X80 Steel Research Articles

Hydrogen-Induced Cracking in CGHAZ of Welded X80 Steel under Tension Load

X80 steel is extensively used in hydrogen environments and is susceptible to hydrogen embrittlement (HE). This paper studied the hydrogen-induced cracking (HIC) behavior in the coarse-grained heat-affected zone (CGHAZ) of X80 steel welds, through applying in situ hydrogen-charging tensile experiments, hydrogen permeation experiments, and various surface analysis techniques. It is shown that a few hydrogen atoms can significantly decrease a material’s elongation and reduction of area. When the heat input (HI) was 29.2 kJ/cm, the material had minor sensitivity to hydrogen embrittlement. The tensile fractures were ductile without hydrogen. However, the fracture surface exhibited brittle fracture with hydrogen. With increased HI, the HE fracture showed a transition of intergranular fracture→intergranular and transgranular mixed fracture→transgranular fracture. In the presence of hydrogen, the grain boundaries of elongated strips were prone to the formation of intergranular cracks under a tension load, and the hydrogen embrittlement resistance of the bulk lath bainite (LB) was weak. The hydrogen embrittlement susceptibility of pure granular bainite (GB) was lower. Fine LB and GB composite structures could remarkably inhibit intergranular cracks, giving the steel a superior resistance to hydrogen embrittlement.

Perspectives on Corrosion Inhibition Features of Novel Synthesized Gemini-Fluorinated Cationic Surfactants Bearing Varied Spacers for Acid Pickling of X60-Steel: Practical, and In Silico Calculations.

Through our present study, three novel Gemini-fluorinated cationic surfactants bearing different spacers (FSG6-2, FSG6-4, and FSG6-6) were synthesized, and their structures were explained via different spectroscopic instruments such as 1H, 13C, and 19F NMR spectra. The surface activity of the as-prepared surfactants was examined. The inhibiting influence of FSG6 molecules on the X60 steel corrosion in the pickling solution (HCl) was examined by diverse methods comprising electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and X-ray photoelectron spectroscopy (XPS) experimentations, and computational calculations. The inhibition effectiveness of FSG6 surfactants followed the order of 93.37% (FSG6-2) < 96.74% (FSG6-4) < 98.37% (FSG6-6) at 2.0 × 10-4 M. The FSG6 surfactants function as mixed-type inhibitors, according to PDP investigations. The H2O molecules that adsorbed on the steel interface were substituted with surfactant molecules, and the surfactant's inhibitory activity is likely caused by the improvement in an adsorptive layer on the steel substrate, as specified by the EIS results. The Langmuir isotherm describes the absorption of FSG6 molecules on the metal surface. The XPS investigations validate the steel interface's extremely protective nature. The mechanism of interaction between FSG6 molecules with an X60-steel employing the DFT calculations and MC simulations methods was also examined and discussed.

Microbiologically influenced corrosion of a novel pipeline steel containing Cu and Cr elements in the presence of Desulfovibrio vulgaris Hildenborough

Inspired by the principle of copper-containing antibacterial stainless steel, a new type of Cu-Cr-bearing pipeline steel has been developed. Through a variety of surface characterization and electrochemical tests, the antibacterial property and microbiologically influenced corrosion resistance (MIC) of the novel type of steel were studied. Although the addition of Cu did not make this steel exhibit ideal antibacterial properties, all the results still showed that MIC resistance of the novel pipeline steel was better than that of X70 and Cr-bearing steels. The synergistic effect of Cr and Cu in the Cu-Cr-bearing pipeline steel contributed a beneficial effect to the improved MIC resistance.

Stress corrosion cracking under extreme near-neutral GCC conditions, parametric and comparative study using phase field modeling

