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CHAPTER 1
INTRODUCTION
1.1TRANSIENT LIQUID PHASE BONDING
Transient liquid phase (TLP) bonding is a relatively new bonding
process that joins materials
using an interlayer. On heating, the interlayer melts and the
interlayer element (or a
constituent of an alloy interlayer) diffuses into the substrate
materials, causing isothermal
solidification. The result of this process is a bond that has a
higher melting point than the
bonding temperature. It is capable of producing nearly invisible
joints that have strengths and
other properties similar to the base metal.
PRINCIPLE
The main principle of the process is solid state diffusion into
the material to be joined. The
process has been applied to several metallic systems but the
concept is not limited to any
particular class of materials, but rather to systems whereby a
chemical or other driving force
inherently leads to solid state equilibrium.
1.2 STEPS IN TLP BONDING PROCESS:
1. Setting up the bond
Bond setup usually consists of placing a thin interlayer between
the substrates.
The interlayer can be in many different formats:
1. Thin foil
2. Amorphous foil
3. Fine powder
4. Powder compact
5. Brazing paste
6. Physical vapour deposition process
7. Electroplating
2. Heating upto bonding temperature to produce liquid in bond
region
3. Holding the assembly at bonding temperature until the liquid
has solidified
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4. Homogenizing the bond at a suitable heat-treating
temperature
The modes of heating in the above three stages can be:
1. Radiation
2. Conduction
3. Radio-frequency induction
4. Resistance
5. Laser
6. Infrared
1.3 PHASE DIAGRAM REPRESENTING THE PROCESS
Upon heating an interlayer of B rapidly dissolves the parent
metal A until the composition at
CL is reached. Widening next occurs lowering the concentration
of B in the liquid to CL.
Isothermal solidification then reduces the amount of liquid
although the composition
remains constant at CL. Once solidification is complete, the
maximum concentration in the
joint can be reduced from CL by homogenization.
Fig 2. Schematic of a binary eutectic phase diagram showing the
stages in TLP bonding. [3]
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1.4 STAGES
The TLP process has been divided into four stages by Tuah Poku
et al[13] namely. Each
stage is shown in the figure 2.
1. Dissolution
2. Widening
3. Isothermal solidification
4. Homogenization
A fifth stage termed stage 0 has been shown to account for the
effects during heating up to
bonding temperature.
1. Dissolution
A layer of pure metal B is sandwiched between a structure of
metal A. Upon heating
to the bonding temperature the interlayer and parent metal
undergo interdiffusion
to form a liquid phase. As the dissolution progresses, the
liquid composition moves
from CL to CL. The time required for this step has been
estimated to be on the
order of seconds. Therefore any MPD previously diffused would be
remelted.
2. Widening
Upon the completion of the dissolution stage, the widening of
the interlayer drives
the composition to the alpha rich liquidus at CL. The widening
process requires
times on the order of minutes.
3. Isothermal solidification
This is the most important step as it requires the greastest
amount of time and is
dependent on the width of liquid interlayer formed and the rate
of diffusion into the
bulk. During this stage the diffusion of the MPD into the parent
metal occurs at a
rate dependant on the diffusion constant in the bulk, provided
there are no kinetic
restrictions at the interface.
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4. Homogenization
Homogenization completes the process and is dependant on the
time at
temperature. It is controlled by a solid state diffusion rate
similar to other
homogenization processes. The homogenization time is a function
of the required
maximum tolerable MPD concentration.
Fig 2. Four stages of TLP bonding. Stage 0 has been included to
account for interdiffusion
occurring duing heat up. The grey shading indicates the
concentration of MPD. The arrows
indicate the direction of movement of solid liquid
interface.[2]
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1.5 CLASSIFICATION OF TLP BONDING ON THE BASIS OF INTERLAYER
COMPOSITION
1. TYPE I
In type I processes the interlayer is a pure metal and hence is
the MPD(melting
point dpressant). This type of interlayer requires all four
stages including
interdiffusion with the parent metal before liquefying. The
extent of widening is
maximized as the concentration of the MPD must be reduced from
unity to
liquidus composition at CL.
2. TYPE II
In type II processes, an interlayer at or close to the liquidus
composition is used.
In this case, only stage III and IV occur and the amount of MPD
for a given initial
thickness is reduced. This approach used in superalloy TLP
bonding, requires
bonding times on the order of minutes versus hours in the type I
approach.
