wear behaviour of smaw hardfaced mild steel and … · 2017. 7. 30. · kapil chawla assistant...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 1652–1661, Article ID: IJMET_08_07_181

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

WEAR BEHAVIOUR OF SMAW HARDFACED

MILD STEEL AND INFLUENCE OF DILUTION

UPON HARDFACING PROPERTIES.

Mandeep Singh

Research Scholar, I.K.G. Punjab technical University and working as Assistant professor,

Lovely professional university, Phagwara, India.

Mohd. Majid

Assistant professor, SLIET, Longowal, India.

M. A. Akhtar

Associate professor, SLIET, Longowal, India.

Hitesh Arora

Assistant professor, Lovely professional university, Phagwara, India.

Kapil Chawla

Assistant professor, Lovely professional university, Phagwara India.

ABSTRACT

Hardfacing is a technique used to enhance surface properties of a metallic

component, as a specially designed alloy is welded to achieve required wear

properties. Surface properties and quality depend upon the selected alloy metal

composition and welding methods. In the present work, hardfacing of mild steel was

carried out and wear resistance was measured on different layers of hardfacing.

Dilution plays important role in hardfacing and can be defined as the chemical

composition modification of weld metal, caused by the portion of base metal that

suffers melting and starts to form the fusion zone.

For the above purpose, mild steel plate with dimensions of 100*50*10 mm was

hardfaced with Fe-Cr-C alloy with the help of SMAW process. Bead on plate type

specimens were prepared for the measurement of dilution. The dilution was measured

with the help of image analyzer. Wear and hardness tests were carried out to compare

them with respective dilution levels. Chemical compositional analysis was also done

to measure the effect of dilution upon carbide forming elements. Wear test was carried

out on a pin on disc machine. The pins of 6*25 mm size were prepared by cutting the

welded plates with the help of CNC wire cut EDM. Hardness was measured with

hardness tester in Vickers hardness scale. Optical microscopy of specimens was also

carried out to study the micro-structural properties of hardfacing layers.

Mandeep Sing, Mohd. Majid, M. A. Akhtar, Hitesh Arora and Kapil Chawla


Results show wear resistance and hardness is maximum at lower dilution.

Hardness decreases with increase in dilution due to fact that higher amounts of

dilution results in coarser grained microstructure, which is relatively softer than fine

grained microstructure.

Key words: Dilution, Wear Resistance, Mild Steel, Hardness and Hardfacing.

Cite this Article: Mandeep Sing, Mohd. Majid, M. A. Akhtar, Hitesh Arora and Kapil

Chawla Wear behaviour of SMAW hardfaced mild steel and influence of dilution

upon hardfacing properties.. International Journal of Mechanical Engineering and

Technology, 8(7), 2017, pp. 1652–1661.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

1. INTRODUCTION

Hardfacing is a process of depositing a hard, wear, oxidation and corrosion resistant material

to the surface by welding, spraying or allied welding processes to control wear or loss of

material under different service conditions [1]. Hardfacing is economical as compared to

improve the desired properties of the entire component, as Hardfacing involves the

application of a coating to the surface of a low cost base metal [2]. The surfaces are generally

coated by using welding or allied welding processes excluding the use of post weld heat

treatment [3].

1.1. Concept of dilution in Hardfacing

Dilution can be defined as the ratio of substrate melted area to the total melted area as

described in figure I.

Figure 1 Schematic representation of weldment cross-section

%age Dilution =�.�

�.�� .�∗ 100 (1.1)

Where A.P - Area of penetration, A.R - Area of reinforcement, B.M - Base metal.

A lot of work has been done to establish the relationship between welding parameters and

dilution through different welding processes [4], since abrasive wear resistance is influenced

greatly by the dilution [5]. In arc welding, arc voltage, arc current, travel speed and polarity

have a significant influence on the dilution. Arc current has considerable influence as high

current gives rise to more dilution, because high current intensities causes larger penetration

area, causing a higher level of dilution [6]. Number of deposit layers can be increased so as to

minimize dilution as more number of layers results in an increase in reinforcement, hence

decreased dilution [7]. Buffer layer can be used to provide proper bonding between the

hardfacing deposit and the base metal[6]. To some extent, buffer layer acts as intermediate

metallic layer that reduce dilution as there is very less intermixing of deposit to the base

metal[8].

