Interfacial microstructure evolution and mechanical properties of FGH98 superalloy TLP joints with BNi-2 interlayer

FGH98 nickel-based powder metallurgy superalloy was successfully bonded via transient liquid phase (TLP) bonding technique with a BNi-2 interlayer. The typical joint consisted of three characteristic zones including: ASZ composed of multiple silicon borides, ISZ with uniform γ solid solution and dispersed small γ′ phases and DAZ containing multiple kinds of borides which exist within and at grain boundaries. With the increase of bonding temperature and holding time, ASZ was gradually replaced by the ISZ, and eutectic structure disappeared. But excessive temperature or time will cause grain coarsening, deteriorating the joint performance. Under the bonding parameters of 1130 °C −60 min, the joint with optimal shear strength was obtained, which is 882 MPa (94% of the base metal strength). The fracture occurs in the DAZ, which is a mixed fracture.