Corrosion Fatigue Conditions Research Articles

Determination of the residual life of the pipe metal under conditions of corrosion fatigue

This paper presents a method for calculating the residual metal life of pipelines with crack-like defects. The results of corrosion and fatigue tests of ordinary grade structural steel VSt3sp, widely used in the oil and gas industry, are presented. The work carried out studies on the effect of cathodic polarization on the cyclic crack resistance of VSt3sp steel under the influence of a carbonate-bicarbonate medium.

Fatigue corrosion behavior of friction‐welded stainless and carbon steel dissimilar joint

AbstractThis study investigates the fatigue corrosion behavior of direct drive friction welded ASTM A105 and AISI 304L steels joints. Axial fatigue tests were carried out at a stress ratio of R = 0.1 in air and different corrosive environments using a 3D printed environmental test cell. The samples were tested in 3.5%wt NaCl aqueous solution at free corrosion potential (Ecorr) and other two polarization conditions (−0.85 and −1.30 V vs. Ag/AgCl) with the objective to highlight the influence of the cathodic protection and the influence of evolved hydrogen on the fatigue behavior. Fracture analyses were conducted through optical and electron microscopy to identify the possible causes of failure nucleation and the different damage mechanisms dictated by the aggressive environment. Principal results quantify the detrimental effect of the corrosive environment and the positive role played by the cathodic protection. Moreover, a clear differentiation in the failure site and mechanism was observed for the different corrosion fatigue conditions.

Reduction of Life Time Expectation of Standard Duplex Stainless Steel Exposed to Hydrogen under Corrosion Fatigue Conditions

In geothermal environment corrosion fatigue lowers the lifetime expectancy of high alloyed steels. Therefore, cathodic protection enhances corrosion resistance although hydrogen is produced during the cathodic reactions under applied potential. Corrosion fatigue of standard duplex stainless steel X2CrNiMoN22-5-3, 1.4462 specimen loaded with hydrogen was investigated in a specifically designed corrosion chamber surrounded by the Northern German Basin electrolyte at 369 K. The reactions of the microstructure associated with hydrogen incorporation lowers the number of cycles to failure of specimen significantly at various stress amplitudes, for example at σa = 275 MPa and USHE = -36 mV by 80%. Hydrogen enhances crack propagation and early failure due to the degradation of the mechanical properties of the ferritic phase.

A review study on Corrosion Fatigue and its related testing methodologies

Corrosion Fatigue is the mechanical degradation of a material under the joint action of damage mechanisms corrosion and fatigue. Corrosive nature of the seawater puts severe durability requirements on materials of which are often exposed to corrosion fatigue and abrasive conditions simultaneously. Therefore, identification of the combined effects of both corrosion and fatigue damage mechanisms is necessary to improve predictive models for the corrosion fatigue phenomenon. Present article is the result of a desktop study (scientific literature and standards) with the aim of study the feasibility of designing and manufacturing of a corrosion fatigue testing set-up that would allow the designer to compare the performance of different materials exposed to corrosion fatigue, permitting also the comparison with results from dry fatigue testing. The corrosion fatigue mechanism is described in more detail and a short presentation of some typical lab-scale corrosion fatigue test setups is given. This is followed by illustration of international standards and guidelines which will be used to design a new corrosion fatigue test set-up for evaluating the fatigue behavior of material in seawater environment. Finally the experimental techniques for corrosion fatigue crack detection and propagation along with the fundamental basic of corrosion fatigue modeling are illustrated.

Big Data Approach Application for Steel Pipelines in the Conditions of Corrosion Fatigue

Big Data Approach Application for Steel Pipelines in the Conditions of Corrosion Fatigue

Improvement of Regulatory Requirements for Ensuring the Quality of Underground Gas Pipelines in Conditions of Corrosion Fatigue

The article develops recommendations for improvement of normative documents concerning the quality of underground pipelines (gas pipelines) under conditions of fatigue and the impact of an aggressive environment, taking into account cathodic (electrochemical) protection. It is established that the basis of information provision of normative documents is the method which includes the following main criteria: the value of the minimum current density of cathode protection; minimum security potential; maximum protective potential, minimal displacement of protective potential; strength criteria of pipe material; criteria of strength of phase layer between the and the coating; the strength of the in the defect of the insulation coating. It has been found out that the system metal pipe - insulating dielectric coating is characterized by such basic procedures as: identification of hazards; various variants of load asymmetry; evaluation of the boundary and optimal values of potentials and currents for the system of cathodic protection of the pipeline. The prospect of further research in this area is determination of the complex indicator of quality and reliability of the linear part of underground main gas pipelines on the basis of research results (submitted information support).

