| Polymer based composites have been increasingly used as engineeringmaterials, in which the applications concerning tribology are the most. Thefrictional transfer often takes place in the process of friction of polymer basedcomposites, which results in the formation of a transfer film on the counterpartsurface. The transfer film plays a decisive role in tribological properties of thepolymer based composites. The formation of transfer film is affected by the frictioncondition, counterpart surface morphology, filler type and content, etc. Therefore,the PTFE based composites with Al2O3, or ZnO, or SiO2, or graphite, or TiC, or SiCas main filler were selected as studied materials. The transfer films were studiedunder different test conditions, such as different filler contents, different loads andsliding speeds, different surface textures. The morphological features of the formedtransfer film were observed and analyzed by Optical Microscope, ScanningElectron Microscope （SEM）, and so on. The mechanical properties of the transferfilm were examined by nano-indentation and nano-scratch method. The mainresults are listed below.（1） In our work, the filling effects of SiO2and TiC were the best of the sixkinds of fillers, the formed transfer films were better. The formation tendency ofthe transfer films of SiO2/PTFE and TiC/PTFE composites was gradually gettingbetter with the increase of the filler contents and becoming poor more than the bestcontent. And the transfer film of TiC/PTFE was thicker than that of SiO2/PTFE.The best content of SiO2and TiC was10%, the composites with the best contentshad good friction and wear properties, and the formed transfer films were moreuniform, denser, and smoother and flatter.（2） The load has an important influence on the transfer film, an appropriateload will promote the formation of transfer film. With the increase of load, thetransfer film became gradually continuous, uniform and dense. Under ourexperimental conditions, the best load for the best transfer film of SiO2/PTFE andTiC/PTFE composites were about471N.（3） The sliding speed also has an influence on the formation of transfer film.The best transfer film of PTFE based composites corresponds to a suitable slidingspeed, of course, different PTFE based composites may correspond to different optimum speed. For example, in our work, the best speed for the best transfer filmof SiO2/PTFE was0.1062m/s, and for TiC/PTFE was0.1327m/s.（4） The surface morphology of the transfer film formed on the counterfacewith different texture is quite different. The transfer film was relatively uniformand continuous but thinner on the0°textured surface. And the transfer film wascomplete and thicker on45°textured surface. However, of the three texturedsurfaces, the90°corresponds to the worst transfer film.（5） The nano-hardness and elastic modulus of the transfer film of SiO2/PTFEwere higher than those of Al2O3/PTFE, namely mechanical properties of thetransfer film of SiO2/PTFE are better than those of Al2O3/PTFE. The transfer filmof SiO2/PTFE is thinner than that of Al2O3/PTFE. The interfacial bonding strengthof the transfer film of SiO2/PTFE is greater than that of Al2O3/PTFE. The formationof the transfer film of PTFE composites is related to the interfacial bondingstrength of the film-to-counterface. The best transfer film not only has a higherinterfacial bonding strength, but also is beneficial to improve the tribologicalproperties of composites. |
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