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    Item-typ:Veröffentlichung,
    Tribologische Bewertung von Tribometer- und Streifenziehversuch zur Nachbildung eines Trockenumformprozesses von Aluminium
    (2015) ; ;
    Weber, Martin
    ;
    Bräuer, Günter
    ;
    Resch, Franziska
    Im Rahmen dieser Untersuchung wurden Tribometer- und Streifenziehversuche nach Abbild eines Trockenumformprozesses von Reinaluminium abgeleitet. Die beobachteten Grundphänome, wie Verschleißart, Verschleißort und Aufbaumechanismus der Adhäsionserscheinungen, sind in beiden experimentellen Untersuchungen identisch und bilden die Ausfallursache eines industriellen Umformwerkzeugs nach. Die gewählte Versuchsanordnung konnte als anwendungsnahe, effiziente Prüfmethode von aktuellen Adhäsionstheorien sowie als Prüfstand zur Entwicklung neuer, antiadhäsiver Tribosysteme qualifiziert werden. Eine Erweiterung der Tribometerversuche mit DLC-beschichteten Prüfkugeln zeigt den derzeitigen Stand der Technik für die Trockenumformung von Reinaluminium auf. Die Verschleißausprägungen auf der beschichteten Kugel verdeutlichen den weiterhin existierenden Entwicklungsbedarf zur Minimierung der Adhäsionsneigung von Aluminiumwerkstoffen gegenüber gängigen Werkzeugwerkstoffen bzw. Verschleißschutzschichten. Die gewonnenen Ergebnisse bilden zudem die Grundlage zur Bewertung von neuen, antiadhäsiven Tribosystemen.
    Wissenschaftlicher Artikel
    Band:
      407  172
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    Item-typ:Veröffentlichung,
    Dry forming of aluminum
    Aluminum parts are used in a wide range of applications. However, the strong adhesion of aluminum to numerous tool materials is challenging for production processes. To ensure an economic production of aluminum sheet parts a high quantity of lubricants is currently needed. The additional process steps and operating resources associated with their use considerably reduce the sustainability of production. Ecological advantages achieved by lightweight construction during the use phase of aluminum products lose their value drastically when the entire life cycle is considered. The aim of the research project is therefore the development, qualification and transfer of a surface technology system solution for the optimization of tools, whereby the use of lubricants is dispensed with and an environmentally friendly production of aluminum parts is achieved. Within the scope of the research project, the basic wear mechanisms during the lubricant-free forming of aluminum sheets were investigated and strategies for industrial implementation were explored. Starting point of the investigations was a holistic view of the tribological system. In addition to process-driven variables such as contact normal stress and temperature, a significant influence of the semi-finished product in terms of surface chemistry and topography was found. The inert and particularly smooth design of the tribological contact plays a decisive role in this respect. On the sheet side, the native aluminum oxide layer ensures a separation of the reactive aluminum matrix and its performance was improved by additional electrolytic treatment. Further-more, the adhesive wear was significantly reduced by providing sheet material with a high proportion of ma-terial close to the surface. On the tool side, amorphous hydrogenated carbon (a-C:H) caotings were deposited to provide an inert surface. In order to additionally create a nanoscopic smooth tool surface economically, different action strategies along the process chain for tool production were investigated. In addition to various approaches for optimizing the coating process, these strategies consist of a roughness-oriented material selection and different polishing processes that are variable in the process sequence. All investigations were based on a sequential qualification method (tribometer, strip drawing, application) in order to narrow down the scope of solutions for application tests. Finally, the mechanical-chemical polishing of a-C:H coated forming tools was qualified for industrial application in deep-drawing tests.
    Wissenschaftlicher Artikel
      416  340
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    Item-typ:Veröffentlichung,
    Evaluation of silicon-modified DLC coatings in a dry sliding contact against aluminum EN AW-5083
    (2016) ; ;
    Bräuer, Günter
    ;
    Kretz, Felix
    ;
    Groche, Peter
    Diamond-like carbon (DLC) coatings are known to reduce friction and wear. In a dry contact with steel the tribological behavior can be further optimized by adding a certain concentration of silicon to the amorphous hydrogenated carbon coatings structure (a-C:H:Si). However, in a dry contact with aluminum the tribological performance of a-C:H:Si coatings and the optimal silicon concentration is still unknown. In order to define an optimum regarding the silicon concentration, a-C:H:Si-coatings with different silicon contents were deposited on 1.2379 tool material by plasma assisted chemical vapor deposition (PACVD) technology. Tribometer tests were used to analyze the friction and adhesive wear behavior against EN AW 5083 aluminum. Additional, strip drawing were conducted tests to investigate the efficiency of the different silicon contents with a higher proximity to industrial processes. The tests showed a deteriorating friction behavior of the a-C:H:Si coatings with an increase of the silicon concentration. Superposing wear mechanisms between the silicon and the aluminum were determined by a subsequent investigation of the wear tracks as an explanation for the tribological behavior.
    Wissenschaftlicher Artikel
    Band:
      488  172