ICMCTF2007 Session EP: Symposium E Poster Session

Thursday, April 26, 2007 5:00 PM in Room Town & Country
Thursday Afternoon

Time Period ThP Sessions | Topic E Sessions | Time Periods | Topics | ICMCTF2007 Schedule

EP-1 Effect of CrZrN Thin Film Coating on the Improvement of the Low-Speed Torque Efficiency of a Hydraulic Piston Pump
Y.S. Hong, S.Y. Lee (HanKuk Aviation University, Korea); S.H. Kim (Korea Institute of Machinery and Metals, Korea)
The electro-hydraulic actuators (abbreviated as EHA in the following) consist of a constant displacement pump and a hydraulic cylinder forming a closed circuit, where the pump is driven by an electrical servomotor whose angular velocity is controlled to position the hydraulic cylinder. The pump for the EHA operates in almost unsteady condition because it has to continuously compensate the position control error. Therefore, the lubrication condition of the pump is much worse than that of normally constant speed - running pumps. It means that the internal pump parts are repeatedly subjected to the mixed lubrication which leads to increased friction loss and wear rate. This paper is dealing a hydraulic piston type pump which is widely applied for the EHAs. In order to improve the tribological interaction between its valve plate and cylinderbarrel, the PVD-coating process was applied. The contact surface of the cylinder barrel was coated with CrZrN in the form of multi-layers which are expected to reduce the wear rate of the valve plate and the friction loss even under the mixed friction condition.There have been carried out a lot of researches aimed at the improvement of the tribological property of hydraulic pumps handling environment-friendly fluids by the PVD-coating technology. For example, many types of coatings including CrN, TiN, CrSiN, etc were tried and tested. CrZrN was proposed in this study since the additional Zr-content was expected to modify the surface morphologies of coating. The experimental results showed that the friction torque of the valve plate mated with a CrZrN-coated cylinder barrel could be reduced to more than 20% of that with an uncoated original one when load pressure was 300 bar and rotational speed 100 rpm. It means that the torque efficiency of the test pump was expected to increase more than 1.5 % under the same working condition. Detailed experimental results will be presented.
EP-2 Mechanical Properties and Coefficient of Friction of Cu/a-C Films
M. Louda, J. Suna, J. Musil (University of West Bohemia, Czech Republic)

Recently, the TMC/a-C and TMC/a-C:H nanocomposite films were developed to overcome inherent limits of pure a-C:H hydrogenated diamond-like carbon (DLC) films; i.e. low thermal stability and high compressive macrostress (σ<0), here TM=Ti, W, Ta, etc. and a- denotes the amorphous phase. Properties of MeC/a-C nanocomposites strongly depend on the volume ratio of amorphous and crystalline phases, the grain size and the distance between grains. The boundaries or coupling between grains and amorphous a-C matrix is, however, different from those in Me/a-C nanocomposites; here Me=Cu, Ag etc are the elements which do not form compounds with C. Me/a-C nanocomposites exhibit very abrupt boundaries with very weak interatomic forces between grains and amorphous a-C matrix. This fact results in new properties of Me/a-C nanocomposites. The deformation of Me/a-C nanocomposite is easier than that of MeC/a-C and it results in their higher toughness, improved tribological behavior and lower coefficient of friction.

