Corrosion Fatigue Mechanism Research Articles

Corrosion fatigue damage and mechanism evolution of Q420B steel in simulated dry/wet cyclic coastal atmosphere

Q420B low-alloy high-strength steel is the primary material used in China's ultra-high voltage (UHV) transmission towers. In coastal regions, the interaction of wind-induced fatigue and atmospheric corrosion makes it vulnerable to corrosion fatigue (CF), endangering grid safety. This study investigates the CF behavior and underlying mechanisms of Q420B steel, utilizing a specially designed dry/wet cyclic CF device. The results indicate that Q420B steel exhibits high sensitivity to CF, with the failure mechanism being controlled by anodic dissolution and hydrogen embrittlement. The crack initiation process unfolds in three stages: the formation of surface corrosion products, pitting corrosion beneath the rust layer, and nucleation of corrosion fatigue cracks (CFCs). Under low peak stress, anodic dissolution, hydrogen diffusion, and plastic deformation at the crack tip collectively hasten the propagation of CFCs. Under high peak stress, the mechanical effect at the crack tip dominates CFCs propagation. These insights are vital for optimizing the design and maintenance of UHV transmission towers.

The Corrosion Fatigue Behavior and Mechanism of AerMet 100 Steel in 3.5% NaCl at Room Temperature.

AerMet 100 steel is a new type of double-hardened high-strength steel, which is often used as landing gear material in amphibious aircraft. In the present paper, the corrosion fatigue behavior and mechanism of AerMet 100 high-strength steel in a 3.5% NaCl solution was studied by stress-controlled fatigue tests and a series of subsequent characterizations of the fracture surface, microstructure, and cracks. The results indicated that the fatigue life of AerMet 100 high-strength steel decreased with a decrease in the stress level in a 3.5% NaCl solution, satisfying the relationship lgN = -2.69 × 10-3 σ + 6.49. The corrosion fatigue crack usually initiated from the corrosion pit and propagated across the martensitic flat noodles. Meanwhile, the corrosion fatigue crack tip was filled with Cr2O3, Fe2O3, and amorphous material; it propagated in the transgranular mode by a slip dissolution mechanism. This study provides some engineering significant for the fatigue performance of AerMet 100 steel in a 3.5% NaCl solution.

Study on S-N Curve and Fatigue Limit of Drill Pipe in Offshore Short-Radius Sidetracking Process

To evaluate the fatigue reliability of different types of drill pipes during an offshore short-radius sidetracking process, the fatigue life and limit of G105, S135, and V150 steel and a new titanium alloy drill pipe were studied in air, high-temperature conditions, drilling fluid, and drilling fluid containing H2S. First, the chemical composition, microstructure, and tensile properties of four kinds of drill pipe materials were tested. Secondly, the fitting effects of different S-N models were evaluated and identified, a fatigue test of four kinds of drill pipe under different environments (air, high temperature, drilling fluid, and H2S drilling fluid) was carried out, and the S-N curves and fatigue limits of different drill pipes under different environments were obtained. Finally, the fatigue sensitivity of drill pipes to different factors was studied, and the potential corrosion fatigue mechanism was explained. The research results show that the fatigue life of a drill pipe in a non-corrosive environment (air and high temperature) is mainly related to steel grade, and the fatigue life of a titanium alloy drill pipe is better than that of a steel drill pipe in a corrosive environment. The dense passivation film on the surface of a titanium alloy drill pipe is an important reason for its better corrosion fatigue life than that of a steel drill pipe. This study provides important data support for selecting drill pipes in offshore short-radius sidetracking.

Influence of Hydrogen on the Failure Mechanism of Standard Duplex Stainless Steel X2CrNiMoN22-5-3 Exposed to Corrosion Fatigue

IIn a geothermal environment, cathodic protection is employed to improve resistance against corrosion fatigue. However, during the cathodic reactions under applied potential, hydrogen is generated and assimilated, leading to a reduced lifetime expectancy of high-alloyed steels. The corrosion fatigue mechanism of a standard duplex stainless steel X2CrNiMoN22-5-3 (1.4462) specimen loaded with hydrogen was studied in a corrosion chamber specifically designed for the purpose, surrounded by the electrolyte of the Northern German Basin at 369 K. The microstructural reactions resulting in hydrogen incorporation significantly decrease the number of cycles to failure of the specimen. This reduction is attributed to hydrogen enhancing crack propagation and causing early failure, primarily due to the deterioration of the mechanical properties of the ferritic phase rather than corrosion reactions or corrosive degradation.

