Effect of bonding time and homogenization heat treatment on the microstructure and mechanical properties of the transient liquid phase bonded dissimilar GTD-111/FSX-414 TLP superalloys

Abstract

Dissimilar transient liquid phase joints were fabricated between Ni-based GTD-111 and Co-based FSX-414 superalloys using a 50 μm thick amorphous NiSiB interlayer. The athermally solidified zone in the middle of joint contained the ternary eutectic of γ/Ni3B/Ni6Si2B and few amounts of Ni3Si. The amount of eutectic phase was decreased by increasing the bonding time. The complete isothermal solidification was obtained at the joining time of 100 min. The completion of isothermal solidification was controlled by several factors including the diffusion of Si and B from the bonding zone into the base metals, the diffusion of Ti, Al, Co and Cr from the base metals into the bonding zone and proportional re-distribution of them throughout the joint. The width of bonded zone (about 80 μm) was greater than the thickness of interlayer due to the coupled diffusion and dissolution phenomena. After the homogenization heat treatment, an increase of 34% in shear strength of the joint was observed due to the uniform distribution of strengthening precipitates across the bonding area.