ICMCTF2000 Session EP: E Poster
Time Period WeP Sessions | Topic E Sessions | Time Periods | Topics | ICMCTF2000 Schedule
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EP-1 Corrosion and Tribological Studies of Chromium Nitride Coated on Steel Through an Interlayer of Chromium
S. Han (National Chung Hsing University, Taiwan, ROC); J.H. Lin (National Tsing Hua University, Taiwan, ROC); X.J. Guo, F.H. Lu (National Chung Hsing University, Taiwan, ROC); H.C. Shih (National Tsing Hua University, Taiwan,ROC) The electrochemical and tribological behavior of CrN coatings on steel are investigated. A single layer of the chromium nitride coating is compared with double layer coatings ( CrN/Cr/steel ) with the aim of improving the corrosion and tribological resistance of the steel . The CrN is deposited by using a reactive cathodic arc evaporation technology in an industrial scale, while the intermediate chromium layer is deposited by electroplating. The coatings have been characterized in term of hardness, adhesion, wear and corrosion resistance. The composition and structure of the chromium nitride has been studied by Auger electron spectroscopy and X-ray diffraction (XRD) . The morphology was investigated using AFM, and SEM. The nitride coatings are fairly dense with a microcolumnar morphology. Adhesion is as good as usually observed with this technology. The improvement in wear and corrosion resistance after cathodic arc evaporation with and without a hard chrome are discussed considering microstructure changes. |
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EP-2 Coating Tribology: A Comparative Study of Test Methods
M.C. Joseph, A. Wilson, A. Leyland, A. Matthews (University of Hull, United Kingdom); L.E. Seitzman (Caterpillar Inc.); S.L. Rohde (University of Nebraska - Lincoln) Plasma assisted electron beam PVD chromium nitride and carbon-based coatings produced by a PI3 method were deposited on 52100 steel substrates, as single layers, and in combination. Several substrates geometries were coated to accommodate different testing methods. The coatings were tested in pure sliding conditions using two ball-on-flat reciprocating test configurations, a ring-on-ring reciprocating test, and a scratch test. These were used to rank the coatings based on galling resistance, abrasive wear, and contact pressure/velocity limit. The coatings were further characterised, for thickness, hardness/adhesion and morphology by ball cratering, instrumented indentation and scanning electron microscopy, respectively. Differences in performance ranking are discussed in terms of the failure mechanisms and their relationship to coating properties. They reveal the benefits of duplex combinations of processes to provide optimal tribological characteristics. |
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EP-3 Use of a Micro-abrasion Test to Evaluate Single-layered and Duplex Coatings
M.C. Joseph, A. Wilson, A. Leyland, A. Matthews (University of Hull, United Kingdom); L.E. Seitzman (Caterpillar Inc.); E. Preston (CSIRO, Australia) An abrasive wear test, based on the ball-crater technique, has been used to evaluate the wear resistance of TiN, CrN and other PVD ceramic coatings, on untreated and plasma pre-treated steels. The results are described, illustrating how the respective wear resistances compare, including the effect of the pre-treatment layer. The characteristics of the test are compared with those of other tribological test methods, for example in terms of the ability to obtain depth-related wear rate information and therefore assess the load-support provided beneath the surface. |
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EP-4 Tribology of Diamond and Diamondlike Carbon Coatings with Aluminium
K.H. Taube, J. Gäbler (Fraunhofer Institut für Schicht- und Oberflächentechnik, Germany) In forming and cutting of aluminium high amounts of lubricating agents are often needed to prevent galling of the worked metals. Built-on edges limit the lifetime of the tools. Punching tools prematurely fail due to an intolerable decrease of the gap between punch and die. In cutting of silicon alloyed aluminium also the high abrasive wear of the cutting tools is a problem. Therefor there is high interest in friction reducing and antigalling hard coatings like diamond like carbon (DLC) for forming and punching tools and crystalline diamond for cutting tools. This talk discusses results from reciprocating ball-on-disk-tests of DLC and smooth diamond coatings (DiaTex® by Fraunhofer IST) against aluminium balls and DLC coated balls versus aluminium sheet metal under lubricated (oil, water) and dry conditions. The development of low friction of DLC coatings depends strongly on the kind of test and of course on testing conditions. An extensive running-in period accompanied by rather high friction coefficient when run dry is followed by the commonly known steady state with low friction coefficients. To avoid galling of aluminium to tools this first period should be minimized. This can be achieved either by unwanted high amounts of lubrication or just by using pure water. In the case of diamond high friction coefficients are observed to due ploughing of the rather rough coating surface through the aluminium. Aluminium transfer is limited to the gaps between crystallites, but no aluminium adheres to the oriented surface of the crystallites. A companion paper ("Use of DLC and Diamond Coatings in Forming and Cutting of Aluminium") correlates these results with application oriented testing and results from production. |
