High creep resistance of (Hf0.2Ta0.2Ti0.2Nb0.2Zr0.2)C high entropy ceramics prepared by spark plasma sintering of the self-propagating high temperature synthesized powders

The compressive creep properties of (Hf_0.2Ta_0.2Ti_0.2Nb_0.2Zr_0.2)C high entropy ceramic (HEC), prepared by spark plasma sintering of the self-propagating high temperature synthesized powders, are investigated at 1400–1600 °C with stresses of 150∼300 MPa. The as-received HEC was annealed at 2000 °C and 2100 °C for 1 h (HT2000 and HT2100) to eliminated the impurities. The phase composition, microstructure, and dislocation structures are characterized by an X-ray diffractometer, scan electron microscopy, and transmission electron microscopy, respectively. It is found that the steady creep rates of the HT2000 and HT2100 are similar at the same creep conditions, both being 10⁻⁸∼10⁻⁹ s⁻¹. The creep resistance of both HECs is superior to those of the monolithic carbides. The creep damage includes the grains growth, formation of pores and cracks at the grain boundaries. The creep mechanisms of both HECs include atomic diffusion, grain boundary sliding and dislocation slip. At 1600 °C, Burgers vector of dislocation is a/2 $<0\bar{1}1>$, and the main slip system is a/2 $<0\bar{1}1>\left\{111\right\}$. The excellent creep resistance of the HECs is contributed by the slow atomic diffusion and restricted dislocation motion.