Sublayer design and ablation resistance of CVD-TaC alternate coatings with different crystallite morphologies for C/C composites

Tantalum carbon (TaC) alternate coatings with sublayers comprised of different crystallite morphologies were prepared on carbon/carbon composites by chemical vapor deposition. Their ablative behaviors and defending mechanisms were both investigated. The specimen with the sublayer composed of columnar crystals exhibited a better ablation resistance due to the toughness enhancement induced by the laminated structure. However, the mechanical denudation of the sample only containing acicular crystals and the coating spallation caused by superfluous gaseous products of the sample with the sublayer composed of nanocrystals both indicate their inferior anti-ablation properties. It is believed that the results will be helpful for the structural design and practical application of chemical vapor deposition (CVD) alternate coatings.