Effect of welding parameters on microstructure and high temperature tensile properties of FGH96 superalloy inertial friction welded joints

This study aims to evaluate the FGH96 superalloy joints fabricated by inertia friction welding (IFW) in different welding parameters, such as initial rotational speed and axial friction pressure, where the moment of inertia remained constant. The microstructure and the width of the weld nugget zone (WNZ) were analyzed, and tensile property of joints was examined. The effect of welding parameters on high temperature tensile property of FGH96 joints was investigated. The results show that the joint presents a significant microstructure change across the faying interface, characterized by the very small uniform equiaxed grains of WNZ, coarse and fine grain coexistence of the thermo-mechanically affected zone (TMAZ). As the rotation speed increases, the tensile property remains constant. However, with increasing friction pressure, they show a substantial increase.The change tendency of the width of WNZ with welding parameters is in agreement with that of tensile property, which is related to the weld heat input and the plastic flow of the material. The high temperature tensile specimens are fractured in the WNZ. This is related to the complete γ′-phase dissolution which softens the joint and decreases the joint tensile property. Therefore, the post-weld heat treatments are necessary for IFW FGH96 superalloy in order to further improve the joint properties.