SiC/Si–MoSi2 oxidation protective coatings for carbon materials

In order to improve the oxidation resistance of carbon material, a SiC/Si–MoSi2 oxidation protective coating was prepared on graphite substrate. The graphite substrate was firstly infiltrated with silicon in vacuum atmosphere to obtain 220 μm thickness SiC inner layer, and 80 μm thickness Si–MoSi2 outer layer was made by using a Si–Mo slurry. The effect of Mo/Si of slurry and SiC inner layer on the oxidation resistance of coating was studied. Results indicated that the as-received coating with the Mo/Si of 40% in the slurry has excellent oxidation protection for long life at 1673 K in air. The SiC inner layer acts as a barrier to prevent the infiltration of liquid Si into the pores of the graphite substrate during the sintering of the outer layer and is beneficial to maintain the Mo/Si of 40% in the slurry. The improvement of coating properties can be attributed to the well-coating microstructure. The mechanism of the oxidation resistance of the coated graphite is also discussed.