This article reports on the preparation and characterization of Cu/a-C nanocomposite films prepared by magnetron sputtering of a composed target (C target with Cu fixing ring of different inner diameter Φin. By selection of Φin of Cu fixing ring in the interval from 70 to 96 mm the Cu/a-C composite films with Cu content ranging from 1 to 60 at.% were prepared. The effect of amount of Cu addition into a-C film on its properties was investigated in detail. It was found that (i) mechanical and tribological properties of the a-C film are strongly influenced by Cu addition, (ii) hardness H and compressive macrostress σ of 2500 nm thick Cu/a-C film increases with decreasing Cu content in the film from 3 to 8 GPa and from -0.05 to -0.4 GPa, respectively, (iii) Cu/a-C film with H=5 GPa exhibits low coefficient of friction 0.12 and low wear 0.22x10-6 mm3/Nm.
EP-3 Improvement of Bonding Strength to Titanium Surface by Sol-Gel Derived Hybrid Coating of Hydroxyapatite and Titania
K.H. Im, K.N. Kim, K.M. Kim, Y.K. Lee (Yonsei University College of Dentistry, Korea)
Hydroxyapatite(HA) coating on titanium(Ti) substrate has been taken a great deal of attention to improve the poor osteoinductivity of Ti. HA coatings are traditionally produced by a plasma-spraying. However, the plasma-sprayed HA coating layer is known to be inhomogeneous and have low bonding strength. Thin HA film obtained by sol-gel process was reported to have high purity and relatively higher strength, but the bonding strength was still not satisfied. Therefore, the effect of hybrid coating of HA and TiO2 on the bonding strength between coated film and Ti substrate was investigated in this study. HA sol was synthesized by mixing 2M of calcium nitrate tetrahydrate solution with a stoichiometric amount of triethyl phophite solution. Titanium propoxide was selected as a precursor of Ti sol. Hybrid sols were prepared dropping Ti sol into HA sol with various ratios from 10-70 mol%. They were spin-coated onto the rectangular Ti substrates (10x10 mm) at 20 rpm for 10 s. The coated Ti substrates were dried and heat treated at 500°C for 2 h. Coating thickness, roughness, crystal phase, and morphology were determined by surface profiler, XRD, and SEM, respectively. The bonding strength between coatings and substrates were evaluated by scratch test. The coated films were highly dense and homogeneous. With increasing the amount of TiO2, the thickness of the film was decreased, while the roughness increased. The bonding strength was remarkably increased with the amount of TiO2 increased up to 70 mol%. It could be concluded that the hybrid coating of HA and and TiO2 should be effective to improve the bonding strength between HA and Ti substrate.
EP-4 Microstructure and Tribological Properties of Anodic Oxide Layer Formed on AlSi Alloy Produced by Semisolid Processing
A. Forn, J.A. Picas, M.T. Baile (Technical University of Catalonia, Spain); E. Martin (Technical University of Catalonia,, Spain); V.G. Garcia (Technical University of Catalonia, Spain)
One of the problems when hard anodizing cast aluminum alloys is being able to grow a sufficiently thick and homogeneous anodic oxide layer. This work analyses the possibility of being able to use semisolid metal forming technology (SSM), like Thixocasting, to solve this surface treatment problem. When compared to conventional castings, SSM involves a reduced porosity and amount of trapped gas, which allow cast components to be heat treated without blistering and the chemical reactivity of the surface also changes. The aim of this work is to study the heat treatment influence (T5 and T6) on the anodization of A357 aluminium alloy produced by SSM process. In particular, the microstructure influence on the growth of anodic oxide layer. Optical microscopy, SEM and EDS analyses were used to examine the microstructural features found on, within and under the anodized layer. Experiments using a tribometer (pin on disc configuration) have been performed in order to evaluate the friction and wear properties of the different layers. The anodic oxide layer formed on the SSM as-cast and T5 substrates had a similar appearance. However, the anodic oxide layer formed over the T6 substrate showed a more homogeneous thickness and spheroidized silicon particles became embedded in the anodic oxide layer. Furthermore, the T6 anodized samples showed a slight reduction in friction coefficient and wear rate than the as-cast anodized substrate.
EP-5 Wear Resistance of Multilayered Sol-Gel Silica Coatings on Aluminium SiC Composites
J. Rams, A.J. Lopez, M.D. Lopez, A. Ureña (Rey Juan Carlos University, Spain)
Aluminium alloys and aluminium matrix composite are reference materials for many applications but their properties can be improved by coating them with ceramic layers. The mechanical properties and the wear resistance of silica coatings obtained through a sol gel route on aluminium matrix composites reinforced with SiC particles and on aluminium alloys have been studied. Up to 20 microns thick silica coatings have been deposited by using single and multiple layers, and extensive crack free surfaces have been achieved with both methods. Wear resistances of the different coatings have been measured in dry conditions in a pin-on-disk configuration, and their mechanical properties have been measured using the nanoindentation technique independently from the substrate underneath. Wear resistance of coated substrates is about 3 times that of uncoated material, and a change in the wear mechanism has been determined. This is due to the hardness of the silica coating which is even higher than that of fused silica in the case of multilayered sol-gel coatings. The topography of the layers and of the worn surfaces have been characterised by Scanning Electronic Microscopy and Atomic Force Microscopy. The microstructure of the coatings has been studied by Transmission Electronic Microscopy, and the appearance of nanocrystals on the flat surfaces has been considered responsible of the mechanical properties measured. The use of sol-gel silica multilayer seems to be a practical route to improve the application range of aluminium alloys and composites.
EP-7 Tribological Behaviour of Pulsed Magnetron Sputtered CrB2 Coatings Examined by the Reciprocating Sliding Wear Testing
M. Audronis, Z.M. Rosli, A. Leyland (University of Sheffield, United Kingdom); P.J. Kelly (Manchester Metropolitan University, United Kingdom); A. Matthews (University of Sheffield, United Kingdom)

