Excessive P content (≥ 10 wt%) easily leads to cracks on the surface of electrodeposited NiP coatings, causing rapid deterioration of corrosion performance. This study uses picosecond laser remelting ...(LR) technology to close cracks and improve corrosion performance. The influence of the laser parameters on the quality of laser-remelted (LRed) coatings in ambient air is discussed in detail, and the corrosion performance is evaluated through electrochemical corrosion tests. The results indicated that the scanning rate, laser power, and repetition frequency significantly affect the degree of crack closure and LRed defects. For cracks of similar sizes, both multiple-LR with a lower power (10.4 W, five times) and single-LR with a higher power (19.2 W, once) achieved an excellent crack closure. After single-LR, the surface roughness increased from 3.9 ± 0.3 nm to 33.4 ± 3.2 nm. In addition, the LRed layer crystallized from the initial amorphous state. Although the energy-dispersive spectroscopy results indicated that the oxidation behavior during the LR process was insignificant, X-ray photoelectron spectroscopy showed that the surface composition evolved from Ni/Ni–P compounds to Ni–POx after LR. Electrochemical corrosion tests indicated that the corrosion current density decreased approximately three times from 9.19 × 10−6 to 2.91 × 10−6 A/cm2 after LR. Moreover, the corrosion mechanism shifted from the original stress corrosion to pitting corrosion. Thus, the LR technology can effectively improve the corrosion performance and reduce the issues caused by cracks.
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•Picosecond laser remelting removes surface cracks in NiP coating.•Laser remelted quality mainly affected by laser power and spot overlap rate.•The corrosion rate after laser remelting reduces by approximately three times.•The corrosion mechanism evolved from stress to pitting corrosion.
The effect of nanosized NbC precipitates on electrochemical corrosion behavior of high-strength low-alloy (HSLA) steels in 3.5%NaCl solution has been investigated by the means of precipitate ...modulation, microstructure observation, electrochemical and immersion tests. The results showed that NbC precipitates markedly enhance the corrosion resistance of the H-contained steel, and the mechanism is that the plentiful and highly dispersed nanosized NbC particles acting as massive and effective hydrogen traps play a decisive role in the resistance to hydrogen activated corrosion. Moreover, it is evident that the inhibiting effect is related with the amount, size and distribution of the precipitates, and the optimized microstructures and precipitated phases improve the mechanical properties and resistance to hydrogen activated corrosion of HSLA steel.
•NbC precipitates enhance the corrosion resistance of H-contained HSLA steel.•The mechanism is nanosized NbC acting as H traps with high activation energy.•The amount, size and distribution of the precipitates are effective factors.
TA2 pure titanium (Titan Grade 2-EN) is commonly used in marine and biomedical applications due to its outstanding biocompatibility and resistance to corrosion. Nevertheless, the limited hardness of ...TA2 presently reduces the service life of the components. Directed energy deposition (DED) technology can improve the properties of conformal materials, opening up new possibilities. In this work, 8% micro-TiC/TA2, 8% nano-TiC/TA2, and 4% micro/4% nano-TiC/TA2 composites were fabricated by DED to investigate the effects of different scales of TiC reinforcement on the properties of TA2. The majority of micro-TiC remaining unmelted in the composite, exhibiting only a small amount of micro-TiC dissolution. In comparison, the nano-TiC/TA2 displays a conspicuous dendritic structure with well-developed dendritic growth, boasting up to three dendrites. In contrast, the 4%micro/4%nano-TiC/TA2 exhibits a mixed crystal morphology, characterized predominantly by dendritic growth along the unmelted TiC, with other TiC phases also present in the deposited layer. Performance tests demonstrated that TiC can increase the microhardness of titanium. The 4% micro/4% nano-TiC/TA2 composite achieved the highest average microhardness of 542 HV0.2, representing a 160.58% increase compared to TA2. Additionally, the composites demonstrated improved corrosion resistance relative to TA2, with the 8% micro-TiC/TA2 composite exhibiting the best corrosion resistance. This outcome can be attributed to the effective physical barrier properties of the micron-sized TiC.
