EFFECTS OF PREFORM STRUCTURES ON RHENIUM COATING PREPARED ON C/C COMPOSITES BY CHEMICAL VAPOR DEPOSITION

摘要

Rhenium coating is prepared on the surface of C/C composites either as a protective coating to improve scour resistance or as a transition layer before preparing anti-oxidation iridium coating. In this study, rhenium coatings were prepared on C/C composites of three different preform architectures by chemical vapor deposition. Surface morphologies of C/C and the distributions of cracks in the rhenium coatings were studied by scanning electron microscopy. The results show that interfaces between Cf bundles in different C/C have different distributions, which greatly influence the prolongations of cracks in the rhenium coating of different C/C composites. The cracks between the Cf bundles in the C/C, called the original-cracks are often the ancestors for the cracks in the rhenium coating. Besides, the location and extended direction of the cracks in the coatings are consistent with the interface distribution. The pores in the C/C are also the sources for the cracks in the rhenium coating owing to stress concentration during the cooling process, so the density of the C/C has a noticeable effect on the rhenium coating.