Influence of MoSi 2 content in suspension on the phase, microstructure and properties of hydrothermal electrophoretic deposited SiC n –MoSi 2 coating for SiC pre-coated C/C composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a nano SiC–MoSi 2 (SiC n –MoSi 2 ) coating on SiC pre-coated C/C composites was prepared by hydrothermal electrophoretic deposition. The phase composition, surface and cross-section microstructures of the prepared SiC n –MoSi 2 coating deposited with different MoSi 2 /SiC n mass ratio were characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The influence of MoSi 2 content in the hydrothermal electrophoretic deposition suspension on the phase composition, microstructure and high-temperature oxidation resistance of the multi-layer coatings were investigated. Results showed that the content of MoSi 2 phase in the prepared coating increases with the increase of MoSi 2 content in the suspension. The density and oxidation resistance of the SiC n -MoSi 2 coating improve with the increase of MoSi 2 mass content from 20 to 60 wt% in the deposition suspension. However, micro-cracks and micro-holes in the coating are found when deposited with 80 wt% MoSi 2 , and a decrease in oxidation resistance was also detected. The multi-layer coatings deposited with suspension of 60 wt% MoSi 2 exhibited the best anti-oxidation ability, which can effectively protect C/C composites from oxidation in air at 1,873 K for 90 h with weight loss of 2.08%.