Journal Article10.1179/174892312X13269692038851
Mechanisms for boron effect on microstructure and creep strength of ferritic power plant steels
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TL;DR: In this paper, boundary and sub-boundary hardening are shown to be the most important strengthening mechanism in 9%Cr steel steel, and the enhancement of boundary hardening retards the onset of acceleration creep, which decreases the minimum creep rate and improves the creep life.
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Abstract: Boundary and sub-boundary hardening are shown to be the most important strengthening mechanism in creep of 9%Cr steel. Soluble boron reduces the coarsening rate of M23C6 carbides near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening for long times at 650°C. The enhancement of boundary and sub-boundary hardening retards the onset of acceleration creep, which decreases the minimum creep rate and improves the creep life. Excess addition of boron and nitrogen promotes the formation of boron nitrides during normalising heat treatment, which significantly reduces soluble boron and soluble nitrogen concentrations. The boundary and sub-boundary hardening are significantly reduced in the fine grained region of the heat affected zone (HAZ) of Gr.92 welded joints, promoting type IV fracture. Soluble boron produces substantially the same microstructure between base metal and HAZ in 9Cr steel welded joints, resulting in no type IV fracture at 650°C.
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Citations
Research and Development of Heat-Resistant Materials for Advanced USC Power Plants with Steam Temperatures of 700 °C and Above
TL;DR: In this paper, the research and development of Ni-base alloys and martensitic 9%−12% Cr steels for thick section boiler and turbine components of A-USC power plants, mainly focusing on the long-term creep-rupture strength of base metal and welded joints, strength loss in welded joint, creepfatigue properties, and microstructure evolution during exposure at elevated temperatures.
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Effect of tempering temperature on the toughness of 9Cr–3W–3Co martensitic heat resistant steel
TL;DR: In this paper, the effect of tempering temperature on the toughness of 9Cr-3W-3Co martensitic heat resistant steel was studied on the basis of the microstructures after normalized at 1100 ǫ c for 1h and then tempered at 740-780 c for 3h.
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Progress in Creep-Resistant Steels for High Efficiency Coal-Fired Power Plants
TL;DR: In this article, the authors comprehensively reviewed the recent progress in creep-resistant bainitic, martensitic, and austenitic steels for high efficiency coal-fired power plants with emphasis on long-term creep strength and microstructure stability at grain boundaries (GBs).
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Effect of microstructural evolution on high-temperature strength of 9Cr–3W–3Co martensitic heat resistant steel under different aging conditions
TL;DR: In this article, the evolution of microstructures and high-temperature strength of 9Cr-3W-3Co martensitic heat resistant steel after aging at 650°C and 700°C for different time durations have been experimentally investigated using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), field emission transmission electron microscope (FETEM), and post-aged tensile tests.
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Effect of normalizing temperature on the strength of 9Cr–3W–3Co martensitic heat resistant steel
TL;DR: In this article, the authors investigated the structural and room temperature strength of 9Cr-3W-3Co martensitic heat resistant steel after normalizing at 900-1200°C for 1 1/h and then tempering at 750-1/h for 1/4h.
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References
Precipitate design for creep strengthening of 9% Cr tempered martensitic steel for ultra-supercritical power plants
TL;DR: The suppression of particle coarsening during creep and the maintenance of a homogeneous distribution of M23C6 carbides near prior austenite grain boundaries are effective for preventing the long-term degradation of creep strength and for improving long- term creep strength by the addition of boron.
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Creep-strengthening of steel at high temperatures using nano-sized carbonitride dispersions
TL;DR: The production of a 9 per cent Cr martensitic steel dispersed with nanometre-scale carbonitride particles using conventional processing techniques is reported, which should lead to improved grades of creep-resistant steels and to the economical manufacture of large-scale steel components for high-temperature applications.
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Overview no. 63 Non-equilibrium grain boundary segregation of boron in austenitic stainless steel—I. Large scale segregation behaviour
TL;DR: In this paper, secondary ion mass spectrometry (SIMS) has been used to study boron grain boundary segregation in austenitic stainless steels of the types 316L and Mo-free 316L.
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Development of the MPC Omega Method for Life Assessment in the Creep Range
TL;DR: In this article, a methodology for characterizing and assessing the behavior of materials after service in the creep range has been developed and used on a broad range of materials and components, incorporating the results of relatively short-term tests and improved databases on materials properties.
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Alloy design and creep strength of advanced 9%Cr USC boiler steels containing high concentration of boron
TL;DR: The research and development project of National Institute for Materials Science (NIMS) for advanced ferritic heat resistant steels for 650°C ultra super critical (USC) plants, revealed that the addition of > 0·01 mass% boron to a 0·08C-9Cr-3W-3Co-V-Nb-Nk, 0·003N steel remarkably improves the long term creep strength.
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