TY - JOUR
T1 - Creep lifetime and microstructure evolution in boron-added 9Cr–1Mo heat-resistant steel
AU - Matsunaga, Tetsuya
AU - Hongo, Hiromichi
AU - Tabuchi, Masaaki
AU - Souissi, Maaouia
AU - Sahara, Ryoji
AU - Whitt, Collin
AU - Zhang, Wei
AU - Mills, M. J.
N1 - Funding Information:
The authors are grateful for experimental support from personnel at the Center for Electron Microscopy and Analysis (CEMAS) , The Ohio State University ; the Center for Computational Materials Science of the Institute for Materials Research , Tohoku University ; and the NIMS microstructural characterization platform as a program of “Nanotechnology Platform” of the Ministry of Education, Culture, Sports, Science and Technology , Japan and the Numerical Materials Simulator at NIMS. We also thank A-USC technology development, the Ministry of Economy, Trade, and Industry of Japan, and the Inamori Foundation for financial support. Finally, WZ and MJM acknowledge the support from US Department of Energy NEUP Grant DE-NE0000708 .
Funding Information:
The authors are grateful for experimental support from personnel at the Center for Electron Microscopy and Analysis (CEMAS), The Ohio State University; the Center for Computational Materials Science of the Institute for Materials Research, Tohoku University; and the NIMS microstructural characterization platform as a program of “Nanotechnology Platform” of the Ministry of Education, Culture, Sports, Science and Technology, Japan and the Numerical Materials Simulator at NIMS. We also thank A-USC technology development, the Ministry of Economy, Trade, and Industry of Japan, and the Inamori Foundation for financial support. Finally, WZ and MJM acknowledge the support from US Department of Energy NEUP Grant DE-NE0000708.
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/7/8
Y1 - 2019/7/8
N2 - The relationship between creep lifetime and microstructure, especially precipitate morphology, of a new 9Cr heat-resistant steel containing 0.011 wt% boron was examined. The B-added steel showed superior creep lifetime compared to conventional Gr. 91 steel due to the microstructural stability of the new steel at 873 K. The new steel also exhibited prior-austenite grain boundaries with a high coverage of precipitates, which increased from ~30% to ~40% during creep tests, whereas that of the conventional Gr. 91 steel was nearly stable, at ~25%. In addition, the B-containing M23C6 in the B-added steel had a lower coherency, i.e., a higher interface energy, between the precipitate and the matrix when compared to conventional Gr, 91 steel. These factors led to a higher pinning pressure to resist interface migration in the B-added steel. Microscopy revealed that chemical stabilization had a significant effect on the coarsening behavior of M23C6. Chemical analyses revealed that M23C6 became Cr-rich during the early stages of creep, in which rapid coarsening was observed at a rate contrast of >1.0 × 10−28 m3/s; in this state, M23C6 was approaching equilibrium Cr concentration. In later stages of creep, moderate coarsening occurred with a rate constant of ~8.1 × 10−30 m3/s; in this state, chemical stability was achieved but diffusion and dissolution of small precipitates were dominant.
AB - The relationship between creep lifetime and microstructure, especially precipitate morphology, of a new 9Cr heat-resistant steel containing 0.011 wt% boron was examined. The B-added steel showed superior creep lifetime compared to conventional Gr. 91 steel due to the microstructural stability of the new steel at 873 K. The new steel also exhibited prior-austenite grain boundaries with a high coverage of precipitates, which increased from ~30% to ~40% during creep tests, whereas that of the conventional Gr. 91 steel was nearly stable, at ~25%. In addition, the B-containing M23C6 in the B-added steel had a lower coherency, i.e., a higher interface energy, between the precipitate and the matrix when compared to conventional Gr, 91 steel. These factors led to a higher pinning pressure to resist interface migration in the B-added steel. Microscopy revealed that chemical stabilization had a significant effect on the coarsening behavior of M23C6. Chemical analyses revealed that M23C6 became Cr-rich during the early stages of creep, in which rapid coarsening was observed at a rate contrast of >1.0 × 10−28 m3/s; in this state, M23C6 was approaching equilibrium Cr concentration. In later stages of creep, moderate coarsening occurred with a rate constant of ~8.1 × 10−30 m3/s; in this state, chemical stability was achieved but diffusion and dissolution of small precipitates were dominant.
KW - Creep
KW - Grains and interfaces
KW - Heat resistant steel
KW - Precipitate
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U2 - 10.1016/j.msea.2019.05.114
DO - 10.1016/j.msea.2019.05.114
M3 - Article
AN - SCOPUS:85066960067
SN - 0921-5093
VL - 760
SP - 267
EP - 276
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
ER -