Reduced Corrosion Resistance Research Articles

Optimization of Welding Process for 825 Bimetallic Composite Pipes Based on Corrosion Testing

Abstract In the process of welding bimetallic composite pipe ring joints, a problem arises where the outer layer of carbon steel dilutes the inner corrosion-resistant alloy lining, resulting in a reduction in corrosion resistance. Therefore, selecting the appropriate welding process and parameters is crucial. This study established manual, semi-automatic, and fully automatic welding processes for welding 825 bimetallic composite pipes, conducted simulated corrosion tests on weld joint ring seams under sulfur-containing conditions, and performed comprehensive evaluations of physical and chemical properties, as well as corrosion resistance. The research findings are as follows: (1) There is a phenomenon of softening in the heat-affected zone of bimetallic composite pipe ring seams. Among them, the fully automatic welding method exhibits significant fluctuations in weld joint strength, higher toughness in the weld and heat-affected zone, and higher hardness values with less variation compared to other welding methods. (2) Under the manual, semi-automatic, and automatic welding processes, the intergranular corrosion rates are 1.08 mm/a, 1.64 mm/a, and 1.11 mm/a, respectively, and the pitting corrosion rates are 0.41 g/m2, 0.25 g/m2, and 0.31 g/m2, respectively. The uniform corrosion rates are 0.0002305 mm/a, 0.0002183 mm/a, and 0.0002197 mm/a, respectively. (3) High-temperature solution heat treatment (above 980 ° C for 30 minutes) can effectively promote the dissolution of carbides into the matrix, improving the intergranular corrosion resistance of alloy 825. The research demonstrates that under sulfur-containing conditions, weld joints obtained using the fully automatic welding process developed in this study exhibit better physical characteristics and corrosion resistance. This can effectively prevent corrosion failures and leakage incidents.

Wear and corrosion properties of low-temperature nitrocarburized 17-4PH SLM components

3D printing has demonstrated manufacturing and economic advantages in terms of customization, flexibility and rapid prototyping of precision complex geometric components. The 17-4PH precipitate hardening steel is notable for its excellent corrosion resistance. This study aims on enhancing the wear resistance of SLM-printed 17-4PH components through interstitial surface hardening. To eliminate microstructural defects introduced by the SLM process, the components were first subjected to solution heat treatment. Following this, a low-temperature nitrocarburizing (LTNC) process was applied at temperatures below 400 °C, resulting in the formation of an interstitial surface layer with an average thickness of approximately 17 μm. Optical microscopy and XRD analyses confirmed the presence of a dual-phase structure composed of expanded BCC and FCC phases within the hardened layer, with no detectable nitride/carbide precipitates. Quantitatively, the LTNC process significantly enhanced the surface microhardness of the components, increasing it to a minimum of 1000 HV0.2. The bulk microhardness also increased from 360 HV0.2 to 480 HV0.2, indicating an aging effect during the diffusion treatment. In terms of performance, LTNC substantially improved the wear resistance of the components. However, a slight reduction in corrosion resistance was observed, attributed to increased surface roughness and the presence of the dual-phase expanded structure.

Electrochemical Behavior of Plasma-Nitrided Austenitic Stainless Steel in Chloride Solutions.

The application possibilities of austenitic stainless steels in high friction, abrasion, and sliding wear conditions are limited by their inadequate hardness and tribological characteristics. In order to improve these properties, the thermochemical treatment of their surface by plasma nitriding is suitable. This article is focused on the corrosion resistance of conventionally plasma-nitrided AISI 304 stainless steel (530 °C, 24 h) in 0.05 M and 0.5 M sodium chloride solutions at room temperature (20 ± 3 °C), tested by potentiodynamic polarization and electrochemical impedance spectroscopy. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are used for nitrided layer characterization. The experiment results confirmed the plasma-nitrided layer formation of increased micro-hardness related to the presence of Cr2N chromium nitrides and higher surface roughness compared to the as-received state. Both of the performed independent electrochemical corrosion tests point to a significant reduction in corrosion resistance after the performed plasma nitriding, even in a solution with a very low chloride concentration (0.05 mol/L).

