Pore defects in Laser Powder Bed Fusion: Formation mechanism, control method, and perspectives

Abstract

Laser powder bed fusion (LPBF) additive manufacturing (AM) technology has been applied to manufacture complex components which have already been used in aerospace, biomedical, and many other fields. However, the LPBF-ed parts still suffer from porosity defects due to the rapid cooling solidification and complex molten pool flow during fabrication. These defects will affect the mechanical properties of the fabricated parts. Therefore, it is necessary to study LPBF pore defects and their formation mechanism, for further improving the development of LPBF technology. This paper carries out a systematic review on this topic. Firstly, the formation mechanisms are summarized based on the current in-situ imaging and modeling research. Secondly, the effects of porosity and pore characteristics (such as size, distribution, and shape) on tensile and fatigue properties are clarified based on the literature of defect characterization and mechanical properties testing. Thirdly, the control methods of the pore defects are characterized, including the laser energy distribution characteristics, processing parameters, powder feedstock, and in-situ laser remelting (ILR). Fourthly, the strategies to reduce pore defects are discussed, including process, laser post-processing remelting, and hot isostatic pressing (HIP). Finally, current research gaps and future directions are given in four aspects.