Analysis, predictive modelling and multi-response optimization in electrical discharge machining of Al-22%SiC metal matrix composite for minimization of surface roughness and hole overcut

Open Access

Table 1

Literature overview.

References	Workpiece materials	Electrode materials	Dielectric medium	Process parameters	Machining characteristics	Techniques	Research findings
[1]	Al–SiC metal matrix composite	Brass	Kerosene	Discharge current, pulse duration, speed of electrode rotation, hole diameter of the electrode, polarity of the electrode, volume percentage of SiC	Material removal rate, electrode wear rate, surface roughness	GA	• With the increase in volume percentage of SiC, MRR decreases and EWR increases. • With the decrease in hole diameter and increase in speed of the rotating tube electrode, MRR increases and EWR and SR decreases.
[2]	WC/30%Co composite	Copper	Kerosene	Electrode rotation, pulse on time, current, flushing pressure	Material removal rate, surface roughness	RSM	• Combination of low pulse time and high peak current, rotational speed, and flushing pressure yields more MRR and less Ra. • Surface finish improves at higher levels of electrode rotation and flushing pressure
[3]	Titanium alloy (Ti-6Al-4V)	Copper	EDM oil	Pulse-on time, peak current, gap voltage, spindle speed, flushing pressure	Material removal rate, surface roughness	Taguchi method	• Peak current has the most significant effect on MRR, whereas the pulse-on time and gap voltage show almost the same effect, over MRR • Surface roughness is affected by peak current and pulse-on time while gap voltage and spindle speed have no effect.
[4]	AISI D3 tool steel	Copper	Kerosene	Pulse current, pulse-on time, pulse-off time, gap voltage	Overcut	RSM	• Overcut is significantly affected by pulse-on time and pulse current but pulse-off time and gap voltage have less effect.
[5]	Inconel 718	Brass		Discharge current, open-circuit voltage, pulse-on time, duty factor, flushing pressure, cryogenic treatment soaking duration of brass tool	Electrode wear ratio, surface roughness, radial overcut	TOPSIS, TLBO	• Deep cryogenic treated brass tool with longer soaking duration has been proven to be an ideal EDM tool to machine hard materials like Inconel 718.
[6]	Inconel 718	Copper, graphite, brass	Paraffin oil	Open circuit voltage, discharge current, pulse-on-time, duty factor, flushing pressure, electrode material	Material removal rate, tool wear rate, surface roughness, radial overcut	PSO	• Material removal rate can be maximized with the use of graphite tool and minimized using brass electrode but better surface integrity can be obtained using brass electrode. • Tool wear decreases using graphite tool compared to copper and brass tool. • QPSO provides better result than PSO resulting.
[7]	Tungsten carbide	Copper, tungsten	EDM 22 mineral oil	Electrode material, polarity, open-circuit voltage, peak current, pulse duration, pulse interval, flushing pressure	Material removal rate, relative wear ratio, surface roughness		• Material removal rate and the surface roughness are directly proportional to the peak current.
[8]	Titanium Grade 6 alloy (Ti-5Al-2.5Sn)	Copper, brass, zinc		Pulse on time, peak current, gap voltage. Duty cycle	Material removal rate, tool wear rate	RSM	• Material removal rate can be maximized with the use of brass and zinc electrodes compared to copper electrode. • Tool wear and recast layer can be reduced with the use of brass and zinc electrodes.
[9]	Titanium alloy (Ti-6Al-4V)	Tungsten, copper, cryogenically treated copper	EDM 30 oil	Peak discharge current, pulse-on time, gap voltage, duty factor, dielectric flushing pressure, spark gap, machining time	Material removal efficiency, surface roughness, surface crack density, white layer thickness		• Cryogenically treated Copper has exhibited higher micro-hardness value, higher MRR, improved surface finish and lower tool wear as compared to normal Copper. • Lower MRR and too rough surface has obtained by using tungsten electrode.
[10]	Al6061-SiC MMC	Copper, brass, stainless steel	Kerosene oil mixed with grapheme nanoparticle	Current intensity, pulse duration, duty cycle	Material removal rate, surface roughness, electrode wear ratio	RSM	• Brass electrode yielded higher MRR and better surface finish than copper and stainless steel electrodes. • Lower EWR resulted by using stainless steel electrode than copper and brass electrodes.
