Hydrogen environment embrittlement testing at low temperatures and high pressures

Hydrogen environment embrittlement (HEE) of several heats of austenitic stainless steels was measured by slow strain rate tensile testing in hydrogen atmosphere at different temperature–pressure combinations.The relative reduction of area decreased (means increasing hydrogen embrittlement) in the following order: 20 °C/10 bar > 20 °C/700 bar > −50 °C/10 bar > −50 °C/400 bar ≈ −80 °C/200 bar. An assessment of the most severe error sources revealed that tensile tests in hydrogen can be performed with a very high repeatability and reproducibility with a total deviation of about 10% with respect to the relative reduction of area (RRA = RAH2/RAHe). Higher deviations in RRA are due to local deviations in metallurgy and chemical composition, which are very sensitive to HEE.Screening tests of several austenitic SS at 20 °C/700 bar show decreasing HEE with increasing Ni content. For RRA > 90%, a minimum Ni content of >11.5 wt% is required.