Effect of Bias Voltage on Structure, Mechanical Properties, and High-Temperature Water Vapor Corrosion of AlCrNbSiTi High Entropy Alloy Coatings

Fuel cladding tubes are devices used in reactors to encapsulate fuel clots and transmit heat to coolants. However, zirconium alloy materials which are widely used in the fuel cladding pipe of pressurized water reactors have noticeable safety risks in resisting design basis accidents. Therefore, it is very important to improve the corrosion resistance of fuel envelope tubes to high-temperature water vapor oxidation. High-entropy alloys are considered to be a potential protective coating material for cladding tubes. In this study, AlCrNbSiTi high-entropy alloy (HEA) coatings were prepared by magnetron sputtering at different bias voltages. The effect of bias on coating morphologies, structure, mechanical properties, and resistance to high-temperature water vapor corrosion were studied. Experimental results showed that the bias significantly affects the coating surface roughness. In terms of mechanical properties, the sample at 50 V bias exhibited maximum hardness and elastic modulus of 18.2 GPa and 232.4 GPa, respectively. The highest adhesive force of the coating to the substrate of 36 N was obtained at 100 V bias. The optimum water vapor corrosion resistance of the AlCrNbSiTi HEA coating was achieved at 50 V bias, in which sample-point corrosion was the main corrosion failure mechanism.