Low Temperature Plasma Hardening Treatment Of Martensitic Stainless Steel

Because of its higher strength, higher surface hardness, higher wear resistanceand better corrosion resistance, martensite stainless steel is more widely used in manyfields than austenitic stainless steel. But the steel strength, abrasion resistance andcorrosion resistance of martensite stainless steel still cannot meet the requirements inthe use of extreme environments. We used AISI420mastenitic stainless steel as anexample to have some low temperature plasma hardening treatments without reducingits corrosion resistance in this article. This treatment could improve its surfacehardness and to expand its scope of application.Through the study of the low temperature plasma nitriding, low temperatureplasma nitrocarburizing and low temperature plasma carburizing treatment to AISI420martensitic stainless steel， the samples which after treated were analyzed. Theexperimental results showed that low temperature plasma nitriding, low temperatureplasma nitrocarburizing and low temperature plasma carburizing treatment couldimprove the surface hardness of AISI420martensitic stainless steel. These processescould make the stainless steel surface to obtain a certain thickness of hardening layer.Low temperature plasma nitriding processing sample has the highest hardness underthe same processing temperature. Under the same process, the higher the processingtemperature, the greater the permeability layer thickness. The wear results show thatplasma carburizing sample has the best wear resistance. From the point of view of theperformance of the hardening layer and difficulty of the processing, low temperatureplasma carburizing is superior to the low temperature plasma nitriding and lowtemperature plasma nitrocarburizing.The influence in low temperature plasma carburizing by carburizing temperature, carburizing time, gas ratio, and furnace pressure to the martensitic stainless steel arefurther studied in this article. The experimental results shows that improving thecarburizing temperature can make the stainless steel to obtain harder and thicker ofcarburized layer. When the carburizing temperature is more than500℃, the corrosionresistance will decline due to lots of precipitation of CrN. As lengthening thecarburizing time of low temperature plasma carburizing to AISI420martensiticstainless steel, the hardness and thickness of hardening layer is increased. Addition oflayer thickness and hardness will get slowly when plasma carburizing for more than6h.There isn’t positive relationship between gas ratio，furnace pressure and the result ofthe plasma carburizing treatment. However，there is extreme somewhere. The optimumcarburizing process of AISI420stainless steel is obtained by the result of singlevariable method.