INVESTIGATION OF MICROSTRUCTURAL EVOLUTION IN TI-48AL-2CR-2NB ALLOY UNDER MICRO-EDM DRILLING: AN EXPERIMENTAL APPROACH

Ti-48Al-2Cr-2Nb (commonly known as TiAl) is a lightweight intermetallic alloy with excellent high-temperature strength and oxidation resistance, making it a candidate for aerospace and automotive turbocharger applications. However, its brittleness and low thermal conductivity pose significant challenges in conventional machining, especially when creating small, precision features. In this study, micro Electrical Discharge Machining (micro-EDM) is used to drill holes in Ti-48Al-2Cr-2Nb using a hollow copper electrode (0.5 mm outer, mm inner). A Taguchi L27 design of experiments was implemented, systematically varying tool rotational speed, current, pulse on/off times, and power to investigate how these parameters affect the microstructural integrity of drilled holes.Microstructural analyses of the machined holes were conducted under optical microscopy across all 27 parameter sets. Emphasis was placed on characterizing recast layer formation, micro-crack propagation, surface oxidation, and heat-affected zones (HAZ). Observations show that parameter combinations involving high current, short off time, and elevated power tend to induce thicker recast layers and more pronounced micro-cracking. Conversely, lower current, longer off time, and moderate tool rotation yielded minimal thermal damage. This study provides new insights into balancing machining speed and surface integrity for TiAl alloys via micro-EDM, guiding future optimization of advanced manufacturing processes for high-performance intermetallic materials.