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

Abstract

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.