[11]	Inconel 825	Graphite, tungsten, brass, copper	EDM 30 oil	Peak discharge current, gap voltage, pulse-on time, duty factor, flushing pressure	Material removal rate, surface roughness, surface crack density, white layer thickness		• Copper electrode yielded higher MRR. • Increase in peak discharge current, increases the material removal rate, surface roughness, white layer thickness etc.
[12]	Titanium alloy (Ti-6Al-4V)	Cu-TaC composite	Urea solution, distilled water	Peak current, pulse duration	Surface roughness, microhardness		• Distilled water dielectric fluid gave better surface roughness, while use of urea solution gives higher surface roughness.
[13]	AISI 8407 steel	Steel needle	Oxygen, air, kerosene, deionized water, water-in-oil emulsion	Pulse duration, type of dielectrics	Hole geometry, craters, recast layer thickness, material removal rate		• Different shape of craters formed in different dielectrics with the same experimental conditions • Higher removal has been obtained in liquid dielectrics compared to gaseous dielectrics • Kerosene resulted in higher removal efficiency; less volume of material was melted compared to other dielectrics.
[14]	Aluminium alloy 6063	Copper	Biodiesel, transformer oil, kerosene	Peak current, pulse on time, pulse off time, different dielectrics	Material removal rate, electrode Wear, surface roughness	Taguchi method	• biodiesel gives high MRR and less EWR compared to kerosene dielectric • The material removal rate and electrode wear rate are mainly affected by peak current followed by the pulse on time with negligible effect of pulse off time.
[15]	Inconel 738	Brass	Kerosene, deionized, water, EDM emulsion, water solution EDM fluid	Open circuit voltage, current peak, pulse duration, pulse interval	Material removal rate, electrode wear, holes generation, recast layer formation	Taguchi method	• The recast layer became thicker with the increase in electric conductivity of dielectric fluids. • The recast layer became thin with kerosene but due to decomposition of kerosene, the machining speed was low.
[16]	Spheroidal graphite cast iron	Copper	Kerosene	Diameter of graphite particle, quantity of graphite particle, area fraction of graphite particle	Layer thickness, Ridge density	RSM	• Layer thickness increases with the increase of the quantity and area fraction of graphite particle but it reduces with the increase of diameter of graphite particle.
[17]	Al/SiC metal matrix composite	Copper	Kerosene	Pulse on time, peak current, average gap voltage, volume fraction of SiC in aluminium matrix	Material removal rate, electrode wear ratio, gap size, surface finish	RSM	• MRR becomes higher with an increase of pulse on time, peak current and relatively with gap voltage and reduces with increase of SiC percentage. • EWR becomes higher with an increase of both pulse on time and peak current and reduces with increase of both of SiC percentage and gap voltage. • Surface roughness increases with the increase of pulse on time, SiC percentage, peak current, gap voltage.
[18]	AISI D2 tool steel	Graphite	Kerosene mixed with carbon nanotube	Discharge current, discharge duration, discharge voltage	Surface roughness, morphology, micro-cracks	RSM, fuzzy logic modelling	• Micro-cracks with CNT are less than that without CNTs. • The maximum test errors for surface roughness and micro-cracks using response surface model are more without CNTs compared to with CNTs.
[19]	Al-Mg₂Si metal matrix composite	Copper	Dielectric fluid mixed with aluminium powder	Voltage, current, pulse on time, duty factor	Material removal rate, electrode wear ratio, microstructure changes	RSM	• MRR is significantly affected by voltage, current and EWR is significantly affected by pulses ON time. • It was obtained from the microstructure analysis that voltage, current, and pulse ON time have a significant effect on machined surface profile.
[20]	AISI D6 tool steel	Copper	Kerosene	Pulse on time, pulse current, voltage	Material removal rate, tool wear ratio	RSM	• Increased pulse on time resulted in higher material removal rate and reduced tool wear ratio. • Both material removal rate and tool wear ratio become maximum by increasing the pulse current and reduces at higher value of the input voltage respectively.
