Corrosion Fatigue Performance Research Articles

Environmental fatigue of superelastic NiTi wire with two surface finishes

Surface finish of NiTi is widely perceived to affect its biocompatibility and corrosion fatigue performance. The aim of this work was to find out, whether a carefully engineered surface oxide shows any beneficial effect over electropolished surface on the fatigue performance of superelastic NiTi wire mechanically cycled in simulated biofluid. Series of corrosion and environmental fatigue tensile tests was performed on superelastic NiTi wire with two different surface finishes frequently used in medical device industry. Open Circuit Potential reflecting the activity of chemical reactions on the surface of the wire cycled in electrochemical cell was continuously monitored during the fatigue tests. Microcracks at the surface of the fatigued NiTi wires were characterized by SEM and TEM. It was found that the carefully engineered 70 nm thick TiO2 oxide provides the NiTi wire with similar level of protection against the static corrosion as the less than 10 nm thin natural oxide on the electropolished wire and that it does not have any positive effect on its performance in environmental fatigue tests, whatsoever. On the contrary, the wire covered by the carefully engineered 70 nm thick TiO2 oxide displayed systematically poorer fatigue performance upon tensile cycling under specific critical loading conditions (strain amplitude <0.5% at large mean strains 1–7%).

Corrosion performance, corrosion fatigue behavior and mechanical integrity of an extruded Mg4Zn0.2Sn alloy

Magnesium alloys are promising as load bearing components. They are inevitably exposed to cyclic loading and corrosive environment in actual service, which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material. Therefore, in the present study, the corrosion behavior, corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn (wt.%) alloy were thoroughly studied in two corrosive electrolytes. Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride (NaCl) solution. The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution. In comparison, the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers. This consequently conferred longer fatigue life on the alloy in the electrolyte. Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys.

The effect of near-surface plastic deformation on the hot corrosion and high temperature corrosion-fatigue response of a nickel-based superalloy

Abstract Surface treatments such as shot peening to inhibit fatigue crack initiation are essential processes when designing gas turbine components for aerospace applications. It is therefore crucial to understand the effects of shot peening in representative service environments. Here, the influence of surface treatment on the high temperature corrosion fatigue response of a polycrystalline nickel-based superalloy is considered, an area that has not previously been explored. Two shot peening conditions; 110H 7A 200% and 330H 7A 200%, along with a polished surface were chosen. Specimens were salted and exposed to SO2 gas during fatigue testing at 700 °C. A range of novel techniques including SEM, EBSD and axial chromatism profilometry were used to analyse the near surface cold work and surface condition before and after testing. EBSD local misorientation maps, paired with an increase in corrosion-fatigue life, suggest that a greater depth of cold work produced by the smaller shot size (110H), is providing a significant benefit in terms of hot corrosion and corrosion-fatigue performance. This paper concludes that the presence of a substantial layer of cold work is required to account for any metal loss due to the effects of hot corrosion. It is also evident that cold work hinders fatigue crack initiation and delays the onset of pit to crack transition.

Experimental Study on Corrosion Fatigue Performance of High-Strength Steel Wire with Initial Defect for Bridge Cable

The durability problem in high-strength steel wire used for bridge cable is becoming more and more severe due to chlorine salt erosion, with the primary corrosion morphology of steel wire surfaces being pit corrosion. To simplify the pitting formation process, a machine-cut notch was used to represent a corrosion pit caused by electrochemical non-uniformity, and then the fatigue performance and corrosion fatigue performance of steel wire with initial defects were studied experimentally. A new type of test device was designed to carry out synchronous pulsating fatigue loading on multiple wires. A series of S-N curves of steel wire with initial defects under various loading conditions was obtained, and the effects of the concentration and pH value of the corrosive solution, and the shape and dimension of the initial defect on the fatigue corrosion performance of steel wire for bridge cables were investigated. The results show that the test device designed in this paper can effectively perform the life test under the combined action of corrosive medium and fatigue load, and can considerably shorten the duration of the fatigue test. Under the combined action of corrosive medium and fatigue load, the life of steel wire with an initial defect is significantly lower than that without consideration of the corrosion effect. The corrosion fatigue performance of steel wire decreases with the increase of acidity of the corrosive solution, rather than the increase of solution concentration. The life of steel wire with a narrow deep notch is much lower than that with a wide shallow notch. The stress concentration leads to a sharp reduction in wire life.

