Oxidation of ZrB₂ and ZrB₂-Sic Ceramics with Tungsten Additions

The effect of tungsten additions on the oxidation behavior of zirconium diboride-based ceramics was studied. Four mole percent tungsten carbide was added to ZrB2. the oxidation behavior was studied using thermal gravimetric analysis and isothermal testing in flowing air. Upon heating to 1500⁰C, the mass gain decreased from ~14 mg/cm2 for nominally pure ZrB2 to ~4.5 mg/cm2 for tungsten containing ZrB2. After heating to 1500⁰C for three hours, the scale thickness on nominally pure ZrB2 was ~500 µm compared to ~100 µm for tungsten containing ZrB2. Tungsten additions improved the oxidation resistance of ZrB2 by modifying the morphology of the ZrO2 scale by liquid phase sintering, providing an improved barrier to oxygen diffusion