Synthesis of MWCNT nanofluid and evaluation of its potential besides soluble oil as micro cooling-lubrication medium in SQL grinding

Abstract

Grinding, being a high specific energy involving process, essentially requires a high-performance cutting fluid when small quantity lubrication (SQL) is employed. In SQL, a small volume of metal working fluid is broken into micro-droplets by a compressed air jet so that the aerosol jet cools and lubricates machining zone more efficiently than flood cooling. In the present work, a new generation grinding fluid was indigenously synthesized by dispersing multi-walled carbon nanotube (MWCNT) in deionized water for SQL grinding of steel by an alumina wheel, and its capability was evaluated in depth in comparison with the commercially used soluble oil. It was observed that a maximum of 1 vol% MWCNT could be dispersed without any settling tendency over 48 h, which subsequently rendered the highest thermal conductivity to the nanofluid sample. It was approximately 35 % higher than that of soluble oil. In a simulative ball (Al₂O₃) on disc (hardened AISI 52100 steel) test, it was further found that this nanofluid sample was 30 % more lubricious than its counterpart. The higher heat dissipation ability and better lubricity finally resulted in remarkably superior performance of MWCNT nanofluid to that of soluble oil. In comparison with the later MWCNT nanofluid, in particular, at 3 bar of atomizing air pressure and 350 ml/h flow rate, could offer substantially better G ratio, significantly reduce tangential grinding force and produce comparable surface finish. Additionally, presence of more number of long and sheared chips and less spherical chips in the collected sample was a clear indicator of reduction in grinding temperature when soluble oil was replaced by MWCNT in SQL mode.