ICMCTF2002 Session EP-1: Symposium E Poster Session

Tuesday, April 23, 2002 5:00 PM in Room Town & Country

Tuesday Afternoon

Time Period TuP Sessions | Topic E Sessions | Time Periods | Topics | ICMCTF2002 Schedule

EP-1-1 Structural and Mechanical Properties of SiO_x and Al_xO_x Coatings V. Baghdasaryan (Yerevan Physics Institute, Armenia); A. Torosyan, S. Aloyan, H. Balayan (Yerevan, Institute of General & Inorg. Chemistry, Armenia); H. Navasardyan (Yerevan Physics Institute, Armenia) The deposition and characterization of crystalline and nanocomposite SiO_x and Al_xO_x coatings on steel and aluminum substrates are reviewed. The drive towards coatings with novel properties that can be deposited economically and in an environmentally friendly manner has resulted in a new strategy for processing of advanced materials, "soft solution processing". The presented coating technique, which is a combination of mechanical perturbation and the sol-gel method, makes it possible to deposit ceramic and composite coatings at room temperature. The objective of this technique is to fabricate functional coatings from advanced materials with minimum consumption of energy at low costs. The coating deposition was carried out in a vibration mill at the vial amplitude of 2 mm and the frequency of 25 Hz. A specially designed ball mill vial was used for this purpose. The substrate specimen from aluminum alloys (UNS number A91100) and low carbons steel (UNS number G10100) were rectangles 5x10 mm. The precursor solution used for forming the SiO_x and Al_xO_x coatings were 30% silica-sols with the nanodispersed spherical particle up to 10nm and 25% alumina-sols with the average particle size up to 5nm. The coating deposition was carried out in sol-gel medium of the vibration ball mill together with mechanical processing of metallic specimens. Thickness, microhardness and adhesion of these coatings are defined. The thickness of coatings can vary up to 30 micrometers. The microhardness of the coating increases several times with respect to that of the substrate. The adhesion of the coatings is about 5 times better than that of coatings deposited by conventional coating technologies. Combinations of film characteristics and the cost efficiency makes this technique attractive as compared to conventional techniques and particularly suitable for large-area industrial coatings. .
EP-1-2 Micro Mechanical and Chemical Properties of Silicon Processed by Diamond Tip J.D. KIM, S. Miyake (Nippon Institute of Technology, Japan) The properties and mechanism of silicon protuberance and groove processing by diamond tip sliding using atomic force microscope (AFM) in an atmosphere were studied. To control the height of protuberance and the depth of groove, the processed height and depth dependencies on load and diamond tip radius were evaluated. Diamond tip of about 200 nm radius sliding produces 0-5 nm height protuberances on the silicon surface. In contrast, about 50 nm radius tip sliding produces 0-20 nm deep grooves on the silicon surface. Protuberance height processed with 200 nm tip and groove depth processed with 50 nm tip increase with applied load increase. Using about 100 nm radius tip both protuberance and groove are produced. The hardness of processed parts is higher than that of unprocessed parts, therefore, oxidation of silicon is speculated to be caused at the rear edge of sliding contact area that the elongation stress is the highest. To clarify the mechanical and chemical properties of these processed parts, changes in the protuberance and groove profiles due to additional diamond tip sliding and potassium hydroxide (KOH) solution etching were evaluated. Processed protuberances were negligibly removed, and processed grooves were easily removed by additional diamond tip sliding. The KOH solution selectively etched the unprocessed silicon area, while the protuberances, grooves and flat surfaces processed by diamond tip sliding were negligibly etched. Three-dimensional nanofabrication is performed in this study by utilizing these tribo-chemically processed parts as a protective etching mask.
EP-1-3 Assessing the Micro-abrasive Wear Resistance of Coatings. C. Tsotsos, A. Leyland, M.C Joseph, A. Matthews (University of Hull, United Kingdom) A micro-scale abrasive wear test has been used to study the wear resistance of thin ceramic films (e.g. CrN and ZrCN) deposited on AISI 316 stainless steels against a silicon carbide abrasive in aqueous slurries. Wear craters were produced by an SAE 52100 ball, 25mm in diameter, rotating against the coated specimen for a number of revolutions (100, 200, 300, 600 and 1000revs) with the presence of small abrasive particles creating an imposed wear volume. In this research a modified Archard equation was used to investigate the combined wear volume of the coating and the substrate. This is a simple and fast method of producing comparative results for routine testing, by measuring the diameter of the wear crater of the combined coating and substrate wear volume. This overcomes the main problems faced by the, previously used, linear regression analysis; as it gives improved reproducibility and reliability in assessing the volumetric wear rate of the combined coating-substrate system.
EP-1-4 Stress and Deformations of Composite Tribological Coatings J.L. Endrino, J.E. Krzanowski (University of New Hampshire) Our recent work in the study of carbide-silver coatings demonstrates that the wear resistance and friction under vacuum of mechanical components can be optimized by a combination of a ceramic material and a metallic solid lubricant such as silver. In a vacuum environment, where oxidational wear is not likely to occur, a combination of adhesion, abrasion and fatigue describe the wear mode. The relevance of the study of the stresses is that it is the main cause for the deformations and fracture of the material that ultimately produces material flow. This research, which is based on an object-oriented finite element approach with elastic deformation of the ceramic phase and elastic-linear-kinematic-hardening-plastic deformation of the metal lubricant, analyzes the influence of phase percentages, materials properties and coefficients of thermal expansion in the stress field.
