A tool-based hybrid laser-electrochemical micromachining process: Experimental investigations and synergistic effects

This paper proposes a novel tool-based hybrid laser-ECM process which exploits synergy of laser and electrochemical process energies along the same machining axis, thereby enhancing the potential of both processes while compensating and minimizing their limitations. This process combines features from jet-ECM and water jet guided laser processes into a new micromachining process. In this study, details of this tool-based hybrid laser-electrochemical micromachining process are presented and an experimental study on process-material interaction is performed using Inconel IN718 as workpiece material. According to the experimental results, material removal rates of the order of 0.6 mm(3)/min are obtained. It has been observed that while the process response is material-dependent as well as ECM parameter dependent, the effective laser pulse energy reaching the workpiece surface is the main factor influencing the surface characteristics. Additionally, the electrolyte flow rate affects material removal and also influences laser coupling into the tool-electrode. It has been observed that within a specific process window i.e. pulse-energy 30-45 mu J, flow rate 32-48 ml/min, IEG 20-30 mu m, voltage 20-25 V; high quality surfaces are observed with less defects. At pulse energies higher than 60 mu J, the process speed becomes higher but the surface becomes rough due to combined material removal mechanisms taking place. Furthermore, metallographic investigations on the machined surface reveal presence of multiple removal mechanisms such as laser removal, laser assisted electrochemical removal and electrochemical removal depending on the applied laser pulse energy. Overall, this study has shown that hybrid laser-electrochemical micromachining has a high potential to machine advanced metallic alloys with conductivity variations even for high aspect ratio features and needs further research developments.