Stress Corrosion Cracking (SCC) is a failure mechanism that occurs when certain materials are subjected to both external or residual stresses and corrosion. This combined effect leads to the development of cracks in the susceptible materials. Submerged steel pipelines in the petroleum sector are built of low-alloy steels having a ferrite-cementite composition, including API 5L X70. Such materials are sensitive to SCC damage in aqueous systems. The film rupture dissolution repassivation (FRDR) process is used in this study to evaluate the cracks and pits growth in oil and gas pipelines in the Gulf area under diverse SCC environmental conditions. The SCC crack propagation and pit growth under near-neutral environmental conditions were analyzed using phase field modelling. X70 steel under NS4 the solution was used for the analysis to represent the anodic dissolution film rupture mechanism. A parametric study was done to study the impact of different electrochemistry and phase field parameters on crack growth behaviour. The study assess the susceptibility to SCC caused by an pit by employing diverse settings to evaluate the impact of corrosion parameters and the interaction among the FRDR mechanism. The corrosion rates are influenced by the interface kinetics coefficient (L), which exhibits an accelerated effect as L increases. This transition from fracture-controlled to dissolution-controlled SCC growth occurs until the system reaches the diffusion limit, beyond which further increases in L do not significantly impact corrosion rates. Moreover, higher values of the kinetic coefficient (k) advance the creation of SCC cracks at the crack front, resulting from corrosion originating from pitting at the crack mouth. This process leads to the refinement of the pit and its transformation into a crack. A comparison analysis was utilized to validate our simulation under a near-neutral NS4 solution for X70 steel by correlating the findings with other numerical methods for crack growth utilizing the same material and environmental parameters. The results show decent agreement with the comparative study.

Internal localized corrosion of X100 pipeline steel under simulated flow conditions

In this paper, a wire beam electrode (WBE) was used to explore the local corrosion processes of X100 pipeline steel in simulated solution containing HCO3− in static and flow conditions. The results indicated that the WBE's current density mapper was remarkably consistent with the polarization curves. Therefore, WBE is an efficient online corrosion monitoring approach. The WBE discovered undetectable pitting and passivation qualities within the X100 pipeline steel under static conditions. However, the corrosion current density of X100 steel was substantially higher under flow conditions than under static ones. The addition of HCO3− ions significantly decreased the corrosion resistance of the X100 steel. In the 0.3 mol/L HCO3− simulated solution, dynamic corrosion was 92 times faster than static. The corrosion of X100 steel was enhanced by the combined effects of fluid movement and HCO3− ions. Additionally, X100 steel produced significant irregular edge pitting when the critical level of HCO3− was 0.2 mol/L under dynamic conditions, and an erosion theory was proposed to explain this phenomenon.

Numerical analysis of hydrogen atom diffusion and trapping at an unconstrained dent on pipelines

In this work, a three-dimensional finite element-based mechanics-diffusion coupling model is developed to determine the stress/strain distribution and hydrogen (H) atom concentration at an unconstrained dent on an X52 steel pipe which is to be used for transport of high-pressure hydrogen gas. Both von Mises stress and equivalent plastic strain concentrations and a high hydrostatic stress gradient exist at the dent. The distribution of H atom concentration coincides with that of the hydrostatic stress. The maximum H atom concentration in the steel lattice locates at the dent bottom, while the distribution of the H atom concentration at metallurgical traps is consistent with that of the equivalent plastic strain. A competitive effect exists between the hydrostatic stress and the plastic strain on the H atom distribution. At low initial H atom concentrations (e.g., 0.001 mol/m3), the equivalent plastic strain dominates the distribution of H atoms. At high initial H atom concentrations (e.g., 0.1 and 1 mol/m3), the hydrostatic stress is more important to determine the distribution of H atom concentration. As the dent depth increases, both the von Mises stress and plastic strain at the dent increases, while the total H atom concentration decreases due to decreased hydrostatic stress. When the internal pressure increases from 5 MPa to 15 MPa, there are slightly increases in von Mises stress, equivalent plastic strain and the total H atom concentration.

An Experimental Study on the Influence of the Fractal Characteristics of X80 Steel Surface Morphology on Water Ring Stability

The surface morphology of X80 steel with hydrophilic underwater oleophobic characteristic is described greater comprehensively and quantitatively in this work by combining fractal dimension and multifractal. X80 steel with hydrophilic underwater oleophobic surface characteristics was constructed using a chemical etching method. Then, with the aid of three wettability parameters—contact angle, rolling angle, and adhesion work—this study investigated the relationship between the surface fractal dimension of X80 and the stability of the water ring in the core annular flow. The results showed that: (1) the fractal dimension of X80 steel specimens increased first and then decreased with the increase of reaction time. Besides that, the value of it was greater than 2, indicating that the surface had obvious fractal characteristics. The spectral difference, Δf(α), and the spectral width, Δα, supplemented the description of the X80 steel surface morphology, which was consistent with the scanning electron microscope results. (2) When the maximum fractal dimension was 2.0808, the minimum contact angle of distilled water on its surface was 50.2°, and the maximum contact angle of underwater oil droplets was 166.4°. The larger the fractal dimension of X80 steel with hydrophilic underwater oleophobic properties, the more hydrophilic and underwater oleophobic it is. This illustrated that there was a strong binding force between the water and the X80 steel pipe wall, and hence the quality and efficiency of the core annular flow was improved, which was more conducive to the promotion of this technology in the field of heavy oil transportation.

