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采用等离子体电解氧化(PEO)工艺在Mg-9Gd-3Y镁合金表面制备了复相陶瓷层。通过微观结构分析及电化学测试技术研究了PEO陶瓷层的微观组织及腐蚀行为。结果表明,偏铝酸盐体系中PEO法制备的陶瓷涂层主要由MgO和MgAl2O4相组成,还有少量MgF2相,其中MgAl2O4尖晶石相约占陶瓷层的19.87%,且由非贯通的等离子体放电微孔与喷射沉积复相氧化物组成。浸泡初期,PEO陶瓷层表现出较好的耐蚀性;浸泡后期,陶瓷层腐蚀电流密度Icorr逐渐增大,陶瓷层电阻Rct快速减小,144 h后陶瓷层的保护能力迅速下降,且陶瓷层表面出现点蚀及裂纹萌生;浸泡过程中,交流阻抗谱由浸泡0~72 h的两个容抗弧转变为浸泡144~300 h的单容抗弧和感抗弧组成,表明腐蚀介质已渗透整个陶瓷层,并萌生点蚀。腐蚀产物主要由Mg(OH)2相组成。陶瓷层的腐蚀主要由等离子体放电微孔开始,逐渐向四周蔓延并形成放射状裂纹而加速腐蚀。
The composite ceramic layer was prepared on the surface of Mg-9Gd-3Y magnesium alloy by plasma electrolytic oxidation (PEO). The microstructure and corrosion behavior of PEO ceramic layers were investigated by microstructure analysis and electrochemical testing. The results show that the ceramic coating prepared by PEO method in the partial aluminate system mainly consists of MgO and MgAl2O4 phases with a small amount of MgF2 phase, in which the MgAl2O4 spinel accounts for about 19.87% of the ceramic layer and consists of non-through plasma Body discharge micropore and spray deposited complex oxide composition. In the early stage of immersion, the PEO ceramic layer showed better corrosion resistance. At the late immersion stage, the corrosion current density Icorr of the ceramic layer gradually increased, the resistance of the ceramic layer Rct decreased rapidly, and the protective ability of the ceramic layer decreased rapidly after 144 hours. During the immersion process, the AC impedance spectra were changed from two capacitive arcs of immersion for 0 ~ 72 h to single capacitive arcs and inductive arcs soaked for 144 ~ 300 h, indicating that the corrosive medium had penetrated The entire ceramic layer, and initiation pitting. The corrosion products mainly consist of Mg (OH) 2 phase. Ceramic layer corrosion mainly by the plasma discharge micro-pores began to gradually spread around and the formation of radial cracks and accelerate corrosion.