ICMCTF1998 Session AP: A- Posters
Wednesday, April 29, 1998 5:00 PM in Room Atlas Foyer
Wednesday Posters
Time Period WeP Sessions | Topic A Sessions | Time Periods | Topics | ICMCTF1998 Schedule
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AP-1 Fiber Coating by Industrial-Scale Laser CVD: Layer Structure and Process Diagnostics
V. Hopfe, B. Schultrich, W. Graehlert, B. Dresler, O. Throl (Fraunhofer Institute - IWS, Germany) The main advantage of fiber reinforced ceramic composites (CMC) over monolithic ceramics is their much higher toughness which makes them candidate materials for high temperature applications, e.g. for gas turbines and heat exchangers. Toughness and chemical stability of CMC are strongly influenced by the fiber-matrix interface which can be effectively engineered by coating the fibers. Based on an 6 kW cw-CO2 laser, an atmospheric pressure laser CVD process (LCVD) has been established which performs a continuous high rate coating of fiber bundles with ceramic layers. The laser based method is characterized by several significant advantages: high deposition rates of typically 1μm/s, almost no restrictions on deposition temperature, a wide variety of materials to be deposited, and short residence time (<100 ms) of the fibers in the deposition chamber, which avoids fiber degradation. The reactor is equipped with an FTIR extraction system to control gas phase chemistry continuously. The structure of the coated fibers has been checked by SEM, Raman microscopy and FTIR reflectance microscopy. With C2H4, CH4, C2H2 and C6H6 as precursors, uniform layers of partially graphitizised py-C are deposited onto C fibers and SiC fibers. |
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AP-2 Influence on High-Temperature Sulphide - Oxide Corrosion on Structure of CoCrAlY VPS Coatings.
L.V. Markova, P.A. Vitiaz, V.A. Chekan (Powder Metallurgy Institute, Belarus) In this work a structural condition of CoCrAlY plasma coatings in result of influence of high-temperature sulphide - oxide corrosion is investigated. A composition consisting of 66,2 % Na2SO4 + 1,8 % V2O5 + 20,4 % Fe2O3 + 8,3 % NiO + 3,3% CaO in a kind of alcohol suspension was used as corrosion media at temperatures 700 and 800 deg. C and stress 300 Mpa. In result of spent researches large structural changes in a coating depending on time of realization of test caused by diffusion processes are revealed. Under action of temperature and time is observed diffusion both of Al and Cr to a coating surface for creation of oxide film constantly being destroyed under the action of corrosion media. The destruction of the oxide film proceeds due to acidic - basic fluxing. Deep penetration of sulfur and oxygen in a coating at correctly generated structure is not observed because of a dense film of protective oxides. It is established, that the catastrophic destruction of a coating is observed only when in result of diffusion processes Ni from a basis reaches a zone of corrosive attac. |
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AP-3 Effects of Plasma Nitriding on the Chromizing Diffusion Layer in Various Alloys
S.Y. Lee, H.J. Park (Hankuk Aviation University, Korea); J.G. Han, S.S. Kim (SungKyunKwan University, Korea) Duplex plasma surface treatments of chromizing and plasma nitriding on various alloys such as mild steel, 1Cr-0.5Mo steel and Nickel-base superalloy were carried out to improve elevated temperature properties. Specimens were chromized at 1,050C for various hours and were subsequently plasma nitrided at 530C for various hours. Effects of Cr-diffusion coating on the plasma nitriding behaviors and the characteristics of the final duplex treated specimens were analyzed using SEM, EDS, XRD, AES and microhardness tester. The chromizing for 5 hours by pack cementization process had created Cr diffusion layer of approximately 100 μm thickness and the surface microhardness was increased by a factor of 2 - 2.5, independent upon the alloy composition. Subsequent plasma nitriding induced a large improvement in the microhardness above 1200Hv(0.1Kg). The main cause for the large improvement in the surface hardness is currently investigated. Also being studied are the effects of the plasma nitriding on the isothermal and cyclic oxidation behaviors of the chromized diffusion coating layers in various alloys. Characteristics of the oxidation behaviours of the surface layer and its oxidation mechanisms will be lluminated. |
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AP-4 Corrosion Protection of 13CrMo44 Ferritic Steel by Si, and Ce by Ion Implantation for High Temperature Applications
