Surface Alternating Current Treatment And Low Temperature Plasma Nitriding Of Austenitic Stainless Steel

Lots of performance of metal materials ties up with their grain size, and refining grain is deemed to a kind of effective approach being used to ameliorate the combination property of metal materials all the while. At attended time, destabilization of metal materials more begins with the surface, so the surface nanocrystalline treatment which induces forming nanostructure on the surface of metals can obviously improve the surface and combination property of materials. There is not obvious interface between the layer of nanostructures and the matrix, thus the nanostructures layer don't separate and appear breadcrust because of the change of external condition.High volume fraction interface begins to form on the surface by surface nanocrystalline treatment, supplying ideal entryway for the diffuseness of chemical elements, and can markedly lower the temperature and time of chemical treatment and enhance infiltration concentration and deepness. The surface nanocrystalline treatment affords powerful supply for developing new surface treatment process.A plastic deformation surface layer with nanocrystalline grains was produced on AISI 316L austenitic stainless steel by means of suface alternating current treatment (SACT). Low-temperature nitriding of SACT and un- SACT AISI 316L stainless steel was carried out in pulsed-DC glow discharge. The effect of SACT pretreatment on the microstructure and properties of the stainless stee lwere invetigated using X-ray diffraction, scanning electron microscopy, Vickers hardness tester and friction wear testing machine WWM-1. The results show that the plasma nitriding of AISI 316L stainless steel can be enhanced considerably by means of SACT process before nitriding, and a much thicker nitrogen diffusion layer with higher hardness was obtained for the SACT samples when compared with un- SACT samples. In addition, the wear resistance and load capacity of the nitrided layers on the SACT samples was much higher than that of the un- SACT samples due to the thicker S phase case and the gradient nitrogen diffusion layer. At low temperature and in short time,a precipitation-free nitrided layer of S phases trueture can be produced,which exhibits not only high hardness but also very good corrosion resistance.At higher temperatures and with prolonged nitriding time,the depth of nitrided layer increases,but the CrN precipition appeared in the nitrided layer,which reduced corrosion resistance of the nitrided layer.In this paper, we systematically study the surface nanocrystalline treatment process and low temperature nitriding process of steels. The task mainly includes three parts: First, we utilize alternating current to treat AISI 316L stainless steel in electrolyte at different parameter for forming nanostructure on the sample surface, characterize the sample by multiform test methods and discuss the mechanics of forming nanostructures. Secondly, the samples are nitridized respectively at 420℃,450℃,500℃and characterized by multiform test methods, then we bring forward the principium of low temperature nitriding. Lastly, we study the frictional wear corrosion resistant characters of nitriding samples.