Degradation mechanism of SiCf/SiC composites after long-time water vapor and oxygen corrosion at 1300 °C. (1st April 2022) - Zhang, Jin
Abstract: The corrosion behavior and corresponding mechanisms of SiCf /SiC composites have been studied in a mixed water vapor and oxygen environment at 1300 ℃ for up to 120 h.It has been unveiled that, the formation of liquid amorphous silica fulfilling gaps left by the oxidation of pyrolytic carbon interphase is extremely detrimental due to that: 1) the precipitation of liquid amorphous silica generates a very strong bonding with fibers; and that 2) the stress accumulation within silica layers owing to phase transformation and growth of silica drives them crack. These cracks would inevitably propagate to break fibers, thereby almost completely degrading composites. Highlights: ● The SiCf /SiC composite follows a linear weight gain rule for long-time corrosion in a stimulated combustion environment at 1300 ℃. ● The formation of SiO2 by the SiC oxidation has a distinct volume expansion effect. ● Two distinctive microstructure evolutions have been observed in the center and close to the surface of composites. ● The degradation mechanism is clarified for composites oxidized in a stimulated combustion environment at 1300 ℃.