Burst tests of cold drawn and heat treated austenitic stainless steel (316L) tubes charged in pressurized hydrogen

Global decarbonization targets are driving expansion of green hydrogen infrastructure, yet high-pressure hydrogen exposure can degrade the mechanical performance of critical stainless-steel components, typically made of the common steel 316L. This study evaluates the strength and fracture behaviour of both cold-drawn and heat treated 316L austenitic stainless-steel tubular specimens fabricated from 1/2" (12.7 mm) and 3/8" (9.53 mm) tube after gaseous high pressure pre-charging. Hydrogen concentration in the range between 76–100 ppm was measured in precharged sample in both states and the record of 2–5 ppm in the none-precharged specimen. Hydrostatic burst tests at ambient temperature were carried out with precharged specimens and revealed an increase in burst pressure for both material states, as compared to non-precharged specimens as a reference. In addition, fractographic analysis by scanning electron microscopy identified deeper dimples and wider microvoids in hydrogen-precharged specimens, indicating also some softening of the material in the cold drawn as well as in the heat-treated state. As the time to failure also increased, it is anticipated that the hydrogen introduced in the specimens caused a respective increase in both, ductility in terms of the straining and deformation capacity, as well as an increase in strength. For engineering applications, the findings indicate some beneficial effect that, despite exposure to extreme hydrogen conditions, 316L tubes retain, and even modestly enhance, their structural integrity, supporting a safe deployment in green hydrogen transport and storage systems, at least at ambient temperature.