Assessing the influence of superabsorbent polymers on corrosion resistance of reinforced ultra-high performance concrete exposed to chloride and compound saltwater via electrochemical impedance spectroscopy

The corrosion resistance of ultra-high performance concrete (UHPC) with superabsorbent polymers (SAPs) submerged in deionized water, chloride saltwater, and compound saltwater was studied. The investigated mixtures included a control UHPC mixture and UHPC mixtures with 0.3 % sodium polyacrylates and 0.3 % polyacrylate-co-acrylamide. The corrosion performance was evaluated using electrochemical impedance spectroscopy, while scanning electron microscopy-energy dispersive X-ray (SEM/EDX) analysis was used to analyze micro-morphology changes and chemical composition. Polarization analysis revealed that the control specimens exhibited the highest resistance to chloride and sulfate penetration, resulting in negligible corrosion rates after 240 days (icorr from 0.0013 to 0.0063 µA/cm2). The SAP-modified specimens also showed high resistance, with an initial low corrosion rate (icorr of 0.101 µA/cm2) that decreased to negligible levels after 28 days (icorr from 0.047 to 0.088 µA/cm2). SEM/EDX results revealed that SAPs facilitate the formation of Friedel’s salt and Ettringite crystals in chloride and compound saltwater, contributing to the reduction in corrosion resistance.

Effect of TIG remelting on the microstructure, mechanical properties, and corrosion behavior of 5052 aluminum alloy joints in MIG welding

In this work, the effect of tungsten inert gas (TIG) remelting on the microstructure, mechanical properties, and corrosion resistance of 5052 aluminum alloy joints produced by metal inert gas (MIG) welding is investigated. The results indicate that after TIG remelting of MIG welds, the proportion of dendrites increases in the remelted weld zone (WZ), porosity decreases by 76.9%, and the Fe elements in the second phase become coarser and more segregated. In contrast, the Mg elements form a solid solution with a decreased degree of segregation. In addition, the average grain size of the remelted structure decreases, while the proportion of sub-grain boundaries (SGBs) and the kernel average misorientation (KAM) values increase. Moreover, the heat-affected zone (HAZ) widens, and the grains become coarser. An increase of 4.5% in tensile strength and 20.0% in elongation was observed in the TIG-remelted joints after TIG remelting. Electrochemical and immersion tests on the TIG-remelted microstructure showed reduced corrosion resistance. Electrochemical tests mainly exhibited galvanic corrosion, resulting in the formation of pits. The types of corrosions observed in the immersion test differ from those in the electrochemical test, primarily exhibiting exfoliation corrosion and pitting corrosion. A higher geometric dislocation density (ρGND) in the structure increases the susceptibility to corrosion.

Comparative corrosion behavior of three titanium alloy base materials and their welds in a simulated chimney environment

This study investigates the corrosion behavior of titanium alloys (TA2, TC4, TB6) in a 3 % sulfuric acid flue gas environment using electrochemical tests and microscopic analyses (SEM/EDS, XRD, metallographic microscopy). Results show that TA2 base metal has lower corrosion resistance compared to its weld metal, while TC4 and TB6 exhibit opposite trends. Specifically, TC4 and TB6 base metals have lower corrosion current densities (0.9 and 0.5 μA/cm2) and higher corrosion potentials then their weld metals (1.93 and 2 μA/cm2). In contrast, TA2 base metal showed higher corrosion current density (2 μA/cm2) than its weld metal (0.35 μA/cm2) and HAZ metal (0.16 μA/cm2).Microscopic analyses reveal β phase transitions in TC4 and TB6 weld areas, leading to larger grain sizes and reduced corrosion resistance. Conversely, TA2 retains finer grains post-welding, enhancing its corrosion resistance. These insights clarify weld corrosion effects and provide valuable guidance for industrial applications of titanium alloys, particularly in designing and maintaining titanium alloy chimneys.

