Surface integrity and fatigue behavior when turning γ-TiAl alloy with optimized PVD-coated carbide inserts

This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning γ-TiAl alloy. The wear of inserts surface, cutting forces, and surface roughness were studied to optimize PVD-coated carbide inserts. Surface topography, residual stresses, microhardness, and microstructure were analyzed to characterize the surfaces layer under different turning parameters. Surface integrity and fatigue life tests of γ-TiAl alloy were conducted under turning and turning-polishing processes. The results show that compared to CNMG120412-MF4, CNMG120408-SM is more suitable because it obtained low cutting force, surface roughness, and tool wear. With increasing the cutting speed and depth, the depths of the compressive residual stress layer, hardening layer, and plastic deformation layer increased. For turning and turning-polishing specimens, the compressive residual stress was relaxed by less than 20%-30% after 107 cycles. The fatigue life of a turning-polishing specimen with Ra = 0.15 µm has increased 3 times from that of a turning specimen with Ra = 0.43 µm.