Influence of superimposed pulse position in superimposed pulse current waveform on surface integrity in electrical discharge machining

In electrical discharge machining (EDM), it is a much more effective method to improve working characteristics by changing the input process of pulse energy. However, it has not been investigated enough whether pulse form is the most adequate or not. In this study, the effect of superimposed pulse current waveform and its parameter on surface integrity was investigated. The surface topography, roughness, microstructure, white layer thickness, and residual stress were analyzed and discussed. Moreover, the material removal rate was also tested and compared. The results show that with the backward movement of the superimposed pulse current, the material removal rate and surface roughness decrease, while the white layer thickness, residual stress, and surface defects increase. The current waveform has little influence on microstructure. Under the same pulse discharge energy and pulse-on time, the samples processed by superimposed pulse current waveform instead of rectangular current waveform can obtain a thinner white layer, lower residual stress, fewer surface defects, and high surface roughness. With the increase of superimposed pulse-on time and current, the surface integrity becomes worse due to the increase of pulse energy. This paper provides a guide to the development and selection of EDM discharge current waveforms in EDM.