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The effects of supersonic particle bombardment (SFPB) on the microstructure, microhardness and wear property of Ti6Al4V alloy prepared by laser metal deposition (LMD) were investigated in this paper. The electrochemical corrosion behaviors of the LMDed Ti6Al4V alloy samples before and after SFPB treatment in 3.5% NaCl solution were measured. The results showed that a gradient severe deformation layer of ~ 350 μm thickness was formed with refined equiaxed grains oriented in various directions on the surface of LMDed Ti6Al4V alloy after SFPB treatment. The microhardness of the deformation layer was significantly increased due to the plastic deformation, grain refinement, dislocations and deformation twins increment. After SFPB treatment, the LMDed Ti6Al4V exhibited higher wear resistance which is about 55.6% decrease in wear loss than that of the untreated sample. Moreover, the corrosion resistance and corrosion rate of the SFPB-treated samples in 3.5% NaCl solution improved due to the finer hexagonal grains and high density of grain boundary in the severe deformation layer. [ABSTRACT FROM AUTHOR]

The bottleneck challenge of laser‐cladded coating preparation of magnesium alloys is the low melting point of alloys. This greatly restricts the selection of coating material. In this article, the composition of Ni–Ti–Cu coating is designed by cluster line criterion, and the thermal properties of the coating are simulated by JMatPro software. Through the analysis of simulation results, the Ni51.6Ti34.4Cu14 coating is selected and successfully prepared on AZ91D magnesium alloy via laser cladding technology. Then the microstructure, wear resistance, and corrosion resistance of the coating are studied in detail. The results of X‐Ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and transmission electron microscope (TEM) demonstrated that there is a good metallurgical bond between the coating and the substrate, and the coating is mainly composed of Ni3Ti, TiNi0.8Cu0.2, and (Cu, Ni) solid solution phases. Also, there are no obvious pores and crack defects in the coating. Remarkably, AZ91D alloy showed significant improvement in corrosion resistance and wear resistance. Among them, the wear volume of the coating is decreased by 71.9% than that of AZ91D alloy. In particular, the corrosion current density of the coating is three orders of magnitude lower than that of AZ91D alloy. [ABSTRACT FROM AUTHOR]

Two kinds of layered double hydroxides inhibition materials were synthesized on graphene oxide, and applied to strengthen the Ni-based coating on Mg-Li alloy. The composition and release properties of corrosion inhibition materials were studied. The formation of passivated film and the corrosion resistance mechanism of coating were summarized. The results show that two kinds of corrosion inhibition materials had good release properties. The addition of corrosion inhibition materials was helpful to form Ni-based composite coatings with fine and dense cell clusters, which strengthened the corrosion resistance of the coating, especially for a long time. • Two kinds of graphene-based corrosion inhibition materials were synthesized. • Corrosion resistance of Ni-based coatings in different soaking time was studied. • Inhibition materials enhanced the corrosion resistance of coatings on Mg-Li alloy. • Passivation film formation and corrosion resistance mechanism were studied. [ABSTRACT FROM AUTHOR]

This study proposes the utilization of rare earth combined with ultrasonic-assisted laser cladding technology to address the dilution problem encountered during the laser cladding coating of Ti alloy. The aim is to improve the performance of the coating. Using Ti alloy surface as a base, a novel Ti-Al-Si-Cr-SiC multi-principal element alloy coating is fabricated. To characterize the coating, various techniques such as transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM) are employed to examine the microstructure and phase composition. The interface between the coating and the substrate is analyzed using focused ion beam and TEM. The coatings are also evaluated for corrosion and wear resistance through potentiodynamic polarization, electrochemical impedance spectroscopy, hardness, and friction tests. The results reveal that the rare earth combined with ultrasonic-assisted Ti-Al-Si-Cr-SiC coating consists of Ti 4 Cr phase, TiC phase, and eutectic phase (Ti 3 Al and Ti 5 Si 3). The combined effect of ultrasonic energy and rare earth reduces the dilution rate of the coating, resulting in a refined coating structure that improves the wear resistance and corrosion resistance. • A new preparation method of ultrasonic composite rare earth assisted laser cladding was proposed. • The dilution rate of the coating prepared by rare earth-ultrasonic assisted laser cladding is significantly reduced. • Microstructure refinement promotes the formation of stable passivation film and improves the corrosion resistance. • The coating prepared by rare earth combined with ultrasonic assisted laser cladding has good wear and corrosion resistance. [ABSTRACT FROM AUTHOR]

