Carburising is a case hardening process that introduces carbon into a solid ferrous alloy. This is accomplished by heating the metal in a carbonaceous atmosphere above transformation temperature for a pre-determined time. Subsequent to carburising, parts are quenched to harden the surface carburising layer. The core remains unaffected.
It is a widely used surface hardening process for low carbon steel. The industrial importance of carburising is expressed in its market share, as one third of all hardening heat treatment is covered by carburising and hardening.