ICMCTF2003 Session AP: Symposium A Poster Session
Monday, April 28, 2003 5:00 PM in Room Town & Country
AP-1 Study on Characteristics of CrN/Cr2O3 Composite Coatings for Aluminum Die Casting Applications
W.-Y. Ho (Mingdao University, Taiwan, ROC); L.T. Hwang, C.H. Hsu (Tatung University, Taiwan, ROC)
Aluminum casting dies experience serious cyclic thermal stress, high temperature oxidation, liquid metal attack and erosion wear during their service life. For extended die life, durable surface coatings capable of withstanding harsh condition are needed. In this study, we deposited Cr2O3 and CrN duplex coatings, structure of a thin Cr2O3 oxide film on top of the CrN layer, by using PVD cathodic arc evaporation technique. Microstructure and phases characterization will be conducted with Auger electron spectrometer (AES), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical evaluations are also investigated by a scratch tester and pin-on-disc tribometer to demonstrate well-adherent Cr2O3 and CrN duplex coatings. Experimental result will also show an oxidation and corrosion behaviors of duplex layers on exposure to high temperature test and aluminum molten alloy.
AP-2 Mechanical Properties of Duplex Layer Formed on AISI 403 Stainless Steel by Chromizing and Boronizing Treatment
B.S. Kim, G.S. Kim, S.Y. Lee (Hankuk Aviation University, South Korea); J.H. Hahn (Korea Research Institute of Standards and Science, South Korea)
In this study, we investigated the characterizations of duplex treated AISI 403 stainless steel by pack cementation. AISI 403 steel was treated by duplex treatment such as chromizing and boronizing. Metallographic cross sections of the duplex treated specimen was consisted of duplex layer(Cr and B diffusion layer). intermedium layer, Cr diffusion layer and matrix. The microstructure of duplex layer and others layers was examined by SEM and XRD. The surface properties of duplex layer were evaluated by micro-vickers hardness tester, nanoindentation tester, wear tester and oxidation test. From the XRD analysis of the duplex layer, various phases such as FeB, Fe2B, CrB were identified. The result from EDS analysis showed that intermedium layer contained much more Cr than any other layers. Microhardness of duplex layer was measured to be approximately Hv2100???2300(50gf) and result from oxidation test at 700°C showed duplex treated specimen has an excellent oxidation resistance property than only boronizing treated specimen. Detailed results including fracture toughness property of duplex layer will be presented.
AP-4 Codeposition of Aluminum and Silicon as Part of Multilayer Systems for Corrosion Protection at High Temperatures
F.J. Pérez, M.P. Hierro, M.C. Carpintero, C. Gómez (Universidad Complutense de Madrid, Spain)
The ceramic coatings are excellent candidates to protect metallic structures that work at high temperature. Inside these ceramic coatings, the mullite is a good option, since it presents very good mechanical properties, great corrosion resistance, high thermal resistance and high durability. The CVD-FBR (Chemical Vapor Deposition by Fluidized Bed Reactor) is an interesting technique to create thin and adherent films on metallic surfaces to protect them. The first step to obtain mullite coatings would be the co-deposition of aluminum and silicon coatings by CVD-FBR. These depositions take place in fluidized bed reactor and the base material used is a commercial AISI-304 stainless. This technique is based upon reaction among aluminum chloride (AlCl3 (g)) and silicon chloride (SiCl4 g)). The optimization of the deposition conditions (deposition temperature, time, fluxes, etc) is discussed in the present work. The analysis of the results is carried out by X-Ray Diffraction (XRD), Optical Microscopy (OM), and Scanning Electron Microscopy (SEM) and Energy Dispersion Spectroscopy (EDS) methods. In addition further oxidation of these precursor coatings is made in order to obtain the definitive system of protective ceramic layer. The oxidation of the coated samples is made at different temperatures and time conditions to obtain the best mullite structure.
AP-5 Aluminization of Ferritic Steels by the use of the CVD.FBR Technology
F.J. Pérez, M.P. Hierro, J.A. Trilleros, C. Gómez, M.C. Carpintero, F.J. Bolivar (Universidad Complutense de Madrid, Spain)
Ferritic steels in the average of chromium content of 9-12% are currently employed in power plants where the operation temperature is in the average of 650-680°C. The use of coatings for this kind of environments is a possible option in order to increase the operation temperature of those plants with the subsequent increase in efficiency and with lower contaminant emissions.
The use of CVD in order to protect part of this power plants is an option to be consider taking into account the advantages that present this techniques such as coatings at lower temperatures and times in comparison with another traditional CVD techniques or pack cementation.
In this work preliminary results of the aluminization of this samples in oxidation and with steam oxidation are presented, in different coating conditions in order to propose industrial coating treatments. Important improvements in the corrosion behaviour are observed.
AP-6 Long-time Cyclic Oxidation of Al-Si Diffusion Coating Deposited by Arc-PVD on TiAlCrNb Alloy
L. Swadzba, M. Hetmanczyk, B. Mendala, G. Moskal (Silesian University of Technology, Poland); G. Jarczyk (ALD Vacuum Technologies GmbH, Germany)
The excellent density specific properties of the γ-class of titanium aluminides make them attractive for temperature 600°C - 850° C aerospace applications. However titanium aluminides exhibit a strong TiO2 forming tendency rather than formation of the protective Al2O3 at high temperatures. For application at such temperature, an oxidation resistance coatings will likely be needed.
The article presents research results of long-time cyclic oxidation of TiAlNbCr intermetallic with Al-Si and without coating. Protective coating were deposited by Arc-PVD method in two steps. In first the AlSi layer was deposited. In the second step the temperature of samples in vacuum chamber was increased and diffusion TiAlSi coating was formed. After coating deposition the heat treatment of samples in vacuum was made. The temperature of heat treatment was 950°C and the time 2 hours.
The cyclic oxidation tests were conducted at temperature 950°C. The cycle time was 23 hours (multiplied by). After each cycle mass changes was registered. The number of cycles was 50.
An analysis of the results obtained from two methods of cyclic oxidation was performed. Phase composition, morphology and the distribution of elements were defined by EDX, XRD and SEM in AlSi layers as well as in the scale.
AP-7 Effect of Aluminium Ion Implantation on the Oxidation Resistance of D.C. Magnetron Sputtered TiB2 Thin Films
S. Mollica, D.K. Sood (RMIT University, Australia); P.J. Evans, J.T. Noorman, N. Dytlewski (ANSTO, Australia); N. Brak, P. Pigram (LaTrobe University, Australia); K. Latham (RMIT University, Australia)
This work presents a novel approach to providing high temperature oxidation protection for titanium diboride thin films via aluminium ion implantation. Through ion beam modification, it was anticipated that metastable phases; not otherwise observed in stoichiometric TiB2, would form, giving rise to a stable oxidation barrier layer upon oxidation. Films, deposited onto single-crystal Si (100) substrates, were subjected to Metal Vapour Vacuum Arc (MEVVA) ion implantation at a dose of 3x1017 ions/cm2 using extraction voltages of up to 35 kV, vacuum annealed at 1100°C at 1x10-7 Torr, then oxidised in air at 650°C for durations of between 1 and 240 minutes. Analysis was completed using Rutherford Backscattering Spectroscopy (RBS), Heavy Ion Elastic Recoil Detection Analysis (HIERDA), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Aluminium ion implantation resulted in the development of various Ti-Al and Al-B metastable phases. Upon oxidation, the preferential oxidation of aluminium was observed, giving rise to a protective Al2O3 surface barrier layer. Aluminium ion implantation was observed to reduce the oxidation rate of titanium diboride thin films.