Recent research activities on hydrogen embrittlement, especially Hydrogen Environment Embrittlement (HEE) susceptibility of stainless steels in highly pressurized gaseous hydrogen environments were reviewed from the viewpoints of effects of chemical compositions, hydrogen absorption and fatigue properties.
HEE susceptibility of austenitic stainless steels evaluated by Slow Strain Rate Test (SSRT) in high pressure hydrogen environments strongly depended on their chemical compositions which affect strain-induced martensitic transformation. Stainless steels with low levels of alloying elements such as SUS304L showed a remarkable ductility loss in hydrogen environments due to martensitic transformation. Stable austenitic stainless steels such as SUS316L or A286 showed sufficient resistance to HEE.
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 imply HEE occurs by hydrogen absorption from external gaseous hydrogen environments.
Fatigue properties in high pressure gaseous hydrogen environments were evaluated by internal or external pressurization tests. Metastable stainless steels such as SUS304 showed degradation in fatigue life by hydrogen gas than an inert environment, while stable stainless steels such as SUS316L showed little decrease in fatigue life by hydrogen. A286, precipitation hardened stainless steel, showed a decrease in fatigue life by hydrogen because of planar dislocation or
η phase precipitation along grain boundaries.
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