Water spray electrical discharge drilling of WC-Co to prevent electrolytic corrosion

In this study, electrical discharge drilling (ED-drilling) with water spray for suppressing electrolytic corrosion was investigated. The water spray is composed of tap water and compressed air. In conventional ED-drilling with tap water, the machining results suffer from electrolytic corrosion resulting in poor accuracy because cobalt, which is the bonding material in WC-Co, is easily dissolved in water. The use of water spray instead of tap water prevented electrolytic corrosion around the machined holes without deterioration in the machining speed. The machining characteristics such as corrosion prevention effects, machining rate and electrode wear were investigated according to water spray conditions such as water flow rate and air flow rate. Using the water spray with air flow rate of 1500 ml/min and water flow rate of 60 ml/min, electrolytic-corrosion-free holes were successfully machined on WC-Co. The new machining method was applied to a diemaking process with high accuracy and no corrosion.