Study on Vacuum Gas Nitriding Process and Surface Properties of AISI 430 Stainless Steel

AISI 430 stainless steel is widely used in engineering applications due to its low cost and excellent corrosion resistance. Vacuum gas nitriding is a commonly used surface modification technique, and in industrial production, it is necessary to prepare a thick and uniform nitrided layer. To comprehensively analyze the microstructure, phase composition, mechanical properties and diffusion kinetics of the nitrided layer, vacuum gas nitriding experiments were conducted on AISI 430 stainless steel. The results showed that the nitriding layer thickness increased with rising temperature. At 620°C, the nitriding layer thickness after 6 hours of nitriding was 56.7 µm, with a surface hardness of 912 HV0.025; however, its surface ductility and toughness were poor. It was found that within a certain nitriding time range, the nitrided layer thickness increased with time. At 560°C, nitriding for 18 hours resulted in the maximum nitrided layer thickness of 123.6 µm and a surface hardness of 1440 HV0.025, but its wear resistance decreased. Compared to AISI 430 stainless steel, specimens treated with 14 hours of vacuum gas nitriding at 560°C achieved a nitrided layer thickness of 115.9 µm, with surface hardness increased by 8–9 times and wear loss reduced by 83%. The nitrided layer primarily consists of iron-nitride phases, with a small amount of chromium-nitride phases contributing to hardness enhancement.