Review on Environmentally Assisted Static and Fatigue Cracking of Al-Mg-Si-(Cu) Alloys

This paper reviews the relevant literature and covers the main aspects of the environmentally assisted cracking of Al-Mg-Si-(Cu) alloys. Apart from a brief overview of the major microstructural and mechanical properties, it presents research results on the corrosion sensitivity and stress corrosion susceptibility of Al-Mg-Si alloys. Possible mechanisms of stress corrosion cracking and corrosion fatigue in aluminum alloys, such as anodic dissolution and/or interaction with hydrogen, are considered. A number of factors, including atmospheric or solution conditions, applied stress, and material properties, can affect these mechanisms, leading to environmentally assisted cracking. Specific attention is given to Al-Mg-Si alloys with copper, which may increase the sensitivity to intergranular corrosion. The susceptibility to both intergranular corrosion and stress corrosion cracking of Cu-containing Al-Mg-Si alloys is mostly associated with a very thin layer (segregation) of Cu on the grain boundaries. However, the effect of Cu on the corrosion fatigue and fatigue crack growth rate of Al-Mg-Si alloys has received limited attention in the literature. At the current state of the research, it has not yet been holistically assessed, although a few studies have shown that a certain content of copper can improve the resistance of aluminum alloys to the environment with regard to corrosion fatigue. Furthermore, considerations of the synergistic actions of various factors remain essential for further studying environmentally assisted cracking phenomena in aluminum alloys.

Corrosion fatigue mechanisms and evaluation methods of high‐strength steel wires: A state‐of‐the‐art review

AbstractCorrosion significantly degrades the fatigue performance of high‐strength steel wires. This study conducts an extensive review of corrosion fatigue in corroded steel wires based on relevant literature. It outlines corrosion fatigue evolution mechanisms and discusses various test methodologies. Six distinct approaches are employed to assess corrosion fatigue life. A three‐stage multiscale corrosion fatigue evolution process involves pitting formation and growth, short crack propagation, and long crack propagation. Advanced fatigue assessment methods like the theory of critical distances (TCD) and the strain energy density (SED) are explored for predicting the corrosion fatigue life for corroded steel wires. A model utilizes an elastoplastic corrosion fatigue damage framework to comprehensively represent the complex interactions. The physics‐data‐driven method has garnered increasing attention due to its requirement of fewer sample data and good robustness. Moreover, the reliability method underscores its pivotal role in guaranteeing the longevity of suspenders and cables in practical settings.

Numerical and experimental failure analysis of wind turbine blade fastener

The objective of this study is to conduct a root cause failure analysis on wind turbine fasteners constructed from carbon steel Grade 10.9. The presence of corrosion pits at the thread root, as well as beach and ratchet marks on the fracture surface, suggests that the fastener failed due to a corrosion-fatigue mechanism. The microstructure of the failed fastener predominantly consisted of 98 % tempered martensite, with some bainite and a small amount of chromium carbides, which is characteristic of quenched and tempered low alloy steel. Magnetic particle testing revealed similar crack marks on other fasteners in similar locations, indicating the points of maximum stress in these fasteners. Furthermore, finite element analysis using Abaqus software demonstrated that for a corrosion pit to grow, it required a minimum pit length and depth of 0.5 mm and 0.6 mm, respectively.

Experimental investigation on corrosion fatigue crack initiation and growth of heat-treated U75V rail steel

Understanding the corrosion fatigue mechanism of rail materials is of great importance to guide the assessment of the structural integrity of modern railway components. To this purpose, the corrosion fatigue crack (CFC) initiation and growth behaviors of heat-treated U75V rail steel are investigated under 3.5 wt% NaCl solution in terms of high-cycle fatigue, fatigue crack growth (FCG) rate, together with surface morphology and microstructure. Experimental results reveal that the U75V rail steel is susceptible to corrosion fatigue failure. Examinations on fractured samples clearly show that the electric potential difference between ferrite and cementite triggers the preferential anodic dissolution of ferrite, leading to corrosion fatigue crack initiation. The crack initiation is not only solely determined by the size of the corrosion pit, but also strongly influenced by its local shape. In comparison with the fatigue crack growth in air, the corrosion FCG tends to grow in a relatively straight path, because of hydrogen embrittlement. Additionally, the CFC behaviors indicate a tendency to transverse through soft-oriented grains and deflect upon encountering hard-oriented grains.