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EP-5 Durability of DLC-Coated Gear Pair under the Non-Lubrication Condition
M. Murakawa (Nippon Institute of Technology, Japan); T. Komori (Kyouiku Gear Mfg, Co.,Ltd., Japan); S. Takeuchi (Nippon Institute of Technology, Japan); K. Miyoshi (NASA) DLC film has some merits such as excellent antiwear capability and a low coefficient of friction as well as excellent self-lubrication ability, leading to its application even to the most typical machine element, i.e., gears from the perspective of, e.g., compensating the loss of lubricant. However, recent technological developments have resulted in the need for elimination of conventional lubricants for gear pairs that are expected to operate under atmospheres such as vacuum or those in which an oil lubricant is impossible to use. Accordingly, in an attempt to satisfy such a requirement we investigate the possibility of coating gear pairs with DLC film as an alternative to using oil or other conventional lubricants. We have found from an endurance test for a rotating gear pair coated with DLC film using a load-absorbing-type gear tester that the DLC-coated gear pair showed a substantially long lifetime even in the absence of a lubricant from the beginning of the test. |
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EP-6 Mechanical Characterization of Thin Films Used in Outer Space
N. Novikov, O. Lysenko, V. Grushko (V.Bakul Institute for Superhard Materials, Ukraine); S. Khandozhko (ENSAM, France) The behavior of thin films at atmospheric and vacuum conditions during various mechanical actions was investigated. The optimum deposition parameters of DLC films for work in conditions of outer space are established. For an evaluation of possibility of such films using as lubricants we have developed a new Scanning Tunneling Probe Apparatus that allows to measure friction, and obtain acoustic emission (AE) spectra of a contact during sliding by tunneling probe with diamond tip. An unique feature of this instrument is the ability to perform AE spectroscopy through the transparent slider in order to visually monitor the buildup and breakdown of transfer films in the contact area during sliding. We are currently performing studies of the correlation between the friction force and nanostructure on solid carbon lubricant thin films. Our researches of the nanoscale mechanisms responsible for mechanical properties of lubricant thin films would be indispensable in the design of novel lubricants for outer space. |
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EP-7 PVD Coatings of TiN on Boron Carbide for Cutting Tools
P.T.M. Larsson (Uppsala University, Sweden); M. Berger (The Ångström Laboratory, Sweden); N. Axen (Consultant) Boron carbide B4C is the third hardest material known, following diamond and cubic boron nitride. Boron carbide also retains its hardness up to about 1300oC and has an excellent wear resistance. The properties that have limited the use of B4C are the poor resistance to oxidation and its sensitivity to spalling at the surface. Therefore, the combination of a hard, rigid B4C substrate, with a heat conductive and tough coating may be favourable. TiN coatings were deposited using electron beam evaporation in a Balzers BAI640R coating unit. The compositions of the coatings were determined by X-ray diffraction; their tribological properties were evaluated with nanoindentation (hardness and modulus), scratch test (cohesion and adhesion), single impacts erosion and microabrasion. Also cutting tests were carried out with aluminium-silicon alloys. The TiN coating increased the resistance to spalling and to oxidation compared to uncoated B4C. The critical load and the abrasive wear resistance of the TiN coated B4C were sufficient for use of this material as a cutting tool. |
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EP-8 A Comparative Study of State-of-the-Art Diamond-Like Carbon Films
