Microstructural porosity in additive manufacturing: The formation and detection of pores in metal parts fabricated by powder bed fusion

Metal additive manufacturing (AM) is an innovative manufacturing technique that can build complex and high value metal parts layer by layer using a computerized three‐dimensional solid model. Powder bed fusion (PBF) is one of the most common AM techniques. It sequentially processes a powdered feedstock in thin layers and solidifies it by either a laser beam or an electron beam. However, PBF induces microstructural defects that can adversely affect the performance of the manufactured components. These undesirable defects including voids and porosities must be avoided or minimized to limit their negative effects on mechanical properties and to ensure the consistency and repeatability of AM parts. The present article provides an overview of the formation mechanisms of pores in AM metals and some emerging techniques for the detection and quantification of pores. The review also highlights other common defects in PBF parts such as microstructural features associated with keyhole mode of melting.