Liquid carbonitriding is the process of diffusion enrichment of the surface layer of a part with carbon and nitrogen provided by a molten salt.The process is carried out at the temperatures 820-860°C
Carbonitriding is used primarily to impart a hard, wear-resistant case, generally from 0.075 to 0.75 mm deep. A carbonitrided case has better hardenability than a carburized case (nitrogen increases the hardenability of steel; it is also an austenite stabilizer, and high nitrogen levels can result in retained austenite, particularly in alloy steels).
Consequently, by carbonitriding and quenching, a hardened case can be produced at less expense within the case-depth range indicated, using either carbon or low-alloy steel. Full hardness with less distortion can be achieved with oil quenching, or, in some instances, even gas quenching, employing a protective atmosphere as the quenching medium.