Wear resistance enhancement of Inconel 718 via high-speed ultrasonic vibration cutting and associated surface integrity evaluation under high-pressure coolant supply

Abstract

Machining-induced surface integrity evaluation and functional performance are considered as the most representative problems for evaluating the machining quality of Ni-based superalloys (for example, Inconel 718). Although high-speed ultrasonic vibration cutting (HUVC) has been proved to be effective for improving the machinability of Inconel 718, the surface integrity and its effect on functional performance (for example, wear resistance) are still unclear. By applying scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and white light interferometry (WLI), the surface integrity induced by HUVC and the wear resistance of the machined surface were comprehensively evaluated; the grain refinement, hardness increase, and wear mechanism of the machined surface were thoroughly studied, which were compared with the conventional cutting (CC) process. Compared with the CC process, the HUVC process achieves superior grain refinement, thicker surface plastic deformation layer, lower surface roughness Ra and Rz, higher hardness and compressive residual stress, and thicker hardening layer. The wear rate of the machined surface processed by HUVC is reduced by at most 24.01%. This study shows that the HUVC process can be potentially used to improve the wear resistance, which can effectively achieve grain refinement, surface roughness reduction, and wear resistance improvement while reducing the machining cost and process procedure.