Cyaniding

It consists in producing a layer of hard surface on low or medium carbon steels by immersing the metal in a molten salt containing cyanide (like NaCN) at a temperature of about 800-850^oC and then quenching them in oil or water. The salt bath in addition to cyanide contains soda ash and sodium chloride to the extent of 40%. The hard surface is produced due to the absorption of carbon and nitrogen in the metal surface. The resulting case has 0.6 to 0.8% carbon and 0.4 to 0.5% N. The case hardness varies from 56 to 60 RC, and case depth varies between 0.075 to 2.5 mm.