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SuperalloysAlloying and Performance

Blaine GeddesHugo LeonXiao Huang

ASM International®

Materials Park, Ohio 44073-0002www.asminternational.org

Superalloys: Alloying and Performance (#05300G) B. Geddes, H. Leon and X. Huang

Copyright © 2010, ASM International® All rights reserved. www.asminternational.org

Copyright © 2010 by

ASM International® All rights reserved

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First printing, November 2010

Great care is taken in the compilation and production of this book, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by ASM, ASM cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of ASM’s control, ASM assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products or information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OF BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY. As with any material, evaluation of the material under end-use conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended.

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Comments, criticisms, and suggestions are invited, and should be forwarded to ASM Inter-national.

Prepared under the direction of the ASM International Technical Book Committee (2009–2010), Michael J. Pfeifer, Chair.

ASM International staff who worked on this project include Scott Henry, Senior Manager, Content Development and Publishing; Steven R. Lampman, Content Developer; Eileen De Guire, Senior Content Developer; Ann Britton, Editorial Assistant; Bonnie Sanders, Manager of Production; Madrid Tramble, Senior Production Coordinator; Diane Whitelaw, Production Coordinator; and Patricia Conti, Production Coordinator.

Library of Congress Control Number: 2010937091 ISBN-13: 978-1-61503-040-8

ISBN-10: 0-61503-040-9SAN: 204-7586

ASM International® Materials Park, OH 44073-0002

www.asminternational.org

Printed in the United States of America



iii

Contents

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

ChaPTer 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Historical Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 Applications of Superalloys in the GTE . . . . . . . . . . . . . . . . . . . . 6

ChaPTer 2 Overview of Superalloys . . . . . . . . . . . . . . . . . . . 9

2.1 Nickel-Iron-Base Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2 Cobalt-Base Superalloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.3 Nickel-Base Superalloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

ChaPTer 3 Strengthening Mechanisms . . . . . . . . . . . . . . . . 17

3.1 Solid-Solution Hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2 Precipitation Hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.3 Oxide Dispersion Strengthening . . . . . . . . . . . . . . . . . . . . . . . . . 213.4 Carbide Hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

ChaPTer 4 Phases and Microstructure of Superalloys . . . . . 25

4.1 Matrix Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.2 Geometrically Close-Packed Phases . . . . . . . . . . . . . . . . . . . . . . 294.3 Carbides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344.4 Borides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394.5 Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394.6 Nitrides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.7 Sulfocarbides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414.8 Topologically Close-Packed Phases. . . . . . . . . . . . . . . . . . . . . . . 414.9 Microstructural Modifications through Heat Treatment . . . . . . . 44



4.10 Rafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.11 Directionally Solidified Superalloys . . . . . . . . . . . . . . . . . . . . . 46

ChaPTer 5 Compositional effects . . . . . . . . . . . . . . . . . . . . 59

5.1 Typical Compositional Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . 605.2 Base Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635.3 Chromium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665.4 Aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685.5 Titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705.6 Refractory Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725.7 Grain-Boundary Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835.8 Reactive Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.9 Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955.10 Trace Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

ChaPTer 6 Some Considerations in the Selection of a Superalloy . . . . . . . . . . . . . . . . . . . . . . 111

6.1 Environmental Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1116.2 Machinability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1136.3 Forging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1136.4 Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

appendix a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

appendix b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

appendix C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

appendix d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

iv / Contents



v

List of Figures

Fig. 1.1 Environmental resistance and strength for various metallic families . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Fig. 2.1 Mean coefficient of thermal expansion (CTE) between 25 °C (77 °F) and the temperature shown for a conventional nickel-base superalloy (Inconel 718), a conventional low-CTE superalloy (Incoloy 909), and a three-phase-strengthened low-CTE superalloy (Inconel 783). . . . . . . . . . . . . . . . . . . . . . . . . .11

Fig. 3.1 Tensile properties of solid-solution-hardened Inconel 625. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Fig. 3.2 Creep strength of solid-solution-hardened Inconel 625 . . . . . . 19Fig. 3.3 Mechanical properties of solid-solution-hardened and

aged Inconel 718 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Fig. 3.4 Stress-rupture life as a function of grain aspect ratio for

