ibid., September 30, 1969. 7. "Nickel in February 1969," ibid., June 3, 1969. 8. "Nickel in December 1969," ibid., March 9, 1970. 9. J. R. Boldt, Jr. and Paul Queneau, The Winning of Nickel, Van Nostrand (1967).

Chapter 2

Nickel

The element nickel is a member of the transition group in the fourth series of the periodic table, which includes iron, nickel, and cobalt. It has the atomic number 28.

The atomic weight of nickel is 58.71 and it is a composite of five stable isotopes, having atomic weights of 58,60,61,62, and 64 in the proportions of 67.7, 26.2, 1.25,3.66, and 1.16 % respectively. Seven unstable radioactive isotopes have also been identified. These have atomic weights of 54, 56, 57, 59,63,65, and 66 and have half-lives, respectively, of 0.16 second, about 6 days, 36 hours, about 100,000 years, approximately 85 years, 2.6 hours, and 56 hours.!

The normal crystal structure of nickel is face-centered cubic and it has a lattice constant of 3.5238 A at 68 F.

Although nickel with a purity of 99.99 % has been made, the properties reported for "high purity" nickel have generally been determined on material having a nickel content of99.95 %. By contrast, commercial nickel in wrought form generally contains about 99.5 % nickel + cobalt and specifications, such as those of the ASTM for wrought material, set a minimum of 99 % nickel + cobalt. This is the material on which most properties of nickel have been determined.

EFFECT OF IMPURITIES

As has been mentioned in Chapter I, nickel is produced in various areas of the free world and the sources are expanding as new discoveries are made. Although significant production originates in New Caledonia, the major

8

Nickel 9

source of nickel for the next few years at least will be Canada. The impurities normally found in nickel from Canadian sources are carbon, cobalt, copper, iron, silicon, and sulfur. They are introduced from the ore or during pro­cessing.

Carbon is soluble in nickel to a limited extent at room temperature. When it is in solid solution, carbon increases the ease of hot working, but in the quantity usually present, causes work hardening which is detrimental to cold working operations. To reduce the effect of work hardening, a low carbon modification was developed. This material work hardens at a signif­icantly lower rate which facilitates deep drawing and other severe cold forming operations.

Cobalt is present in Canadian ores, and nickel produced from these ores, except by the carbonyl process, normally contains about 0.5 % cobalt. Although this cobalt content slightly increases the electrical resistivity and raises the Curie temperature, it has little effect on other properties.! Con­sequently, in commercial practice, a single determination is made for nickel and cobalt and the result is reported as nickel plus cobalt. In recent years, improved processing methods have been developed which permit reducing the cobalt content to about 0.1 %.

Copper, iron, and silicon, in the amounts normally present in nickel, have relatively minor effects on the properties, although some physical properties are more sensitive to their presence than others. Sulfur, however, does have a significant effect. Even in the amounts normally present, sulfur reduces both the hot and cold workability of nickel.

PHYSICAL PROPERTIES

Some of the physical properties, for example the electrical resistivity, are influenced to a considerable degree by minor amounts of impurities. For this reason, Table 2-1 includes a compilation from various sources of the thermal, electrical, magnetic, elastic, and miscellaneous properties of both "high purity" and commercially pure nickel,1,2,3

Thermal Properties

The melting (or freezing) point of nickel is 1453 C (2647.4 F) and has been selected as a secondary fixed point on the International Temperature Scale. Impurities not only lower the melting point but extend it into a range as indicated in the values given for commercial nickel in the table. The boil­ing point has not been determined directly but was extrapolated from vapor

10 Chapter 2

Table 2-1. Physical Properties of Nickep·2.3

"High purity" Commercial nickel nickel

(99.97% min) (99.5% nom)

Melting point, F Boiling point, F Vapor pressure (at m.p.), mm Hg Specific heat (70 F), BtujlbtF Thermal conductivity (200 F), Btujhrjft2tFjft Coefficient of thermal expansion (70-1000 F), per of Electrical resistivity,

microhm-cm ohmsjcir mil ft

Temperature coefficient of resistance (68-212 F), microhm-cm tF

Curie temperature, F Saturation magnetization, gauss Maximum permeability (H = I), gauss Initial permeability, gauss Residual induction, gauss Coercive force, Oe Modulus of elasticity, ksi Modulus of rigidity, ksi Poisson's ratio Density,lbjin. 3

2650 4950

9.4 x 10- 3

0.11 45.7

9.2 x 10-6

7.16 43.17

0.0038 667

6170 2000-3000

200 3000

3.0 30,000 12,000

0.322

2615-2635

0.109 39

8.5 X 10-6

9.5 57.2

0.0027 680

6000 1500-2000 200

3100 3.0

29,600 11,700

0.26 0.321

pressure data. Morris et al. 4 give the following equation for the vapor pres­sure of liquid nickel in the temperature range 2800 to 2950 F:

log Pmm = -21,030jT + 9.689

where T is the absolute temperature in degrees Kelvin. As shown in the table, the specific heat is practically unaffected by the

difference in purity between "high purity" and commercial nickel but both the thermal conductivity and the coefficient of thermal expansion show the influence of increasing impurities.

The relationship between temperature and thermal conductivity of "high purity" nickel is shown in Fig. 2-1 based on the work of Ro, Powell, and Liley. S As shown in this figure, the thermal conductivity increases to a maximum at very low temperatures. Based on data reported by Rosenberg, 1

commercial nickel shows little change in thermal conductivity at low tem­peratures. The thermal conductivity has a minimum value near the Curie point.

Nickel expands uniformly with temperature up to the Curie point, where there is a sharp discontinuity; above this point uniform expansion again

Nickel

:::: LL LLIO 0 It... '-

N en ..... ] "-

'- 80 8 "-

.£: 'E '-

.2 C 6 lD 60 0

~ '00 c:

'S: 0

g40 ~4 '0 w c: '1V 0 u 0

0 20 u 2 E 1fj

Q) E .£: I-

Temperature, K 100 200 300 400 500 600 700 800 900 1000

-200 o 200 400 600 800 1000 1200 1400 Temperature, F

11

50 E u ,

o u -= 10 U Q)

GJ

Fig, 2-1. Effect of temperature on the thermal expansion, thermal conductivity, and electrical resistivity of "high purity" nickel. I. S

occurs. The relation between temperature and expansion for "high purity" nickel is shown also in Fig. 2-1. I

Electrical Properties

The electrical resistivity of nickel increases with temperature and also with impurity content, As shown in Table 2-1, the resistivity of "high purity" nickel is considerably lower than that of commercial nickel. At temperatures below -200 F, the resistivity of "high purity" nickel is very low but it in­creases with rising temperatures as indicated in Fig. 2-1. I Unlike the curves for thermal conductivity and thermal expansion in the same graph, which show sharp discontinuities at the Curie temperature, the curve for resistivity shows only a change in slope near this temperature. Rosenbergl points out, however, that if the rate of change with temperature is plotted against the temperature there is a sharp break at the Curie point.

Magnetic Properties

Ferromagnetic materials, which include nickel, iron, cobalt, the rare earth gadolinium, and certain oxides, are capable of retaining magnetic order at room temperature after being magnetized. As the temperature is increased, however, they reach a point where ordering disappears and they become paramagnetic (nonmagnetic). This change occurs at the Curie tem-

12 Chapter 2

perature and a reasonably high Curie point is essential if the material is to be useful for magnetic applications. Bouwman6 notes that although gado­linium is ferromagnetic, it has a Curie point of only 59 F, which greatly limits its usefulness. On the other hand, nickel, iron, and cobalt have Curie points of 667 F, 1418 F, and 2012 F, respectively and all of them are potentially useful as magnetic materials. It should be noted that although the Curie point is the temperature at which ferromagnetism ceases, the decrease in magnetism with increasing temperature is somewhat gradual and its effect is spread over a considerable temperature range below the Curie point.

The temperature of the Curie point depends on such factors as the mechanical or thermal treatment the material has received and the type and amount of impurities. For example, most alloying elements lower the Curie point of nickel but iron and cobalt raise it. As indicated in Table 2-1, the Curie point of "high purity" nickel is somewhat lower than that of commer­cial nickel.

Nickel becomes magnetically saturated at a flux of about 6500 gauss. After removal from the magnetic field, the residual magnetism is approximately 3000 gauss. The coercive force, i.e., the strength offield required to neutralize the residual field, is about 3 Oe (oersteds). As shown in Table 2-1, the magnetic properties are not greatly influenced by the differences in impurity content between "high purity" and commercial nickel. These properties indicate that nickel is neither magnetically hard nor especially soft.

One of the unique properties of nickel is its strong response to magne­tostrictive effects, i.e., the change in the dimensions of a ferromagnetic ma­terial when it is placed in a magnetic field. For practical purposes, the most important of these changes is the Joule effect, which deals with the fractional change in length along the axis of the applied magnetic field when the field is changed. This change can be either expansion or contraction. Although iron, for example, expands in low fields and contracts slightly in high fields, nickel contracts in all magnetic fields. Nickel shows one of the largest changes in length of all materials which have been investigated, a change of 30 parts per million in a magnetic field strong enough to saturate the nickel. 7

Elastic Properties

Studies on single crystals have shown strong anisotropy in the elastic properties of nickel, but this effect is not apparent in the measurements made on polycrystalline material. The average values of the modulus of elasticity in tension (Young's modulus) are 30,000 ksi for "high purity" nickel and 29,600 ksi for commercial nickel. According to Rosenberg,l the modulus of elasticity in compression is the same as that in tension.

Nickel 13

The modulus of rigidity is approximately 12,000 ksi for "high purity" nickel and 11,700 ksi for commercial nickel.I· 2

Poisson's ratio, i.e., the ratio of transverse contraction to longitudinal expansion under tensile stress, is 0.26. 2

Miscellaneous Physical Properties

The density of "high purity" nickel is reported to be slightly higher than that of commercial nickel, 0.322Ibjin. 3 and 0.321Ibjin. 3, respectively. Rosen­berg! notes that direct determinations of density are influenced by composi­tion, physical condition, and prior treatment.

The reflectivity of polished nickel increases with increase in the wave­length of the impinging light from about 10 % for a wavelength of approxi­mately 1000 A to 90 % for wavelengths of the order of 40,000 A.

The total emissivity of nickel rises approximately linearly from 0.045 at 68 F to 0.19 at 1830 F.!

The velocity of sound in commercial nickel as measured on a wrought bar is reported as 2.92 miles per second.!

MECHANICAL PROPERTIES

The mechanical properties of nickel are influenced by purity and the prior history of the material. Commercial nickel has the nominal compo­sition 99.5 % nickel + cobalt, 0.08 % carbon, 0.18 % silicon, 0.18 % man­ganese, 0.2 % iron, 0.13 % copper, and 0.005 % sulfur. A number of modi­fications are produced for special purposes. A low carbon nickel (0.02 % C max), which work hardens at a lower rate than the usual variety, is used for severe cold forming operations and is preferred for service at temperatures above 600 F. Three other modifications, nominally 99.5 % nickel + cobalt, are produced specifically for electronic applications as is a high purity (nominally 99.98 % nickel) material containing less than 0.001 % cobalt.

Room-Temperature Properties

Nickel is a single-phase material with a face-centered cubic structure. It can be hardened and strengthened only by cold work. In general, com­mercial nickel is stronger and less ductile than "high purity" nickel.

Tensile Properties

Nominal tensile properties of wrought commercial nickel in a number of mill forms are given in Table 2-28. In its softest condition, commercial

14 Chapter 2

Table 2-2. Nominal Tensile and Hardness Properties of Commercial Nickels

Yield strength Tensile Elongation (0.2% offset), strength, (2 in.), Rockwell

Form ksi ksi % hardness

Rod and bar Hot finished 15-45 60-85 55-35 B45-80 Cold drawn 40-100 65-110 35-10 B75-98 Annealed 15-30 55-75 55-40 B45-70

Plate Hot rolled 20-80 55-100 55-35 B55-80 Annealed 15-40 55-80 60-40 B45-75

Sheet Hard 70-105 90-115 15-2 B90 min Annealed 15-30 55-75 55-40 B70 max

Strip Spring 70-115 90-130 15-2 B95 min Annealed 15-30 55-75 55-40 B64max

Tubing Stress-relieved 40-90 65-110 35-15 B75-98 Annealed 12-30 55-75 60-40 B70max

Wire Spring 105-135 125-145 15-4 Annealed 15-50 55-85 50-30

nickel has a tensile strength of about 55 ksi, but the strength can be increased to as much as 145 ksi by cold working. Of course, the increase in strength is accompanied by loss of ductility, as measured by the elongation, from a maximum of about 60 % to a minimum of about 2 % over a 2 inch gage length.

ASTM Specifications B161 for nickel rod and bar, Bl62 for seamless pipe and tube, and B162 for plate, sheet, and strip, require a minimum tensile strength of 55 ksi for annealed 99 % nickel (0.15 % C max) and 50 ksi for 99 % nickel (0.02 % C max). These specifications also include minimum tensile properties for nickel after various amounts of cold work. 9

The effect of cold drawing on the tensile properties of commercial nickel is indicated in Fig. 2_2.10 The strength increases uniformly to a maximum of about 140 ksi at a cold reduction of 80 %. At the same time, the ductility falls, reaching a minimum elongation of about 8 % in 2 inches.

The effect of heating at a series of temperatures on the softening of commercial nickel, cold worked to a tensile strength of 96 ksi, is indicated in Fig. 2_3. 10 Strength increases slightly up to about 500 F with an accom­panying reduction in ductility particularly as indicated by the data for reduc-

Nickel

160

140 "iii ..><:

..c cr. 120 60 ~ c Q) C ...

iI5 N ~ 100 40 c "iii "Q c -0 ~ 0-

80 20 § w

o 20 40 60 80 100 Reduction by Drawing, %

Fig. 2-2. Effect of cold work on the tensile properties of com­mercial nickel.! 0

"iii ..><:

vi en ~ -(f)

Temperature, K 400 600 800 1000 1200

120 r---,----,----.-----,,---,..---,

100

80

60

40

20

IS.

80 ~ 0 Q) ....

60 <[ -0

-0 Q)

40 0::

~ c 0

20 [jJ

o 400 800 1200 1600 2000 Temperature, F

Fig. 2-3. Effect of annealing on the tensile properties of com­mercial nickel cold drawn to a tensile strength of 96 ksi.! 0

15

16 Chapter 2

80

. iii 60 ..:.::.

vl (f) Q) '--

U5 40

20

Temperature, K

300 400 500 600 700 800 900

80 ~ o ~

60 « '+­o "D

40 &! 0> C o

20 W

o 200 400 600 800 1000 1200 Temperature, F

Fig. 2-4. Effect of annealing on the tensile properties of commercial nickel cold drawn with a reduction of 22 %.1

tion of area. Above this temperature, there is a gradual decrease in strength accompanied by an increase in ductility. The increase in strength with ac­companying decrease in ductility at about 400 F is quite apparent in commer­cial nickel which had been cold drawn with a reduction of 22 % as shown in Fig. 2-4. 1

Hardness

"High purity" nickel in the annealed condition has a hardness as low as Rockwell B35 which is considerably lower than that of commercial nickel. Nominal values for annealed commercial material, given in Table 2-2, show Rockwell hardness values ranging from B45 to B70 depending on the form of the material. ASTM Specification Bl62 for nickel plate, sheet, and strip specifies Rockwell B64 minimum for annealed commercial material with normal carbon content and B55 for annealed low carbon nickel. 9

Nickel is hardened by cold work, the rate of work hardening being generally similar to that of mild steel. The effect of cold working on the hardness of commercial nickel is shown in Fig. 2-5. 1

There is a definite relationship between the hardness and the tensile properties which is advantageous in offering the engineer the opportunity of estimating these properties if he knows the hardness of the material he is handling. This relationship for sheet and strip is shown in Fig. 2-6. 8

Nickel

250~--~--~----~--~--~----~~

~ 200 E ::J

Z

~ 150 Q)

c "2 :E 100

o 10 20 30 40 50 60 70 Cold Work, %

Fig. 2-5. Effect of cold working on the hardness of commercial nickel.!

120

100

80 'Vi .><:

(j')-

60 ~ (j') 60 Q) ~ - ~

(f) .~

40 40~ c 0

'';::::

0 0'>

20 20 § W

40 50 60 70 80 90 100 Rockwell B Hardness

Fig. 2-6. Relationship between tensile properties and hardness of commercial nickel sheet and strip. 8

17

18 Chapter 2

Fatigue Properties

The fatigue strength of commercial nickel at 108 cycles is reported to be 24 ksi for annealed, 30 ksi for hot rolled, and 42.5 ksi for cold drawn material. I Tensile and fatigue strengths of annealed and cold worked sheet and rod are given in Table 2-3. Based on the fatigue strength at 108 cycles, the fatigue

Table 2-3. Fatigue Strength of Commercial Nickel

Tensile Fatigue strength (ksi)

strength, at indicated cycles

Material and condition ksi lOS 106 107 108 Ref.

Sheet, 0.2 in. Annealed 72.0 45.5 35.0 27.0 22.9 11 Half hard, 37 % reduction 113.5 49.0 41.0 40.0 Hard, 60 % reduction 121.5 43.0 41.0

Rod, liz in. Annealed 74-74 28-31 11 Hot rolled 66-72 23-25 Cold drawn 98-126 38-45 Cold drawn, stress-relieved at 525 F 88-94 34-38

Rod Annealed 78 52 40 34 33 8 Cold drawn 132 84 63 52 50

ratios for both annealed and cold worked material lie in the range 0.31 to 0.42.

Fatigue curves for cold drawn and annealed commercial nickel are given in Fig. 2-7. 8 The cold drawn material had a tensile strength of 132 ksi and the annealed material, 78 ksi. The resulting endurance ratios were 0.37 and 0.42, respectively. Although the cold worked material had a higher endurance limit in air than the annealed material, corrosion fatigue limits in fresh and brackish water were practically the same for both. 8

Impact Properties

As measured by notched-bar tests, nickel is a very tough material. Charpy values for commercial nickel have been given as 216 ft-Ib for annealed, 195 ft-Ib for hot rolled, and 185 ft-Ib for cold drawn materia}.!

Data from another source give Charpy V -notch values of 228 ft-Ib for annealed, 200 ft-Ib for hot rolled, and 204 ft-Ib for cold drawn material which had been reduced 24 %.8 Additional data on impact properties are given under low-temperature properties.

Nickel

120

100

80 . iii ~

en 60 If)

Q) .... -(j) 40

20

4 10

5 10

6 10 Cycles

Ann.

7 10

8 10

Fig. 2-7 S-N curves for cold drawn and annealed commercial nickel. 8

Neutron Irradiation

19

Shober l2 reports that the effect of fast neutron irradiation on the mechanical properties of metals is unusual because while some properties are enhanced others are adversely affected. He notes that, in general, yield strengths are significantly increased, hardness and tensile strengths are increased moderately, and elongations are reduced. For example, the neutron irradiation of annealed commercial nickel at 1 X 1019 neutrons/cm2 and 240 F resulted in an increase in the Brinell hardness from 64 to 137, an increase in tensile strength from 65 to 69 ksi, and a reduction in elongation from 45 to 34 % in? inches.

Makin 13 also investigated the effects of neutron irradiation on nickel. After irradiation at 5 X 1019 neutrons/cm2 and 212 F, he found only a small increase in the room-temperature tensile strength from about 58 to 63 ksi, but there was a significant increase in yield strength from 34 to 59 ksi.

E Ie va ted- Temperature Properties

The short-time elevated-temperature tensile properties of annealed nickel are given in Fig. 2-8. 8 There is a slight increase in tensile strength in the 400 to 500 F range accompanied by a minimum in the elongation.

20

60

50

"VI .:s:. 40 (/) (/)

~ en 30

20

10

Temperature, K

400 600 800 1000 1200

240

200

160

120

80

o 400 800 1200 1600 2000 Temperature, F

~

C 0

".,= a 01 c: 0 W

Fig. 2-8. Short-time elevated-temperature tensile properties of annealed commercial nickel. 8

Chapter 2

Above this range, the strength falls quite uniformly and the ductility as measured by the elongation increases rapidly.

The creep properties of "high purity" nickel were investigated by Jenkins, Digges, and Johnson l4 and by Jenkins and Willard. ls Some of their data are included in Table 2-4 as a basis for the comparison of the properties of commercial nickel. Although only limited data were available by which "high purity" nickel and commercial nickel could be compared, these data indicate that the low carbon commercial nickel and the "high purity" nickel have comparable creep properties.

In the commercial grades of nickel, the low carbon modifications have superior creep and stress-rupture properties at temperatures above 600 F.8 Some indications of the effect of carbon content on the creep and stress­rupture properties are given in Table 2_4. 8• 16 These data indicate that low carbon nickel (0.02 % C max) has higher resistance to creep at 1000 F than commercial nickel (0.15% C max) has at 800 F. Although the differences

Ta

ble

2-4

. C

ree

p a

nd

S

tre

ss

-Ru

ptu

re P

rop

ert

ies

of

Nic

ke

l

Tes

t te

mpe

ratu

re,

Str

ess

(ksi

) fo

r cr

eep

rate

of

Mat

eria

l C

ondi

tion

F

0.

0000

1 %

/hr

0.00

01 %

/hr

0.00

1 %

/hr

0,01

%/h

r

99.8

5% N

i A

nnea

led

700

20

26

900

9.8

15.5

12

00

5

99.8

5% N

i C

old

draw

n, 4

0 %

70

0 41

45

90

0 25

31

12

00

2.5

4.5

Com

mer

cial

Ni

Ann

eale

d 12

00

5 (0

.008

% C

) 15

00

Com

mer

cial

Ni

Ann

eale

d 80

0 8

11

(0.0

2 %

C m

ax)

900

5.6

8 10

00

3.5

5.6

8 12

00

1.2

2 3.

8

Com

mer

cial

Ni

Ann

eale

d 60

0 13

40

(0

.15%

C m

ax)

700

3 9

800

2 6

Com

mer

cial

Ni

Ann

eale

d 75

0 93

0 11

10

Str

ess

(ksi

) fo

r ru

ptur

e in

10

hr

7.5

3.6

20

13

37

24

10.7

Ref

.

14

15

16 8 8 17

z ii'

~

!!.

II.)

...

22 Chapter 2

in stress-rupture properties are less pronounced, they are significant. For example, low carbon nickel has a 100-hour rupture strength of 13 ksi at 1200 F compared with a value of 10.7 ksi for commercial nickel at 1110 F.

Lozinskiy and Pertsivskiyl7 investigated the effects of "thermomechan­ical" treatments on the creep and stress-rupture properties of nickel. This treatment consists of rolling annealed commercial nickel at elevated tem­peratures with reductions of 2 to 45 % and water quenching prior to cold rolling. They concluded that the most effective conditions for strengthening nickel were:

1. Cold rolling with 40 to 45 % reduction with no preliminary hot roll­ing for service at 750 F.

2. Hot rolling at 930 F with reductions of 40 to 45 %, followed by cold rolling for service at 930 F.

3. Hot rolling at 1650 F with reductions of about 30%, followed by cold rolling for service at 1100 F.

280

240

200 ..0 --,

U 160

0 Q

E 120

>, Q

0 .c U 80

40

Temperature, K

50 100 150 200 250 300

Ann - HR

CD

Cast

~"....--------

-400 -300 -200 -100 Temperature, F

o 100

Fig. 2-9. Subzero-ter.1perature impact properties of commercial nickel. I 8

Nickel 23

Low-Temperature Properties

Like other face-centered cubic metals, nickel shows no transition from ductile to brittle behavior as the temperature falls into the cryogenic range. The notched bar test is often used as a criterion of low-temperature toughness. As shown in Fig. 2-9,!8 there is no loss of toughness in annealed or worked nickel at temperatures down to -300 F, and cast nickel, also, is as resistant at this low temperature as it is at to om temperature.

The tensile and yield strengths of both forged and annealed nickel increase as the temperature is reduced below zero, as shown in Fig. 2_10 18 •

. if)

.:L

c.tl If)

~ -(f)

Temperature, K 50 100 150 200 250 300

140 70

120 60

100 50 0 0-::

c:

80 40 .2 0 a> c: 0

60 30 W

40 20

20 -------------------___ 10 ----,

-300 -200 -100 Temperature, F

o 100

Fig. 2-10. Subzero-temperature tensile properties of commercial nickel. 18 1. Tensile strength, forged; 2. yield strength, forged; 3. elongation, annealed; 4. tensile strength, annealed; 5. elongation, forged; 6. yield strength, annealed.

24

. iii ~

u) if) Q)

~ (f)

160

120

80

40

3 10

Chapter 2

-Unnotched ----Notched

~ _______ ~4 ______ I ____ ~

_______ 2

---------====:-------------3 ---~---=======--_.-- 4

4 10

5 10

Cycles

--. ----------6

10 7

10

Fig. 2-11. Subzero-temperature S-N curves in reverse bending for annealed com­mercial nickel sheet. 19 Notch factor, K, = 3.0. Tested at (1) -423 F, (2) -320 F, (3) -110 F, (4) 70 F.

The ductility as measured by the elongation also improves although the an­nealed material passes through a minimum at about -200 F.

The effect of low temperature on the fatigue strength of commercial nickel sheet, having a tensile strength of 61.6 ksi, is shown in Fig. 2-11Y In line with the tensile strength, the fatigue strength also increases as the tem­perature is reduced. Apparently, notches reduce the fatigue strength by approximately the same degree at low temperatures as they do at room temperature.

CAST NICKEL

The compositions of alloys used for castings usually differ from those used for the corresponding wrought material because, for example, greater fluidity is required in order to fill the mold properly. Although commercial wrought nickel has the nominal composition 99 % nickel + cobalt, com­mercial cast nickel contains about 1.5 % silicon and has a higher carbon content. The nominal composition is 97 % nickel + cobalt, 1.5 % silicon, 0.50% manganese, 0.50% carbon, 0.30% copper, 0.25% iron, and 0.015% maximum sulfur.

Nickel can be melted for the production of castings in electric, oil-fired, or gas-fired furnaces using practices which follow those used for steel cast­ings. The melt can be made under a thin limestone slag with additions of nickel oxide and carbon to cause a boil to eliminate gases. After the boil, the metal is killed with silicon, the carbon content is adjusted, manganese

Nickel 25

is added, and the metal is allowed to lie quietly in the furnace for a period sufficient to permit the trapped oxides to rise into the slag. After this period, the metal is poured at temperatures ranging from 2725 to 2900 F, following final deoxidation in the ladle. Although sand mixtures similar to those used for steel can be used for nickel castings, gates and risers should be larger than those used for steel. Pattern equipment should provided for a linear shrinkage of 1 14 in. 1ft. 1

Grobecker20 described a method of producing castings of nickel having a higher purity than that used for commercial cast nickel, which is a modi­fication of the commercial method. This procedure requires melting under highly oxidizing conditions, a conventional boil, and deoxidation with car­bon, manganese, aluminum, and magnesium. The metal had high shrinkage during cooling in the liquid state, also during solidification, and in the solid state. Because of this high shrinkage, it was necessary to increase the shrink­age allowance to 5/16 in./ft. The composition of the product was 98.5-99.0% nickel + cobalt, 0.5-0.7% carbon, 0.15-0.40% silicon, 0.15-0.25% iron, 0.05-0.25 % manganese, and 0.004 % maximum sulfur. The castings showed a slight tendency to be brittle, but lack of ductility was not severe and castings of the desired shape could be produced in sand molds. The procedures are fully described.

Physical Properties

Reflecting the greater impurity content, the physical properties of cast nickel are somewhat different from those of commercial wrought nickel.

The melting range is reduced to 2450-2600 F from 2615-2635 F, a reduction of the solidus temperature of 165 F. The electrical resistivity is about double that of the wrought material which might be expected since this property is very sensitive to impurity content. However, the thermal conductivity and coefficient of expansion are less seriously affected. The modulus of elasticity of cast nickel is also significantly lower than that of the wrought material. Properties of the cast grade are given in Table 2_5. 21

Comparisons can be made with those of the commercial wrought type which are given in Table 2-1.

Mechanical Properties

The "as cast" mechanical properties of cast nickel are also included in Table 2-5. These are the properties which can be expected to be achieved in commercial castings.

Both the yield and tensile strengths are comparable with those of an­nealed wrought material although they are on the low side of the range. On the other hand, the ductility, as measured by the elongation, is much lower

26 Chapter 2

Table 2-5. Physical and Mechanical Properties of Commercial Cast Nickepo

Physical properties Melting range, F Specific heat (80--750 F), Btu/lb;oF Thermal conductivity (212 F), Btu/hr/ftz/"F/ft Coefficient of thermal expansion (70--1400 F), per of Electrical resistivity (32 F), ohms/cir mil ft Modulus of elasticity, ksi

Mechanical properties Yield strength, ksi Tensile strength, ksi Elongation (2 in.), % Brinell hardness Charpy impact, ft-lb

2450--2600 0.13

34.2 8.9 x 10-6

125 21,500

20-30 45-60 30-15 80-125 60

than that of the wrought material although still very good for a material in cast form.

The Brinell hardness is about the same as that of the wrought type, values ranging from 80 to 125 for cast nickel and 90 to 120 for annealed wrought nickel in the form of bars or plates.

Cast nickel is a tough material as measured by the notched-bar test but considerably less tough than its wrought counterpart. The resistance of cast nickel as determined by the Charpy impact test is given as 60 ft-Ib but the type of notch is not indicated.zl This compares with about 215 ft-Ib for annealed and 185 ft-lb for cold drawn wrought nickel. I

The effect of subzero temperatures on the impact properties of cast nickel is indicated in Fig. 2-9, which includes data on wrought nickel also. This source gives the room temperature Charpy value for cast nickel as about 38 ft-lb as contrasted with that previously mentioned, but it is apparent that there is no indication of embrittlement at low temperatures and the cast nickel is as tough at - 320 F as it is at room temperature. IS

NICKEL POWDER

Nickel powder can be produced by a number of methods. However, the major commercial procedures in use today are the chemical reduction and the carbonyl nickel processes.

Carbonyl Nickel

In the production of nickel powder by the carbonyl process, nickel is extracted from reduced nickel oxide by reaction with carbon monoxide under

Nickel 27

pressure. The product is liquid nickel carbonyl which may contain some iron carbonyl also picked up from the raw material but is essentially free of other impurities. Because of the differences in boiling points of nickel and iron carbonyl, it is possible to separate them by fractionation. The nickel car­bonyl is distilled off as a gas and is subsequently liquefied in a condenser.

The liquid nickel carbonyl is decomposed at elevated temperature to produce nickel powder. 22 Adjustment of the conditions permits some control over the characteristics of the powder produced. The carbonyl process yields nickel powder of uniform size and high purity with particles less than 10 microns in size and with quite low density.

Prill and Upthegrove23 determined the properties of compacts produced from commercial carbonyl nickel powder having the following characteristics: average particle size, 3.8 microns; apparent density, 1.87 g/cm3 ; composi­tion-O.lO % carbon, 0.08 % oxygen, 0.004 % iron, less than 1 part per mil­lion sulfur, balance nickel.

The material was compacted at pressures ranging from 30 to 70 tons per square inch and sintered in hydrogen at 2000 to 2100 F for periods ranging from 5 min to 24 hr. After this series of treatments, the range in properties was

Sintered density, % of theoretical Yield strength (0.2 % offset), ksi Tensile strength, ksi Elongation (1 in.), % Charpy impact (V-notch), ft-lb

84-95 8-30

33-77 l3-35 3-24

This range of properties, which is achieved by varying the compacting pressure to achieve differences in sintered density, indicates that powder metallurgy (P/M) parts having good strength, ductility, and toughness can be produced from carbonyl nickel powder. Of course, the best properties are obtained with the highest density, i.e., the parts having the lowest porosity.

Worn and Morton24 determined the properties of extruded rod pro­duced from carbonyl nickel powder. The powder was pressed at 35 tons/in. 2

and given a preliminary sintering at 1100 F for 2 hours in hydrogen. It was then sintered at 2000 F for 2 hours in hydrogen, extruded in a steel sheath, heated for 1 hour at 1830 F, and cooled in air. Finally the sheath was re­moved by machining. This procedure yielded a bar of nickel which had been worked and annealed out of contact with the air and had practically theoret­ical density. The properties resulting from this working procedure were:

Vickers hardness Proof stress (0.2 %), ksi Tensile strength, ksi Elongation, % Reduction of area, %

75 16 40 46 65

28 Chapter 2

Reflecting the purity of the starting material, the strength of this bar is quite low. The tensile strength of 40 ksi compares with 46 to 52 ksi reported for "high purity" nickel by Rosenberg.! The ductility, as measured by the elongation and reduction of area, is somewhat lower than that reported for "high purity" wrought nickel but is excellent.

Worn and Morton also reported that the stress for rupture in 100 hours at 1500 F was 2.2 ksi for the bar produced from powder. This value is fairly close to the value of 3.6 ksi reported for low carbon commercial nickel under the same conditions in Table 2-4.

Chemically Reduced Nickel Powder

In the production of nickel powder by chemical reduction on a com­mercial scale, nickel sulfide ores are leached with ammonia at moderately elevated temperatures and pressures, according to Cockburn and LoreeY After boiling the leach solution to remove the excess ammonia and precipi­tating the copper as sulfide, nickel powder is precipitated from solution by reduction with hydrogen under pressure in an autoclave. The powder is separated from the liquid by filtering on a vacuum filter and is dried in a rotary drier.

The characteristics of the powder produced by chemical reduction can be varied by changes in the operating procedures. The apparent density of powder produced by this process ranges from 33 to 4.3 gjcm3 and a typical analysis is 99.8-99.9 % nickel + cobalt, 0.006-0.071 % iron, 0.012-0.019 % sulfur, and 0.05-0.18 % hydrogen loss.

This type of powder is used commercially for the direct rolling of nickel sheet. Some of the properties obtained on sheet after compacting, sintering, hot and cold rolling are given in Table 2-6. The powder had the nominal

Table 2-6. Properties of Nickel Sheet Rolled from Powderz6

Physical properties Thermal conductivity (158 F), BtuJhrJftzrF/ft Coefficient of thermal expansion (68-212 F), per OF Electrical resistivity, ohms/cir mil ft Modulus of elasticity, ksi Density,lb/in. 3

Mechanical properties of annealed material Yield strength (0.2 % offset), ksi Tensile strength, ksi Elongation (1 in.), % Shear strength, ksi Rockwell hardness, 30T scale

49.9 7.7 x 10-6

45.9 30,100

0.322

8 50 45 47.5 25

"Nickel 29

composition 99.93 % nickel + cobalt, 0.08 % cobalt, 0.006 % copper, 0.04 % iron, and 0.007 % carbon. 26

Physical Properties

The density of sheet rolled from powder is the same as that of wrought "high purity" nickel as shown in Table 2-1. The electrical resistivity, thermal conductivity, coefficient of expansion, and modulus of elasticity also compare favorably with those of wrought "high purity" nickel. The close relationship between properties of material produced conventionally and that produced from powder shows that the latter procedure is an excellent means of pro­ducing a mill form for further processing by conventional secondary fab­ricating procedures.

Mechanical Properties

The tensile strength of the sheet, 50 ksi, lies within the range reported by Rosenberg for "high purity" nickel. l As in the case of the bar produced from carbonyl nickel powder, the sheet rolled from powder is somewhat less ductile than that of "high purity" nickel produced conventionally.

An interesting comparison can be made of this rolled strip with the ex­truded bar produced from carbonyl nickel. The chemically reduced powder

100

80

"Vi 60 60 ~ -"=

vJ -~ <f) c' Q) '- 40 40 C\J if)

c 0

B 20 20 0>

c 0

W

0 20 40 60 80 Reduction by Rolling, %

Fig. 2-12. Effect of cold rolling on the tensile proper­ties of nickel strip prepared from powder. 25

30 Chapter 2

is somewhat lower in purity than the carbonyl product and this difference is reflected in the higher strength of the former. The ductilities of the two materials, however, are quite comparable.

The effect of cold rolling on the tensile properties of strip rolled from powder is indicated in Fig. 2_12.26 The tensile strength rises to a maximum of about 90 ksi at a reduction by rolling of 70% and the yield strength rises rapidly, approaching the tensile strength at a reduction of about 40%. How­ever, the ductility, as measured by the elongation, falls to a very low value with a reduction of 40%.

REFERENCES

1. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards (1968).

2. Handbook of Huntington Alloys, Huntington Alloy Products Division, The Inter­national Nickel Co., Inc. (1968).

3. Nickel-Containing Magnetic Materials, The International Nickel Co., Ltd. (1961). 4. J. P. Morris, G. R. Zellars, S. L. Payne, and R. L. Kipp, Vapor Pressures of Liquid

Iron and Liquid Nickel, RI 5364, Bureau of Mines (1957). 5. C. Y. Ho, R. W. Powell, and P. E. Liley, Thermal Conductivity of Selected Materials,

NSRDS-NBS 16, National Bureau of Standards (1968). 6. S. Bouwman, "Magnetic materials," International Science and Technology, Dec. 1962,

p.20. 7. Magnetostriction, The International Nickel Co., Inc., (1960). 8. Huntington Nickel Alloys, Huntington Alloy Products Division, The International

Nickel Co., Inc. (1968). 9. ASTM Standards, Part 7, American Society for Testing and Materials (1969).

10. J. L. Everhart, E. Lindlief, J. Kanegis, P. G. Weissler, and F. Siegel, Mechanical Prop­erties of Metals and Alloys, Circular 447, National Bureau of Standards (1943).

11. H. J. Grover, R. A. Gordon, and L. R. Jackson, Fatigue of Metals and Structures, NAVWEPS 00-25-534, Department of the Navy (1961).

12. F. R. Shober, The Effect of Nuclear Radiation on Structural Materials, DMIC Report 166, Battelle Memorial Institute (1961).

13. M. J. Mekin, "The effect of neutron radiation on the mechanical properties of copper and nickel," J. Inst. Metals 86, 449 (1957).

14. W. D. Jenkins, T. G. Digges, and C. R. Johnson, "Creep of high purity nickel," J. Res. Nat. Bur. of Std. 53, 329 (1954).

15. W. D. Jenkins and W. A. Willard, "Creep of cold drawn nickel, copper, 70% nickel-30% copper and 30% nickel-70% copper," J. Res. Nat. Bur, Std. C 66,59 (1962).

16. P. Shahinean and M. R. Achter, "Comparison of the creep rupture properties of nickel in air and vacuum," Trans. A/ME 215,37 (1959).

17. M. G. Lozinskiy and N. Z. Pertsivskiy, "Influence of temperature and degree of deformation in thermomechanical treatment on the creep resistance of nickel," Physics of Metals and Metallography 23 (2), 68 (1967).

18. R. M. McClintock and H. P. Gibbons, Mechanical Properties of Structural Materials at Low Temperatures, Monograph 13, National Bureau of Standards (t 960).

Nickel 31

19. F. R. Schwartzberg, S. H. Osgood, R. D. Keys, and T. F. Kiefer, Cryogenic Materials Data Handbook, AD609652, The Martin Co. (1964).

20. D. W. Grobecker, "An investigation of melting and casting procedures for high purity nickel," Trans. Amer. Foundrymen's Soc. 58, 720 (1950).

21. "Nickel and its aIIoys-cast," Materials in Design Engineering, Mid-October 1966, p.175.

22. J. R. Boldt, The Winning of Nickel, Van Nostrand (1967). 23. A. L. Prill and W. R. Upthegrove, "Properties of sintered carbonyl nickel compacts,"

Progress in Powder Metallurgy 20, 94 (1964). 24. D. K. Worn and S. F. Morton, "Some properties of nickel containing a dispersed

phase of thoria," Powder Metallurgy, Interscience (1961), p. 109. 25. K. O. Cockburn, R. J. Loree, and J. B. Haworth, "The production and characteristics

of chemicaIIy precipitated nickel powder," Proc. 13th Annual Meeting, Metul Powder Assn., April 30-May 1, 1957, p. 10.

26. "Nickel strip by powder metaIIurgy," Precision Metal Molding 22, 33 (1964).

Chapter 3

Nickel-Base Corrosion- and

Heat-Resistant Alloys-I

This and the following two chapters will deal with several groups of alloys which are in a sense related either through their major applications or through their compositions. The original materials were developed for corrosion resistance; later alloys extended the range of applications to heat resistance at higher temperatures, finally culminating in the alloys which extended the range to the highest temperatures at which nickel-base alloys are used, the so-called superalloy range.

It is essential to point out that the breakdown is strictly arbitrary. The corrosion-resistant alloys are frequently used in heat-resistant applications and the latter are used in corrosion-resistant applications, even at cryogenic temperatures. Because of their high alloy content and hence rather high cost, the superalloys are generally used in high-temperature service.

Unfortunately, there is no simple numbering system for the nickel­base alloys like that used by the AISI to classify steels. Several technical societies are working together to develop a universal numbering system for metallic materials but it is in the early stages of development. Consequently, many of the materials to be discussed are familiar to engineers by the names assigned to them by the originators of the alloys. Although use of trademarks does not seem to be a particularly desirable procedure in a general publica­tion, it appears to be the best method of identifying the alloys for the benefit of the reader and therefore will be used. A list of trademarks and their owners is included in the appendix.

Many alloys have been developed that would fit into the classification of nickel-base corrosion- and heat-resistant materials and it is impossible to cover them all. Therefore, representative alloys in various systems have

32

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 33

been selected to indicate the properties that can be expected of the nickel­base alloys. The most widely used materials can be broken down into the following groups:

Nickel-copper alloys Nickel-molybdenum and nickel-chromium-molybdenum alloys Nickel-silicon alloys Nickel-chromium alloys Nickel-chromium-iron and nickel-iron-chromium alloys Nickel-chromium-cobalt alloys Superalloys which are generally age hardenable modifications of

the alloy systems containing chromium

The first three groups will be considered in this chapter. Others will be discussed in succeeding chapters.

NICKEL-COPPER ALLOYS

Nickel and copper are soluble in each other in all proportions. The only transition in the solid alloys is the magnetic transition at the Curie tempera­ture which, according to Rosenberg,l varies from 639 F for nickel to -274 F for the 50% nickel-50 % copper alloy. This chapter deals only with the high­nickel end of the system. The high-copper alloys will be discussed in Chapter 6.

The most important of the nickel-copper alloys are those containing approximately 67 % nickel and 33 % copper, and modifications of this basic composition. These alloys are called "Monel" alloys by their originator. The basic member of the series is Monel alloy 400. This alloy has good strength, is weldable, and has excellent corrosion resistance and toughness over a wide range of temperatures. The nominal composition is given in Table 3-1. 2

Several modifications of this basic composition are:

Table 3-1. Nominal Compositions of Some Commercial Nickel-Copper Alloys2

Composition, %

Designation Nia Cu C Mn Fe S Si Others

Monel alloy 400 66.5 31.5 0.15 1.0 1.25 0.12 0.25 Money alloy 404 54.5 44.0 0.08 0.05 0.D25 0.12 0.05 0.03 Al Money alloy R405 66.5 31.5 0.15 1.0 1.25 0.43 0.25 Monel alloy K-500 66.5 29.5 0.13 0.75 1.00 0.005 0.5 3.0 AI, 0.63 Ti

"Nickel + cobalt.

34 Chapter 3

I. Monel alloy 404, which was developed to obtain an alloy having low magnetic permeability and excellent brazing characteristics. Alloy 404 has a low Curie temperature and its magnetic properties are not significantly affected by fabrication.

2. Monel alloy R-405, a material similar to alloy 400 to which sulfur has been added to improve the machining characteristics for use as stock for automatic screw machines.

3. Monel alloy K-500, an age harden able modification of alloy 400. Heating the solution-annealed alloy to about 1100 F causes a precipi­tation of an intermetallic compound, Ni3(AI, Ti), which increases the strength and hardness of the material.

The compositions of these three alloys are given in Table 3-1.2 A number of other modifications of alloy 400 are available. They in­

clude Monel alloy 401, produced for specialized electronic applications; alloy 402, developed for resistance to pickling solutions; alloy 403, developed for nonmagnetic applications in minesweepers; alloy 406, for use in cor­rosive mine waters; and alloy 474, a higher-purity modification of alloy 404. 3

These materials will not be discussed in this publication.

Physical Properties

Representative physical properties of Monel alloy 400, alloy 404, and alloy K-500 are given in Table 3_2.2,4 According to the producer, the physical

Table 3-2. Physical Properties of Some Nickel-Copper AIIoys2,4

Monel Monel Monel alloy alloy alloy 400 404 K-500

Melting range, F 2370-2460 2400-2460 Specific heat (70 F), Btujlb;oF 0.102 0.099 0.100 Thermal conductivity (70 F), Btujhrjft2;oFjft 12.6 12.2 10.1 Coefficient thermal expansion (70-1000 F),

per of 9.0 x 10-6 9.2 X 10-6 8.7 X 10-6

Electrical resistivity (70 F), ohmsjcir mil ft 307 300 370 Temperature coefficient of resistance

(68-212 F) 0.0011 0.0001 Curie temperature, F 20-50 -110 -210a, -153b

Permeability (70 F, H = 2000e) 1.002 1.001 Modulus of elasticity, ksi 26,000 25,000 26,000 Modulus of rigidity, ksi 10,000 9,400 9,500 Poisson's ratio 0.32 0.32 Density, Ibjin. 3 0.319 0.321 0.306

aAnnealed. • Age hardened.

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 35

properties of alloy R-405 are identical with those of alloy 400 and, therefore, they have not been included in the table.

The electrical resistivities and thermal conductivities of alloy 400 and alloy 404 are quite similar. Reflecting the higher alloy content, Monel alloy K-500 has a considerably higher electrical resistivity and a correspondingly low thermal conductivity. Other physical properties of the three alloys are also quite close together with the exception of the magnetic transformation point.

