Direct Ink Writing for Sintering of Tungsten Metal Parts

Tungsten (W) metal is known for its ability to withstand high temperatures with a melting point at 3422℃. W materials are also durable, dense, and thermally conductive. Currently, there is no viable method of fabricating W in complex shapes, but this ability would be extremely useful. These complex W parts would be able to be used for nuclear-thermal-propulsion (NTP) engines for space travel, hypersonic aircraft leading edges, and solar sensors that require specifically designed parts.

The purpose of this project is to use direct ink writing (DIW), a type of 3D printing, to fabricate metal-doped tungsten parts. Certain dispersed metal dopants can be used to reduce the sintering temperatures of tungsten, and DIW allows for the W to be printed into complex shapes. Because there is no current way of making complex W shapes, this is a very novel method.

An initial W ink was formulated using tungsten powder, water, a binder, dispersant, and flocculant. The ink is uniform, of ideal consistency, and prints solid figures that hold their shape. The method of printing was studied using a design of experiments. The size of the syringe tip that the W ink flows out of, the speed at which the shape is printed, and the space between each layer when the part is printing were each varied. The parts were then sintered in a furnace at 1800℃ and their densities and surface roughness were analyzed to determine how each factor, or combination of factors, affects the quality of the printed part. This allowed us to find the optimal ink to be used to print complex tungsten shapes.