1.6 VARIANTS OF TLP BONDING
1. TEMPERATURE GRADIENT TLP BONDING
The application of a temperature gradient causes a non-planar
bond interface which
tends to result in stronger bonds
2. WIDE-GAP TLP BONDING
Gaps of 100-500m can be bonded or repaired by the use of a
melting and non-
melting constituent. This technique can also be used in
conventional TLP bonding to
accelerate isothermal solidification.
3. ACTIVE TLP BONDING
A ceramic and metal can be joined by a multi-component
interlayer in which atleast
one componenet reacts with the ceramic while another diffuses
into the metal to
cause isothermal solidification
4. PARTIAL TLP BONDING
This technique is used to join ceramics. The interlayer consists
of thin layers of low-
melting-point metals or alloys on each side of a much thicker
refractory metal or
alloy layer.
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1.7 APPLICATIONS OF TLP BONDING
TLP bonding is often used in high-stress, high-temperature
applications where
brazing, welding, and diffusion bonding cannot be used for
various reasons. The
requirement of metal systems suitable for TLP bonding must have
stability at
elevated temperatures and high diffusion coefficient of MPD
through the matrix.
This makes Ni based superalloys as the ideal metal for TLP
bonding. The process has
been successfully applied to other metals as well.
1. Al-based alloys
2. Ti-based alloys
3. Ceramics
4. Dissimilar metals
5. Metal to ceramic
6. Fe based alloys
Table 1. APPLICATION TO Fe-BASED ALLOYS[1]
SUBSTRATE INTERLAYER
304SS Ni-Cr,304L SS, BNi-2
304L SS NB 51
Duplex SS Cu, Fe-B-Si, Ni-Si-B, MBF-30, MBF-35,MBF-50,
MBF-80
Carbon steel Cu, Fe-B
Fe-Ni-Cr Ni-B-Cr-Si(various combinations)
Incoloy MA956 B,Fe-B-Si
Incoloy MA957 Fe-B-Si, BNi-1a, BNi-3
Low carbon steel Fe-B-Si, BNi-2
ODS(oxide dispersion strengthened) steel(Fe-Cr-W-YO-Ti)
Fe-Si-B
PM2000(Fe-Cr-Al) B, Fe-B-Si
T91 steel Fe-B-Si, Fe-Ni-Cr-Si-B, BNi-2
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1.8 CHARACTERISTICS OF TLP BONDING
Table3. characteristics of TLP bonding process[1]
ADVANTAGES DISADVANTAGES
Base metal properties at joint Long bonding time (hours)
No interface remains after bonding Restricted to high
temperatures,T/Tm=0.6
Self homogenizing Fast diffusers required preferable
interstitial elements
Intermetallic formation can be achieved Rapid heat up
required
Minimum suface preparation Close fit-up required
Large and complex shapes bonded simultaneously
Post bonding heat treatment for age hardening alloys is
required
1.9 PARAMETERS
1. Interlayer thickness
2. vaccuum
3. fixturing pressure
4. Interlayer composition
5. Time
6. Bonding temperature
1. Interlayer thickness
Interlayer or foil thickness has a strong influence on the
solidification time and
thereby productivity. Higher foil thickness creates higher
volume of the liquid
metal which requires more time to solidify. Also it calls for
more time required
for homogenization as large volume of the interlayer element has
to be diffused
through the parent metal matrix. Therefore a minimum amount of
foil thickness
should be the ideal case. It is clear from figure3., as the foil
thickness is
decreased the minimum time required for isothermal
solidification decreases.
The minimum in the bonding time arises due to the trade off
between the
increase in the diffusivity and the amount of dissolution which
also increases
with temperature. Over the range of permissible bonding
temperatures, the
bonding time varies by less than an order of magnitude. Hence, a
significant
reduction in bonding time can only be achieved by reducing foil
thickness.
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Fig3. Isothermal solidification time for TLP bonding of copper
using a silver foil.[2]
The various values of interlayer thickness frequently used are
shown in table 4 below.
Table 4. Common values of inter layer thicknesses used[1]
Thickness range(m) Common thickness(es)m
Frequency(%)
500 2
2. Vacuum
The bonding process is usually confined in a vacuum to avoid
oxide formation.
Although an inert atmosphere, such as argon, can be used. The
vacuum
pressures used in the experiments referenced in [1] are normally
distributed
about 0.1 mHg (millitorr) with minimum and maximum values of
0.00015 and
34 mHg, respectively.
