Microstructure and Mechanical Properties of Yttria Partially Stabilized Zirconia Coatings Deposited by Laser-assisted Air Plasma Spraying : PDF Download
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Author: Laurent Dubourg
Publisher:
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Category :
Languages : en
Pages : 12
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Author: Laurent Dubourg
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Category :
Languages : en
Pages : 12
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Author: ashkan baadi
Publisher:
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Category :
Languages : en
Pages : 0
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ABSTRACT Laser Remelting of Yttria Stabilized Zirconia Coatings Deposited by Suspension Plasma Spraying ASHKAN BAADI CONCORDIA UNIVERSITY, 2020 Thermal barrier coatings (TBCs) are applied as a protective layer in a range of applications, mainly in the aero-engine and power generation industries to protect the metallic parts from high operating temperatures, especially in gas turbine-engines. One way to improve the efficiency of the engines is to increase the combustion temperature; in order to reduce potential damage to the metallic parts, TBCs are commonly applied to these components. The TBC comprises a bond coat and a top coat. Since Yttria Stabilize Zirconia (YSZ) has the best combination of properties among the various options, this material is most commonly used as the top coat on commercial TBCs. The top coat in TBCs can be applied by different methods, including Electron Beam - Physical Vapour Deposition (EB-PVD), Atmospheric Plasma Spraying (APS) and the recently developed Suspension Plasma Spraying (SPS) which is one of the newest methods in applying top coat layers. SPS has the potential to generate columnar microstructures with a beneficial range of porosity: these columns reduce thermal stresses in the TBCs and at the same time provide an acceptable range of porosity which reduces the thermal conductivity of the coated layers. The columnar structure of this type of coating, despite having a potential to increase the life cycle of the top coat in terms of thermal stresses, can be a way of penetration for calcium-magnesium- aluminosilicates (CMAS) into the TBC structure, which will result in deterioration of the TBC.IV In this thesis, the formation of a variety of top coats using Suspension Plasma Spraying SPS method is used in order to obtain the desired columnar microstructure. Subsequently, these layers are laser treated to study the possibility of creating a remelted layer across the TBC surface which should reduce the CMAS penetration. In this regard, advantages and disadvantages of the major laser parameters such as scanning speed, output power, power density and energy density were observed. Based on the experimental tests on columnar structures, it was found that increasing scanning speed and power does not have a linear relation and that increasing the laser travel speed above 2 m/min will cause nonuniform melting and create different phases on the surface of the substrate. At the same time, decreasing power below a certain amount will not cause significant changes to the substrate. A specific range of energy and power density need to be considered in order to obtain a uniform melted layer over the substrate.
Author: Dan C. Dumitras
Publisher: BoD – Books on Demand
ISBN: 9535101056
Category : Technology & Engineering
Languages : en
Pages : 332
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Discovered almost fifty years ago at Bell Labs (1964), the Nd:YAG laser has undergone an enormous evolution in the years, being now widely used in both basic research and technological applications. Nd:YAG Laser covers a wide range of topics, from new systems (diode pumping, short pulse generation) and components (a new semiorganic nonlinear crystal) to applications in material processing (coating, welding, polishing, drilling, processing of metallic thin films), medicine (treatment, drug administration) and other various fields (semiconductor nanotechnology, plasma spectroscopy, laser induced breakdown spectroscopy).
Author: Peter Glenn Valentine
Publisher:
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Category :
Languages : en
Pages : 86
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Category : Metallurgy
Languages : en
Pages : 1076
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Author: Alper Öztürk
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Category :
Languages : en
Pages : 382
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Author:
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Category :
Languages : en
Pages :
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Yttria-stabilized zirconia (YSZ) is used as a thermal barrier coating (TBC) to protect super-alloy blades such as Mar-M247 or Rene-N5 during engine operation. The current method for YSZ fabrication for TBC applications is by air-plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) (Haynes 1997). APS gives reasonable deposition rates, but has a limited life and aging effects due to its porous and lamellar structure. The EB-PVD coatings are more stable and can accommodate thermomechanical stresses due to their characteristic strain-tolerant, columnar microstructure. EB-PVD, however, is primarily line-of-sight, which often leaves ''hidden areas'' uncoated, has low throughput, and has high capital cost. The process of metal-organic chemical vapor deposition (MOCVD) is investigated here as an economical alternative to EB-PVD and APS, with the potential for better overall coverage as well as the ability to produce thick (100-250 [micro]m), strain-tolerant, columnar coatings. MOCVD of YSZ involves the use of zirconium and yttrium organometallic precursors reacting with an oxygen source. Previous researchers have used diketonate or chloride precursors and oxygen (Wahl et al. 2001a, Wahl et al. 2001b, Yamane and Harai 1989). These precursors have low transport rates due to their low carrier solvent solubility (Varanasi et al. 2003). Solvated zirconium and yttrium butoxide precursors were investigated here due to their higher vapor pressures and high solvent solubility. This work uses predictive equilibrium modeling and experiments involving butoxide precursors for tetragonal YSZ fabrication.
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Category : Aeronautics
Languages : en
Pages : 934
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Category : City planning
Languages : en
Pages : 66
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Category : Ceramics
Languages : en
Pages : 250
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