Ultrafast drilling of Inconel 718 using hybrid EDM with different electrode materials

In recent years, the popularity of nickel-based super alloys has been on the rise due to their widespread application in oil and gas, aerospace and automobile, marine and biomedical industries. The unique combination of superior mechanical and chemical properties like hardness, strength, temperature and corrosion resistance is responsible for the extensive application of these alloys. However, these properties pose challenges during the conventional machining of nickel-based super alloys. The low thermal conductivity and high work-hardening characteristics of Inconel 718 make it difficult to machine. To overcome the aforementioned problem, a hybrid non-contact electrical discharge and arc-machining process has been employed. In this process, an additional DC power supply is employed in conjunction with the normal EDM-pulsed power supply. Furthermore, the selection of proper electrode material plays an important role in defining the machining performance. In this study, in order to select a suitable electrode material for the newly developed process, several experimental investigations have been conducted with three different electrode materials, namely brass, copper (Cu) and copper tungsten (CuW). The results have shown that, for all the current settings, brass electrode provides the highest material removal rate (MRR), followed by Cu and CuW electrodes. However, CuW exhibited the lowest electrode wear rate (EWR). Moreover, the average surface roughness and surface characteristics of the electrodes after machining were investigated as well. Based on all the performance parameters, CuW appears to be the best choice for the hybrid process to machine Inconel 718.