Hydrogen Induced Cracking Cracks Research Articles

Research on Hydrogen-Induced Induced Cracking Sensitivity of X80 Pipeline Steel under Different Heat Treatments.

X80 pipeline steel has played a vital role in oil and gas transportation in recent years. However, hydrogen-related issues frequently lead to pipeline failures during service, resulting in significant losses of properties and lives. Three heat treatment processes (furnace cooling (FC), air cooling (AC), and water cooling (WC)) were carried out to investigate the effect of different microstructures on hydrogen-induced cracking (HIC) susceptibility of X80 pipeline steel. The WC sample demonstrated the highest hydrogen embrittlement index, registering at 21.9%, while the AC and FC samples exhibited progressively lower values of 15.45% and 10.98%, respectively. Under equivalent hydrogen charging durations, crack dimensions with a maximum length exceeding 30 μm in the WC sample generally exceed those in the FC sample and AC sample. The variation is attributed to the difference in microstructures of the samples, predominantly lath bainite (LB) in water-cooled samples, granular bainite (GB) in air-cooled samples, and ferrite/pearlite (F/P) in FC samples. The research results demonstrate that the sensitivity of lath bainite (LB) to HIC is significantly higher than that of pearlite, ferrite, and granular bainite (GB). The presence of a large amount of martensite/austenite (M/A) constituents within bainite results in a multitude of hydrogen trap sites. HIC cracks in bainite generally propagate along the profiles of M/A constituents, showing both intergranular and transgranular cracking modes.

Finite element modeling of HIC propagation in pipeline steel with regard to experimental observations

In this research, hydrogen induced cracking (HIC) phenomenon in pipeline steel has been investigated by finite element modeling (FEM) with the help of experimental observations. Abaqus software has been utilized to model the crack. To this, first an API 5L X70 pipeline steel was electrochemically charged by hydrogen for 8 h to create different types of HIC cracks. Then, SEM was used to observe different types of hydrogen cracks. Based on the observations, most of HIC cracks were observed at the center of cross section where center segregation of some elements occurred. The results showed that HIC cracks propagated in stepwise, sinusoidal, straight and disordered manner. Moreover, HIC crack nucleated from a point with high stress concentration factor which was between non-metallic inclusion or void and metal matrix. The initiated micro-cracks from two neighbor inclusions link together to form a long HIC crack. Based on the experimental observations and FEM modeling, it was concluded that the driving force for the HIC crack propagation is the presence of hydrogen at the crack tip after it is initiated. Crack tip usually acts as a very small void and the combination of hydrogen atoms makes a high pressure which propel the crack forward. Moreover, the HIC crack propagation path was predicted by fracture mechanics approach showing that the J-integral had its maximum amount when the HIC crack tended to propagate horizontally.

Investigation into Mechanism of Hydrogen Induced Cracking Failure in Carbon Steel: A Case Study of Oil and Gas Industry

Abstract Although the hydrogen induced cracking (HIC) is recognized as one of the destructive modes for pipeline and component steels serving in sour environments, the behavior of the HIC is still not fully understood. On the other hand, although many efforts have been made to identify the effects of hydrogen on laboratory steel specimens, the study of actual industrial samples has received less attention. In this paper, we have studied the mechanism of the HIC in a damaged pipe of a real case study of the oil and gas industry (finger type slug catcher) using detection, characterization, and microstructural investigation methods. The detection of the HIC in the specimens by advanced ultrasonic techniques, failure analysis using tensile tests, chemical composition analysis, optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive spectroscopy (EDS) techniques and their correlation with the microstructure, type, and morphology of the inclusions were conducted. The results indicated that the value of elements, especially carbon (0.13 wt %) and manganese (1.44 wt %), satisfies the requirement of API 5L specification. Furthermore, the inclusions, such as elongated manganese sulfide and spherical aluminum oxide, and the pearlite grains or the interfaces of the ferrite–pearlite phases played an essential role in the HIC phenomenon as nucleation and propagation places of cracks. It was also observed that HIC cracks were mostly initiated and propagated through the center or near the center of a cross-section of specimens. This region was a segregated zone where the center segregation of elements has occurred. Finally, we recognized a linear correlation between the HIC susceptibility and hardness value in steel, where by moving away from the cracks (1800 µm) to the crack edges, the hardness value increased significantly (179–203 HV), confirming the diffusion of hydrogen into hydrogen traps.

