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