The Effect of Tungsten Powder Particle Size on Printability in Laser Powder Bed Fusion

Due to the high melting temperature and high brittleness, how to mitigate the formation of pores and cracking is still the primary issue in laser manufacturing tungsten components. A novel of strategy of using fine-sized powder was proposed in this study. Two types of pure tungsten powder, with particle size range of 18.3-63.4 μm, 3.5-28.1 μm, respectively, were used to comparatively study the printability in laser powder bed fusion. A highly dense tungsten bulk sample with relative density higher than 99%was successfully manufactured within the latter fine-sized powder. Grid samples were also fabricated with the same processing strategy. The surface and cross-sectional morphology of the as-printed samples were observed to characterize the laser scan tracks, inter-layer and defect structures. Fairly low density of surface cracks was observed on surface. The results show that the fine-sized powder enhances the printability by stabilizing melt pool. This can also be verified by finite element analysis of the temperature distribution and several micron-sized melt pool. The surface cracks have been fully removed in the grid samples. The results provide a processing strategy for further manufacturing of tungsten grid structure and industrial applications.