Cesium on the Tungsten Coating of Niobium-Zirconium Alloy Oxidized at 550-1300 °C

The results of the investigation of oxygen films and binary oxygen and cesium films on the gas-phase polycrystalline tungsten coating of NB-1%Zr alloy demonstrated that such a coating possesses rather the properties of W-Nb alloy than of pure W. All the specific features distinguishing this coating from the homogeneous one are related with the diffusion Nb onto the surface. With account for oxygen which is not removed till the temperature reaches 1800 ℃C, on smooth and the most perfect areas of the lower level, there exist at least three-level relief of the substrate of the film of intermetallic suboxide Nb₂W₂O. Such a film, which has a three-dimensional structure with maximum saturation of metal-oxygen chemical bonds, prevents both further segregation of Nb on the surface and further oxidation of Nb and also W which is not bound to Nb, i.e. it leads to formation of heat-resisting coating. (author)