Molten Salt Corrosion Behaviors and Mechanisms of Ytterbium Silicate Environmental Barrier Coating

Abstract

Environmental barrier coating (EBC) is essential for protection of ceramic matrix composite hot-sections in future gas turbine engines with high thrust-to-weight ratio. Rare-earth silicates, such as Yb 2 SiO 5 and Yb 2 Si 2 O 7 , have been developed for potential application as EBC. However, the corrosion behaviors and mechanisms of EBC in molten salt environment such as Na 2 SO 4 at high temperature are not clear. In this work, the Yb 2 SiO 5 /Yb 2 Si 2 O 7 /Si coating was prepared by vacuum plasma spraying (VPS). The molten salt (Na 2 SO 4 +25% NaCl, in mass) corrosion behaviors and mechanisms of the coating at 900 ℃ for 60-240 h were investigated. Results showed that the Yb 2 SiO 5 /Yb 2 Si 2 O 7 /Si coating exhibited dense structure with good bonding between the triple ceramic layers. The molten salt of Na 2 SO 4 +25% NaCl penetrated the Yb 2 SiO 5 top layer and enriched in the Yb 2 Si 2 O 7 interlayer, while the interfacial

The interplay of surface stability and oxygen vacancy dynamics in RE2Si2O7‐based environmental barrier coatings

“…14,15,22,23 Rare earth disilicates (RE 2 Si 2 O 7 ) are considered the suitable materials of the EBCs, owing to their moderate mechanical/thermal properties and good corrosion resistance. [24][25][26][27][28][29][30] RE 2 Si 2 O 7 with different rare earth elements shows multiple crystal phases at different temperatures. 31 During the service, phase transformation may result in the volume changes, which will lead to the formation of cracks in the EBCs and accelerate the failure of the coatings.…”

Mechanical and thermal properties for corrosion products of lutetium silicates against CMAS

“…1,2 Rare-earth (RE) silicates are considered as promising novel E/TBC candidates, which exhibit excellent mechanical properties and thermal properties, such as low modulus, good damage tolerance, low thermal conductivity, coefficient of thermal expansion (CTE), and so on. [3][4][5][6][7] Among all silicates, lutetium silicates are widely studied owing to their excellent CMAS corrosion resistance and similar CTE values with SiC and mullite. 8 Tian et al observed that Lu 2 SiO 5 has excellent hightemperature durability and low thermal conductivity (1.72 W ⋅ m −1 ⋅ K −1 at 1273 K).…”

“…Environmental/thermal barrier coatings (E/TBCs) are used to protect silicon‐based ceramic matrix composites (CMCs) substrates in aerospace engines from oxidation and corrosion, prolonging the service life of engine components 1,2 . Rare‐earth ( RE ) silicates are considered as promising novel E/TBC candidates, which exhibit excellent mechanical properties and thermal properties, such as low modulus, good damage tolerance, low thermal conductivity, coefficient of thermal expansion (CTE), and so on 3–7 . Among all silicates, lutetium silicates are widely studied owing to their excellent CMAS corrosion resistance and similar CTE values with SiC and mullite 8 .…”

Unveiling surface stability and oxygen vacancy segregation of Yb2SiO5 and Lu2SiO5 by first‐principles calculations

“…Yb 2 SiO 5 and Lu 2 SiO 5 are considered promising candidates for the EBC materials because they are excellent in resisting molten CMAS and water vapor and show low thermal conductivity (1.7-4.6 W/(m k)), compatible thermal expansion coefficients, and good chemical compatibility with CMCs substrates. [25][26][27][28][29][30][31][32][33] For example, Tian et al found that Yb 2 SiO 5 and Lu 2 SiO 5 which are high in internal friction can help build up the damage tolerance and passivate the cracks of the materials. 18 Zhao et al proved that Yb 2 SiO 5 /Yb 2 SiO 7 coatings demonstrate good resistance against the CMAS corrosion attack.…”

“…These factors make it impossible for them to become the perfect EBC in the real setting. Yb 2 SiO 5 and Lu 2 SiO 5 are considered promising candidates for the EBC materials because they are excellent in resisting molten CMAS and water vapor and show low thermal conductivity (1.7–4.6 W/(m k)), compatible thermal expansion coefficients, and good chemical compatibility with CMCs substrates 25–33 . For example, Tian et al.…”