Effect of ZrB₂ and Polyvinyl Butyral Content on the Oxidation Resistance of ZrB₂–SiC Coatings Produced by Slurry Brushing Method

Abstract

ZrB2–SiC coatings are prepared on the surface of graphite by slurry brushing method to improve the oxidation resistance. Effects of ZrB2 content and polyvinyl butyral (PVB)–ethanol solution concentration on microstructure and static oxidation behavior of the ZrB2–SiC coatings are investigated at 1200 °C in air. The results indicate that increasing ZrB2 content improves the oxidation resistance of the coatings. When ZrB2 content increases from 30 to 45 wt%, weight loss rates of the coated samples after oxidation at 1200 °C for 120 min decrease from −0.92% to −1.67%. Increasing binder solution concentration raises component content in the coatings. As PVB–ethanol binder concentration increases from 0.025 to 0.075 g mL−1, weight loss rates of the coated samples after oxidation at 1200 °C for 120 min decrease from 0.32% to −0.38%. Excellent oxidation resistance of ZrB2–SiC coating is attributed to self‐sealing ability of B2O3 and borosilicate glass. The composite glass can inhibit oxygen diffusion by filling defects in the coating promptly. The borosilicate glass phase can enhance the fluidity of the composite glass. ZrO2 and ZrSiO4 particles restrict the growth of the microcrack, which improves the oxidation resistance of ZrB2–SiC coating.