Carbonitriding and carburising are two widely used treatments for hardening and strengthening high-precision steel parts and components, ensuring maximum wear resistance during assembly and subsequent use.
However, there are differences between the two processes – differences that, in most cases, make carbonitriding preferable to carburising.
Differences between carbonitriding and carburising
As we said, these are two very similar treatments, but they have substantial differences that make carbonitriding applicable to a wider range of steels, including low-alloy steels, and even to iron.
The first difference is the treatment temperature: carbonitriding takes place at a slightly lower temperature.
The second difference concerns the composition of the gas the steel is exposed to while heated: in carburising it is an endothermic gas with methane and propane added in varying proportions; in carbonitriding, a percentage of ammonia, which releases nitrogen, is added to the gas. This helps avoid the distortion that generally results from exposing steel to high temperatures, which does occur with carburising and often requires a subsequent grinding stage to restore the component’s original shape. For this reason carbonitriding is also suitable for small components.
The third difference is the case depth: carburising gives a deeper hardened layer, while carbonitriding produces a hardened layer of at most 0.50–0.80 mm.