Program Organizers: Narendra B. Dahotre, Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, TN 37388; Janet M. Hampikian, School of Materials Science & Engineering, Georgia Institute of Technology, Atlanta, GA 30332; Jacob J. Stiglich, PO Box 206, Sierra Madre, CA 91025
Wednesday, AM Room: B1
February 7, 1996 Location: Anaheim Convention Center
Session Chairpersons: P. P. Patil, School of Physical Sciences, North Maharashtra University, Jalgaon, 425001, India; Narendra B. Dahotre, Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, TN 37388
8:30 am
PHYSICAL PROPERTIES OF AND PHASE TRANSFORMATION IN V-Cr-Ti-O SOLID SOLUTIONS: J.-H. Park, Energy Technology Division, Argonne National Laboratory, Argonne, IL 60439. E.-T. Park, Metallurgy and Materials Engineering, Illinois Institute of Technology, Chicago, IL 60616
Incorporation of O in the surface of V-Ti-Cr alloys has been investigated by adding O to the alloys in controlled environments at 550-750[[ring]]C. Several tests were performed to determine the physical properties of V-Cr-Ti-O solid solutions. The amount of O in the alloys has been determined by the weight change before and after incorporation of the O. Microhardness was measured to define the O depth profile across the alloys. X-ray diffraction studies indicated a cubic-to-tetragonal phase transformation and a highly stressed lattice because of O incorporation. O atoms occupied face-centered interstitial sites and sites between corners in the BCC sublattice. Elastic modulus and Vickers hardness also increased in the O-enriched V-Cr-Ti alloys. Work supported by the U.S. Department of Energy, under Contract W-31-109-Eng-38.
8:50 am
EFFECT OF MECHANICAL PROPERTIES ON EROSION RESISTANCE OF WELD OVERLAY COATINGS: B.F. Levin, J.N. DuPont, A.R. Marder, Lehigh University, Energy Research Center, Bethlehem, PA 18015
The elevated temperature (400deg.C) erosion behavior of eleven commercially available weld overlay coatings, deposited on 1020 steel substrates, was evaluated. A relative ranking of their erosion resistance has been developed. It was found that as a result of erosion, one group of coatings did not deform plastically while another group experienced significant plastic deformation. For coatings that did not deform plastically, increased hardness led to a decrease in their erosion resistance. For plastically deformed coatings, a new toughness parameter has been determined which shows good correlation with erosion resistance. In order to further investigate the relation between mechanical properties and erosion resistance of plastically deformed materials, erosion tests and elevated temperature mechanical tests were conducted on wrought alloys of similar compositions. Their erosion resistance also showed good correlation with the new toughness parameter. The physical significance of the new toughness parameter is discussed along with relationships between hardness, tensile properties and erosion resistance.
9:10 am
STRUCTURAL AND MECHANICAL PROPERTIES OF PULSED LASER PROCESSED HIGH TEMPERATURE COATINGS: Ashok Kumar, U. Ekanayake, D. Kjendal, Department of Electrical Engineering, University of South Alabama, Mobile, AL 36688; R.B. Inturi, J.A. Barnard, Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487
Over the past few years, the pulsed laser deposition (PLD) technique has emerged one of the simplest and the most versatile methods for the deposition of thin films and coatings of a wide variety of materials. We are currently investigating the thin film coatings of nitrides (TiN, Si3N4, BN, CN, NbN etc.), carbides (SiC, TiC, B4C etc.), and also polymer coatings of polytetraflouroethylene (PTFE) on various commercial useful substrates by PLD method. The coatings of these materials have many desirable properties for application at elevated temperatures because of extremely high melting point, hardness, high temperature strength, good thermal shock resistance, and high thermal conductivity. The mechanical properties of the films will be evaluated at different processed conditions by nanoindentation. The in-situ UV/VIS emission spectroscopy technique will be used to understand the nature of excited atoms, molecules, and ions in the ablated plume. The films will be characterized by X-ray diffraction, scanning electron microscope and FTIR techniques. The chemical and structural properties of these coatings will be correlated to the mechanical properties. Optimization of laser deposition parameters (energy density, repetition rate etc.,) to obtain high quality thin films will be discussed in detail. This research was supported by Alabama NASA EPSCoR Program.
