Surface characterisation of plasma-nitrided iron by X-ray photoelectron spectroscopy

The nitriding by plasma has the potential to improve the tribological and mechanical properties on a number of substrates, and offers various advantages as compared with other methods used in the modification of surfaces. We prepared four samples by nitriding the iron substrates in a gas mixture 80% H2and 20% N2.under a pressure of 9.0 mbar, discharge frequency of 10 kHz and temperature of 773 K, for periods of 1, 2, 4 and 6 h. We characterised the samples by scanning electron microscopy SEM., X-ray diffraction XRD.and microhardness techniques, and detected the presence of Fe4N and Fe2 –3N phases. We employed X-ray photoelectron spectroscopy XPS.to obtain chemical-state and quantitative information of the plasma-nitrided iron surfaces. In situ cleaning was carried out by argon ion bombardment. The Fe 2p3r2 photoelectron peaks for all samples presented three components, associated with Fe0, Fe2q and Fe3q, while the N 1s lines showed two components, the main one due to iron nitride and the other is connected with oxidised nitrogen. q1999 Elsevier Science B.V. All rights reserved.