Diffusion bonding of copper alloy to nickel-based superalloy: effect of heat treatment on the microstructure and mechanical properties of the joints

Successful joining of heat conducting materials, to high-temperature components is of significant importance for heat management in nuclear power plants and liquid propellant launch vehicles. Solid-state processes are considered for joining such dissimilar materials. Diffusion bonding of a copper alloy (C18150) to a Ni-based superalloy (GH4169) was investigated in this work. The bonding trials at 900°C for 60 min under a constant 10 MPa pressure led to formation of sound joints free from intermetallic, pores, voids and discontinuities. Conventional tensile testing led to the failure within the copper alloy and away from the joint. Due to the softening of the copper alloy during the bonding process, the maximum tensile strength of the as-bonded copper alloy was only 48% of its as-received strength. Post-bonding solution treatment at 960°C for 60 min followed by ageing at 450°C for 3.5 h, restored the tensile strength of the copper alloy up to 77%.