Surface Topographical Characteristics of Electro- Discharge Machined Ti-5Al-2.5Sn: Effects of Peak Current

Abstract

In the present work, topographical study of machined Ti-5Al- 2.5Sn surface is carried out in the context of Electro-Discharge Machining (EDM). EDM experiments are conducted by varying peak discharge current. Machining performance is evaluated in purview of surface topography which includes study of crater dimension, surface roughness, surface crack density, white layer thickness, material migration, phase alteration and micro- indentation hardness. Results indicated that EDM produces disappointing surface morphology of the machined specimen. Increase in peak currents results in formation of rough surface with severe surface cracks and deposition of thick white layer. Significant transfer of carbon and copper elements is detected through EDS analysis of the machined surface. Pyrolysis of dielectric media and electrode wear promote immigration of such carbon and copper element transfer, respectively. Carbon migration at the machined surface causes precipitation of titanium carbides traced through XRD analysis. Formation of such carbides contributes to higher micro-hardness value up to certain depth beneath the machined surface. Below this hardened layer, microhardness values follow gradual truncation as distance is increased towards bulk of the parent material.