The mechanical behavior of hydrogen-charged 316L stainless steel has been studied in samples containing sharp fatigue-induced pre-cracks, and compared with material that had been carburized at low temperatures following pre-cracking. The hydrogen charging involved exposure to high pressure (~138 MPa) H2 at 573 K for 24 days.
Non-treated samples either stayed elastic in low stress intensity range or exhibited plasticity at the crack tip at high range; no hydrogen-induced cracking could be observed. On the carburized sample, however, the main crack extended during loading. The variation of crack depth along the crack was verified and reveals that the crack becomes shallower as it approached the newly extended crack tip. The threshold stress intensity factor for the hardened case, Kth, is calculated based on this observation. Plastic zone evolution at the crack tip suggests the presence of hydrogen facilitates the motion of dislocations at the room temperature.