Improving the surface integrity of additively manufactured curved and inclined metallic surfaces using thermo-electric energy assisted polishing

Abstract

Laser powder bed fusion (LPBF) is an advanced layer by layer manufacturing process gaining increased interest in industrial sector owing to its complex design flexibility. However, the parts produced using LPBF are not directly used in practical applications due to the geometrical inaccuracy and poor surface quality resulting from surface irregularities and defects. The established methods for post-processing LPBF parts/components such as laser polishing, abrasive polishing, chemical polishing and conventional finishing methods have inherent limitations depending on the variation in geometric shape/profile of the components. Hence, the present study analyses the effectiveness of a low energy wire electrical discharge polishing (WEDP) method in improving the surface quality and form accuracy of curved and inclined AlSi10Mg samples fabricated using laser powder bed fusion (LPBF). A geometrical model is proposed in the study for estimating the depth of material removed in each polishing pass. The developed model is capable of predicting the number of polishing passes required for the removal of irregularities on the surface. The geometrical form accuracy of metallic AM samples was improved significantly after WEDP with more than 68 % reduction in cylindricity error and 75 % reduction in flatness error. In addition, the samples exhibited uniform surface finish after WEDP with ~50–60 % reduction in as-built roughness. The SEM analysis conducted in the study reveals that WEDP is capable of eliminating the stair stepping surface defect with enhancement in geometrical profile. Furthermore, the EDS analysis confirmed the formation of oxide layer on the LPBF surface after WEDP post-processing.