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01-12 

1 

 

 

 

Article 

Analyzing process variables for WEDM of Nimonic 

alloy 75 with a cryogenic treated tool 
Saidulu G*, P Prasanna 
Department of Mechanical Engineering, Jawaharlal Nehru Technological University, Hyderabad, India,500085 

A R T I C L E   I N F O 
 

Article history: 
Received 27 July 2025  
Received in revised form 
11 August 2025 
Accepted 24 September 2025 
 
Keywords:  
Wire Electric Discharge Machining (WEDM), 
Taguchi orthogonal technique,  
Material remova rate (MRR), Vertex Angle,  
Micro Hardness and Cryogenic treated brass wire 
 
*Corresponding author 
Email address: 
gilla.saidulu@gmail.com 
 
DOI: 10.55670/fpll.futech.5.1.1 

A B S T R A C T 
 

The present experimentation employs a Wire Electric Discharge Machining 
(WEDM) technique to investigate how various operational limiting factors 
influence Material Removal Rate (MRR), Micro Hardness (MH), and Vertex 
Angles (VA). Nimonic Alloy 75 sheets were used as the raw material for the 
experiments. Two types of tools were utilized: cryogenically treated brass wires 
and non-cryogenically treated brass wires. The primary process parameters 
analyzed in this research include the tool electrode, Ton, Wire Feed rate (WF), 
Wire Tension (WT), and Toff. The wire diameter was kept uniform at 0.25mm, 
as was the thickness of the work material Nimonic Alloy 75. The study compares 
MRR, MH, and VA when using a cryogenically treated tool versus a non-
cryogenic tool, considering Ton, WF, WT, and Toff. The experimentations were 
structured with the help of a Taguchi L-9 OA, and an ANOVA was used to 
determine the maximum contribution of the variables: vertex angle, 
microhardness, and MRR. The microstructure of the machined samples, using 
untreated and CT brass wires, was examined with a Scanning Electron 
Microscope (SEM). Furthermore, chemical analysis was performed using EDS, 
comparing weight percentages before and after treatment. 

1. Introduction 

Electric Discharge Machining (EDM), particularly wire-

cut EDM, is an electro-thermal subtractive manufacturing 

technique that cuts materials by rapidly melting and 

evaporating them using a wire electrode. This wire generates 

electrical pulses that create sparks between the workpiece 

and the electrode. Various dielectric fluids are used to cool, 

flush, and remove debris from the work material, with 

common choices including transformer oil, paraffin oil, and 

deionized water. Different types of wire can be used as the 

cutting tool, including brass wire coated with copper or zinc, 

an annealed brass electrode, and an abrasive-coated brass 

electrode. The diameter of the electrode wire can range from 

0.1 mm to 3 mm, depending on the specific cutting 

requirements. Wire cut EDM is an electro-thermal subtractive 

manufacturing technique that cuts hard materials by rapidly 

melting and evaporating them using a wire electrode [1]. The 

electrode generates electrical pulses, creating sparks 

between itself and the workpiece. Dielectric fluids, such as 

transformer oil, paraffin oil, and deionized water, are used to 

cool, flush, and remove debris from the material [2-4]. Cutting 

wire types include brass wire coated with copper or zinc, 

annealed brass electrode, and abrasive-coated brass 

electrode [5]. Electrode wire diameters range from 0.1 mm to 

3 mm, depending on cutting requirements [6]. Ashish Goyal et 

al. [7] used a cryogenically treated brass tool to improve 

maximum MRR and surface roughness on Nimonic alloy 80A. 

Rajesh Choudhary et al. [8] compared cryogenic and non-

cryogenic tools to explore tool wear rate and recast layer 

thickness. Suresh Kumar Myilsamy et al. [9] reported that 

cryogenically treated molybdenum wire showed greater 

hardness, wear resistance, and electrical conductivity than 

untreated wire. Neeraj Sharma et al. [10] subjected D-2 tool 

steel to subzero treatment and used a brass tool, finding that 

surface roughness was highly influenced by Ton. Ashish Goyal 

[11] evaluated MRR and surface roughness of Inconel-625 

with CT-treated Zn wire, considering wire diameter, tool, 

current, wire tension, Ton, Toff, and tool feed. Ramesh 

Krishnan et al. [12] used cryogenic-treated brass tools and 

micro EDM to conduct research on EN 24, taking into 

consideration input constraints like current, capacitance, Ton, 

and voltage in order to maximize linear characteristics such 

as overcut, circularity, and taper angle. Ranjit Singh et al. [13] 

