Deformation and Damage Behavior of Single Crystal Nickel-based Superalloy During Elevated Temperature Creep

The deformation and damage behavior of the single crystal Ni-based alloy during elevated temperature creep were investigated through analyzing creep properties and microstructure. The results show that the creep life of Ni alloy under the condition of 1040 degrees C/137 MPa is 556 h, displaying an excellent creep resistance of Ni alloy. The creep feature of Ni alloy at steady state is the dislocation glide in gamma phase and dislocation climb over the gamma' rafts. In the late stage of creep, the deformation feature of Ni alloy is that the gamma' rafts are sheared by the dislocations of cross-slip, which forms the Kear-Wilsdorf (K-W) locks to restrain the dislocation glide and cross-slip dislocation. The cross-slip dislocations cause the distortion of gamma/gamma' rafts, thereby promoting the initiation of cracks along the gamma'/gamma interfaces and the interface fracture, which is the damage and fracture features of Ni alloy. The condition of sigma > eta/alpha is considered as the prerequisite for unstable crack propagation.