High-temperature ablation behavior and failure mechanism of (Hf0.25Zr0.25Ti0.25Ta0.25)C high-entropy carbide in wide temperature range

Abstract

The ablation behavior of (Hf0.25Zr0.25Ti0.25Ta0.25)C was investigated using a plasma flame gun over a wide temperature range of 2070–2600℃. The structural transformation during ablation and the effect of temperature on the failure mechanism were discussed. Results showed a sharp increase in mass and linear ablation rates from 0.23 mg·cm−2·s−1 and 4.6 μm·s−1 at 2070℃ to 4.6 mg·cm−2·s−1 and 37 μm·s−1 at 2600℃. This variation was attributed to the temperature's impact on on the microstructure and composition of the oxide layer. During ablation, Hf/Zr-rich oxycarbides preferentially nucleated within the amorphous Hf-Zr-Ti-Ta-C-O layer, leading to phase separation of the oxide layer. With increasing ablation temperature, the filler and binder oxides with low melting point (e.g., (Hf,Zr)TiO4, TaZr2.75O8) were rapidly consumed. The skeleton oxides (e.g., (Hf,Zr)O2) failed to bond and peeled off. The transiently formed (Hf,Zr,Ti,Ta)Ox layer was repeatedly destroyed and reconstructed, resulting in the continuous damage and eventual failure of the matrix.