Fabrication of SiCN–Sc2Si2O7 coatings on C/SiC composites at low temperatures

SiCN–Sc2Si2O7 environmental barrier coatings were fabricated on the surface of C/SiC composites at low temperatures by adding Li2CO3 as sintering aids. With this addition, the fabrication temperature could be lowered about 100–200 °C. The shrinkage of the polysilazane–Sc2Si2O7 bars with and without Li2CO3 was tested by dilatometer. The results indicate that the shrinkage speed of the polysilazane–Sc2Si2O7 bar with Li2CO3 is faster than the one without Li2CO3, indicating that the Li2CO3 greatly promotes the sintering of polysilazane–Sc2Si2O7. Water-vapor corrosion behavior of the SiCN–Sc2Si2O7 coated C/SiC composites was carried out at 1250 °C. The results reveal that the SiCN–Sc2Si2O7 coatings can effectively protect the C/SiC composites. The corrosion resistance of SiCN–Sc2Si2O7 coatings is not degraded by adding Li2CO3.