Feasibility study of the ultrasonic vibration assisted drilling of Inconel superalloy

The ultrasonic vibration assisted drilling of Inconel 718 superalloy is studied in this paper. The tool holder of a machining center is retrofitted so that axial resonant vibration can be provided. Experimental results show that the chip size is reduced, and the variation of torque in drilling becomes smaller. These phenomena are particularly apparent at the final stage of a drill's usable life. It is also found that there is little improvement in drilling performance when the frequency of the ultrasonic vibration is varied. On the contrary, a drill's life is greatly increased when the vibration with a smaller amplitude is applied. But too large a vibration amplitude, such as over 12 μm in this study, could lead to negative effects. For the testing conditions, the frequency of 31.8 kHz and the amplitude of 4 μm result in the best drill life and quality of the drilled hole in this study. Under this condition a drill's life is prolonged by as much as 2.7 times of that without vibration assisted drilling process. Concerning drilling efficiency, it is found that by applying ultrasonic vibration assisted drilling, lifting of the drill for chip removal as commonly employed in conventional drilling of a high aspect ratio hole is not necessary, and saving of the working time is obtained.