High Content of Boride-Forming Elements in IN617 Nickel-Based Superalloy Enables Short Isothermal Solidification Time During Transient Liquid Phase Bonding

Abstract

Isothermal solidification stage during transient liquid phase bonding is the key to preclude intermetallic phase formation during solidification of the liquid phase. The rate of isothermal solidification is controlled by solid-state diffusion. Therefore, the bonding time required to complete isothermal solidification is generally long. This paper reports a very short isothermal solidification time for transient liquid phase bonding of IN617 solid solution nickel-based superalloy using a boron-containing filler metal. A eutectic-free bond with limited grain growth in the base material with high shear strength is achievable by utilizing a short (i.e., 5 minutes) thermal bonding strategy. The fast isothermal solidification of IN617 is unveiled by considering the role of in-situ boride precipitation during TLP bonding. The presence of a high amount of boride-forming elements (Cr and Mo) in the base material composition promotes the formation of a high volume fraction of the boride precipitates in the diffusion affected zone. The boron-free regions in the vicinity of boride precipitates cause a steep concentration gradient for boron diffusion during isothermal solidification, which enables fast isothermal solidification.