Laser Powder Bed Fusion (LPBF) is a prominent additive manufacturing technology that enables the production of complex metallic components with high precision and design flexibility. However, porosity formed during the process directly affects density, repeatability, and service life, thereby representing one of the primary factors limiting the reliability of industrial applications. In this study, porosity formation in LPBF is comprehensively evaluated through a systematic literature analysis framework, focusing on volumetric energy density (VED) regimes, melt pool phase dynamics, and their relationship with mechanical performance.

The findings indicate that pores predominantly develop through three principal mechanisms: lack-of-fusion (LOF) pores resulting from insufficient track and layer bonding under low VED conditions; keyhole pores formed due to unstable collapse of a deep vapor cavity under high VED regimes; and gas-induced pores originating from entrapped gases within powder particles and irregular gas flow in the process atmosphere. LOF pores, characterized by sharp and irregular morphologies, significantly intensify stress concentrations and act as critical initiation sites for fatigue cracks. Although keyhole pores generally exhibit a more spherical morphology, their increasing size reduces the effective load-bearing cross-section and consequently decreases strength. Gas-induced pores introduce an additional control dimension independent of direct energy input, highlighting the importance of powder quality and atmosphere management.

In conclusion, effective porosity control in LPBF should not be limited to parameter adjustment alone; rather, it requires a holistic process optimization strategy supported by controlled energy regimes, stable melt pool behavior, and in-situ monitoring-based quality assurance systems.