X80 Pipeline Steel Research Articles

Unraveling short-term O2 contamination on under deposit corrosion of X65 pipeline steel in CO2 saturated solution

The impact of short-term O2 contamination on the deposit-covered pipeline steel under a CO2-saturated solution was investigated using steel coupon and wire beam electrode. Results show that the brief exposure to O2 destroyed the FeCO3 film, and converted it into porous iron oxides, weakening its protection property. However, upon CO2 reinjection, the dense FeCO3 film regrew soon underneath the damaged FeCO3 layer on the bare steel, restoring its protective properties. Conversely, the localized corrosion beneath the deposits persisted and worsened, fueled by macro-cell current between the bare steel and the deposit-covered steel.

Investigation of the influence of nano-CrN concentration on the performance of Ni-W coatings in X80 pipeline steel

A novel nano Ni-W-CrN composite coating was developed for X80 pipeline steel to enhance its structural properties and corrosion resistance. The study explored the effects of varying CrN nanoparticle concentrations (0, 5, 10, 15, 20 g/L) in the deposition solution using techniques such as SEM, EDS, and XRD for analysis and an electrochemical workstation for corrosion testing. The optimal CrN concentration was identified at 10 g/L, resulting in a coating with peak hardness (811HV), low friction coefficient (0.16), minimal wear rate (1.18×10−4 mm3·(N·m)−1), and improved corrosion resistance. This coating significantly outperforms Ni-W alloy coatings in hardness, wear resistance, and elastic recovery, offering a promising approach for enhancing the performance of X80 pipeline steel surfaces.

Effect of pre-strain on microstructure evolution and fracture behavior of undermatching X80 pipeline steel girth weld

This work aims to study the effect of pre-strain on the fracture behavior of X80 pipeline girth weld joint, a comprehensive analysis was conducted on the microstructure and mechanical properties of the girth weld before and after pre-strain treatment. The mechanical properties were evaluated through tensile testing, Charpy impact testing, and digital image correlation (DIC) strain analysis. Furthermore, the microstructure and fracture morphology of the girth weld were observed using optical electron microscopy (OM) and scanning electron microscopy (SEM). The results show that the application of pre-strain treatment leads to dislocation accumulation at the grain boundary of X80 pipeline girth weld, resulting in stress concentration and subsequent formation of damage holes. This process disrupts the continuity of chain M-A island and initiates small cracks at the grain boundary, ultimately causing a significant decrease in impact toughness and impact work from 177 J to about 10 J.

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.

CO2 effect on the fatigue crack growth of X80 pipeline steel in hydrogen-enriched natural gas: Experiment vs DFT

Utilizing the existing natural gas grid presents a promising method for transporting hydrogen on a large scale. However, the effects of natural gas and its impurities on hydrogen-assisted cracking in pipeline steel have not been adequately studied. This study aims to investigate the fatigue performance of X80 pipeline steel in hydrogen-enriched natural gas (HENG) environments and in mixtures containing the impurity CO2. This is achieved through fatigue crack growth rate (FCGR) tests and density functional theory (DFT) calculations. The experimental results show that the FCGR in H2 is slightly faster than that in HENG, whereas it is slower than that in the N2/CO2/H2 mixtures. The enhanced FCGR by CO2 further increases with the increasing CO2 content. DFT computational results indicate that the adsorbed CO2 on the iron surface significantly accelerates the migration of H atoms from surface to subsurface. This promotes the entry of hydrogen into the steel.

Effect of Mg-treatment on transformation of oxide inclusions in X80 pipeline steel

Effect of Mg-treatment on transformation of oxide inclusions in X80 pipeline steel

Hydrogen blistering and cracking of high-strength pipeline steel welds produced by electrochemical hydrogen charging

Pipeline steel system always faces a challenge of hydrogen embrittlement (HE) not only due to corrosion environments but also because of cathodic protection strategy. Especially in welded joint, heterogeneous microstructures lead to the difference in intrinsic HE resistance for different subzones. However, this aspect was often neglected when external loading was applied during evaluation of the HE. To eliminate the effect of external loading, the hydrogen damage behaviors of X100 pipeline steel weld were investigated only based on electrochemical hydrogen charging and the intrinsic HE resistance of each subzone was explored. The results showed that the HE resistance of the main regions in weld was decreased in order of weld metal, heat affected zone (HAZ) and base metal (BM), with different surface damage modes: the BM had predominantly hydrogen blistering; while others displayed mainly hydrogen cracking. The corresponding features for cross-sectional cracking were intergranular propagation along the pancaked grain boundaries in the BM and trangranular propagation in HAZ. For transgranular cracking propagation, the path first trended to initiate on the {100} cleavage plane, then grew on the {110} slip planes. The intergranular cracking was mainly attributed to the lamellar-structural prior grain boundaries that inherited numerous deformation dislocations during hot rolling of the base metal.

