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J. A. Szpunar - One of the best experts on this subject based on the ideXlab platform.
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investigation of the hydrogen induced Cracking behaviour of api 5l x65 pipeline steel
International Journal of Hydrogen Energy, 2020Co-Authors: Tonye Alaso Jack, Enyinnaya Ohaeri, J. A. Szpunar, Reza Pourazizi, Jiming ZhangAbstract:Abstract The effect of microstructural features on the hydrogen induced Cracking (HIC) susceptibility of two API 5L X65 pipeline steels were investigated by cathodic charging, hydrogen permeation and hydrogen microprint experiments. Microstructural evaluation after hydrogen charging revealed cracks at the mid-thickness (segregation zone) of both plates. However, more severe cracks were observed in the plate with higher dislocation density and residual stresses. The plate with lower plastic strain and more {111}-oriented grains had less severe cracks. Inclusions found along the crack path, comprising of Si-enriched oxides and carbides contributed to the initiation and propagation of cracks. The variation of the trapping behaviour and hydrogen diffusion through the plates were examined. The results confirmed that a higher ratio of reversible to irreversible traps contributes to increasing HIC severity in steels. Additionally, hydrogen transport through the steels was most prominent along the grain boundaries, indicating the importance of grain boundary character to HIC.
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role of cold rolled followed by annealing on improvement of hydrogen induced Cracking resistance in pipeline steel
Engineering Failure Analysis, 2018Co-Authors: M A Mohtadibonab, M. Eskandari, J. A. SzpunarAbstract:Abstract In this study, we investigated the effect of cold rolled followed by annealing on hydrogen induced Cracking susceptibility in an API X60 pipeline steel. To this, we carried out cold rolling on X60 steel up to 20%, 50% and 90% in thickness reduction to change the microstructure and texture of steel. Then, we annealed all specimens at 850 °C for 90 s. We studied all tested specimens by electron backscatter and X-ray diffraction techniques. EBSD results showed that the grain refinement process was properly done via cold rolling and annealing treatments in tested specimens. However, the dislocation density was high for all tested steels. Moreover, electrochemical hydrogen charging experiment on tested steels proved that all specimens were still highly susceptible to hydrogen induced Cracking. Therefore, we increased the annealing temperature and its duration of the 90% cold rolled specimen (the specimen with finest grains) up to 950 °C for 5 min. Interestingly, there was no HIC crack on this steel after hydrogen charging experiment. EBSD measurements on this steel showed strong textures of {100}//ND and {111}//ND. As a result, such strong textures, low Kernel Average Misorientation data, a high proportion of recovered grains and coincidence site lattice boundaries were recognized as the most important reasons for the highest HIC resistance in the mentioned steel.
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effect of different microstructural parameters on hydrogen induced Cracking in an api x70 pipeline steel
Metals and Materials International, 2017Co-Authors: M A Mohtadibonab, M. Eskandari, R. Karimdadashi, J. A. SzpunarAbstract:In this study, the surface and cross section of an as-received API X70 pipeline steel was studied by SEM and EDS techniques in order to categorize the shape and morphology of inclusions. Then, an electrochemical hydrogen charging using a mixed solution of 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate has been utilized to create hydrogen cracks in X70 steel. After hydrogen charging experiments, the cross section of this steel has been accurately checked by SEM in order to find out hydrogen cracks. The region of hydrogen cracks was investigated by SEM and EBSD techniques to predict the role of different microstructural parameters involving hydrogen induced Cracking (HIC) phenomenon. The results showed that inclusions were randomly distributed in the cross section of tested specimens. Moreover, different types of inclusions in as-received X70 steel were found. However, only inclusions which were hard, brittle and incoherent with the metal matrix, such as manganese sulfide and carbonitride precipitates, were recognized to be harmful to HIC phenomenon. Moreover, HIC cracks propagate dominantly in transgraular manner through differently oriented grains with no clear preferential trend. Moreover, a different type of HIC crack with about 15-20 degrees of deviation from the rolling direction was found and studied by EBSD technique and role of micro-texture parameters on HIC was discussed.