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3. Fixturing pressure
A pressure is usually applied to the bonding assembly to keep
the substrates
aligned and to promote bonding. Specific pressures are
categorized in table 2 by
their nearest order of magnitude.
Table 2. fixturing pressures used during TLP bonding[1]
Nearest order Frequency (%)
1 kPa 8
10 kPa 5
100 kPa 16
1 MPa 36
10 MPa 31
100MPa 4
4. Interlayer composition
Use of different interlayers in terms of composition and form
with different
metal systems has been by far the most widely experimented among
all the work
that has been done on the transient liquid phase bonding. The
process starts
from interlayer and ends at interlayer. The properties and
reaction of interlayer
elements with that of the base metal determines the
microstructure and other
properties of the TLP joint.
Requirements of interlayerMPD(melting point depressant)
Atleast one element of interlayer, MPD, must have solubility in
the base metal.
The MPD must have a significant diffusivity at the bonding
temperature to
ensure reasonable bonding times. Finally the elements in the
interlayer must not
be detrimental to the physical and mechanical properties of the
base metal.
It is desirable to have the interlayer composition as close to
the liquidus at the
bonding temperature as possible. Taking two foil interlayers,
one pure metal B
and the other an A-B alloy close to the liquidus composition.
The amount of MPD
that must diffuse in the pure metal case is,
w(C-CL)grams/cm
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where C, the initial concentration of the MPD, is unity for a
pure metal
interlayer and W is the initial foil thickness. the
solidification time, as presented
in [2] and derived by Tuah et al.[13] is,
t= { w( C/ CL)}/16D
which indicates that the bonding time varies as the square of
the initial MPD
concentration and foil width. This equation illustrates the
advantage of using
electroplated alloy interlayers which minimize both thickness
and MPD
concentration.
If the MPD is a minor constituent of the interlayer and other
constituents foran
an intermetallic with the parent metal, an increase in the
bonding time will
result. In this situation, the MPD has to diffuse through the
intermetallic. Since
diffusion in intermetallics is slow, the temperature must be
raised above the
melting point of the highest melting intermetallic in order to
achieve rapid
bonding times.
5. Time
Duration of the isothermal solidification stage to complete is
the most important
to determine the overall bonding time of the process as it is
the longest stage. If
the holding at bonding temperature is less than the time
required for complete
solidification the left over liquid can solidify has brittle
eutectic phase which can
be detrimental to the mechanical properties and the melting
point of the
resultant bond and microstructure may not be as the intended
one.
But the prediction of isothermal solidification time is a costly
and time
consuming process. This is one of the reason why the process has
not been
industrialized for mass application.
6. Temperature
The bonding temperature is dependent on the melting point of the
interlayer. It
is always below the melting point of the base metal. Bonding
temperature has to
be determined and selected in uniformity with the phase diagram
to avoid any
intermetallic compound in the final joint.
Bonding temperature has a strong influence on the microstructure
and thereby
mechanical properties of the joint. Increase in temperature
causes an increase in
the diffusion coefficient.
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CHAPTER 2
2.1 LITERATURE SURVEY
The work on TLP bonding of steels was the emphasis and basis for
the present literature
survey done. Although the process of TLP bonding has been mostly
applied to Ni based
super alloys but the process is suitable to other metal systems
as well. Use of TLP bonding
process for joining similar and dissimilar steels and also steel
with other metal system has
been attempted and has been successful. Present and future work
would be directed to join
steel(similar or dissmilar). The effect of various parameters on
the quality of joints obtained
and the productivity has been studied from the past work. Along
with that few novel
methods for interlayer fabrication and modification to the
process, such as, effect of plastic
deformation and two step heating process instead of one, were
also studied.
The papers discussed in the present literature survey are
grouped according to their
objective and parameter.
1. Interlayer thickness
As explained before less thickness leads to increase in
productivity. But there is a
certain amount of minimum thickness that is required to avoid
the pore formation in
the joint region.
N. S. Bosco et al.[3] demonstrated this on the Cu-Sn system.
They suggested that such
pores are a consequence of the growth and subsequent contact of
CuSn intermetallic
grains on the two surfaces to be bonded, prior to the formation
of transient liquid
phase. Hence they proposed a criterion stated as the thickness
of the interlayer must
exceed that which is consumed through solid state diffusion;
otherwise, no liquid is
formed at the bonding temperature. This sets a minimal
requirement on the interlayer
thickness.
