Enhancement of Pitting Corrosion Resistance of Austenitic Stainless Steel Through Deposition of Amorphous/Nanocrystalline Oxy-nitrided Phases by Active Screen Plasma Treatment

In this research, AISI 304 austenitic stainless steels were efficient treatment using active screen plasma oxy-nitriding technique. The modified layers were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopes, and atomic force microscopy. In addition, the pitting corrosion resistances of untreated and oxy-nitrided samples were analyzed by polarization method in 3.5 wt.% NaCl solution. The results showed that a duplex-layer consisting of a deposition layer and a diffusion layer (including CrN+α phase and nitrogen expanded austenite phase) was generated. Special concern has been given to the formation of an amorphous top layer for the deposition of nano sized oxy-nitrides. It believed that the deposition layer of oxy-nitrides formed on steel surface during active screen plasma oxy-nitriding that lead to improved corrosion resistance of AISI 304 austenitic stainless steel, so that the pitting corrosive attack can be avoided.