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Effect of arisen dislocation density and texture components during cold rolling and annealing treatments on hydrogen induced Cracking susceptibility in pipeline steel
Journal of Materials Research, 2016Co-Authors: M.a. Mohtadi-bonab, M. Eskandari, J. A. SzpunarAbstract:In this study, we used thermo–mechanical control process (TMCP) technique to investigate the effect of arisen dislocation density and texture components on hydrogen induced Cracking susceptibility in as-received API X60 pipeline steel. Dislocations and texture components appeared during cold rolling and annealing treatments. X-ray diffraction and electron backscatter diffraction measurements were used to study these phenomena. We observed that the cold rolling and annealing treatments produced higher dislocation density in deformed and recovered regions. The increase of dislocation density also caused the increased hydrogen trap density. Macro-texture studies by x-ray method indicates that initial weak texture of as-received X60 steel was changed from ζ-fiber to γ-fiber and θ-fiber in 90% cold rolled and annealed specimen. Therefore, the number of grains with {100}ND orientation which had a harmful effect on hydrogen induced Cracking susceptibility increased. The {100} dominant texture and high density of hydrogen traps mitigated against any possible benefits of the other microstructural parameters such as coincidence site lattice boundaries and grain size. As a result, we could not consider this process as a suitable method to increase hydrogen induced Cracking resistance in pipeline steel.
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Hydrogen-Induced Cracking Assessment in Pipeline Steels Through Permeation and Crystallographic Texture Measurements
Journal of Materials Engineering and Performance, 2016Co-Authors: M.a. Mohtadi-bonab, M. Eskandari, R. Karimdadashi, J. A. SzpunarAbstract:Electrochemical hydrogen charging and permeation techniques were used to characterize hydrogen distribution, trapping, and diffusion in X60 and X60 sour service (X60SS) pipeline steels. The results obtained contribute to better understanding of Hydrogen-Induced Cracking (HIC). SEM observations illustrated that all HIC cracks were formed at the center of cross section in the X60 steel after 3-h hydrogen charging and length of cracks increased with charging time. No HIC cracks were recorded at the cross section of X60SS steel after the same charging for different durations. Hydrogen permeation tests showed that the density of reversible hydrogen traps was lower at the center of cross section in the X60SS steel compared to the X60 one, and this is considered as one of the main reasons for high resistance of X60SS steel to HIC. EBSD orientation imaging results proved that the accumulation of ||ND-oriented grains at the center of the cross section in the X60SS steel was high. This is also considered as another reason for higher resistance of this steel to HIC. Finally, the center segregation zone with higher hardness value in the X60 steel was more pronounced than in the X60SS steel which made the X60 steel susceptible to HIC Cracking.
M A Mohtadibonab - One of the best experts on this subject based on the ideXlab platform.
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role of cold rolled followed by annealing on improvement of hydrogen induced Cracking resistance in pipeline steel
Engineering Failure Analysis, 2018Co-Authors: M A Mohtadibonab, M. Eskandari, J. A. SzpunarAbstract:Abstract In this study, we investigated the effect of cold rolled followed by annealing on hydrogen induced Cracking susceptibility in an API X60 pipeline steel. To this, we carried out cold rolling on X60 steel up to 20%, 50% and 90% in thickness reduction to change the microstructure and texture of steel. Then, we annealed all specimens at 850 °C for 90 s. We studied all tested specimens by electron backscatter and X-ray diffraction techniques. EBSD results showed that the grain refinement process was properly done via cold rolling and annealing treatments in tested specimens. However, the dislocation density was high for all tested steels. Moreover, electrochemical hydrogen charging experiment on tested steels proved that all specimens were still highly susceptible to hydrogen induced Cracking. Therefore, we increased the annealing temperature and its duration of the 90% cold rolled specimen (the specimen with finest grains) up to 950 °C for 5 min. Interestingly, there was no HIC crack on this steel after hydrogen charging experiment. EBSD measurements on this steel showed strong textures of {100}//ND and {111}//ND. As a result, such strong textures, low Kernel Average Misorientation data, a high proportion of recovered grains and coincidence site lattice boundaries were recognized as the most important reasons for the highest HIC resistance in the mentioned steel.
