ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2026 22 for the International Thermonuclear Energy Reactor (ITER)[25]. The composition was tailored to enable age hardening during the formation treatment of the NbSn superconductor. To facilitate coil winding the sheath was produced as a square OD with a round ID tube made by cold drawing or pilgering. The alloy was not actually used in the final ITER design, but it is a good illustration of manipulation of alloy chemistry to achieve an engineering objective. The alloy 718 derivative is a fascinating metallurgical saga, and certainly additional alloys based on the niobium strengthening system perhaps enabled by additive technologies will emerge. But the overall dominance of 718 in the industry remains as it continues to exceed the volume of all the derivatives including 625 and 706 combined. Note: Allvac 718Plus is a registered trademark of ATI Allvac. Carpenter 625 Plus is registered with Carpenter Technology. Inconel and INCOLOY each retain individual trademarks. For more information: John deBar- badillo, consultant, Nitech LLC, Barboursville, WV 25504, 304.809.4801, jdebarba42@icloud.com. References 1. D.F. Paulonis, J.M. Oblak, and D.S. Duvall, Precipitation in Nickel-Base Alloy 718, Transactions ASM, 62, p 611622, 1969. 2. R. Cozar and A. Pineau, Morphology of Gamma Prime and Gamma Double Prime Precipitates and Thermal Stability of Inconel 718 Type Alloys, Met. Trans, 4, p 47-59, 1973. 3. H.L. Eiselstein and D.J. Tillack, The Invention of Alloy 625, Superalloys 718, 625 and Various Derivatives, TMS, p 1-14, 1991. 4. R.E. Schafrik, D.D. Ward, and J.R. Groh, Application of Alloy 718 in GE Aircraft Engines: Past, Present and Next Five Years, Superalloys 718, 625, 706 and Various Derivatives, TMS, p 1-11, 2001. 5. K.R. Ziegler and J.F. Wallace, Structure/Property Effects of Substitutions for Reduced Columbium in Alloy 718, Superalloy 718: Metallurgy and Applications, TMS, p 611-622, 1989. 6. H.L. Eiselstein and E.F. Clatworthy, Nickel-Chromium-Iron Alloy, U.S. Patent 3,663,213, 1972. 7. P. Schilke, J.J. Pepe, and R.C. Schwant, Alloy 706 Metallurgy and Turbine Wheel Applications, Superalloys 718, 625, 706 and Various Derivatives, TMS, p 1-11, 1994. 8. D.L. Cheever, R.E. Monroe, and D.C. Martin, Mechanical Fastening of Nickel Base Alloys, NASA Technical Memorandum, NTX-53441, April 20, 1966. 9. D.F. Paulonis and J.J. Shirra, Alloy 718 at Pratt & Whitney: Historical Perspective and Future Challenges, Superalloy 718, 625 and Various De- rivatives, TMS, p 13-23, 2001. 10. A. Braun, J.F. Radavich, and C.P. Stinner, A Microstructural and Mechanical Properties Comparison of P/M 718 and P/M TA718, Superalloy 718: Metallurgy and Applications, TMS, p 623-629, 1989. 11. J.P. Collier, A.O. Selius, and J.K. Tien, On Developing a Microstructurally and Thermally Stable Iron-Nickel Base Superalloy, Superalloys 1988, TMS, p 43-52, 1988. 12. K.M. Chang and A.H. Nahm, René 220: 100°F Improvement Over Alloy 718, Superalloy 718: Metallurgy and Applications, TMS, p 631-646, 1989. 13. E.A. Loria, René 220: In Retrospect and Prospect, Superalloys 718, 625, 706 and Various Derivatives, TMS, p 739-750, 1994. 14. W.D. Cao and R.L. Kennedy, Role of Chemistry in 718 Type Alloys – Allvac 718Plus Alloy Development, Superalloy 2004, TMS, p 91-99, 2004. 15. X. Xie, et al., Structure Stability Study on a Newly Developed NickelBase Superalloy – Allvac 718Plus, Superalloys 718, 625, 706 and Various Derivatives 2005, TMS, p 179-191, 2005. 16. M. Bergner, et al., Effect of Heat Treatment on Microstructure and Mechanical Properties of VDM Alloy 780 Premium, Proc. 9th Int. Symp on Superalloy 718 & Derivatives, TMS, p 480-499, 2018. 17. R.B. Frank and T.A. DeBold, Properties of an Age-Hardenable, Corrosion-Resistant Nickel-Base Alloy, NACE Corrosion 88, paper No. 88075, March 21-25, 1988. 18. E.L. Hibner, A New Age-Hardenable Corrosion Resistant Alloy for Deep Sour Gas Well Service, NACE Corrosion 90, paper No. 90050, April 23-27, 1990. 19. F.J. Rizzo and S.B. Justus, PM Alloy 625M – A High Strength Modification of Alloy 625 Superalloy 718, 625, 706 and Various Derivatives, TMS, p 903-911, 1994. 20. S.K. Mannan and S.K. Patel, A New High Strength Corrosion Resistant Alloy for Oil and Gas Applications, NACE Corrosion 2008, paper No. 08084, March 2008. 21. L. Feroni, L. Lherbier, and C. Malara, High Performance New Ni-Base Alloy AF955 for Oil and Gas Industry, 9th International Symposium on Superalloy 718 and Derivatives, TMS, p 193-207, 2018. 22. H.L. Eiselstein and J.K. Bell, New Ni-Fe-Co Alloys Provide Constant Modulus + High Temperature Strength, Materials in Design Engineering, November 1965. 23. D.F. Smith, et al., Heat Resistant Low Expansion Alloy, U.S. Patent 4,200,459, April 29, 1980. 24. D.F. Smith, J.S. Smith, and S. Floreen, A Silicon-Containing Low Expansion Alloy with Improved Properties, Superalloys 1984, TMS, p 591-600, 1984. 25. M.M. Morra, R.G. Ballinger, and I.S. Hwang, INCOLOY 908, A Low Coefficient of Expansion Alloy for High Strength Cryogenic Applications, Met. Trans. A, TMS/ASM, 23, p 3177-3192, 1992. Read Parts I and II of this article series in AM&P May and July to learn more about the initial discovery of alloy 718 and its early applications.
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