Effect of boric acid in powder mixed EDM of Ti-6al-4V ELI

ABSTRACT

Ti-6Al-4 V ELI is an advanced titanium alloy used in different sectors. Being a hard-to-machine material, it is crucial to explore the machinability of Ti-6Al-4 V ELI. Boric acid powder mixed with deionized water is utilized as a dielectric to machine Ti-6Al-4 V ELI in electrical discharge machining (EDM). The effect of powder concentration (PC), current, and pulse-on time on material removal rate (MRR), tool wear rate (TWR), surface roughness (SR), and specific energy consumption (SEC) is evaluated. X-ray diffraction (XRD) analysis revealed the formation of TiO₂, TiB, and Al₂O₃-like hard compounds over the surface. Scanning electron microscope (SEM) test indicates that there are more craters and globules on the surface machined in 5 g/l PC compared to that of 15 g/l PC. The overall evaluation criteria are designed to maximize the MRR and minimize the TWR, SR, and SEC by optimizing the variable parameters.

KEYWORDS:

• PMEDM
• MRR
• SEC
• boric-powder
• DI-water

Nomenclature

List of symbols	=
Ip	=	Current
$i\left(t\right)$	=	Current varying with time
${\rho }_w$	=	Density of the workpiece
${\rho }_t$	=	Density of the tool material
$t$	=	Discharge duration for a single pulse $\left(\mu s\right)$
$E$	=	Energy of a single pulse (J)
Ton	=	Pulse-on time
Toff	=	Pulse-off time
V	=	Voltage
$u\left(t\right)$	=	Voltage (V) varying with time
$W_{ta}$	=	Weights of electrodes post machining
$W_{tb}$	=	Weights of electrodes prior machining
$W_{wa}$	=	Workpiece weight post machining
$W_{wa}$	=	Workpiece weight prior machining
List of abbreviations	=
R2 (adj)	=	Adjusted correlation coefficient
ANOVA	=	Analysis of variance
Ra	=	Center line average
R2	=	Correlation coefficient
DI	=	Deionized
DSO	=	Digital storage oscilloscope
EDM	=	Electrical discharge machining
MRR	=	Material removal rate
OEC	=	Overall evaluation criteria
PC	=	Powder concentration
PMEDM	=	Powder mixed EDM
QC	=	Quality characteristic
RLT	=	Recast layer thickness
SEM	=	Scanning electron microscope
SEC	=	Specific energy consumption
SR	=	Surface roughness
TWR	=	Tool wear rate
V-I	=	Voltage-current
WEDM	=	Wire electrical discharge machine
XRD	=	X-ray diffraction

Disclosure statement

No potential conflict of interest was reported by the authors.