C/C复合材料密度及预氧化处理对SiC涂层的影响

采用包埋法分别在密度为0.8、1.4和1.8 g/cm³的炭/炭(C/C)复合材料表面制备SiC涂层,选择密度为1.8 g/cm³的试样研究预氧化处理对涂层结构和抗氧化性能的影响。利用扫描电子显微镜和X射线衍射仪研究涂层的显微组织和物相组成,用1500℃静态空气氧化方法测试涂层的抗氧化性能。结果表明,随C/C复合材料密度增大,涂层嵌入基体的深度越小,涂层与基体的分界越明显。密度为1.8 g/cm³的C/C复合材料进行预氧化处理后,表面粗糙度增大,表面的炭纤维周围产生了环形孔隙,再经过包埋制备SiC涂层,涂层厚度增加且更加均匀致密。将样品于1500℃静态空气中氧化334 h后,氧化质量损失率为0.684×10^?4 g/(cm²·h),氧化后表面生成了莫来石相,抗氧化性能有明显提升。

Effect of the density of C/C composites and pre-oxidation process on SiC coatings

SiC coatings were prepared on the surface of carbon/carbon(C/C)composites with densities of 0.8,1.4 and 1.8 g/cm³ by the pack cementation.The samples with a density of 1.8 g/cm³ were selected to research the effect of pre-oxidation treatment on structure and oxidation resistance of the coating.Scanning electron microscope and X-ray diffractometer were used to study the microstructure and phase composition of the coating.The anti-oxidation resistance of the coating was tested by static air oxidation at 1500℃.The results show that as the density of the C/C composites increases,the thickness of the coating decreases,and the boundary between the coating and the substrate becomes more obvious.After the pre-oxidation treatment of 1.8 g/cm³ C/C composites,the surface roughness increases,and the ring pores around the carbon fibers on the surface are generated.After pack cementation process,the thickness of coating increases and becomes more uniform and compact.After the sample is oxidized in static air at 1500℃for 334 h,the oxidation mass loss rate is 0.684×10^?4 g/(cm²·h).The mullite phase is formed on the surface of the sample,and the oxidation resistance was significantly improved.