Due to low density and high specific strength, titanium alloys have been widely used for marine applications. However, the severe wear and corrosion of titanium alloy components is still a problem. ...To alleviate this problem, protective coatings are applied. In here, the influence of Mo content on the protective performance of CrMoCN coating for Ti-6Al-4V substrate has been investigated. The short- and long-term corrosion resistances of coating in artificial seawater are studied using an electrochemical workstation with three-electrode configuration. The tribological behaviors of CrMoCN coating sliding against Al2O3 ball are evaluated using a ball-on-disk tribo-meter. The results reveal that the CrMoCN coated samples have higher wear- and corrosion-resistances than the bare substrate. The CrMoCN coating with 8.1 at.% Mo displays the highest values of OCP (0.22 V), Rct ((8.639 ± 0.270) × 107 Ω·cm2) and Rp ((3.04 ± 0.24) × 106 Ω·cm2). However, their protective performances are degraded in the long-term, and then the Rp of CrMoCN-2.5 coating continuously decreases from (5.99 ± 0.47) × 105 Ω·cm2 at 7 days to (0.13 ± 0.01) × 105 Ω·cm2 at 35 days. With an increase in the Mo content, the friction coefficient of CrMoCN coating/Al2O3 tribopair decreases from 0.36 to 0.31 while the coating wear rate increases from 4.65 × 10−7 mm3/Nm to 1.01 × 10−6 mm3/Nm.
•CrMoCN coating with 8.1 at.% Mo content shows the most excellent corrosion resistance.•The electrochemical and mechanical properties of CrMoCN-2.5 coating after long-term immersion in seawater are elucidated.•The friction coefficients of CrMoCN/Al2O3 tribo-pairs reduce with an increase in the Mo content.•The wear rates of coatings increase linearly with the increasing Mo content.
•Effects of high-frequency vibration on residual stress, impact toughness and electrochemical performance of S355 steel welded joint are studied.•The mechanism of the high-frequency vibration on the ...impact toughness and the electrochemical corrosion resistance is discussed.•The residual tensile stress is effectively decreased, the impact toughness is improved, and the electrochemical performance is improved by high-frequency vibration.
The influences of the high-frequency vibratory stress relief (VSR) on the surface residual stress, the impact toughness, the fracture morphology, the chemical composition, the microstructure, and the electrochemical corrosion resistance of S355 steel welded joints were analyzed. The improvement mechanism of the high-frequency vibration on the impact toughness and the electrochemical corrosion resistance were discussed. The SEM and EDS results indicated that the plasticity of the metal material was enhanced since the size and depth of the dimples in each region of the impact specimens were increased, the uniformity was better. In this case, the impact toughness of the S355 steel welded joints after the high-frequency VSR was improved. Moreover, the electrochemical corrosion resistance of the heat affected zone of the S355 steel welded joints was improved by the high-frequency VSR. Meanwhile, the grain size and the microstructure morphology of the S355 steel welded joints remained almost the same before and after the high-frequency VSR. The findings confirm that the reduced residual tensile stress could improve the impact toughness and the electrochemical corrosion resistance of the S355 steel welded joints.
Corrosion behavior of friction stir welded Al-Cu alloy and Al-Cu-Li alloy joints were revealed via immersion, intergranular, exfoliation and electrochemical corrosion. Precipitation-driven corrosion ...was discussed based on experiments and theoretical modeling. The corrosion potential of the entire joint was nobler than base materials, which was mainly attributed to solid solution and precipitation evolution of high equilibrium potential elements. The macro/micro galvanic effect induced by the redistribution of copper was studied with a numerical model to explain the relationship between precipitation evolution and corrosion resistance. Reducing heat input by increasing welding speed was an effective strategy to improve corrosion resistance.
•The corrosion resistance of friction stir welded 2195/2219 joint was enhanced.•Dissolution of the precipitates contributed to better corrosion resistance.•Macro and micro corrosion behaviors intra and inter micro zones were discussed.•Wagner Kampmann precipitation evolution was applied to analyze corrosion.•Reducing heat input can effectively improve corrosion resistance.
