Effect of Al2O3 and TiO2 Contents in the Refining Slag on Al and Ti Contents of Incoloy825 Alloy

Abstract

During the refining process of Incoloy825 nickel-based alloy, the reaction between the refining slag and Al and Ti in the alloy can result in the oxidation loss. Therefore, the effect of the TiO₂ and Al₂O₃ contents in the refining slag (CaO–SiO₂–Al₂O₃–MgO–CaF₂–TiO₂) on the final Al and Ti contents in Incoloy825 alloy was investigated by slag-metal reaction experiment in a 1-kg MoSi₂ resistance furnace. The thermodynamic model was established based on ion and molecular coexistence theory and the kinetic model was established based on two-film theory. The experimental results show that an increase in TiO₂ (Al₂O₃) content in the slag leads to an increase (decrease) in Ti content and a decrease (increase) in Al content in the final alloy. The thermodynamic model demonstrates that the activities of SiO₂, Al₂O₃, and TiO₂ in the slag are negatively correlated with the content of CaO and positively correlated with SiO₂, Al₂O₃, and TiO₂ in the slag. The kinetic model indicates that the slag-metal reaction reaches equilibrium within 10 min, and the model has good applicability for the reaction process of Incoloy825 alloy and slag refining.