DEVELOPMENT OF INFORMATION SUPPORT OF QUALITY MANAGEMENT OF UNDERGROUND PIPELINES

Recommendations are worked out in relation to the evaluation of longevity and quality of underground metallic pipelines in the conditions of corrosion fatigue. The features of early exposure of crisis (before accident) situations are set. A complex qualimetric criterion is offered for determination of level of quality of pipeline by the account of his technological specific. The elements of investment project and methodology of estimation of resource are worked out. and also influences of factors of different nature on risks and possibility of accident of gas pipelines. The model of corrosion fatigue of metal is based on power criterion of destruction mechanics according to which there is an act of destruction in an arbitrary elemental volume of a material if the total irreversibly scattered energy of plastic deformation for all load cycles will reach a critical value equal to the energy of destruction. In order to control the corrosion process taking the polarization potential into account, a criterion relation is used to determine the rate of residual corrosion of a metal in the defect of the insulation coating, in particular, at the top of the crack, which is an anode region. The adhesive strength criteria of biocorrosive aggressive soil, mechanical criteria for the stress intensity factor, the criterion of corrosion resistance defect, criterion correlation for estimating the speed of residual corrosion in defect of insulation coating with imposed diagnostic weight characteristics and diagnostic value of tests, that complement, clarify and improve the corrosion monitoring system of pipelines, helpful for controlling and optimizing of the corrosion process, and Development of recommendations for anti-corrosion protection of metal are used in areas with non-stationary plastic deformation.

Crack growth behavior of 4340 steel under corrosion and corrosion fatigue conditions

Abstract Crack initiation and growth behavior in 4340 steel under static and cyclic loads in various environments are examined using the two-parameter approach developed by the authors. It is shown that environmental effects can be time dependent, stress dependent, or both, depending on the amplitude, peak stress, and aggressiveness of the environment. It is shown that the tests under vacuum are required to establish the reference state for the quantification of the chemical driving forces involved in crack initiation and growth in aggressive environments. Failure diagrams are proposed by extending the Kitagawa-Takahashi diagram for fatigue. It is shown that these can be used to quantify the mechanical and chemical internal stresses required to cause both initiation and growth of an incipient crack in a smooth as well as notched specimens. Conditions for propagating and nonpropagating incipient cracks that are initiated under stress concentrations are also discussed, taking the example of the 4340 steel data available.

Influence of prior corrosion on the high cycle fatigue behavior of microarc oxidation coated 6061-T6 Aluminum alloy

The objective of this study is to evaluate the influence of prior immersion of microarc oxidation coated and uncoated Al alloy in 3.5% NaCl solution up to 168 h on their high cycle fatigue behavior. The prior immersion caused pitting on uncoated Al alloy while in the case of MAO coated Al alloy no pits were observed. Electrochemical impedance spectroscopy revealed progressive degradation of the MAO coated Al alloy with increasing duration of immersion. The fatigue life of MAO coated Al alloy decreased with increasing duration of immersion but at a significantly lower rate than in the case of the uncoated Al alloy. Thus, MAO coatings provided a measure of protection under corrosion fatigue conditions as compared to the uncoated Al alloy.