experimented on M 42 HSS, using CT brass wire to evaluate 

electrical conductivity and dimensional variation. Working 

with Inconel 601, Neelesh Singh et al. [14] employed a CT 

copper tool and optimized MRR, TWR, and SR by altering 

input variables. Rahul et al. [15] used a cryogenically cooled 

copper tool to analyze the metallurgical properties and 

surface integrity of Inconel 825; they discovered that the CT 

tool gave better results compared to the standard tool.  

 

 

 

Future Technology 

Open Access Journal 

https://doi.org/10.55670/fpll.futech.5.1.1 

 

 

 

 

 

February 2026| Volume 05 | Issue 01 | Pages 01-12 

Journal homepage: https://fupubco.com/futech 

 

ISSN 2832-0379 

mailto:gilla.saidulu@gmail.com
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Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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In the case of Inconel 718, B.K. Tharian et al. [16] 

machined it using a CT graphite electrode and found that MRR 

was high compared with a non-treated tool. WWR of CT brass 

wire was less when machining EN-31 than when using non-

treated wire, as shown by Kapoor et al. [17]. On Monel 400 

alloy, N.E. Arun Kumar et al. [18] ran experiments with CT 

brass wire to obtain MRR, SR, and kerf width, declaring that 

CT brass gave better results than the non-treated variant. For 

cutting speed and SR measurements of M-42 AISI steel, Anish 

Kumar et al. [19] used a CT brass tool during machining, 

finding high cutting speed and lower SR. Jatinder Kapoor et al. 

[20] conducted experiments on EN-31 to evaluate SR; they 

found that a shallow cryogenically treated brass tool resulted 

in a good surface finish. Waseem Tahir et al. [21] machined 

HSLA steel by CT brass wire and found that the treated wire 

gave less RLT (Recast Layer Thickness) and infusion of wire 

on the machined surface. AISI D3 steel was machined with Zn-

coated brass wire and CT Zn-coated brass wires to evaluate 

SR and MRR by Husandeep Sharma et al. [22] and found that 

the treated tool gave the best results. Satyanarayana et al. [23] 

machined Inconel 600 by CT and non-treated Zn wires to 

optimize the MRR and SR and stated that CT wire gave the 

best results. Using CT-treated brass wire, EN-31 material was 

machined by Jitender Kapoor et al. [24], and MRR was 

evaluated. From the experimentation, it was announced that 

the grain refinement and electrical conductivity of treated 

wire improved. Cryo-treated Ti6Al4V machined by WEDM 

showed discharge current as the major factor affecting MRR 

and SR [25].  Incoloy 925 with cryo-treatment and tempering 

exhibited refined microstructure, better surface morphology, 

and, when furnace-cooled, higher hardness and machinability 

[26]. Naveed Ahmed et al. [27] found errors in dimensions on 

Al2024/Al2O3/W using CT electrodes and concluded that CT 

electrodes gave less error on various dimensions. Muhammad 

Huzaifa Raza et al. [28] investigated Al2024/Al2O3/W with 

CT and non-CT wires and announced that there were fewer 

defects with CT wires as compared to non-CT wires. A 

cryogenically treated tool exhibits increased tool life, reduced 

surface cracks, and a thinner white layer on the machined part 

compared to a non-cryogenically treated tool [29]. 

Cryogenically treated wire also leads to reduced surface 

cracking, lower residual stresses, and a thinner white layer 

formation compared to standard tools [30]. Cryogenic 

treatment refines the grain structure and increases the 

hardness of Nimonic-90. The extent of these enhancements 

depends on the soaking period; longer soaking durations lead 

to greater hardness [31]. According to the experiments 

mentioned above, many researchers are studying the effect of 

various cryogenically treated wires on a variety of alloys; 

however, limited studies are focused on Nimonic alloy 75, 

which is widely used in aerospace and heat treatment 

equipment. When the Nimonic alloy 75 is machined using 

cryogenically treated brass wire, out puts such as MRR, 

microhardness, vertex angles, and microstructural changes 

are less investigated. Brass wire can be made more resilient 

and stronger by employing cryogenic treatment, which also 

enhances the wire's consistent grain size and minimizes 

flaws. 

