Formation and extreme thickness controlling mechanism of ultra-thin-wall tungsten grids fabricated via selective laser melting

It is presently challenging for selective laser melting (SLM) additive manufacturing technique to fabricate metal parts with wall thickness below 100 μm. This work investigated the critical conditions of the extremely thin wall thickness of tungsten grids fabricated by SLM. Specifically, the effect of low energy density on the printability of tungsten single tracks and grids via SLM was studied. A thermo-fluid flow model of the molten pool created in the SLM process was developed based on a computational fluid dynamics approach to illustrate the single-track morphology variation corresponding to printability. The findings demonstrate that at low energy densities, the molten track exhibits four different morphologies: balling, discontinuity and winding, discontinuity but straightness, as well as continuity and straightness. The simulation model, reliably validated by these results, effectively reveals the correlation between printability and the extent of melting in the powder bed. The energy density impacts the heat transfer mechanism and recoil pressure magnitude within the molten pool, thereby determining its flowability to fill voids in the powder bed. Based on these findings, SLM process parameters were adjusted to achieve an ultra-thin wall thickness of the printed anti-scatter tungsten grid reaching 92 μm. This work not only provides theoretical insights but also presents a viable methodology for determining minimum energy density threshold and wall thickness required for SLM fabrication of ultra-thin-wall structural components.