Deformation Features of a High Mo Nickel-Based Single Crystal Superalloy during Creep at High Temperature

Abstract

The deformation and damage features of a high Mo single crystal Ni-based superalloy during creep at high temperature are investigated by means of measuring creep properties and observing microstructure. Results show that, compared to 4%Mo single crystal nickel-based superalloy, the 6%Mo superalloy displays a better creep resistance, and the creep life of 6%Mo single crystal superalloy at 1040°C/137MPa is measured to be 556 h. In the ranges of applied temperatures and stresses, the creep activation energy of the alloy is measured to be 484.7kJ/mol. Wherein, the deformation mechanisms of the 6%Mo superalloy during steady state creep are dislocations slipping in ϒ matrix and climbing over the rafted ϒ' phase. In the later stage of creep, the deformation mechanism of alloy is dislocations shearing into the rafted ϒ' phase, the alternate activation of dislocations slipping results in the twisted of the rafted ϒ'/ϒ phases, as the creep goes on, to promote the initiation and propagation of cracks along the interface of the twisted ϒ/ϒ' phase perpendicular to the stress axis, up to creep fracture, which is thought to be the damage and fracture features of the alloy during creep at high temperature.