EP-1-5 Nano Adhesion, Friction and Wear of Hydrophobic Surfaces using SPM E.-S. Yoon, S.H. Yang, H.-G. Han, H. Kong (Korea Institute of Science and Technology, Korea) Nanotribological properties of hydrophobic surfaces for MEMS application was experimentally studied. The adhesion, friction and wear properties between tip and modified surfaces under nano scale applied load were measured using scaning prove microscope(SPM). DLC(diamond-like carbon) films coated by PACVD (plasma assisted chemical vapor deposition) methods and thin silver films coated by IBAD (ion beam assisted deposition) were prepared on a silicon wafer (100). Also several kinds of self-assembled monolayers (SAM) with different surface terminal, spacer chain and head group were prepared on a silicon wafer (100). Si₃N₄ oxide-sharpened tips were used for measurements of adhesion and friction forces and diamond tip was used for measurements of wear. Friction forces were measured with the normal load. Tests were conducted in ambient temperature and especially various ranges of relative humidity such as 30%, 50% and 70%. When the surface was hydrophobic, the wetting angle increased and the adhesion and friction forces were found lower than those of bare Si-wafer. Low adhesion force was caused by the properties of surface and terminal group with its low work of adhesion. Adhesion force varied linearly with work of adhesion. Friction force was increased with the applied normal load. Though normal load was not applied friction force existed at zero point in normal load, which resulted from adhesion force. This result must be considered to calculate the coefficient of friction. Results also showed that adhesion force increased as the relative humidity increased. The main parameter for affecting the adhesion and friction was found the absorbed humidity on the contact surface. These results were discussed with the JKR model and a capillary force due to the condensed water.
EP-1-6 The Effects of Sealing Process on the Tribological Beahvior of the Plasma Sprayed Zirconia Based Coatings D.S. Lim, J.H. Shin (Korea University, Korea); H.-S. Ahn (Korea Institute of Science and Technology, Korea) Plasma sprayed ceramic coatings inevitably contain pores and cracks. These pores and cracks are believed to be the main source of tribological failure in the plasma sprayed coatings. The dipping process was performed to seal the pores and cracks in the plasma sprayed coatings. As-sprayed coating was dipped in zirconia-sol to infilltrate up the pores and the cracks. After dipping process, the porosity was decreased and micro-hardness was increased. The wear experiments were carried out on a ring-on-plate type reciprocating wear tester at selected temperature in the range of 20~600°C. The tribological properties of zirconia-based coating were also improved by dipping process. These results could be explained by the improvement of coating quality and the stabilization of tetragonal phase. The annealing treatment followed by dipping process relaxed the tensile residual stress in the sprayed coating and stabilized the tetragonal phase. Thermal degradation generally observed at about 400°C in zirconia based coatings was also decreased by annealing process.
EP-1-7 Mechanical Behaviour of W-S-N/C Sputtered Coatings Deposited with a Ti Interlayer A. Nossa (Escola Superior de Tecnologia e Gestao, Instituto Politecnico da Guarda, Portugal); A. Cavaleiro (ICEMS, Mechanical Engineering Department, University of Coimbra, Portugal) WS₂ has structure and properties similar to MoS₂, although the research works carried out on this material arise essentially due to its electrical and semiconductor properties. Recently, some investigation on the deposition of WS₂ films was carried out for tribological applications, once this material has also low friction coefficient and high environmental stability in vacuum and dry conditions. In previous work the addition of C/N to W-S sputtered coatings was studied. Although improvement on the mechanical properties of the coatings had been obtained, the adhesion of the films was very low. The main objective of this work is to study the influence of a titanium interlayer between the substrate and W-S-N/C films on their mechanical properties. Firstly, the deposition of the Ti interlayer was optimised, varying its thickness and substrate bias used in the deposition. Afterwards, W-S-N/C films were deposited by sputtering with increasing N or C contents, using the optimised Ti interlayer. The characterization of the Ti/W-S-N/C films concerns: chemical composition, morphology, structure, adhesion, hardness, friction and wear coefficients obtained by alternative sliding and pin-on-disk tests. Much higher adhesive critical loads (scratch-testing) were reached (>25N) in comparison to previous work, leading to improvements in the wear resistance of the coatings, with wear coefficients in alternating sliding pin-on-disk testing as low as 8x10^-16 m³/Nm.
EP-1-8 Novel Hard/Soft Composite Materials for Tribological Applications M.Y. Chen (Air Force Research Laboratory); S.C. Tan (Wright Materials Research Co.) In recent years, there is great interests in the development of innovative wear resistant solid lubricant and hard coating materials aimed at improvements in space based mechanical systems, and aircraft propulsion and structures. This study focuses on the use of bulk composites and nanocomposite films composed of hard and soft materials for these potential applications. Hard phases include: B4C, SiC, and Al2O3, and the Soft phases include MoS2, WS2 and graphite in the form of carbon nanotube. Examples of their different roles as a load support, lubricant, or lubricant retainer, as well as their synergistic effects will be presented. In specific, we investigated multilayers of boron carbide/DLC films which were deposited using dc magnetron sputtering as well as co-continuous alumina/aluminum composites with and without SiC reinforcement or lubricious composite thin films which were spin coated onto the composites. Correlations will be established between compositions/composite architecture and tribological properties. These novel, wear resistant materials will find parallel application in the automotive industry, machine tool industry and commercial aerospace industry.
EP-1-9 MoS₂-Ti Composite Solid Lubricant Deposited by Bias-dc and Pulsed-dc I. Efeoglu, E. Arslan, F. Bulbul (Ataturk University, Turkey) A closed field unbalanced magnetron sputter ion plating (Teer-CFUBMSIP/550) system has been used for the deposition of MoS₂Ti composite coatings on different types of substrate with using bias-dc and pulsed-dc. The mechanical and tribological properties of MoS₂Ti coated composites onto selected steel substrates were characterized using microhardness test, friction-wear test under atmospheric conditions any dry nitrogen. Structural analysis was pointed out using X-ray diffraction and SEM-EPMA.
EP-1-10 Evaluation of Tribological Properties of DLC Films Used for Sheet Forming of Aluminum Sheet M. Murakawa, S. Takeuchi (Nippon Institute of Technology, Japan) A DLC (Diamond-Like Carbon) film, i.e., a hard carbon film having amorphous structure, is known to have excellent tribological properties against various materials. However, because of its low adhesion strength to a substrate and/or its difficulty of the preparation of thick film required, they have not been so much applied to the field of tool as expected. This paper reports basic tribological properties of DLC films against aluminum alloys which are known to cause adhesion easily when tools are used without DLC coatings or films. More specifically, the films prepared by various techniques with different compositions and coated to the forming tools were subjected to tribology tests using aluminum alloys as the mate material. A heavy-load friction tester was home-made to enable us to apply load similar to actual metal forming of the material. It was found that among various hydrogenated carbon films with or without inclusion of metal element the one with no inclusion of metal element shows most excellent tribological properties.
