TY - JOUR
T1 - Investigation of precipitation sequence during creep in 2.25Cr-1Mo steel
AU - Chu, Dong Ju
AU - Kim, Han Yeol
AU - Lee, Joonho
AU - Jung, Woo Sang
N1 - Funding Information:
The authors gratefully acknowledge the financial support from the Energy Technology Development Program of Korea Institute of Energy Technology Evaluation and Planning (grant no. 20152010103430 ) and World Class 300 R&D Program of Korea Institute for Advancement of Technology (grant no. S2482209 ) and Competency Development Program for Industry Specialists of Korea Institute for Advancement of Technology (grant no. P0002019 ) in the Republic of Korea.
Funding Information:
The authors gratefully acknowledge the financial support from the Energy Technology Development Program of Korea Institute of Energy Technology Evaluation and Planning (grant no. 20152010103430) and World Class 300 R&D Program of Korea Institute for Advancement of Technology (grant no. S2482209) and Competency Development Program for Industry Specialists of Korea Institute for Advancement of Technology (grant no. P0002019) in the Republic of Korea.
PY - 2020/6
Y1 - 2020/6
N2 - Precipitate evolutions of 2.25Cr-1Mo heat-resistant steel during creep, under stress ranges of 30–300 MPa at 500–650 °C, were investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) equipped with energy dispersive spectroscopy (EDS). As-tempered microstructure was composed of ferrite and pearlite. Major precipitates in the pearlite region were identified as M3C, M7C3 and M23C6 (M = Fe, Cr, Mo) carbides. It was found that the precipitation sequence was changed according to the creep exposure temperatures and times. The composition of the carbide was shifted to the Cr-rich side as the creep exposure time at 550 °C or lower increases without changing the ferrite and pearlite structures. On the other hand, M2C was formed in an early stage of creep at 600 °C. The amount of M2C was decreased and M6C was newly precipitated after a long time creep exposure at 600 °C or higher. The amount of M3C decreased with increase in exposure time and fully disappeared even after a very short time creep exposure at temperatures higher than 600 °C. The overall precipitation sequence in the 2.25Cr-1Mo steel during creep was found to be M3C, M7C3, M23C6 → M3C, M7C3, M23C6, M2C → M7C3, M23C6, M6C. It was considered that the slope change in Larson-Miller Parameter (LMP) plot was attributed to the formation of Mo-rich M2C and dissolution of M7C3 precipitates during creep in the 2.25Cr-1Mo steel.
AB - Precipitate evolutions of 2.25Cr-1Mo heat-resistant steel during creep, under stress ranges of 30–300 MPa at 500–650 °C, were investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) equipped with energy dispersive spectroscopy (EDS). As-tempered microstructure was composed of ferrite and pearlite. Major precipitates in the pearlite region were identified as M3C, M7C3 and M23C6 (M = Fe, Cr, Mo) carbides. It was found that the precipitation sequence was changed according to the creep exposure temperatures and times. The composition of the carbide was shifted to the Cr-rich side as the creep exposure time at 550 °C or lower increases without changing the ferrite and pearlite structures. On the other hand, M2C was formed in an early stage of creep at 600 °C. The amount of M2C was decreased and M6C was newly precipitated after a long time creep exposure at 600 °C or higher. The amount of M3C decreased with increase in exposure time and fully disappeared even after a very short time creep exposure at temperatures higher than 600 °C. The overall precipitation sequence in the 2.25Cr-1Mo steel during creep was found to be M3C, M7C3, M23C6 → M3C, M7C3, M23C6, M2C → M7C3, M23C6, M6C. It was considered that the slope change in Larson-Miller Parameter (LMP) plot was attributed to the formation of Mo-rich M2C and dissolution of M7C3 precipitates during creep in the 2.25Cr-1Mo steel.
KW - 2.25Cr-1Mo steel
KW - Carbides
KW - Carbon replica
KW - Creep
KW - Precipitation sequence
KW - TEM
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U2 - 10.1016/j.matchar.2020.110328
DO - 10.1016/j.matchar.2020.110328
M3 - Article
AN - SCOPUS:85084443686
VL - 164
JO - Materials Characterization
JF - Materials Characterization
SN - 1044-5803
M1 - 110328
ER -