Electrochemical milling–grinding of high volume fraction SiCp/Al composites with high surface quality via trajectory and process optimization

Abstract

Silicon carbide particle-reinforced aluminum matrix (SiC_p/Al) is a composite material that is difficult to machine, particularly at high volume fractions. This study investigated the feasibility and stability of machining high volume fraction SiC_p/Al using electrochemical milling–grinding (ECMG). Unstable electrochemical discharge machining (ECDM) can easily occur during traditional vertical plunge ECMG. Burn marks were observed on the machined surface, and energy-dispersive X-ray spectroscopy detected the presence of tool electroplating materials such as Ni and Cu on the workpiece, implying tool material adhesion. Modeling and simulations of the electrolyte flow field during the ECMG process demonstrated the critical role of electrolyte convection in material removal. A slow electrolyte flow velocity allowed machining debris and heat to build up in the machining gap, creating favorable conditions for abnormal discharge and material removal via ECDM. Therefore, the tool trajectory was modified from the original vertical plunge cut followed by horizontal cutting to an angled cut followed by reversed horizontal cutting. Simulation results indicated that the modified tool trajectory improved electrolyte flow field uniformity and velocity in the machining gap. Consequently, the electrolyte in the machining gap was continuously refreshed, leading to a stable ECMG process that was confirmed by the electrical signals collected from the power supply during machining. Finally, the voltage, cutting depth, and feed rate parameters were optimized to increase the grinding effect and machining efficiency, thereby improving the surface quality of the machined material. A 90 mm × 25 mm plane SiC_p/Al specimen with a volume fraction of 63 % was successfully processed using the modified trajectory with the optimal parameters.