EP-1-11 Application of Platelet CVD Diamond to Micromachine Elements H. Noguchi, S. Takeuchi, M. Murakawa (Nippon Institute of Technology, Japan) In order to realize micromachines, taking into consideration their environment of use, they must function without lubrication, and also have a low friction coefficient and high resistance to wear. Since diamond has excellent tribologic characteristics and tolerance to chemical reaction, it is anticipated to be a suitable material for such micromachines. However, it is difficult to use generally available diamond grains for micromachines due to the extreme hardness met when they are processed into definite shapes. Fortunately, platelet diamond prepared by the combustion flame method is composed of hexagonal microplates and has a shape from the beginning promising for its use as a micromachine material without so much elaborate machining operation. However, there have been no reports on the use of platelet diamond as a micromachine material. This paper reports a trial of applying such diamond to micromachine elements, e.g., such as a micropivot bearing or a knife edge.
EP-1-12 Tribological Behaviour of the Diamond/Steel Couple: Experimental and Modelling Approaches M. Schmitt, D. Paulmier (Institut de Chimie des Surfaces et Interfaces, France); A. Eleod, J. Devecz (Budapest University of Technology and Economics, Hungary) The technical and technological evolvments over the last decade have made the machining a more and more widespread process in many industrial applications ; its use, always increasing, induces it had to be optimised in order to diminish its cost, that means a work at very high speed and directly in final surface state. Various solutions were considered to treat the cutting tools, but, with its low wear rate combined with its extreme hardness, diamond is one of the most suitable candidate to coat the cutting surfaces. In this way of looking at things, the tribological behaviour of the diamond/steel couple was studied : experiments were realised with diamond coatings, obtained by flame process, sliding against High Speed Steel ; the influence of various parameters was more particularly highlighted : the diamond crystals orientation, the nature of the environment and the applied normal load. The morphology and sight of both the contact areas and the transfer were observed by Scanning Electron Microscopy, and their chemical composition analysed by Energy Dispersive Spectroscopy. A numerical modelling of the dynamical pin-disc contact was concurrently realised : this allowed the determination of the stress state in every part of the system, after the pin motion on the disc, as well as the evaluation of the critical stress the interface can support before the diamond-counterface decohesion. Numerical simulation and experimental tests are then complementary : experimental results are required for the finalising of the modelling, and this latest gives information allowing a clarification of the phenomena observed during the tests ; that consequently leads to a better understanding of the processes occurring during the friction, and avoids thus long and expensive tests.
EP-1-13 Deposition of Carbon Nitride Thin Films by Means of Ion-Plating and Their Tribological Properties S. Watanabe, S. Miyake, M. Sutoh, M. Murakawa (Nippon Institute of Technology, Japan) Carbon nitride films have been synthesized by several kinds of vapor phase techniques including plasma-CVD, sputtering and ion-beam techniques, because of considerable interest in the super-hard cubic or beta-type C₃N₄ compound. In particular, carbon nitride films show excellent mechanical properties such as low friction and high wear resistance, similar to diamond-like carbon (DLC). Therefore, it is expected the films will be very useful for tribological coatings on various industrial substrates. The authors are researching the use of an ion plating method, with the goal of synthesizing crystalline carbon nitride thin films. The tribological properties of films deposited under various conditions were investigated. The magnetically enhanced plasma ion plating method, which has been used successfully to form cubic boron nitride films, was used as the film formation method. Carbon nitride films were deposited on Si substrate by reactive evaporation in carbon vapor using an electron beam and highly ionized gas was supplied adjacent to the substrate. Ar-N₂-C₂H₂ mixed gas was flowed into the chamber. The micro-mechanical properties of the films were examined by means of the nano-indentation test together with a micro-scratch test, utilizing an atomic force microscope. A composition analysis of the film was performed by AES and XPS.
EP-1-14 Delamination Behavior of Boron Nitride Thin Films Deposited by Hybrid Ion Plating-ion Implantation Technique S. Lee, E Byon, J.-K. Kim, G.-H. Lee (Korea Institute of Machinery & Materials, Korea); M. Isshiki (Tohoku University, Japan) Cubic boron nitride (cBN) has a technological potential application because of its unique properties such as highly mechanical, thermal, electrical and optical properties. In particular, cBN is desirable thin film material for protective overcoats. However, It is reported that it has a significant barrier in the industrial application due to adhesion problem.In this study, boron nitride thin films were deposited by the hybrid technique. The synthesis process consisted of deposition and post-ion implantation. Boron nitride films with various contents of the cubic phase were obtained in this way, and they showed various delamination behaviors. Firstly the relationship between delamination behaviors and compressive stress was investigated. FTIR analysis, measurement of the stress and observation of surface morphologies were conducted. The compressive stress of the boron nitride film was in the range of about 2-20 GPa. As compressive stress of the boron nitride film increased, boron nitride film showed different delamination behavior in terms of the size and/or shape of cracked fragments and lifetime to the whole delamination. Besides, the other effective parameters on the delamination with exception of stress of the boron nitride film have to be considered because delamination of films was dependent on the environmental conditions as well as stress. Delamination mechanism of boron nitride films will be discussed.
EP-1-15 Influence of (C, Ti, B, Zr, Al, Mo) Ion Implantation on Mechanical and Tribological Properties of Ti-6Al-4V alloy C.-L. Chang (Mingdao University, Taiwan (ROC)); Y.W. Huang (National Chung-Hsing University, Taiwan (ROC)); D.-Y. Wang (Mingdao University, Taiwan (ROC)) A metal plasma ion implantation device has been built and used to study various elements ion implantation into different materials for improving the hardness, friction, wear and corrosion properties. In this work we was to study the effect of surface modification of C, Ti, B, Zr, Al, Mo ion implantation on mechanical and tribological properties of Ti-6Al-4V alloy, which is a material used for surgical implants such as artificial hip and knee joints and has been extensively studied for surface modification by metal plasma ion implantation (MPII). Ion implantation was carried out at doses ranging from 1015 to 1018 ion cm-2 and energies from 30 to 140 keV. The characterization of surface modified Ti-6Al-4V alloy after MPII treatments were investigated by SEM/EDS, microhardness, and pin-on-disc tribometer.
