A comparison study of the electrochemical polishing of laser powder bed fusion HR-2 stainless steel and AlSi10Mg

Electrochemical polishing (ECP) is effective for improving the surface quality of additively manufactured (AM) parts. However, ECP effects of AM parts manufactured from varied materials show significant differences owing to the complexity of phase composition, chemical composition, and specific surface defects. Accordingly, this paper compares the electrochemical polishing (ECP) results and mechanisms of the laser powder bed fusion (LPBF) additive manufacturing (AM) of HR-2 stainless steel (single-phase) and AlSi10Mg (multi-phase). Both kinds of LPBF parts show a significantly smoother surface after the ECP process. Following ECP, the Sa of HR-2 was reduced from 11.50 μm to 1.73 μm, while the Sa of AlSi10Mg was reduced from 14.91 μm to 4.70 μm. Notably, compared with LPBF HR-2, LPBF AlSi10Mg forms a solid viscous layer due to the buildup of polishing products after ECP, thus inhibiting the diffusion and reaction of the ions during the polishing process, resulting in a decrease in the polishing effect. Therefore, an in situ mechanical brushing (ECMP) targeting the product layer is conducted along with the ECP, and the surface roughness of the LPBF AlSi10Mg is further reduced to 2.19 μm. Due to the properties of the viscous layer, such an ECMP method is only suitable for the AlSi10Mg but not the HR-2 to further reduce the surface roughness as the ECMP LPBF HR-2 surface quality deteriorated from 1.73 to 2.51 μm. Graphical Abstract