2. Heating rate
N. S. Bosco et al.[3] demstrated that reductions in bonding time
can be achieved
with increasing heating rate, because of the corresponding
reductions in the
required interlayer thickness fig4. The resulting grain size was
also larger with slow
heating rates fig5.
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Fig 4. Effects of heating rate on the bonding time needed for
complete consumption of the
intermetallics, leaving the Cu solid solution as the terminal
phase.[3]
Fig5. SEM images of the coated and etched growth samples in plan
view; (a) 2 K/min, (b) 5 K/min, (c) 15 K/min. [3]
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Xuegnag Wang et al.[4] investigated the effect of two stage
heating process on the
microstructure and the mechanical properties of TLP bonding of
dissimilar steels. In this
method the samples were heated to a high temperature for short
duration and then
solidified at low temperatures for longer duration in the
isothermal solidification stage.
Table5. parameters used in TLP bonding[4]
sample Short-time heating stage Isothermal solidification
stage
Temperature(C) Time (s) Temperature(C) Time (s)
1 1270 10 1250 120
2 1260 10 1240 120
3 1240 120
4 1240 10 1220 120
5 1220 10 1200 120
Figure 6. shows the cross-sections of TLP bonds made using
conventional heating and the
two-step heating processes. A non-planar interface is observed
in all the joints by
conventional heating and the two-step heating process. However,
a planar interface is
also observed in the joint by conventional heating process.The
curvature of the interface in
conventional TLP bond is smaller than that in two-step TLP
bonds.
Some voids are found along the center line of the conventional
TLP bond at 1240 1C (Fig.
6c). No voids are found in the two-step TLP bonds at the
isothermal solidification
temperature of 1240C or above (Fig. 6a and b), and some voids
are found under the
isothermal solidification temperature of 1240C (Fig. 6d and
e).The voids in the two-step TLP
bonds depend on the short-time high temperature and isothermal
solidification
temperature. The amount of voids is decreased with the increase
of isothermal
solidification temperature during two-step TLP bonding which is
evident from the figure 6.
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Fig6. Optical micrograph of 45MnMoB-30CrMnSi dissimilar joints
made using different heating processes: (a) sample 1; (b) sample 2;
(c) sample 3; (d) sample 4. [4]
The observed mechanical properties were also better as compared
to conventional TLP
bonding process because Voids are decreased and bending strength
is increased.
Figure7. The mechanical properties of all the samples. (a)
tensile strength and (b) bending
strength. [4]
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3. TIME
H Noto et al.[5] investigated the effect of different holding
times at bonding temperature of
9CrODS(oxide dispersion strengthened) steels using
Fe-3B-2Si-0.5C filler, on elemental
distribution and nano-indentation hardness. The results were
compared with 19CrODS steel.
They observed that chromium-boride needle-like precipitates,
which induce
embrittlement, were absent in low Cr steel as is clear from fig.
8
Fig8. Maps of B and Cr distribution in the TLP bonding region
for 30 min, 1180 C bonds in:
(a) 9CrODS steel, (b) high CrODS steel. [6]
It was observed that increase in holding time causes better
diffusion and uniformity. From
the quantitative line analysis, shown in fig. 9, it is can be
clearly seen that chromium-boride
peaks diminished as the holding time was increased from 0.5 to
4.0 h. Cr diffused into the
bonding zone and its content increased. B also diffused
uniformly and Si had slow diffusion.
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Fig. 9 Results of quantitative line analyses for various
elements in 0.5 h and 4 h
bonds formed at 1180 C: (a) bonding zone, (b) DAZ, (c) parent
alloy. [5]
As the holding time increases from 0.5 to 4.0 h the uniformity
in hardness profile
occurs as the Cr boride phase present was diminished due to
better diffusion of Cr.
This is observed from the hardness plot at various regions of
the joint. Hardness
increased in the DAZ from the base metal value of 600mgf/m
clearly denotes the
formation of hard and brittle phases.
Fig. 10 Nano-indentation hardness for bonding times of 0.5, 1.0
and 4.0 h at 1180 C,
without additional heat-treatment: (a) bonding zone, (b) DAZ,
(c) parent alloy. [5]
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4. TEMPERATURE
T Vigraman et al.[6] used TLP bonding to join AISI304L to low
carbon steel with an
AISI304L interlayer at various temperatures for fixed holding
time of 90min. It was
observed from the microstructure shown in fig. 11 that reaction
zone thickness
increases with the temperature. Also coarse grains are observed
due to higher
temperatures.
