Interfacial Regulation and High-temperature Combustion-gas Thermal-cycling Performance of High-entropy Rare-earth Silicate Environmental Barrier Coatings

doi:10.15541/jim20260238

Abstract

Abstract: Environmental barrier coatings (EBCs) for C/C-based hot-section components must retain phase stability and interfacial integrity under severe thermal cycling. However, thermal-expansion mismatch and interfacial oxidation can lead to premature spallation of high-entropy rare-earth silicate coatings. Here, (Tm_0.2Yb_0.2Er_0.2Lu_0.2Ho_0.2)₂SiO₅, denoted as (5RE_0.2)₂SiO₅, powder was synthesized, and (5RE_0.2)₂SiO₅ and (5RE_0.2)₂SiO₅-SiC coating systems were fabricated by combining pack cementation with supersonic atmospheric plasma spraying. The synthesized powder formed a stable monoclinic (5RE_0.2)₂SiO₅-type solid solution with a homogeneous distribution of the five rare-earth elements. The approximately (230 ± 5) μm-thick sprayed coating was partially amorphized and contained 5.88%(in mass) (5RE_0.2)₂SiO₅ owing to rapid melting and solidification. Without the SiC bond coat, the coating spalled extensively after only six burner-rig thermal cycles at 1400 °C, accompanied by an increase in the (5RE_0.2)₂O₃ content to 12.01%. Through-thickness cracks accelerated the transport of oxygen and steam to the interface, promoting the oxidation of C, Si and SiC and weakening interfacial bonding. By contrast, the SiC-bonded coating remained macroscopically intact after 100 cycles. The rough SiC surface provided mechanical interlocking, while oxidation-derived SiO₂ reacted in situ with (5RE_0.2)₂SiO₅ to form a (5RE_0.2)₂Si₂O₇ transition phase. The resulting compositionally graded reaction zone improved thermal-expansion compatibility near the SiC interface and suppressed crack penetration and interfacial oxidation, thereby markedly extending the thermal-cycling lifetime.

Key words: high-entropy rare-earth silicate, environmental barrier coating, thermal spraying, combustion-gas thermal cycling, C/C composites

CLC Number:

TB332

ZHANG Yujia, WU Keke, GUO Lingxiang, OU Hongkang, ZHANG Shuo, SUN Jia. Interfacial Regulation and High-temperature Combustion-gas Thermal-cycling Performance of High-entropy Rare-earth Silicate Environmental Barrier Coatings[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20260238.

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