Microstructure, mechanical properties and corrosion behavior of high-entropy (WZrNbTaM)C (M= Cr, Ni, Ti) carbides

In this work, the high-entropy stability is predicted based on density functional theory (DFT) firstly. Then, the (WZrNbTaM)C (M=Cr, Ni, Ti) high-entropy carbide powders are synthesized by carbothermal reduction reaction. The synthesized high-entropy carbide powders are densified with addition of Co and Ni at a lower temperature. The phase analysis and microstructure observation, followed by mechanical property test, including Vickers hardness and fracture toughness of the high-entropy carbides are investigated. Finally, electrochemical corrosion behavior test of the samples is conducted in NaCl solution. It is found that a small amount of metal (2.5 wt.% Co and 2.5 wt.% Ni) can reduce the sintering temperature of high-entropy carbides, and the relative density can reach more than 96% at 1600 °C. The metal is uniformly dispersed among the high-entropy ceramic particles, facilitating liquid-phase mass transfer and pore elimination. (WZrNbTaNi)C-Co-Ni has the best comprehensive mechanical properties, with hardness and fracture toughness reaching 19.7 GPa and 6.6 MPa·m 1/2 , respectively. In 3.5 wt.% NaCl solution, oxides have formed on the surface of the samples after electrochemical corrosion test, and (WZrNbTaCr)C-Co-Ni shows excellent corrosion resistance.