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Layered double hydroxide (LDH) has been widely used as a two-dimensional nanomaterial in the corrosion protection of epoxy (EP) coatings due to its physical barrier properties and excellent ion exchange capacity. However, conventional LDH with an interlayer of NO3– (LDH-NO3) is prone to failure in corrosive environments due to its limited ion exchange ability. It is demonstrated in this work that, compared to an EP coating containing LDH-NO3 (EP/LDH-NO3), EP coatings containing ZnAl-LDH-MoO42– (EP/LDH-MoO4) and ZnAl-LDH-PO43– (EP/LDH-PO4) have stronger corrosion resistance and self-healing abilities. This is attributed to the trapping effect of corrosion anions between the LDH layers by the inhibitor ions, which prevents the direct contact of the corrosion anions with the substrate. In addition, the inhibitor ions can combine with metal ions from the substrate to form insoluble complexes in localized corrosion areas, thus blocking further deterioration. Furthermore, EP/LDH-MoO4 has superior corrosion resistance and self-healing properties compared to EP/LDH-PO4, as the more active MoO42– anions have a stronger ion exchange ability than PO43–. This study not only highlights the potential of inhibitor ions inserted in LDH layers for anticorrosion but also paves the way toward the design of more effective EP-based coatings. [ABSTRACT FROM AUTHOR]

A CoCrCuNiAl0.5 high-entropy alloy (HEA) was prepared by spark plasma sintering (SPS). The effect of plasma transferred arc (PTA) remelting on the microstructures and properties of the SPS-ed HEA was studied. The results showed that, after PTA remelting, the microstructures transformed from randomly-oriented equiaxed grains to dendrites with a directional solidified morphology. The coarse plate-like precipitates (~ 130 nm in diameter and ~ 20 nm in thickness) containing ordered L12 and disordered FCC structures inside the matrix grains were replaced by the disordered FCC spherical Cu-rich precipitates with several nanometers within the dendritic matrix. In the intergranular region, the size of the L12 cubic precipitates was decreased from ~ 55 nm to ~ 2 nm, and dislocations and lattice distortions were also observed. In addition, the brittle B2 phase was disappeared, and the extent of Cu segregation was decreased in the interdendritic region. The SPS-ed sample has a compressive yield strength of 913.8 MPa and a fracture strain of 21.7%. However, the PTA remelted sample exhibits a much higher fracture strain (> 70%, without fracture) and an appreciable yield strength of 739.4 MPa, which indicates an excellent balance between strength and ductility was achieved after PTA remelting. Furthermore, the corrosion resistance of the PTA remelted sample was higher than that of the SPS-ed sample, which was mainly due to the decreased elemental segregation, and the reduced sizes and types of the precipitates. [ABSTRACT FROM AUTHOR]

Ni-xCr (x = 20, 30 and 40 wt pct, respectively) alloy corrosion resistant coatings were manufactured on Q235 substrate by plasma cladding. The effects of the Cr content on the phase composition, microstructure, and corrosion resistance of the Ni-xCr coatings were investigated in detail. The results showed that the main phases of the Ni-xCr coatings were γ-[Ni, Fe] solid solutions with face-centered cubic (FCC) structure. Electrochemical corrosion tests of different polarization voltages showed that the inhomogeneous distribution of composition and the presence of the multiphase structure led to the occurrence of corrosion. The occurrence of the Cr-rich phase increased the sensitivity of the Cr-poor phase and further accelerated the corrosion process. The Ni-xCr coating with intermediate Cr content (Ni-30Cr) had the best corrosion resistance, which depends on the phase composition of the coating. [ABSTRACT FROM AUTHOR]

