Effect of depositing position on microstructure of SiC coating by chemical vapor deposition

Using CH₃SiCl₃(MTS) and H₂ as precursors, SiC coating was prepared on the surface of C/C composites by chemical vapor deposition (CVD) under normal atmosphere pressure. The microstructures and phase compositions of the CVD-SiC coating at different depositing positions were measured by scanning electron microscopy and X-ray diffraction. The qualitative relation between the depositing position and the supersaturating degree of MTS was deducted, and the effects of the supersaturating degree of MTS on the microstructures, crystal dimensions and thickness of CVD-SiC coating were analyzed. The results indicate that along the gas flow direction in the CVD hearth, the microstructures of β-SiC coating change from grains to whiskers, and the crystal dimensions and coating thickness decrease gradually.