K. Vercammen (VITO, Belgium); H. Haefke, E. Pflüger (CSEM, Switzerland); A. Van Hulsel (VITO, Belgium); Y. Gerbig (CSEM, Switzerland); J. Meneve (VITO, Belgium) Diamond-like carbon (DLC) coatings represent a group of very alike but still very different materials. Their characteristics range from graphite-like over diamond-like to polymer-like behaviour depending on the deposition techniques. The sensitivity of DLC coating properties to process conditions can be considered as a problem, on the other hand it creates the opportunity to adapt the coating properties to specific applications. In this study the mechanical and tribological properties of various state-of-the art DLC coatings (from 6 suppliers) were investigated to generate comparable data that should facilitate the selection of DLC coatings for particular applications. Hardness and modulus of elasticity were measured by depth-sensing indentation. Scratch testing was used to determine the adhesive strength of the coatings. The friction and wear tests were conducted using a ball-on-flat and flat-on-flat tribometer under unidirectional and reciprocating motion, respectively. The abrasive wear resistance was evaluated by the microabrasion tester designed to characterise thin coatings and by the standard Taber abraser test. The results of this work demonstrated that the mechanical and tribological properties of DLC coatings vary strongly. Each coating type has specific advantages and the total of properties should be studied carefully to select the appropriate coating in a particular application. A more general guideline for DLC selection is discussed. |
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EP-9 Finite Element Analysis of Hard Coating with Particles Under Sliding Contact
D. Diao, A. Satoshi (Shizuoka University, Japan) In this paper, Von Mises stress distribution in coatings with particles under sliding contact were analyzed by the finite element method. An elliptical distribution of normal and traction contact pressure was assumed in the analysis. The critical maximum contact pressure for yielding and the yielding position were calculated for various combinations of the coating thickness, the numbers of particle, the yield strength and the friction coefficient. Also, the ratio of critical maximum contact pressure for the case of hard coating without particle to that with particles was calculated for checking the effect of particles in the field of increasing the critical pressure. Finally, a design method for the hard coating with particles was pointed out. |
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EP-10 Tribological Behaviour and Surface Modifications of the Copper/3D Carbon-carbon Composite Couple in a Sliding Electrical Contact
A. Samah, D. Paulmier (National Polytechnics Institute of Lorraine, France) Metallic composite materials containing solid lubricants like carbon or MoS2 are used in sliding electric contact. The tribological behaviour of a 3D carbon-carbon composite disc reinforced by fibres, and used in electrical contacts is studied here. The experimental device is a pin on disc tribometer ; the pin is made of copper. During the tests, the friction coefficient and the contact resistance are simultaneously recorded as a function of the applied normal load, of the sliding speed and of the current density; all these parameters are maintained constant during the 60 minutes of the experiment. The contact resistance decreases with an increase of the current intensity, and the friction remains stable as long as the current density is lower than a critical value, Ic which depends on the current polarity. The friction coefficient and the contact resistance increase with an increase of the sliding speed when I Generally, the specific wear of the copper pin and of the carbon-carbon composite disc is influenced by the polarity, and decreases when increasing the current intensity. In order to explain this tribological behaviour, the sliding tracks were observed by Scanning Electron Microscopy, and analysed by Electron Diffraction Spectroscopy. |
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EP-11 Impact of Ion Modification of HSS Surface on Wear Resistance of Cutting Tools with Surface Engineered Coatings
G.S. Fox-Rabinovich (Sputtek Inc., Canada); A.I. Kovalev (SPRG, Russia); S.N. Korshunov (RIMET, Russia); L.S. Shuster (Ufa State Aircraft Technical University, Russia) This paper considers some ways to improve surface engineered coatings for cutting tools. These coatings being formed by double hardening: diffusion saturation with nitrogen (by ion nitriding), on the one hand, and applying the hard coating with complexly alloyed nitrides (Ti,Cr)N by means of the cathode arc plasma deposition process (CAPDP), on the other. Proposed is the multilayered coating for cutting tools created on the basis of surface engineered coatings. The coating includes an additional ion modified layer applied to the surface previously nitrided in the glow discharge of HSS. The modified surface is covered with a coating of complexly alloyed nitrides (Ti,Cr)N by the CAPDP method. Such multilayered coating makes it possible to significantly - by a factor of 2,1 -2,4 - increase the wear resistance of a cutting tool by extending the range of normal wear. Studied were effects of 16 chemical elements implanted into the base surface and those of 4 antifrictional materials on the tool life of a