2. Objectives of research 

The specific objective of the experimentation as follows: 

The study aims to analyze the effect of cryogenically treated 

brass wire on the machining performance of Nimonic alloy 75 

using WEDM by evaluating input parameters such as Ton, 

Wire Feed Rate (WF), Wire Tension (WT), and Toff on MRR, 

microhardness, and vertex angle. The results are to be 

compared between cryo-treated and non-treated brass wires, 

with process optimization carried out using the Taguchi L-9 

orthogonal array and ANOVA. Additionally, microstructural 

changes and EDS analysis of the machined surfaces with both 

wires are to be examined. Nimonic alloys are frequently 

utilized in the production of aero engine components due to 

their high strength and resistance to higher temperatures. 

Over time, exposure to elevated temperatures can lead to 

various metals experiencing corrosion, fatigue, cracking, and 

distortion. These are widely used due to their exceptional 

resistance to corrosion. The various properties of Nimonic 

alloy 75 at 20°C have been shown in Table 1. 

Table 1. Various properties of Nimonic alloy 75 at 20°C 

Mechanical properties Value 
Ultimate Tensile Strength 750 MPa  

Youngs Modulus 221 GPa 
Yield Strength 250 MPa  

Electrical properties Value 
Resistivity 1.09 µΩ.m 

Physical/Thermal properties Value 
Melting point  1340–1380°C 

Thermal Conductivity 11.7 W/mK 
Density 8.37 g/cm³ 

Specific Heat 461 J/kg °C 
Coefficient of Thermal Expansion 11 µm/m°C 

  

Nimonic alloy-75 was cut by an untreated brass tool and 

a cryogenically treated brass tool, which was treated to -

184°C. Cryogenic treatment is also known as cryogenic 

processing. It is a special type of cold treatment method, 

where the metals are exposed to very low temperatures to 

improve various mechanical properties of the materials. In 

this method, the metals are cooled to very low temperatures, 

i.e., up to -190°C. By using this method, manufacturers can 

improve the performance and durability of metals and alloys. 

Cryogenic treatment methods can be categorized based on 

the soaking temperature into two main types. The first 

method, known as the SCT method, was established by early 

investigators to boost the performance of softer materials like 

steel and its alloys. This method involves soaking the 

Abbreviations 
ANOVA  Analysis of Variance 
CT  Cryogenic Treated 
EDM  Electric Discharge Machining 
EDS  Energy Dispersive Spectroscopy 
MH  Micro Hardness  
MRR  Material Removal Rate 
SEM  Scanning Electron Microscope 
SR  Surface Roughness 
TOFF  Pulse time off 
TON   Pulse time on 
VA  Vertex Angle 
WEDM  Wire Electric Discharge Machining 
WF  Wire Feed Rate 
WT  Wire Tension 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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materials from -70°C to -140°C. Later, the deep cryogenic 

treatment (DCT) method was developed for super-hard 

materials, using a temperature from -140°C to -196°C to 

achieve even greater performance improvements. The 

Schematic diagram of Cryogenic process as shown in Figure1. 

 
Figure1. Schematic diagram of cryogenic process 

3. Experimental flow chart 

In this research study, the following experimental 

process was conducted throughout the investigation as 

shown in Figure 2. Both treated and untreated brass tools 

were utilized for machining the Nimonic alloy 75. The 

parameters evaluated included WF, WT, Ton, and Toff to 

optimize the MRR, microhardness, and vertex angle. 

 

 

Figure 2. Flow diagram for experimental process 

 

 

 

 

4. Specifications of cryogenic-treatment setup 

The cryogenic chamber is made up of a stainless-steel 
body to resist corrosion, with proper insulation. The volume 
of the chamber is 1000 L. The temperature control range is up 
to -184°C. Power supply range is 230V. Liquefied nitrogen gas 
is used as a medium, with 300 psi pressure.   A cryogenic plant 
is used to maintain the metals at very low temperatures, such 
as -184°C, and a liquified nitrogen gas LN2 (purity ≥ 99.9%) 
is used as a cryogenic fluid. The storage tank supplies the gas 
to the chamber by means of control valves. A temperature 
control unit is arranged in the chamber. The brass tool is 
placed in a cryogenic handling chamber, as shown in Figure 3, 
to enhance various mechanical properties. The process 
begins with the brass wire at room temperature, roughly 
25°C. The chamber is then evacuated and filled with nitrogen 
gas. The cryogenic treatment involves three stages: ramp 
down, soaking, and ramp up, shown in Figure 4. 
• During the ramp-down stage, the temperature was slowed 

down to -184°C at a rate of 1°C per minute. 
• The wire is then soaked at this temperature for 24 hours. 
• Finally, in the ramp-up stage, the temperature was raised 

back to 25°C at a rate of 1°C per minute, and no tempering 
was considered. 

