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Development of Fe-C-Si-Mn-B Electrode for
Overlaying Low Carbon Steel Substrate by MMAW Santhosham. M
1, Rajendra boopathy.S
2
1Professor , Department of Mechanical Engineering C.Abdul Hakeem College of Engineering &Technology, Melvisharam,
Vellore-632509, Tamil Nadu, India. 2Professor, Department of Mechanical Engineering, CEG Campus, Chennai-600025, Tamil Nadu, India.
Absract ---- Hard facing of functional components of
heavy engineering equipments enhances the resistance to
wear and abrasion. To facilitate such a need, a set of iron
base electrodes are made in the laboratory. The Iron base
alloys made contain carbon, silicon, manganese and boron.
Overlay of the alloys are made on low carbon steel plates by
manual metal arc welding. The Fe-C-Si-Mn-B deposits
exhibited an average hardness of 700VHN.The intermixing
between the substrate and the deposit is quite appreciable.
The evidence of the shift of C-curve to the right in the
isothermal transformation diagram by promoting tempered
martensite and lower bainite without quenching is evident.
Boron addition in very small quantities in steel with
enhanced contents of silicon and manganese generates the
formation of tempered martensite and lower bainite, which
shall be utilized for hardfacing
Keywords ---- Carbon, Silicon, Manganese, Boron C-
Curve, Tempered Martensite, Lower Bainite, Hardness,
Hardfacing
I. INTRODUCTION
Most of the functional components of heavy
engineering equipments are subjected to wear and
abrasion. Such never ending natural problems create a
need for protection and extension of service life of
functional components in huge equipments from wear
and abrasion. The loss on economy is also quite alarming
due to material deterioration. By wear and abrasion, there
is a progressive deterioration of metallic surfaces leading
to plant inefficiency and shut down. When non metallic
materials slide or roll over a metallic surface, abrasive
wear occurs. An approximate ratio of wear categories
generally occur are metal to metal wear-22%, impact
wear-16%, abrasive wear-52% and corrosive wear-10%.
Abrasive wear has a linear relationship with hardness.
Hardness is the index, which is inversely proportional
to material loss by wear and abrasion. It is quite evident
that abrasive wear is the most prominent of all other
categories. The Simplified wear theory equation is
Q=N/H, Where Q is the volume loss due to abrasive
wear, N is the applied load, H is the hardness [1]. To
combat such material deterioration due to abrasion,
several methods of protections such as cladding, coating
and hard facing are followed. For wear resistance and
dimensional restoration weld overlays by hardfacing are
preferred [2].
The surface metallurgy can be changed by overlaying
the substrate. The microstructure of the deposit plays the
major role in achieving the hardness. In all the specified
methods, hard facing can be done for higher thickness of
deposit by manual metal arc welding. The advantage of
hardfacing is that, it may be applied to functional areas of
the component, which is subjected to wear and make the
availability of hard wear resistant phases to resist
material deterioration. Such wear resistant deposits
provide extension of surface life and protection in depth
to the predetermined level. Efficient deposition of metal
or alloy can be done by manual metal arc welding
(MMAW). Most of the engineering industries adopt
MMAW, since it a versatile, cost effective, easy
technique adopted in shop floor and in field applications
[3]. Fe-C-Cr electrodes are utilized in many engineering
industries for hard facing since; the deposit gives the
anticipated hardness. Due to chromium carbide
formation, the deposits are quite hard and serve the
purpose. At the same time carbon in the deposit is to be
maintained sufficiently in order to form chromium
carbide. Fe-C-Cr welding rods are cheaper than the
electrodes which contain W, Mo, Co, Ti, etc., which form
complex carbides with high hardness [4].Depending on
the application, economy and the surface hardness,
hardfacing electrodes are chosen. To certain extent
hardness can also be achieved with high carbon steels
after heat treatment.
In this work a new iron alloy has been developed with
the addition of boron as well as with an enhancement of
silicon and manganese to deteriorate the abrasive effect
to certain level. The microstructure obtained shows
tempered martensite and lower bainite.
