Effect of additives on EHD friction

Vast of lubricated machine elements consists of non-conformal contacts where EHD lubrication is present. In these contacts, full-film conditions are desired to reduce wear, but at the same time viscous friction within the lubricating film governs the friction performance of these contacts and thus energy losses. In our recent works it had been shown that tailoring the solid-liquid interface can be of the great importance in order to reduce coefficient of friction of EHD contacts with full-film conditions.

In this work it is shown how different additives and surface active agents effect on the solid-liquid interface by changing surface energy of steel surface or surface tension of lubricant and thus on wetting and how these changes further on effect on coefficient of friction for EHD contacts.

The tribological tests were performed on mini-traction-machine with ball on disc configuration at two different temperatures (25 °C and 100 °C). It is shown that the effect of additives is limited, but in some cases still significant and that their effect can be in terms either of increase either of decrease in coefficient of friction.

Keywords: Additives, EHD lubrication, solid-liquid interface, surface energy, surface tension.

Note:

This contribution has been selected for Oral presentation on Nordtrib 2020: The 19th Nordic Symposium on Tribology that should take place from 9th to 12th of June 2020 in Geiranger, Norway. But due to the Covid-19 issues the conference has been canceled.