Ablation behavior of CVD-TaC coatings with different crystal structures for C/C composites under oxyacetylene flame

TaC coatings with four kinds of crystal structures were prepared on carbon/carbon composites by chemical vapor deposition. The surface morphologies, microstructure transformation, and ablative behaviors of TaC coated C/C specimens were investigated. Results show that the coatings with acicular crystal structure exhibit better ablation resistance with lower ablation rates, especially the needle-piled sample. The bistratal structure composed of dense glass layer and compact TaC layer is beneficial for maintaining the integrity of acicular samples after ablation. But the formation of lamella grains and porous middle layer is the main factor for the damage and even exfoliation of the columnar specimens.