Investigations into lubrication in grinding processes using MWCNTs nanofluids with ultrasonic-assisted dispersion

Abstract To improve the quality of grinding processes, nanofluids can replace traditional cutting fluids, improving cooling, lubrication, and surface finish. However, a disadvantage of nanofluids is that a suspension of nanoparticles tends to agglomerate in the course of a long machining process, leading to cooling performance degradation. Although adding surfactants can improve nanoparticle dispersion, this may pollute the nanoparticles. The present research aims to solve these problems using ultrasonic assistance, first taking advantage of the excellent thermal conductivity of multi-walled carbon nanotubes in nanofluids, with vegetable oil as a cutting fluid, and second, devising an effective ultrasonic-assisted oscillator set-up for Minimum Quantity Lubrication. The oscillator agitates the nanofluid through ultrasonic cavitation to keep the nanoparticles dispersed. This experiment uses NAK80 mold steel as a material for grinding, with four different lubrication methods: dry, MQL, nanofluid (0.25 wt%)/MQL, and nanofluid (0.25 wt%)/ultrasonic MQL. The grinding performance and effects of ultrasonic-assisted dispersion are discussed. The results show that nanofluid/ultrasonic MQL grinding can effectively reduce the agglomeration of nanoparticles, and reduce grinding forces, grinding temperature, and surface roughness to a greater degree than other lubrication methods.