Characterisation and applications of electrodischarge machined cast aluminium alloy surfaces

Abstract

Scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectrometry have been used to characterise cast aluminium surfaces after electrodischarge machining (EDM) using copper electrodes. Depending on the machining conditions EDM produces a surface recast layer, about 20–100 μm thick, with significantly higher hardness than the underlying substrate. For example, the surface hardness of Al 319 was increased from 45 to 65 HK by EDM. HREM and XPS analyses showed that the increase in surface hardness was a result of the formation and dispersion of fine SiC particles in a rapidly resolidified solid solution of Cu–Al. Important tribological applications of electrodischarge machining of aluminium alloys include surface preparation for enhanced thermal spray coating adhesion and abrasive wear resistance improvement on parent aluminium surfaces.