Sequential Solidification of Metal Powder by a Scanning Microwave Applicator

This study examines the fundamental feasibility of sequential metal-powder solidification by localized microwave-heating (LMH) provided by a scanning, all-solid-state microwave applicator. This continuous process is considered for the additive manufacturing (AM) and 3D printing (3DP) applications of metal parts. In previous studies, we employed LMH for the incremental solidification of small batches of metal powder in a stepwise vertical manner. Here, we study a continuous lateral LMH process, layer by layer, in a fashion similar to laser scanning in powder beds, as performed in common laser-based AM systems. LMH solidification at scanning rates of ~1 mm³/s is obtained in bronze powder using ~0.25-kW microwave power. The effect is studied here by LMH scanning in one lateral dimension (~20-mm long) in layers, each of ~1-4 mm thickness and ~2-4 mm width (mechanically confined). Imperfect solid bars of ~20×4×5 mm³ are obtained with rough surfaces. Their joining in an L shape is also demonstrated. The experimental solidified products are tested, and their hardness and density properties are found to be comparable to laser-based AM products. The capabilities and limitations of the LMH scanning concept for metal-powder solidification are evaluated. The potential feasibility of a solid-state LMH-AM technology is discussed.