Influence of machining behavior on severe deformation and corrosionresistance of end milled Nimonic 263 alloy

S GOWTHAMAN1,* , T JAGADEESHA2 and V DHINAKARAN1

1Centre for Additive Manufacturing and Computational Mechanics, Chennai Institute of Technology, Chennai,

India2Department of Mechanical Engineering, National Institute of Technology, Calicut, India

e-mail: gowthammurali1991@gmail.com

MS received 15 January 2021; revised 31 July 2021; accepted 12 August 2021

Abstract. In this study, the critical effects of variants in machining behavior on the microcrystalline char-

acteristics and its dependence on the corrosion as well as Impedance behavior of the machined Nimonic 263

alloy have been investigated. Because the resulting effect, which arises from the machining process (slot

milling) with varying cutter nomenclature or terminology (Radial Rake Angle (RRA)) and machining conditions

(cutting feed) under constant Minimum Quantity Lubrication (MQL) flow rate plays a vital role in severe

deformation process (SDP) on the machined work surface. Additionally, the Electrochemical Impedance

Spectroscopy (EIS) analysis has been conducted over the SDP processed surface to analyze the influence of

variants in machining behavior over the corrosion performance through the impedance of machined samples and

from the above experimentation, it is stated that the SDP through slot milling has a superior influence on the

corrosion and EIS behavior leads to reduction in the resistance against the corrosion tendency of the machined

samples related to the nascent Nimonic 263 sample.

Keywords. Slot milling; deformation and fracture; Nimonic 263; X-ray techniques; corrosion.

1. Introduction

Nimonic 263 is a significant structural material, owing to its

greater inherent features such as corrosion resistance and

modulus of impedance. But, these inherent features are

exclusively influenced by the microcrystalline characteris-

tics of the material. Slot or end milling process is a sig-

nificant and final surface finishing process in various

industrial sectors but along with this surface finishing

process, it invokes more SDP outcome over the machined

surface, owing to the occurrence of massive temperature

and pressure formation over the cutting zone. Rashid et alhave stated that the amendment in cutter terminology is a

prime factor to invoke better shear angle reduction and

offers superior variants in machining behavior [1]. Gow-

thaman et al also have stated that the cutter terminology has

a superior outcome on the surface integrity of machined

nickel samples related to the machining conditions, owing

to its greater shear angle reduction [2]. Lee et al and many

other researchers also shown that the mechanical defor-

mation such as SPD using mechanical method is an easy

and effective way for modifying the surface properties as a

directional dependence with higher accuracy [3, 4]. Addi-

tionally, Shin et al have studied the deformation

mechanism during SPD process and stated that the shearing

of material along the shear plane has a significant role over

the deformation mechanism [5]. Further, Brown et al havequoted that the SDP process on the work surface leads to

upsurge the surface properties through the formation of

more fine grains and microstructural heterogeneity [6].

Additionally, Dugsted et al also have confirmed that the

increment in grain modification is a key factor to ascend the

microstructural heterogeneity and corrosion tendency on

the machined work surface [7]. But, Korchef et al havediscovered that the SDP on any material surface shows a

major reduction in the corrosion resistance, due to the

formation of more grain refinement and dislocation density

[8]. Li et al and Rofagha et al have analyzed the SPD effect

on the grain refinement and surface reactivity of active

metals such as copper and they stated that the grain

refinement has an inverse relationship with the corrosion

rate, due to the increment in chemical affinity and grain

boundary area [9, 10]. Wang et al also have discovered the

effect of grain orientation on the dissolution rate of alloy

690 and insist that the grain orientation such as high angle

and low angle grain boundary has a complex and substan-

tial outcome on the dissolution rate and corrosion resistance

of the material [11].

