Hydrogen-assisted crack growth of austenitic stainless steel hydrogenated by high temperature cathodic charging

Hydrogen-assisted crack growth of AISI 301 austenitic stainless steel was investigated. Hydrogen was cathodically charged at elevated temperatures in molten salt. Crack growth tests were made under cyclic loading at various temperatures between -100C and 1000C. The crack growth rates were much influenced by the test temperature. The growth rates were found to be most accelerated at an intermediate temperature around 600C. This was considered to be due to the combined effect of the increased diffusivity of hydrogen at the crack tip with the decreased ability of stress-induced α' martensite transformation at the intermediate temperature. Fractographic study revealed that a transgranular quasi-cleavage pattern was dominant on the fracture surfaces of the specimens tested at 600C. (author)