Study On The Mechanism Of Tribo-magnetization On The Friction Transfer Of The Polymeric Composites Containing Ferromagnetic Particles

Friction and wear process is usually accompanied by a series of physical, chemical effects, but these effects have a significant impact on the process of material transfer and friction. In this thesis, ferromagnetic Ni particles were selected as filler in PTFE matrix. The tribo-magnetization of Ni/PTFE composites against 45 steel during friction and its influence factors were mainly studied. The quantitative measuring method of transfer film morphology was supposed. Also the transfer film morphology and tribological properties of the composites were correlated. The 3D laser scanning microscopy analysis was employed to characterize the three-dimensional topography of the transfer film formed on the counterface. The composition and morphology of the transfer film were further studied by SEM and energy dispersive spectroscopy (EDS). The anti-friction and anti-wear mechanisms of transfer film were also analyzed. The relationships between tribo-magnetization and friction transfer as well as tribological properties were analyzed in order to obtain the proper conditions of a high quality transfer film, which may provide a new way to active control of the tribological properties of polymeric composites.In our work, the main conclusions are listed below:1. The average tribo-magnetization intensity (ATMI) of the composites increased with the increase of the Ni particle size. The ATMI of the composites increased with the increase of Ni content. With the increase of sliding velocity, the ATMI gradually increased and increased rapidly at high speeds. The ATMI of the composites increased gradually with the load increase.2. Under different conditions, the friction coefficients of the composites were substantially the same trends in the test time. With the increase of the particle size, the average friction coefficient increased and the wear volume decreased. The average coefficient of friction with increasing filler content gradually increases, the wear volume of the composites decreases. The sliding speed has little effect on the average friction coefficient of the composites. When the sliding speed exceeded 0.4m/s, the wear of the composites was higher. With the increase of load, the average friction coefficient of composites decreases gradually, and the wear volume of the composite increases.3. The transfer film coverage area gradually increased and tended to be stable with the increase of filler content, and it will reduced when the filler content was too high. The average thickness of the transfer film gradually decreased with the increase of filler content and gradually increased as the filler particle size increased. The transfer film thickness firstly increased and then decreased with the increase of load. The low speed and light load were more conducive to the formation of transfer film with excellent tribological properties. The thicker the transfer film is, the more easily does the film peel off and the worse is the wear resistance.4. The formation of transfer film is related to the grinding direction of the counterface: when the sliding direction parallel to the grinding direction, it is difficult to form a continuous and uniform transfer film; when the sliding direction perpendicular to the grinding direction, the formed transfer film is more continuous and uniform.5. During friction polymeric composites were cut by the asperities on the metallic counterface, the local contact points on the counterface became the formation nuclei of the transfer film. The tribo-magnetization effect was in favor of increase of the nuclei. With the extension of friction, the transfer film gradually becomes continuous, uniform covered on the counterface, changing the frictional contact mode of the friction pairs.6. The tribo-magnetization can promote the transfer of magnetized metallic debris to the counterface and firmly adsorbed on the counterface. While the adsorbed metallic particles acted as the pins to protect the film to peel off, enhanced the adhesive strength of transfer film. It is expected that the quality of the transfer film could be controlled by adjusting the tribo-magnetization, so as to achieve the control of the tribological properties of the polymeric composites.