Abstract The microstructure and creep strength of three G115 specimens, 9 Cr-(2.3, 2.6, 3.0)W-3 Co (wt%), were investigated after creep test at 650 °C under 120 MPa using field emission transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, and Ultra-high temperature confocal microscope, focusing on martensitic lath, precipitates, dislocation densities and the block boundaries. The results show that the coarsening rates of the laths and Laves phase particles increased with the increase in W concentration during creep test. The majority of cavities was nucleated at high angle boundaries where many Laves phase particles existed in the neck portions of the specimens. The types of the crack were different among the three steels: the cracks in 2.3 W G115 steel specimens mainly resembled “wedge crack”, while the cracks in 2.6 W and 3.0 W G115 steel specimens mainly resembled “flower crack”. The 2.3 W G115 steel has the longest creep rupture life.
Abstract The microstructural evolution and certain mechanical properties of three G115 steels, 9 Cr-(2.3, 2.6, 3.0) W-3 Co (wt%), were investigated after thermal aging at 675 °C for different times using optical microscopy, field emission transmission electron microscopy, X-ray diffraction, post-aged tensile tests and impact tests, focusing on martensitic lath, dislocations and precipitates. The results show that the coarsening rates of the lath and Laves phase particles increased with the incre...
The effect of microstructure on the impact toughness and the temper embrittlement of a SA508Gr.4N steel was investigated. Martensitic and bainitic structures formed in this material were examined via scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and Auger electron spectroscopy (AES) analysis. The martensitic structure had a positive effect on both the strength and toughness. Compared with the bainitic structure, this structure consisted of smal...
Abstract Toughness of G115 martensitic heat resistant steel after heat treatment and aging for different time at 650 °C was tested at room temperature. The corresponding microstructure was also experimentally obtained by field emission scanning electron microscope (FESEM), field emission transmission electron microscope (FETEM), X-Ray diffraction (XRD), electron back-scattered diffraction (EBSD) characterization and phase analysis. The results show that the absorbed energy of G115 steel can reac...
Abstract An improved X-ray diffraction line profile analysis method is developed to determine dislocation density of lath martensitic steels. This method combines the modified Warren–Averbach (MWA) and the modified Williamson–Hall (MWH) methods. The developed method is robust and leads to unique values for the dislocation density, the effective outer cut-off radius of the dislocations ( R e ) and the dislocations distribution parameter ( M ). Dislocation structures of lath martensite in a steel,...
Last. Gunther Eggeler(RUB: Ruhr University Bochum)H-Index: 67
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We study the nucleation of Mo-rich Laves phase particles during aging and creep of 12 wt.% Cr tempered martensite ferritic steels (TMFS). Recently, in Isik et al. (2014) we reported that Laves phase particles tend to form at micrograin boundaries of TMFSs after Mo and Si had segregated from the ferritic matrix to these internal interfaces. In the present work, we employ transmission electron microscopy (TEM) and atom probe tomography (APT) to study the formation of Laves phase particles. We inve...
Last. Gunther Eggeler(RUB: Ruhr University Bochum)H-Index: 67
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Abstract This paper reports on the formation of an Mo-rich Laves phase during high-temperature exposure and creep of a tempered martensite ferritic steel with 12 wt.% Cr and 1 wt.% Mo. The material was exposed to 550 °C for time intervals between 864 and 81,984 h. For comparison, a few creep tests were carried out at 550 °C and 120 MPa (duration between 864 and 12,456 h). All tests were interrupted after specific time periods and microstructures were investigated using transmission electron micr...
Last. Wei Liu(THU: Tsinghua University)H-Index: 24
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Abstract Microstructure and room temperature strength of 9Cr–3W–3Co martensitic heat resistant steel after normalizing at 900–1200 °C for 1 h and then tempering at 750 °C for 1 h have been experimentally investigated using optical microscope (OM), field emission scanning electron microscope (FESEM), electron back-scattered diffraction (EBSD), field emission transmission electron microscope (FETEM) and tensile tests. The results show that with increasing normalizing temperature, the strength of t...
Last. Wei Liu(THU: Tsinghua University)H-Index: 24
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Abstract 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 °C for 1 h and then tempered at 740–780 °C for 3 h. With increasing tempering temperature from 740 °C to 780 °C, the absorbed energy of the 9Cr–3W–3Co steel increased greatly from 26 J to 115 J. The change of the toughness with increasing tempering temperature was attributed to the softening of the base metal and the inc...
Last. Wei Liu(THU: Tsinghua University)H-Index: 24
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Abstract Evolution of microstructures and high-temperature strength at 650 °C 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 microscopy (FETEM) and post-aged tensile tests. The results show that after aging at 650 °C, the high-temperature strength and the microstructures of 9Cr–...
