Electrical discharge machining of ZrO ₂ /TiN particulate composite

Abstract

An experimental study was conducted into the electrical discharge machining (EDM) characteristics of a zirconia based composite with 30 vol.-%of a titanium nitride dispersoid added to provide a conductive network. The material removal rates and tool wear were assessed under normal sparking and induced arcing conditions and the influences of the main machining parameters are discussed for both conditions. The apparent cost effectiveness of material removal by arcing discharges was highlighted by assessment of the specific volumetric power consumption (SVPC). Subsequent microscopic analysis of the arced surface and the debris collected during machining under induced arcing indicated the major mechanism of material removal to be a combination of three distinct fracture events: subsurface lateral cracking caused by rapid heating, vertical cracking caused by the tetragonal/monoclinic phase transformation in the zirconia matrix, and thermal shock induced fracture on rapid cooling.