Diffusion bonding of copper alloy and nickel-based superalloy via hot isostatic pressing

Joining copper alloys to nickel-based superalloys can achieve a combination of their advantages. However, joining these two dissimilar alloys is challenging due to their significant differences in properties. In this paper, the advanced hot isostatic pressing-diffusion bonding (HIP-DB) technology was proposed to directly join the copper alloy and nickel-based superalloy. The interfacial microstructure, element distribution, and phase composition of the obtained joint were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD), respectively. The mechanical properties of the joint were evaluated based on microhardness and tensile strength tests. The results showed that the joint was sound without apparent defects. The interface was tight and complete, and the diffusion layer was continuous and uniform. The highest microhardness of the joint was 216 HV, and the microhardness of the diffusion layer was higher than that of the two base alloys. The average tensile strength of the joint was up to 197 MPa without using interlayer materials. The tensile fracture of the joint was mainly brittle, but some ductile characteristics were also found, as various phases were formed in the joint. It is concluded that a good bonding quality has been achieved by hot isostatic pressing-diffusion bonding under the process parameter of 700 °C/150 MPa/3 h, which provides a feasible joining method for copper alloys and nickel-based superalloys.