The effect of MoAlB substitutions on the oxidation behavior of ZrB 2 -SiC Composites at 1600 °C

ZrB 2 -SiC ceramics are potential candidates for thermal protection materials for re-entry and hypersonic vehicles. Phases are typically added to ZrB 2 -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 ZrB 2 -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 ZrB 2 -SiC-8vol%MoAlB exhibits improved oxidation resistance compared to ZrB 2 -SiC. After being oxidized at 1600 °C for 10 h, the thickness of the oxide layer on ZrB 2 -SiC-8vol%MoAlB was significantly smaller than that on ZrB 2 -SiC. The thickness of the oxide layer in ZrB 2 -SiC was 250 μ m, while the thickness of the oxide layer in ZrB 2 -SiC-8vol%MoAlB was 108 μ m. The formation of dendritic crystals on the surface of ZrB 2 -SiC-4vol%MoAlB destroys the oxide layer, leading to a decrease in the oxidation resistance of material. The mass gain of ZrB 2 -SiC-12vol%MoAlB and ZrB 2 -SiC-16vol%MoAlB is greater, and the oxidation layer is thicker, indicating a lower oxidation resistance.