Papers

ICMCTF2000 Session G4: Hard and Hybrid Coatings: Cutting, Forming, Autolubricated Tools and Machine Parts

Friday, April 14, 2000 8:30 AM in Room Town & Country

Friday Morning

Start	Invited?	Item
8:30 AM		G4-1 Mono- or Multilayer, That is the Question! What Decides About Using or not Using Coating for Cutting Tools T. Cselle (Guhring Inc., R&D, Germany) When one looks at the figures of typical coatings firm, it becomes immediately understandable why so many investors are interested in coating technology. There is no shortage of sales potential, as currently not even one of every two tools is being coated. This number is so high, as nearly all indexable inserts now come with a coating. However, among all solid symmetrical rotating cutting tools only every seventh or eighth tool is coated. If one adds the 5- to 10-time recoatability of solid cutting tools, one can recognize the great promise of the coating technology market. While the current boom in the cutting tool industry appears headed for a slowdown within the next few years, not so with coatings. More and more components and wear parts, as well as cutting tools, will be coated. The latter category will continue to expand primarily in the area of reground and recoated cutting tools. This paper discusses the important application technology trends and questions regarding layers for symmetrical rotating cutting tools. ? Will CVD or MTCVD become more strongly established for symmetrical rotating cutting tools? ? Will multi- and nanolayer coatings replace “good old” TiN coating? ? Why are nanolayers important for cutting tools? ? What problems do droplets present during the ARC process? ? How can you compare the different glide coatings? ? Can we make a Lotus-coating? ? Will ion implantation become established? ? How can decoating determine the performance of coating centers? ? Can big coating centers achieve the world wide spreading of coatings for cutting tools? ? Or are small units, integrated in regrinding shops, necessary to break through? ? Which trends will lead the coating market in the next years?
9:10 AM		G4-3 Performance of Lubricating TiAlN-based PVD-Coatings in Dry Cutting Operations H. Schulz, J. Dörr (TU Darmstadt, Germany); T. Leyendecker, G. Erkens, H.-G. Fuss (CemeCon, Germany); I. Rass, M. Feldhege (Euromat, Germany) To meet the sophisticated demands of dry cutting, lubricious coatings in combination with ternary hard coatings are the focus of present development activities. Elimination of coolants 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. PVD process technique does not influence the toughness of cemented carbide or cermet substrates due to the low deposition temperature compared to CVD processes. 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 oxide- or BN-containing 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 as well as the initial wear. Also the chip flow can be effected positively. Boron and oxygen containing hard coatings e.g. TiAlN- Al₂O₃ multilayer coatings or 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 and ESMA. Furthermore highlighted are influences of coating composition on cutting forces and chip flow in dry drilling of tempered steel and grey cast iron.
9:30 AM		G4-4 Wear Resistance of CrN/MoS₂ Multifunctional Coatings for Milling Applications P. Crausaz, P.-A. Steinmann, L. Zaquini (EICN University of Applied Sciences, Switzerland); P. Jaccard, S. Mikhaïlov (CAFI Ion Beam Center Analysis, Switzerland); A. Savan, E. Pflüger (CSEM Surface Engineering, Switzerland); B. Jouan (UMV Tools Company, Switzerland) Due to environmental, health and economic considerations, there is a strong demand to replace the presently used machining technology based on synthetic lubricants by a technology based on a lubricant free or nearly dry machining. Cutting fluids are non-biodegradable and their waste disposal or recycling are very costly. It is then necessary to develop new tools that offer the advantages of high productivity, excellent surface finish of the machined part and nearly dry lubrication. PVD multifunctional coatings consisting of a hard, tough sub-layer deposited by cathodic arc (CrN) and a soft solid lubricant top-layer deposited by unbalanced magnetron sputtering (MoS₂) have shown promising results in the milling tests of 904L austenitic stainless steels. Parallel to these practical results, depth profile analyses of the chemical composition and stoichiometry of each individual coatings as measured by Rutherford back scattering spectrometry (RBS) and Wavelength dispersive spectrometry (WDS) have been performed. It can be concluded that adhesion layers and/or composition graded interfaces are required and constitute a key factor in terms of the tool lifetime optimization. Comparisons with commercially available milling-cutters will be discussed.
9:50 AM		G4-5 Innovative Hard and Autolubircant PVD Coatings for Dry - Drilling and Other Difficult Machining Operations F. Rabezzana (Metec Technologies, Italy); S. Durante (Centro Richerche Fiat, Italy); D. Franchi (Ferioli & Gianotti, 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 difficult cutting tool applications, and to present the results of high performance and dry or nearly-dry machining tests performed with different tools coated with these innovative PVD layers in comparison with standard HSS and WC uncoated and coated tools. 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 hard + autolubricant PVD coatings, in the system Ti-Al-C-N-Mo-S, for difficult cutting tool applications. For testing the different coatings we have chosen high speed, minimal lubrication and/or dry cutting tool operations for machining ferrous and non-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 tools will be presented and discussed.
