Study of the performance of minimum quantity lubrication (MQL) and type of lubricant in the milling process of stainless steel EN 1.4903

Cooling/lubricant fluids are typically used in machining processes to reduce the tool-workpiece friction, decrease machining heat and improve surface quality. In recent years, however, several laws have been used in place to protect human health and environment, requiring industry to reduce coolants consumption and expand the use of low-risk and renewable ones. For this reason, a recent new lubrication technique called minimum quantity lubrication (MQL) has been developed for the machining processes. Vegetable oils are kinds of bio-based lubricants and have a significant capacity to be used in MQL due to their environmentally friendly and renewable properties. Stainless steels are considered to be difficult to machining materials and hence their machinability improvement has always been the subject of research. In this investigation, the effects of MQL and type of lubricant in the milling process of martensitic stainless steel EN 1.4903 have been studied. For this purpose, one type of vegetable oil derived from sesame seeds in two conditions including non-additive (pure) and with antioxidant additives, as well as one type of mineral oil have been applied in the experiments. Then, milling force, surface roughness and surface texture have been evaluated. Also, in order to compare the results with other lubrication methods, the tests have been performed under dry and wet conditions. The results show that the MQL compared to the conventional lubrication methods increases the machinability of stainless steel by reducing forces and improving surface quality. Moreover, the type of oil applied has a great influence on the process outputs.