A novel approach to the characterization of thin oxide layers

A novel approach to the characterization of thin coatings or surface layers by means of the ASTAR hardware attached to the transmission electron microscope (TEM) and the dedicated software, used for orientation and phase map analyses, was applied to examine the Sanicro 25 steel after 500 h of oxidation in water vapor at 700 °C. Phase composition and grain orientation maps as well as texture analysis of thin (i.e. with a thickness of below 1 µm) oxide layers were performed using a new TEM technique similar to electron backscatter diffraction in the scanning electron microscope. The spatial resolution of this technique was sufficient for the imaging of nm-sized grains and a full characterization of the thin oxide scale. The acquired results were verified using data obtained by means of conventional selected area electron diffraction (TEM-SAED), energy-dispersive X-ray spectroscopy and texture analyses using X-ray diffraction techniques. It should be noted that high-quality TEM samples are required for such investigations.