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Significant advances, both practical and theoretical, have been made in understanding the behaviour of engineering materials when machining at higher cutting conditions. Nano-integrated manufacturing is a subject of immense interest for various sustainable engineered systems. Metal removal processes involve the generation of high cutting forces and temperatures. The use of proper lubricant to reduce forces and temperatures and to improve total cutting phenomena overall is an important aspect. The present investigation analysed a green, petroleum-free lubricant that is produced by mixing two environmentally benign components, canola oil and nano-crystalline boric acid. To study the influence of variation of nano-level boric acid particle size and its weight percentage on the performance of the proposed green particulate fluid lubricant, various turning tests were conducted on AISI 1040 steel using tungsten carbide inserts. Variations in cutting forces, tool temperatures and surface roughness were studied. The experimental results revealed that both cutting forces and tool temperatures increased as the boric acid particle size decreased. The surface quality of the machined surface was reduced as the solid lubricant particle size was reduced to the nanolevel. Interestingly, reductions in both cutting force and tool temperature were observed as the boric acid weight percentage decreased, tending towards the pure canola oil-based machining results. The surface quality of the machined surface was also improved as the volume fraction of boric acid was decreased.

The past few decades have witnessed significant advancements in turning processes, cutting tools and coolant/lubricant chemistry. These developments have enhanced the machining capabilities of hard materials when machining at higher cutting conditions. Turning, being characterized by the development of high temperatures at the cutting zone, is critical with respect to the tool life and surface finish apart from other machining results like the forces generated. This phenomenon of heat generation at the cutting zone plays a negative role during turning operations due to their peculiar characteristics such as poor thermal conductivity, high strength at elevated temperature, resistance to wear and chemical degradation. Cutting fluids and solid lubricants are generally used to overcome the problem of heat generation at the cutting zone. The use of cutting fluids in the conventional way may not effectively control the heat generated in turning operation. Moreover, cutting fluids are a major source of pollution. With the advancement in technology, nano-level particulate solid lubricants are being used nowadays in machining operations, especially grinding and turning. The present work deals with the investigation of using nano-level particulate graphite powder as a solid lubricant and various tests were conducted by machining AISI 1040 steel using tungsten carbide inserts. The experiments were conducted by taking into account the parameters like feed rate ranging from 0.05 mm/rev to 0.125 mm/rev, cutting speed ranging from 51 m/min to 192.6 m/min and depth of cut from 0.25 mm to 1 mm. Four levels of each parameter are considered for experimentation. The results indicate that with the decrease in the nano-sized graphite powder, there is an increase of cutting forces – feed force, cutting force and thrust force. The temperatures at the tool–chip interface also increases with the decrease in the lubricant size. It is found that the surface roughness of the workpiece after machining deteriorated due to the size of the lubricant particle.