Papers

ICMCTF2009 Session G1-1: Innovations in Surface Coatings and Treatments

Wednesday, April 29, 2009 8:00 AM in Room Royal Palm 1-3

Wednesday Morning

Start	Invited?	Item
8:00 AM		G1-1-1 High Ionization Plasma for Advanced Coatings: ANew Approach for Coating Deposition on Temperature Sensitive and Complex-Shaped Substrates J. Alami, G. Erkens, J. Vetter, J. Mueller, T. Rasa, W. Jung (Sulzer Metaplas GmbH, Germany) The success of PVD techniques for deposition of hard and dense coatings on Steel tools and components has initiated the interest of many end-users to develop new coatings for other substrate materials such as plastics and polymers. This, however, gives rise to a number of process difficulties as the substrates are often sensitive to high deposition temperatures. Another concern related to PVD is the deposition flux which, because of the line of sight, results in a low thickness homogeneity of the coating. The present work treats these concerns by using the highly ionized plasma for advance coatings (HIPAC) technology in order to deposit highly adhesive, flat and dense CrN coatings in temperature sensitive substrates. HIPAC is a new further development of the HPPMS (high power pulsed magnetron sputtering) deposition technique and is characterized by a highly ionized target material as well as a highly ionized sputtering gas. Plasma analyses show that the high plasma dens ities during the HIPAC process result n a high ionization of the sputtered material as well as a full ionization of the sputtering gas. The energy distribution in the HIPAC plasma shows a smaller energy distribution compared to other pulsed magnetron depositions. This is a unique feature of this deposition technique and is shown to lead to a deposition flux consisting, to a large extent, of low-energy ions. The CrN coatings were deposited on complex-shaped plastic substrates. The substrate temperature on the substrate was lower than 100°C, while the coating analysis showed a dense and flat surface with minimal variation of the coating thickness. HIPAC is shown thus to be an excellent tool for the control of the deposition process energetics and the substrate temperature during growth.
8:20 AM		G1-1-2 Industrial Scale Deposition of Oxides L.P. Nielsen, K.P. Almtoft, I.H. Andersen (Danish Technological Institute, Denmark); P. Eklund, I. Hansen-Bruhn, B. Thomsen, J. Bottiger (Aarhus University, Denmark) Industrial scale synthesis of advanced oxides is of outmost importance when bringing small-scale state-of-the-art university research results onto a commercial production platform. In the present content we will illustrate optimized and highly reproducible large-scale reactive sputter deposition of TiO₂, Al₂O₃, and Ce_0.9Gd_0.1O₂ oxides on a commercial CC800/9 CemeCon Sinox unit equipped with the newest HIPIMS technology. For the TiO₂ system it will be shown that reproducible growth of dense, as well as highly porous TiO₂ structures can be synthesised and grown in the anatase as well as the rutile crystal phase. The photocatalytic activity and the mechanical properties (hardness) of the deposited TiO₂ coatings will be addressed. Bias ramping enabled control of the morphology and density of the alumina coatings, with columnar growth as evidenced by SEM for negative bias of 30 to 65 V. A dense, featureless, insulating alumina was obtained for bias above 70 V. For application in Solid Oxide Fuel Cell (SOFC) the reactive deposition of a Ce_0.9Gd_0.1O₂ diffusing limiting reaction barrier will be shown and the crystal morphology will be discussed as a function of applied growth parameters.
