Experimental investigation of effects of nano-fluid usage on cooling in machining

Usage of nano-fluids in machining is gaining popularity due to their improved thermo-physical properties. Studies show that adding nano-particles like Al ₂ O ₃ , MWCNT or TiO ₂ to fluids enhances their density, viscosity, and thermal conductivity. This experimental study examines the effects of adding these nano-particles in concentrations of 0.5%, 1%, and 1.5% to the boron oil-water mixture. This study was conducted in three stages: preparation of nano-fluids, measurement of their thermo-physical properties, and machining experiments with Ti-6Al-4V material. The findings of the study revealed that while increasing nano-particles concentration consistently raised the fluid density at 24.5°C but it did not have similar effect on dynamic viscosity and thermal conductivity, which decreased after 1% concentration due to non-conformity of fluid form such as precipitation and sedimentation. Moreover, using nano-fluids reduced tool-workpiece interface temperature notably. Adding MWCNT nano-particle with the concentration of 0.5% reduced the cutting tool-workpiece interface temperature by about 18%. However, higher concentrations led to increasing in interface temperature and deteriorating in surface roughness because of deposit formation. Using MWCNT nano-particle with the concentration of 0.5% improved surface roughness by approximately 25%. The study concluded that nano-fluids provide desired machining improvements only at optimal concentrations, while excessive nano-particle concentrations fail to obtain the expected benefits thanks to SEM images of used cutting inserts.