Graphene nanoplatelets as additives to MQL for improving tool life in machining Inconel 718 alloy

Inconel 718 is widely used in the aerospace sector thanks to its excellent mechanical properties and corrosion resistance. However, these unique characteristics coupled with its low thermal conductivity make Inconel 718 a difficult-to-cut material. To limit the temperature rise within the cutting zone, flooding is conventionally used leading to health risk for operators and environmental impact. The addition of nano-sized particles to the biodegradable oil in Minimum Quantity Lubrication (MQL) to create a mixture called NanoFluid (NF) represents an alternative to flooding. In the present study, Graphene NanoPlatelets (GNPs) were chosen as additives to create NF. Turning trials were performed by spraying NF at different concentrations and flow rates. First, the NF characteristics were studied in terms of viscosity, specific heat capacity, stability and coefficient of friction. Then, the tool wear mechanisms were identified and quantified, and the machined surface finish analyzed at varying cutting length. Finally, on the basis of the experimental findings and the environmental impact of NF, the optimum combination of graphene concentration and flow rate was provided in order to simultaneously accomplish tool life increase and formation of smoother surfaces.