Oxidation Resistance of Fully Dense ZrB2 with SiC, TaB2, and TaSi2 Additives

Specimens of ZrB 2 containing various concentrations of B 4 C, SiC, TaB 2 , and TaSi 2 were pressureless-sintered and post-hot isostatic pressed to their theoretical densities. Oxidation resistances were studied by scanning thermogravimetry over the range 1150°-1550°C. SiC additions improved oxidation resistance over a broadening range of temperatures with increasing SiC content. Tantalum additions to ZrB 2 -B 4 C-SiC in the form of TaB 2 and/or TaSi 2 increased oxidation resistance over the entire evaluated spectrum of temperatures. TaSi 2 proved to be a more effective additive than TaB 2 . Silicon-containing compositions formed a glassy surface layer, covering an interior oxide layer. This interior layer was less porous in tantalum-containing compositions.

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