Among the number of attractive properties that transitional metal diborides (TiB2, CrB2, ZrB2 etc.) possess, the resistance to abrasive wear (due to high hardness) and the chemical inertness are the most important when considering diboride coatings for dry machining of nonferrous materials, such as aluminium and its alloys.

Due mostly to the problematic deposition of chromium diboride (preparation of targets, target cracking during the deposition process, control of stoichiometry etc.), these coatings remain comparatively less studied than, for example, titanium diborides, with regard to their tribological performance.

In this paper we report on the tribological behaviour of pulsed magnetron sputtered, smooth and fully dense, crystalline, 21 to 38 GPa hard CrB2 coatings, examined by the reciprocating sliding wear testing against AISI 2017A aluminium alloy and AISI 52100 chrome steel. Results are compared to those of pulsed magnetron sputter deposited titanium and chromium nitride coatings.
EP-8 The Patterning Characteristic of Cu/80Ni20Cr Layers on PI in FCCL Deposited by Magnetron Sputtering
S.-H. Kim (Korea University of Technology and Education (KUT), Korea)
Flexible copper clad laminates(FCCL) fabricated by sputtering have advantages in fine pitch etching and dimensional accuracy than previous casting or laminating type FCCL. But its lower adhesion is inevitable technical challenge to solve for commercializing it. Chromium(Cr) and Nickel(Ni) alloy which strongly reacts with O moiety was used as tie-coating layer in order to improve low adhesion between copper(Cu) and Polyimide(PI), but Cr and Ni also deteriorate etching ability in patterning process. At the RF magnetron sputtering, the thickness and deposition temperature of 80Ni20Cr tie-coating layer were varied in the range from 5nm to 30nm and from RT to 250, respectively. The effect on the adhesion and patterning compatibility was investigated. As the thickness increase from 10nm to 15nm the adhesion was increased, and the thickness goes more over 15nm then the adhesion was decreased again. Patterning was clearly defined with thinner layer than 15nm, but that became faint with 20nm thick layer. As the deposition temperature, the adhesion and patterning were be optimized at the moderate deposition temperature on the range around 150. Consequently, we could obtain the highest peel strength of 145gf/mm and relatively better patterning characteristic when the 80Ni20Cr tie-coating layer deposited at 150 with thickness of about 15nm. This was discussed in relation to the reaction of PI and/or O moiety with tie-coating layer. Keywords: FCCL, Sputtering, Adhesion, Patterning, Atmospheric plasma surface treatment, Low pressure plasma surface treatment, Polyimide.
EP-9 Tribological Study of Sol-Gel Thin Solid Films
C. Massard, J.L. Taverdet, S. Brouillet (Université Jean Monnet, France); C. Donnet (Université Jean Monnet and University Institute of France)
Sol-gel processes allow the production of a wide range and variety of coatings. The conditions of soft chemistry allow the integration of photocurable organic compounds into an inorganic network, opening the way to the creation of new nanocomposite materials deposited on wide surfaces. Such hybrid thin films may exhibit outstanding properties, stemming from the synergy between the properties of polymers (flexibility) and those of inorganic glasses (hardness, transparency). For various applications, tribological studies on these new materials cannot be bypassed since the future components coated by such films may be submitted to various mechanical sollicitations. The objective of the present study is the deposition (by hydrolysis condensation) and characterization of an organically modified silicon alkoxide containing zirconium alkoxide to modulate the refractive index of the film. After deposition, UV irradiation allows to develop an organic structure entangled in the inorganic network. The resulting thin films, exhibiting a high transparency with a modulable refractive index, have a great potential to be used for components in integrated optical devices. The friction and wear behavior of the films has been investigated depending on the deposition conditions, mainly the organic conversion ratio ranging between 6 and 98%. The organic conversion ratio corresponds to the range of organic network within the film. For the lowest organic conversion ratios, the films do not withstand the friction tests and exhibit poor wear resistance. For conversion ratios above 60 %, friction coefficient in the 0.1 range have been recorded, with a significant wear resistance. The tribological behavior of such inorganic-organic hybrid nanocomposite thin films tested in standard conditions are discussed in agreement with their structure and composition. The potentiality to reach both wear resistance and outstanding optical properties will be evaluated.
EP-10 Surface Characterization and Mechanical Properties of the Electrodeposited Nickel-Phosphorus Binary Coatings
Y.M. Su, F.B. Wu (National United University, Taiwan)