Multi-principal element alloy (MPEA) films demonstrate superior corrosion resistance and tribological properties, which have substantial potential for applications in marine engineering equipment. In this study, the TiNbZrN x MPEA nitride films were successfully deposited on 316 L austenitic stainless steel by direct current (DC) magnetron sputtering at various nitrogen flow ratio (R N2). The phase, composition, microstructure, corrosion and mechanical behaviors were investigated in detail. The results showed that the phase transitioned from amorphous to amorphous/nanocrystalline as R N2 increased. The TiNbZrN x films deposited at R N2 = 0.15–0.4 exhibited better corrosion performance in the electrochemical and salt spray tests. The R N2 = 0.4 film presented the optimal corrosion resistance, with the lowest self-corrosion current density (0.249 μA/cm2) and the largest passivation zone (from OCP to >1.2 V SCE). The amorphous/nanocrystalline film deposited at R N2 = 0.2 showed a remarkable nanohardness of 7.03 GPa and adhesion strength of 18.86 N. The strengthening effect can be attributed to the interstitial dissolution of nitrogen atoms among the metal atoms. The formation of nitride nanocrystalline phases and the existence of interfaces can effectively improve the plastic deformation ability of amorphous alloy films. This work provides theoretical guidance for the development of MPEA nitride films with tunable properties for key moving parts in marine equipment. [Display omitted] • The relationship between the film structure and performance was discussed. • Corrosion resistance and mechanical behaviors were comprehensively enhanced at appropriate nitrogen content. • The mechanism of amorphous/nanocrystalline strengthening of TiNbZrN x films was revealed. • The composition of the passivation layer was confirmed by XPS analysis. [ABSTRACT FROM AUTHOR]

As the environment deteriorates, recycling of solid waste has become increasingly important. This study aimed to optimize the use of the Fe2O3, SiO2, and CaO components in coal fly ash and to convert coal fly ash into stable porous Al2TiO5‐mullite (AT–M) composite ceramic by sintering with AlOOH and TiO2 additives at high temperatures. The phase composition, microstructure, apparent porosity, corrosion resistance, and mechanical properties of porous AT–M composite ceramics were systematically investigated. Results indicated that the sintered samples exhibited pore size distributions within the 0.16‐2.9 μm, apparent porosities of approximately 52.8%, and flexural strength of 29.6 MPa. Corrosion resistance data revealed quality losses in the aqueous NaOH and H2SO4 solutions for 10 hours at 0.42% and 2.19%, respectively. After corrosion for 8 hours, the average flexural strength of the samples remained at 21.6 ± 0.53 and 20.84 ± 0.6 MPa, respectively. These findings show that these porous AT–M ceramics may provide enhanced corrosion resistance under alkaline conditions. The porous AT–M composite ceramics may fabricate high‐performance composite membrane supports for the high temperature flue gas filtration. [ABSTRACT FROM AUTHOR]

A kind of NiCrMo coatings added in different contents of B and C used B 4 C as the precursor, had been designed and fabricated by laser cladding in this study. The phases, microstructure, microhardness, fracture features, and wear and corrosion resistance were thoroughly analyzed. The results showed that due to the addition of B 4 C, the phases changed from fcc-centered cubic (FCC) + σ phase to FCC + carbon-borides, and the eutectic structure appeared in the interdendritic regions. Most noteworthy, there was coherent relationship between the (Cr, Mo) 23 (B, C) 6 and FCC phase. With the increase of B 4 C content, the microhardness of the coatings increased significantly. This factor, together with the eutectic structure, further enhanced the wear resistance of the coatings. Due to the existence of the eutectic structure, the coating maintained ductile fracture + brittle fracture. Furthermore, the formation of carbon-borides also improved the corrosion resistance, instead of causing deterioration, because of the coherent relationship of (Cr, Mo) 23 (B, C) 6 and FCC phase together with no severe segregation of Cr and Mo around interdendritic regions, which reduced the possibility of galvanic corrosion, playing the role of synergistic improvement to the wear resistance and corrosion resistance of the coatings. • Eutectic structure formed by FCC phase and carbon-borides. • Carbon-borides not only improved the hardness and wear resistance of the coating, but also kept the toughness of the coating. • Carbon-borides improved the corrosion resistance, due to the coherent relationship and no severe segregation of Cr and Mo. [ABSTRACT FROM AUTHOR]