Through the comprehensive reviews of the above arti-

cles, it is clear that the cutter nomenclature and machining*For correspondence

Sådhanå (2021) 46:192 � Indian Academy of Sciences

https://doi.org/10.1007/s12046-021-01726-w Sadhana(0123456789().,-volV)FT3](0123456789().,-volV)

process conditions have important effect on the corrosion

behavior of any material. This study has been intended to

analyze the outcome of cutter nomenclature and machining

process condition over the microcrystalline characteristics

and corrosion behavior of SPD processed samples as well

as a comparison has been made with the as-received sam-

ple. This prime objective of this study is to analyze the

effect of machining behavior to increase the surface

features.

2. Materials and methods

In the present work, the Nimonic 263 (as-received) alloy

has been considered for machining operation which is

commonly used for various medium-range temperature

applications and it mainly consists of nickel, molybde-

num, chromium, manganese and titanium as key alloying

elements. The slot milling operation has been carried out

using (Agni BMV45) vertical machining center and

coated (TiAlN) tungsten carbide cutter with various RRA

(helix and axial rake angles of 30� and 10� are kept

constant) to explore its critical effects. For investigation,

a broad range of cutting feed (mm/min) (2 [A], 15

[B] and 45 [C]) and RRA (-7o [N], 0o [Z] and ?7o [P])

has been considered under constant MQL flow rate (7 ml/

min), axial depth of cut (0.6 mm) and cutting speed

(15.7 m/min), due to its negligible influence over the

machining behavior related to the cutting feed. The

machining behavior variations during slot milling process

has been computed using Kistler dynamometer and

acquisition setup (figure 1a) which helps to acquire the

cutting force as a function of time [12]. For simplifica-

tion, the [ij] representation (representations are cited in

brackets) is used in this entire study to denote the cutter

nomenclature (notation i) and machining conditions (no-

tation j), respectively. Additionally, the XRD spectral

analysis (scan rate of 3�/min) has been carried out to

evaluate the microcrystalline characteristics using Wil-

liamson-hall method. The dislocation density (1/crystallite

size2) over the machined surface has been computed to

analyze the effect of machining of behavior and its

impact on the corrosion features of machined samples

[13]. Furthermore, the EIS analysis has been conducted

on the machined and as-received samples (Platinum wire

mesh and saturated calomel electrode (KCl) as in figure 1

are used as a counter and reference electrode in 3.5 wt %

NaCl solution) under a scan rate of 0.166 mv/s to analyze

the influence of machining behavior on the corrosion and

modulus of impedance behavior of SDP and as-received

samples using simplified Randle’s circuit (frequency and

amplitude range of 10 mHz to 100 kHz and ?10 mV to

-10 mV, respectively) [14].

The impedance of an electrical circuit is represented as

follows

Z ¼ aþ jb ð1Þwhere a, b and j represent the resistive part (due to resistor)

and reactive part (due to capacitor) of an electrical circuit

and j imaginary number (j2 = -1), respectively. The

impedance (Z) of an electrical circuit measures the resis-

tance against the flow of current under the influence of

applied voltage and the phase angle (h) helps to measure

the phase difference between the resistive part and impe-

dance vector. The modulus of impedance and phase angle

of a randles circuit are computed using equations (2) and

(3).

Zj j ¼ a2 þ b2 ð2Þ

h ¼ tan�1 b

að3Þ

3. Results and discussions

The slot milling process has been performed on the as-

received Nimonic 263 samples under various cutter

nomenclature and machining conditions and the transfor-

mations are presented in the following subsections.

3.1 Effect of machining behavioron microcrystalline characteristics

To evaluate the nature of influence of cutter nomenclature

and machining conditions, the machining behavior and its

variants are examined and demonstrated (cutting force

along normal to feed directions) in figure 2.

The illustration (figure 2) obviously discloses the impact

of RRA and machining conditions on the variants in

machining performance during successive machining pro-

cess, owing to the existence of severe pressure and tem-

perature during machining process [2, 12]. Besides, the

XRD spectral analysis has been used to evaluate the

influence of variants in machining behavior over the

transformations in microcrystalline characteristics and they

are presented in figure 3.

