Microstructural characterization and mechanical properties of inertia friction welded FGH96 joints

It is considerable to describe comprehensively the synergy effects of grain morphology and γ′ phase on mechanical properties in FGH96 inertia friction welded (IFWed) joints. Herein, the high-strength joining of the precipitation strengthened FGH96 superalloy was successfully realized by inertia friction welding. The evolution of grain morphology and γ′ phase, as well as the mechanical properties at room temperature (RT) and 750 ℃ were systematically investigated. It was discovered that fine equiaxed crystals were observed in the central of the bonding interface due to the dynamic recrystallization. The γ′ phase was progressively dissolved from the base material (BM) to the weld interface, resulting in the gradual flattening of grain boundaries. The evolution of the grain and γ′ phase exhibited a key role on the microhardness of IFWed joint. The impact toughness of joint at RT exceeded that of BM. The tensile strength of joint at RT reached 1514 MPa, showing 94.8 % of that of BM, with the fracture occurring in heat-affected zone. The tensile strength was 1223 MPa at 750 °C, showing 96.3 % of that of BM, with the fracture occurring in weld nugget zone. The tensile fractures subject to both RT and 750 °C were characterized by ductile fracture. [Display omitted]