The Curie temperature of alloy 400 is in the ambient temperature re­gion, that of alloy 404 at -110 F, and that of alloy K-500 ranges from -210 F for the alloy in the solution-annealed condition to -153 F after age hard­ening. The low Curie temperatures of alloy 404 and alloy K-500 indicate that these alloys are virtually nonmagnetic at quite low temperatures.

Mechanical Properties

Room-Temperature Properties

Monel alloy 400, alloy 404, and alloy R-405 are solid-solution alloys which can be hardened only by cold work. On the other hand, alloy K-500, which contains aluminum and titanium, can be age hardened to achieve higher strength and hardness than are obtainable by cold work alone.

Tensile Properties. Nominal tensile property ranges for these alloys are given in Table 3_3. 3,5 They reflect the variation in expected properties which will occur in different mill forms.

The tensile strengh of Monel alloy 400 ranges from about 70 ksi for annealed material to 140 ksi for severely cold worked material. Since the ductility decre2,ses with cold work, the elongation ranges from about 60 % for annealed material to as low as 2 % after cold working.

Alloy R-405, the free-machining version of alloy 400, has strength prop­erties in the same range as those of alloy 400 but the ductility is somewhat lower. The limited data available on alloy 404 indicate properties in the same range as those of alloy 400.

Monel alloy R-500, however, reflecting its ability to be age hardened, has a much broader range of tensile properties than the other three materials. The tensile strength ranges from 90 ksi for annealed material to 220 ksi for material that had been age hardened after severe cold work. The ductility, as measured by the elongation, ranges from about 45 % for annealed material to 2 % for cold worked material, which has not been age hardened. Age hardening, however, results in some improvement in the ductility of severely cold worked material.

The effects of cold work and age hardening after cold work on the

36 Chapter 3

Table 3-3. Nominal Tensile Properties and Hardness Values of Some Nickel-Copper Alloys3.s

Yield strength Tensile Elongation

(0.2 % offset), strength, (2 in.), Rockwell Form and condition ksi ksi % hardness

Monel alloy 400 Rod and bar

Annealed 25-50 70-90 60-35 B60-80 Hot finished 40-100 80-110 60-30 B95-100 Cold drawn, stress-relieved 55-100 84-120 40-22 B85-C20

Plate, hot rolled Annealed 28-50 70-85 50-35 B60-76 As rolled 40-75 75-95 45-30 B70-96

Sheet Annealed 25-45 70-85 50-35 B73 max Cold rolled, hard 90-110 100-120 15-2 B93 min

Strip, cold rolled Annealed 25-45 70-85 55-35 B68 max Spring temper 90-130 100-140 15-2 B98 min

Monel alloy R-405 Rod and bar

Annealed 25-40 70-85 50-35 B60-76 Hot finished 35-60 75-90 45-30 B72-86 Cold drawn 50-105 85-115 35-15 B85-C23

Monel alloy 404 Rod

Annealed 25 67 47 B58 Hot rolled 31 69 45 B67 Cold drawn, stress-relieved 64 77 29 B84

Strip, cold rolled Annealed 22 64 44 B54

Monel alloy K-500 Rod and Bar

Annealed 40-60 90-110 45-25 B75-90 Hot finished 40-110 90-155 45-20 B75-C35 Hot finished, aged 100-150 140-190 30-20 C27-38

Plate Hot finished 40-110 90-135 45-20 B75-C26 Hot finished, aged 100-135 140-180 30-20 C27-37

Strip, cold rolled Annealed 40-65 90-105 45-25 B85 max Annealed, aged 90-120 130-170 25-15 C24 min

Nickel-Base Corrosion- and Heat-Resistant Alloys-I

220~---.---.----.---~----r---,

200

__ 180 (f)

.:.::

(f)

~ 140 iii c Q)

f-120

100

80 ~--~----~--~----~--~~--~ o 10 20 30 40 50 60

Cold Work, %

46

44

42

40 (f) (f)

37 Q) c

34 ~ 0

:r:: 31 0

27 Q)

3 .:.::

22 u 0

0:: 16

9

0

Fig. 3-1. Effect of cold work and age hardening on the strength and hardness of alloy K-500 5 •

37

tensile strength of alloy K -500 are indicated in Fig. 3-1. 5 Age hardening produces a significant improvement in strength. For example, it results in an increase in tensile strength of about 30 ksi in material cold worked with a reduction of 60 %.

Hardness. Rockwell hardness ranges for the four alloys are included in Table 3-3. The hardness values for alloy 400, alloy R-405, and alloy 404 range from about R60 for annealed material to C20 for cold worked material.

Reflecting its ability to be hardened by aging, the hardness of alloy K-5oo ranges from about B75 in the annealed condition to a minimum of C24 in the worked and aged condition. The range of hardness values to be expected as a result of cold working followed by aging is indicated in Fig. 3-1.

There is an approximate relationship between the tensile properties and the hardness of Monel alloy 400, which is useful to the engineer. This rela­tionship is shown in Fig. 3-2 for sheet and strip.3 The tensile strength in­creases gradually from 70 ksi to 115 ksi with yield strength increasing more rapidly as the hardness resulting from cold work increases from Rockwell

38

120

100

80 . iii ..><:

en- 60 60 ~

en -<l> ~ ... c if)

C\J

40 40 c 0 . .;= 0 Cl'

20 20 c 0 W

60 70 80 90 100 Rockwell B Hardness

Fig. 3-2. Relationship between tensile properties and hardness of alloy 400 sheet and strip. 3

Chapter 3

B60 to BlOO. In the same hardness range, the elongation falls from about 48% to 5%.

Fatigue Properties. The effects of working and aging on the fatigue properties of several nickel-copper alloys are indicated in Table 3_4.3 ,5

Monel alloy 400 rod has endurance ratios of about 0.40 in the annealed con­dition and also after cold working; sheet ratios are about 0.31. Alloy R-405 rod has fatigue properties similar to those of alloy 400. The age hardening of alloy K-500 rod and sheet results in a significant reduction in the endur­ance ratio.

Impact Properties. As measured by the notched-bar impact test, Monel alloy 400 is a very tough material. Data are given in Table 3-5 for annealed and cold worked material tested by both the Izod and Charpy methods. The specimens did not fracture completely in these tests.3 Although the resistance to impact is somewhat lower than that of alloy 400, alloy R-405 also has excellent toughness and the specimens did not fracture completely.3

Apparently, Monel alloy K-500 is less tough than alloy 400 although the results are not directly comparable since different procedures were used. A further indication is the fact that the aged materials fractured completely

Nickel-Base Corrosion- and Heat-Resistant Alloy-I

Table 3-4. Fatigue Strengths of Some Nickel-Copper Alloys

Fatigue Tensile strength

strength, (l08 cycles), Endurance Form and condition ksi ksi ratio Ref.

Monel alloy 400 Rod

Annealed 82 33.5 0.41 3 Cold drawn 105 40.5 0.39 Cold drawn, stress-relieved 96.5 17 0.38

Sheet Annealed 74.7 21 0.38 Cold rolled, hard 126 39 0.31

Monel alloy R-405 Rod

Annealed 75.5 30 0.40 3 Cold drawn 90.5 36.5 0.40

Monel alloy K-500 Rod

Annealed 88 38 0.43 5 Cold drawn 120 45 0.37 Cold drawn, aged 170 47 0.28

Sheet Annealed 88 27 0.31 Spring temper, aged 153 37 0.24

Table 3-5. Impact Properties of Some Nickel-Copper Alloys

Condition

Monel alloy 400 Annealed Hot rolled Forged Cold drawn

Monel alloy R-405 Annealed Hot rolled Cold drawn

Monel alloy K-5oo Annealed 1800 F, 1 hr, wqa Hot finished Hot finished, aged 1100 F, 16 hr Cold drawn Cold drawn, aged 1100 F, 16 hr

aWater quenched. bFractured completely.

Impact resistance, ft-Ib

Izod Charpy

90-120+ 100-120+ 75-115 75-115

120+ 96 99

V-notch

215 220

150

196 187 140

Keyhole notch

75 74 39b

40 26b

Ref.

3

3

5

39

40 Chapter 3

in a Charpy test. Additional impact data are included under low-temperature properties.

Elevated- Temperature Properties

A comparison of the short-time elevated-temperature tensile strengths of hot rolled Monel alloy 400 and alloy K-500 is given in Fig. 3_3. 3,5 Alloy K-500 is significantly stronger than alloy 400 at all but the highest tempera­tures. The effect of age hardening on alloy K-500 is also apparent in this figure. The greatly increased strength resulting from aging persists up to about 1000 F but above that temperature softening occurs and the aged material approaches the unaged in strength.

Temperature, K

400 600 800 1000 1200 160 ......... ---..-----,-----,.--,...---..,....---,

140

120

(f)

-"" 100 -£ CJ1 C

~ 80 en -ill § 60 f-

40

20

o 400 800 1200 1600 2000 Temperature, F

Fig. 3-3. Short-time elevated-temperature tensile strengths of two nickeI-<:opper alloys. 3,5 (1) Alloy K-500, hot rolled and aged; (2) alloy K-500, hot rolled; (3) alloy 400, hot rolled.

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 41

Table 3-6. Creep and Rupture Properties of Some Nickel-Copper Alloys

Test Stress (ksi) for creep

Stress (ksi) rate of temperature, for rupture

Condition F 0.001 %/hr 0.Q1 %/hr in 100 hr Ref.

Monel alloy 400 Hot rolled 700 30 40 3

800 14.5 25.5 900 4.0 13.5

1000 3.0 Annealed 800 15 24

900 8 16 46 1000 3.5 9.5

Cold drawn, 800 12 30 54 stress-relieved 900 3.5 12 38

1000 0.6 2.1 24

Monel alloy K-500 Cold drawn, aged 800 47 88 5

900 25 48 1000 8.2 21 1100 9.1

Hot finished, aged 900 66 1000 42 1100 34

Data on the creep and stress-rupture properties of alloy 400 and alloy K-500 are included in Table 3_6. 3 ,5 The creep strengths of alloy 400 in the annealed condition are markedly higher than those of the same alloy in the hot rolled or the cold rolled stress-relieved conditions and the differences increase with rising temperatures. The stress for rupture in 100 hours of annealed material is also somewhat higher than that of material which has been stress-relieved after cold rolling.

Alloy K-500 in the cold worked and aged condition has much higher creep strengths than alloy 400 in the 800 to 1000 F range, as might be ex­pected. As indicated in the table, this alloy has a creep strength at 1100 F practically equivalent to that of annealed alloy 400 at 1000 F. The differences in the 100-hour stress rupture strengths are much lower.

Low-Temperature Properties

The Monel alloys have excellent mechanical properties at subzero temperatures. Strength and hardness increase and there is no ductile to brittle transition even at extremely low temperatures.

42

160

140

120

100

~ 80 ~ -(J)

60

40

20

Temperature, K

50 100 150 200 250 300

...... ......

...... ...... ...... ... ~

~~ f:'Ot; ~~~e(j

...... LI ...... ...... '7 R ......

............ ~ . -- ........... ...... .. ......

-400 -300 -200 -100 Temperature, F

...... ...... .........

o 100

Fig. 3-4. Subzero-temperature tensile and yield strengths of alloy400 in various conditions. 6

Chapter 3

McClintock and Gibbons6 included data on alloy 400 and alloy K-500 in their compilation of low-temperature properties. As shown in Fig. 3-4, the strength of alloy 400 in both the annealed and worked conditions increases continuously with falling temperatures. Similarly, the strength of alloy K-500 also increases, the difference in strength between the aged and unaged material remaining practically constant as the temperature falls (Fig. 3-5).

The ductility of alloy 400 as measured by impact tests remains practi­cally unaffected as the temperature falls to very low values, as shown in Fig. 3-6.6 Although the Izod values are considerably lower than the Charpy, both follow the same trend.

Fatigue data on alloy K-500 cold rolled and aged to a tensile strength of 182 ksi are given in Table 3-7. 5 In common with the other mechanical prop-

Nickel-Base Corrosion- and Heat-Resistant Alloys-I

240

200

160 en

.Y

ul 120 en ~

U5 80

20

50 Temperature, K 100 150 200

-200 -100 Temperature, F

250 300

o 100

Fig. 3-5. Subzero-temperature tensile and yield strengths of alloy K-500 in various conditions. 6

240

200 -

160 -

>. 120-01

50 I

Temperature, K 100 150 200 250

I I Ann. I

I

~=;

300 I

--

-

-"­CLl C

W - ___ • Ann.

-------------, 80 r-

40 r­-CharpyV ----Izod

I I I I -400 -300 -200 -100

Temperature, F

-

-

I o 100

Fig. 3-6. Subzero-temperature impact properties of alloy 400. 6

43

44 Chapter 3

Table 3-7. Fatigue Strength of a Nickel-Copper Alloy at Low Temperatures S

Test Fatigue strength (ksi)

at indicated cycles temperature,

Condition F 105 106

Monel alloy K-500 70 90 55 Cold rolled, half hard, -110 99 67

aged (tensile strength, -320 105 69 182 ksi) -423 143 101

107

37

erties of the Monel alloys, the fatigue strength increases with falling tem­perature.

CAST NICKEL-COPPER ALLOYS

The compositions of the cast nickel-copper alloys differ from those of the wrought types mainly because filling the molds requires greater fluidity in the liquid metal. This is achieved principally by increasing the silicon content of the alloy.

Eash and Kihlgren 7 have pointed out that a wide range of properties can be obtained by controlling the silicon content. By this means, the tensile strengths of cast nickel-copper alloys, nominally containing 30 to 32 % copper, can be varied from 75 ksi at 1.5 % silicon to 150 ksi at 4 % silicon, the high strength of the latter being achieved by precipitation hardening. Recommended practice for casting these alloys is included in their discus­sion.

There are two commercial nickel-copper alloys in common use as cast­int alloys. Designated Monel alloy 410 and alloy 505, they have the following nominal compositions:

Monel alloy 410 Monel alloy 505

Physical Properties

Ni 66 64

eu 30.5 29

Fe 1.0 2.0

Mn 0.8 0.8

Si 1.6 4.0

Typical physical properties of these two casting alloys are given in Table 3_8. 8,9 With the exception of the modulus of elasticity, which is con­siderably lower, the physical properties of alloy 410 are quite similar to those of alloy 400, which were given in Table 3-2.

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 45

Table 3-8. Physical and Mechanical Properties of Cast Nickel-Copper Alloys8,9

Physical properties Melting temperature range, F Specific heat (32-212 F), Btu/lb;oF Thermal conductivity (68-212 F),

Btu/hr/ft2;oF /ft Coefficient of thermal expansion (70-1000 F),

per of Electrical resistivity, ohms/cir mil ft Modulus of elasticity, ksi Density,lb/in. 3

Mechanical properties Yield strength (0.2 % offset), ksi Tensile strength, ksi Elongation (2 in.), % Brinell hardness Charpy impact (V-notch), ft-lb

Monel alloy 410

as cast

2400-2450 0.13

15.5

9.2 x 10-6

320 23,000

0.312

35 75 40

150 70

Monel alloy 505

Annealed Annealed and aged

2300-2350 0.13

11.3

8.9 X 10-6

380 24,000

0.302

75 110 115 135 10 2

225 340

Reflecting the higher silicon content, the melting range of alloy '505 is about 100 F lower than that of alloy 410, whereas the electrical resistivity is considerably higher and the thermal conductivity is somewhat lower.

Mechanical Properties

Typical mechanical properties of the two nickel-copper casting alloys are given in Table 3-8. The "as cast" tensile properties of alloy 410 lie in the same range as those of annealed alloy 400, but the toughness as measured by the Charpy method is considerably lower.

Reflecting the higher silicon content, alloy 505 has considerably higher strength and hardness than alloy 410 but the elongation is much lower. Age hardening of alloy 505 results in a significant increase in strength and hard­ness with a corresponding reduction in ductility.

Warren and Reed! 0 included alloy 410 in their investigation of mechan­ical properties at low temperatures. As shown in Fig. 3-7, both tensile and yield strength increase continuously as the temperature falls from room to -423 F. Charpy V-notch impact tests showed very little loss in energy absorbed as the temperature was reduced: 41 ft-lb at room temperature, 39 ft-Ib at -320 F.

46 Chapter 3

Temperature, K

50 100 150 200 250 300 160

140

~120 en <f) Q) '-

iii 100

80

60 -400 -300 -200 -100 0 100

Temperature, F

Fig. 3-7. Subzero-temperature tensile and yield strengths of alloy 41O.! 0

NICKEL-MOLYBDENUM ALLOYS

The nickel-molybdenum alloys were developed originally as corrosion­resistant materials. They are primarily strengthened by elements which are taken into solid solution in the base metal, nickel. These alloys are work hardenable but can be strengthened moderately by simple heat treatments. However, the corrosion and heat resistance of alloys of this type are greatest in the annealed (solution treated) condition and they are generally used in this condition, particularly for service above the recrystallization tempera­ture.!!

The best known of these corrosion-resistant nickel-molybdenum alloys are those called "Hastelloy" alloys by their originator. These alloys are moderately strong but they retain much of their room-temperature strength at relatively high temperatures and, therefore, they are also used for structural applications at elevated temperatures. Nominal compositions of some of these alloys are given in Table 3-9. 12

Hastelloy alloy B has high resistance to corrosion by hydrochloric acid. It also has good high-temperature properties. In oxidizing atmospheres, it can be used at temperatures up to 1400 F, in reducing atmospheres at sub­stantially higher temperatures.!3

Hastelloy alloy C has excellent resistance to corrosion by strong oxidiz-

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 47

Table 3-9. Nominal Compositions of Some Nickel-Molybdenum Alloys 12

Composition, %

Designation Ni Co Mo Cr Fe C Other

Hastelloy alloy B 61 2.50 28 la 5 0.05a unspecified, 3 Hastelloy alloy C 54 2.5a 16 15.5 5.5 0.080 4 W; unspecified, 3 Hastelloy alloy N 69.5 16.5 7 5a 0.06 0.8 Mna Hastelloy alloy X 47 1.5 9 22 18.5 0.10 0.6 W; unspecified; 1.5

aMaximum.

ing agents, moist chlorine gas and chlorine solutions, and to oxidizing acids and many organic acids and salts. It is resistant to oxidizing and reducing atmospheres up to 2000 F.14

Hastelloy alloy N was developed for resistance to molten fluoride salts. It has good oxidation resistance up to 1800 F.J5

Hastelloy alloy X has excellent strength and oxidation resistance up to 2200 F. It also resists stress-corrosion crackingY

A number of other Hastelloy alloys are available including alloy B 282 for service in strong reducing media in the as-welded condition, alloy C 276 for all-around corrosion resistance in the as-welded condition, and alloy G for resistance to hot sulfuric and phosphoric acids. These alloys will not be discussed in this publication.

Physical Properties

Typical physical properties of the nickel-molybdenum alloys are given in Table 3_10. 13 ,14,15,16 The electrical resistivities, ranging from 712 to 811

Table 3-10. Physical Properties of Nickel-Molybdenum Alloys13,14,15,16

Hastelloy Hastelloy Hastelloy Hastelloy alloy B alloy C alloy N alloy X

Melting temperature range, F 2408-2462 2310-2450 2375-2550 2300-2470 Specific heat (212 F), Btu/lbrF 0.091 0.092 0.116 Thermal conductivity (392 F),

Btu/hr/ft2 rF /ft 7.0 6.5 7.4 5.2 Coefficient of thermal expansion

(70-1500 F), per of 7.0 x 10-6 8.1 X 10-6 8.3 X 10-6 8.9 X 10-6

Electrical resistivity, ohms/cir mil ft 811 779 712

Modulus of elasticity, ksi 30,800 29,800 31,700 28,500 Density (70 F), Ib/in. 3 0.334 0.323 0.317 0.297

48 Chapter 3

ohmsjcir mil ft, are much higher than those of the nickel-copper alloys discussed previously, and the thermal conductivities are considerably lower. The coefficients of thermal expansion are generally lower than those of the nickel-copper alloys but there is no great difference between the two series of alloys. On the other hand, the moduli of elasticity of the nickel-molybdenum alloys are markedly higher than those of the nickel-copper alloys. Although not listed in the table, the nickel-molybdenum alloys under discussion are virtually nonmagnetic.

Mechanical Properties

Nominal tensile properties and hardness values for the four alloys under discussion in several forms and conditions are given in Table

Table 3-11. Nominal Tensile Properties and Hardness Values of Some Nickel-Molybdenum Alloys 13,14,15,16

Form and condition

Hastelloy alloy B Sheet

2000 F, raea

Cold rolled, 10% Cold rolled, 20%

Bar 2125 F, rae

Hastelloy alloy C Sheet

2225 F, rae 2225 F, rae, aged 16 hr,

l100F Cold rolled, 20 %

Bar 2225 F, rae

Hastelloy alloy N Sheet

2150 F, rae

Hastelloy alloy X Sheet

2150 F, rae 2150 F, rae, aged 25 hr,

1400F Plate

2175 F, wqb

aRapid air cooled. bWater quenched.

Yield strength Tensile

(0.2 % offset), strength, ksi ksi

67 110 138

56

68 82

1I8

51

46

50 58

54

104 147 164

127

128 146

145

121

115

112 121

1I4

Elongation (2 in.),

%

51 33 22

52

49 44

23

50

51

43 28

41

Rockwell hardness

B96

B95

B91 B98

B94

B96

B90

Nickel-Base Corrosion and Heat-Resistant Alloys-I 49

3_11. 13 ,14,15,16 Alloy B and alloy N can be hardened only by cold work but alloy C and alloy X can be aged to achieved a moderate improvement in tensile properties.

TensIle Properties. The tensile strength of alloy B ranges from about 105 ksi for annealed material to 165 ksi for material that had been mode­rately cold worked and this increase in strength is accompanied by a cor­responding reduction in ductility as measured by the elongation. Alloy N has tensile properties quite similar to those of alloy B.

The tensile strength of alloy C ranges from about 125 ksi in the annealed condition to 145 ksi after moderate cold working. Aging alloy C after an­nealing increases the strength to approximately the same degree as 20 % cold work, but aging has the advantage that there is less severe raduction in elon­gation accompanying the increase in strength. Age hardening of alloy X after annealing increases the strength moderately.

Impact Properties. Limited data on resistance to impact are given in Table 3-12. These alloys are considerably lower in toughness than the nickel­copper alloys mentioned earlier but have good impact properties. The data

Table 3-12. Impact Properties of Nickel-Molybdenum Alloysl3, 14, 15, 16

Form and condition

Hastelloy alloy B Bar

2150 F, rac·

Hastelloy alloy C Bar

2225 F, rac

Hastelloy alloy N Bar

2150 F, rac

Hastelloy alloy X Plate

2150 F, wqb 2150 F, wq, 168 hr, 1500 F 2150 F, wq, 500 hr, 1600 F 2150 F, wq, 500 hr, 1800 F 2150 F, wq, 50 hr, 1900 F

"Rapid air cooled. ·Water quenched.

Impact resistance, ft-Ib

Izod (V-notch)

58-62

21-23

Charpy (V-notch)

80-88

54 9 9

20 30

50 Chapter 3

on alloy X indicate that this alloy is considerably more shock resistant in the solution-annealed condition than it is after aging. They also indicate that the aging conditions have a marked effect on the toughness.

Elevated-Temperature Properties

Short-time elevated-temperature tensile strengths of the four Hastelloy alloys are shown in Fig. 3_8. 13,14.15.16 These alloys retain more than 50% of their room-temperature strengths up to temperatures of at least 1200 F and all reach approximately the same strength at 2000 F.

Typical stress-rupture properties of the alloys are given in Table 3_13. 13,14,15,16 Alloy X has a lower 100-hour rupture strength at 1200 F than

Temperature, K 400 600 800 1000 1200

140

120

100 ·Vi --X:

£ c;, 80 c: ~

if) (j) 60 Vi c: (j)

f-40

20

o 400 800 1200 1600 2000 Temperature, F

Fig. 3-8. Short-time elevated-temperature tensile strengths of several nickel-molybdenum alloys.13, 14, 15.16 (I) Alloy B, 0.078-in. sheet, heat treated at 2000 F, rapid air cooled; (2) alloy C, 0.109-in. sheet, heat treated at 2225 F, water quenched; (3) alloy X, O. 109-in, sheet, heat treated at 2150 F, rapid air cooled; (4) alloy N, 0.063-in. sheet, heat treated at 2150 F, rapid air cooled.

Nickel-Base Corrosion- and Heat-Resistant Alloys-I

Table 3-13. Rupture Strength of Some Nickel-Molybdenum AlloYS13,14,15,16

Stress (ksi) for rupture in 100 hours at

51

Form and condition 1200 F 1350 F 1500F 1700 F 1800F

Hastelloy alloy B Sheet, 0.078 in.

2000 F, rae· 50 24b 15.9

Hastelloy alloy C Sheet, 0.050-0.141 in.

2250 F, rae 50 33 18 10e

Hastelloy alloy N Sheet, 0.063 in. 2150 F, rae 55d 26e 9 3.7

Hastelloy alloy X Sheet

2150 F, rae 42 26 14 6.2 3.8

aRapid air cooled. ·1400 F. '1600 F. dll00 F. '1300 F.

the other materials but retains a greater proportion of its strength than the others as the temperature increases.

Fatigue tests on alloy B bar, water quenched from 2000 F and aged at 1200 F for 4 hours, showed an endurance limit of 66 ksi at 1200 F and 108

cyclesY Similar tests on alloy N sheet, after rapid air cooling from 2150 F, showed the following stresses for failure in 108 cycles:

47.5 ksi at 1100 F 38 ksi at 1300 F 23 ksi at 1500 F

Low-Temperature Properties

As shown in Fig. 3-9, the tensile strength of alloy B cold rolled sheat increases with falling temperature. 1 7 The increase is gradual for material which had been cold worked 20% but is very marked below about -320 F for material cold worked 40 %. Elongation also increased but there was a downward trend for the material that had been cold worked 40 %, at tempera­tures below -320 F.

Alloy X plate also showed an increase in strength with falling tempera­turesY On material which had been water quenched from 2150 F, the tensile strength was 150 ksi at -321 F compared with 104 ksi at room temperature. The elongation, however, remained virtually the same at the two tempera­tures: 45.5% at -321 F and 46.2% at room temperature.

52

280

260

"Vi 240 ~

.c

g.220 ~ (jj

Temperature, K

50 100 150 200 250 300

60

50 ~ c o

Chapter 3

(!)

~200 c

'"5 40 g

~

180

160

140

-400 -300' - 200 -100 Temperature, F

o

o W

30

20

100

Fig. 3-9. Subzero·temperature tensile properties of alloy B sheet. 17 (1) Tensile strength, O.Oll-in. sheet,40 % cold worked; (2) elongation 0.080-in. sheet, 20% cold worked; (3) tensile strength, 0.080-in. sheet, 20% cold worked; (4) elongation, O.Oll-in. sheet, 40% cold worked.

The effect of low temperatures on the toughness of these alloys as measured by the notched bar test is indicated in Table 3_14.13,14,16 There is no indication of a transition from ductile to brittle behavior down to at least -321 F. Alloy B is considerably tougher at all temperatures than alloy C, but both materials have very good properties. Alloy X cannot be com­pared directiy with the others because of a different testing procedure, but also has very good toughness.

Nickel-Base Corrosion- and Heat-Resistant Alloys-I

Table 3-14. Low-Temperature Impact Properties of Some Nickel-Molybdenum Alloys13,14,16

Test temperature,

F

Impact resistance, ft-lb

Form and condition

Hastelloy alloy B Bar

2125 F, raca

Hastelloy alloy C Bar

2225 F, rac

HasteJloy alloy X Plate

2150 F, wqb

"Rapid air cooled. .Water quenched.

Room -58

-148 -326

Room -58

-148 -326

Room -20

-108 -216 -321

Izod (V-notch)

60 49 53 53

21-23 25 22 27

CAST NICKEL-MOLYBDENUM AND NICKEL-CHROMIUM-MOLYBDENUM ALLOYS

Charpy (V-notch)

54 56 51 44 37

53

The four Hastelloy alloys discussed previously are also produced in cast form. Another group of cast corrosion-resistant alloys is called "IIlium" alloys by its originator. This group includes three nickel-chromium-molyb­denum aIloys having the following designations and nominal compositions:

Designation Composition, % Ni Mo Cr Cu Fe

IIlium B 52 8.5 28 5.5 1.15 IIlium 98 55 8.5 28 5.5 1.0 Illium G 56 6.4 22.5 6.5 6.5

Illium B is a machinable wear- and corrosion-resistant alloy developed

54 Chapter 3

for corrosion resistance where resistance to erosion, galling, and wear must also be considered. I 8

Illium 98 is a machinable casting alloy developed to withstand the cor­rosive attack of 98 % sulfuric acid at elevated temperatures. It is also resistant to other nonhalogen acids. I 8

Illium G is a machinable casting alloy which is resistant to attack by acids and alkalies under oxidizing and reducing conditions up to moderately high temperatures, especially to most sulfur compounds. 18

Physical Properties

The physical properties of the four cast Hastelloy alloys are similar to those of the corresponding wrought alloys and are given in Table 3-2.

No data were found on the physical properties of Illium B or Illium 98 but the following properties were reported for Illium G: 18

Specific heat, Btu/lbtF Thermal conductivity (70 F), Btu/hr/fPtF/ft Coefficient of thermal expansion (32-1472 F), per of Electrical resistivity, ohmsJcir mil ft Modulus of elasticity, ksi Density, Ib/in. 3

0.105 7.0

8.5 X 10- 6

743 24,300

0.31

The electrical resistivity and thermal conductivity of Illium G lie in the same range as those of the Hastelloy alloys and its coefficient of expansion is about the same as that of Hastelloy alloy N.

Mechanical Properties

The properties of the Hastelloy alloys in the form of sand and invest­ment castings are given in Table 3_15. 13 ,14,15,16 The strengths of the cast alloys in the "as cast" condition are somewhat lower than those of the cor­responding wrought alloys in the annealed condition, as will be apparent from a comparison of Table 3-15 with Table 3-11. The ductilities of the cast alloys are much lower than those of the wrought materials. However, the Rockwell hardness values of the cast and wrought materials are comparable. The cast alloys are also less tough than the corresponding wrought materials, as indicated by the data in Tables 3-12 and 3-15.

The strength of alloy B can be improved considerably by aging, and this effect is accompanied by a small increase in ductility. On the other hand, although the strength of alloy C can be improved to some extent by aging, the ductility is adversely affected.

Properties of the Illium alloys in the "as cast" condition are included

Tab

le 3

-15.

N

om

inal

Mec

han

ical

Pro

per

ties

of

Cas

t N

ick

el-

Mo

lyb

de

nu

m a

nd

N

ick

el-

Ch

rom

ium

-Mo

lyb

de

nu

m A

llo

ysI3

,14

,IS

,16

,18

2 n' ,..

Yie

ld s

tren

gth

Ten

sile

E

long

atio

n R

educ

tion

Im

pact

~

(0,2

% of

fset

), st

reng

th,

(in

1 in

,),

of

area

, R

ockw

ell

(V-n

otch

),

l1li

For

m a

nd c

ondi

tion

ks

i j:

si

%

%

hard

ness

ft

-Ib

II>

III CD

Has

tell

oy a

lloy

B

(')

0 S

and

cast

... ;;

2125

F,

1 hr

, ra

ca

50

90

lOb

10

B93

18

c II

I

Inve

stm

ent

cast

0'

~

As

cast

53

85

15

15

B

93

13e

. C

ast,

age

d 25

hr,

147

5 F

64

107

18

21

B97

II>

~ c.

Has

tell

oy a

lloy

C

%

San

d ca

st

CD

II>

2250

F,

1 hr

, ra

e 51

83

9b

12

B

93

20c

1-In

vest

men

t ca

st

:u

CD

As

cast

52

89

11

12

B

96

III iii'

Cas

t, a

ged

25 h

r, 1

475

F 76

98

4

5 C

37

.. II> ~

Has

tell

oy a

lloy

N

.. S

and

cast

~

2150

F,

rae

44

87

22

0'

'<

Inve

stm

ent

cast

II

I I 21

50 F

, ra

e 37

86

17

28

d -

Has

tell

oy a

lloy

X

San

d ca

st

As

cast

43

78

23

27

B

89

Inve

stm

ent

cast

A

s ca

st

46

70

12

17

B87

II

Iium

B

As

cast

62

1.

0b

244-

IIIi

um 9

8 A

s ca

st

54

18b

22

160-

Illi

um G

A

s ca

st

39

68

8b

11

168-

61

CII

CII

-Rap

id a

ir c

oole

d.

.In

2 in

. cI

zod.

·C

har

py

. ·B

rine

ll.

INo

tch

ed s

peci

men

, ty

pe o

f tes

t n

ot

spec

ifie

d.

56 Chapter 3

also in Table 3-15. 18 These alloys are not as strong as the cast Hastelloy alloys. Illium B is quite brittle in the "as cast" condition but Illium 98 and Illium G have ductilities which are comparable with those of the Hastelloy alloys in the "as cast" condition.

NICKEL-SILICON ALLOYS

Hastelloy alloy D is the only commercial representative of the nickel­silicon alloys. Alloy D is a sand-casting alloy best known for its resistance to sulfuric acid at all concentrations and at temperatures up to the boiling points. This alloy is also resistant to organic acids and acid salts. 19

It has the following nominal composition:

Ni Si Cu Mn Co Cr Fe C 82 9 3 0.9 1.5 max 1 max 2 max 0.12 max

Physical Properties

The physical properties of Hastelloy alloy D are given in Table 3-16Y Although the compositions are not comparable in any sense, some of the physical properties of alloy D lie in the same range as those of the nickel­copper alloys previously discussed. These include the specific heat, thermal

Table 3-16. Physical and Mechanical Properties • of Hastelloy Alloy 0 19

Physical properties Melting temperature range, F Specific heat (70 F), Btu/lbrF Thermal conductivity (72 F), Btu/hr/ft2/oF/ft Coefficient of thermal expansion (32-1800 F), per OF Electrical resistivity, ohms/cir mil ft Modulus of elasticity, ksi Density, Ib/in. 3

Mechanical properties Tensile strength, ksi Elongation (1 in.), % Reduction of area, % Rockwell hardness Izod impact, ft-Ib

Transverse breaking strengtha

Load,lb Deflection, in.

a12·in. span, 1/2-in. square bar.

2030-2048 0.11

12 10.1 x 10-6

679 28,800

0.281

115 1 1

C30-39 1-2

5 0.070-0.080

Nickel-Base Corrosion- and Heat-Resistant Alloys-I 57

conductivity, and coefficient of thermal expansion. However, the electrical resistivity of alloy D is more than twice that of Monel alloy 400.

Mechanical Properties

The mechanical properties of Hastelloy alloy D are included also in Table 3-16. The alloy is generally furnished in the solution-annealed condition to provide optimum machinability. This treatment consists of heating at 1800-1850 F followed by furnace cooling.

The tensile strength of Hastelloy alloy D is comparable with that of Monel alloy 505 in the annealed condition and with Hastelloy alloy C "as cast" and age hardened. However, alloy D is much less ductile than the other two alloys as indicated by the low values of elongation and reduction of area.

REFERENCES

1. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards (1968).

2. Handbook of Huntington Alloys, Huntington Alloy Products Division, The International Nickel Co., Inc. (1968).

3. Engineering Properties of Monel Nickel-Copper Alloys, Tech. Bull. T5, Huntington Alloy Products Division, The International Nickel Co., Inc. (1968).

4. M. E. Langston and C. H. Lund, Physical Properties of Some Nickel-Base Alloys, OTS PB 151086, Battelle Memorial Institute (1960).

5. Engineering Properties of Monel Alloy K-500, Huntington Alloy Products Division, The International Nickel Co., Inc. (1965).

6. R. M. McClintock and H. P. Gibbons, Mechanical Properties of Structural Materials at Low Temperatures, Monograph 13, National Bureau of Standards (1960).

7. J. T. Eash and T. E. Kihlgren, "Effect of composition on the properties and structure of cast monel," Trans. Amer. Foundrymen's Soc. 57, 535 (1949).

8. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968). 9. J. S. Yanick, "Nickel-base alloy castings," Cast Metals Handbook, Amer. Foundry­

men's Soc. (1957), p. 291. 10. K. A. Warren and R. 1". Reed, Tensile and Impact Properties of Selected Materials

from 20 to 300 K, Monograph 63, National Bureau of Standards (1963). 11. R. J. Favor, D. A. Roberts, and W. P. Achbach, Design Information on Nickel-Base

Alloys for Aircraft and Missiles, OTS PB 151090, Battelle Memorial Institute (1960). 12. Corrosion Resistance of Union Carbide Alloys, Union Carbide Corp., Stellite Division

(1966). 13. Hastelloy alloy B, ibid. (1967). 14. Hastelloy alloy C, ibid. (1966). 15. Hastelloy alloy N, ibid. (1967). 16. Hastelloy alloy X, ibid. (1968). 17. F. R. Schwartzberg, S. H. Osgood, R. D. Keys, and T. F. Kiefer, Cryogenic Materials

Data Handbook, AD 609562, The Martin Co. (1964). 18. Illium Alloys, Stainless Foundry and Engineering, Inc. (1969). 19. Hastelloyalloy D, Union Carbide Corp., Stellite Division (1960).

Chapter 4

Nickel-Base Corrosion- and

H eat-Resista nt Alloys-II

Chromium is a major alloying element in many of the corrosion-resisting nickel-base alloys and in most of those developed for elevated-temperature service. Chromium increases resistance to oxidation and also assists in solid­solution strengthening. 1

Approximately 30 % chromium is soluble in nickel and the two most important binary alloys are those containing 90 % nickel-lO % chromium and 80% nickel-20% chromium. These alloys are used primarily for elec­trical resistance applications although their corrosion and heat resistance makes them suitable for use as construction materials. 2 They will be discus­sed in Chapter 8, which deals with electrical resistance and thermocouple alloys.

Modifications of these nickel-chromium alloys, together with others based on the nickel-chromium system, are produced for applications in various fields where advantage can be taken of their corrosion- and heat­resisting characteristics. Among the best known of these are the nickel­chromium, also sometimes called nickel-chromium-iron, alloys designated "Inconel" alloys and the nickel-iron-chromium alloys designated "Incoloy" alloys by their originator.

NICKEL-CHROMIUM ALLOYS

The basic member of this group of alloys is Inconel alloy 600. This alloy was developed for use in severely corrosive environments at elevated tem­peratures. It is resistant to oxidation at temperatures up to 2150 F and also

58

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 59

has excellent properties at cryogenic temperatures.3 Modifications of this base composition include alloy 601, a solid-solution alloy with excellent high-tem­perature properties and alloy 625, containing molybdenum and columbium, which has excellent strength and toughness from cryogenic temperatures to 2000 F. For improved strength at elevated temperatures, modifications which are age harden able have been developed. These include alloy 718 and alloy X-750.

Usually age hardening properties have been developed in high-nickel alloys by adding aluminum and titanium to the composition to form a nickel­aluminum-titanium intermetallic compound, generally called gamma prime. Inconel alloy X-750 is an alloy of this type.

Alloy X-750 is a modification of the original composition which can be heat treated to form the intermetallic compound Ni3(AI, Ti). It has excellent creep and stress rupture properties in addition to corrosion and heat resistance up to 1500 F. It also has good strength and ductility down to -423 F.3

Alloy 718 differs from most of the high-temperature alloys in having columbium substituted for much of the aluminum and titanium and iron substituted for the cobalt and much of the molybdenum. The effect of these changes is to reduce the high-temperature strength but, at the same time, to improve the weldability. Alloy 718 was developed for service up to 1300 F. It also has good strength and ductility down to -423 F.3

The compositions of the alloys mentioned above are given in Table 4-1.

There are a number of other modifications of Inconel alloy 600 includ­ing: alloy 604, which contains 2 % columbium to improve creep and rupture properties at intermediate temperatures; alloy 700, primarily intended for jet engine blades operating at intermediate temperatures; alloy 702, which con­tains aluminum to improve the oxidation resistance for high-temperature service; alloy 721 for use in the exhaust valves of piston-type aircraft engines;

Table 4-1. Nominal Compositions of Some Nickel-Chromium Alloys3.4

Composition, %

Designation Nia Cr Fe Al Ti Mo

Inconel alloy 600 76 15.5 8.0 Inconel alloy 601 60.5 23.0 14.1 1.15 Inconel alloy 625 61 21.5 2.5 0.2 0.2 9.0 Inconel alloy 718 52.5 19.0 18.5 0.5 0.9 3.0 Inconel alloy X-750 73 15.5 7.0 0.7 2.5

aplus cobalt.

Cb +Ta

3.65 5.1 0.95

Tab

le 4

-2.

Ph

ysic

al P

rop

erti

es o

f S

om

e N

ick

el-

Ch

rom

ium

All

oys

4,s

,6,7

,8

All

oy 6

00

All

oy 6

01

All

oy 6

25

All

oy 7

18

Mel

ting

ran

ge,

F 25

00-2

600

2375

-249

5 23

50-2

460

2300

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5 S

peci

fic

hea

t (7

0 F

), B

tu/l

btF

0.

106

0.10

7 0.

098

0.10

4 T

herm

al c

ondu

ctiv

ity

(70

F),

Btu

/hr/

ft2

tF/f

t 8.

6 6.

5 5.

7 6.

4c

Coe

ffic

ient

of

ther

mal

exp

ansi

on (

70-1

600

F),

per

of

9.1

x 10

-6

9.5

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10-6

9.

4 X

10

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ctri

cal

resi

stiv

ity

(70

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r m

il f

t 62

0 71

7 77

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ie t

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re,

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92

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d P

erm

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lity

(70

F,

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0 O

e)

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0 1.

003

1.00

6 l.o

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c l.o

o11

d

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ulus

of

elas

tici

ty,

ksi

31,0

00

29,9

00

29,8

()()

a 29

,800

M

odul

us o

f ri

gidi

ty,

ksi

11,0

00

11,8

00

11,4

()()

a 11

,600

P

oiss

on's

rat

io

0.29

0.

267

0.30

8"

0.28

4 D

ensi

ty,

Ib/i

n.3

0.30

4 0.

291

0.30

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.296

aDyn

amic

. "C

ompu

ted.

cA

nnea

led.

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ged.

'A

s h

ot

roll

ed.

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utio

n tr

eate

d an

d do

uble

age

d.

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oy X

-750

2540

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0 0.

1031

7.

01

9.3

X

10-6

759,

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1 -2

25

,' -

19

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0035

1 31

,000

11

,000

0.

29

0.29

8

g o ::r

III

'tI ;- .. ..,.

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 61

alloy 722 for special applications in jet engines; and alloy 751, a modification of alloy X-750. 3 These alloys will not be discussed.

Physical Properties

The physical properties of the nickel-chromium alloys included in Table 4-1 are given in Table 4_2. 4 ,5,6,7,8 In the 600 series, the total alloy content increases from alloy 600 to alloy 625 and this progression is reflected in some of the physical properties.

Thus the thermal conductivity decreases and the electrical resistivity increases markedly from alloy 600 to alloy 625. There is also a moderate decrease in the elastic constants. However, the Curie temperatures of alloy 601 and alloy 625 are much lower than that of alloy 600. All three materials are essentially nonmagnetic to quite low temperatures.

Both alloy 718 and alloy X-750 are age harden able and this property influences some of the physical properties, as can be noted from the table. Age hardening influences the electrical resistivity moderately but has con­siderable effect on the magnetic properties. Thus, the Curie temperatures of the alloys in the solution-annealed condition are considerably lower than those in the aged condition. Essentially, the properties of these two age hardenable alloys fall within the range of those of the 600 series, however.

Mechanical Properties

Room- Temperature Properties

Inconel alloy 600, alloy 601, and alloy 625 are not harden able by heat treatment. Strengthening can be achieved only by cold work. On the other hand, both alloy 718 and alloy X-750 can be strengthened by heat treatments which result in age hardening.

Tensile Properties. Nominal tensile properties of these alloys in various forms and conditions are given in Table 4_3. 4 ,5,6,7,8

The tensile strength of alloy 600 ranges from 80 ksi for annealed material to 150 ksi for cold drawn material and the ductility ranges from an elonga­tion of 55 % for annealed material to 10 % for cold worked. Limited data on alloy 601 indicate that this alloy has tensile properties similar to those of alloy 600. Alloy 625 is somewhat stronger than alloy 600, but the ductilities of the two alloys are comparable.

The effect of age hardening on the tensile properties of alloy 718 is clearly indicated by the property improvement achieved. The tensile strength ranges from 55 ksi for solution-annealed material, which is comparable with

62 Chapter 4

Table 4-3. Nominal Tensile Properties and Hardness Values of Some Nickel-Chromium Alloys4.s.6.7.8

Yield Elon-strength Tensile gation

(0.2 % offset). strength, (2 in.), Rockwell Form and condition ksi ksi % hardness

Inconel alloy 600 Rod and bar

Annealed 25-50 80-100 55-35 B65-85 Hot finished 35-90 85-120 50-30 B75-95 Cold drawn 80-125 105-150 30-10 B90-C30

Plate Annealed 30-50 80-105 55-35 B65-85 Hot rolled 35-65 85-110 50-30 B80-95

Sheet and Strip Annealed 30-45 80-100 55-35 B88 max Cold rolled, hard 90-125 120-150 15-2 C24min Cold rolled, spring temper 120-160 145-170 10-2 C30 min

Inconel alloy 601 Rod

Hot rolled, solution treated 28.5 86.5 58 Flats

Hot finished, annealed 49 107 45 Inconel alloy 625

Rod, bar. plate As rolled 60-110 120-160 60-30 Solution-annealed 42-60 105-130 65-40

Sheet and strip Annealed 60-75 120-140 55-30

Inconel alloy 718 Rod and bar

Annealed 55-80 110-135 62-45 B83-96 Hot rolled 65-105 140-150 45-55 C20-30 Solution-annealed, aged" 165-180 190-210 20-17 C45

Sheet Cold rolled, 18-27 % 115-130 140-155 26-10 Cold rolled, agedb 185-210 205-225 10-8

Inconel alloy X-750 Bar

Hot rolled, heat treatedc 128-146 180-200 26-23 C34-40 Hot rolled, heat treatedd 130-150 185-195 26-21 C38-42

Sheet Cold rolled, aged- 115-130 175-185 28-26 C35-39 Cold rolled, aged! 130-140 180-190 26-23 C35-41

-Solution annealed at 1750 F. aged at 1325 F. 8 hr. furnace cool to 1150 F. held for total aging time of 18 hr. bAged at 1325 F. 8 hr. furnace cool to 1150 F, held for total aging time of 18 hr. cAnnealed 1750 F, 1 hr, air cool; J400 F, 1 hr, furnace cool at 50 F/hr to 1150 F, air cool (total aging time 6hr).

