超音速火焰喷涂制备的WC-WCoB涂层在熔锌中的腐蚀行为及其耐蚀机理  

Corrosion Behavior and Corrosion Resistance Mechanism of HVOF Sprayed WC-WCoB Coating in Molten Zinc

作　　者：严细锋 王海滨[1] 仇庆凡 宋晓艳[1] YAN Xi-feng;WANG Hai-bin;QIU Qing-fan;SONG Xiao-yan(Key Laboratory of Advanced Functional Materials under the Ministry of Education of China, School of MaterialsScience and Engineering, Beijing University of Technology, Beijing 100124, China)

机构地区：[1]北京工业大学材料科学与工程学院新型功能材料教育部重点实验室,北京100124

出　　处：《表面技术》2019年第4期48-54,共7页Surface Technology

基　　金：国家自然科学基金青年项目(51601004);国家自然科学基金重点项目(51631002)~~

摘　　要：目的揭示新型WC-WCoB涂层在锌液中的腐蚀行为及耐蚀机理,从而提高WC基涂层的耐熔锌腐蚀性能。方法以WC、Co和WB粉末为原料,结合离心喷雾干燥和真空热处理,制备得到具有高球形度、结构致密的WC-WCoB热喷涂粉末喂料,并利用超音速火焰喷涂工艺进行涂层的制备。将涂层浸泡于熔融锌液中不同时间,观察其截面组织,以评价涂层的耐熔锌腐蚀性能,并通过X射线衍射仪、热重/差热分析仪、扫描电子显微镜、能谱分析仪对涂层进行结构、性能表征。结果 WCoB相与熔锌间不发生化学反应,制备的WC-WCoB涂层在锌液中浸泡达600 h时,仍未观察到Zn向涂层内的扩散,但在锌液中氧的缓慢作用下,涂层边缘处易产生微裂纹并逐步向内扩展,最终导致涂层材料逐层剥落。WC-WCo B涂层在腐蚀600 h后,完好区域面积占试验涂层总面积的56.3%。结论在传统WC-Co涂层中添加一定量的WB,可使Co相完全转化为WCoB相,与目前广泛使用的WC-η涂层相比,该研究制备的WC-WCoB涂层具有更突出的抗氧化性能,使其在锌液中由于氧化引起的裂纹形成扩展速率显著降低,宏观上表现出更强的耐熔锌腐蚀性能。The work aims to reveal the corrosion behavior and mechanisms of newly developed WC-WCoB coating against molten zinc so as to improve the corrosion resistance of WC-based coatings. WC-WCoB thermal spray feedstock powder with a high sphericity and high density was prepared by the centrifugal spray drying and subsequent vacuum heat-treatment with WC,Co and WB as raw materials. The coating was then fabricated by the high velocity oxy-fuel(HVOF) spraying technique. The cross-sectional microstructures of the coating after immersion in the liquid zinc for various periods were observed to evaluate the corrosion resistance. The composition, structure and oxidation resistance of the coatings were characterized by X-ray diffraction, thermogravimetric/differential thermal analysis, scanning electron microscopy and energy spectrum analysis. WCoB phase had no chemical reaction with the molten zinc. Besides, there was no evidence showing the diffusion of Zn into the prepared WC-WCoB coating even when the coating had been immersed into the liquid zinc for 600 h. However, the microcracks were easy to initiate at the outer surface of the coating due to the slow oxidation of oxygen dissolved in the liquid zinc. The cracks gradually propagated towards the inner and eventually led to the exfoliation of coating materials layer by layer. After the immersion in molten zinc for 600 h, the area without corrosion accounted for 56.3% of the total area of the WC-WCoB coating. The addition of a certain amount of WB to the conventional WC-Co coating can cause the entire transformation of Co into the WCo B phase. As compared to the currently widely used WC-η coating, the developed WC-WCoB coating in the present work exhibits much higher oxidation resistance. As a result, the formation and growth rates of the oxidation-induced cracks in WC-WCoB coating can be significantly decreased, which then contributes to better corrosion resistance to molten zinc at the macro level.

关 键 词：WCoB Η相 WC基涂层 抗氧化性 微裂纹 耐熔锌腐蚀性能 

分 类 号：TG172[金属学及工艺—金属表面处理] TG174.4[金属学及工艺—金属学]