Kinetics of the Gaseous Nitrocarburising Process

Results obtained regarding compound layer phase composition, porosity, and overall thickness after nitrocarburising various steels in various atmospheres are presented. In particular, the gas reactions that take place in the furnace chamber and the mass transfer reactions for nitrogen and carbon are discussed, from practical and theoretical points of view. The compound layer phase compositions obtained with the various types of steel are discussed in connection with the new Fe-N-C phase diagram. It is shown that, by controlling the activity of carbon, oxygen, and nitrogen in the atmosphere, it is possible to control the phase composition, porosity, and growth rate of the compound layer. Furthermore, it is shown that by selecting the atmosphere composition it is possible to obtain optimal results for each type of steel. A brief survey is given characterising the commercial nitrocarburising methods presently available.