Shozo Inoue1, Hitoshi Uchida1, Mika Morii2 and Keiji Koterazawa1
1Faculty of Engineering, Himeji Institute of Technology, Hyogo
Raman spectroscopy should be a useful technique for a nondestructive characterization of surface layers on metals. In this study, Raman spectroscopy has been used to examine oxide layers formed on stainless steels in air at elevated temperatures.
Specimens of commercial austenitic stainless steels (SUS304, SUS316 and SUS310S) were prepared by polishing with \#1200 emery paper and degreasing in an ultrasonic bath of acetone. Oxidations were carried out in a preheated furnace at 573-1073 K for 1.8-3600 ks. Raman spectra were obtained from these oxide layers formed on stainless steels. Auger depth analysis was also used to study the oxide layers.
When oxidation temperature was below about 873 K, it was clarified that iron oxides such as Fe2O3 and Fe3O4 were formed. On the other hand, the surface oxide layers at above 873 K were composed of Cr2O3, MnCr2O4 and FeCr2O4. The composition of stainless steels was less dependent on these oxidation behavior. The thickness of the oxide layer formed at 1073 K for 7.2 ks was estimated at about 400 nm by Auger depth profiling. From a comparison of the Raman spectra with Auger depth profiling, it was concluded that the Raman spectra measured in this study were obtained from the whole layer of the surface oxide film. Therefore, Raman spectroscopy technique can be applied to the characterization of the oxide layers up to about 1 μm thickness formed on stainless steels.
Raman spectroscopy, Auger depth profiling, stainless steel, oxidation
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