Bonding behaviour of nickel base single crystal to polycrystal superalloys by transient liquid phase method

Transient liquid phase bonding between single crystal superalloy DD98 and polycrystal superalloy M963 has been characterised in terms of microstructure, crystallographic orientation analysis and stress rupture test. Result shows that during isothermal solidification (IS), with increasing bonding time, the liquid interlayer thickness decreases. As a result of incomplete IS, many compounds formed in the centreline. After 1190°C/4 h bonding, the IS process has been complete. It is notable that an interface formed in the bonding zone due to crystallographic orientation difference between parent metals. Result of stress rupture test shows that the rupture life of the bonded joint is more than 140 h at 800°C/350 MPa, which is comparable to that of the M963 alloy. Failure of the joint occurs in the segment of M963 alloy.