Papers

ICMCTF2002 Session G4-1: Hard and Hybrid Coatings for Cutting and Forming Tools, and Surface Engineered Components

Wednesday, April 24, 2002 8:30 AM in Room Sunrise

Wednesday Morning

Start	Invited?	Item
8:30 AM		G4-1-1 Carbon Coatings for Dry Machining and Forming Operations Deposited by Non-reactive (ta-C) and Reactive (a-C:H:Me) Cathodic Arc Processes J. Vetter (Metaplas Ionon GmbH, Germany); P. Siemroth, H.-J. Scheibe (Fraunhofer IWS, Germany); T. Schuelke (Fraunhofer USA) Amorphous carbon films, commonly designated as DLC-coatings, deposited by the cathodic vacuum arc deposition are characterized by a variety of properties including medium to extremely high hardnesses, a low surface roughness, a low friction value, and low wear rates. These excellent mechanical and tribological properties make the films interesting as wear- and corrosion protective coatings for various industrial applications. In this work we present the results of structural, mechanical, and functional investigations of amorphous carbon-films deposited using different arc-based techniques. High-current pulsed arc discharges, as used in the LaserArco^Â® and HCA processes, generate a highly excited carbon plasma, which is enabling to deposit super-hard amorphous carbon films consisting of up to 80 % tetrahedral bonded carbon. Application tests have shown the great potential of carbon films, deposited by pulsed arc techniques, as wear resistant dry lubricants for cutting and forming tools in dry and minimum lubrication operations. With an additional filtering, ultra-thin coatings deposited by high-current vacuum arc show promising functional properties, as they are required for micro-mechanical applications, e.g. for as protective films in magnetic hard disk drives. Metal-carbon coatings deposited by the cathodic vacuum arc are a new class of low-friction coatings. They combine a moderate hardness with excellent tribological properties. These advanced DLC coatings of the type a-C:H:Me were developed to increase the life time of different tools under dry operation. The coatings were deposited by reactive cathodic vacuum arc evaporation. Selected properties of the coatings will be presented. The successful application of the coatings includes dry drilling, dry milling for Al-alloys, Cu-alloys and gray cast iron as well as the improvement of the tool performance in a variety of forming processes.
8:50 AM		G4-1-2 Performance of Lubricant Coatings in Dry Drilling Processes E. Abele, J. Dörr (Darmstadt University of Technology, Germany) To meet the sophisticated demands of dry machining operations, lubricant coatings are the focus of present development activities. In the research program MaTech funded by the German government wear resistant lubricant coatings for cutting and forming tools had been prepared by CVD and PVD techniques. In the frame of this project the deposited coatings are evaluated by machining tests. In dry drilling applications the lubricant coatings open up the opportunity to combine wear resistance with the reduction of friction and thus the thermal load of the tool and work piece. Also the chip flow can be affected positively. Influences of coating composition on cutting forces, chip flow and the wear behaviour in dry drilling of steel, grey cast iron, cast aluminium alloy and tempered steel are highlighted by dry machining tests. Additionally the coatings are evaluated by determination of the absolute temperature at the drilling tool. Therefore a suitable measuring technique was developed.
9:10 AM		G4-1-3 Performance and Limitation of Hybrid (Hard Coating) - PVD Magnetron Sputtering (Mos₂/Ti Composite) Coated Inserts Tested for Dry High Speed Milling of Steel and Grey Cast Iron N.M. Renevier (Teer Coatings Ltd., United Kingdom); H. Oosterling (TNO Institute of Industrial Technology, The Netherlands); U. Koenig (Widia GmbH, Germany); H. Dautzenberg, B.J. Kim (Technical University Eindhoven, The Netherlands); L. Geppert (Niles Simmons, Germany); J.M. Koopmans (Unisign B.V., The Netherlands); J. Leopold (FhG-IWU, Germany); D.G. Teer (Teer Coatings Ltd., United Kingdom) In the industry, High Speed Machining (HSM) is recognised as one of the key manufacturing technologies for higher productivity and lower production costs. Existing cutting tools are coated to improve the tool life and the performance. These coatings are all based on the principle that the coating is much harder than the work piece material. The objective of this paper is to present the new coatings for cutting tools based on a new approach: Low friction self-lubricant MoS₂ / Ti composite coatings (MoST) [1] deposited by PVD magnetron sputtering technique. Dry machining (DM) is an important objective in machining industry to reduce environmental- and production costs. DM using MoST is possible in some cases: because of the low friction, the use of coolant is not necessary. Also better chip evacuation and a smoother cutting process will occur, which can lead to higher accuracy of products. The paper included an assessment of machining performance of state of the art PECVD coated inserts (grade, geometry, coating). The consortium included manufacturers of milling machines and lathes, a coating company, a tool manufacturer, a university and two research institutes. Partners have contributed their particular expertise to the paper. The main results obtained with these new ‘’hybrid’’ inserts are: - Tools with MoST can be used in dry milling operations at normal cutting speeds - MoST coatings reach good tool life (1.5 - 2 times longer than "State of the art" tools) at normal cutting speeds. [1] N.M Renevier, V.C Fox, D. G Teer, J. Hampshire, Surf. Coat. Technol., 127 (2000) 24
