Effect of Nanostructure on Wear and Corrosion Behavior of HVAF-Sprayed Eutectic High-Entropy Alloy Coatings

Adopting multi-principal high entropy alloys (HEAs) as wear/corrosion-resistant coatings is a frontier in the field of surface engineering. The eutectic high entropy alloy (EHEA) exhibited excellent mechanical properties, and its dual-phase, lamellar nanostructure effectively prohibited pitting corrosion, making the alloy a potential candidate for wear/corrosion-resistant coatings served in the complicated environments. In the presented study, a dense and non-oxidized CoCrFeNiTaAl EHEA was coated on 304 stainless steel (SUS 304) substrate by a high-velocity air fuel (HVAF) thermal spraying process. The microstructure, corrosion resistance, as well as high temperature wear resistance of the coating were analyzed. The coating consisted of a deformation zone and a solidified zone. The deformation zone had the same structure as the original powders of the hypo-eutectic structure, and the solidified zone exhibited a single-phase solid solution structure. The EHEA coating exhibited an excellent combination of pitting corrosion and room-temperature wear resistance. The wear mechanism of EHEA coatings was abrasive, and oxidation wear at room temperature and 100 °C, while adhesive and oxidation wears occurred at elevated temperatures. The wear resistance decreases as temperature increases.