Mechanical Properties of High Nitrogen - High Strength Stainless Steels in High Pressure Gaseous Hydrogen Environment

Abstract

The susceptibility to hydrogen embrittlement and the fatigue properties of several high nitrogen stainless steels were evaluated by SSRT (Slow Strain Rate Test) and external fatigue test. The tensile properties were evaluated by SSRT in gaseous hydrogen pressurized up to 90MPa in the temperature range from −40 degree C to room temperature. Despite the increase of nitrogen content, high nitrogen stainless steels showed no degradation by hydrogen. The susceptibility to hydrogen embrittlement depended on the chemical compositions. Fatigue properties in high pressure gaseous hydrogen were evaluated by the external cyclic pressurization test using tubular specimens. In this test the tubular specimen was filled with high pressure hydrogen gas filled with hydrogen pressurized up to 90MPa, and the outside of the specimen was cyclically pressurized with water pressurized up to 90MPa. The difference of fatigue life between hydrogen and inert gas was extremely small. Susceptibility to hydrogen embrittlement was discussed based on stability of an austenitic structure.