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Qunjia Peng - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and corrosion behavior of the heat affected zone of a stainless steel 308L-316L weld joint
Journal of Materials Science and Technology, 2018Co-Authors: Cheng Ma, Jinna Mei, Qunjia Peng, En-hou Han, Wei KeAbstract:Microstructure of the heat affected zone (HAZ) of a 308L-316L stainless steel (SS) weld joint and its corrosion behavior in high temperature water were studied. Peak of the residual strain was observed to approach to the Fusion Boundary in the HAZ while the strain increased from the top to root areas of the HAZ. The root area of the HAZ shows a lower corrosion resistance in high temperature water than the top and middle areas of the HAZ. This is attributed to a higher level of residual strain in association with a higher density of tangled dislocations in the top area of the HAZ. The results suggest that the residual strain in the HAZ could also promote the SCC through its effect on corrosion, in addition to that on the local microstructure and mechanical property of the steel.
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correlation of microstructure and stress corrosion cracking initiation behaviour of the Fusion Boundary region in a sa508 cl 3 alloy 52m dissimilar weld joint in primary pressurized water reactor environment
Corrosion Science, 2017Co-Authors: Lijin Dong, Qunjia Peng, Wei KeAbstract:Abstract Correlation of microstructure and stress corrosion cracking (SCC) initiation behaviour of the Fusion Boundary (FB) region in a SA508 Cl. 3-Alloy 52M weld joint in primary pressurized water reactor environment was investigated. Cr-depletion at the grain Boundary and strength mismatch in the FB region are the two causes for SCC initiation in the FB region. The partially mixed zone between the dilution zone (DZ) of Alloy 52M and SA508 Cl. 3 has a retardation effect on SCC initiation. This is attributed to the decrease of strength mismatch and the alleviation of strain concentration adjacent to the grain Boundary in DZ.
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Stress corrosion cracking in the heat affected zone of a stainless steel 308L-316L weld joint in primary water
Corrosion Science, 2016Co-Authors: Lijin Dong, Qunjia Peng, Wei Ke, En-hou Han, Lei WangAbstract:Stress corrosion cracking (SCC) in the heat affected zone (HAZ) of a stainless steel 308L-316L weld joint in primary water of pressurized water reactor was investigated. Stress corrosion crack growth in the HAZ was observed in off-normal primary water chemistry with dissolved oxygen, but not in normal primary water chemistry with dissolved hydrogen. This suggests that it is unlikely a stress corrosion crack propagating in the HAZ could reach the Fusion Boundary and penetrate into the weld metal under normal primary water chemistry conditions. Microstructure analysis of the crack tip suggests that the SCC follows the slip-oxidation mechanism.
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role of water chemistry and microstructure in stress corrosion cracking in the Fusion Boundary region of an alloy 182 a533b low alloy steel dissimilar weld joint in high temperature water
Corrosion Science, 2011Co-Authors: Qunjia Peng, Yoichi Takeda, Jiro Kuniya, Juan Hou, He Xue, Kazuhiko Sakaguchi, Tetsuo ShojiAbstract:abstract Stress corrosion cracking (SCC) in the Fusion Boundary (FB) region of an Alloy 182-low alloy steel (LAS)dissimilar weld joint in 288 C water was investigated by experiments and finite element simulation.Creviced bent beam and crack growth rate (CGR) experiments showed that, while the FB was a barrierto SCC growth, further crack growth into LAS was activated by a combined effect of sulfate and dissolvedoxygen in water. Finite element simulation suggested that a positive gradient of hardness as the crackapproached to the FB in dilution zone caused decreased CGR. Role of microstructure and water chemistryin SCC was discussed. 2011 Elsevier Ltd. All rights reserved. 