Defect suppression and grain refinement during ultrasonic vibration-assisted side milling of GH4169 superalloy

In order to suppress the axial vibration stripes machining defects (AVSMD) and achieve the engineering goal of multi-demand high quality processing with grain refinement during side milling of GH4169 superalloy, the defect formation mechanism in conventional side milling (CSM) and the defect suppression mechanism in ultrasonic vibration-assisted side milling (UVASM) have been investigated respectively. The impact of ultrasonic high-frequency energy field on subsurface grain refinement was also investigated intensively. The results show that the axial vibration stripes width proportion factor (AVSWPF) in UVASM was quantitatively and numerically smaller than the AVSWPF in CSM. Furthermore, the mechanism of machining defect suppression in UVASM was fully analyzed with three aspects. Compared to CSM, the frequency fraction of small diameter grains (3.51 μm) and the average grain diameter in UVASM were respectively reduced by 26.2 % and 10.7 % due to the continuous intervention of ultrasonic high-frequency energy impact. The finer grains and higher residual compressive stress can be achieved in UVASM, thus improving the wear resistance, strength, and fatigue life of the material to some extent. The results show that defect suppression and grain refinement can be achieved simultaneously in UVASM processing, which has great research value for the formability processing of series superalloys.