Analysis on damage evolution and corrosion fatigue performance of high-strength steel wire for bridge cable: Experiments and numerical simulation

Corrosion fatigue (CF) failure is one of the typical failure modes of high-strength steel wires for bridge cables because the cables are subjected to the long-term cyclic loads and exposed to the heavy polluted environment at the same time. In this paper, the damage evolution process and CF performance were investigated, and the service life was predicted for steel wire with machine-cut notch via experiments and numerical simulation. Firstly, a novel experimental device was constructed to apply fatigue load and corrosive medium on multiple specimens simultaneously. With the constructed device, two groups of experiments were conducted to analysis the fatigue performance and CF performance of surface notched wire specimens, and the fatigue life and CF life of steel wire were obtained under fatigue load and the coupling effect of corrosive medium and fatigue load (CCF) respectively. Additionally, in order to study the fatigue damage evolution process and CF damage evolution process of surface notched steel wire under fatigue load and CCF respectively, a fatigue damage constitutive equation and a CF damage constitutive equation were proposed respectively according to continuum damage mechanics, and experimental data were used to determine the value of each parameter in these two equations. With the proposed model, damage evolution process in steel wire was simulated under fatigue loads and CCF respectively. The effect of corrosive medium on wire life was discussed. The results show that the fatigue life and CF life of surface notched wire obtained from simulation are consistent well with the experimental results, which shows that the simulation method can achieve the expected goal, and has high reliability in predicting the fatigue life and CF life, and simulating the fatigue damage evolution and CF damage evolution of surface notched wire. For the fatigue damage evolution process and CF damage evolution process, damage evolves gradually, and the damage evolution rate gradually increases. There are more and more damage elements at the bottom of machine-cut notch, and some elements inside the steel wire are also damaged. Comparing the damage distribution of steel wire subjected to fatigue load only and CCF, it can be found that corrosive medium will cause the damaged elements to appear earlier. Under the same stress range, the fatigue life and CF life of steel wire with machine-cut notch are significantly different, but the fatigue damage evolution rate and CF damage evolution rate are similar. It can be concluded that the difference in service life is mainly due to the corrosive medium that causes the damaged elements near the surface notch appear earlier, especially under higher stress ranges.

Low-cycle fatigue behavior and corrosion mechanism of pre-corroded 2A70-T6 aluminum alloy

PurposeIn summary, it can be found that the current research on the simulation of natural atmospheric dry–wet alternating accelerated corrosion mainly focused on the study of electrochemical corrosion process and the study of corrosion rate; the micro-pre-corrosion mechanism of materials in this environment, especially for materials. The specific effects of fatigue and fracture performance still lack detailed research. Accordingly, this study aims to more realistically simulate the effect of natural atmospheric corrosion environment on the corrosion resistance and fatigue performance of aircraft skin.Design/methodology/approachIn this study, the uniaxial strain control method was used to test the fatigue performance of pre-corrosion samples under simulated natural atmospheric corrosion using MTS809 tensile-torque composite fatigue machine. Scanning electron microscopy, X-ray energy spectrum analysis, atomic force microscopy and X-ray diffraction analysis were used. Fatigue fracture, corrosion morphology and corrosion products were analyzed.FindingsThe results show that the deep corrosion pit caused by pre-corrosion environment leads to multi-source initiation of crack; the fatigue life of pre-corroded sample decreases by about one-half, chloride ion invades the material and promotes intergranular corrosion; life prediction results show that the natural atmospheric corrosive environment mainly affects the plastic term in the Manson–Coffin formula resulting in a decrease in fatigue life.Originality/valueInnovative experimental schemes and materials are used and the test temperature and relative humidity are strictly controlled. The corrosion failure mechanism of 2A70-T6 aluminum alloy under alternating wet and dry accelerated corrosion environment and its influence on fatigue behavior were obtained.

