Microstructure and properties of FGH98 powder superalloy joints by transient liquid phase diffusion bonding

The Ni-Cr-Mo-B interlayer was used to perform transient liquid phase diffusion bonding of FGH98 superalloy. The effect of bonding time on the microstructure, mechanical properties and fracture behavior of the joint was investigated. The results indicated that the eutectic phases in the athermal solidification zone (ASZ) were Ni-rich borides and γ-Ni solid solution. The isothermal solidification zone (ISZ) was mainly composed of γ-Ni solid solution, and the diffusion affected zone (DAZ) contained boride with a variety of morphologies. With the increase of bonding time, the eutectic phase in ASZ gradually decreased and disappeared, the width of DAZ increased and the shear strength of the joint also gradually increased. Increasing the bonding time, the diffusion distance of boron element increased, resulting in a decrease in the density of boride precipitates in DAZ. When the joint was held for 120 min, it achieved complete isothermal solidification, reaching a shear strength of 724 MPa. The joint fracture occurred in DAZ, exhibiting a ductile fracture mode.