ICMCTF1998 Session E3: Coatings Resistant to Erosion, Corrosion and Severe Environments Including Biomedical Environments

Thursday, April 30, 1998 8:30 AM in Room Council/Chamber/Cabinet
Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF1998 Schedule

Start Invited? Item
8:30 AM E3-1 Identification of Transitions Between Erosion-corrosion Regimes for Erosion of PVD Coatings in Aqueous Slurries
M.M. Stack, H.W. Wang (UMIST, United Kingdom); H. Paritong, W.-D. Münz (Sheffield Hallam University, United Kingdom)

A major advance in the study of erosion-corrosion of materials in aqueous conditions in recent years has been the construction of erosion-corrosion maps, showing the transitions between the erosion- corrosion regimes as a function of the main process parameters. Such maps enable the mechanism of damage to be identified, whether erosion- or corrosion-dominated, and provide a basis for optimisation of process parameters in such conditions. However, as there has been little research carried out to study the performance of thin coatings in such environments, the construction of erosion-corrosion maps for such systems has not been attempted.

The objective of this work was to evaluate the effects of velocity and applied potential on the erosion of various coatings, CrN, Ti2N, TiAlN, Nb, and NbN, deposited by combined steered arc unbalanced magnetron sputtering techniques, in order to establish the erosion-corrosion regime transitions for relatively simple coating systems. (The results were bench marked by experimental data evaluated from commercially available TiN, CrN and TiAlN deposited by cathodic arc technology.) The apparatus used was a rotating cylinder electrode system, the particles used for the experiment were 150 μm alumina and the solution a carbonate/bicarbonate buffer. "Synergistic" and "additive" erosion-corrosion effects were evaluated through precise separation of the erosion and corrosion components, by means of electrochemical monitoring during the erosion-corrosion process.

The results showed that the passivation potentials for the five coatings occurred at different values . Differences between the erosion-corrosion resistance of the coatings, as a function of increasing applied potential, were identified. Possible implications of such trends for the construction of erosion-corrosion "regime" maps for these coating/substrate systems are addressed in this paper.

8:50 AM E3-2 Effect of MEMS Compatible Thin Film Hard Coatings on Erosion Resistance of Silicon Micromachined Atomizers
N. Rajan, C.A. Zorman, M. Mehregany (Case Western Reserve University); R.G. DeAnna (Army Research Lab); R.J. Harvey (Parker Hannifin Corporation)

Five different CVD thin films were examined to improve the erosion resistance of silicon micromachined atomizers. This is a follow up of earlier research which examined the effect of APCVD single crystal SiC coatings on the performance of silicon micromachined atomizers1. In addition to single crystal SiC, polycrystalline SiC, silicon nitride, silicon dioxide, and diamond-like carbon (DLC) were also examined as coating materials. The coatings were tested by operating the atomizers at 150 psi and room temperature. The test fluid was augmented by adding an abrasive mixture to intensify the erosion process. Quench tests were also performed to subject the atomizers to thermal stresses similar to those found in a combustion environment.

The results of the erosion test demonstrated that the single crystal SiC coating performed better than the other coatings. The polycrystalline SiC was a high stress film that caused the atomizers to crack after an 18 hour erosion test, though the coating morphology and thickness were unaffected. The silicon nitride and silicon dioxide coatings exhibited the tendency to trap erosion particles, which significantly affected the coating morphology. The DLC coating demonstrated a tendency to flake at the edge of the exit orifice, though morphology elsewhere was unaffected. Film thickness measurements showed no decrease in film thickness in any of the coatings as a result of the erosion test. The results of the quench tests were promising for all coatings, with the exception of DLC. Examination of these films under an SEM showed no cracking or delamination as a result of the thermal stresses imposed on the coatings.

The extended paper will include i) details of the deposition and properties of the thin film coatings, ii) details and results of the erosion and wear tests performed on the coatings, and iii) further details and results from the quench tests.

1Rajan, N., Zorman, C.A., Mehregany, M., DeAnna, R.G., Harvey, R.J. "Performance of 3C-SiC Thin Films as Protective Coatings for Silicon Micromachined Atomizers",Thin Solid Films, in press.

9:10 AM Invited E3-3 Metallic and Ceramic Coatings, Including Biomimetic Coatings for Biomedical Applications
A.A. Campbell, L. Song, X. Li (Pacific Northwest National Laboratory)

Biomedical researchers have used several strategies to improve the strength of the bond between the implant and growing bone. One advance has been the development of porous coatings, which allow mechanical interlocking between the implant and the forming bone. Another advance has been the use of bioactive coatings to improve the strength of the bone/implant interface. To date, hydroxyapatite (HAP) coatings have shown exceptional promise as bioactive coatings for metallic implant devices. It is believed that the apatite can partially dissolve, intergrow, and become partially incorporated with the apatite in growing bone, forming a coating:bone interface as strong as bone itself. Although significant advances have been made to provide mechanically strong and non-toxic metals and alloys, biological integration of devices into natural tissues remains a problem.

In order to address problems associated with current implant tecnologies, PNNL developed he Surface Induced Mineralization (SIM) and Void Metal Composite (VMC) processes. The VMC process produces porous metal materials which have cylindrical pores of uniform diameter which can completely penetrate the structure of the material. The pore diameter, orientation and interconnectivety are easily controlled for optimum bone ingrowth.

