High‐temperature oxidation behavior of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramics in air

Abstract

High‐entropy metal carbides have recently been arousing considerable interest. Nevertheless, their high‐temperature oxidation behavior is rarely studied. Herein the high‐temperature oxidation behavior of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high‐entropy metal carbide (HEC‐1) was investigated at 1573‐1773 K in air for 120 minutes. The results showed that HEC‐1 had good oxidation resistance and its oxidation obeyed a parabolic law at 1573‐1673 K, while HEC‐1 was completely oxidized after isothermal oxidation at 1773 K for 60 minutes and thereby its oxidation followed a parabolic‐linear law at 1773 K. An interesting triple‐layered structure was observed within the formed oxide layer at 1673 K, which was attributed to the inward diffusion of O2 and the outward diffusion of Ti element and CO or CO2 gaseous products.

Enhanced Hardness in High‐Entropy Carbides through Atomic Randomness

“…HECs were successfully fabricated in the form of coatings some years ago, [ 3 ] but have only recently been reported in bulk form. [ 4 ] Due to the emerging fundamental interest and potential applications, several compositions have been fabricated, [ 5–9 ] and properties such as hardness and oxidation behavior [ 10,11 ] have been investigated. These compositions mainly contain refractory transition metal elements, and there is a vast potential compositional space still to explore, where compositions with advantageous properties are likely to exist.…”

Evolution of the oxidation behaviors of highly oxidation-resistant (Ti0.8Nb0.2)C in 1000–1200 °C steam

“…5 . Unlike the oxide scales with uniform elemental distributions for high-entropy ceramics and the (Ti 0.8 Nb 0.2 )C solid solution oxidized in air, 13,17,19 the oxide scales of (Ti 0.8 Nb 0.2 )C show a variable elemental distributions. The oxidation scales for (Ti 0.8 Nb 0.2 )C oxidized at 1200 °C show similar elemental distributions as that oxidized at 1300 °C.…”

A step forward from high-entropy ceramics to compositionally complex ceramics: a new perspective

“…The high-entropy borides and carbides are being examined for their potential use as nextgeneration UHTCs [118,119]. These classes of materials have also shown increased mechanical properties [56,61,62,64,66] and oxidation resistance [48,63,120,121] Notably, a general property of HECs is represented by the increased hardness in comparison with the RoM averages, which have been reported for high-entropy borides [48,50,54,56], carbides [59,61,63,66], and silicides [44,45]. Further discussion can be found in the next section.…”