Incremental solidification (toward 3D-printing) of metal powders by transistor-based microwave applicator

Incremental solidification (IS) of small batches of metal powders is a fundamental process in various additive-manufacturing (AM) and 3-D printing (3DP) operations. Here we show the feasibility of an IS process implemented by a compact, all-solid-state microwave applicator. In this compact scheme, the localized microwave-heating (LMH) process is conducted in a nitrogen shielding environment, and hence the microwave power is reduced to only ∼0.1 kW (compared to ∼1 kW in a previously reported magnetron-based IS process). This shielding prevents the plasma excitation (which intercepted most of the microwave power in the previous experiments in air atmosphere), and hence significantly improves the efficacy of the LMH-IS process. This paper introduces the compact LMH-AM concept, and its novel implementation by a transistor-based microwave system. Experimental and theoretical results of the LMH-AM process applied to bronze- and iron-based powders are presented. The powder is provided to the LMH interaction region in small batches, on demand. A contactless magnetic confinement is demonstrated for ferromagnetic powder batches. The experimental products obtained are tested, and their mechanical properties are evaluated. The potential applicability of the solid-state LMH technology to full AM and 3DP processes is discussed.