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The long-term operation of intermediate temperature-solid oxide fuel cells (IT-SOFCs) could be significantly influenced by the stability of the interconnect itself, especially, its oxidation resistance under the cathode environment. To effectively prevent Cr-volatilization and improve the interconnector performance, application of highly dense and stable protective coatings over the interconnector is indispensable. In this work, Ni-Co-based alloy protective coatings doped with Fe and Cu were applied onto the 441 interconnector via a novel high-speed laser cladding technology. The microstructure evolution, phase composition, oxidation resistance, electrical conductivity and mechanical properties of the coated steels were investigated at different oxidation stages at 800 °C. It was found that the Ni 33.8 Co 34 Fe 32.2 -coated steel shows the best oxidation resistance and electrical properties. The oxidation rate (k p) and ASR of Ni 33.8 Co 34 Fe 32.2 -coated steel is respectively 4.44 × 10−13 g2 cm−4 s−1 and 25.55 mΩ cm2, significantly lower than the uncoated steel and Ni 44.6 Co 44.7 Cu 10.7 -coated steel at the end of 1000-h test cycle. The resultant conductivity of the Ni 44.6 Co 44.7 Cu 10.7 and Ni 33.8 Co 34 Fe 32.2 -coated steels is approximately 7.8 and 4.1 S cm−1, respectively, which could meet the requirement for SOFC stacks. In addition, the nano-hardness of the Ni 33.8 Co 34 Fe 32.2 and Ni 44.6 Co 44.7 Cu 10.7 -coated steels was found to be 8.3 GPa and 8.8 GPa, respectively, through nanoindentation testing. The improved surface hardness is attributed to grain refinement and increased oxide content on the coating surface. The results indicated that the Ni-Co-based alloy coatings effectively improved the long-term stability and mechanical property of the 441 interconnector under the SOFC cathode environment. [Display omitted] [ABSTRACT FROM AUTHOR]

High-temperature oxidation resistance is the major influence on the high-temperature service stability of refractory high entropy alloys. The oxidation behavior of lightweight Al0.2CrNbTiV refractory high entropy alloy coatings with different dilution ratios at 650 °C and 800 °C deposited by high-speed laser cladding was analyzed in this paper. The oxidation kinetic was analyzed, the oxidation resistance mechanism of the Al0.2CrNbTiV coating was clarified with the analysis of the formation and evolution of the oxidation layer, and the effect of the dilution rate on high-temperature performances was revealed. The results showed that the oxide layer was mainly composed of rutile oxides (Ti, Cr, Nb)O2 after isothermal oxidation at 650 °C and 800 °C for 50 h. The Al0.2CrNbTiV coating in low dilution exhibited better oxidation performance at 650 °C, due to the dense oxide layer formed with the synergistic growth of fine AlVO3 particles and (Ti, Cr, Nb)O2, and higher percentage of Cr, Nb in (Ti, Cr, Nb)O2 strengthened the lattice distortion effect to inhibit the penetration of oxygen. The oxide layer formed at 800 °C for the Al0.2CrNbTiV coating was relatively loose, but the oxidation performance of the coating in high dilution improved due to the precipitation of Cr2Nb-type Laves phases along grain boundaries, which inhibits the diffusion of oxygen. [ABSTRACT FROM AUTHOR]

In the case of electrical contact, copper alloys are often unable to withstand arc ablation and premature failure. To solve this issue, Ni-8wt.%Al (Ni–8Al) coatings were successfully prepared on copper substrates utilizing the high-speed laser cladding. In addition, the microstructure evolution, microhardness, electric conductivity and arc ablation resistance of the prepared coatings were investigated in detail. As a result, the achieved Ni–8Al coatings were structurally dense with good metallurgical bonding to the substrate, of which the microstructure showed a bottom-up evolution of fine sub-grain structure. Notably, the microhardness of the coating was 191.7 HV0.2, representing an increase of 82.57% compared to the substrate, and the electrical conductivity was 18.03 %IACS, approaching that of pure nickel. Additionally, the increase in ablation currents led to changes in the ablation behaviors and failure mechanisms of both the substrate and coating. At high currents, a huge arc ablation crater appeared in the center of the substrate due to the reaction force of the anode flame and the difference in surface tension between the liquid metal at the center and the edge of the molten pool. Nevertheless, the coatings showed better arc ablation resistance due to the improvement of molten pool stability during arc ablation by the in situ formed Al2O3 layer on the coating surface.

