See discussions, stats, and author profiles for this publication at: https://www.researchgate.

net/publication/331672862

Study of Electro Chemical Machining Etching Effect on Surface Roughness and

Variation with Chemical Etching Process

Conference Paper · March 2019

CITATIONS READS

0 635

3 authors, including:

Jyotirishwar Kumar Naivn Mahato

Brainware University Tribhuvan University
2 PUBLICATIONS   0 CITATIONS    1 PUBLICATION   0 CITATIONS   

SEE PROFILE SEE PROFILE

Some of the authors of this publication are also working on these related projects:

LAMINAR MODELING AND SIMULATION ON CUTTING FLUID FLOW THROUGH SUDDEN CONTRACTION NOZZLE View project

Study of Electro Chemical Machining Etching Effect on Surface Roughness and Variation with Chemical Etching Process View project

All content following this page was uploaded by Jyotirishwar Kumar on 12 March 2019.

The user has requested enhancement of the downloaded file.

 Study of Electro Chemical Machining Etching Effect on Surface Roughness and
Variation with Chemical Etching Process
J.Kumar, S.Mandal and N. Mahato
Department of Mechanical Engineering
Brainware Group of Institutions-SDET, Kolkata - 700 124, INDIA

Abstract

This project has been made in an attempt to study the electro chemical etching & polishing in some alloys to obtain high surface finish.
Electro chemical machining (ECM) is a non-conventional machining process based on the principle of electrolysis and hence it can be
called as the reverse process of electroplating or anodizing. The removal of material from a substrate by chemical reaction or by ion
bombardment is referred to as an etch process. In this dissertation an experiment is done on the mild steel plate, cast iron plate and
aluminum plate. On which electrochemical etching and polishing is done and shows there effect on surface roughness and texture on
variation of time, flow rate and current density. The results have been shown in great details in the result and discussion sections .

Keywords: Electro chemical machining, electro chemical etching, chemical etching, surface roughness, surface texture Words.
ECM can be thought of a controlled anodic dissolution at
atomic level of the work piece that is electrically conductive by
1. INTRODUCTION a shaped tool due to flow of high current at relatively low
ECM is one of advanced machining technologies and has been potential difference through an electrolyte which is quite often
applied in highly specialized fields, such as aerospace, water based neutral salt solution.
aeronautics, defense and medical industries. In recent years, In ECM, Electrolyte is so chosen that there is no plating on tool
ECM is used in other industries such as automobile and turbo- and shape of tool remains unchanged. If the close gap (0.1 to
machinery because of its various advantages. Some genuine 0.2mm) is maintained between tool and work, the machined
characteristics like negligible tool wear, high precision surface takes the replica of tool shape.
machining in difficult to cut materials, lower thermal and Similar to EDM, the work piece hardness is not a factor,
mechanical stress on work piece etc. makes ECM advantageous making ECM suitable for machining difficult to machine
over other non-conventional machining processes. Still there materials. Difficult shapes can be made by this process on
are some challenges in ECM like generation of hydrogen materials regardless of their hardness. A schematic
bubbles and its effect on Material Removal Rate (MRR), representation of ECM process is shown in Figure 1.2 The
complexity of tool geometry and its effect on various process ECM tool is positioned very close to the work piece and a low
parameters, prediction of electrolyte flow pattern and its impact voltage, high amperage DC current is passed between the work
etc. which have been investigated by various researchers. In piece and electrode. Some of the shapes made by ECM process.
case of complicated shapes of work-piece it’s very difficult to
know the machining variables distribution within the inter 2. CHEMISTRY OF PROCESS
electrode gap (IEG). By studying the flow pattern of electrolyte, During ECM, there will be reactions occurring at the electrodes
we can predict the machining variable distribution accurately i.e. at the anode or work piece and at the cathode or the tool
and thus can avoid the passivation which is the major problem along with within the electrolyte.
in ECM in complicated shape cases. Again, two phase effect Let us take an example of machining of low carbon steel which
(hydrogen bubble generation) has a major role on the is primarily a ferrous alloy mainly containing iron. For
machining variables as well as on the material removal rate and electrochemical machining of steel, generally a neutral salt
surface roughness. The flowing electrolyte collects the evolving solution of sodium chloride (NaCl) is taken as the electrolyte.
hydrogen gas generated at the cathode. The presence of The electrolyte and water undergoes ionic dissociation as
hydrogen in the electrolyte reduces the specific conductivity of shown below as potential difference is applied
the solution and thereby the overall effect is a reduced MRR NaCl ↔ Na+ + Cl- H2O ↔ H+ + OH-
and a deterioration of the surface finish. So we need to study As the potential difference is applied between the work piece
the sources, effects and pattern of hydrogen bubble generation (anode) and the tool (cathode), the positive ions move towards
and its impact on various critical parameters and overall the tool and negative ions move towards the work piece.
machining performance. So, these are the motivating factors Thus the hydrogen ions will take away electrons from the
behind this project work. cathode (tool) and from hydrogen gas as:
The process of metal removal by electro chemical dissolution 2H+ + 2e- = H2 ↑ at cathode
was known as long back as 1780 AD but it is only over the last Similarly, the iron atoms will come out of the anode (work
couple of decades that this method has been used to advantage. piece) as:
It is also known as contact less electrochemical forming Fe = Fe+ + + 2e-
process. The note worthy feature of electrolysis is that electrical Within the electrolyte iron ions would combine with chloride
energy is used to produce a chemical reaction, therefore, the ions to form iron chloride and similarly sodium ions would
machining process based on this principle is known as combine with hydroxyl ions to form sodium hydroxide
Electrochemical machining(ECM). This process works on the Na+ + OH- = NaOH
principle of Faraday’s laws of electrolysis. In practice FeCl 2

