Advanced Manufacturing of Refractory High-Entropy Alloys: What Works, What May Work, and What Does Not Work!

Many advanced manufacturing methods have been applied to manufacture advanced superalloys known as refractory high-entropy alloys (RHEAs). These superalloys are formed from a special subset of elements in the periodic table, comprising mostly of elements having the highest melt temperatures known to science. Researchers seek equiatomic, multi-principal refractory alloys having uniform elemental distribution and enhanced high-temperature/high-strength performance under corrosive environments. RHEAs are ideally suited for such extreme environments, including the oil, geothermal, and gas industries, as well as re-entry vehicles, fusion reactor plasma-facing components, and advanced high-temperature nuclear reactors.

However, researchers have oftentimes struggled with respect to RHEA design, milling, and advanced manufacturing approaches for manufacturing reliable, high-quality solid and coated RHEA components. Herein, we offer proven guidelines to help enable the rapid commercialization of RHEAs. Approaches that work are discussed, as well as coverage of what may work, and what definitely does not work. Some provocative ideas are also discussed with respect to why the application of artificial intelligence (AI) currently offers data-interpolated alloys with marginal 5 to 10% improvements, rather than groundbreaking solutions.

For example, 12 RHEA compositions were recently identified in the literature as potential materials suitable for advanced, high-temperature microturbines. A careful review of the RHEA compositions indicated that only five showed sufficient ductility and machinability (e.g., MoNbTaTiV, CrMoNbV NbMoTaW, NbTaTiV, and MoTaVW). It is fascinating that all five RHEAs were discovered via human means, as opposed to AI.