Evaluation of chromium coatings deposited by standard and bipolar high-power impulse magnetron sputtering (HiPIMS & B-HiPIMS) for nuclear power applications

Chromium coatings, as deposited onto Zircaloy-4 through direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS), are evaluated for usage in advanced nuclear fuel applications. While traditional magnetron sputtering has been documented extensively in literature, HiPIMS remains relatively novel and unexplored within this application space, especially when the sputtering source voltage waveform is modified with the addition of a positive “kick pulse”, as in the case of bipolar HiPIMS (B-HiPIMS). Rigorous analysis of the microstructure and residual stress state of these coatings are correlated to electrochemical observations and 84-day, 360 °C autoclave weights gains to predict the performance of the films within a non-irradiated pressurized water reactor (PWR) environment. Under this scrutiny, differences and similarities are revealed between DCMS, HiPIMS, and B-HiPIMS. It is demonstrated that monolithic Cr coatings deposited by HiPIMS and B-HiPIMS outperform those deposited by DCMS, while exhibiting an order of magnitude reduction in autoclave weight gain relative to the Zircaloy-4 nuclear grade material.