Corrosion Fatigue Performance Research Articles

Enhancing corrosion fatigue performance of 17-4 PH stainless steel by simultaneous aging and plasma nitriding

This study investigated the effects of simultaneous aging and low-temperature plasma nitriding on the corrosion fatigue performance of 17-4 PH stainless steel. Plasma nitriding was conducted under two temperatures of 400 and 500 °C and, for comparison, some other specimens were subjected to aging treatment at the same temperatures and times. Microstructural characterization by scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD) confirmed similar structures at the core in the nitrided and aged specimens, thereby, the influence of nitrogen at the surface of 17-4 alloy could be carefully investigated. X-ray diffraction and grazing incidence X-ray diffraction (GIXRD) identified expanded martensite as the matrix within the nitrided layer, accompanied by CrN, Fe3N, and Fe4N phases. X-ray photoelectron spectroscopy (XPS) analysis revealed high nitrogen concentration, in regions very close to the surface, after nitriding at 500 °C. The N1s spectra shifted towards lower binding energies, indicating interaction between nitrogen and the matrix atoms, and the formation of nitrides in the nitrided layer. The nitrided thicknesses experienced close values at 400 °C (10 h) and 500 °C (5 h), provided at 400 °C the layer was mostly a supersaturated solid solution but at 500 °C it was composed of iron nitrides and chromium nitride. High hardness values of above 1600 HV0.1 were obtained after optimum plasma nitriding as the result of combined effects of solution strengthening induced by nitrogen atoms and the presence of dispersed nitride phases. EBSD results indicated residual stress within the nitrided layer, which would affect the corrosion fatigue resistance. Experimental findings demonstrated that both aging and plasma nitriding substantially enhanced the corrosion fatigue resistance of 17-4 PH stainless steel in 3.5 wt% NaCl. Moreover, simultaneous aging and plasma nitriding proved superior behavior in corrosion fatigue, primarily due to delayed crack initiation and improved fatigue resistance, without the risk of overaging which is detrimental to mechanical properties.

Corrosion fatigue performance of modified 17-4PH in simulated geothermal environment

Corrosion fatigue behavior of a new candidate material for geothermal turbine blade, modified 17-4PH, was investigated in detail. The environmental acceleration of crack growth rate was discussed in terms of ∆K. Fracture surface and side surface were observed by SEM. The crack path on side surface was also analyzed by EBSD. Then, the corrosion mechanism was discussed. Striation width on the fracture surface was compared to the crack growth per cycle. Since pitting occurred during the corrosion fatigue test, anodic polarization test was exercised to measure the pitting potential, and the cause for the pitting was also discussed. The hardness was also characterized by micro-hardness test and auger electron mapping.

Corrosion fatigue behavior of X65 pipeline steel welded joints prepared by CMT/GMAW backing process

The corrosion-fatigue behavior of X65 welded joints, processed by cold metal transfer (CMT) and gas metal arc welding (GMAW) backing, was examined. The application of the CMT backing process led to a 22% increase in the corrosion-fatigue performance, which was attributed to the optimization of the microstructure (synergistic cracking-arrest ability of acicular ferrite (AF) and grain boundary ferrite (GBF)) and the reduction in the stress concentration at the weld root. Nonetheless, a lower heat input contributed to a consequent decrease in corrosion-fatigue performance. In addition, H2S corrosion fatigue was governed by the combined effect of anodic dissolution and hydrogen embrittlement.

Improved corrosion fatigue performance of 316L stainless steel by surface porosification

The corrosion fatigue of 316L stainless steel with different surface morphologies was examined by cyclic deformation tests in a NaCl solution. Three different surface treatments were applied to the steel, i.e., mechanical polishing, electropolishing and anodization. The surface roughness depended on the treatments; the highest roughness was obtained for the anodized specimen owing to the formation of dimple structure. The formation of the dimple structure significantly increased the corrosion fatigue life compared to the other treatments. The improved corrosion fatigue performance was discussed in terms of the formation of slip steps on the steel surface.

