Fabrication and Properties of Transition Metal Borides and MWCNTs Hybrid Reinforced SiC‐Based Ceramics
Liwen He, Yanliang Wu, Jionghui Wang, Jun Fu, Juan WangABSTRACT
Electrical discharge machining (EDM) can fabricate SiC ceramic components with complex shapes and high precision, but pristine SiC is too resistive for EDM. In this study, SiC‐based conductive ceramics were fabricated by pressureless solid‐phase sintering, employing commercially available transition metal borides TiB 2 , NbB 2 , and multi‐walled carbon nanotubes (MWCNTs) as conductive phases. The effects of conductive‐phase content on phase composition, electrical conductivity, and mechanical properties were investigated. The results show that during high‐temperature sintering, SiC undergoes a phase transformation, while TiB 2 and NbB 2 undergo interdiffusion, leading to the formation of a Nb–Ti boride phase indexed as NbTiB 4 by XRD/Rietveld analysis. The electrical results qualitatively suggest that the conductivity enhancement is associated with a reduced contribution from grain‐boundary barriers and progressively improved connectivity of conductive‐phase pathways. The composites reach a minimum resistivity of 0.19 Ω·cm, which is below the commonly cited resistivity criterion for EDM eligibility. Relative to S0, which exhibited a flexural strength of 294.9 ± 14.1 MPa and a fracture toughness of 2.60 ± 0.14 MPa·m 1/2 , the composites achieved maximum values of 539.0 ± 17.1 MPa and 5.67 ± 0.47 MPa·m 1/2 , respectively.