Papers

ICMCTF2007 Session D2-1: Diamond and Diamond-Like Carbon Materials

Wednesday, April 25, 2007 1:30 PM in Room Sunset

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		D2-1-1 The Technology and the Applications of DLC-Si Coating H. Tachikawa, K. Nakanishi, H. Mori, Y. Tsuchiya, S. Igarashi, T. Iseki (Toyota Central Research & Development Laboratories Inc., Japan) In recent a couple of decades, considerable effort toward developing environment-friendly vehicles and automotive production systems have been done. Fuel economy improvement is one of the most prominent challenges facing automotive industry. Tribological improvement like as reduction of friction can lead to significant fuel-efficiency. The friction control of power train parts, by using surface coating technologies like as diamond like carbon (DLC) coatings, has been useful to making higher fuel-efficient cars, and so the coating technologies will establish important place as key technology for solving the tribological issue in the future. DLC coatings have been paid special attention for application to car parts in automotive industry since early. However conventional DLC films are not widely used in automobiles because of their low productivity and poor adhesion of the films to steel substrate. So we paid attention to direct current plasma-enhanced chemical vapor deposition (DC-PECVD), which has a potential for large-scale production because of good throwing power and lower equipment comparing to conventional methods like as sputtering and etc., and grappled with the establishment of DLC coating by this method. Silicon-containing DLC (DLC-Si) synthesized by the DC-PECVD method can be formed on steel substrate with strong bonding through original surface activation treatment prior to the coating. This coating technology led to achieve the first mass production of DLC-Si coated electromagnetic clutch for vehicles, and began to be used widely in car parts, dies and tools. In this report, the DLC-Si coating technology and its application example will be introduced.
2:10 PM		D2-1-3 DLC Film Properties Obtained by Low Cost and Modified Pulsed-DC Discharge V.J. Trava-Airoldi (Instituto Nacional de Pesquisas Espaciais, Brazil); L.F. Bonetti (Instituto Nacional de Pesquisas Espaciais INPe and Instituto Tecnologico da Aeronautia ITA, Brazil); L.V. Santos (Instituto Nacional de Pesquisas Espacial INPE, Brazil); G.C. Rodrigues (Instituto Nacional de Pesquisas Espaciais INPE, Brazil); E.J. Corat (São José dos Campos, Brazil) Surface and bulk properties of diamond-like carbon films prepared by using different techniques and under different conditions have been of great concern. The main focus is to reach low friction coefficient, low total stress, high hardness, and very high adherence with the substrate, including the deposition in large area at large growth rate. In this work, DLC films were obtained by using a low cost modified Pulsed-DC Discharge technique. Different pulse bursts with different pulse width and delay time were considered. Studies have been carried out in order to match the best set of parameters as mentioned above for different applications, as required in the frame work of our project. The sp²/sp³ ratio measurements, growth rate, hardness, friction coefficient, total stress, and the adherence on Ti6AL4V substrate were studied as a function of the pulse burst characteristic. Micro indentation ranging from 10 to 50 mN was used to measure the hardness on thin DLC films, the friction coefficient and critical load were performed by using a trybometer ranging form 0.2 up to 50 N, a conventional perphilometry technique was used to measure the total stress and thicknesses ranging from 0.2 to 4 micrometers. Raman analysis besides the quality, also were used to evaluate the sp²/sp³ ratio. Finally, low friction coefficient, low total stress, high hardness and very high adherence were obtained, so that, some consideration concerning scaling up for industrial production of DLC films will be presented.
2:30 PM		D2-1-4 Characterization of Diamond-Like Carbon Coatings Prepared by Pulsed Bias Cathodic Vacuum Arc Deposition J.-B. Wu, J.-J. Chang (Industrial Technology Research Institute, Taiwan); M.-Y. Li (National Nano Device Laboratories, Taiwan); M.S. Leu, A.-K. Li (Industrial Technology Research Institute, Taiwan) Hydrogen free diamond-like carbon (DLC) coatings have been deposited on Si(100) and stainless steel substrates by cathodic vacuum arc plasma deposition in conjunction with substrate pulse voltage. In order to increase the adherence to the substrate, graded transition layers, namely Ti/TiC/DLC multilayer, have been applied. The microstructures and composition of DLC film were identified by the instrumental analyses such as scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The hardness behavior of DLC coatings was measured by nano-indentation. The results show that duty cycle has strongly influenced the hardness and sp³ content on the DLC coatings. The pulse bias of -100 V was applied to the substrate to achieve a dense structure of around 1 µm coatings of DLC and the hardness can increase from 26 GPa to 49 GPa with the increase of duty cycle from 2.5 % to 12.5 %. Moreover, the residual gas and its partial pressure during deposition play a significant role in hardness characteristic. For example, under a duty cycle of 5 %, the hardness was decreased from 28 GPa to 14 GPa as the deposition pressure was increased from 3x10^-3 Pa to 1 Pa. Other film properties like sp³ fraction, adherence and interlayer composition have also been investigated.
