The effects of differing nitrogen implantation conditions on penetration depth, mechanical properties, and tribological behavior of plasma-nitrided AISI 304 stainless steel

In the present study, the plasma immersion ion implantation (PIII) technique was applied to enhance the mechanical properties of AISI 304 stainless steel by plasma nitriding. Nine kinds of specimens were prepared by differing the implantation parameters such as voltage, temperature, and time. The variations of nitrogen concentration at the specimen surface and in the subsurface regime were investigated using a glow discharge spectrometer (GDS). A nanotester was used to obtain the mechanical hardnesses and Young's moduli varying at different penetration depths. A comparison of the results reveals that the hardness distributions at different penetration depths are related to the nitrogen concentration distributions. The experimental results indicated that the mechanical hardness is elevated by increasing the penetration depth of nitrogen, whereas the Young's modulus is significantly elevated by PIII, but is almost independent of the penetration depth. The average scratch depth of a specimen is lowered by increasing the penetration depth. The combination of an implantation temperature not lower than 400 °C and a relatively high implantation voltage is helpful for increasing the penetration depth, thus resulting in a relatively small scratch depth.