Addressing temperature challenges in machining: Deep-eutectic metalworking fluids and their influence on surface integrity

• Chemically-designed DEF offers solutions for demanding machining applications. • Citric acid and choline chloride mixture acts as a novel DEF metalworking media. • DEF-based MWF promotes comparable post-process surface integrity to water-based MWF. • Novel solid MWF design improves surface finish and reduces severely deformed layers. In manufacturing, cutting tools and component integrity are subjected to high-performance thresholds. The role of cutting fluids is pivotal in mitigating heat generation and friction at the tool-workpiece interface. This study explores the application of specifically designed, unconventional, and eco-friendly media, Deep-Eutectic Fluids (DEFs), which provide optimized fluid delivery to the cutting zone, regulating lubrication and cooling, while maintaining the surface integrity of the machined parts. To benchmark DEFs against traditional material removal methods, including dry, and wet (emulsion-based, Hocut 3380) processes, grinding was selected due to its thermal and lubrication demands. The results indicate that DEFs reduce the formation of severely deformed layers by 47% in comparison to conventional water-based coolants exhibiting superior lubricity, yielding more consistent deformation profiles and lower surface roughness. The generated residual stresses are closely comparable to those achieved using water-based metalworking fluids. This was substantiated by micromechanical testing, revealing a coherent failure mechanism at the machined edges for both DEF and wet-cutting media, significantly mitigating the adverse effects of dry machining. These findings highlight DEFs’ potential for industrial-scale adoption as a sustainable alternative in material removal processes, underscoring their capability to enhance process efficiency and environmental sustainability, or as an in-field portable cutting fluid.