 
Figure 3. (a) Cryogenic treatment equipment (b) Wire placed inside 
the chamber         

 

 
Figure 4. Time -Temperature cure considered without tempering 

4.1 Electrical conductivity of brass wire  
The electrical resistivity of brass wire was measured by 

the four-probe electrical resistivity testing method. The brass 
wire is placed on the platform, and four equally spaced probes 
are touched to the wire at four places as shown in Figure 5. 
From the two outer probes, current was passed, and the 
voltage drop was found using two inner probes. This will 
permit the exact circulation of electrical resistivity [32]. A 500 
mm length of brass wire was taken for testing. Three CT and 
untreated wire samples were tested, and the average value of 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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conductivity was plotted in the table for both wires. The 
electrical conductivity of treated and untreated brass wires 
was compared, and the results are summarized in the Table 2. 
After treatment, the brass wire's electrical conductivity rose 
by 23.88%. 

 
Figure 5. Testing Electrical Resistivity of cryo-treated brass wire 

 
Table 2. Electrical conductivity of brass wire before and after CT 

Tool Chemical  Conductivity 

 
material 

constituent   in S/m 

    Before 
CT 

After CT Rise 
in % 

Brass  Cu 60%, 
Zn40%  

15.567 x 
106 

19.285 x 
106 

23.88 

 

5. Experimental methodology 

The tests were performed by means of an Electronica 
Sprint cut wire EDM machine with Nimonic Alloy 75 material, 
measuring 200 mm x 100 mm x 2 mm. This machining process 
was followed by a cryogenic treatment. The experimental 
setup is as shown in Figure 6. 

 
Figure 6. (a) Electronica sprint cut wire EDM setup, (b) Fixing of 
Nimonic alloy 75 sheets on Wire cut EDM table, (c) Machined Nimonic 
alloy 75 sheets 

5.1 Video profile projector 
A video profile projector is an optical precision 

measuring instrument that magnifies and projects a 

machined profile onto a computer screen. This tool allows for 

accurate measurement of the profile's dimensions and is 

widely used for inspecting manufactured components. Once 

the machining process is complete, the vertex angle is 

measured using the video profile projector.  

5.2 Material removal rate 
The experiments utilized brass wires 0.25 millimeters in 

diameter. To achieve outcomes, a digital stopwatch was 

employed to record the time taken for each experiment. A 

total of three trials were conducted to reduce the likelihood of 

errors. The MRR was intended to be used using the following 

equation: 

 MRR=Lt/T   mm2/min           (1) 
In this equation:  
"L" denotes the length of the trimmed cut.  
"t" stands for the thickness of the part, and  
"T" represents the total duration of the machining process. 

5.3 Microhardness  
Microhardness is one type of mechanical property in 

which the material's surface is tested by applying a load using 
an indenter. Microhardness testing is similar to hardness 
testing but focuses on a small area. A load of 15 to 1000 gf can 
be applied, and the microhardness of the material can be 
evaluated. A microscope with a certain magnification can be 
used for observing indentations on the surface of the 
specimen and can evaluate the microhardness of the material. 
For each sample, the average of three readings was taken.  

5.4 Vertex angle 
The angle formed between the slots machined by the 

wire is referred to as the vertex angle, and it is measured in 
degrees. Depending on the geometry of the workpiece, the 
machined vertex angle was maintained at a constant of 60° 
shown in Figure 7. The deviation of the machined vertex angle 
was tested using a video profile projector. The average value 
of the vertex angle was taken from the bottom side and top 
side of the machined plate for 9 slots. The main process 
parameters that were selected are T on, T off, wire feed rate, 
and wire tension in three levels as shown in Table 3. 