The corrosion and wear requirements of Zr alloys for application as fuel cladding materials are becoming increasingly stringent. Accordingly, developing surface engineering techniques and high-performance coating materials is crucial for achieving improved surface properties of these alloys. Herein, we propose a strategy for preparing high-performance coatings on Zr alloys using the multilayer cladding technique to prevent the high dilution of Zr alloy substrates because of high-energy beams. A novel Al 0.2 NbTiV 0.1 W 0.5 Zr 0.3 high-entropy alloy (HEA) coating with a multilayer structure was prepared on a Zr alloy using multiple laser claddings. The top-layer and interlayer were composed of two body-centered cubic (BCC) phases and a Zr-rich phase. Owing to the multilayer cladding, the top-layer was almost unaffected by matrix dilution and substrate evaporation, leading to a significantly reduced precipitation of the Zr-rich phase in the top-layer. The high hardness and excellent wear resistance of the coating were attributed to the two BCC phases; moreover, both, the Zr-containing HEA and substrate, exhibited adhesive wear. The top-layer exhibited superior pitting corrosion properties, whereas the microstructural inhomogeneity in the interlayer led to intergranular corrosion, dominating the corrosion process. Thus, this study presents a coating material system suitable for Zr alloys with excellent wear and corrosion resistances. The findings can potentially contribute to expanding the application of the high-energy beam technology to Zr alloys. [Display omitted] • Al 0.2 NbTiV 0.1 W 0.5 Zr 0.3 HEA coating with multilayer structure was prepared on Zr alloy by multiple laser cladding. • The microstructure and properties of top-layer and interlayer on the multi-layer strategy were investigated. • The Zr-rich phase and two coexisting BCC phases are formed in the coating. • IGC dominates the corrosion process in the interlayer owing to microstructural inhomogeneity. • The corrosion and wear resistance of Zr alloy surface are significantly improved. [ABSTRACT FROM AUTHOR]

It is challenging to obtain the underwater wet laser cladding layer with excellent properties while maintaining formability. In this paper, the method of using synchronous mechanical vibration assisted in the underwater wet laser cladding process of TiN/Fe-based cladding layer was introduced. The effect of mechanical vibration frequency on the dilution rate, microstructure, corrosion resistance, tribo-corrosion behavior of the cladding layer was studied. The result displayed that with increase of mechanical vibration frequency, the dilution effect of the substrate was obviously weakened and the phase changed from ferrite to ferrite and austenite, and TiN particles were evenly distributed. In addition, the grain size of the cladding layer showed a tendency to decrease first and then increase. When the mechanical vibration frequency was 400 Hz, the grain refinement phenomenon was the most obvious and the average grain size was 8.39 μm. Based on the effect of dispersion strengthening and fine grain strengthening, the microhardness and wear resistance of the cladding layer assisted at 400 Hz were improved, and the wear rate was 1.17 × 10−15m3N−1 m−1. While the cladding layer assisted at 400 Hz exhibited better corrosion resistance by forming a dense passivation film. In addition, the mechanism of mechanical vibration on microstructure evolution and performance enhancement of the cladding layer was also analyzed. This study provided the theoretical support for the formability of the underwater laser wet cladding assisted by mechanical vibration. • The TiN/Fe-based underwater wet cladding layer was successfully prepared assisted with mechanical vibration. • Action mechanism of mechanical vibration on TiN/Fe-based underwater wet cladding layer is explained. • The grain refinement mechanism of TiN/Fe-based underwater wet cladding layer is proposed. • Dispersion strengthening and grain refining strengthening are the main strengthening mechanisms. [ABSTRACT FROM AUTHOR]

Underwater wet laser cladding technology has become one of the research hotspots in the marine engineering, but the existence of the water environment inevitably leads to process instability and defects. In this study, the nano-ZrO 2 protective layer was used to increase the viscosity of the molten pool surface to resist the impact force generated by the high-speed water jet, and the underwater wet laser Fe-based cladding layer with good forming quality and desirable performance was successfully prepared. The nano-ZrO 2 protective layer improved the formability of the cladding layer and guaranteed the depth of the melt pool, while reducing the depth of the heat affected zone. The addition of nano-ZrO 2 particles reduced the average grain size of the cladding layer from 4.90 μm to 3.66 μm. In addition,the corrosion resistance of the cladding layer was greatly improved with the application of the nano-ZrO 2 protective layer, with the evident passivation region of 0.74 V. The wear rate of the cladding layer with the nano-ZrO 2 protective layer (0.64×10-15m3N-1m-1) was significantly lower than that of the substrate (9.01×10-15m3N-1m-1), and the excellent wear resistance of the cladding layer with nano-ZrO 2 protective layer benefited from the good carrying capacities and high microhardness of the microstructure with ZrO 2 particles. This study reveals the strengthening mechanism of nano-ZrO 2 protective layer on the Fe-based cladding layer, which can provide theoretical guidance for the development of the underwater laser cladding. • The Fe-based cladding layer with good formability was successfully prepared underwater. • The protective mechanism of the nano-ZrO 2 protective layer is studied in detail. • The nano-ZrO 2 protective layer can refine grains and decline heat effect. • The corrosion and wear performances of Fe-based cladding layer were improved by nano-ZrO 2 protective layer. • The nano-ZrO 2 induced grain refinement enabled Fe-based cladding layer to be further wear resistant. [ABSTRACT FROM AUTHOR]