10:30 AM		G4-7 Influence of Substrate and Counterpart Grades on the MoS₂/Titanium Composite Coatings Tested in Several Conditions N.M. Renevier, V.C. Fox, D.G. Teer, J. Hamphire (Company Teer Coatings Ltd, United Kingdom) As previously reported [¹, ²] the properties of MoS₂ coatings can be improved by the co-deposition of a small amount of titanium. These MoS₂ /Ti coatings known as MoST MoST^TM, were harder, much more wear resistant and also less sensitive to atmosphere water vapour than pure MoS₂ during tribological testing. These coatings have given excellent industrial results for a wide range of cutting and forming applications. Samples of carbides, stainless steel, high speed steel and mild steel. They were rubbed against WC, Cr steels, Aluminium and braze balls in pin on disc and reciprocating wear tests at several loads and under several conditions (humidity, oil, water, …) and their friction and hardness were reported. Counterparts as well as the coated samples were studied. Structural analysis was also carried out using different techniques such as reflection X-ray, optical microscopy, scanning electron microscopy and transmission electron microscopy on unworn and rubbed samples. Correlation with real applications will be given. ¹ - V.C. Fox, N.M. Renevier, D.G. Teer and J. Hampshire, V. Rigato, Proceedings of the PSE Conference in Garmisch Partenkirchen, 14-18 September 1998, Germany, in press in Surf. Coat. Technol.. ² - N.M. Renevier, V.C. Fox, D.G. Teer and J. Hampshire, ICMCTF Conference in San Diego, April 1999, USA. in press in Surf. Coat. Technol..
10:50 AM		G4-8 A New Class of High Performance PVD Coatings for Carbide Cutting Tools H.-G. Prengel (Kennametal Hertel AG, Germany); A.T. Santhanam (Kennametal Inc., Latrobe); K.H. Wendt (Kennametal Hertel AG, Germany); P.C. Jindal, R.M. Penich (Kennametal Inc., Latrobe) During the past three decades, hard coatings applied to cemented carbide substrates by chemical vapor deposition (CVD) and physical vapor deposition (PVD) have significantly improved metalcutting productivity. CVD coatings were developed first and presently see widest use. PVD coatings, commercialized in the last fifteen years, have evolved from single layer TiN designs to high performance coating configurations out of the system Ti-Al-N-C-B. Cutting tool manufacturers are currently developing a new class of high-performance PVD coatings based on Ti/Al with C, N, or B as nonmetallic components. These coatings are applied as mono- or multilayer using either high-ionization magnetron sputtering or improved cathodic arc processes. The new coatings are providing further advances in metalcutting productivity. In this paper we will describe several advanced PVD coating designs based on Ti-Al-N-C-B, and will document their metalcutting performance on a variety of workpiece materials including gray cast iron, ductile cast iron, and aluminum alloys.
11:10 AM		G4-9 Environment-Controlled Machining of Al-Si Alloys with Polycrystalline and CVD Diamond Tool Inserts T.C. Ovaert, J. Zhou (Penn State University) Experiments have been conducted by machining high silicon aluminum alloys (11% and 17.8% Si), using both polycrystalline (PCD) and chemical vapor deposited (CVD) thin film diamond cutting tools in a controlled environment. Environment-controlled machining (turning) has been conducted with a specially-designed apparatus in air, vacuum, dry oxygen, and oxygen with 400 ppm H₂O vapor to investigate the role of oxide formation in the machining process. Three orthogonal cutting forces were recorded as a method of monitoring tool performance. The friction and normal forces on the rake face were also estimated. SEM micrographs and EDX elemental analysis of the chips were also performed in this study. The results suggest that the silicon in the aluminum functions as a preferential sliding interface that inhibits intimate contact at the chip-tool interface. In addition, improved surface finish, reduced built-up-edge, and reduced material transfer occurred when using the PCD tool as compared to the thin film tool. The lowest friction and normal forces were obtained when machining in air and in moist oxygen, while the largest forces occurred in dry oxygen or vacuum. The elemental analysis indicated that a greater degree of oxidation occurred while machining in dry oxygen than in air or in moist oxygen. This suggests that the level of oxidation in the machining process impacts tool performance and overall machinability of the workpiece, in addition to rake face roughness.
11:30 AM		G4-10 Production Scale ZrO₂-TiAlN Sputter Coating Development for Dry Machining Operations M. Schulze, M. Feldhege, I. Rass (Euromat GmbH, Germany); T. Leyendecker, G. Erkens (CemeCon GmbH, Germany) Thin film oxide coatings are of increasing nterest in the last years thin film developments. Due to high binding energies oxide materials such as Al₂O₃ or ZrO₂ are highly resistant against adhesive wear. Furthermore, with increasing temperature the sliding coefficient decreases and the hardness reduction is slow. This leads to high abrasion resistance and a high potential for dry machining applications. This paper describes the development of a ZrO₂-TiAlN coating using a combined DC/RF Sputter Ion Plating process. All coatings were applied under production conditions at moderate temperatures below 400°C in order to coat HSS as well as cemented carbide tools. Different layer arrangements and main metallographic data are presented. Furthermore, the results of tribological tests and first performance tests in dry machining operations are shown.