Obtaining S-phase layer: Glow-discharge nitriding at low temperature x SHTPN - Part 1

Samples of stainless steel ISO 5832-1 were nitrided by two different processes, plasma nitriding at low temperature and SHTPN, in order to obtain a nitrogen rich surface layer (S-phase or gamma(N)) free from precipitates. The nitriding time for both processes was the same (3 h), to enable a comparison of the results obtained. Treated samples were characterized by means of scanning electron microscopy (SEM), optical microscopy, microhardness, X-ray diffraction (XRD) and wavelength dispersive spectrometry (WDS). The results indicate that low-temperature nitriding enables the formation of S-phase layer with nitrogen concentrations about 0.90 wt.% with a thickness of 2.15 mu m, while SHTPN generates layers with 0.45 wt.% and thicknesses up to 200 mu m.