Effects of TiO 2 addition on phase, mechanical properties, and microstructure of Cr 2 O 3 –Al 2 O 3 ceramic composite

TiO 2 is a sintering additive that can significantly improve the sintering and mechanical properties of Cr 2 O 3 –Al 2 O 3 refractory materials with high Cr 2 O 3 contents. In this study, TiO 2 -reinforced Cr 2 O 3 –Al 2 O 3 composite refractories were prepared using a reaction-sintering process. The microstructure, phase composition, mechanical properties, and strengthening mechanism of the TiO 2 -reinforced Cr 2 O 3 –Al 2 O 3 composite refractories were investigated. The results indicated that the Al 2 O 3 –Cr 2 O 3 –TiO 2 composite refractory with a TiO 2 content of 3.0–4.5 wt% had good compactness (porosity of 5.89%), hardness (17.21 GPa), wear resistance (wear rate of 0.4 mm 3 /Nm), flexural strength (101.10 MPa), and compressive strength (420.90 MPa). This is mainly because when the added amount of TiO 2 was <3.0 wt%, TiO 2 was solidly soluble in the matrix, forming a Ti 3+ -doped (Cr, Al) 2 O 3 solid solution, inhibiting abnormal grain growth, rapidly increasing the sintering shrinkage of the sample, rapidly increasing the bulk density, rapidly decreasing the apparent porosity, and improving the sintering and mechanical properties of the composite resistant material. When the TiO 2 addition exceeded 4.5 wt%, a large amount of (Cr, Al) 2 TiO 5 phase was distributed between the grain boundaries of the solid solution, and its bulk density started to decrease. The sintering shrinkage and apparent porosity did not change significantly, and the bonding between the solid solution was not improved. Thus, the sintering and mechanical properties of the composite resistant material deteriorated. Taking into account the slag resistance and mechanical properties of the material, Al 2 O 3 –Cr 2 O 3 –TiO 2 with a TiO 2 content of 3.0–4.5 wt% can meet the service requirements for mechanical properties of the lining of smelting reduction ironmaking furnaces.