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a focus on different factors affecting hydrogen induced Cracking in oil and natural gas pipeline steel
Engineering Failure Analysis, 2017Co-Authors: M A Mohtadibonab, M. EskandariAbstract:Abstract In this research, hydrogen induced Cracking (HIC) behavior of an API X70 pipeline steel has been studied. In order to create HIC cracks, an electrochemical hydrogen charging experiment was carried out on X70 steel by using 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate for 8 h. Moreover, SEM, EDS and EBSD techniques were used to characterize the as-received (AR) steel and investigate the different aspects of HIC phenomenon as well. The results showed that the inclusions and precipitates which play a key role in HIC phenomenon have been distributed randomly through the cross-section of tested steel. However, the concentration of them was higher at the center of cross-section than other areas. All HIC cracks initiated and propagated through the center of thickness where center segregation of elements has occurred. It is also observed that HIC cracks were initiated from several special types of inclusions and precipitates such as manganese sulphide and carbonitride precipitates. EBSD results showed that the dominant local texture of center of thickness in RD-TD plane was {001}//ND and {111}//ND. Moreover, HIC cracks propagate through differently oriented grains where the local texture is random.
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effect of different microstructural parameters on hydrogen induced Cracking in an api x70 pipeline steel
Metals and Materials International, 2017Co-Authors: M A Mohtadibonab, M. Eskandari, R. Karimdadashi, J. A. SzpunarAbstract:In this study, the surface and cross section of an as-received API X70 pipeline steel was studied by SEM and EDS techniques in order to categorize the shape and morphology of inclusions. Then, an electrochemical hydrogen charging using a mixed solution of 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate has been utilized to create hydrogen cracks in X70 steel. After hydrogen charging experiments, the cross section of this steel has been accurately checked by SEM in order to find out hydrogen cracks. The region of hydrogen cracks was investigated by SEM and EBSD techniques to predict the role of different microstructural parameters involving hydrogen induced Cracking (HIC) phenomenon. The results showed that inclusions were randomly distributed in the cross section of tested specimens. Moreover, different types of inclusions in as-received X70 steel were found. However, only inclusions which were hard, brittle and incoherent with the metal matrix, such as manganese sulfide and carbonitride precipitates, were recognized to be harmful to HIC phenomenon. Moreover, HIC cracks propagate dominantly in transgraular manner through differently oriented grains with no clear preferential trend. Moreover, a different type of HIC crack with about 15-20 degrees of deviation from the rolling direction was found and studied by EBSD technique and role of micro-texture parameters on HIC was discussed.
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an extensive study of hydrogen induced Cracking susceptibility in an api x60 sour service pipeline steel
International Journal of Hydrogen Energy, 2016Co-Authors: M A Mohtadibonab, M. Eskandari, K M M Rahman, Ryan Ouellet, J. A. SzpunarAbstract:Abstract API X60 sour service (X60SS) pipeline steel was subjected to electrochemical hydrogen-charging for different durations in order to evaluate its Hydrogen-Induced Cracking (HIC) susceptibility. SEM observations of the hydrogen-charged specimens documented that no HIC cracks appeared at the cross section of steel, which is strong evidence of a high resistance to HIC. However, hydrogen-discharging results show that a considerable amount of hydrogen can enter the X60SS steel through its hydrogen traps. Moreover, a hydrogen-permeation test proved that the trapping behavior was almost identical at the center and surface layers of the cross section in this steel. However, the density of hydrogen traps at the center of the cross section was slightly higher than at the surface. Tensile and fatigue experiments were carried out in the air and in a hydrogen-charging environment using a newly constructed experimental setup. Tensile results show that the ductility dropped by 83% in the hydrogen-charging environment. Electron backscatter diffraction (EBSD) technique was used to analyze the HIC cracks in the X60SS steel. HIC cracks appeared after charging under tensile/fatigue tests. Therefore, high HIC-resistant steel showed susceptibility to HIC when charging and tensile stresses were applied simultaneously. The effects of different factors on HIC crack propagation such as micro-texture, type of grain boundaries, Kernel Average Misorientation (KAM), special coincidence site lattice (CSL) boundaries and recrystallization fraction, were discussed.
