Nitriding of stainless steel in an rf plasma

Abstract
Treatment of stainless steels in an rf-powered nitrogen plasma achieves a much increased rate of nitriding, as well as higher hardness and corrosion resistance than traditional nitriding. Small amounts of adsorbed hydrogen are found to be necessary initially, and the process of nitriding is modeled on the basis of this hydrogen increasing the surface sticking coefficient for nitrogen, which is followed by nitrogen diffusion into bulk in the form of nitrogen-vacancy (weakly bound) pairs. The detailed microstructural role of chromium in the process is also discussed.