Electrical Discharge Machinable SiC–TiB ₂ Composites Fabricated by Reactive Spark Plasma Sintering

SiC–TiB 2 composite ceramics were fabricated via spark plasma sintering (SPS) using TiSi 2 , B 4 C, and graphite as raw materials. During the sintering process, TiSi 2 first reacts with B 4 C to form TiB 2 , SiC, and Si, followed by the reaction of the liberated Si with graphite to yield additional SiC in the cubic 3C polytype, which fully transforms into the hexagonal 6H‐SiC phase at higher temperature. Notably, TiB 2 grains exhibited preferential (001) orientation perpendicular to the pressing direction; however, this texturing weakened with increasing TiB 2 content, indicating a self‐mitigating effect that reduces microstructural anisotropy. All composites achieved relative densities >97.5%. Mechanical properties showed a strong dependence on TiB 2 content: flexural strength peaked at 470 MPa (20 vol% TiB 2 ), while Vickers hardness and fracture toughness increased monotonically, reaching 26.5 GPa and 6.8 MPa·m 1/2 at 25 vol% TiB 2 , respectively. Toughening mechanisms included crack deflection, branching, and grain pull‐out induced by thermal residual stresses from the mismatch in coefficients of thermal expansion between SiC and TiB 2 . Electrical resistivity decreased sharply within the 15–20 vol% TiB 2 range, exhibiting clear percolation behavior. At 20 vol% TiB 2 , the electrical conductivity reached 1.12 × 10 4 S/m, enabling stable electrical discharge machining (EDM), with excellent machinability. Further increasing TiB 2 to 25 vol% boosted conductivity fivefold but slightly reduced material removal rate and doubled surface roughness due to enhanced thermal conductivity promoting heat dissipation and lower mechanical strength facilitating spallation during EDM. These findings demonstrate that the in‐situ reaction‐assisted SPS route is highly effective for producing dense, high‐performance SiC–TiB 2 composites suitable for EDM applications.