Characterization of Fe–C–Cr Based Hardfacing Alloys

Abstract

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.

Full text

1 23
Transactions of the Indian Institute of
Metals
ISSN 0972-2815
Trans Indian Inst Met
DOI 10.1007/s12666-018-1352-6
Characterization of Fe–C–Cr Based
Hardfacing Alloys
Vineet Shibe & Vikas Chawla

1 23
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TECHNICAL PAPER
Characterization of Fe–C–Cr Based Hardfacing Alloys
Vineet Shibe
1
•Vikas Chawla
1
Received: 25 November 2017 / Accepted: 5 June 2018
ÓThe Indian Institute of Metals - IIM 2018
Abstract Hardfacing is one of the adaptable methods that
can build up the hard and wear resistant surface layer of
different materials on the surface of substrate material. It
helps them withstand wear, as well as prevent corrosion
and high temperature oxidation. In the present investiga-
tion three different types of Fe–C–Cr based hardfacing
electrodes with varying chemical compositions were
deposited on ASTM A36 steel substrate by using manual
metal arc welding (MMAW) process. ASTM A36 steel
was selected as a base material after consulting with
Pressure and Process Boilers, Saharanpur (India), which is
a leading manufacturer of boilers. ASTM A36 steel is
mostly used by this company for the production of
induced draft fans. MMAW process with direct current
constant current type power source was used to deposit
the hardfaced layers of uniform quality. Straight polarity
was used for MMAW process so that more of the arc heat
should be concentrated on the electrode. The hardfaced
samples were characterized using various characterization
techniques and the results of the same were also outlined
in the present investigation.
Keywords ASTM A36 steel Characterization 
Hardfacing Manual metal arc welding
1 Introduction
Hardfacing is a metalworking technique in which harder or
tougher material is imposed on the surface of a substrate
material. Hardfacing alloy is uniformly deposited on the
surface of base material by welding, with the motivation
behind being enhancing the hardness and wear resistance
without substantial loss in ductility and toughness of the
base metal [1].
Hardfacing by welding or thermal spraying is a surface
modification technique in which a layer of superior and
hard alloys is deposited on the surface of the base material
in order to enhance their desirable properties, such as,
wear, erosion and corrosion resistance, etc. [2]. Hardfacing
is one of the flexible techniques that can develop the hard
and wear resistant surface layer of different metals and
alloys on metallic base material which enables them to
withstand wear, as well as prevent corrosion and high
temperature oxidation [3].
Various welding techniques can be utilized in applying
hardfacing materials ranging from the conventional pro-
cesses, for example, oxyacetylene torch to new and modern
processes, for example, plasma transferred arc and laser
techniques [4]. Hardfacing processes are broadly classified
as: hardfacing by arc welding, hardfacing by gas welding,
hardfacing by combination of arc and gas welding, powder
spraying and laser hardfacing or cladding [5].
The most widely recognized substrates that can be
hardfaced are mild steels, low-alloy steels, medium-carbon
steels, high-carbon steels, low-manganese steels, low-
nickel chrome steels, low-alloy chromium steels, stainless
steel, cast iron, copper-base alloys and nickel-base alloys
[5]. The hardfacing materials are classified into four broad
groups: tungsten carbide materials, low-alloy iron-base
alloys, high-alloy iron-base alloys, cobalt-base alloys and
&Vineet Shibe
shibevineet@gmail.com
1
Department of Mechanical Engineering, IKG Punjab
Technical University, Main Campus, Kapurthala, Punjab,
India
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nickel-base alloys [5]. Hardfacing materials in intense
abrasive conditions broadly utilize Fe–Cr–C alloys because
of their excellent abrasion resistance. Incredible abrasive
wear resistance results from a high volume of carbides and
matrix toughness [6]. The profitability of hardfacing tech-
nique relies upon careful or judicious application of the
hardfacing material and its chemical composition for a
specific application [7].
A few advantages of hardfacing are: most flexible
technique, can be done on any steel using different
welding processes, expands the life of worn-out parts,
improves the productivity of machinery by decreasing
downtime, decreases the cost of replacement, increases the
service life of parts, cause less shutdowns and subse-
quently improves the profitability, decreases overall
expenses. Hardfaced parts can be produced from inex-
pensive substrate materials, minimize the inventory of
spare parts and any desirable characteristic, for example,
hardness, wear resistance, abrasive resistance, etc. can be
achieved at less cost [8].
