Evaluation of Tribological Behavior of PEEK Composite Bearing Using Thermal Decomposition Analysis of Wear Debris and Its Application to Condition Monitoring

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The friction and wear behaviors of PEEK composite were studied under severe lubricated conditions such as high load and high sliding velocity. Wear debris was analyzed using thermal decomposition analysis, spectrometric oil analysis procedure (SOAP), laser diffraction particle size analyzer and ferrographic technique. The following conclusions were obtained.1.The sudden transit from mixed lubrication to seizure occurred at a certain load in both of white metal and PEEK composite, as the load increased.2.The onset of seizure in PEEK composite was strongly dependent on the ring temperature. As the ring temperature reached about 100℃, the transition from fluid lubrication to mixed lubrication occurred. When it was over 180-190℃, seizure occurred.3.Severe plastic flow and tearing type fracture were predominant on the wear scars of PEEK composite in seizure. Thus It was suggested that seizure caused severe plastic flow of PEEK material due to softening and melting at high temperature and might lead to failure of PEEK composite bearing.4.Seizure could be characterized by generation of cylindrical, ribbon-like, plate-like and carbon fiber war debris. Most of them were less than a few tens micrometer in size.5.The thermal decomposition analysis could detect PEEK wear debris because it was decomposed into phenol at high temperature. However, the amount of PEEK wear debris generated in laboratory test was only a few. In order to increase the detection accuracy, it is indispensable to develop new method for concentration of oil sample in a short time. This is the subject in future. Thus, it was suggested that the thermal decomposition analysis had a high potential as a failure diagnosis tool of PEEK composite bearing as well as other wear debris analysis.