Effect of Sputtering Voltage on the Microstructure, Hardness, and Corrosion Resistance of Ni-Cr Coatings on Zirconium for Accident-Tolerant Fuel Applications

Abstract

Zirconium alloys are commonly employed as fuel cladding materials in pressurized water reactors; nevertheless, their low corrosion and oxidation resistance under harsh operating circumstances remain a significant barrier for accident-tolerant fuel applications. This work investigates how sputtering voltage affects the microstructural evolution, as well as the mechanical and corrosion performance, of DC-sputtered Ni-20Cr coatings deposited on Zr-4 substrates. The coatings were formed at sputtering voltages of 4, 5, and 6 kV and evaluated by X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, microhardness and nanoindentation tests, and potentiodynamic polarization in a simulated PWR primary coolant. The findings show that sputtering voltage has a significant impact on crystallite refinement, coating compactness, and the integrity of the coating-substrate interface, all of which influence the functional performance of coatings. Among the investigated deposition conditions, the coating deposited at 5 kV had the best combination of microstructural, mechanical, and corrosion properties, whereas increasing the sputtering voltage to 6 kV resulted in microstructural degradation, which reduced protective performance despite increasing thickness. These results show a clear relationship between sputtering voltage, microstructural evolution, and the mechanical and corrosion performance of Ni-Cr coatings. The study offers important guidance for optimizing sputtering parameters and illustrates the efficacy of DC-sputtered Ni-Cr coatings for accident-tolerant nuclear fuel cladding.