InterEHL - Novel design of EHL contacts by employing solid-liquid interface phenomena

Project duration

2019 - 2021

Project Category


Contact Information

doc. dr. Marko Polajnar


TOTAL Marketing & Services, France

Oerlikon Sorevi S.A.S., France

Prosed project focuses on the design of novel and innovative elasto-hydrodynamic (EHD) contacts that provide remarkably low energy losses due to significantly reduced friction at the solid-liquid interfaces in fully-realistic lubrication conditions.

Namely, in the last years, we succeeded to make one of the major lubrication step-changes and present an immensely reduced friction due to a completely new lubrication phenomena at the macro-scale EHD contacts; i.e. the lubricant slip at the surface wall. We were the first to report on almost 50 % reduction of friction in EHL contacts – by changing the wetting and polar surface energy of solid surfaces and tailoring them for a lubricants surface tension. This paramount achievement gained great attention in scientific and industrial community. However, this breath-taking phenomenon has only been confirmed in pure base oils, while for the success in industrial and automotive applications, it has to be confirmed in realistic oils, namely fully formulated oils. Due to additives competition and even stronger “passivation” of the surfaces, the outcome of this project is very promising and may completely change the future additive technology and result in an immensely reduced energy consumption due to friction, which in total accounts for 25 % of all energy produced world-wide.

In this project, we will innovatively design extremely-efficient EHD contacts, with taking into an account interactions and phenomena at the solid-liquid interface that significantly effect EHD friction. To achieve this, low-surface energy, slip-inducing DLC coatings will be combined with formulated-oils by employing both, the coatings and oils that are commonly used in automotive and industrial applications. To provide proof-of-concept for this project, we already possess supporting results with some DLC coatings and some formulated oils, but this has to be systematically and scientifically confirmed in a broad range of contact conditions and materials used. Therefore, for actual industrial implementation, this concept should be proven for several commonly used formulated oils, DLC and other surfaces, together with complete and in-depth understanding of the effect of all the additives in formulation on solid-liquid interactions. Proposed project will thus address a paramount scientific goal: to find fundamental understanding and synergistic effect of additives and DLC coatings, on lubricant-DLC interactions to achieve solid-liquid slip that will provide significant EHD friction reduction in real-engineering contacts.

To achieve this goal following tasks will be tackled in the proposed project:

1. The effect of oil additives on surface properties of oils will reveal how oil surface tension that significantly define the strength of solid-liquid interactions is influenced by different additives in formulated oils.

2. Surface energy determination of selected surfaces will reveal the effect of additives adsorption on surface chemistry changes.

3. Iterative wetting analysis of different solid-liquid interfaces will provide the best surface-oil combination to induce maximum solid-liquid slip.

These tasks, together with the new concept of EHD contact design, represent world novelties that have never been achieved so far. They will enable a step-change in future EHD contact design, with significant impact on economic, environmental and social aspects.