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Junjie Xiu - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of specimen size effect on creep crack growth behavior in p92 steel Welded Joint
Materials & Design, 2014Co-Authors: Junjie Xiu, Yongdian HanAbstract:Abstract In order to clarify the effect of constraint induced by specimen size on creep crack growth behavior of P92 steel Welded Joint, creep crack tests were carried out on the compact tension specimens with thick thickness and thin thickness, the crack tip of which were located at different distinct zones of Welded Joint. Tested results revealed that even in thin thickness specimens, fine grained heat affected zone specimens exhibited a fast creep crack growth rate compared with other micro-zones specimens due to a low creep crack resistance and a high multistress state. The fractographies of these specimens exhibited an accelerated number of spherical particles that were caused by the coalescence of creep voids. Furthermore, the correlation of C * with creep crack growth rate was dependent on specimen thickness. As the specimen thickness increased from 10 to 30 mm, the creep crack growth rate increased. This was due to the increase in constraint level ahead of crack tip during creep crack propagation.
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evaluating of creep property of distinct zones in p92 steel Welded Joint by small punch creep test
Materials & Design, 2013Co-Authors: Lei Zhao, Hongyang Jing, Yongdian Han, Junjie Xiu, Yaxia QiaoAbstract:Abstract Small punch creep tests were carried out on four different micro zones in P92 steel Welded Joint: base metal, Welded metal, fine grain heat affected zone and coarse grain heat affected zone. In addition to the creep rupture times, the full deflection curves during creep were also obtained, from which the creep properties of different Welded Joint micro zones could be derived. Furthermore, finite element method (FEM) analysis implanted with continuum damage mechanics was performed to investigate the variation of the creep damage, stress and strain during the test process. The validity of FEM results was certified by the agreement with experimental results. Then, on the basis of the experimental data, FEM results and theoretical models, the relationship of load in small punch creep test and stress in uniaxial creep test and the correlation of deflection and strain were established, respectively. According to these relations, the creep properties of the different distinct zones in P92 steel Welded Joint were obtained.
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Prediction of creep crack growth behavior in ASME P92 steel Welded Joint
Computational Materials Science, 2012Co-Authors: Yongdian Han, Junjie XiuAbstract:Abstract In the present study, the prediction of creep crack growth behavior in ASME P92 steel Welded Joint at 650 °C was carried out using elastic–plastic–creep finite element method (FEM) and theoretical prediction models, respectively. Then the predicted creep crack growth rate was correlated with parameter C* and compared with experimental data. It was observed that the creep crack growth behaviors calculated by the FEM and predicted by the modified NSW model under plain stress condition agreed well with experimental results. Hence, the appropriate creep residual life for the in-service components containing defects could be provided without conducting creep crack growth tests. Furthermore, creep crack growth behaviors of specimens with the initial crack located in the different zones of Welded Joint were also calculated. The simulation results revealed that the highest creep crack growth rate occurred at the interface between the fine grain heat affected zone and the base metal due to low creep strength and high constraint.
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Analysis of creep crack growth behavior of P92 steel Welded Joint by experiment and numerical simulation
Materials Science and Engineering: A, 2012Co-Authors: Yongdian Han, Junjie XiuAbstract:Abstract High temperature creep crack growth tests were carried out on standard compact specimens machined from the Welded Joint of ASME P92 steel pipe. The creep crack growth behaviors of the distinct sub-regions of Welded Joint were investigated to clarify the ability of creep crack resistance under high temperature. In addition, good correlations between creep crack growth rate and C ⁎ for different microzones of Welded Joint were obtained. The tested results revealed that the sub-regions of Welded Joint exhibited different creep crack behaviors and at the same value of C * the highest creep crack growth rate occurred in the fine grained heat affected zone (FGHAZ) which was known as Type IV cracking zone. Furthermore, finite element method analyses coupled with continuum damage mechanics were conducted to predict the creep crack growth behavior and to study the effect of multistress state on crack propagation.
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experimental study on creep damage evolution process of type iv cracking in 9cr 0 5mo 1 8w vnb steel Welded Joint
Engineering Failure Analysis, 2012Co-Authors: Lei Zhao, Hongyang Jing, Yongdian Han, Junjie XiuAbstract:Abstract The microstructure degradation and creep damage evolution process of Type IV cracking in a 9Cr–0.5Mo–1.8 W–VNb steel (ASME P92) Welded Joint during creep were investigated. Creep tests were carried out at 923 K and 70 MPa, and terminated at specific times in order to analyze the microstructure change and the creep voids formation in the Welded Joint. The Welded Joint finally ruptured in the fine grained heat affected zone adjacent to the base metal, identified as Type IV cracking. It revealed that the creep strength in the fine grained heat affected zone was lower than other zones of the Welded Joint. Creep voids were likely to nucleate and grow in this zone. In addition, carbides played an important role as nucleating sites for creep voids. As the creep time increased, creep voids linked to each other and finally formed micro-cracks resulting in the fracture in the fine grained heat affected zone. On the basis of microstructure degradation and creep voids propagation, the creep damage evolution process was proposed.
