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

Shengchao Duan; Xiao Shi; Mingtao Mao; Wensheng Yang; Shaowei Han; Hanjie Guo; Jing Guo

doi:10.1038/s41598-018-23556-3

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

Sci Rep. 2018 Mar 27;8(1):5232. doi: 10.1038/s41598-018-23556-3.

Authors

Shengchao Duan^{1

2}, Xiao Shi^{1

2}, Mingtao Mao^{1

3}, Wensheng Yang^{1

2}, Shaowei Han^{1

2}, Hanjie Guo^{4

5}, Jing Guo^{1

2}

Affiliations

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing, 100083, P. R. China.
² Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing, 100083, P. R. China.
³ Research Institute of High Temperature Materials, Central Iron and Steel Research Institute (CISRI), Beijing, 100081, P. R. China.
⁴ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing, 100083, P. R. China. guohanjie@ustb.edu.cn.
⁵ Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing, 100083, P. R. China. guohanjie@ustb.edu.cn.

Abstract

In the current study, the thermodynamics of the slag-metal equilibrium reaction between Inconel 718 Ni-based alloy and CaF₂-CaO-Al₂O₃-MgO-TiO₂ 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 TiO₂ > Al₂O₃ > CaO > CaF₂ > 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] + (TiO₂) = [Ti] + (Al₂O₃)) was controlled by the mass transfer of [Ti], [Al], (TiO₂) and (Al₂O₃) in the boundary layer, respectively.