Developing environmental barrier coating (EBC) materials with superior CMAS corrosion resistance represents a current research priority in rare-earth silicates. Previous studies have demonstrated that multicomponent rare-earth design can significantly enhance CMAS resistance performance, driven by differential rare-earth behavior during the corrosion process. This study investigates RE element synergy mechanisms in disilicates. We designed three multicomponent (RE_1/4Tm_1/4Yb_1/4Lu_1/4)₂Si₂O₇ (RE = Gd, Ho and Sc) materials and subjected them to CMAS corrosion at 1300 °C for durations of 1, 4, and 50 h to elucidate the synergistic mechanisms of multicomponent rare-earth elements on CMAS corrosion. We systematically analyzed the role of rare-earth cations in CMAS corrosion by examining their influence on evolution of reactants and products. Results reveal that performance divergence in corrosion primarily stems from a mechanistic transition, from dissolution-reprecipitation to intergranular penetration, dictated by rare-earth ionic characteristics (mainly the cation radius). Comparative analysis confirms that an optimal active/inert stoichiometric ratio could simultaneously stimulate the precipitation-induced corrosion mitigation and the intrinsic resistance enhancement, establishing a design framework for multicomponent rare-earth disilicates for anti-CMAS EBC applications.

Al₂O₃-based directionally solidified eutectic (DSE) ceramics are recognized as promising candidates for high-temperature structural materials in advanced aeroengines. Nevertheless, their corrosion resistance at elevated temperatures continues to pose a critical challenge, limiting broader application in hot-section components. This study investigates corrosion behavior of RE₃Al₅O₁₂ (REAG)/Al₂O₃ (RE = rare earth) DSE ceramics in water vapor atmosphere (90 H₂O(g) + 10 vol% air(g)) at 1500℃ for durations up to 200 h, with focus on the influence of eutectic structure and RE elements in garnet phases via examining three samples (high-entropy (Y_0.2Gd_0.2Ho_0.2Er_0.2Yb_0.2)₃Al₅O₁₂ DSEs fabricated at 10 and 300 mm/h and YAG/Al₂O₃ DSE grown at 10 mm/h). The results indicate that REAG/Al₂O₃ DSE ceramics exhibit excellent water vapor corrosion resistance at 1500℃ for up to 200 h, with mass loss values ranging from −0.00757 to −0.00708 mg·cm⁻²·mg⁻¹. During corrosion, Al₂O₃ phase acts as corrosion-susceptible component compared to REAG phase, with corrosion depth showing a nearly linear relationship with the average Al₂O₃ lamellar width. In addition, garnet phases experience slight grain growth, reducing the contact area between water vapor and Al₂O₃ phase; Gd demonstrates the slowest diffusion rate when compared to other RE elements. Despite these changes, all samples maintain their preferred crystallographic orientations, confirming the structural stability of REAG/Al₂O₃ DSEs under water vapor atmosphere at 1500℃.

The search for new materials with reliable molten calcium–magnesium–alumino–silicate (CMAS) resistance at elevated temperatures is important for the development of advanced aeroengines. In the present study, a novel Y₄Al₂O₉ (YAM)/Y₂O₃ composite was designed and fabricated from dense samples via the hot-pressing method. The interactions and mechanisms between the Y₄Al₂O₉/Y₂O₃ composite and CMAS at 1300 and 1500 °C for durations of 1, 4, 25, and 50 h were thoroughly explored. The results revealed that Y₄Al₂O₉/Y₂O₃ exhibited substantial resistance to CMAS infiltration at both temperatures, without notable grain-boundary penetration by CMAS glass. More importantly, the incorporation of reaction-active components in the composite accelerated the consumption of molten CMAS constituents and reduced their corrosive activity, which is recognized as the crucial principle for the composition design of anti-CMAS materials. This work provides valuable insights that can guide the design of the composition and advancement of superior CMAS-resistant materials.