Yongdian Han - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of specimen size effect on creep crack growth behavior in p92 steel Welded Joint
Materials & Design, 2014Co-Authors: Junjie Xiu, Yongdian HanAbstract:Abstract In order to clarify the effect of constraint induced by specimen size on creep crack growth behavior of P92 steel Welded Joint, creep crack tests were carried out on the compact tension specimens with thick thickness and thin thickness, the crack tip of which were located at different distinct zones of Welded Joint. Tested results revealed that even in thin thickness specimens, fine grained heat affected zone specimens exhibited a fast creep crack growth rate compared with other micro-zones specimens due to a low creep crack resistance and a high multistress state. The fractographies of these specimens exhibited an accelerated number of spherical particles that were caused by the coalescence of creep voids. Furthermore, the correlation of C * with creep crack growth rate was dependent on specimen thickness. As the specimen thickness increased from 10 to 30 mm, the creep crack growth rate increased. This was due to the increase in constraint level ahead of crack tip during creep crack propagation.
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evaluating of creep property of distinct zones in p92 steel Welded Joint by small punch creep test
Materials & Design, 2013Co-Authors: Lei Zhao, Hongyang Jing, Yongdian Han, Junjie Xiu, Yaxia QiaoAbstract:Abstract Small punch creep tests were carried out on four different micro zones in P92 steel Welded Joint: base metal, Welded metal, fine grain heat affected zone and coarse grain heat affected zone. In addition to the creep rupture times, the full deflection curves during creep were also obtained, from which the creep properties of different Welded Joint micro zones could be derived. Furthermore, finite element method (FEM) analysis implanted with continuum damage mechanics was performed to investigate the variation of the creep damage, stress and strain during the test process. The validity of FEM results was certified by the agreement with experimental results. Then, on the basis of the experimental data, FEM results and theoretical models, the relationship of load in small punch creep test and stress in uniaxial creep test and the correlation of deflection and strain were established, respectively. According to these relations, the creep properties of the different distinct zones in P92 steel Welded Joint were obtained.
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Prediction of creep crack growth behavior in ASME P92 steel Welded Joint
Computational Materials Science, 2012Co-Authors: Yongdian Han, Junjie XiuAbstract:Abstract In the present study, the prediction of creep crack growth behavior in ASME P92 steel Welded Joint at 650 °C was carried out using elastic–plastic–creep finite element method (FEM) and theoretical prediction models, respectively. Then the predicted creep crack growth rate was correlated with parameter C* and compared with experimental data. It was observed that the creep crack growth behaviors calculated by the FEM and predicted by the modified NSW model under plain stress condition agreed well with experimental results. Hence, the appropriate creep residual life for the in-service components containing defects could be provided without conducting creep crack growth tests. Furthermore, creep crack growth behaviors of specimens with the initial crack located in the different zones of Welded Joint were also calculated. The simulation results revealed that the highest creep crack growth rate occurred at the interface between the fine grain heat affected zone and the base metal due to low creep strength and high constraint.
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Analysis of creep crack growth behavior of P92 steel Welded Joint by experiment and numerical simulation
Materials Science and Engineering: A, 2012Co-Authors: Yongdian Han, Junjie XiuAbstract:Abstract High temperature creep crack growth tests were carried out on standard compact specimens machined from the Welded Joint of ASME P92 steel pipe. The creep crack growth behaviors of the distinct sub-regions of Welded Joint were investigated to clarify the ability of creep crack resistance under high temperature. In addition, good correlations between creep crack growth rate and C ⁎ for different microzones of Welded Joint were obtained. The tested results revealed that the sub-regions of Welded Joint exhibited different creep crack behaviors and at the same value of C * the highest creep crack growth rate occurred in the fine grained heat affected zone (FGHAZ) which was known as Type IV cracking zone. Furthermore, finite element method analyses coupled with continuum damage mechanics were conducted to predict the creep crack growth behavior and to study the effect of multistress state on crack propagation.
