Investigation of desulfurization of Inconel 718 superalloys by ESR type slags with different TiO2 content

In the present study, effect of CaF2–CaO–Al2O3–MgO–TiO2 slag with various TiO2 contents on the desulfurization of Inconel 718 alloy was investigated at 1773K to provide the fundamental information for the establishment of desulfurization procedure during electroslag remelting (ESR) process. The melt...

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Bibliographic Details
Published in:Journal of materials research and technology 2019-05, Vol.8 (3), p.2508-2516
Main Authors: Duan, Sheng-Chao, Shi, Xiao, Wang, Fei, Zhang, Man-Cang, Li, Bin, Yang, Wen-Sheng, Guo, Han-Jie, Guo, Jing
Format: Article
Language:English
Subjects:
Desulfurization mechanism
Ion and molecule coexistence theory
Mass transfer model
Nickel-based alloy
Oxygen activity
Specific reaction interface
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Summary:In the present study, effect of CaF2–CaO–Al2O3–MgO–TiO2 slag with various TiO2 contents on the desulfurization of Inconel 718 alloy was investigated at 1773K to provide the fundamental information for the establishment of desulfurization procedure during electroslag remelting (ESR) process. The melt-quenching method did not accurately determine the change in content of sulfur and oxygen in the nickel-based alloy with time for the present study, which uses a novel experimental apparatus. The results indicated that the final sulfur content in the nickel-based alloy increased from 7 to 9ppm when the TiO2 content in slag of CaF2–CaO–Al2O3–MgO–TiO2 system increased from 2.17 to 10% without addition of deoxidizer. In order to further expound the desulfurization mechanism, meanwhile, the relationship between the oxygen activity at slag–metal interface and reaction time under conditions of various TiO2 in the slag was studied by coupling with the developed mass transfer model. The calculated oxygen content in bulk metal has a good corresponding relationship with the measured oxygen content in the nickel-based alloy. The oxygen activity at slag–metal interface increased up to 9.6ppm when TiO2 content was 10% in the slag, giving rise to the decrease in desulfurization ratio in high TiO2 content. The optimal condition for simultaneously ensuring low sulfur content and maintaining oxidative elements, such as Al and Ti, uniformly from bottom to top of the ESR ingot is also discussed.
ISSN:2238-7854
DOI:10.1016/j.jmrt.2019.01.027