Nitriding Steel

Definition - What does Nitriding Steel mean?

Nitriding steel is steel treated with a highly specialized surface hardening process known as "nitriding." Nitriding is a heat-treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface.

Case hardening, or surface hardening, is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal at the surface. It is predominantly used for steel, but also used for titanium, aluminum and molybdenum.

Corrosionpedia explains Nitriding Steel

Nitriding steel is produced when steel is subjected to the nitriding process. The nitriding process involves the diffusion of nitrogen into the base steel. This diffusion takes place at relatively low temperatures (typical process temperature is around 524 °C / 975 °F) and the hardening occurs without quenching.

Core properties are not affected by the nitriding process provided the final tempering temperature for the product was higher than the nitriding process temperature. Nitride surfaces are highly wear resistant and provide anti-galling properties. Fatigue life is improved, and the process improves the corrosion resistance of the part. An additional advantage of nitriding is that the surface hardness is resistant to softening by temperatures up to the process temperature.

A wide variety of steel can be nitrided, however, the three most commonly used nitriding steels are:

  • AISI 4140
  • AISI 4340
  • Nitralloy

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