Papers

ICMCTF1999 Session G5-2: Hard and Hybrid Coatings: Cutting, Forming, Autolubricated Tools and Machine Parts, Upscaling of Coated Parts

Monday, April 12, 1999 1:30 PM in Room Town & Country

Monday Afternoon

Start	Invited?	Item
1:30 PM		G5-2-1 Carbon Based Lubricious Top Layers on Hard Coatings Deposited with the High Ion Sputtering (H.I.S.^TM) - PACVD Hybride Process Technique G. Erkens, T. Leyendecker, R. Wenke, H.-G. Fuss (CemeCon, Germany); R. Kleber, K. Kouptsidis, H. Wolf (Wolf Beschichtungstechnologie GmbH, Germany) Lubricious coatings have been under discussion since several years. Especially the amorphous carbon coatings show high potential in the reduction of wear and friction that can be utilized in dry operation. The combination of hard coatings and DLC coatings open up a wide range of applications. The demands on the process technique are different for machine parts and cutting tools. Machine parts of complex shape usually require process sequences that keep the temperature below 200°C whereas carbide and HSS cutting tools can be coated at a standard process temperature of 450°C. Lubricious coatings on top of hard coatings can reduce the initial wear and improve the chip flow. This is of most interest for those hard coatings that show very good performance in dry cutting anyway. The process technique to deposite hydrogen free a-C coatings, a-C:H and Me-C:H overlay coatings is discribed. The process technique offers the option to deposite DLC either in a hydrocarbon dc / r.f. - glow discharge or by sputtering pure carbon on top of hard coatings in one process respectively. The characteristics of such coatings can be varied within a wide range and thus the quality can be adapted best to the demands of the substrate and the application. A review of the typical mechanical coating properties is given. The illustrated results will show the potential of the H.I.S.^TM - PACVD process module to deposite lubricious DLC top layers on hard coated machine parts and tools in a temperature range of 160°-450°C.
1:50 PM		G5-2-2 a-C:HMe Coatings Deposited by the Cathodic Vacuum Arc Evaporation: Properties and Application Potential J.V. Vetter (Metaplas Ionon GmbH, Germany); A. Nevoigt (Aachen University of Technology, Germany) a-C:HMe coatings were deposited by the Cathodic Vaccum Arc Evaporation. Selected mechanical and tribological properties of the a-C:HMe coatings are presented. It is shown that the coatings are characterized by a low solid state friction, by a high seizure load and by a high wear resistance. The functional behaviour was investigated both for dry and lubricated friction couples. Besides results achieved by laboratory model tests also tests of components from socket joints, hydraulic cylinders and hydraulic piston pumps are presented. These investigations showed that the a-C:HMe coatings have a high application potential in fluid power transmission systems and in dry friction couples. Note: Requested an Oral Session.
2:10 PM		G5-2-3 Integrated PVD Coating Process of Hard and MoS₂ Soft Coatings on Tools and Machine Parts W. Fleischer, M. Franck (Hauzer Coating Center B.V., The Netherlands); A. Savan, E. Pflüger (Centre Suisse D'Electronique et de Microtechnique S.A., Switzerland) This paper will present an integrated PVD process to apply a hard coating and a MoS₂ wear reduction coating in one run. The combination can be made by choosing pure MoS₂, a compound layer or a multilayer. For different applications, CrN or TiAlN were used as hard coating material. The integration of the deposition processes for these materials realizes cost savings and allows further industrialization. For dry lubricant applications, the compound layer delivers constant results in tool applications and in machine parts. The results for large forming tools will be presented.
2:30 PM		G5-2-4 Successful Running with Soft Solid Lubricant Coatings J. Rechberger (Vilab, Ltd., Switzerland); H. Curtins (Platit Ltd., Switzerland) The presentation of soft tool coatings on the market has stimulated world wide activities in the field of solid lubricant coatings for industrial use. These coatings can be most advantageous in very difficult machining operations and in many applications they are the only solution to a successful running. A careful performance analysis on tools has shown, that in machining operations very critical running-in processes take place. This can be compared to a car engine, where such behaviour had been recognized already a long time ago. The present investigation has shown, that in particular the new generation complex alloy tool coatings perform much better and more reliable with the unique "start-up" protection of a soft overlay coating. A new dedicated Platit cathodic arc coating process has allowed to push these soft solie lubricant coatings into very demanding industrial applications.
