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Weld macro overview of the girth weld including measurements of the wall thickness, weld thickness and thicknesses of the first and last weld passes.
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This work discusses the design and demonstration of an in-situ test setup for testing pipeline steels in a high pressure gaseous hydrogen (H2) environment. A miniature hollow pipe-like tensile specimen was designed that acts as the gas containment volume during the test. Specific areas of the specimen can be forced to fracture by selective notching...
Contexts in source publication
Context 1
... the pipe was not used for offshore gas transportation, the girth weld was made according to industrial standards. A weld macro is shown in Figure 1, which also shows measurements of the wall thickness of 15.4 mm and weld thickness of 6 mm. The thickness of the first and last weld passes were both measured to be under 2.5 mm, meaning that these were not included in the specimen geometry which is discussed later. ...
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... Figure 2a, it can be seen that the BM consists predominantly of polygonal ferrite with a small fraction of pearlite grains which can be identified as the black areas. The WM consists of large prior austenite grain boundaries that can also be observed in Figure 1, which contain a more refined microstructure that is shown in Figure 2b. Widmanstätten ferrite structures grow from the prior austenite grain boundaries but eventually transition into a fine grained acicular ferrite phase that comprises most of the bulk of the WM. ...
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... difference between the two metals is that the weld specimen fracture surfaces undergo a change from HE related QC fracture toward ductile shear failure during the fracture propagation process. This is shown in Figure 10a. The inside of the specimen fracture surface behaves like the BM samples, and these regions show the QC fracture mode. ...
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... voids can also be observed, which might originate as lack of fusion defects in the weld before testing. Furthermore, a transition zone exists on the surfaces of all weld specimens in between the QC and MVC regions that has a morphology of mixed features such as shown in Figure 10b. The quasi-cleavage mode also contains voids in the weld specimens that originate from ductile failure mechanisms. ...
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... metal with a lower availability of diffusible hydrogen like the WM will therefore require slower crack growth to accumulate enough hydrogen at the crack tip to cause QC fracture. If the crack outgrows this required speed, the fracture mechanism will revert back to ductile fracture as was observed in Figure 10a. ...
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Citations
... It was found that the results with the polished specimens were similar to those with solid ones, and were more sensitive to the change in environmental conditions. Boot et al. (2021) developed a testing machine to evaluate the tensile properties of X60 pipeline steel and its welds, varying the hydrogen pressure in the hole, while Michler et al. (2022) investigated the effects of different gaseous impurities, highlighting the role of purge cycles to reach the desired hydrogen purity within the hole. It turned out that since the volume of hydrogen is smaller, the impact of impurities becomes stronger. ...
Hydrogen has great potential on the path towards decarbonization of the energy and transport sectors and can mitigate the urgent issue of global warming. It can be sustainably produced through water electrolysis with potentially zero emissions, and efficiently used (e.g., in fuel cell systems). Despite its environmental advantages, hydrogen-metal interactions could result in the degradation of the mechanical properties of several structural materials. In order to determine the magnitude of the material degradation in relation to hydrogen exposure, extensive material testing is required. The standardized procedure for in-situ testing for the quantification of the impact of compressed gaseous hydrogen (CGH 2) relies on the utilization of an autoclave around the tested specimen. Such test setup is complex, expensive, time-consuming and requires special equipment, trained personnel, and strict safety procedures. A relatively recent method to circumvent these issues and provide affordable results consists of using hollow specimens, thus applying the hydrogen pressure inside rather than outside the specimen. It allows to reduce the volume of hydrogen by several orders of magnitude and to perform the tests more efficiently and in a safer manner. This study focuses on evaluating the tensile properties of X65 vintage pipeline steel tested in a high-pressure hydrogen environment using hollow specimens. Tests are performed in 6 MPa H 2 and Ar at the nominal strain rate of 10 −6 s −1 to evaluate the reduced area at fracture and the elongation loss. The effect of surface finishing on crack initiation and propagation is investigated by comparing two different manufacturing techniques. In this way, this study provides insights into the applicability of a novel, reliable, and safe testing method which can be used to assess the hydrogen-assisted ductility loss in metallic materials. Abstract Hydrogen has great potential on the path towards decarbonization of the energy and transport sectors and can mitigate the urgent issue of global warming. It can be sustainably produced through water electrolysis with potentially zero emissions, and efficiently used (e.g., in fuel cell systems). Despite its environmental advantages, hydrogen-metal interactions could result in the degradation of the mechanical properties of several structural materials. In order to determine the magnitude of the material degradation in relation to hydrogen exposure, extensive material testing is required. The standardized procedure for in-situ testing for the quantification of the impact of compressed gaseous hydrogen (CGH 2) relies on the utilization of an autoclave around the tested specimen. Such test setup is complex, expensive, time-consuming and requires special equipment, trained personnel, and strict safety procedures. A relatively recent method to circumvent these issues and provide affordable results consists of using hollow specimens, thus applying the hydrogen pressure inside rather than outside the specimen. It allows to reduce the volume of hydrogen by several orders of magnitude and to perform the tests more efficiently and in a safer manner. This study focuses on evaluating the tensile properties of X65 vintage pipeline steel tested in a high-pressure hydrogen environment using hollow specimens. Tests are performed in 6 MPa H 2 and Ar at the nominal strain rate of 10 −6 s −1 to evaluate the reduced area at fracture and the elongation loss. The effect of surface finishing on crack initiation and propagation is investigated by comparing two different manufacturing techniques. In this way, this study provides insights into the applicability of a novel, reliable, and safe testing method which can be used to assess the hydrogen-assisted ductility loss in metallic materials.
