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NANO2021-Nanoteknologi og nye materiale

Green high-performance and low-friction interfaces tailored by the reactivity of novel DLC coatings and ionic liquids

Alternative title: Green high-performance and low-friction interfaces tailored by the reactivity of novel DLC coatings and ionic liquids

Awarded: NOK 4.7 mill.

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. The results achieved in this project in the context of the objectives can be divided in three categories, scientific, technological and socio-economic. Proper lubricant performance depends on the ability of lubricants to interact or react with the surfaces they are in contact with. This interaction should result in the formation of tribofilms providing with a functionality to the system (i.e. low friction, low wear, etc) or in the adsorption of chemical substances that prevent direct surface contact minimizing energy losses during operation. In the past, strategies to improve lubricant formulations were very much focused on increasing the viscosity to have an impact on the rheology in the contact region. In the latest years, due to the environmental concerns, this has proven to be non-beneficial and strategies are very much focused on low viscosity lubricants combined with new materials. Diamond-like-carbon (DLC) coatings are surface solutions that provide anti-wear and low-friction properties in many applications. They are very promising solutions to achieve the goal of increased use of low viscosity lubricants. However, they do not interact with conventional lubricants, which is a challenge for their extended use. In this project, with the aim to overcoming this challenge, we have developed DLC coatings doped with metals (W, Ag) to enhance their interaction with lubricant additives. In this respect, the strategy has been focused on highly reactive additives and environmentally friendly, i.e. ionic liquids (ILs). The project selected the DLC coatings with different metal dopants (W, Ag) and 4 different ILs. The performance of ILs as lubricant additives was compared with state-of-the-art anti-wear additive zinc dithiophosphate (ZDDP) and an organic friction modifier (dodecanoic acid). Doped (Ag, W) DLC coatings were deposited with DC magnetron sputtering. A new fundamental understanding of the tribological formation/removal of the adsorbed ILs on DLC coatings, their adsorption, and chemical nature, as well the electrochemical and tribocorrosion properties, was developed. A highly industry-relevant nanoscale engineered solution was designed based on boundary film interface (metal-doped DLC) combined with green-lubrication technology. This is applicable in, for example, fluid-power hydraulics machinery, as well as the automotive and other industrial sectors. This project represents a step forward in green lubrication, with a direct impact on greenhouse gas emissions, pollution, hazardous materials, saving resources, reduced maintenance.

The significance of the results obtained in this project are huge. In terms of the research field, this project has for the first time develop deep understanding on the adsorption mechanisms of ILs as lubricant additives on different media and substrates. This knowledge and the methodology developed within the project can be easily transferred and applied to other substances beyond ILs, but also to other context beyond tribology. The expertise built up in this project is of high quality and it will have an impact on future project proposals and future research activities in the field of tribology (and nano-tribology) at national level, with impact on the international arena. Industry has much to learn and implement from the results obtained in this project since we have clearly shown that getting a good tribological performance with greener lubricant and materials solutions is possible.

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. Without new green lubrication solutions, the performance of machinery will deteriorate, reducing operating lifetimes, shortening maintenance intervals, wasting materials, and generating higher energy losses, all leading to large-scale technical and economic consequences for the EU. This urgent need to replace the current technology means the development of high-performance green lubrication is one of Europe?s most urgent priorities.

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NANO2021-Nanoteknologi og nye materiale