FRICTION TORQUE IN THRUST BALL BEARINGS LUBRICATED BY GRAPHENE-ENRICHED GREASE WITH A MODIFIED PIN-ON-DISC METHOD

This paper describes a special test setup developed for simplified tribological testing on thrust ball bearings with a pin-on-disc tribometer. The rolling friction force was measured with a portion of a bearing while reproducing the actual rolling motion of the spheres inside the raceways. The friction torque expected for an entire bearing in equivalent operative conditions was also estimated through an analytical model and validated with the SKF Model of Friction. The proposed testing methodology was exploited to investigate the effect on rolling friction by graphene as an additive for greases. Graphene-grease compounds were prepared with increasing graphene content and rolling friction tests were carried out in grease lubrication conditions. The impact of increasing load and speed was investigated and associated with the quantity of graphene in the grease. The results proved that enriching grease with graphene is generally not beneficial on rolling friction. The friction force measured by the tribometer increased with increasing the graphene content in the specific test conditions explored here.