Ni-Al intermetallic compounds synthesised by a vacuum melting method, designed with different composition and microstructure and corresponding to molar ratios of Ni: Al = 1:1, 2:1 and 3:1, respectively, were investigated. The phase constitution, microstructure, morphology, and corrosion resistance of products were analysed. The results show that single NiAl and Ni 3 Al phases are obtained with composition corresponding to Ni: Al = 1:1 and Ni: Al = 3:1, respectively, while with the molar ratio of Ni: Al = 2:1, the phases of the product are composed of Ni 3 Al and small amounts of NiAl. The corrosion morphology of Ni: Al = 1:1 and Ni: Al = 3:1 present dendritic structures due to the preferential corrosion of grain boundaries. In addition, stacked layers of laminated structures and even structures created by flaking are formed in the corrosion process. However, in the sample with a molar ratio of Ni: Al = 2:1, Ni 3 Al with a large number of radial and chrysanthemum-like microstructures serve as anodes, and NiAl with lath-shaped microstructures serve as cathodes. This exacerbates the grain boundary corrosion and causes the fast anodic dissolution of Ni 3 Al. Moreover, the corrosion resistance of Ni-Al intermetallic compounds are in the order of Ni: Al = 1:1 > Ni: Al = 3:1 > Ni: Al = 2:1. In conclusion, single phase and homogeneous microstructures can improve corrosion resistance. [ABSTRACT FROM AUTHOR]

• The addition of Co can improve the corrosion resistance of the coatings. • Co can reduce composition and potential differences of different phases. • Co can increase electronic work function and interface bonding strength. CoCrNiMoCB high-entropy alloy composite coatings were made by laser cladding, then the effects of Co concentration on corrosion resistance were studied. The addition of Co can reduce the composition difference between the FCC matrix and strengthening phase, thus reducing the potential difference and the driving force for galvanic corrosion. Through first-principle calculation, it was concluded that the addition of Co can increase the electronic work function and reduce the interface bonding energy, thus, enhancing the corrosion resistance and improving the interface bonding strength. [ABSTRACT FROM AUTHOR]

To develop a high-performance coating for marine engineering equipment, we successfully designed amorphous-nanocrystalline NiCr 0.25 Mo x (x = 0, 0.02, 0.05, 0.1, 0.2, 0.4) alloy coatings via direct current (DC) magnetron sputtering. The compositional, microstructural, corrosion and mechanical properties, specifically the relationship between the coating structure and performance were discussed in detail. The results showed that the amorphous phase sharply alleviated grain boundary corrosion, and the addition of Cr and Mo was beneficial to improve repassivation ability with the formation of a dense passive film. In the nanoindentation and micro-scratch tests, the nanohardness and adhesion strength of the coatings first increased remarkably with Mo content and then declined due to the formation of an amorphous phase. The enhancement of strength was caused by nanocrystals hindering the formation of shear banding, while the addition of Mo improved the tendency of amorphous formation due to the difference in atomic size and lattice distortion. Most importantly, the NiCr 0.25 Mo 0.1 coating exhibited excellent corrosion performance and mechanical behavior through the formation of a dense passivation film composed of Cr 2 O 3 and Cr(OH) 3. These ductile solid solution crystalline phases promoted homogeneous plastic deformation and decelerated crack propagation during the scratching process. • The relationship between the coating structure and performance was discussed. • The mechanism of amorphous-nanocrystalline toughening of NiCr 0.25 Mo x coating was revealed. • Corrosion resistance of coating was improved by proper addition of Mo. • The bilayer passive film was confirmed by EIS and XPS analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • A synergistic improvement of wear and corrosion resistance was realized with the increasing content of Mo. • Mo can enhanced pitting resistance, and pitting can be eliminated with the addition of Mo between 4 at.% to 8 at.% • Coherent interfaces and their composition transition explain the excellent wear and corrosion improvement of the coatings. Herein, ceramic-reinforced CoCrNiMo x CB high-entropy alloy coatings were prepared by laser cladding, and the synergistic improvement of wear and corrosion resistance was realized. The effects of molybdenum on the phases, microstructures, and chemical compositions of the coatings were also studied. Wear mechanisms changed from adhesive wear to abrasive plough with the increase of Mo content, leading to excellent improvement in wear resistance. The corrosion resistance was remarkably improved with excellent passive ability and pitting resistance. Coherent interfaces and composition transition at the interfaces provide a nano-scale explanation for the excellent wear and corrosion trade-off of the Mo-8 coating. The results show that the wear and corrosion resistance of the coatings can be improved with the addition of molybdenum. [ABSTRACT FROM AUTHOR]

