Machining Behavior of X33CrS16 Stainless Steel Under Eco-Friendly MQL Conditions: a Comparative Study

This study investigated the machinability metrics of X33CrS16 stainless steel, a widely used industrial alloy, under different cooling/lubrication conditions using an MQL system during CNC milling. Numerous studies in the literature examine the machinability of stainless steels with MQL systems. However, there is a significant gap in the study regarding the machinability of these materials with mineral-based oils and nanofluids derived from these oils, which are used in traditional flood coolants. The use of fluids from traditional flood coolants in the MQL system, thereby preventing excess fluid and achieving a more environmentally friendly process, is a critical point of this study. The study was conducted at 2 cutting speeds (Vc = 120–150 m/min), 2 feed rates (fn = 0.08–0.15 mm/rev), and 5 cooling/lubrication environments (dry, MQL-Mineral Oil, N1-MQL Emulsion, N2-MQL Emulsion, and MQL-Emulsion (mineral oil + water)). The results of machinability metrics such as surface roughness, cutting temperature, cutting tool wear, and energy consumption were examined. In addition, pH, viscosity, SEM, EDX analyses, and contact angle measurements were performed. As a result, it was determined that mineral-based emulsions with nanopowder additives significantly improved machinability metrics compared to other media. With this result, this study serves as a model for paving the way for and promoting the use of these fluids in industrial MQL systems.