Inconel 92 at 950 °C (1740 °F) and 250 MPa (36 ksi). . . . . . . . . . 22Fig. 4.1 Evolution of microstructure and chromium content of

selected nickel-base superalloys. . . . . . . . . . . . . . . . . . . . . . . . . . . 27Fig. 4.2 Selected morphologies of the γ′ phase . . . . . . . . . . . . . . . . . . . 30Fig. 4.3 Variation of γ′morphology with difference in γ/γ′ lattice

parameter mismatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Fig. 4.4 Hardness versus particle diameter in a low-γ′-volume-

fraction nickel-base superalloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Fig. 4.5 Variation of γ′ peak flow stress with alloying additions . . . . . . 33Fig. 4.6 Standard Gibbs free energy of formation for several

carbides as a function of temperature and solubility in nickel at 1250 °C (2280 °F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Fig. 4.7 Scanning electron micrograph showing carbide distribution in an as-cast cobalt-base superalloy . . . . . . . . . . . . . . . . . . . . . . . . 36

Fig. 4.8 Examples of carbides in nickel- and cobalt-base superalloys . . 37Fig. 4.9 Favorable discrete grain-boundary M23C6 at 10,000× and

less favorable discontinuous zipperlike precipitation at 6800× in Waspaloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38



vi / List of Figures

Fig. 4.10 Transmission electron micrograph showing mixed (yttrium, aluminum) oxide particles dispersed in a ferritic matrix in MA-956. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Fig. 4.11 Electron micrograph of experimental Ni-20.7Cr-17Co-0.63 Mo-4.75Ti-10Al (at.%) showing σ plates within the grains and cellular σ/γ′ colonies at the grain boundaries . . . . . . . . . . . . . . . . . 42

Fig. 4.12 IN-100 nickel-base alloy casting, held at 815 °C (1500 °F) for 5000 h. (a) Structure consists of massive MC particles, platelets of σ phase, and primary and precipitated γ′ in the γ matrix. (b) Replica-electron micrograph shows a massive particle of MC, Widmanstätten platelets of σ phase, and γ′ in the γ matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Fig. 4.13 Transmission electron micrograph of the microstructure of γ′ in a dendrite in as-cast CMSX-10 and after standard heat treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Fig. 4.14 Cast dendritic structure of IN-738 nickel-base alloy. The varying features of the microstructure are revealed by using different etchants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Fig. 4.15 Formation of σ plates adjacent to interdendritic MC carbides in SX-RR2072 during exposure at 950 °C (1740 °F) . . . . . . . . . . 51

Fig. 4.16 Scanning electron micrographs of the longitudinal section of MC2 and AM3 stress-aged alloys. Μ-phase precipitates appear white in backscattered electron mode. . . . . . . . . . . . . . . . . . . . . . . 52

Fig. 4.17 Scanning electron micrograph of μ-phase precipitates electrochemically extracted from an overaged MC2 single- crystal sample. The γ/γ′ matrix observed in the background is only partially dissolved. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Fig. 5.1 Alloying elements in nickel-base superalloys. Beneficial minor elements are indicated by cross-hatching, while detri- mental tramp elements are marked with horizontal lines. . . . . . . . 59

Fig. 5.2 Rupture strength at 1020 °C (1870 °F) of a nickel-base superalloy as a function of cobalt content . . . . . . . . . . . . . . . . . . . 65

Fig. 5.3 Effect of aluminum and titanium contents on the phases present at 800 °C (1470 °F) in Fe-15Cr-25Ni-modified stainless steel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Fig. 5.4 Weldability assessment diagram for superalloys . . . . . . . . . . . 71Fig. 5.5 Influence of molybdenum in the 982 °C/234 MPa (1800

71°F/34,000 psi) creep life and creep rate of an experimental single-crystal superalloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Fig. 5.6 Influence of molybdenum content on γ′ solvus for a Ni-Cr-Al-Ti-Mo alloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Fig. 5.7 (a) Secondary electron image showing a γ/γ′ eutectic pool in as-cast UM-F13 alloy. (b) Backscattered electron image showing the typical microstructure of UM-F13 alloy after solution treatment at 1300 °C (2370 °F) for 4 h and aging at



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