High Temperature Performance Study Of Micro-arc Oxidation Ceramic Coating On LY12 Aluminum Alloy

Studies on aluminum alloy micro-arc oxidation are mainly concentrated on the influence of the organizational structure, the solution system and electric parameters on the ceramic coating performance. And the research about the micro-arc oxidation ceramic coating on aluminum alloy of high temperature corrosion resistance, wear resistance, oxidation resistance is relatively less. Therefore, the study about high temperature performance of the ceramic coating on aluminum alloy has important significance for its high temperature service behavior.The high temperature oxidation kinetics, microstructure, corrosion resistance, thermal shock resistance and erosion resistance of micro-arc oxidation ceramic coating on LY12 aluminum alloy are studied. This paper analyzed that the micro-arc oxidation ceramic coating in different voltage have the influence on the high temperature oxidation performance, thermal shock resistance and erosion resistance.The results show that, with the increase of micro-arc oxidation voltage, its film thickness and surface roughness also will increase. In high temperature oxidation experimental, the expansion of micro cracks provides a channel of oxygen diffusion. And this causes that the weight of the micro-arc oxidation sample increases obviously at the beginning, and its coefficient of oxidation rate is relatively smaller than the aluminum alloy original sample, which has protective effect on aluminium alloys substrate. The analysis of polarization curves and salt spray test shows that compared with the ceramic coating without high temperature oxidation experiment, the corrosion resistance of the ceramic coating after high temperature oxidation is better. And it doesn’t has much influence on the salt spray corrosion resistance of the ceramic coating. The reason is that during the high temperature oxidation experiment, the micro-arc oxidation samples are secondary oxidated. New oxide is generated which fills pore and micro cracks on the ceramic coating, which protects the aluminium alloys substrate. The thermal shock experiment shows that the holes on the ceramic coating reduce the internal stress concentration, passivate cracks and inhibit crack’s extension, which have great help to improve the thermal shock resistance. The different surface morphology and the size of the micro cracks leds to the difference of the situation when the ceramic coating falls off in thermal shock experiments. The flame ablation experiment shows that the ceramic coating may effectively protect substrates from flame ablation.