The oxidation/ablation differences of multi-phase carbide ceramics evaluated by atomic simulations and performance data validation

Composition design of ultra-high temperature ceramic (UHTC)-coated carbon/carbon composites gradually becomes a critical issue for aerospace applications, particularly for hot-end components exposed to severe thermal environments exceeding 2000 °C, where high-temperature oxidation and mechanical denudation prevail. This study combined atomic simulations and experimental validation to investigate the oxidation behavior of multi-phase carbides (HfC, ZrC, TaC and TiC), as well as multicomponent oxidation products’ solid solution behavior and ablation mechanism (Ta/Ti-doped (Hf, Zr)O₂). The simulations displayed a higher oxidation sensitivity of Ta-doped (Hf, Zr)O₂ (HfC-ZrC-TaC), due to higher O-migration of 2.52 Å at 25 °C and 5.86 Å at 2000 °C than those of 2.39 Å at 25 °C and 5.02 Å at 2000 °C for Ti-doped (Hf, Zr)O₂ (HfC-ZrC-TiC). The thermogravimetric static oxidation and ablation tests demonstrated the inferior oxidation resistance of HfC-ZrC-TaC. It had a smaller onset oxidation temperature (440 °C) than HfC-ZrC-TiC (475 °C). Additionally, HfC-ZrC-TaC coating failed after 120 s with linear and mass ablation rates of 0.565 μm/s and 2.653 mg/s, respectively, while the HfC-ZrC-TiC coating expired after 180 s with 0.321 μm/s and 1.262 mg/s. These findings provided valuable insights into the inverse compositional optimization for UHTC systems including multi-phase monocarbides and medium-/high-entropy carbides, thus expanding the design space for advanced high-temperature structural materials.