Modified gas carburizing in which ammonia is added to the carrier gas so nitrogen and carbon diffuse in together at about 790 to 900 °C. Nitrogen raises surface hardenability, letting plain carbon steels harden in oil, and the lower temperature means less distortion. Cases are usually shallow, around 0.08 to 0.75 mm, and suit small high-volume parts such as pins, fasteners and stampings.
Seat-belt pins get carbonitrided, 0.005 to 0.010 case, oil quench, temper, out the door by lunch.
Also heard as
- carbonitride
- CN
Do not mix it up with
- FNC: Ferritic nitrocarburizing runs below the critical temperature with no quench hardening, while carbonitriding austenitizes the steel and quenches it.
Related terms
Carburizing
Diffusing carbon into the surface of low-carbon steel at high heat, then quenching for a hard case.
Nitriding
Diffusing nitrogen into steel below its critical temperature to form a hard case with no quench.
FNC
Ferritic nitrocarburizing: adding nitrogen and carbon below the critical temperature for a thin, hard layer.
Case depth
Thickness of a hardened surface layer, measured from the surface to a specified hardness or structure.