Formation of keyhole and lack of fusion pores during the laser powder bed fusion process

Abstract

During the laser powder bed fusion (LPBF) process, keyhole pores or lack of fusion pores may form depending on the energy density used to fabricate the part. In this study, different levels of energy densities are used to investigate the pores formed within the 2.5 mm × 2.5 mm × 1 mm cuboid specimen. Micro-CT is used to characterize and measure the pores, and the results show that the keyhole porosity increases with an increase in energy density, while the lack of fusion porosity increases with a decrease in the energy density. Besides, metallography is performed to observe the melt profile and the 2D pores. The keyhole pores are a result of deep penetration melting and form within the track. In contrast, the lack of fusion pores formed between the tracks, due to incomplete melting of the tracks, or improper overlap between the scan tracks.