Abstract
The current research presents a novel methodology for surface finishing of printed AlSi10Mg parts by electroless deposited gold–silver (electrum) alloys. The parts were printed by additive manufacturing laser powder-bed fusion (AM-LPBF). The electrum was chosen due to its appearance and good electrical and thermal properties and was deposited on disk-shaped specimens at 80 and 90 °C. The coating quality and appearance were studied by different methods for various deposition times and film thicknesses. The results indicate that Au–Ag coatings of AM-LPBF AlSi10Mg yield satisfactory results. The XRD analysis revealed that the coatings were composed of Au–Ag crystalline phases and beneath them, a quasi-amorphous or mixed quasi-amorphous and nanocrystalline Ni–P interlayer. The mechanism of electrum formation was studied based on the XPS analysis results as a function of the temperature and concentration. At 80 °C, the Ag was dominant at the beginning of the deposition process, while at 90 °C the Au was first detected on the interface. This result was explained by the electrochemical properties of alloying metals and the binding energies required to form metal–Ni and Au–Ag bonding. The results indicate that the electrum coatings are satisfactory, and the developed surface finishing process could be used for many applications.
Highlights
The LM observation of the AlSi10Mg 3D-printed specimens demonstrated that the surfaces are relatively rough and slightly porous (Figure 5a,e,f)
A simple to use environmentally friendly electroless Au–Ag plating was developed and applied to additive manufacturing laser powder-bed fusion (AM-Laser powder bed fusion (LPBF)) AlSi10Mg specimens for the first time in order to improve the surface appearance based on aesthetic considerations
A significant advantage of the developed electroless electrum coating process is the avoidance of environmentally hazardous material such as cyanide chemical compounds, low processing temperature, and low cost
Summary
Additive manufacturing (AM) is a group of advanced technologies fabricating three-dimensional custom-built and sophisticated components by addition instead of removal of material. The parts are built layer by layer with fewer tools and less scrap production than the conventional manufacturing technologies, while saving time and expenses [1,2]. AM enables the formation of complex geometries that up until recently were considered impossible by conventional technologies [3,4,5]. Topology-optimized assemblies can be created without significant extra cost. AM technologies allow optimization of lightweight products and are currently used in various industries such as the biomedical, automotive, aerospace, and others [6,7,8,9,10]
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