Research on deep hole drilling of nickel-based superalloy with low-frequency vibration: Chip evacuation characteristic, chip formation and surface morphology

Abstract

Owing to the difficult-to-machine characteristics of nickel-based superalloy, the deep hole drilling (DHD) is prone to various issues, including high thrust force and torque, high cutting temperature, difficult chip breaking, tool fracture and poor surface quality caused by poor chip evacuation. Low-frequency vibration-assisted drilling (LFVAD) facilitates the tool-workpiece periodic contact and separation, as well as effective chip breaking, which provides a high potential for the DHD of difficult-to-machine materials. In the present study, the DHD of nickel-based superalloy with LFVAD and conventional drilling (CD) is comparatively analyzed in detail. Firstly, the theoretical analysis shows that the good chip breaking ability of LFVAD can effectively enhance the chip evacuation of DHD. The chip unfolded areas of LFVAD are much smaller compared to those of CD. Then, LFVAD can effectively reduce the average drilling forces (by 14.6 % and 16.3 % for average thrust force and average torque, respectively) due to the less friction and enhanced cooling effect. As for chip morphologies, there are irregular small burrs at the edge of the chip for CD with dense and tight segmentation, while LFVAD shows a relatively smooth bottom edge with hypertrophic segmentation. Finally, LFVAD is benefit for improving surface quality under appropriate vibration condition. The findings of this paper indicate that LFVAD offers several machinability advantages, making it a promising technique for the DHD of difficult-to-machine materials.