HSS-cutter with a surface engineered coating. It was shown that leading positions in wear resistance are taken by coatings with a modified sublayer of elements with high antifrictional properties. A compromise between the high wear resistance and reliability of a coating, which is characterized by a high adhesion to the base, is observed in the multilayered coating that contains a sublayer enriched with indium. Indium is present in the sublayer both in metal and bound states (InN). The positive effect of indium on wear resistance appears to be connected to two types of secondary structures, developing on the friction surface. Acting as a liquid lubricant, indium in metal state will aid in reducing the friction coefficient. At the same time, when heated at cutting, indium is oxidized with oxygen-containing secondary structures developing to protect the surface when passing from the normal stage of tool wear to the avalanche-like one. This is beneficial for extending the range of normal friction, considerably enhancing the tool life. |
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EP-12 Wear Mechanism of Autocatalytic Composite Ni-P-BN(h) Coatings
O.A. León, M.H. Staia (Central University of Venezuela); H.E. Hintermann (University of Neuchatel, Switzerland) Wear experiments using pin-on-disc configuration has been used in testing autocatalytic composite Ni-P-BN(h) coatings against AISI 53100 steel balls at room temperature. Coating with 11, 35, 45 and 67 vol.% BN(h) have been obtained by dispersing the BN of an average particle size of 6.16 µm in a sodium hipophosphite based autocatalytic bath with enhanced agitation and surfactant adition. Wear scars have been studied by using Scanning Electron Microscopy and 3D perfilometry in order to elucidate the wear mechanism of the composite coatings. Knoop microhardness, roughness, friction coefficients and wear resistance of the coatings are also reported. |
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EP-13 Characteristics of a Plasma Electrolytic Nitrocarburising Treatment for Stainless Steels
X. Nie, A. Leyland, A. Matthews (University of Hull, United Kingdom) Plasma electrolytic nitrocarburising/carbonitriding (PECN) diffusion treatment techniques can be successfully used to treat mild steel [1, 2], to produce a 10 µm nitride top layer (i.e. the so-called ‘white’ layer) and 100µm C/N diffusion layer with good mechanical and corrosion properties over a wide range of substrate bulk temperatures (between 2500C and the melting point of the substrate) within only a few minutes of treatment time. In this work, we investigate the feasibility (and process characteristics) of a PECN treatment applied to AISI 316L stainless steel. A modified aqueous solution of urea (and other active ingredients) was used as the treatment electrolyte. The sample substrates were connected cathodically to a high current DC power supply and biased with a voltage in the range 220-260V. The treatment time was typically in the range 0.5-2.0 minutes. Surface morphology and microstructural composition of the treated layers were analysed using scanning electron microscopy (SEM), glow-discharge optical emission spectroscopy (GDOES) and X-ray diffractometry, respectively. Linear reciprocating-sliding wear tests, ball-crater micro-abrasion tests and ball-on-plate impact tests were used to assess the improvement in mechanical properties after treatment. Potentiodynamic polarisation tests were performed using a Solartron 1260 corrosion measurement system. The investigations show that the friction coefficient of PECN-treated stainless steels against a WC-Co ball counterface can be significantly reduced, and that the wear rate decreases by several decades. The microstructure of the treated layers depends strongly on the electrical parameters (e.g. the applied voltage, which controls the treatment temperature) and can be adjusted from a single expanded austenite phase (?N) to multi-phase combinations including mixtures of ?N, CrNx, CrCx and Cr,Fe(CN)x. The corrosion properties of the treated layers can be closely correlated to the microstructure and composition. References: 1. X. Nie, Q. Hao and M. Wei, J. of Wuhan University of Technology, materials science edition, No. 1 (1996) 2. A. Yerokhin, X. Nie, A. Leyland, A. Matthews and S.J. Dowey, Review: Plasma Electrolysis, Surf. and Coat. Technol., in press. |
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EP-14 Characteristics of Carbon Incorporated BN Films Deposited by Radio-frequency PACVD