Fig. 11. Microstructures of bonded sample interfaces processed
at temperatures (a) 850
C (SI), (c) 900 C (SII), (e) 950 C (SIII), the corresponding
magnified images are shown in
the right hand side, namely, (b), (d), and (f). [6]
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From the SEM images, fig. 12, the presence of voids and lack of
diffusion at the interface
on account of low temperature was observed. An increase in the
width of diffused
region occurred with increasing temperature. This increase
indicates the diffusion of
increased amounts of elements such as Cr, Ni, Si and Mn towards
the low carbon steel
when the temperature is increased.
Fig12. SEM micrographs (a and b) for sample SI, (c and d) for
sample SII, and, (e and f) for
sample SIII[6]
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An increase in temperature has a direct effect on hardness
values due to higher diffusivity.
The reason may be the increase in the thermal activation and the
migration of atoms from
either side of the diffusion couple. In the interface between
low carbon steel and the
interlayer, the picking up of elements, namely, Cr, Ni, Mn, and
Si, has been
observed due to the migration of atoms. Here, elements
especially Cr, react with carbon and
form carbides, which increases the hardness of the other
interface (interlayer and AISI 304L
base metal) due to carbon pick up and formation of carbides.
Therefore, the hardness value
increases.
5. INTERLAYER COMPOSITION
S. J. Chen et al. [7] joined T91 steel pipes bys TLP bonding
using 3 different
interlayers to find out the most suitable interlayer based on
Fe-Ni-Si-B system. Based
on the properties of the joint obtained the the best interlayer
has been identified.
The optimum process has been obtained with the result : bond
made at 1250c for
3min under 6Mpa with FeNiCrSiB composite interlayer.
Table 6. Mechanical properties were observed [7]
Sanghoon Noh et al. [8] investigated the behaviour of TLP bonded
ODS steel using
and amorphous insert material based on Fe-3B-5Si. They observed
that bonding does
not affect nano-oxide morphology of base material. It was noted
during the tensile
testing that Y-Ti-O precipitates at bonding interface triggers
micro-cracks at joint
region with proceeding deformation and enhances ductile
rupture.
Interlayer Temperature Tensile strength Bond strength Breaking
position
BNi2 1225 358 100 Joints
Fe78Si9B13 1225 736 400 Joints
FeNiCrSiB 1250 780 679 Base metal
860 980 Base metal
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Nicolas Di Luozzo et al.[9] joined carbon steel tubes using Cu
interlayer and
compared with amorphous Fe-B-Si interlayer bonds. It was
observed that the
process does not lead to completion throughout the width which
is proved by the
presence of athermally solidified Cu rich phase as noted in fig
13.
Fig 13. microstructure of the JR for the TLPB using a Cu
interlayer as obtained by FEG-SEM (Back
scattered electron mode). White contrast phase corresponds to
ASL(athermally solidified
liquid). [9]
Hiroyuki Noto et al.[10] attempted to refine the grains of TLP
bonded ODS steel by using a
newly developed ODS insert foil (Fe9Cr2W0.2Ti0.35YO0.5C3B2Si).
The grains were
refined from 40m to 14m when compared with non ODS amorphous
insert foil(F-B-Si-C)
which can be seen from the fig. 14.
The reason was attritubted to the coherency with the parent
metal matrix. The coherency
(or inoherency) between the oxide particles and the matrix can
be key to the quality of
bonding. The incoherency calculated by Bramfit equation was
quite low compared with
other oxides and carbides. It is also considered that the oxide
particles hinder the motion of
grain boundaries and suppress grain growth
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Fig. 14 The microstructure of TLP bonding using (a) amorphous
foil and (b) ODS foil. [10]
.
Xinjian Yuan et al. [11] devised a novel method of manufacturing
iron-based interlayer
based on a duplex stainless steel and a MPD (B). The position of
interlayer on the Schaeffler
diagram was selected very close to the base metal fig15. B
content of 3.93% was selected in
view of the necessary difference required in melting point
between base metal and
interlayer. Also higher B content leads to longer solidification
and homogenization time as
can be seen from fig. 16.
It was noted that as the holding time increased from 60s to
1800s the presence of Cr boride
and B nitride reduces and was completely absent at 7200s.