The Al 2-x CoCrFeNiTi x (x = 0, 0.2, 0.5, 0.8, 1.0, and 1.2) high-entropy alloys (HEAs) were prepared via vacuum arc melting. With the increase of the molar ratios of Ti-to-Al, the phases, microstructures, mechanical properties, and corrosion resistance of the HEAs were changed. The microstructures were transformed from BCC1+B2, and BCC2+BCC1+B2, to BCC2+Laves + BCC1 phases. The addition of Ti, on the one hand promoted the formation of another BCC phase and Laves phase, and on the other hand refined the microstructure of the as-cast alloys. Good comprehensive mechanical properties with the highest compressive fracture strength of 1919 MPa and fracture strains of 11.85% were obtained in the Al 1.5 CoCrFeNiTi 0.5 alloy. With further increase in the ratio of Ti, the fracture strength and strains of the HEAs decreased because of the increase in the fraction and the size of the brittle Laves phase. Furthermore, compared with the Ti-free Al 2 CoCrFeNi alloy, all Ti-containing Al 2-x CoCrFeNiTi x alloys exhibited higher pitting corrosion resistance with a wide passive window. The existence of noble and unoxidized metal atoms in the passive film, particularly Ti, enhanced the alloy's resistance to pitting corrosion. Our report provides an effective method for the design of high Al-content HEAs to balance the strength-ductility trade-off and improve the pitting corrosion resistance synergistically. • The addition of Ti promotes formation of a Ni 2 AlTi-type body-centered cubic phase. • A moderate ratio of Ti/Al is beneficial for strength-ductility trade-off. • The unoxidized Ti atom in passive film improves pitting corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, amorphous/nanocrystalline TiAlCrNbZr x (x = 0, 0.3, 0.7, 1) multi-component alloy films have been successfully prepared on the surface of 316L stainless steel using direct current magnetron sputtering technique. The composition, microstructure, corrosion and mechanical properties, especially the effect of Zr content and structure on the properties, are discussed in detail. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data revealed the presence of nanocrystalline phases among the amorphous phase. The results showed that the amorphous phase can effectively mitigate corrosion, while the nanocrystals can improve the mechanical properties and adhesion of the films as the Zr content increased. The lattice distortion caused by the incorporation of large atomic Zr contributed to a significant change in the film structure. TiAlCrNbZr films with the most nanocrystals showed better plastic deformation ability, while TiAlCrNbZr0.3 has a suitable amorphous/nanocrystal ratio, good corrosion resistance, and excellent mechanical properties. • In this study, the effect of Zr content on the structure and properties of TiAlCrNbZrx thin films was carefully investigated. • The role of nanocrystals appearing in the film structure in improving the mechanical properties was also investigated. • The effect of Zr content and structure on the corrosion resistance and mechanical properties of the films was carefully investigated. [ABSTRACT FROM AUTHOR]

