Effect of chemical compositions on embrittlement properties of stainless steels in highly pressurized gaseous hydrogen environments

Abstract

Effects of chemical compositions of austenitic stainless steel parent metals and weld metals on hydrogen environment embrittlement (HEE) properties were investigated by Slow Strain Rate Testing (SSRT) in gaseous hydrogen environment pressurized at 45MPa. Test results were discussed based on the formation of strain-induced martensite (α′) phase and δ-ferrite phase. Both solution heat treated parent metals and as-welded metals with higher Md30 showed higher HEE susceptibility at lower testing temperatures due to an increase in volume fraction of α′ phase during straining, δ-ferrite phase in weld metals, below 20 volume % in this study, showed no effect on hydrogen embrittlement. The detrimental effect of α′ phase would be due to their successive formation at the crack tip. On the contrary, δ-ferrite phase which was finely dispersed in advance in the weld metals did not affect hydrogen induced crack propagation.