Laser Finishing of the Multi-Scale Surface Structure of Additive Manufactured Parts
Final Report Abstract
The conclusions drawn from the studies on the improvement of surface finish and mechanical properties, e.g., fatigue life, of additively manufactured parts by laser remelting can be summarized as follows: • No correlation could be found between the number of local remelting processes and the pore distribution. However, the variability of the pore size decreases with increasing overlap distance. • The suspected mechanism that higher degrees of overlap resulting in multiple melted areas lead to a large reduction in pore size cannot be confirmed. • Laser polishing can result in a near full dense sub-surface layer with only micropores remaining. • It has been shown that the final surface after laser polishing is dependent not only on laser polishing parameters but also the initial state of a surface. • Surface features can alter the keyhole shape and can result in changed multiple reflection conditions, which can lead to a different keyhole shape after passing the feature at otherwise same processing conditions. This shows that the process itself can also be significantly influenced by surface features having a size comparable to those of PBF-LB/M surfaces. • Using radii in the reversal points of the meandering scan strategy, conditions can be created which are close to steady-state conditions and therefore reduce the surface features over a broad spatial wavelength range. This is particularly advantageous when several scan fields have to be placed next to each other in order to polish larger areas. • The fatigue life of 316L stainless steel was not reduced for either conventionally or additively manufactured parts at the laser polishing parameters used. • Laser polishing can thus provide a net benefit in terms of reduced surface roughness while maintaining fatigue behavior under certain polishing parameters on 316L stainless steel.
Publications
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Effect of Initial Surface Features on Laser Polishing of Co-Cr-Mo Alloy Made by Powder-Bed Fusion. JOM, 71(3), 912-919.
Richter, B.; Blanke, N.; Werner, C.; Vollertsen, F. & Pfefferkorn, F. E.
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High-speed X-ray investigation of melt dynamics during continuous-wave laser remelting of selective laser melted Co-Cr alloy. CIRP Annals, 68(1), 229-232.
Richter, Brodan; Blanke, Nena; Werner, Christian; Parab, Niranjan D.; Sun, Tao; Vollertsen, Frank & Pfefferkorn, Frank E.
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Increased Laser Polishing Rates of LPBF Components. PhotonicsViews, 18(S1), 22-23.
Beste, Lucas‐H.; Schadewald, Florian; Radel, Tim; Richter, Brodan; Faue, Patrick J.; Pfefferkorn, Frank E. & Vollertsen, Frank
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Roughness Parameters for Classification of As-Built AM Surfaces. (2021, 1, 28). American Geophysical Union (AGU).
Richter, B.; Blanke, N.; Werner, C.; Vollertsen, F. & Pfefferkorn, F.
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Influence of laser polishing on fatigue life of conventionally machined and laser powder bed fusion 316L stainless steel. Manufacturing Letters, 33, 670-677.
Faue, P.J.; Beste, L.-H.; Richter, B.; Agrawal, A.; Klingbeil, K.; Thoma, D.; Radel, T. & Pfefferkorn, F.E.
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Macro-pore free sub-surface PBF-LB/M components through laser polishing. Proceedings of the 12th Laser Application Forum (2022), 37-40.
Rathmann, L.; Beste, L.-H.; Faue, P.J.; Richter, B.; Klingbeil, K.; Pfefferkorn, F.E. & Radel, T.
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Sensitivity of surface roughness to laser parameters used for polishing additively manufactured Co-Cr alloy. Surface and Coatings Technology, 451 (2022, 12), 128872.
Richter, Brodan; Radel, Tim & Pfefferkorn, Frank E.
