Corrosion behavior and interface characterizations of CoCrFeNiMoNb/WC high-entropy alloy composite coatings in molten aluminum

• The WC ceramic particles are beneficial for improving the corrosion resistance of high-entropy alloy composite coatings in molten aluminum. • The corrosion behaviors mainly involve two processes: high-temperature oxidation and molten aluminum reaction. • When the binder phase within the composite coating is corroded by aluminum, a brittle transition layer will form around the WC particles. These transition layers will fracture under the combined driving forces of phase transformation and thermal stress, leading to the overall failure of the coating. Molten aluminum corrosion presents a major challenge in industrial applications because of its extreme aggressiveness at high temperatures. In this study, novel CoCrFeNiMo 0.2 Nb 0.2 /WC composite coatings are developed via laser cladding, and the WC ceramic is demonstrated to be beneficial for improving the corrosion resistance of the coatings in molten aluminum. As the WC content increases to 60 wt%, the corrosion rate of the coatings reaches a minimum value of 2.0 × 10 -14 m 2 /s. The corrosion mechanism involves two key processes: (1) the formation of a protective Fe/Cr oxide layer, followed by (2) its reaction with molten Al, forming brittle intermetallics that degrade the integrity of the coating. A critical finding is that WC particles delay failure by resisting dissolution, but degradation of the surrounding binder phase generates crack-prone transition layers under thermal stress. This work provides both a high-performance coating solution and fundamental insights into molten-metal corrosion mechanisms.