2:50 PM		D2-1-5 Reactive Magnetron Sputter Processes for Preparation of DLC Based Coatings in Large Scale Batch Coaters K. Bewilogua, H. Thomsen, K. Weigel, R. Wittorf (Fraunhofer IST, Germany); D. Hofmann, S. Kunkel, W.D. Münz (SVS Vacuum Coating Technologies, Germany); H. Richter Sr., Y. Yamazaki (Richter Precision Inc.) Hard amorphous hydrogenated carbon (a-C:H) as well as metal containing a-C:H:Me coatings were prepared in a large scale batch coater equipped with 4 targets and electromagnetic coils. Coils around each target and an additional coil generating a magnetic field over the chamber volume caused high ion current densities at substrates rotating on a planetary. For the deposition of a-C:H:Ti, titanium targets and for the deposition of metal free a-C:H graphite targets were used. In both cases the sputter gas was a mixture of Argon and acetylene. To improve the adhesion different interlayers like titanium, chromium and chromium nitride were tested. Coatings with Ti/C slightly lower than 1 had a hardness maximum (> 30 GPa). Such a maximum can be explained assuming a structure consisting of TiC nanocrystallites in an a-C:H matrix. For Ti/C < 0.3 the typical medium hardness values between 10 and 20 GPa were measured. Metal free a-C:H coatings were deposited varying parameters like substrate bias (pulsed d.c., between 50 and 300 V), acetylene flow (0 to 50 %) and coil currents (up to 250 A). The highest hardness values were reproducibly measured with up to 45 GPa. The coatings were characterized by SIMS and Raman spectroscopy as well as by hardness and wear tests. Furthermore contact angles of liquids were measured for coatings with different surface modifications. Obviously the hydrogen content decreased with increasing hardness. The hardest coatings had H contents of about 10 atom %. Reasons for the relative high hardness values will be discussed considering the effect of the most essential process parameters substrate bias and coil currents.
3:10 PM		D2-1-6 Synthesis of Functional Amorphous Carbon Films Under Atmospheric Pressure for Food Package H. Kodama, S. Suemitsu (Kanagawa Academy of Science and Technology, Japan); M. Nakaya, A. Shirakura (Kirin Brewery, Japan); A. Hotta, T. Suzuki (Keio University, Japan) Amorphous carbon films with high gas barrier properties were successfully synthesized by atmospheric pressure glow plasma CVD method. Equipment we developed was line-type parallel-plate system (width of electrode is 100 mm) which enables to treat continuously by transferring grounded electrode. Deposition rate of the films on polyethylene terephthalate substrate was around 10 to 60 µmm/min using acetylene for process gas. Oxygen transmission rate was under 0.01 cc/m²/day/atm which indicates that gas barrier properties of the films were almost perfect. Furthermore, we will introduce larger scale (width of electrode is 500 mm) roll-to-roll CVD system for continuous plastic film treatment.
3:30 PM		D2-1-7 Structure and Properties of Ag-Incorporated DLC Films Prepared by a Hybrid Ion Beam Deposition System H.W. Choi (Korea Institute of Science and Technology and Seoul National Univ, Korea); J.-H. Choi (Korea Institute of Science and Technology, Korea); K.-R. Lee (Korea Institute of Science and Technology,, Korea); J.-P. Ahn (Korea Institute of Science and Technology, Korea); K.H. Oh (Seoul National University, Korea) Diamond-like carbon (DLC) films incorporated with Ag were prepared on Si(100) substrate by a hybrid process composed of ion-beam deposition and magnetron sputtering. The concentration of Ag in the films varied by controlling the fraction of Ar in the reaction gas mixture with benzene. To explain the role of incorporated Ag on the mechanical properties of DLC films, the chemical composition, atomic bond characteristics and microstructures were investigated. When the Ag concentration was 0.1 at. %, the Ag atoms were fully dissolved in the amorphous carbon matrix. The first-principles calculation results suggested that Ag atoms in the carbon matrix play a pivotal role due to a weak bond between C and Ag atoms, resulting in the reduction in the residual stress. However, the mechanical properties of the film did not show significant decrease since the three-dimensional interlink of the atomic bond network in the carbon matrix remains nearly unchanged. Amorphous and crystalline Ag particles were observed when the Ag concentration was 1.7 and 6.8 at. %, respectively. In this composition range, the metallic second particles are supposed to act as efficient buffer sites to absorb the residual stress in the carbon matrix, resulting in the considerable decrease in the residual stress. In order to examine the effect of incorporated Ag on biological properties, the surface energy and the Haemo-compatibility were measured. The surface energy decreased while the haemo-compatibility improved with the increase in the Ag concentration. The mechanical and biological behaviors of the films will be discussed in terms of the atomic bond characteristics and microstructure induced by Ag incorporation.