The deposition of surface coatings, by hardfacing or
thermal spraying techniques, is often utilized in industry,
either while repair and maintenance or in the production of
new parts in order to enhance the wear resistant charac-
teristics of surfaces in contact [9]. Hardfacing by welding is
accepted by several industries, for instance, steel and
foundry, textiles, cement, mining, chemical, power gener-
ation, sugar cane and food processing, agriculture, auto-
motive, construction, glass, ceramic, metal working, public
works and shop machinery, and so forth in order to
improve the service life of parts [8]. In the present exam-
ination, three distinct sorts of Fe–C–Cr based hardfacing
electrodes with varying chemical compositions were
deposited on ASTM A36 steel substrate by utilizing
MMAW process. The hardfaced samples were character-
ized using techniques such as field emission scanning
electron microscopy (FE-SEM), energy dispersive X-ray
(EDAX) analysis, X-ray diffraction (XRD) analysis, met-
allographic studies, measurement of surface roughness,
microhardness along the cross-section, X-ray mapping, etc.
and the results of the same have also been outlined in the
present investigation.
2 Experimental Procedure
2.1 Substrate Material
ASTM A36 steel was selected as a base material after
consulting with Pressure and Process Boilers, Saharanpur
(India). Pressure and Process Boilers, Saharanpur, Uttar
Pradesh (India) is a leading manufacturer of boilers and the
major problem being faced by this company is of erosion of
I.D. fans, especially in the case of coal-fired boilers. The
material mostly used by this company for the production of
I.D. fans is ASTM A36 steel. The actual percentage
chemical composition of ASTM A36 steel was determined
with the help of Optical Emission Spectrometer (Polyvac
2000 manufactured by Hilger Analytical Ltd., United
Kingdom) at the National Institute of Secondary Steel
Technology, Mandigobindgarh, Punjab (India); which is
reported in Table 1along with the nominal chemical
composition.
Figure 1shows the optical micrograph (2009) of the
ASTM A36 substrate material using metallurgical micro-
scope (Epiphot 200 of Nikon make). The microstructure
consists of ferrite grains and at few locations, pearlite
colonies are evidenced.
2.2 Selection of the Hardfacing Electrodes
Three different types of commercially available hardfacing
electrodes which are wear and erosion resistant as well as
suitable for hardfacing on an ASTM A36 steel substrate
material were selected. The hardfacing electrode 1 was a
stainless hardfacing electrode of size 4 mm 9350 mm,
hardfacing electrode 2 was a tubular electrode of size
6.30 mm 9450 mm and the hardfacing electrode 3 was a
tubular electrode of size 6.30 mm 9450 mm. The reasons
for choosing these hardfacing alloys was that, they provide
high resistance to wear and erosion as well as were avail-
able at reasonable prices in the market. Figure 2shows the
image of (a) Hardfacing electrode 1 (b) Hardfacing elec-
trode 2 and (c) Hardfacing electrode 3.
The percentage chemical composition of the hardfacing
alloys is given in Table 2.
2.3 Deposition of Hardfacing Layers
MMAW technique was used to deposit the hardfaced layers
on an ASTM A36 steel substrate. Constant current type
power source was utilized, the reason being that with this
type of characteristics, the welding current remains con-
siderably uniform, regardless of small variation in arc
length and subsequent slight change in arc voltage, which
are certain even in the case of a proficient or skilled welder.
As the welding current was fairly constant, the weld quality
was consistent. Approximately, total thickness of 4–5 mm
of the hardfaced layers was achieved.
2.4 Welding Parameters Taken
MMAW process with direct current (DC) constant current
type power source was used to deposit the hardfaced layers
of uniform quality. Electrode negative (Straight polarity)
was used for MMAW process so that more of the arc heat
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was concentrated on the electrode. As a result, higher
melting and deposition rates were achieved with less dis-
tortion of the test specimen. Three layers were deposited on
the surface of the specimen to achieve a thickness of about
4–5 mm of the hardfaced layer and in order to minimize
the effect of dilution with base material. The welding
conditions or parameters taken are presented in the
Table 3.
