Revealing corrosion mechanisms and enabling predictive lifetime assessment of high-entropy rare-earth disilicates with superior CMAS corrosion resistance

High-entropy rare earth disilicates are promising next-generation thermal/environmental barrier coating (T/EBC) materials. However, their resistance to calcium–magnesium–aluminosilicate (CMAS) corrosion and the underlying mechanisms remain insufficiently understood and require further improvement. This study aims to systematically investigate the CMAS corrosion behavior and predictive lifetime assessment of designed stoichiometric (Er_1/4Y_1/4Lu_1/4Yb_1/4)₂Si₂O₇ and non-stoichiometric (Er_1/6Tm_1/6Y_1/15Gd_1/15Lu_4/15Yb_4/15)₂Si₂O₇. The incorporation of Tm and Gd, characterized by their distinct ionic radii, is designed to enhance its phase stability. Mechanistic analysis reveals that lattice distortion induced by multi-cation doping suppresses CMAS infiltration, while the introduction of larger-radius RE³⁺ ions promotes Ca²⁺ depletion in the CMAS melt, reducing its corrosive activity. A temperature-dependent transition in corrosion mechanisms is also elucidated. A thermodynamic-kinetic competition dominates at 1300 °C, whereas a dissolution-reprecipitation mechanism prevails at 1500 °C due to accelerated ion diffusion. Furthermore, an innovative Extended Kalman Filter (EKF) model is developed, enabling highly accurate prediction of long-term corrosion depth and rate at 1300 °C, with an error of less than 3%. Experimental results demonstrate that both materials exhibit exceptional CMAS corrosion resistance, reducing corrosion depth by approximately 70% compared to single-component RE₂Si₂O₇. This work does not only clarify the corrosion mechanisms and compositional design principles of high-entropy rare earth disilicates but also provides a novel methodology for predictive lifetime assessment, advancing the development of next-generation T/EBC systems.