Temperature dependence of hydrogen embrittlement susceptibility of nickel-based single crystal superalloy

This study explores the susceptibility to hydrogen embrittlement (HE) and the mechanisms of hydrogen-assisted cracking in nickel-based single crystal (SX) superalloys at 25 °C and 1000 °C using the electrochemical hydrogen pre-charging technique. Hydrogen susceptibility decreases as the temperature increases, and hydrogen facilitates the formation of additional secondary cracks and micro-voids. Hydrogen also improves fracture and strain localization at carbides at 1000 °C. First-principles calculations confirm that hydrogen reduces stacking fault energy and atomic cohesive strength, thereby promoting the shearing of γ' precipitates by partial dislocations and stacking faults at 25 °C. Moreover, hydrogen trapping in the γ matrix and at the γ/γ' and carbide/γ interfaces is observed, and the desorption activation energies at different trapping sites are assessed. The decrease in HE susceptibility at elevated temperatures is attributed to enhanced hydrogen desorption and de-trapping from hydrogen traps. These findings offer valuable insights for developing HE-resistant SX superalloys, which could ultimately strength the performance of hydrogen-powered aircraft engines.