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ePaper created 2014-04-30, 16:22:09 | version 1.30.01
FOCUS// The HZDR Research Magazine WWW.Hzdr.DE 14 15 Initiative of Excellence of the Free State of Saxony. According to Gemming, "Dresden is perceived as one of Germany's top materials research sites. In the cluster's 14 sub-projects, chemists, physicists, materials researchers, and engineers are all working side by side. The entire spectrum of expertise is represented." Maximizing Saxony's knowledge potential HZDR researchers coordinate the sub-project CarboFunctCoat. The abbreviation stands for "Carbon-based functional coatings for use in tribological applications." Within the project the researchers have specialized in components that are constantly exposed to motion and thus to great stresses like piston rings or pins, eccentric shafts, or parts of the fuel pump. "All these various parts of a car engine have very sophisticated three-dimensional geometries," says Sibylle Gemming. Especially the use of fuels from renewable sources places unique demands on coatings as the combustion chemistry of these biogenic fuels is much more diverse than that of fossil fuels. Until now, the researchers have identified two types of coatings that could help curb energy losses in moving engines. One of the coatings is based on so-called tetrahedral amorphous carbon (ta-C). The material is a version of what is known as diamond-like carbon (DLC), first described 20 years ago in this context and used extensively in different industrial settings. ta-C is even harder and denser than DLC, and also contains fewer hydrogen atoms, which positively affects its properties for the purpose of the project. The other coating, which is investigated to offset friction, contains additional metals and exhibits a highly ordered nanostructure. Both coatings are very resilient – even in the face of high temperatures as they exist in a car engine –, act to offset friction, and thereby prevent excessive wear of the engine parts. New kinds of carbon-based materials "At the HZDR's ion beam center as well as at the site of our project partner, the Fraunhofer Institute for Material and Beam Technology (IWS, Eckhard Beyer), we have the option of coating engine components using carbon-based coats, thereby improving their friction behavior," explains Gemming. The ion beams that are used at the HZDR open up unique possibilities for material synthesis and modification. A new high-tech facility allows us to evenly coat even complex forms and thus eliminate surface inhomogeneities. Together with engineers at Dresden-based VON ARDENNE GmbH, Sibylle Gemming and her team have recently filed a patent application for a process allowing them to deposit even thicker coats without prolonging the coating process. The coated components are regularly tested under real- life conditions. This testing takes place at TU Dresden's Institute of Automotive Technology lead by Hans Zellbeck, another partner within the ECEMP consortium. The engineers incorporate the coated components into several drag-test and fired benches. In this way they track how fuel consumption HIGH-TECH COATING SYSTEM: Inside a specialized plasma chamber, HZDR scientists produce functional coats for high-impact engine parts. This is based on a sputter protocol for generating electrically charged argon atoms. If these are accelerated, atoms are being "knocked" out of a cathode, make their way to the material surface that is supposed to be coated, and upon their arrival produce the desired coat. Photo: Jürgen Jeibmann