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Tribological investigations of the applicability of surface functionalization for dry extrusion processes

: Teller, M.; Prünte, S.; Ross, I.; Temmler, A.; Schneider, J.M.; Hirt, G.


Brabazon, D. ; American Institute of Physics -AIP-, New York:
20th International ESAFORM Conference on Material Forming 2017. Proceedings : 26th-28th April 2017, Dublin City University, Ireland
Melville/NY: AIP Publishing, 2017 (AIP Conference Proceedings 1896)
ISBN: 978-0-7354-1580-5
Art. 140001, 6 pp.
International Conference on Material Forming (ESAFORM) <20, 2017, Dublin>
Conference Paper
Fraunhofer ILT ()

Cold extrusion processes are characterized by large relative contact stresses combined with a severe surface enlargement of the workpiece. Under these process conditions a high risk for galling of workpiece material to the tool steel occurs especially in processing of aluminum and aluminum alloys. In order to reduce adhesive wear lubricants for separation of workpiece and tool surfaces are used. As a consequence additional process steps (e.g. preparation and cleaning of workpieces) are necessary. Thus, the realization of a dry forming process is aspired from an environmental and economic perspective. In this paper a surface functionalization with self-assembled-monolayers (SAM) of the tool steels AISI D2 (DIN 1.2379) and AISI H11 (DIN 1.2343) is evaluated by a process-oriented tribological test. The tribological experiment is able to resemble and scale the process conditions of cold extrusion related to relative contact stress and surface enlargement for the forming of pure aluminum (Al99.5). The effect of reduced relative contact stress, surface enlargement and relative velocity on adhesive wear and tool lifetime is evaluated. Similar process conditions are achievable by different die designs with decreased extrusion ratios and adjusted die angles. The effect of surface functionalization critically depends on the substrate material. The different microstructure and the resulting differences in surface chemistry of the two tested tool steels appear to affect the performance of the tool surface functionalization with SAM.