The Effects of Content of Zr(NO3)4 on Formation and Characteristics of Micro-arc Oxidation Coatings Formed on ZAlSi12Cu2Mg1 Surface

The aims of this work are to prepare micro-arc oxidation coatings on the surface of ZAlSi₁₂Cu₂Mg₁ aluminum alloy in Na₂SiO₃+NaOH+Na₂EDTA electrolytes with and without Zr(NO₃)₄ and study their formation and characteristics. The phase constituent, surface microscopic morphology and cross-sectional morphology of the ceramic coatings were analyzed by XRD(X-ray diffraction), SEM(scanning electron microscope) and optical microscope. The thickness of the ceramic layer were measured by eddy current thickness gauge. The results show that the micro-arc oxidation films are mainly composed of mullite, α-Al₂O₃ and γ-Al₂O₃, it provides excellent adhesion with the substrate. With the content of Zr(NO₃)₄ in electrolyte varies from 0g/L to 1.0g/L, the thickness of the ceramic coating increases sharply at first, but afterwards reduces slowly, and the maximum of thickness up to 202μm when content of Zr(NO₃)₄ is 0.5g/L. The addition of Zr(NO₃)₄ into the base electrolyte solution is helpful in coatings formation and the coating formed in the solution containing 0.5g/L Zr(NO₃)₄ exhibits the best comprehensive features.