Gelcasting for the densification repair of delamination defects in SiCf/SiC composites

SiC fiber-reinforced SiC ceramic matrix composites (SiC f /SiC CMCs) are promising for aero-engine hot-end components due to their excellent high-temperature strength and corrosion resistance. However, they are prone to damage during service, highlighting the need for efficient, low-cost repair technologies. This study proposes a gelcasting repair method for SiC f /SiC composites. By optimizing bimodal SiC powder distribution and employing a N,N-dimethylacrylamide (DMAA)-based gel system, a repair slurry with high fluidity and strong gel-curing ability was developed. This slurry effectively infiltrated pores at the fiber/matrix interface and within fiber bundles. Subsequent silicon infiltration produced β-SiC through reaction with residual carbon, strengthening interfacial bonding. Postrepair characterization showed porosity reduction from 38.01% to 0.85% and density increase from 1.46 to 2.61 g/cm 3 . Flexural strength improved from 29.51 to 125.33 MPa, a 324.7% enhancement. After oxidation at 1200°C for 2 h, the repaired composite retained 91.4% of its original flexural strength. This technique provides a rapid, low-cost pathway for repairing CMCs in aero-engine applications.