2:50 PM		G5-2-5 Performance of MoS₂/Metal Composited Coatings Used for Dry Machining and Other Industrial Applications N.M. Renevier, K. Laing (Teer Coatings Ltd., United Kingdom); N. Lobiondo (Multi-Arc Inc.); V.C. Fox, D.G. Teer, J. Hampshire (Teer Coatings Ltd., United Kingdom) As previously reported, [1] the properties of MoS₂ coatings can be improved by the co-deposition of small amounts of titanium. These MoS₂/Ti coatings known as MoST produced by Closed Field Unbalanced Magnetron Sputtering, were harder, much more wear resistant and also less sensitive to atmosphere water vapour during tribolotical testing. These coatings have given excellent industrial results for a wide range of cutting and forming applications. Two forms of MoST coatings have been developed MoST and MoST(h). The MoST exhibits a coating hardness of 500HV, a coefficient of friction of 0.02 during 100N applied load pin on disc testing and a low wear rate while the MoST(h) exhibits a coating hardness similar to TiN, a coefficient of friction of 0.4 during 100 N applied load pin on disc testing and an extremely low wear rate. The choice of coatings is dependent upon the application. Recent industrial performance data related to the characteristics of these MoST autol ubricating coatings, which are utilized today in large scale production, is presented. [1] V.C Fox, N.M. Renevier, D.G. Teer and J. Hampshire, The Structure of Tribologically Improved MoS₂/Metal Composite Coatings and Their Industrial Applications, Proceedings of the PSE Conference in Garmisch Partenkirchen, 14-18 September 1998.
3:10 PM		G5-2-6 Tool Coatings Deposited by PVD-Processes for the Protection Against Corrosion and Wear of the Aluminium Thixoforming-Process O. Knotek (University of Technology Aachen, Germamy); St. Baerwulf, E. Lugscheider, C. Wolff (University of Technology Aachen, Germany) The study reports about various PVD-hard material coatings deposited on thixoforming-tools. The focus of this work is on the protection against corrosion and wear occuring in the thixoforming-process of aluminium alloys. Especially the extreme corrosive problems caused by the molten and partial congealed phases of the aluminium alloys, which interact with the tool-steel have to be reduced by new compound concepts to increase the tool-life. For that purpose AIP- and MSIP-PVD hard materials coatings on Ti- and Cr-basis were deposited, developed and analyzed by different testing methods to characterize the mechanical and structural properties. Therefore SEM, microhardness, scratch testing and pin-on-disk investigations were carried out. Further an adhesion test was established to get a quantitative dimension of the toolcoating adhesion against the aluminium counterbody. To receive detailed information about the corrosive reactions and the interaction between the coated tools and the aluminium two methods were used a) a dipping test and b) an annealing test, which characterize and simulate the conditions in a thixoforming process. It will be shown, that it is possible to inhibit corrosion effects completly by using previously optimized PVD-coatings on tool-steels. Especially the homogeneous and dense microstructure of the PVD-coating is important for the protective function. Further a multiple adhesion force reduction of the aluminium alloys was obtained by using titanium based and BN coatings.
