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

The effect of temperature on the extreme-pressure (EP) properties of CuO and TiO2nanoparticle-filled polymeric lubricants for metal-forming processes. was studied. EP measurements were performed with a four-ball tribotester according to the ITeE-PIB Polish method for testing lubricants under scuffing conditions. Tests were 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. 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 TiO2nanoparticles due to their smaller size compared to CuO.