"Annealed 1750 F. 1 hr. air cool; 1350 F. 8 hr. furnace cool at 25 F/hr to 1150 F. air cool (total aging time 16hr).

'Age 1300 F. 20 hr. air cool. fAge 1350 F. 8 hr. furnace cool at 25 Flhr to 1150 F .air cool.

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 63

that of alloy 600, to 225 ksi for sheet which had been aged after cold rolling. The corresponding elongations were 62 % and 8 %.

Inconel alloy X-750 is also age hardenable with tensile strengths ranging up to 200 ksi in the aged condition. Even as aged, however, the ductility of alloy X-750, as measured by the elongation, is considerably higher than that of alloy 718.

The relationship between the tensile properties and hardness of alloy 600 is indicated in Fig. 4-1 for hot rolled and cold drawn rods. s The yield strength rises rapidly, the tensile strength more gradually as the hardness resulting from cold work increases from Rockwell B70 to BI05. The ductility is reduced during cold work but the reduction of area is less affected than the elongation.

The effect of cold reduction on the tensile properties of alloy 625 is shown in Fig. 4-2.6 Although the strength levels achieved are considerably

160

140

120

100 'Vi .::r:.

ul 80 (/)

Q) "-

en 60

40

20

60 70 80 90 100 Rockwell 8 Hardness

~ 80 ~

Q) "-

<{

60 '0 -0 Q)

n:: 40.-.:­

.S C\J

20 g' o W

110

Fig. 4-1. Relationship between the tensile properties and hard­ness of hot rolled and cold drawn alloy 600 rods. 5

64

'Vi -'<::

c.n-c.n (l) .... (jj

220 r---~----r-----r-----.

200

180

160

140

120

100

80

60

o 20 40 60 Cold Reduction, %

80

60 0 ~

<! '+-

40 0

"0 (l)

0:::

20 CJl

80

c o

W

Fig. 4-2. Effect of cold work on the tensile properties of alloy 625 strip.6

Chapter 4

higher than those of alloy 600, a similar relationship exists between cold work and the properties developed.

Hardness. Rockwell hardness values for some of the alloys are included also in Table 4-3. The hardness of alloy 600 ranges from B65 in the annealed condition to C30 for strip cold rolled to spring temper. The hardness of alloy 718 ranges from B83 in the annealed condition to C45 in the aged condition and that of alloy X-750 ranges up to C41 in the age hardened condition.

Fatigue Properties. The effects of working and annealing on the fatigue properties of alloy 600, alloy 601, and alloy 625 are given in Table 4_4. 4 • 5•6 • 9

Nickel-Base Corrision- and Heat-Resistant Alloys-II 65

Table 4-4. Fatigue Properties of Some Nickel-Chromium Alloys

Tensile strength, Fatigue strength (ksi) at

Form and condition ksi 106 cycles 107 cycles 108 cycles Ref.

Inconel alloy 600 Bar

Annealed 67 54 52 50 9 Cold drawn 178 76 73 71

Bar Annealed 85-114 39 5 Hot rolled 87-130 40.5 Cold drawn 112-202 45 Cold drawn, stress-equalized

525 F, 3 hr 122-173 52.5

Inconel alloy 601 Bar

Hot .olled, solution treated 40 4

Inconel alloy 625 Bar

Hot rolled, annealed 1800 F, 1 hr 104 100 100 6

Sheet Cold rolled, mill anneal 96 92 90

Inconel alloy 718 Forgings

Annealed 1750 F 143 74 67.5 66.5 7 Annealed and aged· 191 77.5 71 69.5

Plate Hot rolled 132 73 70 70 Annealed and aged 196 91 82 77

Inconel alloy X-750 Bar

Annealed and agedh 90 81 80 8

aSee footnote a, Table 4-3. ·See footnote d, Table 4-3.

The limited data indicate that the endurance ratio of alloy 600 is reduced moderately by cold work.

The effects of aging treatments on the fatigue properties of alloy 718 are also included in Table 4-4. 7 Aging this alloy reduces the endurance ratio. The fatigue strength of alloy X-750 in the aged condition approximates that of alloy 718.

Impact Properties. As indicated in Table 4-5, Inconel alloy 600 is a very tough material. 5 The limited data on the other alloys indicate that they

66 Chapter 4

Table 4-5. Impact Properties of Some Nickel-Chromium Alloys

Form and condition

Inconel alloy 600 Rod and bar

Annealed Cold drawn

Inconel alloy 625 Plate

As rolled

Inconel alloy 718 Plate

Hot rolled, heat treated· Hot rolled, heat treatedb

Inconel alloy X-750 Bar

Hot rolled, heat treatedc

Hot rolled, heat treatedd

Impact resistance, ft-lb

Izod Charpy

V-notch Keyhole

120 70-100

11-18 26-33

37 38

230 151

49

Ref.

5

6

7

8

"1750 F, I hr, air cooled; 1325 F, 8 hr, furnace cooled to 1150 F and held for total aging time of 18 hr. "1950 F, I hr, air cooled; 1400 F, 10 hr, furnace cooled to 1200 F and held for total aging time of 20 hr. '2100 F, 2 hr, 1550 F, 24 hr, 1300 F, 20 hr. '1300 F, 20 hr.

are quite tough, although the treatment given the age hardenable alloys influences the impact resistance. Thus, changing the aging conditions for alloy 718 more than doubles the toughness as measured by the impact test. Additional data on toughness are included in the section on low-temperature properties.

Elevated-Temperature Properties

The short-time elevated-temperature tensile strengths of several of the Inconel alloys are given in Fig. 4-3. S,6, 7,8 The alloys fall into three distinct groups. Alloy 600 has the lowest strength, next is alloy 625, and highest are alloy 718 and alloy X-750. All of the alloys retain much of their strength up to temperatures of 1000-1200 F but above that range strength falls off rapidly.

Typical creep and stress-rupture properties are given in Table 4-6. The creep strength and the 100-hour rupture strength of alloy 600 are consider­ably below those of the other materials. The rupture and creep properties of

Tab

le 4

-6.

Cre

ep a

nd

Ru

ptu

re P

rop

erti

es o

f S

om

e N

ick

el-

Ch

rom

ium

All

oys

z o· ~

Tes

t S

tres

s (k

si)

for

cree

p ra

te o

f S

tres

s (k

si)

~

for

rupt

ure

1:11

tem

pera

ture

, at

Con

diti

on

F 0.

0000

1 %

/hr

0.00

01 %

/hr

0.00

1 %

/hr

0.01

%/h

r in

100

hr

Ref

. II

I CD

0 In

cone

l al

loy

600

0 .. .. A

nnea

led

1750

F,

3 h

r 80

0 30

.0

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5

0 III

1000

6.

1 12

.5

50

o· :::I

1200

2.

2 23

, at

1400

0.

97

8.4

:::I

Q,

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t ro

lled

80

0 47

54

::

t 10

00

13

25

CD

at

1200

8

9.5

't

:II

1400

0.

77

3.6

CD

III

Inco

nel

allo

y 62

5 iii

' .. at

Sol

utio

n-an

neal

ed

1200

37

42

57

66

68

6

:::I ..

1400

9

12

18

24

30

~

1600

2.

6 3.

5 5

7 12

0'

-<

II

I'

Inco

nel

allo

y 71

8 ~

Bar

H

eat

trea

teda

12

00

104

7 13

00

80

Inco

nel

allo

y X

-750

B

ar

Hea

t tr

eate

db

1200

53

64

73

81

80

8

1500

14

18

21

25

28

16

00

8 9

11

14

1800

3.

2

"Ann

eale

d 17

00-1

850

F;

aged

132

5 F

, 8

hr,

fur

nace

coo

led

to 1

150

F an

d h

eld

for

tota

l agi

ng ti

me

of

18 h

r.

GI

.Ann

eale

d 21

00 F

, 2-

4 hr

, ai

r co

oled

; 15

50 F

, 24

hr,

air

coo

led;

130

0 F

, 20

hr.

....

68

(f) ..0.:::

-L

"& c ~

(f)

~ -Vi c Q)

I-

Temperature, K

300 500 700 900 1100 1300 200 r-r----r-----.-----..----.----,--r

180

160

140

120

100

80

60

40

400 800 1200 1600 2000 Temperature, F

Fig. 4-3. Short-time elevated-temperature tensile strengths of several nickel--chromium alIoys.s, 6, 7, 8 AlIoy 718, solution annealed and aged; alIoy X-750, solution annealed and aged, alIoy 625, mill annealed; alIoy 600, hot rolIed.

Chapter 4

alloy 625 are given in the solution-annealed condition. Material in this condition has higher long-time strength properties than that in the mill­annealed condition, although the latter has properties adequate for many applications. 6

For optimum creep and rupture properties, alloy 718 is annealed at 1700 to 1850 F and aged at 1350 F for 8 hours, furnace cooled to 1150 F, and held at that temperature for a total aging time of 18 hours.7 The 100-hour rupture strengths of alloy 718, heat treated by this procedure, are given in Table 4-6.

For maximum creep and rupture properties at temperatures above 1100 F,

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 69

bar stock of alloy X-750 is given a three-step heat treatment. It is solution­annealed at 2100 F for 2 to 4 hours, air cooled, aged at 1550 F for 24 hours, air cooled, aged at 1300 F for 20 hours, and air cooled. It is usually not practical to apply this treatment to sheet because the 2100 F solution anneal could cause distortion of the material. However, the stress rupture strength of sheet hardened by a furnace aging treatment beginning at 1350 F is about the same as that achieved by the three-step treatment. The sheet is held at 1350 F for 8 hours, furnace cooled at 25 F per hour to 1150 F, and air cooled. 8

Creep and rupture properties of bar heat treated by the three-step process are included in Table 4-6.

Temperature, K 50 100 150 200 250 300

240 r-~.---.---~--~--~--~

220

200

"(j)

.:.: 180

..r:::. 0> c ~ 160 (f)

-'!! "(j)

a3 140 f-

120

100

80 ~~--~----~--~--~--~ -400 -300 -200 -100

Temperature, F o 100

Fig. 4-4. Subzero-temperature tensile strengths of some nickel-chromium alloys. 7, 10 (1) Alloy X-750, solution an­nealed and aged; (2) alloy 718, solution annealed and aged; (3) alloy 600, cold reduced 50%; (4) alloy 600, cold reduced 20%; (5) alloy 600, as rolled.

70 Chapter 4

Low-Temperature Properties

Inconel alloy 600 has excellent mechanical properties at subzero tem­peratures. Strength increases substantially without appreciable loss in ductility, according to the producer. United States Navy tear tests on alloy 600 plate showed a considerable increase in maximum load with excellent ductility and fracture characteristics as the temperature was reduced from ambient to -320 F.S

The effect of low temperatures on the tensile strengths of alloy 600, alloy 718, and alloy X-750 is shown in Fig. 4_4. 7,10 Regardless of the condi­tion of these alloys, the strengths increase markedly as the temperature is reduced.

The effect of low temperatures on the impact resistance of several of the alloys is given in Table 4_7. 2,7,8 Alloy 600 is considerably tougher in the annealed condition than after hot rolling. Cold drawing reduces the tough­ness markedly.

Table 4-7. Impact Properties at Low Temperatures of Some Nickel-Chromium Alloys

Test Charpy impact temperature, (V-notch),

Form and condition F ft-lb Ref.

Inconel alloy 600 Annealed Room 236 2

-110 206 -310 187

Hot rolled Room 213 -315 169

Cold drawn, 50 % Room 69 -315 64

Inconel alloy 718 Plate

Annealed and ageda Room 21 7 -320 19

Inconel alloy X-750 Bar

Hot rolled, annealed and agedb Room 37 8 -109 36 -320 33

Hot rolled, agedc Room 38 -109 37 -320 34

"Annealed 1750 F; aged 1350 F, 8 hr, furnace cooled to 1150 F and held for total aging time of 18 hr. "Annealed 2100 F, 2 hr; aged 1500 F, 24 hr; aged 1300 F, 20 hr. CAged 1300 F, 20 hr.

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 71

In the age hardened condition, alloy X-750 is considerably tougher than alloy 718, but both of these alloys are much lower in impact resistance than alloy 600. There is no indication of a transition from ductile to brittle behav­ior in these alloys.

CAST NICKEL-CHROMIUM ALLOYS

Modifications of the basic Inconel alloy 600 composition are used as casting alloys. The major change in composition lies in increasing the silicon content to increase the fluidity of the alloys and improve the filling of the molds. Two commercial materials are alloy 610, having a nominal silicon content of 1.6 %, and alloy 705, with a nominal silicon content of 5.5 %.11 The high silicon content of alloy 705 makes the alloy age hardenable to some degree. By contrast, the basic wrought material, Inconel alloy 600, has a nominal silicon content of 0.25 %.

Two nickel-chromium alloys are included in the Alloy Casting Institute heat-resisting alloy category. They are designated HW and HX.

Nominal compositions of all four of these materials, given in Table 4-8, indicate that they range from 60 to 68 % nickel and 12 to 17 % chromium.

Table 4-8. Nominal Compositions of Some Cast Nickel-Chromium Alloys 1 1, 12

Composition, %

Designation Ni Cr Fe Si Cu C

Inconel alloy 610 68.5 15.5 Bal. 1.5 0.5 0.2 Inconel alloy 705 68 15.5 Bal. 5.5 0.5 0.2 HW 60 12 Bal. 2.5a 0.55 HX 66 17 Bal. 2.5a 0.55

aMaximum.

Physical Properties

Cb +Ti

2.0

Limited physical property data on the four alloys are given in Table 4_9. 11 ,13 Alloy 705, reflecting the higher silicon content, has a higher electrical resistivity than alloy 610, which in turn has a much higher resistivity than that of wrought alloy 600. However, the thermal conductivities of alloy 600 and 610 are comparable.

The coefficients of thermal expansion of these cast materials lie in the same range as those of the wrought nickel-chromium alloys.

The modulus of elasticity of alloy 610 is comparable with that of alloy

Tab

le 4

-9.

Ph

ysic

al a

nd

Me

ch

an

ica

l P

rop

erti

es o

f S

om

e C

ast

Nic

ke

l-C

hro

miu

m A

llo

ys

ll.1

3

Phy

sica

l pr

oper

ties

M

elti

ng p

oint

, F

Spec

ific

hea

t (7

0 F

), B

tujl

brF

T

herm

al c

ondu

ctiv

ity

(212

F),

Btu

jhrj

ft2rF

jft

Coe

ffic

ient

of

ther

mal

exp

ansi

on (

70-1

400

F),

per

of

Ele

ctri

cal

resi

stiv

ity

(32

F),

ohm

s/ci

r m

il f

t M

odul

us o

f el

asti

city

, ks

i D

ensi

ty,l

bjin

.3

Mec

hani

cal

prop

erti

es (

as c

ast)

Y

ield

str

engt

h (0

.5 %

exte

nsio

n),

ksi

Ten

sile

str

engt

h, k

si

Elo

ngat

ion

(2 in

.),

%

Bri

nell

har

dnes

s C

harp

y im

pact

(V

-not

ch),

ft-

lb

"70-

1800

F.

.0.2

% o

ffse

t.

All

oy 6

10

2500

-255

0 0.

11

8.7

8.9

x 10

-6

709

31,0

00 0.30

0

30-4

5 70

-95

30-1

0 19

0 60

All

oy 7

05

9.2

X

10-6

757

25,0

00

0.29

2

80-1

00

90-1

20

3-1

300-

380

HW

H

X

2350

23

50

0.11

0.

11

7.7

8.8

x 10

-6 a

9.

2 X

10

-6 a

25,0

00

25,0

00

0.29

4 0.

294

36b

36b

68

65

4 9

185

176

.....

N o :::r

til ~ ... ...

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 73

600. However, the three other cast alloys have moduli considerably lower than those of the wrought nickel-chromium alloys.

Mechanical Properties

Typical mechanical properties of the four casting grades of nickel­chromium alloys are included also in Table 4-9.

Reflecting the higher silicon content, alloy 705 is somewhat stronger and, in particular, has a much higher yield strength than alloy 610. This improvement in strength, however, is accompanied by a drastic reduction in ductility as measured by the elongation. Alloy 705 can be age hardened after annealing to achieve properties which are practically the same as those given in the table for the "as cast" condition.

Alloys HW and HX are not as strong as the other two alloys but they are somewhat more ductile than alloy 705. Alloys 610, HW, and HX have comparable hardness values as cast but all are much softer than alloy 705.

NICKEL-IRON-CHROMIUM ALLOYS

Most widely know members of the nickel-iron-chromium family of alloys are those known as the Incoloy alloys. These materials are charac­terized by much lower nickel content and higher chromium content than the Inconel alloys. 2

Incoloy alloy 800, prototype alloy of the group, was developed to provide a material having good strength combined with resistance to oxidation and carburization at elevated temperatures. The alloy has a stable austenitic structure and does not form the brittle sigma phase even after long periods of exposure in the temperature range 1200 to 1600 F. 14

Other members of this group are alloy 804, formulated to produce high strength at elevated temperatures combined with resistance to oxidizing and sulfidizing atmospheres,1 S and alloy 825, which was developed for use in corrosive environments such as sea water, sulfuric and phosphoric acids, and reducing solutions. 1 6 Nominal compositions of these materials are given in Table 4-10.

Among other modifications of the base composition are a number devel­oped for special purposes. These include alloy 801, which contains 1% titanium to increase the strength at intermediate temperatures; alloy 805, developed to provide a low-temperature coefficient of the modulus of elastic­ity; and alloy 901, an age harden able alloy for use at temperatures near 1200 F. These alloys will not be discussed. Another nickel-iron-chromium alloy, Ni-Span-C, is an alloy having a controllable rate of change of the

74

Table 4-10. Nominal Compositions of Some Nickel-Iron-Chromium Alloys 3

Composition, %

Chapter 4

Designation Nia Fe Cr Al Ti Mo Cu

Incoloy alloy 800 32.5 46.0 21.0 0.38 0.38 Incoloy alloy 804 41.0 25.4 29.5 0.30 0.60 Incoloy alloy 825 42.0 30.0 30.0 0.10 0.90 3.0 2.25

"Plus cobalt.

modulus of elasticity with temperature. This alloy will be discussed in Chapter 9.

Physical Properties

Typical physical properties of the three alloys mentioned above are given in Table 4_11.14,1 S, 16 The thermal conductivities of the materials do not differ significantly but their electrical resistivities increase markedly from alloy 800 to alloy 825. As a basis of comparison, the electrical resistivity of alloy 800 is relatively close to that of Inconel alloy 600.

There is a progressive decrease in the coefficient of thermal expansion from alloy 800 to alloy 825.

The Curie temperatures of alloy 804 and alloy 825 are much lower than that of alloy 800. All three alloys, however, are virtually nonmagnetic to very low temperatures.

Table 4-11. Physical Properties of Some Nickel-Iron-Chromium Ailoys I4,ls,16

Alloy 800 Alloy 804

Melting range, F 2475-2525 Specific heat (32-212 F), Btu/lbrF 0.12 Thermal conductivity (70 F), Btu/hr/ft2rF/ft 6.6 Coefficient of expansion (70-1600 F), per OF 10.2 x 10-6 9.8 X 10-6 a

Electrical resistivity, ohms/cir mil ft 595 652 Curie temperature, F -175 -321 Permeability (70 F, H = 2000e) 1.0092 1.0032 Modulus of elasticity, ksi 28,500 27,800 Modulus of rigidity, ksi 10,600 Poisson's ratio 0.339 Density, Ib/in. 3 0.290 0.286

"70-1750 F.

Alloy 825

2500-2550

6.4 9.7 X 10-6

678 -320

1.005 28,300

0.294

Nickel-Base Corrosion- and Heat-Resistant Alloys-II

Mechanical Properties

Room-Temperature Properties

75

None of these alloys can be hardened by heat treatment. Strength and hardness can be increased only by cold work. As will be mentioned later, special annealing is used to enhance certain properties.

Tensile Properties. Nominal tensile properties of the three Incoloy alloys in various forms and conditions are given in Table4-12.14,ls.16 The

Table 4-12. Nominal Tensile Properties and Hardness Values of Some Nickel-Iron-Chromium Alloys I4,IS.16

Yield strength Tensile Elongation

(0.2 % offset), strength, (2 in.), Rockwell Form and condition ksi ksi % hardness

Incoloy alloy 800 Rod and bar

Annealed 30-60 75-100 60-30 B65-90 Hot finished 35-90 80-120 50-25 B75-95 Cold drawn 75-125 100-150 30-10 B85-C35

Plate Annealed 30-60 75-105 50-30 Hot rolled 30-65 80-110 50-25

Sheet and strip Annealed 30-55 75-105 50-30 B88 max

All forms and sizes Solution-annealed 20-50 70-95 50-30 B55-90

Incoloy alloy 804 Mill-annealed (1900 F, 1/2 hr) 45 95 40 B85

Solution-annealed (2000 F, 2 hr) 34 89 53 B69

Incoloy alloy 825 Rod and bar

Annealed (1725 F, 1 hr) 44 100 43

tensile strength of alloy 800 ranges from about 75 ksi for annealed material to about 150 ksi for material that has been cold worked and the elongation ranges from 60 % for annealed to 10 % for cold worked material. Solution annealing results in somewhat lower strength. The purpose of this treatment will be discussed under elevated-temperature properties.

Only limited data are available for alloy 804 and alloy 825. Both have tensile properties in the annealed condition which are comparable with those of alloy 800. The solution annealing of alloy 804 yields a product that is

76 Chapter 4

somewhat lower in strength than that achieved by normal annealing practice, an affect similar that obtained with alloy 800.

Hardness. Rockwell hardness values for the Incoloy alloys are included also in Table 4-12. The hardness of alloy 800 ranges from about B95 for material which has been given a conventional anneal to C35 after cold work­ing. Solution annealing yields the lowest hardness obtainable in this alloy, a minimum of about B55.

The hardness of alloy 804 lies in the same range as that of alloy 800 and solution annealing again reduces the hardness.

Fatigue Properties. The effects of working and annealing on the fatigue properties of alloy 800 are given in Fig. 4_5. 14 The fatigue properties are influenced markedly by the condition of the material. Hot rolled material appears to be most resistant to fatigue and cold drawn material the least. As the following data show, the endurance ratio ranges from 0.51 for hot rolled to 0.29 for cold drawn material.

Condition Annealed Hot rolled Cold drawn

70

60

~ 50 vi If) Q) "-

(j) 40

30

20

104

Tensile Fatigue strength strength, ksi at 108 cycles, ksi

82 31 92 51

114 33

106

Cycles

7 10

Endurance ratio 0.38 0.51 0.29

Fig. 4-5. S-N curves for alloy 800 in several conditions. 1 0

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 77

Impact Properties. Limited data on the impact properties of these Incoloy alloys are given in Table 4-13. All three alloys are quite tough in the annealed condition with alloy 800 having the greatest resistance to impact followed by alloy 825.

Table 4-13. Impact Properties of Some Nickel-Iron-Chromium Alloys

Form and condition

Incoloy alloy 800 Annealed at 2050 F Plate, annealed at 1800 F, 1 hr

Incoloy alloy 804 Annealed Cold worked

Incoloy alloy 825 Plate

"Keyhole notch. ·Notch not specified.

Charpy impact (V-notch),

ft-lb

207 90a

56b

28b

79-

Ref.

14

15

16

A comparison of the impact resistance of alloy 804 in the annealed and cold drawn conditions indicates that the shock resistance of this alloy is reduced significantly by cold working.

Additional data on impact properties are included in the discussion of the low-temperature properties of these alloys.

Elevated- Temperature Properties

The short-time elevated-temperature tensile strengths of alloy 800 and alloy 825 are shown in Fig. 4_6. 14.16 Alloy 800 retains more than 80 % of its room-temperature strength, in both the annealed and cold rolled conditions, up to temperatures of about 1000 F, above which temperature strength falls rapidly. At 1250 F, for example, the strength has been reduced by 50%. These properties are similar to those of the Inconel alloys.

Alloy 825 in the annealed condition shows a more gradual reduction in strength with rising temperatures and this alloy also retains more than 80 % of its strength at 1000 F. Like alloy 800, strength is reduced by 50% as the temperature rises to 1250 F.

Typical creep and rupture properties of alloy 800 and alloy 804 are given in Table 4_14.14,15 The properties of alloy 800 indicate the advantage of solu­tion annealing over conventional annealing. The coarse grain structure, resulting from solution annealing, markedly improves the creep and rupture properties of this material. At 1600 F, for example, the stress for a creep rate

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8 18

00

2.9

Ref

.

14

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.....

co o ::T

DI

"C :: .. .po.

Nickel-Base Corrosion- and Heat-Resistant Alloys-II

Temperature, K

300 500 700 900 1100 120 r-r---r---r----r---,.----,,...:..,

100

-Vi

.0<:,80

..c Q, 3 c

~ 60 (f)

~ Vi c 40 ~

20

o 400 800 1200 1600 2000 Temperature, F

Fig. 4-6. Short-time elevated-temperature tensile strengths of two nickel-iron-chromium alloys. 1 4. 16 (1) Alloy 800, cold rolled; (2) alloy 825, annealed 1725 F, 1 hr; (3) alloy 800, annealed 2100 F, 1 hr.

79

of 0.0001 % per hour of solution-annealed material is more than twice that for mill-annealed stock. The stress for rupture in 100 hours at the same temperature follows a similar pattern.

A similar effect is achieved with alloy 804. According to the producer, 1 6

solution annealing to produce grain coarsening in alloy 804 results in the best properties for long-time service in the range 1400 to 1600 F. Thus the stress for rupture in 100 hours at 1600 F, for example, of solution-annealed material is more than twice that for mill-annealed material.

Although material in the solution-annealed condition is generally super­ior at 1800 F, as shown in the table, the advantage of large grain size becomes negligible in long-time exposure under equivalent stress. For example, under a stress of 1 ksi at 1800 F, mill-annealed material had a life of 29,026 hours, solution annealed material one of 29,460 hours. 1 6

Low-Temperature Properties

The impact resistance of alloy 800 and alloy 825 plate at subzero tem­peratures is indicated in Fig. 4_7. 14• 16 Both of these materials exhibit excel-

80

Temperature, K

.g ~IOO~~--~--~---.---.---n

50 100 150 200 250 300

--L U

-0 80 c Q) (5 L

ii)' 60 ~

u o Cl. 40 .£ >-Cl.

~ Alloy 800

~ ~AlIoy825 ----

2 20~~----~----~--~~--~----~ <.) -400 -300 -200 -100 0 100

Temperature, F

Fig. 4-7. Subzero-temperature impact properties of two nickel­iron---<:hromium alloys in the annealed condition. 14• 16

Chapter 4

lent toughness at low temperatures although there is some reduction in impact resistance as the temperature is reduced. There is no indication of a transition from ductile to brittle behavior down to at least -400 F.

REFERENCES

1. R. J. Favor, D. A. Roberts, and W. F. Ashbach, Design Information on Nickel-Base Alloys for Aircraft and Missiles, OTS PB 151090, Battelle Memorial Institute (1960).

2. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards (1968).

3. Handbook of Huntington Alloys, Huntington Alloy Products Division, The Interna-tional Nickel Co., Inc. (1969).

4. Inconel alloy 601, ibid. (1969). 5. Engineering Properties of Inconel Alloy 600, Bull. T-7, ibid. (1968). 6. Engineering Properties of Inconel Alloy 625, Bull. T-42, ibid. (1968). 7. Inconel Alloy 718, ibid. (1968). 8. Engineering Properties of Inconel Alloy X-750, Bull. T-38, ibid. (1967). 9. H. J. Grover, S. A. Gordon, and L. R. Jackson, Fatigue of Metals and Structures,

NAVWEPS 00-25-534, Department of the Navy (1960). 10. F. R. Schwartzberg, S. H. Osgood, and T. F. Kiefer, Cryogenic Materials Data Hand­

book, AD 609562, The Martin Co. (1964). 11. "Nickel and its alloys-cast," Materials in Design Engineering, Mid-October 1966,

p.175. 12. "Heat resistant iron-chromium and iron-chromium-nickel castings for general appli­

cations," Designation A 297, ASTM Standards, Part 2,1969.

Nickel-Base Corrosion- and Heat-Resistant Alloys-II 81

13. "Heat resisting alloys-cast," Materials in Design Engineering, Mid-October, 1966, p.93.

14. Engineering Properties of Incoloy Alloy 800, Bull. T-40, Huntington Alloy Products Division, The International Nickel Co., Inc. (1968).

15. Basic Data-Incoloy Alloy 804, ibid. (1964). 16. Incoloy Alloy 825, ibid. (1968).

Chapter 5

Nickel-Base Superalloys

The so-called nickel-base superalloys or high-strength high-temperature alloys are, in general, modifications of the corrosion- and heat-resisting alloys of the types discussed in Chapters 3 and 4. Their improved strength and creep resistance at elevated temperatures have been developed by including ele­ments which will produce a stable hard phase or phases, such as precipitated carbides or intermetallic compounds. As Rosenberg! points out, most of the commercial nickel-base superalloys are made age hardenable by the intro­duction of aluminum and titanium into their alloy compositions.

In the nickel-base superalloys, chromium is present to provide resistance to oxidation and to contribute some strengthening. Columbium, molyb­denum, tungsten, and tantalum are often present in various combinations to assist in the solid-solution strengthening of the matrix. The major improve­ment in high-temperature strength, however, is the result of the precipitation of the intermetallic compound, Ni 3(AI, Ti), usually called gamma prime. In some of the alloys, cobalt is used as a replacement for part of the nickel. Boron and zirconium are also added to some alloys to improve the high­temperature creep properties and increase the hot workability of the materi­als.

The strengths of the superalloys at high temperatures make hot working difficult and introduce forming problems. Therefore, some of the more highly alloyed materials are used in cast form, particularly as investment castings.!

According to Sims,2 the phases usually present in wrought nickel-base superalloys are gamma (the matrix, which has a face-centered cubic structure), gamma prime, and a series of carbides. In the solution-treated condition, the alloy consists essentially of the gamma matrix with some high-temperature carbides. After a solution anneal, usually at 1900 to 2150 F, a series of aging

82

Nickel-Base Superalloys 83

treatments is used to develop the strengthening phases which consist of gam­ma prime and complex carbides. The mechanism is discussed in some detail by Sims.

In general, cast nickel-base superalloys have compositions similar to those of the wrought materials but, according to Sims, there is a tendency for them to contain less chromium and more aluminum than the wrought types. As in the wrought materials, the major phases are the alloy matrix, gamma, the intermetallic compound, gamma prime, and various carbides.

Generally, the cast alloys can be heat treated by procedures that are less complicated than those used for the wrought materials. For example, the investment cast part is usually cooled and then aged at a temperature such as 1400 F for a sufficient time to insure the full development of gamma prime. For greater stability, however, the cast alloys can be given heat treatments similar to those used for the wrought alloys.

Some indication of the range of stress-rupture properties which can be developed in the nickel-base superalloys is given in Fig. 5-1. 3 The cast alloys tend to have higher rupture strengths than the wrought alloys, but there is some overlapping, as is apparent from this graph.

The line of demarcation between heat resisting alloys and superalloys is very poorly defined and no systematic classification of these materials has

"in ~

~ .r::. 0 Q

.r::. "& c ~ i/)

~ ~ Q. :::J

a:::

Temperature, K 1000 1100 1200 1300

100 r--....--.,.----~----..-------,I'"t

80

60

40

20

1300 1400 1500 1600 1700 1800 1900 Temperature, F

Fig. 5-1. Range of loo-hour rupture strengths for nickel-base super­alloys. 3

84 Chapter 5

been developed. Thus a number of the alloys discussed previously in Chapters 3 and 4 are usually included among the superalloys, particularly Hastelloy alloy X and Inconel alloy X-750 and Inconel alloy 718.

Although the Western world has based most nickel-base superalloy development on nickel--chromium-aluminum-titanium combinations, Prock and Wagner4 report that the Soviet Union has used a different approach. In their alloy development, molybdenum, which is in short supply, has been replaced by tungsten wherever possible and the use of cobalt has been re­stricted for the same reason. In addition, the aluminum and titanium addi­tions have been reduced and vanadium has been added. Prock and Wagner note that they appear to have been successful in devising means of coping with limited supplies of cobalt and molybdenum and apparently have devel­oped cast and wrought alloys which compare favorably with those produced in the United States and Great Britain. These Soviet alloys will not be dis­cussed. Information on them can be found in the publication cited.

In the Western world there are more than fifty commercial superalloys and many others are in various stages of development. Space is not available to discuss all of these materials and therefore a limited number of wrought and cast alloys have been selected to indicate the properties that can be expected.

WROUGHT ALLOYS

The compositions of five representative nickel-base superalloys, whose properties are determined primarily by the precipitation of the gamma prime phase, are listed in Table 5-1. These alloys are arranged in the order of increasing content of aluminum plus titanium and were selected to indicate

Table 5-1. Nominal Compositions of Some Wrought Nickel-Base Superalloys3

Composition, %a

Designation C Cr Co Mo Ti Al Other

M-252 0.15 20.0 10.0 10.0 2.6 1.0 0.005 B Waspaloy 0.08 19.5 13.5 4.3 3.0 1.3 0.006 B; 0.06 Zr Rene 41 0.09 19.0 11.0 10.0 3.1 1.5 0.005 B Udimet 500 0.08 18.0 18.5 4.0 2.9 2.9 0.006 B; 0.05 Zr Nimonic 115 0.15 15.0 15.0 3.5 4.0 5.0 TDNickel 2.2 ThO z

"Nickel remainder. With the exception of TD Nickel, the alloys are arranged in order of increasing Al + Ti content.

Nickel-Base Superalloys 85

the influence of these elements on the properties. A sixth superalloy, TD Nickel, has also been included because it is hardened by a different mechan­ism.

The alloys that are hardened by precipitation of the gamma prime phase are very strong within the temperature range in which the precipitated phase is stable. At temperatures above about 1800 F, however, these precipi­tates begin to dissolve and the strength falls off rapidly at higher tempera­tures.

On the other hand, TD Nickel is hardened by a different mechanism. This mechanism is dispersion strengthening achieved by incorporating stable, insoluble particles in the matrix. Since these particles are not soluble, TD Nickel can be expected to extend the service temperature range of nickel­base alloys to higher temperatures, as noted by Rice. S

Physical Properties

Representative physical properties of the six selected alloys are given in Table 5-2.3, S, 6, 7 With the exception of TD Nickel, the physical properties of these materials are quite comparable with each other. The electrical resistivities of the precipitation harden able alloys are quite high and their thermal conductivities correspondingly low. These properties lie in the same range as those of the nickel-chromium alloys discussed in Chapter 4. They are practically nonmagnetic and have permeabilities in the same range as those of the nickel-chromium alloys. Their coefficients of thermal expansion are comparable with those of certain of the chromium-nickel stainless steels.

The physical properties of TD Nickel are quite different. Rices noted that this material is approximately 98 % nickel with 2 % inert oxide. Therefore its properties are quite close to those of nickel. For example, the electrical resistivity and thermal conductivity lie within the same range as those of commercial nickel. Thus TD Nickel is a much better conductor of electricity and heat than the precipitation harden able superalloys. The coefficient of thermal expansion of TD Nickel also approaches that of commercial nickel but is also comparable with those of the other superalloys under discussion.

The elastic properties of these alloys, again with the exception of TD Nickel, lie within the same range as those of other wrought nickel-base alloys discussed previously. The modulus of elasticity of TD Nickel, on the other hand, is much lower than that of commercial wrought nickel and is compa­rable with that of commercial cast nickel.

The effects of temperature on the dynamic modulus of elasticity of these materials are indicated in Fig. 5-2.3 The age hardenable alloys are shown as a band because their properties are quite close together. This modulus can be determined from the natural frequency of a length of rod or sheet of known

Ta

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Nickel-Base Superalloys

Temperature, K

40000 300 500 700 900 1100 1300 ,

.£ 30,000 u Ui o w '+­o If) :::J :; 20,000 D o ~

10,000 L..-._-'--_ .......... __ L....-_-'--_--'

400 800 1200 1600 2000 Temperature, F

Fig. 5-2. Effect of temperature on the dynamic modulus of elasticity of some wrought superalloys.3 (Band plotted from data for Mimonic 115, Udimet 500, Rene 41, Waspaloy, and M-252. Lower curve TD Nickel.)

87

density. According to Stokes,8 the dynamic modulus is the adiabatic modulus, Ea, and is related to the isothermal modulus, E;, as determined by static methods by the following equation:

where T is the absolute temperature, IX is the coefficient of thermal expansion, c is the specific heat, and p is the density.

The moduli of Nimonic 115, Udimet 500, Waspaloy, and Rene 41 range from about 32,000 ksi at room temperature to about 22,000 ksi at 1800 F. M-252 lies on the low side of the band, ranging from 29,900 ksi at room temperature to 21,000 ksi at 1600 F. In its elastic properties, again TD Nickel differs markedly from the other materials. Its modulus ranges from about 22,000 ksi at room temperature to 11,000 ksi at 2000 F. Stokes notes that the dynamic modulus is generally slightly higher than the static modulus.

88 Chapter 5

Mechanical Properties

R oom-Temperature Properties

Typical tensile properties of the six materials are given in Table 5_3.3,5,9 The heat treatments used in developing the properties are given as footnotes to the table. Although these heat treatments varied considerably among the alloys, the strengths of M-252, Waspaloy, Udimet 500, and Nimonic 115 are quite close together and their ductilities, as measured by the elongation, do not differ greatly although Waspaloy and Nimonic 115 appear to be

Table 5-3. Typical Tensile Properties of Some Wrought Nickel-Base Superalloys

Form and condition

M-252 Bar

Heat treated­Sheet

Heat treated-

Waspaloy Bar

Heat treatedb

Rene 41 Bar

Heat treated­Heat treatedc

Sheet Heat treated­Heat treatedc

Udimet 500 Rolled bar and forgings

Heat treatedb

Sheet Heat treatedb

Nimonic 115 Bar

Heat treatedd

TD Nickel Bar Sheet

Yield strength (0.2 % offset),

ksi

120

110

115

154 120

145 97

110

130

125

48-87 47-60

Tensile strength,

ksi

180

180

188

206 160

185 140

175

190

180

61-103 64--70

-Solution treated 1950 F, 4 hr, air cooled; aged 1400 F, 16 hr, air cooled.

Elongation (2 in.),

%

16

20

28

14 18

9 12

15

18

27

31-22 19-12

·Solution treated 1975 F, 4 hr, air cooled; aged 1500 F, 24 hr, air cooled; 1400 F, 16 hr, air cooled. cSolution treated 2150 F, 2 hr, air cooled; aged 1650 F, 4 hr, air cooled. 'Solution treated 2175 F, 1.5 hr, air cooled; 2010 F, 6 hr, air cooled.

Ref.

9

9

9

9

3

5

Nickel-Base Superalloys 89

somewhat more ductile than the other two alloys. The two heat treatments used for Rene 41 resulted in considerable variations in strength properties with less variation in ductility. The ductility of Rene 41 appears to be com­parable with those of M-252 and Udimet 500.

TD Nickel is produced by compacting and rolling a powder produced by the aqueous reduction of nickel ammonium carbonate in which an aquesol of thoria is incorporated according to Rice. S After compaction, the material is usually sintered in hydrogen. Subsequent hot rolling, cold rolling, and annealing determine the properties. As shown in Table 5-3, the room-tempera­ture strength of TD Nickel is much lower than those of the precipitation harden able alloys, but the ductility lies approximately in the same range.

RiceS notes that exposure to elevated temperatures has virtually no effect on the room-temperature tensile strength or on the shock resistance of TD Nickel. As an example, he notes that the Charpy V-notch impact value was 34 ft-Ib for material in the "as received" condition and fell only to 30 ft-Ib after exposure of 100 hours at 2400 F.

Elevated- Temperature Properties

Short-time elevated-temperature tensile strengths of the six materials under discussion are presented in Fig. 5_3. 3 ,9 Since the strengths of the five age hardenable materials were quite close together, they have been indicated as a band. These alloys retain much of their room-temperature strength up to about 1200 F. Above that temperature, however, strength begins to fall off rapidly and at 1600 F is only about 40% of the room-temperature strength.

The tensile strength of TD Nickel is much lower than those of the age hardenable alloys at all temperatures and it falls continuously as the tem­perature is increased. At 1600 F, its strength is only about 25 % of the room­temperature strength.

Typical stress-rupture properties of the materials are given in Table 5-4. 3 Although there was no significant difference in the short-time strengths of the age hardenable alloys above 1200 F, the effect of increasing the alumi­num plus titanium content is clearly indicated by the progressive increase in rupture strength.

For example, the aluminum plus titanium content of M-252 is 3.6 % and its WOO-hour rupture s"trength at 1600 F is 10 ksi. Nimonic 115 has an alumi­numplus titanium content of9% and its WOO-hour rupture strength at 1600 F is 27 ksi. As can be noted in the table, the WOO-hour rupture strength of Nimonic 115 at 1800 F is almost as high as that of M-252 at 1600 F. Thus, the increase in titanium and aluminum content of Nimonic 115 has resulted in a significant increase in the useful temperature range.

The value of TD Nickel is clearly indicated by these long-time tests.

90 Chapter 5

~

..c

Temperature, K

300 500 700 900 1100 1300 200 ,....,...---r----,----..,.----,---,I""""'I

180

160

140

0, 120 c ~ .....

Cf)

.Si! 100 'iii c ~

80

60

40

20 L-_....l-_---'-__ ....L.-_---I..._;::a..J

400 800 1200 1600 2000 Temperature, F

Fig. 5~3. Short-time elevated-temperature tensile strengths of some wrought superalloys.s,9 (Band plotted from data for Waspaloy, Rene 41, M-252, and Udimet 5()(). Lower curve TO Nickel.)

Although its room-temperature strength is much lower than that of the age hardenable alloys and the short-time elevated-temperature tensile prop­erties are not impressive, TD Nickel retains its strength to higher tempera­tures than the age hardenable alloys. For example, the lOoo-hour rupture strength of TD Nickel at 2000 F is equal to that of Nimonic 115 at 1800 F, a very significant advance.

In this connection, Donachie and Bradley! 0 reported that in a test in which TD Nickel and Hastelloy alloy X were compared by service tests in

Nickel-Base Superalloys

Table 5-4. Stress Rupture Properties of Some Wrought Nickel-Base Superalloys3

Test Stress (ksi) for rupture in temperature,

100hr Form and condition F

M-252 Bar, heat treateda 1200 98

1400 52 1600 23

Waspaloy Bar, heat treatedb 1200 110

1400 60 1600 25

Rene 41 Bar, heat treatedc 1200

1400 64 1600 23

Udimet 500 Bar, heat treatedb 1200 135

1400 66 1600 29

Nimonic 115 Bar, heat treatedd 1400 79

1600 38 1800 16

TD Nickel Stress-relieved 1200 28

1400 23 1600 18 1800 14 2000 11

"1900 F, 4 hr, air cooled; 1400 F, 16 hr, air cooled. '1975 F, 4 hr, air cooled; 1550 F, 24 hr, air cooled; 1400 F. 16 hr, air cooled. c1950 F, air cooled; 1400 F, 16 hr, air cooled. "2175 F, 1.5 hr, air cooled; 2010 F, 6 hr, air cooled.

1000 hr

79 38 10

86 42 16

100 40 14

110 47 18

61 27 9.5

26 21 16 13 9.5

91

jet-engine burner cans, the former was superior by a wide margin after 151 hours.

Low-Temperature Properties

The high strengths of the nickel-base superalloys have led to the investi­gation of some of them for possible service at subzero temperatures. Among these are Rene 41, Waspaloy, and TD Nickel. Others were discussed in Chapters 3 and 4.

92

Temperature, K 50 100 150 200 250 300

260~~----~--~--T---~--~

240

220

200

"Vi ->C 180 ..c 0, c QJ

In 160

~ Vi ~ 140 f-

120

100

80

-400 -300 -200 -100 Temperature, F

o 100

Fig. 5-4. Subzero-temperature tensile strengths of some wrought superalloys.ll.12 (1) Rene 41 bar, solution annealed; (2) Waspaloy, aged; (3) Rene 41 sheet, aged; (4) Waspaloy, solution annealed; (5) Rene 41 sheet, solution annealed; (6) TD Nickel.

Chapter 5

As shown in Fig. 5-4, the strengths of all three of the alloys mentioned in the preceding paragraph increase as the temperature is reduced below zero. There is, however, some difference in the rate of change. The greatest increase in strength occurs in material which has been solution annealed.

The tensile strength of Rene 41 bar stock in the solution-annealed condi-

Nickel-Base Superalloys 93

tion increased from 188 ksi at room temperature to 255 ksi at -400 F. The tensile strength of Rene 41 sheet increased from about 135 ksi at room temperature to 200 ksi at -400 F, whereas the strength of aged hardened sheet increased only from 181 ksi to 209 ksi with the same temperature change.

