Corrosion Resistance Of Steel Research Articles

Corrosion behavior of aluminum reinforced austenitic steel in liquid lead bismuth at 550 ℃

The key material issue for the commercialization of advanced lead cooled fast reactors and accelerator driven subcritical systems is the compatibility between structural materials and lead based coolants. Structural steel materials require excellent corrosion resistance in high-temperature liquid lead bismuth eutectic (LBE) alloy. Aluminum forming austenitic steel (AFA steel) has excellent corrosion resistance in extreme environments due to its ability to form an Al<sub>2</sub>O<sub>3</sub> film on its surface. However, excessively high Ni elements are more easily dissolved or oxidized in LBE than Fe and Cr elements. Therefore, this work investigates the effect of reducing Ni element composition (25-Ni steel and 18-Ni steel) on the corrosion resistance of steel in LBE. Surface treatment can protect the substrate from corrosion to some extent, so herein we explore whether it has a protective effect on AFA steel in LBE by generating Al<sub>2</sub>O<sub>3</sub> through high-temperature pre oxidation. The morphology and structure of the oxide layer of AFA steel corroded for 600 h in LBE with saturated dissolved oxygen at 550 ℃ are characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and other technologies. The results indicate that the oxide film formed after corrosion of 18-Ni steel is thinner than that after corrosion of 25-Ni steel. Performing high-temperature pre oxidation is beneficial to forming a protective Al<sub>2</sub>O<sub>3</sub> oxide film on the surface of the sample, thereby reducing the thickness of the oxide layer and improving the material's LBE corrosion resistance. The reduction in thickness of the oxide layer generated after pre oxidation of 18-Ni steel is greater than that of 25-Ni steel, so the anti-corrosion effect of 18-Ni steel after pre oxidation is better than that of 25-Ni steel.

АНАЛИЗ МАТЕРИАЛОВ ДЕТАЛЕЙ, РАБОТАЮЩИХ В АГРЕССИВНЫХ СРЕДАХ ПЕРЕРАБАТЫВАЮЩИХ ПРОИЗВОДСТВ

Processing and food industries, as well as animal husbandry, play a significant role in the structure of the agro-industrial complex of Russia. The specifics of working in these industries imply constant contact of equipment parts with aggressive environments, due to which mechanical wear is enhanced by corrosion wear. In processing, food production and animal husbandry, the task is further complicated by the fact that special sanitary and hygienic requirements are imposed on materials in contact with products. (Research purpose) The research purpose is studying the materials used for the manufacture of parts operating in aggressive environments in animal husbandry and processing production; identifying the most characteristic defects during operation; offering analogues of materials for repair and restoration. (Materials and methods) Used literary and patent sources, studied the principle and working conditions of milking machines and packaging machines. (Results and discussion) It was pointed out that the use of materials from which equipment parts are made in processing and food production is determined by such factors as the neutrality of the material to the product, the neutrality of the product to the material, the operability within the technological process. It was noted that the most versatile materials in terms of strength, rigidity, heat resistance, corrosion resistance, low cost, high hygienic properties are corrosion-resistant steels. However, such materials also wear out over time as a result of mechanical wear, which is enhanced by corrosion. Most often, guides, drive rollers and discs suffer, which experience loads in the form of friction. (Conclusions) In the equipment of processing and food production, as well as in animal husbandry, parts made of corrosion-resistant steels are most often used. It is advisable to restore such parts using laser technologies or plasma-powder surfacing, since alloyed steels are difficult to weld.

The corrosion resistance of maraging steel 1.2709 produced by L-PBF in contact with molten Al-alloys

Nowadays there is a growing interest in the use of secondary Al-alloys for high-pressure die casting to obtain structural parts. To guarantee appropriate performance, these alloys are characterized by a lower Fe content (< 0.15%) than conventional secondary ones, commonly used in the production of non-structural parts. This makes them more susceptible to the phenomenon of die-soldering, thus resulting in a decrease in the service life of dies and inserts. The production of complex and demanding castings requires appropriate dies and materials, especially in high stressed areas where higher-performance steel inserts are used. Recently, maraging steel has been applied for these issues. Thanks to the good weldability of maraging steels, these alloys are nowadays also processed by additive manufacturing (AM) techniques, to obtain very complex parts like inserts with conformal cooling channels, able to extend the life of the inserts themselves, increasing productivity. In this context, this work aimed at the evaluation of the dissolution of maraging steel (1.2709) samples obtained via laser-based powder bed fusion (L-PBF) into molten AlSi7Mg (B356.2) through static immersion tests carried out at 720°C for different times, to evaluate their response to the die-soldering phenomenon. For comparison, forged maraging steel samples were also considered, to investigate the effect of the different microstructure on the dissolution behavior. As well as a conventional H11 steel, to obtain benchmark data. The corrosion resistance of the samples was evaluated by measuring the samples’ dimensional variation after the tests. Furthermore, SEM-EDS analysis was carried out to investigate the extent and the composition of the intermetallic layer formed on the samples’ surface.

