Effects of processing time and temperature on the surface properties of AISI 316L stainless steel during low temperature plasma nitriding after low temperature plasma carburizing

The 2-step low temperature plasma processes (the combined carburizing and post-nitriding) were carried out for improving both the surface hardness and corrosion resistance of AISI 316L stainless steel. The effects of processing time and temperature on the surface properties during nitriding step were investigated. The expanded austenite (γN)was formed on all of the treated surface. The thickness of γN was increased up to about 20 μm and the thickness of entire hardened layer was determined to be about 40 μm. The surface hardness reached up to 1,200 HV0.1 which is about 5 times higher than that of untreated sample (250 HV0.1). The thickness of γN and concentration of N on the surface were increased with increasing processing time and temperature. The corrosion resistance in 2-step low temperature plasma processed austenitic stainless steels was enhanced more than that in the untreated austenitic stainless steels due to a high concentration of N on the surface