The Effect of Microstructural Imperfections on Corrosion Fatigue of Additively Manufactured ER70S-6 Alloy Produced by Wire Arc Deposition

This study aims at evaluating the effect of microstructure imperfections on the corrosion fatigue performance of an ER70S-6 alloy produced by wire arc additive manufacturing (WAAM) process, in a 3.5% NaCl solution. For reference, a regular ST-37 alloy with relatively similar chemical composition was considered as a counterpart alloy. This was justified by the fact that the ER70S-6 alloy is usually used for conventional welding of ST-37 steel. The results obtained indicated that while the ST-37 alloy exhibited fatigue strength of 240 MPa in the corrosive solution, the additively manufactured ER70S-6 alloy showed fatigue strength of only 140 MPa. These differences were related to microstructural imperfections that are inherently produced during the WAAM process.

Comparison of Additively Manufactured vs. Conventional Maraging Steel in Corrosion-Fatigue Performance after various surface treatments

Additive manufacturing (AM) exhibits some inherent processing characteristics that affect the grain structure, phase formation, microstructure, roughness and porosity, compared to conventionally manufactured components. Consequently, the surface originating functional life, especially corrosion, can be severely affected.The present study highlights and compares the fatigue life of maraging steel 18Ni-C300 (1.2709, X3NiCoMoTi18-9-5) obtained by the SLM-fabricated specimens with the corresponding ones machined to the same geometry from a rolled bar. Metallography, microscopy, surface scanning, FEM and hardness measurements were employed to help understand the results obtained. To make a more realistic estimation of the life expectancy, fatigue was performed both in a corrosion-free environment and in a typical 3.5% wt. NaCl aqueous solution. Additionally, the effect of glass- blasting (GB) performed as a post-treatment in the SLM specimens was investigated both. There is a clear superiority of the wrought material both in pure fatigue and in corrosion-fatigue, because of its dense and homogeneous microstructure as well as its lower resulting surface roughness. The AM material, due to multiple melt pools created from the consecutive laser passes, the cellular-dendritic structure and the inherent higher roughness they possess, has an inferior fatigue and corrosion-fatigue performance. Glass-blasting improves surface integrity by imposing residual stresses and reducing the roughness, both offering a positive impact on the corrosion and fatigue performance.

Mechanical and corrosion fatigue behaviors of gradient structured 7B50-T7751 aluminum alloy processed via ultrasonic surface rolling

In this work, ultrasonic surface rolling process (USRP) was utilized to produce a gradient structured layer on 7B50-T7751 aluminum alloy, and the mechanical properties and corrosion fatigue behavior of treated samples were studied. These results reveal that underwent USRP, a 425 μm thick gradient structure and a 700 μm deep compressive residual stress field are created, aluminum grain size become fine(∼ 67 nm), and the corrosion rate of treated surface reduces by 60.08% owing to the combined effect of compressive residual stress and surface nanocrystallization. The corrosion fatigue strength is enhanced to 117% of that of 7B50 Al alloys by means of USRP due to the introduced compressive residual stress, which is considered as the major favorable factor in suppressing the initiation and early propagation of corrosion fatigue cracks. Besides, the gradient structure is an important factor in providing a significant synergistic contribution to the improvement of corrosion fatigue performance.

