Investigation of recast layers generated by a powder-mixed dielectric micro electrical discharge machining process

The use of powder-mixed dielectrics in micro-electrical discharge machining (micro-EDM) is an important technological development with the potential to improve machined surface quality and impart functional properties to machined surfaces. These process capabilities are vital in the manufacture of microcomponents since enhancing machined surface characteristics can extend their service life and improve their functionality. While studies have been conducted on gap enlargement and surface roughness, there is limited work on subsurface characteristics. The present study assessed the recast layer thickness, given the potential of applying powder-mixed dielectrics to recast layer reduction and surface modification. Moreover, its process characteristics under specific micro-EDM process parameters, such as low powder concentrations, nano-sized powder granularities, and sub-microsecond pulse-on time durations, which have received limited coverage, have been elucidated. The study has revealed evident changes in recast layer thickness under different machining conditions. The reductions in recast layer thickness at a powder concentration of 0.1 g/l were found to range between 15 per cent and 35 per cent for pulse-on time durations between 166 ns and 606 ns. Furthermore, flushing effects from tool electrode rotation have been shown to exert an influence on recast layer thickness as well as on the amount of powder particles within the discharge gap.