Abstract: In order to improve the surface quality of titanium alloy TC4 processed by electric discharge machining (EDM), this article presents a new combined machining method of ultrasonic vibration assisted EDM by mixing the kerosene fluid with 12 g/L SiC abrasive particles. By comparing the surface roughness between EDM and the abrasive particle ultrasonic vibration assisted EDM in short pulses (with pulse width less than 1 μs), it is found that the ultrasonic vibration of SiC particles can improve the surface roughness R_a from 0.5 μm to 0.2 μm. The recast layer and surface cracks are analyzed by a scanning electron microscope (SEM). Results show that the thickness of recast layer is reduced by 20-30 μm and surface cracks decreased obviously with the action of abrasive particle ultrasonic vibration. Theoretical analysis indicates that the high frequency vibration of the fluid and the abrasive impulse forces of the abrasive particles on the workpieces are the major factors for improving their surface quality. It demonstrates that the combined action of ultrasonic vibration and abrasive particles can considerably improve the surface quality of titanium alloy TC4 in EDM.

Key words: ultrasonic vibration, abrasive particle, electric discharge machining, surface roughness, surface crack, recast layer