The influence of pulsed gas metal arc welding on the fatigue and corrosion-fatigue properties of wrought aluminium 6061-T651

Purpose This paper aims to characterise the hardness, tensile properties, corrosion behaviour and fatigue properties (in air and in a 3.5 per cent NaCl solution) of aluminium 6061-T651 in the as-received and as-welded conditions. Design/methodology/approach Aluminium 6061-T651 plate material, prepared with double-V or square butt joint preparations was welded using semi-mechanised or mechanised pulsed gas metal arc welding. Magnesium-alloyed ER5356 or ER5183 filler material or silicon-alloyed ER4043 filler wire was used. The material was characterised in the as-supplied and as-welded conditions, and fatigue tests were performed in air and in a 3.5 per cent NaCl solution. The fatigue results were compared to the reference fatigue design curves for aluminium published in Eurocode 9 – Part 1-3. Findings Significant softening, attributed to the partial dissolution and coarsening of precipitates, grain growth and recrystallisation during welding, was observed in the heat-affected zone (HAZ) of the 6061-T651 welds. During tensile testing, failure occurred in the HAZ of all 6061 welds tested. Welding reduced the room temperature fatigue life of all specimens evaluated. In 6061 welds, failure occurred preferentially in the softened HAZ of the welds. The presence of a corrosive environment (a 3.5 per cent NaCl solution in this investigation) during fatigue testing reduced the fatigue properties of all the samples tested. Corrosion pits formed preferentially at second phase particles and reduced the overall fatigue life by accelerating fatigue crack initiation. Originality/value The fatigue properties of welded aluminium structures under dynamic loading conditions have been studied extensively. Welding is known to create tensile residual stresses, to promote grain growth, recrystallisation and softening in the HAZ, and to introduce weld defects that act as stress concentrations and preferential fatigue crack initiation sites. Several fatigue studies of aluminium welds emphasised the role of precipitates, second phase particles and inclusions in initiating fatigue cracks. When simultaneously subjected to a corrosive environment and dynamic loading, the fatigue properties are often adversely affected and even alloys with good corrosion resistance may fail prematurely under conditions promoting fatigue failure. The corrosion-fatigue performance of aluminium welds has not been systematically examined to date.

Influence of combined shot peening and PEO treatment on corrosion fatigue behavior of 7A85 aluminum alloy

The plasma electrolytic oxidation (PEO) with coating thickness of ~10 μm and ~35 μm on 7A85 aluminum alloy was performed using the alkaline silicate based electrolyte, and the corresponding influence on fatigue behavior in air and 3.5% NaCl solution was studied. Results show that PEO treatments reduced the corrosion fatigue life of 7A85 aluminum alloy. The corrosion fatigue life of samples with thin PEO coatings (10 μm-thick) is decreased for the occluded battery promoted localized corrosion, while that of samples with thicker PEO coatings (35 μm-thick) is reduced for the low ductility of the oxide coating. The shot peening (SP) treatment with ceramic shots was introduced as pretreatment of PEO, The surface residual stresses as well as the residual stress of the substrate beneath the coating were analyzed by X-ray stress analyzer. The corrosion fatigue performance of shot peening combined PEO treated samples is improved for the residual compressive stress field induced by shot peening. Whereas, enhanced notch effect was induced by shot peeing surface roughening and oxide coating local overgrowth, so the corrosion fatigue life of samples with SP, surface polishing, PEO, respectively is further improved for the reduction of notch effect.

Influence of ultrasonic rolling on surface integrity and corrosion fatigue behavior of 7B50-T7751 aluminum alloy

The surface integrity and corrosion fatigue (CF) performance of the 7B50-T7751 aluminum alloy treated by one (UR1), three (UR3), and six passes (UR6) of ultrasonic surface rolling process (USRP) were investigated in this paper. The results revealed that a modified surface layer with refined microstructure and increased microhardness was formed after the USRP, and a compressive residual stress (CRS) was induced. The CF life of all USRP-treated samples was improved, especially the life of the UR1 sample with an optimal surface integrity. The synergistic effect of surface layer microstructure refinement and CRS effectively have inhibited the occurrence and development of pitting and intergranular corrosion, prevented the initiation of CF cracks at the surface, thus led to the movement of the fatigue crack nucleation site toward the subsurface. Overall, the CRS has played a major critical role. The severe surface damage in the modified layer of the UR6 sample resulted in a partial relaxation of the CRS, in favor of secondary fatigue crack initiation, therefore when using the USRP treatment to improve the CF life of the 7B50 aluminum alloy, the effect of surface integrity should be fully considered.