Study by finite element modeling of hydrogen atom diffusion and distribution at a dent on existing pipelines for hydrogen transport

Pipelines, especially existing natural gas pipelines, provide an efficient and economical means for hydrogen transport, accelerating realization of a full-scale hydrogen economy. However, the existing aged pipelines usually contain dents, which serve as effective traps to accumulate hydrogen atoms, potentially causing hydrogen embrittlement and pipeline failures. To date, there has been a strong interest in development techniques for assessment of hydrogen atom distribution at a dent on pipelines. In this work, a three-dimensional nonlinear finite element-based model was developed to investigate the hydrogen atom diffusion and distribution at a constrained dent on an X52 steel pipe. Parametric effects, including dent depth and internal pressure, were determined. The presence of a dent on pipelines drastically changes the local stress and strain distributions, facilitating diffusion and accumulation of hydrogen atoms at the dent. The minimum hydrogen atom concentration at the crystalline lattice sites, (i.e., 3.8 mol/m3) is located on the outer surface of the dent center, and the maximum hydrogen atom concentration (i.e., 12.1 mol/m3) is found on both sides of the dent with 103 mm from the dent center in the circumferential direction. The hydrogen atom concentration at trap sites at the dent is much lower than that at the lattice sites. The diffusion and accumulation of hydrogen atoms at the dent area is affected by two competitive mechanisms, i.e., hydrostatic stress and plastic strain, depending on the initial concentration of hydrogen atoms entering the interior of the pipe steel. At a low initial concentration such as 0.001 mol/m3, the equivalent plastic strain dominates the distribution of hydrogen atoms at the dent, and the hydrogen atom concentration at the lattice sites is much lower than the concentration at the trap sites. At high initial hydrogen atom concentrations such as 0.1 and 1 mol/m3, the hydrostatic stress is the dominant factor to determine the distribution of hydrogen atoms, which mainly accumulate at the lattice sites. With an increased depth of the dent, both the von Mises stress and plastic strain concentrations increase, and so is the hydrogen atom concentration. The increase of internal pressure from 5 MPa to 15 MPa only slightly elevates the von Mises stress, equivalent plastic strain and the hydrogen atom concentration.

Investigation on regression model for the force of small punch test using machine learning

The analytical solution for the force-deflection curve of the small punch test (SPT) is still a challenge. Machine learning is employed in the present study to establish a model for estimating SPT forces by using the strength of a material. The yield strength and ultimate tensile strength of materials and corresponding SPT force-deflection curves generated by finite element simulations are the training and testing data for machine learning. Pearson correlation analysis was performed first to measure the statistical association between the SPT force at a given deflection and the strength of materials. It was shown that a binary linear regression model was capable of correlating SPT forces to the yield strength and ultimate tensile strength of a material. The model parameters were determined after training, and then this model was tested by testing data. The accuracy of the regression model was verified by hypothetical materials, X70 steel and Incoloy 800H alloy. This study gives a new insight into the relationship between force responses of SPT and material properties, and can promote the development of novel approaches for determining material tensile properties using SPT.

Finite element simulation method for combined Ductile-Brittle fracture of small punch test in hydrogen

This paper presents a simulation method for combined ductile–brittle fracture of small punch (SP) test in hydrogen and application to test data of API X70 steel. For ductile fracture simulation, the multi-axial fracture strain damage model determined from un-embrittled material with the hydrogen-embrittlement constant determined from SP test in hydrogen is used. To simulate brittle fracture, the critical stress method is proposed, where the critical stress is determined using the V notch round bar tensile test in hydrogen. The determined models are applied to simulate the SP test in hydrogen showing combined ductile and brittle fracture mode. Simulation can well reproduce not only the load–displacement curve but also the circumferential ductile cracking, followed by radial brittle cracking, observed in the test.

