包覆法制备G_p/SiC复合材料的显微结构和性能

Microstructure and properties of G_p/SiC composite by coating method

以不同粒径的石墨颗粒和SiC粉体为原料,采用SiC粉体包覆石墨颗粒的方法,于2000℃热压制备了石墨/碳化硅(Gp/SiC)复合材料.利用扫描电子显微镜(SEM,EDS)分析了材料的金相和断口显微结构.研究表明,石墨粒径较小且质量分数较少的复合材料比石墨粒径较大且质量分数较多的复合材料在热压工艺中更致密.石墨颗粒呈岛状紧密地镶嵌在SiC基体中,石墨与SiC界面处C和Si的扩散不明显.复合材料的相对密度、抗折强度,断裂韧性和硬度随石墨粒径和质量分数的减少而增加.断口形貌表明SiC陶瓷基体为脆性,石墨为韧性断裂.当石墨粒径为125μm、SiC与石墨的质量比为3.5时,复合材料的综合性能最佳,开口气孔率为0.3%,相对密度为97.9%,抗折强度为75±15 MPa,断裂韧性为5.4±0.5 MPa.m1/2,硬度为26.8±3GPa.

Gp/SiC composites have been prepare with such raw materials as the graphite particle of different size and SiC powder by coating and hot-pressing process at 2 000 ℃.The microstructure and fracture morphology were measured by scanning electron microscopy（SEM） and electron energy spectrum（EDS）.The results show that small size graphite particles and less graphite content improves the densification behavior of the composites during the hot-pressing process,compared with that of large size graphite particles and more graphite content.The graphite particles are embedded tightly in the SiC matrix as the islands,and the diffusion of C atom and Si atom is not obvious located the interface of graphite cores and SiC matrix.The fractograph exhibited typical ductile fracture of graphite,while the brittle fracture of SiC.The relative density,flexural strength,fracture toughness,and hardness increase with particle size of graphite and graphite content decreasing.The apparent porosity,relative density,flexural strength,fracture toughness,and hardness of the composite are 0.3%,97.9%,75±15 MPa,5.4±0.5 MPa·m1/2,26.8±3 GPa,respectively,which containing the mass rate of SiC and graphite of the size 125 μm is 3.5.