Discussion on structural parameters of the multilayer ZrC/TaC coatings based on stress analysis and ablation behaviors

The multilayer ZrC/TaC ablation resistant coatings with different layers were designed and fabricated on the SiC coated carbon/carbon composites by plasma spraying. Based on stress distribution and ablation performance under heat flux of 2.4 MW/m2, structural parameters of the multilayer ZrC/TaC coatings (total thickness d, number of layers n and thickness ratio R) were discussed and optimized. When R was equal to 1 and d was ~300 μm, the multilayer ZrC/TaC coating with three layers (n = 3) exhibited moderate stress distribution and the best ablation resistance, induced by the ZrC anti-scouring layer with sufficient thickness and effective crack deflection at the interface. The optimized structural parameters for multilayer ZrC/TaC system are considered as follows: (i) the larger d value was beneficial to reducing the residual thermal stress during ablation process; (ii) d/n for the ZrC layer was between 100–150 μm, while d/n for the TaC layer was between 40–100 μm.