Surface integrity, corrosion resistance, and low-temperature impact property of FH36 marine steel subjected to ultrasonic surface rolling process

Surface integrity, corrosion resistance, and low-temperature impact property of FH36 marine steel subjected to ultrasonic surface rolling process

Enhancing corrosion resistance of mild steel in hydrochloric acid with Chiquita banana sap extract.

The corrosion of metals is still a huge challenge for various industries, and the pursuit of effective treatments ensures environmental sustainability. In this study, we utilized Chiquita banana sap-water extract (BSWE) to prevent mild steel from electrochemical corrosion in a 0.1 M HCl at room temperature. Corrosion resistance was assessed using various electrochemical methodologies, combining with surface characterization techniques. The results showed a high level of effectiveness when the corrosion current density decreased from 3292.67 μA cm-2 (for the sample immerged in the blank solution) to 187.33 μA cm-2 after 24 hours of immersion in the solution containing BSWE at a 2000 ppm concentration, equivalent to corrosion efficiency of 94.32%. Surface characterization revealed diminished corrosion on the inhibited steel surface due to the formation of a protective layer. X-ray photoelectron spectroscopy results demonstrated the presence of BSWE ingredients combining with iron oxides and hydroxides to form a smooth protective layer. Furthermore, theoretical calculations also indicated that the addition of BSWE can reduce steel surface damage when exposing to corrosive environment. The inhibitor based on banana sap extract can be referred to as a sustainable protective coating since it is biodegradable, abundantly available in banana plants and free of other harmful substances.

Evaluation of efficiency of rotary friction welding in obtaining joints from corrosion and heat resistant steel

The efficiency of using rotary friction welding in obtaining joints from 20Cr13 steel has been evaluated. For this purpose, test samples with welded joint and from the base metal were made, and then microstructure studies and tensile tests were carried out. As part of the microstructure study, the structure of the welded joint metal and base metal was determined. As a result of tensile tests, the tensile strength, relative elongation after rupture, and fracture area were determined for the base metal and welded joint specimens. These tests have shown that friction welding can produce joints without the use of heating during welding.

Improvement of centerless grinding process. Part 1. Problem and methodological justifi cation of its solution

The need to process hard-to-process corrosion-resistant stainless steels such as steel grade 12Kh18N10T is growing sharply due to the growing demand for such steels. There was a demand for high-performance grinding of blanks of parts made of such steels. The paper discusses the features and results of the development of an abrasive tool for centerless grinding of one of these parts. The possibility of designing and/or selecting abrasive tools for rational and efficient grinding without cauterization with the required accuracy and roughness of processing has been established. Appropriate recommendations have been developed that reduce the complexity of designing (selecting) an abrasive wheel from 1.5 hours to 2 minutes and reduce the defect of parts to 0.1 % due to surface burns and the error of the obtained part dimensions.

Improving Life Cycle Value of Oil Tankers through Development and Application of Non-coated Low Alloy Corrosion Resistant Steels (NSGP-1,2) in Line with Revision of SOLAS Treaty - Innovative Product for Resource Saving, Longer Life, Optimization and Maintenance Load Reduction

Improving Life Cycle Value of Oil Tankers through Development and Application of Non-coated Low Alloy Corrosion Resistant Steels (NSGP-1,2) in Line with Revision of SOLAS Treaty - Innovative Product for Resource Saving, Longer Life, Optimization and Maintenance Load Reduction

Study of corrosion-resistant steels in hydrogen sulfide-containing environments of oil and gas fields

Hydrogen sulfide corrosion cracking of steel occurs in deposits containing corrosive components - hydrogen sulfide and carbon dioxide (carbon dioxide). The mechanism of corrosion cracking of steel in hydrogen sulfide-containing environments of corrosive oil and gas fields is considered, and factors influencing hydrogen sulfide cracking are identified. Increasing the performance properties of carbon, low-alloy, structural steels resistant to hydrogen sulfide and sulfide cracking was carried out on the basis of improving the composition of the components of chemical elements and the structural state through the choice of heat treatment methods depending on the acidity and temperature of the environment, partial pressures of carbon dioxide and hydrogen sulfide. Laboratory and production tests have shown the durability of the proposed compositions chemical elements of steels to hydrogen sulfide cracking, sulfide cracking and hydrogen swelling in deposits containing corrosive components was 70–80% compared to existing carbon structural steels.

