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目的：提高镁合金有机涂层的耐磨性能。方法用KH450硅烷改性SiO2粉体,并充分分散于电泳漆中。用KH460硅烷预处理镁合金表面,并阴极电泳复合涂层。通过铅笔硬度测试、摩擦磨损实验、画圈附着力测试、NMP ( N甲基吡咯烷酮)试验和Machu试验,分别评价阴极电泳涂层的硬度、耐磨性能、附着力、抗NMP溶胀性能和耐蚀性,并通过扫描电子显微镜和光学显微镜对磨痕形貌进行分析。结果在镁合金用KH460预处理的前提下,添加SiO2粉体使涂层硬度由4H上升为5H,同时也提高了涂层的耐蚀性,并且涂层的附着力保持为1级,抗NMP溶胀性能仍>120 h。在预处理镁合金基体上制得的原漆涂层和添加纳米SiO2的涂层耐磨性较好,磨痕深度与涂层厚度的比值分别为0.47和0.475,摩擦系数均低于0.4；在未预处理镁合金基体上制备的原漆涂层和在预处理镁合金基体上制备的添加微米SiO2的涂层耐磨性较差,磨痕深度与涂层厚度的比值分别为0.665和0.673,摩擦系数均大于0.7。四种涂层磨损破坏的机制主要为疲劳破坏。结论 SiO2粉体的加入可以有效提高涂层的耐蚀性和铅笔硬度,同时不降低涂层的附着力和抗NMP溶胀性能。用硅烷对镁合金进行预处理,向电泳漆中添加硅烷处理的纳米SiO2,可有效提高阴极电泳涂层的耐磨性。

ABSTRACT:Objective To improve the abrasion resistance of organic coating on magnesium alloys. Methods In this paper, SiO2 powders were modified with KH450 silane and dispersed in electrophoretic paint. The surface of magnesium alloys was modified by KH460 silane,and then composite cathode electrophoresis coatings were prepared on it. The pencil hardness test, friction and wear test, circle adhesion method,NMP ( n methyl pyrrolidone) test and Machu test were taken to value the hardness, wear resistance, adhesion, anti-swelling properties of NMP and corrosion resistance of electrophoresis cathode coatings, respectively. Their morphol-ogies were studied by SEM and optical microscopy ( OM) . Results The pencil hardness of the coating,which was prepared on the magnesium alloy modified with KH460, was improved from 4H to 5H by adding SiO2 powders and the corrosion resistance was also increased. And their adhesion and anti-swelling properties of NMP were still kept at 1 class and >120 h respectively. The original coating and the coating containing Nano SiO2 powder, both prepared on the magnesium alloy modified with KH460, had good wear resistance, and their ratios of wear scar depth and coating thickness were 0. 47 and 0. 475 respectively, their friction coefficients were lower than 0. 4. The coating prepared directly on magnesium alloy and the coating containing Micron SiO2 powder prepared on the magnesium alloy modified with KH460 had poor wear resistance, and their ratios of wear scar depth and coating thickness were 0. 665 and 0. 673 respectively, friction coefficients of them were higher than 0. 7. The mainly wear failure mechanism of the four coatings was fatigue failure. Conclusion The addition of SiO2 powder can improve the corrosion resistance and pencil hardness of coatings effectively, and did not decrease adhesion and anti-swelling properties of NMP. The pretreatment of magnesium alloy with silane and the addition of Nano SiO2 in the electrophoretic paint can improve the wear resistance of coating.