Study on the durability of steel wire under the coupling effects of harsh environment and variable loads

steel wire is regarded as the most important component of cable-stayed bridges, and it has been widely used in practical engineering. Most of the studies only considered the effect of variable loads and chloride corrosion on the durability of steel wires separately. However, few studies have reported their coupling effects. In order to investigate the durability of steel wires considering their coupling effects, A physical test was performed to investigate the corrosion–fatigue performance. After the experiment finished, a tensile device was used to test the mechanical properties of corroded steel wires with different corrosion degrees. Then the corrosion characteristics of different specimens and fracture surface morphology of the steel wires were investigated using a 3D scanner, which was used to analyse the failure mode of each type of steel wires. In addition, a model was proposed to evaluate the reliability of corroded steel wires. Finally, a fatigue test was conducted to explore their fatigue performance and the S-N curve of steel wires with different corrosion degrees was obtained. The results show that the fatigue life of the steel wires is mainly affected by environmental effects when the steel wire at low stress amplitudes. However, as the stress amplitude increases, the fatigue life of it is decided by the stress amplitude. The fracture morphology of the corroded steel wires can be two categories: single-source fracture and multi-source fracture, For the steel wires corroded slightly, cracks often drive from one fatigue source (pit defect). As the corrosion degrees increase, the depth of pits enhances, cracks drive from different fatigue sources. In addition, the propagation zones decrease, and the rupture regions increase, as the steel wires corroded seriously.

Fatigue crack growth of EH36 steel in air and corrosive marine environments

EH36 steel used in offshore platforms is susceptible to corrosion fatigue in marine environment. The corrosion fatigue performance in EH36 steel is influenced by various factors, such as maximum applied load, loading frequency and stress ratio. To investigate such effects, fatigue crack growth (FCG) tests on compact tensile (CT) specimens of EH36 steel were carried out in three different environments, including air, immersed seawater and wet-dry cyclic environment, by considering different maximum loads, loading frequencies and stress ratios. From the experimental tests, the relation of crack development and loading cycles and the relation of fatigue crack growth rate (FCGR) and stress intensity factor (SIF) range were obtained. Constants (C and m) in Paris law were obtained through fitting technique based on experimental data. Due to corrosion of marine environment, the fatigue life of EH36 steel decreases while the FCGR increases. The corrosion fatigue crack growth (CFCG) experimental results were compared with the predictions from Paris-law recommended in BS7910. A new CFCG calculation model consisting of environmental acceleration factors was proposed and evaluated for accuracy, and such model can be used for predicting the remaining fatigue life of EH36 steel in marine corrosive environment under the specified conditions. The fracture morphology of the specimens in different environments was observed by scanning electron microscope (SEM) to analyze the fracture mechanism. The fracture morphology of the CT specimens in two corrosive environments is almost same and appears as cleavage fracture.

Effect of 0.1 wt% Nb on the microstructure and corrosion fatigue performance of high strength steels

In this manuscript, the effect of 0.1% Nb addition on the corrosion fatigue behavior of the marine engineering steel has been studied through corrosion fatigue experiments, electrochemical hydrogen charging, and a series of microscopic characterization methods. The results show that BM steel has a high corrosion fatigue sensitivity in the marine environment. Compared to BM steel, the corrosion fatigue sensitivity of 0.1 Nb steel is reduced by 8% in the marine environment, and it reduced by 40% in the hydrogen charging environment. 0.1% Nb adding inhibits hydrogen concentration in local areas by forming irreversible hydrogen traps NbC and by improving the microstructure, and it lowers the diffusible hydrogen content and total hydrogen content inside the steel by inhibiting electrochemical hydrogen evolution reaction to hold back the corrosion fatigue crack initiation and propagation, thereby improving the ability of resisting corrosion fatigue cracking for the marine engineering steel.

Influence of residual stress and its relaxation on the corrosion bending fatigue resistance of EA4T axle steel treated by ultrasonic surface rolling

The fatigue properties and residual stress relaxation behavior of EA4T axle steel treated by ultrasonic surface rolling process (USRP) are investigated in air and corrosive environments. The result reveals that the surface roughness (Ra) is decreased from 1.42 to 0.17 μm after the USRP. A surface layer with ultrafine grains, work hardening, and compressive residual stress (CRS) is achieved by the USRP. Compared with the as-machined specimens, the USRP specimens exhibit slightly lower electrochemical corrosion resistance but superior fatigue performance in air and corrosive environments. The dislocation density is significantly decreased in the corrosive environment during fatigue loads, accompanied by a rapid relaxation of surface CRS. The influence of USRP on the corrosion fatigue performance is elucidated. The residual stress relaxation mechanism and its influence on fatigue resistance are also analyzed.

