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

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.