Ablation resistance and mechanism of SiC/ZrC-ZrB 2 double layer coating for C/C composites under plasma flame
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Ablation resistance and mechanism of SiC/ZrC-ZrB2 double layer coating for C/C composites under plasma flame LIU Han-zhou(刘汉周)1, YANG Xin(杨鑫)1, 2, FANG Cun-qian(方存谦)1, SHI An-hong(石安红)1, CHEN Lei(陈蕾)1, HUANG Qi-zhong(黄启忠)1 1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 2. Science and Technology of Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: To improve the ablation resistance of carbon/carbon (C/C) composites, a SiC/ZrC-ZrB2 double layer coating was fabricated by pack cementation and slurry-sintering method. The ablation resistance of the SiC/ZrC-ZrB2 coating was tested under plasma flame above 2300 °C. The results indicate that the SiC/ZrC-ZrB2 double layer coating exhibits superior ablation resistance than the ZrC-ZrB2 single layer coating. After being ablated under the plasma flame for 20 s, the mass and linear ablation rates of the ZrC-ZrB2 coating are 0.89 mg/s and 15.3 μm/s, while those for SiC/ZrC-ZrB2 coating are 0.09 mg/s and 24.15 μm/s, respectively. During ablation, the SiC inner layer can generate SiO2 glass and result in the formation of ZrO2-SiO2 molten film. Compared with the ZrO2 molten film formed on the ZrC-ZrB2 coating surface, the ZrO2-SiO2 molten film with lower oxygen diffusion rate and viscosity enables the SiC/ZrC-ZrB2 coating to have better self-healing ability. Therefore, the enhanced ablation resistance of the SiC/ZrC-ZrB2 coating can be attributed to the formation of dense ZrO2-SiO2 molten film under the plasma flame. Key words: ablation; pack cementation; slurry; SiC/ZrC-ZrB2 coating Cite this article as: LIU Han-zhou, YANG Xin, FANG Cun-qian, SHI An-hong, CHEN Lei, HUANG Qi-zhong. Ablation resistance and mechanism of SiC/ZrC-ZrB2 double layer coating for C/C composites under plasma flame [J]. Journal of Central South University, 2020, 27(9): 2538−2547. DOI: https://doi.org/10.1007/s11771-020-4479-7.
1 Introduction Owing to excellent thermal shock resistance, high thermal conductivity and low density, carbon/carbon (C/C) composites are considered the most promising candidate thermal structural components applied in aerospace and astronautics area such as engine nozzles and heat protection systems [1−8]. However, the rapid oxidation of C/C composites in an oxidizing atmosphere above 500 °C results in degradation of their high temperature performance [9−11]. Therefore, to
extend their application in severe environment, it is essential to improve the ablative property of C/C composites. At present, preparing an ablative coating that isolates the C/C composites and the external atmosphere is an effective method to improve the ablation resistance of the C/C composites [1, 5, 12, 13]. Among the developed anti-ablation coatings, Zr-base ultra-high temperature ceramics (such as ZrB2 and ZrC) are the attractive coating material due to their high melting point
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