Friction and Wear of a Nano ZrO2 Particle Filled PEEK-Matrix Composite with Short Carbon Fibers and PTFE Particulates

Abstract

Effects of adding nano-size zirconium oxide (ZrO2) particles were investigated on friction, wear and flash temperature of carbon-fiber reinforced PEEK-matrix composite with solid state lubricant PTFE. A fabrication technique, using hot pressing method, is developed to manufacture the composite with distinct nano particle dispersions of different volume fractions of ZrO2. The morphology and microstructure of the nano composite were characterized with differential scanning calorimetry (DSC) and X-ray diffraction (XRD), and also with scanning electron microscopy (SEM) and high-resolution optical microscope. The nano oxide addition on changes in glass transition, melting and crystallinity of PEEK matrix with PTFE fillers and carbon fibers in the composite were thoroughly examined. Tribological tests were conducted, using a pin-on-disk tribometer. The effects of nano ZrO2 dispersion on friction, wear and flash temperature of the composite sliding in different directions on principal material planes were investigated. The tribological properties of the nano composite were very sensitive to the addition of even a small amount of nano-size ZrO2, but the effect depended on sliding directions and planes due to processing-induced carbon fiber orientation. The maximum reductions in coefficient of friction (64%), specific wear rate (82%) and flash temperature (49%) were obtained with adding up to 5% (by volume) nano ZrO2 to the PEEK/PTFE blend matrix. The mechanisms and characteristics of reduction in friction, wear and flash temperature were addressed. The critical and complex interaction between carbon fibers and ZrO2 nano particles during friction and wear were discussed.