Zirconium carbide (ZrC) is an ultra-high-temperature ceramic valued for its excellent thermomechanical properties, yet its vulnerability to oxidation and its thermal shock behavior upon oxidation remain insufficiently understood. This study examines how prior oxidation history, defined by cyclic exposure temperature and duration, affects the thermal shock response of monolithic ZrC. Near-stoichiometric specimens were oxidized in atmospheric air across a temperature range of 600°C–800°C, then water-quenched from those temperatures. Increasing oxidation severity produced thicker oxide scales, higher monoclinic ZrO₂ content, and greater crack density. A transition to failure-prone behavior occurred between 700°C and 800°C, when monoclinic ZrO₂ and crack density both exceeded approximately 10%, leading to critical degradation. Given the oxidation parameters explored, the temperature threshold for thermal shock occurrence was identified as 700°C–800°C. The combined oxidation–quench approach establishes oxidation-dependent thresholds for thermal shock resistance and provides a framework for evaluating the stability of oxidized structures in harsh thermal environments.

ZrC Ultra-High Temperature Ceramic is a promising material for future extreme environment applications. However, its susceptibility to oxidation at elevated temperatures poses a significant challenge. There remains unresolved controversy in literature regarding its oxidation kinetics and activation energies. The temperature, oxygen pressure and time effects on the oxidation and passivation of ZrC are still not fully understood. To address these questions, we fabricated near-stoichiometric ZrC ceramic via spark plasma sintering (SPS) and for the first time investigated the temperature-oxygen pressure-time (T-P-t) dependent oxidation kinetics of SPS-sintered ZrC. A three-stage oxidation mechanism including a passivation stage was reported. The study also revealed the complexity of activation energy dependence on temperature and pressure within the 3D T-P-t space. Additionally, it uncovered the conditions necessary to maintain the passivation of ZrC. These findings provide valuable insights for future design of oxidation-resistant ZrC and carbides, paving the way for advancements in materials for extremes.

Zirconium carbide (ZrC) is a candidate material for extreme environments due to its exceptional thermal and mechanical properties. However, its oxidation behavior, particularly the formation of the Zr–C–O layer, requires further clarification. In this study, we investigated the oxidation of spark plasma sintered ZrC under varying temperatures and oxygen partial pressures, revealing a double-layer oxide scale. At the interface between ZrC and the Zr–C–O layer, we identified previously unreported oxidation front stripes composed of cubic zirconia, along which elliptical submicropores formed, suggesting preferential CO₂ release pathways. The Zr–C–O layer itself was significantly enriched with amorphous free carbon. Based on these findings, we developed a phenomenological model that incorporated the formation of the compact Zr–C–O layer to predict oxide scale growth. This multiscale approach provides new insights into ZrC oxidation mechanisms and supports the design of oxidation-resistant ceramics for aerospace and nuclear applications.