Definition - What does Carbonitriding mean?

Carbonitriding is a surface modification process that involves diffusion of carbon and nitrogen atoms into interstices (small spaces) in the surface of metal.

This process is used to develop hard, wear-resistant surfaces. The hardness of a surface is directly proportional to the amount of diffusion of carbon and nitrogen in the surface. This process is used to improve corrosion properties of material that are subjected to wear.

Corrosionpedia explains Carbonitriding

Carbonitriding involves the addition of carbon (0.5 to 0.8%) and ammonia to a substrate's surface (ammonia acts as a source of nitrogen 0.2-0.4% N2). Nitrogen is adsorbed into the surface and diffuses into the work piece along with carbon. This process requires temperature to be maintained in range of 820-900°C in a gaseous atmosphere. After diffusion time the components are immediately quenched in oil.

Typical thickness is around 0.75 mm and this phenomenon alters only the surface of the material. Thickness cannot be increased rapidly, as diffusion is diminished once the top layer is carbonitrided.

Typical applications of carbonitriding include:

  • Gears and shafts
  • Pistons
  • Rollers and bearings

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