Low-temperature plasma nitriding of martensitic stainless steel

This study presents the plasma nitriding of Cr–Mo–V tool steel to protect it from environmental degradation. The steel samples after metallographic polishing were nitrided in the glow discharge plasma of N2 and H2 gas mixture (80:20). Nitriding was performed at two different temperatures, a lower temperature of 450 °C and the higher temperature of 500 °C. The potentiodynamic polarization tests in 3.5% NaCl electrolyte had shown the enhancement of corrosion resistance of steels after nitriding. X-ray diffraction (XRD) studies and scanning electron microscopic analysis coupled with energy dispersive spectroscopic analysis (SEM/EDS) was performed to understand the modification of surface microstructure. XRD analysis of the nitrided steels revealed the presence of γ′- and ε-nitrides of iron, which were responsible for the improvement of corrosion resistance.