电泳—电沉积Ni-PTFE复合镀层的制备及其摩擦学行为研究

发布时间：2018-06-22 02:12

本文选题：电泳沉积 + 电沉积　；参考：《南京航空航天大学》2015年硕士论文

【摘要】：将PTFE(聚四氟乙烯)颗粒加入到Ni镀层中制备出Ni-PTFE复合镀层,可以改善纯Ni镀层的摩擦学性能,从而获得具有良好的自润滑特性的镀层。以往的研究中,Ni-PTFE自润滑复合镀层通常采用复合共沉积和化学复合镀工艺进行制备。由复合共沉积工艺制备的自润滑复合镀层颗粒含量低,很难完全发挥颗粒的自润滑作用;由化学复合镀工艺制备自润滑复合镀层,镀液温度较高,并且容易发生分解,很不稳定,制备出的复合镀层也会存在应力裂纹的问题。为了提高复合镀层中PTFE的颗粒含量,改善镀层性能,本文采用电泳沉积和电沉积两步法进行了Ni-PTFE复合镀层的制备。该工艺首先在基体表面电泳沉积一层PTFE沉积层,然后通过电沉积将基质金属Ni嵌入到PTFE层的孔隙中,从而形成Ni-PTFE复合镀层。本文主要工作及结论如下:(1)开展了PTFE颗粒(5μm)的电泳沉积研究。探讨了电泳沉积的参数:电泳电压、电泳时间、PTFE浓度和Mg Cl2·6H2O浓度对PTFE电泳沉积的影响。研究发现,电泳时间、电泳电压和PTFE浓度均与电泳沉积量呈正比关系,但是电泳时间的延长会降低电泳沉积的效率并且影响电泳液的稳定性。Mg Cl2·6H2O浓度对电泳沉积层分布的致密度有重要影响。初期优化后的的电泳沉积工艺能够制备出均匀、致密的PTFE电泳沉积层。(2)通过正交试验对电泳-电沉积法制备Ni-PTFE复合镀层的工艺进行了研究,同时分析和总结了各工艺参数对复合镀层的性能的影响规律。研究发现,电泳-电沉积工艺能够显著的提高复合镀层中PTFE含量,该工艺能够制备出PTFE复合量高达63.4vol.%的Ni-PTFE复合镀层。电沉积阴极电流密度对复合镀层的镀速影响最大,同时电沉积阴极电流密度对复合镀层的厚度和沉积效率有重要影响。电泳时间对复合镀层的表面粗糙度和PTFE的复合量、显微硬度影响最大,电泳液中PTFE浓度的增加也会提高复合镀层中PTFE的复合量,但是此时PTFE的团聚现象较为严重。(3)研究了PTFE的复合量对复合镀层的摩擦学性能的影响。研究发现,随着复合镀层中PTFE粒子含量的增加,其自润滑性能得到了充分的发挥,复合镀层的摩擦学性能得到很大的改善。在复合镀层中PTFE体积分数为44%时,Ni-PTFE复合镀层具有最佳的减摩效果,此时的摩擦系数为0.067。当PTFE体积分数为63.4%时,Ni-PTFE复合镀层耐磨性最好。(4)采用电泳-电沉积法对制备Ni-PTFE-Al2O3复合镀层的工艺进行了探索,研究发现,相对于连续电泳沉积法而言,电泳共沉积法能够制备出较为均匀的电泳沉积层。同时,对制备出的Ni-PTFE-Al2O3复合镀层的耐磨性能与Ni-PTFE和Ni-Al2O3进行了对比研究。Ni-Al2O3复合镀层的耐磨性能最佳,Ni-PTFE-Al2O3复合镀层的耐磨性与镀层中的Al2O3颗粒和PTFE复合量密切相关,当Al2O3复合量较少时,其耐磨性比Ni-PTFE复合镀层差;当Al2O3复合量较高时,其耐磨性能要强于Ni-PTFE复合镀层。
[Abstract]:Ni-PTFE composite coating was prepared by adding PTFE (PTFE) particles into Ni coating. The tribological properties of pure Ni coating were improved and the coating with good self-lubricating properties was obtained. In the past, Ni-PTFE self-lubricating composite coatings were prepared by co-deposition and electroless composite plating. The self-lubricating composite coating prepared by the composite co-deposition process has low particle content and is difficult to give full play to the self-lubricating effect of the particles. The self-lubricating composite coating prepared by the electroless composite plating process has a higher bath temperature and is easy to decompose. Because of the instability, the composite coating also has the problem of stress crack. In order to improve the content of PTFE particles and the properties of composite coatings, electrophoretic deposition and electrodeposition were used to prepare Ni-PTFE composite coatings. Firstly, a layer of PTFE was deposited on the substrate surface by electrophoretic deposition, and then Ni matrix was embedded into the pores of the PTFE layer by electrodeposition to form Ni-PTFE composite coating. The main work and conclusions are as follows: (1) Electrophoretic deposition of PTFE particles (5 渭 m) was carried out. The effects of electrophoretic deposition parameters, such as electrophoretic voltage, electrophoretic time, PTFE concentration and MgCl _ 2 路6H _ 2O concentration, on the electrophoretic deposition of PTFE were investigated. It was found that the electrophoretic time, electrophoretic voltage and PTFE concentration were proportional to the amount of electrophoretic