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

• 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.

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]).

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