Carburizing

Absorption and diffusion of carbon into solid ferrous alloys by heating, to a temperature usually above Ac3, in contact with a suitable carbonaceous material which may be solid, liquid, or controlled atmosphere gas. A form of case hardening that produces a carbon gradient extending inward from the surface, enabling the surface layer to be hardened either by quenching directly from the carburizing temperature or by cooling to room temperature, then reaustenitizing and quenching.