Corrosion Fatigue Behavior Research Articles

Effect of Industrial Atmospheric Environment on Corrosion Fatigue Behavior of Al-Mg-Si Alloy

Effect of Industrial Atmospheric Environment on Corrosion Fatigue Behavior of Al-Mg-Si Alloy

Evaluating corrosion and corrosion fatigue behavior via laboratory testing techniques in highly corrosive CCS-environment

In CCS environment (carbon capture and storage) pipes are loaded statically and/or cyclically and at the same time exposed constantly to the highly corrosive hot thermal water. Experimental procedures such as ambient pressure immersions tests, in-situ corrosion fatigue experiments using a flexibly designed corrosion chamber at ambient pressure and a specially designed corrosion chamber at high pressure. Experimental set-ups for push/pull and rotation bending load are introduced. The corrosion behavior and lifetime reduction of high alloyed steels (X46Cr13, 1.4043), (X5CrNiCuNb16-4, 1.4542) and (X2CrNiMoN22-5-3, 1.4462) is demonstrated (T=60 °C, geothermal brine: Stuttgart Aquifer flow rate: 9 l/h, CO2).

Influence of surface-roughness on the corrosion-fatigue behavior of MAO coated 6061-T6 Al alloy assessed in NaCl medium

The micro arc oxidation (MAO) coatings corresponding to 50 μm and 90 μm thicknesses were formed on bare and shot-peened Al alloy and then subjected to polishing process. The influence of post-polishing on the resultant corrosion-fatigue life was systematically studied under completely reversed loading (R = −1) for each material condition in 3.5 wt% NaCl corrosion medium. The electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP) techniques were utilized to evaluate the corrosion behavior of MAO coatings in 3.5 wt% NaCl solution. The MAO coatings were examined for surface and cross-sectional morphologies, constituting phases were identified, surface-roughness in as coated and polished conditions was evaluated. Further, the fractography studies were also carried out to understand the corrosion-fatigue failure mechanism. The reduced surface roughness had a beneficial role in enhancing overall corrosion-fatigue life of Al alloy.

Differences of corrosion fatigue behaviors among 316LN base metal, 316LN heat-affected zone and 308L weld metal in a safe-end weld joint in borated and lithiated high-temperature water

Corrosion fatigue behaviors of 316LN base metal (BM), 316LN heat-affected zone (HAZ) and 308L weld metal (WM) in a safe-end weld joint were investigated in borated and lithiated high-temperature water. It was found that the 316LN HAZ showed the highest environmentally assisted fatigue (EAF) effect and the 308L WM had the lowest EAF effect. The corrosion fatigue cracking mechanisms are discussed in 316LN BM, 316LN HAZ and 308L WM by considering the effects of welding residual strain, corrosion resistance and δ-ferrite.

Corrosion Fatigue Characteristics of SUS316L Steel with Ti Undercoat using Plasma Spray Method

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 μm below the surface of the base material; however, when the depth exceeds 100 μm, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

Corrosion fatigue behavior of Fe-16Mn-0.6C-1.68Al twinning-induced plasticity steel in simulated seawater

The nature of corrosion fatigue of twinning-induced plasticity (TWIP) steel in a simulated seawater environment was investigated through various tests. Results indicated that TWIP steel has high corrosion fatigue susceptibility, which is mainly caused by anodic dissolution at grain boundaries and twin boundaries. However, uniform plastic deformation tends to inhibit corrosion fatigue. The influence of plastic deformation on corrosion fatigue of TWIP steel was clarified through the aspects of microstructure evolution, mechano-electrochemical effect, fatigue damage, etc. Findings reveal that plastic deformation or metallurgical design for high grain boundary strength will improve the resistance of corrosion fatigue for TWIP steel.

On the Influence of the Microstructure upon the Fatigue and Corrosion Fatigue Behavior of UNS N07718

Due to the challenging operational conditions occurring during drilling, e.g., in the oil and gas industry, the corrosion fatigue (CF) behavior of materials used in drillstring components needs to be well understood. The combination of cyclic mechanic loads and a corrosive environment can affect significantly the integrity of a material, which has to be taken into account when selecting and qualifying materials for drilling equipment. Nickel alloys such as the precipitation-hardenable alloy 718 (UNS N07718) are widely used in many industrial applications including subterranean drilling. In the present study, the fatigue and CF behavior of alloy 718 in three different metallurgical conditions was investigated. The CF behavior of the different conditions was determined using customized rotating bending machines enabling testing in a simulated drilling environment at 125 °C. Results have shown that the fatigue and CF strength of alloy 718 is affected by its microstructural particularities, for instance, the amount of strengthening phases and δ-phase.

