Ablation mechanism mechanism of ZrB2-SiC coating for SiC-coated graphite under an oxyacetylene flame

摘要

ZrB2-SiC coating was fabricated on SiC-coated graphite using shrouded plasma spray (SPS). Ablation resistance of the coating was evaluated through oxyacetylene for 15 s, 30 s, 120 s and 360 s. The sample weight has increased after ablation for 15 s, 30 s and 120 s with generation of oxide products. The ZrO2 layer was produced from ZrB2-SiC oxidation and acted as a thermal barrier. In the case of 360 s ablation, the SiC inner layer is oxidized and evaporated and a gap remained between ZrO2 layer and graphite. Phase transformation of ZrO2 during cooling induces the volume expansion. As a result, cracks are generated in the central region during cooling from high temperature to room temperature.