Reciprocating sliding wear behaviour of PEEK-based hybrid composites

•The tribological behaviour of PEEK hybrid composites in sliding contact was studied.•Transfer film formation was examined by dark field imaging and optical microscopy.•Transfer film area was calculated by segmentation technique.•The calculated area was used in the analytical model.•A mathematical model was developed based on a dimensional analysis.

The present research deals with the effects of fillers in Polyetheretherketone (PEEK) based hybrid composites from the view point of mechanical and tribological properties. In this background, nano-sized silica (SiO2), short carbon fibre (SCF), graphite, titanium dioxide (TiO2) and zinc sulphide (ZnS) were added as the additives. Reciprocating sliding wear tests (flat-on-flat) against AISI 52100 bearing steel were performed at contact pressures ranging from 4 MPa to 10 MPa and with sliding velocities of 20 mm/s and 50 mm/s. Under most test conditions, the nanoparticles reduced the friction coefficient. The morphologies of the worn surfaces and the transfer films, were observed by surface topography (ST), optical microscopy (OM) and scanning electron microscopy (SEM). A dimensional analysis was used to evaluate the influence of nanoparticles on transfer film formation on bearing steel counter surface. It is evident that the effect of nanoparticles on wear rate depended on the contact pressure and sliding speed. Results indicated a limited wear resistance for neat PEEK, but PEEK filled with nano-sized silica exhibited superior wear resistance at the highest contact pressure for both sliding speeds. The nanoparticles seem to have a polishing effect on the steel counter surface. The nanoparticle additives may account for their lower friction coefficient and improved wear resistance in comparison to micro-particle-filled and unfilled PEEK. The output from the dimensional analysis based on transfer layer characteristics is in good agreement with the friction result.