| In this thesis, the friction induced magnetization as well as its effects on thefriction transfer and the tribological properties of the polymeric composites containingferromagnetic fillers were mainly studied. Through the analysis of the friction inducedmagnetization we can further find new ways to improve the friction transfer and thetribological properties of the composites.In our work, three ferromagnetic powders (Fe powder, FeSi powder, FeAl powder)were selected as fillers to prepare the PTFE composites. The friction inducedmagnetization and its effects on the friction transfer and the tribological properties ofthe composites were studied under different conditions such as filler particle size,content, load and sliding velocity. The friction induced magnetization and friction andwear were recorded and characterized by using optical microscopy, scanning electronmicroscopy, energy depressive spectroscopy and Hall-type milliteslameter. The resultsshowed that:1. The effect the particle size of the ferromagnetic fillers on the frictionmagnetization was stronger, and the tribo-magnetization of the larger particles was moreobvious. Due to the limited content of ferromagnetic particles, the generated magneticflux density of the composites during friction was much weaker than that of the bulkferromagnetic materials. The increase of speed reduced the magnetization effect; but theincrease of load increased the magnetization effect.2. There were little differences in the friction coefficients of the tested three kindsof composites in our test conditions. The friction coefficient of the Fe/PTFE compositewas slightly higher than those of the FeSi/PTFE and FeAl/PTFE composites. With theincrease in speed and load, the wear resistances of the FeSi/PTFE and FeAl/PTFEcomposites were better than that of the Fe/PTFE composites, and the wear resistances ofFeSi/PTFE and FeAl/PTFE composites were very close each other.3. There are two main effects of tribo-magnetization on the friction transfer andtribological properties. On the one hand, the tribo-magnetization is good for the debris easily absorbed to the counterface (45steel), promoting the formation and stability ofthe transfer film. On the other hand, the ferromagnetic particles off the matrix aredifficult to depart from the friction surface by the tribo-magnetization effect, and theadsorbed transfer film or some debris are absorbed on the composite surface. Theexistence of the transfer film changes the friction interface of polymer-metal to that ofpolymer-polymer, which reduces the friction coefficient of the composites. |
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