Reaction mechanisms of Gd2Zr2O7 in silicate melts derived from CAS. Issue 15 (December 2022)

• Record Type: Journal Article
• Authors: Dolmaire, Alice; Béchade, Emilie; Geffroy, Pierre-Marie; Goutier, Simon; Vardelle, Michel; Vilasi, Michel; Joulia, Aurélien
• Is Part Of: Journal of the European Ceramic Society. Volume 42:Issue 15(2022)
• Page Start: 7247
• Page End: 7257
• Publication Date: 2022-12
• Subjects: Thermal barrier coatings -- Diffusion mechanisms -- CMAS -- Gadolinium zirconate -- Reactivity; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2022.08.051
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: Infiltration mechanisms at high temperatures of sand & ashes (CAS) in aircraft thermal barrier coatings (TBC) have been widely studied using the pyrochlore phase Gd2 Zr2 O7 (GZ) as TBC. Novelty of this study is GZ reactivity with each or a mix of oxides derived from CMAS have been scrutinized in order to better assess the diffusion, stability and role of each reactivity products in mitigation mechanisms across the CAS-GZ system. In particular, Gd +III, Si +IV, O -II diffusion mechanisms at the GZ/SiO2 interface have been discussed. These mechanisms shed light on why Gd-oxyapatites are the predominant phases at interfaces between silica-rich medium such as CAS and GZ when reactions are not complete, in contrast to thermodynamic data. Moreover, Gd2 Si2 O7 phases are closely linked to the growth of Gd-oxyapatites and are the seat of the diffusion barrier to Si +IV species, which further explains why GZ coatings shortly stops CMAS infiltration.