Preparation of oxidation-protective SiC coatings for C/SiC composites by pulsed chemical vapor deposition

摘要

Single-layer SiC coatings and multilayer (C/SiC)_n coatings for oxidation protection of C/SiC composites were prepared by a pulsed chemical vapor deposition (pulsed CVD) method,a modification of pulsed chemical vapor infiltration (pulsed CVI). Pulsed CVD enabled the original pores in the substrates to be filled by the coatings,which contributed to improved adhesion between the coatings and the substrates. No deposition defects were observed in the dense SiC coatings. Multilayer (C/SiC)_n coatings could dissipate thermal stresses in the coatings,which reduced the number and width of micro-cracks in the coatings and accordingly improved the oxidation-protection capability of the coatings. Oxidation tests in dry air showed that the oxidation resistance of the coated composites was significantly improved compared with that of the uncoated ones.