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The corrosive–wear and electrochemical properties of high–speed laser cladded Ni60WC coatings in 3.5 % and 5 % NaCl solutions were comparatively investigated, and the corrosive–wear mechanism was discussed in detail. The results show that the average coefficients of friction of Ni60WC coatings are increased with the laser scanning speed, and their maximal values in 3.5 % and 5 % NaCl solutions are 0.379 and 0.449, respectively; while the wear rates of Ni60WC coatings are first decreased and then increased, and their minimal values in 3.5 % and 5 % NaCl solutions are 199.2 ± 16 and 227.9 ± 31 μm3 s−1•N−1, respectively. The wear mechanism is combined of abrasive wear and pitting corrosion, which are attributed to the high hardness WC and soft Ni binder. Moreover, the Ni60WC coating fabricated at the laser scanning speed of 70 mm/s has the best corrosion resistance and stability, and its maximal charge transfer resistance in 3.5 % and 5% NaCl solutions is 2.45 × 105 and 9.67 × 104 Ω•cm−2, respectively, showing that the passive film with the p–n property contributed to the largest resistance. [ABSTRACT FROM AUTHOR]

Nickel-copper alloy is widely used because of its strong corrosion resistance in marine environment. There are great potentials to prepare NiCu alloy coatings on the surface of structural steel to replace cast NiCu alloys due to its high cost. High-speed laser cladding has characteristics of fast melting rate, low surface roughness, fine microstructure and low dilution ratio. However, nickel alloy coatings has the problem of solidification cracks. In this study, a series of composite coatings were prepared by using NiCu powders with different h-BN contents, then the effect of h-BN on structure and anti-corrosion of coatings was analyzed. The study shows that the structure of the NiCu composite alloy coatings was equiaxed crystals, columnar crystals and planar crystals from top to bottom portion. After adding h-BN, the coating had a lower oxygen vacancy mobility rate, resulted in the optimal corrosion resistance of passive film.

High-speed laser cladding was introduced to prepare a CoCrFeNiMo high-entropy alloy (HEA) coating. The microstructure, composition distribution, micromechanical properties, and corrosion resistance of the CoCrFeNiMo coating were characterized. As a result, the coating exhibited a dual FCC- and BCC-phase structure, and the grain size of the coating prepared through high-speed laser cladding was only 2~5 μm. The upper and lower parts of the coating were composed of equiaxed cellular crystals and slender columnar crystals, respectively. The interdendritic structure was a Mo-rich phase that was distributed in a network-like pattern. The nanoindentation tests revealed that the interdendritic BCC phase had high hardness and an elastic modulus as well as excellent resistance to deformation, while the intradendritic FCC phase possessed superior crack propagation resistance. In addition, the two phases could generate cooperative elastic deformation during the elastic deformation stage. The electrochemical performance of the coating was tested in 3.5 wt% NaCl solution, and the corrosion potential Ecorr and corrosion current density Icorr of the coating were −0.362 V and 3.69 × 10−6 A/cm2, respectively. The high-speed laser cladding CoCrFeNiMo HEA coating had excellent corrosion resistance thanks to the presence of the easily passivating element Mo and grain refinement. [ABSTRACT FROM AUTHOR]

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Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High quality 431 steel coatings were prepared on a 27SiMn substrate by extreme-high-speed laser cladding (EHLA) and conventional laser cladding (CLA), respectively. The cladding speed of the EHLA process was 150 m/min, and the surface rate could reach up to 1.14 m2/h, which is four times higher than that of the CLA process. The microstructure of the coatings was investigated in detail. The microstructure of both coatings was dominated by dendrites. Benefitting from the ultrahigh cooling rate, the dendrites of EHLA coatings were more refined than that of CLA coatings. The element distribution between dendrites and interdendritic regions was more uniform. The corrosion resistance was evaluated by electrochemical tests. The results indicated that the EHLA coatings performed better corrosion resistance due to the fine uniform microstructure. [ABSTRACT FROM AUTHOR]

