Joining of Ni based Superalloys for Sustainable High-temperature Hybrid Turbine Rotors (18-RD-993)

The fabrication of a hybrid Ni based superalloy disc will be expanded from the demonstrated size of 2.75� diameter to 8� diameter, using FAST, where the formation of a heat affected zone will be eliminated, thereby retaining the properties of both parent alloys in on their respective sides of the bond-line. Powder processing optimization and NDE analysis will be implemented for the improved densification and bonding of Ni powder based alloys during FAST. Microstructural and hardness data will guide the development of post FAST heat treatments for optimization of the mechanical properties of both the core and rim sections of the hybrid disc. Evaluation of tensile strengths at both room and elevated temperature strengths, along with failure analysis will guide processing changes. Elevated temperature mechanical properties, such as fatigue creep testing will validate the selection of core and rim alloys, as well as their heat treatments. Optimization of the FAST hybrid disc fabrication process will enable the demonstration of 8� diameter hybrid Ni-based superalloy discs, where the rim of the disk will satisfy criteria for high temperature use, such as low creep resistance, and the core of the disk will satisfy turbine disk core criteria, such as low cycle fatigue.