Densification and comprehensive properties of h-BN-based refractories with in-situ formation of Y3Al5O12

Abstract

BN-based refractories have been applied successfully in side-dam and nozzle due to their excellent thermal shock resistance and non-wettability against molten steel and slag. However, the intrinsic covalent bonds between B and N and the platelet-structure of BN restrain the densification behavior during high temperature sintering. In the present work, nano Y2O3 and Al2O3 additives were introduced and the phase compositions, microstructure, mechanical properties, thermal shock resistance and oxidation resistance of BN-based refractories were comparatively investigated. The results showed that Y3Al5O12 (YAG) can be formed in-situ and it could promote the densification behavior through generating a transient liquid. Although the presence of sintering additives (up to 35 wt%), h-BN-based refractories still obtained quasi-isotropic microstructures due to the limited BN plates growth. h-BN-based refractories with 26.25 wt% YAG and 8.75 wt% Al2O3 as additives presented the best comprehensive properties, including the mechanical properties, thermal shock resistance and oxidation resistance.