High Temperature Oxidation Mechanism of Ti_3SiC_2-64vol%SiC Ceramics

Full dense Ti3SiC2-64vol%SiC ceramics were successfully fabricated by in situ synthesis under hot isostatic pressing (HIP). The high temperature oxidation behaviors and mechanisms of the ceramics were studied by thermogravimetry tests (TG) at 1100-1450℃ in air. Testing results indicate the curves of isothermal kinetics of the ceramics obey parabolic oxidized law or parabolic-linear oxidized law. The addition of SiC (64vol%) efficiently improves the oxidation resistance of Ti3SiC2-SiC ceramics. According to XRD and SEM-EDS results,the oxidized layers are composed of an outer layer of TiO2 (rutile) and SiO2 (glass),and a transition layer of mixture of TiO2 and SiO2. At high temperature (1400℃),the growth morphology of TiO2 layer can be influenced by the formation of glassy SiO2. The continuous and dense TiO2 films which can efficiently prevent the diffusion of oxygen are formed. The parabolic rate constants decrease about one order of being oxidized at 1400℃ for long time compared with that oxidized at 1200℃. The oxidation resistance of Ti3SiC2-64vol% SiC ceramics at 1400℃ is better than that oxidized at 1200℃.