Study On The Controllability Of The Friction Interface Transfer Of The PTFE Composites Containing Ferromagnetic Fillers By The Friction Induced Magnetization

The friction induced magnetization (FIM) phenomenon and the transfer film of the friction pair of FeNi50/PTFE composites and45steel were mainly investigated in this thesis. The relationship between the FIM and the friction transfer as well as the tribological properties was discussed, which may provide a new way to control the transfer film and to improve the tribological properties of polymeric composites.According to our experimental results, some conclusions can be obtained as follows:1. Effect of filler on the FIM of the compositesWith the increase of the filler content, the average FIM intensity of the composites increases linearly. With the increase of the filler size, the average FIM intensity of the composites decreases when the filler content is a certain value. With the increase of velocity, the average FIM intensity of the composites increases. With the increase of applied load, the average FIM intensity of the composites increases.2. Effect of filler on the tribological properties of the compositesWith the increase of the filler content, the average friction coefficient of FeNi50/PTFE composites increases slightly and the wear loss decreases. The influence of particle size on the friction coefficient is small, which becomes stable at about0.16. With the increase of the filler size, their wear loss increases. With the increase of velocity, the average friction coefficient decreases, and when the velocity is more than0.3m/s, their wear loss increases rapidly. With the increase of load, the average friction coefficient increases at first and then decreases, however, their wear loss increases rapidly.3. Effect of filler on the friction transfer of the compositesThe radial distribution of the transfer film is wave-like, and its thickness isn’t constant. The transfer film thickness increases as the velocity increases rapidly at first, then becomes stable at about2.0μm. With the increase of load, the average thickness of the transfer film increases at first and then decreases, the maximum value is around2.4um at3.5MPa. With the increase of filler size, the average thickness of transfer film increases at first and then decreases, and the maximum value appears at81μm. With the increase of the filler content, the average thickness of transfer film decreases. When the content is more than10%, the average transfer film thickness is almost the same. With the increasing of time, the average thickness of transfer film increases at first and then reaches a stable value.4. Formation process of the transfer filmThe formation process of the transfer film is considered including three stages as described below.The first stage is the nucleation stage of the transfer film. At the friction initial stage, some of the worn particles of the PTFE composites is transferred into the grooves in the counterface, and some of the composites is transferred on to the counterface by adhesive wear.The second stage is the growth stage of the transfer film. With the continuous friction, the worn particles will partially accumulate around the nuclei to cause the growth of the transfer film. At the same time, many new nuclei also generate, for example, the magnetized alloy debris are readily to adhere on the counterface to form the nuclei, which will promote the growth of the transfer film and act as the "pins" to fix the formed film.The third stage is the transfer film stable stage. The lateral growth of the transfer film gradually causes the connection of the individual parts evenly distributed on the counterface. The transfer film will be partially damaged and repaired constantly during friction. In fact, there is a dynamic equilibrium between the transfer film peeling and repairing in this stage.5. Relationship between FIM and tribological properties or friction transferWith the increasing of FIM intensity of FeNi50/PTFE composites, the friction coefficient decreases and the wear loss increases slightly. The transfer film thickness increases at the initial stage as the FIM intensity increases, then the thickness will be a stable at about2μm.