摘要
目的探究正负脉冲占空比对5005铝合金表面赤泥(RM)等离子体电解氧化(PEO)复合陶瓷层的生长机制、组织结构和抗腐蚀性能的影响。方法以赤泥为电解液添加剂,采用PEO技术,以不同正负占空比配比在5005铝合金表面制备陶瓷层,利用X射线衍射仪(XRD)、附带能谱仪(EDS)的扫描电镜(SEM)和电化学工作站,测试和表征陶瓷层的物相组成、微观形貌和成分以及抗腐蚀性能。结果单独升高正、负占空比,电流均增大,击穿放电作用加强,赤泥颗粒扩散速率和参与成膜的浓度增加,陶瓷层生长速度加快,厚度增大,颜色变深,受负占空比的影响比较明显,反应时间为20 min时,厚度最大分别可达27.70μm和35.82μm。陶瓷层主要由γ-Al2O3组成,并含有少量的无定形相、α-Al2O3以及赤泥矿物相Fe2O3、CaCO3和SiO2,其中α-Al2O3和Fe2O3含量随负占空比的升高而快速增加,最多可分别达到6.40%和2.86%。陶瓷层的致密性和抗腐蚀性能随正负占空比的升高,均先增加后降低,但负占空比的影响较正占空比的大,当正占空比为28%~42%和负占空比为12%~18%时,陶瓷层的结构致密,腐蚀电流密度和腐蚀速率小,阻抗大,抗腐蚀性能好。结论 PEO陶瓷层的组织结构和性能受正占空比的影响较负占空比的小,适当的正负占空比配比可获得结构致密、抗腐蚀性能好的赤泥PEO复合陶瓷层。
The work aims to study the effects of various positive and negative duty cycles on the growth mechanism, structure and corrosion resistance of red mud (RM) plasma electrolytic oxidation (PEO) composite ceramic coatings on 5005 aluminum alloy surface. The ceramic coatings were prepared on the surface of 5005 aluminum alloy at various positive and negative duty cycles with RM as electrolyte additive by PEO technology. Phase composition, microstructure, constitution and corrosion resistance of ceramic coating were tested and characterized with X-ray diffractometer (XRD), scanning electron microscope (SEM) with energy disperse spectrometer (EDS) and electrochemical workstation. When the positive or negative duty cycle was increased separately, the current increased and the breakdown discharge function improved. With the increase of diffusion rate of RM particles and the concentration in the coating formation, the ceramic coating grew faster with higher thickness and darker color, but was significantly affected by the negative duty cycle. When the reaction time was 20 min, the maximum thickness could be 27.70 μm and 35.82 μm, respectively. The coating consisted mainly of γ-Al2O3 and a small percentage of amorphous phase,α-Al2O3 and RM minerals including Fe2O3, CaCO3 and SiO2.α-Al2O3 and Fe2O3 went up rapidly with the increase of negative duty cycle, which could be up to 6.40% and 2.86%, respectively. With the increase of duty cycle, the coating compactness and corrosion resistance firstly increased and then decreased, but the effect of negative duty cycle was greater than that of positive duty cycle. When the positive duty cycle was 24%~42% and negative duty cycle was 12%~18%, the coating was compact with smaller corrosion current density and corrosion rate, and larger impedance, showing a good corrosion resistance. The structures and properties of PEO coatings are affected by positive duty cycle less than by negative duty cycle, and a RM-PEO composite coating with dense structure and good corrosion resistance ca
作者
刘世丰
曾建民
LIU Shi-feng;ZENG Jian-min(State Key Laboratory of Solidification Processing, School of Materials Science and Engineering,Northwestern Polytechnical University, Xi凷an 710072, China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2019年第6期287-298,共12页
Surface Technology
基金
广西创新驱动发展专项(桂科AA17202001)
广西有色金属及特色材料加工重点实验室开放课题(GXKFJ16-05)~~
关键词
赤泥
PEO技术
5005铝合金
正负占空比
抗腐蚀性能
red mud
plasma electrolytic oxidation technique
5005 aluminum alloy
positive and negative duty cycle
corrosion resistance
