Study On The Tribological Properties Of Filled PTFE Three-layer Composite Materials

The three layer composite (DU material) with steel backing - porous bronze sinter -modified PTFE is a new type of self-lubricating composite, it is widely used because of its good tribological properties under oilless conditions. In this thesis, the tribological properties of the PTFE composites with the fillers, such as graphite (GR), molybdenum disulfide (M0S2), calcium fluoride (CaF₂) and Ekonol, were investigated in detail by adding the as-mentioned fillers individually and multiply. The wear mechanisms of the PTFE composites were also analyzed.The results showed that when the fillers were added individually, the coefficient of friction of the composites increased with the increase of the filler content, meanwhile the wear of the composites decreased obviously, which means that the filler can improve the wear resistance of the composites. When filled with several fillings, the wear of composites decrease more, so we can use several fillings to improve the materal's anti-wear property. When filled with GR, the composite had a smaller coefficient of friction compared with other fillers, but a larger wear; the wear of the composites was smaller filled with M0S2 or Ekonol than filled with GR. The tribological properties of the composites filled with CaF₂ were worse under the dry friction conditions, but can be improved by oil-soaked method. The observation of the worn surfaces revealed that the wear mechanism of the filled composites is the easy formation of the transfer film and the small sheet debris unlike the wear performance of pure PTFE with strip-like damage. When the fillers were added multiply, the composites exhibited a greatly improved wear resistance although there was a small increase in coefficient of friction. Therefore the composites with several fillers were used in many applications due to their super synthetical tribological performance. The wear mechanism of the composites filled with several fillers was the formation of the transfer film with small sheets of debris.