Temperature-dependent microscopic deformation mechanisms and performance enhancement prospects in high-cycle fatigue of nickel-based single crystal superalloys

Abstract

Given the limited systematic analysis of microstructural deformation mechanisms in high-cycle fatigue, this study investigates the high-cycle fatigue failure of a fourth-generation nickel-based single crystal superalloy across temperatures of 700 °C, 850 °C, and 980 °C. The results indicate that the alloy exhibits optimal performance at 980 °C, followed by 700 °C and then 850 °C. At 700 °C, stacking fault locks and Lomer-Cottrell dislocations were identified, whereas, at 850 °C, elongated stacking fault shearing and typical cross-slip were observed. Notably, at 980 °C, intense dislocation activity was detected, including Kear-Wilsdorf locks, dislocation pile-up, and entanglement. The observed changes in microstructural mechanisms with increasing temperature are attributed to elevated stacking fault energy and critical shear stress, alongside reduced critical stress for various dislocation movements. Furthermore, the types of Lomer-Cottrell dislocation and Kear-Wilsdorf lock were accurately identified. In conclusion, the dominant micro-deformation mechanisms—stacking fault locks, Lomer-Cottrell dislocations, and dislocation hardening behaviors such as Kear-Wilsdorf locks—significantly enhance high-cycle fatigue performance. This research addresses the scarcity of studies on microscopic deformation mechanisms in single crystal high-cycle fatigue and provides valuable insights for optimizing the high-cycle fatigue performance of nickel-based superalloys.