Interfacial microstructure investigation of diffusion bonded new Ni-Cr-W superalloy using Cu interlayer

The solid-state diffusion bonding processes were successfully carried out to join new Ni-Cr-W superalloys at different temperatures (850°C -950°C), under pressures of 20MPa and holding 45min in a vacuum furnace by taking Cu foil as interlayer. The influence of bonding temperature on the microstructural evolution and the diffusion behavior across the joints was investigated in details. Results indicate that the Ni-Cu solid solutions in the interface lead to a sound bonding interface without any void or impurity. As the temperature increases, the reaction layers become thicker due to the decrease of M₂₃C₆precipitation in the grain boundaries and the rise of atoms diffusion capability. Furthermore, hardness measuremental result also reveals that the increased thickness of reaction layers cannot improve the microhardness of bonding interfaces apparently.