The demonstration in figure 3 clearly shows the effect of

machining conditions and cutter nomenclature on the XRD

spectra of machined samples compared to the as-received

sample and additionally, it is stated that the nascent sample

is attributed to the face centered cubic system with the

lattice parameter of 3.57 A. Moreover, the observed dis-

similarities in the XRD spectra clearly indicate the influ-

ence of invoked strain and size effect, owing to the

presence of various crystal defects over the machined sur-

face and it reflects in the microcrystalline characteristics

such as lattice strain and crystallite size [8]. Amongst

various crystal defects, the line and planar defects are the

most commonly occurring defects in machining processes

192 Page 2 of 9 Sådhanå (2021) 46:192

through the formation of more dislocations and stacking

fault. The presence of peak broadening in figure 3d and 3e

clearly discovers the existence of lattice distortion and

disorder on the machined surface which lead to increase

more dislocation and fine grains. For example, the observed

variants in the microcrystalline characteristics are minimal

in the machined sample at the lowest cutting feed, owing to

the existence of lowermost strain toughening and thermal

soothing effects [6]. Further, successive increment in cut-

ting feed (up to 15 and 45 mm/min), the observed crystallite

size and dislocation density are moderate and high, due to

the interactive outcome of thermal soothing and strain

toughening effect [15]. These variations lead to increase the

overall area of grain boundaries and grain refinement on the

machined work surface compared to the as-received sample

as demonstrated by Shin et al [5]. The above illustration

noticeably reveals that after machining at a 15 mm/min

cutting feed, it exhibits a maximum reduction in crystallite

size of up to 26 lm, due to the superior outcome of strain

toughening effect. Normally, the movements of

Figure 1. (a) Machining setup, (b) Cutting force acquisition setup, (c) Ametek electrochemical instrument, (d) Electrode setup and

(e) Schematic diagram of corrosion setup.

Sådhanå (2021) 46:192 Page 3 of 9 192

dislocations are transpired alongside of grain and through

grain boundaries which arise the stress filed along grain

boundaries. The similar tendency (lattice strain) is observed

for the dislocation density ( 1Crystallitesize2

), due to the forma-

tion of more grain refinement and crystal defects which

leads to offer better enhancement in surface properties

through grain boundary strengthening according to Hall-

Petch relationship (equation (4)) [16, 17].

r ¼ ro þ kffiffiffi

dp ð4Þ

where r, ro, k and d are the novel yield stress, initial yield

of as-received sample, strengthening coefficient and grain

diameter, respectively [8]. Additionally, the present grain

orientations are the prime and influential factors for the

stress field vector, surface energy and dissolution rate on

the work surfaces according to Wang et al [11]. The grain

orientation of as-received sample (Figures 3a-c) exhibits

more uniform orientation compared to the SPD processed

samples. It occurs due to the accrued dislocation which

leads to intensify the refinement and stress among the

grains. This accrued dislocation and refinement in grain on

the SPD processed surface leads to increase in the varia-

tions in crystallite orientation as mentioned by Alvarez et al[17]. Besides, the maximum fraction of grains are oriented

on (111) plane direction compared to (200), (220) and (311)

plane directions, which arises due to the formation of tex-

ture over the machined work surface. Normally, the grain

oriented towards (110) directions dissolve faster in acidic

solution, due to the presence of lowest surface energy

compared to (200), (220) and (311) plane directions as

demonstrated in Wang et al and it leads to decrease the

corrosion resistance of machined work surface [11].

Additionally, the introduction of this stress field leads to

invoke the formation of more dislocations and evolution of

more stress field around the grain. The correlation between

the stress field and dislocation is as in eq. (5)

Figure 2. Cutting force along Normal to feed directions. (a) Positive, (b) Negative and (c) Zero RRA cutter.

192 Page 4 of 9 Sådhanå (2021) 46:192

Figure 3. XRD spectrum of (a) Zero, (b) Negative, (c) Positive RRA cutter XRD spectrum, (d) Disorder with XRD Peak broadening,

(e) Peak shift, (f) Effect of various machining conditions on microcrystalline characteristics and (g) Dislocation density.