Influence of heat treatment on the microstructure evolution and corrosion performance of biodegradable Zn-Mg alloys

Zinc and zinc-based alloys have garnered increasing attention as biodegradable materials due to their excellent mechanical properties, lower degradation rates compared to magnesium, and favorable biocompatibility. This study investigates the impact of homogenization treatment on the microstructure and corrosion behavior of Zn-Mg alloys using scanning electron microscopy, X-ray diffraction, hardness testing, and accelerated corrosion immersion tests. The results reveal that homogenization treatment induces the fusion of eutectic cells within the alloys, causing significant morphological alternations in the eutectic structure and varying proportions of the Mg2Zn11 phase, These changes notably affect material properties. The raised content of Mg2Zn11 phase in the eutectic structure correlates with higher hardness but reduced corrosion resistance, whereas the reduced Mg2Zn11 phase content leads to enhanced corrosion resistance. Furthermore, in-situ corrosion observations demonstrate that corrosion initiates at the eutectic phase, with corrosion pits forming due to the ion release as corrosion progresses, leading to gradual enlargement of the corrosion pits. In summary, this study provides comprehensive insights into the microstructural changes in Zn-Mg alloys and their impact on corrosion resistance, offering valuable references for their engineering applications.

Corrosion behavior of combination of laser beam welded UNS S32304 + SS304L in 3.5% NaCl solution

This study investigates the corrosion behavior of laser beam-welded UNS S32304 and SS304L in 3.5% NaCl solutions, focusing on the effects of temperature. The primary objective is to enhance the understanding of corrosion resistance in welded materials and inspire advancements in corrosion mitigation strategies. The methodology involves assessing corrosion resistance under varying temperatures and comparing the performance of laser beam welding (LBW) with that of the base metals. Scanning electron microscopy analysis reveals effective passivation, while quantitative analysis indicates differences in chloride ion coverage between the weld metal and base metals. Tafel plots and electrochemical impedance spectroscopy demonstrate enhanced corrosion potential and improved barrier properties for the weld metal. Results indicate a marginal reduction in corrosion resistance at 50 °C for both base metals. LBW metals corrosion resistance demonstrates superior performance, with only 5% reduction in breakdown potential compared to 10% in base metals. Compared to the base metal, it exhibits a substantial reduction in corrosion rate, ranging from 60 to 75%. This supports enhanced corrosion resistance and material stability. Additionally, similar results are observed after the analysis with scanning electron microscopy images, reinforcing the efficacy of LBW in improving corrosion resistance of LBW UNS S32304 and SS304L. These findings underscore the potential of LBW for applications requiring robust corrosion performance. By contributing to the understanding of the corrosion behavior of laser beam-welded materials, this study addresses a critical research gap in material science and corrosion engineering. Future research may explore long-term durability and corrosion resistance under diverse environmental conditions to further elucidate the mechanisms driving the observed differences in corrosion behavior.

Formulation of silver-loaded zeolitic imidazole framework-67 and its antibacterial coating on titanium surface for bioimplant applications

Artificial bioimplant infections caused by bacteria have been a persistent problem that requires re-surgery and is harmful to human tissue. A facile, inexpensive and stable antibacterial agent coating can be a significant alternative. The present study attempted to construct titanium (Ti) implant coated with silver loaded zeolitic imidazole framework (ZIF)-67 (Ag@ZIF-67)-chitosan composite through a casting technique. The as-prepared nanocomposite and its coating were subjected to various characterization techniques, including XPS, XRD, SEM, and TEM to understand the material properties. Antibacterial activity was assessed through a standard spread-plate method, and the cytocompatibility of the fabricated materials was examined upon the skin fibroblast (L929) cell line. Corrosion studies were performed by using anodic polarization and impedance methods. The bactericidal efficacy of the coating was validated in vivo by utilizing a subcutaneous mouse model. The nanocomposite and coating exhibited a significant antibacterial efficiency of above 95 % against S. aureus and E. coli as the combined release of Co2+ and Ag+ ions entailed cellular membrane disintegration. The Ag@ZIF-67 composite revealed negligible cytotoxicity and its coating exhibited strong bone cell attachment. In contrast to pure Ti surface, the Ag@ZIF-67-chitosan coated Ti exhibited a minor reduction in corrosion resistance and modifications to its passivation properties as a result of the formation of a galvanic cell. A remarkable antibacterial effect was evinced through the in vivo experiments demonstrating a complete disinfection with 99 % of S. aureus lysis with no bacterial growth in the nearby healthy tissues. In conclusion, the current results demonstrated that the fabricated Ag@ZIF-67 could be applied as an antibacterial coating material of Ti for bioimplant applications.