• A metallurgical AlCuTiVCr HEA coating was prepared on Mg-Li alloy. • Cu-Al layer can balance the thermal matching disparity among HEA layer and Mg-Li. • HEA coating consists of (V, Cr)-rich BCC 1 , Mg-rich BCC 2 , AlCu 2 Ti and β-Ti phases. • The corrosion resistance of Mg-Li alloy was significantly improved. AlCuTiVCr/Cu-Al lightweight high-entropy alloy gradient coating was successfully prepared by laser cladding to improve the corrosion resistance of Mg-Li alloy. The boundaries between AlCuTiVCr protective layer, Cu-Al transition layer and Mg-Li alloy substrate are distinct, forming an excellent metallurgical bonding. The gradient coating design has effectively balanced the thermal matching difference between HEA coating. The prepared AlCuTiVCr protective layer comprises (V, Cr)-rich BCC 1 , Mg-rich BCC 2 , AlCu 2 Ti and β-Ti phases. The Cu-Al transition layer is composed of β-Li, Cu 2 Mg and Al 2 Cu 3 phases. The corrosion potential of AlCuTiVCr protective layer (−0.46 V SEC) is 1.09 V SEC higher than that of Mg-Li alloy (−1.55 V SEC), while the corrosion current density of the protective layer (9.41 × 10−7 A cm−2) is about three orders of magnitude lower than that of the substrate (5.97 × 10−4 A cm−2). [ABSTRACT FROM AUTHOR]

Abstract The requirement of repairing damaged surface of nickel aluminum bronze (NAB) parts from underwater environment is urgent in recent years. In this paper, a novel approach to underwater laser cladded NAB by adding Ti and applying Zn protective layer has been reported. The materials fabricated underwater from this approach possess desirable performance. Ti additives increases the surface tension in melting pool, and prevents the high-speed water jet from invading the melting pool. Therefore, pores are almost disappearing. Due to the fast heat loss during underwater laser cladding process, the microstructure of underwater laser cladded nickel aluminum with adding titanium is fine, homogeneous and stable, in addition, the heat affected zone is small. Electrochemical results shows that the corrosion resistance of underwater laser cladded nickel aluminum bronze with adding titanium is better than that of substrate. In this study, the underwater environment is favorable for manufacturing a good material by using laser processing technology. The results of this study will provide meaningful reference to repairing NAB parts in underwater environment. [ABSTRACT FROM AUTHOR]

As a lightweight material, the wide application of Mg-Li alloy is restricted by its corrosion resistance. Focusing on this, an innovative superhydrophobic composite coatings of nickel-based metal coupled with layered double hydroxides (LDHs) was prepared on Mg-Li alloy. The microstructure, hydrophobic property and corrosion resistance of coatings were investigated by SEM, TEM, XRD, FT-IR, AFM, contact angle tester and electrochemical test. The results indicated that the MgAl LDHs uniformly grown in situ on the NiP coating deposited on Mg-Li alloy through electroless plating and hydrothermal treatment. The MgAl LDHs with a complex honeycomb micro-nano structure improved the surface roughness of the composite coating to 126 nm. The two-step treatment achieved an excellent coupling between the metal-based coating and inorganic compounds. The low surface energy treatment of micro-nano structure on NiP coating surface with stearic acid (@SA) realized the superhydrophobic transition of the composite coating (WAC=154.27° ± 2.56°). Besides, MgAl LDHs showed better trapping properties for Cl-. Under the synergistic effect of anion capture and hydrophobic effect, the corrosion current density (1.35 ×10−7 A⋅cm−2) and impedance modulus of NiP/MgAl LDHs@SA coating were significantly better than those of NiP and NiP/MgAl LDHs coating. The superhydrophobic composite coating provided a better anticorrosion choice for Mg-Li alloy. [Display omitted] • A new superhydrophobic double-layer coatings were prepared on the Mg-Li alloy. • MgAl LDHs with uniform honeycomb structure were in situ grown on the NiP coating. • Modified by stearic acid, the double-layer coatings had good superhydrophobicity. • The superhydrophobic double-layer coatings showed excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

