In-situ nanopolishing by nanolubricants for enhanced elastohydrodynamic lubrication

This paper describes a method of utilizing oil-based nanolubricants containing abrasive nanoparticles for in-situ nanopolishing (ISN) of surfaces of rolling elements. Nanopolishing reduces the composite surface roughness of bearing elements and results in an increased film thickness ratio. Using a four-ball tester, the test and material conditions such as normal load, rotational speed, and initial surface roughness of balls were selected so that the initial film thickness ratio λ varied in the 1-3 range, i.e. within the partial (mixed) elastohydrodynamic (EHL) regime. The lubricant was either engine oil or engine oil-based nanolubricants containing diamond nanoparticles. The rolling ring track on the top ball was examined by a non-contact profilometer. The root mean square (RMS) roughness of the wear track using the nanolubricant was decreased. In-situ nanopolishing by the nanolubricant resulted in a significant increase in the film thickness ratio and a lower frictional torque.