Nitrogen Case Hardening

a type of thermochemical treatment consisting of diffusion saturation of the surface of steel or cast iron with nitrogen and carbon from a gaseous medium at 500°–700°C (low-temperature process) or at 840°–930°C (high-temperature process).

The diffusion layer formed upon nitrogen case hardening is 0.25–1.50 mm thick and is similar in structure and properties to a cyanided layer. Nitrogen case hardening increases the wear resistance, fatigue strength, and contact strength of the metal. In many cases it also increases corrosion resistance. Nitrogen case hardening is used to increase the durability and operating life of machine parts.