Failure analysis of a tandem mill ring gear

A roll end ring gear of a tandem hot rolling mill suddenly fractured in service after 21 years, with no record of a sudden overload. The component was made of hardened and tempered Nitralloy N steel with a core hardness of 40 HRC. The case hardness specified in the construction project was 60 HRC. Two goals were set in this investigation: to verify whether the component followed the chemical, microstructural, and mechanical properties established in AMS 6475L standard and in the gear project and to determine the fracture mechanism and its probable root cause in order to propose preventive actions and to avoid similar failures in the rolling mill. Metallographic and fractographic examinations showed that the roll end ring gear failed due to a corrosion fatigue mechanism in which multiple cracks nucleated from corrosion pits on the outer surface of the component, and propagated through the wall with the cyclic stresses associated with its operation. The corrosion mechanism was differential aeration corrosion promoted by the formation of sludge deposits, possibly aided by microbiologically influenced corrosion (MIC).

Stress corrosion cracking and corrosion fatigue analysis of API X70 steel exposed to a circulating ethanol environment

API X70 steel has been widely used to manufacture pipes to carry ethanol. However, a recognized problem in carbon steel pipes exposed to ethanol is stress corrosion cracking (SCC) and, during their operation, pipelines are also subject to pressure fluctuations, causing concern regarding fatigue behavior. In this study, slow strain rate (SSR), constant load (CL), staggered constant load (SCL) and fatigue crack growth (FCG) tests were performed on API X70 steel specimens in a circulating synthetic ethanol solution (CSES) and in air to evaluate SCC susceptibility and corrosion fatigue. Results revealed a significant strain decrease for notched specimens under SSR, indicating a significant SCC effect, but it showed to be minimized in unnotched specimens. Under CL, the steel appears not to be sensitive to SCC at stress levels below the yield point; however, under SCL, clear evidence of the phenomenon at the fracture surface was revealed. Alteration in initial portion of the da/dN-ΔK curves obtained in CSES was observed, shifting ΔKth (threshold) to higher values. The Paris-Erdogan linear regions in CSES exhibited a steeper slope relative to the air baseline, i.e., showed crack acceleration, thus indicating some influence of the corrosion fatigue mechanism. Changes caused by SCC in the linear region at certain levels of ΔK at 0.25 Hz were also revealed.

Study on Fatigue Behavior of S135 Steel and Titanium Alloy Drillpipes: Experiment and Modeling

Summary This paper studies the fatigue failure behavior of S135 steel and titanium alloy drillpipe, tries to reveal the mechanism of fatigue fracture, and evaluates the degree of fatigue damage. First, the chemical composition, tensile test, and microstructure analysis of two types of pipes were carried out, and the difference in microstructure affects its macroscopic fatigue performance. Second, the stress vs. fatigue life (S-N) curve equation and fatigue limit of S135 steel and titanium alloy drillpipes in air and mud were obtained through the fatigue test. The equations of the S-N curves in air are NS135−air=9.45×1037(S+1776)−9.3 and NTi−air=1.41×1028(S+1124)−6.7, while in mud, they are NS135−mud=6.68×1034(S+551)−9.6and NTi−mud=5.74×1032(S+973)−8.3. Scanning electron microscope analysis results show that the S135 steel drillpipe presents brittle fracture, while titanium alloy drillpipe presents mixed fracture of quasi-cleavage and dimple. Finally, a case study of actual horizontal well was carried out to evaluate the fatigue damage of two drillpipes; compared with conventional steel drillpipe, titanium alloy drillpipe can effectively resist fatigue damage in the drilling fluid environment. The fatigue test results and corrosion fatigue mechanism analysis in this paper can provide data and theoretical guidance for the study of drillpipe fatigue life.

