CORROSION KINETIC AND LIFE PREDICTION EQUATION OF AN SiC-C/SiC COMPOSITE UNDER LOW FREQUENCY CYCLE STRESS AT HIGH TEMPERATURES

Stress oxidation and stress corrosion of an SiC-C/SiC composite under low frequency tensile-tensile cycle stress in multi-atmospheres at 1000℃, 1200℃ and 1300℃ were studied. The atmospheres include dry oxygen, water vapor, wet oxygen and Na₂SO₄ vapor mixed gas.The stress corrosion kinetic of the composite at 1300℃ was discussed by comparing the differences of lives when the specimens were exposed at different temperatures and in different atmospheres under the same cycle stress. It was found that oxygen is the major factor decreasing the life of the SiC-C/SiC composite under low frequency cycle stress at 1300℃. And the oxidation kinetic is controlled by the reaction between carbon fibers and oxygen under low frequency cycle stress between 1000℃ and 1300℃. The life prediction equation of SiC-C/SiC composites under cycle stress is suggested and validated well by experimental results.