The morphology of γ′(Ni3Al) phase is essential for the performance of laser additive manufacturing repaired Ni-based single crystal superalloy, thereby, it is of crucial significance to manipulate γ′ ...phase in order to optimize the corrosion performance of laser cladded component. In this research, the morphology of γ′ phase is tuned via different heat treatments. The microstructure and corrosion behaviors of laser repaired superalloy are analyzed by electron microscopy and electrochemical measurements. It is found that the electrochemical corrosion resistance of as-deposited part is superior than that of the substrate, and the dominant morphology of γ′ phase changes from spherical shape to cuboidal shape and to rafted morphology with increasing heat treatment temperature. The corrosion resistance peaks at 1050 °C, attributing to the combined effects of decreased volume fraction of γ′ phase and favored distribution of Cr, W, and Al. Our results offer a practical means for the post-repair heat treatment of single crystal turbine blades.
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•γ′ changes from spherical to cuboidal and to rafted microstructure with temperature.•The corrosion resistance rises and then declines with increasing temperature.•The favorable distribution of Cr, W, and Al leads to the optimal corrosion resistance.
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By means of first-principles calculations, we have proposed an ab initio modeling to establish a formula between the hydrogen evolution rate and its overpotential of hydrogen ...evolution reaction (HER), relating with three different rate determining mechanisms, when Volmer reaction, Tafel reaction and Heyrowsky reaction are the rate determining steps of the entire reaction, respectively. Within this modeling, the free energy (ΔGH*) of the adsorbed hydrogen atom and the concentration of hydrogen ions in the solution have been correlated to the exchange current density. The hydrogen evolution modeling has been validated by available experimental results. Furthermore, by combining the previously proposed first-principles modeling of the anodic dissolution and this modeling of the HER in the electrochemical corrosion, the polarization curves of the 18 crystallographic surfaces of pure Mg have been theoretically derived. It has been found that in a neutral solution (pH=7) the corrosion current densities (icorr) of the 18 crystallographic surfaces range from 10−3.477 to 10−0.455 A/cm2 and their corresponding corrosion potentials (Ecorr) range from −1.36 to −0.892 VSHE, respectively. The base (0001) surface exhibits a lower corrosion rate of 10−3.345 A/cm2, whereas the crystal (213¯0) surface has a fast corrosion rate of 10−0.455A/cm2. The calculations even reveal that except for Ag, all the other alloying elements considered here accelerate the rates of the cathodic HER. In agreement with theoretical results, the experimentally measured polarization curves of the Mg-1Zn and Mg-2Sn alloys verify that both Zn and Sn additions accelerate the rate of the HER of Mg.
This study analyzed cavitation erosion (CE) and cavitation erosion-corrosion (CE-C) of single-phase face-centered cubic structured Fe23.7Co23.8Ni23.8Cr23.7Mo5 multi-principal element alloy (MPEA) ...with varying grain sizes obtained through post-deformation annealing (PDA). The average grain sizes of the samples after annealing at 1100 °C for 60 s, 1150 °C for 60 s, and 1100 °C for 200 s are 4.1 µm, 10.3 µm, and 15.2 µm, respectively. Among them, the 4.1 µm sample exhibits the best combination of high ultimate tensile strength (889 MPa) and large elongation (40.3%), as well as good electrochemical corrosion resistance in NaCl solution. Under the conditions of CE and CE-C for a duration of 10 h, the 4.1 µm specimen exhibits cumulative mass losses of approximately 1.4 mg and 2.6 mg, respectively. In contrast, under identical conditions, the 316 L SS registers cumulative mass losses of approximately 16.7 mg and 24.8 mg, respectively. Due to the excellent mechanical properties and work hardening ability of the 4.1 µm sample, it can effectively resist the plastic deformation caused by cavitation erosion, reducing mass loss. In addition, the stable passivation film enhances its resistance to Cl- destruction, thus demonstrating notable corrosion resistance. Ultimately, under conditions where cavitation erosion and corrosion coexist, these combined properties enable the 4.1 µm sample to exhibit the least mass loss and damage.
•Cavitation erosion-corrosion (CE-C) behavior of FeCoNiCrMo5 MPEA in NaCl solution was studied.•MPEA’s tensile strength, corrosion, and CE-C resistance decreased as grain size grown.•Cavitation erosion mechanisms of the MPEA with different grain sizes were elucidated.•Synergistic damage mechanisms of cavitation erosion and corrosion were revealed.