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texture local misorientation grain boundary and recrystallization fraction in pipeline steels related to hydrogen induced Cracking
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: M A Mohtadibonab, M. Eskandari, J. A. SzpunarAbstract:Abstract In the present study, API X60 and X60SS pipeline steels were cathodically charged by hydrogen for 8 h using 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate. After charging, SEM observations showed that the hydrogen induced Cracking (HIC) appeared at the center of cross section in the X60 specimen. However, HIC did not appear in the X60SS steel. Therefore, electron backscatter diffraction (EBSD) technique was used to analyze the center of cross section of as-received X60SS, X60 and HIC tested X60 specimens. The results showed that the HIC crack not only can propagate through 〈100〉||ND oriented grains but also its growth may happen in various orientations. In HIC tested X60 specimen, an accumulation of low angle grain boundaries around the crack path documented that full recrystallization was not achieved during hot rolling. Kernel Average Misorientaion (KAM) histogram illustrated that the deformation is more concentrated in as-received and HIC tested X60 specimens rather than in as-received X60SS specimen. Moreover, the concentration of coincidence site lattice (CSL) boundary in HIC tested X60 specimen was very low compared with other samples. The recrystallization area fraction in X60SS steel was very high. This high amount of recrystallization fraction with no stored energy is one of the main reasons for high HIC resistance of this steel to HIC. The orientation distribution function (ODF) of the recrystallized, substructured and deformed fractions in as-received X60SS and X60 steel showed relative close orientations in both as-received specimens.
Hamilton Ferreira Gomes De Abreu - One of the best experts on this subject based on the ideXlab platform.
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role of crystallographic texture on the improvement of hydrogen induced crack resistance in api 5l x70 pipeline steel
International Journal of Hydrogen Energy, 2017Co-Authors: Mohammad Masoumi, Cleiton Carvalho Silva, Miloslav Beres, Duberney Hincapie Ladino, Hamilton Ferreira Gomes De AbreuAbstract:Abstract The purpose of this work was to improve the resistance of Hydrogen-Induced Cracking in API 5L X70 steel by engineering the crystallographic texture and grain boundary distributions via different rolling temperatures. Hydrogen-Induced Cracking and electrochemical hydrogen charging tests were carried out in two different conditions: commercially produced and isothermally rolled at 850 °C in laboratory. The results showed that the development of dominant {011} grains parallel to the normal direction, and a small number of {001}//ND grains obtained by isothermal rolling at 850 °C, increased the Hydrogen-Induced crack resistance; while the hot rolled sample with sharp {001}//ND textures was highly susceptible to Cracking.
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effect of crystallographic orientations on the hydrogen induced Cracking resistance improvement of api 5l x70 pipeline steel under various thermomechanical processing
Corrosion Science, 2016Co-Authors: Mohammad Masoumi, Cleiton Carvalho Silva, Hamilton Ferreira Gomes De AbreuAbstract:Abstract In this study a thermomechanical processing was suggested to improve the Hydrogen-Induced Cracking (HIC) resistance in X70 pipeline steel. Proposed thermomechanical treatment produced favorable crystallographic textures and significantly increased HIC resistance which is of great interest to petroleum industry. The results showed that the high angle grain boundaries and Kernel parameter values acted as hydrogen-trapping sites, leading to increased HIC susceptibility. Highest HIC resistance was obtained in sample rolled isothermally at 850 °C, due to the high proportion of grains oriented with {110} planes parallel to the normal direction and {111}//ND fibers accompanied by negligible fraction of grains oriented in {001}//ND.
Y F Cheng - One of the best experts on this subject based on the ideXlab platform.
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characterization of inclusions of x80 pipeline steel and its correlation with hydrogen induced Cracking
Corrosion Science, 2011Co-Authors: H B Xue, Y F ChengAbstract:Abstract In this work, the microstructures of an X80 pipeline steel were characterized, and their susceptibilities to Hydrogen-Induced Cracking (HIC) were investigated by hydrogen-charging, electrochemical hydrogen permeation and surface characterization. It is found that the microstructure of X80 pipeline steel consists of a polygonal ferrite and bainitic ferrite matrix, with martensite/austenite (M/A) constituents distributing along grain boundaries. The inclusions existing in the steel include those enriched with Si, Al oxide, Si–ferric carbide and Al–Mg–Ca–O mixture, respectively. The majority of inclusions are Si-enriched. Upon hydrogen-charging, cracks could be initiated in the steel in the absence of external stress. The cracks are primarily associated with the Si- and Al oxide-enriched inclusions. The diffusivity of hydrogen in X80 steel at room temperature is 2.0 × 10−11 m2/s, and the estimated hydrogen trapping density in the steel is as high as 3.33 × 1027 m−3.
