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7333 |
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Thursday, May 05, 2022, Hall D 11:00 AM Industrial Gas Turbines |
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Multilayer ceramic YSZ coatings for industrial TBCs: How architecture and powder morphology influence the coating performance |
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Simone Bursich* / Lincotek Rubbiano S.p.A., Italy Giovanni Bolelli / Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Italy Luca Lusvarghi/ Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Italy Stefania Morelli/ Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Italy Veronica Testa/ Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Italy Francesco Gerardo Mecca/ Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Italy |
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The demand of advanced multilayer Thermal Barrier Coating (TBC) systems with high-yttrium zirconia or rare earth-doped ZrO2 is rising because of the increasingly high turbine inlet temperatures in the Oil&Gas and Aviation fields. High-yttrium composition have better phase stability and chemical resistance to molten silicate deposits (“CMAS”), whose formation is an increasing concern at high temperatures. and the related need for improved stability. On the other hand, it is known that the morphology of Yttria-Stabilized Zirconia (YSZ) powders is an important factor that affects the performance and the characteristics of plasma sprayed TBCs. The objective of this work was to study how the performances of ceramic bi-layer coating systems deposited by Atmospheric Plasma Spraying (APS) is influenced by the use of different powder morphologies: porous Agglomerated and Sintered (A&S) granules, Hollow Spherical (HOSP) powders and dense, irregular Fused and Crushed (F&C) particles. The ceramic bilayer system consisted of a bottom/base layer of standard 7-8YSZ to provide suitable toughness at the highly stressed interface with the bond coat, and a top layer of high-yttrium ZrO2-55wt.% Y2O3. Both the bottom and top layers were obtained using either A&S, HOSP or F&C powders of the respective compositions, producing porous microstructures for both layers. All coatings were sprayed onto a Hastelloy-X substrate with a HVOF-APS “Flash” NiCoCrAlY bond coat. The samples were attacked by a molten CMAS (CaO-MgO-Al2O3-SiO2) deposit at high temperature and characterized by FEG-SEM and Raman Spectroscopy techniques to reveal the resistance of different coating systems against chemical degradation. Thermal Cycling Fatigue (TCF) resistance and tensile adhesion (ASTM C633) tests were also carried out in order to study how the feedstock powder and coating structure influence the thermomechanical response and bond strength of the samples. |