Effect of Annealing Temperature on Hydrogen Damage Behavior of Mn–N Bearing Lean Duplex Stainless Steel

The effect of the annealing temperatures on the hydrogen damage behaviors of Mn–N alloyed duplex stainless steel (DSS) was investigated by comparing the mechanical behaviors, martensitic transformation, hydrogen embrittlement sensitivity, hydrogen‐induced crack, and dislocation evolution of experimental steels at different conditions. The results indicate that the Cr 2 N precipitated at low annealing temperature leads to a decrease in the stability of austenite, and the volume fraction of ferrite increases as annealing temperature increases. A higher volume fraction of ferrite and lower stability of austenite increase the hydrogen embrittlement sensitivity index of DSS from 0.13 to 0.43, thus degrading the hydrogen embrittlement resistance of the experimental steels to some extent. A higher volume fraction of ferrite induced by the high temperature makes the hydrogen‐influenced zone more than the sample annealed at low temperature. The strain‐induced martensitic transformation, with two typical sequences: γ → ε → α ′ and γ → α ′, occurs in samples annealed at various temperatures uncharged and charged. The dissolution of austenite and the trapping effect of Cr 2 N on hydrogen lead to the local plastic strain, increasing the dislocation density and the degree of martensitic transformation. Besides, the lower stability of austenite reduces the nucleation of stacking faults, and the lower diffusion rate of H amplifies this effect.