Elevated temperature rusting characteristics of UNS 31254 weldments within the operational confines of fossil fuel-fired plants and municipal waste incinerator surroundings at 700 °C

ABSTRACT This study investigates the air oxidation and rusting traits of fully austenitic alloy 254 stainless steel samples at 700°C after pulse current gas tungsten arc welding (PCGTA) and CO2 laser beam welding (CO2 LBW), with or without molten salt, relevant to coal-fired plants and waste incinerator settings. Among the weldments studied, CO2 laser weldments demonstrate greater resilience to corrosive gas and salt amalgamation, as well as air oxidation, compared to gas tungsten arc weldments, possibly due to thermal disparities and microstructural differences inherent in the welding processes. Protective oxides enhance corrosion resistance in air-oxidised samples, while corrosive compounds like CrS, Cr2K2O7, etc., reduce corrosion resistance and promote spallation in salt-degraded material. A thermogravimetric approach was used to assess rusting effects, alongside microstructural analysis employing optical, Scanning electron microscopy/ Energy dispersive x-ray spectroscopy (SEM/EDS), and X-Ray diffraction analysis (XRD) techniques.

Effects of Al2O3 micro/nanoparticles on the microstructure and corrosion behavior of W–Ni–Fe matrix through spark plasma sintering process

The purpose of this research is to examine the effect of Al2O3 micro/nanoparticles on the properties of the W–Ni–Fe matrix. The study involved analyzing the microstructure, hardness, density, and corrosion behavior of the W-4.9Ni-2.1Fe matrix with varying percentages of Al2O3 micro/nanoparticles (0.5, 1, and 1.5 wt%) that were sintered using the spark plasma method. The corrosion properties of different composites were studied using electrochemical impedance spectroscopy, Tafel polarization, and weight loss measurements. Furthermore, microstructural evaluations were carried out on samples before and after corrosion tests using optical and field emission scanning electron microscopy. The results indicated that a 1% increase in the percentage of Al2O3 nanoparticles led to approximately a 16% increase in the matrix hardness. This increase was attributed to the reduction in grain size and the distribution of pores in the nanocomposites. Tafel polarization measurements also showed that adding 1% Al2O3 nanoparticles resulted in an 83% improvement in the corrosion resistance of the W–Ni–Fe matrix in a 3.5 wt% NaCl solution. The improved corrosion resistance of the fabricated nanocomposites was attributed to the uniform distribution of Al2O3 nanoparticles in the matrix and reduction in the cathodic region. However, it was found that the formation of galvanic microcells was a critical cause of corrosion in micro-composites, leading to a reduction in corrosion resistance compared to the W–Ni–Fe matrix. Raman spectroscopy patterns indicated that Fe3O4, Fe(OH)2, NiO, and Ni(OH)2 were the main corrosion products.

