Green lubrication technique for sustainable machining of AISI 4340 alloy steel

Machining with AISI 4340 usually involves an excessive consumption of cutting oil to ensure a good surface finish and to extend the tool life. Accordingly, three highly sustainable and green cooling techniques that consume zero or a minute amount of cutting fluid, namely, dry cutting, minimum quantity lubrication and cryogenic machining, have been explored in the literature. This paper comprehensively reviews the machinability of AISI 4340 steel by using these sustainable machining techniques. Results show that compared with conventional cooling methods, the aforementioned techniques can enhance the machinability of AISI 4340 with respect to tool wear, cutting force, surface roughness and chips formation. Machining under green conditions also improves the economic aspect of metal cutting in terms of material removal rate. Each process constraint when machining with AISI 4340 has been identified in this article. As such, hybrid green machining can be seen as a solution to the limitations of standalone coolant techniques.