... The main advantage of this technique is the fact that an autoclave is not needed to expose the sample to a pressurized gaseous hydrogen atmosphere. Several investigations have shown, how this technique in various modifications can asses the impact of hydrogen atmospheres on the material properties in comparison to reference atmosphere [16][17][18][19][20]. ...
... The most significant difference is observed in the maximum elongation. While the reference sample with argon is elongated to 5.2 mm, the sample tested with hydrogen failed at an elongation of 2.9 mm: This indicates a significant loss of ductility, which has been shown for these types of steels under hydrogen atmosphere [7,8,[16][17][18]26,27]. ...
... The region closer to the inner hole is characterized by quasi-cleavage fracture (Fig. 3e). This type of fracture indicates a clear change in the material's properties and the influence of hydrogen, as it was shown by other authors in the last decade [8,17,18,26]. ...
The high potential of hydrogen as a key factor on the pathway towards a climate neutral economy, leads to rising
demand in technical applications, where gaseous hydrogen is used. For several metals, hydrogen-metal interactions
could cause a degradation of the material properties. This is especially valid for low carbon and highstrength
structural steels, as they are commonly used in natural gas pipelines and analyzed in this work.
This work provides an insight to the impact of hydrogen on the mechanical properties of an API 5L X65
pipeline steel tested in 60 bar gaseous hydrogen atmosphere. The analyses were performed using the hollow
specimen technique with slow strain rate testing (SSRT). The nature of the crack was visualized thereafter utilizing
μCT imaging of the sample pressurized with gaseous hydrogen in comparison to one tested in an inert
atmosphere.
The combination of the results from non-conventional mechanical testing procedures and nondestructive
imaging techniques has shown unambiguously how the exposure to hydrogen under realistic service pressure
influences the mechanical properties of the material and the appearance of failure.
... Hydrogen absorption in pipeline steels increases as cathodic potential is applied to inhibit corrosion or due to H 2 S present in the gaseous transport medium. As pipeline systems have completely different charging environments, especially over long-term use, hydrogen molecules dissociate into hydrogen atoms that interact with the steel surface [66]. A partial pressure difference is thus created between the bulk and the steel surface. ...
... Electrochemical charging forces hydrogen into the bulk by forcing ions into traps due to a potential difference mechanism. Therefore, electrochemical charging can overestimate hydrogen adsorption and diffusion [66]. ...
Hydrogen has been studied extensively as a potential enabler of the energy transition from fossil fuels to renewable sources. It promises a feasible decarbonisation route because it can act as an energy carrier, a heat source, or a chemical reactant in industrial processes. Hydrogen can be produced via renewable energy sources, such as solar, hydro, or geothermic routes, and is a more stable energy carrier than intermittent renewable sources. If hydrogen can be stored efficiently, it could play a crucial role in decarbonising industries. For hydrogen to be successfully implemented in industrial systems, its impact on infrastructure needs to be understood, quantified, and controlled. If hydrogen technology is to be economically feasible, we need to investigate and understand the retrofitting of current industrial infrastructure. Currently, there is a lack of comprehensive knowledge regarding alloys and components performance in long-term hydrogen-containing environments at industrial conditions associated with high-temperature hydrogen processing/production. This review summarises insights into the gaps in hydrogen embrittlement (HE) research that apply to high-temperature, high-pressure systems in industrial processes and applications. It illustrates why it is still important to develop characterisation techniques and methods for hydrogen interaction with metals and surfaces under these conditions. The review also describes the implications of using hydrogen in large-scale industrial processes.
... Fractographic images showing the macroscopic fractures of a notched weld metal surface due to hydrogen embrittlement[11] ...
