Mechanical properties and microstructure of Cr2O3 reinforced 3Al2O3·2SiO2 composite refractories

Abstract

Chromium-containing refractories have excellent high-temperature corrosion resistance. In this work, Cr2O3 reinforced Al2O3–SiO2 composite refractories were prepared by reaction sintering process. The microstructure, phase composition, mechanical properties and strengthening mechanism of the Cr2O3 reinforced Al2O3–SiO2 composite refractories were investigated. The results show that when the Cr2O3 content is 10–20 wt%, the composites are mainly composed of Cr-mullite (Al3.94Cr0.50Si1.56O10.44), (Al, Cr)2O3, and a small amount of SiO2 phase. When the Cr2O3 content exceeds 20%, the composite refractories mainly consist of (Al, Cr)2O3 and SiO2 phases. The appropriate amount of Cr2O3 can effectively enhance the mechanical properties and compactness of the Cr2O3 reinforced Al2O3–SiO2 composites. This is mainly due to the formation of Cr doped mullite and SiO2 phases, which reduces the sintering temperature of mullite ceramics and improves its density and mechanical properties. The highest hardness (27.03 GPa), flexural strength (213.21 MPa) and compressive strength (528 MPa) values are observed at a Cr2O3 content of 20 wt%. However, excessive addition of Cr2O3 will deteriorate the mechanical properties of the composites. The formation of a large amount of (Al, Cr)2O3 solid solution phase will increase the porosity of the composites, and reduce the compactness and sintering properties of the composites.