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.
Publisher Copyright:
© 2020 Elsevier Inc.
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
UR - http://www.scopus.com/inward/record.url?scp=85084443686&partnerID=8YFLogxK
U2 - 10.1016/j.matchar.2020.110328
DO - 10.1016/j.matchar.2020.110328
M3 - Article
AN - SCOPUS:85084443686
SN - 1044-5803
VL - 164
JO - Materials Characterization
JF - Materials Characterization
M1 - 110328
ER -