Dislocation motion in a NI-Fe-based superalloy during creep-rupture beyond 700°C

A Ni-Fe based superalloys with excellent high temperature mechanical properties and low cost have been evaluated as the promising candidate materials for advanced ultra-supercritical coal-fired power plants. The major concerns with the Ni-Fe-based alloys are the insufficient fundamental deformation mechanisms at intermediate temperatures. In this study, dislocation-based deformation mechanisms were identified carefully in creep ruptured specimens beyond 700°C. The motion of dislocations allows plastic deformation to occur. Two types of dislocation configurations mainly occurred during the creep rupture tests beyond 700°C. Below 750°C, Orowan looping are more likely occur and considered as the predominant deformation mechanism. Above 750°C, the predominant model of deformation mechanism becomes γ′ precipitates shearing. Detailed identification of dislocation configurations were performed in the creep rupture specimens in order to correlate the macroscopic behavior with the creep controlling mechanisms.