Influence of milling-finishing-shot peening hybrid machining on the surface integrity and fatigue performance of TC11 titanium integral impeller

For the milling-finishing-shot peening hybrid machining, the influence of machining parameters on the surface integrity and fatigue performance of the TC11 titanium alloy integral impeller is studied. The results show that during the milling process, the surface roughness increases with increasing row spacing. Meanwhile, the row spacing changes the friction heat by influencing the milling force, which changes the surface hardness. The effect of row spacing on fatigue performance is related to the combination effect of surface roughness and hardness. During the milling-finishing process, finishing effectively removes the surface tool marks. Because tool marks can easily become crack nucleation sites, the removal of tool marks leads to a significant increase in fatigue performance. In the case of milling-peening-shot peening hybrid machining, the surface roughness increases with the increase of shot peening intensity. The shot peening also effectively introduces residual compressive stress. The fatigue performance increases with the increase of shot peening intensity and then decreases due to the negative effect of the surface roughness. Comparative analysis of the effects of residual compressive stress, tool marks, and surface roughness on the fatigue performance reveals that the fatigue performance is more sensitive to the tool marks, removal of which can effectively reduce crack nucleation sites and improve the fatigue performance significantly.