3:50 PM		D2-1-8 Micro- and Nano-Crystalline Diamond Coatings on the Advance for Abrasive Materials O. Lemmer, R. Cremer, M. Alunovic (CemeCon AG, Germany) More and more high-tech materials are being used in the mass production. Composites, fibre reinforced materials, are very challenging in terms of chipping and they wear the tools enormously. Diamond coatings are especially suitable for strongly abrasive materials like graphite, AlSi-alloys, MMC and many more. In this work the features for manufacturing successful high performance cutting tools will be studied: pure coating quality, sharpness of the edge, adhesion of the coating, wear resistance, wear volume, resistance to adhesive transfer. This study will show the morphology of multilayer diamond coatings, even conducting, which are extremely resistant to abrasion in case of processing aluminium alloys or GFK or CFK, as well as nanocrystalline coatings which have an extremely smooth, shiny and hard surfaces. The efficiency and performance of exactly controlled diamond coatings on cemented carbide tools with almost any geometry and with a high cobalt content of up to 12 percent will be illustrated by representative cutting test results from aircraft and automobile industry.
4:10 PM		D2-1-9 Tribological Properties of DLC Films With Different Hydrogen Content in Ambient Air and Vacuum D. Tabayashi, M. Miyanaga (Sumitomo Electric Industries, LTD., Japan); Y. Utsumi (Nippon ITF, Inc., Japan); K. Oda (Sumitomo Electric Industries, LTD., Japan); H. Ohara (Nippon ITF, Inc., Japan) Tribological and mechanical properties of DLC films depend on hydrogen content in the film. In this study, friction coefficients of hydrogen free DLC film (a-C) and hydrogenated DLC film (a-C:H) were measured by a ball-on-disk test in ambient air and vacuum. The a-C film was deposited by cathodic vacuum arc evaporation method. The a-C:H film was deposited by RF plasma CVD method. The hydrogen content of the a-C:H film was estimated as 34 at.% by Rutherford backscattering spectroscopy and in elastic recoil detection analysis. Their wear debris were investigated with micro FT-IR spectroscopy. The a-C:H film showed low friction coefficients in both ambient air and vacuum. Friction coefficient of the a-C film was low in ambient air, but was high in vacuum. The FT-IR spectrum of wear debris in vacuum from the a-C:H film was similar to that of the film surface except wear track. It was supposed that the low friction coefficient of the a-C:H film in vacuum was caused by self lubrication. By micro FT-IR spectroscopy of the wear debris in ambient air, peaks of the same organic material were observed on both the a-C:H film and the a-C film. Therefore, it seemed that the observed low friction coefficient of the a-C film in ambient air was caused by formation of tribofilm composed of these organic materials. Furthermore these results suggested that this tribofilm was made from humidity in air and carbon contained in the film.
4:30 PM		D2-1-10 Tribological Behavior of Diamond-Like Carbon Films in Aqueous Environment J.-W. Yi, S.-J. Park, K.-R. Lee (Korea Institute of Science and Technology, Korea); S.-S. Kim (Kyungpook University, Korea) Tribological behavior of diamond-like carbon (DLC) films was investigated in aqueous environment. DLC films were prepared by radio frequency plasma-assisted chemical vapor deposition (r.f.-PACVD) using mixture of benzene and hydrogen. Si (100) wafer and polished stainless steel plate (316L) were used as the substrate. DLC film was deposited for various fractions of hydrogen in the precursor gas. A ball-on-disc type wear rig with water jacket was used for the wear test between the DLC film and the sapphire ball of diameter 6 mm. Neither the atomic bond structure nor the coefficient of friction in water is affected by the fraction of hydrogen in the precursor gas. However, the adhesive wear in the wear track significantly decreased as the fraction of hydrogen in precursor gas mixture increased. It was confirmed that the porosity of the DLC decreased with increasing hydrogen fraction. Addition of hydrogen in the precursor gas would decrease the thermodynamic driving force for the carbon particle nucleation. Hence, the present results were discussed in terms of the decreased homogeneous nucleation of carbon particles that can result in submicro or nano pores in the film.