Effect Of Process Parameters On Growing Characteristics Of Micro Arc Oxidation Ceramic Layers On Aluminium Alloy

Corrosion, wear and thermal shock resistances of aluminum alloy elevate notably after microarc oxidation treatment. However, it is difficult to adopt hardness to characterize the properties of ceramic layers due to the distribution of micropores on layers, which leads to hardness value fluctuating largely. On the other hand, layers compactness effects the corrosion and wear resistances and other properties. Therefore it is necessary to develop a nondestructive examination method to characterize layer compactness, which is benefit to improve the application of microarc oxidation technique. In this paper, effects of process parameters such as current density, frequency, duty cycle and oxidation time on growth rate, compactness, breakdown voltage and breakdown field strength were investigated, respectively. The relationship between compactness or rate of weight growth and breakdown field strength was discussed. As a result, breakdown field strength can be adopted to characterize compactness of ceramic layers.The results indicate that at the constant condition, as the increase of current density, ceramic layers thickness increases, large current density is beneficial to rapid growth, the rate of weight growth of layer and breakdown field strength elevate. Layer thickness presented gradually decreasing at first and then tending to stable and the rate of weight growth presented gradually increasing at first and then tending to stable with the elevation of frequency, and the breakdown field strength also presented similar tendency as the rate of weight growth, high frequency is not beneficial to rapid growth. As the increase of duty cycle, layer thickness increases and large duty cycle is beneficial to rapid growth, the rate of weight growth and breakdown field strength exhibit a decrease tendency. Layer thickness increases but layer growth rate and rate of weight growth and breakdown filed strength rapidly reduced with prolonging the oxidation time. In addition, breakdown voltage and field strength can be used to characterize layer compactness in some extend. In a word, the regulation of breakdown field strength and the regulation of the rate of weight growth of microarc oxidation ceramic layers are identical, namely, the lager rate of weight growth, the larger of compactness and breakdown field strength. Therefore, breakdown field strength can be adopted to characterize compactness of ceramic layers.