Formation mechanism of micro-arc oxidation coatings formed on ZrB2–SiC ceramics

The uniform coatings were fabricated successfully on the surface of the ZrB2–SiC ceramic through the micro-arc oxidation (MAO) technique in sodium aluminate solution. The results of XRD analysis of the MAO coatings were obvious to indicate that the predominant phases for the surface of the MAO coatings were α-Al2O3, t-ZrO2 and m-ZrO2. The contents of α-Al2O3 and t-ZrO2 in the MAO coatings gradually decreased as the coating thickness decreased. The effect of the MAO coatings on the ultrahigh temperature oxidation resistance of the ZrB2–SiC ceramic was investigated, indicating that the oxidation resistance of the ZrB2–SiC ceramic with the MAO coatings was significantly improved from 1700 °C to at least 2000 °C compared with bare ZrB2–SiC ceramic.