Research on surface integrity of Inconel 718 with various ultrasonic ball-end milling times

The study aims to study the effect of ultrasonic vibration ball-end milling times on the surface integrity of the Inconel 718 workpiece. Milling experiments are conducted to compare the effects of ultrasonic vibration ball-end milling and conventional ball-end milling processes, with the same parameters but different ultrasonic vibration times. Subsequently, the surface topography, surface roughness, surface microhardness rate, surface residual stress, and subsurface microstructure are characterized. The results demonstrate that ultrasonic vibration-assisted milling significantly enhances the surface integrity index of workpieces by inducing residual compressive stresses with a maximum value of approximately 1339.6 MPa on the workpiece surface. Additionally, the various ultrasonic modes exhibit a notable strengthening effect on the machined surface. Compared to workpieces without ultrasonic vibration treatment, the treated workpieces show a maximum increase in surface hardness of approximately 79.93%. Ultrasonic vibration is also significantly more effective in improving fatigue life, with an average increase of 1.6–2.1 times. Therefore, investigating the surface integrity of ultrasonic vibration milling presents a promising avenue for studying the fatigue life of the workpiece. This research can potentially offer a novel method for effective control of surface integrity in Inconel 718, as well as identifying strategies to enhance the workpiece’s fatigue life in future studies.