Corrosion Fatigue Test and Performance Evaluation of High-Strength Steel Wires Based on the Suspender of a 11-Year-Old Concrete-Filled Steel Tube Arch Bridge

In this study, based on an actual project, the steel wire in the suspender of a concrete-filled steel tube arch bridge was selected from appropriate samples to perform acetic acid-accelerated salt spray tests, and steel wire samples with different corrosion degrees were obtained. A laser microscope was used to measure the roughness of the samples, and three corrosion samples were randomly selected from each group for grinding. Fatigue tests were performed on steel wire samples with different degrees of corrosion and polished steel wire samples, and the fatigue fracture was observed and analyzed. The results showed that few cracks on the steel wire surface could be eliminated by grinding, and the fatigue life of the specimens could be increased. Finally, the stress-life-mass loss rate (S-N-η) probability model based on the Weibull distribution was obtained using the measured fatigue data, which can be further referenced in the planning of the inspection of suspender service status, steel wire corrosion protection, and fatigue life prediction, etc.

Corrosion fatigue behavior and anti-fatigue mechanisms of an additively manufactured biodegradable zinc-magnesium gyroid scaffold

Additively manufactured biodegradable zinc (Zn) alloy scaffolds constitute an important branch in orthopedic implants because of their moderate degradation behavior and bone-mimicking mechanical properties. This work investigated the corrosion fatigue response of a zinc-magnesium (Zn-Mg) alloy gyroid scaffold fabricated via laser-powder-bed-fusion additive manufacturing at the first time. The high-cycle compression-compression fatigue testing of the printed Zn-Mg scaffold was conducted in simulated body fluid, showing its favorable fatigue strength, structural reliability, and anti-fatigue capability. The printed Zn-Mg scaffold obtained a 227% higher fatigue strength than that of the printed Zn scaffold but 17% lower strain accumulation at 106 cycles. The accumulative strain of the Zn-Mg scaffold at its fatigue strength was dominant by fatigue ratcheting, since the fatigue damage strain of the scaffold was approximately zero. The corrosion products (ZnO and Zn(OH)2) were conducive to the inhibition of fatigue ratcheting and fatigue damage. Dislocation pile-up and solid solution phases at the grain boundaries of the Zn-Mg scaffold could retard the spreading of the crack tip and impede excessive grain coarsening, improving its fatigue endurance limit. Notably, the printed Zn-Mg scaffold could dissipate the fatigue energy through moderate grain boundary migration, thus reducing its plastic deformation. These findings illuminated the anti-fatigue mechanisms related to microstructural features and corrosive environments and highlighted the promising prospects of additively manufactured Zn-Mg scaffolds in orthopedic applications. Statement of significanceAdditive manufacturing (AM) of biodegradable metals shows unprecedented prospects for bone tissue regeneration medicine. The corrosion fatigue property is one of the key determinants in the performance of AM biodegradable scaffolds. In this study, a Zn-Mg gyroid scaffold was additively manufactured with admirable fatigue endurance limit and anti-fatigue capability. We reported that the corrosion fatigue performance was highly relevant to the microstructural features, validating that the grain boundary engineering strategy improved fatigue strength and inhibited crack penetration. Notably, moderate grain boundary migration could dissipate fatigue energy and reduce plastic deformation. Furthermore, corrosion products were conducive to impeding fatigue ratcheting and fatigue damage, indicating the promising potential of AM Zn-Mg scaffolds in treating load-bearing bone defects.

Corrosion-fatigue crack growth behaviour of wire arc additively manufactured ER100S-1 steel specimens

The wire arc additive manufacturing (WAAM) technology is a promising fabrication technique which has been proven to have many advantages for producing large structures; however, the fatigue and corrosion-fatigue performance of WAAM steel components for application in the marine environments is still unexplored. In this study, the WAAM technique was employed to fabricate four specimens made of ER100S-1 steel, which were then tested under cyclic loading conditions in seawater to assess the corrosion-fatigue crack growth (CFCG) behaviour and hence suitability of this fabrication technology for offshore renewable energy applications. The test duration, cracking mechanisms and CFCG rate were investigated for each specimen and the material’s behaviour was investigated by considering the microstructural examinations. Furthermore, the obtained results were compared with the BS7910 standard recommended trends and experimental data available in the literature for conventionally built weldments made of different grades of steel which are commonly used for offshore applications.

