Hydrogen Damage in Superaustenitic 904L Stainless Steel

The 904L stainless steel possesses a high level of resistance to hydrogen-induced cracking in synthetic seawater. The susceptibility to hydrogen cracking was strongly dependent on the cathodic current density. The higher the cathodic current density and the lower the ductility, the higher is the susceptibility to hydrogen. A detrimental effect of hydrogen was distinctly observed in the case of RA only. Significant loss of resistance to hydrogen embrittlement was observed for the sample hydrogenated at 20 mA/cm2.

Hydrogen changed the mechanism of microcracking in steel. The ductile failure as revealed by the significant extent of the necking and dimples was obtained in the as-received test. However, after hydrogen charging, fractures became less ductile as well as an increasing number of micro-quasi-cleavage areas were observed, which was highlighted with an increase in the cathodic current density applied during SSRT.

Cathodically evolved hydrogen affects the corrosion resistance of the 904L stainless steel. The presence of hydrogen shifted Ecorr to the more active direction and caused a slight increase of the icorr values.

The presence of hydrogen may seriously disturb and hinder the passivation processes on 904L stainless steel resulting in a decreased resistance to corrosion. This effect was particularly emphasized in the repassivation tendency. Significant loss in corrosion resistance was observed for the sample hydrogenated at 20 mA/cm2.