Graphite nanoplates as grease lubricant additive

This paper presents the results of a study of the effect of the graphite nanoplates (GNP) concentration on the tribological and rheological characteristics of grease lubricants based on used motor oils and calcium soaps. GNP were obtained by the original electrochemical method. Grease lubricants were tested for residual water content, dropping point, penetration, and wear limit. The size of wear spot was determined using a four-ball friction machine. It was found that by GNP content increasing the water content monotonically rises from 0.6 to 2.3 wt. %. The penetration decreases from 44 to 31 mm with increasing GNP content. Also, the dropping point rises from 79 to 88 degrees C at the GNP concentration of 150 ppm, and then decreases to 81 degrees C. The minimal size of wear spot (0.215 mm) is also observed at a GNP concentration equal to 150 ppm. It is 25.1% lower than that of the control sample that does not GNP contain.