RE2O3 dissolution kinetics and mechanisms in CAS silicate melt: Influence of the rare earth

Conference Dates

June 24-29, 2018


Fine particles of sand, dust or volcanic ashes ingested by aircraft engines are well-known to damage 8YPSZ Thermal Barrier Coating (TBC). In service, these particles deposit on hot TBC surface (≥ 1200°C) as molten silicate and infiltrate coating porous microstructure. They are mainly constituted of CaO-MgO-Al2O3-SiO2 (CMAS) in variable proportions and also contain metallic oxides. Gd2Zr2O7 TBC has shown efficiency to mitigate synthetic CMAS infiltration due to its reactivity with CMAS [1]. Indeed, the dissolution reaction leads to rapid formation of a sealing-layer in the topcoat mainly constituted of crystalline Ca2Gd8(SiO4)6O2 apatite. However, this phase is not always stable in contact with CMAS and many rare-earth silicates may compete with apatite crystallization [2]. Several rare-earth oxides RE2O3 can be considered to replace yttria in ZrO2-based TBC but little is known on reaction kinetics and thermodynamics involving RE2O3 and multi-component CMAS system.

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