Laser and electrochemical hybrid machining is a composite processing method that combines laser and electrochemical processing. It can be used to process hard conductive materials. It can accelerate the electrochemical dissolution rate, avoiding recasting layers, thus improving the surface quality. This study proposes a tubular electrode-coupled laser and electrochemical hybrid machining technology that uses a newly designed tubular electrode. This realizes coaxial transmission of laser and electrochemical energy inside the tubular electrode and controllable coupling at the processing gap, which is suitable for high-quality small hole processing with a high aspect ratio. A coupling mechanism dominated by laser and an electrochemical processing is proposed based on the controllable adjustment of the laser and electrochemical energy at the processing gap. The effects of the temperature rise in the laser irradiation zone on the electrolyte conductivity, current density, liquid-phase mass transfer, and electrochemical dissolution rate, as well as the effects of bubbles and impurities generated during electrolysis on the laser energy. Material removal models for laser and electrochemical hybrid machining are established, and preliminary simulation analysis and experimental research on laser and electrochemical hybrid machining are conducted.

This study introduced a tool for laser and electrochemical hybrid machining with a tubular electrode that confined the electrolyte and laser beam coaxially or asynchronously. In addition, it utilized a coaxial optical fiber inside the tubular electrode to enable total internal reflection of the laser, thereby achieving independent control of laser and electrochemical energy within the tubular electrode. Based on this process, a coupling mechanism for the laser and electrochemical energy was explored, as well as the mechanisms where the laser and electrolysis dominate in the hybrid machining process. By investigating the temporal and spatial distributions of local temperature and stress induced by coupled energy, we study the influence of laser on mass transport and electrode potential in the micro-region of electrochemical machining. A theoretical model for the kinetic behavior of materials removal under the action of hybrid energy was established, and a preliminary simulation analysis of laser and electrochemical hybrid machining was conducted. The results of this study laid a theoretical foundation for the fabrication of complex structures with high quality and aspect ratio.

First, the influence of laser power density on the machining capability of workpiece materials is explored (Fig.2). When the laser power density is low, the laser affects the thermal and electrochemical parameters of the workpiece material and the changes in the electrolyte's electrical conductivity, electrolytic current density, ion diffusion rate, bubble rate, and electrode potential within the machining gap through thermal effects. When the laser power density reaches the electrolyte breakdown threshold, the laser impacts the laser and electrochemical hybrid machining process through both thermal and mechanical effects. Second, based on the controllable adjustment of the laser and electrochemical energy within the tubular electrode, the state changes in the coupling region caused by these energy are classified into three mechanisms: laser-assisted electrochemical machining, laser and electrochemical hybrid machining, and electrolysis-assisted laser machining (Fig.4). Furthermore, through theoretical analysis and preliminary simulation studies, the electric field and current density distributions in the laser and electrochemical hybrid energy field, the flow field distribution, the temperature distribution, and the resulting machining surface are investigated. This facilitates in the evaluation of material removal at different locations on the workpiece during the laser and electrochemical hybrid machining processes. Finally, three-dimensional morphologies of blind holes produced by the only electrochemical machining and laser and electrochemical hybrid machining are compared. The advantages of the hybrid laser and electrochemical processing are confirmed (Fig.9). It successfully manufactures through-holes with a diameter of 1.26 mm and a high aspect ratio of 16∶1 and through-holes with a diameter of 1.25 mm and high aspect ratios of 42∶1 (Figs.10 and 11).

Laser and electrochemical hybrid machining typically suffer from defects such as stray corrosion caused by electrochemical machining and resolidification defects caused by laser machining. To avoid the occurrence of defects and improve the surface quality, this study introduces a tool for laser and electrochemical hybrid machining with a tubular electrode. This enables the coaxial transmission of laser and electrochemical energy within the tubular electrode and the controlled coupling at the machining gap, thereby effectively preventing defects such as stray corrosion and resolidification of layers. This approach is suitable for fabricating complex structures with high quality and aspect ratios. Based on the controllable adjustment of the laser and electrochemical energy, this study proposes mechanisms in which laser and electrolysis dominate, and both cooperate in hybrid machining. The thermal effects of the laser on the laser and electrochemical hybrid machining and the influence of the pulse width of electrolysis on the process are analyzed. This study establishes a theoretical model for the kinetic behavior of material removal under the action of hybrid energy. Preliminary investigations are also conducted on the time and spatial distribution of the hybrid energy field and its impact on the machining surface using simulation models. Through experiments, the advantages of laser and electrochemical hybrid machining are verified. Small holes with a diameter of 1.25 mm and aspect ratio of up to 42∶1 without resolidified layers are successfully produced. This study lays a theoretical foundation for the fabrication of complex structures with high quality and aspect ratio.