EP-1-16 Influence of Bias Voltage on the Tribological Properties of Titanium Nitride Films Fabricated by Dynamic Plasma Ion Implantation/Deposition X.B. Tian, T. Zhang, R.K.Y. Fu, P.K. Chu (City University of Hong Kong) Dynamic plasma ion implantation/deposition combining gaseous and metallic plasmas has been shown to an effective technique to fabricate titanium nitride thin films. Pulsed vacuum arc and simultaneous substrate bias provides the unique capability to optimize the film properties through a flexible matching of processing parameters. We have synthesized titanium nitride films on AISI304 stainless steel samples using a filtered titanium cathodic arc and hot filament glow discharge. The influence of the substrate bias (8kV, 16kV, and 23kV) on the tribolgical properties is investigated. The pin-on-disk experiments demonstrate that a higher bias voltage (e.g. 23kV) leads to a better tribological properties compared to a lower bias, but the trend with respect to the corrosion resistance is opposite. The testing time to result in film breakthough for the 23kV sample is 1.25 times that of the 8kV sample. The wear tracks on the 23kV sample are more irregular than those on the untreated or 8kV sample. Our results disclose that the relationship between the metallurgical dynamics and substrate bias is quite complicated. The bias voltage affects the implantation dose, ion mixing, sputtering rate, and surface morphology, and consequently, the wear-resistance of the fabricated films is affected greatly by the bias voltage.
EP-1-17 Properties of Graded Zirconium Carbide Coatings for Tribological Use T. Hornig, E. Lugscheider, K. Bobzin (Werkstoffwissenschaften, RWTH, Germany) Tribological coatings are commonly used on tools for wear protection realizing longer total life time. For components like bearings or gear wheels the usage of PVD-coatings is still in an initial stage. The requirements for these types of coatings and the related processes are low friction coefficients, low deposition temperatures, realization on complex shapes and fatigue resistance. This paper concentrates on a new concept of graded coating structures. Graded zirconium carbide coatings (ZrC-g) have a specific course of hardness with a hardness maximum in the middle of the coating. The above area is characterized by superstochiometric carbon content for low friction and acting as solid lubricant under tribological loads. The area beneath the maximum hardness offers coating stiffness and realizes good bonding between coating and substrate. Furthermore this part of the coating can be tailored to the substrate characteristics. The coatings architecture is discussed for several substrate materials. The characteristics of the coatings are discussed concerning adhesion quality, mechanical properties and structure as well as fatigue behavior measured by impact tests. Experiences in use on hydraulic components are furthermore presented.
EP-1-18 Improvement in Contact Wear Behaviors of α-Al₂O₃ by Metal Plasma Ion Implantation Process D.-Y. Wang (Mingdao University, Taiwan (ROC)); Y.-Y. Chang, Ming-Chei Chui (National Chung-Hsing University, Taiwan, ROC) Flat α-Al₂O₃ disks have been used as ceramic control valves in many modern water faucets. The mechanical integrity of the valve which consists of two counter-rotating alumina disks, relies heavily on the liquid lubricant in between. In this study, a metal plasma ion implantation process was employed to further improve the mechanical and wear performances of α-alumina. Various materials, such as Ti, Nb, Ni, and carbon with different ion charge states were implanted into the surface of alumina disks with the dose of 1 x 10¹⁷ ions/cm² at energy of 50 keV. Tribological and mechanical analyses were performed by pin-on-disk test and microhardness measurement. Atomic force microscopy (AFM), field- emission SEM, x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD) were used to investigate the microstructure and chemical bonding of implanted samples. The improvement in contact wear behavior of α-Al₂O₃ was shown correlated to the improved toughness of the surface layer after the metal plasma ion implantation treatment. Details of the correlation will be discussed.
EP-1-19 Wear Behavior of Nanometric CrN/Cr Multilayers E. Martínez, J. Romero, A. Lousa, J. Esteve (Universitat de Barcelona, Catalunya, Spain); F. Montalà, L.L. Carreras (Tratamientos Térmicos Carreras, Catalunya, Spain) Multilayered structures have attracted much attention as a way of improving the mechanical and tribological properties of hard protective coatings. We have already reported results on nanometric CrN/Cr multilayers deposited by r.f. magnetron sputtering. It was observed that these multilayered structures improve the hardness of the CrN single layer coatings. Therefore, the next step is the evaluation of the tribological behavior of these CrN/Cr multilayers, which is reported in this paper. The multilayers have been evaluated in their abrasive wear resistance, adhesion to the substrate and sliding wear behavior against alumina balls. The influence of the substrate on the tribological behavior of the coatings has also been investigated. It has been observed that the wear resistance of the multilayers greatly improves when decreasing the bilayer period thickness for a fixed overall coating thickness. The determining parameters on the sliding wear resistance are hardness and toughness, which are also known to be the important parameters on abrasive wear. The main sliding wear mechanisms have been identified as abrasion, tribochemical wear and also coating delamination. In the case of coatings deposited onto steel it is also important the plastic deformation of the substrate during the test and the adhesion of the coatings, which influence the wear rate of the coatings.