The SIM process uses the idea of nature's template-mediated mineralization by chemically modifying the implant to produce a surface which induces heterogeneous nucleation from aqueous solution. SIM produced bioactive coatings provide 1) control of the thickness and density of the mineral phase, 2) a way to coat porous metals, complex shapes and large objects, 3) the ability to coat a wide variety of materials, 4) potential choice for the phase of the mineral formed.

9:50 AM E3-5 Magnetron Sputtered Hard Material Coatings on Thermoplastic Polymers for Clean Room Applications
E. Lugscheider (Materials Science Institute, University of Technology, Aachen, Germany); S. Baerwulf (Materials Science Institute, University of Technology, Aachen, Germany); C. Barimani (Materials Science Institute, University of Technology, Aachen, Germany); M. Riester (IBM Storage Systems Germany, GmbH); H. Hilgers (IBM Storage Systems Germany, GmbH, Germany)
Even under demanding environments, like clean rooms, polymers are already used in different ranges of applications. The wear and particle generation within a specific particle size even under mechanical stress is a limiting factor. So it was the aim to develop an innovative material concept, that enables to apply a thermoplastic polymer coated with a thin hard material (thickness up to 2.5 micronmeter), which also prevents for electrostatical discharges and is usable for complex bodies. Therefore it was necessary to improve the wear resistance and the adherence between the polymer and the coating. To take also economic aspects into consideration a two step production process sequence was required, consisting of the injection moulding process and then the plasma deposition process including a plasma pretreatment. In this investigation, poly (butyleneterephthalate) (PBT) and poly (amide) 6.6 (PA) were chosen as substrate material. The coating materials used, which were mainly deposited by Magnetron Sputter Ion Plating (MSIP), were on titanium basis (Ti-N, Ti-Zr-N). To get detailed chemical information about the coatings and the interfacial region they were analyzed by X-ray Photoelectron Spectroscopy (XPS), additionally Secondary Ion Mass Spectrometry (SIMS) experiments were carried out to confirm the results. The process parameters influence on the microstructure, which extend from amorphous to columnar (crystalline), and the film thickness were analyzed by SEM. It will be shown and discussed, that it is possible to improve the coating's adherence by plasmapretreatment as well as to reduce the particle generation after a suitable etching and coating process.
10:30 AM Invited E3-7 Application of Coatings in Various Energy Technology Systems
K. Natesan (Argonne National Laboratory)

Surface engineering and, in particular, coatings are being applied in several energy technology systems to achieve a variety of objectives such as improved in corrosion and erosion resistance, protection from elevated temperatures, desired electrical properties, and establishing barriers to the transport of specific elements and/or gases. Corrosion and erosion of metallic structural materials at elevated temperatures in complex multicomponent gas environments that include particulates are potential problems in many fossil energy systems, especially those that are coal-fired. The use of appropriate corrosion-resistant coatings on metallic components can minimize material degradation and extend component life. Similarly, ceramic thermal barrier coatings offer protection to nickel-base superalloys in both aviation and land-based gas turbine systems. Pack diffusion and electrospark-deposited coatings of intermetallic compounds provide protection against sulfur transport and sulfidation corrosion. Highly specialized coatings with electrical insulating characteristics are being sought in fusion energy blanket systems. This paper reviews the requirements and/or performances of coatings in the environments of several energy technologies. The complexity of environments in different systems is discussed, together with coating characteristics needed for acceptable performance.

*Work supported by the U.S. Department of Energy, office of Fossil Energy, Advanced Research and Special Technologies Materials Program, under Contract W-31-109-Eng.38.

11:10 AM E3-9 Wear Resistant Aluminide Composite Surfaces by Electro Spark Deposition (ESD)
R.N. Johnson (Pacific Northwest National Laboratory); J.E. Kelley (Advanced Surfaces and Processes, Inc.)
The aluminide intermetallic compounds are known for their outstanding corrosion and oxidation resistance in severe environments. Recent studies have shown that coatings of the aluminide compounds applied by the ElectroSpark Deposition (ESD) process can provide these corrosion benefits to structural materials. This paper reports on progress in enhancing the wear resistance of such coatings through the addition of hard, stable compounds such as titanium diboride and titanium carbide to a matrix of the aluminides of iron, nickel or titanium. Comparisons of wear performance, hardness properties and metallographic structures of the ESD deposits are presented.
11:30 AM E3-10 Modification and Characterization of Mineralization Surface for Corrosion Protection
J.J. Hahn, R.L. Heimann, N.G. McGowan (Elisha Technologies Co., L.L.C.); T.L. Barr (University of Wisconsin-Milwaukee)
A unique mineral-like thin film technology has been developed to provide improved corrosion protection. The protection is based upon a selective mineralization of various metallic substrate surfaces using such cost effective and environmentally friendly additives, such as alkali metal silicates, which have been shown to be delivered by a variety of carriers and techniques. The composition and structure of the resulting reaction-product thin film surface has been characterized in detail using ESCA, AFM and other surface techniques. The results of the study of this surface will be described.
Time Period ThM Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF1998 Schedule