Ytterbium Disilicate/Monosilicate Multilayer Environmental Barrier Coatings: Influence of Atmospheric Plasma Spray Parameters on Composition and Microstructure

• Published in: Coatings (Basel) 2023-09, Vol.13 (9), p.1602
• Main Authors: Di Iorio, Giulia, Paglia, Laura, Pedrizzetti, Giulia, Genova, Virgilio, Marra, Francesco, Bartuli, Cecilia, Pulci, Giovanni
• Format: Article
• Language: English
• Subjects: Aeronautics; Aircraft; Aircraft engines; Aviation; Ceramic fiber reinforced ceramics; Ceramic matrix composites; Ceramics; Coatings; Combustion; Composition; Corrosion and anti-corrosives; Corrosion resistance; Density; Deposition; Energy consumption; Gas turbine engines; Heat conductivity; High temperature; Microstructure; Multilayers; Oxidation; Parameters; Phase transitions; Polymorphism; Porosity; Protective coatings; Shock resistance; Silica; Silicon; Silicon carbide; Substrates; Superalloys; Thermal expansion; Thermal properties; Thermal resistance; Thermal shock; Thermodynamics; Turbines; Vapor resistance; Water vapor; Ytterbium
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings13091602

SiC/SiC ceramic matrix composites (SiCf/SiC CMCs) are regarded as the new materials for the hot-section components of aircraft gas turbine engines, since they have one-third of the density of metallic superalloys, a higher temperature capability, good mechanical strength, and excellent thermal shock resistance. However, high-temperature water-vapor-rich combustion gases can induce severe surface recession phenomena in SiC/SiC leading to component failure. For this reason, it is necessary to design protective coatings, i.e., environmental barrier coatings (EBCs), able to protect the SiC/SiC surface in combustion environments. In the present work, ytterbium monosilicate (Yb2SiO5), stable when exposed to water vapor at high temperatures, and ytterbium disilicate (Yb2Si2O7), characterized by a thermal expansion coefficient closer to that of the substrate, were selected for a multilayer EBC system. EBCs were processed using the atmospheric plasma spray (APS) technique. A set of deposition parameters were tested, varying the power of the torch, and the composition and microstructure of the deposited coatings were studied in terms of porosity, crack density, and post-deposition phase retention by performing SEM, EDS, and XRD analysis. The results allow for the definition of the influence of deposition parameters on the final properties of multilayer EBC coatings.