Linking Oxide Scale Evolution to Thermal Shock Failure in Zirconium Carbide

Abstract

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.