Surface texture and integrity of electrical discharged machined titanium alloy

Electrical discharge machining (EDM) is a non-conventional machining process, extensively applicable in the modern industry. Owing the non-contact nature of the process, any electrical conductive material can be machined in high quality, regardless its mechanical properties. Titanium alloys are commonly machined by EDM, as difficulties related with their low thermal conductivity and the high chemical reactivity can be overcome. As titanium alloys are utilized in quality demanding applications and industries, high machined surface quality is required, as well surface integrity. The current study presents an experimental investigation of how ED machining parameters affect the MRR, the TWR, and the SQ on machining Titanium Grade 2 by EDM. For pulse current 9/13/17/25A, and pulse on time 25/50/100/200 μs, a full-scale experiment has been carried out, using graphite electrode. The surface texture (ST) has been estimated in terms of arithmetic mean height (Sa), maximum height of scale-limited surface (Sz), and skewness of the scale-limited surface (Ssk), while also measurements of the surface waviness were conducted as well. For all the aforementioned parameters an analysis of variance (ANOVA) has been performed. Finally, the surface topography and integrity were evaluated through optical and SEM microscopy observation, through which the surface cracks and micro-cracks due to high pressure and temperature gradients can be distinguished and characterized.