Degradation and dislocation evolution of the nickel-based single crystal superalloy DD6 under the coupling high-speed rotating and high temperature environments

To model the centrifugal loads and complex geometries experienced by turbine blades during service, the nickelbased single crystal superalloy DD6 samples with a groove structure are designed and tested under the coupling conditions of high-speed rotating of 20,000 r/min and high temperature of 980 C-degrees. Scanning electron microscopy and transmission electron microscopy are used to analyze the microstructural evolution of gamma-gamma' phases and dislocation morphologies of 400 h and 1000 h samples. The results indicate that microstructural degradation of the gamma-gamma' phase attributes to the larger centrifugal tensile stress S-11 in the applied physical stress compositions until deformation occurs. Our observations suggest that a/2 < 101 > -type dislocations initiate plastic deformation by slipping within the gamma phase. However, their movement is constrained at the interface between the gamma and gamma' phases, resulting in their tendency to aggregate at this boundary. After the formation of stable interfacial dislocation networks, these dislocations then react to generate either a< 010 > -type dislocations or a/2 < 112 > -type dislocations, which cut into the gamma' phase. However, under high stress conditions, the a/2 < 101 > -type dislocations are primarily cut directly in the form of dislocation pairs.