C/C复合材料SiC涂层裂纹形貌及分布的研究

由于涂层与C/C复合材料之间热膨胀系数不匹配,当冷却至室温时在高温下制备的抗氧化涂层会产生裂纹,为分析涂层裂纹的组态,通过在碳毡和真空穿刺两种C/C复合材料基体上制备单层、双层SiC涂层来研究涂层裂纹的形貌及分布.利用金相显微镜和扫描电镜观察两种涂层裂纹的形貌和分布,解释了裂纹与涂层所受热应力及基体原有缺陷的关系,利用XRD分析了单层和双层涂层的成分,说明了不同类型SiC结构与涂层裂纹之间的联系.结果表明涂层裂纹分布及裂纹宽度与基体纤维方向有关；随着涂层厚度增大,微裂纹数量减少；基体原有缺陷会导致涂层产生穿透性裂纹.

Crack Morphology and Distribution of SiC Coating on Carbon/Carbon Composites

Due to the mismatch of the thermal expansion coefficient between the coating and carbon/carbon composites,coating cracks inevitably appeared when the coating was cooled from the production temperature to the ambient temperature.To study the coating crack configuration,single-layer and double-layer SiC coatings on carbon-felt C/C composite and intertexture C/C composite were prepared,and the crack morphology and distribution were investigated.The optical microscope and scanning electron microscope were used to discuss the crack morphology and distribution,to explain the relationship of the coating cracks with the thermal stress on the coating and substrate defects.The XRD method was conducted to analyze the ingredient of single-layer and double-layer SiC coating,to describe the relationship of different types of SiC coating structure with the coating cracks.The results showed that the crack distribution and spacing were related to the fiber direction of substrate.With the increase of coating thickness,the number of cracks decreased.The intrinsic defects on the substrate would cause through-the-thickness cracks in the coating.