2.5 Specimen Preparation for Characterization
For the characterization of the hardfacings, the specimens
with dimensions of about 20 mm 915 mm 95 mm were
cut from the ASTM A36 steel sheets. The specimens were
polished using emery papers of grit sizes 220, 400 and 600.
These samples were then hardfaced using MMAW process.
Afterwards the specimens were machined to the specified
size on the surface grinding machine due to the tremendous
hardness of the deposited layers.
2.6 Characterization of Hardfaced Specimens
2.6.1 Metallographic Studies
The hardfaced specimens were polished using emery
papers of grit sizes 220, 400, 600 and subsequently on 1/0,
2/0, 3/0 and 4/0 grades polishing papers. Further, the
samples were mirror polished using cloth polishing wheel
machine with 1 lm lavigated alumina powder suspension.
After getting the mirror like surface, an etchant (3% nital,
i.e. 3% nitric acid and 97% ethylalcohal) was applied to the
surface of the specimen with cotton and rubbing was car-
ried out for some time. The specimen was cleaned with dry
cotton. Consequently, the hardfaced specimens (HF1, HF2
and HF3) were examined under Metallurgical Microscope
Table 1 Nominal and actual percentage composition of ASTM A36 steel
Percentage chemical composition of ASTM A36 steel substrate (IS 2062)
%C %Si %Ma %P %S %Al %Cu %Cr %Mo %Ni %Pb %Ti %V %W %Fe
Nominal composition 0.16 0.17 0.46 0.026 0.019 0.007 0.048 0.084 0.018 0.039 0.007 \0.001 0.003 \0.001 98.89
Actual composition 0.19 0.18 0.92 0.019 0.022 0.01 0.01 0.01 0.0002 0.01 – – 0.001 – 98.626
Fig. 1 Optical micrograph of the ASTM A36 steel substrate material,
200X
Fig. 2 Image of ahardfacing electrode 1 (HF1) bhardfacing
electrode 2 (HF2) and chardfacing electrode 3 (HF3)
Table 2 Percentage chemical composition of hardfacing alloys
Hardfacing electrode type C Mn Si Cr Mo V Ti Fe
Hardfacing electrode 1 (HF1) 3.5 1.0 – 23.0 – 1.0 0.5 Rem.
Hardfacing electrode 2 (HF2) 4.0 1.2 1.0 30.0 1.9 – – Rem.
Hardfacing electrode 3 (HF3) 4.5 1.2 1.0 33.0 – – – Rem.
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(Epiphot 200 of Nikon make) at a magnification of 2009.
The optical micrographs (200X) of the hardfaced speci-
mens (HF1, HF2 and HF3) were captured and have been
reported in the results Sect. 3.2.1.
2.6.2 Measurement of Microhardness
For obtaining microhardness of the hardfacings, the spec-
imens were cut, mounted and polished. The microhardness
of the hardfacings was measured by using microhardness
tester Miniload 2 (Leitz, Germany) fitted with a Vickers
pyramidal diamond indenter. Each reported value of the
microhardness was the mean value of five measurements
made and are reported in results Sect. 3.2.2. These
microhardness values were plotted as a function of distance
from the hardfacing/substrate interface.
2.6.3 X-ray Diffraction (XRD) Analysis
XRD analysis was performed on all the hardfaced speci-
mens in order to determine the various phases present on
their surfaces. The X-ray diffraction patterns were acquired
by using a Bruker AXS D-8 Advance Diffractometer
(Germany) with CuK
a
radiation and nickel filter at 30 mA
under a voltage of 40 kV. X-Ray diffraction patterns of
hardfaced ASTM A36 steel specimens have been reported
in the results Sect. 3.2.3.
2.6.4 Field Emission Scanning Electron Microscopy (FE-
SEM) and Energy Dispersive X-ray (EDAX) Analysis
2.6.4.1 Surface Morphology/EDAX Analysis The surface
morphologies of the hardfaced specimens were examined
with the help of a Field Emission Scanning Electron
Microscope (FEI Quanta 200F, Made in Czech Republic)
fitted with an EDAX Genesis software attachment. SEM/
EDAX analysis describing the typical microstructures and
elemental analysis of the hardfaced specimens has been
reported in results Sect. 3.2.4.