Sådhanå (2021) 46:192 Page 5 of 9 192

Figure 4. (a) Equivalent Electrical Circuit Bode impedance plot and nyquist plot of (b) As-received, (c) PA, (d) ZA, (e) NA samples,

(f) Modulus of Impedance (Max) and g) Phase angle.

192 Page 6 of 9 Sådhanå (2021) 46:192

r ¼ Gb

rð5Þ

where r, G, r and b are the stress, shear modulus, stress

field distance and burger vector, respectively. This variation

in grain boundary energy is a higher influential parameter

on etching and formation of more dislocations which lead

to increase in the activation energy and chemical affinity of

work surface. Among various cutting conditions, PL cutting

condition (Positive RRAcutter with a table feed of 40 mm/

min) offer more uniform and equiaxed grains followed by

PC cutting condition (positive RRAcutter with a table feed

of 15 mm/min), due to higher and dominant effect of strain

hardening compared to the thermal softening effect and

they lead to induce the minimal modifications in the cor-

rosion behavior of machined work surfaces. Based on the

above analyses, it is stated that the variants in machining

behavior through the slot milling process leads to ascend

the reduction in microcrystalline characteristics and tailor

the surface characteristics [18].

3.2 Effect of machining behavior on EIS Studies

The effects of SDP process over the corrosion behavior

such as Modulus of impedance and phase angle have been

analyzed through EIS method using Randle’s circuit (fig-

ure 4a) and a comparative study has been presented in the

following section. In figure 4a Rs, CPE and Rq represent

the solution resistance, Capacitive Phase Elements (CPE)

and resistance of work surface, respectively.

The illustration in figure 4 noticeably shows the effect of

variants in machining behavior over the corrosion behavior

such as modulus of impedance and phase angle (due to the

interactive effect of solution and SDP processed surface) of

the machined samples related to the as-received samples

and it is stated that the observed tendency is similar and

irrespective of cutter nomenclature with some numerical

dissimilarity, owing to the existence of more disorder and

dislocation density. Additionally, it is understood that the

as-received samples exhibit the higher impedance charac-

teristics (3.5±0.001 9 104 ohm cm2), related to the

machined samples, owing to the establishment of more-

coarse crystallite size and minimal dislocation density over

the work surface [7, 18]. Subsequently, the machining

process through the aid of the cutter with positive RRA at a

2 and 15 mm/min cutting feed shows the modulus of

impedance of 3 9 104 ohm cm2 and 2.9 9 104 ohm cm2,

owing to the introduction of lowermost strain toughening

outcome during slot milling process. But it is not appro-

priate, due to its minimal productivity and higher cost of

production. Amongst several machining circumstances, the

cutter with positive RRA provoke enhanced modulus of

resistance trailed by a cutter with zero RRA machined work

surface, owing to its minimal SPD effect and reduction in

grain size compared to the zero and negative RRA cutter

machined work surfaces and the observed tendency is

similar and irrespective of cutting conditions except some

numerical dissimilarity. Amongst various cutter nomen-

clature and machining circumstances, the cutter with posi-

tive RRA machined sample has higher modulus of

impedance followed by the cutter with zero and negative

RRA machined samples which lead to induce better cor-

rosion resistance compared to other machined samples.

Further, the phase angle analysis also illustrates that the

upsurge in variants of machining behavior leads to offer the

lowermost corrosion resistance related to the as-received

samples. From the above observations, it is understood that

(figure 4e), the positive RRA cutter processed sample

shows higher corrosion resistance, owing to the presence of

higher phase angle and modulus of impedance against the

flow of current related to the machined samples [19, 20].

Through the above interpretations, it is concluded that, the

positive radial rake angle cutter along with the MQL cut-

ting environment offers better corrosion resistance, owing

to the occurrence of negligible SDP effect and variants in

grain size which induces better corrosion resistance.