Influence of Solution Treatment Process on the Properties of Duplex Stainless Steels: A Comparative Study on Microstructure and Corrosion Properties of UNS S32205 and UNS S32760

The study investigated the effect of the solution treatment process on the corrosion behavior and microstructure of the duplex stainless steel. It was also aimed to reveal this effect comparatively depending on the chemical composition and alloying element content. For this purpose, UNS S32205 and UNS S32760 alloys were treated at 1000 °C, 1020 °C and 1040 °C for an hour. A solution treatment temperature was determined according to Thermo-Calc analysis. The examined samples were characterized by an optical microscope, scanning electron microscope, and XRD analysis. Also, electrochemical impedance spectroscopy and potentiodynamic polarization analyses revealed the corrosion properties of solution-treated samples. Microstructural studies showed that enhanced solution treatment temperature increased ferrite content for both alloys. A lower solution treatment temperature caused the formation of sigma in the microstructure of S32760 alloy. On the other hand, the charge transfer resistance of the passive layer was reduced after solution treatment at 1000 °C and 1020 °C, indicating decreasing corrosion resistance. A higher austenite ratio in S32205 led to pitting, while corrosion resistance improved with higher treatment temperatures. The presence of the sigma phase in S32760 significantly impacted corrosion properties by increasing ion transfer on the surface, leading to reduced corrosion resistance. It was determined that solution treatment at 1040 °C was appropriate for both alloys to achieve the desired microstructure and corrosion properties.

Corrosion behaviors of W-doped laser-cladded high-entropy alloy of AlCoCrFeNi in a simulated sulfur-containing seawater environment

The localized corrosion in a simulated seawater environment is related to sulfide, and few studies have investigated the corrosion behaviors of laser-cladded AlCoCrFeNi high-entropy alloy (HEA) systems in a simulated sulfur-containing seawater environment. Corrosion behaviors of HEA/Wx (x = 0, 5, and 15 wt%) coatings have been worked out by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, X-ray photoelectron spectroscopy (XPS) analysis, and immersion corrosion tests. W-doped HEA coatings can change the ratio of A2 to B2 phases and affect the corrosion resistance. The potentiodynamic polarization and EIS results reveal that a small quantity of W-doped (5 wt%) HEA coatings form a denser passivation film that is particularly resistant to localized corrosion. By analyzing the corrosion behaviors of the HEA/Wx coatings, it was determined that a small amount of W-doped (5 wt%) HEA coatings had better localized and improved corrosion resistance. However, excessively W-doped (15 wt%) HEA coatings have reduced corrosion resistance. The Mott-Schottky analysis revealed that the HEA/Wx coatings (x = 0, 5, and 15 wt%) have the property of P–N-type semiconductors. XPS analysis was used to analyze the film composition. The results demonstrated that the passivation film combined Cr2O3, Al2O3, Fe2O3, and WO3. Based on the immersion corrosion test, localized corrosion types were mainly intergranular and crevice.

Tribological and corrosion behavior of hydrided zirconium alloy

Zirconium alloys (Zr-alloys) are used for the core components of nuclear reactors due to their exceptional properties, which make them suitable for the given applications such as low neutron absorption cross-section, good corrosion resistance, good wear resistance, good mechanical stability at high temperatures etc. The coolant water that flows inside the pressure tube contains LiOH to control the pH value of the coolant water, which can cause corrosion. The flow of coolant water produces low amplitude vibration, which can cause fretting wear of the components. Further, the coolant water at high temperature causes the hydride formation in the material, degrading the properties of zirconium alloys. The safe working of nuclear reactors is the prime objective, and the corrosion and wear behavior of the core components must be explored to prevent possible failure. Fretting wear or tribo-corrosion experiments were conducted on Zr‐2.5Nb alloy against SS-410 for varied fretting duration to understand the tribological response. Electrochemical corrosion experiments were performed under the aqueous solution of LiOH (10.4 pH) using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization technique. The comparison was made between the tribological and corrosion response of unhydrided‐Zr‐2.5Nb alloy (Zr‐2.5Nb) and hydrided- Zr‐2.5Nb alloy (Zr‐2.5Nb‐H). The hydride formation causes the reduction in corrosion resistance of Zr‐2.5Nb alloy. The oxide layer is formed during the wear and corrosion process which protects the material from further wear and corrosion respectively.

