Effect of the Y2O3 amount on the oxidation behavior of ZrB2-SiC-based coatings for carbon/carbon composites

In this paper, the effect of Y2O3 addition on the oxidation resistance of ZrB2-SiC-Y2O3 coating for the SiC coated carbon/carbon composites was investigated. Results confirmed the great benefits of adding Y2O3 to the oxidation-resistant properties of the original coating from different aspects. The dense structure of surface and cross-section and formation of yttria stabilized zirconia, Y2Si2O7, t-ZrO2 phases were observed after adding Y2O3. Additionally, according to the TEM results, yttrium silicate existed in the form of nanoparticles, while yttria stabilized zirconia existed in the form of agglomeration within the SiO2 liquid phase. This superior oxidation resistance was attributed to the following reasons: (i) the formed Zr-Si-Y-O glass barrier layer blocked the oxygen diffusion and healed the cracks; (ii) the reduced m-ZrO2 content weakened the volume expansion of the coating and avoided spallation; (iii) Y2Si2O7 served as a pinning phase which modified the stability of liquid SiO2 at elevated temperatures.

Automated summary

This study investigates the effect of Y2O3 addition on the oxidation resistance of ZrB2-SiC-Y2O3 coating on SiC coated carbon/carbon composites. The results show that adding Y2O3 greatly enhances the oxidation-resistant properties of the coating, leading to the formation of a dense structure and yttria stabilized zirconia, Y2Si2O7, t-ZrO2 phases. The improved oxidation resistance is attributed to the formation of a Zr-Si-Y-O glass barrier layer, reduced m-ZrO2 content, and the presence of Y2Si2O7 as a pinning phase.