Effect of Microstructural Constituents on Hydrogen Embrittlement Resistance of API X60, X70, and X80 Pipeline Steels

This study describes how microstructural constituents affected the hydrogen embrittlement resistance of high-strength pipeline steels. The American Petroleum Institute (API) X60, X70, and X80 pipeline steels demonstrated complicated microstructure comprising polygonal ferrite (PF), acicular ferrite, granular bainite (GB), bainitic ferrite (BF), and secondary phases, e.g., the martensite-austenite (MA) constituent, and the volume fraction of the microstructures was dependent on alloying elements and processing conditions. To evaluate the hydrogen embrittlement resistance, a slow strain rate test (SSRT) was performed after electrochemical hydrogen charging. The SSRT results indicated that the X80 steel with the highest volume fraction of the MA constituent demonstrated relatively high yield strength but exhibited the lowest hydrogen embrittlement resistance because the MA constituent acted as a reversible hydrogen trap site.

Corrosion behavior and mechanism of FeCoNi high-entropy alloy compared with X100 pipeline steel in a simulated alkaline soil environment

In this work, the corrosion behavior of FeCoNi HEA and X100 pipeline steel in a simulated Golmud soil environment was systematically studied utilizing electrochemical tests, surface analysis techniques and immersion measurement. The results indicate that FeCoNi HEA possesses superior anti-corrosion property than X100 steel by comparing the charge transfer resistance (Rct), passive current density (ip) and corrosion morphology. The microstructure and surface film are the principal factors causing the difference in corrosion resistance of the two alloys. More intact, uniform and dense passive film enhances the anti-corrosion performance of the HEA, while the nonprotective, loose and defective corrosion product film covering the surface of X100 steel is not conducive to inhibiting the corrosion of the steel substrate. The appearance of inclusions within the HEA can generate the micro-galvanic corrosion effect with the matrix, which promotes the substrate as an anode to induce pitting. Furthermore, multiple phases of X100 steel exhibits higher electrochemical activity compared to the HEA with a single Face Center Cubic (FCC) phase, which accelerates the corrosion of the steel. Moreover, the matrix of the HEA primarily experiences selected dissolution of Ni element.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 1 — Microstructure

Laser welding with cold versus hot wire feed was employed as a root pass to weld X80 pipeline steel. The influences of wire feed rate and preheat on the fusion zone microstructure were investigated. Increasing the wire feed rate helped generate acicular ferrite in the weld metal, and preheating the wire further suppressed the formation of bainite. The acicular ferrite in the upper region of the fusion zone was finer than that in the lower region, which was due to an increase in nucleation sites available. Five fill and cap passes were applied by gas metal arc welding to fill the remaining top part of the groove. Compared to arc welding with a higher heat input, laser welding led to finer prior austenite grains and smaller bainite packet size in the coarse-grained heat-affected zone and limited the formation of martensite-austenite constituents in the intercritically reheated coarse-grained heat-affected zone.

Simulation of damage under cyclic loading for API 5L X70 steel pipelines (fatigue test)

The most efficient way to move large volumes of gas and oil is through pipelines, either from points of production to storage locations or from storage locations to distributed points of end use. One of the main materials of gas transportation pipes is X70 material. Base on the importance of in-service API 5L X70 pipelines, it is important for the safe operation of this system to know the lifespan of pipelines, and predict fatigue crack growth (FCG) of API 5L X70 steel pipeline. The objective of this theme is to study the lifespan of pipelines used for the transport of natural gas, oil and water, manufactured by the company ALFAPIPE in the wilaya of Ghardaïa. The judicious choice for manufacturing metal is a crucial factor to ensure prolonged life duration and improve resistance to fatigue, as materials respond to loading with elastic or plastic deformation. Stresses applied to materials can result in permanent deformation, rupture, cracking or progressive degradation. Understanding the effects of applied stresses is essential for the selection and implementation of materials in industrial applications. Fatigue tests were carried out on API 5L X70 steel using simulations using ANSYS software. The life of different samples was determined for different thicknesses after applying repeated stresses. The obtained results demonstrate the material API 5L X70's sensitivity to fatigue and emphasize the significance of designing pipelines with sufficient safety margins to prevent premature failures caused by fatigue.

Effect of immersion time on the corrosion behaviour of X70 and X80 line pipe steels in simulated concrete pore solution

Effect of immersion time on the corrosion behaviour of X70 and X80 line pipe steels in simulated concrete pore solution

Inhibition of corrosion on API 5L X52 pipeline steel in acid media by Tradescantia spathacea.

