Understanding the third body formation during sliding friction utilizing multilayer model alloys
Final Report Abstract
By performing sliding experiments with Au-Ni multilayer samples under well-defined UHV conditions as well as under controlled N2 atmosphere, it has been shown that the initial layer thickness of Au-Ni multilayer systems has a strong impact on the resulting friction force due to the microstructure evolution close to the surface. A significant increase of the COF with increasing layer thickness has been found in both cases ,but the lowest friction coefficients were found for the 10 nm and 20 nm layer spacing in ultra-high vacuum. It was also shown that the effects of ambient conditions are crucial and need to be carefully controlled. A fully mixed structure and most likely shear-induced formation of an AuNi alloy has been observed for the first time under tribological stressing. Conversely, a partially mixed; Au rich layer has been formed when increasing the layer thickness of the multilayer system to 50 nm. When further increasing the layer thickness (100 nm), rather than a partially or fully mechanical mixing, the thinning of the uppermost Au layer eventuated by plowing and accumulating some Au at the end of the wear track was found. Using a recent model for the determination of the deformation mechanisms associated with the friction force and the grain size the friction behavior can be explained. With the formation of ultrafine grains by mechanical mixing (fully or partially), the number of grain boundaries strongly increased and grain boundary-mediated deformation resulted in the low friction coefficient for thinner multilayer samples. On the other side, dislocation-mediated deformation has been considered to be dominant in the 100 nm multilayer sample in which higher friction has been obtained.
Publications
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Low friction of metallic multilayers by formation of a shear-induced alloy, Scientific Reports 9, 9480 (2019)
Cihan, Ebru; Störmer, Heike; Leiste, Harald; Stüber, Michael; Dienwiebel, Martin
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Structure evolution in tribological interfaces studied by multilayer model alloys, Karlsruhe Institute of Technology KIT, 30.09.2019
Cihan, Ebru
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Effect of Environment on Microstructure Evolution and Friction of Au–Ni Multilayers, Tribology Letters 68, 30 (2020)
Cihan, Ebru; Jungjohann, Katherine; Argibay, Nicolas; Chandross, Michael; Dienwiebel, Martin
