Microstructure and properties of α-FeSi2 modified C/C–SiC brake composites

• Metallic α-FeSi2 owns lower value of hardness and modulus, and higher toughness than SiC and Si in the matrix of C/C–SiC brake composites.
• By introducing α-FeSi2 into C/C–SiC, both flexural strength and fracture toughness was improved.
• By introducing α-FeSi2 into C/C–SiC, brittle fracture of the matrix was reduced and wear resistance was effectively improved.
• α-FeSi2 was oxidized to Fe2O3 at higher braking speeds, this oxidation reduced the coefficient of friction but did not cause increase of wear rate.

In order to simultaneously reduce the fabrication cost and improve the properties of C/C–SiC brake composites fabricated by chemical vapor infiltration (CVI) combined with liquid silicon infiltration (LSI), αα-FeSi2 modified C/C–SiC brake composites were fabricated by infiltrate cost-saving FeSi75 alloy powders into porous CVI-C/C composites. Microstructure, mechanical properties and tribological behaviors of the modified composites were studied. The results indicated that continuous infiltration was realized. The modified composites achieved higher flexural strength and fracture toughness. Brake temperature was decreased and the wear resistibility was significantly enhanced. It indicates that introducing metallic αα-FeSi2 phase with lower modulus and higher toughness into the matrix can improve the mechanical properties and tribological behaviors of the C/C–SiC brake composites.