deposition. However, the increase of electrophoretic time will decrease the efficiency of electrophoretic deposition and affect the stability of the electrophoretic solution. The concentration of MgCl _ 2 路6H _ 2O has an important effect on the density of the electrophoretic deposit. The initial optimized electrophoretic deposition process can produce uniform and dense PTFE electrophoretic deposits. (2) the electrophoretic electrodeposition method was used to prepare Ni-PTFE composite coatings. At the same time, the influence of various process parameters on the properties of composite coating was analyzed and summarized. It was found that the electrophoretic electrodeposition process could significantly increase the content of PTFE in the composite coating, and the Ni-PTFE composite coating with 63.4 vol.% PTFE composite coating could be prepared by this process. The cathodic current density of electrodeposition has the greatest influence on the plating rate of composite coating, and the cathodic current density of electrodeposition has an important effect on the thickness and deposition efficiency of composite coating. The effect of electrophoretic time on the surface roughness and the composite amount of PTFE and microhardness of the composite coating was the greatest, and the increase of PTFE concentration in the electrophoretic solution also increased the composite amount of PTFE in the composite coating. However, the agglomeration of PTFE is serious. (3) the effect of PTFE composition on the tribological properties of the composite coating is studied. It is found that with the increase of PTFE particle content, the self-lubricating property of the composite coating is fully developed, and the tribological properties of the composite coating are greatly improved. When the volume fraction of PTFE is 44, Ni-PTFE composite coating has the best antifriction effect, and the friction coefficient is 0.067. When the volume fraction of PTFE is 63.4, the wear resistance of Ni-PTFE composite coating is the best. (4) the electrophoretic electrodeposition method is used to investigate the preparation process of Ni-PTFE-Al _ 2O _ 3 composite coating, and it is found that compared with the continuous electrophoretic deposition method, A more uniform electrophoretic deposition layer can be prepared by electrophoretic codeposition. At the same time, the wear resistance of Ni-PTFE-Al _ 2O _ 3 composite coating was compared with that of Ni-PTFE and Ni-Al _ 2O _ 3 composite coating. The wear resistance of Ni-PTFE-Al _ 2O _ 3 composite coating was closely related to the Al _ 2O _ 3 particle and PTFE composite content in the coating. The wear resistance of Ni-PTFE composite coating is lower than that of Ni-PTFE composite coating, and the wear resistance of Al _ 2O _ 3 composite coating is better than that of Ni-PTFE composite coating when the amount of Al _ 2O _ 3 composite coating is higher.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB306

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