9:30 AM		G4-1-4 New Material Classes for Dry Lubricant Coatings K. Bewilogua (Fraunhofer IST, Germany); M. Lahres (DaimlerChrysler Company, Germany) Cooling lubricants will be applied in many cutting and forming operations. Production and disposal of these lubricants cause high costs and they can be dangerous for the environmental and humans health. The goal of the joint project sponsored by the German government was to develop optimum wear resistant dry lubricant coatings for different cutting and forming operations for different workpiece materials. New coating materials, so far not considered for dry lubricant applications, such as modified sulfides and selenides, oxides, modified amorphous carbon as well as borides and silicides, were prepared and tested. All these coatings were deposited by CVD or by PVD techniques. A first pre-selection step for these new coatings was done with standard adhesion, friction and wear tests. Following to that pre-selection, the coated tools were tested in a next step at different institutes under production near conditions. The successful coatings finally were implemented in field tests under production conditions at the different plants of the partners. Examples for the preparation and properties of some of these dry lubricant coating materials will be reported. Additionally, the potential of these choosen coatings with regard to specific machining and forming will be shown. Finally, some test results from field tests in serial production will give a view of the great potential of such dry lubricant coatings.
9:50 AM		G4-1-5 Polishing of CVD Diamond Coated Tools and Their Application in Dry Machining of Aluminum-Silicon Alloy P.U. Arumugam, A.P. Malshe, S.A. Batzer, D.G. Bhat (University of Arkansas) The generation of fine mist of cutting fluid during conventional wet machining, and associated environmental and operator health concerns make environmentally benign machining and manufacturing a major research thrust in the US, Europe, Japan and other parts of the world. In this context, high speed machining in combination with environmentally benign methods make diamond coating a unique candidate for dry machining. Research on CVD diamond coating in the past few decades has resulted in many new products, including diamond-coated cutting tools. Diamond tools, in the form of polycrystalline diamond (PCD), CVD thin film (polished and unpolished) and thick-film forms offer unique advantages for dry machining. Some findings in the literature indicate that polishing of diamond coated tools helps in reducing the cutting forces and improving surface finish of the machined component. The present work was undertaken to investigate the performance of polished tools and compare it with the un-polished tools in the dry turning of Al-18%Si alloy, in terms of tool wear, work-piece surface finish and aerosol generation. The hypereutectic Al-Si alloy has a tendency to form considerable dust during machining due to the presence of hard Si particles in the matrix, which causes rapid tool wear. In this paper, we report results obtained with PCD, polished and un-polished diamond-coated cemented carbide cutting tools in the dry machining of Al-Si alloys. The results show that conventional diamond tools (PCD and CVD) cause the formation of respirable air-borne fine particles during machining; however, CVD diamond-coated and polished tools generate considerably less respirable aerosol particles, in addition to improving tool life, and reducing the cutting forces. Thus, it is shown that polishing of CVD diamond tools provides a better opportunity for environmentally benign machining environment as compared to conventional diamond tools.
10:10 AM		G4-1-6 Investigating Nitriding and Duplex Surface Treatments for the Reduction of Dissolution and Soldering in Die Casting Shot Sleeves V. Joshi, A. Srivastava, R. Shivpuri (The Ohio State University); E. Rolinsky (Advanced Heat Treat Inc.) A major reason for process down time and loss of casting quality in aluminum die casting is failure of the shot sleeve of the die casting machine. As the liquid aluminum at 1450oF is pored into the horizontal shot sleeve, the oxides in the shot sleeve surface gets washed out by the molten stream exposing the die steel to chemical dissolution and soldering. This leads to the generation of pre-solidified metal, soldering and dissolution failure of the shot sleeve. This paper describes this problem in detail and investigates nitriding and duplex surface treatments for the prevention of dissolution and soldering. Cylindrical coupons with various nitriding depths and coatings are dipped in hot liquid aluminum melt to evaluate their performance in reducing soldering and dissolution. The change in temper hardness with dip times is also noted. It is found that that nitriding not only reduces the thermo-chemical reactions at the surface but also wettability, which reduces the adhesive force between of the soldered material and the treated surface.
