电流密度对硅磷酸盐电解液中2195铝锂合金微弧氧化涂层微观结构、耐腐蚀性及耐磨性的影响

Effect of Current Density on Microstructure, Corrosion Resistance, and Wear Resistance of Micro-arc Oxidation Coatings on 2195 Al-Li Alloy in a Silicate-Phosphate Electrolyte Solution

摘要:

在硅酸盐-磷酸盐电解液中，采用微弧氧化技术在2195铝锂合金表面制备陶瓷涂层，研究了不同电流密度（200~800 A/m²）对微弧氧化涂层微观结构、耐蚀性和耐磨性的影响。通过扫描电子显微镜、能谱仪、X射线衍射仪、X射线光电子能谱仪和表面粗糙度仪分析了微弧氧化涂层的表面及截面形貌、成分和粗糙度。结果表明，随着电流密度的增大，微弧氧化涂层的粗糙度和厚度均增加。该涂层主要由γ-Al₂O₃组成，并含有少量α-Al₂O₃。在最大电流密度下制备的微弧氧化涂层最为致密。动电位极化测试表明，涂层的耐蚀性随电流密度的增大而提高。当电流密度为800 A/m²时，微弧氧化涂层的耐蚀性最佳，其腐蚀电位为-0.536 V，腐蚀电流密度为4.32×10^-7 A/cm²，较基体降低了两个数量级。电化学阻抗谱结果显示，电流密度为800 A/m²时，试样的容抗弧半径最大，且在低频区具有最高的阻抗值。微弧氧化涂层的耐磨性随电流密度的增大而提高。当电流密度为200 A/m²时，磨损机制主要为磨粒磨损；进一步增大电流密度后，磨损机制仍为磨粒磨损。在800 A/m²下制备的微弧氧化涂层耐磨性最佳，磨损率为1.355×10^-4 mm³/(N?m)。

Abstract:

Ceramic coatings were prepared on 2195 Al-Li alloy by micro-arc oxidation (MAO) in a silicate-phosphate electrolyte solution under different current densities. The effect of current density varying from 200 A/m² to 800 A/m² on the microstructure, corrosion resistance, and wear resistance of MAO coatings was investigated. The surface and cross-sectional morphologies, composition, and roughness of MAO coatings were analyzed by scanning electron microscope, energy disperse spectrometer, X-ray diffractometer, X-ray photoelectron spectroscope, and surface roughness tester. The results show that with the increase in current density, the roughness and thickness of MAO coating increase. MAO coatings are mainly composed of γ-Al₂O₃ and a small amount of α-Al₂O₃. MAO coatings prepared under the maximum current density is the densest. Potentiodynamic polarization tests indicate that the corrosion resistance of coatings increases with the increase in current density. When the current density is 800 A/m², MAO coating exhibits the best corrosion resistance, with a corrosion potential of -0.536 V and a corrosion current density of 4.32×10^-7 A/cm², which is two orders of magnitude lower than that of the substrate. Electrochemical impedance spectroscopy results indicate that, at a current density of 800 A/m², the sample possesses the largest capacitive arc radius and the highest impedance magnitude in the low-frequency region. The wear resistance of MAO coatings increases with the increase in current density. When the current density is 200 A/m², the wear mechanism is dominated by abrasive wear. With further increase in current density, the wear mechanism remains abrasive wear. MAO coatings prepared at 800 A/m² show the best wear resistance with a wear rate of 1.355×10^-4 mm³/(N?m).