Microstructure, Mechanical and Tribological Properties of High-Entropy Carbide Ceramics (VNbTaMoW)C5–SiC

The (VNbTaMoW)C₅–SiC high-entropy ceramics were prepared by spark plasma sintering at 1900°C and 40 MPa. The effects of SiC content (0–30 wt.%) on the microstructure, mechanical properties, and tribological properties were examined. The results showed that the matrix phase (VNbTaMoW)C₅ exhibited a face-centered cubic structure, and the second phase (SiC) was uniformly distributed, inhibiting excessive grain growth. The relative density of (VNbTaMoW)C₅– SiC composite ceramics decreased first and then dropped as SiC content increased. The fracture mode of (VNbTaMoW)C₅–SiC composite ceramics changed from transgranular to mixed (transgranular fracture and intergranular) fracture with an increase in SiC content due to weak bonding between (VNbTaMoW)C₅ and SiC. The grains of the (VNbTaMoW)C₅ in multiphase ceramics were refined because of the grain growth-inhibiting effect of SiC. With the increase in SiC content, the hardness of (VNbTaMoW)C₅–SiC multiphase ceramics increased, and the fracture toughness first increased and then decreased. The (VNbTaMoW)C₅–20 wt.% SiC multiphase ceramics exhibited the best mechanical properties with Vickers' hardness and fracture toughness of 18.2 GPa and 5.7 MPa ∙ m^1/2, respectively. Coupled with WC, (VNbTaMoW)C₅–SiC multiphase ceramics exhibit good wear resistance with a specific wear rate of (5.7–8.1) ∙ 10^–8 mm³/N ∙ m.