Investigation of microstructural evolution and property optimization of pure tungsten via powder extrusion 3D printing

Abstract

Powder extrusion printing (PEP) of tungsten addresses the limitations of residual stress cracking and the high costs associated with direct 3D printing of powder materials. It shows significant potential for producing tungsten products with complex geometries. In this study, green parts made from fine and medium-sized tungsten powders were fabricated using PEP, followed by solvent-thermal debinding and vacuum sintering to create samples with varying densities. The rheological behavior of both feedstock, process parameters affecting print quality, solvent debinding, and microstructural evolution during sintering were investigated. The results indicate that the viscosity of fine tungsten powder feedstock is higher and more sensitive to temperature changes. Key factors influencing print quality include layer thickness, nozzle diameter, and printing speed. Solvent debinding progresses from the sample's edge towards its center, with the debinding rate primarily governed by solute dissolution and diffusion. After sintering at 1750 °C, the relative density of medium-sized tungsten powder reached only 74.0 %, whereas the fine powder achieved a density of 96.8 %. These findings confirm that extrusion 3D printing, combined with sintering, is an effective method for producing high-density tungsten parts with intricate shapes.