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Wenden, Germany

Osterle W.,BAM Federal Institute of Materials Research and Testing | Dmitriev A.I.,Tomsk State University | Gradt T.,BAM Federal Institute of Materials Research and Testing | Hausler I.,BAM Federal Institute of Materials Research and Testing | And 6 more authors.
Tribology International | Year: 2015

Abstract The composition and nanostructure of a beneficial tribofilm formed during sliding of a hybrid nanocomposite against steel were characterized comprehensively. A similar nanostructure was produced by high energy ball milling of the three identified tribofilm constituents: silica, hematite and graphite. By supplying powders to a pin-on-disc test it has been shown that neither silica, nor hematite, nor a mixture of both provide the low coefficient of friction (COF) observed for the hybrid composite. Only if graphite was blended with the oxides, the low COF was obtained. Thus, a film of finely dispersed stable inorganic wear products containing 15 vol% graphite provides low friction and wear in the considered case. © 2015 Elsevier Ltd. All rights reserved. Source


Osterle W.,BAM Federal Institute of Materials Research and Testing | Dmitriev A.I.,RAS Institute of Strength Physics and Materials Science | Orts-Gil G.,BAM Federal Institute of Materials Research and Testing | Schneider T.,BAM Federal Institute of Materials Research and Testing | And 2 more authors.
Tribology International | Year: 2013

A model based on movable cellular automata has been applied to study the sliding behaviour of tribofilms formed during automotive braking. Since it is not possible yet to determine the composition of real tribofilms quantitatively, final verification of modelling results is needed. This was done by preparing artificial third bodies with compositions and nanostructures matching the ones assumed for modelling. Pin-on-disc tests were performed while applying the artificial third bodies to the contact. The results revealed that not only the structure of the third body but also the amount of the applied normal pressure determines the COF obtained by modelling and that much better correlation between experimental and modelling results was obtained while assuming high normal pressures at asperity contacts. © 2013 Elsevier Ltd. Source


Osterle W.,BAM Federal Institute of Materials Research and Testing | Orts-Gil G.,BAM Federal Institute of Materials Research and Testing | Gross T.,BAM Federal Institute of Materials Research and Testing | Deutsch C.,BAM Federal Institute of Materials Research and Testing | And 5 more authors.
Materials Characterization | Year: 2013

Different, partly complementary and partly redundant characterization methods were applied to study the transition of magnetite, graphite and MoS 2 powders to mechanically alloyed nanostructures. The applied methods were: Transmission electron microscopy (TEM), Mössbauer spectroscopy (MS), Raman spectroscopy (RS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The main objective was to prepare a model material providing the essential features of a typical tribofilm forming during automotive braking, and to assess the impact of different constituents on sliding behaviour and friction level. Irrespective of the initial grain size, the raw materials were transferred to a nanocrystalline structure and mixed on a nanoscopic scale during high energy ball milling. Whereas magnetite remained almost unchanged, graphite and molybdenum disulphide were transformed to a nanocrystalline and highly disordered structure. The observed increase of the coefficient of friction was attributed to a loss of lubricity of the latter ingredient due to this transformation and subsequent oxidation. © 2013 Elsevier Inc. All rights reserved. Source

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