Oxygen Effects in Plasma Nitriding of Ferrous Alloys

In this paper, we study the oxygen effect in low energy nitrogen implanted stainless steel AISI 316 at different oxygen partial pressures and temperatures. The samples were studied by photoemission electron spectroscopy (XPS) and sputtered neutral mass spectrometry (SNMS). Increasing the oxygen partial pressure during nitriding decreases the nitrogen content in the material depth. Surface oxidation induces phase segregation. The presence of oxygen forms CrO(x) on the top most layer of the sample and, subsequently, a nickel layer appears at approximately 9-10 nm beneath the surface. Moreover, the surface oxidation reaction of metal elements depends more strongly on the oxygen atoms landing on the surface rather than on the temperature process. At higher temperatures, on the other hand, the NO(x) species are degraded.41S732S73