| The polymer matrix composites have been more widely used in manufacturing sliding or rotating parts, therefore, it becomes very important to improve the friction and wear properties and service life of the polymer matrix composites. In this thesis, the self-excitation magnetic flux density during friction of the polymer composites can be adjusted by adjusting the ferromagnetic fillers, which can be used to optimize the friction and wear performance of the composites.In our work, PTFE was used as the matrix and three ferromagnetic powders (iron powder (Fe), cobalt powder (Co), nickel powder (Ni)) served as the fillers to prepare the PTFE composites. The frictional counterpart is made of45steel. The effects of the Fe size and content on the friction induced magnetization and its influence on the tribological properties of the Fe/PTFE composites were studied. After that, we mainly investigated the effects of two ferromagnetic fillers (Fe-Co, Fe-Ni and Co-Ni) and their content ratios on the friction induced magnetization and its influence on the tribological properties of the composites. The main results are as follows:1. Effects of ferromagnetic fillers on the friction induced magnetization:(1) The influence of a single ferromagnetic filler on the friction induced magnetization of the composites:In different Fe sizes, the friction induced magnetization△B of the composites increase with the increase of the average particle diameter of Fe. However, when Fe size increases to150um, the AB declines slightly. In different Fe contents,△B increases with the increase of iron content.(2) The influence of Fe-Co fillers on the friction induced magnetization of the composites:In different content ratios of Fe-Co,△B increases with the increase of the relative content of Co.(3) The influence of Fe-Ni fillers on the friction induced magnetization of the composites:In different content ratios of Fe-Ni,△B increases as the content of Ni decreases.(4) The influence of Co-Ni fillers on the friction induced magnetization of the composites:In different content ratios of Co-Ni,△B decreases with the increase of Co.2. Effects of ferromagnetic fillers on the tribological properties:(1) The influence of Fe on the tribological properties:In the cases with different Fe particle diameters, the friction coefficient of the composites decreases gradually with the increase in the particle diameter of Fe, but when the average particle size is more than115μm, the friction coefficient changes to increase. The trend of the wear of the composites was substantially same as that of the friction coefficient. Under different Fe contents, with the increase in the Fe content, the friction coefficient of the composites is substantially upward trend. But the wear is gradually decreased.(2) The influence of Fe-Co on the tribological properties:In different Fe-Co content ratios, the change of friction coefficient is small, and the trends for different Fe-Co content ratios are basically the same. With the increase of Fe-Co content ratio, the wear loss is a slightly upward trend.(3) The influence of the Fe-Ni on the tribological properties:In different Fe-Ni content ratios, the friction coefficient is a growing trend along with the increase in Fe-Ni content ratio, and the wear trend is basically the same with that of the friction coefficient.(4) The influence of the Co-Ni on the tribological properties:Under different Co-Ni content ratios, the friction coefficient gradually increases as Co-Ni content ratio increases. The wear trend is same to the friction coefficient.3. Fluence mechanism of friction induced magnetization on the tribological properties of the composites:(1) In the condition of a single ferromagnetic filler or several ferromagnetic fillers, with the enhancement of the friction induced magnetization, the friction coefficient and wear of the composites were downward.(2) The friction induced magnetic field can promote the ferromagnetic particles to adsorb onto the counterpart surface. These adsorbed particles can promote the formation and complete of the transfer film on the surface of45steel. Further, the friction induced magnetic field will also facilitate the ferromagnetic particles to move toward the friction surface, and to increase filler particles on the surfaces. |
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