Additive manufacturing of refractory niobium alloys: a review of processing, properties, modeling, and applications

Alloys and intermetallics based on the refractory element niobium (Nb) have proven useful in many high-temperature applications requiring high strength, ductility, and corrosion resistance. However, its high raw material cost, a high affinity for oxygen embrittlement, and exceptional thermal properties and strength in harsh environments makes the processing of Nb alloys through conventional techniques difficult. Recent advances in additive manufacturing (AM) of these materials have demonstrated mechanical properties comparable to those produced by conventional casting. Furthermore, high-throughput computing, machine learning, and automation have opened up unprecedented opportunities to overcome AM processing challenges like process window selection, oxidation mitigation, and porosity defects. Thus, this review describes the AM processes that have been applied to Nb alloys, assesses their microstructures, and explains their effects on the mechanical and physical properties. It also highlights how computation can aid in the design and processing of Nb alloys for AM. Ultimately, it provides a roadmap for processing Nb alloys via AM, highlighting their most promising applications as well as where further research is needed.