Break | AIChE


Tungsten is a refractory metal which possesses unique characteristics: high melting point, high density, a low thermal expansion coefficient, high tensile strength, high thermal conductivity, and favorable corrosion resistance. These attributes make it ideal for high-temperature applications such as heat pipe cooling solutions for hypersonic aircraft, the construction of cermet fuel elements for nuclear thermal propulsion, and advanced radiation shielding. Rhenium is a well-known additive that can improve both the ductility and strength of tungsten at high temperatures. Rhenium is generally added to solid tungsten substrates through arc-melt or electron beam techniques. For additive manufacturing applications such as direct ink writing, rhenium must be successfully added to a tungsten powder substrate whilst remaining in a form conducive for incorporation into an ink.

This work utilizes incipient wetness impregnation with perrhenic acid to deposit controlled quantities of rhenium upon a tungsten powder substrate. After impregnation, it was observed that 1 wt% rhenium concentrations and higher resulted in the formation of a red precipitate. Powder XRD confirms the red precipitate as crystallized ReO3, which likely formed during the drying process in air. The resulting Re-W powder was crushed, sieved, and ball milled to ensure homogeneity amongst the samples. Inspection by ICP-OES indicated successful incipient wetness impregnation, with the deposited rhenium quantity falling within the expected range of compositions. TOF-SIMS was conducted to determine the nature of the rhenium deposition upon the tungsten substrate. The results demonstrated uniform dispersion of rhenium upon the substrate, which is crucial for the manufacturing of complex tungsten parts.

Conventional pressing and sintering of the Re-W samples will be performed to indicate whether the utilized Re doping strategy affects tungsten densification kinetics or its density post-sintering. Versatile micro-indentation techniques will be utilized to ascertain whether advantageous mechanical properties are achieved. Future work will incorporate Re-W powders into printable inks that can be used to additively manufacture tungsten prototypes to scrutinize against conventionally pressed samples. This work shows a novel approach to rhenium doping that could facilitate the mass fabrication of complex tungsten parts with exceptional properties.