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering 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.)

Inconel 625 alloy cladding layer was prepared by high-speed laser cladding (HLC) on Q245R steel substrate to improve the service performance of the structural components in the power industry in this work. A comprehensive study on the HLC Inconel 625 coating with different scanning speeds was conducted utilizing Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Laser Scanning Confocal Microscope (LSCM), X-Ray Diffraction (XRD), a microhardness tester, and an SRV-4 high-temperature friction and wear testing machine. The results show that the cladding layer's thickness and surface roughness decrease with the scanning speed increase. The cladding layers with different scanning speeds contain different microstructures. The phases mainly consist of γ-Ni and NbC. The microhardness of HLC coatings is generally higher than that of substrate, but decreased as the scanning speed increased. After the friction wear test at 500 °C, the cladding layer at the scanning speed of 2 m/min showed the best high-temperature wear resistance. The grain boundary area increases due to the formation of small-sized equiaxed dendrites, which resists dislocation slip and crack propagation, thereby enhancing high-temperature wear resistance. For the cladding layers at the higher scanning speed, the abrasive wear and the fatigue wear occur due to the precipitation of solid soluble elements such as Nb and Mo and the columnar crystal structures prone to deformation.

Fe-based coatings have been prepared by utilizing laser cladding with the scanning speed ranging from 1.57 to 20.4 m/min. The microstructure and corrosion properties have been further investigated to evaluate the effects of scanning speed. The results show that, both coating's thickness and dilution rate gradually decrease with the increase of scanning speed. However, the deposition efficiency on the surface can be greatly improved by around 4 times. Under high scanning speed, the Fe-based coatings show the similar microstructure feature, comprising with dendrites and inter-dendritic structures. But the coating's microstructure can be significantly refined with the secondary dendritic arm spacing less than 1 μm. Furthermore, the gap of Cr concentration between the two structures can be effectively reduced, which shrinks the difference in corrosion resistance. On the other hand, the Fe-based coating's hardness gradually decreases resulting from the retained austenite and ferrite under high scanning speed. Compared to Q235 steel, the cladded Fe-based coatings show superior corrosion resistance with much higher corrosion potential and lower corrosion current density. Pitting dominates the corrosion forms of high-speed laser Fe-based coatings, which initially takes place on the boundaries of different structures. With the increase of scanning speed, the coating's corrosion resistance increases firstly and then decreases, and the coating cladded with the speed of 15.7 m/min shows the best corrosion resistance. Higher average Cr content and more uniform Cr distribution account for the better corrosion resistance. However, excessive microstructure refinement plays a negative role in the coating's corrosion resistance owing to more grain boundaries.

The initial melting quality of a high-speed laser cladding layer has an important impact on its post-treatment and practical application. In this study, based on the repair of hydraulic support columns of coal mining machines, the influence of high-speed laser cladding process parameters on the quality of Fe-Cr-Ni alloy coatings was investigated to realize the accurate prediction of coating quality. The Taguchi orthogonal method was used to design the L25(56) test. The prediction models of the relationship between the cladding process and the coating quality were established using the Random Forest (RF) and AdaBoost (Adaptive Boosting, AB) algorithms, respectively. Then, the prediction accuracy of the two models was compared, and the process parameter features were screened for importance evaluation. The results show that the AB prediction model is more accurate than the RF prediction model and more sensitive to abnormal data. The importance evaluation based on the AdaBoost model shows that the scanning speed has a great influence on the height and surface roughness of the coating. On the other hand, the overlap rate is the most important factor in controlling the dilution ratio and near-surface grain size of high-speed laser melting coatings. In addition, the micro-hardness of the coating and the thermal effect of the substrate can be effectively enhanced by adjusting the laser power and scanning speed. Finally, it was verified that the AB prediction model could accurately estimate the quality indexes of the coating with a prediction error less than 6%. The results show that it is feasible to predict the quality of high-speed laser cladding with the AB algorithm. It provides a basis for the adjustment of process parameters in the subsequent quality control process of cladding. [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.

