Corrosion resistance of HiPIMS tungsten and tungsten-aluminium coatings in contact with liquid Sn

Pure‑tungsten and tungsten-aluminium films deposited by high power impulse magnetron sputtering (HiPIMS) on copper‑chromium‑zirconium substrates were investigated as protective coatings against liquid tin corrosion, a critical issue for nuclear fusion applications. The growth of pure‑tungsten coatings was controlled by using a negative substrate bias synchronized to the HiPIMS pulse onset, resulting in columnar films with various degree of compactness and crystallinity according to the set bias amplitude (0, 400 and 800 V). Differently, the co-sputtering of W and Al favored the formation of an amorphous layer with a compact morphology. During liquid tin corrosion experiments at 400 °C for up to 600 min, all produced coatings were not dissolved, but different protective performances were observed after localized liquid tin interaction. Pure-W coated samples suffered from tin penetration after brittle failure of the protective layer. On the contrary, under the same experimental condition, W–Al coatings proved to be effective in limiting liquid tin attack.