Corrosion performance of high-entropy (Ho_0.2Er_0.2Tm_0.2Yb_0.2Lu_0.2)₂Si₂O₇ environmental barrier coating material under CMAS conditions at 1500 ℃

Improving the corrosion resistance of environmental barrier coatings (EBCs) to molten calcium-magnesium-aluminosilicate (CMAS) salt is an urgent requirement for aeroengine blades. In this work, a novel high-entropy (Ho_0.2Er_0.2Tm_0.2Yb_0.2Lu_0.2)₂Si₂O₇ ((5RE_0.2)₂Si₂O₇) environmental barrier coating material was developed, and molten CMAS corrosion resistance of (5RE_0.2)₂Si₂O₇) was systematically investigated at 1500 ℃. The prepared (5RE_0.2)₂Si₂O₇ ceramic possesses a single and stable β-phase structure with high-temperature stability from room temperature to 1500 ℃. The thermal conductivity of (5RE_0.2)₂Si₂O₇ ranges from 1.46 to 3.49 W·m⁻¹·K⁻¹ at room temperature to 1500 ℃. A rapid reaction of (5RE_0.2)₂Si₂O₇ with molten CMAS produced Ca₂RE₈(SiO₄)₆O₂ apatite at 1500 ℃. The reaction layer thickness was only 95.9 ± 8.6 μm which effectively inhibited the infiltration and diffusion of molten CMAS salt. In contrast, Yb₂Si₂O₇ ceramic, when exposed to molten CMAS at 1500 ℃, showed no reaction. Instead, the molten CMAS salt penetrated into the interior of Yb₂Si₂O₇ along grain boundaries and voids, forming bubble cracking and ultimately, structural degradation. These results suggest that the high-entropy (5RE_0.2)₂Si₂O₇ ceramic material is a potential candidate for next-generation EBC with excellent resistance to CMAS corrosion.