A dense and continuous Cr coating with a thickness of approximately 140 μm was successfully deposited on the surface of a thin-walled Zr alloy cladding tube using high-speed laser cladding technology in this study. The microstructure, phase composition, microhardness, and resistance to high-temperature oxidation of the coating were investigated. The experimental results showed that the Cr coating exhibited high-strength metallurgical bond with the Zr alloy substrate, forming a narrow heat-affected zone with a thickness of 25 μm, and the coating consists of ZrCr2 and α-Zr phase. The average microhardness of the coating was 589 HV0.05, about 2.3 times that of the substrate. After oxidation at 1200 °C for 1200 s in air, with the formation of complete and dense protective Cr2O3 scale, the Cr-coated Zr alloy cladding tube showed better high-temperature oxidation resistance than uncoated tube. [ABSTRACT FROM AUTHOR]

Due to the rapid advancement in processing efficiency, high-speed laser cladding has demonstrated significant potential in the repair and protection of various substrates. In this study, we established a comprehensive evaluation model for the coating quality of Fe-Cr-Ni-based alloy with high-speed laser cladding using the analytic hierarchy process and fuzzy comprehensive evaluation method (AHP-FCE). The weights obtained through the analytic hierarchy process for forming quality, microstructure, and surface performance are as follows: WB1 = 0.1365, WB2 = 0.2385, and WB3 = 0.625, respectively. During the fuzzy comprehensive evaluation step, an evaluation level was graded while quantifying the level range through membership function judgment. By combining subjective and objective evaluations, qualitative issues were transformed into quantitative assessment methods. Through comprehensive evaluation analysis, it was concluded that the scanning speed of high-speed laser cladding had a greater impact on coating thickness compared to powder feeding speed while significantly enhancing microstructure densification. The overlap rate exerted the most influence on dilution rate homogenization of near-surface dendrites. Simultaneously, the optimal preparation technology was determined: laser power 660 W, scanning speed 14,400 mm/min, overlap rate/min. This study transforms multi-objective quality evaluation of high-speed laser cladding coatings into a single objective problem by realizing comprehensive quality quantification and providing a new method for quantitative evaluation and visualization of coating quality. [ABSTRACT FROM AUTHOR]

Establishing the relationship between thermal cycling and the induced evolution of microstructures and cladding layer properties is crucial to achieving microstructural and performance control, given the complexity involved in high-speed laser cladding process. We hereby report our new findings from laser cladding of Inconel 625 on Q245R steel substrate using a high-speed laser cladding technique. The microstructure evolution and microhardness variations in the first cladding track with different thermal cycles were examined by XRD, SEM, EBSD, TEM, and microhardness tests in detail. Numerical simulation was also conducted to characteristically illustrate the complex thermal cycles during the laser cladding process. Our work revealed that the first six thermal cycles resulted in significant variations of microstructure in the laser cladding layers. The dislocation density and low angle grain boundaries (LAGBs) of the first cladding track decreased after two thermal cycles due to the high peak temperature (above 1000 °C) of thermal cycles and subsequently increased when subjected to further thermal cycles with low peak temperature (below 500 °C). The microhardness value increased from 220 HV0.2 to 320 HV0.2, mainly caused by the formation of precipitated phase during the first four thermal cycles, and through by the enhancement of dislocations after six thermal cycles.

The initial melting quality of a high-speed laser cladding layer has an important impact on its post-treatment and practical application. In this study, based on the repair of hydraulic support columns of coal mining machines, the influence of high-speed laser cladding process parameters on the quality of Fe-Cr-Ni alloy coatings was investigated to realize the accurate prediction of coating quality. The Taguchi orthogonal method was used to design the L25(56) test. The prediction models of the relationship between the cladding process and the coating quality were established using the Random Forest (RF) and AdaBoost (Adaptive Boosting, AB) algorithms, respectively. Then, the prediction accuracy of the two models was compared, and the process parameter features were screened for importance evaluation. The results show that the AB prediction model is more accurate than the RF prediction model and more sensitive to abnormal data. The importance evaluation based on the AdaBoost model shows that the scanning speed has a great influence on the height and surface roughness of the coating. On the other hand, the overlap rate is the most important factor in controlling the dilution ratio and near-surface grain size of high-speed laser melting coatings. In addition, the micro-hardness of the coating and the thermal effect of the substrate can be effectively enhanced by adjusting the laser power and scanning speed. Finally, it was verified that the AB prediction model could accurately estimate the quality indexes of the coating with a prediction error less than 6%. The results show that it is feasible to predict the quality of high-speed laser cladding with the AB algorithm. It provides a basis for the adjustment of process parameters in the subsequent quality control process of cladding.

