Effect Of Graphene On The Structure And Properties Of Pure Aluminum Microarc Oxidation Coatings

This paper starts with the micro-arc oxidation(MAO)process and explores a process method that uses graphene as an auxiliary phase to optimize the ceramic coating properties,finally obtaining a more functional aluminum-based coating material.This article uses two methods to prepare the ceramic layer:one is to directly add graphene to the alkaline sodium silicate electrolyte for micro-arc oxidation to explore the effect of graphene on the structure,corrosion resistance and friction properties of the pure aluminum MAO coating.The other is to combine the preparation process of micro-arc oxidation technology with electrophoretic deposition technology to make graphene electrophoretic deposition doped into the coating,and to explore the effect of this method on the microstructure of the coating and its corrosion resistance and friction properties influences.Analyze the growth process and structure of the coating from the current-time curve,surface and cross-sectional morphology,internal surface morphology,element composition,and phase composition.In terms of functionality,electrochemical methods(potential polarization curve and electrochemical impedance spectroscopy)and friction experiments to evaluate the corrosion resistance and friction performance of the coating.Using different concentrations of graphene as a variable,the effect of graphene addition on the growth,structure and properties of the coating was explored.The results show that the addition of graphene to the electrolyte can effectively reduce the arcing voltage and the reaction current.The micropore size and microcrack defects on the surface of the coating have been improved.Through the phase analysis,it can be seen that the addition of graphene promotes the reaction between the anode and the electrolyte and the nucleation of the Mullite.The results show that graphene in the electrolyte can participate in the growth of the coating,which increases the content of C element.Moreover,the addition of graphene improves the corrosion resistance of the coating and reduces the friction coefficient.The experiment indicates when the graphene concentration reaches0.15g/L,the corrosion resistance of the prepared coating reaches the best,and the friction coefficient was also smaller.The preparation method of micro-arc oxidation and electrophoretic deposition graphene composite film is to take the interruption time of two micro-arc oxidation and the presence of electrophoretic deposition graphene as multiple variables to explore the influence on the growth,structure and functionality of the film.The results show that the second micro-arc oxidation has a more stable reaction current.This process makes the mullite phase more crystalline and promotes the formation of?-Al₂O₃ phase.The densification and thickness of the graphene composite film deposited by micro-arc oxidation and electrophoresis are improved,and the content of C element is slightly increased.According to the electrochemical method,the composite film with dense outer structure has better corrosion resistance,among which the sample Al8+5+2 has the best corrosion resistance.The friction experiments show that this process has little effect on the friction coefficient of the film.