Influence of Minimum Quantity Lubrication on Friction Coefficient and Work-Material Adhesion During Machining of Cast Aluminum With Various Cutting Tool Substrates Made of Polycrystalline Diamond, High Speed Steel, and Carbides

Due to the increasing emphasis on environmental constraints, industry works on how to limit the massive use of lubricants by using the micro-pulverization of oil in machining processes and, especially, in the machining of aluminum alloys for the automotive industry. The success of a machining operation is dependent on a friction coefficient and weak adhesion with the tool-work material interface. This paper aims at identifying the influence of cutting tool substrates (high speed steel (HSS), carbide, polycrystalline diamond (PCD)) and of minimum quantity lubrication (MQL) on the friction coefficient and on adhesion in tribological conditions corresponding to the ones observed in the cutting of aluminum alloys (sliding velocity: 20-1500 m/min). An open ball-on-cylinder tribometer, especially designed to simulate these tribological conditions through Hertz contact, has been used. It has been shown that HSS and carbide substrates lead to large friction coefficients (0.8-1) and substantial adhesion in dry conditions, whereas PCD substrates would lead to lower average friction coefficient values (0.4-0.5) and very limited adhesion, which proves the necessity of using PCD tools in the dry machining of aluminum. It has also been shown that the application of MQL leads to a large decrease of the friction coefficient (0.1-0.2) and eliminates almost all traces of adhesions on pins for any substrates, which shows that MQL is an interesting compromise between dry machining and flood cooling.