2.6.4.2 X-ray Mapping Analysis Elemental X-ray map-
ping analysis of the top surface of the weld bead of the
hardfaced samples was accomplished on field emission
scanning electron microscope (FEI, Quanta 200F Com-
pany) for image acquisition required a back scattered
electron image (BSEI) and secondary electron image (SEI)
mode. This elemental X-ray mapping of the top surface of
the weld bead or hardfacings was conducted to identify the
distribution of the different alloying elements in the hard-
facing alloys or materials and has been reported in results
Sect. 3.2.5.
3 Results
3.1 Visual Observations
The three different hardfacing electrodes were successfully
deposited on ASTM A36 substrate material. The macro-
graphs of hardfaced ASTM A36 steel specimens are shown
in Fig. 3. After deposition of the hardfacing material by
MMAW, the specimens were machined to the specified
size on the surface grinding machine due to the tremendous
hardness of the deposited layers. Further, the hardfaced
specimens were polished using emery papers of grit sizes
220, 400, 600 and subsequently on 1/0, 2/0, 3/0 and 4/0
grades polishing papers. The hardfaced specimens had the
shining top surface.
3.2 Surface Analysis
3.2.1 Metallographic Studies
Figure 4shows the optical micrographs (2009) of the
hardfaced specimens. The microstructure of hardfacing
material 1 (HF1) consisted of dendritic structure and the
microstructure of hardfacing material 2 (HF2) and hard-
facing material 3 (HF3) consisted of non-uniform grains.
The microstructure of the hardfacings was overlaid with a
number of carbides that increased with the addition of Cr
and C content in the hardfacing electrodes. Moreover, the
Table 3 Welding parameters taken
Parameters Hardfacing alloys
Hardfacing 1 Hardfacing 2 Hardfacing 3
Electrode diameter (mm) 4.0 6.3 6.3
Electrode length (mm) 350 450 450
Welding current (A) 125 125 125
Welding speed (mm/min) 100–120 100–120 100–120
Preheating for 1 h (°C) 200 200 200
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microstructure consisted of a network of primary carbides
(M
7
C
3
: (Cr,Fe)
7
C
3
) in the form of long spine, such as
blades and hexagonal platelet (hollow hexagons) in case of
the hardfacings containing high Cr and C content.
3.2.2 Evaluation of Microhardness of the Coatings
The microhardness of the hardfacings materials was mea-
sured along the cross-section of the hardfaced-ASTM A36
steel substrate. Figure 5shows the microhardness profiles
along the cross-section of the hardfacings as a function of
distance from the hardfacing-substrate interface. The crit-
ical hardness values of the ASTM A36 steel (substrate)
were found to be in the range of 210–220 Hv. From the
microhardness profiles, it is obvious that the hardfacing 3
(HF3) had maximum microhardness in the order of
718–722 Hv. The hardfacing 1 (HF1) and hardfacing 2
(HF2) had microhardness in the range of 433–440 and
550–555 Hv respectively.
3.2.3 X-ray Diffraction Analysis (XRD) of the Hardfacings
XRD diffractograms for hardfacing 1(HF1), hardfacing 2
(HF2) and hardfacing 3 (HF3) on ASTM A36 steel are
depicted in Fig. 6. The diffractometer interfaced with
Bruker DIFFRACplus X-Ray diffraction software provided
‘d-spacing’ values directly on the diffraction pattern. These
‘d’ values were then used for recognition of various phases
with the help of JCPDS data cards. As indicated by the
diffractograms, Cr
3
C
2
,Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
and
Cr
23
C
6
were the main phases present in the hardfacing 1
(HF1). Further, in case of hardfacing 2 (HF2) the promi-
nent phases were Cr
3
C
2
,Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
,Cr
23
C
6
and FeC. The phases identified in case of hardfacing 3
(HF3) were Cr
3
C
2
,Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
,Cr
23
C
6
, FeC
and Fe
2
C.