EP-1-20 High Temperature Wear of an Electroless Ni-P-BN(h) Composite Coating. O.A. León (Polytechnic Experimental National University, Venezuela); M.H. Staia (Central University of Venezuela); H.E. Hintermann (University of Neuchatel, Switzerland) Wear behavior at room temperature of as-deposited and heat treated electroless Ni-P-BN(h) coatings has been previously studied by the authors. It was determined that these composite coatings presented a wear resistance two orders of magnitude higher than the traditional electroless Ni-P coatings, in the as-deposited and heat treated form, which leads to a diverse field of applications in different industries. Nevertheless, data regarding the influence of temperature on the tribological behavior of the Ni-P-BN(h) coatings are unavailable in the literature. The present study reports the results on the high temperature tribological behavior of a Ni-P-BN(h) autocatalytic coatings deposited on AISI 316L stainless steel discs. A ball-on-disc configuration was employed and 6 mm diameter alumina balls were used as static counterpart. The as-deposited samples were previously post heat treated at 400°C for 1 hour and wear tested at temperatures of 25, 100, 200, 300 and 400°C, respectively. Friction coefficients and wear constants are reported. Scanning electron microscopy was used to determine the morphology of the wear scars on both tribological pair. As the wear test temperature increases, the autocatalytic Ni-P-BN(h) coating exhibits a higher friction coefficient and lower wear resistance. A mild adhesive wear mechanism (adhesive ploughing) was found for the samples tested at room temperature, whereas for those tested at higher temperature a mixed adhesive and fatigue wear mechanism, accompanied by high plastic deformation of coatings and high coating transfer to the ball were observed.
EP-1-21 Wear Mechanism of Autocatalytic Composite Ni-P-BN (h) Coatings. O.A. León (Polytechnic Experimental National University, Venezuela); M.H. Staia (Central University of Venezuela); H.E. Hintermann (University of Neuchatel, Switzerland) Wear experiments, using pin-on-disc configuration, have been employed in testing at room temperature autocatalytic composite Ni-P-BN(h) coatings against AISI 52100 steel balls. Coatings with 11, 35, 45 and 67 vol.% BN(h) were obtained by dispersing the BN(h) of an average particle size of 5.16 µm in a sodium hipophosphite based autocatalytic bath with enhanced agitation and surfactant addition. Scanning Electron Microscopy and 3D perfilometry techniques were employed to study the wear scars and to elucidate the wear mechanism of these composite coatings. Knoop microhardness, roughness, friction coefficients and wear resistance of the coatings for all experimental conditions are also reported.
EP-1-22 Superhard Ti-SiN Coatings by a Hybrid System of AlP and Sputtering Techniques S. Yoon, J.-M. Yoo, K.H. Kim (Pusan National University, Korea); S.R. Choi (NASA Glenn Research Center) TiSiN coatings were deposited onto SKD 11 steel substrates by a DC reactive magnetron sputtering technique using separate titanium and silicon targets, in an Ar/N2 gas mixture. The various Ti-Si-N coating layers were prepared using different deposition conditions of gas composition, bias voltage, and substrate temperature. The structures and surface morphologies of deposited films were characterized by X-ray diffraction and scanning electron microscopy. To investigate the tribological behavior of the Ti-Si-N deposits on SKD11 steel substrate, dry sliding wear experiments were conducted over a range of contact loads (10-100N) and sliding speeds (0.1-0.5m/s) against steel and alumina ball using a conventional ball-on-disc wear apparatus. Each wear test was run up to a constant sliding distance of 1000m (32,000 revolution) regardless of load and sliding speed settings. In addition, the effect of atmospheric humidity on the tribological behavior of the Ti-Si-N coatings was investigated. Wear behaviors and mechanisms at different deposition parameters were determined using scanning electron microscopy, and energy dispersive spectroscopy techniques that were used to analyses morphologies, microstructures and chemical compositions of worn surface and wear debris.
EP-1-23 Tribological Behavior of PACVD TiN Coatings in the Temperature Range up to 500°C E. Badisch, G. Fontalvo, M. Stoiber (Materials Center Leoben, Austria); C Mitterer (University of Leoben, Austria) Titanium nitride is still the standard coating for cutting as well as forming applications. Very recently, it has been reported in another paper by the authors¹ and also by Mitsuo et al.² that chlorine incorporations in nitride coatings are well suited to lower the friction coefficient to extremely low values of about 0.2. Therefore, the aim of this study was to use the PACVD (plasma-assisted chemical vapor deposition) technique to deposit TiN coatings with defined chlorine contents and to investigate the tribological properties of these coatings as well as the thermal stability of the low-friction effect. Dry sliding wear experiments at temperatures ranging from 25 to 500°C were carried out in ambient air. The coatings were worn against ball-bearing steel and Al₂O₃ balls using a high-temperature tribometer. Wear tracks on the coatings after ball-on-disc testing as well as the chemical composition of the coatings were characterized using scanning electron microscopy (SEM) and wavelength dispersive electron probe microanalysis (EPMA). An optical profiler was used to investigate the wear tracks after ball-on-disc testing. Extremely low friction coefficients against ball-bearing steel and Al₂O₃ of about or even below 0.2 have been obtained at room temperature for coatings with chlorine contents between 3.2 and 4.4 at.-%. The friction coefficient against Al₂O₃ increases to values of about 0.6 to 0.8 for temperatures exceeding 70°C. The lowest coating wear coefficient with 1.93x10^-16 m²/N was obtained for Al₂O₃ balls at room temperature, whereas for temperatures exceeding 200°C increased abrasion of the coating takes place, consequently resulting in higher wear rates with values up to 1.5x10^-14 m²/N. ¹ M.Stoiber, G.Fontalvo, E.Badisch, C.Lugmair, C.Mitterer, ICMCTF2002 ² A.Mitsuo, T.Aizawa, Mater. Trans. 40(12) (1999) 1361.
EP-1-24 Wet Abrasion Wear of H13 Steel Coated with TiN/Ti Multilayers M. Vite, J. Aguilar (SEPI, ESIME, IPN, Mexico); M. Flores, S. Muhl (IIM-UNAM, Mexico) We reported the results of the abrasion wet resistance of the TiN/Ti multilayers deposited on steel H13 substrates. The hard coatings were obtained by a balanced magnetron sputtering with a coil concetric to the magnetron. For abrasive wear tests we employed a rubber wheel wet abrasion type tribotester, built under specifications ASTM G 109 by our tribological group. We studied the wet abrasion resistance wear of the steel H13 substrates coated with TiN/Ti multilayers and the steel H13 substrates alone. Composition analysis of the scar wear was performed by means of EDS. The TiN/Ti multilayers were caracterized by XRD, SEM , and Vickers hardness .
