Achieving high-quality hybrid laser-arc directed energy deposition of titanium alloy

This study employs hybrid laser–arc directed energy deposition (DED) technology to stabilize the arc, improve the forming quality, and refine the grain structure, thereby enabling the efficient fabrication of high-performance Ti6Al4V alloy. The formation mechanism of titanium dual-cathode jets, and physical critical conditions for a laser stabilizing the arc are revealed. When titanium serves as the cathode, the cathodic jet is primarily composed of Ti I, Ti II metal species. The formation site of the cathodic jet corresponds to the highest melt temperature region on the molten surface. A dual-cathode jet phenomenon occurs when the melt temperatures in the laser-irradiated and arc-heated regions are comparable. The Ti II intensity reaches its maximum within the cathodic jet region, thereby providing a conductive channel for the arc. The physical critical conditions for a laser stabilizing the arc are that the melt temperature in the laser irradiated region exceeds that of arc-heated region in a single molten pool, and the laser-induced cathode jet has a minor influence on the droplet. Under comparable line energy input, increasing the laser power enhances the tensile strength of titanium alloy fabricated via hybrid laser–arc DED.