Microstructure and mechanical response of transient liquid phase joint in Haynes 282 superalloy

Microstructure and mechanical response of transient liquid phase joint in a newly developed nickel-based superalloy, Haynes 282, was studied. Insufficient holding time for complete isothermal solidification of liquated insert resulted in the formation of eutectic solidification product along the joint centreline region. Micro-hardness test showed that the eutectic is extremely hard, and it provides an easy preferential path for crack initiation and propagation. In contrast to general expectation, an increase in the bonding temperature above a certain temperature promoted the formation of the deleterious eutectic. Application of a 2-D fully implicit finite element analysis method to simulate the bonding process showed that the anomalous behaviour can be explained by a decrease in the isothermal solidification rate caused by deviation from parabolic relationship between solid/liquid interface migration and holding time. Comparison of the results in Haynes 282 with those in a nickel-based superalloy, IN 738, showed that the phenomenon was significantly less pronounced in the Haynes 282, which could be related to its higher Mo content.