Binary nickel-phosphorus coatings were fabricated by direct current electrodeposition with Brenner-type plating bath on various metal and alloy substrates, including pure Cu, Al and brass. The deposition parameters, including working distance, anode-to-cathode area ratio, current density, and substrate material were controlled to optimize the homogeneity and related mechanical and surface properties of the Ni-P coatings. The morphology and elemental distribution of Ni and P were investigated by scanning electron microscopy and electron probe microanalysis, respectively. A well-distributed Ni and P concentrations and uniform coating thickness were found under the optimal cathodic current density of 100 mA/cm2 and working distance of 7.5 cm. Severe dissolution causing rough surface morphology for pure Ni anode were observed under low anode-to-cathode area ratio less than 0.75 and high current density over 150 mA/cm2. Surface roughness and edge dendrite formation were intensively discussed in terms of current distribution during plating process. In addition, the microhardness, adhesion strength and scratch behavior of the Ni-P deposits on various metallic substrates were evaluated and analyzed.
EP-12 Residual Stress and Nano-Hardness Behavior of the C/Si Nanocomposites
C.K. Chung, C.C. Peng, B.H. Wu, T.S. Chen (National Cheng Kung University, Taiwan)
In this paper, carbon/silicon (C/Si) nanocomposites were formed by ion beam sputtering (IBS) at room temperature (RT) under ultra high vacuum at a base pressure of 10-6-10-7 Pa. The microstructure, residual stress and nano-hardness properties of the C/Si nanocomposites were studied using grazing incident X-ray diffractometer (GIXRD), atomic force microscope (AFM), thin films stress analyze nanoindentation and Raman spectroscopy, respectively. The as-deposited C is a tetrahedral amorphous carbon (ta-C) with primary sp3 bonding determined by Raman spectra. It was analyzed to obtain the intensity ratio (ID/IG) and peak position.. The residual stress of single a-C film with thickness 100 nm measured was about 11.98 GPa in compression and its nano-hardness was 18.35 GPa at RT. The residual stress of C/Si nanocomposite films measured was decreasing down to 5.76 GPa in compression after the addition of amorphous Silicon (a-Si) layer of 50 nm and its nano-hardness were about 17.69 GPa at RT. The compressive residual stress and nano-hardness of the C/Si films were affected by a-Si contents. Further, Effect of C thickness on C/a-Si stress and hardness were discussed. The addition of a-Si layer has a great contribution to decrease the compressive residual stress which is good for the suppression of the cracks growth in the C-nanocomposite film.
EP-13 Fatigue Properties of DLC Coated Stainless Steel
S. Hirota (Kobe Steel Ltd., Japan); T. Morita (Kyoto Institute of Technology, Japan); T. Kumakiri (Kobe Steel Ltd., Japan)
This study was conducted to investigate the effect of diamond-like carbon (DLC) coating on the fatigue properties of stainless steel SUS 304. For the DLC coating, unbalanced magnetron sputtering (UBMS) method was used. The generated surface layer possessing about 2 µm thickness was composed with the DLC layer with a high hardness and an intermediate layer to improve the adhesion to the substrate. The DLC coating at a relatively low temperature had no influence to the microstructure so that the mechanical properties of stainless steel were unchanged. The results of plane-bending fatigue test showed that the DLC coating increased the fatigue strength by 18 %. From the detailed observation on the fracture surface, it was suggested that the improvement of the fatigue strength was made through the suppression of fatigue crack initiation from the surface due to the existence of the surface layer with a high adhesion and strength.
EP-14 Wear Behavior of Unbalanced Magnetron Sputtered Multilayer TiN/TiAlYN Coatings Deposited on Plasma Nitrided Steels
M. Flores (Universidad de Guadalajara, Mexico); E. De las Heras (INTI, Mexico); I. Rodriguez (Universidad de Guadalajara, Mexico); P. Corengia (INTI, Mexico)
The influence of pretreatment on the wear behavior of AISI D2 and Vanadis 6 tool steels coated with TiN and TiN/TiAlYN multilayers were experimentally investigated. The two substrate materials were nitrided using plasma nitriding. The thin films were deposited using unbalanced magnetron sputtering technique. A comparison between the wear resistances of nitrided, coated, nitrided and coated samples were made. The TiN coatings and TiN/TiAlYN multilayer grown on pulse plasma nitriding steels have been characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), micro-indentation and abrasive wear tests. The duplex coatings showed low wear respect to coated samples. The out-performance of the prenitrided TiN and TiN/TiAlYN coatings can be attributed to the presence of a nitrided subsurface.
EP-16 Statistical Characterization of the Strength of Wear-Resistant Hard Coatings
S. Kamiya (Nagoya Institute of Technology, Japan); H. Hanyu (OSG corporation, Japan); S. Amaki, H. Yanase (Nagoya Institute of Technology, Japan)

