Effect of EDM parameters on hole quality characteristics in deep hole drilling of Inconel 718 superalloy

This paper presents the effect of electrical discharge machining parameters on the hole quality characteristics during small hole deep drilling of Inconel 718 superalloy. Through holes of 62 mm depth and diameters ranging from 3.055 to 3.316 mm are drilled. The hole quality are characterised by surface roughness value (Ra), depth averaged radial overcut (DAROC) and hole profile. The experimental results show that process parameters such as peak current and pulse on–time are significant parameters on Ra and the parameter pulse on–time is significant on DAROC. Analysis of hole profiles show three distinct segments along the depth of hole: wide mouth at the top; barrel shaped at the midway; narrow end at the bottom. Further, surface topography of EDM drilled surfaces are studied at different depths along the hole using SEM and are reported here. [Received 9 September 2013; Revised 30 July 2014; Accepted 2 October 2014]