Study On Mocrostructure And Properties Of Ceramic Coatings Formed By Micro-arc Oxidation On ADC12 High Silicon Aluminum Alloy

ADC12 high silicon aluminum alloy,which has the characteristics of cheap,good fluidity,good die casting performance,strong plasticity and so on.It is mainly used in textile,sensor support,aerospace and other fields.But ADC12 high silicon aluminum alloy is easy to be corroded and worn in corrosive environment.Therefore,it is of great significance to find the corrosion resistance and wear method of ADC12 high silicon aluminum alloy.Micro-arc oxidation(MAO)is the most widely used technology for surface modification of aluminum alloy and magnesium alloy,and also the most deeply studied and developed technology by scholars at home and abroad.The technology is green and easy to operate.It can be applied to the surface modification of large and complex workpieces and improve the corrosion resistance of the matrix.The spinning cup in the field of textile machinery is generally made of ADC12 high silicon aluminum alloy.The spinning cup carries on the transportation to the raw cotton through the high-speed rotation,and the raw cotton contains the insect secretion and other corrosive media,so that it is subjected to the fiber wear and environmental corrosion in the service process.Therefore,the research had practical significance for the promotion and application of micro-arc oxidation ADC12 high-silicon aluminum alloy in textile industry and other industries.In this paper,the effects of power mode and oxidation time on microstructure and properties of micro-arc oxidation ADC12 high-silicon aluminum alloy were studied and analyzed by scanning electron microscope,electrochemical workstation and high temperature wear testing machine.The main conclusions are as follows:(1)In unipolar/bipolar pulse constant current mode,ac mode test conditions,the wear resistance of ADC12 high-silicon aluminum alloy could be improved by these three power modes,and it ccould effectively avoid the reduction of mechanical properties caused by wear.The corrosion resistance of ADC12 high silicon aluminum alloy could be improved,and the service life of ADC12 high-silicon aluminum alloy also could be improved Significantly.The wear resistance of ADC12 aluminum alloy could be improved by the two-stage pulse constant current mode.(2)In constant voltage,constant current,constant current then constant voltage and constant current then constant voltage four test conditions,the coating thickness prepared by constant pressure for 50 min was the thickest,while the coating thickness was reduced by constant current for 15 min and constant voltage for 35 min.(3)In constant voltage,constant current,constant current then constant voltage and constant current then constant voltage four test conditions,the specific corrosion resistance was as follows: in the early stage of corrosion(0h-12 h),the corrosion resistance of the film prepared by constant pressure for15 min and constant current for 35 min is high.In the middle corrosion period(24 h-120 h),the film prepared by constant flow for 50 min has high corrosion resistance.In the later stage of corrosion(240 h-360 h),the corrosion resistance of constant current for 15 min and then constant pressure for 35 min is higher.This indicates that the combination of constant pressure15 min and then constant flow 35 min or constant flow 15 min and then constant pressure 35 min can improve the corrosion resistance of the film.(4)The thickness of micro-arc oxidation coating of ADC12 high-silicon aluminum alloy was influenced by the different oxidation time.The thickness of the MAO coating increases with the constant current oxidation time.(5)In constant voltage for 15 min first and then constant current for different oxidation time conditions,the wear rate of MAO coating increases firstly and then keeps flat with the increase of constant current oxidation time.(6)In constant voltage for 15 min first and then constant current for different oxidation time conditions,the corrosion resistance of MAO coating increases with the increase of constant current oxidation time before the constant current for 50 min.The corrosion resistance of MAO coating began to decrease due to microcracks in the film after constant current for 50 min.