TY - JOUR
T1 - Temperature Dependence of CaO Desulfurization Mechanism in Molten Ni-Base Superalloy
AU - Kishimoto, Yuki
AU - Kono, Takaaki
AU - Horie, Takahide
AU - Yokokawa, Tadaharu
AU - Osawa, Makoto
AU - Kawagishi, Kyoko
AU - Suzuki, Shinsuke
AU - Harada, Hiroshi
N1 - Funding Information:
This research was financially supported by Japan Science and Technology (JST), under the Advanced Low Carbon Technology Research and Development Program (ALCA) project “Development of Direct and Complete Recycling Method for Superalloy Turbine Aerofoils (Grant No. JPMJAL1302)”.
Publisher Copyright:
© 2021, The Minerals, Metals & Materials Society and ASM International.
PY - 2021/6
Y1 - 2021/6
N2 - Desulfurization phenomenon of Ni-base superalloy using a solid CaO was identified by adjusting the temperature of melt. Ni-base superalloy and NiS powder were heated together at 1400 °C, 1500 °C, and 1600 °C. Dense and porous CaO rods were inserted into the melts individually. After the rods were pulled out, CaO, CaS, and calcium aluminates were detected on the rods by X-ray diffraction analysis. Electron probe microanalysis showed that only Ca, O, Al, and S distributed at the melt/CaO interfaces. At 1500 °C and 1600 °C, Al and S were also detected at particle boundaries in the rods. S contents in the alloys decreased as the desulfurization time passed and the temperature was raised. There was no prominent correlation between the rod porosity and the S contents. The desulfurization reaction was suggested to be that CaO, Al, and S react to generate CaS and calcium aluminates. When the temperature is high enough, the calcium aluminates form a solid–liquid coexisting state. Effective diffusion coefficient, which shows the S diffusivity in the generated layer at the melt/CaO interface, depends on the temperature and can be expressed by the Arrhenius equation. It has been supposed that the desulfurization reaction mainly occurs on CaO, and a macroscale surface area controls the desulfurization rate.
AB - Desulfurization phenomenon of Ni-base superalloy using a solid CaO was identified by adjusting the temperature of melt. Ni-base superalloy and NiS powder were heated together at 1400 °C, 1500 °C, and 1600 °C. Dense and porous CaO rods were inserted into the melts individually. After the rods were pulled out, CaO, CaS, and calcium aluminates were detected on the rods by X-ray diffraction analysis. Electron probe microanalysis showed that only Ca, O, Al, and S distributed at the melt/CaO interfaces. At 1500 °C and 1600 °C, Al and S were also detected at particle boundaries in the rods. S contents in the alloys decreased as the desulfurization time passed and the temperature was raised. There was no prominent correlation between the rod porosity and the S contents. The desulfurization reaction was suggested to be that CaO, Al, and S react to generate CaS and calcium aluminates. When the temperature is high enough, the calcium aluminates form a solid–liquid coexisting state. Effective diffusion coefficient, which shows the S diffusivity in the generated layer at the melt/CaO interface, depends on the temperature and can be expressed by the Arrhenius equation. It has been supposed that the desulfurization reaction mainly occurs on CaO, and a macroscale surface area controls the desulfurization rate.
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U2 - 10.1007/s11663-021-02112-x
DO - 10.1007/s11663-021-02112-x
M3 - Article
AN - SCOPUS:85103253424
SN - 1073-5615
VL - 52
SP - 1450
EP - 1462
JO - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
JF - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
IS - 3
ER -