Sustainable Machining of Hardened Inconel 718: A Comparative Study

Recent trends in metal cutting shows the increasing of demand at the global stage for the application of eco-friendly machining approaches in order to eliminate the adverse effects of conventional cutting fluids. Thus, this experimental work was conducted to evaluate the performance of sustainable cooling techniques of cryogenic carbon dioxide (CO2), Minimum Quantity Lubrication (MQL), cryogenic liquid nitrogen (LN2) and dry cutting on machinability of Inconel 718. For the cryogenic CO2 approach, a new concept of cryogenic cooling technique was introduced for efficient and consistent cooling performance. The findings displayed cryogenic CO2 as a promising coolant since it resulted in slower tool wear rate compared to cryogenic LN2 and dry cutting, while being more effective in decreasing cutting forces and surface roughness compared to other approaches. Its adequate and consistent cooling efficiently disperses the generated heat and creates an ideal cutting condition for the tool and workpiece to interact with each another during cutting. In contrast to MQL cutting, the usefulness of CO2 was supplanted due to the resulting shorter tool life. As such, the MQL approach is preferred as it extends the tool life longer by 67.2% with the maximum volume of material removal as compared to cryogenic CO2. Its lubrication impact shows effectiveness in diminishing the tool wear rate than the cooling effect by the cryogenic CO2. However, from the viewpoint of sustainability, MQL could be less preferable due to unpleasant odour and settling of MQL mist around the cutting area.