22%
16%
52%
10%
Ratio of wear categories
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551
Mostly these alloys can be utilized for buildup of
layers under other alloy compositions that show better
abrasion resistance and toughness. Where ever there is no
possibility of heat treating a component after hardfacing,
due to constraints in size, etc., this new alloy can be
employed. Deposition of hardfacing material is facilitated
in the form of an electrode with 4.0 to 6.0 mm in
diameter, with sufficient flux coating containing the
alloying elements required. Hardfacing of carbon steel
substrates are very easy, particularly which contain
carbon content below 0.35%. The composition of the
substrate, especially the carbon content is to be
maintained at a specific level. Higher the carbon content
of the substrate, more difficult will be the hardfacing.
High carbon alloy steel deposits must be pre and post
treated after hard facing to attain uniform microstructure
[5]. A substrate of plain carbon steel with 0.15%C is
chosen in this work and there is no need for pre and post
heat treatment. Carbon content with an average of
0.7wt% is maintained in the Fe-C-Si-Mn –B alloy, such
that martensite structure is formed at room temperature.
Same carbon content is maintained for the electrode Fe-
C-Si-Mn alloy which has no boron. Addition of
manganese is made to stabilize the formation of
martensite and lower bainite and as well reduce the
eutectoid composition of the alloy as per Gulliet’s
diagram. Further, manganese shifts the A1 and A3
temperatures to aid the formation of martensite and
bainite [6]. Silicon beyond 2% eliminates the austenite
and is expected to aid the flow ability of the alloy in
order to obtain defect less deposits and also increases the
toughness. Combination of silicon with manganese
increases the tendency of formation of martensite in air
cooling. It is also being a very strong oxidizer, recovers
the manganese to a larger extent and allows the eutectic
temperature to be lowered. Boron shifts nose of the C-
curve to the right sufficiently in the isothermal
transformation diagram and facilitates the easy formation
of hard phases, like martensite and lower bainite. But
boron addition should be maintained below 1% to get
optimum results [7].Therefore sufficient addition of
manganese, silicon and boron are made in the alloy
expecting the anticipated hardness in air cooling after
depositing the alloy by MMAW. The expected hardness
is achieved, without the addition of costly elements,
which form complex carbides.
An average hardness of 400VHN in Fe-C-Si-Mn alloy
and an average hardness of 700BHN in Fe-C-Si-Mn-B
are expected on the deposits and are attained.
II. EXPERIMENTAL PROCEDURE
Fe-C-Si-Mn and Fe-C-Si-Mn-B electrodes are made in
the laboratory by manually coating the flux on bare wire.
Required amount of various ingredients are mixed in a
mini muller to form the flux. The flux mixture contains
oxidizing agent, reducing agent, binder, slag remover,
coating strengthener and gas shield to obtain defect free
deposits [8, 9, 10, and 11].
Required amount of silicon and manganese are added
in the form of ferrosilicon and ferromanganese.
Ferromanganese plays a dual role, while being an
oxidizing agent, it also acts as an alloying element. Borax
is added to obtain boron in the deposit. Charcoal is added
to pick up carbon. Detail of raw materials in flux is as
shown in table.1.
After manual coating, the electrodes are dried in the
muffle furnace at 350° C for four hours. A flux to bare
wire ratio of 1.5:1 is maintained. Mild steel wire with 4
mm diameter is chosen for flux coating to form the
electrodes. Overlaying is done on 5mm thick low carbon
steel plate.
Fig.1 Pm Vs (Ac3-Ac1)
Fig .2 Weld deposit by
60708090
100
1.1197 1.2316 1.005 0.9579
(Pm) Vs (Ac3-Ac1)
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Table 1.