3.3 Comparative studies on the effect of RRAand machining conditions on corrosion behavior

The schematic representation of the effect of cutter

nomenclature and machining conditions on the corrosion

resistance of slot milled Nimonic 263 has been discussed as

follows.

This entire study clearly shows the influence of

machining behavior over the variations in corrosion

behavior such as Corrosion Rate (C.R), and microcrys-

talline characteristics machined samples related to the as-

received sample (figure 5). Additionally, it clearly confirms

that the nascent sample exhibits superior material features

trailed by a positive and zero RRA cutter processed sam-

ples. Negative RRA cutter machined work surface exhibits

Figure 5. Schematic representation of the effect of cutter

nomenclature and machining conditions on the corrosion

resistance.

Sådhanå (2021) 46:192 Page 7 of 9 192

least corrosion resistance which was mainly recognized the

highest reduction in grain size. Further, it concludes that the

grain refinement through SPD process leads to increase in

the tendency against corrosion and among various

machining conditions, the machining with a 15 mm/min

table feed under positive RRA cutter offer enhanced cor-

rosion behavior and material features.

4. Conclusion

The examination of the operational slot milling under

varying cutter terminology and machining circumstances

has been investigated. The major observations of this study

have been summarized as follows:

1. The effect of machining conditions and cutter nomen-

clature on microcrystalline characteristics and deteriora-

tion resistance of slot milled Nimonic 263 has been

investigated and found that the cutter nomenclature has a

highest influence over the microcrystalline characteris-

tics such as microstructure, etc. and corrosion resistance

related to the cutting conditions.

2. Corrosion behavior of slot milled sample discovers an

ineffective evolution with decline in cutter terminology

and increment in cutting feed.

3. Amidst various machining process conditions, the cutter

with the positive RRA invokes superior corrosion

resistance trailed by a cutter with zero and negative

RRA which leads to inhibit the corrosion tendency of

work surfaces.

4. Additionally, the EIS analysis shows that the positive

radial rake angle cutter exhibits better resistance against

the corrosion tendency and corrosion fatigue related to

the negative and zero RRA cutter, owing to the presence

of better machining behavior and microcrystalline

characteristics.

Acknowledgements

This research work did not receive any specific grant from

funding agencies in the public, commercial, or not-for-

profit sectors.

References

[1] Rashid W B, Goel S, Davim J P and Joshi S N 2016

Parametric design optimization of hard turning of AISI 4340

steel (69 HRC). Int. J. Adv. Technol. 82(1–4): 451–462.

https://doi.org/10.1007/s00170-015-7337-2

[2] Gowthaman S and Jagadeesha T 2019 Effect of variation in

behavioural changes during end milling on Nimonic 263

elastic constants. Mater. Res. Express 6(12): 126504. https://doi.org/10.1088/2053-1591/ab5345

[3] Lee N S, Chen J H, Kao P W, Chang L W, Seng T Y and Su J

R 2017 Anisotropic tensile ductility of cold-rolled and

annealed aluminum alloy sheet and the beneficial effect of

post-anneal rolling. Scr. Mater. 60(5): 340–343. https://doi.org/10.1016/j.scriptamat.2008.10.036

[4] Choudhary S, Nanda V, Shekhar S, Garg A and Mondal K

2017 Effect of microstructural anisotropy on the electro-

chemical behavior of rolled mild steel. J. Mater. Eng.Perform. 26(1): 185–194. https://doi.org/10.1007/s11665-

016-2465-x

[5] Shin D H, Kim I, Kim J and Park K T 2001 Grain refinement

mechanism during equal-channel angular pressing of a low-

carbon steel. Acta Mater. 49: 1285–1292. https://doi.org/10.1016/S1359-6454(01)00010-6

[6] Brown T L, Saldana C, Murthy T G, Mann J B, Guo Y,

Allard L F, King A H, Compton W D, Trumble K P and

Chandrasekar S 2009 A study of the interactive effects of

strain, strain rate and temperature in severe plastic deforma-

tion of copper. Acta Mater. 57: 5491–5500. https://doi.org/10.1016/j.actamat.2009.07.052

