Effect of in-situ non-oxide bonding phases on fracture behaviour and microstructure of alumina-based castables with different bonding systems

Abstract

Bonding phases play a crucial role in refractories as they significantly affect the mechanical properties of these materials. Wedge splitting test (WST) was used to reveal the influence of in-situ non-oxides bonding phases on fracture behaviour of alumina-based castables with different binding systems. The results show that in-situ non-oxide bonded alumina-based castables can be prepared by incorporating Si powders and then in situ nitriding. Unlike oxide bonded alumina-based castables, the castables bonded with in situ non-oxides display typical non-linear fracture behaviour. The index of toughness, GF/σNT, was 44.2–55.4 μm for the non-oxide bonded alumina-based castables, which is nearly twice the corresponding value for the oxide bonded alumina-based castables (20.3–28.9 μm). The improvement in toughness is attributed to formation of micro-crack network in the microstructure of non-oxide bonded alumina-based castables, which caused by coefficient of thermal expansion (CTE) mismatch existing between corundum aggregates and in-situ non-oxide bonding phase. Compared with oxide bonded alumina-based castables, the fracture behaviour of in-situ non-oxide bonded alumina-based castables is not sensitive to changes in the bonding system.