Mechanism and experimental study of laser-electrochemical synchronous hybrid machining using a combination of a spherical-end optical fiber and a tubular metal electrode

The difficult-to-machine characteristics of Titanium alloys pose significant challenges to achieving high-efficiency and high-precision microstructural fabrication in these materials. In the present study, a coaxial hybrid laser–electrochemical machining method was proposed, which innovatively combined a spherical‑end optical fiber with focusing capability and a tubular metal electrode. The material removal mechanism of TC4 alloy (Ti-6Al-4V) under the combined action of laser and electrochemical energy fields was investigated. In addition to increasing the electrolyte conductivity, the laser also enhanced the current efficiency of the hybrid process. At a laser power of 40 W, the current efficiency of the hybrid machining increased by 23.9%. The effects of machining voltage and laser power on the depth, width, and shape of the machined groove structures were examined. It was observed that the groove width was minimized under laser‑assisted electrochemical machining. The groove depth was influenced by the laser power. When the laser power exceeded 20 W, the groove depth was governed by the laser machining depth and varied only slightly with changes in machining voltage. When the laser power was below 20 W, the groove depth resulted from the combined action of laser and electrochemical machining. Furthermore, the maximum material removal rate and the flatness‑preserving removal parameters within the investigated process window were identified. Finally, by optimizing the tool electrode horizontal feed rate to integrate high‑efficiency removal with surface finishing, a U‑shaped groove structure was successfully obtained, featuring a bottom surface roughness of 4.1 μm, free of laser machining marks and without molten residue.