Microstructure of transient liquid phase bonded FGH97 superalloy joint

Transient liquid phase (TLP) bonding of FGH97 superalloy was conducted with BNi82CrSiB interlayer at 1 150℃ for different holding time,and the microstructure of the resultant joint was examined.The results reveal that,when the holding time increased,the width of bonded region broadened, and the amount of γ solid solution in isothermally solidified zone gradually increased,but the amount of dendritic γ/Ni₂B eutectic, γ/γ' eutectic,Ni₃Si,M₂₃B₆ and Cr₂B phases in non-isothermally solidified zone gradually decreased and finally vanished, consequently,the microstructure with compacted γ solid solution formed.Acicular,granular and vermiculate M3B2 phases, enriching in Cr,W,Co and Mo,precipitated in the diffusion zone,of which width increased with increasing of holding time.It was found that the interdiffusion between molten interlayer and base metal occurred during TLP bonding and thus resulted in the local melting of base metal and massive precipitating of borides in DAZ.