TY - JOUR
T1 - Unveiling the Mechanism of Improved Oxidation Resistance for CaO Crucible Melting Using Ni-Al Alloy
AU - Tabata, Chihiro
AU - Kawagishi, Kyoko
AU - Uzuhashi, Jun
AU - Ohkubo, Tadakatsu
AU - Yokokawa, Tadaharu
AU - Harada, Hiroshi
AU - Suzuki, Shinsuke
N1 - Funding Information:
This research was financially supported by the Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Program (SIP), “Materials Integration for revolutionary design system of structural materials” (Funding agency: JST). The authors would like to show our gratitude to Dr. Makoto Osawa, Dr. Toshio Osada, Dr. Yuhi Mori, and Dr. Taichi Abe for the helpful discussions. We also would like to thank Ms. Kyoko Suzuki for the support of microstructural investigation, and Mr. Yuji Takata for the preparation of the single-crystal alloys.
Publisher Copyright:
© 2022, The Minerals, Metals & Materials Society and ASM International.
PY - 2022/7
Y1 - 2022/7
N2 - Melting the ingot or alloy using a CaO crucible is a method known to substantially improve the oxidation resistance of superalloys. But the mechanism is unclear due to the lack of investigation on the inclusions that supposedly prevent S segregation at the oxide/substrate interface, which suppress oxide spallation. To clarify the reaction during the melting process, simplified binary Ni-9.8 wt pct Al single-crystal alloys were cast via melting in both an Al2O3 crucible and a CaO crucible. Cyclic oxidation tests were done on both samples at 1100 °C to compare the oxidation resistance between these samples. Samples were also oxidized at 1100 °C only for 1 hour to investigate the inclusions found within the substrate melted in a CaO crucible using aberration-corrected scanning transmission electron microscope with energy-dispersive X-ray spectroscopy (STEM-EDS). Crystalline CaS and MgAl2O4 inclusions were found near the sub-grain boundary of the sample. This finding proved that the Ca from the CaO crucible reacts with S in the melt to form CaS, preventing S from segregating at the oxide/substrate interface.
AB - Melting the ingot or alloy using a CaO crucible is a method known to substantially improve the oxidation resistance of superalloys. But the mechanism is unclear due to the lack of investigation on the inclusions that supposedly prevent S segregation at the oxide/substrate interface, which suppress oxide spallation. To clarify the reaction during the melting process, simplified binary Ni-9.8 wt pct Al single-crystal alloys were cast via melting in both an Al2O3 crucible and a CaO crucible. Cyclic oxidation tests were done on both samples at 1100 °C to compare the oxidation resistance between these samples. Samples were also oxidized at 1100 °C only for 1 hour to investigate the inclusions found within the substrate melted in a CaO crucible using aberration-corrected scanning transmission electron microscope with energy-dispersive X-ray spectroscopy (STEM-EDS). Crystalline CaS and MgAl2O4 inclusions were found near the sub-grain boundary of the sample. This finding proved that the Ca from the CaO crucible reacts with S in the melt to form CaS, preventing S from segregating at the oxide/substrate interface.
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U2 - 10.1007/s11661-022-06678-2
DO - 10.1007/s11661-022-06678-2
M3 - Article
AN - SCOPUS:85128605637
SN - 1073-5623
VL - 53
SP - 2452
EP - 2458
JO - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
JF - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
IS - 7
ER -