 
Figure 7. (a) Machined Nimonic alloy 75 sheet (b) Detailed view of 
machined slot 

Table 3. List of controlling factors and levels 

 

6. Investigational outcomes of Non cryogenic and 

cryogenic treated tool 

The experimental results of material removal rate, 

microhardness, and vertex angle are shown in Table 4 with a 

non-cryogenic treated brass tool by considering Ton, Toff, 

WT, and WF. 

 

 

Process  Symbol  Level 1 Level 2 Level 3 

variable  

Ton (µs)  A 105 115 125 

T off (µs) B 40 50 60 

Wire feed 
rate 

C 3 6 9 

(mm/min)  

Wire tension 
(N)  

D 4 8 12 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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Table 4. Experimental results with Non cryogenic treated tool 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The experimental results of material removal rate, 

microhardness, and vertex angle are shown in Table 5 with a 

cryogenic treated brass tool by considering Ton, Toff, WT, and 

WF. 

6.1 Comparison of MRR with cryogenic treated and non-
treated wires under different parameters 
The first graph shows that the MRR increases as the Ton 

value rises. Additionally, the MRR is higher for the treated tool 

than the non-cryogenically treated tool. However, in the 

second graph, it can be detected that as the value of Toff rises, 

the MRR declines for both types of wire. The overall value of 

the MRR has decreased due to a rise in the WF for both 

cryogenic and non-cryogenic treated wire. Initially, the MRR 

decreased with a rise in WT, but as the WT continued to rise, 

the MRR began to increase again as shown in Figure 8. 

6.2 Comparison of microhardness with cryogenic 
treated and non-treated wires under different 
parameters 
From Figure 9, the microhardness value tends to 

increase with a rise in Ton. Additionally, the overall 

microhardness of cryogenically treated wire is higher than 

that of non-treated wire. In the second graph, which plots 

microhardness against Toff, it shows that microhardness 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

increases with higher values of Toff but then decreases when 

the value of Toff continues to increase further. The 

microhardness value decreased with an increase in WF, then 

increased again with a higher WF for both cryogenically 

treated and untreated wires. As the wire tension increases, 

the microhardness value rises, and further, as the wire 

tension increases, the hardness increases for both 

cryogenically treated and non-treated wires. 

6.3 Evaluation of vertex angle with cryogenic treated 
and non-treated wires under different constraints 
The graph above illustrates in Figure 10 how the Ton 

value affects the vertex angle. It shows that the vertex angle 

slightly decreases as the Ton value increases for both 

cryogenically treated and non-treated wires. Additionally, the 

vertex angle decreases when the Toff value increases, but 

then it rises again as the Toff value continues to increase for 

both types of wires. The vertex angle increases with the wire 

feed rate in both cryogenic-treated and non-treated cases. 

However, after a certain point, further increases in the WF led 

to a reduction in the vertex angle, as illustrated in the graph. 

The trend for the WF follows a similar pattern.  

 

No. Ton (µsec) Toff (µsec) WF (mm/min) WT (N) 

With Non cryogenic treated tool 

MRR (mm2/min) MH (N/mm2) VA  (degree) 

1 105 40 3 4 5.427 256 60.735 

2 105 50 6 8 6.282 274 60.985 

3 105 60 9 12 5.273 379 60.758 

4 115 40 6 12 6.346 315 60.915 

5 115 50 9 4 7.823 423 60.559 

6 115 60 3 8 5.213 403 60.873 

7 125 40 9 8 6.722 489 60.721 

8 125 50 3 12 10.65 465 60.684 

9 125 60 6 4 8.387 346 60.853 

 

Table 5. Experimental results with cryogenic treated tool 

No. Ton (µsec) Toff (µsec) WF (mm/min) WT (N) 

With Cryogenic treated tool 

MRR (mm2/min) MH (N/mm2) VA  (degree) 

1 105 40 3 4 6.427 266 60.156 

2 105 50 6 8 6.828 282 60.129 

3 105 60 9 12 7.275 391 60.278 

4 115 40 6 12 6.526 382 60.092 

5 115 50 9 4 8.913 458 60.119 

6 115 60 3 8 6.203 453 60.172 

7 125 40 9 8 7.024 478 60.183 

8 125 50 3 12 12.05 459 60.159 

9 125 60 6 4 9.584 358 60.214 

 

 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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Figure 8. Assessment of MRR with cryogenic treated and non-treated wires under different parameters 