1. IntroductionStress corrosion cracking (SCC) of Alloy 182 weld metal in hightemperature water has caused concerns in recent years on the SCCbehavior of the Fusion Boundary (FB) region of an Alloy 182-lowalloy steel (LAS) dissimilar weld joint in light water reactors[1,2]. The FB region has a complex microstructure due to the jumpof the composition across the FB and the heat input from the weld-ing process, including the change in the crystallographic structurefrom FCC (the weld metal) to BCC (the base metal), the dilution ofthe weld metal, the heated affected microstructure in the basemetal, and the high residual strain adjacent to the FB, etc. [3–5].Further, Nelson et al. [6–8] found that a random-misorientationrelationship existed at the FB between the base and weld metalgrains in a dissimilar weld joint of 409 stainless steel-AISI 1080 al-loy. They also concluded that the type-II Boundary, which parallelsthe FB in the weld metal within 100
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role of water chemistry and microstructure in stress corrosion cracking in the Fusion Boundary region of an alloy 182 a533b low alloy steel dissimilar weld joint in high temperature water
Corrosion Science, 2011Co-Authors: Qunjia Peng, Yoichi Takeda, Jiro Kuniya, Juan Hou, He Xue, Kazuhiko Sakaguchi, Tetsuo ShojiAbstract:Abstract Stress corrosion cracking (SCC) in the Fusion Boundary (FB) region of an Alloy 182-low alloy steel (LAS) dissimilar weld joint in 288 °C water was investigated by experiments and finite element simulation. Creviced bent beam and crack growth rate (CGR) experiments showed that, while the FB was a barrier to SCC growth, further crack growth into LAS was activated by a combined effect of sulfate and dissolved oxygen in water. Finite element simulation suggested that a positive gradient of hardness as the crack approached to the FB in dilution zone caused decreased CGR. Role of microstructure and water chemistry in SCC was discussed.
Tetsuo Shoji - One of the best experts on this subject based on the ideXlab platform.
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characterizations of the microstructure of 9cr 1mo steel weld joint after long term service in a supercritical fossil power plant
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2018Co-Authors: Xiangyu Zhong, Tetsuo Shoji, Tadashi Tatsuki, Yuji Matsumura, Makoto NakashimaAbstract:In the present work, the microstructure, micro-hardness, and chemical composition of 9Cr-1Mo weld joint after long-term service in a supercritical power plant were analyzed by using various analytical techniques. The hardness profile showed a maximum at the Fusion Boundary and a minimum in the region of the fine grain heat-affected zone (FGHAZ). Many cavities along the grain boundaries and in grains were also observed in the FGHAZ. Ferrite zones with lower hardness and larger grain sizes were observed in the weld metal. The formation mechanisms of the cavities and ferrite zones were discussed based on the results.
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microstructures and microhardness at Fusion Boundary of 316 stainless steel inconel 182 dissimilar welding
Materials Characterization, 2015Co-Authors: Wei Wang, Tetsuo Shoji, Xianfei DingAbstract:Abstract Microstructures and microhardness at Fusion Boundary of a weld joint were investigated in a 316 stainless steel/Inconel 182 dissimilar weldment. The results showed that there were two alternately distributed typical Fusion boundaries, a narrow random Boundary (possessed 15% in length) with a clear sharp interface and an epitaxial Fusion one with (100) BM //(100) WM at the joint interface. The composition transition, microstructure and hardness across the Fusion Boundary strongly depended on the type of the Fusion Boundary. For the random Boundary, there was a clear sharp interface and the composition transition with a width of 100 μm took place symmetrically across the grain Boundary. For the epitaxial Fusion one, however, there were Type-I and Type-II grain boundaries perpendicular and parallel to the epitaxial Fusion Boundary, respectively. The composition transition took place in the Inconel 182 weld side. Σ3 boundaries in the HAZ of 316SS side and Σ5 grain boundaries in weld metal were usually observed, despite the type of Fusion Boundary, however the former was much more in epitaxial Fusion Boundary. Microhardness was continuously decreased across the random Fusion Boundary from the side of Inconel 182 to 316SS, but a hardening phenomenon appeared in the epitaxial Fusion Boundary zone because of its fine cellular microstructure.
