Coatings to Protect Materials from Extreme Environments: Environmental and Thermal Barrier Coatings I
Sponsored by: ACerS Engineering Ceramics Division
Program Organizers: Kang Lee, NASA Glenn Research Center; Yutaka Kagawa, High Performance Materials; Daniel Mumm, University of California, Irvine; Rodney Trice, Purdue University; Emmanuel Boakye, UES Inc.; Valerie Wiesner, NASA Langley Research Center; Edward Gorzkowski, Naval Research Laboratory; Scooter Johnson, Naval Research Laboratory; Richard Chromik, McGill University; Jun Song, McGill University; Christian Moreau, Concordia University; Stephen Yue, Mcgill University

Wednesday 8:00 AM
November 4, 2020
Room: Virtual Meeting Room 31
Location: MS&T Virtual

Session Chair: Emmanuel Boakye, UES Inc.; Valerie Wiesner, NASA Langley Research Center; Daniel Mumm, University of California, Irvine; Bryan Harder, NASA Glenn Research Center

8:00 AM
Cyclic Steam Oxidation of Single Layer Ytterbium Disilicate Environmental Barrier Coatings: Kenneth Kane¹; Padraig Stack²; Eugenio Garcia³; Sanjay Sampath³; Bruce Pint¹; ¹Oak Ridge National Laboratory; ²University of Akron; ³Center for Thermal Spray Research
    Environmental barrier coatings (EBCs) have become an industry standard for protecting SiC-based ceramic matrix composites (CMCs) in water vapor containing combustion environments, primarily being utilized as post-combustion stationary components in aerospace jet turbines. The current generation of EBCs are temperature limited by the melting point of the silicon bond coat, 1414°C. The next generation of EBCs without a bond coating are now being evaluated for industrial gas turbine applications where longer lifetimes and potentially increased temperatures are required. The current study examines the response of single layer atmospheric plasma spray (APS) ytterbium disilicate (YbDS) EBCs deposited onto CVD SiC to 1-h furnace cycle testing in air-90%H2O at 1250°-1350°C and evaluates the impact of substrate roughness on coating adhesion. Research sponsored by the U. S. Department of Energy, Office of Fossil Energy, Advanced Turbine Program.

8:30 AM
Anisotropic Wettability of CaO-MgO-Al₂O₃-SiO₂ Deposits on YAlO₃: Implications for Grain Boundary Engineering of Environmental Barrier Coatings for Gas Engine Applications: Amanda Velazquez Plaza¹; Amanda Krause¹; ¹University of Florida
    Yttrium aluminate perovskite (YAP) is an environmental barrier coating (EBC) candidate for oxide-based ceramic-matrix composite components in gas turbine engines. EBCs protect the composites from volatilization and from attack by ingested airborne calcia-magnesia-aluminosilicates (CMAS). CMAS melts and infiltrates EBC grain boundaries, inducing spallation during engine operation. The penetration rate is dependent on the melt’s wetting behavior and reaction products that can block penetration pathways. Anisotropic differences in these interactions were considered in this study to ascertain the merits of applying grain boundary engineering to CMAS-resilience. We measured contact angles of quenched CMAS on three different orientations of YAP single crystals and characterized the interfacial region with scanning electron microscopy. A wetting transition accompanies the nucleation of several crystalline phases, suggesting the reaction products strongly alter the interfacial energy. We discuss the crystallographic relationships uncovered and its implications for designing future EBC microstructures.

8:50 AM  Invited
Cathodic Arc Deposition of Silicon Aluminum Nitride Coating on SiC: Emmanuel Boakye¹; Ming Ming Chen¹; Keller¹; Brian Sirn¹; Rabi Bhattacharya¹; A.K Rai¹; ¹UES Inc.
    A silicon aluminum nitride (SiAlN) based nanocomposite bond coat comprising 20:80 Si3N4:AlN volume ratio was deposited on Hexoloy SiC substrate using direct cathodic arc (DC) and filtered arc (FA) methods. The coatings were produced using a 20% Si - aluminum alloy in nitrogen. The coated substrates were characterized for uniformity of Si3N4/AlN nanocomposite mixture by SEM-EDX. SEM cross sectional examination showed continuous 20ľm well adhered coating on SiC. The coated substrates were thermally cycled at 1480°C for up to 50 times in 50% H2O, 50% oxygen environment. The SiAlN phase transformed to mullite with a trace amount of silica. The SiAlN coating adhesion prior to and after thermal cycling was evaluated using scanning electron microscopy and X-ray diffraction.

9:20 AM
Real-time Observation of Impact Damage in Coated Silicon Carbide (SiC): nesredin kedir¹; Wayne Chen¹; Kamel Fezzaa²; ¹Purdue University; ²ANL/APS
    Silicon carbide (SiC) and its composites are enabling materials for advanced gas turbine engines. However, these materials require an environmental barrier coating (EBC) to prevent deterioration via hot corrosion and oxidation reactions. Additionally, the combined EBC/Ceramic must withstand damage via impact from ingested and internally originating debris. Very limited attention has been given to the latter issue, despite the understanding that both the coating and substrate are inherently brittle. Thus, the current effort aimed to elucidate the underlying damage mechanisms for a model air plasma sprayed EBC consisting of a Mullite topcoat, Silicon bond-coat and α-SiC substrate. In addition to postmortem inspection, a pulsed Synchrotron X-ray source was used to visualize, in-situ, the damage evolution with temporal and spatial resolutions of 0.5ľs and 6.4ľm respectively. The in-line impact was performed at room temperature using 1.5mm diameter Partially Stabilized Zirconia and Silicon Nitride spheres at velocities ranging between 300-355 m/s.

9:40 AM
Novel Multiscale Shear Adhesion Testing of Thermal Barrier Coatings: John Daspit¹; Clifton Bumgardner¹; Xiaodong Li¹; ¹University of Virginia
    Advanced testing techniques are required to elucidate the materials properties of advanced materials and coatings. Island Shear Adhesion testing (ISAT) allows for mitigation of bending forces to directly target Mode II fracture mechanics at a range of length scales. Here, we apply ISAT to shear pre-milled coating islands. This test differs from other adhesion tests by targeting precise regions and interfaces of interest. In typical interlaminar adhesion tests, the weakest link (whether interfacial or intercoating) fractures, preventing further information from being gathered on other layers. ISAT has been performed on thermal barrier coatings with success and will be compared with results from pull off tests and interlaminar tensile tests.