Effect of aging state on corrosion fatigue properties of 7075 aluminum alloy

The corrosion fatigue performance of Al alloy components is crucial for their engineering applications. This study focuses on the corrosion fatigue properties of 7075 Al alloys in three different aging states, i.e. over-aging (OA), peak-aging (PA) and under-aging (UA) states. The results show that the fatigue damage mechanism of the Al alloy is greatly affected by the stress level. In the high-stress region where the cyclic number is short, the fatigue damage is mainly caused by dislocations accumulation and stress concentration on the grain boundary. Compared with the UA state, the wave slip dislocations at the OA state are easy to accumulate and annihilate at the second phase boundaries, which reduces the fatigue damage degree at the grain boundaries. However, in the low-stress range where the cyclic number is large, the corrosion fatigue life of the Al alloy is mainly controlled by pitting-induced crack initiation. For the OA state, the spacing and size of the precipitated phase are large, so it is easy to trigger corrosive pitting, which reduces the corrosion fatigue performance of the alloy.

A Simplified Approach for the Corrosion Fatigue Assessment of Steel Structures in Aggressive Environments.

Fatigue performance is often a key aspect when dealing with existing steel structures such as steel bridges or offshore constructions. This issue proves to be more critical as these structures are usually located in aggressive environments and are thus exposed to progressive degradation. Indeed, disruptive phenomena such as corrosion can severely worsen the fatigue performance of the steel components. Currently, the normative standards do not provide a codified procedure for the fatigue checks of steel structures subjected to ongoing corrosion. Within this framework, in this paper a simplified approach for the life-cycle assessment of corroded steel structures is proposed. For this purpose, the concept of “critical corrosion degree” is introduced, allowing the expression of corrosion fatigue checks in a more direct “demand vs. capacity” form with respect to the currently available methods. A first validation of such methodology is reported for the corrosion fatigue tests drawn from the literature. The predicted levels of critical corrosion are in good agreement with the values of artificially induced corrosion (i.e., 4, 8, and 12% of mass loss, respectively), with a maximum relative error of ≈9.3% for the most corroded specimen. Finally, parametrical analyses are performed, highlighting the influence of the model parameters on the corrosion fatigue performance of the steel elements.

Effect of ultrasonic impact treatment on corrosion fatigue performance of friction stir welded 2024-T4 aluminum alloy

ABSTRACT Friction stir weld joints of 2024-T4 are strengthened by ultrasonic impact treatment (UIT). After ultrasonic impact treatment, the grains on the surface of the sample are refined to form a dense deformation layer, and residual compressive stress is applied on the surface of the sample. The corrosion rate and mass-loss rate of the UIT sample are significantly lower than those of the non-UIT sample, and uniform corrosion is exhibited. The average life of the UIT samples in the air is 1.74 times that of the non-UIT samples; meanwhile, the average life of the UIT samples in 3.5% NaCl solution is twice that of the non-UIT samples. The crack sources of the UIT sample in the air shift from the surface to the subsurface below the strengthening layer, whereas those of the sample in the 3.5% NaCl solution are located in the corroded area on the surface of the sample.

The effect of salt composition on the stress-free and corrosion-fatigue performance of a fine-grained nickel-based superalloy

This paper describes work to study hot corrosion damage in the nickel-based gas turbine alloy RR1000 coated with various salts at 600 °C. Interest in type-II hot corrosion on the fatigue resistance of gas turbine alloys has increased to minimise power/thermal inefficiencies. Stress-free corrosion demonstrated a greater impact of sulphate (versus chloride) on maximum pit depth, a key influencing factor of fatigue lives. In corrosion-fatigue testing, at low stresses sulphate was shown to be more influential of fatigue life. At high stresses, the presence of greater crack initiation sites, reduced initiation lives and cracked oxide suggests chlorine influenced the crack-initiation behaviour.

