Surface Characterization of Laser Polished Indirect-SLS Parts

Surface analysis was performed on laser polished indirect-SLS samples made from 420 stainless steel sintered powder - bronze infiltrated. The goal was to determine variations from the as-received condition in surface chemical composition, morphological structure, presence of contaminants as well as the formation of new phases. Comprehensive characterization of the laser polished surfaces was performed using scanning electron microscopy (SEM), energy dispersive spectrochemical analysis (EDS), x-ray diffraction analysis (XRD) and Vickers hardness. A large quantity of carbon (i.e. > 29 wt%) was present on the as-received surface mostly from the polymer binder present in the green part. Although surface-shallow-melting is the principal mechanism for the roughness reduction of the as-received surface, the chemical composition of the latter after processing changed to a higher carbon and oxygen content and a lower copper content. Additionally, clusters were formed periodically over the polished surface consisting of Fe, Cr, Si and Al oxides. The surface analysis demonstrated that the laser polished surfaces differ significantly more from a morphological rather than a microstructural perspective.