Carbo Nitriding is a thermochemical case hardening process in which both carbon and nitrogen are diffused into the surface of steel components at controlled temperatures. Following diffusion, the components are quenched and tempered to develop a hard outer case while maintaining a tough and ductile core.

Compared with conventional carburizing, the addition of nitrogen improves hardenability and allows effective treatment at relatively lower temperatures.

The process is widely used for components subjected to repeated wear, contact stress and fatigue loading where dimensional accuracy and surface durability are important.