| Due to its excellent property of self-lubricating and corrosion resistance, Ni-PTFE composite coating prepared by electrodeposition can effectively reduce the frictional wear and corrosion of friction pairs under unlubricatingfirction, which has great significance of improving the reliability of equipments and reducing the consumption of resources and energy. However,the hardness and bearing capacity of Ni-PTFE composite coatings are relatively low and accordingly the coatings appear to be seriously worn. Therefore, improving the hardness and wear resistance of self-lubricatingcoatings to make them retain good self-lubrication become the primary research direction of self-lubricating coatings.The traditional method of Strengthening coating is added hard particles into the bath. But particles easy to agglomerate in the bath and in the coating are unevenly distributed, no significant performance improvement.In this paper, experiments were designed and Ni-PTFE composite coatings were prepared using the method of combining the composite electrodeposition technology and nano-sol technology. The nanophased TiO2 was added in the form of sol to strengthen the electrodeposition coatings, which obtained the Ni-TiO2 and Ni-PTFE-TiO2 coatings. The effect of added nano-sol TiO2 on the structure and performance of pure Ni coating and Ni-PTFE coating was investigated. In the experiment, pretreatment process,experiment processing conditions, addition of particles and selection of particles were optimized to obtain the optimum coatingspreparation method and improving the hardness, wear resistance,lubricating property and bonding strength. In order to investigate the property of researched coatings, hardness test, micro-morphology test, composition analysis, deposition rate calculation,bond strength test and friction-wear test were carried out.Particles PTFE in the experiment were extremely hydrophobic and the reinforcement particles of nano-sol TiO2 were apt to agglomerate. In order to make the particles disperse uniformly in the solution, through a large number of experimental analysis,non-ionic surface active agent TX-10 was added into the electrolyte. The concentration of particles PTFE and nano-sol TiO2 in the electrolyte were 30g/L and 30ml/L respectively. Another process which had great influence on the quality of coating was the pretreatment process. So the author normalized the process and degree of pretreatment.Results show that Ni based coating incorporating particles PTFE has higher hardness,bonding strength and better tribological properties by contrast to pure Ni coating. Ni-PTFE composite coating obtained in the optimum condition owns thethe peak hardness at 400HV and its corresponding frictional coefficient is 0.1463. Furthermore, the bonding strength and micro hardness of Ni-TiO2 and Ni-PTFE-TiO2 coating are improved remarkably and wearing mass loss is greatly reduced by contrast to the Ni coating and Ni-PTFE coating. As to the micro-morphology, the added nanophased TiO2 refines the grain size of composite coatings. The grains of Ni-TiO2appear to be the shape of needle and own the size of nanometer and unregular distribution. Ni-PTFE-TiO2 composite coating has very fine grains and sharp comers appear on the refined grains. Result of composition analysis shows that element Ti from reinforcement particles TiO2 has weight proportions ranging from 0.2%-0.6%. in the composite coatings. The incorporation of nanophased particles improves the wear resistance and hardness of Ni-PTFE composite coating greatly, which makes the coating retain the good self-lubricating performance. |
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