Thermal durability of ytterbium silicate environmental barrier coating prepared by suspension plasma spray
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ORIGINAL ARTICLE
Thermal durability of ytterbium silicate environmental barrier coating prepared by suspension plasma spray Soo Min Park1 · Sahn Nahm2 · Yoon Suk Oh1 Received: 6 August 2020 / Revised: 17 September 2020 / Accepted: 25 September 2020 © The Korean Ceramic Society 2020
Abstract Owing to their superior high-temperature stability, SiC-based ceramic matrix composites are widely used in turbine engine components for launch vehicles and other applications in the aerospace industry. However, because of the deterioration that occurs in these materials in high-temperature wet operating environments, researchers have developed environmental barrier coating technologies to protect the substrate. In this study, a top coat was prepared using Y b2SiO5 and Y b2Si2O7 as the third-generation coating of a rare-earth silicate with high thermal, chemical, and mechanical stability in high-temperature environments above 1400 °C. A new bond coat was prepared, incorporating Si, whose thermal expansion coefficient is similar to that of the SiC substrate, and Hf, which is expected to significantly contribute to high-temperature stability. The coating was prepared by suspension plasma spraying rather than atmospheric plasma spraying to realize a fine coating particle structure; to densify the coating layers, secondary densification coatings were created using ytterbium (III) nitrate pentahydrate (Yb(NO3)3∙5H2O) and tetraethyl orthosilicate (C8H20O4Si). The prepared specimens were measured in terms of weight change and weight change ratio with respect to temperature under high-temperature flames (1400 ℃ and 1700 ℃). After the secondary densification coating, the microstructure of the specimen was observed to be denser and the surface layer of the coating exhibited crystallinity. For the tested samples, a decrease in weight was observed. The largest weight loss was observed under the 1700 ℃ flame. Keywords Environmental barrier coatings · Suspension plasma spray · Ytterbium silicate · Si–Hf bond coat · Secondary densification coatings
1 Introduction In general, materials used in the defense industry and aerospace turbine blades easily experience deterioration at high temperatures and pressures [1, 2]. As such, demand is rising for materials with excellent thermal stability and oxidation resistance to protect and maintain core components and substrates under extreme conditions. Ceramic matrix composites (CMCs) based on silicon carbide (SiC), which have better durability and high-temperature stability than conventional materials, have recently become a key component in such applications [1, 3–5]. However, * Yoon Suk Oh [email protected] 1
Engineering Ceramic Center, Korea Institute of Ceramic Engineering and Technology, Icheon, Republic of Korea
Department of Materials Science and Engineering, Korea University, Seoul, Republic of Korea
2
deterioration of these materials occurs when continuously exposed to CMAS in high-temperature, high-pressure steam environments above 1300 ℃, thus shortening the life of the sub
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