Self-repairing Al_(2)O_(3)-TiO_(2)coatings fabricated through plasma electrolytic oxidation with various cathodic pulse parameters  

阴极脉冲参数对等离子体电解氧化制备自修复Al_(2)O_(3)-TiO_(2)涂层的影响

作　　者：Mehri HASHEMZADEH Keyvan RAEISSI Fakhreddin ASHRAFIZADEH Frank SIMCHEN Amin HAKIMIZAD Monica SANTAMARIA Thomas LAMPKE 

机构地区：[1]Department of Materials Engineering,Isfahan University of Technology,Isfahan 84156-83111,Iran [2]Materials and Surface Engineering Group,Institute of Materials Science and Engineering,Chemnitz University of Technology,Chemnitz 09107,Germany [3]Yekta Mobaddel Pars Co.,Science and Technology Campus,Yazd University,Yazd 89158-18411,Iran [4]Dipartimento di Ingegneria,Universitàdi Palermo,Viale Delle Scienze,Ed.6,90128,Palermo,Italy

出　　处：《Transactions of Nonferrous Metals Society of China》2024年第10期3326-3343,共18页中国有色金属学报（英文版）

摘　　要：The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.在含草酸钛钾(Potassium titanyl oxalate,PTO)的硅酸盐电解液中采用不同阴极占空比和阴极电流密度的脉冲双极波形,在7075铝合金上生长等离子电解氧化(Plasma electrolytic oxidation,PEO)涂层,研究阴极脉冲参数对PEO涂层的影响。通过扫描电子显微镜、能量色散X射线光谱(EDS)和X射线衍射(XRD)对涂层进行了表征。使用电化学阻抗谱(Electrochemical impedance spectroscopy,EIS)研究其电化学性能。结果表明,当阴极占空比和阴极电流密度分别从20%和6 A/dm^(2)增加到40%和12 A/dm^(2)时,内层的生长速率从0.22μm/min提高到0.75μm/min。向电解液中加入PTO增强了阴极脉冲的影响,由此产生的阴极脉冲参数的变化使得内层生长速率从0.25μm/min增加到1.10μm/min。EDS分析结果表明,Si和Ti主要分布在涂层的上部。XRD仅检测到γ-Al_(2)O_(3),未检测到与Ti和Si化合物相关的峰。然而,EIS结果证实,Ti^(4+)掺入氧化铝改变了涂层的电性能。在含有PTO的电解液中使用40%阴极占空比和大于6 A/dm^(2)电流密度的双极波形获得的涂层,在240 d的浸泡期间表现出优异的电化学行为,这归因于有效的修复机制。关于研究参数对涂层性能的影响,强调了阴极脉冲参数和PTO在PEO过程中的作用。

关 键 词：Al_(2)O_(3)-TiO_(2)coating plasma electrolytic oxidation potassium titanyl oxalate electrochemical impedance spectroscopy 

分 类 号：TG178[金属学及工艺—金属表面处理]