Prediction of SIF range for plain API 5L Grade X65 steel under corrosion using AI & ML models

Corrosion is one of the significant aspects of science & engineering and the effects of corrosion on various infrastructures due to fatigue loading are paramount. Experimental investigations to evaluate fracture parameters and fatigue crack growth life take a considerable amount of time and effort. Recently, the computational boon in the form of Artificial Intelligence (AI) and Machine Learning (ML) has paved the way for predicting the required fracture parameters through training with the available limited experimental data. In this paper, the fracture parameter, Stress Intensity Factor (SIF) of plain API 5L X65 grade steel is predicted using the experimental data of crack growth studies performed on the specimen with single edge notch, eccentrically loaded, subjected to inert and corrosive environments (2.0% and 3.5% NaCl). From the experimental data, the fracture parameter, SIF range is determined for various crack lengths corresponding to certain loading cycles. Multivariate Adaptive regression splines (MARS), Artificial Neural Network (ANN), and relevance vector machine (RVM) based models are developed by using the experimental data to predict the SIF range. The efficiencies of the developed models are verified through several statistical parameters. The studies show that the proposed models are capable of predicting the SIF range for plain API 5L X65 grade steel effectively with the available experimental data. The predicted SIF range is highly useful for the prediction of crack growth life and the evaluation of the residual strength of structural components.

CO2 Corrosion Behavior of X70 Steel under Typical Gas–Liquid Intermittent Flow

CO2 Corrosion Behavior of X70 Steel under Typical Gas–Liquid Intermittent Flow

Impact of residual cementite on inhibition of CO2 corrosion of mild steel

A thick cementite skeleton exposed on a ferritic-pearlitic C1018 steel surface after pre-corrosion significantly compromised inhibition efficiency. However, this detrimental effect was insignificant for a lower carbon X65 steel with dispersed cementite microstructure, due to the insignificant amount of cementite that remained on its surface after pre-corrosion. After normalizing the increased cathodic area in the presence of residual cementite back to original area, both anodic and cathodic reactions were inhibited to the same extent as on bare steel with a sufficient inhibitor concentration. However, the detrimental effect of cementite cannot be completely eliminated due to its galvanic coupling effect.

Feasibility of orbital friction stir welding on clad pipes of API X65 steel and Inconel 625

Orbital friction stir welding (FSW) has been applied to clad pipes, which is certainly of interest to the oil and gas industry. In this context, an FSW system capable of performing sound joints in one pass with full tool penetration was developed. Orbital FSW was executed in 6 mm thick API X65 PSL2 steel clad pipes with 3 mm thick Inconel 625 using a polycrystalline cubic boron nitride (pcBN) tool. The metallurgical and mechanical properties of the joints were investigated. Sound joints with axial forces of 45–50 kN, tool rotational speeds of 400–500 rpm, and a welding speed of 2 mm/s were obtained, illustrating that the developed system can perform FSW joints without volumetric defects.

Electrochemical, surface analysis, computational and anticorrosive studies of novel di-imine Schiff base on X65 steel surface

The inhibitory effect of di-imine-SB namely ((N1Z, N4E)-N1, N4-bis (4 (dimethylamino) benzylidene) butane 1,4-diamine) on X65-steel in 1 M HCl has been investigated experimentally and theoretically. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss outcomes display the anticorrosion properties of “di-imine- SB”. The inhibitory efficiency exceeds 90% at the optimal concentration of 1 × 10–3 M “di-imine- SB”. The metal surface was examined further using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The effectiveness of the di-imine-SB is returned into its adsorption on X65-steel surface and found in agreement with Langmuir adsorption isotherm. According to the standard Gibbs free energy of adsorption ({Delta G}_{ads}^{^circ }), di-imine-SB adsorption tends to be chemical rather than physical, it increases the activation energy ({mathrm{E}}_{a}) of metal dissolution reaction and makes it hard to occur. The PDP data suggested anodic and cathodic type of the di-imine-SB inhibitor. Meanwhile, increasing the resistance of X65-steel to 301 Ω cm2 after adding 1 mM of di-imine-SB confirms its protective effect. Whereas, the positive value of the fraction of electron transference (ΔN, 0.746), confirms the affinity of di-imine-SB to share electrons to the partially filed 3d-orbital of Fe forming strong protective film over X65-steel surface. Aided by Monte Carlo (MC) simulation, the calculated adsorption energy (Eads) suggests excessive adsorption affinity of di-imine-SB on metal surface over the corrosive chlorides and hydronium ions. A good correlation between the theoretical hypothesis and the experimental inhibition efficiency has been achieved. The comparative study showed the superior of the di-imine-SB as potential corrosion inhibitor compared with those reported before. Finally, global reactivity descriptors; electron affinity (A), ionization potential (I), electronegativity (χ), dipole moment (µ), global hardness (eta), electrophilicity index and, Fukui indices were also calculated and found well correlated to the reactivity of di-imine-SB.

