Synthesis of high entropy carbide powders by low temperature processing

Abstract

AbstractHigh‐entropy carbides (HECs) possess superior properties such as favorable corrosion resistance and marvelous hardness and are widely applied in specific extreme environments. Herein, a novel method was proposed for synthesizing HECs powders with raw materials of corresponding oxides and carbon black, which was composed of steps of ball‐milling in stainless jar, carbothermic reduction at 1873 K, as well as the following calcium posttreatment at 1273 K to remove residual carbon by generating CaC2. Finally, pure HECs powders could be fabricated after acid leaching treatment. Under the current experimental conditions, besides HfC‐TaC‐ZrC‐NbC quaternary system, a homogeneous solid solution could be fabricated by adding Mo or/and Ti, but it could not be achieved for systems with addition of V, W, or Cr, owing to the low lattice constant or different crystal structure of corresponding carbides. In the reduction step, iron resulted from ball milling process acted as the diffusion channel to promote the mutual diffusion of different components. Meanwhile, the calcium treatment temperature had a weak effect on particle size of HEC powders. HfC‐TaC‐ZrC‐NbC‐MoC‐TiC powders prepared at the calcium posttreatment temperature of 1273 K had an oxygen content of .302% and an average grain size of 252 nm.