Biodegradable cutting fluids for sustainable manufacturing: a review of machining mechanisms and performance

The application of biodegradable cutting fluids in metal cutting processes has raised interest among multidisciplinary researchers. Vegetable oils with long and polar fatty acid chains provide thick lubricant coatings that interact strongly with metallic surfaces, making them ideal biodegradable cutting fluids. In this review, the viscosity, oxidation performance, and machining performance of several vegetable oils, including palm, coconut, neem, and jatropha oils, were analysed and compared with conventional cutting fluids. The associated challenges in this field are discussed, and future research directions presented. Through this review, vegetable oils with particle additives, like alumina, silicon dioxide, molybdenum disulfide, and hexagonal boron nitride, were identified to be capable of improving the machining performance. The particles' mending, polishing, and rolling effects are effective mechanisms for improving machining performance. Furthermore, chemical modification processes, such as transesterification and epoxidation, improve the anti-oxidation ability of vegetable oils by altering the carboxyl group (esterification/transesterification) or the fatty acid chain (epoxidation). Consequently, vegetable oils with particle additives and chemical modification surpass conventional cutting fluids in metal cutting operations and contribute to sustainable manufacturing technologies.