Enhanced ablation resistance of HfB2-HfC/SiBCN ceramics under an oxyacetylene torch environment

To further improve the ablation resistance of SiBCN ceramics, nanosized HfB2 was introduced by mechanical alloying and subsequent reactive hot-pressing techniques to fabricate HfB2-HfC/SiBCN multiphase ceramics. The mass and linear ablation rates of the 30 vol% HfB2-HfC containing SiBCN ceramics under an oxyacetylene flame for 10 s were lower than those of ZrB2-ZrN/SiBCN and SiBCN, reaching to 0.0025 mg/s and 0.0004 mm/s respectively. Even ablated for 60 s, no trace of cracks appeared on the ablation surface. Oxidation of ceramic matrix, denudation of oxides, erosion by the combustion flow and the re-oxidation of the exposed matrix governed the ablation process.

Automated summary

By introducing nanosized HfB2, HfB2-HfC/SiBCN multiphase ceramics were fabricated with lower ablation rates and no cracks under combustion conditions, governed by oxidation of ceramic matrix, denudation of oxides, erosion by combustion flow, and re-oxidation of exposed matrix.