Papers

ICMCTF2001 Session E2-1: Wear Resistance of Ceramic, Metallic and Composite Coatings

Tuesday, May 1, 2001 1:30 PM in Room California

Tuesday Afternoon

Start	Invited?	Item
1:30 PM		E2-1-1 Work Material and the Effectiveness of Coated Tools C.Y.H. Lim, P.P.T. Lau, S.C. Lim (National University of Singapore) Earlier studies have suggested, through the use of wear maps, that significant benefits of coated tools (in terms of lower tool wear rates) may only be realized when the appropriate machining conditions (cutting speed and speed rate) are chosen. This paper investigates the effects of work material on the performance of coated tools by comparing uncoated and titanium carbide- (TiC-) coated cemented carbide tools when cutting two medium carbon steel grades: AISI 1045 and AISI 4340. Wear maps constructed for these tool-work combinations show that the TiC coating is more effective when machining the softer plain carbon 1045 grade, decreasing tool wear rates by half an order of magnitude or more over a wide range of cutting conditions. More modest reductions are achieved with the harder 4340 alloy. Nonetheless, with both steel grades, the TiC coating still significantly expands the range of machining conditions under which acceptable levels of tool wear are obtained.
1:50 PM		E2-1-2 Dry Cutting Performance of Partially Filtered Arc Deposited Titanium Aluminium Nitride Coatings With Various Metal Nitride Base Coatings S.G. Harris, E.D. Doyle, A.C. Vlasveld (Swinburne University of Technology, Australia); P.J. Dolder (Ford Motor Company of Australia) The presence of macroparticles in the plasma generated from cathodic arc sources has long been the bane of cathodic arc coatings, particularly in those coatings designed for aggressive machining applications such as dry and high-speed machining. Numerous attempts have been made to reduce the number of macroparticles in cathodic arc coatings by filtering of the plasma flux. However, most filtered arc systems reduce the number of macroparticles by avoiding line of site plasma trajectories, which adversely affects coating deposition rate. Recent research by Münz et al has focussed on reducing macroparticles in PVD coatings by use of high melting temperature cathode targets for enhanced metal ion etching ¹. It was shown that the number and size of macroparticles depends on the melting temperature of the cathode target. The lower melting point TiAl cathode produced the highest number of macroparticles, whilst niobium and molybdenum, with melting temperatures above 2000°C, produced the least number of macroparticles ¹. The objective of the current research paper is to systematically quantify the affects of a range of metallic interlayers, and subsequent nitride base coatings, on the performance of partially filtered cathodic arc TiAlN coatings. Coating characterisation methods include measurement of coating adhesion, surface roughness, hardness and residual stress. The size, shape and distribution of macroparticles are reported for a number of metallic interlayers, respective nitride base coatings and subsequent TiAlN top coatings deposited onto high-speed steel coupons. Coatings were also deposited onto high-speed steel twist drills for comparative dry machining tests. Drill performance is reported in terms of the rate of drill wear, and maximum drill life as indicated by audible screech, which is indicative of catastrophic drill failure. ¹ W.-D. Münz, I.J. Smith, D.B. Lewis, S. Creasey, Vacuum, V48, N5 1997 p473.
2:10 PM		E2-1-3 FEA Design of a Coating Architecture for Glass Molding Dies D. Zhong, G.G.W Mustoe, J.J. Moore (Colorado School of Mines); S. Thiel, J. Disam (Schott Glas, Germany) Finite element analysis (FEA) is being used as an integral part of an overall research program that is being conducted to develop a non-sticking, oxidation resistant, and wear resistant coating system for glass molding dies and forming tools. In this work, a non-linear thermomechanical FE model has been used to analyze the residual stresses generated in the coating system during a simulated glass molding process, and to predict an optimal coating architecture with minimized residual stress and optimized stress distribution. The FEA was performed with the general purpose FE code in the MARC system. In this paper, layer thickness, temperature, intrinsic stress and architecture effects will be discussed. The results proposed a FGM multilayer coating architecture that could benefit the performance of the coating system for glass molding dies.