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experimental study on creep damage evolution process of type iv cracking in 9cr 0 5mo 1 8w vnb steel Welded Joint
Engineering Failure Analysis, 2012Co-Authors: Lei Zhao, Hongyang Jing, Yongdian Han, Junjie XiuAbstract:Abstract The microstructure degradation and creep damage evolution process of Type IV cracking in a 9Cr–0.5Mo–1.8 W–VNb steel (ASME P92) Welded Joint during creep were investigated. Creep tests were carried out at 923 K and 70 MPa, and terminated at specific times in order to analyze the microstructure change and the creep voids formation in the Welded Joint. The Welded Joint finally ruptured in the fine grained heat affected zone adjacent to the base metal, identified as Type IV cracking. It revealed that the creep strength in the fine grained heat affected zone was lower than other zones of the Welded Joint. Creep voids were likely to nucleate and grow in this zone. In addition, carbides played an important role as nucleating sites for creep voids. As the creep time increased, creep voids linked to each other and finally formed micro-cracks resulting in the fracture in the fine grained heat affected zone. On the basis of microstructure degradation and creep voids propagation, the creep damage evolution process was proposed.
Fuzhen Xuan - One of the best experts on this subject based on the ideXlab platform.
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effect of frequency on very high cycle fatigue behavior of a low strength cr ni mo v steel Welded Joint
International Journal of Fatigue, 2015Co-Authors: Fuzhen XuanAbstract:Abstract Axially fully-reversed fatigue test of a low strength Cr–Ni–Mo–V steel Welded Joint was conducted up to the very high cycle fatigue regime under the frequency of 110 Hz and 20 kHz. The S–N curve shows a duplex shape at low frequency while decreases continuously at high frequency. Sites of crack initiation and fracture of the welds depend on stress level and loading frequency, hence leading to changed fatigue strength. In addition, frequency effect varies among different parts of the Welded Joint and fatigue lifetime.
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local mechanical properties of a dissimilar metal Welded Joint in nuclear powersystems
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Guoying Wang, Fuzhen Xuan, Shantung TuAbstract:Abstract In this paper, the local mechanical properties (yield/ultimate strength, ductility as well as stress–strain curves) of an Alloy52M dissimilar metal Welded Joint (DMWJ) in nuclear power systems were determined by using the mini-sized flat tensile specimens, and the local microstructures in the Joint were characterized and analyzed. The results show that there are drastic variations in the local mechanical properties in the interface regions between materials. The heterogeneous mechanical properties are mainly related to the local microstructures of the DMWJ. The complex microstructures in the interface regions between materials were mainly caused by the heat flow and element migration during welding process. The local mechanical properties and their mismatches may have significant effect on crack-tip fracture mechanics parameter, plastic deformation behavior, local fracture resistance and crack growth behavior. Therefore, they need to be obtained and used in the integrity assessment of theDMWJs.
Haichao Cui - One of the best experts on this subject based on the ideXlab platform.
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pitting behavior of Welded Joint and the role of carbon ring in improving corrosion resistance
Materials & Design, 2019Co-Authors: Tongjiao Chu, Yanna Nuli, Haichao CuiAbstract:Abstract Pitting behavior and its transition process to cracking were investigated after immersion at 180 °C in pure water and 3.5% NaCl solution for NiCrMoV Welded Joint manufactured by narrow gap submerged arc welding technology. Dislocation outcrops in the interior of the grains formed small anodes, which mainly attributed to the pit growth for weld metal (WM) and heat-affected zone (HAZ). The serious pitting in WM was induced by strong strain concentration generating from welding thermal stress. Competition behavior between pitting and cracking for WM in pure water and chloride solution was also proposed. Chloride accelerating anodic dissolution caused serious pitting that predominated over cracking in chloride solution, while cracking preferentially formed and replaced mild pitting in pure water. In addition, carbon rings around pits decreased pitting susceptibility for HAZ. The formation of carbon rings generated from carbon diffusion was driven by strain aging and selective corrosion. Moreover, micro-Raman manifested the carbon ring was covered by protective oxide layer that inhibited pit growth and improved pitting resistance for HAZ. This work contributes to the understanding of pit growth and crack initiation for Welded Joint used in nuclear turbine.
