Microstructure evolution in a single crystal nickel-based superalloy joint by linear friction welding

Highlights: • Single crystal nickel-based superalloy was linear friction welded successfully. • Weld zone consists of the recrystallised polycrystals instead of single crystal. • Weld zone has a higher microhardness than parent metal. • The joint tensile strength (837.5 ± 50 MPa) is comparable to parent metal. - Abstract: Linear friction welding (LFW) was used with a single crystal nickel-based superalloy to produce sound welds. Microstructural examination shows that the joint has a distinct weld zone (WZ) and thermomechanically affected zone (TMAZ). In the WZ, the microstructure has recrystallized polycrystals instead of a single crystal. In the TMAZ, the amount of γ′ phase increased from the TMAZ/WZ interface to the parent material (PM) and decreased from the periphery to the centre along the weld creating a U-shaped microhardness profile in the TMAZ. The microhardness is however lower than that in the WZ. The average tensile strength was found to be 837.5 ± 50 MPa, comparable to the PM (880 MPa [26]).