Evaluation of the effectiveness of natural origin metalworking fluids in reducing the environmental impact and the tool wear

In the present work, due to the key role played by the environmental compliance and the operators' safety when using Metalworking Fluids (MWFs), a novel Natural Origin (NO) lubricant has been comparatively investigated with a commercial Mineral Based (MB) one in terms of: (i) environmental impact and (ii) lubricating/anti-wear performance. As for the former aspect, the values of Non-Ionic Surfactants (NIS) and Chemical Oxygen Demand (COD) in the aqueous phase obtained after the chemical breaking of the emulsions were evaluated; as for the second aspect, the performance of emulsions with different concentrations and oil types (the mineral and the natural one) were assessed both in laboratory (tests using Falex tribometer) and in real production environment (tool flank wear evaluation during machining). The chemical breaking demonstrated that the aqueous phase extracted from the NO emulsion (fresh or after several months of working) was characterized by very low contents of NIS and COD (3 orders of magnitude and 3 times, respectively, less than the MB emulsion if considering fresh emulsions; 3 orders of magnitude and 4 times, respectively, less than the MB emulsion if considering emulsions after several months of working) thus making possible to re-use it in the production process. On the other hand, from the process point of view, tribological and wear tests revealed that the NO emulsion always led to a tool wear smaller than the one determined by MB: around 30% if using an oil content of 5% for both the emulsions; around 19% if using an oil content of 5% for NO and 9% for MB.