Temperature dependence of the extreme-pressure behavior of CuO and TiO₂ nanoparticle additives in metal-forming polymeric lubricants

The purpose of this work is to investigate the effect of temperature on the extreme-pressure (EP) properties of CuO and TiO₂ nanoparticle-filled polymeric lubricants for metal-forming processes.

This paper studies the effect of nanoparticle additives of CuO and TiO₂ on the load-carrying capacity of a metal-forming polymer lubricant used for deep-drawing at varying temperatures. EP measurements are performed with a four-ball tribotester according to the ITeE-PIB Polish method for testing lubricants under scuffing conditions. Tests are run at 25, 40, 60 and 75°C to further decrease the lubricant film thickness and determine the effect on the load-carrying capacity and the tribological mechanisms of nanoparticles. The tribological mechanisms of nanoparticles is studied using energy dispersive spectrometry (EDS).

Results indicate that nanoparticle additives increase the load-carrying capacity of the polymeric lubricant at all concentrations up to 60°C attributed to a mending effect and a reduction in the area of contact of moving surfaces; at 75°C, the improvement is lowered due to nanoparticle re-agglomeration. The best results are found with TiO₂ nanoparticles due to their smaller size compared to CuO.

Nanoparticles of CuO and TiO₂ are potential EP additives for metal-forming lubricants, providing protection to working components and extending tool life.

These results show the effectiveness and the tribological mechanisms of nanoparticle additives under EP conditions and increasing temperatures found in metal-forming processes.