Competing effects of cold rolling on strength and hydrogen embrittlement susceptibility in superaustenitic 904L stainless steel: A small punch test approach

Austenitic stainless steels resist hydrogen embrittlement but have low yield strength. Cold rolling increases strength but may affect hydrogen tolerance. This work uses the Small Punch Test (SPT) to evaluate hydrogen-assisted degradation in stable superaustenitic AISI 904L after 0, 10, 20 and 30% cold-rolling reductions. Hydrogen was introduced by high-pressure gas precharging (19.5 MPa, 300 °C, 24 h), and specimens were tested ex situ at different punch displacement rates. Cold rolling significantly increased strength while reducing ductility and fracture toughness. No strain-induced martensite was detected by EBSD and XRD under the investigated conditions. Hydrogen embrittlement was limited in the annealed and 10% cold-rolled conditions but became significant after 20 and 30% reduction. Hydrogen mainly affected ductility and energy-related SPT parameters, with greater effects at lower punch rates, stabilizing below 0.0025 mm/min. Results show that SPT captures the competing effects of cold-work strengthening and hydrogen degradation in the 904L conditions investigated.