The effect of O2/H2 gas ratio of post-oxidation treatment on corrosion behaviour of plasma nitrided AISI 316 austenitic Stainless Steel

In this research, the microstructure and corrosion properties of plasma nitriding and post oxidation treated AISI 316 austenitic stainless steel have been studied. Plasma nitriding was carried out at 450 °C for 5 hr in a D.C plasma with gas mixture of 25% N2- 75% H2 followed by post-oxidation process in gas mixtures of O2/H2: 1/3, 1/5, 1/9 and 1/12 for 30 min. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical polarization readings. The results showed that the plasma nitriding decreases the corrosion resistance of the steel substrate. However, post-oxidizing treatment improves both uniform and pitting corrosion resistances of the nitrided specimens. This effect was most pronounced by post-oxidizing treatment at lower O2/H2 ratios due to the development of magnetite as a more dense oxide phase

The effect of O2/H2 gas ratio of post-oxidation treatment on corrosion behaviour of plasma nitrided AISI 316 austenitic Stainless Steel Keywords:

plasma nitriding , stainless steel , corrosion , post- oxidation