[21]	Titanium Ti-13Nb-13Zr alloy	Graphite	Kerosene	Current, voltage, pulse on time, pulse off time	Material removal rate, electrode wear rate, surface roughness	RSM	• The absolute error between predictions and actual values fall within 10% for which the model can be effectively used to predict the EDM machining parameters.
[24]	AISI D2 steel	Copper	EDM oil	Pulse current, pulse on time, duty cycle	Surface roughness	ANN	• The process performance with accuracy could be predicted using neural models under different machining conditions. • RBFN is faster than the BPNs and the BPN is reasonably more accurate.
[25]	Al/SiC MMC	Copper, graphite, copper–graphite composite	EDM oil, EDM oil + copper powder, EDM oil + graphite powder	Workpiece, electrode, current, pulse-on time, pulse-off time, dielectric fluid	Residual stress	ANN	• MMCs with low coefficient of thermal expansion and a high density of reinforced particle have lower residual stresses. • The residual stresses reduced by adding powder in the dielectric.
[26]	Titanium alloy	Copper, copper-chromium, copper-tungsten	Ferrolac 3M EDM oil	Peak current, pulse-on-time, pulse-off-time, dielectric fluid mixed with powder, electrode material, cryogenic of electrode material, workpiece material, cryogenic workpiece material	Surface roughness	Hybrid Taguchi-ANN approach	• High discharge energy resulted as surface defects such as cracks, craters, thick recast layer, micro pores, pin holes, residual stresses and debris.
[27]	Polycrystalline diamond	Copper-tungsten, copper-nickel	Kerosene	Peak current, pulse interval, pulse duration	Material removal rate, electrode wear rate	ANN	• Copper tungsten electrode gave lower EWR, in comparison with the copper nickel electrode.
[28]	Inconel 718	Tungsten carbide	Kerosene	Peak current, pulse on-time, pulse off-time, spark gap	Electrode wear, material removal rate, working gap	Grey-Taguchi method	• Grey-Taguchi method is very suitable for solving the quality problem of machining in the micro milling EDM of Inconel 718
[29]	Maraging steel (MDN 300)	Copper		Discharge current, pulse on time, pulse off time	Material removal rate, tool wear rate, relative wear ratio, surface roughness	Taguchi method	• Discharge current is more significant than pulse on time for MRR and TWR. • Higher discharge current and longer pulse on duration gives rougher surface with more craters, globules of debris, and microcracks.
[30]	S-03 special stainless steel	Copper	Kerosene	Gap voltage, peak discharge current, pulse width, pulse interval	Material removal rate, surface roughness	Taguchi method, grey relational analysis	• The EDM high-accuracy process parameters sequenced in order of: peak discharge current, pulse interval, gap voltage, and pulse width. • The machined work piece has no surface modification layer.
[31]	NiTi alloys	Copper		Gap current, pulse on time, pulse off time, workpiece electrical conductivity, tool conductivity	Material removal rate	Taguchi method	• The material removal rate affected by the significant the material removal rate parameters like work electrical conductivity, gap current and pulse on time.
[32]	SS 304	WC	Kerosene	Voltage, capacitance, resistance, feed rate, spindle speed	Electrode wear, entrance clearance, exit clearance, machining time, number of shorts	Taguchi method, grey relational analysis	• Electrode wear and the entrance and exit clearances have a significant effect on the diameter of the micro-hole when the diameter of the electrode is identical.
[33]	6061Al/Al₂O₃p/20P aluminium MMC	Copper		Pulse current, pulse ON time, duty cycle, gap voltage, tool electrode lift time	Material removal rate, tool wear rate, surface roughness	Grey relational analysis	• The sequence of the process parameters to the multi-performance characteristics is in the order of: pulse current, aspect ratio, tool electrode lift time, pulse ON time, gap voltage and duty cycle. • Grey system theory is designed to work with system where the available information is not sufficient to characterise the system.