Effect of electrochemical hydrogen charging on an API X70 pipeline steel with focus on characterization of inclusions

Environmental conditions of service affect the resistance of pipeline steels to failure, as a result, the applied stress which would be otherwise considered safe can be responsible for fracture due to hydrogen induced cracking (HIC). The presence of hydrogen sulfide in natural gas is one of the main sources of hydrogen in steel. HIC testing showed that cracks initiated from inclusions and propagated through the steel matrix along the crack path that was occupied by inclusions. The number of inclusions and the distance between them as well as the grain size between them was considered to be important for predicting failure. Shorter distance between inclusions and smaller grains were found to facilitate HIC propagation. The hydrided specimens were subjected to tensile stress until failure to generate stress-strain curves, ductility and toughness data. It was revealed that even though most of the cracks initiate from rectangular and spinel inclusions, the globular inclusions have also contributed to reducing the tensile strength, ductility and toughness. Synchrotron radiation 3D imaging of steel structure was used to explain the features of the HIC cracks formation during tensile tests.

Important Factors on the Failure of Pipeline Steels with Focus on Hydrogen Induced Cracks and Improvement of Their Resistance: Review Paper

Currently, thousands of kilometers of pipeline steels are transferring hydrocarbon fluids such as oil and natural gas in the world. Due to the fact that these pipes transport corrosive and high-pressure fluids from harsh environments, they are damaged and eventually degraded. Previous studies showed that sulphide stress cracking, hydrogen induced cracking (HIC) and stress corrosion cracking are the main destructive factors in these types of pipes. This paper focused on the HIC related failure in pipeline steel, since the role of texture and grain boundary character has not been completely recognized. Moreover, if pipeline damage is occurred by hydrogen cracks, besides the environmental pollutions, it will cost a lot to repair or replace the damaged pipeline steels. In this research, the factors influencing the initiation and propagation of the HIC cracks, such as hydrogen traps, inclusions, precipitates, microstructure and texture of steel have been investigated. Also, the existing solutions for improving the steel resistance to the HIC have been investigated based on the control of micro-alloy elements, texture and grain boundary engineering. For instance, some special dominant texture components and coincidence site lattice boundaries decrease the HIC susceptibility by providing the resistant path for crack propagation.

Investigation of Stress-Oriented Hydrogen-Induced Cracking (SOHIC) in an Amine Absorber Column of an Oil Refinery

Stress-oriented hydrogen-induced cracking (SOHIC) of an amine absorber column made of a Hydrogen Induced Cracking (HIC) resistant steel and operating under wet H2S service was investigated. SOHIC was not related to welds in the column and evolved in two steps: initiation of HIC cracks in the rolling plane and through-thickness linking of the HIC cracks. Both the original HIC cracks as well as the linking cracks propagated with a cleavage mechanism. The key factors identified were periods with high hydrogen charging conditions, manifested by high H2S/amine ratio, and stress triaxiality, imposed by the relatively large thickness of the plate. In addition, the mechanical properties of the steel away from cracked regions were unaffected, indicating the localized nature of SOHIC.

Hydrogen trapping and hydrogen induced cracking of welded X100 pipeline steel in H2S environments

Hydrogen induced cracking (HIC) susceptibility of the welded X100 pipeline steel was evaluated in NACE “A” solution at room temperature according to the NACE TM0284-2011 standard. Both the kinetic parameters of the permeability (J∞L), the apparent diffusivity (Dapp) and the concentration of reversible and irreversible hydrogen in the base metal and welded joint of X100 pipeline steel were quantitatively investigated by hydrogen permeation test. The results showed that the welded joint with an inhomogeneous microstructure had a higher trap density and more susceptible to HIC due to two orders of magnitude larger in the concentration of irreversible hydrogen than that of base metal, though all presenting poor HIC resistance for both base metal and the welded joint. The HIC cracks initiated from the inclusions enriching in Al, Ca, Si, Mn. The cracks are primarily transgranular, accompanying with limited intergranular ones.

Effect of different microstructural parameters on hydrogen induced cracking in an API X70 pipeline steel

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.