The concentration effect of Tradescantia spathacea (T. spathacea) as corrosion inhibitor of API 5L X52 steel in 0.5M of H2SO4 was studied here through electrochemical and gravimetric techniques. To achieve it, samples of the material were prepared to be submitted to each of the tests. Results from electrochemical impedance spectroscopy (EIS) showed that there was an optimum concentration of the inhibitor in which is reached the maximum inhibition efficiency, displaying the best inhibition characteristics for this system with a maximum inhibition of 89% by using 400ppm. However, the efficiency decreased until 40% when the temperature was increased to 60°C. Potentiodynamic polarization curves (PDP) revealed that some of the present compounds of T. spathacea may affect anodic and cathodic process, so it can be classified as a mix-type corrosion inhibitor for API 5L X52 in sulfuric acid. Also, this compound followed an adsorption mechanism; this can be described through a Frumkin isotherm with an adsorption standard free energy difference (ΔG°) of -56.59kJmol-1. Metal surface was studied through scanning electron microscope, results revealed that by adding inhibitor, the metal surface is protected; also, they evidenced low damages compared with the surface with no inhibitor. Finally, Tradescantia spathacea inhibited the corrosion process with 82% efficiency.

Distribution of hydrogen atoms at a notch on X52 steel under various loads and displacements studied by scanning Kelvin probe and finite element modeling

Abstract In this work, the distribution of hydrogen (H) atoms at a notch on an X52 pipeline steel under various applied loads or displacements were investigated by Volta potential measurements using a scanning Kelvin probe (SKP) and finite element modeling. The stress concentration at the notch is elastic under the test condition. The H atom diffusion and distribution is driven by stress, rather than strain, in the steel. However, when displacements are applied on the steel specimen, the strain dominates the H atom distribution. As the local stress or strain increases, the H atom concentration increases, as indicated by negative shifts of the Volta potential. By establishing the quantitative relationships among Volta potential, von Mises stress, and H atom distribution, this work attempts to provide a novel method for H atom detection in steels through the Volta potential measurement.

Corrosion of API 5L X60 Pipeline Steel in Soil and Surface Defects Detection by Ultrasonic Analysis

The corrosion steels phenomenon is one of the main problems in the oil industry, such as in buried transmission pipelines used for high gas pressure for long distances. Steels are protected from the external soil corrosion through a bituminous coating, whose action is coupled with a cathodic protection system, which aims to maintain steel in its protection field and thus to avoid any corrosion risk. However, steels in service may experience external surface defects like corrosion pitting and cracking due to electrochemical or mechanical interactions of bare steel with an aggressive soil solution after steel protection failure. These are concerning phenomena and are the major threats of the pipeline transmission system’s reliability and ecological safety. Corrosion mechanisms are varied and can be evaluated by different methods, such as electrochemical measurements, which are influenced by various factors like temperature, pH, soil characteristics, resistivity, water content, and as well mechanical stresses. Corrosion results from simulated artificial soil solutions showed that steel is sensitive to corrosion by soil. Surface defects detection was carried out using an ultrasonic non-destructive method such as C-Scan Emission testing and the time of flight diffraction technique (TOFD) ultrasonic non-contact testing method. After propagation of the ultrasonic waves, the diffracted ultrasonic reflected wave occurring at the edges of the defects appears due to the presence of a corrosion defect by generating defect echoes. The C-Scan ultrasonic image shows surface reflection, including corrosion defects on interfaces with varying acoustic impedances. The cross-transverse speed ultrasonic propagation through the plate including defect is modified, revealing more surface defects, and cross-transverse speed is shown to increase ultrasonic detection presents some advantages, such as precision and speed of detection without alteration to the structure. This method can be used in the industrial context as an intelligent industrial robotics technique.

Corrosion behavior of steel exposed to "zero" pollution atmosphere environment for 20 years

In this study, the corrosion behavior of Q235 carbon steel, 09CuPTiRE weathering steel and X60 pipeline steel after 20 years exposure in "zero" pollution atmosphere environment was investigated by corrosion rate analysis, macroscopic observation, scanning electron microscopy, X-ray diffraction, white light interferometers and electrochemical analysis were conducted to analyze. The results showed that the corrosion rate of the three kinds of steels increases first and then decreases with time, and the results indicated that the empirical formula D=Atn was suitable for corrosion kinetics of three materials, and the three kinds of steels all form a relatively dense rust layer, which can effectively protect the metal matrix, inhibit the corrosion process and reduce the rate of corrosion. Under the same exposure time and the same corrosion conditions, the corrosion degree of the three materials is: X60 pipeline steel > Q235 Carbon steel >09CuPTiRE Weathering steel, three kinds of steel corrosion products are the same, only α-FeOOH and γ-FeOOH exist in the rust layer, and the relative content of α-FeOOH is more than γ-FeOOH of each steel in both skyward side and fieldward sides. X60 Pipeline steel has the worst corrosion resistance, and 09CuPTiRE weathering steel has the best corrosion resistance, so 09CuPTiRE weathering steel has better adaptability to this environment.