H.S. Kim (Korea Institute of Science and Technology, Korea); I.H. Choi (Korea University, Korea); Y.-J. Baik (Korea Institute of Science and Technology, Korea) The incorporation of carbon during the deposition of BN films was investigated with a view point of structural stability and tribological property. (100) silicon wafers were used as a substrate. BCl3 and NH3 were chosen as source gases and Ar gas was used as a carrier gas with the purpose of ion bombarding effect to the growing surface. The carbon concentration of the films was controlled by adding CH4. Deposition temperatures were varied from room temperature to 500 °C while deposition pressure and substrate bias were kept at 15 mTorr and -500 V respectively. The structures and phases of carbon incorporated BN films were investigated by FT-IR, Raman, X-ray diffraction and XPS. Plasmas were analyzed by optical emission spectroscopy. Growth temperature had an effect on the crystallinity and alignment of c-axis of BN films. These properties were related to the stability of the films in the ambient condition. The films deposited at room temperature were very unstable and carbon incorporation accelerated the degradation. But BN and carbon incorporated films deposited above 300 °C were stable, which was believed due to the improvement of crystallinity. The BN films deposited at 300, 400 °C showed high coefficients of friction above 1, which were measured with a rotating type ball-on-disc wear-rig. As the carbon was incorporated to the BN films, the coefficients decreased to 0.55. Hardness and elastic constants of the films, measured by nano-indenter, were varied according to the structure of carbon incorporated films. |
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EP-15 Plasma Polymerization Treatment of Wood Surfaces Using RF Glow Discharges of Siloxanes and Siloxones-Hydrocarbons Mixtures
R.P. Mota, R.Y. Honda, J.C. Teixeira, M.E. Kayama, E.A. Aramaki, R.P.C. Costa, G. Telles, M.A. Algatti (UNESP - Universidade Estadual Paulista, Brazil) Plasma Polymerization process is a widely applied technique in several technological issues encompassing microelectronics and biomaterials industry. The main reason is that such kind of polymers are pinhole free and can resist to the attack of mild acidic and moderate basic solutions. This paper deals with plasma polymerization process of wood surfaces by RF excited glow discharges in Siloxanes, and Siloxanes-Hydrocarbon mixtures in atmospheres at pressures running from 70 to 200 mTorr. Polymeric films of 0,1 mm and 0,5 mm thick where grown over polished Pinus and Cedrus surfaces in glow discharges with 10 to 30 minutes duration. Polymeric films were submitted to adhesion ScotchTM tape and distilled boiling water. The results showed that all the films presented a good adhesion showing that the polymeric films were efficient in wood’s surface protection. Optical and scanning electron microscopy were performed on several samples. The results showed that the wood porosity was completely recovered by polymeric films resulting in a good wood’s impermeability. These recovered wood surfaces may resist the exposition to an extremely aggressive environment like boiling water, for instance. |
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EP-16 CrN Hard Coatings Deposited with PVD Methods on Tools for Wood Machining
M.A. Djouadi, C. Nouveau, P. Beer (ENSAM, France) Well known and widely used tools modified with hard coatings are still not applied to wood industry. Difficulties come from mechanical, physical and tribological properties of wood and of wood based materials together with particular parameters of their processing (average cutting speed about 80m/s, average feed speed about 80m/min). The aim of our study was to examine the influence of chromium nitride coated cutting tools on wood based product machining. Industrial tools made of cemented carbide were modified with two methods: triode and magnetron sputtering and with two structures of chromium nitride: cubic CrN and hexagonal Cr2N and with three modes: on rake face and clearance face jointly and just on rake or just on clearance face. The material subjected to cutting was wood based material called OSB (Oriented Standard Board), which is made of glued veneer flakes pressed together. This is abrasive material widely used in building industry. OSB has got determined mechanical parameters. The process was conducted on ordinary wood routing centre. The scope of experiment involved: optimisation of coating deposition parameters, physical and mechanical characterisation of the coatings and evaluation of reduction of cutting tools edges and spindle motor power consumption. Comparison have been made between the results obtained for CrN and Cr2N deposited by triode and magnetron sputtering methods. It appears that tools modified with CrN coating have had twice lower edged reduction after 3000m of the cutting path and six times longer. |
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EP-17 Plasma Immersion Ion Implantation Treatment of AlSl304 Stainless Steel Employing a Hybrid Elevated-Temperature, Low-Voltage and Ambient Temperature Process
