两步包埋法制备C/C复合材料SiC/Cr-Al-Si涂层研究

采用两步包埋法在碳/碳复合材料表面制备了SiC/Cr-Al-Si涂层.采用XRD、SEM和EDS分析了涂层的物相组成、微观结构及断面元素分布,测试了双涂层碳/碳复合材料试样在1 500℃静态空气中的抗氧化性能.结果表明:SiC/Cr-Al-Si涂层主要由SiC、AlCr2Si及Al4Si2C三相组成,厚度约为120μm,无穿透性裂纹;与一步包埋法所得SiC涂层相比,SiC/Cr-Al-Si涂层碳/碳复合材料试样的抗氧化性能有所提高,该涂层试样氧化12 h后的失重不超过5%.两步包埋法所得SiC/Cr-Al-Si涂层表面存在微裂纹,并且包埋过程易于使Cr-Al-Si合金成分扩散到SiC涂层内部,从而无法形成内SiC涂层、外Cr-Al-Si涂层的双层涂层结构,降低了Cr-Al-Si合金涂层对C/C复合材料基体的高温氧化保护效果.

Preparation of SiC/Cr-Al-Si coating for C/C composites by two-step pack cementation method

SiC/Cr-Al-Si anti-oxidation coating on the surface of carbon-carbon composites is prepared by two-step pack cementation method.The phase compositions,microstructure and element distribution on the section of samples of the received SiC/Cr-Al-Si coating are studied by XRD,SEM,and the isothermal oxidation test of samples in air is finished at 1 500℃.The study results show that a SiC/Cr-Al-Si coating of 120 mm thickness is obtained,which consists of mainly three phases of SiC,AlCr2Si and Al4Si2C.Compared with the SiC coating prepared by one-step pack cementation method,the SiC/Cr-Al-Si coating prepared by two-step pack cementation method shows better oxidation resistance.The weight loss of the carbon-carbon sample with SiC/Cr-Al-Si coating is less than 5% after oxidizing for 12 hours.There are microcracks in the SiC/Cr-Al-Si coating,which is thought the main reason why the received SiC/Cr-Al-Si coating failed.In the secondary pack cementation,Cr-Al-Si diffuses into SiC coating but not covers on SiC coating,which is though the other reason why the received SiC/Cr-Al-Si coating failed.