Deformation Mechanism of Single-Crystal Nickel-based Superalloys During Ultra-High-Temperature Creep

The creep behavior and deformation mechanism of the nickel-based single-crystal superalloy containing 6wt% Re and 5wt% Ru at ultra-high temperatures were studied via microstructure observation and creep property analysis. The results show that under the condition of 1160 degrees C/120 MPa, the Ni-based superalloy has a creep life of 206 h. During the steady state creep period, the deformation mechanism is dominated by dislocation glide in the gamma matrix and dislocation climb over the gamma' raft phases. The refractory elements dissolved in the gamma matrix can improve the resistance to dislocation movement. In the late creep stage, the cross-slip occurs from (111) plane to the {100} plane with the dislocations used for shearing the gamma' phase, and then the Kear-Wilsdorf (K-W) dislocation locks are formed. A large number of K-W dislocation locks can inhibit the dislocation glide and cross-slip, thus improving the creep resistance and reducing the strain rate for Ni-based superalloys. In the late creep stage, the cross-slip dislocations are initiated to twist the gamma'/gamma raft phases, and the crack initiation and propagation occur in the gamma'/gamma interfaces until fracture. These phenomena are the damage and fracture features of the Ni-based superalloys. The Ru atoms dissolved in the gamma' phase can replace the Al atoms. When Ru, Re, and W atoms react in the Ni-based superalloy, more Re and W atoms can be dissolved into the gamma' phase, which reduces the element diffusion rate and hinders the dislocation movement, thereby retaining more K-W dislocation locks and excellent creep resistance of Ni-based superalloys at ultra-high temperatures.