A systematic study to achieve cleaner and sustainable manufacturing process by using bio-degradable dielectrics

Abstract

Inconel 600 is widely used in aeronautical and aerospace industry owing to its excellent mechanical, wear and corrosion characteristics. This high strength alloy requires a special machining environment which justifies the use of Electric Discharge Machining (EDM). However, low cutting rate, which accounts for the productivity aspect, and emission of toxic fumes generated by thermal breakdown of kerosene dielectric currently limit the use of EDM. Moreover, since EDM is an energy intensive machining process, industry has a stringent emphasis to make this process sustainable and eco-friendly. In this context, the potentiality of six bio-degradable dielectrics was comprehensively investigated here for the first time ever to achieve cleaner and sustainable production of Inconel 600. Each biodegradable dielectric was coupled to four electrode materials to find the best tool-dielectric combinations for the EDM processing of this Ni-based super alloy. The responses were defined considering the three key ingredients of sustainability: i.e. productivity (assessed in terms of material removal rate and tool wear ratio), quality (expressed in terms of surface finish and dimensional deviation) and power consumption (expressed in terms of specific energy consumption). Experimentation was performed with a full factorial design taking dielectric type and electrode material as input variables. The EDM configuration including amla oil as dielectric and brass electrode was the best in terms of maximum MRR (19.8 mm3/min), 560% better than the standard EDM configuration including the same brass tool and kerosene dielectric. The lowest surface roughness SR (quality aspect) was obtained by the EDM configuration including a brass electrode and the sunflower oil dielectric: surface quality improved by 30.6% with respect to standard EDM using the same electrode and kerosene dielectric. Considering the specific energy consumption, the EDM setup with brass electrode and amla oil dielectric was 6.6 times more efficient than standard EDM with the same electrode and kerosene dielectric. The combination of coconut dielectric and Cu electrode results in a 5.4 times lower tool wear ratio than the traditional dielectric. In terms of achieving a better dimensional control, graphite electrode is a preferred choice against olive oil dielectric. Based on the measured values for EDM responses, it was revealed that relative percentage of carbon dioxide emissions reduces by 83.95% if amla oil is used in comparison to the CO2 emissions noted for standard kerosene oil considering brass as electrode. Finally, an optimal combination of the best biodegradable dielectric fluid and electrode material to satisfy all performance indicators was proposed through MOGA technique. Experimental data were properly fitted by using artificial neural networks. The EDM setup with copper electrode and amla oil dielectric achieved the best global performance with respect to all responses.