Insight into the anti-corrosive performance of Persea Americana seed extract as a high-efficiency and sustainable corrosion inhibitor for API 5 L X65 pipeline steel in 1 M HCl solution

Presently, there is high demand for less toxic and effective corrosion inhibitors for the acidizing process owing to the toxicity of the existing inhibitors. Therefore, the objective of this study is to explore the feasibility of Persea Americana seed extracts (PASE) as sustainable corrosion inhibitors to mitigate the corrosive effect of 1 M HCl on API 5 L X65 pipeline steel using weight loss, and potentiodynamic polarization techniques. Fourier transform infrared spectroscopy (FTIR) was utilized to establish the inhibitor’s functional group. The result obtained shows that the inhibition efficiency increased with concentration, with the best inhibitor efficiency obtained as 95.65% for 5 g PASE in 1 M HCl solution. The electrochemical tests revealed that PASE behaves as a mixed-type corrosion inhibitor. The adsorption of PASE followed the Langmuir adsorption isotherm. Results from FTIR confirm that PASE extracts contain hydroxyl group compound, flavonoid, and phenolic content which can be utilized as corrosion inhibitors. The SEM analysis shows a notable difference in the steel surface with inhibitor owing to the protective barrier formed on the metal surface. In the formulation of acidizing corrosion inhibitors, PASE is a promising active compound. The data obtained from the weight loss test is in agreement with the electrochemical tests and demonstrates excellent inhibitive behavior of PASE on X65 steel in the acid solutions. This research provides insight into the development of sustainable corrosion inhibitors for X65 steel.

Electrochemical Investigations of Simulated Surface Scales Formed on X65 and J55 Pipeline Steel

Electrochemical Investigations of Simulated Surface Scales Formed on X65 and J55 Pipeline Steel

Corrosion inhibition of X70 steel by tetrabutylammonium iodide in 1 M HCl at different temperatures

Corrosion inhibition of X70 steel by tetrabutylammonium iodide in 1 M HCl at different temperatures

Synergistic effect of different testing environments on the hydrogen-induced mechanical degradation to establish the role of microstructural features on the failure of X70 pipeline steel

Hydrogen-induced mechanical degradation was evaluated in different environmental conditions on two X70 pipeline steels having the same composition but different thermomechanical processing parameters, and a further correlation between microstructural features and hydrogen embrittlement (HE) susceptibility was established. HE susceptibility was determined by performing the Slow Strain Rate Tensile Test (SSRT) in air, ex-situ hydrogen-charged, in corrosive media, in-situ hydrogen-charged and Charpy impact tests before and after hydrogen charging in a wide range of temperatures.The SSRT results indicated that the synergistic action of stress and hydrogen in in-situ charged sample leads to maximum HE susceptibility in both X70 steels. Charpy results demonstrated that ductile-to-brittle transition temperature (DBTT) increases after hydrogen charging. The texture analysis revealed that X70-2 with a higher volume fraction ratio of Ƴ-fiber/{100}<011> demonstrated improved HE resistance, whereas X70-1 with higher fractions of {113}<110> and {100} || ND demonstrated a higher DBTT than before and after hydrogen charged X70-2.

Sustainable and Green Approach for Api 5L Pipeline Steel Acidic Corrosion Inhibition Using Agro-Industrial Waste: Experimental and Theoretical

Currently, the use of synthetic inhibitors in preventing corrosion is destructive to the environment; therefore, natural inhibitors might be an alternative and innovative solution to this challenge, owing to their sustainability. Herein, wasted avocado seed extract was examined as a sustainable and green inhibitor for API 5L X65 pipeline steel at an ambient temperature using the gravimetric analysis, the potentiodynamic polarization curve, and linear polarization resistance techniques. The inhibitor’s chemical characterization was carried out with Fourier-transform infrared spectroscopy (FTIR), and the morphological characterization was carried out by detailed scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). The result showed that the extract decreased the corrosion rate by retarding the cathodic and anodic electrochemical reactions, with a maximum efficiency of 88% at 5 g/L. The extract was adsorbed physically onto the X 65 steel following the Langmuir adsorption isotherms. The electrochemical studies showed that the agro-waste was a mixed-type inhibitor. The SEM image of the X65 steel with the extract showed thin film formation on the steel surface. The extract can be substituted for synthetic inhibitors, which are toxic, scarce, and costly.