Assessing the effect of low oxygen concentrations in gaseous hydrogen embrittlement of DIN 1.4301 and 1.1200 steels at high gas pressures

A high strength pearlitic-sorbitic steel (DIN 1.1200/K08500) and a metastable austenitic stainless steel (DIN 1.4301/AISI 304) were tensile tested in H2–O2 gas mixtures of high total gas pressures without any prior precharging and in inert environment after gaseous precharging in different H2–O2 gas mixtures. Tests at various total pressures revealed that the effect of oxygen to suppress hydrogen environment embrittlement is a function of oxygen partial pressure and not of total oxygen content. For steel 1.1200 tested at room temperature the threshold O2 partial pressure was 30–40 kPa whereas for steel 1.4301 tested at −50 °C a partial pressure of 160 kPa was not sufficient to influence embrittlement effects. Reviewing literature results in the context of this work revealed that threshold partial pressures vary by at least 3 orders of magnitude depending on steel grade and temperature. For tests in inert environment after gaseous precharging threshold O2 partial pressure was one order of magnitude lower compared to tests in H2–O2 gas mixtures.

► The effect of oxygen to suppress HE is a function of partial pressure.
► In H2–O2 gas mixtures at RT, pO2pO2 was 30–40 kPa for steel 1.1200.
► For steel 1.4301 tested at −50 °C, no positive effect was measured up to 160 kPa.
► For hydrogen precharged specimens threshold partial pressure was lower.