Effect Of Ultrasonic On Characteristics Of Micro-arc Oxidation Coating Of6061Aluminum Alloy

In this paper, aluminum alloy6061was surface treated by WH-1A micro-arcoxidation device. Ultrasonic device was introduced into the process. By comparing thesurface arc-discharge characteristics, the growth dynamics, thickness, chemicalcomposition, structure and properties of ceramic coatings formed in the systems with andwithout ultrasonic wave action, the influence of ultrasonic wave on the growth of microarc oxidation ceramic coatings and the growth mechanism were studied.The results showed that with the introduction of ultrasonic wave, the arc startingvoltage was decreased, the density of arc discharges was increased, the balanceddevelopment of discharge evolution was promoted, the growth rate and the thickness ofceramic coatings was increased. Ultrasonic wave caused the number of residual pores onthe coating surface increased and the ablation areas decreased and the surface became flatwith the quality improving of ceramic coating. Meantime ultrasonic wave promoted theuniform distribution of element Si and P and increased the content of O in the coating.Also ultrasonic wave promoted the transformation of γ-Al2O3to α-Al2O3, and decreasedthe roughness of the coating. Under constant current density of4.4A/dm2, with theintroduction of ultrasonic wave, when the micro arc oxidation time was30min, theroughness of the ceramic coating was improved most. With the increase of current density,the roughness of the coating became larger, however, when ultrasonic wave wasintroduced, the increasing amplitude of roughness decreased. The roughness of theceramic coating became large with the increasing distance between ultrasonic wavesource and the specimen. The micro-hardness of the coating was increased with theintroduction of ultrasonic wave, and the impact of ultrasonic wave increased withincreasing the current density. The corrosion potential and corrosion current of thespecimen was increased and decreased, respectively, with the introduction of ultrasonicwave, which increased the corrosion resistance of the specimen.