Comparisons of SiC and TiC inner coatings of three layers composite coatings on the surface of carbon fiber reinforced carbon composites

SiC or TiC first layer (inner) coatings as a bond layer and SiC+TiC composite external (top) coating with a interlayer of SiC or TiC on the surface of carbon fiber reinforced carbon (C/C) composites were prepared by pack cementation technique in an argon atmosphere. The surface topography and the cross-section structure of the coatings were evaluated using a field emission scanning electron microscopy and X-ray diffraction. The elements existed in the coatings were analyzed by energy-dispersive spectroscopy. The results indicate that the TiC inner coating is thin and it adhered with C/C base weakly. Compared with TiC inner coating the SiC inner coating is thicker and compacted, and it is with a porous structure and adhered with C/C base tightly. The thick composite top SiC+TiC coating is composed of SiC, TiC and Ti₃SiC₂.