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<strong>.&nbsp;</strong>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.&nbsp;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.&nbsp;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%.<strong>&nbsp;</strong>Experimental results demonstrate that both materials exhibit exceptional CMAS corrosion resistance, reducing corrosion depth by approximately 70% compared to single-component RE₂Si₂O₇.&nbsp;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.