X.B. Tian, Z.M. Zeng (Department of Physics and Materials Science, City University of Hong Kong); B.Y. Tang, P.K. Chu (City University of Hong Kong) AISI304 stainless steel is widely used in the industry due to its good corrosion resistance. Nevertheless, its relatively low surface hardness and inferior wear resistance lead to a short working lifetime, especially for abrasively stressed components made of the materials. High-frequency low-voltage plasma immersion ion implantation (HLPIII) has been shown to be an effective means to enhance the surface properties of steels. However, experimental results indicate that the total amount of implanted nitrogen does not exceed 20 atomic% under these conditions. In this work, we present a novel hybrid treatment process incorporating a sequence of processes using high and low voltages to attain a thicker modified layer with higher surface nitrogen concentration. The samples are characterized by AES, GXRD, microhardness testing and other techniques. |
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EP-18 Surface Modification of 9Cr18 Bearing Steel by Ti and C Co-implantation and TiC Deposition in a Plasma Immersion Configuration
Z.M. Zeng, X.B. Tian (Department of Physics and Materials Science, City University of Hong Kong); B.Y. Tang, P.K. Chu (City University of Hong Kong) 9Cr18 Martensitic stainless steel (AISI440) is often used as an aerospace bearing material because of its good corrosion resistance. Previous studies have shown that bearing failure occurs mainly on its working surface or in the near surface region. Therefore, surface modification techniques provide an important way to prolong the lifetime of industrial bearings. Plasma immersion ion implantation (PIII) circumvents the line-of-sight restriction characteristic of conventional ion beam implantation and is an effective method to treat complex-shaped industrial components. In this work, sequential titanium and carbon PIII is conducted in conjunction with TiC film deposition on 9Cr18 samples using metal arc plasma sources. The microhardness and wear properties of the treated samples were measured to assess the surface property enhancement. Our results indicate that Ti+C implantation and TiC deposition can significantly enhance the microhardness and wear properties and reduce surface friction. We will also discuss the influence of different processing and experimental conditions on the tribological properties of the treated samples. |
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EP-19 Elevated Temperature Oxidation Behavior of Cr-Al-N Films Synthesized by Cathodic Arc Plasma Deposition
S.S. Kim, J.G. Han (Sung Kyun Kwan University, Korea) CrN coatings are successfully being applied for various metal forming molds and dies, for plastic manufacturing as well as for machinery partsn1. However, with a reported oxidation threshold temperature of 700°C, CrN coatings may be limited for oxidation resistant application at elevated temperature. For this reason, higher oxidation resistance than that of CrN coatings is required. It is well known that the TiAlN coatings have higher oxidation resistance because of the Al2O3layer formation on the film surface at elevated temperaturen2. In this study the Cr-Al-N films were deposited on the hot working tool steels (AISI H13steel) by cathodic arc plasma deposition (CAPD) process. The films were deposited at various substrate bias voltages of 0-400V and different target current ratio of chromium and aluminum. Relative chemical compositions of the deposited Cr-Al-N films were evaluated by EDX as well as AES. The microstructure and morphology were studied by XRD and SEM respectively.The microstructure of Cr-Al-N films were strongly depended upon target current ratio of the chromium and aluminum as well as substrate bias voltages. Moreover, we found that the microhardness of the Cr-Al-N films were higher than that of the CrN film. Detail results including oxidation behavior will be presented. |
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EP-20 Corrosion of Stainless Steel Coated with Thick TiN/Ti Multilayers
M. Flores, S. Muhl, C. Piña (UNAM, Mexico) TiN/Ti multilayers, 0.1-0.5 µm, have been deposited by various PVD methods to improve the toughness of coating wear resistance. It is also known that such multilayers improve the corrosion resistance of stainless steel and high speed steels. The titanium layer helps to reduce the incidence of pinholes, that arise because of the irregularities in substrates surfaces, and decrease the porosity of subsequent TiN coatings by improving this layer's microstructure. Similarly the titanium layer helps to decreased the pitting corrosion through the formation of TiOx. It can be expected that thicker Ti layers, >0.5µm, should produced even greater corrosion resistance. In this work we report the results of preparing multiple thick TiN/Ti layers on 316 stainless steel substrates by reactive magnetron sputtering. The corrosion resistance of these layers was studied by means of potentiodynamic polarization in a 0.5 M NaCl solution. We present the results of corrosion studies, composition analysis and the hardness measurements as a function of Ti layer thickness, number of layers and bias applied to substrate during the multilayer formation. |
