Corrosion Behavior of Structural Ceramics in Supercritical Water

Abstract

The corrosion behavior of Si₃N₄ SiC, mullite, alumina and sapphire was investigated in supercritical water at 450°C and 45MPa for 2 to 50h. Corrosion resistance for the ceramics was as follows in the order; Si₃N₄<SiC<mullite<alumina<sapphire. Pitting corrosion with formation of amorphous layer and intergranular corrosion due to dissolution of additives were observed in PLS-Si₃N₄ and PLS-SiC, respectively. The corrosion behavior of mullite was characterized by dissolution of SiO₂ and formation of boehmite residue layer. High purity alumina ceramics showed the highest corrosion resistance in the ceramics. Intergranular corrosion proceeded in the alumina ceramics and its corrosion rate was strongly dependent on the impurity content.