Mechanical strength of coatings is of serious concern, especially from a view point of reliability issue for those wear-resistant hard coatings used to protect coated materials from severe mechanical loadings. Although various kinds of advanced hard coatings have been developed, there is not enough information to enable mechanical design of these systems against external loadings. In order to clarify basic strength properties of hard coatings, microscopic bending tests were performed in this study on those advanced physically vapor deposited (PVD) coatings as well as chemically vapor deposited (CVD) diamond coatings.

Free standing part of coatings, which was made by selective etching processes of substrates, was cut into narrow beams by focused ion beam to serve as the bending specimens. These bending specimens were fabricated of two representative PVD coatings, TiN and CrN, and a CVD diamond coating. In order to see the effect of substrate surfaces, those coatings on two different kinds of substrates were subjected to the experiment, i.e., polished silicon wafers and ground WC-Co.

As large scatters were observed in their critical bending strength which was calculated by finite element method with the maximum load applied, the results were analyzed on the basis of Weibull statistics. It was found that the scatter was generally larger for the case of PVD coatings than CVD diamond and that it was influenced by the conditions of substrate surfaces. It is speculated that the former was due to possible introduction of larger defects during the highly nonequilibrium deposition process. The latter may be simply attributed to stress concentration when interface side surface was subjected to tension. These information supply a new insight for the possibility to design mechanical integrity and improve performance of hard coating systems.
E3-6 Cutting Performance of DLC Coated WC Insert for Machining of Aluminum Alloy
K.Y. Lee (Pukyong National University, Korea); C.S. Hong (Pukyong National University, Koea); R. Wei (Southwest Research Institute)
We have applied DLC (diamond-like carbon) coatings on tungsten carbide cutting inserts tools using PIID (plasma immersion ion deposition) and magnetron sputtering deposition technique. The DLC coated specimens have been tested the physical and chemical properties of the film to observe the survivability of the DLC coatings during the machining process and the tests were done under a wider range of conditions for the basic tribological properties of DLC coated WC. Cutting performance experiments were carried out in a high speed NC machining center to the milling of aluminum alloy. The results showed that the wear life of DLC-coated cutting inserts was improved by double and the cutting resistances were drastically reduced. The DLC-coated tools have great advantages for dry machining of Al alloy materials compared to uncoated mirror finished cemented carbide tools which were produced only for Al alloy machining. Prior to and after the machining tests, the specimens were carefully analyzed using SEM with EDS to characterize the adhesion of active Al alloy on the WC surface and the worn or damaged surfaces as well as the cross sections of the DLC films. Morphological changes of the DLC coated surfaces were studied using AFM. In addition, Nano-indentation, Scratch test, AES, XPS, Raman, GDOES and GXRD were adopted to characterize the properties of the DLC thin film and the elemental changes of the DLC coatings for the cutting and deposition processes. These properties of the both coating techniques are compared.
EP-19 Mechanical and Tribological Properties of Compositionally Graded CrAlN Films by AC Reactive Magnetron Sputtering
S. Pulugurtha, D. Bhat, M.H. Gordon, J. Shultz (University of Arkansas); M.H. Staia (Universidad Central de Venezuela); S.V. Joshi, S. Govindarajan (ARC-I, India)

