One-step preparation and ablation behavior of ZrC-SiC-Si coating for nose-shaped ZrC/C composites with gradient pore structure by vapor silicon infiltration

To improve the ablation resistance of the nose-shaped ZrC/C composites with gradient pore structure (ZrC/C-GS), a ZrC-SiC-Si coating was prepared by one-step vapor silicon infiltration. The bonding strength between the ZrC-SiC-Si coating and the ZrC/C-GS composite was 21.2 MPa. The hardness and elastic modulus of the ZrC-SiC-Si coating were 1650.5 +/- 30.5 HV and 176.7 +/- 3.2 GPa. As the temperature increased from 200 to 1500 degrees C, the CTE of the ZrC-SiC-Si coated ZrC/C-GS composites increased from 4.9 x 10(-6) K-1 to 6.18 x 10(-6) K-1. After ablation for 40 s using oxyacetylene torch with a heat flux 2.4 MW/m(2), the linear ablation rate of the ZrC-SiC-Si coated ZrC/C-GS composites decreased by 54.8% compared with that of the ZrC/C-GS composites, and it could be maintained at 97.4% of the original heat resistance capacity. The finite element simulation results showed that the residual thermal stresses at the coating/matrix interface were in the range of 10.7-20.2 MPa. After ablation for 40 x 3 s, the ZrC-SiC-Si coating failed.