3.2.4 Surface Morphology of Hardfacings
The microstructure of the hardfacings comprised of pri-
mary carbides (M
7
C
3
: (Cr,Fe)
7
C
3
) and eutectic colonies of
[Cr–Fe ?(Cr,Fe)
7
C
3
] as shown in Fig. 7. It was observed
that with an increase in the C and Cr content in the hard-
facing electrodes, there was an increase in the fraction of
primary M
7
C
3
carbides but their size was decreased. Fur-
ther, with an increase in the C and Cr content, the fraction
of primary carbides increased, though the fraction of
eutectic colonies decreased. Accordingly, when the C and
Cr content of hardfacing electrodes were increased, the size
of primary carbides decreased.
Insignificant effect was noticed on the morphology of
primary carbides with the increase in Cr and C content,
Fig. 3 Surface macrographs for the hardfaced specimens ahardfacing material 1 (HF1), hardfacing material 2 (HF2) and hardfacing material 3
(HF3)
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however the size of the primary carbides seemed to be
refined. The hardfacings were free from cracks, defects,
unmelted particles and pores. The increase in Cr and C
content was found to be beneficial in increasing the area
fraction of carbides which in turn increased the hardness
and improved the wear resistance. EDAX point analysis at
point 1 and point 2 confirmed the presence of desired
hardfacing electrode 1 elements like C, Cr, Mn, V, Ti and
Fe on the surface of hardfacing 1 (HF1) with some amount
of O as shown in Fig. 7a. EDAX point analysis at point 3
and point 4 confirmed the presence of desired hardfacing
electrode 2 elements such as C, Cr, Mn, Si, Mo and Fe on
the surface of hardfacing 2 (HF2) as shown in Fig. 7b. The
presence of minute amounts of O was also noticed. EDAX
point analysis at Point 5 and point 6 confirmed the presence
desired hardfacing electrode 3 elements such as C, Cr, Mn,
Si and Fe on the surface of the hardfacing 3 (HF3) along
with some amount of O as shown in Fig. 7c.
3.2.5 X-ray Mapping
Elemental X-ray mapping (surface scan analysis) of the top
surface of the weld bead of the hardfaced specimens was
conducted to identify the distribution of the different
alloying elements of the hardfacing alloys or materials on
the hardfaced surface and is displayed in Fig. 8. Elemental
X-ray mapping of the top surface of the weld bead of the
hardfacing material 1 (HF1) on ASTM A36 steel as shown
in Fig. 8a demonstrated the presence of Cr, C, Mn, V, Ti
and Fe as well as small amount of O. Figure 8b depicts the
elemental X-ray mapping of the top surface of the weld
bead of the hardfacing material 2 (HF2) on ASTM A36
steel which indicated the presence of Cr, C, Mn, Si, Mo and
Fe with some amount of O. Figure 8c illustrates the ele-
mental X-ray mapping of the top surface of the weld bead
of the hardfacing material 3 (HF3) on ASTM A36 steel
which indicated the presence of Cr, C, Mn, Si and Fe as
well as small amount of O.
Fig. 4 Optical micrographs (200 X) of the surface of hardfaced specimens ahardfacing material 1 (HF1), hardfacing material 2 (HF2) and
hardfacing material 3 (HF3)
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4 Discussion
The microstructure of the hardfacings was overlaid with a
number of carbides that increased with the addition of Cr
and C content in the hardfacing electrodes. Moreover, the
microstructure comprised of a network of primary carbides
(M
7
C
3
: (Cr, Fe)
7
C
3
) in the form of long spine, such as
blades and hexagonal platelet (hollow hexagons) in case of
the hardfacings containing high Cr and C content as shown
in the optical micrographs (2009) of the hardfaced speci-
mens in Fig. 4. The microstructure of hardfacing material 1
(HF1) comprised of dendritic structure and the
microstructure of hardfacing material 2 (HF2) and hard-
facing material 3 (HF3) composed of non-uniform grains.
