Brightening Treatment Of Austenitics Stainless Steel After Low Temperature Plasma Surface Harding

Under the premise of without changing its corrosion-resistance, although the hardness and the abrasion resistance of austenitic stainless steel will both increase substantially by low temperature plasma hardening treatment, a black film which is strongly-combined, compact and paper-thin will come into being on its surface. This black film will not only influence the surface roughness and the beauty of the steel, but also impact on its corrosion-resistance. So it’s really necessary to eliminate this black film by chemical brightening treatment.This dissertation analyzes the chemical brightening treatment of austenitic stainless steel after low temperature plasma carburizing.Through the preparatory work, the surface morphologies, microstructures, phase structure, element component, microhardness and corrosion resistance of the surface black film of the carburized layers were observed. Then it analyzes the reason that the black film forms on the low temperature plasma hardening treatment and infers ingredients of the black film. It also does further research into how to get rid of this black film by employing chemical method. The results show that the chemical method: acid-washing, removing accumulated carbon, alkali-washing, finally acid-washing again, can eliminate the black film on stainless steel hardened by low temperature plasma hardening treatment, more thoroughly with less damage of the hardened layer and relative good corrosion resistance.Then the thesis analyzes the electrochemical brightening treatment of austenitic stainless steel after low temperature plasma nitrocarburing. During the study of the electrochemical surface brightening technology,the best method of treatment was chosen by discussing the surface appearance, the surface roughness, microstructures, the removed thicknesses, microhardness and corrosion resistance of the carburized layer. Experiences have shown that the electrochemical brightening treatment after plasma carburizing of austenitic stainless steel can renew the original color of the plasma carburized austenitic stainless steel surface, and the carburized layer after electrochemical brightening can still retains high hardness and satisfactory thickness. The electrochemical brightening not only can improve the presentation quality of the stainless steel surface, but also can greatly increase the corrosion resistance of the carburized stainless steel.It is of great significance to austenitic stainless steel parts applied in the severe corrosion environment.