Densification, mechanical properties, and oxidation behavior of spark plasma sintered TaB₂-SiC-BN composites

TaB₂-30 vol% SiC binary and TaB₂-SiC-BN ternary composites with varying hexagonal boron nitride (BN) ratios (1–3–5–7–10 vol%) were consolidated by spark plasma sintering at 1650℃ under 40 MPa for 5 min. The densification characteristics, phase formation, mechanical properties, and oxidation behavior of both the TaB₂-SiC and TaB₂-SiC-BN composites were investigated. No new peaks other than the characteristic peaks associated with the starting materials were observed. Among all compositions, that containing 27 and 3 vol% of SiC and BN, respectively, exhibited the highest densification, ∼99.9 %. Homogeneous heating during sintering due to the thermal conductivity of hexagonal BN, along with the reduction in porosity by BN entering between TaB₂ and SiC grains improved the densification behavior of the ternary composites. Besides, the incorporation of BN led to significant improvements also on the fracture toughness, which increased by ∼46 %. In ternary composites, crack deflection and branching were identified to be effective toughening mechanisms. The addition of BN had a negligible effect on Vickers hardness when agglomeration was minimal. The oxidation resistance at 1100 and 1200 °C increased with the addition of BN.