Dr. Florian Pape

Leibniz University Hannover, Germany

Title: Investigation on graphene platelet based dry lubricating film formation in tribological contacts

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Biography

Dr. Florian Pape works at the Institute of Machine Design and Tribology, Leibniz Universität Hannover, as a Post-Doc. His research is in Materials Engineering, Manufacturing Engineering, and Tribology. Besides the influence of residual stresses on bearing fatigue life and hybrid bearing materials he works on the influence of Tribofilms and micro-textures regarding friction and wear. His current projects includes studies on sensor integration to bearings (direct deposited) and graphene as dry-lubricant or grease additive for roller bearings.

Abstract

The application of dry lubrication in rolling contacts is challenging due to wear. In previous studies graphene platelets as dry lubricants applied on angular contact ball bearing surfaces proved superior properties. In this specific bearings besides rolling also spinning motion results in harsher conditions for dry lubricants. The applied graphene platelets have a thickness of few graphene layers in the nm range and a diameter in the µm range. They can be produced by mechanical exfoliation from graphite allowing to achieve affordable graphene platelets. To gain deeper insights in the lubrication effects investigations on a Milli Tribometer were performed. In the tests, a fixed steel ball is placed against an oscillating counterpart under defined load. During the measurements, the applied load and tangential forces on the ball are recorded to calculate the friction. In our case, a steel ball with a diameter of 6 mm was used against graphene-based films on flat bearing surfaces (axial bearing washers). To increase the adhesion of the films on the surfaces a pre-rolling process was conducted. Afterwards the friction on the compressed films was measured. It could be shown, that such a pre-rolling process helps to reduce the friction of the system. After the tests, the surfaces were analyzed in terms of laser scanning microscopy to conclude on the formed films and wear as well as material transfer. It could be shown, that by pre-rolling a very thin compacted film is formed. On the ball partly graphene platelets form a transfer film on the surface on the contacting zone.