The TiB2 particles reinforced AlSi10Mg composites were prepared by selective laser melting (SLM). The effect of TiB2 particles on the microstructure and electrochemical corrosion properties of the ...Al-based composites was studied. The phase structure was examined by X-ray diffraction (XRD). The morphology was observed by the metallographic microscope and scanning electron microscope. The corrosion behavior was evaluated by Potetiodynamic polarization and electrochemical impedance spectroscopy. In this experiment, the corrosion resistance of TiB2 aluminum matrix composites with different contents in 3.5 % NaCl solution at 25 °C (room temperature) was mainly tested. Firstly, the addition of TiB2 can effectively improve the morphology of the molten pool. Secondly, the addition of TiB2 will change the corrosion type of Al matrix composites: from uniform / comprehensive corrosion to pitting corrosion, which is easy to occur around TiB2 particles. Through the experimental data, it was observed that the corrosion potential of the sample was positively shifted by adding TiB2, and the electrochemical stability was improved. The addition of TiB2 can effectively reduce the corrosion tendency of the samples. When the content of TiB2 increases to 5 %, the pitting corrosion occurs seriously, and when TiB2 is added to 15 %, the corrosion resistance of the samples increases again.
Selectivity for C–C coupled products remains a major challenge for electrochemical CO2 reduction. Herein, we report a facile method by modifying a Cu foil surface with a layer of porous carbon. The ...structure of carbon has a major influence on C1 and C2,3 product selectivity. A carbon aerogel modifier leads to higher C2,3 product formation than that of a carbon black modifier, demonstrating the non-innocent role of carbon materials. In both cases, major surface reconstruction on the Cu foilsuch as pitting and particle formationis observed during electrocatalysis. In addition, the restructured Cu surface shows distinctly lower activity toward CO2 reduction when the carbon modifier is removed. This is likely due to the fact that the carbon modifiers influence the product distribution by (i) modulating the local pH and CO2 concentration by serving as a highly porous and hydrophobic barrier, and (ii) restructuring the metal surface that generates more active sites. Our findings illustrate that the carbon in carbon-based catalysts can have an disproportionate role in directing product formation in electrocatalytic carbon dioxide reduction.
One of the major subjects for evaluating the corrosive conditions in the PWR primary coolant was to determine the optimal hydrogen concentration for mitigating PWSCC without any adverse effects on ...major structural materials. As suitable procedures for evaluating the corrosive conditions in PWR primary coolant, a couple of procedures, i.e. water radiolysis and ECP analyses, were proposed. The previous article showed the radiolysis calculation in the PWR primary coolant, which was followed by an ECP study here. The ECP analysis based on a couple of a mixed potential model and an oxide layer growth model was developed originally for BWR conditions, which was extended to PWR conditions with adding Li
+
(Na
+
) and H
+
effects on the anodic polarization curves. As a result of comparison of the calculated results with INCA in-pile-loop experiment data as well as other experimental data, it was confirmed that the ECPs calculated with the coupled analyses agreed with the measured within ±100 mV discrepancies.
Graphene has long been considered a superlative protection material due to its extraordinary characteristics and properties. However, its high electrical conductivity can facilitate the ...electrochemical corrosion of metal, which strongly limits its anti-corrosion applications. Here, we developed a facile fluorination strategy to suppress the corrosion promotion activity of graphene. Fluorinated reduced graphene oxide (FrGO) exhibited low electrical conductivity (3.643 × 10−13 S/cm), which proved unable to trigger micro-galvanic corrosion. Furthermore, acridizinium ionic liquid (IL) MAcBr was noncovalently grafted on FrGO to achieve the well dispersion in the polymer matrix. Results revealed that FrGO-IL nanohybrid can be stably dispersed in the epoxy resin. Electrochemical impedance spectroscopy revealed that incorporating a small percentage of FrGO-IL into waterborne epoxy matrix effectively improved the corrosion resistance performance of the coating by exerting the superior shielding effect and inhibiting the ability for micro-galvanic corrosion. Moreover, local electrochemical and scratching tests further confirmed that FrGO-IL significantly reinforced the corrosion protection capability of waterborne epoxy coating because the well-dispersed nanohybrid enhanced the integrity of the composite coating, effectively utilizing the labyrinth effect. Our finding could inspire the development of new graphene-based materials with superior protection properties for metal materials.
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