Effect of Y2O3 on the oxidation properties of ZrSi2/SiC coating prepared by SAPS on the carbon-carbon composites

In order to improve the oxidation resistance of carbon-carbon (C/C) composites at high temperature, different content of Y2O3 modified ZrSi2/SiC coating for C/C composites were prepared by pack cementation and supersonic atmosphere plasma spraying (SAPS). Microstructure observation and phase identification of the coatings were analyzed by SEM, XRD, DSC/TG and EDS. Experimental results shown that the coating with 10 wt% Y2O3 effectively protected C/C composites from oxidation at 1500 °C in air for 301 h with a mass loss of 0.13% and experienced 18 thermal shock times from room temperature (RT) to 1500 °C. First, Y2O3 could restrain the phase transition of ZrO2 to reduce the formation of thermal stresses of the coating; second, the random distribution of ZrO2 ceramic particles and the formation of ZrSiO4 enhanced the stability of the SiO2; third, the formation of Y2Si2O7 and Y2SiO5 could relieve the thermal mismatch between ZrSi2-Y2O3 outer layer and the inner layer.