The Coatings in Manufacturing Engineering

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Authors: Berend Denkena, Luis de Leon, E. Bassett, M. Rehe
Abstract: The need for new cutting tool technologies is driven by the constantly increasing performance of machine tools and the rising market competition. Current research results show that an improved combination of the cutting edge macro- and microgeometry, together with an appropriate substrate and coating, leads to a significant enhancement of cutting tool performance. Furthermore, inappropriate cutting edge microgeometries cause, in addition to the higher production costs, a reduction of the tool life. Hence, it is essential to produce tailored cutting edge microgeometries with high precision and process reliability. This paper presents the influence of brushing process parameters on the size and the form of produced cutting edges of indexable inserts. This leads to a better understanding and higher quality of the cutting edge preparation process by means of abrasive brushes. Furthermore, the process reliability of 5-axes brushing is analyzed. An example of a tool life map presents the significantly enhanced tool performance through cutting edge preparation and its sensitivity towards varying the cutting edge microgeometry.
Authors: Fritz Klocke, Olaf Dambon, Kyriakos Georgiadis
Abstract: The complexity of optical components increases steadily in recent years, while their dimension de-crease. This situation makes the production of state of the art optical components by grinding and polishing very difficult and expensive. However, the technology of precision glass molding can be used to replace these traditional manufacturing methods by a single step replicative process. To achieve economies of scale with precision glass molding, a long molding tool lifetime is necessary. This can only be realized by applying protective PVD coatings on the molding tool surfaces. Well known thin hard coatings like TiAlN or CrN, as well as noble metal coatings are possible candidates. However, practical testing of carious coating-glass combinations in precision glass molding machines is not feasible due to long process times that make such testing very expensive and time consuming. In this work, these coatings are compared with each other and in combination with various glass types by performing oxidation and contact angle tests. The results of these tests are compared to the results of practical tests, in order to determine to which extent such model tests can replace practical testing.
Authors: Berend Denkena, Bernd Breidenstein
Abstract: Cohesive damage of PVD-coated cemented carbide cutting tools is ascribed to the residual stress state of the substrate subsurface. The present paper shows the formation of the substrate residual stress in the process chain as well as the stability of the single process steps referred to the scattering of the residual stress values. Depth resolved residual stress measurements across coating and substrate subsurface show a layer in the substrate, where possibly tensile stress occurs, from where cohesive damage may be initialized during tool use. Results of experiments are presented, where the influence of parameter variations in pre coating processes on the residual stress state is investigated. The characteristics of compressive residual substrate stress during the final PVD-process is presented as well as a correlation between coating and substrate stress.
Authors: Fritz Klocke, Christof Gorgels, Arne Stuckenberg, Emmanouil Bouzakis
Abstract: In today’s production engineering nearly every cutting tool is coated. In the field of coating technology and tool treatment blasting is a common way to increase tool life or hold it on a constant level for several reconditioning steps. The latest innovation referring blasting are micro blasted coatings. For this technology a parameter variation was examined and the consequential tool life was compared with common testing method for tool systems in order to qualify the coating treatment. The investigations were carried out using an aluminum and zirconium oxide as blasting abrasive and by varying the blasting parameters pressure and duration. Finally, the treatment led to an optimized tool wear behavior due to micro blasting of the coating and the wear behavior could be referenced against the testing methods.
Authors: Ekkard Brinksmeier, Ralf Gläbe, Jen Osmer
Abstract: The mass production of glass or plastic components by replication techniques, like hot pressing or injection moulding, requires inserts made of temperature resistant and hard materials. Generating an optical surface finish in these materials is time consuming and difficult. By using thermo-chemically treated steels as mould materials diamond cutting processes generating high form accuracies and low surface roughness can be applied without significant tool wear.
Authors: Jörn Kohlscheen, Hans Joachim Knoche, Martin Hipke, Andreas Lümkemann
Abstract: Pre-machining of gear wheels is often done by hobbing using a soft work-piece material. Today, almost all of the hobs are used with a hard coating to enhance their life-time considerably. This paper describes the results obtained with a tailored coating in a single tooth cutting test (fly cutting). We show that a nano-structured multi-layer coating based on AlCrN is able to protect a tool better than conventional single-layer coatings. The specific mechanical and structural properties of the coating are explained in detail.
Authors: Wolfgang Tillmann, Evelina Vogli, Jan Herper, Matthias Haase
Abstract: It is very important to minimize wear and friction in forming processes in order to avoid adhesion between work piece and tool. For the realization of these requirements, the PVD-coating system CrAlN was deposited and tested on substrates made from high speed steel 1.3343 by means of a reactive sputter process. The coatings were deposited as single- and multilayers with a metallic Cr-interlayer. Prior to realizing the appropriate coating design, the substrates were pre-structured. For this purpose natural surfaces were used as a pattern and tested in this research work. The skin of an insect serves as a model and its fine structures were reproduced on the substrate surface by milling. The generated specimens were analyzed with a scanning electron microscope, nanoindenter and ball on disc tester to compare the performance of the coating systems.

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