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Fig. 15 Positions of the selected interlayer, the duplex
stainless steel base metal and the
bond zone in Schaefller diagram[11]
Fig. 16. change in the melting temperature of filler as a
function of B concentration[11]
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23
M. A. Arafin et al. [12] investigated the effect of alloying
elements on isothermal
solidification during TLP bonding of SS410 (stainless steel) and
SS321 using a BNi-2
interlayer. They used random walk modelling technique to model
the diffusion coefficients
of the elements. Migrating solid/liquid interface modelling and
solute distribution law were
used for the study of kinetics of isothermal solidification. The
results were compared with
experimental data fig.17 . It clearly shows that the predicted
time values are very close to
the experimental data.
Fig17. Comparison of predicted isothermal solidification times
with different confidence
levels (modified migrating solid/liquid interface model) with
experimental data for an initial
joint gap of 70m for (a) SS 410/BNi-2 and (b) SS 321/BNi-2.
[12]
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2.2 SUMMARY OF LITERATURE SURVEY TRANSIENT LIQUID PHASE
BONDING S
No.
AUTHOR TITLE MATERIAL SYSTEM CHARATERISTICS
1
Xinjian yuan et al. Microstructural
characteristics
in vaccuum tlp
alloyed
Duplex stainless
steel
1.method for making iron
based interlayer developed
2.JR was free from carbide
and nitride phases
2 M. Mazar Atabaki Microstucture
evolution in
partial tlp
bonding
Zircalloy-4 to ss321 1.active titanium filler used
2.Ti and Zr led to low
isothermal solidification and
proven that Cu has the same
effect
3 H. Noto el al. TLP of ODS
steels
ODS steels 1.sequential process for tlp
for 9CrODS steel confirmed
2.precipitation of Crboride
found in 19CrODS absent in
9CrODS steel
4 H. Noto et al. Grain
refinement of
tlp bonding
zone using ODS
insert foil
ODS martensitic
steel
1.ODS insert foil(Fe-9Cr-2W-
0.2Ti-0.35Y2O3-0.5Cr-3B-2S)
fabricated using spark plasma
sintering
2.grain size is one third of
conventional insert
3. hardness increased
5 M A Arafin et al. Effect of
alloying
elements on
isothermal
solidification
during tlp
SS410 and SS321
using BNi-2
interlayer
1.theorical isothermal
solidification time verified by
experiment
2.solubility of B for SS410
decreased by 0.3% at high
temp
6 S J Chen et al. Tlp bonding of
T-91 steel pipes
using
amorphous foil
T-91 steel with BNi2,
Fe78Si9B13 and
FeNiCrSiB
amorphous filler
1.microstructure and element
distribution examined
2.tensile and bend strength
with FeNiCrSiB eqtual to
substrate
3.fracture caused by brittle
intermetallics at interface
7 Nicolas Di Luozzo
et al.
Tlp of carbon
steel tubes
using Cu
interlayer:
characterization
and comparison
Carbon steel ,
interlayer pure Cu
1.Cu interlayer to led to
partial completion of bonding
2. cementite concentration
higher in JR with Cu
interlayers
3.tensile test specimen failed
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25
with Fe-B-Si
interlayer
at HAZ and UTS same as BM
8 Waled M.
Elthalabawy et al.
Microstuctural
development of
diffusion brazed
joint
316L SS, magnesium
alloy(AZ31) and Ni
interlayer
1.double stage bonding
process used
2.B2 intermetallics formed
during diffusion brazing stage
and had detrimental effects
9 M. I Barrena et al. Interracial
microstructure
and mechanical
strength of
diffusion
bonded joint
WC-Co/90MnCrV8
cold worked tool
steel using Cu-Ni
interlayer
1.Maximum tensile strength
obtained confirms promising
technology
2. effect of bonding time and
temp on joint quality was
studied
10 T Vigraman et al. Diffusion
bonding
AISI304L to low
carbon steel using
AISI304L interlayer
1.fracture occurred at BM
low carbon steel
2.formation of brittle phases
at high temp
3. tensile strength of
340.5Mpa
11 M. Mazar Atabaki Partial transient
liquid phase
diffusion
bonding
Zr2.5-Nb to SS321
Interlayer- one
active Ti based and
two Zr based
1.infulence of bonding temp
and time on microstructre,
microhardness, shear
strength and interlayer
thickness
2.titanium based interlayer
has better wetting behavior
on Zr surface
3.increase in temp caused
reduction in wetting
properties
4. height of interlayer was
decreased on substrate by
increasing temperature
5. Ti based interlayer
prevented formation of
brittle intermetallics
12 R. Soltani Tashi Diffusion
brazing
Ti-6Al-4v and
austenitic ss using
silver based
interlayer
1.shear strength decreased
with increasing brazing temp
and time
2.increase in temp led to
formation of intermetallics
namely Cu-Ti and Fe-Cu-Ti
-
26
13 Hongsheng
Chen et al.
