Oxidation behavior and kinetics of ZrB2 containing SiC chopped fibers

The oxidation of ZrB2 toughened with SiC short fibers has been evaluated in a thermo-gravimetric analyzer from 1200 to 1500°C for 10 hours and in a bottom-up loading furnace up to 1650°C for 5-30 minutes. The microstructure has been investigated by SEM and TEM. The oxidation kinetics, after a transient stage, follows a linear behavior, indicating that the outer oxide layer is not protective above 1400°C. Fibers notably oxidize above 1500°C with formation of silica glass and a carbon-rich phase. Mechanisms of SiC fiber oxidation and formation of the various scales are proposed for the various temperature ranges. Comparisons with the oxidation of ZrB2 containing SiC in form of particles, whiskers and previous generation fibers are also discussed.