An investigation on surface grinding of AISI 4140 hardened steel using minimum quantity lubrication-MQL technique

In dry grinding, as there is no coolant lubricant to transfer the heat from the contact zone, generation of surface damages are not preventable. Promising alternatives to conventional flood coolant applications are also Minimum Quantity Lubricant (MQL) or Near Dry Machining (NDM) or Semi Dry Machining (SDM). As the name implies, MQL machining uses a very small quantity of lubricant delivered precisely to the cutting zone. Often the quantity used is so small that no lubricant is recovered from the parts. Any remaining lubricant may form a film that protects the parts from oxidation or the lubricant may vaporize completely due to high temperatures of the cutting zone. A number of studies have shown that MQL grinding can show satisfactory performance in practical grinding processes. However, there has been little investigation of cutting fluids to be used in MQL grinding. In this study, several grinding fluids, including mineral, vegetable and synthetic esters oil, are compared on the basis of the grinding forces and surface quality properties that would be suitable for MQL grinding applications, to develop a multifunctional fluid having the MQL results such as cooling, lubrication and high ecological and environmental safety performances. The grinding performance of fluids is also evaluated in dry and conventional fluid grinding techniques.