Publication: Structure of the protective chromium coating obtained by a thermal evaporation method in a magnetron discharge on the cladding tube from e110 alloy
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2019
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© Designed by: “Ore and Metals” Publishing House, journal “Tsvetnye Metally”, 2019.The creation of fuel claddings with enhanced mechanical properties, which are stable under normal conditions and by short-term overheating, is an important task for the modern development of light-water thermal-neutron reactors, along with the elaboration of a more efficient fuel material. This paper presents the X-ray data on the inhomogeneity of structure and crystallographic texture of a protective chromium coating obtained by thermal evaporation in a magnetron discharge, and a zirconium substrate (cladding tube from E110-alloy). It is established that the coating thickness of 7-8 microns consists of chromium, which is characterized by the bcc structure. The transition from the coating to the substrate occurs within a zone 3 µm thick, in which the bcc phase is gradually replaced by the hcp phase. High compressive tangential macrostress, significantly exceeding the yield strength of chromium, is found in the chromium coating. The presence of compressive stresses is also confirmed by layer-by-layer changes in the measured parameters of the crystal structure of chromium and its mechanical properties, such as microhardness, elastic modulus and the fraction of plastic deformation. It is shown, that the coating is characterized by the high layerby-layer uniformity of texture, which is not related to the orientation of the substrate. The coating grows on zirconium layers with a weakly pronounced preferential orientation of the grains. The scattering of the crystallographic texture of upper layers of the cladding tubes is associated with the effect of high-energy ionic beams on the zirconium substrate in the process of ion etching of the tube surface, which precedes to magnetron application of the chrome coating. The scattering of the substrate texture confirms the orientation independence of the growth of the coating, where a direction close to one of <111> axes, being the most densely packed in the bcc structure, is oriented perpendicular to the cylindrical surface of the tube. The sharp crystallographic texture of the chrome coating causes a substantial anisotropy of the elastic moduli along the axial and tangential directions, determined from the continuous indentation curves. Crystallographic directions <114> <111> and <110> are located along the indicated directions, respectively.
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Isaenkova, M. G. Structure of the protective chromium coating obtained by a thermal evaporation method in a magnetron discharge on the cladding tube from e110 alloy / Isaenkova, M.G., Klyukova, K.E., Stolbov, S.D. // Tsvetnye Metally. - 2019. - № 4. - P. 33-40. - 10.17580/tsm.2019.04.04