The Spray Cast Process and its Applications in Gas Turbine Engines

Abstract

The need for advanced material processing to reduce manufacturing cost and cycle times has never been as great as at this time in our nation’s history. Howmet Corporation has licensed and modified the Osprey, or spray forming, process to produce high quality nickel base superalloys for gas turbine engine applications. The modified process, known as the “Spraycast-X™” process, combined vacuum induction melting with high purity argon gas atomization to produce billet and ring shape products. Process parameters were established to produce fine grain size (ASTM 6-8) billet up to 10” (254 mm) in diameter and ring shape preforms up to 33” (838 mm) in diameter. Mechanical properties of HIP’ed Spraycast-X plus isoforged U720 and Spraycast-X and HIP’ed MERL 76 (no Hf) were comparable to their wrought counterparts. Mechanical property data for ring rolled IN718, René 41, and Waspaloy were all above specification limits.

Task 8.4 - High Temperature Turbine Disk Development

“…4, it appears that future use of Spraycast Mar-M-247LC would require optimization of the processing and heat treatment to improve ductility and to avoid notch sensitivity in rupture. Despite the notch sensitive behavior, the life prediction effort calculated a life of 180,000 hours, and suggesting the possibility of temperatures above 1280°F.…”

“…Spraycast is a modified version of the OSPREY process in which vacuum melted material is argon gas atomized and spray formed in a one-step conversion directly into a ring shape (Ref. 4). In addition to the Dual-Alloy application, spray casting technology has spin-off potential in the manufacture of other gas turbine ring shaped components since it can provide one or more of the following:…”

“…To address these issues, Task 8. 4 also examines advanced stress analysis and life prediction techniques for high temperature materials, and Non-Destruction Inspection (NDI) techniques to find cracks in the structure as a result of cyclic operation, should they occur. Thus, Task 8.…”

“…4 is to demonstrate a bonding technique to produce a dual-alloy turbine disk concept which will satisfy the diverse property requirements of the rim and hub areas of the disk. The program examines methods of attaching a cast superalloy rim with sufficient rupture strength to a fine grain hub material with the required LCF properties.…”

“…Thus, Task 8. 4 attempted to take a holistic approach to introduce the Dual-Alloy Disk concept by considering three interrelated areas:…”