CeO2对超音速火焰喷涂WC-12Co涂层腐蚀行为的影响*
收稿日期: 2016-01-18
网络出版日期: 2016-08-18
基金资助
* 国家自然科学基金项目51474178, 51505393及中央高校基本科研业务费专项资金项目A0920502051513-4资助
EFFECT OF CeO2 ON CORROSION BEHAVIOR OF WC-12Co COATINGS BY HIGH VELOCITY OXYGEN FUEL
Received date: 2016-01-18
Online published: 2016-08-18
Supported by
Supported by National Natural Science Foundation of China (Nos.51474178 and 51505393) and Fundamental Research Funds for the Central Universities (No.A0920502051513-4)
采用超音速火焰喷涂在Q345基体上制备了微米WC-12Co, 纳米改性WC-12Co和CeO2改性WC-12Co涂层, 利用SEM, XRD和显微硬度计等手段观察表征了涂层的微观组织、相成分和显微硬度, 通过LSCM, SEM, 极化实验和浸泡腐蚀实验等方法研究分析了涂层在1 mol/L H2SO4溶液中的腐蚀行为和腐蚀机理. 结果表明: 纳米CeO2的加入可以显著降低涂层的孔隙率, 有效减少局部腐蚀的发生; 同时添加纳米CeO2可以使涂层电极电位发生正移, 降低腐蚀电流密度, 生成稳定的钝化膜, 降低涂层的维钝电流密度, 提高涂层的耐腐蚀性能; 纳米CeO2改性WC-12Co涂层的腐蚀机制为由孔隙诱发的局部腐蚀, 孔隙处的Co黏结相不断被腐蚀导致WC颗粒失去了支撑作用而脱落, 从而露出新的Co黏结相, 促进了涂层的腐蚀, 使孔隙不断扩大形成腐蚀坑. 而微米WC-12Co涂层和纳米改性WC-12Co涂层不仅最外层的Co黏结相被腐蚀, 而且在孔隙处也发生了严重的局部腐蚀.
关键词： 超音速火焰喷涂,; WC-12Co涂层,; 纳米CeO2,; 极化曲线,; 浸泡腐蚀
岑升波 , 陈辉 , 刘艳 , 马元明 , 吴影 . CeO2对超音速火焰喷涂WC-12Co涂层腐蚀行为的影响*[J]. 金属学报, 2016 , 52(11) : 1441 -1448 . DOI: 10.11900/0412.1961.2016.00031
High velocity oxygen fuel (HVOF) sprayed WC-Co coating has been widely used in the surface protection of components for excellent corrosion resistance and wear resistance. However, with the increasing deteriorated service environment, higher comprehensive properties of WC-Co coating are required. Addition of rare earth elements into WC-Co powder is expected to be an effective way. In this work, the micro WC-12Co, nano modified WC-12Co and CeO2 modified WC-12Co coatings were prepared by HVOF on the Q345 steel substrate. The microstructure, corrosion morphology and phase structure of coatings were observed by SEM and XRD, and the micro-hardness is measured. The corrosion behavior of the coatings in 1 mol/L H2SO4 solution was investigated by polarization test and immersion corrosion test. The results show that the addition of nano-sized CeO2 in the WC-12Co coating not only purifies the grain boundary and increases the micro hardness, but also significantly reduces the porosity of the coating, which can effectively decrease the occurrence of local corrosion. Meanwhile, the addition of nano CeO2 can make the electrode potential of coatings shift positively, reduce the corrosion current density and passivation current density, and then improve the corrosion resistance of the coating. The corrosion mechanism of nano CeO2 modified WC-12Co coating is local corrosion which induced by the pore. Co bonding phase at the pore is constantly being corroded, causing WC particles to lose the support function and to fall off, which promotes the corrosion of the coating, so that the pores are enlarged to form corrosion pits. For the micro WC-12Co coating and nano modified WC-12Co coating, not only the outermost layer of the Co bonding phase is corroded, but also serious local corrosion occurred in the pores.
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