Last. Aidang Shan(SJTU: Shanghai Jiao Tong University)H-Index: 24
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Abstract The effect of thermo-mechanical treatment on the microstructure and mechanical properties of commercial P92 steel was investigated. The steels were warm-rolled in metastable austenitic state with reductions of 75 and 93%, respectively. Tempering in a certain temperature range from 650 to 765 °C for 1 h was subsequently used to optimize the size of precipitates and form a homogeneous steady-state dislocation structure through recovery process. The results showed that the microstructure w...
In this study, the short-term aging was carried out to reveal the evolution of precipitates and mechanical properties of heat resistant 9CrMoCoB steel during the early creep, replacing the conventional creeping. The tempered martensite lath structure (TMLS) and precipitates were observed in the as-aged 9CrMoCoB steel. TMLS in the matrix underwent a transition to the polygonal ferrite after aging only for 300 h. In comparison, the mean diameter of the precipitates increased from 183 to 267 nm aft...
Last. Zhigang Yang(THU: Tsinghua University)H-Index: 22
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Abstract null null The mechanical properties and microstructure of reduced activation ferritic/martensitic (RAFM) steel after austenitizing at 930–1080 °C for 30 min and tempering at 760 °C for 90 min were investigated using field emission scanning electron microscopy, field emission transmission electron microscopy, electron back-scattered diffraction, X-ray diffraction, tensile, and impact tests. The results showed that the size of the M23C6 particles decreased from 930 to 1030 °C and then inc...
The creep behavior of Fe–17Cr–1.2Cu–0.5Nb–0.01C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa. The evolution of precipitates after creep deformation was analyzed by scanning electron microscopy, energy dispersion spectrum, and transmission electron microscopy. The minimum creep rate decreased with the decrease in the applied load and temperature, thereby extending the rupture life. Cu-rich phase and Nb-rich Lave...
Abstract The nucleation of the Laves phase particles in a Re-containing 10% wt. Cr-3% Co-3% W steel with a low nitrogen and a high boron contents during creep is characterized by distinctive features. The precipitation process can be written as M23C6 carbide → M6C carbide → Laves phase. The nucleation of all phases in this precipitation sequence is heterogeneous. The M23C6 carbides precipitate on the boundaries of martensitic structure during tempering at temperature of 770 °C. The M6C (Fe3W3C) ...
The effect of the post-weld heat treatment on the microstructures and mechanical properties of the dissimilar joint of G115, a novel developed martensite heat resistant steel, and CB2 steel, currently used in an ultra-super-critical power unit, was investigated. The results indicate that the quenched martensite underwent decomposition and transformation, and the amount of dislocations were sharply decreased in the weld metal after post-weld heat treatment (PWHT). Many nano-scale M23C6 precipitat...
#1Zhen Liu(USTB: University of Science and Technology Beijing)H-Index: 6
#2Xitao Wang(USTB: University of Science and Technology Beijing)H-Index: 29
Last. Chen Dong(USTB: University of Science and Technology Beijing)H-Index: 1
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Abstract Microstructure and strength evolution of the G115 steels with different B content aging at 650 °C for 5000 h were investigated in this research. The results showed that properly increasing B content in steels would reduce the coarsening rate of M23C6 carbides and martensitic laths, slow down the reduction rate of dislocation density, and decelerate the evolution of microstructure. Phase analysis and electron probe micro-analyzer (EPMA) studies showed that when B was added to the steel, ...
Last. Haiwen Luo(USTB: University of Science and Technology Beijing)H-Index: 19
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In the past decades, several 9–12 wt% Cr-containing martensitic steels have been researched for the application in ultra-supercritical power plants at 650 °C, which is still a worldwide challenge. Among them, G115 martensitic steel, which was developed in China, is one of promising candidates. It has the basic composition of 9% Cr-3% W-3% Co and contains 1% Cu (all in wt%) and the optimized contents of B and N, leading to much better creep strength and creep ductility than P92 steel. Both M23C6 ...
#1Jianqiao Li(BIT: Beijing Institute of Technology)
#2Xiangzhao Xu(BIT: Beijing Institute of Technology)H-Index: 5
Last. Huilan Ren(BIT: Beijing Institute of Technology)H-Index: 7
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Abstract The fracture mechanism of in-plane notched steel plate were experimentally investigated under the loading of the triangle shock waves. A series of 20 mm thick steel plates were loaded by explosive charges with different weights and the steel plates were notched in the load surface and free surface. The explosives cut the central part of the plate along the notches and the recovered specimens were processed and analyzed by the scanning electron microscope (SEM). It was found that the exp...
