Speaker
Description
Geometric accuracy of parts manufactured by Laser Powder Bed Fusion (LPBF) is deteriorated by powder particles sintered to the part surface as well as excessive melting due to overheating by limited heat flow at sharp contour corners. While the sintered powder particles increase the surface roughness, overheating leads to deviations of the as-built part geometry from the CAD geometry. Use of pulsed wave Laser Powder Bed Fusion (pw-LPBF) has shown an increase in detail resolution as well as an improvement of the part accuracy in the field of micro Powder Bed Fusion (µ-PBF) due to improved melt pool controlling by discrete solidification of adjacent melt pools generated by the laser pulses. However, process efficiency (e.g. build up rate) of pw-LPBF is in general lower compared to continuous wave LPBF (cw-LPBF). Hence, to transfer the results to large-scale parts, an adaptive processing strategy is developed for alloy Inconel 718. Pw and cw laser emission are combined, while pw irradiation is used for contour exposure and cw irradiation for volume exposure, respectively. In this study, process parameters are developed for different part geometries (e.g. sharp contours). Geometric deviations and surface quality of the parts are evaluated using light optical microscopy, Scanning Electron Microscopy and optical surface measurement, respectively. It can be shown that both geometric accuracy and surface roughness is improved by pw contour exposure compared to state of the art cw exposure while sufficient process efficiency is ensured by cw volume exposure.