Reactive-precursor-assisted low-temperature densification of high-entropy (TiVNbTaMo)C_x ceramics with tunable mechanical and tribological properties

The preparation of dense high-entropy carbide ceramics (HECCs) is extremely challenging owing to their strong covalent bonding and sluggish diffusion associated with high-entropy effects, which necessitate ultrahigh sintering temperatures that in turn cause severe grain coarsening and excessive energy consumption. In this study, a novel low-temperature consolidation route is developed based on Ti₃AlC₂ reactive sintering. Specifically, the reactive precursor Ti₃AlC₂ decomposes into TiC_x and Al during spark plasma sintering. The in situ formed TiC_x accelerates interdiffusion and solid-solution formation among transition-metal carbides, while the released Al effectively activates particle interfaces. This dual-activation mechanism markedly enhances sintering kinetics, enabling the densification of (TiVNbTaMo)C_x ceramics at 1550 °C. The optimized sample achieved a relative density of 98.5%, a Vickers hardness of 22.94 GPa under a load of 9.8 N, a flexural strength of 1018 MPa, and a fracture toughness of 5.67 MPa·m^1/2, showing superior strength and hardness compared with most reported high-entropy carbides while maintaining an acceptable level of toughness. Furthermore, the interfacial modification results in a stable friction coefficient from room temperature to 900 °C, accompanied by nonadhesive wear behavior at elevated temperatures, making the obtained samples promising for high-temperature structural and wear-resistant applications. Therefore, reactive-Ti₃AlC₂ precursor-assisted sintering provides a new pathway for the design and scalable fabrication of advanced dense high-entropy ceramics under low-temperature conditions.