Creep properties and mechanisms of (Ti-Zr-Nb-Ta-Cr)C high entropy ceramics with various Cr content

The compressive creep properties of (Ti-Zr-Nb-Ta-Cr)C high-entropy carbides (HECs) with Cr contents of 1.83 at%, 3.42 at% and 5.64 at% were studied at 1400∼1600 °C with stresses of 150∼250 MPa. Metal element contents were measured by inductively coupled plasma optical emission spectrometry. The phase composition, microstructural morphology, phase distribution and creep damage of the HECs were characterized by X-ray diffraction, scan electron microscopy, and electron back scatter diffraction, respectively. The steady-state creep rates of the HECs range from 4.14 × 10⁻⁹/s to 6.22 × 10⁻⁷/s. The HEC with 3.42 at% Cr has the lowest steady-state creep rate among the three kinds of HECs. It is found that the Cr can refine the grain size of the HECs. Appropriate amount of Cr can enhance the grain boundary strength, thereby improve creep resistance and reduce the steady-state creep rate. However, excessive Cr leads to the formation of brittle phases, which degrades the creep resistance. The creep damage includes the grain growth, pore formation, and grain boundary cracking. The creep mechanisms mainly involve atomic diffusion, grain boundary sliding, and dislocation slip with slip system of a/2011111.