To repair or improve the performance of H13 hot working molds through the additive manufacturing process, IN 718 was coated on H13 die steel by high-speed laser cladding followed by an ultrasonic surface rolling process (USRP). The mechanism of ultrasonic surface rolling on the mechanical properties of the coating was studied. After USRP, the coating exhibited severe plastic deformation; the microscopic organization of the surface layer was refined and the particle size was significantly reduced. The violent plastic deformation of the coating caused by USRP improved the dislocation density and the grain boundary density, providing an improved yield strength of the coating and improving the high-temperature wear resistance of the coating. After USRP, the surface hardness of the coating increased by 30%. Compared with the coating without USRP, the wear resistance of the coating greatly improved; the wear rate was reduced by 51% and the wear mechanism of the coating changed from large-area adhesive wear and severe abrasive wear to small-area adhesive wear and slight abrasive wear. The IN 718 coating after USRP had a higher hardness and greater wear resistance, significantly improving the service life of H13 steel. [ABSTRACT FROM AUTHOR]

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]

Copyright of Journal of Central South University is the property of Springer Nature 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.)

To repair or improve the performance of H13 hot working molds through the additive manufacturing process, IN 718 was coated on H13 die steel by high-speed laser cladding followed by an ultrasonic surface rolling process (USRP). The mechanism of ultrasonic surface rolling on the mechanical properties of the coating was studied. After USRP, the coating exhibited severe plastic deformation; the microscopic organization of the surface layer was refined and the particle size was significantly reduced. The violent plastic deformation of the coating caused by USRP improved the dislocation density and the grain boundary density, providing an improved yield strength of the coating and improving the high-temperature wear resistance of the coating. After USRP, the surface hardness of the coating increased by 30%. Compared with the coating without USRP, the wear resistance of the coating greatly improved; the wear rate was reduced by 51% and the wear mechanism of the coating changed from large-area adhesive wear and severe abrasive wear to small-area adhesive wear and slight abrasive wear. The IN 718 coating after USRP had a higher hardness and greater wear resistance, significantly improving the service life of H13 steel.

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.)

To enhance the wear-resistance of nickel-based blade surfaces, a (CoCrNi) 88 Al 6 Ti 6 -cBN composite coating was produced on GH4169 substrates using HSLC. The microstructure, microhardness and tribology properties of the coating at 25 and 600 °C were evaluated. The finding demonstrates that the hardness of the cBN composite coating increase by 91.6 HV 0.3 attributed to precipitation strengthening, second phase strengthening and dislocation strengthening. Furthermore, the anti-wear performance of the coating increased by 3.72 times at 25 °C and by 3.23 times at 600 °C, respectively. Additionally, the friction coefficient exhibited by the coating diminished significantly by converting a portion of the cBN to hBN under the high temperatures generated by laser and oxides generating. [ABSTRACT FROM AUTHOR]

In this work, the NiCr-Cr 3 C 2 coatings with different Cr 3 C 2 contents were prepared via high-speed laser cladding. The relationships between the composition, microstructure, and high-temperature tribological properties in fluoride molten salts were systematically studied. The results suggest that with the increase of Cr 3 C 2 content, the friction coefficient tends to decrease and stabilize, while the wear rate initially decreases and then increases. Especially for the coating with 60 wt% Cr 3 C 2 , it exhibits a favorable tribological performance mainly due to the enhanced hardness imparted by Cr 3 C 2 , with an average friction coefficient of 0.12 and a wear rate of 2.78 × 10−6 mm3/Nm. However, the coating experiences delamination damage at 70 wt% Cr 3 C 2 content, leading to an increase in wear rate. [ABSTRACT FROM AUTHOR]

