Degradation mechanism of SiCf/SiC composites after long-time water vapor and oxygen corrosion at 1300 °C

The corrosion behavior and corresponding mechanisms of SiCf/SiC composites have been studied in a mixed water vapor and oxygen environment at 1300 degrees C 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.

Automated summary

The corrosion behavior of SiCf/SiC composites in a high-temperature mixed vapor and oxygen environment has been studied. It has been found that the formation of liquid amorphous silica, which fills the gaps left by the oxidation of the carbon interphase, is highly detrimental due to its strong bonding with fibers and the stress accumulation and cracking within the silica layers, causing fiber breakage and severe degradation of the composites.