9:30 am
FINITE ELEMENT MODELING OF THE STRAIN AND TEMPERATURE DISTRIBUTION ON TURBINE BLADES AND ITS RELATIONSHIP WITH THE DIFFUSIONAL PHENOMENA UNDER REAL WORKING CONDITIONS: Alejandro Sanz, J.-P. Bemadou, Laboratoire de Metallugrgie, 10 Avenue E. Belin, 31055 Toulouse cedex, France; L. Llanes, M. Anglada, M. Gomez, UPC ETSII, Dep de Ciencia de loc Materiales y Metalurgia, Av, Diagonal 647, 08028 Barcelona, Spain; M. B. Rapaccini, Polytecnico di Milano, Dipartimento de Ingenieria Aeroespaziale, Piazza Leonardo da Vinci, Milano, Italy
Computer similation of temperature and stress field associated with turbine blades under different working conditions are presented. The calculation problem was solved using CATIA system finite element code. The improvement of the gas turbine engine efficiency requires to have the highest possible Turbine Inlet Temperature (T.I.T.). Turbine's turbine blades and nozzle vanes are commonly protected against high temperature degredation with NiCoCrAlYTa coatings. Important element diffusion is observed across the substrate/coating interfaceleading to substantial changes in the chemical and mechanical behavior of the coated system. The computed results were used to compae the diffusional phenomena in real AM-3 superalloy single-crystal blades under real working conditions, and laboratory samples after creep tests and four points bending fatigue test. Blades as well as laboratory samples were single crystals, [001] oriented, coated with a Low Pressure Plasma Spray (LPPS) NiCoCrAlYTa coating. Samples were submitted to four points bending isothermal low cycle fatigue during 1000 cycles until fracture. The stress controlled test was performed usind a 10-10-10 second cycle at 1323K (1050deg.C) and 140 Mpa; other laboratory samples were tested under creep conditions underthe same conditions of stress and temperature during different times. Analyzing directly the concentration profiles the information of the interdiffusion fluxes of all componentscan be obtained fomm Energy Dispersive microprobe Spectroscopy (EDS) the diffusional phenomena between the coating and the substrate is characterized and correlated with finite element calculated field stresses and temperature at the point in which the EDS data was obtained.
9:50 am
SYNTHESIS AND CHARACTERIZATION OF POLY (2-ANISIDINE) THIN FILMS: P. P. Patil, J. R. Mahajan, V. V. Talele, P. P. Kumbhar, M. A. More, School of Physical Sciences, North Maharashtra University, Jalgaon 425 OOl, India
Poly (2-anisidine) thin films have been synthesized by electrochemical deposition technique on transparent SnO2: F conducting glass substrates under galvanostatic conditions. The effect of current density, monomer concentration, deposition temperature and time on the UV-visible absorption and morphology of the films has been investigated. The UV-visible absorption spectra clearly indicate a peak at~850 nm which is attributed to the presence of conducting emeraldine salt phase. In addition the spectra show a shoulder like structure at~450 nm corresponding to the formation of lattice polaron. The extent of the sharpness of the peaks decreases with increase in monomer concentration, thereby suggesting that a lower monomer concentration favors the formation of conducting emeraldine salt phase. The morphology of the films strongly depends on the monomer concentration and reaction temperature. which may be due to the difference in the growth speeds of the films. Some characteristics of synthesized polymer were examined by Infrared spectroscopy (IR) Nuclear Magnetic Resonance (NMR) spectrometry and X ray diffraction (XRD) measurements.
10:15 am BREAK
10:25 am
LIFE ASSESSMENT OF SERVICE STRESSED HIGH TEMPERATURE COATINGS BY PERMEABILITY MEASUREMENTS: N. Czech, F. Kirchner, W. Stamm, Siemens AG, Power Generation Group (KWU), Materials Technology, D-45466 Mulheim a.d. Ruhr, Germany
During service blades and vanes of stationary gas turbines are subjected to different kind of loadings like mechanical and thermal stresses as well as corrosion, oxidation and erosion. The increase in surface temperature causes a more severe attack to the blade coating which commonly is an MCrAlY-type. The time for refurbishing the blade must be determined depending on the effective life of the protecting coating. This should be done by a simple measurement and an equipment which is portable. In the new method applied by Siemens the physical effect used is the change of magnetism of the coating during service: By the loss of [[beta]]-phase the magnetic state of the coating will change from para-to ferromagnetism. By measuring the magnetic permeability it is possible to assess the coating. We will present permeability measurements on different bladings which will be compared with calibration curves.