Wear resistance and other desirable properties are dependent on dilution as service

performance decrease with dilution. Hardfacing alloys can be deposited in multi layers to

minimize the effect of dilution [9].

Wear behaviour of SMAW hardfaced mild steel and influence of dilution upon hardfacing

properties.


2. EXPERIMENTATION

Weld beads on mild steel plates have been deposited using Fe based hardfacing alloy by

Shielded metal arc welding process. The process parameters, base metal composition, hard

facing alloy and buffer layer composition is described in following table I. Buffer layer

electrode is also used to provide proper bonding of hardfacing alloy and base metal. An

interpass temperature of 250 degree was maintained between the successive layers of hard

facing alloy.

Table 1 percentage Chemical composition of materials

Materials C Si Mn P S Fe

Mo Cr V

Base plate 0.26 0.17 0.401 0.095 0.033 Rest

Hardfacing

electrode 0.65 1 0.7 Rest

1.1 7.8 0.8

Buffer

electrode 0.1 0.65 1.5 0.03 0.03 Rest

3. TESTING

Following tests have been carried out on the samples, with the parameters given in table II.

1. Hardness test, 2 Microstructural analysis, 3 Wear resistance test, 4 Chemical compositional

analysis, 5 dilution measurement.

2. Hardness test

3. The hardness test is carried out by polishing the cross-sectioned samples with amri papers

upto grade 800 with a load of 500 grams. The hardness tester is used to measure the hardness

across the weld bead in Vickers hardness scale. The readings are taken at three different spots

and their mean has been taken.

Table 2 Process parameters selected for testing

Sample number Parameters

Current

(ampere)

Hardfacing layers

1 170 3

2 170 1

3 150 3

4 150 1

2. THE MICROSTRUCTURAL ANALYSIS

Microstructural observations have been taken by optical microscope at the magnification of

100X. Prior to observations, the samples are polished and etched with 3% nital for 10

seconds.

3. WEAR RESISTANCE TESTING

Wear resistance testing has been done with pin on disc machine. Prior to wear resistance

testing, the pins with dimensions of 6mm dia. ×25 mm length has been prepared7. Wear test is

performed with disc rotating speed of 250 RPM on a disc diameter of 80 mm with 3 kg load

for the sliding distance of 1500m in 4 intervals.



Figure 3. Pins for wear resistance testing

The sliding distance is divided into 4 parts and at every 375 meters of sliding distance, the

weight of pin is measured with micro-weighing machine having the least count of 0.0001

gms. The weight loss in every 375 meters is then used for further calculations of wear volume

loss and wear resistance etc. [10]

�� ! ��" =#$%&'( )*++

,-∗.$/%+(0 1

�� 1�!2� ! 3�/��" =,

#$56 65($…… 2

�� 1�!2� ! 3�/��" =,

#$56 65($… 3

4. CHEMICAL COMPOSITIONAL ANALYSIS

Chemical compositional analysis has been done on the mild steel and hardfacing layers and

increase in %age of elements in hardfacing layers were evaluated to measure the effect of

dilution upon wear resistance and hardness.

5. DILUTION MEASUREMENT

Dilution level were measured with image analyser. Macrostructures were taken at 10× (figure

III) and area of reinforcement and penetration were measured to measure %age dilution.

Figure 3 Macrostructures for dilution measurement.

Sample 1 Sample 2 Sample 3 Sample 4


properties.


4. RESULTS AND DISCUSSIONS

4.1. Microstructural observations

The microstructures for all the samples are shown in figure IV.

Figure 4 a) Microstructural images for sample number 1.

Figure 4 b) Microstructural images for sample number 2.

Figure 4 c) Microstructural images for sample number 3.

Figure d) Microstructural images for sample number 4

Figure e) Microstructural image for base metal.

Weldment

H.A.Z

At 170 amp., 3 layers and at 100×

At 170 amp., 1 layer, 100×

100×

Mild steel

Weldment

H.A.Z

H.A.Z

H.A.Z

Weldment

Weldment

At 150 amp., 3 layer, 100×

At 150 amp., 1 layer, 100×



All the hardfaced samples in figure IV (a to d) show a microstructure consists of

martensite and retained austenite with a pattern of dendritic segregation, which becomes

refined as current has been reduced. Figure IV (a and c) shows the microstructure tempered

by multi passes, produces more precipitation of small carbides. Figure IV (b and d) shows

coarse grains as compared to Figure IV (a and c) due to reduced cooling rates. There is proper

bonding between the hardfacing layers and the base metal.