(Flux weight distribution for each electrode. All weights are in grams)
Material Bentonite FeO FMn CaF2 Asbestos Caco3 Sodium Carbon FeSi H3BO3
Silicate
E0 1.80 2.04 3.08 0.50 2.10 3.16 0.47 0.50 1.80 -
E1 1.80 2.04 3.08 0.50 2.10 3.16 0.47 0.50 2.20 0.60
E2 1.80 2.04 3.08 0.50 2.10 3.16 0.47 0.50 1.80 0.60
E3 1.80 2.04 3.08 0.50 2.10 3.16 0.47 0.50 1.60 0.60
E4 1.80 2.04 3.08 0.50 2.10 3.16 0.47 0.50 1.00 0.60
E0 is the deposit produced with Fe-C-Si-Mn electrode and E1, E2, E3, E4 are the deposits produced with Fe-C-Si-Mn-B electrodes.
Table 2
________________________________________
Welding Parameters
Welding Welding Preheat Rate of Number of Voltage
Current Deposition layers
----------------------------------------------------------------
120V 80A Nil 4.0 mm /s 03
_______________________________________
Table.2 represents the welding parameters maintained
during weld deposition for three layers. An average
voltage of 120V is maintained during the deposition and
a constant current of 80A is generated from the MMAW
equipment. Perfect ripples of weld beads are deposited
with 4.0 mm per second and three layers are made.
Continuous overlaying without any interval is done to
avoid idle time to resemble the field conditions. But,
cleaning is done after the completion of each layer. After
finishing the last layer the deposit is allowed to cool to
room temperature. Then it is cut across the layer along
with the substrate and subjected to metallographic
examination at 500x.
Hardness is measured at various locations on the cut
section. Spectrographic analysis is made on substrate and
on the deposits to check the chemical composition. Fig .2
shows the weld deposit made in three layers over the low
carbon steel substrate.SEM analysis is done for the
deposits.
III. RESULT AND DISCUSSION
The chemical composition of the alloys produced is
shown in the table.3. Fig. 9 shows the microstructure of
the substrate, which comprises the phases of ferrite and
pearlite. Fig. 10a, 11a, 12a and 13a show the
microstructure of the deposit with considerable variations
in the content of tempered martensite and lower bainite.
From the microstructures 10b, 11b, 12b and 13b, it is
understood that the intermixing is quite good. The
intermixing between the substrate and the deposit in all
four cases is found to be satisfactory [12].
The deposit of composition 0.707%C-4.084%Si-
3.852%Mn-0.0168%B exhibiting an hardness of
711VHN.(electrode2)
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Table 3
Mat %C %Si %Mn % S % P %B %Fe
Average
Hardness
(VHN)
Sub 0.150 0.240 0.900 0.0010 0.0013 - Rest 143
E0 0.712 3.995 3.725 00386 0.0122 - Rest 450
E1 0.751 4.656 3.828 0.0493 0.0229 0.0168 ,, 663
E2 0.707 4.084 3.852 0.0316 0.0178 0.0168 ,, 711
E 3 0.698 3.668 3.715 0.0419 0.0222 0.0168 ,, 688
E4 0.611 2.591 3.529 0.0375 0.0285 0.0168 ,, 581
E0-Electrode without Boron addition, E1, E2, E3, E4 - Electrodes with Boron addition, Sub-Substrate, Mat-Material
Fig .3 C/Si+Mn Vs C/B
Fig.4 (Ac3-Ac3) Vs Hardness
Fig.5 Pm Vs Hardness
The deposit of electrode 2 shows the maximum
hardness of all the four deposits. Since the cooling curve
shifts to the right side, the formation of martensite and
lower bainite occurred in the deposits instantaneously.
Boron addition causes the shift of C-curve to the right
side eliminating the continuous cooling transformation,
which is shown by pictorial illustration (temperature vs.
time, transformation diagram) in fig.7. Lower bainite is
formed to certain extent, which contributes to the overall
hardness Large amount of martensite forms during
solidification and gets tempered by the heat supplied
from the top or bottom layer as the welding process is in
progress [13, 14, 15].But the Fe-C-S-Mn alloy without
boron addition forms lower bainite and the
transformation touches the nose of the c-curve as seen in
fig.8, exhibiting lesser hardness than that of Fe-C-Si-Mn-
B deposits.
High silicon available in the solution increases the
fluidity of the alloy to form a quite satisfactory and
defect free deposit.
