Effect of Cold Deformation and Solid Solution Temperature on σ-phase Precipitation Behavior in HR3C Heat Resistant Steel
CAO Tieshan1,2, ZHAO Jinyi1, CHENG Congqian1, MENG Xianming3, ZHAO Jie1()
1.School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China 2.State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China 3.China Automotive Technology & Research Center, Tianjin 300300, China
Cite this article:
CAO Tieshan, ZHAO Jinyi, CHENG Congqian, MENG Xianming, ZHAO Jie. Effect of Cold Deformation and Solid Solution Temperature on σ-phase Precipitation Behavior in HR3C Heat Resistant Steel. Acta Metall Sin, 2020, 56(5): 673-682.
HR3C steel, widely applied in ultra-supercritical power plant, suffers an intergranular embrittlement problem during long-term high-temperature ageing or service, which will be enhanced by the precipitation of σ phase. Research has showed that the precipitation behaviors of σ phase are different significantly as the difference of manufacturers, which relates to the preparation process of cold-deformation & solid-solution treatment. In this work, the effects of cold deformation and solution treatment on the precipitation kinetics of σ phase and related mechanical properties for HR3C steel during the ageing process were studied. The results show that cold-deformation and solid solution temperature both have a significant influence on the precipitation of σ phase in the steel. The increase of cold-deformation will promote the precipitation of σ phase, and rising solution temperature helps to inhibit the growth of σ phase but increase the grain size. The precipitation kinetics study of σ phase in HR3C steel with different pre-treatment shows that σ phase growths slowly at first, and then gets into a rapid precipitation period, and finally reaches a steady-state with a value of about 5.7% (volume fraction). The impact toughness analysis shows that the increase of cold-deformation would lower down the impact toughness of HR3C steel during the ageing procedure, while the rise of the solid-solution temperature increases the impact toughness before ageing and reduces it during ageing.
Fund: National Natural Science Foundation of China(U1610256);National High Technology Research and Development Program of China(2015AA034402);Dalian University of Technology Fundamental Research Fund (No.DUT19RC(4)010)
Fig.1 OM images of microstructures of HR3C steel at the states of 8% cold deformation (a), 50% cold deformation (b), 8% cold deformation+1093 ℃ solid solution (c) and 50% cold deformation+1093 ℃ solid solution (d)
Fig.2 OM images of microstructures of 8% cold-deformed HR3C steel after solution treated at 1093 ℃ (a), 1143 ℃ (b) and 1193 ℃ (c)
Fig.3 OM images of microstructues of different cold-deformation+1093 ℃, 20 min solution treated HR3C steel ageing at 750 ℃ for different time (a) 8% deformation & ageing 100 h (b) 8% deformation & ageing 500 h (c) 8% deformation & ageing 1500 h (d) 50% deformation & ageing 100 h (e) 50% deformation & ageing 300 h (f) 50% deformation & ageing 500 h
Fig.4 OM images of microstructues of HR3C steel with 8% cold-deformation after different solution treatments and ageing at 750 ℃ for different time (a) 1143 ℃ solution and ageing 1500 h (b) 1143 ℃ solution and ageing 2000 h (c) 1193 ℃ solution and ageing 1500 h (d) 1193 ℃ solution and ageing 3000 h
Fig.5 SEM image (a) and EDS analysis on point 1 (b) of the 8% cold-deformed+1093 ℃, 20 min solution treated HR3C steel after ageing at 750 ℃ for 2000 h
Fig.6 Chromogenic morphologies of the cold-deformed+1093 ℃, 20 min solution treated HR3C steel after ageing at 750 ℃ (a) 8% cold-deformation & ageing 2000 h (b) 50% cold-deformation & ageing 500 h
Fig.7 Volume fraction of σ phase versus time for HR3C steel ageing at 750 ℃
Fig.8 - relationship (a) and Avrami curves calculated (b) of σ phase for HR3C steel with different processing states (y—precipitation fraction of σ phase, t—ageing time)
Deformation state
Solution temperature
Ageing temperature
b
n
℃
℃
As received
1093
750
1.787
50%
1093
700
2.598
50%
1093
750
2.313
8%
1093
700
5.816
8%
1093
750
2.600
8%
1143
750
5.369
Table 1 Parameters b and n in Avrami equation obtained from - linear relationship
Fig.9 TTT curves of σ phase for HR3C steel aged at 700 and 750 ℃ for different cold-deformations (a) and different solid-solution temperatures (b)
Fig.10 Effect of cold-deformation (a) and solution temperature (b) on the Charpy impact absorption of HR3C steel during 700 ℃ ageing
Fig.11 Impact fracture morphologies for HR3C steel sample with 8% cold-deformation+1093 ℃ solid solution after ageing at 700 ℃ for 0 h (a) and 2000 h (b, c)
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