Dry, MQL, and Nanofluid MQL Machining of Ti–6Al–4V Using Uncoated WC–Co Insert: Application of Jatropha Oil as Base Cutting Fluid and Graphene Nanoplatelets as Additives

Abstract

Nanocutting fluids are very popular due to their excellent thermo-physical and tribological properties which provide adequate cooling and lubrication during metal cutting. Conventional dry machining of difficult-to-cut superalloy Ti–6Al–4V faces several challenges. To overcome this, application of cutting fluid is indeed a necessity. However, performance of conventional minimum quantity lubrication (MQL) system, in which air–oil mist is sprayed into cutting zone, is somewhat limited due to inadequate penetration into tool–work and tool–chip interfacial regions, especially at high cutting speeds. MQL performance can further be enhanced by applying nanocutting fluid in which nano-sized additives are dispersed into the base cutting fluid; this is known as nanofluid MQL (NFMQL). In order to take care of several alarming issues related to environmental protection and occupational health hazards, the present study explores application feasibility of biodegradable Jatropha oil added with graphene nanoplatelets as nanocutting fluid. Machinability of Ti–6Al–4V is assessed under NFMQL; results are compared to that of dry and conventional MQL machining. Cutting force magnitude, tool-tip temperature, morphology of worn-out insert, chip’s macro/micro-morphology and surface roughness of the machined work part, etc., are studied in detail. For MQL and NFMQL, tool wear morphology detects existence of ‘unaffected zones’ which indicates sustenance of strong hydrodynamic tribo-film of cutting fluid, thus protecting the insert against wear. Up to 82 m/min cutting speed, NFMQL causes lower tool flank wear than dry and conventional MQL. On the other hand, superior machined surface finish is obtained under NFMQL up to 106 m/min cutting speed.