Analysis of Layers: X-Ray Maps of Change in Thickness Obtained by Electron Macroprobe

Abstract

Surface coatings on steels can significantly change the properties of this material, thus the characterization of such thin films is an important objective of the steelmakers. The aim of the present work is to investigate a method of obtaining elemental compositions and thickness profiles of coatings using X-ray mapping. The analyses are carried out by electron probe micro analysis using a technique based on the phi-rho-Z model of the depth distribution of X-ray emission. Thickness X-ray maps of multilayered coatings can be built using suitable computer software combined with an accurate calibration method. The software used in STRATA from SAMx (France). The analyser used is a Camebax SXmacro from CAMECA. It is shown that, for the simple case of a chromium film (100 to 600 nm thick) on a steel substrate, the analysis can be performed at a single excitation voltage of 20 keV. Of course, in a more complicated case, such as multilayers containing many elements it is necessary to work with several accelerating voltages. In a second example, a thin film containing Fe, Cr, Mo, Si and Ti was deposited on the previous chromium layer. With Strata computer software and our calibration procedure it is possible to obtain the composition and the coating thickness variation in the regions where the film was not too thick for analysis.