Projects / Programmes
Mechanisms and formation of tribological nanolayers in boundary lubrication of DLC coatings
| Code |
Science |
Field |
Subfield |
| 2.04.00 |
Engineering sciences and technologies |
Materials science and technology |
|
| Code |
Science |
Field |
| T000 |
Technological sciences |
|
| T110 |
Technological sciences |
Instrumentation technology |
| T150 |
Technological sciences |
Material technology |
| T152 |
Technological sciences |
Composite materials |
| T155 |
Technological sciences |
Coatings and surface treatment |
nanotribology, nanotechnology, nanomaterials, boundary lubrication, diamond-like carbon coatings, aditives, nanotubes, oils
Researchers (9)
Organisations (1)
Abstract
Improvements of diamond-like carbon (DLC) coatings over the past 10 years has made it possible for them to become the most valuable and promising types of coatings for many mechanical engineering applications. Extensive growth of applications with DLC in last few years clearly confirms these advancements. In particular, their low friction and sometimes “super-low” friction, corrosion-, adhesion-, and stiction prevention, low wear etc. are the most valuable properties. As a result, DLC coatings are nowadays expected to perform in a superior manner in various mechanical systems, including high-stressed and lubricated applications. However, DLC coatings are known as “inert” coatings with a low surface energy, and are therefore considered not to react with the various oil additives and/or attract polar groups from the additives and the oil, which are typical for conventional steel/metal boundary lubrication mechanisms. Currently, no boundary lubrication mechanism for DLC coatings is established or convincingly proposed in open literature. Due to early stage of research of boundary lubrication of DLC coatings (just slightly more than 5 years), there exist mainly the data on empirical performance, and even these are, due to many different DLCs, additivies, oils, and contact conditions investigated, quite contradictory and difficult to compare. Therefore, for a qualitatively new and inventive step, which would allow optimization and tailoring of these tribological systems, true acting boundary lubrication mechanisms need to be determined. Questions like when, why, under which conditions, what are the coatings and lubricants structure and composition required for the interactions to occur and to form protective tribochemical nano-films need to be answered and consequently the actual boundary “lubrication” mechanisms can be postulated. Accordingly, in the proposed project we would like to continue our recognized current and previous efforts and findings, however by focus on these processes at a more fundamental, nano-scale level, by using a high-purity and well-characterized coatings, oils and additives or their active components, aiming to determine correlations between the basic physical-chemical and structural properties of the coatings and lubricants with the formation of protective nano tribochemical films and their efficiency in boundary lubrication, thus determining the acting boundary lubrication mechanisms of DLC coatings under selected contact conditions.
Significance for science
Requirements for reduced energy and material resources consumption brought up a new research field called Nano-technology. In the development of this field knowledge about friction on the atomic level is essential. This field is called Nano-tribology. In our research program investigation will be focused on nano-structured materials, nano lubrication films and dry friction on nano level. Based on experts’ opinion, these fields are essential for the development of many mechanical components and system, at the same time being still largely unexplored. We expect for our work on these fields to contribute to the knowledge and research development.
The second field proposed is the investigation of coatings for machine elements with complex geometry. Here we have two points of interest. The first concern is how to manufacture a reliable coating that can carry high loads and be self-regulating (intelligent coatings). The second concern is chemically inertness of these coatings. For normal operation of machine elements lubricants are more or less essential. Therefore, our task is to develop reliable coatings with high load-carrying capacity on one side, and lubricating fluids which are environmentally adapted and capable of forming nano-micro lubricating films in the contact. In this field, we are one of the leading centres in the world. As an example, dr. M. Kalin was a chair of the intl. conference "Advances in boundary lubrication and surface boundary films" held in Seville, Spain, which just finished (28.3.-2.4. 2009) and was organised by the Engineering Conferences International (ECI). This was a top class dedicated conference.
Significance for the country
Slovenia is highly dependent on import of energy and raw materials for material production. Therefore, it is necessary to focus toward the smallest possible consumption of energy and raw materials per product unit. According to some analysts, the direct expense of friction and wear in industrially developed countries is as high as 5% GDP. It is also estimated that it could be possible to achieve savings of up to 1% GDP, only with the reduction of friction obtained by the use of appropriate lubricants. In practice, knowledge of tribology is used to improve different properties of moving elements, with intention to reduce friction and wear losses and consequentially prolong durability and reliability of machines and transmission systems. It is well known that in Germany energy losses and damage of contact surfaces, related to wear and friction, are responsible for costs equal to about 35 billion €. It is clear that this is extremely important field.
Less common observation is that fuel consumption in automotive sector can be substantially recued, up to 5 %, with proper additives and base fluids. EU research showed that CO2 emissions could be reduced from 200 below 140 g/km. This would suggest that in Slovenia, we could omit undesired polluting emissions in amount of few hundreds of tons per year. Therefore, in our project we target also these goals that are becoming more and more important in Slovenia, like other developed countries.
Today we know that we need to achieve the development in a sustainable and environmentally friendly way, which requires the use of new materials and lubricants. Friction can also be reduced through use of nanostructured materials, coated surfaces and nanolubricationg films. However, it is essential to understand the interactions between the advanced materials and lubricants on the nano scale, since they do have a key role in controlling friction and wear of materials. Within the project we focused on the use of base oils without additives, because the global trends tend to use smaller quantities of lubricants, which must also be ecologically acceptable. With this approach, we focused on the mechanisms of physical adsorption of the lubricant on the surface, which has been previously completely unknown for DLC coatings. We demonstrated that with use of the base polyalphaolefin oils or pure alkanes boundary lubrication layer is formed in DLC contact, which affects the tribological properties of the contact as a function of viscosity and molecular chain length. All these findings represent a new challenge for Slovenia, both from a scientific as well as the production point of view, as they are opening brand new, still unexplored and/or poorly known areas.
Most important scientific results
Annual report
2008,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2008,
final report,
complete report on dLib.si
