ADVANCED MATERIALS & PROCESSES | MAY 2026 19 for fatigue strength and sonic inspectability. Alloy 718 also has moderate resistance to pitting and crevice corrosion in sulfide and halide environments and to hydrogen embrittlement and it maintains its toughness to cryogenic temperatures. This facilitates many non- aeroengine applications that will be discussed in a future article. There are additional factors that paved the path to success. One is Inco’s decision to freely license the alloy before the patent was issued. This generated competition and process innovation that was critical to its success[10,12,15,18]. Another factor is that alloy 718 is cobalt-free with substantial iron content, which makes its intrinsic metal cost lower than that of Waspaloy. This combined with a disruption in the supply of cobalt in the late 1970s accelerated the adoption of alloy 718 for aircraft rotor applications[12,15,18]. As aircraft engine designs evolve, the volume of alloy 718 in traditional cast and cast/wrought form will likely decrease. Some of that volume will be replaced by derivative alloys and additive manufacturing processes, but the advantages of lower intrinsic cost and a worldwide supplier base will ensure that alloy 718 will be the predominant nickel-base alloy for many years to come.~AM&P Note: Inconel and Nimonic are registered trademarks of Special Metals. Many other producers of alloys 718 and 80A use their own unique trademarks. René is a trademark of GE. Waspaloy is a trademark of Pratt & Whitney. For more information: John deBarbadillo, consultant, Nitech LLC, Barboursville, WV 25504, 304.809.4801, jdebarba42@icloud.com. References 1. J.F. Henry, G. Zhou, and T. Ward, Lessons from the Past: Materials Related Issues in an Ultra-Supercritical Boiler at Eddystone Plant, Materials at High Temperatures, 24, p 249-258, 2007. 2. H.L. Eiselstein and D.J. Tillack, The Invention and Definition of Alloy 625, Superalloys 718, 625 and Various Derivatives, ed. E.A. Loria, TMS, p 1-14, 1991. 3. L.B. Pfeil, U.K. Patent No. 583,162, 1940. 4. H.L. Eiselstein, Age Hardenable Nickel Alloy, U.S. Patent 3,046,108, July 24, 1962. 5. H.L. Eiselstein, Metallurgy of Columbium-Hardened Nickel-Chromium Alloy, Advances in the Technology of Stainless Steels and Related Alloys, ASTM STP No. 369, p 62-79, 1965. 6. R.R. Irving, Alloy 718: The Workhorse of Superalloys, Iron Age, June 10, 1981. 7. R.F. Decker, Strengthening Mechanisms in Nickel-base Alloys, presented at Steel Strengthening Mechanisms Symposium, May 5-6, 1969, AMAX Publication reprinted by Inco, Ltd. 8. D.F. Paulonis, J.M. Oblak, and D.S. Duvall, Precipitation in Nickel-base Alloy 718, Trans ASM, 62, p 611-622, 1969. 9. J.J. deBarbadillo, Alloy 718: 68 Years of Process Innovation, to be published in Proceedings of 11th International Symposium on Superalloy 718 and Derivatives, TMS, 2026. 10. J.F. Barker, The Initial Years of Alloy 718 – A GE Perspective, Superalloy 718: Metallurgy and Applications, ed. E.A. Loria, TMS, p 269-277, 1989. 11. O.W. Ballou and M.W. Coffey, History of Cast Inco 718, Superalloys 1988, eds. Reichman, et al., TMS, p 469-473, 1988. 12. D.F. Paulonis and J.J. Shirra, Alloy 718 at Pratt & Whitney: Historical Perspective and Future Challenges, Superalloy 718 and Various Derivatives, TMS, p 13-23, 2001. 13. A.H. Jones, An Overview of Alloy 718 in Large Structural Castings, Superalloy 718: Metallurgy and Applications, ed. E.A. Loria, TMS, p 307-318, 1989. 14. R. Schafrik and R. Sprague, Superalloy Technology—A Perspective on Critical Innovations for Turbine Engines, Key Engineering Materials, 380, p 113-134, 2008. 15. R.E. Shafrik, D.D. Ward, and J.R. Groh, Application of Alloy 718 in GE Aircraft Engines: Past, Present and Next 5 Years, Superalloy 718, 625, 706 and Various Derivatives, TMS, p 1-11, 2001. 16. E.A. Loria, The Status and Prospects of Alloy 718, Journal of Metals, p 36-41, July 1988. 17. A. Lingenfelter, Welding of Inconel Alloy 718: A Historical Overview, Superalloy 718: Metallurgy and Applications, ed. E.A. Loria, TMS, p 673-683, 1989. 18. A. Kracke, Superalloys, the Most Successful Alloy System of Modern Times – Past, Present and Future, 7th International Symposium on Superalloy 718 and Derivatives, TMS, p 13-50, 2010. The Lockheed SR-71 Blackbird surveillance plane incorporated a Pratt & Whitney JT11 engine with a welded alloy 718 diffuser case. This was the first significant use of the alloy in military aircraft. Courtesy of Dreamstime.com.
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