Synthesis of SiC Coatings and Evaluation of Their Emissivity

Thermal protection coatings are one of the important parts of thermal protection system (TPS) for hypersonic vehicles. The coatings with high emissivity can enhance the thermal protection effect of TPS. SiC coatings were prepared by mixing SiC and Co3O4 mixture slurry into Al2O3 sol-gel on the nickel superalloy surface by the method of dip-coating. The microstructures of coatings were investigated by scanning electron microscope (SEM). The emissivity of SiC coatings was measured by Fourier transform infrared spectrometer. The relationship between emissivity and thickness of coatings was examined. The results show that SiC-Co3O4 coatings have high emissivity at full-wave band. When the thickness of coatings is 20 similar to 30 mu m, SiC-Co3O4 coatings take on the highest emissivity.