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Roller chains from the iwis Antriebssysteme company are used, for example, in agricultural machinery. Innovative coatings can reduce wear and significantly extend the maintenance intervals.
© Iwis Antriebssysteme
Material coatings
05.01.2016

Once coated, everything runs smoothly

The wear and energy consumption of machinery increase dramatically if the machines are not optimally lubricated. In many cases, however, ideal lubrication is impossible, for example, in free-running motorcycle chains or agricultural machinery. To meet these operating conditions, researchers are therefore developing new coatings, and lubricants adapted to them, as part of the CHEOPS3 project. The twelve project partners from industry and science want to achieve long-term protection against wear, even with minimal lubrication and dry friction, so as to increase the efficiency of machines.

In engines, gearboxes, roller bearings – in fact everywhere where machine surfaces rub against one another, lubricants ensure low wear and keep energy consumption in check. This ideally succeeds if a lubricating film completely separates the friction partners. When constructing machines, this full lubrication is generally aimed for. However, under extreme conditions, such as when an engine is overheated, the lubricant film may fail, which can lead to high friction and damage the tribological system. The CHEOPS³ research project (Characterisation of efficiency optimised layer lubrication systems), which was launched in October 2015, is focussing on applications where full, so-called flood lubrication is anyway not possible. For the operation of motorcycles, centrifugal pumps, chain conveyor units, railcar couplings and harvesting equipment, the scientists are developing diamond like carbon (DLC) coatings and, in a second development line, nitride hard coatings. With minimal or no use of lubricants, the material coatings are designed to enable low-maintenance and service-friendly continuous operation, while also increasing the service life and energy efficiency of these applications. “Ideally, we hope that we can reduce the energy losses caused by dry friction and minimal quantity lubrication by up to 50%,” says Dr Kai Arens, project manager at iwis motorsysteme. The serviceability would be improved, for example, by eliminating the need to re-lubricate a motorcycle chain coated in this manner; initial lubrication would suffice. In addition to less maintenance, this also offers another advantage with harvesting equipment: the fewer lubricants required by the machine parts, the less they can contaminate the soil and groundwater.

The iwis motorsysteme company from Munich is coordinating the research project. The consortium includes a total of twelve partners that represent the entire spectrum of the value chain. In addition to component and system suppliers, research institutes, coating manufacturers, contract coaters and end users are also represented.

Amongst others, the coating development is focussing on diamond-like tetrahedral amorphous carbon coatings (ta-C), which are being developed by Fraunhofer IWS in Dresden. Diamond-like coatings combine extraordinary lubricity with anti-adhesive properties, chemical stability and extreme material hardness. They are already used in engine components and research is continuing on them in many places. In the PegasusII research project, for example, scientists are working on their large-scale use for powertrains in vehicles. With these machine components, however, dry friction does not play a role.

The second focus of the coating development relates to nitride, triboactive hard coatings. For this purpose, the (Cr, Al)N hard material layer system, which has been successfully developed and tested by the Institute for Surface Technology (IOT) in numerous research projects, is being further developed by adding triboactive elements and adapted to conditions with minimal quantity lubrication.

With standard tribocontacts, steel-steel contacts still prevail today in almost all industrial applications. Coated surfaces, however, are placing new demands on lubricants, as they bring with them new properties. Therefore another focus will be on developing adapted lubricant formulations that can optimise the frictional properties of the surface coatings in operation, prevent wear and significantly extend the maintenance intervals.

The researchers are expecting the first results in 2017.

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Addresses

Motorcycles
BMW Group

Curved tooth couplings for railway vehicles
Henschel GmbH

Gearboxes
Herzog GmbH

Coating developer
RWTH Aachen, IOT

Coating developer
Fraunhofer IWS

Coating plants
VTD Vakuumtechnik

Lubricants
Addresses

Assessment of the tribological potential
FZG TU München

Contract coater
H-O-T