Evaluation of hydrogen-Induced cracking resistance of the In625 laser coating system on a C-Mn steel substrate

Abstract The corrosion of C-Mn steels in the presence of hydrogen sulfide (H2S) represents a significant challenge to oil production and natural gas treatment facilities. The failure mechanism induced by hydrogen-induced cracking (HIC) in a Inconel 625 coating / C-Mn steel has not been extensively investigated in the past. In the present work, an API 5CT steel was coated with In625 alloy using laser cladding and the HIC resistance of different regions, such as the coating surface, the substrate and HAZ, were evaluated. SEM observations illustrated that all HIC cracks were formed at the hard HAZ after 96h of exposure. No HIC cracks were observed in the substrate and the In625 coating after the same exposure duration. Pitting was recorded in the substrate caused by non-metallic inclusion dissolving.

A focus on different factors affecting hydrogen induced cracking in oil and natural gas pipeline steel

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.

Hydrogen-Induced Cracking Assessment in Pipeline Steels Through Permeation and Crystallographic Texture Measurements

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.

An extensive study of hydrogen-induced cracking susceptibility in an API X60 sour service pipeline steel

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.

Hydrogen failure sensitivity of A516-Gr70 and API 5L-X70 steels in sour environments

Purpose – This paper aims to clarify the corrosion behavior of two famous structural steels in sour environment. These steels have a vast application in oil and gas industries. The study aims to find the effect of different concentrations of sour solution on the origin of crack in these steels. Design/methodology/approach – After preparation of specimens, different sour solutions were made using the synthetic brine (according to National Association of Corrosion Engineers [NACE], Technical Committee Report 1D182) and various amounts of Na2S.9H2O and CH3COOH. The polarization test was done by Potansiostat apparatus model Zahner-IM6 at two temperatures, 25°C and 50°C. The corrosion current densities were obtained from the polarization curves. Finally, the corrosion products and hydrogen-induced cracking (HIC) were investigated by Tescan Vega II XMU scanning electron microscope (SEM) linked to a Rontec energy-dispersive X-ray spectroscopy (EDS) system. Findings – API 5L-X70 steel showed smaller corrosion current values than A516-Gr70 steel. The HIC cracks propagated parallel to the surface of A516-Gr70 steel in three solutions and confirmed the inappropriateness of this steel for sour environment applications. Originality/value – This paper studies the effect of sour environment on the behavior of two famous industrial steels at two temperatures by new method.

The mechanism of failure by hydrogen induced cracking in an acidic environment for API 5L X70 pipeline steel

Mechanism of failure by hydrogen induced cracking (HIC) in pipeline steel has not been extensively investigated in the past. In the present work, an API X70 pipeline steel was electrochemically charged with hydrogen for different durations in order to find crack nucleation and propagation sites. After 3 h charging, suitable regions for crack initiation and propagation were found. These regions were studied by color metallography, EDS and EBSD techniques. The results brought out that HIC cracks nucleated from regions rich of manganese sulphide inclusions, some complex carbonitride precipitates such as (Ti, Nb, V) (C, N) and further propagated through the segregation area of some elements, such as manganese, carbon, silicon and sulfur. It is worth-mentioning that all these potential sites for crack nucleation and propagation appeared at the center of cross section of the specimens. EBSD measurements were carried out at the center of cross section in as-received and hydrogen-charged specimens in order to find a pattern between microstructural parameters (texture, grain boundary nature and Taylor factor) and probability of HIC cracking. The results showed that fine grain colonies (less than 3.5 μm in length) with dominant ND||<001> orientations were prone to intergranular HIC crack propagation. The grain boundaries identified between two grains with a mismatch in Taylor factor were more susceptible to intergranular fracture while transgranular fracture occurred in fragmented grains with high and similar Taylor factor that were less likely to yield. HIC cracking occurred in a wide range of orientations such as ND||<123>, ND||<100>, ND||<112>, ND||<110> and even ND||<111>; however, role of high angle grain boundaries and type of fracture would be of great importance in crack propagation.

Hydrogen-induced cracking susceptibility and hydrogen trapping efficiency of different microstructure X80 pipeline steel

The hydrogen-induced cracking (HIC) susceptibility of the X80 steel in H2S environment and its heated-treatment microstructure was evaluated. The field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and energy dispersive spectroscopy (EDS) were employed to study the morphology and chemical composition of the inclusions, precipitates and HIC cracks in the X80 steel. The hydrogen trapping efficiency was investigated by measuring the permeability (J ∞L) and the apparent diffusivity (D app). The results showed that heat-treated specimens had lower trapping efficiency, but were more susceptible to HIC. Most of the HIC cracks initiated from the inclusions rich in Mn, Al, Ca, and Ti, and propagated transgranularly in the original and air cooled specimens, but mainly intergranularly in water quenched specimens.