Effect of Sulfide and Chloride Ions on Pitting Corrosion of Type 316 Austenitic Stainless Steel in Groundwater Conditions Using Response Surface Methodology.

This study investigates the corrosion resistance of Type 316 stainless steel as a candidate material for radioactive waste disposal canisters. The viability of stainless steel is examined under groundwater conditions with variations in pH, bisulfide ions (HS-), and chloride ions (Cl-) concentrations. Utilizing response surface methodology, correlations between corrosion factors and two crucial response variables, passive film breakdown potential and protection potential, are established. Cyclic potentiodynamic polarization tests and advanced analytical techniques provide detailed insights into the material's behavior. This research goes beyond, deriving an equation through response surface methodology that elucidates the relationship between the factors and breakdown potential. HS- weakens the passive film and reduces the pitting corrosion resistance of the stainless steel. However, this study highlights the inhibitory effect of HS- on pitting corrosion when Cl- concentrations are below 0.001 M and at equivalent concentrations of HS-. Under these conditions, immediate re-passivation occurs from the destroyed passive film to metal sulfides such as FeS2, MoS2, and MoS3. As a result, no hysteresis loop occurs in the cyclic polarization curve in these conditions. This research contributes to the understanding of Type 316 stainless-steel corrosion behavior, offering implications for the disposal of radioactive waste in geological repositories.

Influence of corrosion-active non-metallic inclusions on the accelerated destruction of the internal surface of the Oplot-M tank barrel

The metallographic features of operational damage to the inner surface of the barrel of the Oplot-M tank were analyzed. It was established that with the movement from the chamber to the cut of the barrel, the number and size of damage decreases, which is related to the distribution of pressures of working gases, temperature and aggressiveness of the environment. It is shown that the damage is placed on the inner surface chaotically and the nature of their destruction is corrosive and corrosive-mechanical in origin. Local analysis of their chemical composition revealed a high oxygen content, which indicates the formation of oxide-hydroxide compounds. The surface layers of the barrel were studied and it was established that a "white" layer with a thickness of ~50 μm and a microhardness of 930 kg/mm2 is formed on the surface, the structure of the inner layer of the steel of the barrel is troostite (HW 225 kg/mm2). &#x0D; The effect of corrosion-active non-metallic inclusions (KANV) on the destruction of the surface of a barrel made of steel 38KHN3MFA was studied. It is shown that more sensitive to changes in the technical state of steel due to degradation are studies of corrosion resistance, microelectrochemical heterogeneity and impact toughness of steel. It was established that the presence of KANV in the steel structure leads to an increase in corrosion currents by 4 times and microelectrochemical heterogeneity, in particular, non-periodic potential peaks of 50-70 and 200-230 mV. Due to the influence of tap water on the surface of the steel, corrosion ulcers of a rounded shape and a size of 50-80 μm were recorded, which contribute to the local corrosion of the steel. The analysis of steel fractures revealed that inclusions of a round shape with a size of 3-5 μm contain impurities of harmful elements Al, Mg, F, which accelerate local corrosion on the surface of the steel of the tank barrel. It is shown that the study of fractures, and not of samples, provides an opportunity to estimate not only the size and density of inclusions, but also their chemical composition.

Enhanced corrosion resistance of epoxy resin coating via addition of CeO2 and benzotriazole

The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied. In this work, CeO2 and Benzotriazole (BTA) were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel. SEM results indicated that the CeO2 grains were rod-like and ellipsoidal in shape, and the distribution pattern of BTA was analyzed by EDS. The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO2 and BTA co-addition; and electrochemical impedance spectroscopy test (EIS) analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating. And the optimal protective performance was provided by the coating containing 0.3 wt.% CeO2 and 20 wt.% BTA, which attributed to the barrier performance of CeO2 particles and chemical barrier effect of BTA. The formation of corrosion products was analyzed using XRD. In addition, the corrosion resistance mechanism of the coating was also discussed in detail.

