Heterogeneous TiC-based composite ceramics with high toughness

Electrically conductive carbide ceramics with high hardness and fracture toughness are promising for advanced applications. However, enhancing both electrical conductivity and fracture toughness simultaneous is challenging. This study reports the synthesis of (Ti_0.2W_0.2Ta_0.2Hf_0.2Mo_0.2)C-diamond composites with varying densities using high-pressure and high-temperature (HPHT) method. The carbides are uniformly dispersed in a titanium carbide matrix, forming conductive channels that reduce resistivity to 4.6 × 10⁻⁷ Ω⋅m. These composite materials exhibit metallic conductivity with a superconducting transition at 8.5 K. Superconducting behavior may result from d–p orbital hybridization and electron–phonon coupling in transition metal carbides, such as TaC, Mo₂C, and MoC. Optimizing intergranular bonding improves the fracture toughness without compromising hardness. The highest indentation toughness value is 10.1 ± 0.4 MPa⋅m^1/2, a 130% increase compare to pure TiC. Enhanced toughness arises from transgranular and intergranular fracture modes, multiple crack bridging, and large-angle crack deflection, which dissipate fracture energy and inhibit crack propagation. This study introduces a novel microstructure engineering strategy for carbide ceramics to achieve superior mechanical and electrical properties.