Ablation-oxidation behavior and mechanisms of C/SiC–HfB2 composite wedges in an arc wind tunnel

Purpose This work aims to investigate the ablation-oxidation behavior and mechanism of a realistic wedge-shaped C/SiC–HfB2 leading-edge sample under high-enthalpy conditions, to provide insights for designing advanced thermal protection systems. Design/methodology/approach In this study, a leading-edge sample consistent with the actual geometry (R5 radius, 16-cornered wedge-shaped leading edge) and material (C/SiC–HfB2) was fabricated. The sample was subjected to arc wind tunnel ablation and finite element simulation. Subsequently, a range of analytical techniques, including microscope, micro-computed tomography, scanning electron microscope, energy dispersive spectroscopy, and X-ray diffractometer, were employed to examine the sample from macroscopic to microscopic levels. Finally, the formation mechanism of ablative oxide layer on the leading edge of C/SiC–HfB2 composites was analyzed. Findings The results of this study indicate that under the ablation conditions of the arc wind tunnel, the C/SiC–HfB2 composite wedge-shaped sample form a white crescent-shaped oxide layer that covers the surface of the specimen, providing protection. In the stagnation point region, the extreme temperature causes component vaporization, resulting in cracks and micropores in the oxide layer. Due to the presence of Hf element, HfSiO4 is formed at high temperatures to protect the matrix material, thus significantly enhancing the high-temperature ablation resistance of the leading-edge specimens. Originality/value This is the first study to investigate a realistic wedge-shaped C/SiC–HfB2 leading-edge sample under arc-jet ablation. Our multi-scale analysis reveals that Hf addition leads to formation of a protective HfO2–HfSiO4-rich oxide layer, significantly enhancing the high-temperature ablation resistance of the material.