•The directed energy deposition technique was employed to prepare TiC/TA2 composites.•An innovative proposal was put forth for the simultaneous utilization of micro- and nano-scale TiC-reinforced pure titanium TA2.•This resulted in a remarkable increase of up to 160.78% in the hardness of the composites.•The micron/nano-TiC/TA2 composites exhibited a substantial improvement in both hardness and corrosion resistance when compared to the original materials.
•The micro-pit structure formed on the IN718 surface is the main influencing factor for the surface quality enhancement.•The corrosion behaviour of the IN718 was investigated by electrochemical ...techniques in C6H5K3O7 solution.•The ligand structure in C6H5K3O7 solution dramatically beneficial to eliminate the electrolytic products in ECM.•The reaction mechanism and quantitative corrosion model of the IN718 were discussed in ECM using C6H5K3O7 solution.
The mechanism by which electrolytic products are removed during ECM of Inconel 718 in a C6H5K3O7 electrolyte was clarified. Experimental results revealed that Cit3− ions decrease the amounts of flocculent and insoluble products in the machining region considerably. The resulting passivating film presented a looser, more porous structure than that from a NaNO3 solution. This made the Inconel 718 more prone to electrochemical corrosion. The uniformity and microscale nature of the micro-pit structure dispersed on the machined surface improved substantially as the current density increased. This improved the surface quality dramatically. Finally, the anodic dissolution characteristic models were established.
The corrosion resistance of CrMnFeCoNi coatings with varying TiC contents and the evolution of TiC within these coatings were comprehensively investigated. These CrMnFeCoNi coatings, with different ...TiC concentrations, were fabricated using laser cladding technology. The behavior of TiC evolution in CrMnFeCoNi coatings was observed to follow a distinct pattern. At a TiC loading of 2 wt%, TiC exhibited a dispersed distribution. Interestingly, in coatings loaded with 4 wt% TiC, TiC was observed in various shapes, including elongated, square, petaled, and circular forms owing to the melting of TiC particles under the influence of a high-energy laser beam. The convection action of the molten pool combined several unmelted, partially melted, and precipitated TiC particles, resulting in diverse shapes. Furthermore, increasing the TiC content to 10 wt% led to the aggregation and fusion of TiC into clusters. Additionally, the electrochemical corrosion resistance behavior of CrMnFeCoNi coatings with varying TiC content displayed a significant correlation with the TiC concentration. As the TiC content increased, the galvanic corrosion resistance also increased. At lower TiC content levels, a higher number of electrochemical cells formed between the CrMnFeCoNi matrix and the dispersed TiC, leading to an elevated corrosion rate. In contrast, as the TiC content increased, the dispersed TiC phase fused together, reducing the likelihood of electrochemical cell formation. Notably, the electrochemical corrosion resistance of the CrMnFeCoNi coating containing 10 wt% TiC resembled that of the TiC-free coating.
•The evolution behavior of TiC in CrMnFeCoNi coatings are described.•Corrosion resistance behavior of coating shows markable relation with TiC content.•Dispersive TiC facilitates the formation of galvanic cells between TiC and substrate.
In this study, CoCrFeNiMn high entropy alloy (HEA) composite coatings reinforced with different WC particle contents were prepared by induction cladding technology for the first time. The effects of ...WC particle contents (0–70 wt%) on the microstructure, hardness, wear resistance and corrosion resistance of the coatings were analyzed. The results showed that the coatings prepared by induction cladding exhibited good metallurgical bonding with the substrate. The addition of WC particles led to grain refinement in the CoCrFeNiMn HEA together with second-phase strengthening and solid solution strengthening, improving the microhardness of the coatings. Compared to the average hardness value of 183 HV0.5 for the CoCrFeNiMn HEA coating, the composite coating with 60 wt% WC particle content exhibited the highest average hardness value of 679 HV0.5. The addition of WC particles significantly enhanced the wear resistance of the composite coating, with wear mechanisms including adhesive wear, abrasive wear, fatigue wear and oxidation wear. The composite coating with 60 wt% WC particle content demonstrated outstanding wear resistance, with a specific wear rate value of 0.491 × 10−6 mm3N−1 m−1, representing a reduction of approximately 670 times compared to the CoCrFeNiMn HEA coating. However, the addition of WC particles caused uneven potential distribution within the composite coatings, leading to galvanic corrosion. The WC particles and precipitated carbides increased the defects in the passive film, thus reducing the corrosion resistance of the composite coatings.
