ICMCTF1998 Session G7: Vapor Deposition and Electroplating: Competing Processes?

Tuesday, April 28, 1998 8:30 AM in Room Town & Country

Tuesday Morning

Time Period TuM Sessions | Abstract Timeline | Topic G Sessions | Time Periods | Topics | ICMCTF1998 Schedule

Start Invited? Item
8:30 AM G7-1 Graded Ni-SiC Composite Coating by Electrodeposition
S.K. Kim (University of Ulsan, Korea)
Composite plating is a method to co-deposit fine particles of metallic, nonmetallic compound or polymers in the plated layer to improve material properties such as wear resistance, lubrication, or corrosion resistance. In this work, the effect of particle size, particle content, pH, temperature, current density, stirring rate on the co-deposition of silicon carbide particles in the nickel layer was determined experimentally. Through manipulation of these process variables, a discretely graded structure of Ni-SiC was produced. Micro-hardness tests were performed to evaluate the mechanical properties of the electroplated coatings.
8:50 AM G7-2 Wet or Dry Plating, Which Serves Best? - Potentials and Limitations of ECD and PVD
H.A. Jehn (Forschungsinstitut fur Edelmetalle und Metallchemie, Germany)
Electrochemical deposition (ECD) and physical vapour deposition (PVD) - i.e. wet and dry processes - both lead to a film formation by the deposition of the material in atomic scale. On the base of advanced vacuum and plasma technologies, PVD processes have found their role in coating and thin film deposition, even if not comparable with "traditional" processes regarding the application volume. Lacking knowledge, rivalry minding and, in part, arrogance often result in false estimation of the one or the other technique. Also judging the processses as inexorably competing is ostensible and does not meet all aspects. On the base of the fundamentals of both techniques, the potentials and limitations, the advantages and disadvantages are outlined in this paper. As a result in practical application the one or the other technique will be applied for a special need. In other cases the processes might be competing, and often combinations solve problems best. The final decision with respect to process selection is often governed by non-technical aspects like economical or ecological facts.
9:30 AM G7-4 PVD and Ion Assisted Coatings- Alternatives to Hard Chrome Plating
P.C. Patnaik (Orenda Aerospace Corporation, Canada)
There is considerable interest in replacing the hard chrome plating in every industrial sector whether aerosapce, defence or automotive. This paper will bring forward some of the issues related to the choice of application of PVD and Ion Beam technologies particularly to critical aircraft engine components. Importance of qualification Testing necessary to introduce these products into service will be highlighted.
9:50 AM G7-5 Large Area Application of Chromium by High-rate Plasma-activated Physical Vapor Deposition
Chr. Metzner, K. Goedicke, J. Faber, F. Fietzke (Fraunhofer Institut Elektronenstrahl- und Plasmatechnik, FEP, Germany)
Two plasma-activated high-rate PVD processes for the deposition of chromium were investigated. Magnetron sputtering and high-rate electron beam evaporation shows great promise in depositing chromium onto large areas like metallic strips and sheets. With regards to magnetron sputtered chromium layers, the introduction of the pulse sputter technology and other new features concerning the reactive process yields advantageous layer properties. For thick films, the high-rate electron beam evaporation of chromium, from a molten pool and our unique plasma activation of the process open fields of applications. Best suited for the plasma activation of this process is a diffused cathodic vacuum arc discharge (SAD = Spotless Activated Deposition). Presented in this paper are our latest results in process developments. The deposited chromium layers are characterized by their high density and smooth surface. For the coating of sheet steel with chromium by means of magnetron sputtering and SAD, the resulting properties of the coated product are shown in detail. Of particular significance is the high corrosion protection effect of the coatings applied by our two high-rate plasma-activated PVD processes. Finally, an outlook of the potential applications of technologies with a rough estimation concerning the process cost will be presented.
10:10 AM G7-6 Break

10:30 AM G7-7 Microstructure-Property Relationships of Crystalline Coatings Obtained by ECD and PVD
P. Klimanek, H. Oettel (Freiberg University of Mining and Technology, Germany)

In spite of the fact that the underlying physical phenomena and macroscopic process variables of ECD and PVD are obviously very different, technically interesting crystalline coatings formed by both techniques have a series of similar features as, for instance,

- significant internal stress and preferred orientation,

- microcrystallinity and/or high content of lattice defects, and

condiderable thickness dependence of internal stress, texture, grain size etc.

Accordingly, similar microstructure - property relationships should often be realized. In order to test and to explain them, both reliable quantitative microstructure analysis and application of physically realistic structure-related models of coating behaviour is necessary. Starting with some comments concerning the techniques available for the quantitative microstructure parameters of thin layers and coatings, the paper gives a survey of important microstructure types occurring in ECD and PVD and presents some background especially for the description of the mechanical behaviour of the deposits in terms of microstructure characteristics. Experimental results illustrating e.g. the connections between hardness, the defect content, and grain or particle size, respectively, are mainly given for electrodeposited Cu and NI layers, and nitride and boride hard coatings obtained by magnetron sputtering.

