Enhanced oxidation/ablation resistance of (Hf0.5Zr0.5)C over HfC-ZrC via high oxygen-atom storage capacity across temperatures

Abstract

The essential reason for the oxidation/ablation behavior of multi-phase carbides and single-phase solid solution carbides with the same composition is obscure. Herein, the oxidation/ablation behaviors of HfC-ZrC multi-phase carbide (HZMC) and (Hf_0.5Zr_0.5)C single-phase solid solution carbide (HZSC) at different temperatures were studied. Experimental results confirmed a higher onset oxidation temperature of HZSC powders (640 °C) than HZMC powders (440 °C), and HZSC coating demonstrated superior ablation resistance (240 s) relative to HZMC coating (180 s). First-principle calculations by VASP displayed a higher O storage capacity in the HZSC lattice due to a lower average O-interstice energy of HZSC (-2.10 eV) than HZMC (44.52 eV). It avoided the rapid consumption of C atoms and subsequent HZSC lattice collapse during initial oxidation/ablation, followed by slowing down the average high-temperature O atom migration of HZSC (2.58 Å-6.83 Å, from 25 °C to 2180 °C) in comparison to HZMC (3.09 Å-7.66 Å). Therefore, performance data validation integrated with computational optimization revealed the enhanced O storage capacity of HZSC endowed it with superior oxidation/ablation resistance. These findings provided valuable insights into the expansion of the design space for high-temperature structural materials.