10:45 am
CHARACTERIZATION OF THE INTERFACIAL TOUGHNESS A SUPERALLOY PROTECTED BY A NiCoCrAlYTa COATING UNDER CREEP: Alejandro Sanz, J.-P. Bernadou, Laboratoire de Metallugrgie, 10 Avenue E. Belin,31055 Toulouse cedex, France; L. Llanes, M. Anglada, M. Gomez, UPC ETSII, Dep de Ciencia de loc Materiales y Metalurgia, Av, Diagonal 647, 08028 Barcelona, Spain; M.B. Rapaccini, Polytecnico di Milano, Dipartimento de Ingenieria Aeroespaziale, Piazza Leonardo da Vinci, Milano, Italy
One of the main parameters in the quality of a coating is its adhesion to the substrate. NiCoCrAlYTa coatings frequently used to protect the components in the hot path of the gas turbine engines are commonly deposited by the Low Pressure Plasma Spray (LPPS) technique. Unfortunately, the tests which are commonly used measure the adhesion have a number of drawbacks and thus do not provide useful data for the study of the adhesion mechanisms. The interface indentation test, based on the fracture mechanics method, is an attempt to determine the interface thoughness or interface cracking energy. Although some questions arise about the physical meaning of such an interface toughness, this test may be used fruitfully to compare the cracking resistance at the substrate/coating interface. AM-3 single-crystals, [001] orientated, coated with a LPPS NiCoCrAlYTa coating were tested under 1323 K (1050C) and 140 Mpa for different times and until fracture. The paper reports the evolution of the interface toughness relating it with the microstructural and chemical evolution of both the substrate and the coating.
11:05 am Invited
INTERMETALLIC PHASE FORMATION AT THE SOLID-LIQUID INTERFACE IN THE "BASE METAL-THIN MELT LAYER" SYSTEM: L. P. Efimenko, E.A. Antonova, L.P. Petrova, Institute of Silicate Chemistry of Russia Academy of Sciences, ul.Odoevskogo,24, korp.2, St. Petersburg,199155, Russia
The general regularities of liquid phase formation were studied in the binary multi-compound Fe-Ti, Ni-Ti, Ni-Zr, etc. systems in the temperature range involving several eutectics (950-1350C). It was shown that in the "solid metal-thin melt layer" system the eutectic is formed, which is closest to the base metal ad in the system studied the partial thermodynamic equilibrium is attained. The growth kinetics of intermetallic and solid solution layers formed by multiphase diffusion were studied at various temperatures in different solid-liquid diffusion couples. It was found that the thickness of the grown layers varies parabolically with time. The diffusion coefficients were determined. The activation energies of the diffusion were compared with those of growth. The expirimental results obtained were summarized and analyzed on the basis of equilibrium phase diagrams.
11:30 am
MICROSTRUCTURE OF BONDING ZONE IN LASER CLAD Ni-ALLOY BASED COMPOSITE COATINGS REINFORCED WITH VARIOUS CERAMIC PARTICLES: J. H. Ouyang, Y. T. Pei, T. C. Lei, Department of Metals and Technology, P.O. Box 433, Harbin Institute of Technology, Harbin,150001, China
Microstructure of the bonding zones between laser clad Ni-alloy based coatings and their substrates was studied by means of SEM and TEM techniques. Observation indicated that for pure Ni-alloy coating the changes of laser parameters selected for good interface fusion has no effect on the microstructure of the bonding zone except its thickness. However, the addition of ceramic particles (TiC, SiC, or ZrO2) in the Ni-alloy changes the compositional or constitutional undercooling of the alloy melt near the solid/liquid interface and consequently leads to the obvious changes of microstructure of the bonding zones. For TiC/Ni-alloy coating, the morphology of u-Ni solid solution in the bonding zone changes from dendritic to planar form with increasing scanning speed. A colony structure of eutectic is found in the bonding zone of SiC/Ni-alloy coating in which the complete decomposition of SiC particles takes place during laser cladding. The immiscible melting of ZrQ and Ni-alloy powders induce the stratification of ZrO2/Ni-alloy coating which consists of a pure ZrO2 layer in the upper region and a bonding zone composed mainly of u-Ni dendrites adjacent to the substrate. All the bonding zones studied in this study give good metallurgical combination between the coating and the substrate.
11:50 am
THE OXIDATION RESISTANCE AND HIGH THERMAL, CONDUCTIVITY ON NOVEL CU BASED ALLOYS CONTAINING SI, RE ELEMENTS: Shou Hong Huang, Wei He, Wen Liu Huang, S. China Univ. of Tech. Guangzhou, China; Tie Fan Li, Inst. of Cor. and Prot. of Metals, Academia Sinica, Shenyang, China
Using the chemical heat-treatment process, we diffuse Si, Re etc elements
into Cu and its alloys which has an excellent thermal conductivity and a better
oxidation resistance at 600deg.C. The electrodeposition of Ni onto Cu followed
by co-diffusion of Si etc, can greatly improve liquid metal corrosion
resistance of samples in molten Sn-Pb alloy at 250deg.C. Diffusing Re into Cu,
the microhardness and layer depth are increased. The oxidation behavior was
characterized by weight-gain-time data. The samples appeared Cu5Y, Al203, SiO2
etc, it showed an excellent stability at 600C. The composition, phases,
microstructures were analyzed by means of electron microanalyzer, x-ray
diffraction and SEM respectively.
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