Effect of additive manufacturing and subsequent heat and/or surface treatment on the hydrogen embrittlement sensitivity of 316L austenitic stainless steel

Austenitic stainless steels (ASS) offer attractive characteristics for use in hydrogen service, such as low hydrogen diffusivity and high solubility. The role of the production process is, however, still unclear. Especially the effect of additive manufacturing (AM) on the hydrogen interaction is not extensively researched yet. The present work compares the hydrogen embrittlement sensitivity of conventional (cold rolled and annealed) and additive manufactured 316L ASS and evaluates the possible advantage of performing a heat treatment and/or reducing the surface roughness post printing. AM increases the hydrogen solubility but the hydrogen diffusivity was only slightly reduced. The heat treatment reduced the hydrogen solubility of the AM materials and significantly increased the hydrogen diffusivity. Despite these observations, the conventional 316L ASS shows a higher hydrogen embrittlement (HE) sensitivity compared to AM316L. This is linked to the increased hydrogen-assisted cracking sensitivity of conventional 316L ASS. The heat treated microstructure behaves similarly as the as-built material in terms of HE sensitivity, while a major improvement is observed when the surface oxide layer formed during the heat treatment is maintained since this reduces hydrogen absorption. Surface polishing intensifies the HE sensitivity which is linked to a higher surface hydrogen concentration leading to more crack initiation.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.