Characterisation and applications of electrodischarge machined cast aluminium alloy surfaces

Scanning electron microscopy, transmission electron microscopy, and X-ray p hotoelectron spectrometry have been used to characterise cast aluminium sur faces after electrodischarge machining (EDM) using copper electrodes. Depen ding on the machining conditions EDM produces a surface recast layer, about 20-100 mu m thick, with significantly higher hardness than the underlying substrate. For example, the surface hardness of Al 319 was increased from 4 5 to 65 HK by EDM. HREM and XPS analyses showed that the increase in surfac e hardness was a result of the formation and dispersion of fine SiC particl es in a rapidly resolidified solid solution of Cu-Al. Important tribologica l applications of electrodischarge machining of aluminium alloys include su rface preparation for enhanced thermal spray coating adhesion and abrasive wear resistance improvement on par ent aluminium surfaces. (C) 1999 IoM Com munications Ltd.