0
10
20
30
40
50
0.0885 0.0891 0.0945 0.0998
C/B
C/Si+Mn
Elemental Ratio
0
100
200
300
400
500
600
700
800
88.980492.94781.831577.5836
0
1000
1.1197 1.2316 1.005 0.9579
(Pm) Vs Hardness(VHN)
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Silicon enables the matrix to remain tough enough
[16].Manganese contributes to the enhancement of
hardness by reducing the eutectic composition,
facilitating the instantaneous formation of hard phases.
During solidification of Fe-C-Si-Mn-B alloy, silicon
reduces the solubility of carbon and diffuses in to the
austenite which is an iron rich phase. Silicon forms
substitution solid solution in the crystalline phase which
leads to micro transformation [17, 18]. Boron addition
increased the hardenability of the steel resulting in better
wear and abrasion resistance and making it to be utilized
for hardfacing purposes. It also occupies the grain
boundaries and suppresses the formation of ferrite to a
greater extent(19,20,21).The martensite transformation
does not depend on the carbon content of an alloy.
Moreover higher the carbon content, lower will be the
acceleration of the martenstic transformation. Therefore
nominal carbon content is maintained as shown in the
table.3. Graphitization is arrested as there is
transformation of martensite simultaneously. The content
of transformed martensite and bainite depends on the
carbon content and it is quite evident from the fig 10a,
11a, 12a, 13a. The content of martensite and lower
bainite depends on the carbon while silicon and
manganese facilitate the formation of the hard phases in
air cooling itself.
The relationship between manganese and the
microstructure are depicted from the Gulliet’s diagram.
Manganese stabilizes austenite by raising the A1 and A3
temperatures in steel. In Fe-C-S-Mn-B alloy A1 and A3
are shifted by manganese addition such a way that hard
structures are allowed to form. In the Fe-C-Si-Mn-B
alloys silicon varies from 2.591 to 4.656 wt%.
Manganese varies from 3.715to3.852wt%. Such variation
of compositions cause variations in the hardness
values.The Fe-C-Si-Mn (electrode 0) alloy is also of
similar composition, which is almost equivalent to the
electrode2. Hardness varies from 581 to 711 VHN, for
alloys with boron and 475VHN for alloys without boron,
while the substrate shows a hardness of 143VHN.
Content of martensite and lower bainite in the
microstructure vary depending on the content of carbon,
silicon and manganese.When the martensite content is
increased, it is found that the hardness is enhanced.
Especially, this is evidently observed in the
microstructure of electrode 2 (Fig 6a). Electrode 1, 3 and
4 also show higher hardness when compared to the
electrode 0. But depending on the carbon, silicon and
manganese content the hardness variation is found in the
deposits of the electrodes.
Fig.6
0
100
200
300
400
500
600
700
800
0.00885 0.0891 0.0945 0.0998
Har
dn
ess
, (V
HN
)
(C/Si+Mn)
(C/Si+Mn) vs (Hardness of the deposit)
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Fig.7 Fig.8
Deposit of electrode 4 showed an hardness of
581VHN, since the carbon content is 0.611%, which is
low, compared to the other deposits .But due to the boron
addition the hardness value is more than the E0 electrode
even though it contains is 0.712% carbon.
Hardness of the plain carbon steels are increased by
the process of heat treatment. But Silicon and manganese
enhance the hardness without heat treatment as seen in
the microstructures of the deposits, shown in fig 10a, 11a,
12a and 13a. Fig 2shows the effect of boron addition
(shift of the nose of CCT–curve) which allows the
formation of martensite and lower bainite, which is
similar to the quenching effect [21].
