Investigation of Parameters Affecting Surface Integrity and Material Removal during Electrical Discharge Machining of HARDOX-400 Steel

Hardox-400 with an extra-high yield strength of ~1000 MPa and excellent abrasion resistance is a good candidate for several industrial applications including automotive parts, working tools, barges, loaders, etc. Due to high dimensional precision and to avoid mechanical abrasion of the work-piece, electrical discharge machining (EDM) is a proper machining technique for such steel. The influences of important process parameters, i.e. discharge current and spark pulse cycle on the electrode wear, material removal, surface roughness, and integrity of the machined material is investigated. It was observed in this work that as the discharge current increased, the electrode wear also increased but this occurred with a gradually decreasing rate. On the other hand, increasing the ratio of pulse-on to pulse-off time decreased material removal. Furthermore, it was observed that increasing both the discharge current and the pulse-on time led to a thicker solidified so-called white layer which is more susceptible to cracking and thus is detrimental to the material integrity.