The GreenCOAT project is about designing a green DLC coating for contact interfaces based on a new DLC deposition technology that is tailored for harmless ionic-liquid lubrication. Only such a technology will be able to satisfy the strict legislation about the environment and greenhouse-gas emissions, and as such it is simply indispensable for heavily loaded, mechanical components that require lubrication in transport and industrial systems. This is particularly related to those systems operating in nature, like fluid-power hydraulics machinery in wind and off-shore energy, marine systems, bioenergy from forests, geothermal energy, mining, agriculture, etc. Existing UN, EU and national emission regulations are already affecting the performance of some modern machinery, and as these restrictions become tighter, a number of lubricants with regulated additives will have to be abandoned.
In the last months of the project the activities have been focused on the adsorption studies of different ionic liquids on different surfaces (stainless steel, H-DLC, W-DLC and Ag-DLC) with the aim of correlating the adsorption kinetics with the frictional and wear response of the materials in polar and non-polar media. It has been found that in polar media, the dissociation of the moieties of the ionic liquids is the most relevant parameter in order to reach low friction and low wear. Also, the type of metal dopant in the DLC coatings plays a role in the frictional response of the different lubricant additives used. The friction and wear mechanisms of ionic liquids as lubricant additives are highly dependent on the media (polar vs non polar) and their dissociation in it, and also the affinity they have for the contacting surface (adsorption kinetics).
