Abstract
Important properties of tool steel such as fatigue strength and toughness can be degraded by electrical discharge machining (ED M) through its influence on the surface microstructure of the machined material. In an attempt to reduce these negative effects, EDM was performed at various dielectric fluid temperatures. The dielectrics investigated were silicone oil, a hydrocarbon based fluid, and liquid nitrogen; both copper and graphite electrodes were used. The type of dielectric fluid used was found to have a greater influence on themicrostructure and the properties of the surface layers than its temperature. The only beneficial effect of changing the temperature was a reduced hardness in the layer beneath the recast layer when the tool steel was machined at an elevated temperature. Removal rate was very low for EDMin liquid nitrogen. Instead, a recast layer rich in material from the electrode was produced. Hence, electrode material has a great influence on the properties and composition of thesurface layers in this case. No significant difference in the thickness of the affected layers was found when varying the temperature, the dielectric, or the electrode material.
Get full access to this article
View all access options for this article.