Preparation and Tribological Properties of Dual-Coated TiO₂ Nanoparticles as Water-Based Lubricant Additives

Figure 6

SEM image of the machined inside surface of drilling hole lubricated (a) without lubricant liquid; (b) using cutting fluids without nanoparticles; (c) using cutting fluids with 2 vt.% nanoparticles; (d) using cutting fluids with 6 vt.% nanoparticles.