The Structure of Oxide Layers on Tungsten

The oxidation of tungsten metal becomes appreciable at about 600°C. A thin, black adherent layer is first formed and at higher temperatures is eventually overlain by a bright yellow scale. The structure of these oxides has been studied by x‐ray diffraction. It is concluded that the essential difference between the black and yellow oxides is one of structural perfection and orientation rather than composition. The observations are shown to be consistent with the protective nature of the black film.