Linear friction welding of a solid-solution strengthened Ni-based superalloy: Microstructure evolution and mechanical properties studies

A solid-solution strengthened Ni-based superalloy was welded with linear friction welding (LFW) under different process parameters. Microstructural examination of the sound joints showed a refined microstructure in the weld zone (WZ) and the thermo-mechanically affected zone (TMAZ), with limited oxide presence at the edge of the weld for certain welding conditions. The flow line feature was present in the WZ and TMAZ due to carbide rearrangement. However, the mechanical properties of the joints, i.e. microhardness and tensile strength, were higher than those of the base metal. The weld microstructure underwent a discontinuous dynamic recrystallization during LFW, which was accompanied by limited continuous dynamic recrystallization and static recrystallization, which lead to a remarkable increase in the fraction of low-angle grain boundaries (LAGBs) and a dramatic decrease of the Σ3 twin boundaries in WZ and TMAZ. In comparison to WZ, the TMAZ had a higher fraction of LAGBs because of the presence of stronger microtexture and less recrystallization.