High Temperature Oxidation of Metals and Ceramics: Environmental Barrier Coatings, Thermal Barrier Coatings, and Hypersonics
Sponsored by: TMS Corrosion and Environmental Effects Committee
Program Organizers: Kenneth Kane, Oak Ridge National Laboratory; Elizabeth Sooby, University Of Texas At San Antonio; Patrick Brennan, General Electric Research; Lavina Backman, U.S. Naval Research Laboratory; Kinga Unocic, Oak Ridge National Laboratory; Richard Oleksak, National Energy Technology Laboratory; David Shifler, Office of Naval Research; Raul Rebak, GE Global Research
Wednesday 8:00 AM
October 12, 2022
Room: 335
Location: David L. Lawrence Convention Center
Session Chair: Kinga Unocic, Oak Ridge National Laboratory; David Shifler, Office of Naval Research
8:00 AM Invited
Oxidation and Erosion Implications of CMAS on Environmental Barrier Coatings: Bryan Harder1; Kang Lee1; Michael Presby1; Benjamin Kowalski1; Jamesa Stokes1; John Setlock2; 1NASA Glenn Research Center; 2University of Toledo
In recent years, silicon-based ceramic matrix composites (CMCs) with environmental barrier coatings (EBCs) have been incorporated into the hot section components of gas turbine engines. These materials offer the possibility of higher operating temperatures as well as reduced cooling requirements, which can provide increased turbine efficiencies. However, with component temperatures exceeding 1300°C, environmental challenges become increasingly complex. Coating systems must endure steam-induced oxidation and volatilization, thermomechanical loads, erosion, foreign object damage, as well as calcia-magnesia-aluminosilicate (CMAS) exposure. While it important to characterize these individual failure mechanisms, it is likely the summation and interactions of them that will ultimately determine coating and component lifetimes. In this work, we will explore oxidation in steam environments and erosion performance of an EBC/SiC system that has been exposed to various CMAS compositions. Performance of these coatings exposed to CMAS will be compared to state-of-the-art coatings and the degradation modes will be discussed.
8:30 AM
Rare-earth Monosilicate Interactions with Calcium-magnesium Aluminosilicate: Cameron Miller1; Elizabeth Opila1; 1University of Virginia
Rare-earth silicates are excellent candidate materials for environmental barrier coatings in next generation aero turbine engines. Siliceous debris, such as ash and dust, can be ingested into engines and deposits as molten calcium-magnesium aluminosilicate (CMAS) glass on hot section components, degrading them. Single-cation rare-earth monosilicates were exposed to CMAS for 24h at 1300°C in a stagnant air box furnace, and their reactions characterized by SEM and EDS. Monosilicates containing the largest and the smallest rare-earth cations formed the thinnest, most protective reaction product layers, while the middle of the rare-earth series produced thick, low density reaction layers. These results are important for the selection of constituents used in multicomponent silicate coatings, which are designed for enhanced thermal properties in addition to thermochemical stability.
8:50 AM
Investigating Fifth Oxide Effect on CMXAS Glass Properties: Clark Luckhardt1; Elizabeth Opila1; 1University of Virginia
Calcium-magnesium-aluminosilicate (CMAS) interactions with coatings for hot section airplane structural materials are a prominent thermochemical degradation mechanism. Coating infiltration rates depend on CMAS viscosity and viscosity is influenced by CMAS composition. The ingested CMAS composition is subject to change by the engine environment and dissolution of the underlying coating. This work assesses environmental- and coating-CMAS interactions via the fifth oxide effect on CMXAS glasses (Ca30.75-Mg9-X5-Al13-Si42.25 in single cation mole percent), where X is a fifth oxide. Viscosity of CMXAS glasses was measured using a spindle-dipped viscometer, where X = Fe, Ti, Yb, Y, Gd, Zr, Hf. A critical temperature was observed in CMXAS glasses, for X = Hf, Zr additions, in which HfO2 and ZrO2 crystals precipitated, indicating there is a critical solubility limit. Computational databases including FactSage, ThermoCalc, and Giordano were used to calculate glass properties and compared to measured values to continue validating the most accurate computational model.
9:10 AM
High-temperature High-velocity Water Vapor Exposures of Ytterbium-silicate Dual-phase Mixture Compositions: Eric Stone1; Elizabeth Opila1; 1University of Virginia
Projecting environmental barrier coating (EBC) lifetimes for hot-section turbine engine SiC-based ceramic matrix composite components under realistic service conditions is needed. Toward this end, the effect of controlled amounts of second-phase ytterbium monosilicate (YbMS) on SiO2-depletion of ytterbium disilicate (YbDS) EBC candidate materials was investigated. Dual-phase mixtures of 10/20/30 vol% YbMS/balance YbDS were fabricated by spark-plasma-sintering. High-temperature (T=1200, 1300, and 1400 °C) high-velocity (50-150 m/s) water vapor exposures were conducted at a total pressure of 1 atmosphere. YbDS reacted with high-velocity steam forming a porous YbMS reaction product layer that increased in thickness with exposure time and temperature. Average SiO2-depletion depths of 1200 °C exposed samples were similar for all phase mixtures. Otherwise, average SiO2-depletion reaction depth decreased as YbMS second-phase content was increased. The temperature dependence of parabolic rate constants calculated from 10 and 30 vol% YbMS reaction depth trends are presented and discussed.
