Carbonitriding is an austenitic (above A3) case hardening process similar to carburising, with the addition of nitrogen (via NH3 gas), used to increase wear resistance and surface hardness through the creation of a hardened surface layer.
Carbonitriding is applied primarily to produce a hard and wear resistant case. The diffusion of both carbon and nitrogen increases the hardenability of plain carbon and low alloy steels, and creates a harder case than carburising. The carbonitriding process is particularly suited for clean mass production of small components. Due to the lower temperature required for the carbonitriding, compared to carburising, distortion is reduced. Mild quenching speed reduces the risk of quench cracking.
Application & materials
Austenitic carbonitriding is successfully applied to generally mass produced components, and those of smaller dimensions, where great resistance to wear is required and where the case depth requirements ranges from 0.1 to max 0.75 mm. Typical applications include:
gears and shafts
rollers and bearings
levers in hydraulic, pneumatic and mechanical actuated systems.
Primarily to improve wear resistance and fatigue strength of plain carbon steels.
A wide variety of steels can be carbonitrided from plain carbon steels to mild steels (with reduced aluminium content), low alloy steels with max. 0.25% carbon, free cutting steels, and sintered steel.