Oxidation Resistance of Fully Dense ZrB 2 with SiC, TaB 2 , and TaSi 2 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.