In-situ engineered ZrB2-ZrSi2-MoSi2 coatings with self-healing multiphase glass networks for superior oxidation protection at 1973 K

To address the protection failure of ZrB 2 -based coatings caused by structural loosening during oxidation, an in-situ alloying strategy with dual-silicide synergistic enhancement via one-step powder-source alloying is presented in this study. The approach successfully produced ZrB 2 -ZrSi 2 -MoSi 2 composite powders with precisely controllable composition, which were subsequently used to construct high-performance oxidation resistant coatings on graphite substrates. The optimized ZZM40 coating with 40 vol% MoSi 2 demonstrated a remarkable 98.21 % reduction in oxygen permeability and an 84.03 % reduction in carbon loss rate at 1973 K compared to the undoped coating, achieving a protection efficiency of 99.58 %. The performance enhancement is attributed to the in-situ formation of a self-generated glass phase during oxidation, which exhibits high fluidity and self-healing properties. Additionally, the in-situ precipitated nanoscale MoB phase effectively suppresses the volatilization of B 2 O 3 through a pinning effect, achieving a synergistic enhancement in thermal stability and oxygen blocking capabilities. Notably, excessive MoSi 2 doping at 50 vol% leads to detrimental effects. Intensified MoO 3 volatilization reduces the viscosity of the glass phase and triggers a chain reaction of defect propagation, consequently increasing the carbon loss rate by 34.43 % compared to ZZM40. The proposed powder-source in-situ alloying strategy validates the defect-repair mechanism driven by dual-silicide oxygen-blocking reinforcement, providing crucial theoretical foundations for the design and application of next-generation high-temperature thermal protection materials. • A dual-silicide co-enhanced alloying strategy is proposed for ZrB 2 -based coatings. • The strategy shortens Si-source transport and boosts glass-phase supply efficiency. • Optimized coating reduces oxygen permeability by 98.21 % and carbon loss by 84.03 %. • Appropriate MoSi 2 content improves glass mobility and defect healing performance. • MoB nanophase enhances glass stability and limits B 2 O 3 loss for better protection.