Figure 9. Assessment of microhardness with cryogenic treated and non-treated wires under different parameters 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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7. Results and discussions 

The experimental work, known as the Design of 
Experiments, was conducted on a Nimonic alloy 75 sheet 
using both cryogenically treated and untreated brass wire, 
following the L-9 OA Taguchi method. The process outcomes 
evaluated included Material removal rate, microhardness, 
and vertex angle, while considering process variables such as 
Ton, Toff, WF, and WT to optimize the results. Tables for S/N 
ratios for MRR, MH and VA have shown below. The S/N ratios 
of MRR, MH, and VA are shown in Table 6 by considering Ton, 
Toff, WF, and WT in three levels. The ANOVA for MRR, MH, 
and VA are shown in Table 7 by considering Ton, Toff, WF, and 
WT in three levels. The MRR ANOVA results indicate that Ton 
(42.7%) and Toff (34.06%) are the most influential 
parameters, both of which are statistically significant at the 
95% confidence level (p = 0.029 and p = 0.036, respectively). 
Although WF exhibited statistical significance (p = 0.016), its 
contribution was negligible (1.93%), indicating limited 
practical importance. WT contributed 21.31%, but the 
difference was not statistically significant (p = 0.231). 
Therefore, Ton and Toff are the primary factors influencing 
the machining response. The MH ANOVA results indicate that 
Ton (p = 0.043; 56.93% contribution) and WF (p = 0.021; 
31.52% contribution) are statistically significant at the 95% 
confidence level, together explaining approximately 88.5% of 
the total variation. Therefore, machining performance is 
primarily influenced by Ton and WF, whereas Toff and WT 
contribute marginally. 

 

 

 
Table 6. Result analysis of S/N Ratios for MRR, MH and VA 

 

S/N ratios for MRR 

Level Ton Toff WF WT 

1 16.69 16.46 17.88 18.26 

2 17.05 19.1 17.54 16.49 

3 19.39 17.57 17.72 18.38 

Delta 2.7 2.64 0.34 1.89 

Rank 1 2 4 3 

S/N ratios for MH 

Level Ton Toff WF WT 

1 49.78 51.24 51.62 50.93 

2 52.66 51.82 50.57 51.91 

3 52.63 52.01 52.88 52.24 

Delta 2.88 0.77 2.31 1.31 

Rank 1 4 2 3 

S/N ratios for VA 

Level Ton Toff WF WT 

1 35.59 35.58 35.59 35.59 

2 35.58 35.58 35.58 35.59 

3 35.59 35.6 35.59 35.59 

Delta 0.01 0.01 0.01 0 

Rank 2 1 3 4 

Figure 10. Assessment of Vertex angle with cryogenic treated and non-treated wires under different constraints 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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Table 7. ANOVA for MRR, MH and VA 

ANOVA for MRR 

Source DF Adj SS Adj MS 
p-

value  
Percentage 

contribution 

 Ton 2 12.947 6.4736 0.029 42.7 

 Toff 2 10.327 5.1633 0.036 34.06 

  WF 2 0.585 0.2925 0.016 1.93 

  WT 2 6.4622 3.2311 0.231 21.31 

Error 0 - - - 0 

Total 8 30.321   100 

ANOVA for MH 

Source DF Adj SS Adj MS 
p-

value  
Percentage 

contribution 

 Ton 2 28006 14003.1 0.043 56.93 

 Toff 2 1235 617.4 0.36 2.51 

  WF 2 15507 7753.4 0.021 31.52 

  WT 2 4447 2223.4 0.314 9.04 

Error 0 - - - 0 

Total 8 49195   100 

ANOVA for VA 

Source DF Adj SS Adj MS 
p-

value  
Percentage 

contribution 

 Ton 2 0.00693 0.00347 0.042 28.44 

 Toff 2 0.01344 0.00672 0.018 55.13 

  WF 2 0.0036 0.0018 0.219 14.76 

  WT 2 0.00041 0.0002 0.314 1.67 

Error 0 - - - 0 

Total 8 0.02437     100 

 

ANOVA results for VA show that Toff (p = 0.018, 55.13%) 
is the most influential factor, followed by Ton (p = 0.042, 
28.44%), both significant at the 95% confidence level. WF 
(14.76%) and WT (1.67%) have minimal effect, indicating 
that Toff and Ton together account for over 83% of the 
variation in machining performance. 
 

