Papers

ICMCTF2002 Session G1-1: Innovations in Surface Coatings and Treatments

Thursday, April 25, 2002 8:30 AM in Room Sunrise

Thursday Morning

Start	Invited?	Item
8:30 AM		G1-1-1 New Horizons of Surface Engineering in Industrial Manufacturing of PVD Coatings G.J. van der Kolk (Hauzer Techno Coating BV, Netherlands) An overview will be given to the status of present applications and engineering tools and expected developments for the next years in the field of industrial manufacturing of PVD coatings. PVD and PACVD coatings are increasingly used for applications which are very demanding with regard to elastic deformation, abrasive and adhesive wear, low friction and corrosive wear (e.g. automotive coatings). All of these parameters can be optimized individually. Unfortunately, for most applications a combination of low abrasive wear and high fatigue is required that is more difficult to realize. Low abrasive wear is normally linked to high hardness; low fatigue wear is related to high elasticity (low E-modulus). Furthermore optimization of the coating itself is not sufficient, the whole system coating and substrate has to be optimized. The tools for substrate optimization are found in pre-treatments like heat treatment and/or plasma treatment. The coating optimization is partly by coating composition. However, that in itself is not sufficient. One of the major tools to increase the ratio between hardness and E-modulus is nano-multilayers and nano-composites. Increasingly it is also tried to optimize the pre treatment in relation to the coating or to realise new combinations of nitriding, carburising with PVD.
9:10 AM		G1-1-3 Cleaning Prior to PVD-Coating Gains Importance for Industrial Production. M.G. Ertl (UCM AG Switzerland, Germany) Cleaning prior to PVD-Coating gains Importance for Industrial Production M. Ertl, ECE, Bensheim, Germany; R. Hohl, UCM, St. Margrethen, Switzerland All the years ago, substrate cleaning prior to PVD-coating was not interesting enough to be subject on technical conferences. Cleanliness of substrate sufaces was taken as a "has to be". With the entrance of decorative and functional coating, into the mass-production industry during the last few years, suddenly a new problematic arose. The required high productivity on the one side created a new generation of PVD-coating equipment with a capacity of many hundrets or thousands of parts in one batch. And mass production on the other side, as we have it in the sanitary or door hardware industry, means different substrate materials, brass, die-cast, plastic, etc. in a variation of different shaped parts, manufactured with different production processes and with a wider range of quality tolerances. A very unequal bunch of substrates must be pre-treated in a process simply called "cleaning prior to coating" with the performance "suitable to be coated without problems in a PVD-process". The paper mentions the necessary theoretical fundamentals and principles of aqueous ultrasonic cleaning, explains the mechanisms of cleaning and shows the importance of a multi-stage process technology. Main requests and features for industrial cleaning lines are discussed; questions for planning and engineering the suitable cleaning system are indicated. Several exemples of well established units for metal, plastic and glass prior to decorative, functional and optical coating with high production security and reproducibility are demonstrated. A short economical survey will summerize the presentation.}
9:30 AM		G1-1-4 Characteristics of PVD-Coatings on AZ31HP-Magnesium-Alloys F. Hollstein (TECHNO-COAT Oberflaechentechnik GmbH, Germany); R. Wiedemann (Freiberg University of Mining and Technology, Germany) Magnesium-based light-metal alloys belong to a class of structural materials with increasing industrial attention. Magnesium alloys show lowest density among the engineering metallic materials, low cost and large reserves. However, the limitations according to mechanical strength and the low corrosion resistance restrict their practical application. To improve the surface hardness and the corrosion resistance PVD-coating techniques offer possibilities to overcome these drawbacks. In the here presented paper, relevant mechanical and chemical properties of various PVD-coatings on high purity (HP) AZ31-magnesium-alloy specimens are evaluated. In detail the industrial very important double/multi layer systems Ti-TiN, Cr-CrN, TiAl-TiAlN and Cr-CrN-TiCN and the multi-layer composite AlN/TiN are considered. All of these coatings were deposited by d.c. magnetron sputtering. To circumvent up-scaling problems the sputtering processes have been performed by two different coating devices, namely PLS 500 (laboratory scale) and HTC 1000/4 ABS (industrial scale). After coating the mechanical behaviours and the corrosion resistance of the specimens have been studied. The chemical composition of the thin films were analyzed by GDO(E)S.
9:50 AM		G1-1-5 Deposition of Amorphous Hydrogenated Carbon Films by Atmospheric Pressure Plasma Glow Discahrge H.R. Lee, D.J. Kim, K. Hoon Lee, K. Ho Lee (Institute for Advanced Engineering, Korea) Amorphous hydrogenated carbon films (a-C:H) were deposited by dielectric barrier discharge (DBD) at medium frequencies(5~100kHz) in an atmosphere. Substrates were polycarbonate and glass, and deposition temperatures are 25~100°C and 25~300°C, respectively. CH₄, H₂ were used as main gases and Ar or He was introduced for stabilizing glow discharge. The film qualities such as uniformity, transparency and adhesion properties are critically affected by plasma discharge characteristics, which were systematically controlled by electrode design, frequency and precision supply of power and voltage. A-C:H film deposited above 100°C shows both anti-scratch and hydrophobic properties(contact angle with water, 90~110°). Especially, surface hardness is greatly improved by the film deposition on polycarbonate, compared to substrate. The films show better anti-scratch property at higher temperatures, while better hydrophobic property at lower temperatures without any treatment such as fluorination. By the Raman and FT-IR analysis, the amounts of C-C bonds were much increased at higher deposition temperature, which contributes to the better anti-scratch property. Adhesion of the films on polycarbonate was excellent, however, the films deposited on glass substrates around room temperature showed poor adhesion, And, it was much improved by post-baking at 100°C or pre-sputtering of substrate using Ar. This is thought to be due to polymer-like characteristics of the films caused by low deposition temperature.
