Gold-Silver Electroless Plating on Laser Powder-Bed Fusion Additively Printed AlSi10Mg Parts

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 degrees 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 degrees C, the Ag was dominant at the beginning of the deposition process, while at 90 degrees 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.