(63b) Improving Uniformity of W-Re Alloys by Pore Volume Impregnation of Tungsten Powder

Refractory metals are a class of materials with high melting points and strong mechanical properties at high temperature. Alloys of rhenium with tungsten exhibit the most impressive properties within this group, and are suitable for use in hypersonic vehicles, nuclear reactors, and space propulsion systems. Due to their high melting point, rhenium-tungsten alloy components are produced by consolidating a powder feedstock through either conventional sintering or nascent additive manufacturing techniques. In both cases, the properties of the powder feedstock greatly affect the final quality of the alloy. However, alloying of refractory metals typically relies on blending or mechanically alloying pure metal or metal precursor powders, which limits control over powder properties and can lead to nonuniformities in alloy composition. This work employs a liquid precursor impregnation method to prepare rhenium-tungsten alloy powder feedstocks without altering the properties of the starting tungsten powder. We show that this approach, which has not previously been demonstrated for refractory metal alloying, improves control over powder feedstock properties and enables production of high-quality, fully homogeneous alloys via conventional sintering techniques.

This work utilizes the incipient wetness impregnation method to incorporate rhenium as an alloying element into two different grades of tungsten powder: irregular 1-5 micron particles and spheroidized 5-25 micron particles. This technique is commonly used for preparation of transition metal catalysts and doped ceramics where a uniform, highly dispersed additive is desired; however, it has not been utilized to prepare refractory metal alloys. After preparing rhenium-impregnated tungsten powders ranging from 1wt% to 20wt% rhenium using this technique, powder composition, particle size, particle shape, bulk density, and flowability will be evaluated to assess how this technique impacts powder properties relevant to powder consolidation. Powders will then be consolidated to near-theoretical density in a graphite sintering furnace, and the achievable density, alloy microstructure, and compositional uniformity will be assessed using standard metallographic techniques and electron microprobe analysis.

Overall, this work will evaluate a novel preparation approach for refractory metal alloy powder feedstocks that can offer improved control over particle properties, consolidation behavior, and final part properties. These findings will improve the efficiency of traditional refractory alloy manufacturing processes and expand the range and availability of feedstocks suitable for additive manufacturing.