Effect of Lubricant Contaminants on Tribological Characteristics During Boundary Lubrication Reciprocating Sliding

This article presents the effect of the presence of solid contaminants, in engine lubricating oil, on the tribological parameters, which impact negatively on the performance of the engine and increase fuel consumption. This study revealed that the lubricant was contaminated by Fe, Cu, Al, Pb and SiO2 particles. The tribological tests were performed using 0.63, 0.85 and 1.1 m s-1 average sliding speeds and 120 N contact load to mimic the boundary lubrication regime of the sliding reciprocating motion of the piston ring/liner interface in an engine. The presence of the solid contaminants in engine oils leads to an increase in friction coefficient, wear and frictional power losses, increasing the surfaces roughness as a consequence. The results showed that grain size and concentrations strongly affected the tribological parameters. In order to minimize the effect of solid contaminants, it is necessary to improve the filtration accuracy for lubricating oils.