Investigation of the Oxidation Behaviour of Ti and Al in Inconel 718 Superalloy During Electroslag Remelting

In the current study, the thermodynamics of the slag-metal equilibrium reaction between Inconel 718 Ni-based alloy and CaF 2 -CaO-Al 2 O 3 -MgO-TiO 2 electroslag remelting (ESR)-type slags were systematically investigated in the temperature range from 1773 to 1973 K (1500 to 1700 °C). The equilibrium Al content increased with increasing temperature, whereas the equilibrium Ti content decreased with increasing temperature at a fixed slag composition. The important factors for controlling the oxidation of Al and Ti in the Inconel 718 superalloy were TiO 2 > Al 2 O 3 > CaO > CaF 2 > MgO in ESR-type slag and Al > Ti in a consumable electrode. The conventional method of sampling by means of a quartz tube could result in contamination of the molten metal and changes in the size of the “special reaction interface”. Therefore, a novel method was used in the present study to investigate the slag-metal reaction kinetics to accurately obtain the kinetic parameters. The mass transfer coefficient was determined by coupling with the kinetic model derived from the assumption that the reaction rate ([Al] + (TiO 2 ) = [Ti] + (Al 2 O 3 )) was controlled by the mass transfer of [Ti], [Al], (TiO 2 ) and (Al 2 O 3 ) in the boundary layer, respectively.