Durable protection and failure mechanism of the multilayer coating system for SiCf/SiC composites under high-temperature oxidation

In this study, a thermal protective coating system was developed for addressing the durable high-temperature application of SiCf/SiC composites under 1200–1400 °C oxidation. The results show that the coated SiCf/SiC samples are almost no degradation on their mechanical strengths, as high as 630–749 MPa after the static oxidation and 585–719 MPa after the H2O/O2/Na2SO4 corrosion oxidation. The lattice strain and the stress distribution in the coating was analyzed and evaluated. It is illustrated that there is inhomogeneous stress and stress migration in the coating, and its excellent thermal protection performance mainly benefits from the formation of dense heterogeneous oxide scale, the mass transfer of liquid convection and the strain compatibility of ZrSiO4.