Investigation on microstructure and mechanical properties of GH5188 superalloy TLP joints using nickel based alloy interlayer

GH5188 was bonded successfully with a commercial BNi-2 interlayer through transient liquid phase (TLP) diffusion bonding. The characteristic bonded joint was formed by following three characteristic zones: diffusion affected zone (DAZ) mainly consisting of boride precipitates, athermal solidification zone (ASZ) composed of multiple silica-boride phases and isothermal solidification zone (ISZ) containing γ solid solution phases. As the holding time increases, ISZ gradually replaced ASZ and a defect-free joints was obtained then. However, excessive holding time can cause ASZ to reappear because of the extravagant dissolution of the base metal. The joints’ shear strength from 574 MPa (1190 °C/5 min) increased to 777 MPa (1190 °C/60 min), and the fracture location shifted from ASZ to DAZ with the fracture mode transferred from cleavage fracture to mixed fracture.