Mg Li alloys have a wide application in the lightweight structure materials on account of their ultra-light-weight, good machinability and high specific strength. However, the low strength, insufficient wear and corrosion resistances of Mg Li alloys have become a critical problem that hinders their applications. In order to achieve excellent wear and corrosion properties, LC-Cu 3 Al, LC-Cu 6 Al and LC-Cu 9 Al coatings are designed and prepared on Mg Li alloy substrates in this study. The phase structure, microstructure, hardness, wear and corrosion properties of Cu Al alloy coatings are investigated in detail. The results show that a good metallurgical bond is achieved between the Cu Al alloy coatings and the substrates. LC-Cu 6 Al coating's hardness, wear and corrosion properties are the best. Compared with the Mg Li alloy substrate, the average hardness of LC-Cu 6 Al coating increases by 6.75 times, while the wear volume decreases by 88.32 % and the corrosion current density decreases by two orders of magnitude. The results suggest that using laser cladding Cu Al alloy coatings is an excellent strategy to enhance the surface properties of Mg Li alloy. [Display omitted] • Cu Al alloy coatings were prepared on Mg Li alloy by laser cladding. • LC-Cu 6 Al coating is mainly composed of Cu 9 Al 4 , Al 2 Cu 3 and Cu 2 Mg phase. • The peritectoid transition of γ 0 → Al 2 Cu 3 + Cu 9 Al 4 occurred during laser cladding. • The wear and corrosion resistance of Mg Li alloy are comprehensively improved. [ABSTRACT FROM AUTHOR]

The carburized 12Cr2Ni4A alloy steel was implanted by Ti + N double elements implantation. The microstructure, nano-hardness and corrosion properties were investigated by EPMA, TEM, XPS, nano-hardness and electrochemistry tests in detail. The results showed that the Ti + N co-implanted layer is composed of FCC TiN and TiC phases with BCC martensite. Compared with the un-implanted layer, the Ti + N implanted layer has higher nano-hardness and better corrosion resistance. In addition, the higher nano-hardness was presented below the surface of 1800 nm compared with un-implanted layer, which is far beyond the thickness of the implanted layer. The results also indicated that the generation of nanoscale ceramic phase and structures are not the only factor to impose the influence on the nano-hardness and corrosion resistance, but the radiation damage and lattice distortion will play an important role. [ABSTRACT FROM AUTHOR]

Fe 60 (NiCrCoTiV x ) 40 (x = 0, 0.5, 1) multicomponent alloy coatings on low-cost AISI 1045 steel were successfully prepared by laser surface alloying. The effect of V content on microstructure, micro-hardness, wear resistance and corrosion resistance were studied in detail. The Fe 60 (NiCrCoTiVx) 40 (x = 0, 0.5, 1) multicomponent alloy coatings are all composed of a FCC solid solution phase and a BCC solid solution phase with a Fe 2 Ti-type Laves phase. The lattice parameter of the BCC solid solution phase is not sensitive to V content, but the addition of V leads to the decrease of FCC content and the refinement of Fe 2 Ti-type Laves phase. The addition of V significantly affects the properties of coatings, and the Fe 60 (NiCrCoTiV 0.5 ) 40 multicomponent alloy coating has higher micro-hardness and better wear resistance while the Fe 60 (NiCrCoTiV 1 ) 40 multicomponent alloy coating has the best corrosion resistance. In addition, the corrosion resistance of Fe 60 (NiCrCoTiVx) 40 (x = 0, 0.5, 1) multicomponent alloy coatings are better than that of the corresponding reference material. The results also indicate that micro-hardness is not the only factor to impose the influence on the wear resistance and the place where corrosion first occurs may be along with the Fe 2 Ti-type Laves phase. [ABSTRACT FROM AUTHOR]

Underwater wet laser cladding technology as a new online repair technology, has a wide application prospect in the field of marine engineering. In this work, the underwater wet laser cladding layers of 316L stainless steel with in-situ Ni interlayer on EH40 were successfully manufactured using the underwater wet laser cladding technology. The effect of the in-situ Ni interlayer on the elemental distribution, microhardness, properties and interfacial characteristics of the underwater wet cladding layer was investigated. The in-situ Ni interlayer formed a diffusion buffer between the substrate and cladding layer to mitigate the Fe, Cr and C element diffusion and increased the Ni content in the cladding layer. The addition of the in-situ Ni interlayer promoted the formation of austenite. The wear resistance of the underwater wet laser cladding layer with in-situ Ni interlayer was higher than that of the in-air laser cladding layer, and the main wear mechanism was abrasive wear. In addition, the corrosion resistance of the underwater wet laser cladding layer was improved effectively by applying the in-situ Ni interlayer, and the corrosion resistance basically reached the same level with the in-air laser cladding layer. Thus, the in-situ Ni interlayer has guiding significance for the underwater wet laser cladding technology of Fe-based materials. • The underwater wet laser cladding 316L layer with in-situ Ni interlayer on EH40 was manufactured. • The in-situ Ni interlayer formed a buffer area for element diffusion. • The corrosion performance of 316L layer was improved by in-situ Ni interlayer. • The promotion mechanism of in-situ Ni interlayer on properties is studied in detail. • The effect mechanism of water environment on the underwater wet laser cladding layer was analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • TiB/Ti 50 Zr 25 Al 15 Cu 10 medium-entropy alloy composite coating (MEACC) was successfully prepared on the surface of magnesium alloy by laser cladding. • La rare earth element was added into the self-designed Ti 50 Zr 25 Al 15 Cu 10 non-equiatomic medium-entropy alloy in the form of LaB 6. • The strengthening mechanism with LaB 6 addition was investigated. • The corrosion and wear resistance of magnesium alloy got huge improvement. The improvement of corrosion resistance and wear resistance levels is of great significance because of the far-ranging impacts of them on the further application of magnesium alloys. In this work, a novel TiB/Ti 50 Zr 25 Al 15 Cu 10 medium-entropy alloy composite coating (MEACC) was successfully prepared on the surface of magnesium alloy by laser cladding. The effect of LaB 6 content on microstructure, micro-hardness, wear resistance and corrosion resistance of Ti 50 Zr 25 Al 15 Cu 10 coatings was studied in detail. The results show that TiB/Ti 50 Zr 25 Al 15 Cu 10 MEACCs are mainly composed of α-Ti, BCC and TiB phases. With LaB 6 content increased, the microstructure of the coating is refined and homogenized. And when the addition amount is excessive, Cu 2 La clusters appear. The lattice distortion caused by La3+ with large ion radius leading to the formation of hard BCC solid solution, as well as the dispersion strengthening of TiB in-situ, the coating presents high micro-hardness and excellent wear resistance. Especially, the average micro-hardness values of Ti 50 Zr 25 Al 15 Cu 10 coating with 4 wt% LaB 6 is ∼679.4 HV 0.3 , which is about 11 times than that of the substrate (∼61.6 HV 0.3). Besides, TiB/Ti 50 Zr 25 Al 15 Cu 10 MEACC displays excellent corrosion resistance. The minimum corrosion current density is 8.52 × 10−7 A·cm−2, and the oxidation phenomenon emerged in the coating. The oxide film is mainly composed of the oxidation state of Ti, Zr, Al, Cu and the sub-oxide state of Cu. [ABSTRACT FROM AUTHOR]

