Improvement of surface porosity and properties of alumina films by incorporation of Fe micrograins in micro-arc oxidation

Micro-arc oxidation (MAO) is an effective approach to improve the properties of aluminum and its alloy by forming ceramic films on the surface. However, the oxide layers often have a porous surface structure, which exhibits relatively high friction coefficients. In this work, in order to enhance the surface and mechanical properties of the films produced by micro-arc oxidation, Al2O3 coatings embedded with Fe micrograins of different thicknesses were produced on aluminum alloys by adding Fe micrograins into the electrolyte during MAO. Compared to the Al2O3 coatings without Fe micrograins, the MAO Al2O3 coatings with Fe micrograins are much denser and harder, and the wear resistance is also improved significantly. The enhancement can be attributed to the enhancement of the surface structure and morphology of the MAO Al2O3 coatings with embedded Fe micrograins.