Processing and microstructural characterisation of RBSiC-TaSi2 composites

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Reaction bonded silicon carbide (RBSiC) ceramics typically contain 10 vol% silicon inherent to the reaction bonding process. However, the relatively low melting point (1410°C) of the silicon phase is a limiting factor in the high temperature use of RBSiC materials. The application temperature can potentially be enhanced by replacing the silicon with more refractory metal disilicide phases. In this paper we report the infiltration of SiC-graphite compacts with alloyed Si-Ta melts in an attempt to precipitate TaSi2 (Tm=2040°C) in place of the residual silicon. High density RBSiC-TaSi2 ceramics with virtually no porosity were readily produced, but subsequent XRD and SEM examination revealed that the silicon phase was not completely removed. In addition, the materials possessed complex, inhomogeneous microstructures and were susceptible to various types of crack formation phenomena.

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