Laser Powder Bed Fusion of Alumina: Effects of Scanning Strategies on External and Internal Defects

This study investigates the surface and internal microstructures of pure alumina fabricated via laser powder bed fusion, focusing on the influence of different scanning strategies on external and internal structures. Two scanning strategies were evaluated: linear 45° and island concentric out‐in, utilizing optimized laser power and scanning speed parameters. The linear 45° strategy produced a smooth, uniform external surface but exhibited significant defects, including cracks and pores, which were attributed to thermal shocks and the low wettability of molten alumina. The internal structure displayed high porosity and closed voids, limiting the effectiveness of post‐processing techniques like infiltration to enhance the relative density. Conversely, the island concentric out‐in strategy generated a distinct surface morphology with regularly distributed holes, resulting from localized heat accumulation at island centers. Internally, this strategy produced vertical through‐holes extending across multiple layers and dense regions away from the island centers, contributing to a higher overall relative density than the linear 45° strategy. These through‐holes offer potential for improved post‐processing, especially infiltration, to enhance relative density. The study highlights the need for further optimization, suggesting that a hybrid scanning strategy may help eliminate defects and achieve a fully dense structure throughout the fabricated alumina parts.