Performance improvement of eco-friendly MQL technique by using hybrid nanofluid and ultrasonic assisted grinding

Minimum quantity lubrication (=MQL) technique has many technological and economic advantages in grinding operation. It not only improves general grinding performance such as surface integrity, grinding forces and wheel wear but also, it is eco-friendly technique because of its small consumption of cutting fluid. Despite these advantages, MQL technique has a serious thermal problem in grinding operations due to small amount of cooling. To overcome this problem combination of hybrid nanofluid and ultrasonic vibration has been suggested. Nanofluid can increase heat transfer from workpiece/wheel interface due to its high thermal conductivity. Also ultrasonic machining can decrease heat generation due to its reciprocating mechanism and reduction of time and length of contact between grain and workpiece. In this research hybrid Multi Walled Carbon Nano Tubes (=MWCNT) (with high thermal conductivity) and Al2O3 (with good lubrication effect) nanofluid has been utilized. The results have been shown that combination of MQL and UAG leads to decreasing of maximum grinding temperature up to 60.2% in comparison to dry grinding (from 254ºC to 101ºC). Moreover, friction coefficient and tangential grinding force have been reduced up to 35.9 and 69.2 percent respectively. Furthermore, any burning has not been observed with combinations of these techniques while severe burning has been observed in dry grinding. Surface morphology analysis has been shown decrease of plastic deformation and side flow. And finally the generated chips have been shown similarity of cutting mechanism in in the utilized techniques and conventional cutting fluids.