Micro-Hardness and Machined Surface Damage Study for Continuous and Discontinuous Ultrasonic Vibration Assisted Electrical Discharge Machining

A versatile process of Electrical Discharge Machining (EDM) using continuous and discontinuous vibrations to workpiece has been developed. The effects of continuous and discontinuous vibration assisted EDM were explored using high Carbon high Chromium steel as work piece and Copper as tool electrode. In this work L18 orthogonal array based on Taguchi design is used to conduct a series of experiments and the experimental data statistically evaluated by analysis of variance (ANOVA). The main machining parameters such as type of vibration, amplitude of vibration, peak current, no-load voltage, pulse-on time and duty factor were chosen to determine the EDM machining characteristics such as micro-hardness and heat affected layer on the machined surface. The advantages of ultrasonic assisted EDM were confirmed from the analysis of micro-hardness and SEM photographs. The experimental results show that the discontinuous ultrasonic assisted EDM has higher micro-hardness with reduced Heat affected layer as compared with continuous ultrasonic vibration assisted EDM. The significant process parameters and the optimal combination levels of machining parameters associated with micro-hardness were also drawn.