Alloy 718 at Pratt & Whitney - Historical perspective and future challenges

The introduction of Alloy 718 at P&W in the early 1960's represented a significant advance in gas turbine engine technology, enabling the manufacture of engines with lower cost, lighter weight and simplified construction. This paper traces the applications and evolution of this unique material over the last four decades at P&W, along with some of the reasons for its introduction. From its initial use in 1963 for the diffuser case of the J58 engine for the SR-71 Blackbird, the alloy is now the most widely used of all nickel alloys at P&W. Applications include disks, cases, shafts, blades, stators, seals, supports, tubes and fasteners. Some of the key studies conducted at P&W to increase our understanding of the alloy and to improve its properties, uniformity and quality are also described. Additional challenges remain, however, if we are to exploit this alloy system even further into the 21(st) century. Most notable among these include a need for improved understanding and process models to allow us to tailor properties to specific applications, and the development of a higher temperature derivative. An alloy is needed which would retain all of the property, cost and fabricability advantages of 718, but with greater resistance to overaging to allow a 50-100F (28-56C) increase in use temperature.