Crude oil pipeline infrastructures represent a high capital investment, and pipelines must be free from the risk of degradation due to corrosion and hydrogen embrittlement, which could cause environmental hazards and potential threats to human life. Pipeline integrity design, monitoring, and management become crucial, especially in subsea pipelines. Corrosion risk assessment is necessary to track pipeline reliability and life prediction effectively. The pipeline inspections cost a lot of money since the pipeline are hundreds of thousands of kilometres, and the maintenance process interrupts the production rates. Moreover, this cost will triple for the subsea pipeline as it requires special personal qualifications and tools, causing the oil and gas company to pay millions for frequent checks. It is proposed to utilize Finite Element Analysis (FEA) modelling technique and Computational Fluid Dynamics (CFD) to optimize the design and preventive maintenance prediction. Hence this paper aims to review the current work on this pipeline design problem, especially in the Tropical region, and discuss the factors that cause the deterioration of structural properties due to the presence of hydrogen within the crude oil.
... Not included in Figure 14 is the data of Xiong et al. (2015) who found that X80 charged at 1 bar hydrogen had an I value of 22%, but this was in the presence of 2 bar CO 2 which may have had a confounding effect. At 100 bar hydrogen and above, there was significant embrittlement (I> 50%) in X70 (Nguyen et al. 2020a), X80 (Moro et al. 2010), and X100 (Nanninga et al. 2012), but less embrittlement for X52, X60 and X65 exposed to 100-150 bar hydrogen which had lower I values between 20 and 30% (Boot et al. 2021;Lee et al. 2011;Nanninga et al. 2012). This indicated a general relationship between increasing steel strength and increasing HE susceptibility. ...
... The stress concentration in the notched tensile specimens correlated with increased HE, and base metal and weld metal were similarly affected by the stress concentration. Boot et al. (2021) found that notched, hollow X60 base metal specimens in 100 bar hydrogen had an I value (as measured from reduction in area) of 28%, while the weld specimens had an I of 11%. These results show that, despite the weld being stronger and more brittle, the base metal was more susceptible to hydrogen than the weld. ...
... Reducing the tested hydrogen pressure from 100 bar to 30 bar produced no change in the ductility, suggesting saturation occurred at a hydrogen pressure below 30 bar. Figure 19 summarises the reduction in ductility in the pipeline weld tensile studies. Nguyen et al. (2020c) found that the weld material was more susceptible to HE than the base metal, while Boot et al. (2021) found the base metal was more susceptible to HE than the weld. More studies are required to reconcile this inconsistency. ...
Hydrogen transport by blending hydrogen into natural gas transmission pipelines and by pure-hydrogen pipelines is a prospective mode of energy transmission during the transition to renewables. The risk of hydrogen embrittlement (HE) in pipeline steels must first be quantified to ensure safe pipeline operation. This review provides an overview of HE in pipeline steels. Most pipeline steels have reduced ductility when exposed to hydrogen partial pressures of 100 bar and above. Higher-strength pipeline steels (X80 and X100) have been found to undergo HE at ∼50 bar hydrogen. Hydrogen-induced subcritical crack growth in pipeline steels has not been reported in the literature. There are few articles on HE in pipeline welds, with some indications that the weld is more susceptible to HE, and some indications that it is less. The relationship between hydrogen pressure and absorbed hydrogen concentration has not been evaluated. Gaps in knowledge are identified in the conclusions.
... The alloy compositions of the base metal and weld metal are shown in Table 1 below. The data regarding this composition identification were extracted from work on the same pipeline material by Boot et al. [32]. In that particular study, composition analysis was performed using X-ray fluorescence scanning and LECO combustion analysis. ...
... The construction of the in situ gaseous hydrogen fatigue set-up is based on concurrent internal pressurization of a hollow specimen by hydrogen gas during fatigue tests. The set-up in this work was developed by modifying the in situ hydrogen gas slow strain rate tensile (SSRT) device engineered by Boot et al. into one compatible with in situ fatigue testing [32]. The main difference regarding the set-up is that in this study, a hydraulic 4-column load frame (MTS 311.21 ServoHydraulic 350 kN Load Frame) is used, integrated with flexible (clevis to clevis) self-aligning adapters. ...
... Bal represents Fe. The data are taken from[32]. ...