Assessing fracture toughness of vintage and modern X65 pipeline steels under in situ electrochemical hydrogen charging using advanced testing methodology

The susceptibility of pipeline steels to hydrogen embrittlement, which can significantly impair mechanical performance, especially fracture toughness, is a critical issue in infrastructure integrity. This study evaluates the fracture toughness of modern and vintage API X65 steels under cathodic polarization (CP) conditions, employing methods such as rising displacement testing, stepwise rising constant load testing, and constant load testing. Tearing crack growth was detected at crack tip opening displacements (CTODs) of 0.032 to 0.055 mm while subsequent crack arrest under constant force loading was observed with CTOD thresholds of 0.148 mm and 0.255 mm for modern and vintage X65, respectively. Electron channelling contrast imaging demonstrated that arrested cracks in both steels exhibited reduced plasticity and a higher propensity for crack branching compared to propagating cracks. These findings highlight the need for tailored strategies to mitigate the effects of hydrogen embrittlement in pipeline materials and underscore the differences in damage tolerance between steel generations.

Effect of post-weld heat treatment on corrosion resistance of X90 pipeline steel joints

Abstract In order to improve the corrosion resistance of welded joints, X90 pipeline steel joints were subjected to post-weld heat treatment at 610 °C, 640 °C, and 670 °C (holding time was 1 h). Through electrochemical corrosion and full immersion corrosion experiments, the corrosion resistance of welded joints under various conditions was tested, and the surface morphology and corrosion products of the corroded samples were analyzed by scanning electron microscopy and X-ray diffraction analysis. The experimental results show that the corrosion products of X90 pipeline steel welded joints in simulated soil solution mainly include Fe(OH)3, γ-FeOOH, α-Fe2O3, γ-Fe2O3, and a small amount of Fe3O4, FeCl3 and Fe. After heat treatment at 610 °C, the corrosion current density of the parent metal, heat-affected zone, and weld metal of the joint changes from 1.081, 2.889, 2.079 (×10−5 A cm−2) to 0.977, 2.211, 1.810 (×10−5 A cm−2), respectively, the corrosion resistance is improved.

Effect of laser beam wobbling and welding speed in X80 steel wire-fed laser root welds

A wobble laser was combined with a wire feed during laser root welding of X80 pipeline steel. The enlarged laser irradiation area and molten pool resulting from the laser beam wobbling provided a better gap-bridging ability, which is critical during laser welding of thick pipes. Applying laser beam wobbling enabled better control of filler metal dilution, which determined the weld metal microstructure and mechanical properties. In the present work, more bainite along with reduced acicular ferrite was formed in the wobble laser weld, due to the effect of dilution resulting from increased base material melting during wobbling beam, along with an inhomogeneous fusion zone microstructure. The instrumented indentation testing was utilized for the first time to distinguish the local yield strength variation of different regions of the fine weld zones, allowing one to verify if the weld metal strength meet the target value in industrial standards. As the productivity being improved when the welding speed increased from 1.0 to 1.5 m/min, the presence of more low temperature transformation products generated with a faster cooling led to a 26 HV higher hardness and a 70 MPa higher yield strength in the upper region of the fusion zone.

Effect of electrochemical hydrogen-charging conditions on nanomechanical properties of X80 pipeline steel

In this work, nanoindentation tests, combined with hydrogen (H)-permeation testing, were used to study the effect of electrochemical H-charging conditions on H-permeating parameters and nanomechanical properties of X80 pipeline steel. The steady-state H-permeating current density, H-permeating flux, and the H subsurface concentration obtained in 0.5 M H2SO4 solution are apparently greater than the parameters obtained in near-neutral pH NS4 and 0.1 M NaOH solutions. The nanomechanical properties of X80 steel are heavily dependent on the electrochemical H-charging conditions (i.e., solution, time, and cathodic current density). The changes in nanohardness of the steel subjected to electrochemical H-charging depend on the charging solution used. In 0.5 M H2SO4 solution, as the electrochemical H-charging time increases, the nanohardness of the steel continues to decrease. However, in NS4 and 0.1 M NaOH solutions, the steel nanohardness increases with time. This phenomenon is attributed to the formation of corrosion product films on the steel surface. The softening and hardening transition phenomenon occurs on the steel subjected to electrochemical H-charging. Although measurement errors may cause variations in the nanohardness results, the evolution of nanohardness upon electrochemical H-charging exhibits a discernible tendency. H atoms could affect the elastic modulus of steel. When electrochemical H-charging promotes a uniform distribution of H atoms within the steel, achieved through either extended charging time or application of a cathodic current density, the elastic modulus of the steel tends to increase.