Investigation of electro-erosion drilling of sleipner cold work tool steel using copper and brass electrodes

Cold work tool steels are widely used in industry, especially in molding, in many machines and equipment due to their properties such as high wear resistance, toughness, compatibility with heat treatment, dimensional stability and high hardness, However, these steels must be processed and holes must be drilled in order to be mounted to the places of use, Processing hard materials with methods such as conventional drilling, orbital milling, laser cutting, water jet cutting, punching is not very suitable in terms of tool wear, cost and processing time, For these reasons, in this study, holes were drilled on Sleipner cold work tool steel with a hardness of 60-62 HRC by using copper and brass electrodes, three different current values (50, 25, 12,5 A) , three different pulse on times (3, 6, 9 µs) and pulse off times (4, 6, 8 µs) parameters in the electrical discharge machining (EDM) method, the effects of these working parameters on the changing metal removal rate and electrode wear rates, especially the operation times, the hole inlet-outlet diameters and surface hardness of the machined parts, the kerf on the workpiece and the electrode were analyzed, As a result of the analyzes made, in the use of copper electrodes, the MRR increased by % 311,25 on average compared to the use of brass electrodes, while the EWR and machining time decreased by % 42,01 and % 38,46, respectively, These conditions were caused by the higher thermal and electrical conductivity of the copper electrode than the brass electrode, The increase in sparking and thermal effects between the workpiece and the electrode resulted in an increase in the MRR and a decrease in the machining time, In the use of copper and brass electrodes with different processing parameters, the inlet diameters of the drilled holes were found to be larger than the outlet diameters as well as an irregular kerf formation was observed due to debris evacuation due to worn electrodes, In addition, it was observed that the hardness data on the workpiece surface increased after the drilling process with the copper electrode, whereas the hardness data decreased after the process with the brass electrode, The differences in the electrical conductivity coefficients and processing times of the electrodes used made the copper electrode have a higher heat density (W/mm2) than the brass electrode under the same conditions.