STUDIES ON CRYOGENIC TREATED DRILLS UNDER NANO-FLUID BASED REDUCED QUANTITY LUBRICATION CONDITIONS FOR MACHINING Ti6Al4V

摘要

Minimum quantity lubrication (MQL) machining is gaining wide acceptance because of the need to make machining more environment friendly. With cutting fluids contributing more than 10-15% of the manufacturing costs, economics of MQL is also gaining interest. The initial cost of commercial MQL systems is one of the limiting factors hindering their adoption in small and medium scale industries. This study, uses a simple commercial paint sprayer with a portable compressor (with a total cost < $ 125) to produce an MQL like spray with a slightly higher flow rate as compared to MQL (and is thus called reduced quantity lubrication) in drilling Ti6Al4V. Tungsten carbide drills of 7 mm diameter were subjected to deep cryogenic treatment, which has been acknowledged as a means of improving tool wear resistance. There was a marginal improvement in drill microhardness as a result of cryogenic treatment. The performance of untreated and cryo-treated drills was compared for tool wear, hole surface roughness and cutting forces. In addition to the normal air-coolant mist, the effect of adding nano-particles in the coolant was also studied. It is found that cryo-treated drills under nano-fluid based reduced quantity lubrication (RQL) conditions performed better than untreated drills and conventional cutting fluids, in terms of all the three measured parameters. This can be attributed to the higher thermal conductivity of nano-fluid based coolants and their ability to reduce the coefficient of friction at the chip-tool interface.