Mechanical Property and Microstructure of IN718/FGH96 Dissimilar Superalloy Linear Friction Weldment

Wrought superalloy IN718 and powder metallurgy (P/M) FGH96 were joined by linear friction welding (LFW). The variation of microstructure and mechanical properties at different welding parameters has been investigated. Macrostructural examination of the double flash morphology indicated a conservative shortening length of 2.57 mm that was recommended to extrude out the original surface contaminants into the flash. Weld zone of the joint was featured with weld interface zone (WIZ) and thermo-mechanically affected zone (TMAZ), where deformed morphology tended to be more narrow with increasing applied pressure. The increasing oscillatory frequency or decreasing applied pressure promoted the refinement of dynamically recrystallised γ matrix grain. The analysis of electron backscatter diffraction (EBSD) mapping of the weldments showed that dynamic recrystallisation (DRX) occurred in the weld zone of dissimilar nickel-based superalloy. Continuous dynamic recrystallisation (CDRX) became the predominant behaviour, accompanied by inconspicuous discontinuous dynamic recrystallisation (DDRX). The scanning electron microscope (SEM) shows that dissolution of the strengthening phase occurred from WIZ to TMAZ, strongly influencing hardness distribution across the interface. Sound joints with a higher interface strength than the base metals of IN718 were obtained.