3:30 PM		G5-2-7 Hard and Autolubricated PVD Coatings for Dry and High Speed Hobbing Machining F. Rabezzana (Metec Technologie, Italy); D. Franchi (Ferioli & Gianotti, Italy); H. Curtins (Platit Ltd., Switzerland); S. Durante (Centro Richerche Fiat, Italy) The aim of the paper is to present data related to the characterization and the use of innovative hybrid hard and autolubricated PVD coatings for cutting tool applications, and to present the results of high performance and dry machining tests performed with different hobs coated with these innovative PVD layers in comparison with standard PVD coatings. In particular the hybrid PVD coatings have been developed with the PLATIT arc technology and the PLATIT MOVIC technology. The novelty is the development of hybrid TiN-TiCN-TiAlN + MoS2 PVD coatings, for cutting tool applications. For testing the different coatings we have chosen high speed, minimal lubrication and/or dry cutting tool operations for machining ferrous materials: this matter is very important and strategic for the industry because due to environmental, health and economic considerations there is a strong need, today, to replace the presently used machining technology based on synthetic lubricants by a technology based on high speed, minimal lubricant and/or lubricant-free machining. Results of tool life tests, investigations into tool wear mechanisms for different coated hobs will be presented and discussed.
3:50 PM		G5-2-8 Development of TiAlN-Al₂O₃ Multilayer Coatings M. Feldhege (EUROMAT GmbH, Germany); I. Rass (Euromat, Germany); T. Leyendecker, G. Erkens (CemeCon, Germany) PVD-TiAlN coatings have proven good performance for metal cutting operations and even for dry cutting operations in many investigations. This is mainly based on the effect of an Al₂O₃ layer which grows on top of the coating due to reaction with the atmospheric oxygen. The alumina top layer prevents the heat transfer into the tools and gives good sliding properties. For improving the coating performance with special regard to dry cutting applications it is a logical step to incorporate Al₂O₃ into the whole coating. This has been done for CVD TiN- Al₂O₃ coated tools for a long time but round edges and crack formations due to the high process temperature may appear. This paper describes a technology of producing TiAlN- Al₂O₃ multilayer coatings with the PVD technology on production scale at moderate temperature. HSS as well as cemented carbides substrates have been coated. The paper shows the influence of different numbers of layers (10,20,40) and of basic coating parameters on the performance and describes the main metallographic data.
4:30 PM		G5-2-10 Improvement of Tool Lifetime by Magnetisation of the Tool Surface M. El Mansori, D. Paulmier (ERMES-LPMM CNRS, France) Cutting of metals and other engineering materials has been and still is the major shaping process used in the production of engineering components Up to now, serious challenger has emerged concerning major improvements in the lifetime of cutting tools by the use of hard and thin surface coating. However, improved performance of cutting tools to give lower wear and extended tool lifetime can be achieved by a magnetisation of the tool surface This paper reviews some very interesting results found when conducting tool wear experiments with HSS turning tools It was observed that considerable tool lifetime improvements have been attained by using an external magnetic field when mild steel bars were turned with HSS tools The most marked improvements with HSS magnetised tool are a better surface finish on the workpiece and an increase of a critical turning speed limit The main favourable effect when using a magnetic field comes from the reduced adhesion to the workpiece resulting in less material transfer from the tool surface, increased hardness of the tool surface resulting both in reduced abrasive wear and in the magnetoplastic effect on mechanical properties of surfaces which are governed by the dislocations movement leading, ultimately, to hardening.
4:50 PM		G5-2-11 On the Use of Acoustic Emission and Motor Current to Study Performance of PVD Coated Drills J.M. Vieira (Universidade de Sao Paulo em Sao Carlos, Brazil); J.R.T. Branco (CETEC, Brazil) Drilling tests have been carried out so far to characterize the performance of cutting materials, hard coatings and for characterization of lubricants, where one cares only about the end of the drill life. However, with the use of real time monitoring techniques much can be learned about the cutting process and tools performance. With this goal in mind, acoustic emission - AE and motor current - MC, were monitored during drilling of AISI D3 with high-speed drills coated with TiN, TiCN and MoS₂. The effect of drill length and coating materials were investigated. The acoustic emission in the range of 10 kHz to 1000 kHz was monitored. The drilling MC and AE energy and frequency were analysed as a function of drilling depth for holes along the drill life. The drill wear was analyzed by light and scanning electron microscopy, 3D profilometry and weight loss. The paper analyses different cutting stages distinguishable by AE and how the wear progresses during the drill life. The effect of TiN, TiCN and MoS₂ coatings on tool performance is discussed.