Preparation Technology And Performance Of AZ91D Magnesium Alloy Magnesium Oxide/Graphene Micro-arc Oxidation Coating

Magnesium is the most promising green material in the 21st century because of its advantages such as high specific strength,good dimensional stability,and easy recycling.Because of its active chemical properties,magnesium is easily corroded in the working environment.Therefore,it is an important step in the application of magnesium alloys to use appropriate surface treatment to improve the corrosion resistance of the magnesium alloy surface.The micro-arc oxidation treatment process is simple,the obtained coating has excellent comprehensive performance,and is a very research surface treatment technology.Graphene is a new type of two-dimensional carbon nanomaterial with excellent chemical and mechanical properties,and has important application prospects in the fields of corrosion protection and friction reduction lubrication.In this work,the graphene dispersion obtained by ultrasonic dispersion was added to the micro-arc oxidation electrolyte,and the Magnesium Oxide/Graphene micro-arc oxide coating was prepared on the surface of the AZ91D magnesium alloy.The effect of Magnesium Oxide/Graphene micro-arc oxidation coating growth mechanism was discussed.Using SEM,EDS,contact angle analyzer and XRD to analyze the coating microstructure,surface wettability and phase composition,the effect of graphene concentration on the coating surface,cross section micromorphology,wetting angle and phase composition was explored.The results showed that after adding graphene to the electrolyte,the roughness of the coating decreased,the thickness increased,the surface pore size decreased,and the porosity increased;when the graphene concentration was 0.15g/L,the pore size of the coating surface was the smallest,and the C content in the micropores of the coating was the highest;adding graphene was beneficial to increase the coating wetting angle and reduce the coating surface wettability;adding graphene had no effect on the phase composition of the coating,and the coating was mainly composed of Mg F₂,Zr O₂,Mg O,and Mg₂Zr₅O₁₂ phases.Electrochemical corrosion test and immersion experiment were used to analyze the effect of graphene concentration on the corrosion resistance of the coating.The results showed that compared with the coating without graphene,the coating with graphene was beneficial to improve the corrosion resistance of the coating.When the graphene concentration was 0.15g/L,the polarization resistance was the largest,the corrosion current density was the smallest,the Nyquist graph arc resistance radius was the largest,and the corrosion resistance of the coating was the best;After immersing in 5%Na Cl solution for 21 days,the coating layer did not show the macroscopically visible corrosion morphology,and was still relatively complete.Friction and wear test was used to analyze the effect of graphene concentration on the wear resistance of the coating.The results showed that compared with the coating without graphene,the coating with graphene was beneficial to reduce the friction coefficient,and improve the wear resistance of the coating.When the graphene concentration was 0.3g/L,the anti-friction and lubricating effect on the coating was most obvious.