Concurrent 6. Presentation for: Environmentally assisted fatigue failure of drill pipe connections

Presented on Tuesday 17 May: Session 6 Failure of three drill pipe connections occurred relatively early in the service life and without the more gradual reduction in operating pressure or other factors that are typically associated with a pending fatigue failure. Of the three drill pipe connections, two had fractured and the third had cracked but remained intact. The drill pipe connections were investigated to determine the mode and likely cause of the failure. Failure of the drill pipe connections was the result of fatigue that had initiated on the outside surface within the first thread root adjacent to the change in section to the barrel or at the change in the section itself. Crack propagation was radially inwards towards the connection bore. Chlorine was present in the drilling mud at low concentrations and fine pitting was identified, but overall, the rods were free of corrosion. However, positive identification of corrosion pits, albeit few in number and significant cracks emanating from said pits, suggest failure of the drill pipes could be attributed to a corrosion fatigue mechanism. This would more so be the case for two of the drill pipe connections, as the stress concentration associated with a corrosion pit would be exacerbated in the threaded region. Fatigue had subsequently propagated under bending loads, likely reverse bending loads, applied to the drill string. Such loads would likely be the result of directional drilling within strata of higher than usual hardness. To access the presentation click the link on the right. To read the full paper click here

Environmentally assisted fatigue failure of drill pipe connections

Failure of three drill pipe connections occurred relatively early in the service life and without the more gradual reduction in operating pressure or other factors that are typically associated with a pending fatigue failure. Of the three drill pipe connections, two had fractured and the third had cracked but remained intact. The drill pipe connections were investigated to determine the mode and likely cause of the failure. Failure of the drill pipe connections was the result of fatigue that had initiated on the outside surface within the first thread root adjacent to the change in section to the barrel or at the change in the section itself. Crack propagation was radially inwards towards the connection bore. Chlorine was present in the drilling mud at low concentrations and fine pitting was identified, but overall, the rods were free of corrosion. However, positive identification of corrosion pits, albeit few in number and significant cracks emanating from said pits, suggest failure of the drill pipes could be attributed to a corrosion fatigue mechanism. This would more so be the case for two of the drill pipe connections, as the stress concentration associated with a corrosion pit would be exacerbated in the threaded region. Fatigue had subsequently propagated under bending loads, likely reverse bending loads, applied to the drill string. Such loads would likely be the result of directional drilling within strata of higher than usual hardness.

Corrosion fatigue mechanism and life prediction of railway axle EA4T steel exposed to artificial rainwater

High-speed railway axle is the critical safety component of modern ground vehicles, which experiences extremely complex environments. In this paper, the effect of corrosion on the fatigue behavior of EA4T axle steel was investigated in an artificial rainwater environment. Combining scanning electron microscopy (SEM) and synchrotron radiation X-ray micro computed microtomography (SR-μCT) with theoretical analysis, damage measurement enabled a full evolution characterization of the corrosion process for exploring the corrosion mechanism and its influence on the fatigue life. It is found that the corrosive environment significantly reduced fatigue strength and facilitated multiple crack initiation, while showed relatively little effect on the long fatigue crack growth. The fitness of the 3-P Weibull distribution was slightly higher than that of the Gumbel distribution in terms of crack population. The life prediction model incorporating the pit growth, short crack, and long crack stages showed a good agreement within the 95% and 5% probabilistic S-N curve.

Corrosion Fatigue Mechanism of Welded Eh36 Steel in Simulated Seawater and Under Cathodic Protection

Corrosion Fatigue Mechanism of Welded Eh36 Steel in Simulated Seawater and Under Cathodic Protection

Corrosion Fatigue Mechanism of Welded Eh36 Steel in Simulated Seawater and Under Cathodic Protection

Corrosion Fatigue Mechanism of Welded Eh36 Steel in Simulated Seawater and Under Cathodic Protection

Experimental investigation on the corrosion and corrosion fatigue behavior of butt weld with G20Mn5QT cast steel and Q355D steel under dry–wet cycle

Corrosion and corrosion fatigue experiments were conducted on a butt weld constructed of G20Mn5QT cast steel and Q355D steel in a dry–wet cycle with 3.5 wt% NaCl solution. The microstructural characterization was analyzed using SEM. The butt weld suffered from pitting corrosion in a dry–wet cycle. Chloride ion erosion and defects (welding defects and casting defects) have important influences on pitting corrosion. Internal defects and corrosion pits are the main cause of corrosion fatigue failure of the butt weld specimens. Drying time accelerates pitting corrosion and corrosion fatigue progression without changing the corrosion and corrosion fatigue mechanism in 3.5 wt% NaCl solution. The three-parameter Weibull model has good applicability for evaluating the corrosion fatigue behavior of G20Mn5QT cast steel and Q355D steel butt welds in simulated seawater.