Addressing the strength-corrosion tradeoff in 316 L stainless steel by introducing cellular ferrite via directed energy deposition

Typical cellular structure composed of high-density dislocation tangle can lead to high strength in directed energy deposition 316 L stainless steel, but with reduced corrosion resistance in acid solution due to accompanied element segregation. Herein, a unique cellular structure consisting of a ferrite phase is manufactured to address the strength-corrosion tradeoff via a direct energy deposition process. The relationship between strength and microstructural features, such as grain type, ferrite phases, and dislocations, as well as the relationships between corrosion resistance and these microstructural characteristics, are identified. Cellular ferrite retains the beneficial effect of the cellular structure on increasing strength and changes the material from a pure austenitic phase to an austenite-ferrite biphasic structure. The ferrite phase has a lower corrosion potential, which promotes the rapid formation of Cr- and Mo-rich corrosion product layers. It can avoid the unfavorable effects of element segregation and suppress the corrosion rate in acid solution. This study shows that directed energy deposition has the potential to customize the microstructure through a printing process that introduces a cellular ferrite phase to improve its corrosion resistance in acidic solutions as well as its strength and ductility.

Effect of Microstructure on Corrosion Resistance of Ultralow‐Carbon Bainitic Steel

The effect of microstructure on the corrosion behaviors of ultralow‐carbon bainitic (ULCB) steel in 3.5 wt% NaCl solution is discussed. Four ULCB steel specimens with different microstructures are designed via controlling the cooling routes after austenization, namely, furnace cooling (FC), air cooling (AC), oil cooling (OC), and water cooling (WC). Their corrosion behaviors are investigated by alternating immersion test (including weight loss and rust layer observation) and electrochemical tests (including polarization curves and electrochemical impedance spectroscopic measurements). Results show that the corrosion resistance of ULCB steel specimens decreases with increase of cooling rate, that is, in the following sequence: FC > AC > OC > WC. Furthermore, the electron backscatter diffraction characterization and scanning Kelvin probe force microscopy are performed to build the relationship between microstructure and corrosion behaviors of ULCB steels. The reduced corrosion resistance of ULCB steels results from the increased number of microgalvanic couples because of the significantly increased density of grain boundaries with increase of cooling rate.

Anticorrosive barrier coatings modified by core-shell rubber particles: effects on the property transients and premature crack initiation susceptibility of particle type and concentration

AbstractProtective epoxy coatings, as a result of their inherent brittleness, show insufficient resistance towards initiation and propagation of cracks, which can occur as early as during the curing process. To improve premature crack initiation resistance, it is essential to understand the underlying mechanisms. In this work, a solvent-based novolac epoxy, cured with a cycloaliphatic amine, was reinforced with either an epoxypropoxypropyl-terminated polydimethylsiloxane (PDMS), nanoparticles of strontium titanate (SrTiO3), or core-shell rubber (CSR) nanoparticles. The effects on coating property transients, curing-induced internal stress, and premature crack initiation susceptibility of the modifier types and CSR (MX 217 and MX 267) concentrations were investigated. In addition, using a digital microscope, the defect and crack morphology in coatings applied to rigid, flat substrates and inner 90-degree angles were characterized. Finally, to evaluate the anticorrosive barrier performance of the reinforced coatings, an electrochemical impedance spectroscopy analysis was employed. Despite a slightly reduced crack initiation susceptibility, the flexible PDMS chains, due to phase separation, resulted in a deteriorated barrier performance. The inclusion of SrTiO3 nanoparticles also led to a reduced anticorrosion performance, relative to a neat epoxy coating, with a slightly lower crack initiation susceptibility and a minor increase (around 0.2 MPa) in the average internal stress. For 5 wt% MX 217 and MX 267 CSR toughened coatings, the maximum internal stress and crack initiation susceptibility in the series, as well as an associated reduced corrosion resistance, were seen. In spite of a reduction in the elastic modulus, an improved barrier performance and a reduced internal stress and crack initiation susceptibility were observed for 25 wt% MX 217 and 37 wt% MX 267 CSR toughened coatings. To improve barrier properties and avoid premature crack initiation of epoxy coatings, guidelines on modifier selection are provided.

