Liquid Sn compatibility of HiPIMS W-based multilayers: Influence of coating architecture and substrate finish

AbstractThe use of liquid tin divertors in future nuclear fusion devices requires effective solutions to mitigate corrosion of structural materials. In this work, tungsten-based coatings deposited by High Power Impulse Magnetron Sputtering (HiPIMS) were investigated as protective barriers for CuCrZr alloys used in fusion heat sink components. The study aimed to identify the key material and engineering parameters governing coating performance under liquid tin exposure. Multilayer coatings with different compositions (tungsten–aluminium, tungsten–nitrogen and tungsten–chromium–titanium), architectures and morphologies were tested using static liquid tin corrosion experiments at 400 °C. Coating adhesion was evaluated prior to corrosion, while morphological and microstructural analyses were performed before and after exposure. Concerning tungsten-aluminium coatings, additional tests at 500 °C assessed the influence of coating thickness and substrate roughness. All tungsten-based coatings exhibited excellent chemical compatibility with liquid tin, with degradation primarily driven by mechanical and morphological factors. Coatings containing amorphous mixed layers showed superior corrosion resistance, attributed to the absence of grain boundaries and improved mechanical compliance. Multilayer architectures further enhanced robustness, while fully crystalline layers were more susceptible to brittle failure. Coating thickness and substrate surface finish were identified as critical parameters for reliable protection. The presented results are valuable to design protective coatings for liquid tin divertor applications and to support the transition toward reactor-relevant fusion components.