On the Influence of the Microstructure upon the Fatigue and Corrosion Fatigue Behavior of UNS N07718

Due to the challenging operational conditions occurring during drilling, e.g., in the oil and gas industry, the corrosion fatigue (CF) behavior of materials used in drillstring components needs to be well understood. The combination of cyclic mechanic loads and a corrosive environment can affect significantly the integrity of a material, which has to be taken into account when selecting and qualifying materials for drilling equipment. Nickel alloys such as the precipitation-hardenable alloy 718 (UNS N07718) are widely used in many industrial applications including subterranean drilling. In the present study, the fatigue and CF behavior of alloy 718 in three different metallurgical conditions was investigated. The CF behavior of the different conditions was determined using customized rotating bending machines enabling testing in a simulated drilling environment at 125 °C. Results have shown that the fatigue and CF strength of alloy 718 is affected by its microstructural particularities, for instance, the amount of strengthening phases and δ-phase.

Effects of welding columnar grain orientation and strain rate on corrosion fatigue behavior of Alloy 52/52M weld metal in high-temperature water

Corrosion fatigue (CF) tests of Alloy 52/52 M weld metal from a safe-end welding joint of reactor pressure vessel were performed in B/Li high-temperature water. The CF cracks developed preferentially in 52 Mw with columnar grain orientation at a 45° - 75° angle to cyclic loading axis, rather than in 52b with columnar grain orientation parallel to loading axis. The environmental assisted fatigue effects were significant under lower strain amplitudes and the effect of strain rate on CF behavior was not significant. The CF cracking mechanism involved with welding columnar grain orientation is discussed.

Corrosion fatigue behaviour of HFMI-treated butt welds

The present study reports on the results of a completed research project, which investigated the corrosion fatigue behaviour of weldments made of structural steel S355J2+N treated with the High Frequency Mechanical Impact (HFMI). Main goal has been the estimation of short corrosion on the surface layer (<1 year) on the fatigue strength of uncoated HFMI-treated specimens. Axial and 4-point bending fatigue tests were carried out on uncorroded and corroded butt welds both for the as-welded and HFMI-treated state. Marine corrosion is simulated in the laboratory with exposure in a Salt Spray Chamber (SSC) tests and deposition in Artificial Seawater (ASW). SSC was applied as pre-corrosion means while corrosion in ASW took place simultaneously during fatigue testing of specimens pre-corroded in the same corrosive medium. Extrapolation of the laboratory results to real marine corrosion (RC) is carried out based on findings from an earlier study of the authors, where specimens corroded in the laboratory were compared with reference specimens exposed to the real marine splash zone in the Baltic Sea. Material removal rate, increase of surface roughness and reduction of fatigue life are considered for this comparison. Significant conclusions regarding corrosion fatigue resistance of both as-welded and HFMI-treated specimens are drawn. Assumptions and initial expectations regarding the influence of corrosion on both fatigue crack initiation and crack growth regimes are either confirmed or overthrown. In all investigated cases for thickness reduction up to 0.1 mm, significant increase in fatigue life is achieved through the application of HFMI. Finally, recommendations for future work regarding the clarification of open questions from the present study are presented.

Corrosion Fatigue Crack Growth Rates of Sensitized AA5456-H116: Contribution of Stress Corrosion Cracking

The interplay between stress corrosion cracking (SCC) and corrosion fatigue was investigated for AA5456-H116 to determine the source of the inverse relationship between fatigue loading (f) and fatigue crack growth rates (da/dN). Sensitization in 5xxx series aluminum alloys refers to the precipitation of β on α-aluminum grain boundaries, which can occur in high-Mg 5xxx alloys after sufficient exposure to temperatures as low as 40°C. Recent research has established that da/dN in sensitized 5xxx series aluminum alloys can be inversely dependent on f. The severity of the inverse relationship between da/dN and f has been attributed to sensitization level, alloy composition, and temper. In this work, the effect that Kmax has on corrosion fatigue da/dN was quantified using fracture mechanics-based experiments conducted at different maximum stress intensity factors (Kmax) but the same ΔK in 3.5 wt% NaCl. Results suggest that the severity of the inverse relationship between da/dN and f (i.e., the slope of the da/dN vs. f trend) is governed by the magnitude of Kmax in relation to the threshold stress intensity factor for SCC (KISCC). In addition, results show that an inverse f-dependence, albeit with a lower slope, can exist even when Kmax is less than KISCC; in other words, absent SCC. This low-slope corrosion fatigue behavior may have been driven by an enhanced rate of hydrogen embrittlement facilitated by the more aggressive local crack tip environment present at progressively lower loading frequencies during corrosion of highly sensitized microstructures.

