Ablation resistance of graphite coated by spark plasma sintered ZrB2–SiC based composites

Abstract

ZrB2–SiC–HfB2–WC coating applied by spark plasma sintering led to the ablation resistance improvement of graphite substrate. The influence of HfB2/WC ratio was investigated on the ablation resistance produced by an oxyacetylene flame. The microstructural evolutions and phase characterization were studied using scanning electron microscopy and X-ray diffraction, respectively. It is confirmed that the ablation resistance of sample with 5% WC and 2.5% HfB2 was significantly increased with minimum ablated materials and rate of 1.1% and 2.2mgs−1 employing the results of oxyacetylene flame test. The important mechanisms of improvement of the ablation resistance were the evaporation of WO3 and SiO upon oxidation of SiC and WC in the coating.