Similarly, the strength of solution annealed Waspaloy sheet increased from approximately 142 ksi at room temperature to about 215 ksi at -423 F, whereas the strength of age hardened material increased only from 178 ksi at room temperature to 197 ksi at -423 F. In addition, the Waspaloy sheet in the aged condition reached a peak value in the -250 to -300 F range and decreased below that range. However, Martin and Miller I 2 note that although the notched-to-unnotched strength ratio (K, = 10) is below unity for Wasp­aloy in both the solution annealed and aged conditions, notch sensitivity would probably not pose any problems at low temperatures.

The tensile strength of TD Nickel also increases significantly with fall­ing temperatures ranging from 67 ksi at room temperature to 117 ksi at -423 F. According to Martin and Miller,12 the ductility also shows a marked increase with falling temperature and no serious problems with notch sen­sitivity would be expected.

An indication of the toughness of Rene 41 sheet in the solution annealed condition is given in Fig. 5_5. 11 Charpy V-notch tests, made on subsize speci­mens, indicated that there was only a small reduction in the energy absorbed as the temperature was reduced from room temperature to -400 F. There

Temperature, K

50 100 150 200 250 300 £20

I +-'+-

~

..c 15 u

0 C I

> +- 10 u 0 Q.

.s 5 >. Q. .... 0

..c () 0

-400 -300 -200 -100 0 100 Temperature, F

Fig. 5-5. Subzero-temperature impact properties of Rene 41 solution annealed bar. I I

94 Chapter 5

was no indication of a transition from ductile to brittle behavior at low temperatures for this material.

CAST ALLOYS

The compositions of five representative cast nickel-base superalloys are given in Table 5-5. 3 GMR-235D is a modification of the original GMR-235 alloy. These alloys are hardened by precipitation of the NilAI, Ti) inter­metallic compound and were developed for service in gas-turbine applica-

Table 5-5. Nominal Compositions of Some Cast Nickel-Base Superalloys 3

Composition, %a

Designation C Cr Co Mo Ti Ai Other

GMR-235D 0.15 15.5 5.0 2.5 3.5 0.05 B; 4.5 Fe Alloy 713C 0.12 12.5 4.2 0.8 6.1 0.12 B; 0.10 Zr; 2.0 Cb IN-loo 0.18 10.0 15.0 3.0 4.7 5.5 0.014 B; 0.06 Zr; 1.0 V MAR-M200 0.15 9.0 10.0 2.0 5.0 0.015 B; 0.05 Zr; 12.5 W; 1.0 Cb Mar-M246 0.15 9.0 10.0 2.5 1.5 5.5 0.Q15 B; 0.05 Zr; 10.0 W; 1.5 Ta

aNickel remainder.

tions. The modified alloy contains increased quantities of aluminum and titanium and less iron than the original. As a result of this modification in composition, the rupture life of GMR-235D, cast in an inert atmosphere from vacuum melted material, is approximately 50% higher at 1600 F than that of vacuum cast GMR-235 alloyP

Alloy 713C and IN-100 are vacuum-melted, vacuum-cast materials of the aluminum-titanium precipitation type. They have excellent strength up to about 1800 FP

MAR-M200 is an age harden able alloy containing relatively large quantities of tungsten which contributes to the strengthening of the matrix and in carbide formation. It also contains cobalt to increase the solvus tem­perature of the gamma-prime phase. 14 MAR-M246 was developed to obtain higher ductility than was achieved in MAR-M200 and also to improve the high-temperature strength and rupture properties.

Physical Properties

Limited data on the physical properties of these alloys are given in Table 5_6. 3• 7 • 14 The thermal expansion data indicate that these cast alloys have expansion characteristics similar to those of the wrought age hardenable

Ta

ble

5-6

. P

hys

ical

Pro

pe

rtie

s o

f S

om

e C

ast

Nic

ke

l-B

as

e S

up

eral

loys

3,7

,14

GM

R-2

35D

A

lloy

713

C

IN-1

00

MA

R-M

200

Mel

ting

poi

nt,

F 23

50-2

450

2435

24

00-2

450

Spec

ific

hea

t (7

0-20

0 F

), B

tu/l

b;oF

0.

100

The

rmal

con

duct

ivit

y (2

00 F

), B

tu/h

r/ft

2;o

F/f

t 12

.2

8.3

Coe

ffic

ient

of

ther

mal

exp

ansi

on (

70-1

600

F),

per

of

8.6

x 10

-6

8.8

X

10-6

8.

2 X

10

-6

Mod

ulus

of

elas

tici

ty,

ksia

28

,700

29

,900

31

,200

31

,600

D

ensi

ty (

70 F

), I

b/in

.3

0.29

1 0.

286

0.28

0 0.

304

aDyn

amic

mod

ulus

.

MA

R-M

246

2450

0.30

5

z n' ~ !!. , III

I»

1/1

CD en

c "C

CD !. 0"

<

1/1

CD

CII

96

Temperature, K 300 500 700 900 1100 1300

40,000 .-.---,----,---,--,---...,.,

f.30,000 .(3 .~

c W '0 VI

-§ 20,000 "0 o ::?!

10,000 L-.._...I..-_-l-_---L __ L...---I

o 400 800 1200 1600 2000 Temperature, F

Fig. 5-6. Effect of temperature on the dynamic modulus of elasticity ofsomecast superalloys.3 (1) MAR-M2oo; (2) IN-loo; (3) 713C; (4) GMR-235D.

Chapter 5

nickel-base superalloys. However, the thermal conductivities of alloy 713C and MAR-M2oo are considerably higher than those of the wrought composi­tions previously discussed in this chapter.

The modulus of elasticity increases progressively from 28,700 ksi for GMR-235D to 31,600 ksi for MAR-M2oo. No values were found for MAR­M246. The effect of temperature on the dynamic modulus of elasticity is indicated in Fig. 5-6.3 The modulus of GMR-235D is considerably lower than those of the other cast alloys under discussion and temperature has a greater effect on it. However, all four of the materials show a relatively uni­form decrease in modulus as the temperature is increased.

Mechanical Properties

Room-Temperature Properties

Typical tensile properties for the five alloys in the "as cast" condition are given in Table 5_7.3.13.14 Alloys GMR-235D, 713C, and IN-loo, which de­pend primarily on the intermetallic compound, gamma prime, for hardening,

Nickel-Base Superalloys

Table 5-7. Typical Tensile Properties and Hardness Values of Some Cast Nickel-Base Superalloys

Yield strength Tensile Elongation (0.2 % offset), strength, (2 in.), Rockwell

97

Condition ksi ksi % hardness Ref.

GMR-235D As casta 103 112 3 C36

Alloy 713C As castb 112 127 6 C38

IN-l 00 As cast 127 146 7

MAR-M200 As cast 120 135 7

MAR-M246 As cast 125 140 5

-Vacuum melted, cast in inert atmosphere. bVacuum melted, vacuum cast.

Temperature, K

300 500 700 900 1100 1300 160 r-T""---,----r--r---.,...--~

140

60

40 '----'-----'---.......... ---'------' o 400 800 1200 1600 2000

Temperature, F

Fig. 5-7. Short-time elevated-temperature tensile strengths of some cast superalloys.3.13 (1) IN-l00; (2) MAR-M246; (3) MAR-M200; (4) GMR-235D; (5) 713C.

13

13

13

14

3

98 Chapter 5

show a progressive increase in strength with increasing aluminum and titani­um content. Alloys MAR-M200 and MAR-M246 do not fit into this pattern, probably because of the inclusion of alloying elements which strengthen the matrix, notably tungsten. Their strengths lie between those of alloy 713C and IN-lOO. The ductility, as indicated by the elongation, is low in all five materials.

Although there is a marked difference in the tensile strengths of GMR-235D and alloy 713C, their Rockwell hardness values are quite close to­gether.

Tests on alloy 713C indicated that some improvement in toughness was achieved by casting in a vacuum over that resulting from casting in an inert atmosphere. Charpy V-notch impact tests indicated that the energy absorbed was 9.4 ft-Ib for vacuum cast material compared with 7.0 ft-Ib for inert-atmosphere-cast material. 1 5

Elevated- Temperature Properties

The short-time elevated-temperature tensile strengths of the five cast alloys under discussion are indicated in Fig. 5_7. 3,13 All of these materials were tested in the "as cast" condition. The effect of the precipitation of the gamma

Table 5-8. Stress-Rupture Properties of Some Cast Nickel-Base Superalloys

Test Stress (ksi) for rupture in temperature,

Condition F 100hr 1000 hr

GMR-235D As casta 1500 48 33.5

1700 20.5 16.9

Alloy 713C As casta 1200 105 91

1500 63 47 1800 20 14.8

IN-1oo As casta 1500 70 56

1800 24 MAR-M2oo

Cast, heat treatedb 1500 72 60 1700 42 29 1800 26 18

MAR-M246 Cast, heat treatedb 1500 78 62

1700 43 30 1800 28 19

aVacuum melted, investment cast. '1600 F, 50 hr, air cooled.

Ref.

13

13

13

3

3

Nickel-Base Superalloys 99

prime phase is indicated by the increase in strength which occurs in the 1200 to 1500 F range. Above that range, the strengths fall off rapidly and are so close together that they have been indicated by a band. At 1800 F, all five of the alloys have strengths in the 70 to 80 ksi range.

Typical stress-rupture properties of these cast alloys are given in Table 5_8. 3 ,13 The effect of increasing the aluminum and titanium content on im­proving the rupture properties is indicated by the data reported for GMR-235D, alloy 713C, and IN-IOO at 1500 F. The stress for rupture in 1000 hours at that temperature, for example, increased from 33.5 ksi for GMR-235D to 56 for IN-lOO, an improvement of about 75 %. MAR-M200 and Mar­M246, which contain large quantities of matrix-strengthening elements in addition to aluminum and titanium, show an additional improvement over IN-JOO. Their 1000-hour rupture strengths at 1500 Fare 60 and 62 ksi, re­spectively. This improvement is maintained at the highest temperature on which data were reported, 1800 F.

REFERENCES

1. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards (1968).

2. C. T. Sims, "A contemporary view of nickel-base superalloys," J. Metals, October 1966, p. 1119.

3. High-Temperature High-Strength Nickel-Base Alloys, The International Nickel Co., Inc. (1965).

4. J. Prock, Jr. and H. J. Wagner, A Primer of Soviet Superalloys, DMIC Report 235, Battelle Memorial Institute (1966).

5. L. P. Rice, Metallurgy and Properties of Thoria-Strengthened Nickel, DMIC Memo 210, ibid. (1965).

6. M. E. Langston and C. H. Lund, Physical Properties of Some Nickel-Base Alloys, DMIC Report 129, ibid. (1960).

7. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968). 8. H. J. Stokes, "Apparatus for the measurement of Young's modulus between -200

and 700 C by transverse vibration in a vacuum," J. Sci. Inst. 37, 117 (1960). 9. R. J. Favor, D. A. Roberts, and W. F. Ashbach, Design Information on Nickel-Base

Alloys for Aircraft and Missiles, OTS PB 151090, Battelle Memorial Institute (1960). 10. M. J. Donachie, Jr. and E. F. Bradley, "Jet engine materials for the 1970's," Metal

Progress, March 1969, p. 60. 11. F. R. Schwartzberg, S. H. Osgood, H. D. Keys, and T. F. Kiefer, Cryogenic Materials

Data Handbook, AD609562, The Martin Co. (1964). 12. H. L. Martin and P. C. Miller, Effects of Low Temperature on the Mechanical Properties

of Structural Materials, NASA SP-5012 (01), 1968. 13. Comparative Properties of Union Carbide High-Temperature Alloys, Union Carbide

Stellite Division (1966). 14. J. A. Van Echo and W. A. Simmons, Mechanical and Physical Properties of MAR­

M280, MAR-M302 and MAR-M322, DMIC Memo 193, Battelle Memorial Institute (1964).

15. Haynes Alloys No. 7J3C, Union Carbide Stellite Division (1966).

Chapter 6

Copper-Base Nickel Alloys

There are quite a number of copper-base alloys which contain nickel as an alloying constituent. The most widely used engineering alloys, however, fall into two groups, the copper-nickel alloys and the copper-nickel-zinc alloys, generally called Nickel Silvers. The latter are also sometimes called Nickel Brasses. These two groups will be discussed in this chapter.

COPPER-NICKEL ALLOYS

Copper and nickel are soluble in each other in all proportions and many alloys have been developed which are based on this binary alloy system. In the high nickel end of the system, the major engineering alloys are the Monel alloys which were discussed in: Chapter 3.

Alloys containing less than 50 % nickel are generally called copper­nickel alloys in America now although they were formerly often called cupro­nickels. Basically, these are binary alloys of copper and nickel but iron is added to some of them to increase the resistance to corrosion and erosion. In addition, about 1 % manganese is generally included in the composition to deoxidize the melt and improve the corrosion resistance.

Practically every combination of copper and nickel up to 50 % nickel has been made and many proprietary alloys are available in this alloy range. However, the most important copper-nickel alloys for engineering applica­tions are those containing from 10 to 30 % nickel, specifically those based on the 90/10, 80/20, and 70/30 compositions. These have been designated CA 706, CA710, and CA 715, respectively, by the Copper Development Associa­tion. Nominal compositions are given in Table 6-1.1 Another alloy containing 55 % copper and 45 % nickel could also be included with this group. This

100

Copper-Base Nickel Alloys 101

Table 6-1. Nominal Compositions of Some Copper-Nickel Alloys!

Composition, %

CDANo. Common name Cu Ni Fe Mn

CA 706 Copper-Nickel, 10% 88.6 10 1.4 l.Oa

CA 710 Copper-Nickel,20% 80 20 l.oa l.oa CA 715 Copper-Nickel,30% 70 30 0.7a l.oa

aMaximum.

alloy, however, has quite high electrical resistivity and a low temperature coefficient of resistance and, as a result of these properties, is generally used in applications which differ from those of the 90/10 to 70/30 groups. It will be discussed in Chapter 8.

Alloy CA 706, also called Copper-Nickel, 10 %, is modified by the ad­dition of iron to the base composition. This alloy is commonly used in the form of tubing for saltwater service lines and heat exchangers. The iron is added to improve resistance to impingement attack that may occur in any tube material carrying water at moderate to high velocity.

Alloy CA 710, also called Copper-Nickel, 20%, is used primarily in tube form for evaporators and heat exchangers. However, it is also used for tur­bine applications and in electrical components.

Alloy CA 715, also called Copper-Nickel, 30%, is the,most widely used of the engineering copper-nickel alloys. With small additions of iron and manganese, it has outstanding resistance to impingement attack and is widely used in condenser applications on shipboard and in power stations where sea water is the cooling medium. Because of its excellent corrosion resistance to a wide variety of media, this alloy is also used in chemical plant construc­tion.

All three of these copper-nickel alloys are very ductile, a property that assures good workability. They can be worked hot or cold and can be readily joined by brazing or welding.

Physical Properties

Typical physical properties of CA 706, CA 710, and CA 715 are given in Table 6-2.1. 2 As indicated in the table, there is a gradual change in many of the physical properties with increasing nickel content.

The melting range increases progressively and that of CA 715 is much higher than the melting point of pure copper. Because of its higher melting range, CA 715 is sometimes used for applications where copper brazing is a

102

Table 6-2. Typical Physical Properties of Some Copper-Nickel Alloysl,2

CA 706 CA 710 90/10 80/20

Melting range, F 2010-2100 2100-2190 Specific heat (68 F), Btu/lbtF 0.09 0.09 Thermal conductivity (68 F), Btu/hr/ft2tF/ft 26 21 Coefficient of thermal expansion (68-572 F),

per of 9.5 x 10-6 9.1 X 10-6

Electrical resistivity, ohms/cir mil ft 115 163 Modulus of elasticity, ksi 18,000 20,000 Modulus of rigidity, ksi 6,800 7,500 Density,lb/in. 3 0.323 0.323

Chapter 6

CA 715 70/30

2140-2260 0.09

17

9.0 X 10-6

225 22,000

8,300 0.323

desirable method of joining but the melting point of copper is too low to permit its use.

The electrical resistivity also increases with increasing nickel content from 115 ohms/cir mil ft for CA 706 to 225 ohms/cir mil ft for CA 715. Incidently, resistivity continues to increase with nickel content and at 55 % copper-45 % nickel reaches a value of 300 ohms/cir mil ft.

As would be expected because of its relationship to the electrical prop­erties, the thermal conductivity decreases with increase in nickel content. The coefficient of thermal expansion also decreases as the nickel content increases. This group of copper-nickel alloys is also practically nonmagnetic.

The modulus of elasticity increases progressively with the nickel content from 18,000 ksi for CA 706 to 22,000 ksi for CA 715. It is noteworthy that the modulus continues to increase with nickel content and at 55 % copper-45 % nickel reaches the highest value that is achieved in copper-base alloys. The modulus of rigidity, like the modulus of elasticity, also increases with the nickel content.

Mechanical Properties

Room- Temperature Properties

Strength and hardness of the standard copper-nickel alloys can be increased only by cold work. Heat treatment is used only to anneal or stress­relieve the material.

Tensile Properties. Typical tensile properties of the three copper-nickel alloys in various forms and conditions are given in Table 6_3. 1,2 Data on the materials in the annealed condition show that the strength increases with the

Copper-Base Nickel Alloys 103

Table 6-3. Nominal Tensile Properties and Hardness Values of Some Copper-Nickel Alloysl,2

Yield strength Tensile Elongation (0.5 % extn.), strength, (2 in.), Rockwell

Form and condition % ksi % hardness

CA 706 Strip, annealeda 15 44 40 BlO Tube, annealeda 16 44 42 B15

Light drawn 57 60 10 B73

CA 710 Strip, annealeda 51 27 Tube, annealeda 14 49 40 B25

Light drawn 75 80 B81

CA 715 Bar, hot rolled 20 55 45 B35 Rod, half hard (20%) 70 75 15 B80 Strip, annealeda 22 60 45 B50

Half hard 68 73 12 B80 Hard 73 80 5 B85

Tube, annealeda 25 60 45 B45 Light drawn 75 B85

·Properties of annealed material vary with grain size.

nickel content. Using annealed strip, for example, the tensile strength of CA 706 is 44 ksi, that of CA 710 is 51 ksi, and that of CA 715 is 60 ksi. The elongation, however, does not show a similar trend, Actually CA 715 is more ductile, as measured by the elongation, than CA 706 and considerably more ductile than CA 710. In particular, cold work has a significant effect on the yield strengths of all three alloys. At the same time the elongation is reduced markedly.

The effect of cold roIling on the tensile properties of a 70/30 copper­nickel alloy is shown in Fig. 6-1.3 This graph points up the significant in­crease in yield strength that results from working; the tensile strength in­creases in a more moderate fashion.

The effect of annealing after cold work on the tensile properties of a 70/30 copper-nickel alloy is shown in Fig. 6-2.3 The alloy had been cold rolled with a reduction of 78 % before annealing. The data indicate that softening is complete in material annealed at 1200 F.

Hardness. Rockwell hardness values for the three copper-nickel alloys in various forms and conditions are included also in Table 6-3. In the annealed alloys, the hardness increases with the nickel content. The hardness of CA 706 ranges from BIO to B15 depending on the form of the material; for alloy

104

100 ---.-----.--.....----,

80

~60 vJ (/) (j)

~ 40 (f)

20

o 20 40 60 Reduction by Rolling, %

40 .~ N

c o 20 B

CJl c o

W

80

Fig. 6-1. Effect of cold rolling on the tensile properties of 70/30 copper-nickel (ready-to-finish grain size 0.025 mm).3

Temperature, K

300 500 700 900 1100 1300 100 ......... ----.----.----,,.----r--..,....,

80

~60 60 (/) (/) (j)

~ 40 (f) 40·!:: N

c o

20 20 :g CJl C o W

o 400 800 1200 1600 2000

Fig. 6-2. Effect of annealing on the tensile properties of 70/30 copper-nickel, cold rolled 78 % betore annealing. 3

Chapter 6

Copper-Base Nickel Alloys 105

CA 715, it ranges from B45 to B50, again depending on the form. The hardness of CA 715 strip ranges from B50 for the annealed condition to B85 for material cold rolled to the hard condition.

Fatigue Properties. Fatigue properties of several copper-nickel alloys in various forms and conditions are given in Table 6_4.4,5,6 These data were obtained from various sources and some of the compositions do not fit into

Table 6-4. Fatigue Strengths of Some Copper-Nickel Alloys

Tensile Fatigue strength (ksi)

strength, at indicated cycles

Form and condition ksi lOS 106 107 108 Ref.

CA 706 Hard 53.8 38 21 4 90/10 Wire, 0.072 in., drawn 88 % 89.5 47 35 28 28 5

CA 710 Annealed 1400 F, 1 hr 24 22 19 18 5 CA 710 Stress-relieved 400 F, 3 hr 35 30 27 26 5 80/20 Rod, 1 in., cold rolled 49.9 18 17.6 6 80/20 Wire, 0.072 in., drawn 88 % 84.3 53 41 34 34 5

CA 715 Annealed 58.5 29 25 4 CA 715 Drawn 33 % 43 36 35 5 70/30 Sheet, 0.025 in., annealed 37 27 26 5 70/30 Rod, 1 in., cold drawn 87.3 35 33 6 70/30 Wire, 0.072 in., drawn 88 % 96.2 59 44 35 35 5

the limits specified for the alloys standardized by the Copper Development Association. Unless the compositions indicate that the alloys met these specifi­cations, therefore, they are listed merely as 90/10, 80/20, and 70/30 copper­nickel alloys.

Grover et al. 6 point out that the fatigue strength of copper-nickel alloys can be increased by cold work but, in general, the increase is not proportional to the increase in tensile strength. No tensile data were given for a number of the alloys included in the table. However, annealed 70/30 copper-nickel alloy had a fatigue strength of 25 ksi at 108 cycles (tensile strength 58.5 ksi) and cold drawn rod had a fatigue strength of 33 ksi at 108 cycles (tensile strength 87.3 ksi) which is in line with Grover's comments.

Listed in the table are tests on wire samples of 90/10, 80/20, and 70/30 copper-nickel alloys. The wires had been drawn with a reduction of 88 % and had fatigue strengths at 108 cycles of 28, 34, and 35 ksi respectively. Apparently, the increase in nickel content had a moderate effect on the fatigue strength.

106 Chapter 6

The excellent resistance of copper-nickel alloys to corrosion by saline and fresh waters is indicated by fatigue tests made in these media. Reed and MikeselP have included fatigue data on both annealed and stress-relieved samples of CA 710 in salt water and in fresh water containing carbon dioxide. The fatigue strengths were practically the same as those obtained on samples tested in air.

Impact Properties. The notch toughness of the copper-nickel alloys in the annealed condition is shown in Table 6-5. 5 Although only scattered data are available, they indicate that the three alloys are quite tough. Apparently.

Table 6-5. Impact Energy of Some Copper-Nickel Alloys5

Condition

CA 706 Annealed 900 F, 40 min CA 710 Annealed CA 715 Annealed 70/30b Annealed 70/30b Annealed

Rockwell hardness

B33

B47 92c

B55

Impact energy, ft-lb

Izod

77

Charpy

115a

73d

65d

aV-notch. bIron content not given. bBrinell hardness. dKeyhole notch.

nickel content has little influence on room temperature toughness, however. For example, CA 706 had a Charpy V-notch impact value of 114 ft-Ib as compared with a value of 115 ft-Ib for CA 715.

Additional impact data are included under low-temperature properties.

Elevated- Temperature Properties

The short-time elevated-temperature tensile strength of a 70/30 copper­nickel alloy in the annealed and cold drawn condition (40% reduction by drawing) are given in Fig. 6_3. 2 •3 As indicated in the graph, the annealed material retains much of its roem-temperature strength up to about 800 F, but above that temperature, the strength decreases rather rapidly.

The graph also indicates that the strength imparted by cold work is lost completely at about 1200 F, and above this temperature both cold worked and annealed material have similar properties. Figure 6-4, based on Jenkins et al.,7 presents the short-time yield strengths of a 70/30 copper-nickel alloy after various amounts of cold work. The data confirm the loss in strength that occurs at about 1200 F.

Representative stress-rupture and creep properties of the 90/10 and 70/30 copper-nickel alloys in the annealed and worked conditions are given in Table 6-6. A comparison of the creep properties of 90/10 (CA 706) and

Copper-Base Nickel Alloys 107

Temperature, K 300 500 700 900 1100 1300

100 r-r----r-~--r---...---........,

80 "iii .><:

o 400 800 1200 1600 2000 Temperature, F

Fig. 6-3. Short-time elevated temperature tensile strength of 70/30 copper-nickel. 2. 3

Temperature, K

300 500 700 900 1100 1300 100 r-r-----r-----r---,.----,.--...,....-.

"iii .><:

Q) 80 (f) .... .... 0

~ 60 N Q

B, 40 c ~

en "D 20 Q) "-;:

o 400 800 1200 1600 2000 Temperature, F

Fig. 6-4. Short-time yield strengths of 70/30 copper­nickel in the annealed and cold worked conditions (figures on curves indicate percentage of cold work). 7

... 0 011

Tab

le 6

-6.

Str

es

s-R

up

ture

an

d C

reep

Pro

per

ties

of

So

me

Co

pp

er-

Nic

ke

l A

lloys

Tes

t S

tres

s (k

si)

for

desi

gnat

ed c

reep

rat

e S

tres

s (k

si)

tem

pera

ture

, fo

r ru

ptur

e C

ondi

tion

F

0.

0000

01 %

/hr

0.00

001

%/h

r 0.

0001

%/h

r in

100

hr

Ref

.

CA

706

A

nnea

led

(0.2

5 m

m g

rain

siz

e)

300

17.0

24

.0

3 40

0 12

.0

17.0

50

0 7.

5 8.

0 40

.0

600

6.0

35.0

80

0 16

.5

CA

706

C

old

draw

n, 2

1 %

30

0 37

.8

2 40

0 25

.6

42.5

46

.0

500

16.7

28

.5

36.0

70/3

0 A

nnea

led

(0.0

20 m

m g

rain

siz

e)

300

24.0

3

500

16.0

A

nnea

led

(0.0

40 m

m g

rain

siz

e)

400

49.0

60

0 44

.0

800

26.5

70

/30

Dra

wn

and

stre

ss-r

elie

ved

500

59.0

3

600

49.0

75

0 17

.0

38.0

56

.0

850

6.0

17.0

40

.0

950

4.0

30.0

(')

:::T

I»

"C

r+

(11 ... Q)

Copper-Base Nickel Alloys 109

70/30 alloys, annealed to approximately the same grain size, indicates that nickel has a marked effect on the long-time strength.

The data in this table show that the copper-nickel alloys retain good strength at moderately high temperatures. These alloys are among the strong­est of the copper-base materials at elevated temperatures.

Low-Temperature Properties

The effects of low temperature on the tensile properties of 90/10 and 70/30 copper-nickel alloys in' the annealed condition are indicated in Fig. 6-5. 5 and 6-6. 2 Yield and tensile strengths increase as the temperature is reduced, although there is less effect on the yield than on the tensile strength. The elongation also rises but the reduction of area shows a slight decrease. A comparison of the properties of the two materials shows that the 70/30 alloy is as strong at -300 F as the 90/10 is at -400 F. The ductility of the 70/30 alloy, as measured by the elongation, remains superior to that of the 90/10 alloy at all temperatures. However, the reduction of area is practically the same at all temperatures for both materials, although there is a slight trend in favor of the 90/10 composition.

For ductile materials, the notched tensile strength is often a better indication of toughness than the notched impact test because the materials

Temperature, K

50 100 150 200 250 300 100 I I I I I I

~

80 r-' R of A

~~ 80 g

~ ....

<! '+-

. iii 60 r--

0 .::.::. 60 -D en

E ---Q)

<f) - a:: Q)

~ 40 - -- 40 ;

- YS N

c 20 - - 20 .g

0 0' C 0

I I J I I W -400 -300 -200 -100 0 100

Temperature, F

Fig. 6-5. Subzero-temperature tensile properties of annealed 90/10 copper-nickel. 5

110

Temperature, K

50 100 150 200 250 300 100 ~--"----'r----r---~--r---n 100

o 80 80 ~

T. s. '+-o ~ 60 'S= -- E 60 "D

If> If> Q)

- Q)

0::

c7) 40 40 c (\J

______ Y S 02 % c o

20 20"5

-400 -300 -200 -100 Temperature, F

o 100

0' c o W

Fig. 6-6. Subzero-temperature tensile properties of annealed 70/30 copper-nickel. 2

Temperature, K 50 100 I~ ~O 2~ ~O

100 I'T----y----y----,r----,...--T"I

80 .ti) .::£

L

"& 60

...... ...... .........

c Q) ...

............ I ------.-i7i ~ 40

_ ... _ 2 ... _ ----------4

20 -Unnotched ----Notched

-400 -300 -200 -100 Temperature, F

o 100

Fig. 6-7. Subzero-temperature tensile strengths of 70/30 (curves 1,2) and 80/20 (curves 3, 4) copper-nickel. 8

Chapter 6

Copper-Base Nickel Alloys

Table 6-7. low-Temperature Impact Properties of Some Copper-Nickel Alloys

Test Impact energy, ft-lb

temperature, Charpy Izod

111

Condition F V-notch Ref.

CA 706 Annealed 72 114 8 -108 113 -323 115 -423 116

80/20 Annealed Room 77 2 -110 79 -170 84 -290 85

CA 715 Annealed 72 115 8 -108 114 -323 114 -423 114

70/30 Annealed Room 68a 5 -50 59a

-100 59a

-195 6Qa

"Keyhole notch.

do not have an impact transition temperature. Figure 6-7. 8 indicates the effect of low temperature on the unnotched and notched tensile strength of annealed 80/20 and 70/30 copper-nickel alloys. The toughness of the 70/30 alloy was not impaired by notches but that of the 80/20 alloy was reduced.

Notch impact tests indicate that the materials are tough to very low temperatures. No indications of embrittlement were found in the standard alloys when tested in the annealed condition at temperatures as low as -423F. Some data on these alloys are given in Table' 6_7. 2 •5 •9 No data were found on the effect of cold working on the low-temperature impact properties.

CAST COPPER-NICKEL ALLOYS

According to Vanick,l 0 cast copper-nickel alloys often have approxi­mately the same compositions as the wrought alloys. Since they cannot be hardened by working, however, they contain hardeners such as carbon, iron, manganese, silicon, aluminum, or tin.

Carbon up to 0.15 % adds some strength; iron up to 1 % improves the resistance to corrosion in sea water; about 1 % manganese assists in deoxidi-

112 Chapter 6

zation and contributes fluidity; and silicon at 0.25 % aids in producing tough, pressure-tight castings.

As a means of producing pressure-tight castings in 70/30 copper-nickel alloy, Kihlgren II suggests melting under oxidizing conditions, adding man­ganese and silicon a few minutes before pouring to deoxidize the melt, and completing the deoxidation by adding magnesium in the ladle. He suggests pouring at 2500 to 2650 F, depending on the section size of the casting, into generously gated molds made of a refractory open sand. Details are given in his paper.

According to Shepherd,13 the use of columbium in connection with silicon yields an alloy considerably stronger than that achieved with silicon alone. The ratio of silicon to columbium which is selected depends on the strength-ductility level required. At 49 ksi yield strength, he suggests that the silicon and columbium content should each be approximately 0.45 %.

A number of copper-nickel casting alloys have been standardized by the Copper Development Association. Nominal compositions are given in Table 6_8. 13

Table 6-8. Nominal Compositions of Some Cast Copper-Nickel Alloysl3

Composition, %

CDA No. Common name Cu Ni Fe Mna Sia

CA 962 90:10 copper-nickel 88.6 10 1.4 1.0 0.25 CA 963 79.3 20 0.7 1.0 0.7 CA 964 70 :30 copper-nickel 69.1 30 0.9 1.5 0.7 CA 966 717C beryllium--copper-nickel 68.5 30 1.0 1.0 0.15

aMaximum.

Other

1.0 Cba

1.0 Cba

0.5 Be

In general, these alloys are used for applications similar to those of the corresponding wrought alloys. Alloys CA 962, CA 963, and CA 964 are modifications of the 90/10, 80/20, and 70/30 compositions, respectively. Alloy 966, however, is a 70/30 alloy modified by the addition of beryllium and is precipitation harden able. It is used for high strength constructional parts for service in sea water.

Physical Properties

Typical physical properties of the cast copper-nickel alloys are given in Table 6_9. 13 With the exception of the precipitation hardenable alloy, CA 966 the properties of the alloys are influenced by the nickel content. The melting range rises with increase in nickel, the thermal and electrical conductivities

Ta

ble

6-9

. P

rop

ert

ies

of

So

me

Cas

t C

op

pe

r-N

ick

el

Allo

ys! 3

CA

962

Phy

sica

l pr

oper

ties

M

elti

ng r

ange

, F

2010

-210

0 Sp

ecif

ic h

eat

(68

F),

Btu

jlb;

oF

0.09

T

herm

al c

ondu

ctiv

ity

(68

F),

Btu

jhrj

ft2;

oFjf

t 26

C

oeff

icie

nt o

f th

erm

al e

xpan

sion

(68

-572

F),

per

of

9.5

x 10

-6

Ele

ctri

cal

cond

ucti

vity

(68

F),

% lA

CS

11

M

odul

us o

f el

asti

city

, ks

i 18

,000

D

ensi

ty,l

bjin

.3

0.32

3

Mec

hani

cal

prop

erti

es (

as s

and

cast

) Y

ield

str

engt

h (0

.5 %

extn

.),

ksi

25

Ten

sile

str

engt

h, k

si

45

Elo

ngat

ion

(2 in

.),

%

20

Bri

nell

har

dnes

s

Not

e:

Ten

sile

pro

pert

ies

for

CA

762

, C

A 7

63,

and

CA

764

are

min

imum

. aT

ypic

al v

alue

s fo

r m

ater

ial s

olut

ion-

trea

ted

at 1

825

F,

1 h

r, w

ater

que

nche

d, a

ged

950

F,

3 h

r.

'Typ

ical

val

ues.

CA

963

C

A 9

64

2100

-219

0 21

40-2

260

0.09

0.

09

21

17

9.1

X

10-6

9.

0 X

10

-6

6.5

5 20

,000

21

,000

0.

323

0.32

3

55

32

75

60

10

20

150b

14

0b

CA

966

2010

-216

0 0.

09

18

9.0

X

10-6

4.3

a

22,0

00 0.31

8

70a

llQa 7a

230a

o o "tI

"tI CD 7 CD

AI

III CD

Z ~ ~ ~

0"

<

III .... .... W

114 Chapter 6

decrease, the coefficient of thermal expansion decreases, and the modulus of elasticity increases. CA 966 does not follow this pattern but it does have the highest modulus of elasticity of the group.

Mechanical Properties

Table 6-9 also gives minimum tensile properties determined on sand cast test bars of alloys CA 962, CA 963, and CA 964. These alloys do not show the same progression in strength with increasing nickel content that was characteristic of the wrought copper-nickel alloys. As measured by the elongation, the alloys have quite good ductility in the "as cast" condition.

Alloy CA 966 can be precipitation hardened to a tensile strength of 110 ksi, which is almost double the strength of CA 965, the conventional 70/30 alloy. However, the elongation of CA 966 in the precipitation hardened condition is rather low.

Gross and Schwab4 included a cast 70/30 copper-nickel alloy in their investigation of fatigue properties. The tensile strength of the alloy "as cast" was 79 ksi and the fatigue strength at 108 cycles was 13 ksi.

Reed and MikeselP reported the effects of low temperatures on the notched-bar impact resistance of a cast 70/30 copper-nickel alloy having an "as cast" Brinell hardness of 65 to 74 as follows:

Temperature, F Charpy impact (keyhole notch), ft-Ib

-320 86

-195 61

-100 50

NICKEL SIL VERS (COPPER-NICKEL-ZINC ALLOYS)

-50 80 60 50

The copper-nickel-zinc alloys, usually called nickel silvers, are essentially brasses in which a part of the zinc has been replaced by nickel. A major reason for the use of nickel, originally, was to obtain a copper-base alloy which is white. Therefore, the composition limits are restricted. Generally nickel silvers contain from 45 to 72 % copper, 5 to 18 % nickel, and the bal­ance zinc. The nickel silvers and the copper-nickel alloys are the only copper­base materials which are white.

Although originally used most widely for architectural and decorative purposes, their excellent mechanical properties and their resistance to cor­rosion by water, the atmosphere, and various organic materials have expanded the applications of the nickel silvers into the industrial field.

At least 25 nickel silver combinations are produced commercially but a few can be used to indicate the properties to be expected of these materials. Those selected are the Copper Development Association standard compos i-

Copper-Base Nickel Alloys 115

tions designated CA 745, CA 752, CA 757, and CA 770. Nominal composi­tions are given in Table 6-10. 1

Of the group, the two that are most important commercially are CA 770 (55 % copper-I 8 % nickel) and CA 752 (65 % copper-I 8 % nickel). The former

Table 6-10. Nominal Compositions of Some Nickel Silvers l

Composition, %

CDA No. Common name Cu Ni Zn

CA 745 Nickel Silver, 65-10 65 10 25 CA 757 Nickel Silver, 65-12 65 12 23 CA 752 Nickel Silver, 65-18 65 18 17 CA 770 Nickel Silver, 55-18 55 18 27

work hardens to the highest yield strength of the group and is commonly used for springs; the latter is used for forming, drawing, spinning, and stamp­ing operations. Alloys CA 745 (65% copper-lO% nickel) and CA 757 (65% copper-I 2 % nickel) are lower nickel modifications of the 65 % copper alloy. With the increase in the price of nickel, they can be expected to take over some of the applications now being served by CA 752.

Physical Properties

Typical physical properties of the four nickel silvers are given in Table 6-11. 1 In the group containing 65 % copper, the melting point (liquidus) increases with the nickel content. The electrical resistivity also increases in the same manner, and the thermal conductivity decreases. The variation in nickel content appears to have little influence on the coefficient of thermal expansion and on the elastic properties.

The 55 % copper-I 8 % nickel alloy, CA 770, has a higher electrical resistivity than that of the 65 % copper-I 8 % nickel alloy, CA 752, and a lower thermal conductivity. Again, however, the variation in composition seems to have little effect on the coefficient of thermal expansion and on the elastic properties.

Since th.se alloys are modifications of yellow brass, a comparison can be made with it. In general, the substitution of nickel for zinc in these materials results in increasing the density and the modulus of elasticity. The electrical resistivity of the nickel silvers is markedly higher than that of yellow brass. These nickel silvers have resistivities ranging from 115 to 189 ohms/cir mil ft as compared with 38 for yellow brass. The thermal conductivity is also markedly lower than that of yellow brass.

Tab

le 6

-11.

T

ypic

al P

hys

ical

Pro

per

ties

of

So

me

Nic

kel

Silv

ers!

CA

745

C

A 7

57

CA

752

(6

5-10

) (6

5-12

) (6

5-18

)

Mel

ting

poi

nt,

F 18

7()a

18

30-1

900

1960

-203

0 Sp

ecif

ic h

eat

(68

F),

Btu

/lb;

oF

0.09

0.

09

0.09

T

herm

al c

ondu

ctiv

ity

(68

F),

Btu

/hr/

ft2/o

F/f

t 26

23

19

C

oeff

icie

nt o

f th

erm

al e

xpan

sion

(68

-572

F),

per

of

9.1

x 10

-6

9.0

X

10-6

9.

0 X

10

-6

Ele

ctri

cal

resi

stiv

ity,

ohm

s/ci

r m

il f

t 11

5 13

0 17

3 M

odul

us o

f el

asti

city

, ks

i 17

,500

18

,000

18

,000

M

odul

us o

f ri

gidi

ty,

ksi

6,60

0 6,

800

6,80

0 D

ensi

ty,

Ib/i

n.3

0.31

4 0.

314

0.31

6

aLiq

uidu

s.

CA

770

(5

5-18

)

1930

a 0.09

17

9.

3 X

10

-6

189

18,0

00

6,80

0 0.31

4

.... .... Q) o ::r

I»

"C .. .,. ... Q)

Copper-Base Nickel Alloys

Mechanical Properties

Room- Temperature Properties

117

The nickel silvers, like the copper-nickel alloys, can be hardened only by cold work. The mechanical properties are determined by the annealing conditions and by the cold work performed after annealing.

Tensile Properties. Nominal tensile properties for the group of nickel silvers in various forms and conditions are given in Table 6-12.1 The properties of annealed material vary with grain size. Generally, the larger the grain, the softer the material. For example, CA 745 flat products annealed to 0.070 mm grain size had a tensile strength of 49 ksi whereas the same material annealed to 0.015 mm grain size had a tensile strength of 60 ksi. Ductility is also affec­ted by grain size, the elongation values for the two materials being 49 and 36 %, respectively.

Comparison of the four materials shows that the nickel content has little effect on the annealed tensile properties. There appears to be little effect on the properties after cold work for the alloys containing 65 % copper. However, CA 770 work hardens to a greater tensile strength than the other three nickel silvers.

The effect of cold work on the tensile properties is shown in Fig. 6-8 for a 65 % copper-lO % nickel alloy and in Fig. 6-9 for a 55 % copper-18 % nickel alloy. 1 These graphs show that the latter work hardens to a greater degree than the former. For example, at 50% cold work, the 65/10 alloy had a yield strength of 76 ksi whereas the 55/18 alloy had a yield strength of 90 ksi. The elongations of the two materials after 50 % cold work, however, were approximately the same, 3 %.

The effect of annealing on the tensile strength and elongation of a 65/10 nickel silver is shown in Fig. 6_10. 14 Little loss of strength occurs with annealing temperatures below about 700 F but above that temperature there is a progressive decrease. The ductility, as measured by the elongation, in­creases as the strength falls.

Hardness. Rockwell hardness values for the four alloys are given also in Table 6-12. The hardness ranges from B22 for alloy CA 745 in the softest condition to B99 for alloy CA 770 in spring temper, For example, in hard temper, flat products ranged from B87 for CA 752 to B92 for CA 745.

Fatigue Properties. Fatigue properties of two types of nickel silver are given in Table 6-13.1 S As indicated in the table, the fatigue strength of the 55/18 alloy can be increased by cold work but, as was the case with the cop­per-nickel alloys, the increase is not proportional to the increase in tensile

118 Chapter 6

Table 6-12. Nominal Tensile Properties and Hardness Values of Some Nickel Silvers!

Yield strength Tensile Elongation (0.5 % extn.), strength, (2 in.), Rockwell

Form and condition ksi ksi % hardness

CA 745 Flat products, 0.040 in.

Annealeda 18-28 49-60 49-36 B22-52 Half hard 60 73 12 B80 Hard 75 86 4 B89 Extra hard 76 95 3 B92

Wire, 0.080 in. Annealeda 50-63 50-35 Spring temper (84 % reduction) 130 1

CA 757 Flat products, 0.040 in.

Annealeda 18-28 52-61 48-35 B22-55 Half hard 60 73 11 B80 Hard 75 85 4 B89 Extra hard 79 93 2 B92

CA 752 Flat products, 0.040 in.

Annealeda 28 59 36 B50 Half hard ')2 74 8 B83 Hard 74 85 3 B87

Rod, 0.500 in. Annealeda 25 56 42 Half hard (20 % reduction) 60 70 20 B78

Wire, 0.082 in. Annealeda 28 59 40 Hard 90 103 3

CA 770 Flat products, 0.040 in.

Annealeda 27 60 40 B55 Hard 85 100 3 B91 Spring temper 115 2.5 B99

Wire, 0.080 in. Annealeda 60 40 Spring temper 145 2

(I Annealed properties vary with grain size.

Copper-Base Nickel Alloys

. iii

.::t: 60

vi ~ <J) Q)

401 .... ii5 N

c

20 20 . .§ 0 0-C 0 W

0 20 40 60 80 Reduction by Roiling, %

Fig. 6-8. Effect of cold rolling on the tensile proper­ties of 65-10 nickel silver.1

120

100

80 . iii .::t:

vi 60 60 <J) Q) .... (/) ~

~

40 40.~ N

c 0

20 20 '"§ 0-C 0 W

0 20 40 60 80 Reduction by Rolling, %

Fig. 6-9. Effect of cold rolling on the tensile properties of 55-18 nickel silver. 1

119

120 Chapter 6

Temperature, K 300 500 700 900 1100 1300

100 n::=::::::::-,i-T-Tl

80 80

..c 0,60 c C1J .;::

(f)

..!!! 40 'Vi c ~

20

60 ~ c:

N

40 ';;' Q o ry

20 § W

o 400 800 1200 1600 1200 Temperature, F

Fig. 6-10. Effect of annealing on the tensile properties of 65-10 nickel silver.I 4

strength. Thus, the endurance ratio ranges from 0.20 for extra spring temper to 0.25 for annealed material. A ratio of 0.35 was reported for cold drawn 65/18 nickel silver.

Elevated- Temperature Properties

Short-time elevated-temperature tensile properties of a 65/10 nickel silver, which had been cold worked with a reduction of 20 %, are given in Fig. 6-11. 1 S The material retained most of its room-temperature strength up

Table 6-13. Fatigue Properties of Two Nickel Silvers ls

Tensile Fatigue strength, strength, No. of Endurance

Condition ksi ksi cycles ratio

65-18 Rod, cold drawn 62.5 22 5 x 107 0.35

55-18 Strip, annealed 66 16.5 108 0.25

Hard 98 20.8 108 0.22 Spring temper 112 24.7 108 0.22 Extra spring 116 23.2 108 0.20

Copper-Base Nickel Alloys

Temperature, K 300 400 500 600 700 800

80 r--T--,.--,.--..,.--,.----.,

Vi ~ 60 ..c "& c

~ 40 (f)

T.S.

E -

40~ c C\J

c 202

o CJ"I c .2 w

o 200 400 600 800 1000 Temperature, F

Fig. 6-11. Short-time elevated-temperature tensile properties of 65-10 nickel silver, cold worked 20 %.! 5

121

to about 500 F but above that temperature there was a continuous decrease in strength with rising temperature. The ductility, as measured by the elonga­tion, also began to decrease at about 500 F and remained low up to 900 F, the highest temperature used in the investigation.

