Plasma nitrocarburising is an alternative nitrocarburising method which provides additional treatment benefits arising from the catalytic effect of the glow discharge and its ability to remove the protective surface layers present on stainless steels and other high alloy steels and alloy cast irons. As a result it is the preferred method for these materials.
Nitrocarburising is a variation of the case hardening process. It is a thermochemical diffusion process where nitrogen, carbon, and to a very small degree, oxygen atoms diffuse into the surface of the steel part, forming a compound layer at the surface, and a diffusion layer. Nitrocarburising is a shallow case variation of the nitriding process. This process is done mainly to provide an anti-wear resistance on the surface layer and to improve fatigue resistance.
Nitrocarburising is carried out at sub-critical temperatures and involves the diffusion of nitrogen and carbon into the surface of carbon steel to give a somewhat harder case and soft core with a very thin compound layer on the surface.
The compound layer is wear and corrosion resistant and yet is not brittle, unlike its counterpart in the nitriding process. Since it provides an essential part of the properties required from the process it must not be removed by subsequent machining. Below the compound layer, the thin case significantly enhances the fatigue resistance of the component.
