Nitrocarburizing (Tufftriding)

Nitrocarburizing (Tufftriding)

Nitrocarburising is a variation of the case hardening process. It is a thermochemical diffusion process where nitrogen, carbon, and to a very small degree, oxygen atoms diffuse into the surface of the steel part, forming a compound layer at the surface, and a diffusion layer. Nitrocarburising is a shallow case variation of the nitriding process. This process is done mainly to provide an anti-wear resistance on the surface layer and to improve fatigue resistance. It can be carried out in gas or molten salt and when carried out in salt, it is commonly referred to as ‘Tufftriding’

The compound layer is wear and corrosion-resistant and yet is not brittle, unlike its counterpart in the nitriding process. Since it provides an essential part of the properties required from the process it must not be removed by subsequent machining. Below the compound layer, the thin case significantly enhances the fatigue resistance of the component.

Benefits

There are several benefits of Nitrocarburising (Tufftriding):

  • Relative low cost;
  • High resistance to wear;
  • Excellent scuffing and seizure resistance;
  • Fatigue properties improved by up to 120%;
  • Considerably improved corrosion resistance;
  • Good surface finish;
  • Negligible shape distortion;
  • Predictable growth characteristics; and
  • Alloy substitution – plain carbon steels replacing low alloy steels.

Application

Advantages of the process include the ability to harden materials which are not pre-hardened, the relatively low temperature of the process ensures minimal distortion.

Typical industries include oil and gas, valve, pump, agriculture equipment, automotive, stamping, textile, extrusion and injection moulding, and firearms components.

Nitrocarburising can be applied to the same materials as in nitriding, as well as unalloyed materials, where good wear resistance and some improved fatigue resistance are needed at a low cost. It is widely used for stampings, as an alternative to hard plating.