In this work, the hydrogen fatigue of pipeline steel X60, its girth welds and weld defects were investigated through in situ fatigue testing. A novel in situ gaseous hydrogen charging fatigue set-up was developed, which involves a sample geometry that mimics a small-scale pipeline with high internal hydrogen gas pressure. The effect of hydrogen was investigated by measuring the crack initiation and growth, using a direct current potential drop (DCPD) set-up, which probes the outer surface of the specimen. The base and weld metal specimens both experienced a reduction in fatigue life in the presence of hydrogen. For the base metal, the reduction in fatigue life manifested solely in the crack growth phase; hydrogen accelerated the crack growth by a factor of 4. The crack growth rate for the weld metal accelerated by a factor of 8. However, in contrast to the base metal, the weld metal also experienced a reduction of 57% in resistance to crack initiation. Macropores (>500 µm in size) on the notch surface reduced the fatigue life by a factor of 11. Varying the pressure from 70 barg to 150 barg of hydrogen caused no difference in the hydrogen fatigue behavior of the weld metal. The fracture path of the base and weld metal transitioned from transgranular and ductile in nature to a mixed-mode transgranular and intergranular quasi-cleavage fracture. Hydrogen accelerated the crack growth by decreasing the roughness- and plasticity-induced crack closure. The worst case scenario for pipelines was found in the case of weld defects. This work therefore highlights the necessity to re-evaluate pipelines for existing defects before they can be reused for hydrogen transport.
... To characterise the effect of gaseous hydrogen on Inconel 718, the sample design developed by Boot et al. [40] (shown in Figure 3) for slow strain rate tensile (SSRT) test was used. This design has the advantage that the sample acts as the gas containment volume throughout the experiment, thus avoiding the need for autoclaves and sophisticated equipment. ...
... After the SSRT tests, the area of cross section after failure (Af) is determined at the fracture location using Keyence VHX-5000 digital microscope. The percentage reduction in area (RA) is found by comparing it with the initial cross sectional area (A0) [40]: ...
... The degree of hydrogen embrittlement is measured as the relative reduction of area of samples tested in nitrogen (%RAN2) and hydrogen (RAH2) environment [40]: The SSRT tests were performed in both nitrogen (N 2 ) and hydrogen (H 2 ) environments, with a pressure of 150 bar at 25 • C. Two repetitions were performed for each testing condition for repeatability. For the hydrogen tests, the samples were additionally charged for 48 h before the test to allow for hydrogen diffusion within the sample. ...
This study investigated the in-situ gaseous (under 150 bar) hydrogen embrittlement behaviour of additively manufactured (AM) Inconel 718 produced from sustainable feedstock. Here, sustainable feedstock refers to the Inconel 718 powder produced by vacuum induction melting inert gas atomisation of failed printed parts or waste from CNC machining. All Inconel 718 samples, namely AM-as-processed, AM-heat-treated and conventional samples showed severe hydrogen embrittlement. Additionally, it was found that despite its higher yield strength (1462 ± 8 MPa) and the presence of δ phase, heat-treated AM Inconel 718 demonstrates 64% lower degree of hydrogen embrittlement compared to the wrought counterpart (Y.S. 1069 ± 4 MPa). This was linked to the anisotropic microstructure induced by the AM process, which was found to cause directional embrittlement unlike the wrought samples showing isotropic embrittlement. In conclusion, this study shows that AM Inconel 718 produced from recycled feedstock shows better hydrogen embrittlement resistance compared to the wrought sample. Furthermore, the unique anisotropic properties, seen in this study for Inconel 718 manufactured by laser powder bed fusion, could be considered further in component design to help minimise the degree of hydrogen embrittlement.
... To bypass these shortcomings, hollow tensile specimen [9] is used in this study and, instead of using a gaseous environment, the hollow tensile specimen has been designed to act as the pressure vessel. Several researchers [10] [11] have used hollow tensile specimens to conduct in-situ tensile testing. One drawback of this method is the additional radial load applied due to the internal gas pressure. ...
... Hydrogen in iron and alloys based on it can be found simultaneously, both in interstices of the crystal lattice in the form of atoms, and in pores and other discontinuities in the form of molecules, into which it can recombine from atoms [34]. The lower the density of the metal and the more defects and lattice discontinuities, the greater the amount of hydrogen absorbed by non-hydride-forming metals and the greater the fraction of the absorbed hydrogen is in the molecular form [35,36]. ...
... The deformation of metals under the influence of molecular hydrogen pressure is accompanied by a change in a number of their properties-surface hardness [36], magnetic properties, clarity of X-ray interference lines, etc. ...
Consideration of the possibility of transporting compressed hydrogen through existing gas pipelines leads to the need to study the regularities of the effect of hydrogen on the mechanical properties of steels in relation to the conditions of their operation in pipelines (operating pressure range, stress state of the pipe metal, etc.). This article provides an overview of the types of influence of hydrogen on the mechanical properties of steels, including those used for the manufacture of pipelines. The effect of elastic and plastic deformations on the intensity of hydrogen saturation of steels and changes in their strength and plastic deformations is analyzed. An assessment of the potential losses of transported hydrogen through the pipeline wall as a result of diffusion has been made. The main issues that need to be solved for the development of a scientifically grounded conclusion on the possibility of using existing gas pipelines for the transportation of compressed hydrogen are outlined.
