Influence of sublayer number on the ablative behaviors and synergistic effect of CVD-TaC/SiC alternate coatings

In this work, TaC/SiC alternate coatings with different sublayer numbers were fabricated on C/C composites by chemical vapor deposition, whose ablation resistance and defect tolerance under oxyacetylene torch can be improved by structural optimization. The two-layer sample with less layer number presented coating spallation owing to the incomplete relaxation of thermal stress, and the six-layer specimen exhibited mechanical denudation of TaC outer layer induced by its thinner thickness, which both indicate their inferior ablative performances. However, the toughness elevation of alternate structure, the synergistic effect of SiO₂-Ta₂O₅ compound oxide and the sublayer reliability of TaC for anti-scouring as well as SiC for oxygen-barrier all result in the better ablation resistance of the four-layer specimen. These results can provide reference values for the structural design of high-temperature applications.