Siliconization elimination for SiC coated C/C composites by a pyrolytic carbon coating and the consequent improvement of the mechanical property and oxidation resistances

• Published in: Journal of the European Ceramic Society Vol. 41; no. 10; pp. 5046 - 5055
• Main Authors: Li, Tao, Zhang, Yulei, Fu, Yanqin, Sun, Jia, Li, Jie
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2021
• Subjects: Carbon/carbon composites; Mechanical property; Oxidation resistance; Pyrolytic carbon coating; Silicon carbide coating; Siliconization; Siliconization; Oxidation resistance; Silicon carbide coating; Pyrolytic carbon coating; Mechanical property; Carbon/carbon composites
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2021.04.008

•A homogeneous PyC coating can improve the flexural strength of SiC coated C/C composites, and its strength retention reached 107.95 %.•The existence of PyC coating can adequately react with molten silicon to form dense SiC coating without silicon phase.•The lower coefficient of thermal expansion of SiC coated C/C sample with PyC coating was helpful to maintain defect-free structure during dynamic oxidation. Carbon/carbon (C/C) composites have a wide application as the thermal structure materials because of their excellent properties at high temperatures. However, C/C composites are easily oxidized in oxygen-containing environment, which limits their potential applications to a great degree. Silicon carbide (SiC) ceramic coating fabricated via pack cementation (PC) was considered as an effective way to protect C/C composites against oxidation. But the mechanical properties of C/C composites were severely damaged due to chemical reaction between the molten silicon and C/C substrate during the preparation of SiC coating by PC. In order to eliminate the siliconization erosion, a pyrolytic carbon (PyC) coating was pre-prepared on C/C composites by the chemical vapor infiltration (CVI) prior to the fabrication of SiC coating. Due to the retardation effect of PyC coating on siliconization erosion, the flexural strength retention of the SiC coated C/C composites with PyC coating increased from 46.27 % to 107.95 % compared with the specimen without PyC coating. Furthermore, the presence of homogeneous and defect-free PyC coating was beneficial to fabricate a compact SiC coating without silicon phase by sufficiently reacting with molten silicon during PC. Therefore, the SiC coated C/C composites with PyC coating had better oxidation resistances under dynamic (between room temperature and 1773 K) and static conditions in air at different temperatures (1773−1973 K).