Optimization and Performance Evaluation of Additives-Enhanced Fluid in Machining Using Split-Plot Design

In recent years, the use of cutting fluids has become crucial in hard metal machining. Traditional non-biodegradable cutting fluids have long dominated various industries for machining. This research presents an innovative approach by suggesting a sustainable alternative: a cutting fluid made from a blend of glycerol (GOL) and distilled water (DW). We conducted a thorough investigation, creating 11 different GOL and DW mixtures in 10% weight increments. These mixtures were rigorously tested through 176 experiments with varying loads and rotational speeds. Using Design-Expert software (DES), we identified the optimal composition to be 70% GOL and 30% DW, with the lowest coefficient of friction (CFN). Building on this promising fluid, we explored further improvements by adding three nanoscale additives: Nano-graphite (GHT), zinc oxide (ZnO), and reduced graphene oxide (RGRO) at different weight percentages (0.06%, 0.08%, 0.1%, and 0.3%). Comparative tests using a four-ball wear tester revealed that the fluid with 0.08% nano-GHT performed the best, boasting a CFN of 0.039, surpassing both the unmodified fluid and conventional commercial cutting fluids (CMCFs). To validate the practicality of this novel cutting fluid, we conducted machining experiments on EN31 material. Our comprehensive analysis, including surface roughness, chip formation, and scanning electron microscopy (SEM) examination, compared the outcomes with those obtained using a CMCF. Overall, our study highlights the advantages of the optimized cutting fluid composed of 70% GOL + 30% DW and 0.08% nano-GHT. It delivers enhanced machining performance while promoting environmental sustainability in machining operations.