Residual stress relaxation in shot peened high strength low alloy steel and its implications for hydrogen assisted cracking

The relaxation of compressive residual stress in shot peened and laser peened 300M high strength low alloy steel in response to applied loads has been investigated and for the shot peened specimens the implication for resistance to hydrogen assisted cracking assessed. The near surface residual stress was measured predominantly by X-ray diffraction (first 10 μm) but supplemented by measurements using high resolution, fine increment hole drilling to yield depth profiling. Relaxation of residual stress was most significant under compressive loading (single load cycle) with a loss of ∼70% of the peak residual stress when the applied stress was at the compressive 0·2% proof stress. Constant load tests in 3·5%NaCl were conducted on cadmium or SermeTel coated specimens at open circuit and with uncoated specimens at an applied potential corresponding to the minimum value of the protection potential associated with these coatings. For all peened specimens, stress relaxation was induced by a prior applied stress, usually close to the compressive 0·2% proof stress. Most tests were conducted with notched specimens with a target notch depth about 50–60 m m, close to the peak residual stress on shot peened specimens. Despite the comparative severity of the tests, with applied tensile stresses up to 95% of the tensile 0·2% proof stress and the maximum expected residual stress relaxation, none of the shot peened specimens failed. This is reassuring from an engineering perspective. However, notched specimens did fail below the tensile 0·2% proof stress under slow strain rate conditions and the performance under corrosion fatigue conditions remains to be established.

Corrosion Fatigue Crack Growth Rate for Petroleum Refining Pressure Vessel Materials (2.25Cr-1Mo Steel)

Abstract The 2.25Cr-1Mo steel is used for pressure vessel components and has sometimes suffered from hydrogen embrittlement. Therefore, it is important to investigate the effect of hydrogen on the embrittlement for 2.25Cr-1Mo steel. Under corrosion fatigue conditions, the effect of hydrogen embrittlement (HE) on corrosion fatigue crack growth rate (CFCGR) appears in different ways depending on the applied stress wave forms. This behavior has been clarified by previous theoretical and experimental analyses. In this paper, based on the cited theoretical analyses, the effect of stress waveform on CFCGR for 2.25Cr-1Mo steel was investigated and the sensitivity to hydrogen embrittlement is examined for this material.

Fatigue behavior of a 7075-T6 aluminum alloy coated with an electroless Ni–P deposit

An investigation has been carried out in order to study the fatigue and corrosion–fatigue behavior of a 7075-T6 aluminum alloy coated with an electroless Ni–P (EN) deposit, in the as-plated condition, of approximately 38–40 μm in thickness and a high P content, of approximately 18 wt%. The results obtained, show that the EN coating can give rise to a significant improvement in the fatigue and corrosion–fatigue performance of the substrate, depending on the testing conditions. When the coated system is tested in air, it is observed that the increase in fatigue properties decreases as the alternating stress applied to the material increases. At stresses of the order of 0.4 σ 0.2% the increase in fatigue life is more than about 100%. However, as the stress increases to values in the range of 0.7 σ 0.2%, no improvement in the fatigue performance of the system is observed and the behavior is similar to that of the uncoated substrate. Under corrosion–fatigue conditions, the fatigue life is observed to increase between approximately 60% and 70%, depending on the stress applied. It is shown that fatigue cracks are associated with nodular-like defects present on the surface of the coated samples. The deleterious effect of such defects seems to be more pronounced as the alternating stress applied to the material increases. A crude estimate of the yield strength of the EN coating from tensile measurements indicates that such a parameter is in the range of 3.8 GPa, in agreement with the computation of the absolute hardness of the deposit, of about 4 GPa, by means of Meyer’s law. It is also shown that the EN deposit has a very good adhesion to the substrate even when the system is subjected to tensile stresses greater than the yield strength. Such characteristics as well as the higher mechanical properties of the EN coating in comparison with the aluminum alloy substrate and the preservation of its integrity during fatigue testing contribute to the better fatigue performance of the coated system.

