TY - JOUR
T1 - Creep Property and Phase Stability of Sulfur-Doped Ni-Base Single-Crystal Superalloys and Effectiveness of CaO Desulfurization
AU - Utada, Satoshi
AU - Joh, Yuichiro
AU - Osawa, Makoto
AU - Yokokawa, Tadaharu
AU - Sugiyama, Takuya
AU - Kobayashi, Toshiharu
AU - Kawagishi, Kyoko
AU - Suzuki, Shinsuke
AU - Harada, Hiroshi
N1 - Funding Information:
The authors are grateful to Dr. M. Yuyama, Superalloy Research Group, NIMS, for technical assistance with the creep tests. We also thank Drs. S. Kawada, S. Ito, and A. Ishitoya, Materials Analysis Station, NIMS, for chemical analysis. A part of this work was supported by the NIMS Microstructural Characterization Platform (NMCP) as a program of the “Nanotechnology Platform” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. We are grateful to Ms. N. Isaka, NMCP, NIMS, and Mr. K. Ogawa, Vibration Control Materials Group, NIMS, for technical support in the TEM observation. We also thank Ms. M. Fazal, Institut Pprime, for her diligent proofreading of this article. 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 Number JPNJAL1302. Manuscript submitted March 14, 2018.
Publisher Copyright:
© 2018, The Minerals, Metals & Materials Society and ASM International.
PY - 2018/9/1
Y1 - 2018/9/1
N2 - The direct and complete recycling method for Ni-base superalloy is being developed and studied to reduce the material cost for cost-effective operation of gas turbine systems. Understanding the effect of sulfur contamination is important to determine allowable sulfur content after the recycling. However, in the case of single-crystal superalloys, this effect on material properties is not well known except for the detrimental effect on the oxidation resistance. In the present study, creep tests, aging tests, and cyclic oxidation tests have been performed on PWA1484 with varying sulfur content. The increasing sulfur content has been found to correlate with degradation of properties evaluated here. It is observed that the decrease in creep life in PWA1484 due to sulfur doping is primarily due to coarsening of the γ/γ′ interfacial dislocation network, increase in precipitation kinetics of topologically closed-packed phase, and decrease in oxidation resistance. For recycling purposes, a CaO crucible was used in the casting process, which successfully decreased the sulfur level in the alloy, and the resulting material showed comparable or even better properties in comparison to the low sulfur content material.
AB - The direct and complete recycling method for Ni-base superalloy is being developed and studied to reduce the material cost for cost-effective operation of gas turbine systems. Understanding the effect of sulfur contamination is important to determine allowable sulfur content after the recycling. However, in the case of single-crystal superalloys, this effect on material properties is not well known except for the detrimental effect on the oxidation resistance. In the present study, creep tests, aging tests, and cyclic oxidation tests have been performed on PWA1484 with varying sulfur content. The increasing sulfur content has been found to correlate with degradation of properties evaluated here. It is observed that the decrease in creep life in PWA1484 due to sulfur doping is primarily due to coarsening of the γ/γ′ interfacial dislocation network, increase in precipitation kinetics of topologically closed-packed phase, and decrease in oxidation resistance. For recycling purposes, a CaO crucible was used in the casting process, which successfully decreased the sulfur level in the alloy, and the resulting material showed comparable or even better properties in comparison to the low sulfur content material.
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U2 - 10.1007/s11661-018-4710-4
DO - 10.1007/s11661-018-4710-4
M3 - Article
AN - SCOPUS:85049144435
SN - 1073-5623
VL - 49
SP - 4029
EP - 4041
JO - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
JF - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
IS - 9
ER -