In-situ laser removal of Cu2O and CuO during laser powder bed fusion of copper parts

Copper laser powder bed fusion (Cu-LPBF) is known as a challenging manufacturing process. Since copper is an excellent thermal and electrical conductor, low to medium laser power is insufficient to provide good wettability and fusion between either adjacent tracks or deposited layers due to heat dissipation and high reflectivity. Particle surface modification has therefore been proposed to improve optical absorptivity. A simple method to enhance optical absorptivity is to create a thin oxide film by heating copper powder in an air furnace. The first phase of the current work emphasizes that this technique is detrimental to the part quality if a medium laser power range is used. The second phase presents a novel technique of two stages of in-situ copper oxide reduction during LPBF. It provides an innovative approach for combining laser cleaning and melting in LPBF. The newly suggested technique uses recycled and surface oxidized Cu powders to develop a simple and chemical-free method to recover the contaminated powder. A significant improvement is achieved by applying laser surface cleaning to the powder and solidified layers. The oxygen content is reduced by 70% in the LPBF samples compared to the initial state of the oxidized powder.