EP-1-25 The Effect of Metal Composition on the Structure and Mechanical Properties of Ti-Me-N Superhard Nanocomposite Coatings H.S. Myung, H.M. Lee, J.G. Han (Sungkyunkwan University, Korea) Superhard coatings over 40GPa in hardness have recently been extensively developed for further improvement of tribological performance in various tools and machinery components. In these superhard coatings, nanocomposite coatings are emerging as a technique for high performance of severe tribological applications. In previous work, we synthesized Ti-Cu-N nanocomposite films with various Cu contents. The hardness of Ti-Cu-N films could be significantly improved by addition of the soft metal copper, provided that and appropriate amount was selected. The maximum hardness of these films reached to 45GPa and friction coefficient was measured 0.3 In this study, using the arc ion plating and unbalanced magnetron sputtering hybrid method, we deposited Ti-Me-N(Me: Ag, Sn etc.) nanocomposite films which composed of one hard phase and one soft metal phase, and investigated the relationship of their microstructure, mechanical properties and amount of metal dopant. Film structure and chemical composition were analyzed by X-ray diffraction(XRD) and Transmission Electron Microscopy(TEM), Energy Dispersive X-ray Spectroscopy(EDS) and Glow Discharge Optical Emission Spectroscopy(GDOES). The mechanical properties of Ti-Me-N films were evaluated by microhardness, residual stress and scratch test.
EP-1-26 Infulence of Ion Implantation on Corrosion Resistances of Ti-6Al-4V Alloy by MPII Treatments C.-L. Chang (Mingdao University, Taiwan (ROC)); Y.W. Huang (National Chung-Hsing University, Taiwan (ROC)); D.-Y. Wang (Mingdao University, Taiwan (ROC)) A metal plasma ion implantation device has been built and used to study various elements ion implantation into different materials for improving the hardness, friction, wear and corrosion properties. In this work we was to study the effect of C, Ti, B, Zr, ion implantation on corrosion resistance of Ti-6Al-4V alloy, which is a material used for surgical implants such as artificial hip and knee joints and has been extensively studied for surface modification by metal plasma ion implantation (MPII). Ion implantation was carried out at doses ranging from 1015 to 1018 ion cm-2 and energies from 30 to 140 keV. The corrosion characterization of Ti-6Al-4V alloy after MPII treatments were investigated by SEM/EDS, microhardness, and electrochemical impedance spectroscopy (EIS) analyses.
EP-1-27 Wettability of Coolants on PVD-Coatings E. Lugscheider (Werkstoffwissenschaften, RWTH, Germany); K. Bobzin (Aachen University of Technology, Germany) The wetting properties of coolants are important for tribological systems. In order to optimize the wettability on steel alloys coolants have been modified for decades. Using PVD-coatings for wear and corrosion resistance the thermodynamical interactions between coolant and surface have been changed. The characteristic factor, which affects interfacial interactions such as adsorption, wetting and adhesion, is the surface free energy. The test results are indicating that all PVD hard film systems have much lower surface energies than the uncoated low-alloyed steel. The surface free energy of solids and liquids can be examined by using the drop shape analysis where as spreading a contact angle of coolants on metals isn't measurable. In this work a theoretical solution is presented. The wetting behaviour can be calculated and is given as the spreading coefficient S. Results of these theoretical equations have been proofed and verified by experimental tests.
EP-1-28 Tribological and Electrochemical Performance of PVD TiN Coatings for the Femoral Head of Ti-6Al-4V Artificial Hip Joints C. Liu (Loughborough University, United Kingdom); Q. BI, A. Matthews (University of Hull, United Kingdom) Replacing the femoral head and the acetabular socket with an artificial prosthetic component is practised throughout the world for patients suffering from disabling hip joint disease to restore painless joint function. Moving and anchored parts of the prosthesis are exposed to different mechanical stresses and chemical actions, thus, various mechanical, chemical, tribological, and corrosion processes are undergone by the implants. With the intention of enhancing the tribological and electrochemical performance of the femoral head, TiN coatings were deposited on Ti-6Al-4V substrates using a plasma-assisted electron beam (EB) PVD technique. The thickness, microhardness, surface roughness, and interfacial adhesion of the TiN coatings were evaluated by means of ball-crater testing, micro-indentation, surface profilometry, and scratch testing, respectively. Impacting under a dynamic repetitive impact load, and multi-pass scratching with a 0.2mm radius diamond indentator on the coated surface under a sub-critical load at 50% of L_c1 were carried out to study wear and contact fatigue failure of the TiN coated systems. The corrosion performance was also evaluated by electrochemical testing including d.c. potentiodynamic and a.c. impedance spectroscopic (EIS) techniques in 0.5N NaCl solution. It was found that adhesive failure during impact was observable after 5x10⁴ cycles. The number of traversals Pc at which the coatings started to fail during multi-pass test were in a range of 300-400. The PVD TiN coatings significantly reduced the corrosion rate, icorr by approximately 2 orders of magnitude. The coated systems also exhibited superior pitting resistance, which greatly suppressed the localised deterioration. In addition, the polarisation resistance (R_p = R_pore + R_s) of the TiN coated Ti-6Al-4V systems, determined through the EIS modelling with an equivalent circuit, was 2-4 x 10⁶ Ω cm² after 15 days of immersion.
