| Microarc oxidation (MAO) is a new technique, which can in-situ form a ceramic film on the surface of valve metal. On the base of studying lots of literature, Progress and application of MAO is summarized as well as the mechanism of the form of MAO ceramic film. Performance of MAO ceramic film and correlative theories are also reviewed.In the part of research of the technic parameter, the effect of initialization voltage, current density and oxidation time on the growth of MAO ceramic film is discussed. The best MAO process conditions are found by the research of the law of film growth, its thickness and hardness. The research show that ceramic film of certain thickness and high hardness on the surface of LY12 aluminium alloy can achieved by MAO under the conditions of proper initialization voltage, current density 50A/dm2, oxidation time 60min.The researches of complex workpiece focus on the gearwheels that contain complex exterior surfaces and the cylindrical objects that contain interior surfaces. Factors that can affect the uniformity of ceramic film on the surface of complex workpiece are studied. By the control of technic parameter, placing anode workpiece properly and puting assistant cathode, uniform ceramic film of good propertis can be formed on the surface of complex workpiece.By SEM, difference in surface morphologis of ceramic film is studied under different initialization voltage. And the difference is analyzed by the mechanism of form of MAO.The phase structures of ceramic film are analyzed by XRD. The results show ceramic film is made up of different kinds of A2O3. And the growth of a - Al2O3, y-Al2O3 is the results of rapid condensation of melt A2O3. Al2O3 product and its mechanism need to be confirmed by more researches. |
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