Nitriding produces a case depth enriched in nitrogen, which diffuses into the surface of the components, combining with nitride forming elements. The steels chosen for nitriding are usually in the heat treated condition, and fully stabilised, at a temperature above that of the nitriding operation. The nitrogen is provided from the breakdown of ammonia gas, which flows through the sealed retort at a rate determined by the dissociation, which is continually measured.

A compound layer is produced during nitriding, which is generally considered beneficial, this layer offers corrosion resistance. However, compound layers above 20 microns thick can be prone to spalling, and are very often removed after the nitriding treatment. With the modern methods of controlling the gaseous atmosphere, the compound layers can be controlled to requirements.

Surface hardness’s far in excess of conventional case hardening are achieved without quenching and eliminates all but the very minimum of distortion.