EP-1-29 Corrosion Resistance of Insulated BaTiO₃ Coating Prepared by Plasma Electrolytic Oxidation C.-T. Wu, F.-H. Lu (National Chung Hsing University, Taiwan, ROC) Crystalline BaTiO₃ films were directly synthesized onto Ti plate in highly alkaline condition using Ba(CH₃COO)₂ and NaOH as electrolyte by plasma electrolytic oxidation. The SEM and XRD results showed that the crater-shaped and large-grained cubic phase BaTiO₃ films were present at electrolytic voltage above the critical voltage about 60 V. The quality of films was influenced on electrolytic voltage and the temperature of the electrolyte. Insulated BaTiO₃ films of 10 µm thick were formed at 90 V electrolytic voltage and 55°C with the electrical resistivity greater than 10¹¹ Ω-cm. The corrosion behavior was investigated by means of the open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements under 0.5 M H₂SO₄, 0.5 M NaCl and 0.1 M NaOH corrosive environment. The improvements of corrosion resistance of the insulated BaTiO₃ films were apparent compared to that of the TiO₂ films by normal anodic oxidation. The analysis of the equivalent circuit from EIS results showed that this effect was attributed to the restrict transport rate of ions or oxygen in the electrolyte to the metal surface.
EP-1-30 Fatigue Behavior of an AISI 4340 Steel Coated with TiNx Films N.Y. Oramas (Universidad Central de Venezuela, Caracas, Venezuela); K.E. Cooke (Teer Coatings Ltd, United Kingdom); E.S. Puchi-Cabrera (Universidad Central de Venezuela, Caracas, Venezuela) The fatigue behavior of an AISI 4340 steel coated with TiN of three different under stoichiometric compositions has been investigated. The standard tensile and fatigue samples were deposited industrially with TiN0.50, TiN0.60 and TiN0.70 films by means of closed field unbalanced magnetron sputtering (PVD). The monotonic mechanical properties determined in tension, particularly yield stress and tensile strength, increase slightly due to the presence of the coatings. Fatigue tests were conducted in air at a frequency of 50 Hz at room temperature, under rotating bending conditions, in the stress range of 642-711 MPa for the sustrate, whereas the specimens with coatings were tested at a stress amplitude range of 688-757 MPa. The increase in fatigue life were evaluated by means of the Basquin parameters of the different materials tested. It has been determined that such an increase, for the materials coated with the films investigated in the present work, ranged between approximately 275-460% at an alternating stress of 688 MPa and between 229-345 % at an stress of 711 MPa. On the other hand, the fatigue limit determined by means of the staircase method, was also observed to increase between approximately 9-10%. The fatigue fracture surfaces of selected specimens were evaluated by means of SEM observations and the coatings thicknesses were corroborated by means of the ball cratering technique. Also, the residual stresses of some of the TiN films were measured. It has been concluded that the application of the surface coatings increases the yield strength and the fatigue properties of the coated materials in comparison with the uncoated substrate, which can be explained in terms of the satisfactory adhesion of the deposits and their higher mechanical strength.
EP-1-33 A Study of the Characteristics of Voltage and Current Pulses during Plasma Electrolytic Oxidation of Metals A.L. Yerokhin, A. Leyland (University of Hull, United Kingdom); S.J. Dowey (Ion Coat Ltd., United Kingdom); A. Matthews (University of Hull, United Kingdom) Electric discharges that appear at the surface of films grown on metals under conditions of plasma electrolytic oxidation (PEO) are considered to play an important role in formation of the film structure and thus affect its performance. The characteristics of discharges are therefore among the principle parameters to be controlled during the process. Obtaining information about their characteristics is however, accompanied by substantial difficulties caused by simultaneity, rapidity and variability of discharge phenomena. In this paper, a possibility of revealing the electrical characteristics of surface discharges is studied using a special experimental arrangement. In this installation, a conventional PEO unit has been equipped with special high voltage and high current probes providing voltage and current signals to a PC-linked high-resolution digital oscilloscope. The system allows the acquisition of signal data during 0.02 sec period of every single minute of the process at a rate up to 2 10⁶ samples/sec. Thus, voltage/current pulses of up to 1 MHz can be continuously monitored throughout the PEO process. Analysis of the obtained electric signals is carried out with the aid of fast Fourier expansion procedures. Dependencies of amplitude and frequency spectra of the signals on the nature of the oxidized metal surface as well as parameters of the PEO process, such as electrolyte composition, current density and oxidation time, are discussed.
EP-1-34 Adhesion Properties of AlP-TiN Coatings with WC Particle Size, CO Content, and Surface Roughness I.-W. Park, O.-N. Park, K.H. Kim (Pusan National University, Korea) Precise quantification of the TiN coatings on WC-Co inserts is important for industrial application. Adhesion between Co-cemented tungsten carbide (WC-Co) substrates and TiN films produced by an arc ion plating (AIP) method has been investigated. Adhesion properties, in general, are strongly influenced by the surface roughness, surface reactivity, grain size, and catalytic effect of Co during AIP-TiN deposition. Five carbide grades were prepared. Each carbide were classified by two different cobalt contents (10% and 15%). Adhesion properties of AIP-TiN coatings onto different types of substrates-grain size of WC and Co content-were investigated by a conventional scratch tester. The morphology and microstructure of the WC-Co substrates were characterized using AFM and SEM. The composition of Co in substrate was evaluated by XRF and EPMA. Besides, the microhardness for the AIP-TiN coatings was measured using the Knoop microhardness.
EP-1-35 Fatigue Behavior of an AISI 316L Steel Coated with and Electroless Ni-P Deposit M. Lugo (Universidad Central de Venezuela, Caracas, Venzuela); H. Hintermann (Swiss National Science Foundation, Switzerland); E.S. Puchi-Cabrera (Universidad Central de Venezuela, Caracas, Venezuela) The fatigue properties of an AISI 316L stainless steel have been evaluated in three different conditions: (a) uncoated; (b) coated with an electroless Ni-P (EN) deposit of a P content of approximately 25 at%, as-deposited, and (c) deposited and post heat treated (PHT) at 673 K for 1 h, condition in which the deposit showed its maximum hardness. The SNMS depth profiles of the coated samples show that the phosphorus content is approximately constant throughout the coating thickness in the as-deposited condition, whereas in the PHT condition, a decrease in the phosphorus content and diffusion of Fe throughout the coating takes place. In relation to the tensile properties of the coated and PHT specimens, it has been determined that both the yield stress and ultimate tensile stress (UTS) do not vary significantly in comparison with the substrate. The results of the fatigue tests indicate an increase in the fatigue life of the coated and PHT specimens of approximately 40%, whereas in the as-deposited condition no substantial differences were found in comparison with the uncoated samples. This behavior has been explained partially in terms of the adhesion of the coating to the substrate and partially in terms of a change in the pattern of residual stresses. The microscopic observations of the fracture surfaces of the samples indicate that the fatigue process is generally initiated at the surface of the coating and that subsequently it is transferred to the substrate.
