Surface integrity and fatigue life of Inconel 718 by ultrasonic peening milling

Inconel 718 is widely used in aeroengine hot end parts, such as turbine disks, blades, drive shafts and so on. Its excellent mechanical and thermal properties also lead to the poor machinability, poor surface integrity, thus affecting the fatigue life of the machined part. This paper proposes an ultrasonic peening milling (UPM) technology which can introduce ultrasonic impact to the machined surface during end milling by applying ultrasonic vibration perpendicular to the machined surface. The effects of vibration on the surface integrity and fatigue life of this material were investigated in comparison with conventional milling (CM). The results showed that the best fatigue life of 2.20 × 106 cycles was achieved by UPM. Compared to the CM process, UPM improved the fatigue life by 16.1 times due to better surface quality with fewer surface defects, thicker stress-affecting layers, and the reinforced machined surface achieved in UPM. The results and findings of this study could contribute to the development of new effective and anti-fatigue machining methods for Inconel 718 in the future.