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role of water chemistry and microstructure in stress corrosion cracking in the Fusion Boundary region of an alloy 182 a533b low alloy steel dissimilar weld joint in high temperature water
Corrosion Science, 2011Co-Authors: Qunjia Peng, Yoichi Takeda, Jiro Kuniya, Juan Hou, He Xue, Kazuhiko Sakaguchi, Tetsuo ShojiAbstract:abstract Stress corrosion cracking (SCC) in the Fusion Boundary (FB) region of an Alloy 182-low alloy steel (LAS)dissimilar weld joint in 288 C water was investigated by experiments and finite element simulation.Creviced bent beam and crack growth rate (CGR) experiments showed that, while the FB was a barrierto SCC growth, further crack growth into LAS was activated by a combined effect of sulfate and dissolvedoxygen in water. Finite element simulation suggested that a positive gradient of hardness as the crackapproached to the FB in dilution zone caused decreased CGR. Role of microstructure and water chemistryin SCC was discussed. 2011 Elsevier Ltd. All rights reserved. 1. IntroductionStress corrosion cracking (SCC) of Alloy 182 weld metal in hightemperature water has caused concerns in recent years on the SCCbehavior of the Fusion Boundary (FB) region of an Alloy 182-lowalloy steel (LAS) dissimilar weld joint in light water reactors[1,2]. The FB region has a complex microstructure due to the jumpof the composition across the FB and the heat input from the weld-ing process, including the change in the crystallographic structurefrom FCC (the weld metal) to BCC (the base metal), the dilution ofthe weld metal, the heated affected microstructure in the basemetal, and the high residual strain adjacent to the FB, etc. [3–5].Further, Nelson et al. [6–8] found that a random-misorientationrelationship existed at the FB between the base and weld metalgrains in a dissimilar weld joint of 409 stainless steel-AISI 1080 al-loy. They also concluded that the type-II Boundary, which parallelsthe FB in the weld metal within 100
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role of water chemistry and microstructure in stress corrosion cracking in the Fusion Boundary region of an alloy 182 a533b low alloy steel dissimilar weld joint in high temperature water
Corrosion Science, 2011Co-Authors: Qunjia Peng, Yoichi Takeda, Jiro Kuniya, Juan Hou, He Xue, Kazuhiko Sakaguchi, Tetsuo ShojiAbstract:Abstract Stress corrosion cracking (SCC) in the Fusion Boundary (FB) region of an Alloy 182-low alloy steel (LAS) dissimilar weld joint in 288 °C water was investigated by experiments and finite element simulation. Creviced bent beam and crack growth rate (CGR) experiments showed that, while the FB was a barrier to SCC growth, further crack growth into LAS was activated by a combined effect of sulfate and dissolved oxygen in water. Finite element simulation suggested that a positive gradient of hardness as the crack approached to the FB in dilution zone caused decreased CGR. Role of microstructure and water chemistry in SCC was discussed.
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microstructure and stress corrosion cracking of the Fusion Boundary region in an alloy 182 a533b low alloy steel dissimilar weld joint
Corrosion Science, 2010Co-Authors: Qunjia Peng, Yoichi Takeda, Jiro Kuniya, Tetsuo ShojiAbstract:Stress corrosion cracking (SCC) in the Fusion Boundary (FB) region of an Alloy 182-A533B low alloy steel (LAS) dissimilar weld joint in high temperature water doped with sulfate was studied following a microstructure characterization of the FB region. The microstructure characterization suggested the type-II and type-I boundaries in the dilution zone (DZ) adjacent to the FB had lower resistance to SCC growth than the FB. Crack propagating perpendicular to the FB in the DZ was observed to be blunted by pitting at the FB, followed by the reactivation from the pitting by localized oxidation along the grain Boundary in LAS.
Jianqiu Wang - One of the best experts on this subject based on the ideXlab platform.
