A thermodynamic model for predicting Ti and Al element of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag in electroslag remelting process

Abstract

The control of titanium and aluminium in nickel-base superalloy with high titanium and low aluminium during the electroslag remelting (ESR) process has not been resolved well so far. The loss of titanium (Ti) and aluminium (Al) during the ESR process is critical to improve the high-temperature performance of GH4065A superalloy. A thermodynamic model based on the ion and molecule coexistence theory (IMCT) was developed to calculate the Ti and Al content of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag system during the ESR process of GH4065A superalloy. Results show that the order of the ability of each element in the slag system to weaken the loss of Al content is in the following order Al2O3 > CaO > CaF2, enhance the loss of Al content is SiO2 > FeO > TiO2, CaF2 > MgO and enhance the loss of Ti content is FeO > SiO2 > Al2O3 > CaO. Considering the influence of the slag system on the elements Al and Ti, the optimal ratio of the slag system is CaO = 15 w%∼20 w%, CaF2 ≥ 60 w%, Al2O3 = 18 w%∼25 w%, SiO2 ≤ 0.5 w%, TiO2 = 1 w%+(0.2 w%∼0.6 w%), MgO ≥ 4 w%, FeO ≤0.1 w%.