9:30 AM
New Approaches to Study Oxygen Transport in SiC-based Ceramic Matrix Composites: Koen Verrijt1; David Poerschke1; 1University of Minnesota Twin Cities - Chemical Engineering & Materials Science
Matrix microstructure heterogeneity in SiC ceramic matrix composites (CMCs) arises in various processing routes. Polymer infiltration and pyrolysis can lead to a spatial variability in composition and crystallinity, residual amorphous phases, and porosity - all at the nanometer scale. It is important to understand the influence of these fine-scale features on oxygen transport to enable better materials and processing protocols designed to limit oxygen transport and to increase CMC lifetimes. The use of polymer-derived ceramics allows for tailoring these microstructural heterogeneities by varying the polymer precursor and processing conditions. A novel experimental setup consisting of solid-state electrochemical cells that can precisely control and monitor the oxygen partial pressure around specimens was designed and built. Preliminary work validated the performance of the oxygen pump and sensor using a one chamber setup. Subsequent work focused on using the setup to compare oxygen transport through various SiC-based materials at elevated temperatures.
9:50 AM
Thermal Expansion Analysis of Mixed and High Entropy Rare Earth Disilicates via Synchrotron X-ray Scattering: Alejandro Salanova1; Ian Brummel1; Elizabeth Opila1; Jon Ihlefeld1; 1University of Virginia
Robust thermal/environmental barrier coatings (T/EBCs) can be developed using entropic stabilization at high temperatures. In this work, the anisotropic thermal expansion behavior of mixed rare earth (RE) and high entropy (HE) disilicate powders will be presented. Through rule of mixtures, combining RE cations resulted in stabilized phases not readily formed in individual compounds. The phase of these mixtures proved stable, as distinguishable by in-lab X-ray diffraction from room temperature to 1200 °C. Lattice parameters and thermal expansion were then determined using synchrotron radiation, showing the direction of maximum thermal expansion varies with temperature. The shifts correspond to changes in eigenvectors with respect to temperature, manifesting as distinctions in shear components in the tensor and lattice parameter changes. The shifts were pronounced in Yb-containing compositions, but less so in compositions devoid of Yb. Initial efforts to elucidate the phenomena leading to these behaviors using pair distribution function analysis will be presented.
10:10 AM Break
10:30 AM
Failure Behavior Analysis of Thermal Barrier Coatings under Adverse Environment: Analytical and Numerical Modeling: Jinrong Yan1; Xin Wang1; Kuiying Chen2; 1Carleton University; 2NRC
Premature failure of thermal barrier coatings (TBCs) is a preliminary phenomenon significantly limiting their applications in gas turbine engines. Delamination of TBCs occurs typically at coating interfaces due to thermal mismatch stress via crack nucleation and propagation. This presentation reports this phenomenon using multi-physics approach. Under high-temperature adverse environment, multiple-factors are coupled to lead to failure through creep, topcoat sintering, oxide growth and interface imperfection. Heat transfer was implemented into TBC model to simulate in-service operation conditions. Periodic model of TBCs was modelled with the phase-field method addressing the fracture-damage evolution of topcoats. The interface degradation was investigated by cohesive zone model. Preliminary results demonstrate that the model well couples the above factors, and topcoat cracks propagate rapidly during an early stage and continue to grow as topcoat is sintered. Using the cohesive zone model at the topcoat, more crack paths are also studied, and the predominated effects were identified.
10:50 AM
Mo-Si-B Coatings for Protection of SiC-based Materials in High Temperature Active Oxidation Environments: Jeffrey Becker1; John Perepezko1; 1University of Wisconsin - Madison
One of the most demanding engineering challenges for sustained hypersonic flight is the development of a suitable thermal protection system for leading edges that experience high temperatures and low pO2 environments. While SiC shows promise, it is rapidly consumed in hypersonic conditions due to active oxidation – a mechanism that occurs at high temperatures and low pO2, leading to the production of volatile SiO(g) that breaks down the SiO2 protective layer. In past work, Mo-Si-B coatings have been shown to improve the oxidation resistance of SiC in air at elevated temperatures by forming an aluminoborosilica scale. In this study, the compatibility of Mo-Si-B coatings on SiC is evaluated by isothermal oxidation experiments conducted at T=1500°C and pO2=~10-5 atm. Mo-Si-B coatings exhibit robust performance under these conditions - an active oxidation range for other silica formers. Additionally, coatings without Al or B showed reduced microstructural stability and poorer performance than aluminoborosilica.
11:10 AM
Investigation of High Emittance, Oxidation Resistant Multi-Layer Coatings for Carbon/Carbon Composites for Hypersonic Application: Abdullah Al Saad1; Carlos Martinez1; Rodney Trice1; 1Purdue University
During a high-speed flight, the leading edges of hypersonic vehicles can experience enormous heat fluxes, with surface temperatures greater than 1600℃ expected. While carbon/carbon (C/C) is a candidate material for leading edges and other hot structures, it is prone to oxidation and increasing ablation damage above 500℃. Oxidation-resistant coatings can protect the C/C, while emittance can be engineered to lower the leading-edge surface temperature via radiative cooling. In this study, a novel multi-layer coating based on individual layers of borides, carbides, zirconium oxides, and rare-earth stabilized oxides with emissivity modifiers is being applied to a C/C surface via pack cementation and plasma spray. Ablation testing is being performed to evaluate the effectiveness of the multi-layer coatings in simulated high-heat flux environments. The results from these experiments will help design and optimize multi-layer high emissivity and oxidation-resistant coating systems for C/C materials.