Purpose – The aim of the present paper is to investigate the mechanical performance of multi-layer films. With the wide application of optic and electronic thin-films, membrane materials and membrane technology have become one of the most active fields of research in contemporary materials science (Dumont et al., 1997). Multi-layer films have evolved as candidates for these applications because of their unique properties. TiN and Ti/TiN multi-layer films were fabricated using the DC magnetron sputtering method. A nano-indentation tester and electronic film distribution tester were utilized to evaluate the mechanical properties and residual stress of the films. The existence of interface effects on the mechanical properties and corrosion resistance of the films were analyzed. Design/methodology/approach – In this study, the Ti/TiN multi-layer films were fabricated using the DC magnetron sputtering method. The films were deposited on polished 45# steels. Ti was used as the sputtering target. Ar and N2 were applied as working and reactive gases, respectively. Surface morphology was measured using transmission electron microscopy. The composition was analyzed using D8 X-ray diffraction. Nano-indentation tests were performed using Nanoindenter G200 with a Berkovich indenter. A BGS 6341 electronic film stress distribution tester was used to measure the distribution of stress in the films. Findings – The film surface was very smooth and the structure was very dense. The elastic modulus and micro-hardness of Ti/TiN multi-layer films were smaller, compared to those of the TiN film. Furthermore, both of these parameters initially decreased and later increased, with a decrease in the modulation period. The residual stress in the film was compressive. The corrosion resistance properties of TiN films were the best in NaCl solution, less so in alkaline solution and worst in acid solution. For the Ti/TiN multi-layer films tested in an acid medium, the corrosion resistance performance was better when the modulation period was decreased to micron grade under exposure conditions at ambient temperature. Originality/value – In the present paper, the Ti/TiN multi-layer films were fabricated using PVD with different variations, and the influence on the performance of Ti/TiN multi-layer films due to each single layer period of TiN was studied. The findings should provide useful guidelines for the preparation of high quality Ti/TiN multi-layer thin films. [ABSTRACT FROM AUTHOR]