Impact of simulated inflammation and food breakdown on the synergistic interaction between corrosion and wear on titanium

This paper investigates the impact of lactic acid and phosphoric acid additives in artificial saliva (AS), simulating inflammation and food breakdown, on the electrochemical and tribo-electrochemical behavior of titanium. The results showed that, unlike lactic acid, phosphoric acid significantly reduced corrosion resistance, mainly due to local damage and heterogeneities on the passive film. Non-additivated AS caused greater wear volume loss, with mechanical wear identified as the main mechanism. However, when additives were present, a synergistic interplay between corrosion and wear was observed. The study concludes that prolonged exposure to food breakdown could accelerate material degradation in titanium.

Design of a smart protective coating with molybdate-loaded halloysite nanotubes towards corrosion protection in reinforced concrete

Using protective coatings is widely acknowledged as an effective strategy for preventing the corrosion of reinforcing steel and improving the durability of reinforced concrete structures. Nevertheless, a common challenge faced by the traditional coatings lies in the significantly reduced corrosion resistance due to its damage and cracking during the service life. Accordingly, a smart protective coating with active anti-corrosion performance was successfully designed and synthesised in this study, including a PA-polyvinyl alcohol (PVA) pretreatment layer and the molybdate-loaded etched halloysite nanotube (EHNT@MO). The PA-PVA grafting solution could fix EHNT@MO on the steel surface due to its strong chelating ability, resulting in an increased thickness of the pretreatment layer (∼5 μm) and exceptional barrier properties. Moreover, the release of molybdate from EHNT enables the smart protective coating to actively repair corrosion pits, thereby exhibiting excellent anti-corrosion performance. As a newly developed smart protective coating, it is expected to confer multifunctional properties to reinforcing steel in cementitious materials when subjected to aggressive environments.

Fabrication of TA2–304 SS laminated metal composite using directed energy deposition-arc: Microstructure, mechanical property, and corrosion resistance

Conventional fabricating methods of TA2–304 SS laminated metal composite (LMC) (e.g., hot rolling, hot stamping, and explosive welding) have difficulty in removing brittle TiFe intermetallic compounds (IMCs) and are not suitable for the preparation of the small size structure components or transition joints. Additive manufacturing of LMCs has the potential to achieve the desired microstructure, properties, and structure. In this study, TA2–304 SS LMC, which has been extensively employed in pipe flanges of nuclear plants and bows of sonar dome, was well fabricated by utilizing directed energy deposition-arc (DED-arc) and copper‑nickel alloy transition interlayers, and the formation of brittle TiFe IMCs was suppressed. The results of this study indicated that the standard deviation of the height of the surface morphology reconstructed by adopting Python VTK technique was evaluated as 0.67. Furthermore, copper‑nickel transition interlayers possessed the capability of isolating Ti from Fe atoms through the formation of laminar-distributed microstructure. Specifically, the Interlayer1 was comprised of (Fe, Cr) grains with different shapes and small-size (Cu) equiaxial grains, Interlayer2 covered large-size (Cu, Ni) dendritic grains and intergranular (Cu), and the TA2 layer comprised α-Ti and Ti2Cu. The result also showed that thermal cycle-induced recovery and recrystallization and diffusion-induced elemental interaction accounted for the different microstructures. Moreover, the interface between the TA2 and Interlayer2 layers contained TiCu4 + (Cu), Ti3Cu4 + TiCu4, Ti2Cu + TiCu, and TiCu + Ti2Cu eutectoid microstructures, which resulted in the highest hardness of 450Hv as well as crack initiation and extension. Furthermore, due to the uniform-distribution of microstructure in the absence of brittle IMCs, the average shear strength was 234.0 MPa, which reached the strength of the conventional method and conformed to the standard requirements. Multiple groups of galvanic reactions between different transition materials can result in reduced corrosion resistance, and the oxidation-reduction reactions can lead to the formation of massive oxides.