About this Abstract |
| Meeting |
11th International Symposium on Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Symposium
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Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Presentation Title |
Alloy 718: 68 Years of Process Innovation |
| Author(s) |
John J. de Barbadillo |
| On-Site Speaker (Planned) |
John J. de Barbadillo |
| Abstract Scope |
The invention of alloy 718 in 1958 was the unexpected outcome of an effort by Herbert Eiselstein to develop an alloy for steam boiler tubing. It was never used for that application, but its advantages for aircraft engine components were quickly recognized. The relatively slow precipitation kinetics and intense hardening conferred by niobium provided much higher strength along with improved formability and weldability compared with gamma prime strengthened nickel-base alloys. These properties along with a critical shortage of cobalt led to a rapid adoption of the alloy for aerospace applications. By the 1980s 718 was the highest volume superalloy and today it is the highest volume nickel-base alloy.
Along with its advantages, the high niobium content of 718 presented significant challenges for commercial scale production of mill forms and components. Niobium segregates strongly during solidification and depresses the solidus temperature into the conventional hot working range. The initial products were air induction melted from virgin raw material, direct air cast into small ingots, hammer forged to shape and super solvus heat-treated resulting in an inhomogeneous and relatively coarse grain microstructure. To adapt the alloy for industry needs, processes to eliminate non-metallic inclusions, unique segregation defects and microstructural inhomogeneity were needed. The processes that we apply today were the result of both proprietary and collaborate efforts over seven decades. This paper describes how innovations in melting, casting, remelting, homogenization, forging and heat treatment were applied for commercial production of alloy 718. The paper concludes with a discussion of some remaining challenges. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |