LLC Laboratory of Vacuum Technologies, Zelenograd, Russia:

E. V. Berlin, General Designer
V. Yu. Grigoriev, Deputy Director for Research

PJSC “Machine-Building Plant”, Elektrostal, Russia:
A. V. Ivanov, Scientific Advisor

National Research Nuclear University “MEPhI”, Moscow, Russia:
M. G. Isaenkova, Professor, the chair “Physical problems of material science”, e-mail: isamarg@mail.ru
K. E. Klyukova, Student of Material Science
S. D. Stolbov, Post-Graduate Student

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 pre ferential 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.

1. Koo Y.-H., Yang J.-H., Park J.-Y., Kim K.-S., Kim H.-G., Kim D.-J., Jung Y.-I., Song K.-W. KAERI’s Development of LWR Accident-Tolerant Fuel. Journal of Nuclear Technology. 2014. Vol. 186, Iss. 2. pp. 295–304.
2. Kim H.-G., Kim I.-H., Jung Y.-I., Park D.-J., Yang J.-H., Koo Y.-H. Development of Surface Modified Zr Cladding by Coating Technology for ATF. Conference Top Fuel 2016. Boise, ID, September 11–15, 2016. pp. 1157–1163.
3. Kim H. G., Yang J. H., Kim W. J., Koo Y. H. Development status of accident-tolerant fuel for light water reactors in Korea. Nucl. Eng. Technol. 2016. Vol. 48. pp. 1–15.
4. Kuprin A. S., Belous V. А., Voyevodin V. N., Bryk V. V., Vasilenko R. L., Ovcharenko V. D., Reshetnyak E. N., Tolmachova G. N., V'yugov P. N. Vacuum-arc chromium-based coatings for protection of zirconium alloys from the high-temperature oxidation in air. J. Nucl. Mater. 2015. Vol. 465. pp. 400–406.
5. Kuprin A. S., Belous V. A., Voyevodin V. N., Bryk V. V., Vasilenko R. L., Ovcharenko V. D., Tolmachova G. N., V’ygov P. N. High-temperature air oxidation of E110 and Zr – 1Nb alloys claddings with coatings. Problems of Atomic Science and Technology. 2014. Vol. 89, No. 1. pp. 126–132.
6. Belous V. A., V'ygov P. N., Kuprin A. S., Leonov S. A., Nosov G. I., Ovcharenko V. D., Ozhigov L. S., Rudenko A. G., Savchenko V. T., Tolmachеva G. N., Khoroshikh V. M. Mechanical characteristics of Zr1Nb alloy tube after deposition of ion-plasma coatings. Problems of Atomic Science and Technology. 2013. Vol. 84, No. № 2. pp. 140–143.
7. Park J. H., Kim H. G., Park J. Y., Jung Y. I., Park D. J., Koo Y. H. High temperature steam-oxidation behavior of arc ion plated Cr coatings for accident fuel claddings. Surf. Coat. Technol. 2015. Vol. 280. pp. 256–259.
8. Carpenter J. S., Nizolek T., McCabe R. J., Knezevic M., Zheng S. J., Eftink B. P., Scott J. E., Vogel S. C., Pollock T. M., Mara N. A., Beyerlein I. J. Bulk texture evolution of nanolamellar Zr – Nb composites processed via accumulative roll bonding. Acta Materialia. 2015. Vol. 92. pp. 97–108.
9. Weijun He, Jiateng Ma, Yanxin Zhang, Hanying Wen, Qing Liu, Effect of the Annealing Process on the Microstructure and Mechanical Properties of Multilayered Zr/Ti Composites. Materials Science & Engineering: A. 2017. Vol. 713. DOI: 10.1016/j.msea.2017.12.072
10. Ivanov A. V., Kuraev A. Yu, Malakhov A. A., Lerner A. E., Lusan Yu. V. Investigation of the protective chromium coating properties of VVER fuel rods simulation samples. VANT: Materials science and new materials. 2018. Vol. 3 (94). pp. 116–130.
11. Patent 2503079 Russian Federation, H 01 J 37/00, H 05 H 1/24. Plasma generator. Berlin E. V., Grigoriev V. Yu. ; published 27.12.2013.
12. Patent 2612113 Russian Federation. The method of combined ion-plasma treatment of products from aluminum alloys. Berlin E. V., Stepanova T. V. ; published 25.08.2017.
13. Isaenkova M. G. Perlovich Y. A., Regularities of development of crystallographic texture and substructure inhomogeneity in zirconium alloys during deformation and heat treatment. Moscow : NRNU MEPhI, 2014. 528 p.
14. Perlovich Y., Isaenkova M., Fesenko V. Modern methods of experimental construction of texture complete direct pole figures by using X-ray data. IOP Conf. Series: Materials Science and Engineering. 2016. Vol. 130.
15. Blokhin M. A., Shveytser I. G. X-ray spectra directory. Moscow : PhML, 1982. 376 p.
16. Khramtsova T. P., Skrytnyy V. I., Yaltsev V. N. Mutual disorientation texture in α-Zr polycrystals. Non-ferrous Мetals. 2015. No. 1. P. 42–44. DOI: 10.17580/nfm.2015.01.09
17. Golovin Yu. I. Nanoindentation and its opportunities. Moscow : Mashinostroenie, 2009. 312 p.
18. Oliver W. C., Pharr G. M. Measurement of hardness and elastic modulus bу instrumented indentation: Advances in understanding and refinements to methodology. Journal of Materials Research. 2004. Vol. 19 (1). pp. 3–20.
19. Umanskiy Ya. S., Skakov Yu. A., Ivanov A. N., Rastorguev L. N. Crystallography, X-ray diffraction and electron microscopy. Moscow : Metallurgy, 1982. 632 p.
20. Perlovich Y. A., Isaenkova M. G., Grekhov M. M., Fesenko V. V., Kalin B. A., Yakushin V. L. Structure and texture changes in the volume of cladding tubes made of zirconium-based alloys during ion-plasma surface treatment. VANT: Physics of radiation damage and radiation materials science. 2004. Vol. 3 (85). pp. 59–65.
21. Yakushin V. L. Modification and materials damage by high temperature pulsed plasma flows. The thesis for the degree of Doctor of Physical and Mathematical Sciences. Moscow, 2006. 357 p.