The nitriding process is defined as the diffusion of nitrogen into steel and consists in subjecting parts of special steel to the action of ammonia at a temperature normally in the range 500 to 530°C. Low and higher temperatures are occasionally used. the duration of treatment is greatly in excess of that used for much deeper cases when carburizing, a normal time for nitriding being of the order of 90-96 hours.
Furnaces are generally of batch type, the temperature having to be kept correct to within ±5°C. Such close control is heat catered for by electric furnaces. Steels for nitriding comes in nitriding steels and austenitic steels. Nitriding furnaces are used in the process of nitriding metals using ammonia. Gas nitriding is a thermochemical treatment, which hardens the product.