8:40 AM		G1-1-3 High Power Pulsed Sputtering and Plasma-Assisted Hybrid Processes for Industrial Scale Hard Layer Deposition H. Klostermann, F. Fietzke, R. Labitzke, T. Modes, O. Zywitzki (Fraunhofer FEP, Germany) During the past few years, hard material film development has made advances in tailoring film structure and properties towards sophisticated ends. Multilayer and nanocomposite structures exhibiting superhardness are one example, crystalline layers with single phase composition of high purity another. The benefit of such development for practical application relies not only on basic research but also on appropriate equipment that allows transfer of processes to an industrial scale with guaranteed long-term stability and reproducibility. A key factor in tailoring film composition and structure is the control of particle energies and densities. These are affected by the mode of plasma generation in physical vapor deposition processes. Pulse power supplies with high flexibility for adaptation to different discharge conditions are a powerful tool for the achievement of specific film structures in a variety of coating materials. However, good adhesion is a further prerequisite for an outstanding performance of a coating. The combination of recently developed pulse current supplies and a hollow cathode plasma source open up a new level of coating development in large scale coating equipment. The versatility of these tools will be shown for different hard layer materials. As one example, the deposition of Zr_1-xNb_xN hard protective layers by reactive co-sputtering of zirconium and niobium will be presented. In this process the choice of pulse mode, namely single bipolar or pulse package mode, and pulse times allows tailoring composition and structure of the coatings. Layers with hardness in the range 24 GPa to 35 GPa are deposited without additional substrate bias. Application of substrate bias can increase layer hardness up to 41 GPa, still with good adhesion even for coatings of thickness 5 µm, for which cohesive failure becomes predominant over adhesive failure. As a second example, the deposition of crystalline alumina coatings will be presented. This reactive sputter process poses a special challenge with regard to arc handling and rate optimization. The influence of the pulse mode on the one hand and of additional hollow cathode plasma activation on the other on crystallinity and deposition rate will be presented. Again, a hollow cathode etching process is the key to excellent adhesion of these fully crystalline coatings.
9:20 AM		G1-1-6 Nanocomposite PVD Coatings to Prevent Failure of Molten Aluminium Forming Dies E.A. Torres Miranda, Z. Brytan, D. Ugues (Politecnico di Torino, Italy); M. Perucca (Clean NT Lab - Environment Park S.p.A., Italy) Forming processes of aluminium parts from liquid state are highly diffused. Both traditional (e.g. gravity and die casting) and recently developed techniques (e.g. liquid forging) are continuously growing in terms of productivity and, as a consequence, in severity of stresses applied on the forming tools surfaces. Chemical aggression of molten aluminium, abrasion by hard solid particles and thermal fatigue are typical damages occurring in such operating environment. In this paper a design process of PVD multilayer coating specifically developed for such complicate operating environment is presented. Nanocomposite (Cr, Al)_1-xN_x/a-Si₃N₄coatings were optimally developed and applied on hot a typical working tool steel. Analysis of the coating morphology, adhesion level, thickness, hardness and crystallographic structure are given. Results of alternate immersions in molten aluminium alloy and Taber wear measurements are reported. X-ray diffraction patterns on coatings before and after the immersion cycles in molten aluminum alloy are given so as to identify the corrosion by-products formed on to the surface. The main results of such study are that the higher is the Al content in mixed nitrides coatings the best is the resistance to the chemical attack and the higher is the hardness and the resistance to abrasion. Furthermore a direct demonstration of efficiency of the multilayer structure in deviating thermal fatigue cracks was recorded by SEM imaging. Finally a relation between the structure and the ultimate properties of the coating is drawn.
9:40 AM		G1-1-7 Magnetron Sputtering of Free-Standing Aluminium-Scandium Alloys for Use in Cold Forming Processes I. Eisbrecher, H.-R. Stock (Stiftung Institut fuer Werkstofftechnik, Germany) Thin sheets of aluminium alloys with thicknesses below 30 µm are very interesting for cold forming processes. However, high strength aluminium alloys cannot be rolled down to such a low thickness. Magnetron sputtering of such films followed by separating the substrate from the films can provide an alternative method. To do so, we manufactured a target of aluminium master alloy with a scandium content of 1.8 %. D.C. magnetron sputtering was carried out in a high vacuum equipment with a base pressure below 10^-4 Pa. As substrate a preoxidized steel foil was used. The maximum temperature during the process was kept below 200 °C measured with a thermocouple mounted behind the substrate. After cooling down the substrate was dissolved in a mixture of H₂SO₄ and H₂O₂. The resulting free-standing sheets had a scandium content of 1.5 % and showed a significant columnar morphology. As these columns decrease formability and cause an unsatisfying tensile strength we applied cold isostatic pressing 400 Mpa for about one hour. The properties of the resulting sheets were examined with analysis by electron microscopy, ultra micro hardness testing, atomic force microscopy and glow discharge optical emission spectrometry.