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effect of non metallic inclusions on hydrogen induced Cracking of api5l x100 steel
International Journal of Hydrogen Energy, 2010Co-Authors: T Y Jin, Zhiyong Liu, Y F ChengAbstract:Abstract In this work, the type, composition and distribution of inclusions contained in an API5L X100 steel were characterized by scanning electron microscopy and energy-dispersive x-ray analysis. A hydrogen-charging at various current densities was used to introduce hydrogen into the steel, and the correlation between HIC and the inclusions was established. The microstructure of the steel consists of a leather-like bainitic ferrite matrix, with martensite/austenite as the second phase particles. At least four types of inclusions are contained in API5L X100 steel, elongated MnS inclusions and spherical Al-, Si- and Ca-Al-O-S-enriched inclusions. In particular, the majority of inclusions in the steel are Al-enriched. Upon hydrogen-charging, hydrogen blisters and HIC could be caused in the steel in the absence of external stress. The cracks are primarily associated with the Al- and Si-enriched inclusions, rather than the elongated MnS inclusion. The critical amount of hydrogen resulting in HIC of the tested API5L X100 steel is determined to be 3.24 ppm under condition in this work.
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effects of hydrogen charging on the susceptibility of x100 pipeline steel to hydrogen induced Cracking
International Journal of Hydrogen Energy, 2009Co-Authors: Chen Dong, Zhiyong Liu, Y F ChengAbstract:Abstract In this work, the Hydrogen-Induced Cracking (HIC) behavior of X100 pipeline steel was investigated by a combination of tensile test, electrochemical hydrogen permeation measurement and surface characterization techniques. The effect of inclusions in the steel on the crack initiation was analyzed. Results demonstrated that the amount of hydrogen-charging into the X100 steel specimen increases with the charging time and charging current density. Hydrogen-charging will enhance the susceptibility of the steel to HIC. The cracks initiate primarily at inclusions, such as aluminum oxides, titanium oxides and ferric carbides, in the steel. The diffusivity of hydrogen at room temperature in X100 steel is determined to be 1.04 × 10 −8 cm 2 /s.
M. Eskandari - One of the best experts on this subject based on the ideXlab platform.
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role of cold rolled followed by annealing on improvement of hydrogen induced Cracking resistance in pipeline steel
Engineering Failure Analysis, 2018Co-Authors: M A Mohtadibonab, M. Eskandari, J. A. SzpunarAbstract:Abstract In this study, we investigated the effect of cold rolled followed by annealing on hydrogen induced Cracking susceptibility in an API X60 pipeline steel. To this, we carried out cold rolling on X60 steel up to 20%, 50% and 90% in thickness reduction to change the microstructure and texture of steel. Then, we annealed all specimens at 850 °C for 90 s. We studied all tested specimens by electron backscatter and X-ray diffraction techniques. EBSD results showed that the grain refinement process was properly done via cold rolling and annealing treatments in tested specimens. However, the dislocation density was high for all tested steels. Moreover, electrochemical hydrogen charging experiment on tested steels proved that all specimens were still highly susceptible to hydrogen induced Cracking. Therefore, we increased the annealing temperature and its duration of the 90% cold rolled specimen (the specimen with finest grains) up to 950 °C for 5 min. Interestingly, there was no HIC crack on this steel after hydrogen charging experiment. EBSD measurements on this steel showed strong textures of {100}//ND and {111}//ND. As a result, such strong textures, low Kernel Average Misorientation data, a high proportion of recovered grains and coincidence site lattice boundaries were recognized as the most important reasons for the highest HIC resistance in the mentioned steel.
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a focus on different factors affecting hydrogen induced Cracking in oil and natural gas pipeline steel
Engineering Failure Analysis, 2017Co-Authors: M A Mohtadibonab, M. EskandariAbstract:Abstract In this research, hydrogen induced Cracking (HIC) behavior of an API X70 pipeline steel has been studied. In order to create HIC cracks, an electrochemical hydrogen charging experiment was carried out on X70 steel by using 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate for 8 h. Moreover, SEM, EDS and EBSD techniques were used to characterize the as-received (AR) steel and investigate the different aspects of HIC phenomenon as well. The results showed that the inclusions and precipitates which play a key role in HIC phenomenon have been distributed randomly through the cross-section of tested steel. However, the concentration of them was higher at the center of cross-section than other areas. All HIC cracks initiated and propagated through the center of thickness where center segregation of elements has occurred. It is also observed that HIC cracks were initiated from several special types of inclusions and precipitates such as manganese sulphide and carbonitride precipitates. EBSD results showed that the dominant local texture of center of thickness in RD-TD plane was {001}//ND and {111}//ND. Moreover, HIC cracks propagate through differently oriented grains where the local texture is random.