EP-1-36 On the Corrosion Behavior of Multilayered WC-Ti1-xAlxN Coatings on AISI D2 Steel S.H. Ahn, J.H. Yoo, Y.S. Choi, J.G. Kim, H.Y. Lee, J.G. Han (SungKyunKwan University, Korea) Multilayered coatings are the new kind of coatings that belong to a more plentiful family of materials. In the present work, multilayered coatings with alternate layers of WC-Ti and WC-Ti_1-xAl_xN were deposited for using as wear resistant and corrosion resistant surfaces. A Ti and TiN base layer is deposited above the substrate prior to multilayer. WC-Ti_1-xAl_xN coatings with variable Al content were deposited onto steel substrate(HSS) by high-ionization sputtered PVD method. The Al content could be controlled by using evaporation source for Al and fixing the evaporation rate of the other target sources. Four kinds of WC-Ti_1-xAl_xN coatings were prepared (WC-Ti_0.6Al_0.4N, WC-Ti_0.53Al_0.47N, WC-Ti_0.5Al_0.5N, and WC-Ti_0.43Al_0.57N). The corrosion behaviors of WC-Ti_1-xAl_xN coatings in deaerated 3.5% NaCl solution were investigated by electrochemical corrosion tests and surface analyses. Particular attention was paid to the effects of Al content on the coating properties related to the corrosion behavior. The measured galvanic corrosion current between coating and substrate shows a low value. The results of potentiodynamic polarization tests indicated that the WC-Ti_0.43Al_0.57N coating with the lower porosity enhanced corrosion resistance. In electrochemical impedance spectroscopy measurements, the WC-Ti_0.43Al_0.57N coating showed two times constant and decreased a charge transfer resistance of coating (R_ct). Multilayered coatings were analyzed by EDS and XRD analysis to evaluate the crystal structure and compounds formation behavior. Surface and cross-section morphologies of the films were observed using SEM. Scratch test was performed to measure film adhesion strength. On the Corrosion Behavior of multilayered WC-Ti_1-xAl_xN Coatings on AISI D2 steel.
EP-1-37 A Comparative Study on Tribological Behavior of TiN and TiAlN Coatings Prepared by Arc Ion Plating Technique S. Yoon (Pusan National University, Korea); J.-K. Kim (Korea Institute of Machinery & Materials, Korea); K.H. Kim (Pusan National University, Korea) TiN and TiAlN films were deposited onto SKD 11 steel substrates using an arc ion plating (AIP) technique. The structures and surface morphologies of both films were characterized by X-ray diffraction and scanning electron microscopy. To investigate the tribological behavior of both films, both dry and wet sliding wear experiments were conducted on AIP-TiN and AIP-TiAlN coated layers over a range of contact loads (10-100N) and sliding speeds (0.1-0.5m/s) against steel and alumina ball using a conventional ball-on-disc wear apparatus. Each wear test was run up to a constant sliding distance of 1000m (32,000 revolutions) regardless of load and sliding speed settings. In addition, the effect of atmospheric humidity on the tribological behavior of the TiN and TiAlN layers was investigated. Wear behaviors and mechanisms of both films were determined using scanning electron microscopy, and energy dispersive spectroscopy techniques that were used to analyses morphologies, microstructures and chemical compositions of worn surface and wear debris. In the case of AIP-TiN layers against steel ball, the average friction coefficient increased with increasing the relative humidity due to tribochemical interaction of steel with moisture. However, in the case of AIP-TiN layers against alumina ball, the behavior of average friction coefficient with relative humidity was different compared to using steel ball. The wear behaviors of AIP-TiAlN film were also comparatively studied in this work.
EP-1-38 A Method of Characterizing Coating/Substrate Interfacial Cleanliness and the Effect of Sputtered Ion Energy on Interfacial Oxide R. Wei (Southwest Research Institute); J.J. Vajo (HRL Laboratories); J.N. Matossian (Boeing Satellite Systems, Inc.); J. Arps (Southwest Research Institute) Ion sputtering is a technique routinely used in vacuum-coating processes to remove surface-oxide contaminants from the surfaces of components prior to applying a metallurgical coating. The effectiveness of the sputter-cleaning process depends on the power density applied to the components (i.e. the bias voltage and current density), the plasma density, as well as the duration of the sputter-cleaning process. In this paper, we first present the results of a systematic study to quantitatively characterize the amount of surface-oxide contamination that remains on the surfaces of gear cutters (specifically the "root" and "tip") prior to applying a coating of TiN using a magnetron sputtering system for various combinations of power density, plasma density, and duration. A thin (0.005 mm-thick) stainless steel foil, previously oxidized with ¹⁸O, is conformally mounted to the root and tip of the gear cutters (shapers). The cutting tool then undergoes a sputter cleaning process using a specific set of operating parameters for power density and duration. A thin (1-2 micrometers) TiN coating is then applied to coat the gear cutter and the foil. The foil is easily removed from the cutting tool and analyzed using secondary ion mass spectroscopy (SIMS) to provide a measurement of the interfacial oxide concentration along the cutting surface of the cutter. By using the ¹⁸O samples, we are able to distinguish the "native" oxide from surface oxidation that can develop prior-to and during the coating process. Our results indicate that effective removal of surface-oxide contamination from the root/tip geometry of a cutting tool is achieved using high-voltage, low-current density tool-bias conditions, rather than low-voltage, high-current tool-bias conditions. In a later section, we will discuss the result from diamondlike carbon (DLC) coated steel gears in a plasma immersion ion deposition (PIID) system using the same technique. This technique is fully compatible with production runs for coating cutting tools or other components in industrial coatings systems and can be used as an accurate "witness coupon" to characterize a coating run.

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