Effect of Different Cooling Strategies on Surface Topography, Microstructure and Residual Stress of Turned γ-TiAl Alloy

This study investigates the surface integrity of γ-TiAl alloy during turning under different cooling strategies and reveals the regulation mechanisms of cooling conditions on surface morphology, plastic deformation, microstructure, and residual stress. Turning experiments were conducted under conventional cooling and high-pressure cooling conditions at different cutting speeds, combined with wavelet-based three-dimensional surface morphology analysis, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and residual stress measurements. The results show that high-pressure cooling reduces the fluctuation of both high- and low-frequency surface morphology components, particularly suppressing low-frequency profile variations, thereby improving machining stability and surface consistency. Plastic deformation layers are formed under both cooling conditions and increase with cutting speed; however, high-pressure cooling reduces de-formation depth and alleviates lamellar bending and deflection. EBSD analysis reveals that machining-induced microstructural characteristics is mainly characterized by grain rotation, crystallographic orientation adjustment, and deformation-induced texture formation, without obvious dynamic recrystallization features. Compared with conventional cooling, high-pressure cooling maintains higher crystal integrity and suppresses excessive microstructural reconstruction. Residual stress results demonstrate that compressive residual stresses are generated under both cooling strategies, while high-pressure cooling produces higher compressive residual stress and a more stable stress distribution. These findings indicate that cooling strategies regulate surface integrity by modifying tool–workpiece interfacial interactions and mechanical load transfer behavior. High-pressure cooling improves interfacial lubrication, reduces friction-induced disturbance, and promotes more coordinated plastic deformation, resulting in reduced surface morphology fluctuation, suppressed microstructural damage, and enhanced compressive residual stress. This work provides theoretical guidance for precision machining of γ-TiAl alloy and other high-value difficult-to-machine materials.