The cross-sectional backscatter image of the fabricated coating is demonstrated in Fig.1. Obviously, the fabricated coating consists of two layers and bonds tightly with the graphite substrate, which is attribute to the exceptional preparation method. Specifically, the inner SiC was fabricated by pack cementation with an average thickness of about 30 um. During the preparation process, melting Si carried SiC into the graphite matrix, and it can also react with the graphite to form SiC in situ. In this way, the adhesion of the coating has been strengthened. The multiphase coating including TaB2, MoSi2, and SiC phases was prepared by liquid phase sintering, and its average thickness is about 50 um. Frankly, it is difficult to distinguish the TaB2 and the MoSi2 from Fig.1(a), but there is a phenomenon that MoSi2 and TaB2 are clustered together from the results of the line scan shown in Fig.1(b). In addition, there is no distinct gap or void in the interface, which is a prerequisite for the coating providing protection against oxidation to the graphite matrix. Consequently, liquid phase sintering is considered to be an extraordinary method to fabricate the coating with outstanding oxidation protective performance.
Fig.1 Cross-sectional morphology of the fabricated 40wt% TaB2-40wt% MoSi2-20wt% SiC coating.
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