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Laser cladding uses a high-energy laser beam as a heat source to rapidly melt and solidify the cladding material onto the substrate to form a high-performance coating. This technology provides an efficient and economical method to repair and remanufacture precision equipment such as engines and spacecraft. However, the inherent non-equilibrium solidification properties of laser cladding often lead to problems such as coating anisotropy, high porosity, and elemental segregation. Optimizing process parameters and heat treatment do not always eliminate these defects. Therefore, it is necessary to seek a more appropriate solution. Introducing laser remelting on the surface or between the layers of the coating to cause it to remelt and redistribute can refine the grain size, reduce defects, and improve the uniformity of the composition, thus enhancing the performance of the coating. This paper reviews and summarizes the application and development status of laser remelting technology in laser cladding and discusses it in terms of surface quality, hardness, wear resistance, and corrosion resistance of the coating. It also identifies the potential of external field-assisted laser remelting technology in further optimizing coating performance. Finally, based on the review, suggestions are provided for selecting remelting parameters. [ABSTRACT FROM AUTHOR]

Laser cladding technology is widely used in component repair and surface strengthening because of its advantages of various powder options and high processing efficiency. This paper outlines the application and research of transition layers in laser cladding and details the advantages of transition layers in terms of bonding performance, defect rate, and cladding thickness. Compared with conventional laser cladding, the composite process with the addition of transition layer has been further improved in terms of organization, mechanical properties, and corrosion resistance. In addition, the repair process of laser cladding to meet the cladding thickness of the parts and avoid the degradation of surface properties is also discussed. [ABSTRACT FROM AUTHOR]

To improve the surface corrosion resistance of ductile iron, Ni-based alloy coatings were prepared using a high-speed laser cladding technology with different levels of laser power. The microstructure, phases, and corrosion properties of the coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and an electrochemical workstation. Variations in laser power did not change the main phases of the coatings, which were composed of γ-Ni, Ni3B, Ni2Si, and Cr23C6. With an increase in power, the degree of segregation in the coating decreased, sufficient melting between elements was achieved, and the chemical composition became more uniform. Enhancement of the laser power resulted in more energy being injected into the cladding, which allowed adequate growth of tissue, and dendrites continued to grow in size as the power increased. The self-corrosion potentials of the coatings at laser power levels of 1.6, 2.0, and 2.4 kW were −625.7, −526.5, and −335.7 mV, respectively. The corrosion potential of the 2.4 kW coating was the highest, and the corroded surface of the cladding layer included mainly sizeable continuous structures with a light degree of corrosion and the highest corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, laser cladding technology was used to prepare Fe-based alloy coating on a 27SiMn hydraulic support, and a turning treatment was used to obtain samples of the upper and middle regions of the cladding layer. The influence of microstructure, phase composition, hardness, and wear resistance in different areas of the cladding layer was studied through scanning electron microscopy (SEM), X-ray diffractometry (XRD), friction and wear tests, and microhardness. The results show that the bcc phase content in the upper region of the cladding layer is less than that in the middle region of the cladding layer, and the upper region of the cladding layer contains more metal compounds. The hardness of the middle region of the cladding layer is higher than that of the upper region of the cladding layer. At the same time, the main wear mechanism of the upper region of the cladding layer is adhesive wear and abrasive wear. The wear mechanism of the middle region of the cladding layer is mainly abrasive wear, with better wear resistance than the upper region of the cladding layer. [ABSTRACT FROM AUTHOR]

In this paper, the corrosion performance of a laser cladding Fe-based alloy coating on the surface of 27SiMn steel was studied. The Fe-based alloy coating was prepared on a 27SiMn steel surface by high-speed laser cladding. The microstructure, morphological characteristics, element content, and phase composition of the cladding layer were analyzed by an optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively. The corrosion resistance of the 27SiMn substrate and Fe-based coating in different corrosive environments was tested through an electrochemical experimental station, a salt spray corrosion test box, and an immersion experiment. The Fe-based alloy cladding layer is mainly composed of a-Fe, M7C3, M2B, and Cr3Si. The cladding layer structure forms planar, cellular, dendrite, and equiaxed dendrite during rapid solidification. The corrosion potential of the cladding layer is higher than that of the substrate, and the arc radius of the cladding layer is larger than that of the substrate. After salt spray corrosion, a large number of red and black corrosion products appeared on the surface of the substrate; the surface of the cladding layer sample was still smooth, and the morphology was almost unchanged. The weight loss results of the cladding layer and 27SiMn matrix after 120 h of immersion are 0.0688 and 0.0993 g·cm−2, respectively. The weight loss of the cladding layer is 30.7% less than that of the matrix. Conclusion: Laser cladding an Fe-based alloy coating on the surface of 27SiMn has better corrosion resistance than the substrate, which improves the corrosion resistance of hydraulic supports. [ABSTRACT FROM AUTHOR]