烧结助剂对ZrSiO_4-Mullite复合涂层组织结构及抗氧化性能的影响

Effect of Additives on Microstructure and Oxidation Resistance of ZrSiO_4-Mullite Multi-layer Coating

采用包埋法和预涂-烧结法相结合的组合工艺在C/C复合材料表面制备出ZrSiO4-Mullite复合涂层,借助XRD、SEM、体式显微镜对涂层组织结构进行了表征,研究了(MgO+CeO2)、(Si+SiO2)和(Mullite+SiO2)三种烧结助剂对复合涂层组织结构和抗氧化性能的影响,揭示了涂层C/C试样的氧化失重原因。结果表明:ZrSiO4-Mullite复合涂层具有双层结构,内层由β-SiC相和α-SiC相组成,外层主要由Mullite相和ZrSiO4相构成。分别采用(MgO+CeO2)、(Si+SiO2)和(Mullite+SiO2)烧结助剂制得的ZrSiO4-Mullite涂层的开裂倾向依次减弱,抗氧化性能依次增强。涂层裂纹的存在是造成ZrSiO4-Mullite涂层C/C试样氧化失重的主要原因。

A ZrSiO4-Mullite multi-layer coating was fabricated on the carbon/carbon（C/C）composites by using the pack cementation technique and the procoating-sintering process. The as-prepared multi-layer coating was characterized by XRD, SEM and optical microscope analysis. The effect of different sintered-additives, such as （MgO＋CeO2）, （Si＋SiO2） and （Mullite ＋ SiO2）, on the microstructure and oxidation resistance of multi-layer coated C/C composites was investigated respectively. The oxidation reason for multi-layer coated C/C composites was discussed finally. The results indicated that the multi-coating was composed of two layers. The inner layer was consisted by β-SiC phase and （α-SiC phase. The outer layer was primarily composed of Mullite and ZrSiO4. The crack content in different ZrSiO4-Mullite coatings, prepared orderly and respectively with sintered-additives of （MgO＋CeO2）, （Si ＋ SiO2） and （Mullite ＋ SiO2）, was decreased gradually. However, the oxidation resistance of those three ZrSiO4-Mullite coatings was increased in turn. The oxidation of ZrSiO4-Mullite multi-layer coated C/C composites was controlled by the diffusion of oxygen in the coating cracks.