Microstructural characterization and mechanical property of GH4169 superalloy joints obtained by linear friction welding

The solid-solution strengthened GH4169 superalloy is joined successfully by linear friction welding (LFW) at various welding parameters in this study. Supported by numerical simulation, the microstructural characterization and mechanical property of the linear friction welded (LFWed) joints are investigated in detail. Refined grains are observed in the weld due to the dynamic recrystallization (DRX). Progressive dissolution of delta phase occurs from the base metal to the weld interface, where almost no delta phase exists. The discontinuous DRX mainly takes place in the weld zone, accompanied with limited continuous DRX. Influenced by the fine grains and strengthening phase, the microhardness first decreases to the minima at the thermo-mechanically affected zone and then gradually increases to that of base metal from the friction interface zone. LFWed joints with excellent appearances achieve the comparable tensile strength to the BM. The deterioration of weld strength is caused by the residual oxides at interface, which can be eliminated with shortening length being beyond 4.8 mm. Finally, the constitutive equations to model the grain size in LFWed GH4169 are developed based on experimental data of hot compressive tests. The reliability of these equations can be well validated.