Microstructure and characterization of (Ti,V,Nb,Ta)(C,N) high-entropy ceramic

(Ti0.25V0.25Nb0.25Ta0.25)(C1-xNx) high-entropy ceramics with various N contents (x = 0, 0.1, 0.2, 0.3) were successfully produced by spark plasma sintering to investigate the influence of N element on their microstructure and properties. The mixed carbide and nitride powders were sintered to form a single-phase face-centered cubic structure ceramic with a uniform composition at 2100 degrees C for 10 min. The introduction of slight nitrides in high-entropy ceramics refined the grain size and enhanced the hardness of ceramics. The (Ti0.25V0.25Nb0.25Ta0.25) (C0.8N0.2) ceramic demonstrated a fine grain size of 5.29 mu m, a high relative density of 96.7% and an excellent hardness values of 20.6 GPa at 9.8 N and 29.3 GPa at 50 mN. With increasing contents of nitrides, the wear resistance and thermal conductivity of high-entropy ceramics increased firstly and then decreased. The ceramic with 30 at.% nitrides showed a relatively low thermal conductivity of 11.27 W m(-1) K-1 at room temperature. The high-entropy carbonitride ceramics had a potential application in high temperature structure parts and machining tools.