A Bayesian Inference Reliability Evaluation on the Corrosion-Affected Underground High-Voltage Power Grid

The underground high-voltage power transmission cables are high value engineering assets that suffer from multiple deteriorations through-out life cycles. Recent studies identified a new failure mode – the pitting corrosion deterioration on the layer of phosphor bronze reinforcing tape, which protects the oil-filled power transmission cables from oil leakage due to deterioration of the leads heath. Two models estimating the phosphor bronze tape life were established separately in this study. The first model, based on mathematical fitting, is generated using a replacement priority model from the power supply industry. This is considered as an empirical-based model. The second model, based on the corrosion fatigue mechanism, utilizes the information of the pit depth distribution and the concept of pit-to-crack transfer probability. The Bayesian inference approach is the conjunction algorithm to update the existing probability of failure (PoF) model with the newly identified failure modes. Through this algorithm, the integrated PoF model contains a more comprehensive background information while maintaining the empirical knowledge on the engineering assets’ performance.

Corrosion mechanism and fatigue behavior of 2A70-T6 aluminum alloy under alternating corrosion and fatigue

PurposeMost supersonic aircraft were manufactured using 2A70 aluminum alloy. The purpose of this paper is to study the corrosion mechanism and fatigue behavior of an aircraft in a semi-industrial atmospheric corrosive environment, alternating effects of corrosion and fatigue were used to simulate the aircraft’s ground parking corrosion and air flight fatigue.Design/methodology/approachFor this purpose, the aluminum alloy samples were subjected to pre-corrosion and alternating corrosion-fatigue experiments. The failure mechanisms of corrosion and corrosion fatigue were analyzed using microscopic characterization methods of electrochemical testing, X-ray diffraction and scanning electron microscopy. Miner’s linear cumulative damage rule was used to predict the fatigue life of aluminum alloy and to obtain its safe fatigue life.FindingsThe results showed that the corrosion damage caused by the corrosive environment was gradually connected by pitting pits to form denudation pits along grain boundaries. The deep excavation of chloride ions and the presence of intergranular copper-rich phases result in severe intergranular corrosion morphology. During cyclic loading, alternating hardening and softening occurred. The stress concentration caused by surface pitting pits and denudation pits initiated fatigue cracks at intergranular corrosion products. At the same time, the initiation of multiple fatigue crack sources was caused by the corrosion environment and the morphology of the transient fracture zone was also changed, but the crack propagation rate was not basically affected. The polarization curve and impedance analysis results showed that the corrosion rate increases first, decreases and then increases. Fatigue failure behavior was directly related to micro characteristics such as corrosion pits and microcracks.Originality/valueIn this research, alternating effects of corrosion and fatigue were used to simulate the aircraft’s ground parking corrosion and air flight fatigue. To study the corrosion mechanism and fatigue behavior of an aircraft in a semi-industrial atmospheric corrosive environment, the Miner’s linear cumulative damage rule was used to predict the fatigue life of aluminum alloy and to obtain its safe fatigue life.

Study on corrosion fatigue behavior and mechanism of 6005A aluminum alloy and welded joint

Purpose The purpose of this paper is to determine the corrosion fatigue behavior and mechanism of 6005A aluminum alloy and welded joint. Design/methodology/approach Electron back-scattered diffraction (EBSD) were adopted to characterize the microstructure of 6005A aluminum alloy and welded joint. Through potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and corrosion fatigue experiments, the corrosion fatigue behavior and mechanism of 6005A aluminum alloy base metal and welded joint were studied. Findings The results show that the corrosion fatigue crack initiation of 6005A aluminum alloy base metal and welded joint is mainly caused by the preferential anodic dissolution and hydrogen concentration in the areas with inclusions and welding defects. Originality/value The research is an originality study on the corrosion fatigue behavior and mechanism of 6005A aluminum alloy and welded joint.