Influence of treatment time on structure and property of ceramic coatings formed on LY12 aluminum alloy by micro-arc oxidation

In K₂ZrF₆ solution, the ceramic coatings composed of a large amount of t-ZrO₂, m-ZrO₂ and a little γ-Al₂O₃ and KZr₂(PO₄)₃ were prepared on LY12 aluminum by a micro-arc oxidation technique. With the increase of micro-arc oxidation (MAO) time, the content of crystalline substances is increased, the coating surface roughness is increased, and the compactness of the coating is improved. The thickness of the coating is increased approximately linearly, and the hardness and the corrosion resistance are both improved, while the heat shock resistance of the coatings turned worse. Meantime, the friction tests show that the anti-abrasion of the coated samples is improved to a large extent, the friction coefficient of the substrate is about 2/3 that of the coated samples. With the increase of MAO time, friction weight loss of the coated samples is first increased, and then decreased, while the friction coefficient is decreased.