Effect of Ni
interlayer on
partial tlp
bonding
ZrSnNb and
304SS
1.a-Zr phases dispersedly
exist in reaction layer
2.reaction is larger than that
without Ni interlayer
14 Sanghoon Noh et
al.
Evaluation of
microstructure
and mechanical
properties of
liquid phase
diffusion
bonded ODS
steels
ODS ferritic steel
and interlayer Fe
3B5Si
1.ODS showed homogeneous
distribution of insert material
2. YTiO precipitation
occurred upto 20micron
3.tensile strength 90% of BM
4.poor elongation and impact
fracture energy
15 T.I. Khan et al. Effect of tlp
bonding
variables on
properties of
micro duplex
steel
2205 micro duplex
SS and interlayer
pure copper and foil
based on the Fe-Si-B
1.rapid cooling and heating
suppressed formation of
sigma phase
2.mechanical and corrosion
properties similar to that of
parent alloy
16 T. Padron Modeling the
tlp bonding
behavior of
duplex SS using
Cu interlayer
Duplex SS and cu as
interlayer
1.analytical and experimental
results were compared
2.lattice and grain boundary
diffusion through alpha phase
played an imp role
3. model for homogenization
stage deviates from
experimental results
17 A.H.M.E. Rahman Tlp bonding of
commercially
pure iron using
Cu and Ag based
interlayer
Interlayer Cu-
25micron
Interlayer Au12Ge
100micron
1.Cu did not diffuse
completely in BM
2.the Au layer diffused
almost completely except
some region
3. UTS with Cu-291Mpa and
with Au 315Mpa
18 Xuegang Wang et
al.
Effect of two
step heating
process on joint
microstructure
and properties
during tlp
bonding of
dissimilar
metals
45MnMoB and
30CrMnS
1.short time high temp
heating followed by low temp
isothermal solidification
2.two step process changes
interface morphology from
planar to non planar
3. voids are decreased and
bending strength is increased
19 Nicolas Di Luozzo Microstructure Carbon steel tubes 1.JR-
ferrite, HAZ and BM
-
27
et al. and mechanical
characterization
of steel tubes
joined by tlp
bonding using
an amorphous
layer
and interlayer based
on Fe-Si-B
cementite and ferrite
2. tubes failed away from the
bond at HAZ and ultimate
tensile strength 96% of BM
20 H.M. Hdz-Garca
et al.
Effect of Si nano
particles on tlp
bonding of 304
SS
304 SS with
interlayer BNi-9
1.Si nano particles act as
MPD
2.Si induces the dissolution of
filler metal
21 M. Mazar Atabaki
et al.
TLP bonding of
SS304
SS304 with Cu
interlayer
1.intermetallic compound
2. elemental distribution
22 N.S. Bosco et al. Critical
interlayer
thickness for
TLP bonding in
Cu-Sn system
Base metal-Cu
Interlayer- Sn
1.benefits of high heating
rate on bonding time and
critical interlayer thickness
23 Hong Li et al. TLP bonding of
steel sandwich
panel under
small plastic
deformation
Interlayer- pure Cu
foil
1.lower solidification time
-
28
CHAPTER 3
METHODOLOGY
3.1GAPS
1. Practically no work has been done to study the effect of
fixturing pressure.
2. So far there has been no work on the TLP bonding using
interlayer in the form of
electroplated film which may be helpful in the reduction of
solidification time
3. Evaluation of critical interlayer thickness for steel system
and to study the
dependence of it on various forms of an interlayer
4. No work has been done on the fatigue and creep behaviour of
the TLP bonded joints.
3.2GENERAL OBSERVATIONS
1. Interlayer coherent with the parent metal matrix gives better
results in terms of
homogeneity and mechanical properties
2. MPD such as B, Si, Cu are quite commonly used for steel
system
3. Boron as the MPD(melting point depressant) has the best
diffusivity in steel
4. Holding for less durations than the required isothermal
solidification time results in
athermally solidified liquid and poor mechanical properties
3.3PROBLEM FORMULATION
1. Steel used at high temperature such as in the nuclear
application where high creep
strength is needed will be selected. The effect of different
forms and composition of
interlayers on the creep strength is proposed to be investigate
and thereby selection
of best interlayer for the selected steel.
