Effect of minimum quantity lubrication (MQL) on tool wear and surface roughness in turning AISI-4340 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluids changes the performance of machining operations because of their lubrication, cooling, and chip flushing functions but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication (MQL) has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL on tool wear and surface roughness in turning AISI-4340 steel at industrial speed-feed combination by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip–tool and work–tool interaction.