7.1 Factors affecting MRR 
Better results for MRR are attained by means of 

cryogenically treated wire compared to a non-treated tool. 

The graph in Figure 11 illustrates how the parameters of Ton, 

Toff, WF, and WT affect MRR. According to the graph, the 

optimal combination identified is A3B2C1D3, which 

corresponds to a Ton of 125 µs, a Toff of 50 µs, a WF of 3 

mm/min, and a WT of 12 N. The optimized MRR obtained 

from the L9 orthogonal array is 12.05 mm²/min. The S/N 

ratios for MRR on Nimonic Alloy 75 using a cryogenically 

treated brass electrode, along with the percentage 

contribution to MRR according to ANOVA, are presented in 

Figure 11. Analysis displays that the Ton is the greatest 

influential parameter on MRR when using cryogenically 

treated wire. In contrast, the WF is the least influential 

parameter, as shown in Figure 12. 

7.2 Factors affecting microhardness 
The best results for microhardness (MH) are achieved by 

means of cryogenically treated wire associated with non-

cryogenically treated tools. The graph illustrates how various 

parameters, specifically the Ton, Toff, WF, and WT, affect MH. 

According to the graph in Figure 13, the optimal combination 

of these parameters is A2B3C3D3, which corresponds to a 

Ton of 115 µs, a Toff of 60 µs, a WF of 9 mm/min, and a WT of 

12 N. The microhardness value of the material does not match 

any one of the nine combinations of the L9 orthogonal array, 

so the optimized value confirmation test was used and 

estimated as 510 N/mm². The S/N ratios for microhardness 

measurements on Nimonic Alloy 75 with a cryogenically 

treated brass electrode, along with the percentage 

contribution regarding microhardness as per ANOVA, are 

presented in Figure 13. Analysis shows that the parameter 

Ton greatly influences the microhardness number when 

machining with cryogenically treated wire. In contrast, the 

Toff rate has the least influence, as shown in Figure 14. 

 
Figure 11. Displaying the S/N ratios of MRR on Nimonic Alloy 75 

utilizing the Cryogenic treated brass electrode 

 

Figure 12. Percentage contribution on MRR with respect to ANOVA 

 

 
Figure 13. Illustrating the S/N ratios of Micro Hardness for Nimonic 

Alloy 75 utilizing the Cryogenic treated brass electrode 



Saidulu G & P Prasanna/Future Technology                                                                       February 2026| Volume 05 | Issue 01 | Pages 01-12 

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Figure 14. Percentage contribution on Microhardness with respect 

to ANOVA 

 

7.3 Factors affecting vertex angle 
Analysis shows from Figure 15 that Ton is the most 

effective parameter on MH when machining with 
cryogenically treated wire. In contrast, Toff is the least 
influential parameter. The results for the Vertex Angle (VA) 
were obtained using cryogenically treated wire compared to 
untreated tools. The accompanying graph illustrates how the 
parameters of Ton, Toff, WF, and WT influence VA. According 
to the graph, the optimal combination identified is A2B2C2D2. 
This combination corresponds to a Ton of 115 µs, a Toff of 50 
µs, a WF of 6 mm/min, and a WT of 8 N. The optimum value 
for VA cannot be selected from the L9 Orthogonal Array, as it 
does not match any values within the array. A confirmation 
test has determined the value of VA to be 60.279. The S/N 
ratios of the vertex angle for Nimonic alloy 75 with the 
cryogenically treated brass electrode, as well as the 
percentage contribution related to the vertex angle according 
to ANOVA, are illustrated in Figure 15. 

Analysis shows that Toff is the most influential 
parameter on VA when machining with cryogenic-treated 
wire. In contrast, wire tension is the least influential 
parameter, as illustrated in Figure 16. The SEM image of 
sample No. 5 is shown in Figure 17. This figure highlights the 
following features: A - blowholes, B - spherical globules, C - 
craters, D - microholes, E - debris, and F - microcracks. 

 

Figure 15. Displaying the S/N ratios of Vertex angle on Nimonic alloy 

75 using the Cryogenic treated brass electrode 

 
 
Figure 16. Percentage contribution on Vertex angle with respect to 

ANOVA 

 

 
Figure 17. SEM image of machined sample No.5 with untreated brass 

wire 

The various features are observed in the SEM image of 

Nimonic alloy 75 sample no. 5 after machining with untreated 

brass wire; those are blowholes, spherical globules, craters, 

microholes, debris, microcracks, etc. EDS result of sample no. 