646
ISBN: 978-93-80689-28-9
And Fe (OH) 2 Would form and get precipitated in the form of removed resulting in patterned regions. The rate of material
sludge. In this manner it can be noted that the work piece gets removal is known as etch rate (ER) and is the thickness
gradually machined and gets precipitated as the sludge. removed per unit time (nm/min). For high production
Moreover, there is not coating on the tool, only hydrogen gas throughput, we need etch rates above 50 nm/min. Depending on
evolves at the tool or cathode. Fig. 1.1 depicts the electro- the etch process and material, the etching can occur in both
chemical reactions schematically. As the material removal takes horizontal and vertical directions. The anisotropy of an etch
place due to atomic level dissociation, the machined surface is process is given by A = 1 –(ERL/ERV) ERL= lateral etch rate,
of excellent surface finish and stress free. ERV= vertical etch rate. Chemical etch processes are typically
Cathode Reaction isotropic; ERL= ERV and A = 0. The effect of an isotropic etch
Na+ + e- = Na; Na+H2O = Na (OH) +H+ ;2H++2e- =H2 ↑ rate is to create undercuts below the mask. An ideal etch
It shows that there is no deposition on tool but only gas is process would transfer the pattern on the mask to the
formed, whereas, in cathode in machining an iron. underlying film with zero lateral etch, creating a vertical
Anode Reaction profile.
Iron (Fe) ↔ Fe++ + 2e- ;Fe++ +2cl- ↔ Fecl2
;Fe++ +2(OH)- ↔ Fe (OH) Fecl2 +2(OH) - ↔ Fe(OH)2 4. CHEMICAL ETCHING PROCESSES
+2cl- Etching is traditionally the process of using strong acid or
mordant to cut into the unprotected parts of a metal surface to
create a design in intaglio (incised) in the metal. In modern
manufacturing, other chemicals may be used on other types of
material.
In traditional pure etching, a metal (usually copper, zinc or
steel) plate is covered with a waxy ground which is resistant to
acid. The artist then scratches off the ground with a pointed
etching needle where he or she wants a line to appear in the
finished piece, so exposing the bare metal. The chopped, a tool
with a slanted oval section, is also used for "swelling" lines.

