Abstract Scope |
Oxidant diffusion through EBC system was studied using physics-based and numerical modelling. Oxygen permeability of dense YbDS top coat and TGO are systematically evaluated in terms of thermodynamics using defect reactions and parabolic rate constant (kp). Dry oxygen and wet oxygen conditions as well as different temperatures, partial pressures and top coat modifiers are investigated.
Results offer evidence that oxygen permeability for YbDS top coat is an order of magnitude higher than for TGO, hindering oxidant diffusion stronger, proving to be the diffusion rate controlling layer. Moreover, water vapor strongly increases the oxidant permeation with defect reactions playing a key role. Mass transfer through top coat is primarily by outward ytterbium ion diffusion and inward oxygen ion movement, with the latter being dominant, particularly in wet environments. The effect of top coat modifiers on oxidant permeation is composition sensitive and related to their interaction with oxygen ions and mobility. |