电流密度对2195铝锂合金微弧氧化涂层微观结构、耐腐蚀性和耐磨性的影响

Effects of current density on microstructure, corrosion and wear resistance of MAO coatings on 2195 Al?Li alloy

摘要:

在硅酸盐 - 磷酸盐电解液中，采用微弧氧化（MAO）技术在 2195 铝锂合金表面制备了陶瓷涂层，研究了不同电流密度（2-8 A/dm2）对涂层微观结构、耐蚀性和耐磨性的影响。通过扫描电子显微镜（SEM）、能谱仪（EDS）、X 射线衍射仪（XRD）、X 射线光电子能谱仪（XPS）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。微弧氧化涂层主要由 γ-Al?O?和少量 α-Al?O?组成。在最大电流密度下制备的微弧氧化涂层最致密。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 8 A/dm2 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?? A/cm2，比基体的腐蚀电流密度低两个数量级。电化学阻抗谱（EIS）结果显示，在电流密度为 8 A/dm2 时，样品的容抗弧半径最大，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 2 A/dm2 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 8 A/dm2 下制备的微弧氧化涂层耐磨性最佳，磨损率为 0.1355×10?3 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 2 to 8 A/dm2 on the microstructure, corrosion and wear behavior of the coatings were investigated. The surface and cross-sectional morphologies, composition and roughness of the MAO coatings were analyzed by scanning electron microscope (SEM), energy spectrometer (EDS), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and surface roughness meter. The results show that with the increase of current density, the roughness and thickness of the MAO coating increase. The MAO coatings are mainly composed of γ-Al2O3 and a small amount of α-Al2O3. The MAO coatings prepared under the maximum current density is densest. Potentiodynamic polarization tests indicate that the corrosion resistance of coatings increase with the current density. When the current density is 8 A/dm2, the MAO coating exhibits the best corrosion resistance, with a corrosion potential of -0.536 V and a corrosion current density of 4.32×10?? A/cm2, which is two orders of magnitude lower than that of the substrate. Electrochemical Impedance Spectroscopy (EIS) results indicate that, at a current density of 8 A/dm2, the sample possesses the largest capacitive arc radius and the highest impedance magnitude in the low-frequency region.The wear resistance of the MAO coatings increases with the current density. When the current density is 2 A/dm2, the wear mechanism Mainly dominated by abrasive wear. Further increasing the current density, the wear mechanism transformed to abrasive wear. The MAO coatings prepared at 8 A/dm2 show the best wear resistance with a wear rate of 0.1355×10-3 mm3/N·m.