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multi scale study of ductility dip cracking in nickel based alloy dissimilar metal weld
Journal of Materials Science & Technology, 2019Co-Authors: Jianqiu Wang, Yifeng Li, Wenbo Wu, Hannu HänninenAbstract:Abstract A ductility-dip-cracking (DDC)-concentrated zone (DCZ) in a width of about 3 mm was observed adjacent to the AISI 316 L/52 Mw Fusion Boundary (FB) in 52 Mw. The morphology, microstructure, mechanical and thermal properties and corrosion behavior in simulated primary water of DDC/DCZ were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), 3D X-ray tomography (XRT), 3D atom probe (3DAP), slow strain rate tensile (SSRT) testing and thermal dilatometry. The results indicate that DDCs are random-shaped and disc-like cavities with corrugated structure of inner surface and are parallel in groups along straight high-angle boundaries of columnar grains, ranging from micrometers to millimeters in size. Large-size M23C6 carbides dominate on the grain boundaries rather than MC (M=Nb, Ti), and thus the bonding effect of carbides is absent for the straight grain boundaries. The impurity segregation of O is confirmed for the inner surfaces of DDC. The oxide film formed on the inner surface of DDC (about 50 nm) is approximately twice as thick as that on the matrix (about 25 nm) in simulated primary water. The yield strength, tensile strength and elongation to fracture of 52 Mw-DCZ (400 MPa, 450 MPa and 20 %, respectively) are lower than those of 52 Mw-MZ (460 MPa, 550 MPa and 28 %, respectively). The intrinsic high-restraint weld structure, the additional stress/strain caused by the thermal expansion difference between AISI 316 L and 52 Mw as well as the detrimental carbide precipitation and the resulting grain Boundary structure all add up to cause the occurrence of DCZ in the dissimilar metal weld.
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stress corrosion cracking of Fusion Boundary for 316l 52m dissimilar metal weld joints in borated and lithiated high temperature water
Corrosion Science, 2017Co-Authors: Ruolin Zhu, Jianqiu Wang, Zhiming Zhang, En-hou HanAbstract:Abstract The stress corrosion cracking (SCC) crack growth rates (CGRs) at the Fusion Boundary (FB) for 316L/52M weld joints were measured using direct current potential drop systems in borated and lithiated high temperature water. The cracks propagated along the FB and were blocked after propagating into the composition transient zone. The cracking mode is both intergranular and transgranular. The CGRs at the FB are similar to those in the heat-affected zone (HAZ) in oxygenated water, but slightly higher than those in the HAZ in hydrogenated water. The temperature dependences of CGR in both hydrogenated and oxygenated water are discussed.
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microstructure of a safe end dissimilar metal weld joint sa508 52 316l prepared by narrow gap gtaw
Materials Characterization, 2017Co-Authors: Hongliang Ming, Jianqiu Wang, Zhiming Zhang, Peipei WangAbstract:Abstract The microstructure, residual strain and interfacial chemical composition distribution of a safe-end dissimilar metal weld joint (DMWJ, SA508-52-316L) prepared by narrow-gap gas-tungsten arc welding (NG-GTAW) were studied by optical microscope (OM) and scanning electron microscope equipped with an energy dispersive X-ray microanalysis (SEM/EDX) and an electron back scattering diffraction (EBSD) system. Complex microstructure and chemical composition distribution are found, especially at the SA508-52 interface and the 52-316L interface. In brief, a complicated microstructure transition exists within the SA508 heat affected zone (HAZ); the residual strain, the fraction of high angle random grain boundaries and low angle boundaries decrease with increasing the distance from the Fusion Boundary in 316L HAZ; neither typical type II Boundary nor obvious carbon-depleted zone is found near the SA508-52 interface; dramatic and complicated changes of the contents of the main elements, Fe, Cr and Ni, are observed at the distinct interfaces, especially at the SA508-52 interface. No carbon concentration is found at the SA508-52 interface.
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stress corrosion cracking of 316l haz for 316l stainless steel inconel 52m dissimilar metal weld joint in simulated primary water
Corrosion Science, 2016Co-Authors: Jianqiu Wang, Litao Zhang, Zhiming ZhangAbstract:Abstract The stress corrosion cracking (SCC) behaviour of 316L heat affected zones (HAZ) in 316L stainless steel/Inconel 52M dissimilar metal welded joint (DMWJ) in simulated primary water was systematically evaluated using direct current potential drop (DCPD) methods. Crack growth rates (CGRs) of 316L HAZ increased with increasing temperature and dissolved oxygen (DO) contents. CGR in hydrogenated water was approximately one order of magnitude slower than in oxygenated water. The fracture surface shows typical mixed intergranular-transgranular SCC characteristics and several fast finger-like cracks. Several intergranular secondary cracks, perpendicular to the main crack and Fusion Boundary, were also observed.