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.

The mechanism of thermal corrosion fatigue (TCF) on nickel-based single crystal superalloy and the corresponding structure shape effect

The thermal fatigue behavior under hot corrosion is studied at 25 ℃ - 900 ℃. The whole process of thermal corrosion fatigue (TCF), including crack initiation and propagation, is analyzed in detail from the perspective of driving force and the intensity factor for cracking. By controlling the Cr content in nickel-based single crystal superalloy, different hot corrosion degrees and reaction products are obtained, and its influence on the thermal fatigue mechanism of the alloy is analyzed comprehensively. It can be concluded from the research that hot corrosion has a great influence on thermal fatigue. Firstly, severe hot corrosion which induces spallation can lead to crack initiation dominantly. Secondly, the thermal mismatch between the hot corrosion products and the matrix provides a high driving force for thermal fatigue. Subsequently, the driving force can influence the thermal corrosion fatigue (TCF) process by stress concentration generated by crack tip and products shape. Finally, the loose and fragile nature of the hot corrosion products can provide a channel for crack propagation. These characteristics of thermal corrosion fatigue (TCF) behaviors are obvious in low Cr content Nickel-based single crystal superalloy.

Crack growth direction effects on corrosion-fatigue behaviour of offshore wind turbine steel weldments

In this study corrosion-fatigue tests have been conducted on fracture mechanics specimens extracted from an S355 G10+M structural steel welded plate. The tests have been performed on compact tension specimens with the crack tip located in the heat affected zone. The corrosion-fatigue test results from this study have been compared with the data available on the base metal as well as air tests on the same material. Moreover, the obtained results have been compared with the corrosion-fatigue data available in the literature on a wide range of steels and also the fatigue trends for welded joints in free-corrosion condition recommended in the BS7910 Standard. The effect of the specimen orientation, with respect to the weld region, is also examined in this study and it has been found that higher corrosion-fatigue crack growth rates are generally observed in the tests with 0° orientation. The results have also shown that the corrosive environment has significant effects on the fatigue crack growth acceleration at the beginning of the tests; however, as the crack propagates, the environmental damage effect on crack growth behaviour becomes less pronounced. The results presented in this study are discussed in terms of improvement in the structural integrity assessment of offshore wind turbine monopiles.

Corrosion Fatigue Behavior of 316LN Stainless Steel Hollow Specimen in High-Temperature Pressurized Water

Corrosion Fatigue Behavior of 316LN Stainless Steel Hollow Specimen in High-Temperature Pressurized Water

The role of microstructure on corrosion fatigue behavior of thick-plate Ti–6Al–4V joint via vacuum electron beam welding

The microstructure and corrosion fatigue behavior under artificial seawater environment of 100-mm-thick Ti–6Al–4V alloy joint via vacuum electron beam welding (EBW) was systematically characterized. Obvious microstructural heterogeneity along the transverse direction of as-welded joint was observed. Bimodal-phases microstructure of granular α colonies and β strips compose the microstructure of the base metal (BM). While the microstructure of fusion zone (FZ) comprises single-phase acicular α/α′ martensite. Under corrosive environment of artificial seawater, FZ shows a lower growth rate of corrosion fatigue cracking (CFC) than that in the BM. Increasing content of residual gas contamination worsens the resistance against corrosion fatigue of the FZ of Ti–6Al–4V alloy joint. Results of local electrochemical characterization indicates that the FZ shows a better resistance against electrochemical corrosion than that of the BM. It is deduced that the slower growth rate of CFC observed in the FZ originates from the combined effects of the excellent corrosion resistance of martensite microstructure and the obstructions of interfaces of fine α/α′ laths against growth of CFC. Moreover, the growth mechanisms of CFC in the BM and FZ were discussed involving the microstructural heterogeneity of the EBW joint.

