The wear and friction in the pitch region of the centre of polymer gear teeth are not well understood. The transition around this point of the tooth between rolling and sliding has an important effect on the durability of polymer gear drives and can be simulated using a twin-disc configuration. This paper investigates the rolling–sliding wear behaviour of two poly-ether-ether-ketone (PEEK) discs running against each other with a simplified method of analysing and understanding the dynamic response of high performance polymeric gear teeth.Tests were conducted without external lubrication over a range of loads and slip ratios, using a twin-disc test rig. The wear and friction mechanisms were closely related to surface morphology, with changes in crystallinity correlating with the severity of operating conditions. Observed failure mechanisms were also related to the structure of the contact surfaces, and included surface melting and contact fatigue.Overall the PEEK discs were capable of running at low slip ratios for both low and high loads. Their performance reduced with an increase of the slip ratio. The results presented can be used in conjunction with the design process to allow the PEEK to be engineered for a specific high performance gear contact conditions

This paper describes a study of the influence of soot contamination on the tribological behavior of engine lubricants. The candidate lubricants were a formulated engine lubricant, (CD SAE 15W-40) and a base oil (150SN). Soot particle contamination was simulated using carbon black with friction and wear measured using a four-ball tribometer. The results show that the antiwear and antifriction properties of the CD SAE 15W-40 formulated oil with varying carbon black contents were better than those of 150SN base oil. The antifriction properties of the SAE 15W‐40 formulated oil with the addition of 2wt% carbon black were strengthened. This was ascribed to uniformly dispersed carbon black and the additives in the CD SAE 15W-40. The antifriction properties of the 150SN base oil with 2, 4wt% carbon black content were upgraded via the addition of 2wt% dispersant polyisobutylene succinimide. The tribological effect of the carbon black in the lubricants was attributed to absorption and agglomerate effects