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microstructure residual strain and stress corrosion cracking behavior in 316l heat affected zone
Acta Metallurgica Sinica (english Letters), 2016Co-Authors: Hongliang Ming, Jianqiu Wang, Zhiming Zhang, Pengyuan Xiu, En-hou HanAbstract:Austenitic stainless steels are usually chosen to make many components of nuclear power plants (NPPs). However, their microstructure in the heat-affected zone (HAZ) will change during the welding process. Some failures of the weld joints, mainly stress corrosion cracking (SCC), have been found to be located in the HAZ. In this research, the microstructure, micro-hardness, residual strain and SCC behavior at different locations of the 316L HAZ cut from a safe-end dissimilar metal weld joint were studied. However, traditional optical microscope observation could not find any microstructural difference between the HAZ and the base metal, higher residual strain and micro-hardness, and higher fraction of random high-angle grain boundaries were found in the HAZ than in the base metal when studied by using electron back-scattering diffraction scanning and micro-hardness test. What’s more, the residual strain, the micro-hardness and the fraction of random grain boundaries decreased, while the fraction of coincidence site lattice grain boundaries increased with increasing the distance from the Fusion Boundary in 316L HAZ. Creviced bent beam test was applied to evaluate the SCC susceptibility at different locations of 316L HAZ and base metal. It was found that the HAZ had higher SCC susceptibility than the base metal and SCC resistance increased when increasing the distance from the Fusion Boundary in 316L HAZ.
Zhiming Zhang - One of the best experts on this subject based on the ideXlab platform.
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stress corrosion cracking of Fusion Boundary for 316l 52m dissimilar metal weld joints in borated and lithiated high temperature water
Corrosion Science, 2017Co-Authors: Ruolin Zhu, Jianqiu Wang, Zhiming Zhang, En-hou HanAbstract:Abstract The stress corrosion cracking (SCC) crack growth rates (CGRs) at the Fusion Boundary (FB) for 316L/52M weld joints were measured using direct current potential drop systems in borated and lithiated high temperature water. The cracks propagated along the FB and were blocked after propagating into the composition transient zone. The cracking mode is both intergranular and transgranular. The CGRs at the FB are similar to those in the heat-affected zone (HAZ) in oxygenated water, but slightly higher than those in the HAZ in hydrogenated water. The temperature dependences of CGR in both hydrogenated and oxygenated water are discussed.
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microstructure of a safe end dissimilar metal weld joint sa508 52 316l prepared by narrow gap gtaw
Materials Characterization, 2017Co-Authors: Hongliang Ming, Jianqiu Wang, Zhiming Zhang, Peipei WangAbstract:Abstract The microstructure, residual strain and interfacial chemical composition distribution of a safe-end dissimilar metal weld joint (DMWJ, SA508-52-316L) prepared by narrow-gap gas-tungsten arc welding (NG-GTAW) were studied by optical microscope (OM) and scanning electron microscope equipped with an energy dispersive X-ray microanalysis (SEM/EDX) and an electron back scattering diffraction (EBSD) system. Complex microstructure and chemical composition distribution are found, especially at the SA508-52 interface and the 52-316L interface. In brief, a complicated microstructure transition exists within the SA508 heat affected zone (HAZ); the residual strain, the fraction of high angle random grain boundaries and low angle boundaries decrease with increasing the distance from the Fusion Boundary in 316L HAZ; neither typical type II Boundary nor obvious carbon-depleted zone is found near the SA508-52 interface; dramatic and complicated changes of the contents of the main elements, Fe, Cr and Ni, are observed at the distinct interfaces, especially at the SA508-52 interface. No carbon concentration is found at the SA508-52 interface.
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stress corrosion cracking of 316l haz for 316l stainless steel inconel 52m dissimilar metal weld joint in simulated primary water
Corrosion Science, 2016Co-Authors: Jianqiu Wang, Litao Zhang, Zhiming ZhangAbstract:Abstract The stress corrosion cracking (SCC) behaviour of 316L heat affected zones (HAZ) in 316L stainless steel/Inconel 52M dissimilar metal welded joint (DMWJ) in simulated primary water was systematically evaluated using direct current potential drop (DCPD) methods. Crack growth rates (CGRs) of 316L HAZ increased with increasing temperature and dissolved oxygen (DO) contents. CGR in hydrogenated water was approximately one order of magnitude slower than in oxygenated water. The fracture surface shows typical mixed intergranular-transgranular SCC characteristics and several fast finger-like cracks. Several intergranular secondary cracks, perpendicular to the main crack and Fusion Boundary, were also observed.
