Removal of the Heat Affect Zone created by EDM with Pico-second LASER Machining

Metallurgical modifications of machined metal surfaces are created by nearly all machining processes based on thermal and or mechanical processes. The EDM – electro-discharge machining –creates a so called “white layer” or “heat affected zone” (HAZ) having a thickness ranging from a few hundred micro-meters (for roughing operation) down to a few micrometers (for finishing). This remaining HAZ is a problem for many industrial applications: the presence of micro-cracks and metallurgic inhomogeneity inherent to thermal stresses reduces part lifetime of tools, etc. due to fatigue stress.The study presents a method to remove the HAZ created by Die-sinking EDM on warm working steel (W300) by cold ablation with a pico-second LASER. Technologies & strategies for Laser machining have been developed. The laser machined samples have been metallurgical analysed to prove the removal of the white layer and assure that no heat impact due the LASER machining was created, eg. only cold ablation took place. Fatigue test samples have been prepared by EDM machining and either EDM finished or finished by pico-second LASER in order to compare the lifetime both kind of samples