Effect of Alumina Content on the Hot Corrosion of SiC by NaCl and Na2SO4

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J. Korean Ceram. Soc. > Volume 28(8); 1991 > Article

Journal of the Korean Ceramic Society 1991;28(8): 625.

NaCl과 Na₂SO₄에 의한 SiC 고온 부식에 미치는 Alumina 첨가량의 영향

이수영

Effect of Alumina Content on the Hot Corrosion of SiC by NaCl and Na2SO4

ABSTRACT

The specimens for the corrosion test were made by hot-pressing of SiC power with 2 wt% Nl2O3 and 10wt% Al2O3 additions at 2000℃ and 2050℃. The specimens were corroded in 37 mole% NaCl and 63 mole% Na2SO4 salt mixture at 1000℃ up to 60 min. SiO2 layer was formed on SiC and then this oxide layer was dissolved by Na2O ion in the salt mixture. The rate of corrosion of the specimen containing 10 wt% Al2O3 was slower than that of the specimen containing 2 wt% Al2O3. This is due to the presence of continuous grain boundary phase in the specimen containing 10 wt% Al2O3. The oxidation of SiC produced gas bubbles at the SiC-SiO2 interface. The rate of corrosion follows a linear rate law up to 50 min. and then was accelerated. This acceleration is due to the disruption oxide layer by the gas evolution at SiC-SiO2 interface. Pitting corrosion has found at open pores and grain boundaries.