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microstructure residual strain and stress corrosion cracking behavior in 316l heat affected zone
Acta Metallurgica Sinica (english Letters), 2016Co-Authors: Hongliang Ming, Jianqiu Wang, Zhiming Zhang, Pengyuan Xiu, En-hou HanAbstract:Austenitic stainless steels are usually chosen to make many components of nuclear power plants (NPPs). However, their microstructure in the heat-affected zone (HAZ) will change during the welding process. Some failures of the weld joints, mainly stress corrosion cracking (SCC), have been found to be located in the HAZ. In this research, the microstructure, micro-hardness, residual strain and SCC behavior at different locations of the 316L HAZ cut from a safe-end dissimilar metal weld joint were studied. However, traditional optical microscope observation could not find any microstructural difference between the HAZ and the base metal, higher residual strain and micro-hardness, and higher fraction of random high-angle grain boundaries were found in the HAZ than in the base metal when studied by using electron back-scattering diffraction scanning and micro-hardness test. What’s more, the residual strain, the micro-hardness and the fraction of random grain boundaries decreased, while the fraction of coincidence site lattice grain boundaries increased with increasing the distance from the Fusion Boundary in 316L HAZ. Creviced bent beam test was applied to evaluate the SCC susceptibility at different locations of 316L HAZ and base metal. It was found that the HAZ had higher SCC susceptibility than the base metal and SCC resistance increased when increasing the distance from the Fusion Boundary in 316L HAZ.
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microstructure local mechanical properties and stress corrosion cracking susceptibility of an sa508 52m 316ln safe end dissimilar metal weld joint by gtaw
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Hongliang Ming, Jianqiu Wang, Wei Ke, Zhiming Zhang, Mingxing SuAbstract:Abstract The microstructure, local mechanical properties and local stress corrosion cracking susceptibility of an SA508-52M-316LN domestic dissimilar metal welded safe-end joint used for AP1000 nuclear power plant prepared by automatic gas tungsten arc welding was studied in this work by optical microscopy, scanning electron microscopy (with electron back scattering diffraction and an energy dispersive X-ray spectroscopy system), micro-hardness testing, local mechanical tensile testing and local slow strain rate tests. The micro-hardness, local mechanical properties and stress corrosion cracking susceptibility across this dissimilar metal weld joint vary because of the complex microstructure across the Fusion area and the dramatic chemical composition change across the Fusion lines. Briefly, Type I boundaries and Type II boundaries exist in 52Mb near the SA508-52Mb interface, a microstructure transition was found in SA508 heat affected zone, the residual strain and grain Boundary character distribution changes as a function of the distance from the Fusion Boundary in 316LN heat affected zone, micro-hardness distribution and local mechanical properties along the DMWJ are heterogeneous, and 52Mw-316LN interface has the highest SCC susceptibility in this DMWJ while 316LN base metal has the lowest one.
En-hou Han - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and corrosion behavior of the heat affected zone of a stainless steel 308L-316L weld joint
Journal of Materials Science and Technology, 2018Co-Authors: Cheng Ma, Jinna Mei, Qunjia Peng, En-hou Han, Wei KeAbstract:Microstructure of the heat affected zone (HAZ) of a 308L-316L stainless steel (SS) weld joint and its corrosion behavior in high temperature water were studied. Peak of the residual strain was observed to approach to the Fusion Boundary in the HAZ while the strain increased from the top to root areas of the HAZ. The root area of the HAZ shows a lower corrosion resistance in high temperature water than the top and middle areas of the HAZ. This is attributed to a higher level of residual strain in association with a higher density of tangled dislocations in the top area of the HAZ. The results suggest that the residual strain in the HAZ could also promote the SCC through its effect on corrosion, in addition to that on the local microstructure and mechanical property of the steel.
