Diffusion Bonding between Ni-Base ODS Alloy and Conventional Ni-Base Superalloy and High-Temperature Fatigue Strength of the Joints
Yasuhiro YAMAZAKI, Masakazu OKAZAKI and Shigetomo NUNOMURA
Abstract:Dissimilar diffusion boning between an oxide dispersion strengthened (ODS) Ni-base alloy, MA758, and conventional casting Ni-base superalloy, CM247LC, was studied by combining and controlling some bonding parameters: bonding temperature, bonding pressure, and the post weld heat treatment. The optimum bonding condition was filtered and refined on the basis of the microstructure and thickness of the diffusion layer, the hardness distribution across the welded interface, and the high temperature tensile properties of the joints. The experimental evidences indicated, the bonding temperature and the post weld heat treatment played an essential role. For example, the longer the post weld heat treatment time, the better the high temperature tensile properties were. The fatigue strength of the joints thus optimized was also evaluated at high temperature in air, and was compared with that of the base material, MA758. The fatigue strength of the joints optimized was slightly lower compared with that of the base material, MA758, however, it was high enough for engineering applications. Key Words:Ni-base ODS alloy, Dissimilar joints, Diffusion bonding, Bonding parameter, Optimization, High-temperature fatigue strength