Corrosion behavior of precracked SiC_f/SiC composites under 1200-1300C Na₂SO₄-wet-oxygen environment

SiCf/SiC composites, as promising materials for the hot-section components of turbine engines, are susceptible to hot corrosion due to the steam environments. Especially, under rotational and thermal stress, numerous microcracks may be generated in the SiCf/SiC ceramic matrix, which can trigger the rapid invasion of corrosive gases and deteriorate the composite mechanical properties. Therefore, it is of great importance to investigate the degradation mechanisms of SiCf/SiC with precracks existing. Here, the corrosion behavior of precracked SiCf/SiC in the Na2SO4-wet-oxygen environment was evaluated. By comparing mechanical evolution under different corrosion conditions, microfailure mechanisms of SiCf/SiC were revealed. The results indicate that brittle cracking of the matrix and oxidation erosion of fibers are the key factors in reducing the tensile strain of composites. Specifically, the composite damage resistance increases at 67 MPa-1300 degrees C. At this point, the prestress level is moderate and close to the matrix cracking limit. The prefabricated microcracks can be healed at 1300 degrees C by liquid oxidation products, which hinders cracks bridging large-scale. This study is conducive to a better understanding of failure mechanisms of SiCf/SiC in complex service environments.