Synthesis, Microstructure and Wear Resistance of High-Entropy (Ti_1/6V_1/6Nb_1/6Ta_1/6Mo_1/3)C Ceramics

Transition metal carbide ceramics are typical representatives of ultra-high temperature ceramics with extremely high melting point and hardness. However, the toughness and wear resistance need to be improved. Based on the high-entropy theory, a multi-carbides solid solution, i.e., high-entropy carbides, has a higher melting point, a good toughness and superior friction/wear characteristics. In this paper, (Ti_1/6V_1/6Nb_1/6Ta_1/6Mo_1/3)C high-entropy ceramics were prepared via spark plasma sintering (SPS) at 1600–2100 ℃ , and the densification behavior, phase composition, microstructure, mechanical properties and wear resistance were investigated. The results show that (Ti_1/6V_1/6Nb_1/6Ta_1/6Mo_1/3)C high-entropy ceramics with a single-phase face-centered cubic structure can be obtained by sintering at 1700 ℃ . The relative density of the high-entropy ceramics is greater than 98% at ≥1900 ℃ . The grain size increases and the elemental distribution becomes uniform as the sintering temperature increases from 1700 ℃ to 2100 ℃ . The grain boundary sliding and oxide impurities (TiO₂) aggregation occur at grain boundaries. The dislocations appear in grains. The optimal mechanical properties of the high-entropy ceramics prepared by sintering at 2100 ℃ can be obtained, i.e., the Vickers hardness of 20 GPa, elastic modulus of 431 GPa and fracture toughness of 4.46 MPa·m^1/2, respectively, and the average specific wear rate is 5×10^–7 mm³/(N·m), showing a superior wear resistance.