Abstract: Nitrogen alloying of 13Cr super-martensitic stainless steel was carried out, quenching and partitioning process was adopted to study the influence of different N content on microstructure and electrochemical corrosion behavior, the results show that with the increase of N content, the lath martensite shows an obvious fining behavior. The austenite content is increased through the formation of VN, which prevents the combination of N and Cr to form Cr₂N, and the Cr forms a corrosion product film dominated by Cr₂O₃ on the surface of the steel, thus improving the corrosion resistance of the steel. The surface of the tested steel is dominated by local corrosion, and pitting corrosion occurs in the specimens. With the increase of N content, the porosity of the corrosion product film decreases, and the surface passivation film is of an electric double layer structure, which increases the stability of the passivation film, and the number of pitting pits is significantly reduced and the pits are smaller. The increase of N content results in the improvement of pitting resistance of the specimens, the corrosion products on surface of the tested steel containing 0.35%N are firmly attached, smooth and compact, and the grain size is uniform, playing a good protective role.

Key words: super-martensitic stainless steel, nitrogen element, corrosion resistance