Durability method on corrosion fatigue performance of AH 32 steel

A durability method in view of cathodic protection is proposed to improve the corrosion fatigue resistance of AH 32 steel in seawater. By aid of corrosion fatigue tests, the effects of thermal spraying Zn (zinc) and Cr (chromium) coating corrosion fatigue lives are quantitatively determined, respectively, and electrochemical measurement and fracture analysis are used to analyze the life-prolonging mechanism of these two coatings on corrosion fatigue. The results show that both Zn and Cr coating improve the corrosion fatigue resistance of AH 32 steel, and the effect enhances with the decrease of stress. The effect of Cr coating on corrosion fatigue of AH 32 steel mainly reflects in extending the crack initiation life for its better corrosion resistance. While the effect of Zn coating on corrosion fatigue lies in not only inhibiting the initiation of corrosion fatigue but also restraining crack propagation as cathodic protection materials. To sun up, Cr coating has a better durability effect than Zn coating at higher stress level, while Zn exceeds Cr at low stress level.

High Performance Fine-Grained Biodegradable Mg-Zn-Ca Alloys Processed by Severe Plastic Deformation

The tensile strength, fatigue, and corrosion fatigue performance of the magnesium alloy ZX40 benefit strongly from hybrid deformation processing involving warm equal-channel angular pressing (ECAP) at the first step and room temperature rotary swaging at the second. The general corrosion resistance improved as well, though to a lesser extent. The observed strengthening is associated with a combined effect of substantial microstructure refinement down to the nanoscale, reducing deformation twinning activity, dislocation accumulation, and texture transformation. The ultimate tensile strength and the endurance limit in the ultrafine-grained material reached or exceeded 380 and 120 MPa, respectively, which are remarkable values for this nominally low strength alloy.

Surface protection of Mg alloys in automotive applications: A review

Mg alloys find widespread applications in transportation industries especially in cars and trucks because of their edges in light-weight design, which can greatly help improve the fuel efficiency and decrease the gas emissions of vehicles; However, Mg alloys’ high sensitivity to the corrosive environments limit their penetration in automotive applications. Surface coating is one of the most effective and economic ways to protect Mg alloys from corrosion. Presently, the currently researched and commercial coatings that are specifically applied to Mg alloys in the automotive industry are reviewed in this paper. With some Mg automotive components subjected to corrosion and repeated load simultaneously, corrosion fatigue of coated Mg alloys are reviewed as well. Additionally, a part of attention in this review is given to the assessment approaches of corrosion and corrosion fatigue performance of coated Mg alloys for the purpose of material/surface coating system selection. Finally, some corrosion-related challenges for the growth of Mg alloys, future developments and research directions on surface coatings and corrosion fatigue testing approaches are discussed.

Improving Corrosion and Corrosion-Fatigue Resistance of AZ31B Cast Mg Alloy Using Combined Cold Spray and Top Coatings

In this paper, we report the application of zinc phosphate electrostatic-painting top coating on cold sprayed AA7075 leading to a significant improvement in corrosion-fatigue performance. High strength AA7075 powder was sprayed on AZ31B substrate, followed by the application of the top coating. The electrochemical corrosion and corrosion-fatigue tests of the coated and uncoated specimens were performed in 3.5% NaCl solution. Transmission electron microscopy (TEM) analysis showed that a continuous nanolayered mixture of Mg/Al was formed at the cold spray coating/substrate interface leading to high bonding strength. The results showed that the combined coatings improved the corrosion resistance remarkably, and significantly increased the fatigue life, with a fatigue strength of 80 MPa at 107 cycles, as compared to the as-cast specimen. Surface topographic analysis of the corrosion-fatigue-tested specimens demonstrated the presence of deep macro-pits on the cold sprayed AA7075 coating after 3.7 million cycles, while there were no such pits on the top-coated specimens, even after 107 cycles when tested at 30 Hz. The fractographic analysis of the fatigue-fractured specimens showed that the formation of pits allowed the NaCl solution to penetrate in the AZ31B substrate, creating localized corrosion pits resulting in premature failure, which eventually reduced the fatigue life.