10:10 AM		G1-1-6 Optimization of the Cutting Edge Roundness and its Manufacturing Procedures of Cementetd Carbide Inserts, to Improve their Milling Performance after a PVD Coating Deposition K.-D. Bouzakis, N. Michailidis, G. Skordaris, S. Kombogiannis, S. Hadjiyiannis, E. Pavlidou, K. Efstathiou (Aristoteles University of Thessaloniki, Greece); G. Erkens, S. Rambadt, I. Witrh (CemeCon GmbH, Germany) The fatigue and wear behaviour of PVD coatings on cemented carbide inserts with various cutting edge radii are investigated experimentally and analytically in milling. The inserts with cutting edge radii from 8 up to 35 µm were manufactured by grinding and micro-blasting. The tool wear progress was depicted through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) microspectral analysis. The Finite Elements Method (FEM) simulation of the contact between the tool and the workpiece highlights the effect of the cutting edge radius on the first coating fracture and the further wear development. The wear behaviour of the cutting edge radii manufactured by grinding, in comparison to the corresponding ones by means of micro-blasting, is significantly enhanced, whereas the cutting edge radius increasing can lead to a higher tool life.
10:30 AM		G1-1-7 A Multilayer Coating Architecture to Reduce Heat Checking of Die Casting Die Surfaces A. Srivastava, V. Joshi, R. Shivpuri (The Ohio State University); R.S. Bhattacharya, S.J. Dixit (UES, Inc.) The primary reason for thermal fatigue cracking in die casting is the thermal load and its cycling during the operation. The temperature of the die surface almost reaches 900oFas it comes in contact with the molten aluminum while that of the core of the die is controlled to approximately 300oF by using internal water lines. This results in steep temperature and strain cycle across the die thickness that leads to low cycle fatigue cracks. This paper presents a three layer coating architecture in which the outer layer is a thermal barrier coating to reduce heat transfer, the middle layer a diffusion barrier coating to reduce thermo-chemical diffusion and the inner layer has good adhesion to the steel substrate. Consequently, this architecture not only protects the coated surface from the thermal and chemical load but also helps reduce this thermal load. Thermal cycling tests in liquid aluminum up to 4000 cycles using this architecture and conventional commercial multi-layer PVD coatings confirm
11:10 AM		G1-1-9 Anti-bacterial Silver Coatings Exhibiting Enhanced Activity Through the Addition of Platinum D.P. Dowling, A.J. Betts, C. Pope, M.L. McConnell (Enterprise Ireland); R. Eloy, M.N. Arnaud (Biomatech, France) Silver exhibits good anti-bacterial properties and in recent years has been used in a variety of medical applications ranging from wound dressings to urinary catheters. The anti-bacterial activity of silver is dependent on the balance between the activity of the Ag+ ions which kill bacteria and the total amount of silver released from the coating, which if too high results in cytotoxicity. In order to enhance the anti bacterial performance of silver it is therefore necessary to increase the concentration of Ag+ ions relative to that of metallic silver released from the coating. In the galvanic series silver is more active than platinum and therefore the latter metal should potentially enhance Ag+ ion formation through galvanic action. In order to evaluate this cyclic voltammetry experiments were performed on several silver/platinum alloys containing 0.5% to 3.0% Pt. Current-time (chronoamperometric) curves were obtained and these demonstrated that Ag+ formation increased with platinum addition. Magnetron sputtering targets were fabricated consisting of 1% Pt in a Ag matrix. These were used to sputter Pt / Ag coatings with thicknesses in the range 5 to 30 nm onto silicone and polyurethane substrates. A Saddle Field source was used in conjunction with the magnetron source both to activate the polymer prior to deposition and for substrate bombardment during sputtering. The bacterial adhesion and bactericidal effects of the coated polymers were assessed using Staphylococcus epidermidis and the cytoxicity using fibroblast cells. The 1%Pt/Ag coatings typically exhibited a two fold increase in the log reduction of bacterial adhesion compared with silver coatings with similar thickness, with no significant increase in the cytoxicity of the coating. These results indicate that by increasing the amount of Ag+, there is increased antimicrobial effectiveness without any overall increase in the quantity of silver released, thus cytoxicity effects are avoided.
11:30 AM		G1-1-10 Effect of Bismuth Addition on the Zinc Consumption in Hot-dip Galvanizing S.K. Kim, J.S. Yoo (University of Ulsan, Korea) Hot-dip galvanizing process is used widely in industry to achieve corrosion resistant coatings. Poor drainage during this process often leads to problems such as icicle formation and bridging. In this work, mild steel specimens were hot-dip galvanized. Influence of the addition of bismuth, aluminum and both(bismuth and aluminum) to the zinc bath on the zinc drainage were determined. Bismuth additions improved the drainage significantly. Zinc bath containing 0.1 % Bi and 0.025 ~ 0.05 % Al showed uniformity of coatings. Industrial trials with this bath composition showed reduction in zinc consumption, reduction of ash and dross, and good luster of workpiece.