La2O3改性ZrB2-SiC涂层C/C复合材料全温域抗氧化行为研究

Antioxidant Behavior of La2O3 Modified ZrB2-SiC Coating for C/C Composites at Full Temperature

采用高温反应熔渗工艺制备了ZrB2-SiC和La2O3改性ZrB2-SiC涂层C/C复合材料,对比了2种涂层试样在中温(7001100℃)、高温(12001500℃)和超高温(2000℃以上)3个温域范围内的抗氧化性能。结果表明:7001100℃范围内,随着温度的升高,La2O3改性涂层试样的抗氧化性能提升幅度在逐渐提高。1200℃1500℃范围内,涂层均表现出良好的长时抗氧化性能,La2O3改性ZrB2-SiC在1200℃下恒温氧化250 h后,仍保持微量的增重;涂层复合材料良好的高温抗氧化性能主要其在是由于氧化过程中涂层表面形成的La-Si-O复合玻璃层和钉扎相ZrSiO4的协同作用提升了氧化膜的高温稳定性。在2000℃以上的氧乙炔火焰烧蚀环境下,La2O3的添加使得ZrB2-SiC涂层的质量烧蚀率和线烧蚀率均降低了近50%,其主要归因于表层La-Si-O和ZrO2玻璃层对烧蚀缺陷的愈合作用。

ZrB2-SiC and La2 O3 modified ZrB2-SiC coated C/C composites were prepared by high temperature reactive infiltration process.The oxidation resistance of the two coated samples in three temperature ranges,i.e.medium temperature(7001100℃),high temperature(12001500℃)and super high temperature(over 2000℃),was compared.The results show that the oxidation resistance of La2 O3 modified coatings increases gradually with the increase in temperature between 7001100℃.The coating exhibits good long-term oxidation resistance in the range of 12001500℃.Slight mass gain occurs in the ZrB2-SiC modified by La2 O3 after 250 h oxidation at 1200℃The excellent oxidation resistance at high temperature is mainly due to the combined effect of La-Si-O composite glass layer and pinning phase ZrSiO4 formed on the surface of the coating during oxidation,which improves the high temperature stability of the oxide film.The mass and linear ablation rates of ZrB2-SiC coatings are reduced by nearly 50%with the addition of La2 O3 under oxyacetylene flame ablation environment above 2000℃,this is mainly attributed to the healing effect of La-Si-O and ZrO2 glass layers on ablation defects.