The use of bipolar current pulses in electrospark alloying of metal surfaces

In the conventional electro spark alloying (ESA), the workpiece is mechanically connected to the discharge circuit of the pulse generator as the cathode and the treating electrode acts as the anode. A novel addition to ESA processing is to include the workpiece electrically in series to the discharge circuit of the pulse generator by discharge through two inter electrode gaps using double treating electrode. The electrical parameters of pulse and electrode materials were investigated to find out under which conditions mass could be deposited on workpiece from both treating electrodes, one was connected as anode and other as cathode. As a result of experiments, an asymmetry in erosion of the treating electrodes was observed, because mass transfer from electrode to specimen was always less when the electrode was cathode than when the electrode was anode. The asymmetry in erosion of treating electrodes could be eliminated by employing a power supply generating symmetrical bipolar pulses that switch polarity of treating electrodes periodically.