Investigation on mechanism of the improvement in tribological properties of carbon fiber reinforced polytetrafluoroethylene composites by surface treatment

Tribological properties of polytetrafluoroethylene (PTFE) composites filled with differently surface treated carbon fibers (CF), sliding against GCr15 steel under dry sliding conditions, were investigated on a block-on-ring M-2000 tribometer. Experimental results reveal that rare earths (RE) surface treatment reduces the friction and wear of CF-reinforced PTFE (CF/PTFE) composites. Scanning electron microscopy (SEM) investigation of worn surfaces of CF/PTFE composites shows that cracks or pores are visible on the worn surfaces of untreated and air-oxidated composite, while no crack and very few pores present on the worn surface of REtreated composite. The fiber-friction-angling effect makes carbon fibers angled and oriented along the frictional shearing force, and finally parallel to the friction surface, which makes interfacial adhesion become a key factor to tribological properties of CF/PTFE composite. With strong interfacial adhesion between carbon fiber and PTFE after RE surface treatment, carbon fibers are not easily detachable from the PTFE matrix in the process of fiber-friction-angling, which prevents the rubbing-off of PTFE, and accordingly improves the friction and wear properties of the composite.