Simulation and Experimental Study of γ-TiAl Alloy Cutting with scCO2-MQL Based on Modified Heat Transfer Coefficient

Current heat transfer coefficient models for scCO2-MQL exhibit critical limitations because they neglect the Mach disk phenomenon and the effects of radial velocity distribution in the scCO2 jets. These theoretical deficiencies result in significant deviations in the thermal predictions, limiting the application potential of scCO2-MQL technology in γ-TiAl machining applications. This study establishes a modified heat transfer coefficient model incorporating Mach disk and radial velocity distribution correction factors to characterise complex jet flow behaviour. Based on the modified heat transfer coefficient model, comprehensive simulation and experimental investigations were conducted to analyse cutting forces, cutting temperatures, stress distributions, and serrated chip formation during scCO2-MQL machining of γ-TiAl alloys. Results demonstrate that the modified model achieves superior predictive accuracy, with average relative error reductions of 21.8% for cutting force predictions and 37.3% for temperature predictions compared to conventional models. The developed modified heat transfer coefficient model establishes a foundation for the widespread application of scCO2-MQL cutting of γ-TiAl alloys.