Corrosion mechanism and microstructure evolution of yttrium-doped marine steel

The effects of Yttrium dosage and heat treatment process on the microstructure, inclusions, and corrosion resistance of marine steel, as well as the electrochemical parameters on corrosion behavior were studied in this work. The results show that Yttrium mainly exists in Yttrium oxide and Yttrium sulfide. In the process of the optimal heat treatment temperature (800°C-5h), the movement of grain boundaries is hindered by the nailing action of Y2O3, which makes the grain size refined. Yttrium can refine the corrosion products and improve the adhesion ability between the corrosion layer and the substrate, which can effectively improve the corrosion resistance of marine steel. The electrochemical parameters mainly affect the proportion and structure of α-FeOOH and α-Fe2O3 in the corrosion layer by affecting the ion diffusion rate or oxygen content, thus affecting the corrosion resistance property. With the increase of temperature, the diffusion coefficient of oxygen in solution increases, and the limiting current density also increases, which is not conducive to the formation of dense corrosion layer and will lead to faster corrosion speed.

Low-angle grain boundary engineering based on texture control for enhancement of corrosion and fatigue resistance in 436L type ferritic stainless steel

Low-angle grain boundary engineering based on texture control for enhancement of corrosion and fatigue resistance in 436L type ferritic stainless steel

Investigating surface integrity, corrosion resistance and biocompatibility of 316L steel using carbon nanotube-assisted EDM process

316L steel employed in biomedical applications has experienced mechanical failure triggered by insufficient biological reactions, a high corrosion rate, and surface impurities. Furthermore, the attenuated surface induced by corrosion and wear releases toxic elements, causing inflammatory effects. The prime aim of this research is to evaluate the carbon nanotube (CNT) based coating for enhancing surface integrity, corrosion resistance, and biological responses. This research also aims to comprehend the relationship between electric discharge machining (EDM) process variables and material properties. Several characterisation techniques, including scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), electron dispersive X-ray (EDX), MTT assays, powder X-ray diffraction (XRD) and potentiodynamic polarisation are utilised. The addition of CNT forms a nanoporous and thin coating of 10.3 μm, resulting in a crack-free surface with an adhesion strength of 23.77 MPa. A low corrosion rate (0.0012 mm/year) and almost 85 % of alive cells are observed on the coated surface of 316L steel. This research shows a method to form carbide and oxide-based coating for biomedical applications.

Characterization of the performance of Ti doped α-C/α-C multilayer coating on SS316L as bipolar plates for PEMFC

In order to improve the corrosion resistance and conductivity of 316L stainless steel (SS316L) in the PEMFC (proton exchange membrane fuel cells) environment, DC-balanced magnetron sputtering was used to deposit Ti doped α-C/α-C multilayer coating on SS316L. The influence of coating structure on its micromorphology and phase composition is characterized, and the coating corrosion and conductivity were further explored. Notably, the investigation reveals that multi-layer structure can inhibit the growth of columnar crystal structure and refine the coating surface, which gradually decreased the coating porosity of from 4.54 % (1 layer) to 0.21 % (4 layers), and the passivation current density decreases to 0.22 μA/cm2 at 0.6 V, remarkably better than the targets. In addition, the introduction of Ti-doped α-C layer further promoted the sp2 hybridization of the coating, its interfacial contact resistance (ICR) value gradually decreased from 5.28 mΩ·cm2 (1 layer) to 2.28 mΩ·cm2 (4 layers) under 1.4 MPa. Therefore, the multilayer composite structure coating significantly enhances the conductivity and corrosion resistance of the SS316L bipolar plate, are more practically applied for commercialization of PEMFC technology.

Differences between Using Mortars and Solutions When Testing Sodium Silicate as Corrosion Inhibitor for Construction Steel