The new carboxylic acid-neodymium anhydrous conversion films were successfully prepared and applied on the AZ91D magnesium alloy surface by taking absolute ethyl alcohol as solvent and four kinds of soluble carboxylic acid as activators. The corrosion resistance of the coating was measured by potentiodynamic polarization test in 3.5 wt.% NaCl solution in pH 7.0. The morphology, structure, and constituents of the coating were observed by scanning electron microscope, energy dispersivespectrum, x-ray photoelectron spectrum, and Fourier infrared spectrometer. Results show that corrosion resistance properties of samples coated with four different anhydrous conversion films were improved obviously. The corrosion potential increased, corrosion current density decreased, and polarization resistance increased. Among these four kinds of conversion films the one added with phytic exhibits the best corrosion resistant property. The mechanism of anhydrous-neodymium conversion film formation is also analyzed in this paper. It reveals that the gadolinium conversion coating is mainly composed of stable NdO, MgO, Mg(OH), and carboxylate of Nd. And that the sample surface is rich in organic functional groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Ti-Cu/Cu-Al functionally graded coating was prepared on Mg-Li alloy by laser cladding. • The graded coating was constructed to solve the problem that the influence of evaporation and dilution about Mg and Li elements on the performance of coating. • Typical hypoeutectic structure composed of Li 3 Mg 7 and CuMg 2 was obtained in the interlayer (Cu-Al). • The corrosion and wear resistance of Mg-Li got huge improvement. The bottleneck challenge of preparing laser cladded coating on Mg-Li alloys is the evaporation and dilution of substrate, which seriously affect the performance of coatings. In order to solve these deficiencies, Ni-Ti-Cu/Cu-Al functionally graded coating was proposed in this work. The graded coating with excellent performance was successfully prepared on Mg-Li alloy. More remarkable, the top-layer was not affected by dilution and substrate evaporation. The top-layer was mainly composed of Ni 3 Ti and NiTi intermetallic compounds, as well as TiNi 0.8 Cu 0.2 phase that dispersed on the surface of Ni 3 Ti. Typical hypoeutectic structure was found in the interlayer, which was composed of Li 3 Mg 7 and CuMg 2. Furthermore, the corrosion and wear resistance of Mg-Li alloy were greatly improved. Specifically, the wear volume of the top-layer and interlayer is reduced by 98.04% and 82.41% than that of substrate, respectively. The corrosion potential of the top-layer (-242 mV) and the interlayer (-991 mV) are 1311 mV and 562 mV higher than that of the substrate (-1553 mV), while the corrosion current density of the top-layer (2.71 × 10-7 A·cm−2) and the interlayer (1.93 × 10-6 A·cm−2) are about three and two orders of magnitude lower than that of the substrate (2.53 × 10-4 A·cm−2). [ABSTRACT FROM AUTHOR]

• The formation of solid solution phase is promoted by increasing Ta content. • The microstructure evolution mechanism with varied Ta content is investigated. • The RHEA coatings possess the good structure stability below 900 °C. • The stability of passive film is improved by increasing Ta content. [Display omitted] In this work, the novel NiTiCrNbTa x (x = 0.1, 0.3, 0.5, 1) refractory high-entropy alloy (RHEA) coatings were successfully synthesized on Ti6Al4V by laser cladding technology. The effect of Ta content on microstructure, thermal stability, micro-hardness and corrosion resistance of RHEA coatings was investigated in detail. The results showed that NiTiCrNbTa x RHEA coatings were composed of BCC, NiTi 2 -Laves and Cr 2 Nb-Laves phases. With Ta content increasing, the formation of BCC phase was promoted while the precipitate of Cr 2 Nb-Laves phase was affected. The average micro-hardness values of Ta 0.1 , Ta 0.3 , Ta 0.5 and Ta 1.0 RHEA coatings were calculated as ~922.8 HV 0.3 , ~985.1 HV 0.3 , ~851.3 HV 0.3 and ~825.4 HV 0.3 , respectively. The decrease of micro-hardness value might be ascribed to the reduction of hard Laves phase. After annealing at 900 °C for 3 h, the phase compositions of all RHEA coatings remained unchanged but the grains of Cr 2 Nb-Laves phase were refined obviously. Besides, RHEA coatings exhibited excellent corrosion resistance and the minimum corrosion current density was 1.08 × 10−7 A/cm2. Moreover, the secondary passivation phenomenon emerged in Ta 0.5 and Ta 1.0 coatings, and the passive film mainly consisted of the oxidation state of Ti, Cr, Nb, Ta and the sub-oxide state of Nb, Ta. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-step ultrasonic assisted laser cladding for Mg-Li alloy was proposed. • A metallurgical Ni 2 MnCuSnAl 0.1 MPEA coating was prepared on Mg-Li alloy. • Typical gradient microstructure was obtained in Ni 2 MnCuSnAl 0.1 MPEA coating. • The corrosion-resistance and wear-resistance of Mg-Li alloy were improved. The evaporation and dilution of substrate are the key deficiencies that limit the performance of laser-cladded coatings on Mg-Li alloys (or Mg alloys). In order to overcome these drawbacks, in this work, a novel Ni 2 MnCuSnAl 0.1 multi-principal element alloy (MPEA) coating and a multi-step ultrasonic assisted laser cladding technique were proposed. Dense metallurgical Ni 2 MnCuSnAl 0.1 MPEA coatings were successfully synthesized on Mg-Li alloy. Typical gradient microstructure of low-diluted layer, diffusive layer and interfacial layer were obtained in the coating. The low-diluted layer was composed of BCC solid solution, Ni 2 MnAl and Ni 2 MnSn while the diffusive layer and interfacial layer showed an interactive microstructure of Mg-CuMg 2 eutectic, Ni 2 MnAl, Li 2 MgSn/SnMg 2 and Mg/Mg-Li substrate. The corrosion potential of Ni 2 MnCuSnAl 0.1 MPEA coating (-108 mV SHE) was 1283 mV SHE higher than that of Mg-Li alloy (-1391 mV SHE), while the corrosion current density of the coating (5.85 × 10−7 A·cm−2) was about three orders of magnitude lower than that of Mg-Li alloy (1.12 × 10−4 A·cm−2). The micro-hardness gradually increased from the substrate to the coating, and the average micro-hardness of the coating was ~ 541.2 HV 0.2 , which is about 10 times higher than that of Mg-Li alloy (~57.8 HV 0.2). The wear resistance of Mg-Li alloy was also improved approximately 10 times by cladding Ni 2 MnCuSnAl 0.1 MPEA coating. [ABSTRACT FROM AUTHOR]

