Simulation of Quenching Process during Microarc Oxidation (MAO) and its Effect on the Microstructure of Al_2O_3 Coating

The convection heat transfer coefficient on Al_2O_3 coating during microarc oxidation process was estimated by experiment and simulation.The Al_2O_3/Al interface was found to be a heat- transfer passage.During quenching,most heat of the micro-melting-pool was transferred through the Al substrate and the Al_2O_3 coating nearby.The micro-melting-pool was modeled by the finite element method (FEM),and the process of quenching was characterized by the simulated temperature-time curves of the nodes along the depth,respectively.The effects of the quenching on the distribution ofα-Al_2O_3 and surface morphology of Al_2O_3 coating were discussed by comparing the relative cooling rate at different positions.The influence of pressure on the microstructure of Al_2O_3 coating was also discussed briefly.