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In view of the perspective to produce near-net shapes of ultra-refractory ceramics, ZrB 2 -SiC composite were produced by slip casting on plaster mould and pressureless sintered at 21501C with a holding time of 120 min, using silicon nitride as a sintering aid. After sintering, slip-cast samples reached a very high relative density over 98%, while for comparison, the density of cold isostatic pressed samples was about 94%. Traces of the formation of secondary phases such as B 4 C, graphite, and BN were found in all samples, while no grain boundary phases were revealed. RT flexural strength of as-sintered slip cast bars was affected by the presence of an external porous layer of coarse ZrB 2 particles, while at 15001C the flexural strength increased, as a glassy layer sealed the superficial defects. Because of the absence of softening grain boundary phases, subcritical crack growth did not occur during high-temperature strength tests.

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