Synthesis and densification of (Zr-Hf-Nb-Ta)C-Co high entropy cermet prepared by pressureless melt infiltration using spark plasma sintering

Novel (Zr-Hf-Nb-Ta)C-xCo (x = 5, 10, 20 wt%) high entropy cermets (HEC4-Co) were successfully synthesized and densified using a simple two-step high temperature process. The high entropy carbide was first synthesized by solid state reaction at 1800 degrees C of a mixed powder compact. The reacted and partially sintered compact was then pressureless melt infiltrated with cobalt at 1600 degrees C. The results show that degassing of the powders in the first step, before the infiltration step, significantly reduced the defects in the cermets. The HEC4-Co cermets consisted of a single-phase high entropy carbide (Zr-Hf-Nb-Ta)C in a single-phase cobalt matrix. The maximum hardness was achieved for a Co content of 10 wt%, 15.38 GPa (1569HV1), while the cermet with a Co content of 20 wt% had the highest indentation crack resistance, 9.72 MPa m1/2. (c) 2021 Elsevier B.V. All rights reserved.