Microstructure and oxidation property of CrSi2-ZrSi2-Y2O3/SiC coating prepared on C/C composites by supersonic atmosphere plasma spraying

Double silicon-based ceramic coatings of CrSi2-ZrSi2-Y2O3/SiC were deposited on the surface of C/C composites to improve their oxidation resistance. The SiC inner coating was prepared by pack cementation while the CrSi2-ZrSi2-Y2O3 outer coatings with different CrSi2 contents were deposited on the surface of the SiC coating by supersonic atmosphere plasma spraying (SAPS). Microstructure feature, phase composition and oxidation resistance of the coatings were studied. The coatings prepared by the two steps had a dense microstructure with few pores and microcracks, and the interface exhibited good coherence. Oxidation experimental results showed that the CrSi2-ZrSi2-Y2O3/SiC coating with 30 wt% CrSi2 effectively protect C/C composites from being oxidized at 1500 degrees C in air, the mass change of which decreased by 1.2% after the oxidation time of 288 h. Meanwhile, it could also withstand 15 times thermal shock cycles from 1500 degrees C to room temperature (RT). A glass layer including SiO2 and Cr2O3 could effectively heal the microcracks and pores of the coating and thus reduce oxygen permeation. Meanwhile, the oxides such as ZrO2, ZrSiO4, Y2Si2O2 and Y2SiO5 could inhibit the growth and propagation of the coating microcracks and improve the oxidation resistance of the specimen.