Only limited creep data have been reported for the nickel silvers. A 74 % copper-20% nickel-5 % zinc alloy, which had been cold drawn and annealed at 1200 F, had the following creep strength at 600 F:!5

Creep rate 0.00001 %/hr 0.0001 %/hr

Stress, ksi 13.8 27.8

As a basis of comparison, data in Table 6-6 indicate that CA 706 (90/10 copper-nickel) in the annealed condition had a 0.00001 %/hr creep rate at 600 F under a stress of 6.0 ksi.

Low- Temperature Properties

Like the copper-nickel alloys, the nickel silvers become stronger as the temperature is reduced and the ductility is retained. The low-temperature tensile properties of a 55% copper-30% nickel-14% zinc alloy, shown in Fig. 6-12, illustrate the effect.! 5 The strength increases continuously and at - 290 F is about 25 % higher than it is at room temperature. At the same time, the elongation increases moderately.

Izod impact tests over the range from room temperature to - 290 F

122

Temperature, K 50 100 150 200 250 300

120 ,---,.--r---,---,..--..,...---n

100

0(j)

-'<::80 £ & c::

~60 en <L>

60

c:: .............. E 40~

c:: o

20 20°g, c:: o

-400 -300 -200 -100 Temperature, F

o 100

Fig. 6-12. Subzero-temperature tensile properties of a 55 Cu-30 Ni-14 Zn nickel silver.I S

W

Chapter 6

showed that the alloy mentioned in the preceding paragraph retained its toughness down to the lowest temperature used in the investigation. 1 S The data obtained were

Temperature, F Izod impact, ft-Ib

CAST NICKEL SIL VERS

-290 79

-180 80

-80 83

-40 87

80 80

According to Vanick,16 the principal strengthening agent in the cast nickel silvers is tin. This element contributes strength and hardness, lowers the melting point, and improves the casting qualities by moderately im­proving the fluidity. Lead is used to improve the machinability but, at the same time, reduces the strength and toughness. As in the wrought types, nickel increases the tensile strength and the corrosion resistance.

In the production of nickel silver castings, rapid melting has been sug­gested as a desirable procedure to avoid gas absorption and, in addition, the crucible should be covered or the contents fluxed with inert fluxes. Triple

Copper-Base Nickel Alloys 123

deoxidation with manganese, magnesium, and phosphorus is desirable and pouring can begin as soon as the melt is quiet. Most nickel silver is cast in sand molds made up of an open sand. Heavy gates and risers are preferred. Pouring temperatures can range from 2250 to 2450 F for light castings and from 2050 to 2350 F for heavy ones. 16• 1 7

Nominal compositions of four nickel silver casting grades as stand­ardized by the Copper Development Association are given in Table 6_14. 13

Table 6-14. Nominal Compositions of Some Cast Nickel Silvers l3

Composition, %

CDANo. Cu Ni Sn Pb Zn

CA973 56 12 2 10 20 CA974 59 17 3 5 16 CA976 64 20 4 4 8 CA978 66 25 5 2 2

These alloys are designated CA 973, CA 974, CA 976, and CA 978. In this series, the copper, nickel, and tin contents increase progressively from CA 973 to CA 978. At the same time, the lead and zinc contents decrease.

Physical Properties

Typical physical properties of the four cast nickel silver alloys are given in Table 6-15,13 As in the wrought types, the melting temperature increases with the nickel content. Unlike the wrought types, however, there are no mar­ked differences in the thermal and electrical conductivities of the four alloys. The coefficient of thermal expansion increases progressively with the nickel content.

Mechanical Properties

Typical mechanical properties of these materials "as cast" in sand molds are included also in Table 6-15. Tensile strength increases progressively with nickel content from 35 ksi for CA 973 to 55 ksi for CA 978. The effects of strengthening elements are evident for these cast alloys approach the wrought nickel silvers in strength. The castings are quite ductile as indicated by the elongation, only alloy CA 978 falling below 20 % elongation. Hardness in­creases progressively with the nickel content.

Alloy CA 976 with a fatigue strength of 15.5 ksi at 108 cycles compares favorably with wrought 55% copper-18% nickel in endurance properties.

Tab

le 6

-15.

P

rop

erti

es o

f S

om

e C

ast

Nic

kel

Silv

ers!

3

CA

97

3

CA

974

C

A9

76

Phy

sica

l pr

oper

ties

M

elti

ng r

ange

, F

1850

-190

4 19

58-2

012

2027

-208

9 S

peci

fic

heat

, B

tujl

btF

0.

09

0.09

0.

09

The

rmal

con

duct

ivit

y (6

8 F

), B

tujh

rjft

2tF

jft

16.5

15

.5

13

Coe

ffic

ient

of

ther

mal

exp

ansi

on (

68-5

00 F

), p

er o

f 9.

0 x

10-6

9.

2 X

10

-6

9.3

X

10-6

Ele

ctri

cal

cond

ucti

vity

, %

lAC

S

5.7

5.5

5 M

odul

us o

f el

asti

city

, ks

i 16

,000

16

,000

19

,000

D

ensi

ty,

lbji

n.3

0.32

1 0.

320

0.32

1

Mec

hani

cal

prop

erti

es

Yie

ld s

tren

gth

(0.5

% ex

tn.)

, ks

i 17

17

24

T

ensi

le s

tren

gth,

ksi

35

38

40

E

long

atio

n (2

in.)

, %

20

20

20

F

atig

ue s

tren

gth

(10

8 cy

cles

), k

si

15.5

B

rine

ll h

ardn

ess

55

70

80

Cha

rpy

impa

ct (

V-n

otch

), f

t-lb

11

CA

978

2084

-215

6 0.

09

14.7

9.

7 X

10

-6

4.5

19,0

00 0.32

0

30

55

16

130

~

~ o :::

T II

"t

I .. CD .. 0)

Copper-Base Nickel Alloys 125

Only limited data on elevated temperatures are available on the cast nickel silvers. The stress for a creep rate of 0.00001 %/hr of alloy CA 976 is reported as 32.5 ksi at 500 F and 22.2 ksi at 550 FY

NICKEL SIL VER POWER

Nickel silver structural parts are also produced by powder metallurgy. A number of compositions are available, among which two have been stand­ardized by the American Society for Testing and Materials and the Metal Powder Industries Federation. The designations and nominal compositions are given in Table 6_16. 18 ,19 The second composition is a leaded version of the first.

Table 6-16. Compositions of Two Nickel Silver Powders l8 ,19

ASTM MPIF Density, Nominal composition, %

designation designation gjcm3 eu Ni Pb Zn

B458, Grade 1, Type I eZn-1818-U 7.5-8.0 64 18 Bal. Type II eZn-1818-W 8.0 min

B458, Grade 2, Type I eZn-1618-U 7.5-8.0 64 18 1.5 Bal. Type II eZn-1618-W 8.0 min

These specifications cover the composition of the powder and include two ranges of density. They do not cover any of the characteristics of the powder, leaving it to the fabricator to meet the density requirements and to the fabricator and customer to devise suitable limits of mechanical proper­ties.

Nickel silver P/M (powder metallurgy) parts can be produced from mixtures of elemental powders or from pre-alloyed powders. Atomization is one method by which a suitable nickel silver powder can be produced in alloy form. The properties of two types of parts produced from atomized nickel silver powders are given in Table 6-17.20

Before discussing these properties, it should be pointed out that a number of variables influence the properties developed in a PjM part. They include the characteristics of the powder, the compacting pressure, and the sintering temperature and atmosphere. Ultimately, however, the sintered density is a major factor in determining the properties developed and, for this reason, sintered densities are used in the specifications mentioned previously rather than physical or mechanical property minimums.

Tab

le 6

-17.

P

rop

erti

es o

f P

/M N

icke

l S

ilve

r P

arts

20

64 C

u-18

Ni

Sin

tere

d de

nsit

y, g

/cm

3

7.7

Phy

sica

l pr

oper

ties

C

oeff

icie

nt o

f th

erm

al e

xpan

sion

, p

er o

f 9.

2 x

10-6

Ele

ctri

cal

cond

ucti

vity

, %

lAC

S

5 M

odul

us o

f el

asti

city

, ks

i 14

,700

Mec

hani

cal

prop

erti

es

Ten

sile

str

engt

h, k

si

34.9

E

long

atio

n (1

in.

), %

14

R

ockw

ell

hard

ness

H

80

Cha

rpy

impa

ct (

unno

tche

d),

ft-l

b 10

M

odul

us o

f ru

ptur

e, k

si

66

Not

e:

Sin

tere

d at

176

0 F

, 30

min

in

nitr

ogen

aft

er p

rehe

at a

t 10

20 F

. 30

m

in i

n ni

trog

en.

·Sin

tere

d de

nsit

y 7.

9 gJ

cm3

•

8.0

9.2

X

10-6

5 14

,000

38.4

-15

-H

84"

13

77

64 C

u-18

Ni-

1.5

Pb

S

inte

red

dens

ity,

g/c

m3

7.7

8.0

9.5

X

10-6

9.

6 X

10

-6

5 5

13,0

00

14,0

00

32.1

35

.7-

15

18-

H76

H

79-

9 12

61

71

... N

0)

o :r

III " ... CD .. 0)

Copper-Base Nickel Alloys 127

Properties

As shown in the table, there is little difference in the physical properties of these two series of PjM nickel silver parts resulting from differences in sintered density. Their coefficients of expansion and their electrical resisti­vities lie in the same range as those of the cast nickel silvers discussed pre­viously. On the other hand, their moduli of elasticity are somewhat lower.

However, differences in density have a marked effect on the mechanical properties. All of these properties increase with increasing density in both compositions. The 64 % copper-I 8 % nickel alloy P/M parts are somewhat stronger and more ductile than the PjM parts produced from the 64 % cop­per-I8 % nickel-I.S % lead composition. The tensile strengths of both com­positions compare favorably with those of the cast nickel silvers. The duc­tilities of the P 1M parts, however, are somewhat lower than those of the cast nickel silvers.

REFERENCES

1. Standards Handbook, Wrought Mill Products Alloys Data, Copper Development Association, Inc. (1968).

2. J. L. Everhart, "Cupro nickels offer corrosion resistance and hot strength," Materials in Design Engineering, May 1958, p. 114.

3. Copper-Nickel Alloys, Basic Engineering Data, The International Nickel Co. Inc. (1962).

4. M. R. Gross and R. C. Schwab, "Fatigue properties of nonferrous alloys for heat exchangers and pumps," Trans. ASME J. Engineering for Power 89, 345 (1967).

5. R. P. Reed and R. P. Mikesell, Low-Temperature Mechanical Properties of Copper and Selected Copper Alloys, Monograph 101, National Bureau of Standards (1967).

6. H. J. Grover, S. A. Gordon, and L. R. Jackson, Fatigue of Metals and Structures, NAVWEPS 00--25-534, Department of the Navy (1960).

7. W. D. Jenkins, T. G. Digges, and C. R. Johnson, "Tensile properties of copper, nickel, 70% copper-30% Nickel, and 30% copper-70% nickel at high temperatures," J. Res. Nat. Bur. Std., 58, 201 (1957).

8. "Copper in cryogenics," Copper, Nos. 20 and 21, Spring and Summer, 1964, pp. 4, 6. 9. Mechanical Properties of Copper and Copper Alloys at Low Temperatures, Copper

Development Association, Inc. (1968). 10. J. S. Yanick, "Cupro-nickel castings," Foundry 80, 100 (Feb. 1952). 11. T. E. Kihlgren, "Production of pressure-tight castings of 30% cupro-nickel," Trans.

Amer. Foundrymen's Soc. 45, 225 (1937). 12. B. F. Shepherd, "Cast 70--30 cupro-nickel: inherent characteristics," Modern Castings

37, 120 (May 1960). 13. Standards Handbook, Cast Products iJata Specifications, Copper Development Asso­

ciation, Inc. (1970). 14. J. L. Everhart, W. E. Lindlief, J. Kanegis, P. G. Weissler, and F. Siegel, Mechanical

Properties of Metals and Alloys, Circular 447, National Bureau of Standards (1943). 15. J. L. Everhart, "Nickel Silvers," Materials & Methods, December 1956, p. 117.

128 Chapter 6

16. J. S. Yanick, "Nickel silver castings," Foundry 79,92 (Dec. 1951). 17. T. E. Kihlgren, N. B. Pilling, and E. M. Wise, "Physical and casting properties of

Nickel Silvers," Trans. AIME 117, 279 (1935). 18. "Nickel Silver sintered metal powder structural parts," Designation B 458-67, ASTM

Standards, Part 7, 1968. 19. PjM Material Standards and Specifications, Metal Powder Industries Federation

(1969). 20. Horsehead Metal Powders Data Sheets, New Jersey Zinc Co. (1969).

Chapter 7

Nickel-Containing

Stainless Steels

Many years ago, it was discovered that chromium increased the corrosion resistance of iron alloys. From this discovery, there has developed a large family of alloys which are termed "stainless steels," a rather inaccurate designation. In order to confer stainless properties, chromium must be pres­ent in amounts above 11.5 % but, with this as a primary requirement, the steels can also contain nickel, manganese, molybdenum, etc. Some of the steels have been standardized, others are produced on a proprietary basis. For the purpose of this chapter, the nickel-containing stainless steels will be divided into three groups: wrought, precipitation hardenable, and cast.

WROUGHT STAINLESS STEELS

There are 24 types of wrought stainless steels containing nickel which are currently designated as standard by the American Iron and Steel Institute. These are chromium-nickel and chromium-nickel-manganese steels which are austenitic in structure and are nonmagnetic in the annealed condition although some of them become slightly magnetic after being cold worked. Compositions of some of these types, together with two others which are not standard but follow the AISI numbering system, are given in Table 7_1. 1•2

This table also indicates the purposes for which the various types have been developed.

The basic composition, Type 302, is widely known as 18-8 and is a general purpose austenitic material. Including the chromium-nickel-man­ganese types, there are 22 standard materials based on Type 302. In the 300

129

Tab

le 7

-1.

Co

mp

osi

tio

ns

of

So

me

Ch

rom

ium

-Nic

ke

l an

d C

hro

miu

m-N

ick

el-

Ma

ng

an

es

e

-Col 0 S

tain

less

Ste

els!

AIS

I C

ompo

siti

on,

%

Pur

pose

ty

pe

C

Mn

Cr

Ni

Oth

er

201

0.15

5.

5-7.

5 16

-18

3.5-

5.5

0.25

N

Low

Ni

equi

vale

nt o

f Typ

e 30

1 20

2 0.

15

7.5-

10

17-1

9 4

-6

0.25

N

Low

Ni

equi

vale

nt o

f Typ

e 30

2 21

10

0.5

6 17

5.

5 1.

5 C

u

Wor

k ha

rden

ing

rate

s ap

prox

imat

e th

ose

of T

ype

304

2160

0.

08

8.25

19

.75

6 2.

5 M

o; 0

.37

N

Low

Ni

equi

vale

nt o

f ty

pe 3

16

301

0.15

2

16-1

8 6-

8 H

igh

wor

k ha

rden

ing

rate

30

2 0.

15

2 17

-19

8-10

G

ener

al p

urpo

se

304

0.08

2

18-2

0 8-

10.5

L

ow c

arbo

n m

odif

icat

ion

of

Typ

e 30

2; s

uper

ior

corr

osio

n re

sist

ance

30

4L

0.03

2

18-2

0 8-

12

Low

er c

arbo

n m

odif

icat

ion

of T

ype

304

for

wel

ding

30

5 0.

12

2 17

-19

10.5

-13

Low

wor

k ha

rden

ing

rate

30

9 0.

20

2 22

-24

12-1

5 E

leva

ted

tem

pera

ture

str

engt

h; s

calin

g re

sist

ance

30

9s

0.08

2

22-2

4 12

-15

Low

car

bon

mod

ific

atio

n o

f Typ

e 30

9 fo

r w

eldi

ng

310

0.25

2

24-2

6 19

-22

Hig

her

elev

ated

tem

pera

ture

str

engt

h an

d sc

alin

g re

sist

ance

th

an T

ype

309

310s

0.

08

2 24

-26

19-2

2 L

ow c

arbo

n m

odif

icat

ion

of T

ype

310

for

wel

ding

31

6 0.

08

2 16

-18

10-1

4 2-

3 M

o M

olyb

denu

m a

dded

to

impr

ove

corr

osio

n re

sist

ance

31

6L

0.03

2

16-1

8 10

-14

2-3

Mo

Low

car

bon

mod

ific

atio

n o

f T

ype

316

for

wel

ding

31

7 0.

08

2 18

-20

11-1

5 3-

4 M

o Im

prov

ed c

orro

sion

res

ista

nce

over

Typ

e 31

6 32

1 0.

08

2 17

-19

9-12

5

x C

min

Ti

Stab

iliz

ed f

or w

eldi

ng;

for

serv

ice

in c

orro

sion

res

istin

g ap

plic

atio

ns

347

0.08

2

17-1

9 9-

12

10 x

C m

in C

b-T

a S

ame

as T

ype

321

384

0.03

2

15-1

7 17

-19

Low

er w

ork

hard

enin

g ra

te t

han

Typ

es 3

04 a

nd 3

85

0 38

5 0.

08

2 11

.5-1

3.5

14-1

6 L

ower

wor

k ha

rden

ing

rate

tha

n T

ype

304

:T

III

"C ..

Not

e:

Sin

gle

valu

es i

ndic

ate

max

imum

. CD

.. "N

ot

AIS

I st

anda

rd s

teel

., ty

pica

l ana

lyse

s (R

ef.

2).

Ooo,j

Nickel-Containing Stainless Steels 131

series, the chromium-nickel ratio has been altered to change the forming characteristics; the carbon content has been reduced to prevent intergranu­lar corrosion after welding; columbium or titanium have been added to stabilize the structure; molybdenum has been added to improve the corro­sion resistance in some environments; or elements such as selenium have been added to improve the machinability. In the 200 series, the desirable austenitic structure has been maintained by replacing part of the nickel with manganese, nitrogen, or copper.

Thus a series of steels has evolved, each having a specific purpose. For example, the chromium-to-nickel ratio in Type 301 has been adjusted to obtain a material having a high rate of work hardening and that in Type 305 to achieve a low rate of work hardening. Recent additions to the AISI stand­ard steels are Types 384 and 385, which have compositions adjusted to work harden at a lower rate than Type 304.

Types 303 and 303Se are free-machining modifications of Type 302 produced by adding sulfur and selenium respectively. The machinability of these two types is perhaps 15 % better than Type 302, for example.

If chromium-nickel stainless steels are heated for long periods or cooled slowly through the temperature range 1450 to 800 F, chromium carbides tend to deposit at the grain boundaries. This robs the adjacent areas of chromium and makes these areas less resistant to corrosive attack than the bulk of the metal. Exposure of the steel in this condition to corrosive environ­ments can result in intergranular failure, a type which often develops adjacent to a weldment.

There are two methods of avoiding intergranular attack. First, the car­bides can be redissolved by heating in the range 1800 to 2050 F and quench­ing in water. Second, precipitation can be avoided by using modified types of steels. This is the reason for the development of the extra-low-carbon types, such as 304L and 316L, and of the stabilized types, 321 and 347. The former minimize chromium carbide precipitation, the latter avoid it. All four can be used in the as-welded condition without post-weld heat treatment.

In both Types 309 and 310, the chromium and nickel contents have been increased considerably over the nominal 18 % chromium-8 % nickel composi­tion. These materials were developed for service at elevated temperatures where scaling resistance is important.

Alloys of the 200 series were developed to conserve nickel while at the same time retaining the properties of the corresponding alloys of the 300 series as closely as possible. For esample, Type 201 can be used as a replace­ment for Type 301 and Type 216 can replace Type 316. The latest alloy in this series, Type 211, has a work hardening rate closely matching that of Type 304 and can be used as a replacement for the latter in deep drawing and roll forming operations. 2

Tab

le 7

-2.

Ph

ysic

al P

rop

erti

es o

f S

om

e W

rou

gh

t S

tain

less

Ste

els

l,z

,3

AIS

I ty

pe

201

216

304

309

310

316

Mel

ting

ran

ge,

F 25

50-2

650

2550

-265

0 24

50-2

650

2500

-255

0 Sp

ecif

ic h

eat

(32-

212

F),

Btu

/lb

rF

0.12

0.

12

0.12

0.

12

The

rmal

con

duct

ivit

y (2

12 F

),

Btu

/hr/

ftZ

rF/f

t 9.

4 9.

0 8.

2 9.

4 C

oeff

icie

nt o

f th

erm

al e

xpan

sion

(3

2-12

00 F

), p

er o

f 10

.1

x 10

-6 a

11

.2 X

10

-6 b

10

.4 X

10

-6

10.0

X

10-6

9.

7 X

10

-6

10.3

X

10

-6

Ele

ctri

cal

resi

stiv

ity,

ohm

s/ci

r m

il ft

42

4 42

0 43

3 46

9 46

9 44

5 M

agne

tic

perm

eabi

lity

(H

=

20

00

e)

Ann

eale

d 1.

004

1.00

3 1.

004

1.00

3 1.

003

1.00

4 C

old

wor

ked,

65

%

1.02

1 2.

12

1.00

4 1.

0070

Col

d w

orke

d, 8

0-90

%

4.75

1.

010

Mod

ulus

of

elas

tici

ty,

ksi

28,6

00

28,0

00

29,0

00

29,0

00

28,0

00

Mod

ulus

of

rigi

dity

, ks

i 12

,500

D

ensi

ty,l

b/in

.3

0.29

0.

29

0.29

0.

29

0.29

0.

29

'32

-90

0 F

. .6

8-1

80

0 F

. 'C

old

wo

rked

60

%.

347

2550

-260

0 0.

12

9.3

10.6

X

10-6

439 1.

004

1.44

0

4.12

28

,000

0.29

... W

N 0 :r

III

"C .. CD ... .....

Nickel-Containing Stainless Steels 133

Physical Properties

Typical physical properties of representative austenitic stainless steels are given in Table 7_2.1. 2 • 3 Several of the properties of these steels are almost identical, for practical purposes, regardless of the composition.

They have densities of about 0.29 lbjin. 3, specific heats of about 0.12 BtujlbtF, and tensile moduli of elasticity of 28,000 to 29,000 ksi. The elec­trical resistivities reflect the alloy content. The various modifications of 18-8, i.e., Types 201,216,304,316, and 347, have resistivities which are quite close together. There is a marked increase in resistivity in Types 309 and 310, which have higher chromium and nickel contents. The thermal conductivity shows a similar trend, the lowest conductivity being that of Type 310.

All of these alloys are practically nonmagnetic in the annealed condition. Cold work affects them to different degrees. Types 304 and 347 become more magnetic after severe cold work than the other alloys which have been included in Table 7-2. The stability of the austenitic structure in Types 216, 316, and 310 is indicated by the very slight effect that cold work has on the permeabilities of Types 216 and 316 and the absence of any effect in Type 310.

Mechanical Properties

Room- Temperature Properties

The austenitic stainless steels can be strengthened only by cold work. Heat treatment is used to soften the material as an intermediate step in cold working, to redissolve the carbides after cold working as mentioned previous­ly, or for stress relieving.

Tensile Properties. Typical tensile properties of representative chro­mium-nickel and chromium-nickel-manganese stainless steels are given in Table 7_3. 1 •2 As indicated in the table, Type 301 can be worked to achieve high tensile strengths. Type 201 has similar characteristics and is a satisfac­tory substitute for Type 301 in many applications.

Type 304 has become the most widely used of the austenitic stainless steels, having to a great extent replaced Type 302 because of its superior corrosion resistance. The tensile properties of annealed Type 304 are repre­sentative of a group which includes most of the 18 % chromium-8 % nickel modifications of Type 302. Type 304L, the low carbon modification of Type 304, has moderately lower tensile properties than the latter.

Type 305 has a lower work hardening rate than Type 304, and the recent­ly standardized Types 384 and 385 also have lower work hardening rates than Type 304. As indicated by the reduction of area values included in Table

134 Chapter 7

Table 7-3. Nominal Tensile Properties and Hardness Values of Some Wrought Stainless Steels\,2

Yield strength Tensile Elongation Reduction (0.2 % offset), strength, (2 in.), of area, Rockwell

Form and condition ksi ksi % % hardness

Chromium-nickel steels Type 301

Sheet and strip Annealed 40 110 60 B85 Half hard temper 11 ()a 15()a 18a C32 Hard temper 140- 185a 9a C41

Type 304 Sheet and strip

Annealed 42 84 55 B80 Bars

Annealed 35 85 60 70 Cold drawn 60--95 100--125 60--25

Wire Annealed 35 90--105 60b 65 B83 Soft temper 60--90 100--125 45b 65 B95 Hard temper 105-125 140--160 25b 55 C33

Type 304L Sheet and Strip

Annealed 39 81 55 B79

Type 305 Sheet and strip

Annealed 38 85 50 B80 Wire

Annealed 47 85 60b 77 B78 Soft temper 54 100 58b 74 B82

Types 309 and 309s Sheet and strip

Annealed 45 90 45 B85 Bars

Annealed 40 95 45 65 B83 Wire

Soft temper 70--80 105-125 35b 60 B98

Types 310 and 310s Sheet and strip

Annealed 45 95 45 B85 Bars

Annealed 45 95 50 65 B89 Wire

Soft temper 75-90 105-125 30b 60 B98

Type 384 Wire

Annealed 35 75 55b 72 B70

Nickel-Containing Stainless Steels 135

Yield strength Tensile Elongation Reduction (0.2 % offset), strength, (2 in.), of area, Rockwell

Form and condition ksi ksi % % hardness

Type 385 Wire

Annealed 30 72 55b 78 B66

Chromium-nickel-manganese steels Type 201

Sheet and strip Annealed 55 115 55 B90 Half hard temper 110a 15Qa 15a C32 Hard temper 14Qa 185a 8a C41

Type 211 Sheet and strip

Annealed 30 89 64 B74 Cold worked, 60 % 169 188 C43

Type 216 Rod Annealed 58 107 53 76 B91

aMinimum. "Gage length 4 x diameter.

7-3, all three of these alloys are markedly more ductile in wire form than Type 304. Type 211 is a chromium-nickel-manganese steel, deVeloped to conserve nickel, which has a work hardening rate approximating that of Type 304.

Types 309 and 310 are more highly alloyed than the other materials discussed above and this compositional difference is reflected in their some­what greater strengths in the annealed condition.

Type 216, the chromium-nickel-manganese alloy developed as a lower nickel modification of Type 316, is considerably stronger than the latter which has tensile properties similar to those shown for Type 304 in the table.

Figure 7_1,2,3 indicates the effect of cold work on the yield strengths of several of the steels mentioned above. It is apparent that Types 201 and 301 work harden at a much higher rate than the other materials shown on the graph and have characteristics which are quite comparable, over at least a part of the range. Type 305 has a lower work hardening rate than Type 304 whereas Type 211 shows comparable rates with Type 304 up to about 40 % reduction, above which it work hardens at a higher rate than the latter.

Hardness. Nominal Rockwell hardness values for a group of austenitic stainless steels in various forms and conditions are shown also in Table 7-3. Hardness ranges from Rockwell B80-85 for annealed material to C33-43 for cold worked material. Composition appears to have little effect on the hardness of these materials in the annealed condition. However, the hardness

136

240

"(j}200 ..>c:.

~ Q) If)

160 '+-'+-0

~ N

g 120 ..c 0, c Q) 80 ~

ifj

"0 Qi 40 ):.

o 10 20 30 40 50 60 Cold Work, %

Fig. 7-1. Effect of cold work on the yield strengths of several wrought stainless steels. 2, 3

Chapter 7

120 ,----r------,--,.....----,---r----r----,

100

E 80 -.J Q) u e 60 ::::l

"0 C

W 40

80 100 120 140 160 180 200 220 Tensile Strength, ksi

Fig. 7-2. Relationship between the endurance limits and the tensile strengths of wrought chromium-nickel stainless steels. 3

Nickel-Containing Stainless Steels 137

after cold work varies. Types 201 and 301 harden to a greater degree than Type 304 with the same amount of cold work. Insufficient data are available for other comparisons.

Fatigue Properties. Representative endurance limits for a number of austenitic stainless steels are given in Table 7_4.1,2,3 The endurance limit ranges from 32-39 ksi for annealed material to 62-88 ksi for cold worked

TalJle 7-4. Fatigue Properties of Some Wrought Stainless Steels

Tensile Endurance strength, limit, Endurance

Form and condition ksi ksi ratio Ref.

Type 301 Sheet and strip

Annealed 110 35 0.32 Hard temper 185a 80

Type 302 Bars

Annealed 85 34 0.40 1 Hard temper 185a 70-80 3

Type 304 Sheet and strip

Annealed 84 35 0.42 Bars

Annealed 85 34 0.40 Half hard temper 150a 70 3

Type 310 Annealed 95 32.5 0.33 3

Type 316 Sheet and strip

Annealed 84 39 0.46 Bars

Annealed 80 38 0.48 Cold drawn 90 40 0.44

Type 321 Annealed 85 38 0.45 3

Type 347 Annealed 90 39 0.43 3 Three-quarter hard temper 175a 88 3

Type 216 Annealed 115 62.5 0.54 2

aMinimum.

138 Chapter 7

materials; the greater spread of the latter arises from the different degrees of cold work. With the exception of Types 301, 310, and 216, the endurance ratios of annealed steels range from 0.40 to 0.48. Types 301 and 310 had endurance ratios of 0.32 and 0.33 respectively, whereas Type 216 had a ratio of 0.54. The relationship between the tensile strength and the endurance limit of chromium-nickel stainless steels is indicated in Fig. 7-2.3

Unlike ferritic steels, these austenitic stainless steels are not notch sensitive. For example, a 60-deg. notch with a 0.010 in. root radius increased the endurance limit of a Type 304 steel from 36 to 43 ksi. 3

Impact Properties. Notch impact properties of a number of stainless steels in the annealed condition are given in Table 7-5.3 There is greater variation in the Charpy test, using a keyhole notch, than in the other tests,

Table 7-5. Impact Properties of Some Annealed Wrought Stainless Steels3

Izod Charpy impact, ft-lb AISI impact, type ft-lb Keyhole notch V-notch

201 76 202 85a

301 70-120 40 110 302 70-120 68-92 100-304 100-120 70-97 100a

304L 65 309 90-120 310 90-110 80 89

aMinimum.

but all three methods indicate that these steels are tough materials. Additional data on impact are included under low-temperature properties.

Elevated- Temperature Properties

Short-time elevated-temperature tensile strengths of selected chromium­nickel and chromium-nickel-manganese stainless steels in the annealed con­dition are plotted in Fig. 7-3 for the purpose of pointing out certain proper­ties of the steels. 2•4 These materials are representative of the groups of wrought steels under discussion.

Although Type 316 has approximately the same tensile properties in the annealed condition at room temperature as Type 304, they differ markedly at elevated temperatures. Type 316 retains its short-time strength

Nickel-Containing Stainless Steels

·in .Y.

..c Q, c Q.l ~

if)

~ in c ~

Temperature, K

300 500 700 900 1100 1300 120 ,...,----r----r---,----,.----,-,

100

80

60

40

20

o 400 800 1200 1600 2000 Temperature, F

Fig. 7-3. Short-time elevated-temperature tensile stren­gths of some wrought stainless steels. 2.4

139

to considerably higher temperatures than Type 304 and has practically the same tensile strength as the more highly alloyed Type 310 in the moderate­temperature range. Limited data on Type 216, a recent addition to the chro­mium-nickel-manganese series, indicate that this steel has higher short-time tensile properties at elevated temperatures than either Type 316 or Type 310. All of the materials included in this graph lose strength quite rapidly at temperatures above 1600 F and approach a common value.

Greep and stress-rupture properties of several compositions are given in Table 7-6. 4 As indicated in the table, the creep properties of Types 316 and 347 are superior to those of Type 304 at moderate temperatures. For example, the 0.0001 %/hr creep stress of Type 347 at 1200 F is twice that of Type 304.

For moderate exposure time (0.0001 %/hr), Types 347 and 310 have almost identical creep properties and the creep strength of Type 316 ap­proaches these values. For longer exposure (0.00001 %/hr), Type 347 is markedly superior to types 316 and 310 up to about 1200 F but above that temperature all have approximately the same properties. Above 1500 F, all of the materials listed in the table have very low resistance to creep. This is true also of the other wrought chromium-nickel stainless steels of the

140 Chapter 7

Table 7-6. Creep and Stress-Rupture Properties of Some Annealed Wrought Stainless Steels4

Test Stress (ksi) for creep rate of Stress (ksi) AISI temperature, for rupture type F 0.00001 %/hr 0.0001 %/hr in 100 hr

304 1000 12 20 47 1200 4 8 23 1500 1 2 7

310 1000 18 33 38 1200 8 15 26 1500 2 3 11

316 1000 17 25 1200 7 12 32 1500 2 3 9

347 1000 28 32 54 1200 10 16 28 1500 1 2 9

Temperature, K 50 100 150 200 250 300

320

280

If) 240 .x:

.c 0> ~ 200

en ~ . iii

160 c: ~

120

80 -400 -300 -200 -100 0 100

Temperature, F

Fig. 7-4. Subzero-temperature tensile strengths of some wrought stainless steels in the annealed condition. S, 6

Nickel-Containing Stainless Steels 141

AISI series. A comprehensive review of the elevated-temperature properties of these steels is contained in reference 4.

Low-Temperature Properties

The tensile strengths of the austenitic stainless steels increase as the temperature is reduced into the subzero range. As shown in Fig. 7_45 • 6 , the strengths of annealed materials at -320 F are more than double their room­temperature strengths. Type 301, strongest at room temperature, retains its superiority at low temperatures.

Figure 7_55,6 shows similar data for full hard materials. Although Types 301 and 304 have practically the same tensile strength at room temperature, the former is superior at -320 F. The increase in strength of Type 304L is parallel to that of Type 304, but strength is lower at all temperatures as a result of the lower carbon content.

Temperature, K 50 100 150 200 250 300

360 r-----,----,----,,..--,..---,..---T'"I

320

280

.c "6>240 c ~

en ~ 200 'Vi c Q)

~ 160

120

-400 -300 -200 -100 Temperature, F

o 100

Fig. 7-5. Subzero-temperature tensile strengths of some wrought stainless steels in the full-hard condition. 5, 6

142 Chapter 7

Table 7-7. Fatigue Strengths of Several Wrought Stainless Steels at Subzero Temperatures

Test Tensile Fatigue strength AISI temperature, strength, (10 6 cycles), type Form and condition F ksi ksi Ref.

301 Sheet, extra full hard 70 241 74 7 -320 116 -423 96

302 Annealed Room 35 5 -40 42

302 Cold worked Room 62 5 -40 75

304 Bar, cold reduced 70 212 115 7 -110 130 -320 155

Table 7-8. Impact Properties of Some Wrought Stainless Steels at Subzero Temperatures7

Test Charpy impact AISI temperature, (keyhole notch), type Form and condition F ft-lb

301 Plate, annealed Room 91 -100 93 -200 84 -320 79

304 Bar, annealed Room 76 -100 82 -200 81 -320 80

Bar, cold reduced 20% Room 50 -100 51 -200 51 -320 51

310 Annealed Room 80 -100 70 -200 66 -320 61

321 Plate, annealed Room 70 -100 71 -200 63 -300 48

347 Plate, annealed Room 58 -100 55 -200 54 -320 54

Nickel-Containing Stainless Steels 143

Endurance tests indicate that the fatigue strength also increases as the temperature is reduced below zero, at least to temperatures of the order of -320 F. However, the fatigue strength of Type 301 sheet in the extra full hard condition appears to be lower at -423 F than at -320 F. Data on several steels are given in Table 7-7. s. 7

Data on notched bar· impact tests on a number of stainless steels are given in Table 7-8. 7 All of the materials are quite tough but there is some variation in properties. The impact resistance of all of the alloys excepting Type 304 falls moderately from room temperature to -320 F. On the other hand, Type 304 in the annealed condition shows an increase in toughness at subzero temperatures down to -320 F. In the cold worked condition (20% reduction), the impact resistance of Type 304 is practically the same at room temperature as it is at -320 F.

PRECIPITATION HARDENABLE STAINLESS STEELS

The precipitation hardenable stainless steels which will be considered here are proprietary chromium-nickel steels to which additional elements have been added to permit hardening by precipitation reactions. As pointed out by Rosenberg,8 these steels may be divided into three groups:

1. Martensitic, which includes Stainless Wand 17-4 PH, for example. These steels are normally martensitic after solution treatment. High strength is developed by a single low-temperature aging treat­ment.

2. Semiaustenitic, which includes AM-355, 17-7 PH, and PH 15-7Mo as examples. These steels are austenitic as supplied by the producer and a two-stage heat treatment is required to develop their aged properties. This treatment involves an austenite conditioning treat­ment followed by heating to a designated temperature to achieve transformation to martensite, and this in turn is followed by a pre­cipitation hardening heat treatment.

3. Austenitic, which includes HNM, 17-IOP, 17-14CuMo, and A 286. These steels are austenitic regardless of heat treatment and improve­ments in strength are achieved by single or double precipitation hardening heat treatments.

New alloys of each type are being continually introduced but those mentioned are representative. Their compositions and producers are given in Table 7-9,8 which also includes designations assigned to some of them by the American Iron and Steel Institute. 9

Tab

le 7

-9.

No

min

al C

om

po

siti

on

s o

f S

om

e P

reci

pit

atio

n H

ard

enab

le S

tain

less

Ste

els

8•9

AIS

I C

ompo

siti

on,

%

type

N

ame

Pro

duce

r C

M

n C

r N

i M

o O

ther

Mar

tens

itic

ste

els

635

Stai

nles

s W

U

. S.

Ste

el

0.07

0.

50

17

7 0.

70 T

i; 0

.20

Al

630

17--

4 P

H

Arm

co

0.04

0.

25

16

4 3.

2 C

u; 0

.25

Cb

-Ta

Sem

iaus

teni

tic

stee

ls

633

AM

350

A

llegh

eny

Lud

lum

0.

10

0.80

16

.5

4.3

2.75

0.

10 N

63

4 A

M 3

55

Alle

ghen

y L

udlu

m

0.13

0.

95

15.5

4.

3 2.

75

0.10

N

631

17-7

PH

A

rmco

0.

07

0.60

17

7

1.15

Al

632

PH

15-

7 M

o A

rmco

0.

07

0.60

15

7

2.2

1.15

Al

Aus

teni

tic

stee

ls

HN

M

Cru

cibl

e 0.

30

3.50

18

.5

9.5

17-1

0 P

Arm

co

0.12

0.

75

17

10

653

17-1

4 C

uMo

Arm

co

0.12

0.

75

16

14

2.5

3 C

u; 0

.25

Ti;

0.5

0 C

b-T

a 66

0 A

-286

A

llegh

eny

Lud

lum

0.

06

1.50

15

26

1.

2 1.

8 T

i; 0

.2 A

I; 0

.3 V

... t (')

:T

DI

'0 S' .. ....

Ta

ble

7-1

0.

Ph

ysic

al P

rop

ert

ies

of

So

me

Pre

cip

ita

tio

n H

ard

en

ab

le S

tain

less

Ste

els

9•1

0

Sta

inle

ss W

A

M 3

55

17-7

PH

H

NM

Ann

eale

d A

ged

Con

do H

S

CT

C

on

d A

. T

H-1

050

RH

-950

A

ged

The

rmal

con

duct

ivit

y, B

tu/h

r/ft

2;oF

/ft

10.8

12

.1

8.72

9.

8 9.

8 C

oeff

icie

nt o

f th

erm

al e

xpan

sion

(6

8-93

2 F

), p

er o

f 6.

3 x

10-6

9.

4 X

10

-6

7.2

X 10

-6

9.6

X 10

-6 a

6.

6 X

10

-6 a

6.9

X 10

-6 a

10.3

X 10

-6 b

Ele

ctri

cal

resi

stiv

ity,

ohm

s/ci

r m

il f

t 60

2 51

1 45

7 48

1 49

3 49

9 46

3 M

agne

tic

perm

eabi

lity

(H

=

100

Oe)

81

10

1 1.

4-3.

5 80

-99

75-8

7 1.

003

c

Mod

ulus

of

elas

tici

ty,

ksi

26,9

00

27,8

00

29,3

00

29,0

00

29,0

00

29,0

00

29,0

00

Mod

ulus

of

rigi

dity

, ks

i 11

,200

11

,600

11

,400

P

oiss

on's

rat

io

0.20

0.

20

Den

sity

,lb/

in.3

0.

28

0.28

0.

286

0.28

1 0.

282

0.27

6 0.

276

0.28

4

·70

to

800

F.

'80

to

100

0 F

. 'H

=

20

00

•.

z (;. ~ ~ (") o :::J ... !!.

:::J 5'

cc

tJl ... !!.

:::J if <II tJl ... CD

CD iii ... .,.. UI

146 Chapter 7

Physical Properties

Physical properties of representative alloys in each of the three groups are given in Table 7_10. 9 • 10 Data are presented in both the solution annealed and aged condition for several of the materials. The conditions shown in the table, such as SeT for example, indicate the heat treatment which has been performed. These heat treatments are given as footnotes to Table 7-11.

As shown in the table, aging has little effect on most of the physical properties of the martensitic steels, as represented by Stainless W. The excep­tion is the electrical resistivity, which is considerably lower in the aged condition than in the solution-annealed condition. These steels are magnetic even in the annealed condition.

The semi austenitic steels, represented by AM-355 and 17-7PH, show definite effects of aging. The coefficients of thermal expansion are much lower in the aged condition than in the solution-annealed condition and approach those of the martensitic steels, such as Stainless W. The electrical resistivities show moderate increases as a result of aging and, in the aged condition, approach those of the standard steels, Types 309 and 310. However the most pronounced effects occur in the magnetic properties. In the solu­tion-annealed condition, these steels are only faintly magnetic but, after aging, they become quite strongly magnetic.

The austenitic steels, as represented by HNM, do not differ greatly from steels of the 300 series in their physical properties. The electrical resistivity is quite close to that of Type 310. Even in the aged condition, alloys of this type are no more magnetic than the standard chromium-nickel stainless steels in the annealed condition.

Mechanical Properties

Room- Temperature Properties

The compositions of the precipitation harden able steels are adjusted to permit hardening by various heat treatments. A comprehensive discussion of the effects of various thermal theatments on the properties of steels of the types under discussion is given by Slunder, Hoenie, and Hall. 12

Tensile Properties. Representative tensile properties of a number of the precipitation hardenable stainless steels, in various conditions, are given in Table 7_11. 9 • 10 The aging treatments are among those recommended by the producers. Other aging treatments have also been suggested to develop different combinations of properties and some are given in reference 10.

Both the martensitic and semiaustenitic steels can be aged to achieve tensile strengths in excess of 200 ksi. They differ somewhat in ductility,

Ii:lUI~ I-I I.

I

yplC

i:l1

IVle

Cn

am

Ca

l t"

rop

en

les

OT

:so

me

t'r

ec

lplt

atl

on

Ha

rde

na

ble

Sta

inle

ss

Ste

els

Y,lU

All

oy

Sta

inle

ss W

17-4

PH

AM

-350

AM

-355

17-7

PH

PH

15-

7 M

o

HN

M

17-1

0 P

17-1

4 C

uM

o

A 2

86

aCha

rpy

impa

ct,

V-n

otch

. "'

Not

es o

n h

eat

trea

tmen

ts:

Con

diti

on*

Sol

. tr

eate

d A

ged

Sol.

trea

ted

Age

d C

ondo

H

Con

do S

CT

C

ondo

H

Con

do S

CT

C

on

d.A

C

ondo

TH

-I05

0 C

ondo

RH

-950

C

ondo

A

Con

do T

H-I

050

Con

do R

H-9

50

Sol

. tr

eate

d A

ged

Sol.

trea

ted

Age

d So

l. tr

eate

d A

ged

Sol

. tr

eate

d A

ged

Yie

ld s

tren

gth

(0.2

% of

fset

),

ksi 95

105

110

185 60

17

3 57

182

40

190

210 55

205

215 50

79

38

88

41

Sta

inle

ss W

S

olut

ion

trea

ted

1900

F,

2-4

hr,

air

coo

led,

age

d 95

0 F

. 17

-4 P

H

Sol

utio

n tr

eate

d 19

00 F

, oi

l qu

ench

ed,

aged

900

F.

AM

-350

an

d A

M 3

55

Con

diti

on H

S

olut

ion

trea

ted

at 1

850-

1950

F

Ten

sile

E

long

atio

n R

educ

tion

st

reng

th,

(2 i

n.),

o

f ar

ea,

ksi

%

%

135

14

16

210

10

25

150

12

45

200

14

50

145

40

206

13.5

16

0 26

21

6 19

38

13

0 35

20

5 9

225

6 13

0 35

21

5 7

235

6 11

6 58

60

13

5 26

40

89

70

76

13

7 25

39

89

45

59

146

25

37

Con

diti

on S

CT

S

olut

ion

trea

ted

1850

-195

0 F

; co

ndit

ion

anne

al 1

710

F;

refr

iger

ate

at -

10

0 F

, 3

hr;

age

at

850

F,

3 hr

. 17

-7 P

H a

nd

PH

15-

7 M

o

Con

diti

on A

S

olut

ion

trea

ted

at 1

950

F.

Con

diti

on T

H-l

05

0

Con

diti

on a

t 14

00 F

, 1.

5 h

r; c

oo

l to

60

F m

ax

wit

jlin

1 h

r; a

ge 1

050

F,

1.5

hr.

Roc

kwel

l ha

rdne

ss

C26

C

44

C44

C

20

C45

B85

C

43

C47

B

88

C44

C

48

C38

C

I0

C30

Con

diti

on R

H-9

50

Con

diti

on a

t 17

50 F

, 10

min

, ai

r co

ol;

coo

l to

-1

00

F,

ho

ld 8

hr,

air

war

m t

o r

oo

m t

empe

ratu

re;

age

at 9

50 F

, I

hr.

