超高频脉冲电流作用下纳米Al_(2)O_(3)颗粒对Mg-Gd-Y-Zr合金微弧氧化涂层的影响  

Effect of Al_(2)O_(3) Nanoparticles on Microarc Oxidation Coatings Formed on Mg-Gd-Y-Zr Alloy under the Action of Ultra-high Frequency Pulse Current

作　　者：刘晓鹤 师春晓 张博 刘磊 董帅[1,2] 董杰 LIU Xiao-he;SHI Chun-xiao;ZHANG Bo;LIU Lei;DONG Shuai;DONG Jie(National Engineering Research Center of Light Alloy Net Forming,Shanghai Jiao Tong University,Shanghai 200240,China;State Key Laboratory of Metal Matrix Composite,Shanghai Jiao Tong University,Shanghai 200240,China;Luoyang Institute of Special Materials Research,Henan Luoyang 471000,China;Shanghai Aerospace Equipments Manufacturer Co.,Ltd.,Shanghai 200245,China)

机构地区：[1]上海交通大学轻合金精密成型国家工程研究中心,上海200240 [2]上海交通大学金属基复合材料国家重点实验室,上海200240 [3]洛阳特种材料研究院,河南洛阳471000 [4]上海航天设备制造总厂有限公司,上海200245

出　　处：《表面技术》2023年第6期41-50,共10页Surface Technology

基　　金：河南省重点研发与推广专项(232102231021);浙江省科技计划项目(2022C01081);山西省关键核心技术和共性技术研发攻关专项项目(2020XXX015)。

摘　　要：目的进一步提高Mg-Gd-Y-Zr合金微弧氧化涂层的耐腐蚀性能。方法采用超高频微弧氧化技术在含有Al_(2)O_(3)纳米颗粒的溶液中制备了微弧氧化涂层。利用扫描电子显微镜(FESEM)、能谱仪(EDS)和X射线衍射仪(XRD)对微弧氧化涂层的表面形貌、截面形貌、成分和晶体结构进行分析。利用极化曲线和电化学阻抗谱(EIS)测试了涂层的耐腐蚀性能。结果频率由0.5 kHz提升至20 kHz后,涂层表面放电孔洞面积由0.07~24.4μm^(2)降低至0.08~6.3μm^(2),涂层的孔隙率由6.47%减小至3.35%。Al_(2)O_(3)纳米颗粒的添加使超高频涂层表面形成大量自封闭孔洞结构,进而进一步降低了涂层表面的孔径面积(0.1~4.63μm^(2))和孔隙率(0.97%)。极化试验表明,提高频率至20 kHz,涂层的自腐蚀电流密度由4.7×10^(-6)A/cm^(2)降低至4.7×10^(-7)A/cm^(2),添加Al_(2)O_(3)纳米颗粒,涂层的自腐蚀电流密度进一步降低至1.7×10^(-7)A/cm^(2),表明其耐蚀性能显著提高。阻抗谱显示,20 kHz-Al涂层具有最大的阻抗,说明该工艺可有效提高微弧氧化涂层的耐蚀性能。结论超高频可有效降低放电孔洞尺寸,提高微弧氧化涂层的致密性,改善涂层的耐腐蚀性能。超高频与Al_(2)O_(3)纳米粒子的协同作用使涂层表面形成自封闭孔洞结构,进一步提高微弧氧化涂层的致密性和耐腐蚀性能。Microarc oxidation(MAO)is a kind of technology that causes partial plasma discharge by applying high voltage to melt metal oxides and form ceramic coatings on light metal(aluminum,magnesium and titanium)and their alloys with the thickness of tens of microns to hundreds of microns,which have the advantages of wear resistance,corrosion resistance,electrical insulation,etc.Due to the inherent plasma discharge phenomenon in the MAO discharge process,the discharge gas and molten metal oxide will be ejected from the inside of the coating.During the ejecting process,defects such as discharge channels and micro-cracks are formed under the rapid quenching effect in the aqueous solution.This defect structure has a high specific surface area and can serve as a penetration channel for the corrosive medium,affecting the overall corrosion resistance of the MAO coating.Therefore,avoiding or sealing these discharge channels is crucial for improving the corrosion resistance of coatings and enhancing the large-scale application of light alloys.In order to further improve the corrosion resistance of Mg-Gd-Y-Zr alloy,this manuscript prepared microarc oxidation coating by ultra-high frequency microarc oxidation technology in the solution containing Al_(2)O_(3) nanoparticles.In the MAO process,Na_(3)PO_(4)(5 g/L),Na_(2)SiO_(3)(5 g/L),KOH(1 g/L),KF(3 g/L)were used as the main solution.The particle size of Al_(2)O_(3) nanoparticles was 20 nm,and the concentration was 8 g/L.The Al_(2)O_(3) nanoparticles were dispersed by sodium dodecyl sulfate(SDS)and then added to the main solution.The experiment was conducted at frequencies of 0.5 kHz and 20 kHz for 600 s at a current density of 4 A/dm^(2).The surface morphology,cross-sectional morphology,composition and crystal structure of the microarc oxidation coating were tested by field-emission scanning electron microscopy(FESEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The corrosion resistance of the coating was tested by polarization curve and electrochemical impedance spe

关 键 词：镁合金 微弧氧化 超高频 Al_(2)O_(3)纳米颗粒 电化学 耐腐蚀性能 

分 类 号：TG172[金属学及工艺—金属表面处理]