2. Dissimilar steels will be selected and effect on their creep
properties using different
interlayers is proposed to be investigated.
3.4OBJECTIVES 1. Selection of steel
2. Identification of the various interlayers to be used.
3. Selection of proper parameters
4. Characterization of the samples
5. Analysis of the results obtained
-
29
REFERENCES [1] Grant O. Cook III and Carl D. Sorensenoverview of
transient liquid phase and partial
transient liquid phase bonding J Mater Sci (2011)
46:53055323
[2] W. D. MacDonald and T. W. Eagar Transient Liquid Phase
Bonding Process, Material
Science of Joining
[3] N. S. Bosco, F. W. Zok,critical interlayer thickness for
transient liquid phase bonding in
the Cu-Sn system Acta Materialia 52 (2004) 29652972
[4] Xuegang Wang , Xingeng Li ,effect of two-step heating
process on joint microstructure
and properties during transient liquid phase bonding of
dissimilar materials Materials
Science & Engineering A 560 (2013) 711716
[5] H. Noto , S. Ukai, S. Hayashi,transient liquid phase bonding
of ODS steels Journal of
Nuclear Materials 417 (2011) 249252
[6] T. Vigraman , D. Ravindran ,diffusion bonding of AISI 304L
steel to low carbon steel
with AISI 304L interlayer Materials and Design 34 (2012)
594602
[7] S.J. Chena, H.J. Tang, X.T. Jing,transient liquid-phase
bonding of T91 steel pipes using
amorphous foil Materials Science and Engineering A 499 (2009)
114117
[8] Sanghoon Noha, Ryuta Kasadab et. al evaluation of
microstructure and mechanical
properties of liquid phase diffusion bonded ODS steels, Fulsion
Engineering and Design
85 (2010) 10331037
[9] N. Di Luozzo, Michel Boudard,Transient liquid phase bonding
of carbon steel tubes
using a Cu interlayer: Characterization and comparison with
amorphous Fe-B-Si
interlayer bonds et al., Journal of Alloys Comp. (2013)
[10] D Hiroyuki Noto , Ryuta Kasada , grain refinement of
transient liquid phase
bonding zone using ODS insert foil, Journal of Nuclear Materials
442 (2013) S567
S571
[11] Xinjian Yuan , Chung Yun Kang,microstructural
characteristics in vacuum TLP bonds
using a novel iron-based interlayer based on duplex stainless
steel base metal alloyed
with a melting-point depressant Vacuum 99 (2014) 12-16
[12] M.A. Arafin, M. Medraj ,effect of alloying elements on the
isothermal solidification
during TLP bonding of SS410 and SS321 using a BNi-2 interlayer,
Materials Chemistry
and Physics 106 (2007) 109119
[13] Tuah-poku, I., Dollar, " A study of the transient liquid
phase bonding process applied
to a Ag/Cu/Ag sandwich joint". Metallurgical Transactions A.
19(A) (1988), 675-686
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30
Contents CHAPTER 1
..............................................................................................................................................
1
INTRODUCTION
...................................................................................................................................
1
1.1TRANSIENT LIQUID PHASE BONDING
............................................................................................
1
1.2 STEPS IN TLP BONDING PROCESS:
................................................................................................
1
1.3 PHASE DIAGRAM REPRESENTING THE PROCESS
..........................................................................
2
1.4 STAGES
.........................................................................................................................................
3
1.5 CLASSIFICATION OF TLP BONDING ON THE BASIS OF INTERLAYER
COMPOSITION ..................... 5
1.6 VARIANTS OF TLP BONDING
.........................................................................................................
5
1.7 APPLICATIONS OF TLP BONDING
..................................................................................................
6
1.8 CHARACTERISTICS OF TLP
BONDING............................................................................................
7
1.9 PARAMETERS
................................................................................................................................
7
CHAPTER 2
............................................................................................................................................
11
2.1 LITERATURE SURVEY
...................................................................................................................
11
2.2 SUMMARY OF LITERATURE SURVEY TRANSIENT LIQUID PHASE
BONDING................................ 24
CHAPTER 3
............................................................................................................................................
28
METHODOLOGY
................................................................................................................................
28
3.1GAPS
.............................................................................................................................................
28
3.2GENERAL OBSERVATIONS
............................................................................................................
28
3.3PROBLEM FORMULATION
............................................................................................................
28
3.4OBJECTIVES
..................................................................................................................................
28
REFERENCES
..........................................................................................................................................
29