Notch sensitivity analysis of a 2205 duplex stainless steel in a gaseous hydrogen environment

• A remarkable notch susceptibility in hydrogen environment is observed for DSS 2205. • HELP and HEDE fracture mechanisms are assessed. • Crack initiation through ferrite–austenite boundaries is observed. • Numerical simulation correlates stress–strain state on notched specimens with fracture mechanisms in hydrogen. Austenitic stainless steels are typically used in hydrogen environments due to their resistance to hydrogen embrittlement, though their mechanical strength is only medium to low. To explore the use of high-strength materials, their susceptibility to hydrogen embrittlement must be studied. Duplex stainless steels, featuring both austenitic and ferritic phases, are among the promising candidates due to their enhanced mechanical properties. They exhibit good mechanical properties but, due to the presence of the ferritic phase, they are sensitive in hydrogen environment. In this study, the notch sensitivity of 2205 duplex is analyzed, both in air and hydrogen environment (at a pressure of 140 bar). Three different specimens are designed with different notch radii, varying the stress concentration factor from K t = 2 to K t = 6. A numerical simulation has been carried out in order to calculate the stress and deformation conditions for each configuration and the failure mechanisms have been analyzed for all the cases, establishing the behavior of this material against different types of notches in air and in a hydrogen environment. Moreover, a coupled diffusion-deformation model has been developed using Comsol finite element software. The model is focused on hydrogen transport and incorporates lattice hydrogen diffusion and a stress-assisted diffusion term to account for the influence of mechanical stress on the diffusion process. The results show a high notch sensitivity of this material in the tensile strength embrittlement index, as a consequence of the high hydrogen susceptibility of the ferritic phase enhanced by the high stress–strain states at the notch tip.