EXPERIMENTAL INVESTIGATION OF CHROMIUM COATED BRASS TUBULAR ELECTRODES IN MICRO EDM DRILLING OF NIMONIC C-263 ALLOY

Abstract

Micro Electrical Discharge Machining (Micro-EDM) is a precision micromachining technique that removes material through controlled electrical spark discharges without mechanical contact, making it suitable for machining high-strength and difficult-to-machine alloys including nickel-based superalloys. This paper presents an experimental investigation of chromium-coated brass tubular electrodes—configured as single channel (CCBTEs) and multi channel (CCBTEm)—for micro-EDM drilling of Nimonic C-263, a precipitation-hardened nickel superalloy extensively used in gas turbine and aerospace components. Experiments were designed using the Taguchi L9 orthogonal array with four process parameters— Pulse On Time (TON), Pulse Off Time (TOFF), Discharge Current (DC), and Rotation Speed (RPS)—each at three levels. The performance measures evaluated are Material Removal Rate (MRR, mm³/min) and Machining Time (min). Results indicate that the chromium coating significantly reduces electrode wear and overcut due to chromium's high hardness (~900 HV) and high melting point (1907°C). The effects of each process parameter on MRR and Machining Time are discussed in detail for both single-channel and multi-channel chromium-coated brass tubular electrode configurations.