To improve the wear and corrosion resistance of key components and ensure the safe operation of offshore equipment, we applied an ∞ oscillating laser to prepare a TiAlSi-Ni composite coating. The effects of Ni addition on the composition, microstructure, corrosion resistance and mechanical properties of the coating were experimentally investigated. The results showed that the coating mainly presented an interdendritic - dendritic structure, and the S4 coating with 17 at% Ni had the best wear and corrosion resistance. In the reciprocating sliding friction and wear test at 10 N and 30 N, the wear rates were 0.83 and 1.66 × 10−7 mm2·N−1, respectively, which is 1/5 and 1/3 of TC4 under this load. The S4 also had the largest passivation interval and passivation film stability. The internal and external double-layer film structure ensures that it is not corroded by corrosive medium. The Ti 3 Al/TiNi semi-coherent interface and lattice distortion gave the Ti 3 Al-Ti 2 Ni and TiAl-TiNi eutectic interfaces a high bonding strength. Moreover, the "labyrinth effect" produced by the lamellar eutectic structure further improved the corrosion resistance. This work provides a new method for obtaining coatings with high adhesion and wear and corrosion resistance for offshore platforms. • "∞" oscillating improve the properties of deposition layer. • The diffusion impedance of the dense outer passivation film obstructs Cl- penetration. • The Semi-coherent relation promotes the improvement of wear and corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, different alloy powders containing nano-sized TiC were prepared using a combination of mixed ball milling adsorption, electroless Ni-P-TiC, and Ni-B-TiC plating techniques. The effects of different nano-TiC addition methods on the microstructure, wear resistance, and corrosion resistance of laser-coated nickel-based self-fusing alloy coatings were comprehensively studied. The effects of the nano-TiC method on the microstructure, wear resistance, and corrosion resistance of laser-coated nickel-based self-fusing alloy coatings were comprehensively studied. The results show that agglomerated TiC particles appeared in the coatings prepared with ball-milled powder. In contrast, the coatings produced by introducing nano-sized TiC through the chemical plating methods exhibited a uniform distribution of the TiC phase. The coatings prepared with Ni-B-TiC plating powder showed a bimodal microstructure and most of the TiC particles are distributed at grain boundaries, which hinders grain growth and refines the microstructure of the coating. The corrosion resistance of the Ni2 coating prepared with ball milling adsorbed nano TiC powder shows the best corrosion resistance. The wear resistance of the Ni4 coating prepared with the Ni-B-TiC plating powder was significantly better than that of the other samples. This study provides an effective way to improve the wear or corrosion resistance of laser cladding nickel-based self-fluxable alloy coatings. • The coating prepared with Ni-B-TiC coated NiFeCrMoBSi powder shows a bimodal microstructure and excellent wear resistance. • Most of the core-shell M 23 C 6 @TiC@TiO 2 nano and micron particles in γ-Ni grain boundaries hindered grain growth. • The addition of B in the coating prevents segregation of Cr, Ni, Ti, and Mo elements, enhancing hardness and wear resistance. [ABSTRACT FROM AUTHOR]

• Al–Ti–O amorphous films were prepared by annealing the sputtered Al–Ti films. • The film transformed from amorphous to nanocrystalline structures after annealing. • The nanocrystallines were consist of Al 2 TiO 5 , Al 2 O 3 and TiO 2. • 4The low galvanic effect and porosity significantly enhanced the corrosion resistance. Amorphous-nanocrystalline composite films of Al–Ti–O with a range of structures from completely amorphous to nanocrystalline were obtained by magnetron sputtering. The Al–Ti–O films obtained at different temperatures of 100°C, 200°C, 300°C and 400°C, and then followed by annealing at 500°C, enabled us to examine the role of substrate temperature and annealing on the microstructure and electrochemical corrosion After annealing at 500°C, all the structures of the Al–Ti–O films were transformed from amorphous to amorphous-nanocrystalline composite, and Al 2 TiO 5 , Al 2 O 3 and TiO 2 began to nucleate and grow from the original amorphous phase. At the same time, the film defects such as holes and cracks were reduced and the densities were increased. The variations of roughness and defects of Al–Ti–O films were consistent with the crystallinity trend. Correlated with the nucleation and growth of Al 2 TiO 5 , Al 2 O 3 and TiO 2 during annealing, the corrosion resistance is significantly enhanced, with a minimum corrosion current density (2.66 nA•cm−2) of two orders of magnitude lower than that of 316L substrate (245 nA•cm−2), when sputtered at 400°C. This is attributed to the lower galvanic effects between the adjacent phases of amorphous and nanocrystalline composite structures, and also the film with low porosity. The observed phase evolution opens up future design routes for magnetron sputtering oxide films with tunable microstructural and electrochemical corrosion properties. [ABSTRACT FROM AUTHOR]

Stabilized Al 2 TiO 5 (AT)-mullite (M) porous ceramics were fabricated by starch consolidation casting using corn starch as curing agent and their microstructure, mechanical properties, pore size distribution and corrosion resistance were examined. Results showed that AT-M porous ceramic with the flexural strength of 11.5 MPa, apparent porosity of about 54.7% and pore size distribution in the range of 1–15 µm could be obtained with 10 wt% corn starch addition. Corrosion resistance results showed mass losses in hot H 2 SO 4 solution and NaOH solution for 10 h to decreased from 1.03% to 0.36% and 4.39–2% when the calcination temperature increased from 1400 °C to 1450 °C, which proved these AT-M porous ceramics to possess an excellent corrosion resistance in acidic condition when calcined at 1450 °C. [ABSTRACT FROM AUTHOR]