• High quality Ni-coated graphene powders were prepared by electroless plating. • Modified graphene was preserved in laser cladded coatings. • Modified graphene was conducive to improving the wear resistance of coatings. • Modified graphene significantly improved the corrosion resistance of coatings. In recent years, graphene (Gr) has attracted much attention owing to its excellent reinforcement effects. However, the application of Gr in laser cladded coatings remains a challenge due to the agglomeration of Gr and poor wettability between Gr and the molten metals. To overcome these problems, in this study, Ni modified Gr (Ni@Gr) powders were synthesized by electroless plating method, and Ni@Gr powders reinforced Ni60 (Ni60-Ni@Gr) composite coatings were prepared on the surface of AISI 1045 steel by laser cladding technique. The microstructure, existential state of Gr nanosheets, micro-hardness, wear resistance and corrosion resistance of Ni60-Ni@Gr coatings, Ni60-Gr coatings and Ni60 coatings were studied by SEM, TEM, XRD, Raman, micro-hardness tester, wear tester and electrochemical tester. The results showed that the wettability between the metal matrix and Gr was improved after modification, which promotes the dispersion of Gr nanosheets. The average micro-hardness value of Ni60-Ni@Gr coating was 920.79 HV 0.2 , which was higher than that of Ni60-Gr coatings (843.80 HV 0.2) and Ni60 coatings (777.13 HV 0.2). Compared with Ni60-Gr coatings and Ni60 coatings, the Ni60-Ni@Gr coatings have the lowest friction coefficient and weight loss, indicating the best wear resistance of Ni60-Ni@Gr coatings. The potentiodynamic polarization test and EIS test indicated that the corrosion resistance of Ni60 coatings was significantly improved after adding Gr. More notably, compared with the Gr without modification, the addition of modified Gr contributes to the further improvement of the corrosion resistance of Ni60 coating, which was related to the excellent barrier property of uniformly dispersed Ni@Gr powders in coatings. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) as nano reinforcement has been extensively used to improve the overall performance of metal-based composite coatings. In this work, GO nanosheets with surface modification and magnetic field (MF) assisted electro-brush plating (EBP) technique were employed to construct Ni-based composite coatings with biomimetic structure to improve the corrosion resistance of coatings. The preparation, deposited behavior and some properties of coatings were investigated. The results showed that after surface modification, GO surface carried numerous Co 7 Fe 3 magnetic nanoparticles with the size of 40–50 nm. During the MF assisted EBP process, the co-deposition of CoFe@GO magnetic powders with the reduced Ni atoms contributed to the formation of Ni-CoFe@GO composite coatings with stripe-like structure that resembled the surface morphology of conch. Besides, induced by the synergistic action of MF and electric field, most magnetic powders were distributed regularly in the stripe-like areas. After two weeks exposure to air, Ni-CoFe@GO composite coatings changed spontaneously from hydrophilic for fresh coatings to hydrophobic. This transformation was mainly attributed to the high surface roughness and the adsorption of a lot of hydrocarbons on the stripe-like surface. Moreover, air pockets that resulted from these hydrocarbons formed on the coating surface impeded the diffusion of corrosive media into coatings. Consequently, Ni-CoFe@GO composite coatings exhibited good corrosion resistance. Therefore, the preparation proposed in this work is desirable and has a prospect in further improving the corrosion resistance of GO reinforced Ni-based composite coatings. • A composite method was employed to prepare a new GO-reinforced Ni-based coating. • This coating presented the stripe-like structure similar to conch surface. • GO changed from non-magnetic to magnetic via surface modification. • Ni-CoFe@GO coatings exhibited hydrophobicity and good corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, FeCrCoAlMn 0.5 Mo 0.1 high-entropy alloy (HEA) coating was successfully synthesized on 316L stainless steel by ultrasonic assisted laser cladding. The effect of dilution rate on the phase composition of FeCrCoAlMn 0.5 Mo 0.1 coatings was investigated by thermodynamic calculation, solidification simulation and microstructure characterization. The mechanical properties, tribological behavior and corrosion resistance of FeCrCoAlMn 0.5 Mo 0.1 coating prepared under optimal dilution rate were also characterized in detail. The results show that the increase of dilution rate results in the transition of single solid solution (BCC) into dual-phase solid solution (FCC and BCC) of FeCrCoAlMn 0.5 Mo 0.1 coating. The TEM analysis reveals that FeCrCoAlMn 0.5 Mo 0.1 coating with optimal dilution rate (∼27.3%) is virtually composed of disordered BCC phase and ordered BCC (B2) phase. The spinodal decomposition structure and numerous dislocations were found in the grains. The average microhardness of FeCrCoAlMn 0.5 Mo 0.1 coating is ∼624.1 HV, which is more than 2.6 times higher than that of the substrate. The wear resistance of FeCrCoAlMn 0.5 Mo 0.1 coating was found significantly improved almost 4 times than that of 316L stainless steel. The passive current density of FeCrCoAlMn 0.5 Mo 0.1 coating is reduced by an order of magnitude compared with that of 316L stainless steel, proving the better corrosion resistance of FeCrCoAlMn 0.5 Mo 0.1 coating. • A new FeCrCoAlMn 0.5 Mo 0.1 HEA coating without defects was successfully prepared by ultrasonic assisted laser cladding. • Excessive dilution will result in phase transition of FeCrCoAlMn 0.5 Mo 0.1 HEA coating. • The spinodal decomposition structure and numerous dislocations are found in the coating. • FeCrCoAlMn 0.5 Mo 0.1 HEA coating shows good wear resistance and corrosion resistance. [ABSTRACT FROM AUTHOR]

