Multi-dimensional oxidation kinetics of TiB₂: Unified modeling across temperature, pressure, and time domains

During atmospheric re-entry, the thermal protection systems (TPS) of hypersonic vehicles are subjected to severe aerodynamic heating and complex thermomechanical loads in oxygen-rich environments. Ultra-high-temperature ceramics (UHTCs), especially TiB₂, are promising TPS materials because of their high melting points, oxidation resistance, and structural stability. However, predicting their oxidation behavior under coupled temperature–pressure conditions remains challenging. In this study, a unified oxidation kinetic model for TiB₂ was developed. First, the applicability of the oxidation activation energy was validated and extended to 1200 ℃ through atmospheric isothermal oxidation experiments. Then, the oxidation behavior under varying pressures was investigated using high-energy laser heating combined with a controlled-atmosphere chamber. By quantifying the growth of the oxide scale, oxygen partial pressure was introduced into the kinetics as an additional experimental parameter, leading to a multidimensional oxidation model integrating temperature, time, and pressure. The model showed good predictive performance, with a relative error of only 3.02% at 1100 ℃ and 4 kPa under stable conditions. Although the long-term prediction accuracy decreased at 1500 ℃ because of porous scale formation and spallation, the model remained effective for short-term oxidation. This work provides a useful basis for predicting the service life of UHTCs in variable-pressure flight environments.