Observation of chip-producing behavior in ultraprecision diamond cutting of additively manufactured Alloy 718 utilizing ultrasonic elliptical vibration

The demand for Ni-based alloys, particularly Alloy 718, is increasing in the gas turbine industry due to their high-temperature resistance and chemical stability. However, Alloy 718 is challenging to cut, owing to its susceptibility to work-harden, its high cutting resistance, and its poor thermal conductivity. Ultrasonic elliptical vibration cutting (UEVC) can be performed on steel materials using diamond tools, which is facilitated by elliptical vibration of the tool. This approach helps suppress heat generation at the tool tip and prevents chemical decomposition. In this study, we explored the precision cutting of Alloy 718 using UEVC with planar cutting and a single-crystal diamond flat tool. We achieved a surface roughness Ra of 8.4 nm at a cutting speed of 2.0 mm/s. We compared surface roughness under various conditions, including cutting speeds, the amplitude of elliptical vibration, and cutting depth, to investigate the effect of these parameters on surface roughness. Additionally, we studied the geometry and thickness of chips under these conditions using scanning electron microscopy (SEM) images. Our findings indicated flow-type chip shapes in all conditions, signifying stable ductile-regime cutting. Moreover, tool life was investigated by observing the cutting edge, which exhibited slight wear, maintaining a mirror surface for a cutting distance of approximately 50 m. These findings reveal an effective method for high-precision surface fabrication of Alloy 718, elucidating the cutting mechanism and the feasible cutting distance.