Abstract

This article explores the influence of the appearance of micropitting in different types of additives added to a polyalphaolefinic low-viscosity base oil, namely a polyalphaolefin PAO6. Additives commonly used in mechanical transmissions by gears were used, i.e., extreme pressure, anti-wear and friction modifier. For the study, we have conducted a series of tests on a disc machine under various operating conditions. The temperature and surface roughness of the test specimens have been changed in order to study different lubricant specific film thicknesses, as the last is one of the most influential parameters on the appearance of micropitting. Tests have shown the important influence of the additives, and their concentration, in the development of micropitting and their associated effects, depending on the operating conditions of the contact. Along with the study of the effect of additives, the influence of specific film thickness on the friction coefficient, surface appearance, conditions of lubrication, and wear was also studied. (C) 2014 Elsevier B.V. All rights reserved.