The effect of MoAlB substitutions on the oxidation behavior of ZrB₂-SiC Composites at 1600 °C

ZrB₂-SiC ceramics are potential candidates for thermal protection materials for re-entry and hypersonic vehicles. Phases are typically added to ZrB₂-SiC to enhance the oxidation resistance of the material. MoAlB is an attractive nanolaminated ternary boride compound. Due to its damage tolerance, crack healing ability, and good oxidation resistance, MoAlB is a promising material for high-temperature applications. Therefore, the effect of MoAlB substitution on the oxidation of ZrB₂-SiC at 1600 °C for 10 h was evaluated. Five samples with different MoAlB contents (0 vol%, 4 vol%, 8 vol%, 12 vol%, 16 vol%) were prepared. The results indicate that ZrB₂-SiC-8vol%MoAlB exhibits improved oxidation resistance compared to ZrB₂-SiC. After being oxidized at 1600 °C for 10 h, the thickness of the oxide layer on ZrB₂-SiC-8vol%MoAlB was significantly smaller than that on ZrB₂-SiC. The thickness of the oxide layer in ZrB₂-SiC was 250 μm, while the thickness of the oxide layer in ZrB₂-SiC-8vol%MoAlB was 108 μm. The formation of dendritic crystals on the surface of ZrB₂-SiC-4vol%MoAlB destroys the oxide layer, leading to a decrease in the oxidation resistance of material. The mass gain of ZrB₂-SiC-12vol%MoAlB and ZrB₂-SiC-16vol%MoAlB is greater, and the oxidation layer is thicker, indicating a lower oxidation resistance.