Gas Nitriding consists of subjecting machined and heat-treated steel, free from surface decarburization, to the action of a nitrogenous medium, usually ammonia gas, at a temperature of approximately 950°F to 1050°F, creating a very hard surface. The surface hardening effect is due to the absorption of nitrogen, and subsequent heat treatment if the steel is unnecessary. The case is less than .020 inch deep and the highest hardness exists in the surface layers to a depth of only a few thousandths of an inch. Because of the low temperatures required for Gas Nitriding, distortion is very low compared to other Case Hardening processes.

Because Gas Nitriding is carried out at a relatively low temperature, it is advantageous to use quenched and tempered steel as the base material. This gives a strong, tough core with an intensely hard wear-resisting case — much harder than can be obtained by quench hardened or carburized steel.