Environmentally sustainable machining of copper alloys: Reducing energy demand and enhancing surface quality in EDM of eco-friendly Cu-Ni-Si-Cr alloys

Abstract

The global shift towards sustainable manufacturing has driven demand for safer, environmentally friendly alternatives to conventional beryllium copper (Be-Cu) alloys, which pose serious health and environmental risks due to beryllium toxicity. This necessitates the use of environmentally friendly copper-nickel-silicon-chromium (Cu-Ni-Si-Cr) alloys, which have properties comparable to those of Be-Cu. They possess high hardness and strength; therefore, non-contact machining techniques, such as electrical discharge machining (EDM), should be employed to machine these materials. This study focuses on advancing green manufacturing practices by utilising Cu-Ni-Si-Cr alloys in place of Be-Cu alloys and optimising the EDM for these materials, with a strong emphasis on reducing process-level energy consumption and improving surface quality. A key parameter investigated in this work is specific energy consumption (SEC), which serves as the primary indicator of the electrical energy used in the process. Three-dimensional (3D) surface topography parameters, such as arithmetic mean height (Sa), autocorrelation length (Sal), and valley void volume (Vvv), are also studied to assess the functionality and potential performance of machined parts, as these parameters are critical for reducing frictional losses and energy consumption. Four input variables, pulse-on time (T_ON), pulse-off time (T_OFF), electrode material, and polarity, were studied using a 36-run full-factorial design in Minitab. A multi-objective optimisation technique is applied to simultaneously reduce SEC and Sa, while improving Sal and Vvv, thereby achieving both improved energy utilisation and enhanced surface characteristics. The optimal setup, which utilised an electrolytic-Cu electrode with negative polarity, a 200 µs T_ON, and a 6 µs T_OFF, resulted in an SEC of 3.02 kJ/mm³, a Vvv of 0.35 ml/m², a Sal of 62.09 µm, and a Sa of 2.56 µm. The findings reveal that Cu-Ni-Si-Cr alloys, when combined with process-level optimisation, can deliver measurable reductions in specific energy demand and improved part performance.