Effects of the process parameters on the layer formation behavior of plasma nitrided steels

In order to investigate the behavior of nitrogen active species during the pulsed d.c. plasma nitriding process, emission spectra measurements by using optical emission spectroscopy (OES) were performed for various treatment temperatures, duty factors and different gas pressures in the reactor. Results of the OES were compared to those of the metallurgical analysis of plasma nitrided sintered steel and high speed steel substrates. The spectral intensities of N2+ and N2 were influenced by process parameters (gas pressure, treatment temperature and duty factor). The thickness of the nitride layer and the size of micro-pore increased with increasing treatment temperature. Especially, the thickness of the compound layer was mainly influenced by the gas pressure in the reactor.