[34]	Nickel-based superalloy	Copper		Gap voltage, gap current, pulse on time, duty factor, polarity, tool & workpiece materials, type of dielectrics, flow rate, flushing pressure, rotation of electrode or workpiece	Material removal rate, surface roughness, circularity	Taguchi method, RSM, PCA-GRA	• MRR become improves with the use of present hybrid approach in this experimental study.
[35]	Al7075	Brass	Deionized water	Pulse on-time, pulse off-time, flushing pressure	Material removal rate, tool wear rate	Grey relational analysis	• The optimization results showed that the MRR become maximum due to combination of higher pulse on-time and reduced pulse off-time. • Tool wear rate was highly affected by pulse on-time, pulse off-time.
[36]	Si₃N₄-TiN composites	Copper		Current, pulse on time, pulse off time, dielectric pressure, gap voltage	MRR, electrode wear rate, surface roughness, radial overcut, taper angle, circularity, cylindricity, perpendicularity	GRA-RSM	• MRR increases with increase in discharge current and pulse on time. • EWR increases with increase in discharge current and pulse on time, and decrease in gap voltage. • The surface roughness decreases with decrease in discharge current whereas increasing gap voltage reduces surface roughness.
[37]	JIS SKD 61 alloy tool steel	Copper		Discharge current, gap voltage, pulse on-time, pulse off-time	Material removal rate, relative electrode wear ratio, surface finish	RSM, GA	• MRR increases due to a more powerful spark energy, at higher discharge current and pulse on time. • Larger thickness of recast layer was formed on the machined surface due to the powerful spark energy. • Relative electrode wear ratio reduces with increase of pulse on-time.
[38]	Al–SiC nano-composites	Copper		Voltage, pulse current, pulse on time, pulse off time	Material removal rate, electrode wear rate, surface roughness	RSM	• MRR increases with an increase in pulse on time and then with further increase in pulse on time. • MRR and surface roughness is mainly affected by pulse current and pulse on time.
[39]	Aluminium-multiwall carbon Nano- tube composites (AL-CNT)	Copper	Kerosene	Machining-on time, discharge current, voltage, total depth of cut	Material removal rate, wear electrode ratio, surface roughness	Taguchi method, RSM	• As the number of trials increases over wider domains of process variables, the accuracy of these models is enhanced. • This methodology gathers experimental results, builds mathematical models in the domain of interest and optimizes the process models.
[40]	Tool steel 55NiCrMoV7	Graphite (EDM-3 POCO)	EDM fluid 108 MP-SE 60		Material removal rate	RSM	• Increase in the discharge current and pulse time leads to generation of craters with a larger depth and diameter. • Inter pulse time did not affect the change in surface integrity and the MRR significantly.
[42]	A2 tool steel	Copper	EDM-30	Discharge current, pulse on time, duty cycle, discharge voltage	Material removal rate, Electrode wear rate	Principal component analysis	• Discharge current is directly proportional to both MRR and EWR • Discharge current is having the maximum contribution towards MRR, while pulse on time is having maximum contribution towards EWR
[43]	Beryllium–copper alloy	C-122 copper	EDM-244 oil, deionized water	Dielectric medium, pulse on/off time, working current	material removal rate, electrode wear ratio, surface roughness	Taguchi method, GRA, RSM	• MRR is mostly affected by the working current, while the dielectric medium is the dominant parameter for EWR and Ra.
[44]	AISI 202 steel	Tungsten carbide	Kerosene	Discharge current, gap voltage, duty factor	Material removal rate, surface roughness	Taguchi method	• Better surface finish with high MRR could be produced by the modified ISO current pulse generator.
[45]	Inconel 600	Graphite	Mineral oil	Current intensity, pulse time, duty cycle, open-circuit voltage, flushing pressure	Material removal rate, electrode wear, surface roughness	RSM	• Positive polarity results in higher MRR. • Both the production costs and production time decreases with an increase in current intensity.
[46]	Inconel 601, 625, 718, 825 super alloys	Graphite	EDM oil	Gap voltage, peak discharge current, pulse-on time, duty factor, flushing pressure	Material removal rate, electrode wear rate; surface roughness, surface crack density	Satisfaction function approach integrated with Taguchi method	• MRR and surface roughness increases with peak current.

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