SANDVIK APM 2327

Abstract Sandvik APM 2327 is a powder metallurgical hot isostatic pressed product that is a super duplex stainless steel with improved mechanical properties, corrosion resistance, and superior corrosion fatigue performance over conventional duplex grades. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: SS-1299. Producer or source: Sandvik Materials Technology.

RSM-based assessment of pavement concrete mechanical properties under joint action of corrosion, fatigue, and fiber content

High-performance synthetic fiber pavement concrete (HPSFPC) samples are prepared with 0.8, 1, 1.2, and 1.4 kg/m3 fiber. HPSFPC corrosion resistance and fatigue performance are analyzed by comparison against plain pavement concrete (PPC). The mechanical properties of pavement concrete under the joint action of corrosion, fatigue, and fiber content are assessed by response surface methodology (RSM), Design Expert, and Central Composite Design (CCD) software. An RSM model of flexural strength index Sf, compressive strength index Sc, and dynamic elasticity modulus Pn is established and used to determine the influence rules of fatigue iterations, number of sulfate wetting and drying cycles (NSWDC), fiber content, and their interactions on Sf, Sc, and Pn. The RSM model fits well and indeed effectively reveals the mechanical properties of pavement concrete under joint action of corrosion, fatigue, and fiber content. The significant effects on Sf are, in order, fatigue iterations > NSWDC > fiber content; the effects on Sc and Pn are NSWDC > fiber content > fatigue iterations. The interaction between fatigue iterations with NSWDC has the most significant influence on Sc and Pn, while the interaction among the three factors has no significant influence on Sf.

Improving the fretting and corrosion fatigue performance of 300M ultra-high strength steel using the ultrasonic surface rolling process

300M ultra-high strength steels (300M steels) are frequently used in the manufacture of aircraft landing gear due to their high strength and ductility. However, their high sensitivity to surface defects accelerates fatigue failure and hinders their wider application. In this work, ultrasonic surface rolling processing (USRP) was used to process 300M steel. The surface roughness, hardness, microstructure, and residual stresses before and after USRP treatment were compared. The surface roughness for USRP-treated samples (0.062 μm) was found to be lower than that for untreated samples (0.32 μm). In addition, a plastically deformed layer was generated on the surface of USRP-treated samples that resulted in higher hardness. Beneficial compressive residual stresses were introduced as a result of USRP treatment. The better surface finish, higher surface hardness and compressive residual stresses lead to significant improvement in the resistance of the 300M steels to fretting fatigue and corrosion fatigue. The fretting fatigue life increased from 11.9 K cycles to 56.3 K cycles, while the corrosion fatigue life increased from 29.9 K cycles to 702.1 K cycles.

Corrosion fatigue behavior of friction stir processed interstitial free steel

In this study, interstitial free (IF) steel plates were subjected to double-sided friction stir processing (FSP). The fine-grained structure with an average grain size of about 12μm was obtained in the processed zone (PZ) with a thickness of about 2.5mm. The yield strength (325MPa) and ultimate tensile strength (451MPa) of FSP IF steel were significantly higher than those of base material (BM) (192 and 314MPa), while the elongation (67.5%) almost remained unchanged compared with the BM (66.2%). The average microhardness value of the PZ was about 130HV, 1.3 times higher than that of the BM. In addition, the FSP IF steel showed a more positive corrosion potential and lower corrosion current density than the BM, exhibiting lower corrosion tendency and corrosion rates in a 3.5wt% NaCl solution. Furthermore, FSP IF steel exhibited higher fatigue life than the BM both in air and NaCl solution. Corrosion fatigue fracture surfaces of FSP IF steel mainly exhibited a typical transgranular fracture with fatigue striations, while the BM predominantly presented an intergranular fracture. Enhanced corrosion fatigue performance was mainly attributed to the increased resistance of nucleation and growth of fatigue cracks. The corrosion fatigue mechanism was primarily controlled by anodic dissolution under the combined effect of cyclic stress and corrosive solution.