Laser butt welding of thin steel sheets without filler material was widely used in many industrial fields. However, it was very difficult to focus the small laser spot on the narrow gap between the sheets during the laser butt welding process. In this study, a new method to weld thin steel sheets using a high-speed laser cladding technique is proposed. Stainless steel sheets with a thickness of 0.5 mm were welded using the high-speed laser cladding process. The results illustrated that good weld joints could be obtained without obvious cracks and pores in most of the specimens. The joints were well formed even if the sheets were not spliced together entirely. The average tensile strength of the specimens was about 500 MPa, which is almost the same as that of the substrate. The results also showed that most of the failures did not happen in the welding region, which could be concluded that the strength of joints was higher than that of the substrate. The microstructure was determined using an optical microscope (OM) and scanning electron microscope (SEM). The results showed that it may be a good choice to use the high-speed laser cladding technique for butt welding of stainless steel sheets.

To address the problem of die steel wear failure, Fe-Ti 2 AlC-Ni composite coatings were fabricated on the Cr 12 MoV matrix by high-speed laser cladding. The mechanism of Ti 2 AlC on tribological properties was explored, providing ideas for the longevity of mould steel. The macroscopic morphology, microstructure, phase composition, hardness, and tribological properties of the composite coatings were also analyzed. Results showed that composite coatings with good surface quality and no internal cracks were obtained with Ti 2 AlC content between 5 and 10 wt%. The Fe-based coating without Ti 2 AlC only comprised the α and γ phases, whereas the composite coatings comprised the α and γ phases as well as the Ti 2 AlC self-lubrication phase, the TiC and Ti 3 Al hard phases. Hardness increase was predominantly attributed to the hard phases generated in situ. The lowest frictional coefficient and wear rate were obtained at Fe-based-10wt%Ti 2 AlC, which were 0.52 and 0.0112 mm3/N·m, respectively. The coating wear mechanism was primarily abrasive, adhesive, and oxidative wear. Moreover, with an increase in Ti 2 AlC content, the wear became slight under the collaborative cooperation of oxide film, self-lubricating and hard phases. • The formation of possible reactions in the molten pool during the laser cladding process is speculated. • Confirmation of the existence of Ti 2 AlC self-lubricating phase, the TiC and Ti 3 Al hard phases in Fe-Ti 2 AlC@Ni composite coatings' microstructure. • The friction-wear mechanism of the Fe-Ti 2 AlC@Ni composite coatings is revealed. [ABSTRACT FROM AUTHOR]

The most commonly used surface protection technologies against wear and corrosion are electrochemical hard chromium plating or thermal spraying. But these coating technologies have limits. Additionally, due to health concerns, hard chromium plating is under increasingly restrictive use in Germany, the European Union, and the Asian market. One technology which is currently under investigation for replacing conventional coating processes, e.g., plating in these instances is the high-speed laser cladding. Using high-speed laser cladding (high-speed laser metal deposition, HS-LMD), which is a DED (directed energy deposition) process, a laser beam is heating powder particles, which are fed coaxially into the laser beam, to nearly melting temperature before these particles hit the surface. Using a laser as the heat source, the heat input into the workpiece can be minimized. This allows a very low dilution of additive material into workpiece--typically < 10 µm--and high feed rates between 100 and 500 m/min can be achieved. Layers generated by this process can be locally adjusted in thickness between 50 and 300 µm per layer. Since each layer is metallurgically bonded to the metallic substrate or the adjacent layer before, multi layers or multi-material approaches are feasible. By use of the aforementioned unique process features, new and in properties tailored coating systems become possible. HS-LMD might be a promising candidate for replacement of hard chromium plating, for example, large rotational symmetric parts. In this paper, we have selected Rockit®401 as a hard, corrosion-resistant, and nearly "cracking-proof" material. Additionally, we have chosen the corrosion resistant Inconel® 625. We will investigate the influence of high surface rates on properties such as defects, hardness, and crack susceptibility, as well as achievable layer thicknesses. [ABSTRACT FROM AUTHOR]

