Friction characterization when combining laser surface texturing and graphite-based lubricants

Abstract

The present work analyzes the friction capabilities at room temperature of three types oflubricants (denoted as A, B and C) with a graphite concentration of 5%. To do that, thestandard pin-on disc test is deployed to study the variation of the friction coefficient whencombining these graphite-based lubricants with surfaces made by grinding and differentlaser surface textures. These lubricants are characterized by measuring the percent of thechemical elements, the average size of the graphite particles and the kinematic viscosity.The experiments show that the lubricant B combined with a higher density of LST presentsthe lowest friction coefficient of about 0.24. Additionally, assuming a hydrodynamic regimefor the textured surfaces, the fluid dynamics simulations carried out as part of the studyshowed, in agreement with the experimental measurements, the lowest friction coefficientvalue for a textured surface with the highest dimple density. This seems to be associatedto the combined effect of an increase of the hydrodynamic pressure with a weak vortexformation within the dimples, due to the low distortion of the streamlines which, ultimately,attenuates the friction coefficient between the surfaces.