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EP-21 Effect of Zinc Inhibition for Some HVOF Thermal Spray Coatings
I.C. Hsu, W-C. Lih, C.Y. Su, Y.W. Lee, H.C. Huang (Industrial Technology Research Institute, Taiwan, ROC) Cermet coating became widely adopted by steel mills in the past decade to enhance the surface quality of continuous galvanizing sink rolls. In order to extend the life and reduce the maintenance time for the sink rolls, it is necessary to minimize the reaction between the cermet coating and zinc atoms in the zinc-aluminum solution at elevated temperature. In this paper, WC/Co, WC/Ni, CrC/NiCr and WC/CrC/NiCr cermet coatings by HVOF were applied to understand the surface stability in the Zn-5wt.%Al solution at 4500C to 5000C. Evidence showed that the zinc atoms diffuse more rapidly in the Ni matrix than Co and NiCr matrix. The zinc penetration speed was strongly influenced by the applied tensile stress on the sink roll. The wetting angle for the zinc and each cermet coating was measured to investigate the ability of zinc inhibition. After long-time immersion in the zinc solution, the bonding tests for the cermet coatings were also conducted in this study. |
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EP-22 Luminecent and Structural Characteristic of NaCl Doped Al2O3 Coatings Prepared by Ultrasonic Spray Pyrolysis Technique
M. García, E. Martínez, O. Alvarez-Fregoso (UNAM, Mexico) NaCl doped Al2O3 luminescent (photo and cathodoluminescent) coatings have been prepared by ultrasonic spray pyrolysis deposition process. The substrate temperature and the doping concentration in the start solution were varied. It is observed that the crystallinity of the films do not depend upon the substrate temperature (300°C-550°C). For this range of used temperatures, the deposited films are highly disordered. The chemical composition was obtained by EDS. The excitation and emission spectra have been obtained. For an excitation wavelength of 270 nm, all the photoluminescent spectra show peaks located at about 450 nm (blue emission). It is observed a concentration quenching of the photoluminescence as a function of the values of the activator concentration. |
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EP-23 Mechanically Induced Surface Modification and Metallic Coating
A. Torosyan (Institute General & Inorganic Chemistry, Armenia) Pulse mechanical treatment of various metals with iron and steel disclosed a new method of modification and finishing of the metal surfaces. The basis of the offered method compose the works concerning to study of solid phase reactions under impulsive mechanical alloying. The coatings from the starting powder materials are formed in the specially designed vibration ball mills. The coatings material particles periodically getting under impact between the balls and the substrate are absorb mechanical energy. As a result the particles with a superfluous of energy are formed. An exited substance from these conditions is relaxed energy with formation new chemical or very strong "cold welding " connections, between particles and surface of a substrate. As it was established, the opportunity of coating formation depends as from the quantity and intensity of transmitted mechanical energy (frequency and amplidude of vibration) as well as by ratio of a powder and balls weights were loaded. The quality of coatings depends on the dynamics of a balls movement during machining. The bolls movement kinetics was investigated by using stroboscopic researches. The hardness and porosity of obtained coatings has been investigated. The conditions of coating formations were established experimentally. Below are listing the basic developed ways of coatings and modified layers. 1. Metallic coatings on the basis of pure metals and their alloys from initial simple elements - Al, Cr, Cu, Mo, Ni, Pb, Mg; alloys Ti-Cu, Al-Cr, Ti-Al, Ni-Ti, Ni-Al and etc. 2. Formation of compositional coatings, such as " metal - firm filler ",( Co-WC, Cr-WC-TiN and etc). 3. Formation of solid lubricant means by means of solid phase synthesis on a surface (for example, Mo2S from Mo and S). These processes held in solid phase under the impact of mechanical energy without disturbing the system thermally. |
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EP-24 Ion Beam Analysis of SiCx Thin Films Using a Deuterium Beam
E. Andrade, A. Mahmood, S. Muhl, E.P. Zavalo, J.C. Pineda, L. Huerta (UNAM, Mexico) SiCx thin films have been prepared by using RF reactive magnetron sputtering technique. The deposition parameters have been varied over a wide range to optimize the quality of the films. The film atomic density per unit area (atoms/cm2) and composition were obtained by NRA and RBS techniques by bombarding the samples with a low energy deuterium beam. The films have been also characterized by X-ray diffraction, FTIR spectroscopy and elipsometry to supplement the RBS and NRA results. |