10:30 AM		G4-1-7 Performance of Coatings Against Wear in Dry Blanking and Forming P. Groche (Technische Universitat Darmstadt, Germany); K. Tibari (Darmstadt University of Technology, Germany) In a blanking and in a forming process tool wear mainly determines part quality and process stability. This paper presents methods to evaluate tool and die wear, prevailing in a blanking process. A high speed mechanical press is equipped with a measurement device to monitor process parameters, e.g. forces vs. time of the traveling punch. Development and magnitude of cutting, rejection and retraction forces are used as criteria to express the current state of punch wear and to derive information on the blanking results. Characteristic part zones of the chip are additionally evaluated. The described methodology was applied to differentiate between the performances of coated punches in dry blanking of sheet metal materials, i.e. brass alloy (CuZn₃₇) and steel (Rfe80). A "strip drawing test with bending" was used to simulate conditions, mainly prevailing in a deep drawing process. To test die coatings for dry forming operations, aluminum sheet (AlMg₃) and steel sheet (St14O₃) was used. Assessment criteria were wear resistance against abrasion and adhesion, magnitude and variation of drawing forces as well as of friction coefficients. The surface roughness of the die after the tests and the surface roughness of the sheet during the tests was evaluated. Selected results are presented in this paper, together with explanation of according physical phenomena.
10:50 AM		G4-1-8 Performance of New Maxit^T^M AlTiN Coatings in Dry and High Speed Cutting M. Arndt, T. Kacsich (Metaplas Ionon, Germany) (Ti,Al)N coatings are well known for cutting applications for about 15 years due to their advanced wear resistance and superior performance under corrosive or high temperature conditions. A recently developed variant of (Ti,Al)N shows a distinctly improved performance in heavy duty machining of e.g. hardened steel or stainless as compared to conventional commercial films. This new Maxit^T^M AlTiN film is characterized by a low droplet density, a very smooth surface, high hardness and extreme fine grained morphology, adjusted by appropriate process parameters. The aluminum content is very high, that means near the phase transition between the cubic and hexagonal structure. The present paper deals with the characterisation of this coating and its performance in dry and high speed cutting. The operational performance on HSS and cemented carbide tools will be compared also with improved TiCN films. For applications where low friction is necessary the properties of Maxit^T^M AlTiN can be further increased by combining it with a lubcrication film like Maxit^T^M W-C:H.
11:10 AM		G4-1-9 Synthesis and Properties of TiAlBN Coatings for Dry Cutting Applications H.-G. Fuss, G. Erkens, T. Leyendecker (CemeCon GmbH, Germany) Elimination of coolants in modern cutting operations involves absence of their positive effects on metal cutting process such as lubrication, heat dissipation and chip flow. Thus lubricious coatings could at least partly substitute coolant functions. To meet the sophisticated demands of dry cutting, lubricious coatings in combination with ternary hard coatings are the focus of present development activities. PVD process technique does not influence the toughness of cemented carbide or cermet substrates due to the low deposition temperature. Therefore PVD coated tools can stand high dynamic loads. Hard coatings reduce the thermal load, adhesive and abrasive wear as well as tribo-chemical wear mechanisms. Wear resistant lubricious coatings such as Boron-containing coatings open up the opportunity to combine wear resistance with the reduction of friction by boron nitride and thus reduce the thermal load of the tool and work piece as well as the initial wear. Also the chip flow can be effected positively. Boron containing TiAlBN coatings can be characterized by high hardness, high chemical stability as well as high oxidation resistance. The deposited coatings were characterized by SEM, EDX, ESMA. Furthermore highlighted are the influences of coating composition on the friction coefficient.
11:30 AM		G4-1-10 Innovative Mono and Multilayer Hard and Autolubricant PVD Coatings for Dry Stamping Operations F. Rabezzana (Metec Technologie, Italy); D. Franchi (Ferioli & Gianotti, Italy); S. Durante (Centro Ficherche Fiat, Italy) The aim of the paper is to present data related to the characterization and the use of innovative mono and multilayer PVD coatings for difficult stamping applications of ferrous materials, and to present the results of high performance and dry or nearly-dry stamping tests performed with different complex dies coated with innovative hard and autolubricant PVD layers in comparison with standard dies. The needs for greater productivity or to press difficult to-cut workpiece materials call for the development of new, higher performance press and dies capable of higher tooling life or pressing conditions. In this paper the performance of different HSS and/or WC dies coated with innovative mono and multilayer Arc cathodic PVD processes are presented. In particular the innovative PVD coatings have been developed with the PLATIT PVD cathodic arc method, and the novelty is the development of low friction, hard and high temperature resistant multiphase coatings, and the development of auto-lubricant coatings for dry dies applications. Results of industrial tests and investigations into wear mechanisms for different coated dies in comparison with the performance of standard coated and uncoated dies will be presented and discussed.