316L SS with different Nb content (0.2, 0.5, 1.0, 3.0, 5.0, 7.0 wt%) coatings were fabricated on Q235 steel plate by laser cladding. The addition of Nb made the phase structure of 316L change from FCC to FCC + BCC + Laves phase. With the Nb content increasing, the microhardness of 316L coating increased gradually. The Nb7.0 coating is about 2.0 times as hardness of the substrate. Electrochemical testing showed that Nb 1.0 coating had the best corrosion resistance in 3.5 wt% NaCl solution. Excess Nb will cause corrosion to occur more easily and decrease the corrosion resistance of the coating. • The compact 316L SS with dissimilar Nb alloy coating was prepared by laser cladding. • The Nb1.0 coating has good corrosion resistance in 3.5 wt% NaCl solution. • Niobium oxide played an important role in improving the corrosion resistance of passive film, but excessive niobium will have adverse effects on the structure. • The Nb7.0 coating has high microhardness. [ABSTRACT FROM AUTHOR]

Inconel 625 + x Al (x = 0, 2.5, 5.0, 7.5, 10.0) alloy coatings were prepared by laser cladding. The addition of Al promoted the formation of the BCC phase, which changed the coating microstructure from an FCC + δ phase + Laves phase to FCC + BCC + δ phase + Laves phase. Inconel 625 + 2.5 Al alloy showed the greatest corrosion resistance among all samples. The formation of an Al 2 O 3 film improved the corrosion resistance of the coating, but excess Al decreased the Cr 2 O 3 content in the film, which decreased the corrosion resistance of the coating. Increasing the Al content aggravated the lattice distortion and improved the solid solution strengthening effect, while also increasing the amount of BCC phase, which improved the coating hardness. After adding Al, the Inconel 625 + x Al alloy coatings displayed strong plastic deformation resistance, and their wear resistance was improved due to the presence of a hard phase. • The compact Inconel 625 + x Al alloy coating was prepared by laser cladding. • The Inconel 625 + 2.5 Al coating has good corrosion resistance in 3.5 wt% NaCl solution. • The corrosion resistance mechanism of the coating is related to the inhomogeneity of the structure. • The main component of passive film is chromium oxide, which plays an important role in corrosion resistance. • The Inconel 625 + 10.0 Al coating has good wear resistance. [ABSTRACT FROM AUTHOR]

• The leakage and corrosion resistance of concrete with inorganic PCM were evaluated. • TESA concrete did not lose strength when subjected to thermal cycles. • The coating method was effective to prevent PCM leakage and improve ITZ in concrete. • The surface temperature of TESA concrete was measured by the Infrared thermography. • The potential corrosion of concrete with inorganic PCM was controlled by the coating method. Over the last few years, phase change materials (PCMs) have been proved capable to improve the thermal performance of cement-based materials. However, the issues of inorganic PCM leakage and corrosion have led to apprehension. The present study aims to investigate the feasibility of using a dual-layer coating system to improve leakage and corrosion resistance of concrete made of macro-encapsulated inorganic PCM-lightweight aggregate (PCM-LWA). The coated PCM-LWA system is referred to thermal energy storage aggregate (TESA). The effect of TESA at different volume fractions on mechanical, thermal and corrosion performances of concrete were investigated. Test results indicated that the compressive strength of TESA concrete reduced by 6–9% compared to the LWA concrete. However, TESA concrete did not lose strength when subjected to thermal cycles between 15 and 40 °C, which represents the thermal reliability of TESA system. The thermogravimetry analysis and differential scanning calorimeter test results indicated that the PCM was thermally stable and reliable. The thermal performance test demonstrated the feasibility and functionality of using TESA in concrete structures. Infrared thermography camera indicated that the surface temperature of TESA concrete was lower than that of the control mixture. The accelerated corrosion test demonstrated the significant role of the dual-layer coating system, which can reduce the leakage of PCM and avoid the detrimental impact of inorganic PCM on the corrosion of reinforcing steel. Besides, the permeability resistance of concrete was improved using TESA. [ABSTRACT FROM AUTHOR]