•WC/CoCrFeNiMn high-entropy alloy composite coatings were prepared by induction cladding.•WC particles showed dissolution-diffusion mechanism during induction cladding.•Composite coatings showed excellent hardness and wear resistance.•Different phases tended to produce galvanic corrosion in the composite coating.
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•Multilayer coatings mixed different Fe-based powders were investigated.•Microstructure and element distribution between both layers were investigated.•Ni element made alloying ...elements more evenly distributed in the LCed coatings.•Ni element improved impact toughness and corrosion resistance of LCed coatings.•Relationship between hardness and impact toughness of LCed coatings was presented.
Multilayer coatings with Fe-based powders that mixed different elements were prepared in the surface layer of 4Cr5MoSiV1 steel by laser cladding, and the corresponding microstructure and element distribution between both adjacent layers were investigated. Mechanical properties and electrochemical corrosion resistance were subsequently measured and analyzed. Results indicated that there were equiaxed dendrites and netlike eutectic structures at the interfaces between both adjacent layers of multilayer cladding, making the alloying elements more evenly distributed due to the addition of excess Ni element. Furthermore, the introduction and increment of Ni element to the Fe-based alloy significantly improved the impact toughness, and exhibited higher corrosion resistance of the cladding coatings.
Sustainable transportation requires energy-efficient automotive oils, and producing lubricant with more effective additives is the goal. This study investigates alternative oil-soluble ionic liquids ...(ILs) as substitutes for ZDDP additives in automotive gear lubricant (85 W/90) to mitigate environmental impacts. Herein, two novel halogen-free Gemini ILs (N16-2-16P4 and N16-2-16P8) were synthesized. The current study used zinc isopropyl-isooctyl-dithiophosphate (T204) at a 1 wt% concentration in 85 W/90 oil to compare the tribological and physicochemical properties of ILs. The tribological data indicate that the N16-2-16P4 and N16-2-16P8 additives reduce friction coefficient and wear volume by 9–12 % and 7–28 %, respectively, compared to the T204 additive. Eventually, this study presents ILs as eco-friendly oil additives in vehicles and mechanical systems.
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•Novel ionic liquids (ILs) additives (N16-2-16P4 and N16-2-16P8) were synthesized.•Zinc isopropyl-isooctyl-dithiophosphate (T204) additive was used to comparison.•Physicochemical properties of ILs additives in gear lubricant (85 W/90) is studied.•Exploring the key mechanism behind the tribolayer formation by XPS, and TOF-SIMS.•N16-2-16P4 and N16-2-16P8 additives improved anti-wear properties by 7–28 %.
Taking the combination of atomic bond density, in this work, the tetrahedral amorphous carbon (ta-C) layer with high sp3 bond were especially introduced into the sp2-riched graphite-like carbon (GLC) ...coatings, using a hybrid filtering cathodic arc and magnetron sputtering deposition technique. The focus was elaborated on the electrochemical behavior of coatings against the stimulated chloride solutions for marine applications. Results showed that inserting dense ta-C layer significantly encapsulated the intrinsic pore defects within GLC growth, thereafter enhancing the corrosion resistance remarkably. In particular, the coating porosity was reduced from 10.84 % for pristine GLC system to 3.19 % for GLC with ta-C sealing layer, accompanying with a reduction in corrosion current to 7.8 × 10−9 A/cm2 and an increment in protective efficiency to maximum value of 95.49 %. The small angle X-ray scattering (SAXS) analysis evidenced qualitatively that the coating porosity was suppressed greatly, which were well consisted with the enhanced corrosion resistance of GLC coating with ta-C sealing layer. Furthermore, the balance between pores sealing and interfacial matching could be tailored by controlling the thickness ratio of ta-C and GLC layers, enabling the achievement of both the compact structure and the superior corrosion resistance. These observations offer a new promising strategy to develop the protective coatings for harsh marine environment that required both excellent capability against corrosion and friction with long lifetime.
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•GLC/ta-C multilayer coatings were fabricated by a hybrid arc/sputtering deposition system.•Electrochemical behavior was studied in terms of structure changes in coating.•SAXS analysis identified the decrease of pore defects due to dense ta-C layer.•Encapsulating GLC/ta-C multilayer enhanced the corrosion resistance of coating.
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