Effect of Sialon‐Fe ₃ Si Multiphase Powder Replacing SiC on the Microstructure and Properties of Al ₂ O ₃ –SiC–C Bricks

ABSTRACT Sialon‐Fe 3 Si multiphase powder was synthesized from coal gasification slag by carbothermal reduction nitridation at 1440°C. The effects of substituting SiC with Sialon‐Fe 3 Si multiphase powder on the microstructure and properties of unfired Al 2 O 3 –SiC–C bricks are investigated in this study. After carbon‐embedded heat treatment at 1400°C for 3 h, the Sialon‐Fe 3 Si specimens exhibited mechanical properties that were significantly higher than those of the S0 specimens. When the replacement ratio of Sialon‐Fe 3 Si ranges from 13.2 to 15.4 wt%, the specimens exhibit optimal mechanical properties at room temperature. The improvement in mechanical properties is primarily attributed to the in situ formation of a dense, three‐dimensional spider‐web‐like (Al 4 O 4 C) 1‐ X (SiC) X solid solution. When compared with specimen S0, the oxidation and slag corrosion resistance of specimens incorporating Sialon‐Fe 3 Si multiphase powder is significantly improved. The oxidation of Sialon creates a mullite layer that is dense and prevents the passage of oxygen. Additionally, Sialon in the matrix uniformly reacts with the slag, forming a glass phase of high viscosity. The precipitation of anorthite and calcium aluminate at the interface between corundum and slag contributes to an increase in slag viscosity and a decrease in the rate of penetration erosion.