“…Moreover, a large area of high carbon is formed in the coating (Figure 5(i)), which leads to the low fluidity of the molten pool and the high sensitivity of the cracks in the coating, as shown in Figure 3(d). As we all know, crack is a critical factor for the service life of coating [27,28]. Figure 5 SEM micrograph of the coating with different contents of CNTs: 1% (a–c), 3% (d–f) and 5% (g–i).…”
To enhance the mechanical properties of Ni-WC coatings, the carbon nanotubes were used as reinforced materials by laser cladding. Optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the effect of CNTs content on the phase composition and microstructure. The microhardness and wear resistance were measured by Vickers hardness testing and friction wear testing. Experimental results showed that the new phases Cr 2 Fe 14 C are found in the coatings with CNTs, the grain size is finer than that of the coating without CNTs. The microhardness and wear resistance of the coatings with CNTs content ranging from 0 to 5 wt-% present increase initially and then decrease trend. The coatings with 3 wt-% CNTs have the highest microhardness and wear resistance, which proved that the appropriate amount of CNTs addition is 3 wt-%.
“…Moreover, a large area of high carbon is formed in the coating (Figure 5(i)), which leads to the low fluidity of the molten pool and the high sensitivity of the cracks in the coating, as shown in Figure 3(d). As we all know, crack is a critical factor for the service life of coating [27,28]. Figure 5 SEM micrograph of the coating with different contents of CNTs: 1% (a–c), 3% (d–f) and 5% (g–i).…”
To enhance the mechanical properties of Ni-WC coatings, the carbon nanotubes were used as reinforced materials by laser cladding. Optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the effect of CNTs content on the phase composition and microstructure. The microhardness and wear resistance were measured by Vickers hardness testing and friction wear testing. Experimental results showed that the new phases Cr 2 Fe 14 C are found in the coatings with CNTs, the grain size is finer than that of the coating without CNTs. The microhardness and wear resistance of the coatings with CNTs content ranging from 0 to 5 wt-% present increase initially and then decrease trend. The coatings with 3 wt-% CNTs have the highest microhardness and wear resistance, which proved that the appropriate amount of CNTs addition is 3 wt-%.
“…The HAM process avoids or reduces the mutual interference between various processes and the adverse effect generated if used separately, while retaining the advantages of these processes. The HAM is more widely applicable in LDED, and the process advantages if brings also vary [13][14][15]. Due to its high processing flexibility, the LDED process has become the most common platform integrated in HAM [16][17][18][19].…”
Laser directed energy deposition (LDED) process has unique advantage in rapid forming of large-sized metal components, gradient material/structural components, or repairing/remanufacturing worn parts. However, the high residual stress and strong anisotropy in mechanical properties of the as-deposit components limit the application of LDED technology in the manufacturing of key structural components. To overcome these problems, various hybrid additive manufacturing (HAM) technologies have been developed, such as plastic deformation, ultrasonic or magnetic field assisted LDED processes to improve the quality and the mechanical properties, where these coupled processes are carried out either simultaneously or cyclically with the LDED process. The hybrid additive manufacturing, while retaining the advantages of individual forming process, avoids the mutual interference between each process and reducing the adverse effects generated if used separately. Hybrid additive manufacturing processes fundamentally change the underlying physical mechanisms of molten pool dynamics, microstructural evolution, temperature and thermal stress gradient in additive manufacturing, thereby optimizing the microstructure and performance of the manufactured components. In this paper, the key technical features of the hybrid additive manufacturing process coupled with plastic deformation were described in details, and the resulting differences in microstructure, residual stress, and mechanical properties of the prepared samples were systematically analyzed. The developing trend of hybrid additive manufacturing processes in coupling mechanisms, parameter optimization, and equipment have been discussed.
“…The FZ showed a polycrystalline structure with cracks and pores in the deposits under higher heat inputs and SC microstructure under lower heat inputs. Rottwinkel et al [13] performed laser cladding experiments on SC turbine parts made of CMSX-4 superalloy for crack repair using a solid-state diode laser with an average energy density of 172 J/mm 2 with a fixed laser beam diameter of 0.86 mm, powder feed rate of 3 g/min and z-elevation per layer of 0.15 mm. They found multiple cracks and pores on the surfaces of the clad deposits due to a non-uniform temperature gradient.…”
Highlights Laser surface remelting was performed on a single-crystal nickel-based superalloy under various energy densities by using a continuous wave fiber laser. A working range of energy densities for keyhole and conduction mode of penetration were derived. The effect of positive focal position on laser-induced surface defects and property was investigated.
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