Experimental study of CO2 jet field and CO2-MQL-assisted turning of Ti-6Al-4V based on mass flow rate and pressure

The effectiveness of jet cooling is significantly influenced by both mass flow rate and pressure, which are interrelated and exhibit a coupled relationship. This study examined the effects of mass flow rate and pressure from the perspectives of thermodynamic theory, jet field temperature, micromorphology, and the performance of CO2-MQL-assisted turning of Ti-6Al-4V alloys. Comparative experiments demonstrated that a small mass flow rate of CO2 (1.00 g/s) can achieve cooling and lubrication effects comparable to those of a larger mass flow rate (1.83 g/s) when applied at pressures of 7.38 and 6.00 MPa, respectively. For varying pressures, the maximum differences in improving the CO2-MQL on turning force, turning zone temperature, and surface roughness were 2.36%, 26.31%, and 39.63%, respectively. Conversely, the maximum differences for varying mass flow rates were 1.32%, 17.53%, and 19.66%. The results indicate that pressure has a more significant impact and that optimizing the combination of pressure and mass flow rate is substantial for cooling and lubrication. This study offers a reference for reducing CO2 consumption in CO2-MQL applications, thereby enhancing the alignment of CO2-MQL with sustainable manufacturing practices.