Corrosion degradation of mullite subject to carbon monoxide atmosphere at 1000 o C–1600°C

Abstract Thus far, studies on the damage to refractory materials under carbon monoxide atmospheres have mostly concentrated on the effects of carbon deposition, and the testing temperature was always set at approximately 500°C to promote the deposition of carbon. However, this testing temperature is far below the operating temperature of most refractories. In this study, mullite, a widely used high‐temperature structural material, was subjected to a carbon monoxide atmosphere at 1000°C‐1600°C to investigate its phase and microstructural evolutions. Changes to the grain boundaries were initially observed in mullite specimens treated at 1000°C and 1200°C. After treatment at 1400°C, the specimen surface comprised α‐Al 2 O 3 , a glass phase, and a small amount of mullite. However, treatment at 1600°C resulted in only α‐Al 2 O 3 and a small amount of glass phase on the surface. Additionally, pores and voids were found in the glass phase on the surface and in the bulk of the specimens treated at 1400°C and 1600°C. This study demonstrated the stability of pure mullite in a carbon monoxide atmosphere and revealed that impurities accelerating generation of the liquid phase in Al 2 O 3 –SiO 2 system significantly affect the stability of mullite in a carbon monoxide atmosphere.