Mapping Defect Formation in Laser Powder Bed Fusion on a Hybrid Matsuura Lumex Avance-25

Additive manufacturing continues to have problems with porosity, surface quality, and residual stress. This two-part study focuses on (1) employing a non-detrimental technique to measure the resulting mechanical properties in additive manufacturing, namely residual stress and microhardness, and (2) improving the print quality in metal additive manufacturing by analyzing porosity formation and surface roughness, especially for overhanging structures. This work presents the first known study utilizing hybrid additive manufacturing as a machining-based sensor to measure mechanical properties. Also, this work investigates the effects of print process parameters within Lumex CAM (Matsuura Lumex Avance-25) on porosity formation and surface topography. The results indicated that the variation of the net cutting specific energy correlated with the residual stress in the first millimeter as well as the microhardness across the build. X-ray CT results and laser profilometry revealed that porosity formation and surface topography were controlled by the melt pool dimensions and the print strategy. In addition, one mechanism explaining the alignment of pores across the build was the position of the recoater according to the gas flow during printing. Advisor: Michael P. Seal