2:30 PM		E2-1-4 Tribological Behaviour of MEVVA Implanted TiN, TiCN and CrN Coatings Deposited on Stainless Steel Substrates P. Kavuri, L.P. Ward (Royal Melbourne Institute of Technology, Melbourne, Australia); R.R. Manory (Osaka University, Japan); P. Evans, H. Noorman (Australia Nuclear Science and Technology Organisation, Australia) Hard metal nitride coatings are now accepted in many engineering applications where enhanced tribological performance is critical, such as cutting tools and metal forming dies. Although TiN is well established in this area, in recent years attention has focussed on the use of alternative nitride coatings, such as CrN and TiCN, because of their high hardness, lower coefficients of friction and excellent wear resistance. Although these coatings perform satisfactorily, further improvements in their tribological performance are expected by modifying the surface using ion implantation. This conclusion is based on prior works on TiN. In the present study, TiN, TiCN, and CrN coatings were deposited onto polished AISI 316 stainless steel substrate using commercially available physical vapour deposition (PVD) technology. Coated samples were MEVVA ion implanted with Cr, Zr, Nb, Mo, and W species at a nominal dose of 4 X 1016 ions / cm2. Friction and wear studies were performed using a pin on disc CSEM Tribometer at 1N load and 450m sliding distance under dry sliding conditions. Analysis of the implanted specimens and resultant wear tracks were carried out using rutherford back scattering, optical / scanning electron microscopy, x-ray diffraction, scanning probe microscopy and microhardness / nano-indentation. The results of the study reveal that with the exception of Nb implantation, the wear performance of TiN and TiCN was improved after modification. In particular, significant reduction in the wear rates were observed for Zr and Mo implanted TiN and Mo implanted TiCN. For modified CrN coatings no wear was observed. The implications of these results are discussed. .
2:50 PM		E2-1-5 Coated Machine Elements - Fiction or Reality? B Podgornik (University of Ljubljana, Slovenia) In the last decade a tremendous progress has been done in the field of hard coatings and surface treatments. The majority of research work refers to improvement of mechanical and tribological properties of coatings, which in most cases are deposited on "hard" substrates, i.e. ceramics and tool steels, and used for cutting tools. However, requirements for machine elements are quite different from those for tools. In addition to a hard, wear resistant surface with good frictional characteristics, a tough, fracture resistant core is necessary. In the contrast to tool steels, hardened and tempered low alloy steels have high fracture toughness. On the other hand high hardness and internal compressive stresses of the case formed by plasma nitriding can lead to increased load carrying capacity of the steel substrate as well as to improved tribological properties of coated parts. Therefore, the combination of plasma nitriding and hard-coating would allow function sharing between the core material, the hardened case and the surface, which is of special interest for application in complex stressed machine elements. The intention of the present work was to investigate the possibilities of successfully using thin hard coatings in the field of machine elements. Therefore, samples made of AISI 4140 steel pre-treated by plasma nitriding and coated by different PVD coatings (TiN, TiAlN and DLC) were investigated with respect to the microhardness, residual stress, scratch adhesion and wear resistance. Unlubricated wear tests in which hardened ball bearing steel was used as a counterface were performed under sliding and rolling conditions.
3:30 PM		E2-1-7 Application of PVD Coatings to Machine Components L.E. Seitzman (Caterpillar, Inc.) Metallurgical coatings grown by physical vapor deposition (PVD) show potential for improving the performance of machine components. Testing in the laboratory and the field clearly indicates that PVD coatings can increase system durability and extend operation to more extreme contact conditions. Post-test analysis illuminates opportunities for improving the coating-substrate system and the limitations in the current art of evaluating potential improvements. We will present specific examples of coating failure analysis and discuss the lessons learned. Finally, we will discuss how this information can provide guidance to the R&D segment of the surface engineering community.
4:10 PM		E2-1-9 Long Term High Load Wear Testing of Carbon Based Coatings S. Yang, A.H.S. Jones, D.G. Teer, M Jarrat (Teer Coatings Ltd., United Kingdom) Graphit-iC^TM is a sputtered carbon coating with low friction and low wear rate at very high loads. The coating retains these properties running dry or under water or oil. It is now being used in a number of automobile applications and is being investigated for very heavily loaded components such as drive gears. This paper presents the results from pin on disc tests run under boundary lubrication conditions at specific loads as high as 3GPa. Wear rates around 10^-19m³/Nm are obtained and thus long term testing is necessary. Although the Graphit-iC coating has excellent adhesion, as indicated by conventional scratch testing and Rockwell indentation, the long term wear tests have revealed for some of the coatings an adhesion failure probably related to fatigue. Methods for improving the adhesion and eliminating this type of failure are studied. A comparison with a number of DLC and other hard coatings is made.
