Preface Free

The superalloys are, indeed, super. For over 6 decades now, they have provided the most reliable and cost effective means of achieving high operating temperature and stress conditions in aircraft and, now, industrial gas turbines. They have resisted all efforts to reduce their importance and decrease the volume of use. Instead, superalloys continue in wide use in the gas turbine field and may well begin to see even more volume of use in other fields. Superalloys now find application in such diverse fields as oil equipment and biomedical implants. As we move through the first decade of the twenty-first century, superalloys seem secure. To be sure, advances in alloy chemistry are not so easy to achieve any more, but it is being done. Surface modification, partly through the application of coating technology, has extended the useful temperature range of alloys concurrent with the introduction of directional structures and then single crystals of superalloys. Melting technology is “head and shoulders” above that of just 15 years ago!

In the late 40s and 50s, there were some conferences and a few published books catering to the developing field of superalloys. At Special Metals, a new generation of processing was dawning as vacuum melting of commercial alloys became a reality. By the mid 60s, the majority of the alloys in use today, except for the directionally solidified ones, existed. The 60s saw the zenith of superalloy development as columnar grain alloys and single crystals were made feasible, and many polycrystalline alloys were brought to commercial reality. Papers on superalloys at the ASM and AIME meetings became fairly routine. At the end of the decade, an important conference was set into being by a dedicated group of metallurgists representing ASM, AIME, and ASME. The first International Conference on Superalloys was not originally intended to be the nucleus of a long running forum, but it did indeed become that. The conference, known as the Seven Springs Conference after the original and only conference location, has continued from 1968 into the twenty-first century. Some other conferences have been initiated and prospered as well. Some conferences cover only specific alloys; e.g. Inconel 718 and related alloys are the subjects of a continuing series of conference.

ASM was an early leader in the presentation of books on high-temperature behavior of metals. In 1979, ASM published Source Book on Materials at Elevated Temperatures, in 1984, the Superalloys Source Book, and in 1988, the first edition of Superalloys: A Technical Guide. Other books on high temperature behavior/properties have been published as well by ASM. The continued success of superalloy technology has encouraged us to undertake a total revision of Superalloys: A Technical Guide. The new Second Edition contains much more information than the previous edition and has been modified in layout to better accommodate the technical information provided. The text has been completely revised and expanded from that of the previous edition with many additional figures and new and revised tables.

Virtually all technical aspects of superalloys are covered in this edition. The book is not intended to be exhaustive in every respect, but we believe that the reader will find it to be most comprehensive. Chapter 4 in particular is probably the most complete and up-to-date presentation on alloy melting available. Selection of alloys is covered with many suggestions to lead the reader to ask appropriate questions either of her/himself or others in the application or development of superalloys. Furthermore, the relation of properties and microstructure is covered in more detail than in previous books. The Guide has been reviewed for accuracy, but it is possible that errors will have occurred. The writers would appreciate receiving either corrections or suggestions (or both) from readers.

If you are new to the use of superalloys, we would strongly suggest starting with Chapter 1. “Superalloys for High Temperatures—A Primer” will suit the needs of readers who want just a brief introduction to superalloys and cannot spend more time on the subject. If you are knowledgeable in metallurgy but have limited knowledge of superalloys, you might wish to start with Chapter 3, “Understanding Superalloy Metallurgy,” before proceeding to one of the specialized chapters for more in-depth information. It is most likely that your immediate needs can be satisfied by perusing this book. However, on completing appropriate chapters, you may wish to pursue reading from one of the references listed in Appendix B.

The writers wish to thank all those who contributed to this book, including the many contributors to other ASM books and the ASM Handbook series. We extend our special thanks to John Marcin and Joe Goebel who extensively reviewed Chapters 5 and 13 respectively. This book is the product of the authors’ experience in superalloys, totaling close to 60 years between them, the authors’ personal biases, their technical files, and the extensive resources of ASM International. We particularly would like to thank Veronica Flint, retired from ASM International, for her encouragement to pursue this work and for her perseverance over the several years as the material made its way into electronic and now hard copy form. Veronica Flint and Matt have worked on several past ASM books. It was always been a pleasure to work with Veronica and was especially so on this significant update of an important technical field. The successful publication of this Second Edition is a tribute once more to the dedication of ASM International to providing the greatest access to materials information for the widest possible audience.