Preparation and structure of microarc oxidation ceramic coatings containing ZrO₂ grown on LY12 Al alloy

Ceramic coatings containing ZrO₂ were prepared in situ on LY12 aluminum alloy by microarc oxidation (MAO) in the mixed solution of zirconate and phosphate solution. The phase composition and morphology of the coatings were studied by XRD and SEM, respectively. The growing mechanism of ceramic coatings was discussed in a preliminary manner. The results show that with an increase in MAO time, the compactness of the coating improved and the thickness increased. From the inner layer to the coating surface, the content of Zr increased, while the content of Al decreased. In addition, the coating was composed of m-ZrO₂, t-ZrO₂, and a little amount of γ-Al₂O₃. With an increase in reaction time, the relative content of t-ZrO₂ within the coating sharply decreased while the relative content of m-ZrO₂ sharply increased, and then both generally kept at a constant level after 60 min.