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What is the difference between plasma nitriding and plasma nitrocarburising?

What is the difference between plasma nitriding and plasma nitrocarburising?

The key difference between plasma nitriding and plasma nitrocarburising is the different treatment gases: In plasma nitriding, the surface layers are enriched with nitrogen; in plasma nitrocarburising, carbon is also introduced. The layers produced by the different processes exhibit various usage properties, enabling optimum adjustment to the requirements of your components.

Examples as to when nitriding is usually employed and for which components nitrocarburising is better suited can be found under nitriding and nitrocarburising. Here you will also find the usual layer thicknesses.

Expert knowledge on the subject

Nitriding and nitrocarburising in plasma

By choosing the nitriding atmosphere, the structure of the compound layer and thus your properties can be specifically set. During plasma nitriding in N2/H2 gas mixtures, wear-proof, ductile Fe4N layers usually arise. These are also referred to as gamma' nitride layers.

For unalloyed steels or components that are corrosively stressed, compound layers consisting predominantly of Fe2-3N are recommended. This layer type is produced through nitrocarburising. Methane or carbon dioxide is usually added to the nitriding atmosphere as a carbon donor. The compound layers arising during nitrocarburising are usually thicker than the layers produced during nitriding. A significantly higher level of surface hardness is to be detected after the nitrocarburising, especially on unalloyed materials. For the planned formation of the compound layer, in addition to the carbon content in the gas phase, the carbon content of the material is to be considered.

Nitrocarburising is often performed at high temperatures (approx. 570°C). However, it can also be performed at lower temperatures; e.g. if maximum hardness increases are desired.

You can find further theoretical background information regarding layer structure during nitriding here.

[1] Th. Lampe, St. Eisenberg, G. Laudin: Verbindungsschichtbildung während der Plasmanitrierung HTM 46 (1991) 5 p. 308–316[2] Kunze, H.-J.: Nitrogen and Carbon in Steel Akademie Verlag 1990