CO2 laser polishing of laser-powder bed fusion produced AlSi10Mg parts

Poor surface quality represents an important issue that needs improvement for metal Additively Manufactured parts. Both short or long wavelength lasers have been applied for surface polishing in order to improve the surface finish. In this work, the possible use of a CO2 laser for the surface polishing of AlSi10Mg parts made by Laser-based Powder Bed Fusion (L-PBF) was explored. The high surface roughness in the as-built condition can lead to increased laser energy absorption. In order to assess the effects of the main laser-related process parameters, the experiments were carried out on L-PBF samples built vertically with respect to the build platform. Their effect on the surface were evaluated by means of the surface arithmetical mean height (Sa), surface skewness (Ssk) and primary profile root mean square slope (Pdq), obtained via confocal microscopy. Microstructure evolution was also investigated by means of SEM and EDS analysis. The results showed a large reduction in surface roughness, ranging from the 67% to the 85% of the starting value. Microstructure of the re-molten layer revealed an increased grain size and an increased Si content that led to an overall hardness increase from 85 to 121 HV.