Abstract: Microstructure and mechanical properties of the high nitrogen martensitic stainless steels with 0.32%V and 0.80%V (named as 0.3V and 0.8V steels) were studied by means of optical microscope, SEM, hardness test, impact test and salt spray corrosion test. The results show that carbide bands appear in both the two as-annealed steels. For the 0.8V steel, the carbide bands are more pronounced, the annealed hardness is 257.0 HBS, which is 7% higher than that of the 0.3V steel, and the increase of V content can reduce the austenite grain size and retained austenite content after quenching. After the same heat treatment (quenched at 1050 ℃ for 30 min, cryogenic treatment at -73 ℃ for 2 h, and tempered at 250 ℃ for 2 h), the hardness and impact absorbed energy of the 0.3V steel are 58.4 HRC and 9.4 J, respectively, while those of the 0.8V steel are 54.4 HRC and 12.7 J, respectively, which implies that the increase in V content reduces the hardness of the tested steel and improves the toughness. After salt spray corrosion for 120 h, the corrosion rate of 0.3V steel is 0.0235 g·m^-2·h^-1and there is no obvious corrosion pit on the steel surface, while the corrosion rate of the 0.8V steel is 0.0258 g·m^-2·h^-1, and there are obvious corrosion pits on the surface, which indicates that the corrosion resistance of the 0.3V steel is slightly better than that of the 0.8V steel, meaning that the corrosion resistance slightly decreases with the increase of V content.

Key words: high nitrogen martensitic stainless steel, V content, microstructure, mechanical properties, corrosion resistance