Transient thermal fatigue crack propagation behavior of a nickel-based single-crystal superalloy

Thermal fatigue crack propagation behaviors of a V-notched Ni-based single-crystal superalloy DD6 were tested at 25 °C ↔ 760 °C/900 °C/1000 °C. The propagation directions of the two main cracks were approximately 45° with the dendrite orientation, and the {1 1 1} 〈1 1 0〉 slip family was mainly activated. Based on 3D transient thermo-mechanical coupling theory and rate-dependent crystal plasticity theory, the stress intensity factor and J-integral were calculated to predict the thermal fatigue crack propagation behavior. Three surface heat transfer stages were considered. The predicted crack propagation rates at three heating temperatures all showed good agreement with those obtained in the experiments.