Corrosion rate and surface hardness optimization in wire electrical discharge machining of AISI A2 tool steel in various conductive states and mediums

Abstract

The current work focuses on optimizing the material characteristics such as surface hardness and corrosion rate on the surface of the machined specimens of A2 Tool Steel (A2TS) under various conditions like normal conductive state (NCS) and superconductive state (SCS) in flushing and submergible medium. The machining parameters such as voltage, current, pulse-on, pulse-off, wire-feed, wire-tension, and fluid-pressure are considered for experimentation through orthogonal array L18 using the Taguchi method. The surface morphology of machined specimens surface is examined using energy dispersive x-ray analysis (EDAX), x-ray diffraction (XRD), and Scanning Electron Microscope (SEM). The experimental results reveal that voltage, pulse off, and fluid pressure increase while corrosion rate decreases and similarly, the increases in voltage, pulse-on, and wire feed the surface hardness increases in various states and mediums. The conductive states and mediums improved the material characteristics, such as corrosion rate and surface hardness of A2TS. The oxide layer (ferric oxides) formation reduces in SCS A2TS machined in submergible as elemental reaction with environment reduced with formation of chromium compounds. The bonding strength of the SCS A2TS material increased during re-solidification of machined specimens in submergible increases the surface hardness as a result, carbon content will increases. These results are noticed from EDAX, XRD and SEM analysis. An improvement of corrosion rate between NCS A2TS and SCS A2TS in flushing medium is 57.59% and in submergible medium is 59.35% respectively. The progress of surface hardness between NCS A2TS and SCS A2TS in flushing medium is 2.58% and in submergible medium is 4.93%, respectively.

Keywords

• corrosion rate
• surface hardness
• AISI A2 tool Steel
• taguchi optimization
• EDAX
• XRD