Hydrogen interaction with post-processed L-PBF 316L stainless steel

Additive manufacturing (AM) offers multiple economic and ecologic advantages with respect to the conventional manufacturing techniques. Post-processing treatments are typically applied to further improve the AM material's performance for industrial applications. However, knowledge is still lacking about the hydrogen interaction with these specific post-processed AM microstructures. Therefore, this research focuses on the hydrogen embrittlement of stress relieved (SR) and hot isostatic pressed (HIP) laser powder bed fused (L-PBF) 316L austenitic stainless steel. An in-depth characterization is performed to examine the degradation of L-PBF 316L upon galvanostatic hydrogen charging, using complementary identification techniques. The results show that the microstructure determines the interaction with hydrogen, which regulates the hydrogen uptake capacity. The SR L-PBF 316L has an underlying substructure consisting of dislocation cells, whereas HIP L-PBF 316L largely resembles conventionally processed 316L stainless steel. Furthermore, it is observed that hydrogen charging introduces slip bands and lattice strains in both microstructures. As a result, the L-PBF 316L microstructure can be tuned by a specific post-processing treatment for an optimal resistance against hydrogen assisted degradation.