The effect of friction welding on the mechanical properties and corrosion fatigue resistance of titanium alloy drill pipe

AbstractTitanium alloys are the best candidates to replace steels for drill pipes in horizontal wells. However, friction welding (FW) may significantly change the properties of titanium alloy drill pipes. In this work, the microstructure, tensile and impact mechanical properties, and corrosion fatigue performance of the FW zone were compared with those of the base alloy. The results show that the base material is mainly composed of equiaxed globular α (hcp)‐Ti, while the acicular α + β (bcc)‐Ti is dominant in the FW zone. Due to these differences in microstructure, the FW zone has higher strength but lower stiffness and toughness than the base alloy. In addition, the fatigue performance and corrosion resistance of the material decrease in drilling fluid. These results indicate that FW zones in titanium alloy drill pipes might be the weakest region where crack, fracture, and corrosion are more likely to occur.

Effect of laser shock peening on stress corrosion sensitivity of 304 stainless steel C-ring weld specimens

As a new surface treatment technology, laser shock peening (LSP) can improve the corrosion resistance and fatigue performance of the metal surface with the help of a high-power density laser beam. In this work, 304 stainless steel C-ring weld specimens were treated with four laser power densities, and the effect of LSP on the surface properties of the specimens was investigated by microhardness measurement, grain size analysis and residual stress test. The research shows that LSP can improve the surface microhardness, produce grain refinement, and transform the residual tensile stress into residual compressive stress in the surface layer of 304 stainless steel. Electrochemical corrosion test and the constant strain corrosion test in boiling magnesium chloride solution were carried out. The results show that the crack initiation time of the C-ring weld specimens treated with LSP is significantly longer than that of the specimens without LSP. As the laser power density of LSP increases, the corrosion current density and the corrosion rate are decreased greatly, the polarization resistance is increased significantly, and the crack initiation time is increased evidently.

Evaluation of an electroless nickel-boron (Ni-B) coating on corrosion fatigue performance of ball burnished AISI 1045 steel

Evaluation of an electroless nickel-boron (Ni-B) coating on corrosion fatigue performance of ball burnished AISI 1045 steel

Effect of electroless Ni-B and Ni-W-B coatings on the corrosion-fatigue behaviour of 7075 Al alloy

This research experimentally determines the effect of electroless Ni-B and Ni-W-B coatings on the fatigue and corrosion-fatigue life of 7075 Al alloy substrate. SEM, XRD, fracture toughness and potentiodynamic polarization tests exhibited the characteristics of the coatings.The fatigue test results revealed that easy crack initiation from the brittle coating is the main responsible for a reduction in fatigue performance of coated specimen. The Ni-B coating offered superior resistance in terms of both corrosion and corrosion fatigue compared to Ni-W-B coating. Considerable improvement was achieved in corrosion fatigue performance of Ni-B coated specimens.

Study on corrosion fatigue properties and fracture characteristics of 7075 aluminum alloy FSW joint

Taking 7075-T6 aluminum alloy friction stir welding joint as the research object, the microstructure, 3.5 wt % NaCl solution corrosion fatigue life and corrosion fatigue fracture characteristics were studied, and the corrosion fatigue performance and fracture process of 7075 aluminum alloy friction stir welding joint were analyzed. The results showed that: the S-N curve equation of corrosion fatigue of 7075-T6 aluminum alloy friction stir welded joint is lgN=5.845-0.014S, With the increasing of stress amplitude, the corrosion fatigue life decreased greatly. The corrosion fatigue crack originated in the thermal affected zone of the joint, gradually expanded and finally broke in the welded core zone of the joint. There were multiple crack sources in the corrosion fatigue fracture, and with the influence of stress concentration, the crack source originated in the corrosion pit. The high stress aggravated the corrosion damage of the corner part of the sample, led to more serious corrosion than that of the plane position. Obvious intergranular fracture and fatigue striation appeared in the crack growth zone. Under the combined action of corrosive medium and alternating load, the crack growth zone suffered the most serious corrosion, and the anodic dissolution occurred at the grain boundary, resulting in the morphology characteristics of “rock candy” and “ant nest”. Instantaneous fault zone was brittle fault,and there were a lot of cleavage steps and secondary cracks in this zone, the pore morphology appeared in the second phase particle distribution region.