Effect of Carbon Nanotube (CNT) Size on Wear Properties of Cu-Based CNT Composite Electrodes in Electrical Discharge Machining

Abstract

The effect of carbon nanotube (CNT) size on the wear properties of Cu-based CNT composite electrode in electrical discharge machining (EDM) was studied. Cu-based CNT electrodes were fabricated by electroplating using a copper sulfate plating bath containing three kinds of CNTs. EDM was performed on stainless steel to evaluate the wear properties of the electrodes. Single pulse discharge was performed to evaluate the craters generated on the electrode surface. The wear ratios of Cu-based CNT composite electrodes decreased by 50-72% in relation to those of electrolytic Cu electrodes. The wear resistance of the composite electrodes was dependent on CNT size. It increased as the length and thickness of CNTs increased. The mechanisms of wear resistance in Cu-based CNT composite electrodes are discussed through observation and analysis of craters formed by single pulse discharge. The diameters of the craters are almost identical and largely independent of the size and presence of CNTs, indicating that CNT addition does not improve the thermal conductivities of the electrodes. Hence, the increase in wear resistance is independent of thermal conductivity. Exposed CNTs observed in craters on electrodes containing large CNTs with high wear-resistance properties do not decrease in diameter via electrical discharge, indicating that large CNTs can be resistant to pyrolysis at the melting points for Cu and Fe. It is suggested that the carbon layer with exposed CNTs on the electrode surface prevents the electrode from spark erosion in a manner identical to that of turbostratic carbon.