Milling Microchannels in Monel 400 Alloy by Wire EDM: An Experimental Analysis

Shafiq Ahmad,Abdualziz El-Tamimi,Muneer Khan Mohammed,Mustafa Saleh,Saqib Anwar

doi:10.3390/mi11050469

Abstract

This paper presents the results of an investigation on the capacity of wire electrical discharge machining (WEDM) to produce microchannels in the Nickel-based alloy, Monel 400. The main objective of the current study is to produce microchannels with desired/target geometry and acceptable surface quality. Square cross-sectional microchannels with dimensions of 500 × 500 µm were investigated. Experiments were conducted based on the one-factor-at-a-time approach for the key input WEDM process parameters, namely pulse-on time (TON), pulse-off time (TOFF), average gap voltage (VGAP), wire feed (WF), and dielectric flow rate (FR). Dimensional accuracy, machining speed, surface roughness, surface morphology, microhardness, and microstructure were analyzed to evaluate the microchannels. The minimum errors of 6% and 3% were observed in the width and depth of the microchannels, respectively. Furthermore, microchannels with enhanced surface integrity could be produced exhibiting smooth surface morphology and shallow recast layer (~0–2.55 µm).

Highlights

Nowadays, nickel-based alloys, such as Monel 400 alloy, find widespread applications, including nuclear processing reactors, heat exchangers and other major industries
It is worth mentioning that, as compared to the laser machining and photochemical machining, the wire electrical discharge machining (WEDM) process has a higher capacity to control the shape of the microchannels, because the laser produces tapered channels as demonstrated by Ahmed et al [8] and has deep detrimental impact [9], whereas, the photochemical machining produces channels with undercuts as shown by Patil and Mudigonda [5]
Regarding the abrasive water jet machining (AWJM), it can produce microchannels [10]; the AWJM process suffers from poor surface texture such as striation marks and the grit embedment issues [9], and tapered geometry of machined features [11,12]

Summary

Introduction

Nickel-based alloys, such as Monel 400 alloy, find widespread applications, including nuclear processing reactors, heat exchangers and other major industries. Selvakumar et al [19] studied the effects of the pulse-on time, pulse frequency, peak current and job thickness on the material removal rate (MRR) and the surface roughness when machining Monel 400 alloy with WEDM by using response surface methodology (RSM). Kumar et al [20] used RSM to optimize the WEDM process parameters including discharge current, pulse-on time, pulse-off time and servo voltage, and investigated their effects on machining rate and surface roughness when machining Monel 400. They used the desirability function for multi-performance optimization. The microchannels are evaluated by dimensional accuracy, machining speed, surface roughness, surface morphology, microhardness and microstructure

Materials and Methods

Microhardness Analysis