Crack Initiation by Cathodic Hydrogen Charging in Nickel Single Crystal

摘要

It has been reported that cracks grow along {100} independent of the tensile direction in hydrogen embit terment in nickel single crystal. Behavior of crack initiation by cathodic hydrogen charging was investigated in the present work to clarify the mechanism of hydrogen embrittlement. Hydrogen was charged on (100) or (111) surface of specimens during 180 hours at 100 A/m~2 cathodic current density. Nickel α phase was trans formed into the hydride by hydrogen. A lot of cracks were observed in the nickel-hydride layer without exter nal stress. They were along {100} independent of the plane charged hydrogen, though the distribution of the cracks on the surface depends on it. Therefore, {100} cracking is preferred in nickel hydride. It corre sponds to the morphology of the fracture surface in hydrogen embrittlement in nickel single crystal.