Nitrocarburising is a thermochemical heat treatment process that enhances the surface properties of treated components (usually ferrous materials) through the formation of a surface nitrocarbide compound layer. The nitrocarbides have superior anti-corrosion, anti-wear and anti-scuffing properties and are commonly used for improvements in surface mechanical and chemical properties. The process is classified in two groups of ferritic and austenitic depending on its treatment temperature. These treatments are performed below and above 590ºC (eutectoid temperature in the Fe-N diagram), respectively.
In ferritic nitrocarburising, a nitrogen diffusion zone is formed beneath the compound layer. This layer is composed of nitrogen saturated ferrite together with dispersed precipitates of iron and alloy elements nitrides.
Austenitic nitrocarburising can produce a thicker compound layer that is supported by an iron-carbon-nitrogen austenite layer followed by a nitrogen diffusion zone.