SiC/ZrB2-SiC-B4C涂层的抗氧化和耐烧蚀性能研究

Oxidation and ablation resistance of SiC/ZrB2-SiC-B4C coatings for C/SiC composites

摘要:

碳/碳化硅复合材料(C/SiC)在使用时经常受到高温氧化和烧蚀作用。本文采用化学气相沉积(CVD)和浆料刷涂-烧结法制备了双层SiC/ZrB2-SiC-B4C涂层,对比研究了无涂层,单层SiC涂层和双层SiC/ZrB2-SiC-B4C涂层C/SiC复合材料在1500℃下的氧化和在4.2 MW/m2热流密度下的烧蚀性能。结果表明,制备态ZrB2-SiC-B4C涂层致密、完整,表面平均粗糙度约为1 μm,孔隙率约为4.2 %。在1500℃氧化30 h后,SiC/ZrB2-SiC-B4C涂层C/SiC复合材料的质量损失率约为10%,涂层表面氧化膜致密,无明显裂纹。高温烧蚀20 s后,SiC/ZrB2-SiC-B4C涂层的线烧蚀率和质量烧蚀率分别为1.0±0.3 μm/s和1.1±0.2 mg/s,与单层SiC涂层相比分别降低了75.0 %和50.0 %,SiC/ZrB2-SiC-B4C涂层烧蚀后形成的ZrO2-SiO2氧化膜可以减缓火焰对复合材料的机械剥蚀作用。

Abstract:

Carbon/silicon-carbide composites (C/SiC) usually suffer from high-temperature oxidation and ablation. In this study, double-layered SiC/ZrB2-SiC-B4C coatings were fabricated by chemical vapor deposition (CVD) and slurry painting-sintering methods. The naked, single-SiC coated and SiC/ZrB2-SiC-B4C double-layered C/SiC composites were oxidized at 1500 °C and ablated under a heat flux of 4.2 MW/m2. The results indicated that the slurry-painted ZrB2-SiC-B4C coating was dense and intact, which had a surface roughness of ~ 1 μm in Ra and the porosity of ~ 4.2 %. After oxidation at 1500 °C for 30 h, the mass loss rate of SiC/ZrB2-SiC-B4C coated C/SiC composite was ~ 10 %. The oxidation scale on the coating surface is compact without obvious cracking. After ablation for 20 s, the linear and mass ablation rates of SiC/ZrB2-SiC-B4C coating were separately 1.0±0.3 μm/s and 1.1±0.2 mg/s, decreased by 75.0 % and 50.0 % relative to the SiC coating. The formed ZrO2-SiO2 scale provided a protection against the mechanical erosion from the flame.