Research on the High Temperature Self-Healing Behavior of Yb₂ Si₂ O₇ -Based Matrix Composites

SiCf/SiC ceramic matrix composites meet the high thrust-to-weight ratio requirements of next-generation aeroengines but require environmental barrier coatings for protection under extreme high-temperature conditions. Current environmental barrier coatings inevitably develop cracks during service, necessitating self-healing coatings for autonomous crack repair. In this study, based on Yb₂Si₂O₇, Yb₂Si₂O₇-SiC and Yb₂Si₂O₇-Yb₂SiO₅ were fabricated via spark plasma sintering and pressureless sintering, respectively. The self-healing behavior of these composites was investigated to evaluate their feasibility as environmental barrier coating materials. Results show that adding 5wt% ~10wt% SiC to Yb₂Si₂O₇ promoted crack healing after 1 h at 1100 °C in air, driven by SiO₂ formation from SiC oxidation, which filled cracks through volume expansion. However, at 1300 °C, excessive SiC oxidation caused significant volumetric stress, generating new cracks within the composites. Yb₂SiO₅ addition enhanced material densification and crack healing. The composite with 50wt% Yb₂SiO₅ achieved optimal healing efficiency (78%), attributed to thermally induced compressive stress from higher thermal expansion coefficient of Yb₂SiO₅. This stress facilitated crack closure in the Yb₂Si₂O₇ matrix.