Determining the Influence of Surface Preparation on Transient Liquid Phase Bonding of Inconel 718/BNi-2

Abstract

Transient liquid phase bonding is a high-performance brazing process used to join superalloys. Alloys that contain stable oxide layers present on the faying surface require surface preparation in order to be successfully brazed. This work examined the effects of different Ni based superalloy surface treatments on TLPB. Differential scanning calorimetry was used in combination with other materials characterization techniques to determine how surface preparation influences the kinetics of the isothermal solidification process, as well as the wetting and spreading of a molten filler metal on a superalloy surface. Surface pre-treatments that included a Ni plating exhibited superior wetting and spreading behaviour. DSC coupled with optical metallography was successful in quantifying the wetting process. The presence of a Ni plating step resulted in an increased rate of isothermal solidification and reduced isothermal solidification due to initial boron uptake.