Influence of MoSi2on oxidation protective ability of TaB2-SiC coating in oxygen-containing environments within a broad temperature range

TaB2-SiC coating modified by different content of MoSi(2)was fabricated on graphite substrate with SiC inner coating by liquid phase sintering to elevate the anti-oxidation capability of the TaB2-SiC coatings. As compared to the sample with the TaB2-40wt%SiC coating, the coating sample modified with MoSi(2)exhibited a weight gain trend at lower temperatures, the fastest weight loss rate went down by 76%, and the relative oxygen permeability value reduced from about 1% to near 0. More importantly, the large amount of SiO(2)glass phase produced over the coating during oxidation was in contact with the modification of MoSi2, which was proved to be beneficial to the dispersion of Ta-oxides. A concomitantly formed continuous Ta-Si-O-B compound glass layer showed excellent capacity to prevent oxygen penetration. However, when the TaB(2)content was sacrificed to increase the MoSi(2)content, the relative oxygen permeability of the coating increased instead of decreased. Thus, on the basis of ample TaB(2)content, increasing the MoSi(2)content of the coating is conducive to reducing the relative oxygen permeability of the coatings in a broad temperature region.