| Abstract Scope |
Most in-situ diagnostics, including laser, pyrometry, and X-ray imaging, are difficult to deploy in additive manufacturing environments for resolving melt-pool dynamics. Here, a single high-speed camera with a narrow-band-pass filter captures the physical mechanisms governing deposition in wire-based directed energy deposition (WDED). At 50,000 fps, low-carbon steel and Cu70Ni30 wire deposition under cold metal transfer mode were imaged at feed rates of 1.5-8 m/min, quantifying melt pool geometry, bubble dynamics, droplet transfer, and Marangoni convection. Cu-Ni exhibited stronger surface fluctuations, higher oscillation frequencies, faster bubble transport, and larger melt pools than steel, with melt pool length increasing from 1.7-8.2 mm in steel to 1.8-9.0 mm in Cu-Ni, and area from 1.3-15.7 to 1.3-18.8 mm2. Bubble coalescence was directly visualized, reflecting alloy-dependent viscosity and thermal conductivity. These dynamics govern porosity formation, spatter generation, and heat flow, establishing high-speed imaging as a practical diagnostic for real-time WDED monitoring and quality control. |