HN

M a

nd

17-

IOP

S

olut

ion

trea

ted

2050

F,

0.5

hr,

wat

er q

uenc

h; a

ge 1

300

F,

16 h

r fo

r H

NM

, 24

hr

for

17-I

OP

. 1

7-1

4C

uM

o

Sol

utio

n tr

eate

d at

205

0 F

, 0.

5 hr

, ag

e 13

50 F

, 5

hr.

A

286

S

olut

ion

trea

ted

at 1

800

F,

aged

at

1325

F.

Izod

im

pact

, ft

-Ib

60

14

20

14<'

17"

11"

64"

z n ,.. !. , 0 0 :::J

... .. 5'

:::J

IC en ... .. 5'

iD

<II

<II en ... CD

CD

iii ... .... ....

148 Chapter 7

however. The elongation of Stainless W, for example, is slightly lower in the aged than in the annealed condition but that of 17-7 PH is markedly lower. Elongation in Condition A is four times higher than that in Condition TH-1050. (The designations for condition are explained in the footnotes to Table 7-11).

Aging of the austenitic alloys does not result in so great an improvement in tensile strength, the maximum reaching approximately the 140 ksi level. In these materials, also, although the ductility as measured by the elongation and reduction of area is reduced by aging, the effect is less drastic than it is in the other two series of alloys.

Hardness. Rockwell hardness values for a number of the alloys are included also in Table 7-11. The hardness values range from B85 to C48, but most ofthese alloys are considerably harder even in the solution-annealed condition than the standard chromium-nickel steels in the annealed condition As an example of the improvement resulting from aging, PH 15-7Mo had a Rockwell hardness of B88 in Condition A and one of C48 after aging to Con­dition RH-950.

Impact Properties. Limited data on impact resistance are included also in Table 7-11. They indicate that the martensitic and semiaustenitic steels are not particularly tough in the aged condition. On the other hand, the austenitic alloys show excellent toughness in the aged condition. Additional impact data are given under low-temperature properties.

Elevated- Temperature Properties

Short-time elevated-temperature tensile strengths of several of the steels are plotted in Fig. 7_6. 10 It is noteworthy that these steels retain their strengths quite well at moderately elevated temperatures and they are used for applica­tions in the range 600 to 1000 F, for example. Since this service range extends into the precipitation hardening range, additional aging may occur in service. This effect is indicated by the increase in tensile strength of one of the steels in the 750 to 800 F range.

The steels have good creep and stress-rupture properties at moderately elevated temperatures. Data on several compositions are included in Table 7-12.10 There is considerable variation in the materials. For example, at 1000 F the stress for rupture in 100 hours ranges from 31.5 ksi for Stainless W, a martensitic steel, to 70 ksi for AM-355, a semiaustenitic steel and to 86 ksi for HNM, an austenitic steel, all three materials being tested in the aged condition. At 1200 F, the stress for rupture in 100 hours of HNM is four times that of Stainless W.

Nickel-Containing Stainless Steels

Temperature, K

300 400 500 600 700 800 900 250 ~~--r---~--~--~--~---n

200 en ~

~ 150 0. c:

<I.l "-(jj

~ 100 "Vi c: ~

50

o 200 400 600 800 1000 1200 Temperature, F

Fig. 7-6. Short-time elevated-temperature tensile strengths of some precipitation hardenable stainless steels.! 0 (1) AM 350, condition SCf; (2) 17-7PH, condition TH 1050; (3) Stainless W, aged; (4) HNM, solution annealed 2050 F, oil quenched, aged 1350 F,16 hr.

Table 7-12. Creep and Stress-Rupture Properties of Some Precipitation Hardenable Stainless Steels!O

149

Test Stress (ksi) for creep rate of Stress (ksi) temperature, for rupture

Alloy Condition'" F 0.00001 %/hr 0.0001 %/hr in lOOhr

Stainless W Aged 1000 31.5 1200 12.5

17-4 PH Aged 800 45 60 140 900 23 95

AM-350 SCT 800 28 107 190 1000 70

AM-355 SCT 800 30 97 190 1000 75

17-7 PH TH-I050 800 45 60 110 900 78

HNM Ageda 1000 86 1200 49

'See notes to Table 7-11. -Solution treated 2000 F, 0.5 hr, oil quenched, aged 1400 F, 16 hr air cooled.

150 Chapter 7

Low- Temperature Properties

The strengths of the precipitation harden able stainless steels, like those of the standard austenitic stainless steels, increase markedly with falling temperatures. However, ductility, as measured by the elongation, is more seriously affected than it is in the standard steels. The temperature at which a significant decrease in elongation occurs depends on the alloy and on the aging conditions. Figure 7-7, showing the tensile properties of 17-7PH, Condition TH-I050, at low temperatures is a typical example of the improve­ment in strength and loss in elongation. I I

The precipitation hardenable steels of the martensitic and semiaustenitic types are martensitic after heat treatment. They become less tough as the testing temperature is reduced but the percentage loss in impact resistance depends on the alloy and its condition. Some indication of this effect is apparent from the data included in Table 7_13.7,10.12 This is particularly indicated by the data for 17-4PH under several aging conditions. The tough­ness is significantly improved at least to temperatures down to -110 F by aging at higher temperatures.

en ..x:

280

260

240

~- 220 ~ en

200

180

Temperature, K

50 100 150 200 250 300

c 20 N

c o

'';:::

10 g, c o W 160 L..-....L...-_--L.. __ I.-_....1-_~ _ ____I 0

-400 -300 -200 100 o 100 Temperature, F

Fig. 7-7. Subzero-temperature tensile properties of 17-7PH, con­dition TH 1050. 11

Nickel-Containing Stainless Steels

Table 7-13. Impact Properties of Some Precipitation Hardenable Stainless Steels at Subzero Temperatures7 ,10,12

Charpy impact (V-notch), ft-Ib, at temperature indicated

151

Alloy Condition* -230F -llOF Room

17-4 PH Condo H-925 3.5 5.5 30 Condo H-I025 4.5 15 75 Condo H-1l50 6.5 48 95

AM-350 SCT 4 9 14 17-7 PH TH 1050 2 4 6 HNM Aged 5 10 A 286 Aged 57 68 64

'See notes to Table 7-11.

Even in an austenitic steel, such as HNM, the resistance to impact at low temperatures is significantly lower than that of the standard steels. Again pointing to the differences resulting from composition, another austenitic steel, A 286, retains excellent resistance to impact at temperatures at least as low as -320 F.

CAST STAINLESS STEELS

Quite a number of stainless and heat resisting steels are produced in cast form. All contain chromium and some also contain nickel. The designations and compositions of modern American cast chromium-nickel stainless steels have been standardized by the Alloy Casting Institute, which prefers to call these materials "High Alloy Castings." The ACI divides the alloys into two groups: those intended primarily for corrosion resisting applications are identified by the letter C, those intended for heat resistant service above 1200 F, by the letter H. There are approximately 26 compositions in the two series which contain nickel in addition to chromium.

The American Society for Testing and Materials uses the ACI designa­tions in its standards, and some of the compositions of these alloys are given in Table 7_14.13.14 For reference purposes, the nearest applicable wrought alloy composition, as designated by the AISI, is also indicated in Table 7-14.

It should be noted that the chemical compositions of the wrought and cast types differ and, therefore, the alloys are not strictly comparable. How­ever, the purposes for which modifications of the original 18 % chromium-8 % nickel composition were made are similar in the cast types to those mentioned previously for the wrought types. On the other hand, Types HW

152 Chapter 7

Table 7-14. Compositions of Some Cast Stainless Steels!3,!4

Nearest Composition, % ACI wrought type type C Mn Si Cr Ni Other

Corrosion·resistant castings

CE·30 0.30 1.5 2 26-30 8-11 CF·3 304L 0.03 1.5 2 17-21 8-12 CF·8 304 0.08 1.5 2 18-21 8-11 CF·20 302 0.20 1.5 2 18-21 8-11 CF·3M 316L 0.03 1.5 1.5 17-21 9-13 2-3 Mo CF·8M 316 0.08 1.5 1.5 18-21 9-12 2-3 Mo CF·8C 347 0.08 1.5 2 18-21 9-12 8xCminCb CF·16F 303 0.16 1.5 2 18-21 9-12 1.5 max Mo;

0.20--0.35 Se; 0.17maxP

CG·8M 317 0.08 1.5 1.5 18-21 9-13 3-4 Mo CG·12 0.12 1.5 2 20-23 10-13 CH~20 309 0.20 1.5 2 22-26 12-15 CK·20 310 0.20 1.5 2 23-27 19-22 CN·7M 0.07 1.5 1.5 18-22 27-31 1.75-2.5 Mo;

3 minCu

Heat·resistant castings

HE 0.2-0.5 2 2 26-30 8-11 HF 302B 0.2-0.4 2 2 18-23 8-12 HH 309 0.2-0.5 2 2 24--28 11-14 HI 0.2-0.5 2 2 26-30 14--18 HK 310 0.2-0.6 2 2 24--28 18-22 HL 0.2-0.6 2 2 28-32 18-22 HN 0.2-0.6 2 2 19-23 23-27 HT 330 0.35-0.75 2 2.5 13-17 33-37 HU 0.35-0.75 2 2.5 17-21 37-41 HW 0.35-0.75 2 2.5 10-14 58-62 HX 0.35-0.75 2 2.5 15-19 64--68

Note: Single values indicate maximum.

and HX are actually high nickel alloys rather than stainless steels, and their properties have been discussed in Chapter 4.

Physical Properties

A number of the physical properties of the cast stainless steels are, for practical purposes, similar to those of the wrought types. These include the specific heats, coefficients of expansion, and moduli of elasticity. The elec­trical resistivities of the cast types, however, are somewhat higher than those

Nickel-Containing Stainless Steels 153

of corresponding wrought types. Probably the most important difference lies in the magnetic permeability. The cast types may contain small quantities of ferrite and, as a result, may be slightly magnetic.

The physical properties of a number of representative cast stainless steels are given in Table 7_15. 15 ,16

Mechanical Properties

Room- Temperature Properties

The cast stainless steels are generally used in the "as cast" condition or are solution-annealed at temperatures of the order of 2000 F and water quenched to improve the corrosion resistance.

Tensile Properties. Typical tensile properties of a group of represen­tative cast steels are given in Table 7_16. 15 ,16 The corrosion resistant types (C series) have tensile properties, including ductility, that compare reasonably well with those of the wrought alloys, of approximately the same composi­tion, in the annealed condition. The heat-resistant types (H series) have strengths similar to those of the corrosion-resistant types but, probably re­flecting the higher carbon content, they are markedly less ductile than the latter.

Hardness. Brinell hardness values are included also in Table 7-16. The hardness ranges from a low of 130 for CN-7M in the solution-annealed and quenched condition to 190 for Type CH-20 in the same condition.

Impact Properties. Notched-bar impact data are included in Table 7-16 for a few of the alloys. They indicate that these alloys are quite tough after solution annealing and quenching, Additional impact data are included under low-temperature properties.

Elevated- Temperature Properties

The compositions of the heat resistant cast stainless steels of the H series have been adjusted especially for high-temperature service and these alloys have good strength properties up to 2200 F combined with surface stability. Short-time tensile properties of several of these alloys, determined at elevated temperatures, are given in Table 7_17. 16 These cast steels show no particular advantage over the corresponding wrought compositions at moderate temperatures; data for the wrought alloys are not available at high temperatures in most cases. The strengths of the cast alloys decrease progres­sively at about the same rate as those of the wrought alloys as the tempera­ture is increased and this is accompanied by an increase in elongation.

Ta

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7-1

5.

Ph

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of

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me

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t S

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less

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s ca

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s ca

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iall

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rrit

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50

80

25

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("")

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A

s ca

st,

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enit

ic

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85

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=

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A

s ca

st

50

75

17

170

"C

r+

CD ...

"Izo

d V

-not

ch.

..,

Nickel-Containing Stainless Steels 155

Table 7-17. Elevated-Temperature Properties of Some Cast Stainless Steels 16

Long-time properties Tensile properties

Stress (ksi) Stress Test Yield strength Tensile Elongation for creep (ksi) for

ACI temperature, (0.2 % offset), strength, (2 in.), rate of rupture in type F ksi ksi % 0.0001 %/hr l00hr

HF 1200 57 16 13 30 1400 21 35 20 6 14 1600 22 22 3.2 6

HHa 1400 17 33 18 3.0 14 1600 14 18 30 1.7 6.4 1800 6.3 9 45 2000 0.3 1.5

HHb 1400 18 35 12 7.0 14 1600 14 22 16 4.0 7.5 1800 7 II 30 2000 0.8 1.8

HK 1400 6.8 14.5 1600 23 21 4.2 7.8 2000 1.0 2.5

apartially ferritic. b Austenitic.

Creep and stress-rupture properties are included also in Table 7-17. In long-time properties, the cast steels have an advantage over their wrought counterparts. For example, the stress for a creep rate of 0.0001 %/hr of Type HK at 1600 F is 1.5 times that of Type 310 at 1500 F.

Low- Temperature Properties

Limited data indicate that the strengths of the cast stainless steels, like those of the wrought types, increase at subzero temperatures, but the duc­tilities, as measured by the elongation, decrease. The effect of low tempera­ture on the tensile properties of Type CF-8 in the annealed condition is shown in Fig. 7_8. 11 The tensile strength is approximately twice as high at -320 F as it is at room temperature although the yield strength shows a more moderate increase. The elongation, however, falls from 60% at room temperature to 30% at -320 F.

The toughness, as measured by the notched-bar test, also decreases at low temperatures, the relative loss apparently depending on the composition. Type CF-8, for example, has an impact resistance, as measured by the Charpy keyhole impact test, of 57 ft-lb at -320 F compared with 75 ft-lb at room

156 Chapter 7

Temperature, K

50 100 150 200 250 300 200

160

(J) 120 1.

vi ~ (J)

Cl> ~ "-

en 80 80 c C\J

60 c 0

40 40 '"5 0'>

20 c 0 W

-400 -300 -200 -100 0 100 Temperature, F

Fig. 7-8. Subzero-temperature tensile properties of cast CF-8 stainless steel in the annealed condition.!!

Table 7-18. Impact Properties of Some Cast Stainless Steels at Subzero Temperatures!!

ACI Charpy impact (keyhole notch), ft-lb, at temperature indicated

type -320F -200F -100F Room

CF-8 57 63 67 75 CF-8M 44 50 58 63 CF-8C 19 21 28 38 CH-20 10 14 20 30 CK-20 15 17 24 30

temperature. On the other hand, Type CH-20 has an impact resistance of 10 ft-lb at -320 F compared with 30 ft-lb at room temperature. Data on a number of cast steels are given in Table 7-18.!!

STAINLESS STEEL PIM PARTS

Chromium-nickel stainless steel P/M (powder metallurgy) parts are produced from powders which have compositions similar to those of the AISI standard types. They can be produced by atomization of prealloyed

Nickel-Containing Stainless Steels 157

material. After being compacted to the desired density, which depends on the application, they are sintered, for example, at 2050 F in dry hydrogen or in dissociated ammonia, with a low dew point of perhaps -40 F.

Stainless steel PjM parts, ranging in density from 6.0 to 6.8 gjcm3 or higher, are used for structural applications in which resistance to corrosion is required in the pharmaceutical, chemical, food processing, and similar industries, particularly for instrumentation. They are also used in low­density parts as filters for various corrosive solutions.! 7

The Metal Powder Industries Federation has established standards for two types of chromium-nickel stainless steels in two ranges of density. They are:

Type 303*

316

MPIF designation SS-303-P SS-303-R

SS-316-P SS-316-R

Sintered density, gjcm 3

6.0-6.4 6.4-6.8

6.0-6.4 6.4-6.8

*Composition within AISI limits, except nickel content, which is higher to improve com­pressibility and strength.

Properties

Typical properties of P jM parts meeting the requirements of the MPIF Standards are given in Table 7-19.!8 As would be expected ofPjM parts, the strength and elongation improve with increasing density. The st~engths and elongations of the Type 316 parts are somewhat superior to those of the Type 303 parts. The ductility, as measured by the elongation, however, is closer to that expected in a cast than in a wrought part.

Porous parts produced from stainless steel powders by compacting to low densities may have tensile strengths of the order of 20 ksi.

Table 7-19. Typical Properties of Some Stainless Steel P/M Parts!8

Yield strength Tensile Elongation Density, (0.2 % offset), strength, (in 1 in.),

Type Condition g/cm3 ksi ksi %

303 As sintered 6.0-6.4 32 35 1.0 6.4-6.8 35 52 2.0

316 As sintered 6.0-6.4 32 38 2.0 6.4-6.8 40 54 4.0

158 Chapter 7

It should be noted that the corrosion resistance of stainless steel P 1M parts is not necessarily equivalent to that of the corresponding wrought material. 1 8

REFERENCES

1. Stainless and Heat Resisting Steels, American Iron and Steel Institute (1953), with 1969 supplement.

2. Private Communication, Allegheny Ludlum Steel Corporation, Jan. 1970. 3. Mechanical and Physical Properties of Austentic Chromium-Nickel Stainless Steels,

The International Nickel Co., Inc. (1963). 4. Mechanical and Physical Properties of Austenitic Chromium-Nickel Stainless Steels at

Elevated Temperatures, ibid. 5. Mechanical and Physical Properties of Austenitic Chromium-Nickel Stainless Steels at

Subzero Temperatures, ibid. 6. "Wrought austenitic stainless steels," Materials in Design Engineering, October 1964,

p.115. 7. F. R. Schwartzberg, S. H. Osgood, R. D. Keys, and T. F. Kiefer Cryogenic Materials

Data Handbook, AD609562, The Martin Co. (1964). 8. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards

(1968). 9. High-Temperature High-Strength Alloys, American Iron and Steel Institute (1963).

10. Precipitation Hardenable Stainless Steels, The International Nickel Co., Inc. (1963). 11. R. M. McClintock and H. P. Gibbons, Mechanical Properties of Selected Materials at

Low Temperatures, Monograph 13, National Bureau of Standards (1960). 12. C. J. Slunder, A. F. Hoenie, and A. M. Hall, Thermal and Mechanical Treatments for

Precipitation Hardening Stainless Steels, AD668900, Battelle Memorial Institute, n.d. 13. "Corrosion resistant iron~hromium and iron~hromium-nickel alloy castings for

general applications," Designation A 296 ASTM Standards, Part 2, 1969. 14. "Heat resistant iron~hromium and iron~hromium-nickel alloy castings for general

applications," Designation A 297 ASTM Standards, Part 2,1969. 15. Cast Stainless Steels, The International Nickel Co., Inc. (1963). 16. "Heat resistant alloys-cast," Materials in Design Engineering, Mid-October 1966,

p.91. 17. J. L. Everhart, "Designing for metal powder structural parts," Materials in Design

Engineering, April 1959, p. 113. 18. PjM Materials Standards and Specifications, Metal Powder Industries Federation

(1969).

Chapter 8

Electrical Resistance

and Thermocouple Alloys

Although materials for specialized electrical resistance applications range across the field from commercially pure nickel to some alloys which have a very low nickel content, certain groups are used most widely and these are the materials which will be discussed in this chapter. Some of the materials also serve other purposes, for example, the nickel-chromium alloys which are used in structural applications. Similarly, the 55 % copper-45 % nickel alloy is used not only as a resistance material in instrumentation but also as a thermocouple alloy which, of course, is a specialized resistance appli­cation.

ELECTRICAL RESISTANCE ALLOYS

A number of nickel-containing alloys are used primarily because of their electrical characteristics. These alloys serve as resistances in instrumen­tation and as heating elements in various applications ranging from house­hold appliances, operating intermittently at moderate temperatures, to industrial furnaces, operating continuously at temperatures of 2000 F or higher.

According to Starr and Gottleib,l the basic parameters for resistance applications are resistivity and the temperature coefficient of resistance. They classifiy the commercial alloys into the following five categories:

1. Low resistivity, high TCR (temperature coefficient of resistance) 2. Low resistivity, moderate TCR 3. Moderate resistivity, low TCR

159

160 Chapter 8

4. High resistivity, low TCR 5. High resistivity, moderate TCR

There are at least 20 alloys in the five groups. They cover a wide range of properties and most of them contain nickel. Among the materials in Group 1 is nickel. Its properties have been discussed in Chapter 2 and they will not be repeated. The nominal compositions of selected alloys in the other four groups are given in Table 8-1.

Table 8-1. Compositions of Some Electrical Resistance Alloys

Nominal composition, %

Alloy Type Ni Si Cu Cr Fe Al

Ni-Si Low resistivity, moderate TCR 97 3 55-45 Moderate resistivity, low TCR 45 55 75-20 High resistivity, low TCR 75 3 20 3 80---20 High resistivity, moderate TCR 79 1 20 60---16 High resistivity, moderate TCR 60 1 16 Bal. 35-20 High resistivity, moderate TCR 35 2 20 Bal.

Group 2 is represented by a 97 % nickel-3 % silicon alloy. This alloy has excellent exidation resistance and can be used for instrumentation at tempera­tures up to 2000 F.l

Group 3 is represented by one of the oldest resistance alloys, 55 % cop­per-45 % nickel, often called constantan but marketed under a variety of trade names. The alloy is frequently modified by the addition of other ele­ments, such as manganese, to alter its characteristics. It can be used as a resistance element up to temperatures of about 930 F.2

Because of its low temperature coefficient of resistance, the 55 % copper-45 % nickel alloy is widely used for resistance banks which control the voltage applied to various types of machines. It is also used in the form of cable in floor and panel heating for homes and offices, wrap-around cables for warm­ing pipes handling various industrial fluids, etc. Its low thermal conductivity combined with an approximately constant electrical resistivity at low tempera­tures lead to quite extensive use of this alloy in cryogenic apparatus.

Group 4 is represented by a heat treatable nickel-chromium-copper­aluminum alloy which can be used to temperatures up to 580 F. It is a solid­solution alloy whose electrical properties are developed by heat treatment at elevated temperatures. This alloy is used primarily in the form of very fine wire for stable precision resistors. l

Group 5 is represented by three alloys because of the importance of the group not only in instrumentation but also in general heating applications.

Electrical Resistance and Thermocouple Alloys 161

The 80 % nickel-20 % chromium composition, oldest of the resistance alloys, can be used to temperatures of about 2000 F, the others to somewhat lower temperatures. 2

Alloys in this group are used for power resistors, elevated-temperature control coils, high-ohm resistors, and potentiometers, for example. The 80 % nickel-20 % chromium and the 35 % nickel-20 % chromium-balance iron alloys are also used extensively for heating elements in industrial furnaces, whereas the 60 % nickel-16 % chromium-balance iron alloy is used primarily for heating elements in appliances.

The 80 % nickel-20 % chromium alloy is highly resistant to oxidation and corrosion at temperatures up to 2150 F. However, it is subject to selec­tive oxidation in partially reducing atmospheres in the temperature range of 1500 to 1800 F. As a result, ductility is reduced, local hot spots can develop, and premature failure may occur. This effect can be prevented by maintaining an oxidizing atmosphere or by using an alloy having a lower nickel content. The 35 % nickel-20 % chromium-balance iron alloy was developed for ser­vice in the 1500 to 1800 F temperature range because it is not subject to the form of internal oxidation mentioned.

Physical Properties

The physical properties of the resistance alloys mentioned above are given in Table 8_2. 1 ,3,4,5 The electrical resistivity ranges from a low of 138 ohms/cir mil ft for the nickel-silicon alloy to a high of 800 ohms/cir mil ft for the nickel-chromium-copper-aluminum alloy. It should be noted that the resistivity given for the latter alloy is developed by heat treatment at elevated temperatures; the fully annealed alloy has a resistivity of 730 ohms/ cir mil f1. 6

In instrumentation, it is advantageous to have a temperature coefficient of resistance as close to zero as possible in order that variations in the ambi­ent temperature will not significantly change the overall resistance of the system. In the materials under consideration, the temperature coefficient of resistance ranges from a low of 3 microhmsfohmtF for the nickel-chromium­copper-aluminum alloy, again achieved by heat treatment, to a high of 1330 for the nickel-silicon alloy. Incidently, the coefficient of annealed nickel­chromium-copper-aluminum is 28 microhms/ohmtF.

The 55 % copper-45 % nickel alloy maintains its low temperature coef­ficient of resistance over the range -70 to 225 F. It has the highest electrical resistivity and the lowest coefficient of resistance of the copper-nickel alloy system. 2 In addition to having the highest electrical resistivity of the alloys under consideration, the nickel-chromium-copper-aluminum alloy main-

Ta

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Pro

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Electrical Resistance and Thermocouple Alloys 163

tains its minimum coefficient of resistance over a wider range than that cov­ered by the 55 % copper-45 % nickel alloy.

The three alloys of group 5 have resistivities ranging from 610 to 675 ohms/cir mil ft and their temperature coefficients of resistance increase with decreasing nickel content. In each of these alloys, the specific electrical resist­ance increases with rising temperature. The greatest increase occurs in the 35 % nickel-20 % chromium-balance iron composition and the least in the 80 % nickel-20 % chromium composition. Fabricating procedure influences the resistance. After cold working, if annealing is followed by slow cooling, the resistance will be near the maximum, but rapid cooling will lower the resistance. An indication of the effect of temperature on the resistance of these three alloys is given in Fig. 8-1.7

In instrumentation, the resistance elements are often connected to cop­per leads and It is advantageous to have a low thermal emf versus copper. For the materials under discussion, the thermal emf versus copper ranges from -23.5 to 2.1 microvoltsrF.

The coefficients of thermal expansion of the alloys in Table 8-2 range from 7.0 X 10- 6 to 8.8 X 10- 6 per OF over the range 32 to 212 F, and are

24

20

~

a.l 16 u c 0

1i'i "V; OJ 12 0::

!;

OJ If) 8 0 OJ ... u .s

4

Temperature, K 300 500 700 900 1100 1300

o 400 800 1200 1600 2000 Temperature, F

Fig. 8-1. Effect of temperature on the electrical resist­ance of several resistance alloys. 5

Tab

le 8

-3.

No

min

al T

ensi

le P

rop

erti

es a

nd

Har

dn

ess

Val

ues

of

So

me

Ele

ctri

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Res

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All

oys

3,s

Har

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s

For

m a

nd c

ondi

tion

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ld s

tren

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(0.2

% of

fset

),

ksi

Ten

sile

st

reng

th,

ksi

Elo

ngat

ion

(2 i

n.),

%

Red

ucti

on

of

area

, %

R

ockw

ell

Bri

nell

55C

u-45

Ni

Rod

A

nnea

led

at 1

400

F H

ot

roll

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Col

d ro

lled

Ni-

Cr-

Cu-

AI

Ann

eale

d

80N

i-20

Cr

Ann

eale

d

60N

i-16

Cr-

Fe

Ann

eale

d

35N

i-20

Cr-

Fe

Ann

eale

d

aYie

ld p

oint

.

27·

35·

65

60

50

55

67

46

69

42

103

15

140

35

100

30

105

30

102

30

78

76

70

B54

B

62

B88

B83

159

200

... ~ o ::T

I»

'tI ... CD .. 00

Electrical Resistance and Thermocouple Alloys 165

relatively close to that of commercial nickel over the same range. In the alloys of Group 5, the coefficient increases with decreasing nickel content. Since the 80 % nickel-20 % chromium is used at high temperatures, its coef­ficient over a broader temperature range may be of interest; it is 9.6 X 10- 6

over the range 68 to 1832 F. The 55 % copper-45 % nickel alloy has the highest modulus of elasticity

of the copper-base alloys. The moduli of the three alloys in Group 5 decrease with decreasing nickel content from 31,000 ksi for the 80% nickel-20% chromium alloy to 27,000 ksi for the 35% nickel-20% chromium-balance iron alloy.

Mechanical Properties

Room- Temperature Properties

One of the essential requirements of electrical resistance alloys is that they be readily fabricated into strip and wire since these are the forms most widely used. All of the materials under discussion meet this requirement although some are more readily worked than others.

Tensile Properties. Nominal tensile properties of several of the alloys are given in Table 8_3. 3 ,s In the annealed condition, the tensile strength ranges from a low of 67 ksi for the 55 % copper-45 % nickel alloy to 140 ksi for the nickel-chromium-copper-aluminum alloy. The alloys have relatively good ductilities as measured by the elongation, ranging from 30 to 46 %.

Cold working increases the tensile strength of the 55 % copper-45 % nickel alloy to more than 100 ksi with a corresponding decrease in the elongation from 46 to 15 %, although the reduction of area is reduced only slightly.

Hardness. The effect of cold work on the hardness of the 97 % nickel-3 % silicon alloy is indicated in Fig. 8-2.9 The alloy work hardens rapidly up to a reduction of about 40 % after which there is little increase in hardness with additional working.

Limited hardness data for the other alloys are given in Table 8-3.

Fatigue Properties. Fatigue strengths for two resistance alloys are given in Table 8-4. They indicate good resistance to fatigue. The endurance ratio of the 55 % copper-45 % nickel alloy is 0.39 for annealed, 0.50 for hot rolled, and 0.41 for cold rolled material. That of the 80% nickel-20% chromium alloy is 0.30 in the annealed condition.

The copper-nickel alloy has excellent resistance to corrosion by sea

166

240

"-Q)

.D E200 :::J z U1 U1 160 Q) c

"D "-0 I

120 "D

E 0 "-

~ 80 "D C 0 E 40 0 6

o 40 60 Cold Work, %

Chapter 8

80 Fig. 8-2. Effect of cold work on the hardness of a nickel-silicon resistance alloy.9

Table 8-4. Fatigue Properties of Two Electrical Resistance Alloys

Tensile Fatigue strength (ksi)

strength, at indicated cycles

Form and condition ksi 105 106 107 108 Ref.

55Cu-45Ni Rod, 1 in., hot rolled 70.5 37 36 35 10 Bar

Annealed 69.4 34 30 28 8 Cold rolled 103.3 50 43 8 Cold drawn, stress-relieved 38 32 31 11

80Ni-20Cr Annealed 112 33.6 5

water. Ellinghausen II reported that the fatigue strength of this alloy after 108 cycles (390 days) in sea water was 18 ksi as compared with 31 ksi in air.

Elevated- Temperature Properties

Short-time elevated-temperature tensile properties of 55 % copper-45 % nickel wire in the annealed condition are given in Fig. 8-3. 5 Strength falls gradually up to about 600 F and then the rate accelerates. The elongation

Electrical Resistance and Thermocouple Alloys 167

Temperature, K

120 300 500 700 900 1100 1300

100

80

60

~ 40 40 C

0

'"6 0>

20 20 c 0 W

o 400 800 1200 1600 2000 Temperature, F

Fig. 8-3. Short-time elevated-temperature tensile properties of 55 % copper-45 % nickel annealed wire. s

passes through a minimum in the range 500 to 700 F and rises with increasing temperatures.

Short-time elevated-temperature tensile properties of the 80 % nickel-20 % chromium alloy are given in Fig. 8-4. S There is little loss of strength up to about 800 F but above that temperature strength falls rapidly. As indicated in the graph, the ductility passes through a minimum in the range 800 to 1100 F, rises to a maximum at about 1400 F, and then decreases at higher temperatures. This alloy is used to some extent as a material of con­struction for high-temperature service. It is, however, subject to plastic flow at relatively light loads and thus its usefulness is limited. 2

Stress-rupture properties of the three alloys of Group 5 are given in Table 8-5.7,12 These materials have rather low rupture strengths in the range for which properties were obtained, 1500 to 1900 F. Since the 80% nickel-20 % chromium is the base from which quite a number of the superalloys were developed, it may be interesting to make a comparison. At 1800 F, for example, this alloy has a 100 hour rupture stress that is only about two­thirds that of Inconel alloy X-750 and only one-eighth that of Nimonic 115.

168 Chapter 8

Temperature, K 300 500 700 900 1100 1300

120

100

80 (f)

x

en 60 60 (f) (j) ....

~ ifi 40 E 40 C-o ."§

CJl c

20 20 .Q w

o 400 800 1200 1600 2000 Temperature, F

Fig. 8-4. Short-time elevated-temperature tensile properties of 80% nickel-20% chromium annealed rod. s

Table 8-5. Stress Rupture Properties of Some Electrical Resistance Alloys

Stress (ksi) for rupture in 100 hr at

Alloy 1500F 1700F 1800F 1900 F

80Ni-20Cr (2350 F, water quenched) 6.5 2.2 80Ni-20Cr 5.0 3.6 2.7 60Ni-16Cr-Fe 5.0 4.2 2.2 35Ni-20Cr-Fe 5.5 2.8 2.05

Low-Temperature Properties

Ref.

12 7 7 7

Limited data on the low-temperature properties of two of the resistance alloys are given in Table 8_6. s ,8 As indicated in the table, the strength of the 55 % copper-45 % nickel alloy increases with falling temperatures, the tensile strength at -292 F being about 1.5 times that at room temperature. The elongation also increases but there is a slight drop in the reduction of area. In addition, the toughness as measured by a notched-bar test remains high.

Electrical Resistance and Thermocouple Alloys 169

Table 8-6. Mechanical Properties of Two Electrical Resistance Alloys at Low Temperatures S,8

Test Yield Tensile Elongation Reduction Izod temperature, point, strength, (2 in.), of area, impact,

Condition F ksi ksi % % ft-lb

55Cu-45Ni Annealed Room 20 60 49 77 80

-292 54 90 60 74 88

80Ni-20Cr Annealed at 1850 F Room 103 133 28a 52

-423 139 188 34a 50

"In 10 diameters.

The tensile strength of the 80% nickel-20% chromium alloy also in­creases at low temperatures; tensile strength at -423 F is 188 ksi compared with 133 ksi at room temperature. The elongation also increases and, in this alloy, the reduction of area shows only a very slight decrease.

THERMOCOUPLE ALLOYS

A thermocouple consists of two dissimilar metals which, when exposed to two different temperatures, produce an electromotive force approximately proportional to the temperature difference between their hot and cold junc­tions. The thermocouples that have been used for fifty years or more are still predominant although some special purpose thermocouples have appeared from time to time.!3 The materials used in these thermocouples are copper, iron, constantan, Chromel, Alumel, platinum, and platinum-rhodium alloys.

The various combinations have been designated by letter symbols and those of interest in this publication are: 14

[SA code symbol T J K E

Couple materials Copper and constantan Iron and constantan Chromel P and Alumel* Chromel P and constantan

The iron-constantan couple was apparently the first base-metal ther­mocouple accepted on a large scale and continues to be used extensively.

*This is the original combination-there are various proprietary alloys which now fit into this classification. This is true also for alternates for Chromel P in the Type E thermo­couple.

170 Chapter 8

The copper-constantan couple has been used for many years. Its elec­tromotive force-temperature coefficient is more linear than that of tho iron-constantan couple, particularly below 400 F. It is the best available base-metal couple for service from -300 to 200 F.13

According to Caldwell,13 the Chromel-Alumel and other Type K couples are probably the most widely used base-metal couples in industrial applications.

The Chromel-constantan couple has excellent thermocouple properties and has the advantage that both elements are resistant to corrosion. It is sometimes used as a replacement for Type K couples in industrial appli­cations.

Representative values of the electromotive force developed by these thermocouples at a series of temperatures are given in Table 8-7. These data were extracted from the complete tables published by the National Bureau of Standards. I S

The table indicates the considerable differences in electromotive force developed by the various couples. Thus, the Chromel-constantan couple produces much higher emf at any temperature than the other couples, the

Table 8-7. Representative Temperature-Electromotive Force (emf) Tables for Thermocouples"

Emf in absolute millivolts, reference junction at 32 F

Copper- Iron- Chromel P- Chromel P-Temp., constantan constantan Alumel constantan

F (Type T) (Type J) (Type K) (Type E)

-300 -5.284 -7.52 -5.51 -8.30 -200 -4.111 -5.76 -4.29 -6.40 -100 -2.559 -3.49 -2.65 -3.94

0 -0.670 -0.89 -0.68 -1.02 100 1.517 1.94 1.52 2.27 200 3.967 4.91 3.82 5.87 400 9.525 11.03 8.31 13.75 600 15.773 17.18 12.86 22.25 800 23.32 17.53 31.09

1000 29.52 22.26 40.00 1200 36.01 26.98 49.04 1400 42.96 31.65 57.92 1600 50.05 36.19 66.68 1800 40.62 75.12 2000 44.91 2200 49.05 2400 53.01

Electrical Resistance and Thermocouple Alloys 171

next highest being the iron-constantan couple. The table also indicates the highest temperature at which the various couples should be used, as discussed in the following paragraph.

There are limitations on the temperatures at which these couples should be used and they are indicated in Table 8_8. 14 Propected couples can be used at considerably higher temperatures than bare couples and wire size must be considered in selecting an operating temperature. The maximum service temperature decreases as the wire diameter is reduced. The copper-constan­tan couple should be used only up to 700 F, the iron-constantan couple to 1400 F, and the Chromel-constantan couple to 1600 F. The Chrome 1-Alumel couple can be used to 2300 F if it is protected from the atmosphere.

Physical Properties

Typical physical properties of Chromel P and Alumel are given in Table 8-9.13 Data on constantan (55 % copper-45 % nickel) were included in Table 8-2.

Table 8-8. Temperature Limits for Thermocouples l4

Temperature limit (F)

Couple for wire size (A WG)

ISA code Thermocouple materials condition 8 14 16 20 24 30.

T Copper---<:onstantan Bare 600 500 400 400 400 Protected 700 600 500 400 400

J Iron---<:onstantan Bare 1200 900 900 800 650 600 Protected 1400 1100 1100 900 700 700

K Chromel-Alumel Bare 2000 1700 1700 1600 1400 1300 Protected 2300 2000 2000 1800 1600 1500

E Chromel---<:onstantan Bare 1400 1100 1100 900 700 700 Protected 1600 1200 1200 1000 800 800

Chromel P has a much higher electrical resistivity than Alumel but also has a much lower temperature coefficient of resistance. The increase in resistance with temperature for the two alloys is indicated in Fig. 8_5. 13

Both the thermal conductivity and the specific heat of Alumel are some­what higher than those of Chromel P, but the coefficient of thermal expansion of the latter is the higher. The thermal conductivities of both alloys are rela­tively close to that of constantan and the thermal expansion of Chromel P is similar to that of the 80% nickel-20% chromium alloy. Chromel P is non­magnetic and Alumel is strongly magnetic. 1 3

172 Chapter 8

Table 8-9. Nominal Physical Properties of Two Thermocouple Alloys13,16

Nominal composition, %

Melting point, F Specific heat (68 F), Btu/lb/"F Thermal conductivity (212 F), Btu/ft2/hr/"F/ft Coefficient of thermal expansion (68-212 F), per OF Electrical resistivity (68 F), ohms/cir mil ft Temperature coefficient of resistance (32-212 F),

microhms/ohm/"F Modulus of elasticity, ksi Modulus of rigidity, ksi Poisson's ratio Density,lb/in. 3

*See appendix.

Temperature, K

Alumel* (Ni 95, Al 2, Mn 2, Si 1)

2550 0.125

17 6.6 X 10-6

177

1670 30,000 11,000

0.35 0.311

300 500 700 900 1100 1300 100 ,.....,..----r------r--r---~--r-.

~ 80 (l) u c o Vi 60 Ui (l)

0:::

c 40 (l) <f)

o ~ ~ 20

o UE~~ ____ ~ __ ~ ____ ~ __ ~

o 400 800 1200 1600 2000 Temperature, F

Fig. 8-5. Effect of temperature on the electrical resistance of two thermocouple alloys. 1 3

Chromel-P* (Ni 90, Cr 10)

2600 0.107

11 7.3 X 10-6

425

300 30,000 11,000

0.35 0.315

Electrical Resistance and Thermocouple Alloys

Temperature, K

300 500 700 900 1100 1300 100 r-r------r----,--,....--..,..--..,.......,

(j) (j)

~

80

i7i 40

20

60

c 40Q

c .Q

20 -0 0> C o W

o 400 800 1200 1600 2000 Temperature, F

Fig. 8-6. Short-time elevated-temperature tensile properties of annealed Alumel wire. 1 6

Mechanical Properties

173

Only limited data were found on mechanical properties. According to Caldwell,13 Chromel P has a tensile strength of 95 ksi in the annealed condi­tion and can be work hardened to a strength of 165 ksi. Alumel has an annealed tensile strength of 85 ksi and this can be increased to 170 ksi by cold work.

Short-time elevated-temperature tensile properties of Alumel in the form of 18 gage annealed wire are given in Fig. 8-6. 16 The tensile strength falls regularly from 85 ksi at room temperature to 9 ksi at 2000 F. The elongation has a minimum at about 1000 F. Chromel P has similar properties, although it is slightly stronger over the entire range and its elongation is somewhat lower.

REFERENCES

1. C. D. Starr and A. J. Gottleib, "How to select electrical resistance alloys," Materials Engineering, Nov. 1967, p. 44.

2. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards (1968).

174 Chapter 8

3. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968). 4. "Drawn or rolled nickel---chromium and nickel---chromium-iron alloys for electrical

heating elements," Designation B 344, ASTM Standards, Part 8,1969. 5. J. L. Everhart, W. E. Lindlief, J. Kenegis, P. G. Weissler, and F. Siegel, Mechanical

Properties of Metals and Alloys, Circular C447, National Bureau of Standards (1943). 6. C. D. Starr, "Properties of wires for resistors," Materials Research and Standards 6,

435 (1966). 7. Nickel Alloys for Resistance Heating Elements, The International Nickel Co. Inc.

(1969). 8. R. P. Reed and R. P. Mikesell, Low-Temperature Mechanical Properties of Copper and

Selected Copper Alloys, Monograph 101, National Bureau of Standards (1967). 9. J. F. Potts and D. L. McElroy, "The effects of cold working, heat treatment, and

oxidation on the thermal emf of nickel-base thermoelements," Temperature-Its Measurement and Control in Science and Industry, Part 2, 1962, p. 243.

10. H. J. Grover, S. A. Gordon, and L. R. Jackson, Fatigue of Metals and Structures, NAVWEPS 00-25-534, Department of the Navy (1960).

11. R. C. Ellinghausen, Endurance and Stressless Corrosion Fatigue Tests of Ni-Cu Alloys and Tobin Bronze in Sea Water, PB 168687, U. S. Naval Exp. Station, Annapolis (1967).

12. R. Widmer and N. J. Grant, "The creep rupture properties of 80Ni-2OCr alloys," Trans. ASME J. Basic Engineering 82, 829 (1960).

13. F. R. Caldwell, Thermocouple Materials, Monograph 40, National Bureau of Stand­ards (1962).

14. "Calibrating and checking thermocouples in plant and laboratory," Metal Treating 17, 3 (Feb.-Mar. 1966).

15. H. Shenker, J.1. Lauritzen, Jr., R. J. Corruccini, and S. T. Louberger, Reference Tables for Thermocouples, Circular 561, National Bureau of Standards (1955).

16. Private Communication from Hoskins Manufacturing Company, May 28, 1970.

Chapter 9

Controlled-Expansion and

Controlled-Modulus Alloys

LOW-EXPANSION ALLOYS

In the late 19th century, discovery of deviations from the expected values of the coefficients of expansion in the nickel-iron system led to a study of the system by Guillaume. He found that the minimum coefficient of expansion occurred in the alloy containing approximately 36 % nickel and called the alloy "Invar." He found also that the addition of 12 % chromium produced an alloy having an invariable modulus of elasticity over a considerable tempera­ture range and called this alloy "Elinvar." Both of these alloys are atill in use. Elinvar will be discussed later.

In a sense, Invar is a misnomer because the low value of coefficient of expansion occurs only over a limited temperature range. It is often regarded as resulting from a combination of a normal dilatational effect and an in­crease in volume on cooling caused by magnetic effects (magnetostriction). In the nonmagnetic state above the Curie point, the alloy has a normal coef­ficient of expansion, similar to that of iron or nickel. As the alloy cools, and passes the Curie point, a range is entered where the coefficient is low, but on additional reduction of temperature the coefficient again increases. These phenomena are characteristic also of iron-nickel alloys ranging from about 30 to 70% nickel, although the abnormality becomes less marked with increas­ing nickel content. 1

The coefficient of expansion ofInvar is influenced by a number offactors. Impurities generally increase the minimum. Annealing tends to increase the expansion coefficient and quenching has the opposite effect. Cold work also has a tendency to lower the value and, in a pure 36 % nickel alloy, can cause the alloy to have a negative expansion coefficient.

175

176 Chapter 9

The 36 % nickel-iron alloy has a coefficient of expansion approximately one-tenth that of carbon steel at temperatures up to 400 F. It is used where dimensional changes resulting from variations in temperature must be mini­mized and also as the low-expansion side of bimetallic thermoelements. Because of its excellent low-temperature characteristics it is used also as a structural material in cryogenic applications. A free-machining modifica­tion, containing about 0.2 % selenium, is used for parts requiring extensive machining. The properties of this alloy approximate those of the normal 36% alloy.

Sands2 reported that cobalt may be substituted for nickel in the 36 % nickel alloy with no effect on the inflection temperature but a beneficial effect on both the minimum and mean coefficients of expansion. For an inflection temperature of 932 F, for example, he noted that the substitution of 28 % cobalt for a like percentage of nickel will lower the minimum coefficient of expansion from 5.2 X 10- 6 to 2.9 X 10- 6 per OF; the mean coefficient will be lowered from 5.5 X 10- 6 to 3.5 X 10- 6 per OF.

Increasing the temperature above room temperature shifts the minimum coefficient toward higher nickel contents. This is advantageous in selecting a low-expansion alloy for service at temperatures above those at which the 36 % alloy is effective. For example, the 42 % nickel-iron alloy has a virtually constant low rate of thermal expansion at temperatures up to about 650 F and the 49 % nickel-iron alloy has a low rate, much lower than that of car­bon steel, up to temperatures of about 1100 F.

