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.