• A lightweight fully convolutional neural network (FCN-Resnet50) model is proposed to more accurately capture and segment the geometric features of high-speed laser cladding melt pool. • The results of this study show that the proposed method has a high segmentation accuracy (greater than 96 %) for the characteristics of melt pool under different cladding conditions. • Combined with the results of the melt pool parameters extracted from the network model, the influence of high-speed laser cladding process parameters on the geometric characteristics of the melt pool was analyzed. High-speed laser cladding is a promising additive manufacturing technology, and the quality of cladding forming is closely related to the forming state of the melt pool. The result of melt pool segmentation is the key to understand the dynamics of the melt pool, and the feature segmentation of the melt pool can provide an effective basis for the subsequent quality diagnosis and real-time feedback control. Due to the traditional image processing algorithm is difficult to adapt to the melt pool image uneven brightness and splash and other disturbing factors, the traditional image processing methods have limitations on the adaptability of the melt pool segmentation. In this paper, a novel method for detecting the features of high-speed laser cladding melt pool based on fully convolutional neural network of FCN-Resnet50 is introduced, and the corresponding melt pool image dataset is produced. The FCN-Resnet50 image segmentation performance is compared with traditional image segmentation methods and other semantic segmentation algorithms. The results show that the validation accuracy rate of FCN-Resnet50 is 96.7 %, which realizes a better image segmentation effect with high robustness. In addition, the relationship between the average melt pool area and melt pool width captured by the melt pool and the laser power, scanning speed and powder feeding speed is analyzed. [ABSTRACT FROM AUTHOR]

Electromagnetic shielding materials can inhibit or reduce the harm of electromagnetic radiation and have become an important means to protect against electromagnetic pollution. In order to overcome the inconveniences of in situ or conformal manufacturing on the specific equipment, and the resulting assembly errors lead to the reduction of electromagnetic interference shielding effectiveness (EMI SE). As a new technology, high-speed laser cladding can directly design multi-walled carbon nanotubes (MWCNTs)-FeCo alloy composites as absorbents, and it is the first time to realize the rapid manufacturing of electromagnetic shielding materials by one-step in-situ deposition without adding auxiliary materials. According to the temperature field and stress field, it is found that the through-crack defects of electromagnetic shielding coating mainly resulted from the residual stress concentration of microcracks near the bottom fusion line. When the cladding strategy is 1600 W power deposition after preheating at 400 °C, a high-quality cladding layer can be obtained. When the addition of MWCNTs is 1.5 wt%, the material exhibits good electromagnetic shielding performance under the synergistic effect of dielectric loss, conductivity loss, and magnetic loss. And the average EMI SE is 23 dB in the range of 2-18GH. The research shows that high-speed laser cladding can simultaneously meet the requirements of flexible material design and efficient preparation, which realizes the integration of electromagnetic shielding material design and manufacturing. [Display omitted] [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]

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]

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]

The microstructure evolution and strengthening mechanism of multi-pass power spinning high-speed laser cladding coatings at room temperature were studied. The theoretical basis and technical support were provided for the power spinning laser cladding coating. The results show that power spinning can effectively improve the macroscopic forming quality of the cladding layer. Multiple actions of the coating surface wave peak metal flow to the trough, effectively reducing the surface roughness of the cladding layer. The EBSD comes about appeared that the surface grain tilted within the nourishing course with the increment of turning passes and changed from dendrites to equipped precious stones with a normal grain measure of 2.3 μm. The surface microstructure was refined and disseminated within the surface layer basically by deformed clear organization. The increment within the number of spinning passes increments the extent of distorted tissue, and more low-angle grain boundaries and geometrically essential separations show up. This can be steady with the TEM comes about of interlacing separations inside the gem , which advances the advancement of tall separation thickness and the improvement of stacking flaws inside the beginning grains. The combined impact of grain refinement and expanded disengagement thickness increments the microhardness and wear resistance of the surface layer with expanding number of spin passes. • A new treatments of cladding coatings were proposed. • Power spinning improves the macroscopic forming quality of the cladding layer. • Homogenization of surface grains by multi-pass spinning. [ABSTRACT FROM AUTHOR]