5 as shown in Figure 18, which shows various elements like 

C,O, Mn, Si, Ti, Cr,Fe, Ni, and Cu. The composition of sample 

No. 5 is presented in the Table 8, showing the weight and 

percentage differences before and after analysis. The SEM 

image of sample No. 6 is illustrated in Figure 19.  

 Table 8. Chemical composition of sample No.5 

 

Element 
Before 

Weight% 
After 

Weight% 
% Difference 

C K 0.08 9.64 -9.56 

O K 0 19.71 -19.71 

Mn K 1 0.15 0.85 

Si K 1 0.94 0.06 

Ti K 0.2 0.38 -0.18 

Cr L 18 14.55 3.45 

Fe L 5 -1.67 6.67 

Ni L 74.22 29.72 44.5 

Cu L 0.5 26.58 -26.08 

Totals 100 100 0 



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Figure 18. EDS result of sample No.5 with graph 

 

 
Figure 19. SEM image of machined sample No.6 with CT brass wire 

 

 
Figure 20. EDS result of sample No.6 with graph 

Table 9. Chemical composition of sample No.6 

Element 
Before 

Weight% 
After 

Weight% 
% Difference 

C K 0.08 8.05 -7.97 

O K 0 18.59 -18.59 

Mn K 1 0.06 0.94 

Si K 1 0.62 0.38 

Ti K 0.2 0.68 -0.48 

Cr L 18 10.59 7.41 

Fe L 5 3.33 1.67 

Ni L 74.22 34.89 39.33 

Cu L 0.5 23.19 -22.69 

Totals 100 100 0 

 

Figure 19 highlights the following features: A - craters, B - 

spherical globules, C - debris, D - blowholes, and E - 

microholes. The various features are observed in the SEM 

image of Nimonic alloy 75 sample no. 6 after machining with 

cryogenically treated brass wire; those are blowholes, 

spherical globules, craters, microholes, debris, etc. EDS result 

of sample no. 5 as shown in Figure 20, which shows various 

elements like C,O, Mn, Si, Ti, Cr,Fe, Ni, and Cu. The composition 

of sample No. 5 is presented in the Table 9, showing the 

weight and percentage differences before and after analysis. 

8. Conclusion 

After CT, the electrical conductivity of the brass wire rose 
by 23.88% when compared to the untreated brass wire due 
to relieving internal stresses, microstructural changes, and 
increased density. Because of higher conductivity, a greater 
amount of heat will be liberated; this leads to a rise in MRR. 
Cryogenically treated (CT) brass wire shows a smoother 
microstructure, free from scratches and imperfections, 
compared to untreated wire. Increasing Ton raises MRR and 
microhardness, while higher Toff reduces microhardness. 
Wire feed (WF) and wire tension (WT) also increase 
microhardness. The vertex angle increases with Ton but 
remains higher for non-treated wire across Toff, WF, and WT 
conditions. SEM images of Nimonis alloy 75 samples revealed 
craters, globules, debris, blowholes, and micro-holes in both 
wires, but no micro-cracks were observed with the CT wire. 
EDS analysis showed reduced Ni and Cr and increased Cu due 
to continuous flushing and higher heat energy. Overall, CT 
brass wire provides higher MRR, better surface quality, no 
micro-cracks, and improved efficiency, reducing material 
waste. This approach is cost-effective and can be applied to 
machining hard aerospace and nuclear alloys. Residual 
stresses in Nimonic alloy 75 can be investigated using 
cryogenically treated brass wire. Additionally, the 
performance of treated molybdenum wire may be examined 
and compared with that of untreated wire to determine 
optimal conditions. 

Ethical issue 
The authors are aware of and comply with best practices in 
publication ethics, specifically with regard to authorship 
(avoidance of guest authorship), dual submission, 
manipulation of figures, competing interests, and compliance 
with policies on research ethics. The authors adhere to 
publication requirements that the submitted work is original 
and has not been published elsewhere. 

Data availability statement 
The manuscript contains all the data. However, more data will 
be available upon request from the authors. 

Conflict of interest 
The authors declare no potential conflict of interest. 

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