10:50 AM G7-8 Improving High- Velocity Oxy-Fuel Spray Coating Process - The Alternative to Hard Chrome Electroplating
J. Mostaghimi, S. Chandra, M.P. Fard, L. Pershin (University of Toronto, Canada)

Chrome electro-plating is widely used in the aerospace industry to provide protective cotaings for engine and landing gear components that ar exposed to corrosion and wear. However, the electro-plating process results in the release of hexavalent chromium, either in mists dispersed in the atmosphere, or in sludge that are a by-product of the plating process. Hexavalent chromium has been identified as carcinogenic, and permissible rexposure limits have recently been reduced by the US Occupational Safety and Health Administration from 0.1 mg/m3 to 0.005 mg/m3. The cost of meeting these environmental standards has led to a search for alternative coating methods. A leading contender to replace hard chrome electroplating is the High Velocity Oxy-Fuel (HVOF) spary deposition since it yields high quality coatings and emit no hazardous by-products. All current HVOF designs operate on similar principles: fuel and oxygen are injected into a high pressure combustion chamber and the combustion products accelerated through a constricting nozzle. Powder is injected either into the combustion chamber or downstream of the chamber. Powder particles are heated and accelerated by the rapidly expanding gas and ejected from the gun towards the substrate.

In this paper, we will present a modification to the HVOF gun and how it affects the coating quality through changes in particles state at the point of impact onto the substrate. When an unconfined HVOF jet issues from a nozzle into the atmosphere it contains cold ambient air. This is detrimental to the quality of coatings produced since gas temperatures are decreased, producing lower heat transfer to the injected powders, and metal particles are oxidized, reducing the integrity of the coating. Oxidation negatively affects the inter-lamellar bonding and, thus, the coating quality. Air entertainment can be reduced significantly by attaching a gas shroud nozzle to the gun which produces a high pressure, helical flowing, non-oxidizing gas stream around the HVOF jet. We compare the performance of a HVOF gun with and without a gas shroud attachment by measuring velocities of particles in the jet, particle temperatures, and gas temperatures and velocities. Coatings produced using a gas shroud showed considerable reduction in oxygen content (up to 80% less). The shroud also affected particle impact velocities and temperatures, which determine the final splat shapes and therby affect coating microsturcture.

We will also present the dynamics of particle impact on the substrate with and without a gas shroud attachment and show how the attachment of a gas shroud affects the final shape of the individual splats. We note that the splats' shape have a significant effect on the microstructure and mechanical properties of thermal spray coatings.

11:10 AM G7-9 Combination of Plasma Pretreatment and Electroplating for the Metallization of Polymers
A. Weber (Fraunhofer-Institut für Schicht- und Oberflächentechnik, Germany.); A. Dietz, I. Hippel, R. Pöckelmann, C.-P. Klages (Fraunhofer-Institut für Schicht- und Oberflächentechnik, Germany)

The conventional pretreatment of polymers for metallization by electroplating is based on hazardous and pollutive agents like chromic acid and various organic solvents. We report on the metallization of glass fiber reinforced polybutylenterephthalate (PBT with 20% glass fiber, Crastin SK 603) and polytetrafluoroethylene (PTFE) by electroplating without using such chemicals as pretreatment. The chemical pretreatment is substituted by a low pressure plasma treatment of the polymer.

The plasma pretreatment of Crastin SK 603 was performed in a parallel plate reactor operating at 13.56 MHz. As plasma gas oxygen or argon/oxygen mixture was used. A plasma pretreatment time of 5-10 minutes leads to excellent adhesion strength up to 2 N/mm as measured by peel tests of the electroplated metal coatings. The roughening and activation of the polymer surface is essential for the adhesion. Pretreatment times above 10 minutes lead to a damage of the polymer surface and low adhesion.

A combination of a selective plasma activation through a metal mask followed by a maskless palladium seeding process lead to the deposition of patterned metal lines on the polymer. Thus, this is a promising method for the direct deposition of conductor lines by electroplating as needed for the 3D Moulded Interconnect Device (3D-MID) technology to replace printed curcuit boards. The plasma pretreatment was also successfully applied for the electroplating of complicated threedimensional moulded Crastin parts by connecting both electrode to the rf generator.

The conventional metallization of PTFE by electroplating needs very aggressive and dangerous chemicals. After plasma activation and subsequent deposition of a thin (30-50 nm) titanium nitride (TiN) layer by plasma enhanced chemical vapor deposition copper could be deposited on PTFE by conventional electroplating. The thin TiN layer on PTFE acts as adhesion promotor and conducting interlayer for electroplated copper. The adhesion strength of electroplated copper using this pretreatment was 15 N/mm2 as measured by a z-axis pull test.

Thus, the combination of low pressure plasma processes and electroplating takes advantage of the specific merits of both processes. The plasma activation of the polymers substitutes hazardous and pollutive chemicals ensuring a safe and fast pretreatment whereas electroplating guarantees an economic metallization of polymers.

11:30 AM G7-10 Chrome Alternatives: A Real Business or Just a Nice Idea?
K. Legg, H.F. Solnick-Legg (Rowan Catalyst, Inc.)

There is a great deal of research and development work under way on chrome (and other electroplating) alternatives. Indeed, almost any wear resistant or lubricious coating is likely to be put forward as a chrome alternative. However, when we look at the industrial drivers, both for change and for the status quo, and when we examine what is happening in many industries, we have to ask where electroplating technologies are really being (or are likely to be) replaced in the production environment. Clearly, there are some places where chrome and other electroplates can be (and are being) readily replaced, while there are others where electroplating remains the technology of choice even in the face of apparently superior alternatives.

The reasons for the continued use of electroplates or the adoption of alternatives are usually a combination of technical considerations and non-technical concerns such as cost, risk, fit with the manufacturing system, and other considerations.

This paper will discuss several markets for chrome plating and its alternatives, evaluating why chrome has or has not been replaced, and what, if anything, it will take to drive adoption of a new technology.

Time Period TuM Sessions | Abstract Timeline | Topic G Sessions | Time Periods | Topics | ICMCTF1998 Schedule