• Two new treatments of cladding coatings were proposed. • The two treatments improved the wear resistance of the coating to different degrees. • Power spinning combined with heat treatment provides the best performance. • After the post-treatment bright and clean grinding marks meet the requirements of use. High-speed laser cladding can improve both processes and the surface quality of the coating, however, post-treatment is still required to meet the requirements. The Power spinning is suitable for processing high-strength, hard-to-deform materials, which can effectively improve the quality of the coating surface and enhance the performance of the coating. In this study, two processes were proposed and explored for the post-treatment of laser cladding, i.e., Power spinning (PS) and post-spinning heat treatment (PSHT). The results show that PSHT treatment can effectively improve the wear resistance of the samples. The PS surface layer grains were refined and showed directionality, and the wear resistance was improved. The PSHT coating with dendritic eutectic was uniformly refined, and the organization became dense. The dislocation density within the crystal decreased and the strength of the material decreased while the plasticity increased, indicating better wear resistance gained. [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]

To further strengthen the AlCoCrFeNi high-entropy alloy (HEA) coating prepared by high-speed laser cladding (HLC), laser remelting (LR) was chosen to reprocess it. The effects of LR on the topography, microstructure, growth orientation, phase distribution, and properties were investigated. It was revealed that there were a large number of liquid phase separation (LPS) zones in the HLC coating because of an ultrafast cooling rate. After LR, the LPS zones were eliminated. Compared to HLC coating, the microhardness increased from 622 HV to 762 HV, and the friction coefficient and the wear weight loss were reduced by 0.1 and 0.5 mg, respectively. In electrochemical testing, the self-corrosion potential increased by 45.9 mV and the self-corrosion current density decreased by one order of magnitude. Meanwhile, EBSD analysis indicated that the LPS zones were prone to recrystallization. The LPS zones were nickel-poor, low hardness, also BCC phase, and had a clearer (101) orientation. With the elimination of the LPS zones, the kernel average misorientation values were reduced, Taylor factor values and high angle grain boundaries were increased, and the average grain size was reduced from 2.43 μm to 2.12 μm. Eventually, for LR coatings, the combination of fine grain strengthening, solid solution strengthening, spalling reduction, and Cr element segregation resulted in better wear and corrosion resistances. The overall results show that a reasonable LR application can induce the microstructure of the HLC coating and improve its service properties. ● The AlCoCrFeNi high-entropy alloy coatings were prepared by high-speed laser cladding (HLC) and reprocessed by laser remelting (LR).● There were a large number of liquid phase separation (LPS) zones in the HLC coating. After LR, the LPS zones were replaced by fine equiaxed crystals.● The LPS zones were nickel-poor and low hardness, had a clearer (101) orientation, and tended to spall off in the wear test, causing a decrease in the overall wear resistance of the coating.● As a result of the elimination of the LPS zones, the microhardness and wear resistance of the LR coating were improved by solid solution strengthening and fine grain strengthening.● Appropriate undercooling and more high angle grain boundaries caused by LR provided a larger driving force for grain boundary segregation. The elemental content of Cr at the grain boundaries became higher, and the corrosion resistance of the LR coatings increased significantly. [Display omitted] • HLC led to a large number of the LPS zones in the AlCoCrFeNi HEA coating. • LR could successfully eliminate the LPS zones. • Recrystallization made the grains of the LPS zones coarse and soft. • The microhardness and wear resistance of the coating were improved by LR. • Higher Cr content at grain boundaries boosted corrosion resistance of LR coating. [ABSTRACT FROM AUTHOR]

• By high-speed laser cladding technology, the decomposition degree of WC is weakened. • The composite coating with high content of WC (60%) is prepared. • Three decomposition mechanisms of WC particles are deeply revealed. Ni/WC composite coatings with different compositions were prepared on the surface of 304 steel by high-speed laser cladding (HSLC). The microstructure and phase composition of Ni/WC composite coatings were analyzed, and the hardness and wear resistance of Ni/WC composite coatings were tested. The results show that the HSLC coatings have good surface formation without defects such as pores or cracks, and WC is uniformly distributed in the coating. WC particles hinder the dendrite growth, and the dendrite structure in the coating is significantly refined with the increase of WC content. The main phases of the coating is Ni 3 Fe, and the W and C elements diffuse into the coating, forming strengthening phases such as W 2 C and Cr 23 C 6. Although WC particles are decomposed, the strengthening effect of the second phase is not weakened, and the decomposed WC produces fine grain strengthening and solid solution strengthening effects, thus producing multiple strengthening mechanisms for the coating. With the increase of WC content, the hardness and wear resistance of the coating are gradually improved. However, when the WC content is in the range of 30–60%, the wear resistance of the coating do not present significant change. The main wear mechanisms are adhesive wear, abrasive wear and oxidation wear. [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]