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effect of different microstructural parameters on hydrogen induced Cracking in an api x70 pipeline steel
Metals and Materials International, 2017Co-Authors: M A Mohtadibonab, M. Eskandari, R. Karimdadashi, J. A. SzpunarAbstract:In this study, the surface and cross section of an as-received API X70 pipeline steel was studied by SEM and EDS techniques in order to categorize the shape and morphology of inclusions. Then, an electrochemical hydrogen charging using a mixed solution of 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate has been utilized to create hydrogen cracks in X70 steel. After hydrogen charging experiments, the cross section of this steel has been accurately checked by SEM in order to find out hydrogen cracks. The region of hydrogen cracks was investigated by SEM and EBSD techniques to predict the role of different microstructural parameters involving hydrogen induced Cracking (HIC) phenomenon. The results showed that inclusions were randomly distributed in the cross section of tested specimens. Moreover, different types of inclusions in as-received X70 steel were found. However, only inclusions which were hard, brittle and incoherent with the metal matrix, such as manganese sulfide and carbonitride precipitates, were recognized to be harmful to HIC phenomenon. Moreover, HIC cracks propagate dominantly in transgraular manner through differently oriented grains with no clear preferential trend. Moreover, a different type of HIC crack with about 15-20 degrees of deviation from the rolling direction was found and studied by EBSD technique and role of micro-texture parameters on HIC was discussed.
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Effect of arisen dislocation density and texture components during cold rolling and annealing treatments on hydrogen induced Cracking susceptibility in pipeline steel
Journal of Materials Research, 2016Co-Authors: M.a. Mohtadi-bonab, M. Eskandari, J. A. SzpunarAbstract:In this study, we used thermo–mechanical control process (TMCP) technique to investigate the effect of arisen dislocation density and texture components on hydrogen induced Cracking susceptibility in as-received API X60 pipeline steel. Dislocations and texture components appeared during cold rolling and annealing treatments. X-ray diffraction and electron backscatter diffraction measurements were used to study these phenomena. We observed that the cold rolling and annealing treatments produced higher dislocation density in deformed and recovered regions. The increase of dislocation density also caused the increased hydrogen trap density. Macro-texture studies by x-ray method indicates that initial weak texture of as-received X60 steel was changed from ζ-fiber to γ-fiber and θ-fiber in 90% cold rolled and annealed specimen. Therefore, the number of grains with {100}ND orientation which had a harmful effect on hydrogen induced Cracking susceptibility increased. The {100} dominant texture and high density of hydrogen traps mitigated against any possible benefits of the other microstructural parameters such as coincidence site lattice boundaries and grain size. As a result, we could not consider this process as a suitable method to increase hydrogen induced Cracking resistance in pipeline steel.
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Hydrogen-Induced Cracking Assessment in Pipeline Steels Through Permeation and Crystallographic Texture Measurements
Journal of Materials Engineering and Performance, 2016Co-Authors: M.a. Mohtadi-bonab, M. Eskandari, R. Karimdadashi, J. A. SzpunarAbstract:Electrochemical hydrogen charging and permeation techniques were used to characterize hydrogen distribution, trapping, and diffusion in X60 and X60 sour service (X60SS) pipeline steels. The results obtained contribute to better understanding of Hydrogen-Induced Cracking (HIC). SEM observations illustrated that all HIC cracks were formed at the center of cross section in the X60 steel after 3-h hydrogen charging and length of cracks increased with charging time. No HIC cracks were recorded at the cross section of X60SS steel after the same charging for different durations. Hydrogen permeation tests showed that the density of reversible hydrogen traps was lower at the center of cross section in the X60SS steel compared to the X60 one, and this is considered as one of the main reasons for high resistance of X60SS steel to HIC. EBSD orientation imaging results proved that the accumulation of ||ND-oriented grains at the center of the cross section in the X60SS steel was high. This is also considered as another reason for higher resistance of this steel to HIC. Finally, the center segregation zone with higher hardness value in the X60 steel was more pronounced than in the X60SS steel which made the X60 steel susceptible to HIC Cracking.