The wide range of expansion coefficients available in the nickel-iron alloys and in modified alloys based on the nickel-iron system leads to their use as glass-sealing materials. Rosenberg3 notes that alloys containing 42 % nickel, 5.5 % chromium, balance iron are suitable for seals in many soft glasses. Alloys containing 29 % nickel, 17 % cobalt, balance iron and 52 % nickel, balance iron are suitable for sealing hard, heat resistant glasses.

The 36 % nickel alloy is the most widely used material for applications requiring low expansivity at temperatures up to about 400 F; the 42 % alloy for applications from 400 to 650 F; and the 49 % alloy for applications at temperatures from 650 to 1000 F.3 There are a number of other low-expan­sion alloys which are modifications of the simple nickel-iron alloys, includ­ing some which are age hardenable. However, the 36 %, 42 %, and 49 % nickel-iron alloys will be used to indicate the properties to be expected of low-expansion alloys.

Physical Properties

Typical physical properties of the three alloys are given in Table 9-1.4 As indicated in the table, a number of the properties show a progressive

Controlled-Expansion and Controlled-Modulus Alloys

Table 9-1. Physical Properties of Some Low­Expansion Alloys4

177

36 % Ni-Bal Fe 42 % Ni-Bal Fe 49 % Ni-Bal Fe

Melting point, F 2600 2600 2600 Specific heat (70-212 F), BtujlbrF 0.123 0.121 0.120 Thermal conductivity (68- 212 F),

Btujhrjft2rFjft 6.0 6.2 7.5 Coefficient of thermal expansion,

per OF 77-212 F 0.655 x 10-6 2.57 X 10-6 4.8 X 10-6

77-292F 0.956 x 10-6 2.54 X 10-6 5.2 X 10-6

77-572F 2.73 x 10-6 2.71 X 10-6 5.17 X 10-6

77-752 F 4.34 x 10-6 3.14 X 10-6 5.07 X 10-6

77-1292 F 6.31 x 10-6 5.50 X 10-6 6.00 X 10-6

77-1652 F 7.70 x 10-6 7.10 X 10-6 7.38 X 10-6

Electrical resistivity, ohms/cir mil ft 495 430 290 Temperature coefficient

resistance (70-212 F), per OF 0.00067 0.0019 Curie temperature, F 535 715 930 Modulus of elasticity, ksi 20,500 21,000 24,000 Modulus of rigidity, ksi 8,100 8,500 9,300 Poisson's ratio 0.29 0.29 0.29 Density,lbjin. 3 0.291 0.29 0.298

increase with increasing nickel content. These include the thermal conduc­tivity, the density, the elastic constants, and the Curie temperature. The electrical resistivity decreases with increasing nickel content.

The most important property of these materials for their practical application is, of course, the coefficient of thermal expansion. As mentioned previously, it is influenced by impurity content, heat treatment, and cold work. According to McCain and Maringer,4 even dropping a sample of quenched and annealed Invar on a hard surface may change its dimensions by as much as 100 microns per meter, which is more than would be expected for a temperature change of 122 F.

The alloys can be stabilized by suitable heat treatments. The following, for example, has been suggested for the 36 % nickel alloy: heat to 1500 F for ~ hour per inch of thickness, water quench, reheat to 600 F for 1 hour, air cool. S

Because of these variables, it is necessary to use the data given in Table 9-1 for the coefficients of thermal expansion with care. However, they can be used to compare the characteristics of the three alloys. As indicated in the table, both the 42 % and 49 % alloys expand at greater rates than the 36 % alloy but their rates are more uniform at the higher temperatures. This effect

178 Chapter 9

Table 9-2. Thermal Expansion of Low-Expansion Alloys4

36% Ni 42%Ni

Coefficient of thermal expansion, per of -200--0 F

0-200 F 200-400 F 400-600 F 600-800F 800-1000 F

u c

7

~ 6 ~ o -£ Q) 5 0.

-c o g; 3 o 0. x

W

02 <5 I-

1.10 x 10-6 3.42 X 10-6

0.70 3.18 1.50 2.97 6.35 3.15 8.61 5.50 9.48 8.55

Temperature, K 300 400 500 600 700 800

o 200 400 600 800 1000 Temperature, F

Fig. 9-1. Total expansion of 36%Ni-Fe, 42% Ni-Fe, 48% Ni-Fe and carbon steel with increasing tempera­tures. 1

49-50% Ni

5.37 X 10-6

5.55 5.55 5.55 5.60 7.26

Controlled-Expansion and Controlled-Modulus Alloys 179

is indicated more clearly by the data included in Table 9-2 which gives the expansion characteristics over progressively higher 200 F temperature ranges.

The total expansion of the three alloys is compared with that of carbon steel in Fig. 9-1. 1 This graph shows that the total expansion of the 36 % alloy reaches that of the 42 % alloy at about 560 F and exceeds it above that temperature. Also indicated is that the total expansion of the 36 % alloy and the 48 % alloy are equal at about 800 F. Although all three alloys expand at a lower rate than low-carbon steel at moderately low temperatures, the 36 % nickel alloy expands at approximately the same rate as the steel at tempera­tures above 400 F.

Mechanical Properties

Room- Temperature Properties

All three of these alloys have austenitic structures and they cannot be hardened by heat treatment. Improvement in strength can be achieved only by cold work.

Tensile Properties. Typical tensile properties of the three alloys are given in Table 9-3. 4 The tensile strengths of the annealed alloys increase with the nickel content but the yield strengths do not show a similar trend.

As indicated in the table, cold work with a reduction of 30 % more than

Table 9-3. Tensile Properties and Hardness Values of Some Low-Expansion Alloys4

Yield strength Tensile Elongation Reduction Hardness (0.2 % offset), strength, (2 in.), of area,

Rockwell Brinell Condition ksi ksi % %

36 % Ni-Bal Fe Annealed 40 71 41 72 131 Cold worked, 15 % 65 93 14 64 187 Cold worked, 25 % 90 100 9 62 207 Cold worked, 30% 95 106 8 59 217

42 % Ni-Bal Fe Annealed 28 76 Cold worked 120 Bloo

49 % Ni-Bal Fe Annealed 31 82 41 72 170 Cold worked 140 B103

180 Chapter 9

doubled the yield strength of the 36 % nickel alloy and increased the tensile strength from 71 to 106 ksi. Under the same conditions, the elongation was reduced from 41 to 8 % but the reduction of area dropped only from 71 to 59%.

Hardness. The hardness of the 36 % nickel alloy increased progressively with cold work from Brinell 131 for annealed material to 217 after 30 % cold work. The effect of cold work on the hardness of this alloy is indicated also in Fig. 9-2.4 As a basis of comparison, mild steel and Type 304 chro­mium-nickel steel are also included in this graph. The data indicate that the 36 % nickel alloy hardens at approximately the same rate as mild steel but at a much lower rate than Type 304 stainless steel.

Other Properties. McGain and Maringer4 also reported the following properties for the 36 % nickel alloy after cold drawing to a Rockwell hardness of B90:

Izod impact, ft-Ib Shear strength, ksi

90

Endurance ratio (approximate) 45 0.40

400 r----r-----r----,.----,

350

w300 .0 E ~

z (,/)250 (,/) (1) c "0

~200 ~ (1)

.><:

.~ 150 >

50 L--_-I.-_---'-__ ..l-_-J

o 20 40 60 80 Cold Reduction, %

Fig. 9-2. Effect of cold work on the hardness of stainless steel, Invar, and mild steel. 4

Controlled-Expansion and Controlled-Modulus Alloys 181

Elevated-Temperature Properties

The short-time elevated-temperature tensile properties of the 36 % nickel alloy in the annealed condition are indicated in Fig. 9-3.4 There is little loss in strength up to the temperature range 400-500 F but the elon-

Temperature, K

300 500 700 900 1100 100 r-r----r----r----r--~

80

]1 60 IJ) IJ)

(l)

~ 40

20

E

~ 80 ~

60 §

40 g, c

20 L3

o 400 800 1200 1600 Temperature, F

Fig. 9-3. Short-time elevated-temperature tensile properties of annealed 36 % Ni-Fe.4

400r---~--~----~--~--~

to '0

~ 300 c

"0 ... (j) 200 Q. c:.> (l) ... u 100 o ;§

25 ksi

15 ksi

o 100 200 300 400 500 Time, hours

Fig. 9-4. Creep of Invar at 200 F.6

182 Chapter 9

gation increases. At higher temperatures, both strength and elongation fall at quite uniform rates up to 1200 F, the highest testing temperature re­ported.

Maringer6 presented total creep curves for the 36 % nickel alloy at room temperature, 150 F and 200 F. The tests were made under a series of stresses for a duration of 500 hours. His data for the 200 F series are given in Fig. 9-4. With a stress of 15 ksi, the creep rate appears to become constant within less than 100 hours. At higher stresses, however, uniform rates do not appear to be reached in 500 hours.

Low-Temperature Properties

The effect of subzero temperatures on the tensile properties of the 36 % nickel alloy in the annealed and cold worked (12-15 % reduction) conditions are indicated in Fig. 9-5. 4 • 7 The strength increases regularly to a value that at -400 F is about twice that at room temperature. Although there is some reduction in elongation, good ductility is retained at low temperatures.

According to Eash,8 the toughness as reflected by the notchfunnotched tensile strength decreases as the temperature falls into the subzero range. This effect is evident also in the notched bar impact test, as shown in Fig. 9-6. 9

Although there is a gradual reduction in toughness, there is no indication of

Temperature, K 50 100 150 200 250 300

200

160

'Vi 120 x

ul Ul (l) '-

en 80 80 ~

E Ann. e 0

40 - - LlO '0 ~

0'

E Cw. c 0

w

-400 -300 -200 100 0 100 Temperature, F

Fig. 9-5. Subzero-temperature tensile properties of 36% Ni-Fe in the annealed and 12-15 % cold worked conditions.4 • 7

Controlled-Expansion and Controlled-Modulus Alloys

.D ,----U 0 a. E >. a. '-0 .c U

100

80

60

40

20

Temperature, K

50 100 150 200 250 300

-

-400 -300 -200 -100 Temperature, F

o 100

Fig. 9-6. Subzero-temperature impact properties of 36 % Ni-Fe in the annealed and 12-15 % cold worked conditions. 9

183

a transition from ductile to brittle behavior. Even at -400 F, reasonably good toughness is indicated for this alloy.

HIGH-EXPANSION ALLOYS

In the nickel-iron alloy system, expansion characteristics vary widely depending on the composition. As the nickel content is reduced below the composition at which minimum expansion occurs, the rate of expansion increases.

Taking advantage of this phenomenon, the developers of a series of materials, which they have designated "Ni-Span" alloys, formulated a com­position called Ni-Span Hi that has high expansivity. This alloy is used primarily for thermostat controls usually as the high-expansion member of a bimetallic element.

The nominal composition of this alloy is:

Ni Cr Ti Si Al Fe 29 3.5 2.4 0.5 0.6 Bal

The inclusion of aluminum and titanium in the composition makes

184 Chapter 9

Table 9-4. Properties of a High-Expansion AlloylO

Physical properties Coefficient of thermal expansion (70-1000 F), per of ................ 10.5 X 10-6

Modulus of elasticity, ksi ........................................ 25,000

Mechanical properties

Yield strength Tensile Elongation (0.2 % offset), strength, (2 in.), Brinell

Condition ksi ksi % hardness

Soln.-annealeda 35 80 30 140 Soln.-annealed and agedb 95 150 20 305 Cold reduced, 50 % 120 140 4 250 Cold reduced, 50 %, agedb 130 180 8 370

01700 to 1850 F, water quenched. "Aged 1100--1350 F, 3-24 hr depending on condition and prior cold work.

the alloy precipitation hardenable by the precipitation of an intermetallic compound, NilAI, Ti), the same compound that is employed for strength­ening many of the nickel-base superalloys. The alloy is austenitic and is nonmagnetic at all temperatures.

Physical Properties

Limited physical properties of Ni-Span Hi are given in Table 9_4. 10

The alloy has a coefficient of expansion that is among the highest that can be achieved in an iron-base alloy. The mean coefficient is about 10.5 X 10-6

per OF between room temperature and 1000 F but it is not constant in this range. At the lower end, it is about 10.0 X 10- 6 per OF and at the high end of the range may reach 11 X 10- 6•

Mechanical Properties

As mentioned previously, the alloy is precipitation hardenable. Heat treatment consists of solution annealing at 1700 to 1850 F, water quenching, and aging at 1100 to 1350 F for periods ranging from 3 to 24 hr depending on such factors as the amount of cold work performed.

The tensile properties and hardness values of Ni-Span Hi in various conditions are given also in Table 9-4. The strength can be almost doubled by age hardening from the solution-annealed condition and the elongation is reduced only moderately by this treatment.

Cold working has almost as much strengthening effect as aging from the solution-annealed condition but has the disadvantage of drastically reducing

Controlled-Expansion and Controlled-Modulus Alloys 185

the ductility as measured by the elongation. Aging after cold working results in a marked improvement in tensile strength accompanied by some improve­ment in the elongation.

The Brinell hardness ranges from 140 for material in the solution­annealed condition to 370 for material that has been cold worked and aged.

CONSTANT-MODULUS ALLOYS

As mentioned previously, the discoverer of Invar also discovered that the replacement of 12 % iron by an equal quantity of chromium resulted in a material which had a constant modulus of elasticity over a considerable range of temperature. He called the alloy Elinvar and its first application was in watch springs, an application for which it is still used. However, various modi­fications have been made of the original alloy to obtain or to intensify secon­dary properties or to increase the ease of fabrication. These modifications are proprietary and no single composition now typifies Elinvar. The modified alloys contain varying percentages of such elements as tungsten, manganese, chromium, etc. as indicated in Table 9-5. 4

Iso-Elastic is an alloy of the Elinvar type which has been modified by the addition of molybdenum. The alloy is austenitic and is hardenable only by cold work. It is used for precision springs.

In an investigation of the temperature dependence of the modulus of elasticity in nickel-iron alloys having compositions between 36 and 50 % nickel, Fine and Ellis!! found that the composition most nearly isoelastic throughout the -40 to 175 F temperature range was the 42.7 % nickel alloy after it had been cold swaged with a reduction of 78 % and annealed 1 hour at 750 F.

Ni-Span C is a modification of the 42 % nickel alloy in which part of the iron has been replaced by chromium and titanium. This alloy is precipitation hardenable. It was developed specifically as a constant-modulus alloy and its

Table 9-5. Compositions of Some Constant-Modulus Alloys4

Alloy Ni Cr

Elinvara 36 12 Iso-Elastic 36 8 Ni-Span C 42 5.2

Ti

2.4

Composition, %

Mo

0.5

Fe

Bal. Bal. Bal.

Other

0.5 AI; 0.06 C max

"Original composition, now varies over the following ranges: 33-35% Ni, 61-53% Fe, 21-5 % Cr, 1-3 % W, 0.5-2 % Mn, 0.5-2 % Si, 0.5-2 % C.

186 Chapter 9

modulus of elasticity is practically constant over the range -50 to 150 F. It is used extensively for helical and flat springs, diaphragms, and bellows.

All three of these materials have characteristics which are highly desir­able in precision devices. They are resistant to oxidation and corrosion at the temperatures at which they are used and have low coefficients of expan­sion, low hysteresis, and low creep rates. Their compositions are given in Table 9-5. 4

Physical Properties

Physical properties of the three constant-modulus alloys mentioned are given in Table 9-6. 4 Very few data are available for Elinvar, possibly because of the wide variation in compositions of the modern modifications of this alloy.

The moduli of Iso-Elastic and Ni-Span C approach those of the 49 % nickel-iron alloy and are considerably higher than those of the 36 % nickel alloy. All three materials have very low temperature coefficients of the mod­ulus of elasticity although they vary: both Elinvar and Ni-Span C have nega­tive coefficients whereas Iso-Elastic has a range from negative to positive.

The effects of subzero temperatures on the modulus of elasticity of Ni­Span C are shown in Fig. 9-7. 12 The modulus is practically constant down

Temperature, K 50 100 150 200 250 300

30,000 r---r---,.---,.----,----,.--M

25,000

~ 20,000 vJ ~

:5 15 15,000 ~

10,000

Mod E

Mod R

-400 -300 -200 -100 Temperature, F ° 100

Fig. 9-7. Subzero-temperature moduli of elasticity (E) and rigidity (R) of Ni-Span C, solution treated and aged at 1200 F, 5 hr.12

Ta

ble

9-6

. P

hys

ical

Pro

pe

rtie

s o

f S

om

e A

nn

ea

led

Co

ns

tan

t-M

od

ulu

s A

llo

ys4

Mel

ting

ran

ge,

F Sp

ecif

ic h

eat,

Btu

/lb;

oF

The

rmal

con

duct

ivit

y (3

2-21

2 F

), B

tu/h

r/ft

2;o

F/f

t C

oeff

icie

nt o

f th

erm

al e

xpan

sion

(-5

0 t

o 15

0 F

), p

er o

f E

lect

rica

l re

sist

ivity

(68

F),

ohm

s/ci

r m

il ft

T

empe

ratu

re c

oeff

icie

nt o

f re

sist

ance

, pe

r of

Mod

ulus

of

elas

tici

ty,

ksi

Tem

pera

ture

coe

ffic

ient

of

mod

ulus

of

elas

tici

ty,

per

OF

Mod

ulus

of

rigi

dity

, ks

i T

empe

ratu

re c

oeff

icie

nt o

f m

odul

us o

f ri

gidi

ty,

per

OF

Den

sity

,lb/

in.3

"Giv

en a

s oh

ms/

mil

ft.

Eli

nvar

3.3

X

10-6

-36

X 10

-6

-40

X 10

-6

Iso-

Ela

stic

4 X

10

-6

528·

26,0

00

-20

to +

15

x 1

0-6

9,20

0

0.29

2

Ni-

Spa

n C

2650

-270

0 0.

12

7.5

4.5

x 10

-6

738

0.00

025

24,0

00

-35

to

-15

x 1

0-6

9,40

0

0.29

4

o o j 0+ 2. CD 9- m

>< 'C

III j III o· j III

j Co o o j 0+ 2. CD 9- s: o Co

c C

III ~ o ~ ... 01) ...,

188 Chapter 9

to about -150 F but below that temperature there is a gradual decrease. The modulus of rigidity, also shown in this graph, appears to be less affected by low temperatures than the modulus of elasticity.

All three materials have low coefficients of thermal expansion over the temperature range in which they are normally used. The electrical resistivity of Ni-Span C is considerably higher than the resistivities of the nickel­iron alloys previously discussed but its temperature coefficient of resistance approaches that of the 36 % nickel-iron alloy.

Mechanical Properties

Room- Temperature Properties

Elinvar and Iso-Elastic are austenitic alloys and are hardenable only by cold work. Ni-Span C is precipitation hardenable.

Tensile Properties. Tensile properties of Iso-Elastic and Ni-Span C in various conditions are given in Table 9_7. 4 ,13,14 As shown in the table, Iso­Elastic can be cold worked with large reductions to achieve a yield strength of more than 100 ksi while retaining adequate ductility. According to McCain and Maringer4 the alloy is usually given a stress-relief heat treatment at about 750 F after cold working.

The effects of aging from the solution-annealed condition and after cold work on the properties of Ni-Span C are indicated also in Table 9-7. Aging

Table 9-7. Tensile Properties and Hardness Values of Some Constant-Modulus Alloys4,13,14

Yield strength Tensile Elongation Hardness (0.2 % offset), strength, (2 in.),

Condition ksi ksi % Brinell Rockwell

Iso-Elastic Annealed 35 85 30 135 Cold worked 135 155 10 305

Ni-Span C Solution-annealed 35 90 40 125 B70

. Soln.-annealed, aged 1250 F 115 180 18 305 C33 Cold worked, 50 % 130 135 6 270 C28 Cold worked, 50 %, aged

1250 F 180 200 7 395 C42 Tubing

Cold reduced, 10% 113 18 C26 Cold reduced, 25 % 128 7 C30

Controlled-Expansion and Controlled-Modulus Alloys 189

alone is sufficient to produce a threefold increase in the yield strength and to double the tensile strength while retaining good ductility. Aging after cold work increases the yield strength markedly above that achieved by aging alone but the tensile strength shows only a moderate improvement. The ductility is markedly reduced by cold work and little improvement is achieved by aging in the cold worked condition.

Table 9-4 also contains data on Ni-Span C tubing that had been cold reduced by 10 % and 25 % after a final anneal. The strength increases mo­derately but the ductility is reduced markedly by a reduction of only 25 %. This work was performed by Duff et al. 14 in an investigation of air-melted and vacuum-melted material to determine the differences in fatigue proper­ties of helical Bourdon elements. They concluded that vacuum melting made no significant improvement in the fatigue properties which were reported as the number of cycles to failure.

Hardness. Hardness values for Iso-Elastic and Ni-Span C are included also in Table 9-7. Cold working increased the Brinell hardness ofIso-Elastic form 135 to 305. Depending on the condition of the alloy, the Brinell hard­ness of Ni-Span C ranged from 125 to 395.

"iii ~

en <II Q) ....

U5

Temperature, K

200 300 400 500 600 220 r-..,.---r---,----r-----r---.,

200

180

160

140

120

100

30 ~ -c (l5

20 ~ c 0

+= 0

10 Ol c 0

[jJ

0 -200 0 200 400 600 800

Temperature, F

Fig. 9-8. Short-time elevated-temperature tensile properties of Ni-Span C wire. 4

190 Chapter 9

Fatigue Properties. Gideon et al. ls reported limited data on the fatigue strength of Ni-Span C sheet material. After aging at 1200 F for 5 hours, the material had a fatigue strength of 82 ksi at 106 cycles. Since the tensile strength was 152 ksi, these values indicate an endurance ratio of better than 0.5 for the alloy.

Other Properties. Both Iso-Elastic and Ni-Span C are reported to have hysteresis errors of less than 0.05 % of deflection and creep errors of not more than 0.02 % of deflection in five minutes. Iso-Elastic has a practical working stress in bending of 90 to 100 ksi and in torsion of 40 to 60 ksi. Safe working stresses for compression springs of Ni-Span Care 62 ksi for light service, 54 ksi for average service, and 44 ksi for severe service. 4

Elevated- Temperature Properties

Short-time elevated-temperature tensile properties of Ni-Span Care given in Fig. 9-8. The alloy retains much of its strength up to 800 F but the ductility falls rather rapidly above 200 F.

280

240

200

'ifi 160 oX

(/)-

(/) Q) '-

(j) 120

80

40

Temperature, K

50 100 150 200 250

E

-

60

~

40 C o "§ CJl

20 § GJ

~~--~----~--~----~--~O -400 -300 -200 -100

Temperature, F o 100

Fig. 9-9. Subzero-temperature tensile properties of Ni-Span C bar, solution treated and aged at 1200 F, 5 hr. 12

Controlled-Expansion and Controlled-Modulus Alloys 191

The relaxation of Ni-Span C under a steady load of 50 ksi is reported as 2% at 600 F, 3% at 700 F, and 9% at 800 F.4

Low-Temperature Properties

The tensile properties of Ni-Span C bars at subzero temperatures are given in Fig. 9-9 for material that had been solution treated and aged at 1200 F for 5 hours. The strength increases as the temperature falls and at -420 F is approximately 1.5 times its room-temperature value. The yield strength shows a more moderate improvement. There is only a moderate reduction in ductility as the temperature falls.

Notched bar impact tests on Ni-Span C, after aging at 1250 F for 5 hours, showed practically no change in the energy absorbed as the tempera­ture was reduced from room temperature to -320 F.12

REFERENCES

1. The Physical Properties of the Nickel-Iron Alloys, The Mond Nickel Co., Ltd., n.d. 2. J. W. Sands, "Invar, Elinvar, and related iron-nickel alloys," Metals and Alloys, June

1932, p. 131. 3. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards

(1968). 4. W. J. McCain and R. E. Maringer, Mechanical and Physical Properties of Invar and

Invar-Type Alloys, DMIC Memo 207, Battelle Memorial Institute (1965). 5. Carpenter Invar "36", Carpenter Steel Company (1966). 6. R. E. Maringer, Review of Dimensional Instability in Metals, DMIC Memo 213,

Battelle Memorial Institute (1966). 7. K. A. Warren and R. P. Reed, Tensile and Impact Properties of Selected Materials

from 20 to 300 K, Monograph 13, National Bureau of Standards (1963). 8. D. T. Eash, Tensile Properties of Invar at Low Temperatures, Report LA-3192-MS

AEC, Los Alamos Scientific Lab. (1965). 9. Invar . .. 36% Nickel Alloy for Low-Temperature Service, The International Nickel

Co., Inc. (1967). 10. W. A. Mudge and A. M. Talbot, "Ni-Span," Iron Age, 157, 66 (April 1946). 11. M. E. Fine and W. C. Ellis, "Young's modulus and its temperature dependence in 36

to 50 percent nickel-iron alloys," Trans. AI ME 188, 1120 (1950). 12. F. R. Schwartzberg, S. H. Osgood, R. D. Keys, and T. F. Kiefer, Cryogenic Materials

Data Handbook, AD609562 The Martin Co. (1964). 13. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968). 14. T. A. Duff, M. W. Keenan, L. E. Smith, and R. H. Moeller, "Elastic and fatigue prop­

erties of vacuum remelted versus air melted Ni-Span C alloy 902," Trans. ASME J. Basic Engineering 89, 561 (1967).

15. D. N. Gideon, R. J. Favor, H. J. Grover, and G. M. McClure, '''The fatigue behavior of certain alloys in the temperature range from room temperature to - 423 F," Advances in Cryogenic Engineering 7, 503 (1961).

Chapter 10

Magnetic Materials

Commercial magnet materials can be classified as nonretentive or magnet­ically soft materials and retentive or magnetically hard materials.

The nonretentive materials become magnetized in the presence of a magnetic field but are virtually demagnetized when the field is removed. fncluded in this group are some nickel-iron alloys. These will be discussed in this chapter.

The retentive or hard magnetic materials are those which remain per­manently magnetized after a magnetic field is applied. fncluded in this group are a number of nickel-containing alloys which will also be discussed in this chapter.

First, however, it seems desirable to consider some of the terms used to define the properties of magnetic materials. The following discussion is based on that of Bouwman.!

Figure 10-1 is a representation of a major hysteresis loop. rt is obtained by applying an alternating field of sufficient amplitude to produce saturation and plotting the magnetic induction, B, as a function of the field strength, H.

As indicated on the curve, B is not zero when H is. This means that the material retains its magnetization in the absence of an applied field. The value of B when H is zero is called the residual induction, or remanence, and is symbolized as B r • rt is generally smaller than the maximum induction, Bmw unless the loop is square.

The value of H when B is zero is called the coercive force and is sym­bolized by He' rt measures the field strength required to reverse the magnet­ization. A large value of He is typical of hard magnetic materials; on the other hand, soft magnetic materials have a small value of He"

192

Magnetic Materials 193

+8

+H

-8

Fig. 10-1. Hysteresis loop.!

Magnetic materials are also characterized by their permeability, sym­bolized by fl, which is the ratio of B to H at any point on the curve. If a material has a small coercive force and a high maximum permeability, for example, a small applied field will produce a high value of B.

The area included within the loop measures the hysteresis loss in the material when it passes through a full cycle from Hmax to -Hmax and returns. This is one of the major losses in magnetic materials, but eddy currents generated in the material also cause losses. The eddy current losses can be reduced by using a material having high electrical resistivity.

The portion of the hysteresis loop lying in the upper left portion of the diagram is involved in the properties desired of a permanent magnet material. It will be discussed under that portion of the chapter dealing with permanent magnets.

SOFT MAGNETIC MATERIALS

The most important soft magnetic materials are iron, nickel, and cobalt and alloys of iron and silicon, iron and nickel, and iron and cobalt. Only the nickel-iron alloys will be considered in this chapter. The desired prop­erties of soft magnetic materials are high initial permeability, high maximum induction, low coercive force, low residual induction, and low hysteresis and eddy current losses. 2

Many years ago it was discovered that nickel-iron alloys containing from 78 to 80 % nickel and those containing from 45 to 50 % nickel developed excellent magnetic properties if they were subjected to suitable heat treatments.

194 Chapter 10

At about 80 % nickel-20 % iron, extremely high permeabilities were found; another peak occurred at about 50 % nickel. The latter had the higher flux density and magnetic saturation but both had low hysteresis and eddy current losses.

Based on these materials, quite a large number of proprietary alloys have been developed for use as soft magnet materials. Most of them have been modifications containing additions of molybdenum, chromium, cop­per, or vanadium to reduce the sensitivity of the nickel-iron alloys to vari­ables occurring during heat treatment, thus simplifying the control of cooling rates to achieve high permeabilities. 3 The following materials have been se­lected to indicate the properties that can be expected of soft magnetic alloys:

Alloy Composition, % Ni Cu Cr Mo Fe

79Ni-4Mo 79 4 Bal. Mu-Metal 76 5 1.5 Bal. 49Ni 49 Bal.

Physical Properties

Typical physical properties of the three soft magnetic materials men­tioned above are given in Table 10_1.3,4,5 It should be noted that the 49% nickel alloy was also included in the discussion of controlled-expansion alloys

Table 10-1. Physical Properties of Several Soft Magnetic Materials3 ,4,5

79Ni-4Mo Mu-Metal 49Ni

Melting point, F 2650 2600 Specific heat, Btu/lbrF 0.118 0.12 Thermal conductivity, Btu/hr/ftzrF/ft 20 7.5 Coefficient of thermal expansion ( -90 to

400 F), per of 7.2 x 10-6 7.0 X 10-6 • 3.2 X 10-6

Electrical resistivity (68 F), ohms/cir mil ft 350 337 270 Curie temperature, Fb 790--860 805 840--930 Initial permeabilityb 20,000 20,000 2,500 Maximum permeabilityb 150,000 150,000 25,000 Coercive force, Oeb 0.05 0.03 0.30 Saturation induction, gaussb 8,700 7,200 16,000 Modulus of elasticity, ksi 33,300 25,000 22,500 Modulus of rigidity, ksi 6,600 7,500 Density,lb/in. 3 0.316 0.307 0.298

-68 to 212 F. "Hydrogen heat treatment, properties vary with heat treatment.

Magnetic Materials 195

in Chapter 9 but the magnetic properties were not stressed. To achieve optimum magnetic properties all three of the alloys must be annealed in dry hydrogen at high temperatures under closely controlled conditions.

The Curie temperatures are relatively high, a desirable feature in magnet­ic materials, and they do not differ markedly. As noted previously, the initial and maximum permeabilities of the 49Ni alloy are much lower than those of the 79Ni-4Mo and Mu-Metal compositions. However, the saturation induc­tion of the 49Ni alloy is roughly twice that of the two higher nickel alloys and its coercive force is markedly higher.

According to Smith,6 the magnetic saturation values of these nickel­iron alloys are never as high as those of pure iron and the difference is par­ticularly apparent in the region of highest permeability. For this reason, the nickel-iron alloys are unsuitable for power plant operations where high flux densities are required. Therefore, they cannot compete with the silicon-iron alloys in applications of this kind. At low flux densities, however, the nickel­iron alloys are outstanding and they have important applications in com­munication engineering and related fields.

F or example, the nickel-iron alloys in the 79 % nickel range have a com­bination of high initial and maximum permeabilities and minimum hys­teresis loss in low-level, low-frequency, or rapidly changing magnetic fields. As a result, these alloys are used to shield sensitive devices from weak magnet­ic fields. The 49 % nickel alloys have high permeabilities in stronger fields and their initial permeabilities are approximately twice those of the iron­silicon alloys. In addition, these nickel-iron alloys have substantially greater resistance to atmospheric corrosion than the iron-silicon alloys. 7

The electrical resistivities of the 79Ni-4Mo and Mu-Metal alloys are considerably higher than that of the 49Ni alloy, but the thermal conductivity does not follow the same trend. The thermal conductivity of the 79Ni-4Mo alloy is higher than that of the 49Ni alloy.

The modulus of elasticity of the 79Ni-4Mo alloy is about 10,000 ksi higher than that of the 49Ni alloy but the modulus of rigidity is about 1000 ksi lower. There seems to be a rather unusual relationship between the two moduli of the 79Ni-4Mo alloy.

Mechanical Properties

Typical tensile properties and hardness values for the three alloys are given in Table 10_2.4,5 The tensile strength of the 79Ni-4Mo alloy ranges from 79 ksi in the hydrogen-annealed condition to 97 ksi after cold drawing, and the cold drawn material retains good ductility. Mu-Metal has con­siderably lower strength in the hydrogen-annealed condition than 79Ni-4Mo and the ductility is also somewhat lower. The 49Ni alloy has tensile

196 Chapter 10

Table 10-2. Tensile Properties and Hardness Values of Some Soft Magnetic Materials4 ,s

Yield strength Tensile Elongation Reduction (0.2 % offset), strength, (2 in.), of area, Rockwell

Form and condition ksi ksi % % hardness

79Ni--4Mo Bar

Hydrogen annealed at 2050 F 22 79 64 70 B62

Cold drawn 69 97 37 71 B97

Mu-Metal Strip

Mill annealed 38 90 35 Hydrogen annealed 38 64 27 B60

49Ni Bar

Hydrogen annealed at 2050 F 22 70 45 68 B62

Cold drawn 80 95 25 62 B98

properties roughly equivalent to those of the 79Ni-4Mo alloy although the ductility is somewhat lower. AlI three of the alloys have approximately the same Rockwell hardness after hydrogen annealing.

Both the 79Ni-4Mo and the 49Ni compositions are tough as measured by notched bar testing. The former had an Izod impact resistance of 120 ft-Ib in the cold rolled condition and 85 ft-Ib after hydrogen annealing; the latter, an Izod impact of 93-95 ft-Ib in the cold rolled condition and 93-98 ft-Ib after hydrogen annealing. 4

According to Eberly,4 the 79Ni-4Mo alloy is produced either by vacuum or air melting but the air melted alloy is used to a greater extent although its magnetic properties are somewhat inferior to those of the vacuum-melted material. The air-melted alloy can withstand severe deep drawing and can be rolled to foil.

Eberly also notes that the 49Ni alloy is available in the form of regular and precision castings, forgings, bars, heavy strip, and light gage strip less than 1 mil thick. Magnetic properties vary with the form and, generally, the heavier the section, the poorer the magnetic properties.

PERMANENT MAGNET MATERIALS

The magnetic properties sought in a permanent magnet material are directly opposed to those desired for soft magnetic materials. According to Stearley,2 permanent magnet materials are characterized by a severely

Magnetic Materials 197

strained lattice, a fine grain structure, high hardness, and high alloy content. For optimum properties, the hysteresis loop must be large and the material requires high values of residual induction and coercive force.

Referring to Fig. 10-1, only that portion of the hysteresis loop which lies in the upper left quadrant is of interest. This is the demagnetization curve. The product of B X H along the demagnetization curve is plotted against B and this value is designated BdHa. The subscript d (for demagnetization) indicates a fixed point on the demagnetization curve. The maximum value of this product is designated (BdHd)max and represents the maximum magnetic energy that a unit volume of the material can produce in an air gap. Maxi­mum efficiency is achieved by employing a magnet at a flux density corre­sponding to (BaHd)max-

Maynard8 noted that the relative efficiency of a permanent magnet, based on the volume of material required, is indicated by the maximum en­ergy product (BdHd)max. According to him, this point indicates the energy that a unit volume of the magnetic material will produce in a magnet designed to take advantage of its optimum characteristics. He notes that if this condition can be achieved, residual induction and coercive force are of little real benefit to the designer of the magnet.

Barta9 notes that the permeance coefficient (also called the slope line, shear line, or air-gap line) is the ratio of the total external permeance to the permeance of the space occupied by the magnet. The slope of this line is determined by the geometry of the magnetic circuit which includes the pole pieces, air gaps, and magnet dimensions. The point of intersection with the demagnetization curve gives thc operating point, a very important point in setting magnet specifications.

There are quite a number of metallic and nonmetallic permanent magnet materials. However, those of interest here are the Alnico series and several copper-base materials.

The Alnicos are a series of dispersion harden able alloys based on alu­minum, nickel, and iron. Many of them also contain cobalt, copper, and/or titanium. These alloys are hard and brittle and are not machinable. They are fabricated by casting and grinding or by the use of powder metallurgy techniques. The latter procedure is particularly applicable to small magnets. Within the limits of the process, intricate shapes can be produced as P/M parts.

The Alnico alloys must be heat treated to develop their magnetic prop­erties and the treatment has a very significant influence on the properties which are developed. Certain of these materials are isotropic, others are anisotropic. The isotropic materials can be heat treated, for example, by heating in the 2100-2200 F range, air cooling, and tempering at 1000-1200 F. The anisotropic alloys are cooled from a high temperature in a magnetic field to temperatures of the order of 1500-1550 F and are tempered at

198 Chapter 10

Table 10-3. Nominal Compositions of Some Permanent Magnet Alloyss, II

Composition, %

Alloy Al Ni Co Cu Ti Fe Remarks

Alnico I 12 20 5 Bal. Low cost; isotropic Alnico II 10 17.5 12.5 6 Bal. Isotropic; higher energy product than I,

III, and IV Alnico III 12 25 Bal. Isotropic; low cost; used for small

magnets Alnico IV 12 28 5 Bal. Isotropic Alnico V 8 14 24 3 Bal. Anisotropic; most widely used Alnico VI 8 15 24 3 Bal. Anisotropic Alnico VII 8.5 18 24 3 5 Bal. Either anisotropic or isotropic Alnico VIII 7.5 14 38 3 8 Bal. High energy product Alnico IX 7 15 35 4 5 Bal. Highest energy product Alnico XII 6 18 35 8 Bal. Cunife I 20 60 20 Anisotropic; magnetic properties similar

to Alnico III Cunico I 21 29 50 Anisotropic; similar to Cunife I

1100 F. To produce special properties, or to improve the magnetic charac­teristics, special casting techniques are employed before heat treatment. I 0

Nominal compositions and certain characteristics of the Alnico alloys are given in Table 10-3. s, II

Copper-base alloys, known as Cunife and Cunico, are also used as permanent magnet materials, They have the advantage over the Alnicos that they are ductile and can be readily cold worked, In addition, they are precipi­tation hardenable. Nominal compositions and characteristics are included also in Table 10-3.

Cunife can be easily fabricated by drawing, punching, and swaging, even in the precipitation hardened condition, and is also machinable in this condition. It is used most widely in wire form but can be cold rolled to strip. The maximum magnetic properties are developed by a heat treatment which may consist of slow cooling from 1900 F and aging at 1200 F or by quench­ing from 1825 F and aging at 1100 F. The heat treatment is followed by drastic cold working with a reduction of 70 to 90 % to develop preferred orientation of the grain. 12

Cooter and Mundyl3 investigated the use of Cunife for the production of wire magnets. They found that permanent magnets as small as 0.005 inch in diameter could be cold drawn from commercial Cunife wire and the magnetic properties could be improved by a simple heat treatment after

Magnetic Materials 199

drawing, which consisted of heating the wire to 1130 F for 1 hour and slow cooling to room temperature.

Physical Properties

Nominal physical properties of a number of representative permanent magnet materials are given in Table 10_4. 5 ,11 It should be noted that the magnetic properties are influenced by such factors as the rate of cooling from the heat treatment temperatures, etc.

The maximum energy product ranges from 800,000 gauss-Oe for Cunico to 5,500,000 gauss-Oe for Alnico VIII. The residual induction ranges from 3400 gauss for Cunico to 12,500 for Alnico V and the coercive force from 500 Oe for Cunife to 2000 for Alnico VIII. The permeance ratio ranges from 3.5 for Alnico VIII to 20 for Alnico V. These alloys, therefore, offer a considerable range of magnetic properties.

The magnetic properties of a single composition can be varied by different methods of preparation. According to Fabian, 11 Alnico V produced by powder metallurgy techniques has a residual induction of 10,500 gauss, a coercive force of 600 Oe, and a maximum energy product of 3,500,000 gauss-Oe as contrasted with 12,500 gauss, 600 Oe, and 5,250,000 gauss-Oe, respectively, for cast Alnico V.

Casting methods can also influence the magnetic properties. Alnico V has a directionally oriented structure and a high maximum energy product. Casting against a chill plate produces a structure having partially columnar grains. This product, caIIed Alnico V-DG, has a maximum energy product approximately 20 % higher than that of Alnico V. Going a step further, and casting to produce a product having a fully columnar structure yields a product, called Alnico V-7, which has the highest maximum energy product obtainable in the Alnico V composition. Cooling from a high temperature in a magnetic field is required to develop the optimum magnetic properties in these modified alloys, just as it is for Alnico V.

The electrical resistivities of the Alnico alloys are much higher than those of the copper-base alloy permanent magnets. Values range from 108 ohms/cir mil ft for Cunife to 450 for Alnico IV. The coefficients of expansion of the Alnicos are quite close to those of many of the other nickel alloys.

Roberts 15 investigated the performance of Alnico V and Alnico VI at elevated temperatures. He concluded that both materials could be used up to temperatures of 900 F with no detriment to their magnetic prop­erties.

Clegg16 investigated the effects of low temperatures on the stability of Alnico II, using magnets which were ellipsoids of revolution. He found that

Ta

ble

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Ph

ysic

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ies

of

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me

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gn

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oys

S,l

l

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ico

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ico

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ico

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N 8 (")

::T

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"C ~ ... ... o

Magnetic Materials 201

there is a reversible change in magnetization on cooling from room tempera­ture to -75 F. Magnetized ellipsoids with working points on the upper por­tion of the demagnetization curve increase in strength on cooling and decrease in strength on reheating with no change in domain orientation.

Mechanical Properties

Limited mechanical properties of some permanent magnet materials are given in Table 10_5. 5 ,11 Although the hardness values of the cast and sintered powder metallurgy materials are quite close together, the tensile strengths and transverse rupture strengths differ markedly. For example, the tensile strength of sintered Alnico V is about ] 0 times that of the cast product although they differ by only 6 points on the Rockwell C hardness scale.

The copper alloys have excellent strength in the cold worked condition and they are much softer than the Alnicos.

Table 10-5. Mechanical Properties of Some Permanent Magnet Alloys5,11

Form and condition

Alnico IV Cast, annealed Sintered

Alnico V Cast, annealed Sintered

Alnico VI Cast, annealed Sintered

Alnico VIII Cast

Cunife I Cold worked

Cunico I Cold worked

Tensile strength,

ksi

9.1 60

5.5 50

23

100

85

Transverse modulus of

rupture, ksi

24 85

10.5

45

Rockwell hardness

C45 C42

C50 C44

C56 C44

C57

B95

B73

202 Chapter 10

REFERENCES

1. S. Bouwman, "Magnetic materials," International Science and Technology, Dec. 1962, p.20.

2. G. A. Stearley, "Magnetic materials," Materials & Methods, April 1953, p. 115. 3. S. J. Rosenberg, Nickel and Its Alloys, Monograph 106, National Bureau of Standards

(1968). 4. W. S. Eberly, "A guide to high-permeability nickel-iron alloys," Materials in Design

Engineering, July 1963, p. 76. 5. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968). 6. C. G. Smith, "Nickel alloys with special properties," Metal Industry 91, 145 (1957). 7. "Nickel-iron alloys effectively shield electronic devices," Nickel Topics 21 (6),1 (1968). 8. C. A. Maynard, "Factors in the selection of permanent magnet materials," Applied

Magnetics 1, (3), 2 (1953). 9. G. T. Barta, "Magnetic testing," Applied Mangetics 4(4),2 (1956).

10. Nickel-Containing Mangetic Materials, The International Nickel Co. Inc. (1961). 11. R. J. Fabian, "Permanent magnet materials," Materials in Design Engineering 50,

108 (July 1959). 12. Copper in Instrumentation, Publication No. 48, Copper Development Association,

London (1957). 13. J. L. Cooter and R. E. Mundy, "Cunife wire magnets of small size," J. Res. Nat. Bur.

Std. 59, 379 (1957). 14. "Printed circuit motors simplify servo devices," Nickel Topics 21(3), 12 (1968). 15. W. H. Roberts, "Performance of permanent magnets at elevated temperatures," J.

App\. Phys. 29, 405 (1958). 16. A. C. Clegg, "Effect of low temperature on the stability of permanent magnets," Brit.

J. App\. Phys. 6, 120 (1955).

Chapter 11

Other Nickel Alloys

The materials included in this chapter do not appear to fit logically into any of the groups discussed in the preceding chapters. They consist of several age hardenable nickel alloys, an intermetallic compound, and a PjM prod­uct.

AGE-HARDENABLE NICKEL ALLOYS

These materials will be arbitrarily defined as nickel alloys containing more than 90 % nickel to which additions have been made to confer age hardening properties on the materials. Among these alloys are the following which are called by their originators Permanickel alloy 300, Duranickel alloy 301, and Berylco Nickel 440.

Permanickel alloy 300, because of its carbon and magnesium content, has mechanical properties that are considerably higher than those of com­mercial nickel. Because of its relatively low alloy content, however, it retains many of the general characteristics of nickel. !

Duranickel alloy 301 contains aluminum and titanium which make the alloy age hardenable. It has excellent corrosion resistance, strength and hardness, and good spring properties up to 600 F.!

Berylco Nickel 440, which is age hardenable as a result of its beryllium and titanium content, has high strength and hardness and retains these prop­erties up to 800 F. 2

Nominal compositions of these three alloys are:

Alloy Ni Ti Al Be Mg C Permanickel alloy 300 97 min 0.2-0.6 0.2-0.5 0.40 max Duranickel alloy 301 93 min 0.25-1.0 4.0-4.75 Berylco Nickel 440 Bal. 0.50 1.95

203

204 Chapter 11

Physical Properties

Typical physical properties of the three alloys are given in Table 11_1. 1,2,3

Some of the physical properties of Permanickel alloy 300 are similar to those of commercial nickel but others, which are more sensitive to impurity content, are markedly different. Those approximating the properties of com­mercial nickel are the specific heat, coefficient of thermal expansion, Curie temperature, and the elastic properties. Reflecting the higher alloy content, the electrical resistivity is considerably higher and the thermal conductivity lower than those of commercial nickel. Precipitation of the constituents which age harden the alloy results in some reduction in the resistivity of this and the other two alloys under discussion, although the sources from which the data in Table 11-1 were obtained did not indicate whether the resistivities were given for annealed or aged material.

