Papers

ICMCTF2008 Session G1-2: Innovations in Surface Coatings and Treatments

Friday, May 2, 2008 8:40 AM in Room Sunset

Friday Morning

Start	Invited?	Item
8:40 AM		G1-2-3 Advanced Fabrication Process and Measurements of Thin-Film Sensors D. Hagedorn, R. Meeß, F. Löffler, A. Buss, J. Ilemann, R. Kumme (Physikalisch-Technische Bundesanstalt, Germany) We have improved our recently developed fabrication technology for sputtered thin-film sensor structures on cylindrical workpieces. With the latest improvements thicker films can be structured allowing to increase the contrivable parameter range of the sensors. In a first production step the functional layer has to be applied to the workpiece using a PVD sputtering system. On metallic or semi-conducting substrates defect free insu-lation is paramount. Huge efforts have been made to optimize both material and thickness of the insulation. A custom-built spray-coating system is used to apply photo resist to the rotating workpiece. The resist is exposed using an UV-laser system and a high precision ro-botics to position the workpiece with respect to the focus of the laser beam achieving an resolution better than 1 µm. In the advance fabrication process the resist serves as a negative mask to structure a hard metal (e.g. Cr) etching mask. Cr withstands the consecutive wet-etching process far longer than photo-resist does, thus providing the possibility to structure thicker functional layers. The fabrication of micro-structured metal thin-film sensor as, for example, strain gauges (MMTSG) opens up the possibility to develop force transducers with proper-ties optimized for dynamic measurements. For a systematic investigation of the met-rological properties, prototypes relying on metal-film strain gauges (MFSG) and MMTSGs, are compared, with focus on creeping (timescale > 10 seconds) and on the transfer function up to 1 kHz. Measurements of the first are realized by a dead-weight force standard machine, of the second by a dynamic force standard machine.
9:00 AM		G1-2-4 Monitoring of Turning Processes by Means of Thin Coatings W. Tillmann, E. Vogli (University of Dortmund, Dortmund, Germany) The wear and friction of chipping tools has a huge influence on quality, productivity and economic efficiency of the production processes. They limit the tools` lifetime as well and lead to damages in billions. Thereby plays the monitoring of the tools wear through the measurement of temperatures, forces and the tool condition a key function in the chipping process. Due to the arising temperatures, tools geometry and tribological demands an employment of the conventional sensors in chipping tools is not possible. In this work a novel method to measure in-situ the temperature in turning processes has been shown. Based on the PVD-technique thin metallic conductive layers have been deposited, in which the layer properties have been designed in related to a thermocouple demand. Coatings adhesion and composition have been systematically analysed in related to the process parameters. Turning experiments have been conducted to scrutinize the efficiency of the new designed sensors.
9:20 AM		G1-2-5 Low Temperature Multilayer α-Alumina Films for Machining Applications A.N. Cloud (University of Arkansas); S. Canovic (Chalmers University of Technology, Sweden); H.H. Abu-Safe, M.H. Gordon (University of Arkansas); M. Halvarsson (Chalmers University of Technology, Sweden); D.G. Bhat (National Science Foundation) Multilayer films of alternating alpha aluminum oxide and alpha chromium oxide layers were deposited at 350°C by AC inverted cylindrical magnetron sputtering on steel and tungsten carbide machining tools. The number (up to six) and thickness (150nm to 350nm) of the individual layers are varied for optimization. The presence of alpha phase alumina has been confirmed by transmission electron microscopy. Film interfaces are examined by scanning electron microscopy. Tribological and machining testing of film adhesion and wear resistance of coated cemented carbide inserts will be conducted to evaluate the performance of the coatings. In prior testing, a coating comprised of a single layer of alumina on a chromia template layer was outperformed by a conventional CVD alumina coating in tests of flank and nose wear. Preliminary multi-layer results indicate improved tool machining performance. A detailed discussion of the effects of varying deposition parameters on the properties and performance of the coatings as well as a comparison to previous machining results will be presented in the full manuscript.
9:40 AM		G1-2-6 Wettability Control of Photocatalytic Crystal Layers by Hydrophobic Coating and Subsequent UV Light Irradiation K. Teshima, S. Suzuki (Shinshu University, Japan); K. Yubuta (Tohoku University, Japan); Y. Sonobayashi (Kyoto University, Japan); T. Suzuki (Shinshu University, Japan); T. Shishido (Tohoku University, Japan); H. Sugimura (Kyoto University, Japan); S. Oishi (Shinshu University, Japan) Wettability of a solid surface is governed by surface morphology and composition. Incorporating fluorine atoms, which have a small atomic radius and high electronegativity, can achieve a low surface energy. A smooth surface covered with regularly aligned and closely packed fluorine atoms shows a water contact angle of about 120 degree, indicating a very low surface energy. By roughening the surface of such a substrate, a surface with a water contact angle greater than 150 degree has been successfully fabricated. In this study, we report on the controlling the wettability of various substrates by a three-step process. First, various substrates were coated with nanosized photocatalytic