The microstructure of figure IV (e) presents pearlitic phase embedded in matrix of ferrite.

The ferrito-pearlitic microstructure with elongated ferrite grains indicates that the steel is in

hot worked conditions.

2. HARDNESS TESTING

For hardness testing, the readings are taken at three different spots across the weld bead and

their mean has been taken for the analyses as shown in figure V.

Figure 5 Schematic representation for Hardness measurement.

In figure V, hardness is maximum (876 Hv) in sample number 3. In which, lower current

(150 amperes) and 3 layers of hardfacing are used which produces finer grained structure as

compared to single layered samples, causing an increase in hardness. Whereas sample 2 has

the lowest hardness (580 Hv) across all the hardfaced samples except base metal. Which is

due to high current (170 amperes) and single layer hardfacing. High current results in slower

cooling rates resulting in a softer matrix having a lower hardness. The hardness of mild steel

is 205 Hv. Which is due to presence of relative softer phases than hardfaced samples. Sample

1 has slightly low hardness (840 Hv) than sample 3, which is due to similar welding

conditions except high current in sample 1 as compared to sample 3. Which results in coarser

dendritic segregation, thereby reduced hardness.

3. CHEMICAL COMPOSITIONAL TESTING

The chemical composition of various layers of harfaced samples along with base metal and

electrodes is given in table III.

Table 3 Chemical composition in %age of weight

Description Elements in %age of weight

C Si Mn P S Cr Mo V Fe

Base metal 0.26 0.17 0.401 0.095 0.033 - - - Rest

Hardfacing 0.65 1.0 0.7 - - 7.8 1.1 0.8 Rest

Buffer 0.1 0.65 1.50 0.03 0.03 - - - Rest

Sample 1 (3rd 0.411 0.351 0.283 0.006 0.026 5.19 0.52 0.43 Rest

Sample 2 (1st

layer) 0.302 0.262 0.313 0.007 0.026 3.08 0.27 0.22 Rest

Sample 3 (3rd

layer)

0.418 0.347 0.266 0.006 0.027 5.22 0.52 0.41 Rest

Sample 4 (1rd

layer)

0.360 0.320 0.313 0.007 0.026 3.73 0.31 0.25 Rest

840

580

876

591

205

0

500

1000

1 2 3 4 Base metal

Ha

rdn

ess

(Hv

)

Sample number


properties.


From table III, It has been observed that the base metal having C content of about 0.26%

represents mild steel. The electrode used for hardfacing has about 7.8% of Cr along with 1.1%

Mo and 0.8% V and Si and Mn as deoxidisers. The buffer layer electrode consists of

composition intermediate of hardfacing electrode and base metal. Thereby it produces good

bonding between the hardfacing electrode and the base metal. Sample number 1 consists of 3

layers of hardfacing, in which there is presence of 5.19% of Cr along with 0.52% of Mo and

0.43% of V. There is decrease in %age of P and S, which are impurities in mild steel being

removed by deoxidisers like Si and Mn into the slag. However there is slight increase in %age

of Si and Mn, which has been provided by the electrodes. In sample number 2, single layer

hardfacing is done. Presence of alloying elements is in the range of 3.08%, 0.27% and 0.22%

for Cr, Mo and V respectively. Sample number 3 is prepared with three hardfacing layers and

low current as compared to sample number 1, which results increased %age of alloying

elements like Cr, Mo and V, which are responsible for enhanced hardfacing properties.

4. WEAR RESISTANCE TESTING

Wear resistance test is carried out to measure the increase in wear resistance of hardfaced

samples. Figure VI shows the mass loss in grams for all samples and base metal.

Figure 6 Mass loss in grams for hardfaced samples and base metal.

Mass loss is measured during the wear resistance test for the sliding distance of 1500

meters. Mass loss is minimum (0.0020 g) in sample number 3 followed by sample number 1

(0.0023 g), sample number 4 (0.0085 g), sample number 2 (0.0090 g) and base metal

(0.0102). Sample number 3 has highest %age of chromium along with negotiable amounts of

Mo and V. Cr increases wear resistance whereas Mo, V increases hardness. Mass loss is

associated with presence of allowing elements and microstructure of an alloy/metal. Base

metal mild steel has highest mass loss among all samples due to softer pearlitic phase in

microstructure and unavailability of alloying elements as compared to other samples.

