Hydrogen Embrittlement Properties of Stainless and Low Alloy Steels in High Pressure Gaseous Hydrogen Environment

Recent research on Hydrogen Environment Embrittlement (HEE) susceptibility of stainless and low alloy steels in highly pressurized gaseous hydrogen environments was reviewed from the viewpoint of tensile properties, hydrogen absorption and fatigue properties. HEE susceptibility evaluated by Slow Strain Rate Test (SSRT) in high pressure hydrogen environments strongly depended on steel chemical compositions. Austenitic stainless steels such as type 316L or iron-based superalloy as A286 showed sufficient resistance to HEE, while stainless steels with low levels of alloying elements such as type 304L showed a remarkable ductility loss in high pressure gaseous hydrogen due to martensitic transformation. Martensitic stainless or low alloy steels also showed a remarkable ductility loss in gaseous hydrogen. Relationship between HEE susceptibility and an amount of hydrogen absorption was investigated. HEE susceptibility and hydrogen embrittlement under cathodic charging in aqueous solution showed the same dependence on the amount of hydrogen absorption, which implies HEE occurs by hydrogen absorption from external gaseous hydrogen environments. Fatigue properties in high pressure gaseous hydrogen environments were evaluated by means of internal or external pressurization tests. Austenitic stainless steels such as type 316L showed little decrease in fatigue life by hydrogen, while metastable stainless steel as type 304 or precipitation hardened superalloy as A286 showed degradation in fatigue life by hydrogen gas. Low alloy steel also showed a decrease in fatigue life in hydrogen, while high strength low alloy steel with much Mo and V showed longer fatigue life than conventional steel.