Effects of hydrogen absorption on the mechanical and fatigue strength of high-strength bolts for a propulsion motor

Abstract This study examined the effects of hydrogen-related degradation on the static and dynamic fatigue strength of high-strength bolts for propulsion motors during electro-galvanization. Two-bolt types were prepared with different baking treatments: B 0h (no baking) and B 8h (baking at 200 °C for 8 h). Baking did not significantly affect the mechanical strength ( p < 0.01) but did increase the elongation of B 8h by 25.3 %. In high-cycle fatigue tests, B 8h exhibited a fatigue life of up to 6.3 times longer than that of B 0h . These results indicate that baking effectively mitigates hydrogen-related degradation and enhances the high-cycle fatigue life, ductility, and toughness of electro-galvanized 42CrMo4 steel bolts.