Commonly the measurement of microhardness across
the cross-section was done rather than on the surface for
the characterization and quality control of coatings. As
reported by Tucker [10], hardness is the utmost repeatedly
discussed mechanical property of the surface coatings. The
microhardness of the three different types of Fe–C–Cr
based hardfacing materials were measured along the cross-
section of the hardfaced-ASTM A36 steel substrate. The
critical hardness values of the ASTM A36 steel were found
to be in the range 210–220 Hv. From the microhardness
profiles along the cross-section of the hardfacings as a
function of distance from the hardfacing-substrate interface
(Fig. 5), it was obvious that the hardfacing 3 (HF3) had
shown maximum microhardness of the order of 718-722
Hv. The hardfacing 1 (HF1) and hardfacing 2 (HF2) had
shown microhardness in the range of 433–440 and
550–555 Hv respectively. The measured microhardness
values for the hardfacing material 1 (HF1), hardfacing
material 2 (HF2) and hardfacing material 3 (HF3) along the
cross-section of the hardfacings were almost within the
range of microhardness values observed for Fe–C–Cr based
hardfacing materials by [1,11,12,14]. Microhardness
profile across the cross-section for hardfacing 1 (HF1),
hardfacing 2 (HF2) and hardfacing 3 (HF3) on ASTM A36
steel (substrate) demonstrated some increase in the
microhardness of ASTM A36 steel at the substrate-hard-
facing interface. The hardening of the ASTM A36 steel as
noticed in the present study might have taken place due to
the formation of primary carbides (M
7
C
3
: (Cr, Fe)
7
C
3
) that
are extremely hard and which is in agreement with the
findings of [9,11–14].
XRD diffractograms for hardfacing 1 (HF1), hardfacing
2 (HF2) and hardfacing 3 (HF3) on ASTM A36 steel are
illustrated in Fig. 6. As indicated by the diffractograms,
Cr
3
C
2
,Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
and Cr
23
C
6
were the main
phases present in the hardfacing 1 (HF1). Further, in case
of hardfacing 2 (HF2) the prominent phases were Cr
3
C
2
,
Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
,Cr
23
C
6
and FeC. The phases
Fig. 5 Microhardness profile across the cross-section for hardfacing
1 (HF1), hardfacing 2 (HF2) and hardfacing 3 (HF3) on ASTM A36
steel
Fig. 6 X-ray diffraction pattern of hardfaced ASTM A36 steel
ahardfacing 1 (HF1), bhardfacing 2 (HF2) and hardfacing 3 (HF3)
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identified in case of hardfacing 3 (HF3) were Cr
3
C
2
,Fe
3
C,
Cr
2
C, Cr
7
C
3
,Fe
7
C
3
,Cr
23
C
6
, FeC and Fe
2
C. The phases
recognized in the hardfacing material 1 (HF1), hardfacing
material 2 (HF2) and hardfacing material 3 (HF3) were
almost in agreement with the findings of [14,15].
The surface morphology of the three different Fe–C–Cr
base hardfacing electrodes deposited on ASTM A36 steel
substrate were displayed by SEM micrographs along with
EDAX analysis in Fig. 7. The microstructure of the these
hardfacings comprised of primary carbides (M
7
C
3
: (Cr,
Fig. 7 Surface morphology and EDAX patterns from different spots on hardfaced ASTM A36 steel ahardfacing 1 (HF1), bhardfacing 2 (HF2)
and hardfacing 3 (HF3)
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Fe)
7
C
3
) and eutectic colonies of [Cr–Fe ?(Cr, Fe)
7
C
3
].
With an increase in the C and Cr content in the hardfacing
electrodes, there was an increase in the fraction of primary
M
7
C
3
carbides but their size was decreased. Further, with
an increase in the C and Cr content, the fraction of primary
carbides increased, though the fraction of eutectic colonies
decreased. Accordingly, when the C and Cr content in the
hardfacing electrodes was raised, the size of primary car-
bides decreased. Insignificant effect was noticed on the
morphology of primary carbides with an increase in Cr and
C content, however the size of the primary carbides seemed
to be refined. The hardfacings were free from cracks,
defects, unmelted particles and pores. The increase in Cr
and C content was found to be beneficial in increasing the
area fraction of carbides that increased the hardness and
improved the wear resistance which is in agreement with
that reported by [12,13,16,17]. Point 1 and 2 in Fig. 7
indicates point of interest. The EDAX genesis software
expresses the percentage elemental compositions present at
the point of interest. Even though the percentage elemental
composition corresponds to the selected points on the as-
sprayed surfaces, but it is quite useful to interpret the
formation of desired compositions in the coatings. EDAX
point analysis at point 1 and point 2 confirmed the presence
of desired hardfacing electrode 1 elements such as C, Cr,
Mn, V, Ti and Fe on the surface of hardfacing 1 (HF1) with
some amount of O as shown in Fig. 7a. EDAX point
analysis at point 3 and point 4 confirmed the presence of
desired hardfacing electrode 2 elements such as C, Cr, Mn,
Si, Mo and Fe on the surface of hardfacing 2 (HF2) as
shown in Fig. 7b. The presence of minute amounts of O
was also noticed. EDAX point analysis at Point 5 and point
6 confirmed the presence desired hardfacing electrode 3
elements such as C, Cr, Mn, Si and Fe on the surface of the
hardfacing 3 (HF3) along with some amount of O as shown
in Fig. 7c.