3515 くり返し応力条件下における動転位群と水素との相互作用効果による劈開破壊機構(S20-3 水素ガス雰囲気での疲労特性,S20 材料強度特性に及ぼす水素の影響)

Transgranular facet like brittle fracture for ductile materials under corrosive conditions is caused by the typical pile-up of dislocations. It was found that the mechanical interaction between dislocations and hydrogen induces the typical pile-up of dislocations. Therefore, the analysis of interaction between dislocations and hydrogen under cyclic loading condition was conducted to investigate the distribution behavior of dislocations under corrosion fatigue conditions. In this analysis, the effect of applied stress wave forms on distribution and pile-up behavior of dislocations was investigated. Furthermore, concerning the concentration of dislocations at the site of hydrogen atom, dislocation pile-up intensity factor A was defined. The effect of stress wave form on ΔA was found to concern the feasibility of the occurrence of facet like fracture. Based on the concept of ΔA, the facet like fracture is found to be promoted under Fast-Slow stress wave form condition.

Corrosion-fatigue of laser-repaired commercially pure titanium and Ti-6Al-4V alloy under different test environments.

This study evaluated the corrosion-fatigue life of laser-repaired specimens fabricated from commercially pure titanium (CP Ti) and Ti-6Al-4V alloy, tested under different storage conditions. For each metal, 30 dumbbell rods with a central 2.3 mm diameter were prepared by lost-wax casting with the Rematitan System. Simulating the failure after service, corrosion-fatigue life in different media at room temperature (air, synthetic saliva and fluoride synthetic saliva) was determined at a testing frequency of 10 Hz for intact specimens and after laser repairing, using a square waveform with equal maximum tensile and compressive stress that was 30% lower than the 0.2% offset yield strength. For laser welding, the fractured specimens were rejoined using a jig to align the sections invested in type-IV dental stone. The adjacent areas of the gap was air-abraded with 100 microm aluminum oxide, laser welded and retested under the same conditions as the initial intact specimens. The number of cycles at failure was recorded, and the fracture surface was examined with a scanning electron microscope (SEM). The number of cycles for failure of the welded and intact specimens was compared by anova and the Tukey test at a 5% probability level. Within the limitations of this study, the number of cycles required for fracture decreased in wet environments and the laser repairing process adversely affected the life of both metals under the corrosion-fatigue conditions.

Corrosion fatigue of cemented carbide cutting tool materials

The influence of a corrosive environment on the fatigue performance of two cemented carbides has been investigated. The corrosive media used were tannic acid and de-ionised water, chosen to simulate the environment encountered during wood cutting and metal cutting, respectively. The results show a corrosive environment to have a strong influence on the fatigue performance of the materials tested, such that specimen failure is observed at stress amplitudes equal to one quarter of the strength of the as-received material. The influence of the environment increases with decreasing stress amplitude and frequency. The mode of failure observed under corrosion fatigue conditions requires the simultaneous action of corrosive attack and cyclic loading.

Investigation of the Initial Stage of Selective Dissolution of Zinc–Aluminum Alloys in Chloride-Containing Media

The energy parameters of interaction of adsorbed corrosive particles of chloride-containing media with the surface of zinc–aluminum alloys are determined by the semiempirical MNDO quantum-chemical method in the cluster approximation. With the help of the proposed sequence of corrosion–adsorption interactions of particles of the medium with clusters of alloys, it is shown that chlorine ions play a significant role in the intensification of the desorption of zinc and aluminum cations into a solution for both strained and strain-free states. The results of theoretical calculations are compared with the data of experimental investigations of selective corrosion of zinc–aluminum alloys under the conditions of corrosion fatigue.

Environmentally induced crack propagation behavior of 2219 aluminum: microstructural effects

Alloy 2219 has been evaluated under corrosion fatigue conditions. The effect of the micro-structures present in the T851 and T6 conditions on crack propagation rates has been determined. Tests were performed on compact tension specimens in air and in NaCI solutions at 23 and 70°C. The corrosion fatigue behavior of the material under these conditions was evaluated by studying the crack propagation kinetics and also crack fractography. The results of this study show that 2219 aluminum is resistant to corrosion fatigue in aqueous solutions containing up to 10% NaCI. However, the material is more resistant in the T6 than in the T851 condition. In the absence of stress corrosion cracking, the initial stages of the crack growth were characterised by ductile fracture while a mixed fracture mode dominated the final stages of the growth. At low loading frequencies (0. 1 Hz), crack branching and blunting were observed when tests were performed at 70°C.