In our work, an equiatomic Ni‐Cr‐Co‐Ti‐V multi‐principal element alloy is prepared by vacuum hot‐pressing sintering. The phase structure is investigated by Transmission electron microscopy (TEM) and properties of hardness, wear and corrosion resistance are studied. Furthermore, some reported high‐entropy alloys (HEAs) and conventional alloys are used as contrast for more intuitive evaluation of properties of Ni‐Cr‐Co‐Ti‐V HEA. The average micro‐hardness of this alloy reaches 1130 ± 15 HV. By nano‐indentation testing, the value of average Young's modulus and nano‐hardness are 318.6 ± 9 GPa and 17.21 ± 0.77 GPa, respectively. Compared with the room temperature, this alloy still keeps a good wear resistance at 600 °C and adhesive wear is the main wear mechanism. In the 3.5 wt% NaCl electrolyte, the passivating capacity of this alloy is significantly higher than that of 304 stainless steel and the corrosion rate of this alloy is relatively low, ≈0.035 mm/year. Thus, this alloy is expected to be applied in the severe interaction work environment of high temperature, wear, and corrosion. [ABSTRACT FROM AUTHOR]

• High entropy alloys (HEAs) was first introduced in underwater laser wetcladding process process. • The utilization rate of laser energy underwater can be enhanced. • The incorporation of Nb can enhance the corrosion resistance and prevent the expansion of pitting pits. Underwater wet laser cladding technology (UWLC) offers advantages such as short repair cycles, low costs, and independence from drainage equipment, making it highly practical. The exceptional design flexibility of high entropy alloys, combined with the convenience of UWLC technology, presents significant application potential. To assess the feasibility of utilizing high entropy alloys (HEAs) in underwater wet laser cladding, (NiCrCoFe) 100-x Nb x (x = 0, 5, 10) coatings were prepared. This study investigates the effects of Nb addition on the formation characteristics and metallurgical process of (NiCrCoFe) 100-x Nb x HEA coatings. The results show that the addition of Nb promotes the efficient utilization of laser energy underwater by altering the melting latent heat of UWLC materials and enhancing the fluidity of the molten pool. Furthermore, the introduction of Nb element improves the corrosion resistance of the coatings and inhibits the expansion of corrosion pits. This study confirms the feasibility of utilizing high entropy alloys for underwater wet laser cladding and offers new ideas and methods for the underwater online repair of marine equipment. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the Zr–Si–N films are prepared by magnetron sputtering and the effects of Si contents on the composition, microstructure and element chemical state of the films are analyzed by X-ray diffractomer (XRD), energy disperse spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. Electrochemical workstation is used to test the corrosion resistance of the films with different Si contents in physiological solution. The biocompatibility is also studied through protein surface absorption experiment. The results indicate that the films are mainly composed of ZrN and Si3N4 and their structures are amorphous. In physiological solution the corrosion resistance of the films first increases, then decreases along with the addition of Si. When the Si content reaches 8.32at.%, the film has the optimum corrosion resistance and good biocompatibility. [Copyright &y& Elsevier]

Abstract: In this paper, Hf–Si–N films were deposited on AZ31 magnesium alloys by ion beam assisted deposition (IBAD) technology. The phase structure, chemical valence state and nano-mechanical property of the films were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nano-indentation test, respectively. The corrosion resistance in physiological solution was studied by electrochemical system. The results show that the main phases of the films are HfN phase and Si3N4 phase. And the films have good corrosion resistance in physiological solution. [Copyright &y& Elsevier]