Oil ageing effect in boundary and mixed lubrication (P5)
Understanding of lubricant ageing mechanism is a difficult task because many factors and changes in several parameters are involved.
The study of ageing effect on the new generation of low SAPS lubricants is an exciting challenge which I am going to face with a lot of motivations.
I am committed to this project with the main aim of clarifying the fundamental mechanisms of lubricant deterioration which follows over time and the physical consequences thereof on the tribological properties.
BSc, MSc/M. Eng. in Chemical Engineering at the University of Salerno, Italy (2011)
Worked in SKF Engineer Researcher Center in the Netherlands from July 2011-October 2012, at the Department of sealing and functional surfaces.
Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon
For more information contact Modestino;
Supervisors: Prof Maria Isabel De Barros Bouchet and Associate Prof. Clotilde Minfray
Monthly reports are available here
European legislation on vehicle emissions continues to become more severe to minimize the impact of Internal Combustion Engines (ICE) on the environment. One area of significant concern in this respect is the reduction of friction losses resulting in reduced emissions and as well as higher fuel efficiency and lower fuel consumption.
To decrease these losses, several approaches have been made particularly at design of mechanical parts stage and at experimental level to optimize lubricant components. A great contribution to solve the problem can be given by the optimization of the additives package blended into the engine lubricants.
The molybdenum dithiocarbamate (MoDTC) is the additive showing the best tribological performance by acting as friction modifier. It decomposes under high temperatures and pressure, forming layered structureson the engine surfaces. However, the use of effective friction reducing additives to achieve low boundary friction coefficient is not enough to have great engine fuel efficiency. In addition, in fact, it is needed also to maximize their durability, preventing premature consumption or depletion of these additives. It has been shown, in fact, that the friction reduction performance of MoDTC is sensitive to engine operating time and that is related to the degradation of MoDTC itself.
In the first part of the project we tried to get a good comprehension of the chemical mechanisms of MoDTC ageing and to study the impact on the tribological properties. The chemical bulk oil characterization of MoDTC blended into the base oil when subjected to thermo-oxidative degradation allowed to propose a new hypothetical chemical pathway followed by the friction modifier molecules during the ageing process. At the same time, these findings were linked to the impact of the MoDTC degradation on its tribological properties.
As reported in literature, another MoDTC drawback is its strong antagonism with DLC coating. In fact, when DLC-involving contacts are lubricated by MoDTC-containing base oil, a catastrophic DLC wear is produced. For this reason, in the second part of the project a multi-techniques approach has been adopted to get a better understanding of this wear mechanism. The combination of all the findings allowed to propose for the first time a new wear mechanism based on the formation of molybdenum carbide species inside the contact. A strong chemical interaction between the molybdenum-based species formed on the steel counter-body and the carbon of the DLC material has been supposed, leading to the formation of MoC species.
All the results found are discussed to clarify the correlation between degradation time, tribological performance and tribofilm characterizations in both steel/steel and DLC/steel contact.