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microstructure correlation and fatigue crack growth behavior in dissimilar 9cr crmov Welded Joint
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Xionglin Deng, Haichao Cui, Xinhua TangAbstract:Abstract The fatigue crack growth behavior and the related microstructure of the dissimilar Welded Joint made from advanced 9Cr and CrMoV steels were systematically investigated in this paper. The dissimilar materials of 9Cr and CrMoV with heavy section were Welded by narrow-gap submerged arc welding (NG-SAW) via multi-layer and multi-pass technology. The fatigue crack growth behavior was comparatively studied for different regions including advanced 9Cr and CrMoV base metals (9Cr-BM, CrMoV-BM), heat affected zones of both sides (9Cr-HAZ, CrMoV-HAZ) and weld metal (WM). The results indicated that a lower fatigue crack growth rate ( da / dN ) as well as a higher fatigue crack growth threshold (Δ K th ) for WM was gained compared to the BMs and HAZs, while a larger da / dN and lower Δ K th for 9Cr-HAZ were obtained under the same stress ratio. The WM showed a better fatigue crack growth resistance than others, while the 9Cr-HAZ with narrow size became the weaker part of the whole Welded Joint. Microstructure was revealed that the different microstructure character such as tempered martensite and tempered bainite could account for this diversity in properties. In addition, the observation of fatigue crack growth path displayed that the obstacles of coarse columnar grains and the ductile equiaxed grains in WM caused the higher resistance of fatigue crack growth, while the tempered martensite with and without lath structure led to the higher and lower fatigue crack growth resistance for 9Cr-BM and 9Cr-HAZ, respectively. However, the fatigue crack growth behavior of 9Cr-HAZ would not great influence the whole Welded Joint for its narrow size.
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creep behavior and microstructure evaluation of Welded Joint in dissimilar modified 9cr 1mo steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Wen Liu, Haichao Cui, Xinhua Tang, Xia Liu, Yulai GaoAbstract:Abstract In the present work, the creep behavior and microstructure before and after creep test of the dissimilar modified 9Cr–1Mo steels Welded Joint were investigated in detail. Firstly, creep tests were carried out at different stress values/levels under the temperature of 538 °C and 500 °C, and then the power law equation of steady-state stage were achieved based on the results. The microstructure of Welded Joint were characterized in detail, the tempered martensite structure is the typical microstructure of whole Welded Joint, and the δ-ferrite phase is observed in heated affect zone (HAZ) and the base metal without Co and B elements (BM1). A soft zone called over-tempering zone (OTZ) occurred in both HAZs, which was determined by micro-hardness measurement, due to the lower dislocation density and coarsened M 23 C 6 carbides of this zone. The fracture location is in OTZ adjacent to BM1 side determined by microstructure, micro-hardness and geometric calculation. Lots of voids are observed along the triple grain boundaries associated with large second phase particles after creep rupture. The stress concentration caused by the coarsened carbides at the triple boundaries and softening matrix are considered as the main factor of creep voids occurring in the OTZ of Welded Joint.
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correlation of microstructure and fracture toughness of advanced 9cr crmov dissimilarly Welded Joint
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Qian Guo, Haichao Cui, Xia Liu, Renjie Yang, Yulai GaoAbstract:Abstract In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly Welded Joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly Welded Joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of Welded Joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole Welded Joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.
Yulai Gao - One of the best experts on this subject based on the ideXlab platform.
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creep behavior and microstructure evaluation of Welded Joint in dissimilar modified 9cr 1mo steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Wen Liu, Haichao Cui, Xinhua Tang, Xia Liu, Yulai GaoAbstract:Abstract In the present work, the creep behavior and microstructure before and after creep test of the dissimilar modified 9Cr–1Mo steels Welded Joint were investigated in detail. Firstly, creep tests were carried out at different stress values/levels under the temperature of 538 °C and 500 °C, and then the power law equation of steady-state stage were achieved based on the results. The microstructure of Welded Joint were characterized in detail, the tempered martensite structure is the typical microstructure of whole Welded Joint, and the δ-ferrite phase is observed in heated affect zone (HAZ) and the base metal without Co and B elements (BM1). A soft zone called over-tempering zone (OTZ) occurred in both HAZs, which was determined by micro-hardness measurement, due to the lower dislocation density and coarsened M 23 C 6 carbides of this zone. The fracture location is in OTZ adjacent to BM1 side determined by microstructure, micro-hardness and geometric calculation. Lots of voids are observed along the triple grain boundaries associated with large second phase particles after creep rupture. The stress concentration caused by the coarsened carbides at the triple boundaries and softening matrix are considered as the main factor of creep voids occurring in the OTZ of Welded Joint.
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correlation of microstructure and fracture toughness of advanced 9cr crmov dissimilarly Welded Joint
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Qian Guo, Haichao Cui, Xia Liu, Renjie Yang, Yulai GaoAbstract:Abstract In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly Welded Joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly Welded Joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of Welded Joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole Welded Joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.
