Yasunobu Tsuji1 and Masayuki Uda2
1Technical Research Laboratory, Citizen Watch Co., Ltd., Tokorozawa
An attempt was made to identify an oxide film formed on the surface of 18Cr-8Ni steel, heated at 500°, 800° and 1050°C in air for less than a few minutes. The structures of the oxide film were determined with the aid of an electron microscope equipped with an X-ray microanalyzer, which enables us to obtain electron micrographs, diffraction patterns and characteristic X-ray spectra from the same selected area of the film. The oxide film was composed of three kinds of common oxides through all the experimental conditions; namely, (1) oxide with a corundum structure detected from the area of a continuous thin film, which is identified to be Cr2O3, (2) oxide with a spinel structure corresponding to aggregates of fine particles, Fe3O4 and (3) oxide of electron opaque clusters in small quantities, either MnO or Mn3O4. From all the oxide films concerned, no spectrum of Ni could be detected. The results differ considerably from those obtained after prolonged oxidation; in the latter, several complex oxides with some metallic components of the alloy are found instead of mono-metallic oxides.
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