Effect of C–N Interaction on Hydrogen Embrittlement of 15Cr–15Mn–4Ni-Based Austenitic Stainless Steels

Hydrogen diffusion and embrittlement in an austenitic steel with 0.2 wt pct carbon and 0.2 wt pct nitrogen were investigated. The simultaneous alloying of both carbon and nitrogen did not reduce hydrogen diffusivity more than single alloying of nitrogen due to the interaction between carbon and nitrogen. During tensile straining, a low density of cracks initiated at the grain boundaries at an early deformation stage. The cracks propagated either along the grain boundaries and twin boundaries, or the paths where e martensite was concentrated, which resulted in mixed intergranular and transgranular fracture modes. Still, the resistance to hydrogen embrittlement improved in comparison with the single alloying of either carbon or nitrogen due to enhanced austenite stability.