Study on Properties of High Emissivity Coating of 2A12 Aluminum Alloy Prepared by Micro-Arc Oxidation
Aluminum alloys are widely used as materials for electric vacuum devices in aerospace electric propulsion systems.However,they tend to overheat during operation,significantly impacting performance and service life,thus limiting their border application.Effectively dissipating the heat accumulated on the surface is a key approach to addressing this issue.In this context,a high-emissivity thermal control and radiative heat dissipation coating was developed on aluminum alloy surfaces using micro-arc oxidation(MAO)technology.Phosphate was selected as the primary component of the electrolyte,with FeSO4 added as an additive.By adjusting the concentration of the additive FeSO4 in the electrolyte,a uniform,high-emissivity infrared coating was successfully fabricated on the surface of 2A12 aluminum alloy.Scanning electron microscope,energy spectrometer,X-ray diffractometer,eddy current thickness meter,roughness meter,universal material testing machine and Fourier transform infrared spectrometer were used to analyze the surface morphology,elemental composition,phase composition,thickness,roughness,bonding strength and infrared emissivity of the micro-arc oxidation coatings prepared at different concentrations of FeSO4.The results show that as the FeSO4 concentration increased from 0 g∙L-1 to 8 g∙L-1,the number of holes on the coating surface gradually decreased,while pore size increased,and cracks began to form.The coating's thickness and roughness of the coating increased from 17.2 μm to 39.1 μm,and from 1.94 μm to 2.96 μm,respectively.XRD and XPS analyzes revealed that the coatings consisted primarily of α-Al2O3,γ-Al2O3 and Fe2O3 phases,which originated from the substrate and electrolyte.Notably,at a FeSO4 concentration of 6 g∙L-1,the coating exhibited optimal bonding strength and infrared emissivity,measured at 39.8 MPa and 0.909,respectively.
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