F.J. Perez, E. Otero, M.P. Hierro, C. Gomez, F. Pedraza (Universidad Complutense de Madrid, Spain); J.L. De Segovia (Instituto Torres Quevedo, Spain); E. Roman (Instituto de Ciencia de los Materiales, Spain) In order to improve the high temperature corrosion behaviour of different materials different heavy ions have been implanted into the surface of 13CrMo44 ferritic steel. Silicon and Cerium elements have been implanted in order to analyse their sinergistics effects against high temperature corrosion protection of this material. Oxidation kinetics have been established up to 150 hours of test. The implanted surface and the corrosion products formed on the surface have been analysed by Auger Electron Espectroscopy (AES), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and X-Ray diffraction patterns. Theoretical calculations have been performed in order to achieve the best deep profile in order to identify the surface damage during the implantation process. A protection mechanism with Cerium have been proposed according to the results obtained. |
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AP-5 High Temperature Corrosion Protection of Austenitic ALSI 304 Stainless Steel by Si, Mo and Ce by Ion Implantation
F.J. Perez, E. Otero, M.P. Hierro, C. Gomez, F. Pedraza (Universidad Complutense de Madrid, Spain); J.L. De Segovia (Instituto Torres Quevedo, Spain); E. Roman (Instituto de Ciencia de los Materiales, Spain) Ion implantation has been used as a surface modification technique in order to improve the high temperature corrosion behaviour of different materials. Silicon and rare earth elements have been implanted in order to analyse their sinergistics effects in the corrosion protection of AISI 304 stainless steel. Oxidation kinetics have been established up to 150 hours of test. The implanted surface and the corrosion products formed on the surface have been analysed by Auger Electron Probe Microanalysis (EPMA), and X-Ray diffraction patterns. Theoretical calculations have been performed in order to achieve the best deep profile. A protection mechanism has been proposed according to the results obtained. |
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AP-6 Coated Blade Operation Experience with a Gas Pumping Gas Turbine
A.I. Rybnikov, A.V. Ivanov (The Polzunov Central Boiler and Turbine Institute, Russia); I.I. Krukov (The Polzunov Central Boiler and Turbine Institute); N.V. Mozhayskaya (The Polzunov Central Boiler and Turbine Insitute, Russia) An electron beam physical vapour deposition CoNiCrAlY coating isu sed for high pressure turbines rotating blades made from ZMI-3 alloy. Studies of coated blades after different service periods (from 16500 to 3000 h) showed that this coating most efficiently protects rotating blades in turbines which operate in northern regions of Russia. Corrosion failure is observed in turbines operating in southern regions of the country. The technology of removing and redeposition for coating layer has been developed. |
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AP-7 Combined Electron-beam and Vacuum-arc Coatings
I.I. Krukov (The Polzunov Central Boiler and Turbine Institute); V.G. Kuznetsov, S.I Rybnikov, S.A. Leontiev, A.S. Osyka (The Polzunov Central Boiler and Turbine Institute, Russia) To increase service properties of protective coatings for stationary energy gas turbine blades were investigated for the exploitation possibility of the combined coatings applied by the different techniques. Vacuum-arc coatings of system NiCrTiAl were applying at electron-beam coatings of system CoCrAlY and CoCrAlY/ZrO2 - Y2o3. The coatings combination allow to increase corrosion resistance, adhesion strength and another coatings' mechanical properties. With allowance for economical advantage the cost of the vacuum-arc coatings must be below in 2-5 times than the cost of the electron-beam coatings. It was shown the possiblility of vacuum-arc coating applying exploitation without following diffusive annealing and reducing treatment. Combination of two technological processes benefits can increases protective properties of coatings and as a consequence to increase a service-life for gas turbine blades. |
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AP-8 Phase Composition of Zr2O3 Coating at Temperatures of 700-900° C
G.D. Pigrova, A.I. Rybnikov, S.I Rybnikov (The Polzunov Central Boiler and Turbine Institute, Russia) The method of X-ray analysis has been applied to study the phase composition of thermal-barrier Zr2-Y2O3 coating used as a surface-protective materials for gas turbine blades. The coating was obtained by electron-beam and vacuum-arc deposition methods. The phase composition of the coating was studied in an as-deposited state, after heat treatment at 700 to 900 °C and turbine blade service in power plant. It has been found that some structural changes due the formation and quantitative redistribution of system phase components can take place during ageing. The data obtained were interpreted based on the temperature and time ageing dependence of the phase composition, as well as on the way of coating manufacture dependence. The studies showed the importance of structural investigations of coating materials during long-term ageing since it is necessary to get some knowledge of the phase equilibrium of the above systems in the service temperature range for giving practical recommendations on coating application. |