Characterization of thermophysical properties of dry ice-based ethanol/ester oil and its influence on surface hardening of machined Ti-6Al-4V alloy.

• Hybrid lubri-coolant is proposed by mixing ethanol-biodegradable ester oil. • Dry ice (solid CO 2) added (−76 °C) to this novel hybrid cooling mixture. • Thermophysical properties of lubri-coolants are investigated experimentally. Recent pandemics played a cardinal role in developing health-conscious behavior and pushed the industries to seek eco-benign cutting fluids to improve machinability. Therefore, a sustainable hybrid lubri-coolant is proposed by mixing ethanol-biodegradable ester oil in varying proportions (1:0.25, 1:0.5, and 1:1). In this work, dry ice (solid CO 2) has been added (−76 °C) to improve the cooling capabilities by sublimation. The thermophysical properties along with the surface hardening of machined Ti-6Al-4V alloy was investigated experimentally and the results were compared to without dry ice. Experimental findings showed a reduction in specific heat, density, and viscosity while an enhancement in thermal conductivity by mixing dry ice. After dry ice was added, the specific heat of ethanol dropped by 40%. When ester oil was combined with dry ice, its specific heat also decreased by 50.4%. Therefore it is worthy to mention that the hybrid lubri coolant based on dry ice-based ethanol/ester oil could be an alternative to achieve high-speed machining parameters in machining hard to cut materials for aerospace Industry. [ABSTRACT FROM AUTHOR]