• When the scanning speed was 80.38 m/min, the volume fraction of amorphous phase was 74.48%. • When the scanning speed was 80.38 m/min, the crack of the coating section almost disappeared completely. • The residual tensile stress on the coating surface decreased with the increase of scanning speed. • Under the scanning speed of 80.38 m/min, the cooling rate of the coating could reach 1.08 × 105 °C/s. Fe-Co-B-Si-Nb amorphous coatings were deposited on 45 medium carbon steel under different scanning speeds by high-speed laser cladding technology. The results showed that the surface roughness of the coating became lower and the surface of the coating became smoother with the increase in scanning speed. In addition, the residual tensile stress and the thermal expansion coefficient decreased with the increase in the scanning speed. When the scanning speed was 80.38 m/min, the residual tensile stress was 106.13 ± 24.03 MPa. The residual stress was reduced by more than 50% compared with the scanning speed of 37.68 m/min. The XRD and TEM observation results of the coating at the scanning speed of 80.38 m/min showed a large volume fraction of amorphous phase and some crystalline dendrites. Under the scanning speed of 80.38 m/min, the cooling rate at the top of the coating could reach 1.08 × 105 °C/s, which greatly increased the amorphous formation ability. The hardness and wear resistance properties of the coating were also tested and analyzed. Better performance of the coatings was obtained when the scanning speed was higher. [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]

A promising new bond coat using CuAlNiCrFe high-entropy alloy was proposed in this paper. The difference in pre-oxidation conditions between the traditional thermal-sprayed MCrAlY bond coat and CuAlNiCrFe high-entropy alloy bond coat deposited using high-speed laser cladding was investigated. The result confirmed that the CuAlNiCrFe high-entropy alloy bond coat deposited using high-speed laser cladding can complete the pre-oxidation faster and form a continuous α-Al 2 O 3 thermally grown oxide (TGO), which shortens the initial oxidation stage, thereby avoiding the formation of other oxides and spinel structures. In the subsequent isothermal oxidation process, the block-like structure of the high-speed laser cladding layer and the sluggish diffusion effect of the high-entropy alloy work together to ensure the slow and continuous supply of aluminum element to TGO layer and obtain a low growth rate. Also, the diffusion between the bonding layer and the substrate is controlled at a low level, and the new CuAlNiCrFe bond coat exhibits excellent oxidation and diffusion resistance. With the consumption of aluminum, the phase structure of the high-entropy alloy bond coat changed from BCC to FCC, but it still maintained a stable simple solid solution structure. • A high entropy alloys bond coat was prepared by ultra-high speed laser cladding. • The laser Cladded high-entropy alloys ensure the sluggish diffusion effect. • The CuAlNiCrFe bond coat shows great oxidation resistance in 1100 °C. • The phase structure of CuAlNiCrFe change to FCC single-phase solid solution. • A new thermal barrier coatings system with high entropy alloys was proposed. [ABSTRACT FROM AUTHOR]

• FeCoNiCrMn coating was prepared by combining HSLC and SMRT techniques. • The changes in the microstructure and composition of the coating were analyzed. • Surface gradient structure was formed in the high-entropy alloy by SMRT. • Role of surface gradient structure in improving corrosion resistance was discussed. The FeCoNiCrMn high-entropy alloy (HEA) coatings were prepared by high-speed laser cladding (HSLC) technology, and the surface was subjected to ultrasonic surface mechanical rolling treatment (SMRT). After SMRT, the surface of the coatings show a gradient structure. The coatings consist of planar crystal, columnar dendrites and equiaxed crystals from inside to outside. Corrosion behavior in a 3.5% NaCl solution indicates that SMRTed coatings exhibit higher corrosion resistance than the coatings without SMRT. Anti-corrosion mechanism was discussed based on grain refinement, grain boundary wetting phase transitions and compressive residual stress. [ABSTRACT FROM AUTHOR]