Additive manufacturing of tungsten, tungsten-based alloys, and tungsten matrix composites

Tungsten (W) materials are gaining more and more attention due to the extended applications of metallic systems in the extreme environments. Given W's unique characteristics like room-temperature brittleness, additive manufacturing (AM) techniques could give them a higher design flexibility and manufacturability. With the growing focus and thriving development of W-faced AM techniques, since the mechanical performance of additively manufactured W parts is still unsatisfactory, a critical review to further explore the possibilities of combining W and AM processes is urgently needed. In this review, we systematically explain the fundamentals of AM processes for W materials. Following the traditional classification, we further discuss the widely used AM processes including wire arc additive manufacturing (WAAM), electron beam melting (EBM), laser powder bed fusion (LPBF), laser direct energy deposition (laser DED), and other modified yet emergent AM techniques. Accordingly, since additively manufacturing W materials is processing parameter-sensitive, we illustrated the effects of various important processing parameters on the AM process control and final parts' quality. With this detailed understanding, various categories of AM-compatible W materials (i.e., pure W, W alloys, and W composites) were presented, and their general mechanical performance, distinct role (particularly the role of different alloying elements and added secondary-phase particles in W), and application-oriented benefits have been summarized. After clarifying the current status, main challenges, and triumphant successes for additively manufacturing W materials, we further provide a concise prospect into the development of additively manufactured (AMed) W materials by integrating potential fabrication, measurement, alloy design, and application's considerations. In summary, this critical review investigates the fundamental and practical problems crucially limiting the applications of AMed W materials, and the comprehensive discussion concentrates the history of the development and combination between AM techniques and W design. All the understanding is of great importance to achieving foreseeable successful future applications of AMed W materials.