Effect of SiC whiskers on the anti-oxidation properties of Yb2Si2O7/mullite/SiC tri-layer environmental barrier coating for CMCs |
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| Authors: | Ling Pan Pengju Chen Peng Xiao Ling He Wei Zhou Yang Li |
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| Affiliation: | 1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China;2. School of Nuclear Science and Technology, University of South China, Hengyang, China;3. College of Metallurgy and Materials Engineering, Hunan University of Technology, Zhuzhou, China |
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| Abstract: | The mullite and ytterbium disilicate (β-Yb2Si2O7) powders as starting materials for the Yb2Si2O7/mullite/SiC tri-layer coating are synthesized by a sol–gel method. The effect of SiC whiskers on the anti-oxidation properties of Yb2Si2O7/mullite/SiC tri-layer coating for C/SiC composites in the air environment is deeply studied. Results show that the formation temperature and complete transition temperature of mullite were 800–1000 and 1300°C, respectively. Yb2SiO5, α-Yb2Si2O7, and β-Yb2Si2O7 were gradually formed between 800 and 1000°C, and Yb2SiO5 and α-Yb2Si2O7 were completely transformed into β-Yb2Si2O7 at a temperature above 1200°C. The weight loss of Yb2Si2O7/(SiCw–mullite)/SiC tri-layer coating coated specimens was 0.15 × 10?3 g cm?2 after 200 h oxidation at 1400°C, which is lower than that of Yb2Si2O7/mullite/SiC tri-layer coating (2.84 × 10?3 g cm?2). The SiC whiskers in mullite middle coating can not only alleviate the coefficient of thermal expansion difference between mullite middle coating and β-Yb2Si2O7 outer coating, but also improve the self-healing performance of the mullite middle coating owing to the self-healing aluminosilicate glass phase formed by the reaction between SiO2 (oxidation of SiC whiskers) and mullite particles. |
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| Keywords: | anti-oxidation β-Yb2Si2O7 coating mullite SiC whisker |
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