An investigation of the friction and wear properties of nanometer Si3N4 filled PEEK

The nanometer Si3N4 filled polyetheretherketone (PEEK) composite blocks were prepared by compression molding. The friction and wear properties of nanometer Si3N4 filled PEEK were investigated on a block-on-ring machine by running the PEEK composite block against a plain carbon steel (AISI 1045 steel) ring. The morphologies of the wear traces and the transfer film were observed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was found that nanometer Si3N4 filled PEEK composite exhibits considerably lower frictional coefficient and wear rate than pure PEEK. Especially, the lowest wear rate is obtained with the composite containing 7.5 wt.% Si3N4. The SEM pictures of the wear traces indicate that with the frictional couple of carbon steel ring/composite block, a thin, uniform, and tenacious transfer film was formed on the ring surface, while XPS results show that Si3N4 was partly oxidized into SiO2 during the rubbing process. Thus the improvement in the tribological behavior of nanometer Si3N4 filled PEEK composite is closely related to the improved characteristics of the transfer film.