Determining the kinetics of transient liquid phase bonding (TLPB) of inconel 625/BNi-2 couples using differential scanning calorimetry

A cyclic DSC method was developed which can measure the rate of isothermal solidification (IS) of the centerline eutectic in a Ni-based superalloy TLPB couple using a single sample. This was done by measuring the enthalpy of solidification of the remaining eutectic liquid, in a half braze joint when cooled from the brazing temperature. The analysis revealed that a rapid diffusional solidification (DS) process occurs during initial melting such that approximately 50% of the eutectic liquid is already diffusionally solidified by the time the peak brazing temperature is reached. This initial DS process greatly reduces the total time for solidification at the brazing temperature. Experimental DSC determinations of the complete isothermal solidification time agree well with theoretical predications.