Corrosion inhibitors are regularly used to minimize corrosion progress in reinforced concrete. Nitrite ions are very effective inorganic inhibitors but not environmentally friendly, since they can leach and contaminate the surrounding soil and water [1, 2]. Among other promising inorganic ions, silicate ions are of particular interest due to their low cost and low toxicity, although most results have been reported in pore simulating solutions. There is little information in the literature where silicate ions are evaluated as corrosion inhibitors in mortar or cement pastes. The purpose of this study is to show some contrasts between the effectiveness of silicate ions as carbon steel inhibitors when they are tested in solution or in mortar.The results in solution (ASCl) were obtained in an alkaline electrolyte (pH=13) that simulates good quality concrete contaminated with chloride ions [3,4]. ASCl contains KOH 0.08 mol/L, NaOH 0.02 mol/L, Ca(OH)2 0.001 mol/L and NaCl 0.3 mol/L, so that [Cl-]/[OH-]=3. The solution containing silicate ions (SSCl) incorporates Na2SiO3.5H2O 0.3 mol/L, corresponding to [inhibitor]/[Cl-]=1. The electrochemical evaluation included standard tests such as cyclic voltammograms, polarization curves, electrochemical impedance spectroscopy (EIS) and weight loss tests involving long exposure times. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to investigate the composition of the surface films. The findings for bare rebars demonstrate that the presence of silicate ions in solution may effectively prevent carbon steel corrosion, with an inhibition efficiency greater than 99% and no localized attack seen after 30 days of immersion. It has also been observed that a 24-hour pretreatment at open circuit potential (OCP) in silicate solutions (SS) improves the corrosion resistance of construction steel when tested in SSCl. The polarization curves show higher pitting potential and lower corrosion current intensities when compared to untreated electrodes. XPS spectra show that silicate ions are incorporated into the surface film. Pretreatments in SS produce passive films that are rich in Fe(II), present mainly as oxohydroxides. EIS shows that the film is more resistive and compact. In contrast, the reference pretreatment in the absence of silicates led to surface films composed mainly of Fe(III) oxides and oxohydroxoxides.Tests in mortars were carried out including reinforcement bars (rebars) in mortar prepared with water/Portland cement=0.6 and sand/cement ratio =3. Mix R (for reference) had no admixed inhibitor and mix S incorporated Na2SiO3.5H2O using a 0.3 mol/L solution to replace the water in the mix. Also, samples P contained rebars pre-treated by previous immersion in silicate ions solutions, in mortars with the same composition as mix R. Once cured for 7 days, the mortar samples were immersed in aerated 0.3 mol/L NaCl solution for 3 months. The electrochemical follow-up included periodical evaluation by EIS and Rp. The alkaline reservoir in the mortar (which is the content of insoluble Ca(OH)2) was investigated by thermogravimetric analysis. Also, a lixiviation test was designed using pH indicators to verify changes in basicity after a lixiviation process. In mortars R and S, charge transfer and polarization resistance (Rt and Rp) remained lower than 50 kΩ cm2 after the first 15 days. However, Rt and Rp higher 100 kΩ cm2 were measured for rebars P after 15 and 60 days of exposure. The differences between P and R tend to flatten after 90 days of exposure. This shows that the inhibitor effect of pretreating the rebars (P) is lost over a longer period of time. According to the results from thermogravimetric tests, silicate ions in mortar consume Ca+2 ions, producing NaOH. Since this is more soluble than Ca(OH)2 it lixiviates quicker, causing the pH to decrease. Lixiviation tests support this theory.In summary, silicate ions are very effective corrosion inhibitors when tested in alkaline solutions. When silicates are used to pretreat the rebars the beneficial effect is lost after 90 days. When solutions containing silicate ions replace water in the mortars´ preparation, the inhibitory effect is lost faster due to the consumption of portlandite and the consequent acidification of the mortars.References Gaidis, J.M., Chemistry of corrosion inhibitors. Cement & Concrete Composites, 2004. 26(3): p. 181. Elsener B., Corrosion inhibitors for steel in concrete. State of the art report. London, ed. M. Publishing. 2001. Montes, F., et al., Silicate Ions as Corrosion Inhibitors for Carbon Steel in Chloride-Contaminated Concrete Pore Simulating Solutions. Corrosion, 2020. 76(12): p. 1147-1154.Rolandi A.C. et al. Corrosion Engineering, Science and Technology 57(5) (2022) 455–463. Figure 1

Thin Sputtered Titanium Nitride Layers for Corrosion Protection of 316L Stainless Steel Under PEM Water Electrolyzer Anode-like Conditions