Corrosion fatigue and electrochemical behaviour of steel wires used in bridge cables

AbstractIn‐service bridge wires often fail prior to the design life subjected to alternating stresses and environmental erosion. In this paper, a novel corrosion fatigue test device, integrating fatigue testing machine and electrochemical accelerated corrosion assemblies, was developed to characterize the corrosion fatigue and electrochemical behaviour of the wires. Using the developed device, corrosion fatigue tests of corroded bridge wires under different corrosion and loading conditions were conducted. Electrochemical characteristics, corrosion fatigue behaviour, failure mechanism, and so forth were investigated according to electrochemical measurements, fracture morphologies and the lifetime of wires. Results evidence the synchronization of corrosion and fatigue and show the accelerated corrosion due to static and fatigue stresses. Additionally, cracking and fracture induced by multiple crack initiation was dominant in corrosion fatigue of corroded wires, and the coexistence of multiple corrosion pits decreased the lifetime significantly.

Influence of Twinning Texture on the Corrosion Fatigue Behavior of Extruded Magnesium Alloys

Bio-magnesium alloys have received great attention due to their degradability and biocompatibility. Corrosion fatigue failure is a huge challenge in vivo for bio-magnesium alloy implants. Understanding the effects of twinning textures on the corrosion fatigue of magnesium alloys is meaningful for the applications. In the current study, pre-compression strains of 2% and 4% were carried out on extruded rods. The effects of twinning texture on the corrosion performance and corrosion fatigue resistance were investigated. The hydrogen evolution tests indicated that twinning texture enhanced the corrosion resistance of longitudinal cross section by improving uniformity of surface energy. The results of corrosion fatigue tests indicated that the differences in mechanical damage caused by twinning texture dominated the corrosion fatigue behavior under high stress amplitude. The secondary cracks of surface deteriorated the corrosion fatigue resistance of the original specimens under low stress amplitude. The compact corrosion film and the re-passivation of matrix suppressed the hydrogen induced cracking, thereby improving the corrosion fatigue resistance of the pre-compression specimens.

Effect of phase formation due to holding time of vacuum brazed AISI 304L/NiCrSiB joints on corrosion fatigue properties

Whether in turbine components or exhaust gas heat exchangers, vacuum-brazed nickel-based joints are subjected to varying cyclical loads during their applications, often in corrosive environments. The microstructure of the brazed seam, which is determined by the alloy composition and the brazing process parameters, is essential for the service life. In this experimental study a modified BNi-5a foil was produced and used to braze cylindrical AISI 304L butt joints with two different holding times. Using energy dispersive spectroscopy analyses, a direct correlation of the element distribution at the brazing seam with the holding time was detected as a result of diffusion processes. Individual phases were identified, and it could be shown that the longer holding time led to a reduction of borides and silicides as well as to a more even microhardness curve through the seam. The effect of the microstructure on the corrosion fatigue properties was evaluated using multiple amplitude tests by a stepwise increase of the maximum stress amplitude in synthetic exhaust gas condensate. Thereby, improved corrosion fatigue and cyclic deformation behaviors were achieved for the more homogeneous microstructure. Afterwards, topography analyses of the fracture surfaces and cross-sectional fracture investigations enabled an understanding of microstructure-dependent damage mechanisms including fatigue crack initiation and propagation.

Influence of Nitrocarburizing and Post-Oxidation on Surface Characteristics, Fatigue, and Corrosion Fatigue Behaviour of AISI 4330V Steel

In the present work, gaseous nitrocarburizing followed by water spray oxidation in vacuum was carried out on 4330V steel. The X-ray diffraction analysis showed that the thermochemically modified surface layer mainly consisted of e-Fe2-3(N,C), γ′-Fe4(N,C), and magnetite (Fe3O4). To quantify the residual stress generated due to surface treatment, the Sin2ψ method was used. Residual stress of compressive nature up to a depth of 1 mm was observed, and its maximum value was 383 MPa. Nitrocarburizing followed by oxidation not only increased the surface hardness but also decreased the wear loss. The synergistic effect of corrosion-resistant phases formed after surface treatment improved surface hardness and compressive residual stress which resulted in the enhancement of corrosion fatigue life.