Corrosion of Rare-Earth Disilicate Environmental Barrier Coatings in Gas Turbine Environments Microstructure Model

Abstract A model for the volatization of ytterbium disilicate (YbDS) by water vapor is developed. The new model is based on the Deal and Grove theory of the thermal oxidation of silicon (1965, “General Relationship for the Thermal Oxidation of Silicon”, J. Appl. Phys, 36, pp. 3770–3778.), generalized here to account for the multistep, second-order chemical reactions for silica depletion, multicomponent mixture effects, and the unsteady porous microstructural evolution of the corroded inner zone. With the new model, the fundamental kinetic rate and standard porous media parameters are determined using the atmospheric steam jet impingement experiment of Ridley and Opila (2021, “Thermochemical Stability and Microstructural Evolution of YbDS in High-Velocity High-Temperature Water Vapor”, J. Euro. Ceram. Soc., 41, pp. 3141–3149.) and compared to results from the original Deal and Grove model. Fixing the input parameters in each respective model, a validation study (blind prediction) is presented for the high Reynolds number (1×105) and high-pressure (14.7 atm) burner rig experiment of Wan et al. (2023, “Modeling Microvoiding Kinetics of Rare-Earth Disilicates in Flowing Atmospheres Containing Water Vapor”, J. Am. Ceram. Soc., 106, pp. 6352–6364.).