硅钽含量对C/C复合材料SiC/TaSi_2复合涂层结构和抗氧化性能的影响

Effect of Si/Ta Ratio on the Microstructure and High Temperature Anti-Oxidation Property of SiC/TaSi_2 Coating for Carbon/Carbon Composites

采用包埋技术在C/C复合材料表面制备SiC/TaSi2抗氧化复合涂层,通过恒温氧化实验以及X射线衍射分析、扫描电镜观察,研究了包埋粉料中硅钽含量对复合涂层微观结构和高温抗氧化性能的影响。结果表明,随着硅钽比的减小,复合涂层的厚度先增大后减小;硅钽比为5:1所制备的复合涂层具有相对较大的厚度和较为致密的结构,且TaSi2含量相对较高,体现出优良的抗氧化和抗热震性能,在1500℃氧化241.8h和经过18次1500℃室温急冷急热后,带有该涂层的C/C试样失重仅为1.04%。穿透性裂纹的形成是长时间氧化后涂层失效的主要原因。

A SiC/TaSi2 multilayer oxidation protective coating for carbon/carbon （C/C） composites was prepared by pack cementation. Effect of the content of Si and Ta in the second-step pack powders on the microstructure and high temperature anti-oxidation property of the multi-coating was studied by XRD, SEM and isothermal oxidation test. The results show that with the ratio of Si and Ta decreasing, the as-received multi-coating thickness first increases and then decreases. The multi-coating prepared at the ratio of 5：1 of Si and Ta has a thicker, denser structure and higher content of TaSi2 than those prepared at the ratio of 6：1, 4：1 and 3：1. After 241.8 h oxidation in air at 1500 ℃ and thermal cycling between 1500 ℃ and room temperature for 18 times, the weight loss of the coated specimen was only 1.04%, implying that the multi-coating prepared at the ratio of 5：1 of Si and Ta has excellent oxidation protective ability and thermal shock resistance. The oxidation protective failure of the SiC/TaSi2 coating was attributed to the formation of some penetrable cracks in the coating after a long time of oxidation.