Effect of buffer layer on oxidation and corrosion resistance of CrN coatings on Zr alloy prepared by FCVAD technology

To improve the oxidation resistance of fuel cladding in case of nuclear accidents, CrN coatings with different metal buffer layers (Cr, Ti, Al) were deposited on Zr 702 alloy via filtered cathode vacuum arc deposition (FCVAD) technology. The phase composition, microstructure, mechanical properties, oxidation resistance and corrosion resistance of the coatings were systematically investigated. CrN coating with Cr buffer layer showed excellent oxidation resistance at 800–1000 °C in air. Cr buffer layer effectively retarded the diffusion of oxygen and the decomposition of CrN by generating a Cr₂O₃ layer. CrN coating with Cr buffer layer had the lowest mass gain and the thinner oxide scale after oxidation at 800–1000 °C compare with that of Ti and Al buffer layer. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test revealed that Cr buffer layer effectively improved the corrosion resistance of CrN coating by generating Cr₂O₃ passive film. In addition, Cr/CrN coating showed excellent mechanical properties. Cr buffer layer made more contribution to the comprehensive properties of CrN coatings than Ti and Al, which illustrated utilization potentiality for the protection of fuel cladding.