Elemental X-ray mapping (surface scan analysis) of the
top surface of the weld bead of the hardfaced specimens
was conducted to identify the distribution of the different
alloying elements of the hardfacing alloys or materials on
the hardfaced surface and is displayed in Fig. 8. Elemental
X-ray mapping of the top surface of the weld bead of the
hardfacing material 1 (HF1) on the ASTM A36 steel
demonstrated the presence of Cr, C, Mn, V, Ti and Fe as
well as small amount of O. The elemental X-ray mapping
of the top surface of the weld bead of the hardfacing
material 2 (HF2) on ASTM A36 steel indicated the pres-
ence of Cr, C, Mn, Si, Mo and Fe with some amount of O.
The elemental X-ray mapping of the top surface of the
weld bead of the hardfacing material 3 (HF3) on ASTM
A36 steel indicated the presence of Cr, C, Mn, Si and Fe as
well as small amount of O. EDAX analysis of the surface
of the hardfacings supported the results obtained by XRD
analysis as shown in Fig. 6and elemental X-ray mapping
of the top surface of the weld bead of all the hardfacings as
shown in Fig. 8.
Fig. 8 a Elemental X-ray mapping of the top surface of the weld bead of hardfacing material 1 (HF1), belemental X-ray mapping of the top
surface of the weld bead of hardfacing material 2 (HF2), celemental X-ray mapping of the top surface of the weld bead of hardfacing material 3
(HF3)
123
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5 Conclusions
Three different Fe–C–Cr based hardfacing electrodes of
ESAB make were successfully deposited on the surface of
substrate material, i.e. ASTM A36 steel by using MMAW
process. These hardfacings were characterized for
microstructural characteristics and microhardness in the
present study. The following inferences were made based
on the present investigation:
1. The surface micrographs and characteristics demon-
strated that these hardfacings were free from cracks,
defects, un-melted particles and pores. The microstruc-
ture of the these hardfacings comprised of primary
carbides (M
7
C
3
: (Cr, Fe)
7
C
3
) and eutectic colonies of
[Cr–Fe ?(Cr, Fe)
7
C
3
].
2. The optical micrographs of the hardfaced samples
validated that in case of the hardfacings containing
high Cr and C, the microstructure comprised of a
network of primary carbides (M
7
C
3
: (Cr, Fe)
7
C
3
) in the
form of long spine, such as blades and hexagonal
platelet.
3. The critical hardness values of the ASTM A36 steel
were found to be in the range 210–220 Hv. The
hardfacing 3 (HF3) had shown maximum microhard-
ness of the order of 718–722 Hv. The hardfacing 1
(HF1) and hardfacing 2 (HF2) had shown microhard-
ness in the range of 433–440 and 550–555 Hv
respectively.
4. The phases recognized by XRD analysis for hardfacing
material 1 (HF1) on ASTM A36 steel were Cr
3
C
2
,
Fe
3
C, Cr
2
C, Cr
7
C
3
,Fe
7
C
3
and Cr
23
C
6
as the main
phases. Further, in case of hardfacing material 2 (HF2)
the prominent phases were Cr
3
C
2
,Fe
3
C, Cr
2
C, Cr
7
C
3
,
Fe
7
C
3
,Cr
23
C
6
and FeC. The main phases identified in
case of hardfacing material 3 (HF3) were Cr
3
C
2
,Fe
3
C,
Cr
2
C, Cr
7
C
3
,Fe
7
C
3
,Cr
23
C
6
, FeC and Fe
2
C.
5. EDAX analysis of the surface of these hardfacings
backed the results obtained by XRD analysis and
elemental X-ray mapping of the top surface of the
weld bead of all hardfacings.
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