Proton exchange membrane water electrolyzers (PEMWE) electrochemically split the water molecule in order to produce high-purity oxygen (at the anode) and hydrogen (at the cathode). When coupled to a renewable energy source (such as wind or sun), green hydrogen can be synthesized, which may contribute to a massive reduction in carbon dioxide emissions in the so-called “hard-to-abate” industrial sectors, like steel and cement manufacturing.Yet, the elevated capital expenditures (capex) deriving from the use of expensive corrosion-resistant materials undermine the economic competitiveness of the PEMWE technology compared to the main hydrogen production processes, like steam reforming. To date, on the PEMWE anode side, metallic bipolar plates (BPP) and porous transport layers (PTL), are essentially made of titanium coated with precious metal layers (platinum, gold) so as to withstand the corrosive and oxidizing environment. Consequently, BPP and PTL account for more than 60% of the capex of the PEMWE stack [1,2]. Without corrosion protection, the harsh operating anodic conditions may lead to performance-killing release of cationic elements from the BPP and PTL into the catalyst layer and the polymer electrolyte [3]. It may also cause the growth of resistive oxide layers at the BPP and PTL surfaces and the development of undesired interfacial contact resistance (ICR).This contribution will focus on the corrosion protection of the anode side of BPP and will first briefly review the most recent investigations driven by capex reduction, notably based on the replacement of titanium by stainless steels and the application of novel, more cost-effective anti-corrosion coatings [3].In a second part, results on the corrosion protection of 316L stainless steel by thin layers of titanium nitride prepared by DC magnetron sputtering will be presented. The thin TiN coatings were deposited on glass, silicon and 316L stainless steel substrates using a titanium target reacting with nitrogen gas. The crystalline phase, the nanostructure and the composition of the thin films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray reflectivity, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy. The corrosion resistance of the TiN-coated stainless steel was evaluated ex situ using open-circuit potential monitoring and electrochemical impedance spectroscopy in dilute H2SO4 solution in a three-electrode electrochemical cell. The interfacial contact resistance was assessed before and after corrosion testing. The protective properties of titanium nitride coatings on 316L under PEMWE anode-like conditions will be discussed.Acknowledgements The authors gratefully acknowledge the financial support of the French National Research Agency (agreement ANR-22-PEHY-0009 under the France 2030 program as well as agreement ANR-22-CE93-0008-01).

Effect of Selenium on Dissolution of Manganese Sulfide Inclusions in Stainless Steel

The pit initiation sites for commercial stainless steels have been attributed to sulfide inclusions such as MnS. The chemical composition of the inclusions affects the pitting corrosion resistance of stainless steels.1,2 It is known that the inclusion solubility in aqueous solutions affects pitting corrosion resistance. The dissolution of sulfide inclusions produces S species and exposes the bare surface of the steel matrix, resulting in high pitting susceptibility near the inclusions. Selenium is known to improve the machinability of stainless steels. However, the effect of selenium on the dissolution and pit initiation of MnS inclusions in stainless steels remains unclear. In this study, a microelectrochemical technique was applied to analyze the effect of Se on the dissolution and pit initiation of MnS inclusions in stainless steels.Two re-sulfurized stainless steels were prepared by vacuum induction melting: one was Se-free, and the other was Se-added. The specimens were heat-treated at 1373 K for 30 min and quenched in water. After heat treatment, the specimens were polished with 1 µm diamond paste. Polarization curves were measured in 0.1 M NaCl and 0.1 M Na2SO4. An optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray spectroscopy system were used to capture images of the specimen surfaces.

Effect of ultrasonic rolled material layer on the corrosion fatigue resistance of railway axle EA4T alloy steel

Surface treatment has been validated to improve the fatigue crack resistance of engineering components, while the coupling effect of corrosive atmosphere and external loading is relatively less reported with detailed experimental studies. In this study, gradient structure (GS) axle EA4T alloy steel specimens were prefabricated by using the ultrasonic surface rolling process (USRP), and their corrosion fatigue resistances were investigated. First, the optimal USRP parameters were determined via orthogonal tests. After the USRP treatment, the microstructure, surface topography, surface roughness, residual stress, and electrochemical corrosion behavior were measured to characterize the surface under various conditions. The electrochemical tests results indicated that the compressive residual stress (CRS) is an important factor in improving the corrosion resistance of axle steel. Rotating bending fatigue tests in both air atmosphere and corrosion liquid showed that the fatigue and corrosion fatigue performances could be significantly improved with the strengthened layer obtained via the USRP. Factor separation analyses substantiated that the remarkable enhancement of fatigue and corrosion fatigue strengths can be mainly attributed to the CRS introduced by the surface strengthening treatment. Simultaneously, the GS layer and hardened layer exhibited a synergistic effect.