Precipitation Behavior of σ Phase in Ultra-Supercritical Boiler Applied HR3C Heat-Resistant Steel

The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confirmed that the precipitations after aging were mainly NbCrN, M...

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Bibliographic Details
Published in:Acta metallurgica sinica : English letters 2019-11, Vol.32 (11), p.1355-1361
Main Authors: Cao, Tie-Shan, Cheng, Cong-Qian, Zhao, Jie, Wang, Hui
Format: Article
Language:English
Subjects:
Aging
Aging (metallurgy)
Aqueous solutions
Austenitic stainless steels
Brittle fracture
Characterization and Evaluation of Materials
Chemistry and Materials Science
Corrosion and Coatings
Corrosion resistance
Ductile fracture
Ductile-brittle transition
Fracture mechanics
Grain boundaries
Grain size
Heat resistant steels
High temperature
Intergranular fracture
Materials Science
Metallic Materials
Morphology
Nanotechnology
Organometallic Chemistry
Oxidation
Sigma phase
Sigma phase precipitation
Solid solutions
Spectroscopy/Spectrometry
Steel pipes
Time dependence
Tribology
TTT curves
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Summary:The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confirmed that the precipitations after aging were mainly NbCrN, M 23 C 6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C–2000 h was transformed from NbCrN phase or M 23 C 6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time–temperature transformation (TTT) curve for σ phase at 1 vol% in two kinds of commercial HR3C steel (different in grain size) was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ -brittle phase after aging.
ISSN:1006-7191
2194-1289
DOI:10.1007/s40195-019-00878-3