等离子喷涂WC-10Co-4Cr涂层的组织演变与抗腐蚀磨损性能

Microstructure Evolution and Corrosion Wear Resistance of Plasma Spraying WC-10Co-4Cr Coatings

为提高不锈钢表面的抗腐蚀耐磨损性能,利用等离子喷涂的方法制备了2种晶粒尺寸的WC-10Co-4Cr涂层,采用SEM及EDS、XRD表征了涂层的组织和物相结构,进行了不同温度下的摩擦磨损试验,研究分析了晶粒尺寸对涂层组织与摩擦性能的影响。研究表明:WC-10Co-4Cr涂层微观结构中包含WC、W2C、W6Co6C,还存在Co/Cr(W,C)、W2(C,O)相;微米涂层中存在析出的W2C沿WC颗粒表面外延生长的包覆结构,而纳米WC涂层中,团聚粒子沿扁平粒子边界收缩,减少了扁平粒子内部的垂直贯穿裂纹。在室温和200℃时,纳米WC-10Co-4Cr涂层的摩擦系数与平均磨损率均优于微米涂层。纳米WC-10Co-4Cr涂层在室温磨损的机制为硬质颗粒诱发的犁削磨损,在200℃时为以粘着磨损为主与微域犁削相结合的磨损形式。在3.5%NaCl溶液中的电化学特性显示,WC-10Co-4Cr涂层将1Cr18Ni9Ti基体的腐蚀电位由–612m V提高到–317～–252 mV,腐蚀倾向得以减弱。

In order to improve the corrosion and wear resistance of stainless steel surface, WC-10 Co-4 Cr coatings with two kinds of grain sizes were prepared by plasma spraying. The microstructure and phase structure of the coatings were characterized by SEM, EDS and XRD. The effects of grain size on the microstructure and friction properties of the coatings were studied. The result shows that they contain WC, W2 C and W6 Co6 C;in addition, the W/C(W, C) and W2(C, O) phases are also present in the coatings. In the micro coating, there is a classical structure of precipitated W2 C epitaxially grown along the surface of WC particles, while in the nano coating, the agglomerated particles contract along the boundary of the flattened particles, thereby reducing vertical-through cracks in the flat particles. At different temperatures, the friction coefficient and wear rate of the nano WC-10 Co-4 Cr coatings are better than those of micro-coatings. The wear mechanism of nano WC-10 Co-4 Cr coating at room temperature is the plowing wear induced by the hard particles;at 200 °C, it is a combination of micro abrasive ploughing and adhesive wear. The electrochemical characteristics in 3.5% NaCl solution show that the corrosion potential of the 1 Cr18 Ni9 Ti substrate increases from ?612 mV to?317~?252 mV, which reduces the corrosion tendency.