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B5 - Bionic Thin Layers



Application of Nanostructured Bionic Thin Layers to Enhance the Wear and Friction Behavior of Forming Tools by Thin-walled Sheet Forming

Project Status: Active

Last Update: 21.02.2019



Members


The aim of sub-project B5 is to influence bulk-sheet metal (BMU) processes by modifying the surfaces of tools, using bionic structures and Cr-based hard coatings. This is realized by adapting the tribological properties in order to foster the three dimensional flow of sheet materials into the filigree functional elements and to enable a high mold filling of cavities in forming tools. The necessary animal and plant-based bionic structures were developed and characterized within the frame of the first two funding periods. The Cr-based nitiridic and carbo-nitridic thin layers proved to be suitable for the protection of filigree elements. However, there were geometrical limitations due to the process conditions, related to the line of sight during the coating of complex BMU-tool surfaces. On the basis of the presented results, the focus of the research activities is on the performance increase and extension of service life of the coated tool surfaces. This is realized by developing CrAlN and CrAlCN-thin films by means of HiPIMS-technology which, due to the high degree of ionization, allows an almost geometry-independent, near-net-shaped coating of bionic structures with PVD-coatings. Furthermore, structural adjustment possibilities, which also result from the high degree of ionization, will be utilized in order to deposit coatings with a higher hardness coupled with a low Young’s Modulus when compared to conventionally magnetron-sputtered coatings.

 Figure 1: Bionic inspired surface structures a) scarab beetle, b) Sasa palmata (bamboo), c) Oryzia sativa (rice plant)

 A further aim besides the improved mechanical properties is to obtain a low roughness profile with HiPIMS-coatings that have a better adhesion of the coating to the substrate and a dense, almost defect-free morphology. This characteristics profile is going to be adjusted for wear-resistant CrAlN as well as for low-friction bearing CrAlCN coatings to increase the performance of BMU-processes. Additionally, influences and interactions of the mechanical processing steps, which result from upstream processes, on the parts of the tools close to the urface are going to be included. The bi-directional interactions on the residual stress of the coating-base-material-compound, resulting from the production, will be closely examined. Different available plasma-etching processes, which take place prior to the coating process, are going to be utilized to modify the state of stress and to ensure a high coating adhesion. These investigations will be complemented by post-treatments of the coatings by means of wet-blasting machining, which should lead to a targeted adjustment of the roughness profile of the thin layers and to the formation of a hardness and residual stress gradient. These surface modifications on the tool side are used to meet the process-adapted tribological requirements of the forming process. The tribological tests are to be evaluated under real forming conditions in wear tests, which for the first time provide an understanding about the stress and performance of thin films in long-term studies for SBMF processes. In addition, the interactions of different structure-layer combinations are investigated to identify and analyze the limiting influencing factors on the service life. The knowledge obtained will be transferred to real forming tools and the influence of the developed surface modification on the process control and the real-shaped components will be investigated. The identification of the interactions between the structural properties of HiPIMS-coatings and the resulting tribological properties in the load configuration of BMU is a significant scientific gain. For the first time, bionic structures are coated with high-energy plasmas in order to specifically adjust their surface property profiles and to increase their wear resistance.

 figure 2

Figure 2: Process chain to develop coating substrate systems for SBMF


Working Groups


Publications

    2018

    • Krebs, E.; Wolf, M.; Biermann, D.; Tillmann, W.; Stangier, D.: High-quality cutting edge preparation of micromilling tools using wet abrasive jet machining process. In: Production Engineering, 12(2018), pp. 45-51
    • Löffler, M.; Schulte, R.; Freiburg, D.; Biermann, D.; Stangier, D.; Tillmann, W.; Merklein, M.: Control of the material flow in sheet-bulk metal forming using modifications of the tool surface. In: International Journal of Material Forming, 12(2018), Springer, pp. 17-26

    2017

    • Tillmann, W.; Stangier, D.; Hagen, L.; Schröder, P.; Krabiell, M.: Influence of the WC grain size on the properties of PVD(HVOF duplex coatings. In: Surface & Coatings Technology, 328(2017), pp. 326-334
    • Tillmann, W.; Stangier, D.; Lopes-Dias, N.-F.; Biermann, D.; Krebs, E.: Adjustment of Friction by Duplex-Treated, Bionic Structures for Sheet-Bulk Metal Forming. In: Tribology International, 111(2017), pp. 9–17
    • Tillmann, W.; Stangier, D.; Nelson-Filipe Lopes Dias: Influence of PVD-Duplex-Treated, Bionic Surface Structures on the Wetting Behavior for Sheet-Bulk Metal Forming Tools. In: Journal of Bionic Engineering, 14(2017), pp. 520-531
    • Sieczkarek, P.; Wernicke, S.; Gies, S.; Tekkaya, A.; Krebs, E.; Wiederkehr, P.; Biermann, D.; Tillmann, W.; Stangier, D.: Improvement strategies for the formfilling in incremental gear forming processes. In: Production Engineering, 11(2017)6, pp. 623-631

    Presentations

      2018

      • 29.03.2018: Stangier, D.: An Examination of Structural and Mechanical Properties of Carbon Doped CrAlN Thin Films Deposited by HiPIMS/DC-hybrid Processes, Incheon Seoul - Korea
      • 26.04.2018: Stangier, D.: Bionisch inspirierte Oberflächenstrukturen und nanostrukturierte PVD-Hartstoffschichten für die Blechmassivumformung, Sigmaringen BisOn Netzwerktagung