5. EXPERIMENTAL METHOD
Fig. 1.1 An Electrolyte Cell 5.1 Specifications
Supply voltage :230V AC 50HZ
It shows that metal (work piece) i.e. Fe goes into solution and Power consumption:280W maximum
hence machined to produce reaction products as iron chloride Polishing voltage :0-60V
and iron-hydroxide as a precipitate. Interesting part is that the Polishing current :0-3 Amp
removal is an atom by atom, resulting in higher surface finish Polishing timer :0-90 sec.
with stress and crack free surface, and independent of the Etching voltage :0-18V(to be set with sample)
hardness of work material Etching current H range :0-750 milliamps
Smaller the inter electrode gap (IEG) the gap, greater will be Etching current L range :5-30 milliamps
the current flow because resistance decreases and higher will be Etching timer :0-90 sec
rate of metal removal from the anode. Higher current density, in Pump speed control :Electronic
small spacing (usually about 0.5mm or less) , promotes rapid Dimensions
generation of reaction products. Length(L) :430 mm
Height(H):330 mm
Width(W) :235 mm
Weight :11 kg (Approx.) Without electrolyte

5.2 Etching Reagent For Micro-Examination

(a)Concentrated Nitric Acid 2c.c.
Absolute Methyl Alcohol 98c.c.
(b)Saturated solution of picric acid in alcohol.
Time required in each case is 10 – 30 seconds. Solution(a) is
used preferably for grain boundary etching and solution (b) for
Fig. 1.2 Electrochemical Machining Set-ups pearlite. A 10% solution by hydrochloric acid in alcohol is
useful for etching hardened steels.
3. ELECTROCHEMICAL ETCHING
There are two types of etching mechanisms: Physical etching
(or sputter etch, and relies on momentum transfer from particles
hitting and eroding the surface) and wet/dry chemical etching
(where reaction products formed are either soluble in the etch
solution or volatile at low pressures). The removal of material
from a substrate by chemical reaction or by ion bombardment is
referred to as an etch process. The material that is not masked is

647
5.3 Surface Roughness Testing by Taly-surf after
electrochemical etching process
Cast Iron
Parameters Symbols Unit Level1 Level2 Level3
Voltage V Volt 18 12 6
Time T Time 5 10 15
Average Ra µm 0.780 1.225 1.465
Roughness
Table No-I
Mild Steel
Parameters Symbols Unit Level1 Level2 Level3
Voltage V Volt 18 12 6
Time T Sec 5 10 15
Average Ra µm 0.995 1.098 1.390
Roughness
Table No-II
Aluminium Fig A Plot between Time and Average Surface Roughness for
Parameters Symbols Unit Level1 Level2 Level3 electrochemical etching process
Voltage V Volt 18 12 6
Time T Sec 5 10 15 6.2 Plot between time and average surface roughness for
Average Ra µm 1.566 2.033 2.418 chemical etching process:
Roughness
Table No-III The Plot shown in fig B between time and average surface
5.4 Surface Roughness Testing by Taly-surf after chemical roughness for chemical etching process shows that variation of
etching process: Ra with time of chemical etching process. From the study of
Cast Iron graph we found that the material having the more ductility is
Parameters Symbols Unit Level1 Level2 Level3 lower surface roughness with increase in time of etching
Time T Sec 5 10 15 process. The study of aluminum shows that have the lower
Average Ra µm 1.234 1.358 1.462 surface roughness then mild steel and cast iron.
Roughness
Table No-IV
Mild Steel
Parameters Symbols Unit Level1 Level2 Level3

Time T Sec 5 10 15
Average Ra µm 0.356 0.59 0.852
Roughness
Table No-V
Aluminium
Parameters Symbols Unit Level1 Level2 Level3
Time T Sec 5 10 15
Average Ra µm 0.391 0.318 0.311
Roughness
Table No-VI

6. EXPERIMENTAL RESULT Fig B Plot between time and average surface roughness for
chemical etching process
6.1 Plot between time and average surface roughness for
electrochemical etching process: 6.3 Plot between voltage and average roughness for
electrochemical etching process:
The plot shown in fig A of between time and average surface
Roughness for electrochemical etching process shows that The Plot shown in fig C of between Voltage and average
variation of Ra with time of electro chemical etching process. surface roughness for electrochemical etching process shows
From the study of graph we found that the material having the that variation of Ra with voltage of electrochemical etching
more ductility is higher surface roughness with increase in time process. From the study of graph we found that the material
of etching process. The study of aluminium shows that have the having the more ductility is higher surface roughness with
higher surface roughness then mild steel and cast iron. increasing in voltage of etching process. The study of
aluminium shows that have higher surface roughness then mild
steel and cast iron.

