The comparative investigation of oxidation behavior and corrosion mechanisms of SiC matrix ceramics under different atmospheres

The oxidation experiments of SiC matrix ceramics were conducted at 1200 degrees C for 10 h under three different atmospheres: dry air, water vapor, and a mixture of H2O/air. The oxidation behaviors and corrosion mechanisms were elucidated through phase and valence bond analysis, morphology examination, as well as elemental distribution analysis of the oxidized surface and cross section. Comparing the oxidation conditions among the three atmospheres, it was found that dry air exhibited the least degree of oxidation, while water vapor showed a more pronounced increase in oxidation. Notably, the most severe oxidative corrosion occurred in the presence of H2O/ air mixed gas conditions. The formation of a dense oxide layer, consisting of precipitated Y2Si2O7 crystals which result from YAG boundary phase on SiC matrix ceramics under dry air conditions, can effectively provide protection against further oxidation. However, introduction of water leads to additional corrosion on this oxide layer, particularly when combined with air.