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

Purpose The purpose of this work is to investigate the effect of temperature on the extreme-pressure (EP) properties of CuO and TiO 2 nanoparticle-filled polymeric lubricants for metal-forming processes. Design/methodology/approach This paper studies the effect of nanoparticle additives of CuO and TiO 2 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). Findings 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 TiO 2 nanoparticles due to their smaller size compared to CuO. Practical implications Nanoparticles of CuO and TiO 2 are potential EP additives for metal-forming lubricants, providing protection to working components and extending tool life. Originality/value These results show the effectiveness and the tribological mechanisms of nanoparticle additives under EP conditions and increasing temperatures found in metal-forming processes.