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

Abstract 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.