Fe-based amorphous coatings were prepared on the surface of the AISI 1020 steel pipe by high-speed laser cladding technique. This study is aimed to investigate the influence of scanning speed on the microstructure, hardness, amorphous content and corrosion resistance offered by the Fe-based amorphous coatings. The results showed that, the coating obtained at 50 mm/s exhibited a distinct three-layer hardness distribution, with the second layer displaying the highest hardness. This phenomenon was primarily ascribed to amorphous strengthening, fine-grain strengthening, and martensitic strengthening. The bottom region of the coatings contains budding crystals, with prominent aggregation of elemental Fe. Away from the budding regions, a transition from columnar to dendritic crystals was observed. The amorphous content of the coatings exhibited an initial rise followed by a decline with increasing scanning speed. Among these, the amorphous phase content of 130 mm/s coating was up to 95 %. Differential Scanning Calorimetry (DSC) test results confirmed the presence of amorphous phases in the bottom and middle regions of the 50 mm/s coating. Electrochemical experiments underscored the exceptional corrosion resistance of the 130 mm/s coating, evidenced by its maximum corrosion potential (−0.471 V), minimal corrosion current density (2.7 × 10−6 A/cm2), and highest polarization resistance value (22,149 Ω·cm2). This superior performance was attributed to the presence of the amorphous phase and the Cr oxide layer formed on the surface, providing robust protection to the substrate. • Fe-based amorphous coatings were prepared by high-speed laser cladding. • High hardness attributed to amorphous strengthening, fine-grain strengthening, and martensitic strengthening. • The amorphous content of the coatings increased initially but decreased at the highest scanning speed. • High amorphous content and the Cr oxide layer formed on the surface provided robust protection to the coating. [ABSTRACT FROM AUTHOR]

Two kinds of CoCrFeMnNi high entropy alloy (HEA) coatings were prepared by high-speed laser cladding (HS-) and normal laser cladding (N-), respectively. The phase, microstructure, micromechanical properties, and corrosion resistance of both coatings were analyzed. According to the results, both coatings are stable single-phase FCC structures with the dendrites microstructure. However, the dendrites of the HS-CoCrFeMnNi coating are finer. Owing to the low heat input and the quick cooling and heating characteristics of high-speed laser cladding, the width of the heat affected zone and the dilution ratio of the HS-CoCrFeMnNi coating are reduced. In addition, the microhardness of the HS-CoCrFeMnNi coating (∼ 184 HV 0.2) is higher than that of the N-CoCrFeMnNi coating (∼ 160 HV 0.2). The elastic modulus (E r) of the HS-CoCrFeMnNi coating is significantly increased in order to enhance its resistance to plastic deformation. The plastic storage energy Q p of the HS-CoCrFeMnNi coating is higher, revealing the improved crack resistance. The self-corrosion potential E corr of the HS-CoCrFeMnNi coating positively shifted by 0.142 V compared with the N-CoCrFeMnNi coating, and the self-corrosion current density I corr decreased from 6.3 × 10−6 A/cm2 to 2.9 × 10−7 A/cm2 in 3.5% NaCl solution. Therefore, the HS-CoCrFeMnNi coating possesses better corrosion resistance and comprehensive mechanical properties. [Display omitted] • Two CoCrFeMnNi coatings were prepared by high-speed and normal laser cladding. • High-speed laser cladding can refine grains, and decline dilution and heat effect. • Ultra non-equilibrium solidification refined grains and altered pore evolution. • Higher plastic deformation storage energy means a decrease in crack sensitivity. • HS-CoCrFeMnNi coating possesses improved microhardness and corrosion resistance. [ABSTRACT FROM AUTHOR]

Two kinds of CoCrFeNi high entropy alloy coatings were prepared by normal laser cladding (N-) and high-speed laser cladding (HS-), respectively. The comparative analyses of crystallographic orientation distribution, microstructure, microhardness, wear resistance and corrosion resistance of both coatings were conducted. The results show that the phase structures of HS-CoCrFeNi and N–CoCrFeNi coatings are single FCC solid solutions. The dendrite size of HS-CoCrFeNi coating is only half of that of N–CoCrFeNi coating. The microhardness of HS-CoCrFeNi coating (380 HV 0.2) is about 2.3 times that of N–CoCrFeNi coating (165 HV 0.2), due to the combined effect of grain refinement, dispersion strengthening and dislocation strengthening. The wear resistance and corrosion resistance of HS-CoCrFeNi coating are better than N–CoCrFeNi coating. With the increase of friction speed, the same wear mechanism of the two coatings is obtained, changing from abrasive wear to adhesive wear and fatigue wear. High-speed laser cladding is a promising technology to promote the development and application of high entropy alloys in the industry. [Display omitted] • Two CoCrFeNi coatings were prepared by high speed and normal speed laser cladding. • Consistent orientation of HS-CoCrFeNi coating ensured the continuity of microstructure. • HS-CoCrFeNi coating possessed better microhardness, wear and corrosion resistance. • High speed laser cladding furthur reduce the dilution ratio of CoCrFeNi HEA coating. [ABSTRACT FROM AUTHOR]

