Nitrogen plasma immersion ion implantation and silicon sputter deposition combined with methane implantation as an in-line process for improving corrosion and wear performance of stainless steels

Plasma immersion ion implantation has been used to combine ion implantation with thermally enhanced diffusion and thus bridge the gap between low temperature ion implantation and plasma diffusion treatment at elevated temperature. Particularly stainless steels were of interest, because they often show a poor tribological behaviour, which can be improved when they are hardened by incorporating nitrogen and forming a hardened surface zone. Using this technique one has to be careful with the temperature because the corrosion performance may easily degrade. The present paper describes a combination of nitrogen PIII treatment of stainless steel at intermediate temperature with depositing a thin silicon carbide film on top of the nitrided zone in an on-line sputtering/PIII process with a methane plasma. The resulting multilayer/gradient layer system of a thin amorphous SiC film on a several micrometer thick nitrided zone of the steel shows a greatly improved performance both with respect to corrosion and wear in comparison to the untreated steel and the nitrided steel without a carbide top layer.