In this work, CrAlN films with Al/Cr atomic ratios between 0.02 and 1.4 were deposited onto tool inserts by AC magnetron sputtering at 5 kW and varying Ar/N2 flow rates. The unique configuration of the inverted cylindrical magnetron sputtering (ICM-10) system enables the deposition of compositionally graded Cr-Al-N coatings under a single deposition condition. This paper reports the effect of aluminum on the structural, mechanical and tribological properties of (Cr,Al)N coatings. The results are compared with Alcrona and CrN coatings from Balzers. Mechanical properties have been evaluated by microhardness indentation technique, while tribological tests have been carried against Mo steel discs and WC pins by pin-on-disc method both at room temperature and 700°C. Initial results indicate that the coefficient of friction at room temperature for the compositionally graded Cr-Al-N coatings, Balzers Alcrona and CrN fall between 0.4-0.6. Increasing Al content in the film leads to an increase in the average roughness (Ra) values from 82 to 110 nm. Decreasing the nitrogen flow rate during deposition leads to much higher roughness values between 150 nm to 189 nm as the Al concentration increases from 1.9 at % to 23 at% in single deposition. In the full paper, we will report on AES, X-ray elemental mapping, and hot hardness studies on (Cr,Al)N coatings for different Ar/N2 gas compositions.

