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Lubrication is an essential factor in the metal forming processes such as forging, since it leads to reducing friction at contact surfaces and increasing the surface quality of the forged parts. In order to create desirable tribological properties in the base lubricants, various metal oxide nanoparticles are mostly used as additives. In the present study, the effects of the nanolubricants made by copper oxide (CuO) and alumina (AL2O3) nanoparticles on the surface quality of the forging process have been investigated. The effects of the nanolubricants have been compared with the graphite as a conventional lubricant. Upsetting forging operation of a ring shape workpiece was used for evaluating the lubricants. Experiments were designed and analyzed using Taguchi method and analysis of variance. Results show that the nanolubricants cause a significant improvement on the surface roughness compared to conventional lubricants. Best condition is obtained when 0.8 wt% of CuO nanoparticles is added in paraffin lubricant. Compared with the case of base lubricants with no additives, roughness reduced by 41% and 33% for paraffin and oil10, respectively. Also, the surface roughness decreased by 496% and 235% compared with dry graphite powder and paraffin with 25% graphite, correspondingly.

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Reducing crude oil reserves and also environmental pollution caused by its excessive use has led to numerous researches to find alternatives to petroleum-based oils. Thus, owing to lower pollution and higher lubrication efficiency, the use of vegetable base lubricants has been widely considered. Due to the unique properties of different nanoparticles such as sphericality and high surface area besides low environmental risk, the subjected nanoparticles can be applied as additives to the base lubricants and create optimal tribological properties. In this study, in order to improve the lubricating efficiency of vegetable base lubricants, SiO2 nanoparticles with different weight concentrations were used in the cold forging process of aluminum alloy. Then, the lubrication proficiency of both nano-lubricants and conventional solid powder lubricants in the forging industry was evaluated. Friction coefficient was determined by standard compression test and friction calibration curves. In order to evaluate the lubricants’ efficiency, two key parameters, namely shear friction coefficient and surface roughness have been considered. Experimental results showed that the presence of SiO2 nanoparticles in the base lubricants significantly increased the lubrication efficiency of the base lubricants and notably reduced both the friction coefficient and surface roughness.

In this study, friction stir processed (FSP) pure copper sheet was equal channel angular pressed (ECAP). The purpose was to investigate the influence of ECAP on the microstructure and mechanical properties of the FSP-treated copper sheet. The dynamically recrystallized grained structure with the average grain size of ∼13 µm was found in the stir zone of the FSP. It was also revealed that FSP caused the enhancement of ultimate tensile strength compared to that of the base metal. Also, it was observed that ECAP led to further grain refinement and a tighter distribution of grains. A refined microstructure with an average grain size of ∼ 2 µm was achieved in copper sheets through FSP, followed by ECAP. The tensile strengths of the ECAP specimens were significantly increased to about 61 and 50% compared to the strengths of base metal and FSP, respectively. An overview of the results of this study showed that combined FSP/ECAP is an effective method for the mechanical improvement of the pure copper sheets.