Tribological Analysis and Operation Issues of SiO₂ Nanolubricants for MQL Machining Operations

Minimum Quantity Lubrication (MQL) has been proved to be an efficient lubricant technique in machining that increases tool life, improves surface roughness, facilitates the recycling of the resulting chips, brings more sustainable practices in terms of minimum use of lubricants, and reduces the operators’ exposures to toxic particles with respect to conventional cooling practices. In order to increase the performance of MQL, nanoparticles of Al 2 O 3 , MoS 2 , SiO 2 graphite and graphene among others have been recently introduced into MQL lubricants. This new approach, called nanoMinimum Quantity Lubrication (NMQL), has been proved to provide better thermal conductivity and lower friction coefficients during cutting, which in turns means higher cutting tool life and lower cutting forces. In this paper, a stable SiO 2 -based nanolubricant was produced and characterized. A tribological analysis was conducted on SiO 2 nanolubricants to be used on MQL operations. Operational issues related to particles deposition along time, loss of nanolubricant properties when it comes from the MQL system and mist generation were also analyzed.