crystals (sodium and potassium tantalates) in order to form a rough surface and introduce hydrophilic functional groups. Subsequently, the nanotextured crystal substrates were coated with a hydrophobic layer by means of chemical vapor deposition (CVD) in order to reduce their surface energies. Since the nanotextures remained after the hydrophobic layer coatings, the substrates showed ultra-water-repellency with water contact angles greater than 150 degree. When ultraviolet light (254-365 nm) is irradiated onto the ultra-water-repellent photocatalytic crystal surfaces having a proper nanotexture and a hydrophobic layer, surface-terminating hydrophobic functional groups changed chemically to hydrophilic functional groups. Finally, the water contact angle of these surfaces changed from greater than 150 degree before UV light irradiation to less than 10 degree afterward.
10:00 AM		G1-2-7 Future Development of Steel Sheet Coating Systems Based on Novel Thin Film Coating Technologies B. Schuhmacher (DOC Dortmunder Oberflachencentrum GmbH - a company of ThyssenKrup Steel, Germany) Steel producers in Europe have strong efforts to create the technological base for new generations of surface coated steel strip products, tailored to the specific needs of customers. The anticipated benefits for customers driven by cost-saving potentials or enlarging of market shares are e.g. easy processing (forming, laser welding, ...) through thickness reduction, added value products in order to omit production steps or to enhance the functionality or 100% green products to meet actual and future legislative constraints in use of coated steel sheet products. An essential mean to achieve these ambitious aims is the introduction of innovative and non-polluting deposition technologies (in particular vapour deposition processes such as PVD, CVD) in continuous processing of steel strip. By such novel technologies the "degree of freedom" for depositing a large variety of materials is enlarged significantly as compared to the established processes. Hence the base for design of new coated products is laid. In this paper, the strategy for developing new coated products will be explained by means of different examples such as thin highly corrosion resistive coating systems with excellent processing properties based on synergetic effects of metallic and organic coatings for the automotive industry or added value products for the domestic appliance and building industry. Added value consists in additional desired functional properties e.g. through hydrophobic, hydrophilic, photo-catalytic scratch/wear resistant or solar-thermic/photovoltaic coatings.
10:40 AM		G1-2-9 Material Transfer Phenomena and Failure Mechanisms of Cr-Al-N Coating L. Wang, X. Nie (University of Windsor, Canada); Z. Yao (Daimler Chrysler Corporation Technology Center); J. Houston (Tecvac Ltd.); A. Matthews (University of Sheffield, United Kingdom) A CrAlN coating has intensively been developing as a promising candidate coating material used for cutting tool or forming die, since the CrAlN has high hardness, wear resistance and oxidation resistance. However, in the previous laboratory works, the tribological properties were mostly evaluated by against hard ceramic materials (alumina and WC-Co). There are few reports on the coating against relatively soft aluminum and steel. However, the real applications in manufacturing actually involve those metallic counterfaces. In this research, the CrAlN coating was characterized by XRD, XPS and TEM. Pin-on-disc tribotests were conducted on the CrAlN coating against counterface materials aluminium AA6061 and steel AISI 52100 in order to investigate wear behaviours especially the material transfer phenomena during the sliding tests against the soft counterface materials. The similar tests were also performed on conventional TiN coating, which acted as a reference to the CrAlN coating. These two coatings were also deposited on industrial punches for piercing high strength steels. After industrial trials, the worn CrAlN, TiN coated punches were investigated by SEM and EDX. The corresponding failure mechanism was discussed.
11:00 AM		G1-2-11 Electric Property Improvement of Electroless Copper Thin Films Prepared by Pulsating Current at Low Dissolved Oxygen Level T.-J. Yang, H.-T. Hsu, C.-K. Lin (Feng Chia University, Taiwan) Electroless Cu plating has attracted increasing R&D interests in present IC industry. In this study, effects of dissolved oxygen and pulsed electric current of different duty cycles on electroless copper plating have been investigated. Microstructures of deposited copper films were examined by FE-SEM, HR-TEM, SIMS, ESCA and GID. Surface morphology and crystalline orientation of copper coating were studied by AFM and XRD. While electric resistivity of copper films was measured by four-point probe method. Experimental results showed that dissolved oxygen in plating bath can be lowered from 7.46 ppm to 212 ppb by Ar gas purging. Electric resistivity of as-plated copper film prepared by the 7.46 ppm bath was 4.9 microΩ-cm . Apparent decrease in electric resistivity can be noticed when copper films were prepared by relative low-dissolved-oxygen plating bath. Electric resistivity of the copper thin film, prepared by the 212 ppb bath using pulsating electric current with peak current density 0.5 A/dm² and duty cycle 40%, exhibited the best electric resistivity of 2.9 microΩ-cm (41% decrease) in the present study. Meanwhile, the ratio of copper to copper plus copper oxides was increased from 56.8% to 65.6%. Less amount of copper oxides were found in the copper thin film as dissolved oxygen level in plating bath was decreased.