Boron enhances the further opportunity of hardening
in air or natural cooling, as the process of solidification in
welding process cooling is generally in ambient
atmosphere.Fig.8 shows the transformation without the
effect of boron, but of the similar chemical composition
of deposit E0. Fig 7and 8 shows the transformation of Fe-
C-Si-Mn-B and Fe-C-Si-Mn alloy during air cooling. In
fig 6, it is clear that the transformation of E1, E2, E3, E4
electrodes are similar to quenching effect. Fig.14 shows
the microstructure of electrode E0. The electrode deposits
E1, E2, E3, and E4 do not touch the nose of the CCT
diagram during solidification, but E0 passes through the
CCT curve to certain extent and retains certain soft
phases. The hardness of E0 is less when compared to E1,
E2, E3, E4.The effect of Boron is evident in the reactions
and results. The microstructure in fig. 11a represents the
deposit of electrode 2, which is Fe-C-Si-Mn alloy
without the addition of boron [22]. The micrograph
shows more of lower bainite and lesser amount of
martensite. Carbon being the important element for the
transformation and leading to hard structures the content
of the same plays an important role.
In this study and development of hard alloys it is
proved that carbon variations lead to the solidification of
hard structures like martensite and lower bainite. The
various combinations of carbon, silicon and manganese
with the aid of boron form hard structure, which shall be
utilized for hardfacing.
Fig 9. Microstructure of substrate
Fig 10a .Microstructure of electrode 1
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Fig 10b. Microstructure of intermixing of Electrode1 with substrate
Fig 11a. Microstructure of electrode 2
Fig 11b. Microstructure of intermixing of Electrode 2 with
substrate
Fig 12a.Microstructure of electrode 3
Fig 12b.Microstructure of intermixing of Electrode 3 with substrate
Fig 13a.Microstructure of electrode 4
Fig 13b.Microstructure of intermixing of Electrode 4
Fig 14.Microstructure of electrode 0
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SEM images are made on the deposits of electrodes
E1, E2, E3, E4 and are shown in the fig 15, 16, 17and
18.The lower bainite content is found to be more in the
micrographs of fig 15,17 an18,of which the martensite
background increases in the order of electrode 1, 3 and
4. And the hardness also varies accordingly. The deposits
which contain more of martensite show higher hardness.
In the deposit of electrode 2 it is very clear that the
martensite content is the highest and with the least lower
bainite, which is the cause for highest hardness of
711VHN, when compared to the other deposits.
Fig 10.SEM image for electrode 1
Fig 11. SEM image for electrode 2
Fig 12.SEM image for electrode 3
Fig 13. SEM image for electrode 4
IV. CONCLUSION
1. Micro segregation of silicon retains austenite phase
before transformation of marten site and bainite.
2. Martensite is formed without quenching, since
boron shifts c-curve to the right.
3. The silicon, manganese combination promotes hard
structures along with sufficient carbon.
4. Since boron occupies the austenitic grain
boundaries, the formation of ferrite is suppressed.
5. Pearlite is suppressed by manganese and bainite is
promoted.
6. Manganese also stabilizes the austenite to a large
extent by raising A1 and A3 temperatures.
7. 0.7 Wt% Carbon is sufficient enough to form hard
structures, with sufficient silicon and manganese
along with boron.
8. It is evident that boron increases the hardenability
of Fe-C-Si-Mn alloys.
Acknowledgement:
The authors thank the management of PSG College of
Technology, Coimbatore, Tamil Nadu, India,
especiallyProf.V.Balusamy of the Department of
Metallurgical Engineering, for providing metallographic
facilities and hardness testing. Thanks to the management
of C.Abdul Hakeem College of Engineering &
Technology, Vellore, Tamil Nadu, India for general
engineering facilities. Authors thank United Foundries
Limited, Ranipet, Vellore, and Tamil Nadu for providing
the spectroscopic analysis. Finally the authors thank
Anna University, Chennai, India for the facility provided
to take images in SEM.
REFERENCES
[1 ] Milo Duminovic, Repair and maintenance procedures for heavy machinery components, Welding innovation, Vol XX.No.1.2003
[2 ] www.asminternational.org, Introduction to surface engineering for
corrosion and wear resistance (#06835G)ASM International, Materials Park, Ohio, USA..
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
558
[3 ] Selvi.S,Sankaran.S.P,Srivatsavan.R,Comparative study of hardfacing of valve seat ring using MMAW process,Journal of
material processing technology,207(2008).356-362.
