Applicability of Laser Polishing on Inconel 738 Surfaces Fabricated Through Direct Laser Deposition

Today's manufacturing industry requires novel technologies capable to improve process versatility, rapidity as well as the surface quality of the parts fabricated through additive manufacturing.A cost/process-effective manufacturing solution capable to meet these requirements is represented by the direct laser deposition (DLD) technology.DLD is essentially an additive manufacturing (AM) process that can accurately fabricate complex freeform geometries.The main drawback of DLD is constituted by the reduced surface quality that is in fact an unavoidable characteristic of the AM processes.It was found that the best areal surface roughness (Sa) occurs on the front wall characterized by a +90 angle (or clockwise rotation) between DLD feed and flow vectors.More specifically, while the front wall is characterize by Sa = 0.704m, the rear/back wall (-90 or counterclockwise rotation) is characterized by Sa = 3.861m because powder is distributed and affixed in an already solidifying molten pool.To counteract this DLD process inconsistency, high-speed laser polishing (LP) can be used as a post processing technique capable to significantly improve the post-DLD surface quality.Along these lines, LP can eliminate and/or reduce the time and the cost of post-DLD surface finishing operations.Preliminary experimental results demonstrate that LP improves the quality of DLDgenerated surfaces by decreasing with up to 70% the surface roughness (Sa LP(90deg) = 0.211 m, Sa LP(-90deg) = 0.444 m) through a redistribution of melted micro-peaks into micro-valleys.The combination of these two laser-based technologies offers an economic, ergonomic, and ecologic fabrication option and opens up avenues for future implementations of computer-based adaptive control, self-optimization, and online monitoring techniques.