Formation of eutectic-type microconstituent during transient liquid phase bonding of nickel: influence of process parameters

Transient liquid phase bonding of nickel by a filler material containing phosphorus as a melting point depressant was performed to study the effects of process parameters on the joint microstructure. Insufficient holding time for complete isothermal solidification of liquated insert resulted in formation of eutectic-type microconstituent along the joint centreline region. An increase in the eutectic thickness with increase in initial filler gap size was observed in joints prepared at a constant temperature and holding time. The eutectic was observed to serve as a preferred continuous path for crack initiation and/or propagation. Two different observation of influence of bonding temperature on the eutectic formation was made, one in which increase in bonding temperature resulted in formation of thicker centreline eutectic and the second in which preclusion of the eutectic was achieved at a shorter time relative to a lower temperature.