[4 ] The relationship between microstructure and abrasive resistance of a hardfacing alloy in FE-Cr-C-Nb-V system, E.O.Correa,
N.G.Alcantra, D.G.Teco and R.V.Kumar. Metallurgical and
materials transactions A, Volume 38A, August 2007, 1671-1680 [5 ] Sydney H Aver, Introduction to Physical metallurgy, Tata
McGraw-Hill, Edition1997
[6 ] Higgins.R.A, Engineering Metallurgy, sixth edition, viva low priced student edition, 1998.
[7 ] H.K.D.H.Bhadeshia and L.-E.Sbvensson,Model for boron effects
in steel welds, International conference on modeling and control of joining processes,Orlando Florida(1993)
ed.T.Zacharia,American Welding Society,pp153-60.
[8 ] Hard surfacing Welding rod, 2, 077, 397, Patent Apr.20, 1937, United States Patent Office, Magnus Christianson Baberton, Ohio,
assigner to the Babcock &Wilcox Company, New wark, N.J., a
corporation of New YorkWark.Moritz, Sale Moor, England, assigner to General Electric Company, a Corporation of New
York.
[9 ] ArcWeldingflux,Patent No.2, 141,929, Dec27,1938,United States Patentoce,March Rudolph Moritz,Sale Moor ,England,Assigner to
General Electric Company corporation of New York.
[10 ] Hardfacing material and methods, Patent No. US6888088B2,May3,21005,Jimmie Brooks
Bolton,10459TwinCir.,Montgomery,TX(US)77356,
BillMarieRogers,10211,Chery Chase Dr.,Houston TX(US)77042. [11 ] Hardfacingalloys, Methods and products, Patent No.US 7,
61411, April22, 2008, Roger Augusta Aemen Grignan (Fr) eith
E.Moline, Houston, TX (US).ATT Technology Ltd., Houston, TX (US)
[12 ] Babu.S.S,David.S.A,Quintana.M.A,Modeling microstructure
development in self shielded flux cored arc welds,Welding Research Supplement,Welding Journal,April,2001.
[13 ] H.K.D.H.Bhadeshia, Tempered martensite, mhtml: file//Tempered%20Martensite.mht.UniversityofCambridge
[14 ] Morra.P.V, Bottttger.A.J, Mittemeijer.E.J, and Decomposition of
iron based martensite, Journal of Thermal analysis and calorimetry, vol.64 (2001), 905-914.
[15 ] H.K.D.H.Bhadeshia, E.V.Edmunds, Bainite in steels, New
composition, property approach .PartI, Metal science, Vol117, pp411-419, September 1983.
[16 ] Atamert.S.H.K.D.H.Bhadeshia,Silicon modification of iron base
hardfacing alloys, Recent trends in welding science and technology(TWR’89) eds,S.A.David and J.M.Vitea,ASM
International,Ohio,U.S.A,1987,273,278.
[17 ] Mullipov.M.A,KulishenkooB.A,Val’kov.E.V,Wear resistance of facing alloy with metastable austenite, Metal science and heat
treatment,vol47,Nos 1-2,Jan2005.
[18 ] Aximi.G, Shamanian.M, Effect of silicon content on the microstructure and properties of Fe-Cr-C hardfcing alloys. J
Material Sci (2010)45:842-849.
[19 ] Hiroshi OHTANI,Mitsuhiro HASEBE,Kiyohito ISHIDA and Taiji NISHIZAWA,Calculation of Fe-C-B Ternary phase
diagram,Research article,Transaction in steels,pp175-177,April
1981. [20 ] L.S.Livshits, V.S.Sheherbakov and Grinberg, Influence of boron
on the structure and properties of hardfacing alloys, VSIIST,
.Translated from Metalovedenie I Termicheskaya Obrasotka metallov, No.6 pp67-70, June 1967.
[21 ] A CCT diagram for an off shore pipeline steel of X70 type,
Supplement to welding journal, January 2009, American Welding Society.
[22 ] Dong Jun Mun,Eun Joo Shin and Yang Mo Koo,A study on the
behavior of boron distribution in low carbon steel by particle tracking autoradiography,Nuclear Engineering and
Technology,Vol 43.No.1,February,2011.