[7] Dugstad A, Hemmer H and Seiersten M 2001 Effect of steel

microstructure on corrosion rate and protective iron carbon-

ate film formation. Corrosion 57(4): 369–378. https://doi.

org/10.5006/1.3290361

[8] Korchef A and Kahoul A 2013 Corrosion behavior of

commercial aluminum alloy processed by equal channel

angular pressing. Int. J. Corros. 1: 983261. https://doi.org/10.1155/2013/983261

[9] Li Y, Wang F and Liu G 2004 Grain size effect on the

electrochemical corrosion behavior of surface nanocrystal-

lized low-carbon steel. Corrosion 60(10): 891–896. https://

doi.org/10.5006/1.3287822

[10] Rofagha R, Langer R, El-Sherik A M, Erb U, Palumbo G and

Aust K T 1991 The corrosion behaviour of nanocrystalline

nickel. Scr. Metall. Mater. 25(12): 2867–2872. https://doi.org/10.1016/0956-716X(91)90171-V

[11] Wang S and Wang J 2014 Effect of grain orientation on the

corrosion behavior of polycrystalline Alloy 690. Corros. Sci.85: 183–192. https://doi.org/10.1016/j.corsci.2014.04.014

[12] Palanisamy P, Rajendran I, Shanmugasundaram S and

Saravanan R 2006 Prediction of cutting force and temper-

ature rise in the end-milling operation. Proc. Inst. Mech.Eng. Part B 220(10): 1577–1587. https://doi.org/10.1243/

09544054JEM542

[13] Gowthaman S and Jagadeesha T 2020 Experimental investiga-

tions on the effect of severe plastic deformation through end

milling on x-ray peak broadening and microcrystalline charac-

teristics of nimonic 263. Trans. Indian Inst. Met. 73(5):

1512–1526. https://doi.org/10.1007/s12666-020-01967-z

[14] ASTM International, ASTM G59-97, 2014

[15] Ozel T and Ulutan D 2014 Effects of machining parameters

and tool geometry on serrated chip formation, specific forces

and energies in orthogonal cutting of nickel-based super

alloy inconel 100. Proc IMechE Part B J. Eng. Manuf.228(7): 673–686. https://doi.org/10.1177/095440541351

0291

[16] Read W T and Shockley W 1950 Dislocation models of

crystal grain boundaries. Phys. Rev. 78: 275–289. https://doi.org/10.1103/PhysRev.78.275

[17] Alvarez M A V, Santisteban J R, Vizcaino P, Ribarik G and

Ungar T 2016 Quantification of dislocations densities in

192 Page 8 of 9 Sådhanå (2021) 46:192

zirconium hydride by X-ray line profile analysis. Acta Mater.117: 1–12. https://doi.org/10.1016/j.actamat.2016.06.058

[18] Yuan Y, Jiang Y, Zhou J, Liu G and Ren X 2019 Influence of

grain boundary character distribution and random high angle

grain boundaries networks on intergranular corrosion in high

purity copper. Mater. Lett. 253: 424–426. https://doi.org/10.1016/j.matlet.2019.07.125

[19] Saikiran A, Hariprasad S, Arun S, Rama Krishna L and

Rameshbabu N 2019 Effect of electrolyte composition on

morphology and corrosion resistance of plasma electrolytic

oxidation coatings on aluminized steel. Surf. Coat. Technol.372: 239–251. https://doi.org/10.1016/j.surfcoat.2019.05.

047

[20] Yan H, Gong X, Chen J and Cheng M 2020 Microstructure,

texture characteristics, mechanical and bio-corrosion prop-

erties of high strain rate rolled Mg–Zn–Sr alloys.Met. Mater.Int. 27: 2249–2263. https://doi.org/10.1007/s12540-019-

00601-y

Sådhanå (2021) 46:192 Page 9 of 9 192