*Currently Program Manager, SBIR/STTR, National Science Foundation, Arlington, VA. .
EP-20 Mechanical Characteristics of AISI 1010 Mild Steel Treated by Plasma Thermochemical Processes
V.H. Baggio-Scheid, A.J. Abdalla (General-Command of Aerospace Technology, Brazil)
Plasma nitriding and nitrocarburizing are thermochemical treatments, which have been used to improve several chemical and physical properties of steels as corrosion and wear resistance, surface hardness and fatigue strength. In this work we investigate the fatigue, tensile and bending behavior of AISI 1010 mild steels specimens treated by plasma nitriding, nitrocarburizing and nitrocarburizing plus post-oxidation. The samples were treated at temperatures varying from 673 K up to 873 K. The influence of the treatment time, and gas concentration on the mechanical properties was also investigated. It was observed that with increasing layer thickness and hardness there is an increase of the yield point and tensile strength, above that plastic deformation starts. A detailed correlation between the layer properties of the treated specimens and the results of the fatigue, tensile and bend tests will be presented and discussed.
EP-21 Effect of Silicon Doping to the Mechanical and Tribological Properties of DLC Thin Films
F. Pighetti Mantini, G. Bolelli, L. Lusvarghi, L. Pasquali, M. Montorsi (University of Modena and Reggio Emilia, Italy); M. Barletta (Universitat degli Studi di Roma Tor Vergata, Italy); A. Farinotti (Lafer Spa, Italy)
Diamond-Like Carbon (DLC) films are largely used in industrial applications for their excellent qualities as high hardness, low friction, wear resistance and chemical inertness. A disadvantage of these coatings is the limited thermal stability, since they cannot retain their superior characteristics with the increasing temperature. The maximum working temperature that the DLC films producers declare is around 400°C. One of the most promising solutions to increase the working temperature is doping DLC coatings with silicon. The aim of the addition of silicon is the improvement of thermal stability of DLC films, which seems to be mainly caused by the formation of silicon carbide. On the other hand, the addition of silicon could decrease the mechanical properties of the films. The aim of the work is to evaluate the right amount of silicon required to increase the working temperature without being too detrimental to the mechanical properties. All DLC coatings with different amounts of silicon were deposited by PECVD on two different steel substrates and on HSS cutting tools. The microstructural and chemical characteristics were studied by FE-SEM and XPS analysis, respectively. Nanoindentation and scratch tests have been carried out to evaluate the elastic modulus, hardness and adhesion of the various coating. To investigate the wear behaviour with increasing temperature, the coatings were subjected to dry sliding ball-on-disk tests against WC-6%Co counterbody at three different temperatures (room temperature, 300°C and 550°C). All mechanical and tribological results were analyzed to find the coating composition, which shows the best compromise between preserving good mechanical properties and increasing the working temperature. The cutting behaviour of both virgin and doped and undoped DLC coated tools were evaluated by cutting tests performed by means of a vertical-spindle column-and-knee type milling machine.
EP-22 Deposition and Tribology of Carbon and Boron Nitride Nanoperiod Multilayer Solid Lubricating Films
S. Miyake, T. Hashizume, W. Kurosaka (Nippon Institute of Technology, Japan); M. Sakurai, M. Wang (Osg Corporation, Japan)
The solid lubricating properties of nano-period multilayer (C/BN)n films is discussed in this article. Nanoperiod multilayer films composed of carbon and boron nitride layers, which have a structure expected to provide solid lubrication such as the h-BN and graphite structures were deposited, and their nanoindentation and tribological properties were evaluated. The nanoindentation hardness and modulus of dissipation of the nano-period multilayer (C/BN)n films change with the layer period. The coating deposited at a 4 nm layer period shows the highest hardness. Tribological properties of the coatings were investigated by ball-on-disk tribotesting, results indicated that the 4-nm-period coating has the lowest friction coefficient compared with the other coatings deposited in this study. The results of the dependence of friction coefficient on the number of sliding cycle and temperature show that the mechanical and tribological properties of the multilayer (C/BN)n films can be significantly improved at the layer period of 4 nm.
EP-23 The Effect of Hydrogen Plasma Treatment on Tribological Behavior of Diamondlike Carbon Films
O.L. Eryilmaz, A. Erdemir (Argonne National Laboratory)
Diamond-like carbon (DLC) films have attracted a great deal of attention for several years for a wide range of tribological applications. These films have the potential to reduce friction under both dry and lubricated sliding conditions. However there is a wide range of films that contain no hydrogen or very high hydrogen. Depending on the type of DLC films, the presence or absence of oxygen and humidity in the test chamber may increase or decrease the friction and wear coefficients of DLC films. For example, hydrogenated DLC seems to work the best, while hydrogen-free DLC films work worst in inert or dry test environments. It is clear that the presence of hydrogen in the deposition chamber makes a huge difference in the tribological behavior of DLC films. In this study, we explored the effect of post hydrogen plasma treatment on tribological properties of non hydrogenated DLC or CNx films. Post hydrogen treatment is done in a capacitively coupled plasma enhanced chemical vapor deposition (CVD) chamber with a 13.56 MHz r.f. BIAS power source. Ar ion etching for 2 minutes is followed by hydrogen treatment of surfaces between 2 to 5 minutes by using pure hydrogen gas as source. Tribological tests were run to treated and untreated DLC coated samples in a ball-on-disk machine under 0.5 to 1N loads in dry nitrogen environment. Test results have confirmed that more than an order of magnitude reductions in friction and more than two orders of magnitude reductions in wear are feasible with very simple post-deposition hydrogen treatment of hydrogen free and CNx type DLC films. Furthermore, we used time of flight secondary ion mass spectroscopy to generate two and three dimensional elemental mapping of hydrogen treated and untreated surfaces prior and after testing. Finally we have correlated these findings with changes in friction and wear of those DLC films.
Time Period ThP Sessions | Topic E Sessions | Time Periods | Topics | ICMCTF2007 Schedule