Micropitting Performance of Oil Additives in Lubricated Rolling Contacts

Abstract

International audienceIn the present study, an existing theoretical micropitting model, based on the competitive interaction between surface fatigue and mild polishing wear, is employed to predict the effects of different base oil/additive solutions and the relative humidity of the environment on micropitting damage. These effects, though expected to be tribochemical in nature, manifest themselves mechanically; for example, by possibly affecting the fatigue strength of the surface and increasing or reducing the boundary friction and/or the mild wear rate, which altogether may cause an appreciable influence on the degree of micropitting. The present model takes into account only the last two issues (i.e., the change in boundary friction and wear) due to the presence of additives; nevertheless, it is able to predict their performance under micropitting conditions in most cases, showing good agreement with the corresponding experimental data. The results of the present work establish the basis of a blueprint for selecting oil additives for bearing applications

Tribochemical study of micropitting in tribocorrosive lubricated contacts: The influence of water and relative humidity

“…Furthermore, AW additives have been shown to accelerate micropitting [33][34][35][36]. ZDDP can rapidly form a tribofilm on the surface resulting in a delayed effect on proper running-in wear and increasing the probability of asperity-asperity contact.…”

“…In order to study the effect of dissolved-water, the rig is coupled with a humidifier capable of applying different RH values. The MPR rig has been described in Morales-Espejel and Brizmer et al [34,35].…”

A Model for Rolling Bearing Life with Surface and Subsurface Survival—Tribological Effects

“…Because of this, there is an increased need for more versatile or generalized rolling bearing life models, able to adapt and incorporate new developed knowledge about the tribology of surface initiated failures of the rolling contact. Despite the progress achieved in the last few years in the numerical modeling of the tribology and surface performance of rolling contacts (e.g., Epstein,et al (16), (17); Morales-Espejel and Brizmer (18); Morales-Espejel and Gabelli (19); Brizmer, et al (20); Warhadpande and Sadeghi (21)), the integration of this new knowledge into an engineering model for bearing life estimation is, to some extent, hindered by the simplicity of present standardized life rating formulation (ISO 281:2007 (15)), which only relies on averaged global de-rating factors. This approach, although sufficient for most common situations, is not designed to give an account and differentiate among surface/subsurface competing failure modes that may occur in a bearing when exposed to a hostile environment and tough operating conditions.…”

Generation of wear particles in lubricated contcats during running-in

“…Brizmer et al [104] introduced the influence of the additives on the micro-pitting behavior by taking into account a modified boundary coefficient of friction and a wear rate. Bosman and Schipper [97,105] developed a mechano-chemical model to calculate wear.…”

“…Morales-Espejel et al [89,90] combined a cumulative damage model and a local Archard wear equation to simulate the generation of micro-pits. They observed a good agreement with the experimental data in the prediction of the size of micro-pits [89] and the topography evolution [91].…”