Microstructural-property correlation of CVI processed Cf/SiC composites and property enhancement as a function of CVD SiC seal coating

Abstract Carbon fiber reinforced silicon carbide composites were prepared by an isothermal chemical vapour infiltration (ICVI) process. The test samples were seal coated by SiC by the chemical vapour deposition process. The nature of pyrocarbon coating (as an interphase) was studied before the infiltration of SiC matrix by a CVI process. The effect of protective SiC seal coating was examined by testing the uncoated and the seal coated samples for flexural properties, coefficient of thermal expansion (CTE) and pore size distribution. The microstructure-property correlation of the flexural test samples showed that the seal coating protected the carbon fibers from oxidation, which resulted in the significant improvement in the flexural strength value at the test temperatures as compared to the uncoated samples. Relatively lesser value of the coefficient of thermal expansion was observed for the seal coated sample.