Effect of bonding temperature on isothermal solidification rate during transient liquid phase bonding of Inconel 738LC superalloy

A commercial cast Inconel 738 superalloy was transient liquid phase (TLP) bonded using a commercial Ni-Cr-B filler alloy, Nicrobraz 150. In contrast to the solidification behavior predicted by the current TLP models, isothermal solidification occurred under two separate regimes, depending on the bonding temperature. The rate of isothermal solidification in the first regime was faster than in the second regime. This led to a deviation in isothermal solidification completion time from that predicted by a conventional TLP model. The change in solidification rate was attributed to the substantial enrichment of the liquid interlayer with the base alloy solute elements and its continuous modification during isothermal solidification. These factors were also influenced in the nature of the phases formed in the centerline eutectic constituents subsequent to the incomplete isothermal solidification.