1. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
2. Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics,Chinese Academy of Sciences, Shanghai 200050, China
3. School of Physical Science and Technology,ShanghaiTech University,Shanghai 200031, China
The mechanical properties of continuous silicon carbide fiber reinforced silicon carbide matrix composites(SiCf / SiC) decrease rapidly under high-temperature
wet oxygen environment due to the corrosion from wet oxygen,which limits the long-life service of the hot end components in aero-engines. It is confirmed that the corrosion of SiC generates gas phase Si(OH)4, which leads to mass dissipation.Therefore, it has been a research hotpot that how to improve the wet-oxidation resistance in terms of composition and structure regulation. This paper contrasted the oxidation behaviors of SiC ceramics with and without Y2O3 addition under wet oxygen environment. Compared with SiC ceramics, the
oxidation rates and the volatilization rates of SiC-Y2O3 ceramics decrease significantly and the difference between the two becomes more obvious with the increase of oxidation temperature. It can be seen that the wet-oxidation resistance of SiC ceramics is improved dramatically by adding Y2O3. The microstructures analyses show that the oxide layer of SiC-Y2O3 ceramics is thinner and denser. The further analyses indicate that these results from the migration and aggregation of Y-contained phase towards the surface of SiC-Y2O3 ceramics. During the oxidation process, the Y2O3 in the ceramic can migrate to the surface and react with SiO2 to form β-Y2Si2O7. Finally, the β-Y2Si2O7 aggregates on the surface of the oxide layer to form a continuous
β-Y2Si2O7 layer. Therefore, a Y2Si2O7 / Y2O3-rich layer is formed at the junction of the oxide layer and the ceramic matrix.The multilayer Y-contained layers can inhibit the corrosion of wet oxygen spreading to the inner matrix. This study provides important ideas for the design and regulation of wet-oxidation resistant SiCf / SiC composites.