Duranickel alloy 301 has an electrical resistivity almost three times that of alloy 300 and a correspondingly low thermal conductivity. The age hardening of a solution-annealed specimen reduced the resistivity from 273 to 259 ohms/cir mil ft.4 This alloy also has a Curie temperature in the room­temperature range as contrasted with 600 F for alloy 300. The other physical properties are approximately the same as those of alloy 300.

Bery1co Nickel 440 has an electrical resistivity somewhat higher than that of alloy 300 but much lower than that of alloy 301. Similarly, the ther-

Table 11-1. Physical Properties of Some Age- Hardenable Nickel Alloys l,2

Permanickel Duranickel Berylco alloy 300 alloy 301 Nickel 440

Melting point, F 2620 2500-2620 Specific heat (70-212 F), BtujlbtF 0.106 0.104 Thermal conductivity (70 F), Btujhrjft2tFjft 33.3 13.8 18.3 Coefficient of thermal expansion (70-1000 F),

per OF 8.4 x 10-6 8.2 X 10-6 8.0 X 10-6

Electrical resistivity, ohmsjcir mil ft 95 259 144 Curie temperature, F 6()()a 60-12()a Permeability (H = 2000e) 4.28-Modulus of elasticity, ksi 30,000 30,000 27,000-30,000 Modulus of rigidity, ksi 11,000 11,000 Poisson's ratio 0.31 0.31 0.295 Density,lbjin. 3 0.316 0.298 0.302

"Annealed.

Other Nickel Alloys 205

mal conductivity lies between those ofthe other two alloys. Limited additional data on the physical properties indicate that the coefficient of thermal expan­sion and the elastic properties are close to those of the other two alloys.

Mechanical Properties

Room-Temperature Properties

All three of the alloys can be aged hardened either from the annealed or cold worked condition.

Tensile Properties. Ranges of tensile properties that can be expected with these alloys in various conditions, with or without age hardening, are given in Table 11_2.1,2 In the annealed or hot finished conditions, all three materials have comparable strengths and ductilities.

If the data on Permanickel alloy 300 are compared with those of com­mercial nickel, given in Chapter 2, it is apparent that even the relatively small alloy additions have considerably increased the strength of alloy 300 with only a moderate effect on the ductility as measured by the elon­gation.

By age hardening the hot finished bar of alloy 300, strength can be increased from approximately 100 ksi to 180 ksi. Age hardening after cold work is also effective in increasing the strength. Age' hardening reduces the elongation but, even in the aged condition, the alloy retains adequate ductility.

Duranickel alloy 301 has approximately the same tensile properties as alloy 300 in the hot finished condition and also after age hardening. A sug­gested heat treatment procedure for this material is: solution annealing at 1800 F for 1 hour, water quenching, aging at 1100 F for 16 hours, furnace cooling to 1000 F, holding at that temperature for 6 hours, air cooling. The effect of cold working on the tensile strength of alloy 301 is indicated in Fig. 11-1.4 The strength is increased by approximately 50% by a cold reduc­tion of 60 % and is more than doubled if the cold working is followed by age hardening.

Berylco Nickel 440 is somewhat stronger and less ductile than the other two materials in the solution-annealed condition although all three are quite close together in this condition. In the aged condition, alloy 440 appears to be considerably stronger and much less ductile than the other materials. The producer supplies the alloy in four heat treatable tempers: solution annealed, 1/4 hard, 1/2 hard, and full hard.2 The suggested age hardening treatments and their designations are:

206 Chapter 11

240

220

200

'in .::.c.

180 £ CJl c CI> .....

160 (/j

~ in c 140 ~

120

100

80 0 10 20 30 40 50 60

Cold Reduction, %

Fig. 11-1. Effect of cold work and age hardening of the tensile strength of alloy 301. 4

Initial temper A 1/4H 1/2H H

Aging cycle Ii hours at 950 F I~ hours at 950 F Ii hours at 925 F Ii hours at 925 F

Aged temper AT 1/4HT 1/2HT HT

If intermediate solution anneals are required to permit further working, the producer suggests that they be made at 1825 F.

Cold rolling of alloy 440, followed by age hardening, yields much higher strengths than are achieved in the other two alloys by aging after cold work. However, the ductility is reduced by this treatment.

Hardness. Hardness values for the three alloys are included also in Table 11-2. In Permanickel alloy 300, the Brinell hardness ranges from 140 in the hot finished condition to 360 after aging from that condition. Aging

Tab

le 1

1-2.

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Pro

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orm

and

con

diti

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ksi

%

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nell

R

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man

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230

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120-

150

160-

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150-

190

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arde

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180-

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6

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Sol

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neal

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30 m

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(A

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215

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47 m

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22-3

2 H

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200

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. 24

5 m

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9 m

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C49

min

. H

ard

(H)

150-

190

155-

195

1 m

in.

C30

-40

Har

d, a

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arde

ned

(HT

)b

230

min

. 27

0 m

in.

8 m

in.

C51

min

. N

C

) .... "A

ge h

arde

ned

1.5

hr

at 9

50.F

. bA

ge h

arde

ned

1.5

hr

at 9

25 F

.

208 Chapter 11

after cold drawing increases the maximum hardness to a limited degree. Duranickel alloy 301 has similar hardness properties. Here again, Berylco Nickel 440 can be aged to considerably higher hardness values from either the solution-annealed or cold worked conditions.

Fatigue Properties. Limited fatigue properties for two of the alloys are given in Table 11_3.2 ,4 The endurance ratio of Duranickel alloy 301 is con­siderably lower in the age hardened condition than in the unaged condition,

Table 11-3. Fatigue Properties of Some Age- Hardenable Nickel Alloys2,4

Tensile strength,

Condition ksi

Duranickel alloy 301 Cold drawn 120 Cold drawn, age hardened· 184 Hot rolled, annealedb 101 Hot rolled, annealed, age hardenedc 162

Bery\co Nickel 440 Solution-annealed, age hardened (AT)d 230

aAged 1100 F, 16 hr, furnace cooled to 1000 F, 6 hr, air cooled. "Annealed 1725 F, 1/4 hr, water quenched.

Fatigue strength Endurance (ksi) at ratio

108 cycles ratio

46.2 0.38 55.4 0.30 45 0.45 48.5 0.30

95 e 0.41

'Annealed 1725 F, 1/4 hr, water quenched, aged 1100 F, 16 hr, furnace cooled to 1000 F, 6 hr, air cooled. dAged 1.5 hr, 950 F. el07 cycles.

regardless of whether the material was aged after hot rolling or after cold drawing. No data were available for Berylco Nickel 440 in the unaged con­dition. The ratios for both alloys are in line with those of other nickel-base alloys.

Elevated- Temperature Properties

Short-time elevated-temperature tensile properties of Duranickel alloy 301 and Berylco Nickel 440 are given in Fig. 11-2 and 11_3.2 ,4 Both alloys retain much of their room-temperature strength up to temperatures of about 800 F but above that temperature strength decreases rapidly. In both alloys, the elongation decreases initially to a minimum at about 900 F for alloy 301 and at about 1100 F for alloy 440. Above these temperatures there is a sharp increase within a relatively short temperature range.

The fatigue strength of Berylco Nickel 440 is reported to be .65 ksi at 107

cycles at 800 F compared with 95 ksi at room temperature. 2

All three of these alloys are used extensively as spring materials for

Other Nickel Alloys 209

Temperature, K

300 500 700 900 1100 200 r-r----r----r----r-~

160

'U5 120 -"" If) If) Q) c:: ~ 80 80N

40 E

o 400 800 1200 1600 Temperature, F

Fig. 11-2. Short-time elevated-temperature tensile properties of alloy 301 in the hot rolled and aged condition. 4

'U5 -""

Temperature, K

300 500 700 900 1100 240r-r----r--r--r--n

200

160 Y.S.

lil20 Q) ...... (iJ

80

60 ~ ~

c:: N

40 c::

.Q "0

40 20 g o W

o 0 o 400 800 1200 1600

Temperature, F

Fig. 11-3. Short-time elevated-temperature tensile properties of Nickel 440 strip in the annealed and aged (AT) condition.2

210 Chapter 11

elevated-temperature service. They are reported to have excellent fatigue properties and corrosion resistance and can be used as follows: Permanickel alloy 300 to 600 F, Duranickel alloy 301 to 650 F, and Berylco Nickel 440 to 700 F.6

The proportional limit, moduli of elasticity and rigidity, and resistance to relaxation are the properties which influence the selection of materials for the design of springs for elevated-temperature service, according to Moeller. 6

Although he gave no specific data, he suggested that design stresses based on the stress required to produce 5 % relaxation in 7 days in coil springs be 70 ksi for metal temperatures up to 600 F for alloys 300 and 301 in spring temper, up to 1/2 inch in diameter, cold coiled and aged after coiling. For similar material and sizes, hot rolled and hot coiled before aging, the design stress would be 70 ksi for temperatures up to 550 F and 60 ksi from 550 to 650 F.

Low-Temperature Properties

Martin and MilIer7 reported the effects of subzero temperatures on the tensile properties of Berylco Nickel 440 in both the un aged and aged condi­tions. Some of their data on the aged condition are given in Fig. 11-4. The tensile strength increases moderately as the temperature is reduced. Similar effects were found regardless of whether the material was in the solution

250 300 360

320 ·Vi .:£ - T. S. (A T) £

0. 280 60 c::: -a.> "-(j)

a.> 240 40 Vi c::: a.>

I-'- 200 E (AT) 20 ~ -

E(1/2HT) 160 L...-.l.-_-!......_-I...._-I..._--'-_---' 0

-400 -300 -200 -100 Temperature, F

o 100

~ -c::: 0 +-0 0' c::: 0

w

Fig. 11-4. Subzero-temperature tensile properties of Nickel 440.7

Other Nickel Alloys 211

Temperature, K 120 50 100 150 200

100

.c- 80 u "0 c

2: 60 ti o 0.. 1; 40 >. 0.. "-o

<5 20

O'----J.....----'---I...-_-'-_.....J -400 -300 -200 -100 0 100

Temperature, F

Fig. 11-5. Subzero-temperature impact properties of nickel 440 plate (overaged, 1300 F, 8 hr; aged 950 F, 1.5 hr).2

annealed (A) or annealed and age hardened (AT) condition. Material in the Icold worked (-~H) and cold worked and age hardened (~HT) conditions also showed similar strengthening effects. There was no significant change in the elongation at temperatures down to -400 F in these materials regardless of condition.

The limited data available on the low-temperature impact properties indicate that Berylco Nickel 440 shows no change from ductile to brittle behavior at temperatures as low as -300 F even in the age hardened condi­tion. Figure 11-5 gives the expected range of Charpy V-notch impact values for this material as aged for maximum strength (condition AT, tensile strength 225 ksi) and as overaged to attain the maximum impact properties. 2 In the latter condition, the tensile strength is 151 ksi.

CAST BERYLLIUM-NICKEL ALLOYS

The addition of 2 to 3 % beryllium to nickel yields alloys that can be cast readily and age hardened to high strengths. The alloys have good casting

212 Chapter 11

characteristics and can be poured into sand or permanent molds, but the most effective method is investment casting. 8

Castings can be produced to close tolerances and machined by con­ventional techniques. In the solution-annealed condition, the 2.3 % beryl­lium alloy has a machinability rating of 65 (that of cast iron is 100).

According to Wikle,8 beryllium-nickel alloys can be melted in induc­tion, indirect arc, and gas-fired furnaces using magnesia or zirconia as the refractory. Pouring temperatures range from 2500 to 2600 F, depending on the size of the casting, the detail, and the mold temperature. Details of a recommended casting procedure are included in Wikle's article.

The alloys are used as hot work tool materials in such applications as compression molds for plastics and glass mold components.

There are a number of beryllium-nickel casting alloys but two will be used to indicate the properties to be expected. These are Type 220C contain­ing 2.0 to 2.3 % beryllium-balance nickel and Type 260C, with 2.55 to 2.8 % beryllium-balance nickel.

Physical Properties

Limited physical properties of the two alloys are given in Table 11_4.8,9

The thermal conductivities and coefficients of thermal expansion are quite close to those of the wrought beryllium-nickel alloy discussed previously.

Table 11-4. Properties of Two Beryllium-Nickel Alloys8,9

Physical properties Melting range, F Thermal conductivity, Btu/hr/ft2 /oF/ft

at 100 F at 1200 F

Coefficient of thermal expansion, per OF 6S-200F 6S-S00F 6S-1200F

Density,lb/in. 3

Mechanical propertiesa

Yield strength (0.2 % offset), ksi Tensile strength, ksi Elongation (2 in.), % Rockwell hardness

·Solution annealed 1950 F, 1 hr, water quenched, aged 950 F, 3 hr.

Type 220C

2100-2300

22 33

7.5 X 10-6

S.2 X 10-6

0.292

170 ISO

1.5 C50

Type 260C

19.6 30.S

9.2 X 10-6

224 242

1 C56

Other Nickel Alloys 213

Mechanical Properties

The alloys are hardened by solution annealing at 1950 F and aging at 950 F. Properties of the two beryllium-nickel alloys in the age hardened condition are given also in Table 11-4. The effect of increasing the beryllium content on the tensile properties is apparent. Type 260C has a tensile strength of 242 ksi compared with 180 ksi for Type 220C. These properties are rela­tively close to those of the wrought alloy after aging from the solution­annealed condition. The ductility, as measured by the elongation, however, is much lower in the castings than in the wrought products. The hardness achieved by aging the castings is practically the same as that of the wrought alloy after aging from the solution-annealed condition.

NITINOL

An investigation into the properties of intermetallic compounds at the United States Naval Ordinance Laboratory disclosed that the compound containing 50 atomic per cent nickel and 50 atomic per cent titanium, cor­responding approximately to 55 weight per cent nickel, had unusual proper­ties. This compound was given the name Nitinol and, according to Buehler and Wiley, 1 0 had a single-phase body-centered cubic structure with good room-temperature ductility. Later work has shown that Nitinol undergoes a martensitic phase transformation near room temperature. 11

One result of this transformation is the fact that this material has an "elastic memory," a property usually associated with certain plastics and, as far as is known at present, unique among metallic materials. According to Wagner and Jackson 12 this "memory" or shape recovery results from a rever­sible stress-induced martensitic transformation. Below the transformation temperature the material is ductile and can be deformed plastically under relatively low stresses. If the strain is limited to about 8 %, highly efficient recovery is possible.

For example, a section of a mill form of Nitinol (wire, tube, sheet, etc.) can be formed to the desired shape, clamped to prevent movement, and given a memory heat treatment, for example, at 900 F. After cooling, under restraint, the shape can be changed as desired. Then a restorative heat treat­ment can be given in the range -60 to 300 F, the exact temperature depend­ing on the processing history. Upon cooling to ambient temperature, the original shape will be restored. 12

According to Rozner and Wasilewski 13 Nitinol can be hot worked read­ily by extrusion, rolling, or swaging at temperatures in the range llOO to

214 Chapter 11

1650 F. Subsequent rolling to strip and wire drawing can be carried out at about 750 F.

Physical Properties

Typical physical properties of Nitinol below the transformation tempera­ture for all properties except thermal expansion are given in Table 11_5. 10 ,13

Some interesting comparisons can be made with more familiar materials. Thus, the elastic properties are similar to those of aluminum alloys whereas the coefficient of thermal expansion is about 60 % of that of the 80 % nickel-20 % chromium alloy over the same range. The electrical resistivity is quite close to that of the 36% nickel-balance iron alloy.

Table 11-5. Physical Properties of Nitinopo,I3

Melting range, F ................................................ 2265-2390 Coefficient of thermal expansion (75-1050 F), per of ................ 5.8 X 10-6

Electrical resistivity, ohms/cir mil ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 Magnetic permeability. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . <1.002 Modulus of elasticity, ksi ........................................ 10,100 Modulus of rigidity, ksi .......................................... 3,800 Poisson's ratio .................................................. 0.31 Density, Ib/in. 3 •••••••• •••• •••••••••••••••••• .••.•••••• •••••. •••• 0.233

According to Hanlon et a/. II the electrical resistivity of the high-tem­perature modification is 493 ohms/cir mil ft whereas that of the low-tem­perature modification is 457. For comparison, these resistivities had been converted to a constant temperature.

The compound is paramagnetic, having a very low and constant per­meability in the range - 320 to 1000 F.I °

Mechanical Properties

Some room temperature mechanical properties of Nitinol are given in Table 11_6. 10 ,12 The form of the material was not stated and no indication of whether the materials were in the low- or high-temperature modification was included. Since transformation occurs close to room temperature, these data are merely indicative of the properties that can be expected of this compound.

The data indicate, however, that Nitinol has good strength properties and fair ductility as measured by the elongation. The type of impact test was not specified. The fatigue strength appears to be very good in relation to the tensile properties.

Other Nickel Alloys 215

Table 11-6. Mechanical Properties of Nitinol'°,12

Yield strength (0.2 % offset), ksi ........................ 33-81 Tensile strength, ksi .. . . . . .. .. . . . . . .. . . . . . . . . . . . .. . . .. 82-140 Elongation (2 in.), % .................................. 10 Rockwell hardness .................................... A65-68 Impact resistance, ft-Iba ••••••••.••••.•..•...•.•......•. 24 Fatigue strength (25 X 106 cycles), ksi .................. 70

"Type of test not given.

The short-time elevated-temperature tensile properties of Nitinol in the normalized condition are given in Fig. 11-6. 13 The tensile strength falls regularly as the temperature increases, but the yield strength passes through a maximum at about 400 F. The ductility, as measured by the elongation, increases at a relatively low rate up to about 700 F but above this tempera­ture the rate increases abruptly.

The low-temperature tensile properties of the material are indicated in Fig. 11-7,13 Both tensile and yield strength increase uniformly as the tem-

~ . iii ..:<: c-vl 0 en '"6 (j)

~ Ol (f) C

0 W

o 1600 Temperature, F

Fig. 11-6. Short-time elevated temperature tensile properties of Nitinol. l 3

216 Chapter 11

Temperature,K

160 50 100 150 200 250 300

140

120

100

Ul 80 80 .¥.

ul Ul ~ E (jj

60 60 ~ c~

0 40 40 B

0> C 0

20 20 w

0 0 -400 -300 -200 -100 0 100

Temperature, F

Fig. 11-7. Subzero-temperature tensile properties of Ni-tinol. 13

perature is reduced. The elongation remains fairly constant down to about -150 F but below that temperature decreases rather rapidly.

According to Buehler and Wiley,! 0 the impact resistance of Nitinol is about 25 % greater at -112 F than it is at room temperature.

In reviewing the effects of temperature on the mechanical properties, Rozner and Tydings!3 note that at temperatures above about 1100 F, the compound is highly ductile, has a low yield strength, low work hardening rate, and high strain rate sensitivity. At temperatures between 70 and 1100 F the yield strength is temperature dependent and work hardening increases rapidly with falling temperatures. At temperatures below 70 F, Nitinol shows con­siderable ductility which they ascribe to a martensitic transformation oc­curring at a temperature of about 150 F.

Other Nickel Alloys 217

TUNGSTEN-NICKEL P/M PRODUCTS

Powder metallurgy procedures are used in the production of tungsten­base compositions, which have been called Heavy Metal because of their high densities. In the production of these P 1M parts, tungsten, nickel, and copper powders were used in the early stages of development.

Tungsten is insoluble in liquid copper but nickel can dissolve about 45 % by weight at 2725 F.15 The solubility decreases as the temperature is reduced. According to Green et al. 16 , copper can be used to reduce the solu­bility of tungsten in nickel. For example, by the use of a ratio of 3 parts nickel to 1 part copper, the solubility can be reduced to about 27 % at 2590 F.

Taking advantage of this relationship, the original commercial alloys contained about 90 % tungsten, 7.5 % nickel, and 2.5 % copper. Many modi­fications have been made of this composition. These are usually proprietary and the actual composition is seldom given.

Although there are various techniques which can be used in the produc­tion of Heavy Metal, the following is representative. A mixture of metal powders such as tungsten, nickel, copper, and iron with a paraffin wax binder is compacted into the desired form and presintered at about 1525 F in a hydrogen atmosphere for periods up to 16 hours. During presintering, the wax melts and the part becomes sufficiently hard to be machinable although it is still in the "green state." The compact is then sintered at 2650 F in a hydrogen atmosphere for periods of 12 to 14 hours. During sintering, the nickel, copper, and iron melt and alloy with the tungsten and, at the same time, the part shrinks by as much as 20 % with a corresponding increase in density.17

Tungsten-base alloys of the type under discussion are machinable and can be readily drilled, tapped and threaded, milled and turned. They can be joined by soft soldering or brazing. I 8

These alloys are used as counterweights for aircraft control surfaces, balancing of flywheels and crankshafts, gyroscope parts, vibration damping, electrical contacts, radiation shielding, and containers for radioactive mate­rials.

Physical Properties

Limited physical properties of severa' Heavy .rvH~tal compositions are given in Table 11_7.16,17,18,19 With densities of the order of 17 g/cm3, these alloys have almost twice the density of nickel. They can be produced in a range of densities by modification of the processing variables. They have low coefficients of expansion and the modulus of elasticity is much higher

218

Table 11-7. Properties of Some Tungsten-Nickel P/M Products

90W, 90W, 90W, 6 Ni, Ni, 7 Ni,

Composition 4Cu Cu 3 Fe

Physical properties

Chapter 11

W, Ni, Cu, Fe

Coefficient of thermal expansion, per of 3.3 x 10-6 3.0 X 10-6 •

Electrical conductivity, % lACS 14 15 Modulus of elasticity, ksi 45,000 Density, g/cm3 17 16.85 17 17

Mechanical properties Yield strength (0.2% offset), ksi 75 95 85b

Tensile strength, ksi 110 94 min. 125 93 Elongation (2 in.), % 6 2 12 Rockwell hardness C30 C32 290c

°68 to 790 F. .Yield point. cBrineli.

than those of the other nickel alloys discussed previously. Their electrical conductivities are quite low.

Mechanical Properties

Tensile properties and hardness values for these materials are included also in Table 11-7. They are quite strong and hard but the ductility is rather low.

According to Green et al. 16 one of the disadvantages of the tungsten­nickel-copper system is its sensitivity to cooling rate. They note that the 90 % tungsten-7.5% nickel-2.5% copper alloy after slow cooling has a tensile strength of 56 ksi and an elongation of less than I %, whereas rapid cooling yields a tensile strength of 90 ksi with an elongation of 1 to 2 %. They mention that the purpose of modifying the alloy by replacing part of the nickel and copper by other elements is to overcome this sensitivity to cooling rate. The 90 % tungsten-7 % nickel-3 % iron alloy which they developed has a tensile strength of 59 ksi with an elongation of 19 % after slow cooling and a tensile strength of 54 ksi with an elongation of 7 % after rapid cooling.

REFERENCES

1. Handbook of Huntington Alloys, Huntington Alloy Products Division, The Interna­tional Nickel Co., Inc. (1968).

2. Berylco Nickel 440 Strip, Tech. Bull. 1105-C, Beryllium Corporation, n.d. 3. Properties of Some Metals and Alloys, The International Nickel Co., Inc. (1968).

Other Nickel Alloys 219

4. Huntington Nickel Alloys, Huntington Alloy Products Division, The International Nickel Co., Inc. (1968).

5. R. W. Carson, "Flat spring materials" Product Engineering March 1, 1965, p. 68. 6. R. H. Moeller, "High nickel alloys for high-temperature springs," Springs Magazine,

October 1965, p. 12. 7. H. L. Martin and P. C. Miller, Effects of Low Temperatures on the Mechanical Prop­

erties of Structural Materials, NASA SP-5012 (01), 1968. 8. K. C. Wikle, "Characteristics and properties of beryllium-nickel alloys," Foundry

90,50 (Dec. 1962). 9. "Beryllium-nickel alloy extends life of glass mold components," Nickel Topics 18(2),

5 (1965). 10. W. J. Buehler and R. C. Wiley, The Properties of TiNi and Associated Phases, U. S.

Naval Ordinance Lab. Tech. Report 61-75, 1961. 11. J. L. Hanlon, S. R. Butler, and R. J. Wasilewski, "Effect of martensitic transformation

on the electrical and magnetic properties of TiNi," Trans. Met. Soc. AIME 239, 1323 (1967).

12. H. J. Wagner and C. M. Jackson, "What you can do with that 'memory' alloy," Materials Engineering, October 1969, p. 28.

13. A. G. Rozner and R. J. Wasilewski, "Tensile properties of NiAI and NiTi," J. Inst. Met. 94, 169 (1966).

14. S. Spinner and A. G. Rozner, "Elastic properties of NiTi as a function of tempera­ture," J. Acoust. Soc. Amer. 40, 1009 (1966).

15. M. Hansen, Constitution of Binary Alloys, McGraw-Hill Book Co. (1958). 16. E. C. Green, D. S. Jones, and W. R. Pitkin, "Development of high-density alloys,"

Symposium on Powder Metallurgy, 1954, Iron and Steel Institute (1956), p. 253. 17. "Heavy alloy in full production," Engineering 177, 670 (1954). 18. Heavy Alloy, Tech. Information Bull. Sylvania Electric Products, Inc. (1969). 19. K. Rose, "High-density alloys for heavy-weight applications," Materials and Methods,

April 1953, p. 86.

Appendix I

Trademarks

A number of alloys discussed in this publication are marketed under trademarks.

Trademark Alumel AM 350 AM 355 Chromel Duranickel Hastelloy HNM Illium Incoloy Inconel Invar

Iso-Elastic Mar-M200 MAR-M246 Monel Nimonic Ni-Span C Ni-Span Hi Permanickel Rene 41 PHI5-7Mo 17-4PH

Owner Hoskins Manufacturing Company Allegheny Ludlum Steel Corporation Allegheny Ludlum Steel Corporation Hoskins Manufacturing Company The International Nickel Company, Inc Union Carbide Corporation Carpenter Steel Company Stainless Foundry and Engineering, Inc. The International Nickel Company, Inc. The International Nickel Company, Inc. Soc. Anon. de Commentry-Fourchambault et Decaziville

(Acieries d'Imphy) John Chatillon & Sons The Martin Company The Martin Company The International Nickel Company, Inc. The International Nickel Company, Inc. The International Nickel Company, Inc. The International Nickel Company, Inc. The International Nickel Company, Inc. Allvac Metals Corporation (Division of Teledyne) Armco Steel Corporation Armco Steel Corporation

221

222

17-7PH 17-lOP 17-14CuMo Stainless W Udimet 500 Waspaloy

Armco Steel Corporation Armco Steel Corporation Armco Steel Corporation United States Steel Corporation Special Metals Corporation United Aircraft Corporation

Appendix I

Appendix II

Conversion Factors and Symbols

The use of the International System of Units (SI), a modernized version of the metric system, is being advocated both in the United States and abroad. Although use of the system is just starting in the United States, some of the new units are appearing, particularly in European publications, and there­fore units most applicable to this book are included in the conversion fac­tors which follow. A full discussion of the SI system can be found in "Metric Practice Guide," Designation E 380, ASTM Standards, Part 30 or in ASTM Metric Practice Guide, Handbook 102, National Bureau of Standards, which is available from the Superintendent of Documents, Washington, D. C.

For readers of this publication, the principal change from the more familiar cgs system is the use of the newton as a unit of force, replacing the kilogram (force). In the SI system, for example, the tensile strength is express­ed in meganewtons per square meter, MNjm2. In addition, temperatures are expressed in degrees Kelvin rather than in degrees Celsius (formerly centi­grade). The Kelvin and Celsius temperature intervals are identical and a Kelvin temperature can be obtained by adding 273.15 to the Celsius tempera­ture.

Multiply

Specific heat BtujlbtF

Thermal conductivity Btujhrjft2tFjft Btujhrjft2tFjft Btujhrjft2tFjft

Conversion Factors

by

0.00413 0.0173 1.73

223

to obtain

caljgtK

caljsecjcm 2 tKjcm wattsjcmtK wattsjmtK*

224

Thermal expansion Coefficient per of 1.8

Appendix II

coefficienWK

Electrical resistivity ohms/cir mil ft 0.16624 microhm-cm

Density Ib/in. 3

Stress units ksi ksi

Temperature Conversion Fahrenheit to Kelvin Fahrenheit to Celsius

27.68

6.8948 0.7031

Symbols

MN/mZ* kgf/mm2t

IK = (IF + 459.67)/1.8 te = (tF - 32)/1.8

The following symbols have been used in the graphs:

Ann. Annealed C.D. Cold drawn C.W. Cold worked E Elongation H.R. Hot rolled Mod E ModR RofA T.S. Y.S. Y.S.O.2% Y.S.O.5%

* SI unit.

Modulus of elasticity Modulus of rigidity Reduction of area Tensile strength Yield strength (unspecified) Yield strength (0.2 % offset) Yield strength (0.5 % extension under load)

t SI unit. To distinguish between mass and force or load, the former is designated kg (for example) and the latter kgf in the SI system.

Index

A-286 see Stainless steels Age-hardenable alloys 34, 44, 49, 61, 68,

71,82,112,143,183,185,197,203 AISI (American Iron and Steel Institute)

32, 129 Alloy Casting Institute 71,151 Alloy 713C see Nickel-base superalloys Alnico see Magnetic materials Alumel see Thermocouple alloys AM 350 see Stainless steels AM 355 see Stainless steels ASTM (American Society for Testing and

Materials) 14, 222

Berylco nickel 440 see Beryllium-nickel alloys .

Beryllium-copper-nickel see Copper-nick­el alloy CA 966

Beryllium-nickel alloys 203, 211 Beryllium-nickel alloys (specific types)

Berylco Nickel 440 203, 204, 205, 206 208,210, 21l

220C 212,2l3 260C 212,213

Boiling point 10

Chromel P see Thermocouple alloys Coefficient of thermal expansion 10, 26,

28, 34, 45, 47, 54, 56, 60, 72, 74, 86, 95, 102, 113, 116, 124, 126, 132, 145, 154, 162, 172, 177, 187, 194,200,204,212,214,218

Coercive force 194, 200 Conductivity see Electrical conductivity,

Thermal conductivity Constantan see Thermocouple alloys

Controlled-expansion alloys High expansion 183 Low expansion 175

Controlled-expansion alloys (specific types) 36% Ni-BaI. Fe 177,179,180,181,182 42 % Ni-BaI. Fe 177, 179 49% Ni-BaI. Fe 177, 179 Ni-Span Hi 183, 184

Constant-modulus alloys 185 Constant-modulus alloys (specific types)

Elinvar 185, 186 Iso-Elastic 185, 186, 188, 189, 190 Ni-Span C 185,186,188,189,190,191

Conversion factors 222 Copper-base nickel alloys see Copper­

nickel alloys, Nickel silvers Copper Development Association 100,

112, 114 Copper-nickel alloys

Cast III Wrought 100

Copper-nickel alloys (specific types) CA 706 101,102,103,105,108,111 CA 710 101,102, 103, 105 CA 715 101, 102, 103, 105, 106, 110 CA 962 112, 114 CA 963 112, 114 CA 964 112, \14 CA 966 112, \14 Copper-Nickel, 10% 105, 109; see also

CA 706 Copper-Nickel,20% 105,110, Ill; see

also CA 710 Copper-Nickel,30% 104,105,106,107,

108, 110, 111; see also CA 715 90-10 Copper-Nickel see CA 962

225

226

Copper-nickel alloys (cont.) 70-30 Copper-Nickel 114; see also CA

964 Copper-nickel-zinc alloys see Nickel

silvers Creep properties 20, 41, 66, 77, 121, 139,

148, 155, 182 Cunico see Magnetic materials Cunife see Magnetic materials Curie temperature 10, 34, 60, 74, 177,

194, 204

Density 10, 28, 34, 45, 47, 54, 56, 60, 72, 74, 86,95, 102, 113, 116, 124, 132, 145, 154, 162, 172, 177, 187,- 194, 200,204,212,214, 218

Duranickel alloy 301 203, 204, 205, 206, 208,210

Electrical conductivity 113, 124, 126, 218 Electrical resistance alloys 159 Electrical resistance alloys (specific types)

35-20 160, 161, 163, 165, 167 55-45 160, 161, 165, 166, 168 60-15 160, 161, 163, 165, 167 75-20 160, 161, 165 80-20 160, 161, 163, 165, 166, 167, 168 Nickel-silicon 160, 161, 165

Electrical resistivity 10, 26, 28, 45, 47, 54, 56,60,72, 86, 102, 116, 132, 145, 154, 162, 172, 177, 187, 194, 200, 204,214

Elinvar see Constant-modulus alloys Electromotive force versus copper 163 Emissivity 13 Energy product see Maximum energy

product

Fatigue properties Ambient temperature 18, 38, 64, 76,

105, 117, 124, 135, 165, 180, 208, 214

Elevated temperature 51, 208 Low temperature 24,42, 143

GMR-235D see Nickel-base superalloys

Hardness 16,26,27,28,37,45,48,55, 56, 64, 73, 76, 97, 103, 112, 117, 124, 127, 135, 148, 153, 165, 180, 184, 188, 195, 201, 206, 212, 214, 217

Hastelloy alloys see Nickel-molybdenum alloys, Nickel-silicon alloys

Heavy metal see Tungsten-nickel P/M parts

Index

HNM see Stainless steels

IlIium alloys see Nickel---<:hromium-molyb­denum alloys

Impact properties Ambient temperature 18, 26, 27, 38,

45,49, 55, 56, 65, 73, 77, 106, 124, 127, 138, 148, 153, 180, 196, 214

Low temperature 42,45, 53, 70, 71, 93, 111, 121, 143, 150, 155, 169, 182, 191,210,216

IN-l00 see Nickel-base superalloys Incoloy alloys see Nickel-iron---<:hromium

alloys Inconel alloys see Nickel---<:hromium alloys International system of units 222 Irradiation, neutron 19 ISA (Instrument Society of America) code

symbols for thermocouples 169 Iso-Elastic see Constant-modulus alloys

M-252 see Nickel-base superalloys Magnetic materials

Definitions 192, 196 Permanent 196 Soft 193

Magnetic materials (specific types) Alnico I 198 Alnico II 198 Alnico III 198 Alnico IV 198, 199,201 Alnico V 198, 199, 201 Alnico VI 198, 199, 201 Alnico VII 198 Alnico VIII 198, 199, 201 Alnico IX 198 Alnico XII 198 Cunico I 198, 199, 201 Cunife I 198, 199,201 49Ni 194, 195, 196 Mu-Metal 194, 195 79Ni-4Mo 194, 195, 196

Magnetostriction 12 MAR-M200 see Nickel-base superalloys MAR-M246 see Nickel-base superalloys Maximum energy product 200 Mechanical properties

Beryllium-nickel alloys 206, 213 Constant-modulus alloys 188, 190, 191 Controlled-expansion alloys 179, 181,

182, 184 Copper-nickel alloys 102, 106, 109,

114 Duranickel alloy 301 205

Index

Mechanical properties (cont.) Electrical resistance alloys 165, 166,

168 Magnetic materials 205, 208, 210, 213,

214,218 Nickel 13, 19, 23, 25, 29 Nickel-base superalloys 88, 89, 91, 96 Nickel--chromium alloys 61, 66, 70 Nickel--chromium-molybdenum alloys

54 Nickel--copper alloys 48, 50, 51, 54 Nickel-iron--chromium alloys 75, 77,79 Nickel-molybdenum alloys 48, 50, 51,

54 Nickel-silicon alloys 57 Nickel silvers 117, 120, 121, 123, 125,

127 Nitinol 214 Permanickel alloy 300 205 Stainless steels 133, 138, 141, 146, 148,

150, 153, 155, 157 Thermocouple alloys 173 Tungsten-nickel P/M parts 218

Melting point 10, 26, 34, 45, 47, 56, 60, 72,74,86,95, 102, 113, 116, 124, 132, 154, 162, 172, 177, 184, 187, 194, 204, 212, 214

Metal Powder Industries Federation 125, 157

Modulus of elasticity 10, 26, 28, 34, 45, 47,54,56,60,72, 74, 86, 95, 102, 113, 116, 124, 126, 132, 145, 154, 162,172,177,184,187,194,204, 214,218

Modulus of rigidity 10, 34, 60, 74, 86, 102, 116, 132, 145, 162, 172, 177, 187, 194, 204, 214

Modulus of rupture 127,201 Monel alloys see Nickel--copper alloys Mu-Metal see Magnetic materials

Neutron irradiation 19 Nickel

Cast 24 Effect of impurities 8 Mechanical properties 13, 19, 23, 25,

27,29 Physical properties 9,25,29 Powder 26 Wrought 8

Nickel deposits 2 Nickel developments 4 Nickel ores 2 Nickel producers 4 Nickel production 4

Nickel recovery 5 Nickel reserves 3

227

Nickel-base corrosion- and heat-resistant alloys 32, 58

Nickel-base superalloys Cast 94 Range of l00-hour rupture strength 83 Wrought 84

Nickel-base superalloys (specific types) Alloy 713C 94, 95, 97, 98 GMR-2350 94, 95, 97, 98 IN-loo 94,95,97, 98 M-252 84, 85, 88, 89, 91 MAR-M2oo 94, 95, 97, 98 MAR-M246 94, 95, 97, 98 Rene 41 84, 85, 88, 89, 91, 92, 93 TO Nickel 84,85,88,89,91,92,93 Udimet 500 84, 85, 88, 89, 91 Waspaloy 84, 85, 88, 89, 91, 92

Nickel--chromium alloys Cast 71 Wrought 58

Nickel--chromium alloys (specific types) HW 71,72, 152 HX 71, 72, 152 Inconel alloy 600 59, 60, 61, 62, 63, 65,

66, 67, 68, 69, 70 Inconel alloy 601 59, 60, 61, 65 Inconel alloy 610 71, 72 Inconel alloy 625 59, 60, 61, 64, 65, 66,

67,68 Inconel alloy 705 71,72 Inconel alloy 718 59,60, 61, 62, 65, 66,

67, 68, 69, 70 Inconel alloy X750 59, 60, 61, 62, 65,

66, 67, 68, 69, 70 Nickel--chromium-molybdenum alloys 53 Nickel--chromium-molybdenum alloys

(specific types) IIlium B 53, 55 Illium G 53, 54, 55 Illium 98 53, 55

Nickel--copper alloys Cast 44 Wrought 33

Nickel--copper alloys (specific types) Monel alloy 400 33, 34, 35, 36, 38, 40,

41,42,43 Monel alloy 404 33, 34, 35, 36 Monel alloy R405 33, 35, 36, 38 Monel alloy 410 44,45 Monel alloy K-5oo 33, 34, 35, 36, 39,

40,41,43,44 Monel alloy 505 44, 45

Nickel-iron--chromium alloys 73

228

Nickel-iron---<:hromium alloys (specific types) Incoloy alloy 800 74, 75, 76, 77, 78, 79 Incoloy alloy 804 74, 75, 77, 78 Incoloy alloy 825 74, 75, 77, 79

Nickel-molybdenum alloys Cast 53 Wrought 47

Nickel-molybdenum alloys (specific types) Hastelloy alloy B 47,48,49, 50, 51, 52,

53, 55 Hastelloy alloy C 47,48,49, 50, 51, 53,

55 Hastelloy alloy N 47, 48, 49, 50, 51, 55 Hastelloy alloy X 47,48,49,50,51,53,

55 Nickel-silicon alloys 56, 160

Hastelloy alloy D 56 Nickel silvers

Cast 122 Powder 125 Wrought 114

Nickel silvers (specific types) CA 745 115,117 CA 752 115,117 CA 757 115, 117 CA 770 115, 117 CA 973 123 CA 974 123 CA 976 123 CA 978 123 Nickel Silver 55-18 119, 129; see also

CA 770 Nickel Silver 55-30 122 Nickel Silver 65-10 119, 120, 121; see

also CA 745 Nickel Silver 65-12 see CA 757 Nickel Silver 65-18 see CA 752 Nickel Silver 74-20 121 Nickel Silver Powder 125, 127

Ni-Span C see Constant-modulus alloys Ni-Span Hi see Controlled-expansion

alloys Nitinol 213,214,215,216

Ores 2

Permanickel alloy 300 203, 204, 205, 206, 210

Permeability 10, 34, 60, 74, 86, 132, 145, 154, 194, 204, 214

Permeance 200 PHI5-7Mo see Stainless steels Physical properties

Beryllium-nickel alloys 204, 212 Constant-modulus alloys 186 Controlled-expansion alloys 176, 184

Physical properties (cont.) Duranickel alloy 301 204 Electrical resistance alloys 161 Magnetic materials 194, 199 Nickel 9, 25, 29

Index

Nickel-base superalloys 85, 94 Nickel---<:hromium alloys 61,71 Nickel---<:hromium-molybdenum alloys

54 Nickel---<:opper alloys 34, 44 Nickel-iron---<:hromium alloys 74 Nickel-molybdenum alloys 47 Nickel-silicon alloys 56 Nickel silvers 115, 123, 127 Nitinol 214 Permanickel alloy 300 204 Stainless steels 133, 146, 152 Thermocouple alloys 171 Tungsten-nickel P/M parts 217

P/M parts see Powder metallurgy products Poisson's ratio 10,34,60,74,86, 145, 162,

172,177,204,214 Powder metallurgy (P/M) products

Magnetic materials 197, 199 Nickel 26, 28, 29 Nickel silver 125 Stainless steel 157 Tungsten-Nickel 217

Precipitation-hardenable alloys see Age­hardenable alloys

Reflectivity 13 Rene 41 see Nickel-base superalloys Residual induction 10,200 Resistivity, electrical see Electrical resis­

tivity

Saturation induction 194 Shear strength 28, 180 17-4PH see Stainless steels 17-7PH see Stainless steels 17-10P see Stainless steels 17-14CuMo see Stainless steels SI system 222 Specific heat 10,26,34,45,47,54, 56, 60,

72,74,86,95, 102, 113, 116, 124, 132, 154, 162, 172, 184, 187, 194, 204, 212, 214

Springs, design stresses 190, 210 Stainless steels

Cast, standard 151 Powder parts 157 Precipitation-hardenable 143 Wrought, standard 129

Stainless steels (specific types) A-286 144, 146, 148, 150

Index

Stainless steels (cont.) AM 350 144, 146, 148, 150 AM 355 144, 146, 148 CE-30 152, 153 CF-3 152 CF-3M 152 CF-8 152, 153, 155 CF-8C 152, 156 CF-8M 152, 153, 155 CF-16F 152 CF-20 152 CO-8M 152, 153 CH-20 152, 153, 155 CK-20 152, 153, 155 CN-7M 152, 153 HE 152 HF 152,153 HH 152, 153 HI 152 HK 152, 153 HL 152 HN 152 HNM 144, 146, 148, 150 HT 152 HU 152 PH15-7Mo 144, 146, 148 17-4PH 144, 146, 148, 150 17-7PH 144, 146, 148, 150 17-10P 144, 146, 148 17-14CuMo 144, 146 Stainless W 144, 146, 148 201 130, 133, 135, 136, 138 202 130, 138, 140 211 130, 133, 135, 136 216 130, 133, 135, 137, 139 301 DO, 133, 135, 136, 137, 138, 140,

141, 142 302 130,133 304 130, 133, 135, 136, 137, 138, 139

140, 141, 142 304L 130, 133, 135, 138, 140, 141 305 130, 133, 135, 136 309 130, 133, 135, 138 309s 130, 133, 135 310 130, 133, 135, 137, 138, 139, 142 310s 130, 133, 135 316 130, 133, 137, 139, 140 316L 130 317 130 321 130, 137, 142 347 130, 133, 137, 139, 142 384 130, 133, 135 385 130, 133, 135 630 see 17-4PH 631 see 17-7PH 632 see PH15-7Mo

Stainless steels (cont.) 633 see AM 350 634 see AM 355 635 see Stainless W 653 see 17-14CuMo 660 see A-286

229

Stainless W see Stainless steels Stress-rupture properties 20, 41, 50, 66,

77,89,98, 106, 139, 148, 155, 167 Superalloys see Nickel-base superalloys Symbols used in graphs 223

TD Nickel see Nickel-base superalloys Temperature coefficient

Modulus of elasticity 187 Modulus of rigidity 187 Resistance 10, 162, 172, 177, 187

Thermal emf versus copper 162 Thermocouples

Temperature-emf tables 170 Temperature limits 171

Tensile properties Ambient temperature 13, 26, 27, 28, 35,

45, 48, 54, 56, 61, 73, 75, 88, 96, 102, 112, 117, 123, 127, 133, 146, 153, 157, 165, 173, 179, 184, 188, 195,201,205,212,214,217

Elevated temperature 19, 40, 50, 56, 66, 77,89,98, 106, 120, 138, 148, 153, 167, 173, 181, 190,208,214

Low temperature 41,45,51,70,91,109, 121, 141, 150, 155, 168, 182, 191, 210, 215

Thermal conductivity 10,26,28,34,45,47 54,56,60,72,74,86,95,102,113, 116, 124, 132, 145, 154, 162, 172, 177, 187, 194,204,212

Thermal expansion coefficient see Coef­ficient of thermal expansion

Thermocouple' alloys 169 Alumel 172, 173 Chromel P 172, 173 Chromel P-Alumel,170, 171 Chromel P-<:onstantan 170, 171 Copper-<:onstantan 170, 171 Iron-<:onstantan 170, 171

Trademarks 32, 220 Transverse breaking strength 56 Tungsten-nickel P/M parts 217, 218

Udimet 500 see Nickel-base superalloys

Vapor pressure 10 Velocity of sound 13

Waspaloy see Nickel-base superalloys