Papers

ICMCTF2002 Session G4-2: Hard and Hybrid Coatings for Cutting and Forming Tools, and Surface Engineered Components

Wednesday, April 24, 2002 1:30 PM in Room Sunrise

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		G4-2-1 About the Performance of Crystalline PVD-Alumina Coatings in Cutting Applications G. Erkens, S. Rambadt, I. Wirth (CemeCon GmbH, Germany); R. Cremer (RWTH Aachen LTH, Germany); K.-D. Bouzakis, N. Michailidis (Aristoteles University of Thessaloniki, Greece) PVD coatings and cutting tool materials experienced a rapid development in the past due to the increased demands of modern, innovative production processes. The development of new materials processed so rapidly that it is partly not known, how these materials can be economally processed with respect to measures of reducing costs. In order to meet the different requirements a range of developments have been brought forward in the area of coating technology. Al₂O₃ was and still is an important component of conventional coatings. Especially the crystalline modifications have gained considerable economic significance for turning and milling. All developments in the area of coating processes have been always closely related to efforts of reducing the coating temperatures to open up the range of materials that are possible to be coated without loss in hardness. Different approaches were followed to deposite crystalline Alumina with PVD at a temperature lower than 500°C to make it commecial available for cemented carbide tools and HSS tools as well. Distinct chemical resistance, higher hot hardness than most hard coatings and the fact that crystlline Al2@O₃has less interaction with most production relevant materials than most hard coatings are the key factors to devolop the PVD technology for the deposition of crystalline Alumina coatings. The High Ion Sputtering (H.I.S.@super TM@) sinOx PVD process to deposite crystalline Alumina will be illustrated. This innovative module opens up the opportunities to deposite fine-grained crystalline Al₂O₃ at a temperature lower than 500°C. The investigated Alumina coatings were deposited reactively by sputtering aluminium in an Argon/Oxygen atmosphere. The deposited films were evaluated by metallographical examinations (microhardness, film thickness, adhesion, structure (SEM, X-ray defraction) etc.). The results from cutting tests will show the high potential of various hard coatings in combination with such Alumina films as top layer.
2:10 PM		G4-2-3 Application Nanostructured Coatings on Cutting Tools T. Cselle (Platit AG, Switzerland); P. Holubar, M. Jilek (SHM, Czech Republic); M. Morstein (Platit AG, Switzerland) 90% of industrial coatings are monolayers today. Multilayers are used for special applications especially in interrupted cuts. The increasing of hardness with the help of nanolayers and nanocomposites can improve wear resistance, tool life and productivity for cutting tools. - To deposit nanolayers with constant periods for different substrates with different geometries is difficult because the control of targets and the rotating of tools must be exactly synchronized. Nanolayers can change their periods with changes working temperature, which can easily happen during cutting. Due to these reasons, nanocomposite coatings seem to have a more promising future. In nanocomposites different materials are deposited, they cannot be mixed. Amorphous Si3N4 fills places between the grains of the nanocrystalline TiAlN and increases the coating hardness. The combination of multilayer and nanocomposite coatings decreases the internal stress and the sizes of macro particles. Controlled changing of hardness within the thickness can give a gradient coating with a tough basis and a hard edge. The gradient TiAlCN is a very good combination for high hardness and low friction coefficient. It seems to become the universal coating of the future. This paper introduces our newest developments to produce and use nanostructured coatings on cutting tools, like inserts, end mills, drills and taps.
2:30 PM		G4-2-4 Chemical Vapor Deposition (CVD) of Wear-resistant Coatings in the Ti-B-C-N System H Holzschuh (Walter AG Germany) Coatings in the Ti-B-C-N system were investigated for potential in dry cutting applications. Ti-B-C-N coatings were deposited on cemented carbides using chemical-vapor deposition (CVD). When keeping the B content below 5% the Ti-B-C-N was maintained in the cubic phase. Increasing the Boron content resulted in mixtures of Ti-C-N and TiB₂. The B:C:N ratio, microstructure, hardness and wear resistance of the coatings were controlled by varying the precursors, deposition temperatures and gas flows in the CVD process. Results showed that Ti(C_xN_y) (x+y=1, x: 0-1) coatings containing B exhibited grain refinement and higher hardness but lower critical loads (L_c) for coating decohesion. Microprobe measurements revealed that B diffusion was responsible for inhomogeneous coating compositions at high deposition temperatures and for the formations of a CoWB phase on the surface of the cemented carbide tool. Milling tests showed the coatings had good abrasion wear resistance. The dominant wear mechanism in turning tests was cratering.
2:50 PM		G4-2-5 Deposition, Characterisation and Machining Performance of Multilayer PVD Coatings on Cemented Carbide Cutting Tools C. Ducros (Mécachrome, France); V. Benevent, F. Sanchette (CEA Grenoble, France) TiN/CrN and TiN/TiAlN multilayer coatings with different periods were deposited on cemented carbide cutting tools in an industrial-size cathodic arc evaporation device. Nanolayer coatings in these systems were particularly studied and the influence of the superlattice period on mechanical behaviours have been investigated. Tribological properties were first correlated to the period of multilayer coatings and, based on these findings, machining performance of coated cemented carbide cutting tools have been evaluated by turning Inconel 718 superalloy. Cutting tests were performed under various cutting and lubrication conditions. The decrease of the mean grain size which is associated with the rise of microhardness when the period decreases, leads to higher tribological performances. Coatings favorably influence flank wear, cutting time and cutting force for machining Inconel 718 at relatively high cutting speeds (Vc>30m/min and f >0,2mm/rev with Vc=cutting speed and f the feed rate). Damaged areas on cutting inserts were also analysed by SEM in order to evaluate modifications of cutting zone due to thin films.
3:10 PM		G4-2-6 Composite Coating Materials for the Moulding of Diffractive and Refractive Optical Components of Inorganic Glasses M. Hock, E. Schäffer, W. Döll, G. Kleer (Fraunhofer-Institut für Werkstoffmechanik, Germany) In future technologies of optics, telecommunication and laser techniques there is a high demand on microoptical components having aspherical or fresnel- and grid-shaped surfaces. For many of these components the strong requirements concerning optical quality and long term stability can only be reached if high quality inorganic glasses, instead of plastic materials, are applied. A key for enabling the fabrication of these components by low cost moulding processes are coating materials for the moulding tools which prevent the sticking between tool and glass. These coatings however must not impede the reproduction of the submicron scale-structures prepared, prior to deposition, in the substrates. In the present investigation TiAlN/ZrN composite coatings with superlattice structures were deposited onto fused silica and silicon substrates by rf-magnetron sputtering. The influence of deposition parameters and of the superlattice period on residual film stress, oxidation behaviour and the behaviour in contact with hot inorganic glasses was investigated. The thermal stability of films was also studied. Fused silica and silicon tool-substrates having optically functional structures generated by lithographic techniques were coated and deployed in moulding experiments performed at temperatures of 600 ^oC and higher. Results obtained will be discussed and examples of first applications of coatings for the moulding of components like micro lens arrays and phase grids from high quality optical glasses will be presented.