Thermomechanical treatment of surface
Carburizing
Themomechanical treatment which is applied to a low-carbon steel in the austentic state to obtain surface enrichment with carbon which is in solid solution in the austenite. The subsequent hardening results in a hard and wear-resistant surface.
Nitriding
Introducing nitrogen into a solid ferrous alloy by holding steel at a suitable temperature (below Ac1 for ferritic steels) in contact with a nitrigenous material, usualy ammoins or molten cyanide of apropriate composition. Contrary to carburization and carbonitriding, hardening is not obtained by a subsequent quench hardening treatment. Quenching is not required to prouce a hard case.
Carbonitriding
Introducing carbon and nitrogen into a solid ferrous alloy by holding above Ac1 in an atmosphere that contains suitable gases, such as hydrocarbon, carbon monoxide and ammonia. The carbonitrided alloy is usually quench hardening
