Effects of SiO

Abstract

Micro-arc oxidation (MAO) is an effective approach to improve the properties of aluminium and its alloys by forming ceramic coatings on the surface. However, the oxide layers often have a porous surface structure, which limits their mechanical properties. In this work, in order to enhance the properties of the layers produced by micro-arc oxidation, AI2O3 coatings embedded with SiO2 nanoparticles were produced on 7A52 aluminium alloy by adding SiO2 nanoparticles into the electrolyte. With the addition of SiO2 nanoparticles in the electrolyte, the formation rate of AI2O3 coating enhanced considerably and the current density through sample surface became much higher than without SiO2 at the same voltage. Coatings were investigated with X-ray fluorescence spectrometry (XRF), Scanning electron microscopy (SEM), Vickers hardness test, and reciprocating friction and wear test. The XRF results showed that SiO2 nanoparticles were successfully embedded in the AI2O3 coatings. Compared with the AI2O3 coatings without SiO2 nanoparticles, the MAO AI2O3 coatings with SiO2 nanoparticles are much denser and harder, and the wear resistance is also improved significantly. The improvement can be attributed to the enhancement of the surface structure and morphology of the MAO AI2O3 coatings embedded with SiO2 nanoparticles.