Nickel-plated carbon nanotubes (CNTs) as additive phases can greatly improve the friction and corrosion properties of composite materials. Nickel-coated CNTs/FeCoNbBSi amorphous composite coatings were prepared on the surface of a 45-steel shaft by using high-speed laser cladding technology. Results showed that the microstructure was refined after the amount of nickel-plated CNTs increased, but the crystallization remained sever, and the amorphous content decreased from 48.36% to 27.18%. The friction coefficient decreased, and the wear morphology improved with increasing amount of nickel-coated CNTs. The friction coefficient was only 0.22 when the amount of nickel-coated CNTs was 1 wt%. In addition, the bridging behavior of the nickel-coated CNTs at the crack increased corrosion time and improved the corrosion resistance of the coating. • The amorphous content decreased with the increase of CNTs content in the coating. • When the CNTs content reached 1 wt%, the surface work of the coating basically remained at 500 mv. • The more CNTs in the coating, the better self-lubrication performance and wear resistance. [ABSTRACT FROM AUTHOR]

• Fe-based coatings were prepared by combining HSLC and PST techniques. • The influence of ferrite on the corrosion resistance of the coating was discussed. • The microstructure and composition of the coating were analysed. Fe-based alloy coatings are promising for protecting the surface of hydraulic columns because of their excellent corrosion resistance. In this study, Fe-based coatings were prepared using high-speed laser cladding (HSLC) technology, and the outer surface of the coating was subjected to powerful spinning treatment (PST). The grains of the surface layer of the coatings were refined, which increased the volume ratio of intergranular ferrite, and subsequent X-ray diffraction detection revealed more α-phases. Their electrochemical corrosion behaviour in a 3.5% NaCl solution indicated that PST coatings exhibited higher corrosion resistance than the coatings without PST. The anti-corrosion mechanism was discussed based on grain refinement, phase composition, and elemental content. [ABSTRACT FROM AUTHOR]

• High quality FeCrMoMn coatings were fabricated by high-speed laser cladding. • Mechanism of laser acting on powders during high-speed laser cladding. • Metallurgical behavior of solute trapping during rapid solidification of laser molten pool. • Evolution mechanism of corrosion resistance of high-speed laser clad coatings. In this research, FeCrMoMn coatings with excellent corrosion resistance and metallurgical quality were deposited on the 45# steel substrate by conventional and high-speed laser cladding at the scanning speed of 0.4 m/min, 40 m/min and 70 m/min, respectively. Their microstructure, phase composition, hardness and corrosion resistance were characterized and compared. The results show that compared with the conventional cladding, high-speed laser cladding leads to a decrease in grain size, heat affected zone, and the dilution rate of the coatings due to solute trapping of coatings. Metallurgical bonding is formed between the substrate and the coatings, and the hardness and electrochemical corrosion resistance of the coatings are also significantly improved. [ABSTRACT FROM AUTHOR]

High-speed laser cladding technology can significantly improve the efficiency of coating preparation and effectively widen the application range of laser cladding. In this study, the Ni45 powders were deposited on steel substrate by traditional low speed laser cladding and high-speed laser cladding process, respectively. The cladding efficiency, surface forming, cross-sectional microstructure, microhardness, wear and corrosion resistance properties of the traditional and high-speed laser cladded Ni45 alloy coatings were compared. It can be seen that the thickness of the high-speed laser cladding coating was much thinner than that of the traditional laser cladding coating. Compared with traditional laser cladding, high-speed laser cladding could achieve a cladding speed of 76.86 m/min and a cladding efficiency of 156.79 cm2/min. The microstructure of the two kinds of coatings shows the same growth law, but the microstructure in high-speed laser cladding was smaller and denser, and the columnar crystal interval was narrower, only about 6 μm. It is found that the cooling rate of the traditional laser cladding coating was smaller than that of the high-speed laser cladding, and as the cladding speed increased, the cooling rate became higher and higher. The cross-section microhardness of the traditional laser cladding coating was relatively uniform of 337 HV 0.2 , while the microhardness of high-speed laser cladding surface increased to about 543 HV 0.2. In addition, the wear and corrosion resistance of high-speed laser cladded coatings were better than that of traditional laser cladded coatings. As the cladding speed increased, the wear and corrosion resistance of the cladded coatings became better. • High-speed laser cladding coating had low roughness and thin coating. • The cooling rate increased exponentially with a decrease of secondary dendrite arm. • The wear and corrosion resistance increased with the increase of cladding speed. • The microstructure was refined continuously with the increase of cladding speed. [ABSTRACT FROM AUTHOR]