Effect of transient liquid phase diffusion bonding on microstructure and properties of a nickel base superalloy Rene 80

A nickel base superalloy Rene 80 was bonded in the as received cast condition using transient liquid phase diffusion bonding with a Ni-base interlayer. The bonding process was carried out at 1100 °C under argon and vacuum atmospheres for various hold times. The bonds then homogenized at 1206 °C for 1 and 2 h. Microstructures of bonds were studied with optical and scanning electron microscopy. Microstructure studies showed intermetallic compounds within the joint region. However, these intermetallic compounds were removed by a post-bond heat treatment at 1206 °C for 2 h. Shear and hardness tests were undertaken to determine the mechanical properties of bonded samples. Results showed that the shear strength of bonds made under vacuum were higher than those of bonds made under argon atmosphere. The poor shear strength of bonds made under argon atmosphere was related to the formation of voids and porosities within the bond region and bond interface during bonding cycle. The variations of hardness within the joint region with bonding hold time and post-bond heat treatment time were discussed by considering the changes of alloying elements within the joint region.