Effects of Constant Current and Constant Voltage Interaction on the Microstructure and Properties of Micro - Arc Oxidation Ceramic Coatings Formed on 6063 Aluminum Alloy

Abstract

In order to study the effect of different micro - arc oxidation (MAO) modes on the properties of MAO ceramic coatings on 6063 aluminum alloy, four micro - arc oxidation modes (constant voltage, constant current, constant current first and then constant voltage, constant voltage first and then constant current) were selected to prepare MAO ceramic coatings. Scanning electron microscopy (SEM), X - ray diffractometer (XRD), friction and wear testing machine and electrochemical workstation were used to characterize the microstructure and properties of the coatings. Results showed that among the ceramic coatings prepared under the above - mentioned four micro - arc oxidation modes, the coating prepared under the constant current first and then constant voltage mode had the best densification with a thickness of 14 μm. In addition, the friction coefficient was about 1.1, which was the smallest. The corrosion voltage (Ecorr) moved positively from -0.63 V (the substrate’s Ecorr) to - 0.46 V, and the corrosion current density (Jcorr) decreased from the 4.83×10-5 A/cm2 (the substrate’s Jcorr) to 1.40×10-6 A/cm2. Thus, this MAO coating possessed the optimal corrosion resistance and wear resistance.

Keywords

• 6063 aluminum alloy|micro - arc oxidation|constant current and constant voltage interaction|microstructure|property