10:00 AM		G1-1-8 Effect of Dry Micro-Blasting Conditions on Pvd Films’ Properties and on Coated Tools Cutting Performance K.-D. Bouzakis, G. Skordaris, S. Gerardis, G. Katirtzoglou, S. Makrimallakis, N. Michailidis (Aristoteles University of Thessaloniki, Greece); F. Klocke, E. Bouzakis (Technical University of Aachen, Germany) The conduct of micro-blasting on PVD films has been documented as an efficient method to improve the cutting performance of coated tools. The increase of tool life is affected significantly by the applied conditions during micro-blasting. Therefore the determination of appropriate process conditions during micro-blasting is of crucial importance. In the paper, the effect of various blasting conditions such as of pressure and process duration on the film properties and cutting performance are investigated. With the aid of nanoindentations, the film superficial hardness growth by increasing the micro-blasting pressure and duration was documented. Ball cratering tests at the flank and rake close to the cutting edge and confocal measurements of the tool wedges were conducted to display the change of coating thickness and cutting edge radius respectively induced by micro-blasting. In this way the occurring film distribution along the cutting edge after micro-blasting was det ermined, demonstrating that the substrate was revealed, under certain process conditions. These results were verified by EDX micro-analyses. Furthermore milling investigations were carried out to monitor the cutting performance of coated tools, subjected to films’ micro-blasting. The results showed that there are restrictions concerning the increase of pressure and the process duration, with regard to the tool wear. Beyond these limits, tool life deterioration occurs.
10:20 AM		G1-1-10 Characterization and Antibacterial Properties of TaON–Ag Nanocomposite Thin Film J.H. Hsieh, C.C. Chang (Mingchi University of Technology, Taiwan) TaON–Ag nanocomposite thin films with Ag nano-particles dispersed in TaON matrix and surface were prepared by reactive co-sputtering of Ta and Ag in the plasma of (O2+ N2)/Ar, followed by rapid thermal annealing (RTA) at 800°C for five minutes. These films were then characterized by a variety of techniques including X-ray diffraction, EDAX, UV-Vis photospectrometer and spectroscopic ellipsometry. In addition, FE-SEM (field-emission scanning electron microscopy) were applied to characterize the surfaced Ag nano-particles on TaON–Ag thin films. Addition of Ag leads to a beneficial change of the film properties. The amorphous structure of the as-deposited TaON films would transform to crystalline state. The results show that annealed TaON-Ag films can have an enhanced antibacterial behavior under the irradiation of visible light due to the synergistic effect of Ag and photocatalytic behavior of TaON.
10:40 AM		G1-1-11 Structure Effect on the Improvement of the Corrosion Resistance in a 4140 Nitrided Steel by Post-Discharge A. Medina (UMSNH-Instituto de Investigaciones Metalúrgicas, Mexico); J. Oseguera (TESM-CEM, Mexico); H. Carreón (UMSNH-Instituto de Investigaciones Metalúrgicas, Mexico); L. Béjar-Gómez (UMSNH-ngenieria Mecanica, Mexico) The influence of the post-discharge microwave nitriding time on surface properties and corrosion resistance of AISI 4140 low-alloy carbon steel has been investigated. The steel samples were nitrided at 810 K between 5 and 25 minutes. The microstructure and the nitride layer were analyzed by X-ray diffractometry, scanning electron microscopy (SEM) as well as microhardness measurements. The corrosion resistance of untreated and nitrided samples was evaluated in several potentiodynamics tests such as Polarization curves and electrochemical noise. The results showed that as the nitriding time is increased the compound layers changed from a dual phase (ε - Fe_2-3N and γ’ - Fe₄N) to a monophase γ’ - Fe₄N. On the hand, the corrosion resistance and corrosion rate were improved on the samples nitrided during 25 min where the surface is composed by the γ’ - Fe₄N phase.
11:20 AM		G1-1-13 Improvement on Low-Temperature Deposited HfO₂ High-Pressure Oxygen/Ozone Treatment P.-C. Yang, T.-C. Chang (National Sun Yat-Sen University, Taiwan) In this study, high-pressure oxygen (O2 and O3) technologies were employed originally to effectively improve the properties of low-temperature-deposited metal oxide dielectric films. In this work, 5 nm ultra-thin HfO₂ films were deposited by sputtering method at room temperature. Then, the low temperature high-pressure oxygen treatments at 150 °C were used to replace the conventional high temperature annealing. According to the XPS analyses, the absorption peaks of Hf-O bonding energies apparently raise and the quantity of oxygen in HfO2 film also increases from XPS measurement. In addition, both the leakage current density of 5nm HfO₂ film can be improved to 10^-8 A/cm² at \|Vg\| = 3 V. The proposed low-temperature and high pressure O2 or O3 treatment for improving high-k dielectric films is novel and applicable for the future flexible electronics.