Improved High-Temperature Oxidation Resistance of Zirconium Alloy via a Cr Coating on a ZrO 2 Interlayer Deposited by Multi-Arc Ion Plating

The purpose of this study is to develop a long-term protective coating for zirconium alloy nuclear fuel cladding to enhance its safety under high-temperature accident conditions, such as a loss-of-coolant accident (LOCA). A dense ZrO2 interlayer was first fabricated on the zirconium alloy substrate via an in-situ pre-oxidation method. By optimizing the target current (100, 120, and 150 A) in the multi-arc ion plating process and analyzing the resultant coating roughness, hardness, and microstructure, 100 A was determined to be the optimal parameter for depositing a dense and flat Cr overlayer. Accordingly, a ZrO2/Cr composite coating was constructed. High-temperature oxidation tests at 800-1200 °C demonstrated that the mass gain of the composite coating was significantly lower than that of both the bare zirconium alloy and a single-layer Cr coating. Microscopic analysis revealed that at temperatures of 1000 °C and below, the ZrO2 interlayer effectively blocked Cr/Zr interdiffusion and oxygen inward diffusion, thereby inhibiting the formation of brittle phases and stabilizing the coating structure. At 1200 °C, although interdiffusion was initiated, the coating exhibited only controlled local oxidation, preventing catastrophic failure. In conclusion, the introduction of a ZrO2 interlayer significantly improves the high-temperature oxidation resistance of the Cr coating, providing an effective strategy for developing advanced accident-tolerant fuel (ATF) coatings.