Hydrogen embrittlement (HE) together withthe hydrogen transport behavior in hydrogen-charged type 304 stainless steel was investigated by combined tension and outgassing experiments. The hydrogen release rate and HE of hydrogen-charged 304 specimens increase with increasing the hydrogen pressure for hydrogen-charging (or hydrogen content) andalmost no HE is observed below the hydrogen content of 8.5mass ppm.Baking at 433 K for 48 hour scan eliminate HE of the hydrogen-charged 304 specimen,while removing the surface layer will restore HE, which indicates that hydrogen in the surface layer plays the primary role in HE. Scanning electron microscopy (SEM) and scanning tunnel microscopy (STM) observations show that particles attributed to the strain-induced 'martensite formation break away from the matrix and the small holes form during deformation in the hydrogen-charged 304 specimen. With increasing strain, the connection among small holes along {111} slip planes of austenite will cause crack initiation on the surface, and then the hydrogen induced crack propagates fromthe surface to interior. This result will be favorable to develop the technology for HE prevention in hydrogen utilization.
Progress in safety of hydrogen technologies and infrastructure: enabling the transition to zero carbon energy. Proceedings of the 5th International Conference on Hydrogen Safety (ICHS). 9-11 Sept 2013, Brussels, Belgium