Towards chrome-free lining for plasma gasifiers using the CA6-SiC castable based on high-temperature water vapor corrosion

Abstract This paper focuses on the water vapor corrosion mechanisms of calcium hexaluminate (CA6)-SiC, SiC, and MgAl2O4-Cr2O3 castables. The weight and linear change, mechanical performance, sintering properties, and pore-size distribution of the three castables were investigated before and after corrosion. Morphologies, chemical bonds, and phases were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) respectively. Thermodynamic analysis was used to explain the chemical reaction during corrosion. The results show that the CA6 aggregates remain stable after 1000 °C × 100 h in wet air. However, SiC and Cr2O3 can react with the wet air. First, SiC reacts with O2 to form SiO2, then the siloxane network (Si-O-Si) of the SiO2 can be corroded to form silanol groups (Si-OH). The MgAl2O4-Cr2O3 castable exhibits weight loss and forms large pores after vapor corrosion because Cr2O3 reacts with H2O (g) and O2 (g) to form CrO2(OH)2 (g).