4:30 PM		E2-1-10 Surface Cementation of Aluminum Alloys by Excimer Laser F. Fariaut (Universite d'Orleans, France); C Boulmer-Leborgne (GREMI, France); E. Le Menn (GREMI-ESPEO, France); T. Sauvage (CERI-CNRS, France); C. Andreazza, P. Andreazza (CRMD-CNRS, France); C. Langlade (Ecole centrale de Lyon, France) The excimer laser cementation process reported is developed to enhance the mechanical and chemical properties of aluminum alloys. It would be interesting to use aluminum alloys in the automotive industry widely because of their low density, corrosion resistance and good workability. The motor weight can be reduced by replacing usual materials such as iron-steel by light alloys treated to increase their wear resistance. Ceramic materials generally exhibit great strength, resistance to wear and oxidation. The use of laser beams allows surface treatment to be located at the parts strongly exposed to wear and friction. The surface undergoes a transformation leading to an increase in hardness without changing the dimensions of the piece, thus avoiding no remachining after treatment. The laser process is especially suitable for environment protection as there is no pollution by chemical solvent or emanation. An excimer laser beam is focused onto the alloy surface in a cell containing 1 bar nitrogen or/and propylene gas. A vapor plasma expands from the surface and shockwave dissociates and ionizes the ambient gas. It is assumed that nitrogen or/and carbon from plasma in contact with the surface penetrates in depth. Thus it is necessary to work with a sufficient laser fluence to create the plasma, but this fluence must be limited to prevent laser-induced surface roughness. The nitrogen or/and carbon concentration profiles are determined from RBS and SEM coupled to EDX analysis. Crystalline quality is evidenced by XRD technique. TEM gives the in-depth microstructure. The polycrystalline cemented layer obtained is several micrometers thick and composed of a pure composition (columnar microstructure) top layer (200-500nm thick) standing on a diffusion layer (grains). Fretting test measurements exhibit an improvement of the surface mechanical behavior for some experimental conditions.
4:50 PM		E2-1-11 Adhesion and Micro-Scale Abrasion of Duplex-treated AISI H13 Steel K.S. Al-Rubaie (Fundacão Centro Tecnologico de Minas Gerais, Brazil); J.R.T. Branco (Fundacão Centro Technológico De Minas Gerais-Cetec, Brazil) In recent years, duplex coatings, consisting of nitriding followed by hard coating, has found increasing applications in metal forming tools such as extrusion and forging. The advantage of duplex coating, in comparing with the conventional PVD coating, is its higher load-bearing capacity due to nitriding. In this investigation, samples of AISI H 13 steel were pre-treated by plasma nitriding and then coated with TiN using a triode ion plating equipment. To study the influence of the nitrided zone on the performance of the duplex coating, two different nitriding conditions were used. Microhardness, surface roughness, and scratch adhesion tests were carried out. Micro-scale abrasion tests and coating thickness measurements were performed using a fixed ball cratering technique. The effect of the pre-nitriding on the critical load and wear behaviour is discussed. Keyword: AISI H 13 steel, Plasma nitriding, PVD deposition, Triode ion plating, Critical load, Wear behaviour.
5:10 PM		E2-1-12 Characterization of (Ti_x Cr_0.6-x)N0.4 Coatings and Their Tribological Behaviors Sliding Against Epoxy Molding Compound J.H. Hsieh (School of MPE, Nanyang Tech. University, Singapore); W Zhang (Gintic Inst. of Manu. Tech., Singapore); C.Q. Sun (Nanyang Tech. Univ., Singapore) Several graded (Ti_x Cr_0.6-x)N0.4 coatings as well as TiN and CrN coatings were deposited by unbalanced magnetron sputtering. These coatings were then characterized using XRD, SEM, TMA, and indentation adhesion testing. The focus was then on the comparison of wear resistance among these coatings against epoxy molding compound. The results show that the properties and wear resistance of the ternary coatings depends strongly on the composition ratio of Ti and Cr. In general, Cr addition remarkably enhances TiN coating's oxidation resistance and wear resistance. The Ti-Cr-N ternary coating exhibits better wear performance against EMC than TiN coating.