Quantitative determination of the composition of nitrided layers on iron using AES

Abstract Within the framework of the study of industrial nitriding of steel, AES was chosen as the principle analysis technique. In order to characterise the nitrided layers quantitatively, reliable sensitivity factors were needed. For that purpose, different reference samples containing the pure γ′‐Fe 4 N 1− x and ε‐Fe 2 N 1− z phases were prepared by gaseous nitriding of pure iron. The characterisation of these references by means of electron probe microanalysis (EPMA) is discussed. The first sample contained a nitrided layer with large γ′‐Fe 4 N 1− x grains (∼30 µm) with 19.6 at.% nitrogen on top of an iron substrate. The second one contained an ε‐Fe 2 N 1− z outer layer (∼6 µm) with 26 at.% nitrogen, on a γ′‐Fe 4 N 1− x layer (∼4 µm) with 19.8 at.% nitrogen, created on top of an iron substrate. In this study, Fe LMM and N KLL Auger electron spectral lines were acquired on the pure γ′‐Fe 4 N 1− x and ε‐Fe 2 N 1− z phases of these two reference samples in order to calculate the sensitivity factors of iron and nitrogen. Different Auger intensities were considered and compared. It was decided to use the peak areas of the direct Auger electron spectral lines. The values of the sensitivity factors are 0.74 for iron and 0.33 for nitrogen. Finally, a set of three independent and well‐characterised samples containing the γ′‐Fe 4 N 1− x and ε‐Fe 2 N 1− z phases was used to validate the elaborated quantification procedure. Copyright © 2007 John Wiley & Sons, Ltd.