No abstract

To investigate the morphology and the growth kinetics of nitrided layers of Fe-Cr alloys, nitriding experiments were performed for alloys with 4.3, 7.7, 14.0, and 21.5 at. pct Cr. The precipitation morphology of the nitrided samples was investigated with light optical microscopy and scanning electron microscopy (SEM). The elemental compositional variation was determined with electron probe microanalysis. To describe the evolution of the thickness of the nitrided layers, a numerical model was developed that has as important (fit) parameters: the surface nitrogen content, the solubility product of chromium and nitrogen dissolved in the ferrite matrix, and a parameter defining the composition of the precipitated chromium nitride. Fitting of the model to the experimental data demonstrated for the first time that mobile and immobile excess nitrogen is present in the nitrided layers and that the mobile excess nitrogen considerably influences the nitriding rate.

No abstract

The composition and thickness of thin iron oxide films on polycrystalline pure iron were evaluated from Fe 2p spectra as measured by x‐ray photoelectron spectroscopy. To this end the experimental spectra were reconstructed from reference spectra of the constituents Fe0, Fe2+ and Fe3+. The background contributions in the spectra owing to inelastic scattering of signal electrons were calculated from the depth distributions of these constituents and their reference spectra. In the reconstruction procedure the film thickness and the concentrations of Fe2+ and Fe3+ in the oxide film were used as fit parameters. The values obtained for the oxide film thickness were compared with thickness values determined from the intensity of the corresponding O 1s spectra and with thickness values resulting from ellipsometric analysis. The sensitivity of the reconstruction procedure with regard to film thickness and film composition was tested. © 1998 John Wiley & Sons, Ltd.