Influence of process parameters on microstructure of transient liquid phase bonded Inconel 738LC superalloy with Amdry DF-3 interlayer

The effect of bonding temperature and time on microstructure of diffusion brazed joint of nickel base superalloy Inconel 738LC using Amdry DF-3 filler, alloy was investigated. It was observed that the formation of eutectic microconstituents, within the joint regions, was significantly influenced by the brazing temperature and time. A deviation from the conventional transient liquid phase (TLP) bonding diffusion models was observed in samples brazed above 1175 °C. The rate of isothermal solidification was substantially reduced at this brazing temperature, and also resulted in the formation of a centerline eutectic microconstituent, which was different from that observed at lower bonding temperatures. It is suggested that a probable factor contributing to the change in isothermal solidification rate and the formation of a different type of eutectic microconstituent from that observed at lower temperatures, is the considerable enrichment of the liquated insert with Ti atoms from the base alloy matrix, since they normally exhibit a lower solidification partition coefficient in nickel based alloys.