4. WEAR RESISTANCE

Wear resistance is estimated with the equation 1. Wear resistance test results are shown in

figure VII.

0.0023

0.009

0.002

0.00850.0102

0

0.005

0.01

0.015

1 2 3 4 Base metal

Ma

ss l

oss

(G

ram

s)

Sample number



Figure 7 Wear resistance vs time

Wear resistance is reciprocal of wear rate. It is observed from figure VII that the wear

resistance is maximum for sample number 3, which has minimum wear rate among all

samples. Similarly, sample number 2 has minimum wear resistance among all hardfaced

samples with a maximum wear rate. Increased wear resistance is associated with the presence

of alloying elements and wear resistance particles in the substrate. Sample number 1 and

sample number 3 has higher amount of Cr ,V and Mo (Table 3), causing better wear

resistance than sample number 2 and sample number 4.

5. DILUTION MEASUREMENT

%age dilution across different samples is given in table IV.

Table 4 %age dilution across different samples

Sample number %age dilution

1 22.7

2 36.1

3 19.8

4 32

6. EFFECT OF DILUTION ON WEAR RESISTANCE

Wear resistance is strongly influenced by the amount of dilution in welding. Higher amounts

of dilution results in mixing of hardfacing deposits into base metal. Which in turn reduces the

desired properties like hardness and wear resistance. Table V shows a comparison between

wear resistance and respective dilution levels.

The chemical composition testing has been carried out to measure the influence of dilution

upon dissolution alloying elements into base metal. In 3rd layer of hardfacing with low current

(150 ampere), dilution is minimum at 19.8%. The wear resistance is maximum at 162.8

Nm/mm3, which is due to The presence Cr, Mo and V elements in the range of 5.22%, 0.52%

and 0.41% respectively. Whereas in hardfacing deposit (electrode) the elements are in the

range of 7.8%, 1.1% and 0.8% respectively. which shows the mixing of alloying elements

with base metal. As there is an increase in amount of wear resistant elements (like Cr),

carbide formation gets increased, which results in enhanced wear resistance. The specimen

0

10

20

30

40

50

60

70

80

360 720 1080 1440

we

ar

resi

sta

nce

(N

m/m

m3)

Time (seconds)

sample 1

sample 2

sample 3

sample 4


properties.


with 3 layers and high current (170 ampere) has dilution of 22.7% and wear resistance of

142.9 Nm/mm3. With an increase in current, there is an increase in area of molten pool.

Which results in increased dilution level and decreased wear resistance as alloying elements

(Cr, Mo and V) are in the range of 5.19%, 0.51% and 0.43% respectively. In single layer

hardfacing with low current, dilution is 32%

Table 5 Wear resistance and dilution

%age dilution 19.8 22.7 32 36.1

Wear resistance

(Nm/mm3) 162.8 142.9 33.4 31.14

and wear resistance is 33.4 Nm/mm3 only. Which is due to lower hardness and decreased

amount of alloying elements. Wear resistance is lowest 31.14 Nm/mm3 in single layer

hardfacing with high current, due to 36.1% of dilution.

5. CONCLUTIONS

Following conclusions have been drawn from this work:

1. Hardness and wear resistance increases with increase in hardfacing layers and decreases with

increase in current.

2. Hardness and wear resistance increases by 31.7% and 78.45% respectively, as the hardfacing

layers are increased from 1 to 3.

3. Hardness and wear resistance decreases by 5.96% and 9.48% respectively, with 13.33%

increase in current.

4. Dilution increases linearly with current. With an increase of 13.33% in current, dilution

increases by 11.19%.

5. Dilution decreases as the hardfacing layers are increased. Dilution decreases by 32.6% , when

the hardfacing layers are increased from 1 to 3.

6. With 82.32% increase in dilution, Wear resistance decreases by 80.8%.

6. FUTURE SCOPE

1. The work can be carried out with design techniques like fractional factorial design, Taguchi

orthogonal array, Response surface methodology etc.

2. The effect of dilution on wear resistance can be studied with other hardfacing deposits based

on titanium, nickel, cobalt, tungsten etc. alloys.

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wear behaviour of smaw hardfaced mild steel and … · 2017. 7. 30. · kapil chawla assistant...

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