Abstract
The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters (i.e., heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance.
Highlights
Refractory metal borides such as zirconium diboride (ZrB2) and hafnium diboride (HfB2) have been commonly referred to as ultra high temperature ceramics (UHTCs), for their extremely high melting temperatures [1]
Oxidation testing results involving both furnace oxidation testing and plasma wind tunnel testing showed that UHTCs have a similar microstructure of the oxide scale and oxidation resistance at a comparable level of the sample surface temperature [7,8,9,10,11,12,13,14,15,16]
The ablation and oxidation of UHTC samples exposed to frequency plasma wind tunnel suggests that SiC content has a significant impact on the surface temperature and oxidation resistance
Summary
Refractory metal borides such as zirconium diboride (ZrB2) and hafnium diboride (HfB2) have been commonly referred to as ultra high temperature ceramics (UHTCs), for their extremely high melting temperatures (around 3300 and 3500 K respectively) [1]. Materials 2013, 6 represent a class of promising materials for use in extreme applications such as sharp leading edge and control surface components on hypersonic vehicles, because of their high melting point, retained strength at elevated temperatures, relatively good oxidation resistance, and dimensional stability in hypersonic flight conditions [2,3,4,5,6,7,8]. A high-temperature thermal protection system (TPS) intended for the leading edge and control surface components of a hypersonic vehicle will likely encounter partially dissociated air in chemical non-equilibrium with the TPS surface. This will cause a different surface temperature for samples with different compositions under the same testing conditions [17]. Data regarding the response of material composition on the surface temperature of UHTCs is not available
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