Creep fracture mechanism of TLP joint of a Ni-base single crystal superalloy

A kind of Ni-base single crystal superalloy was bonded by transient liquid-phase (TLP) process with Ni–Cr–B interlayer. The fracture process of TLP joint during creep test at 982 °C/248 MPa was investigated. Results show that due to assemble mismatch or original orientation discrepancy many subgrain boundaries can form in the bonding zone after bonding, and an amount of microporosities nucleate near those subgrain boundaries during creep deformation. With more creep deformation microcracks can initiate at those micropores. Propagation and interconnection of these microcracks result in the failure of TLP joint just at the bonding zone. The reasons for formation of those subgrain boundaries at bonding zone during isothermal solidification are also discussed.