Experimental study of material removal rate, surface roughness and topography in electrical discharge machining of Titanium Aluminide intermetallic compound

Titanium aluminide intermetallic compounds are a small group of materials that can be used at high temperature structures where the specific strength (strength to density ratio) and specific stiffness (elastic modulus to density ratio) are very important. In this study, some output characteristics of electrical discharge machining (EDM) process; including material removal rate (MRR), surface roughness and topography are investigated for this material. The DOE method of full factorial is used for planning the machining tests that two main input parameters of pulse current and pulse on time are changed in five and four different levels, respectively and other input machining parameters are kept constant during tests. The results show that in lower currents (3 and 6 A), despite the increase in pulse time, there is no significant change in MRR and the MRR for these two currents is negligible, indicating that finishing process of titanium aluminide is difficult and time consuming, but there is no such situation in more currents (12, 24 and 64 A) and the roughing process of this material is optimally carried out. For the currents above the 24 A, the gradient of MRR increase, is decreased because of arc appearance. In the states of higher electrical currents, the lengths of cracks on the machined surface are increased and the widths of cracks are growing. While arc is occurred for the higher electrical discharge energy, the surface roughness and topography are intensively different from the other current and pulse on time conditions.