Abstract
Environmental barrier coating (EBC) materials that are resistant against molten calcia-magnesia-aluminosilicate (CMAS) corrosion are urgently required. Herein, multicomponent rare-earth (RE) disilicate ((Yb0.2Y0.2Lu0.2Sc0.2Gd0.2)2Si2O7, (5RE)2Si2O7) was investigated with regard to its CMAS interaction behavior at 1400 °C. Compared with the individual RE disilicates, the (5RE)2Si2O7 material exhibited improved resistance against CMAS attack. The dominant process involved in the interaction of (5RE)2Si2O7 with CMAS was reaction-recrystallization. A dense and continuous reaction layer protected the substrate from rapid corrosion at high temperatures. The results demonstrated that multicomponent strategy of RE species in disilicate can provide a new perspective in the development of promising EBC materials with improved corrosion resistance.
Highlights
SiC-based ceramic matrix composites (CMC-SiC) are promising candidates to replace Ni-based superalloys for application in engine hot sections due to their superior specific strength and oxidation resistance at elevated temperatures [1,2]
The X-ray diffraction (XRD) patterns of the synthesized (5RE)2Si2O7 powders for all silicon content was high (Si) to RE molar ratios show that a disilicate phase with a β polymorph structure was obtained (Fig. 1)
(5RE)2Si2O7 indicated that the multicomponent disilicate would have good high-temperature stability, which is crucial for the application of Environmental barrier coating (EBC)
Summary
SiC-based ceramic matrix composites (CMC-SiC) are promising candidates to replace Ni-based superalloys for application in engine hot sections due to their superior specific strength and oxidation resistance at elevated temperatures [1,2]. Rare-earth (RE) disilicates are considered as promising materials for EBC applications due to their good corrosion resistance, similar coefficient of thermal expansion (CTE) as CMC-SiC, and excellent high-temperature stability [7,8,9,10,11]. Β-RE2Si2O7 (RE = Sc, Lu, and Yb) and γ-Y2Si2O7 showed similar CTEs to SiC [7] and no polymorphs at elevated temperatures [8,9,10,11], both of which are key requirements for EBC materials. For individual RE2Si2O7 materials, different propensities for reaction-crystallization into apatite were observed due to the varying affinities between the RE elements and Ca. The mechanisms of reactioncrystallization or penetration into grain boundaries depend mainly on the different RE-disilicates and interaction temperatures
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