Achieving high-quality copper alloy to nickel-based superalloy joint by isostatic high-pressure solid-state diffusion bonding

The high-performance joining of copper alloy and nickel-based superalloy to achieve high wear resistance, thermal conductivity and stiffness in the same structure is attracting increasing interest in various industries. However, directly joining to obtain high-quality joints of these two dissimilar materials is a challenge due to the significant differences in physical and chemical properties. In this study, a novel solid-state diffusion bonding method by employing isostatic high pressure has been proposed. The process parameters are optimized to achieve high-quality joints of a new material system (CuAgZn and GH600). The effects of bonding temperatures on microstructure evolution and mechanical properties at the joints under high-pressure conditions have been systematically investigated. The results show that reliable metallurgical joints, free of defects, have been successfully obtained under high isostatic pressure of 170 MPa, and some solid solution and precipitated phases have formed at the interface. The joint has exhibited a maximum tensile strength of 280.9 MPa (about 80 % of the copper alloy) with the bonding temperature of 660 °C. All the joints fractured adjacent to CuAgZn and exhibited brittle fracture features with ductile characteristics after tensile tests. Solution strengthening, precipitation strengthening, and recrystallization softening have been explained as the main mechanisms for the good joint strength. This study provides an effective strategy for achieving high-quality joints by isostatic high-pressure diffusion bonding for dissimilar materials.