Corrosion fatigue in nitrocarburized quenched and tempered steels

In order to investigate the fatigue strength and fracture mechanism of salt bath nitrocarburized steels, specimens of the steels SAE 4135 and SAE 4140, in a quenched and tempered state, and additionally in a salt bath nitrocarburized and oxidizing cooled state as well as in a polished (after the oxidizing cooling) and renewed oxidized state, were subjected to comparative rotating bending fatigue tests in inert oil and 5 pct NaCl solution. In addition, some of the quenched and tempered specimens of SAE 4135 material were provided with an approximately 50-μm-thick electroless Ni-P layer, in order to compare corrosion fatigue behavior between the Ni-P layer and the nitride layers. Long-life corrosion fatigue tests of SAE 4135 material were carried out under small stresses in the long-life range up to 108 cycles with a test frequency of 100 Hz. Fatigue tests of SAE 4140 material were carried out in the range of finite life (low-cycle range) with a test frequency of 13 Hz. The results show that the 5 pct NaCl environment drastically reduced fatigue life, but nitrocarburizing plus oxidation treatment was found to improve the corrosion fatigue life over that of untreated and Ni-P coated specimens. The beneficial effect of nitrocarburizing followed by oxidation treatment on cor-rosion fatigue life results from the protection rendered by the compound layer by means of a well-sealed oxide layer, whereby the pores present in the compound layer fill up with oxides. The role of inclusions in initiating fatigue cracks was investigated. It was found that under corrosion fatigue conditions, the fatigue cracks started at cavities along the interfaces of MnS inclusions and matrix in the case of quenched and tempered specimens. The nitrocarburized specimens, however, showed a superposition of pitting corrosion and corrosion fatigue in which pores and nonmetallic inclusions in the compound layer play a predominant role concerning the formation of pits in the substrate.

Non-destructive evaluation of metallic electrodes under corrosion fatigue conditions by holographic interferometry

A study on the effect of cyclic deformation on the corrosion behaviour of polarised metallic electrodes in aqueous solution was conducted. The study aimed to determine the initial behavior of a nickel (Ni) electrode in 1 m H 2SO 4 and molybdenum (Mo) electrode in 0.75 m KCl solutions under a condition known as corrosion fatigue (CF) by using methods of real time holographic interferometry. As a result, a relationship between the deformation, obtained by holographic interferometry, and corrosion current density, produced by typical electrochemical methods, are established.

Short fatigue crack growth behaviour of a low carbon steel under corrosion fatigue conditions: Akid, R. and Miller, K.J. Fatigue Fract. Eng. Mater. Struct. 1991 14, (6), 637–649

TBI is a significant risk factor for the development of dementia, with the interaction between structural damage from TBI and neuroinflammation potentially driving this relationship. This study investigated the early chronic post-TBI neuroinflammatory response and its relationship to both neurodegenerative pathology and functional impairment up to 3 months post-injury. Sprague-Dawley rats underwent either sham surgery or the Marmarou model of diffuse moderate-severe TBI. At 1-month and 3-months post-injury, a functional battery encompassing motor function, depressive-like behaviour, anxiety and cognition was performed. Western blot and immunohistochemical analysis assessed a range of inflammatory, neurodegenerative and oxidative stress markers. At both 1 and 3-months post injury, depressive-like behaviour was significantly increased in TBI animals, with TBI animals also exhibiting impaired cognitive flexibility at 3 months, although learning and memory remained intact. This was accompanied by a significant decrease in markers of synaptic integrity and astrocytic and microglia number within the pre-frontal cortex at 1-month post-injury, although this resolved by 3-months post-injury. In contrast, minimal pathology was evident within the hippocampus at 1 month, with only a decrease in neurofilament-light seen at 3 months post-injury. Thus, following a moderate-severe diffuse injury, the pre-frontal cortex is most vulnerable to early neuro-structural changes. While these changes are resolved at 3 months post-injury, future studies should investigate whether they re-emerge or progress to other areas, such as the hippocampus, at later time points, which could predispose individuals to the development of dementia.