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stress corrosion cracking of Fusion Boundary for 316l 52m dissimilar metal weld joints in borated and lithiated high temperature water
Corrosion Science, 2017Co-Authors: Ruolin Zhu, Jianqiu Wang, Zhiming Zhang, En-hou HanAbstract:Abstract The stress corrosion cracking (SCC) crack growth rates (CGRs) at the Fusion Boundary (FB) for 316L/52M weld joints were measured using direct current potential drop systems in borated and lithiated high temperature water. The cracks propagated along the FB and were blocked after propagating into the composition transient zone. The cracking mode is both intergranular and transgranular. The CGRs at the FB are similar to those in the heat-affected zone (HAZ) in oxygenated water, but slightly higher than those in the HAZ in hydrogenated water. The temperature dependences of CGR in both hydrogenated and oxygenated water are discussed.
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microstructure residual strain and stress corrosion cracking behavior in 316l heat affected zone
Acta Metallurgica Sinica (english Letters), 2016Co-Authors: Hongliang Ming, Jianqiu Wang, Zhiming Zhang, Pengyuan Xiu, En-hou HanAbstract:Austenitic stainless steels are usually chosen to make many components of nuclear power plants (NPPs). However, their microstructure in the heat-affected zone (HAZ) will change during the welding process. Some failures of the weld joints, mainly stress corrosion cracking (SCC), have been found to be located in the HAZ. In this research, the microstructure, micro-hardness, residual strain and SCC behavior at different locations of the 316L HAZ cut from a safe-end dissimilar metal weld joint were studied. However, traditional optical microscope observation could not find any microstructural difference between the HAZ and the base metal, higher residual strain and micro-hardness, and higher fraction of random high-angle grain boundaries were found in the HAZ than in the base metal when studied by using electron back-scattering diffraction scanning and micro-hardness test. What’s more, the residual strain, the micro-hardness and the fraction of random grain boundaries decreased, while the fraction of coincidence site lattice grain boundaries increased with increasing the distance from the Fusion Boundary in 316L HAZ. Creviced bent beam test was applied to evaluate the SCC susceptibility at different locations of 316L HAZ and base metal. It was found that the HAZ had higher SCC susceptibility than the base metal and SCC resistance increased when increasing the distance from the Fusion Boundary in 316L HAZ.
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Stress corrosion cracking in the heat affected zone of a stainless steel 308L-316L weld joint in primary water
Corrosion Science, 2016Co-Authors: Lijin Dong, Qunjia Peng, Wei Ke, En-hou Han, Lei WangAbstract:Stress corrosion cracking (SCC) in the heat affected zone (HAZ) of a stainless steel 308L-316L weld joint in primary water of pressurized water reactor was investigated. Stress corrosion crack growth in the HAZ was observed in off-normal primary water chemistry with dissolved oxygen, but not in normal primary water chemistry with dissolved hydrogen. This suggests that it is unlikely a stress corrosion crack propagating in the HAZ could reach the Fusion Boundary and penetrate into the weld metal under normal primary water chemistry conditions. Microstructure analysis of the crack tip suggests that the SCC follows the slip-oxidation mechanism.
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microstructure and mechanical property of the Fusion Boundary region in an alloy 182 low alloy steel dissimilar weld joint
Journal of Materials Science, 2010Co-Authors: Qunjia Peng, Tetsuo Shoji, Yoichi Takeda, Jiro Kuniya, Juan Hou, J Q Wang, En-hou HanAbstract:Characterizations of the microstructure and mechanical property of the Fusion Boundary region of an Alloy 182-A533B low alloy steel (LAS) dissimilar weld joint were conducted. The existence of type-II Boundary that parallels to the Fusion Boundary in the dilution zone (DZ) of Alloy 182 within a distance of about 50 μm was observed. The chemical composition transition was found in the narrow zone between the type-II and the Fusion boundaries. Highest hardness was also found in this narrow zone in the Fusion Boundary region, implying a high residual strain level in the narrow zone. Lath martensite was observed in both sides of the type-II Boundary in DZ, suggesting the localized enrichment of Fe and C adjacent to the type-II Boundary due to the difFusion from LAS to DZ. Massive precipitations of carbides were observed on the type-II Boundary but not on the Fusion Boundary. In addition, the orientation relationship at the Fusion Boundary between the lath martensite in the heat-affected zone in LAS and the austenite in the DZ was found to be Bain, K–S and N–W relationships.
