Experimental evaluation of the effect of minimal quantity lubrication with different cutting fluids in drilling AISI 4340 steel

Abstract

Drilling can be described as a process where a multi-point tool is used to remove unwanted materials to produce a desired hole. Its significance has been recognized due to the large Number of holes to be drilled on engineering components and the large amount of costs involved in the process. However, high production machining and drilling with high cutting velocity, feed and depth of cut is inherently associated with generation of large amount of heat and high cutting temperature. Such high cutting temperature not only reduces dimensional accuracy and tool life but also impairs the surface integrity of the product. The use of minimum quantity lubrication (MQL) in drilling of AISI 4340 steel was studied and the MQL machining performance was compared to dry and conventional flooded conditions. An experimental drilling station with an MQL system was built to measure the amount of Minimum quantities Lubricant uses for drilling. Titanium Nitride coated HSS drill bits of 8.0 mm (diameter) were tested against AISI 4340 Alloy Steel and compared with dry, flood cooling using soluble cutting; VG-68 and MQL using 10-50 ml/h of Vegetable Oil based Olive Oil. The results indicated that the resulted in desirable hole surface and chip segments and the Maximum temperature generated in the work piece during MQL machining was lower than that observed in dry drilling and comparable to flooded conditions. The mechanical properties of the material adjacent to drilled holes as evaluated through hardness measurements. In this case, the Minimum Quantity Lubrication (MQL) is very effective to reduce temperature. When temperature is increased a large amount of tool wear appears at the drill bit. In this situation, high temperature either affects roundness of the hole or chip shape and color of Chip. MQL is applied in the same direction as the drill bit. MQL has reduced temperature as well as improving roundness and also provide lubrication in the tool and surface interface.