648
 References

[1] N.N.Li, “High Throughput Fabrication of Titanium

Nanopillars by Maskless Plasma Etching” National Key
laboratory on Micro/Nano Fabrication Technology, Institute of
Micro Electronics, Peking University, China.
[2] D. Berestovskyi, “Electrochemical Polishing of Micro
Component, ICOMN” March 25-28 ,(2013) ,University of
Victoria.
[3] Marek St. Węglowski, “Electrolytic Etching in Welding
Metallographic”(2013) Testing of Materials Weldability &
Welded Construction Dept. PhD.
[4] Niveen J. Abdalkdir, “Study of electrochemical Polishing
Applications in Some Alloy to Obtain High Surface Finish
(2012)”University of Technology/ Materials Engineering.
[5] Niveen J. Abdalkadir, “Study of Electrochemical Polishing
Fig C plot between voltage and average roughness for Applications in Some Alloy For High Surface Finish” July 3-6
electrochemical etching process ,(2012),University of Technology,Baghbad,Iraq.
[6] J.Electrochem, “Electrochemical Studies of Interation of
7. CONCLUSIONS Qurcetin With DNA” College of Chemistry & Chemical
Engineering, Northwest Normal University, Lanzhou 730070
The extensive use of experimental studies preliminary to the ,Gansu, China,(2006).
design & construction of new material or structural elements & [7] F. HAIRER, “Etching Techniques for the Microstructrual
the use of testing procedures for control of established Characterization of Complez Phase Steels by Light
processes of manufacture & construction are significant & well Microscopy” Technical University of Munich Christion
recognized features of ours. Doppler Laboratory of Material Mechanics of High
The plot shown in fig A of between time and average surface performance Alloys, Chair of Materials Science And
Roughness for electrochemical etching process shows that Mechanics of Materials, VOEST ALPINE Straβe 3,postfach,
variation of Ra with time of electro chemical etching process. Linz A-4031, Austria(2004).
From the study of graph we found that the material having the [8] Inger Ekvall, “Preparation and Characterization of
more ductility is higher surface roughness with increase in time Electrochemically Etched W tips for STM” Meas,science.
of etching process. The study of aluminum shows that have the Technol. 10 (1999) 11-18,Physics and Engineering physics
higher surface roughness then mild steel and cast iron. Chalmers University of technology, E-412 96
Goteborg,Sweden, Printed in UK.
The Plot shown in fig B of between time and average surface [9] Inger Ekvall, “Preparation and Characterization of
roughness for chemical etching process shows that variation of Electrochemically Etched W tips for STM” Recived 4th
Ra with time of chemical etching process. From the study of septmber 1998, in final from 29th October 1998, accept for
graph we found that the material having the more ductility is publication 3rd November 1998, Uppsala University, The
lower surface roughness with increase in time of etching Angstrom Laboratory, Box 534, SE-75I 2I Uppsala,Sweden.
process. The study of aluminum shows that have the lower [10] Khadry A. Galil, “Acid Etching Patterns on Buccal
surface roughness then mild steel and cast iron. Surfaces of Permanent” PEDIATRIC DENTISTRY/Copyright
1979 by the American academy of Pedodontics/vol.1
The Plot shown in fig C of between Voltage and average no.4/printed in USA.
surface roughness for electrochemical etching process shows [11] M.Inman, “Electropolishing and Throughmask
that variation of Ra with voltage of electrochemical etching ElectroEtching on Nitinol Stents and other Materials in an
process. From the study of graph we found that the material Aqueous Electrolight” Faraday Technology Clayton, Ohio,
having the more ductility is higher surface roughness with USA.
increasing in voltage of etching process. The study of [12] Avinash P. Nayaket, “Logeeswaran VJ¥ and M Saif Islam”
aluminum shows that have higher surface roughness then mild University of California,davis.California.
steel and cast iron. [13] V.Palmieri, “Fundamental of Electrochemistry-The
Electrolytic Polishing of Metals:Application to copper and
niobium” Istituto Nazionale di Fisica Nuceare, Laboratory
Nazinali di Legnaro.

649

View publication stats