1new themal barrier coating report

THERMALBARRIER COATING
Department Of Mechanical Engineering PLIT & MS Buldana Page 1
CHAPTER 01
INTRODUCTION
1.1Development of TBCs
A surging demand for global air travel has largely thriven the commercial aircraft gas
turbine engine market for decades. Airline traffic is expected to double in the next 10 to 20 years,
and so the number of gas turbine engines is set to see an anticipated growth . According to a
recent international forecast, the manufacturers will build 18,800 more gas turbine engines for
power generation with a production value of £228.7 billion in the 2014-2028 period . As driven
by the needs for stronger thrusts, higher fuel economy and lower emissions of pollutants, the rapid
development of turbine engines requires continuous innovation in gas turbine technology,
especially for the materials employed. However, the increasingly harsh working environments in
the gas turbine engines have pushed the turbine blade materials to the limits of their capability.
For instance, the temperature of gas stream in a Rolls-Royce Trent 800 or General
Electric GE90 is 1400-1500 °C, which is nearly 100 °C above the melting point of superalloys
from which turbine blades are made. An engine (with about 100 blades) could generate a power of
about 500 MW, which is sufficient to supply more than 500 homes. The centrifugal stress on the
blades is also considerable, which is extracted by the significant rotational speeds. This is
equivalent to the weight of a heavy truck hanging on each blade. Each row of blades is expected
to last at least 3 years, assuming being operated at 9 h/day. This is equivalent to about 5 million
miles of flight, or about 500 circumferences of the world. More importantly, turbine blades need
to survive against the exposure to the aggressive environment with severe oxidation and hot-
corrosion, all of which would significantly degrade the turbine blades and put passenger’s lives at
risk.
In history, one major step in increasing engine temperatures and engine efficiencies is the
introduction of thermal barrier coatings (TBCs), which was first applied on rotating blades in the
late 1980s. It is now a key materials technology in the application of advanced gas-turbine
engines. A typical example of TBCs is shown in Figure 1.1. In conjunction with internal cooling
technologies, the use of TBCs has effectively lowered the metal surface temperatures avoiding
superalloy components in contact with hot gases. TBCs also protect superalloy components
against oxidation and hot-corrosion attacks. An intermetallic layer called bond coat is designed to
form a thin layer of thermal grown oxide (TGO) mainly consisting of α-alumina during oxidation
as a robust barrier against inwards diffusion of oxygen and other corrosive gases.

Internal combustion engines are the integral part of every automotive, we come across in our
day-to-day life. The reliability of IC Engines, especially petrol (gasoline) based; make them the
most widely used prime mover in automobiles. However they are having very poor thermal
efficiency. IC engines are constantly being modified in order to meet the rising demand for more
efficient generation of power. The increasing pollution levels caused due to vehicular emissions
also stress the need for intense research. It has been observed that there is an undesirable heat loss
of more than 15% in an IC Engine through its combustion chamber walls and piston. This heat
loss can be avoided by making use of TBC materials. Ceramics have a higher thermal durability
than metals; therefore it is usually not necessary to cool them as fast as metals. Low thermal
conductivity ceramics can be used to control temperature distribution and heat flow in a structure.
Thermal barrier coatings (TBC) provide the potential for higher thermal efficiencies of the engine,
improved combustion and reduced emissions. In addition, ceramics show better wear
characteristics than conventional materials. Lower heat rejection from the combustion chamber
through thermally insulated components causes an increase in available energy that would
increase the in-cylinder work and the amount of energy carried by the exhaust gases, which could
be also utilized .A lot of experimental study has been done to utilize these ceramic properties to
improve thermal efficiency by reducing heat losses, and to improve mechanical efficiency by
eliminating cooling systems. In this article, we propose the use of thermal barrier coating
materials in various components of IC Engine which could greatly improve the thermal efficiency
and volumetric efficiency of the engine. A lining of TBC is provided throughout the combustion
chamber region which includes the cylinder liner, piston, overhead valve block and valves. The
effect of various TBCs is studied by creating a CAD Model of prototype engine and the heat
transfer across the interface has been analysed using analysis software- ANSYS. The results
obtained from the analysis of different TBCs used in the IC Engine Model have been tabulated.
Using these results, the thermal and volumetric efficiencies of IC Engine with different TBCs are
interpreted.

CHAPTER 02
LIETRATURE REVIEW
The earliest thermal barrier coatings for aerospace applications were frit enamels
throughout the 1950s. Figure 2.1 shows the time-line illustrating the history and development
of TBCs from 1950s to 1990s. Since the beginning of the 21th century, the turbine inlet
temperature (TIT) of modern gas turbine engines has surpassed a typical take-off value of 1427
ºC (see Figure 2.2). The aim for such increasingly harsh operating conditions is to provide
more thrust power and higher engine efficiency. The introduction of TBCs and film cooling
has enabled the use of superalloy components at temperatures above their upper limits. The use
of TBCs could effectively lower the surface temperature of superalloy components, and also
protect them from oxidation attack and hot corrosion attacks. In film cooling, cool air is bled
from the compressor stage, ducted to the internal chambers of the turbine blades, and
discharged through small holes in the blade walls. This air provides a thin, cool, insulating
blanket along the external surface of the turbine blade. However, TBCs can substantially
improve the energy efficiency and reduce fuel consumption while the cooling air used in film
cooling will lead to great energy loss.The insulation effect of ceramic coating in a turbine blade
is of great importance for the service of engine in the field of aviation industry. Fabricating
microstructure in the thermal barrier coatings (TBCs) is considered to be able to enhance the
thermal insulation effect. In this study, the traditional three-layer structure, containing ceramic
top coat, bonding coat and substrate, is firstly simplified into a double-layer structure, where
only ceramic layer and substrate are left, for analyzing the thermal insulation. Afterwards, the
thermal insulation effect of the designed microstructure in the bonding coat of the three-layer
structure is further studied. Column-like microstructures, filled with hollow ceramic
microspheres in the interspace, are designed to improve the thermal insulation effect. The size
parameters of the designed microstructure were optimized. The existence of the designed
microstructure can significantly prolong the efficiency of thermal barrier coatings. The
insulation temperature between the heating surface and lower surface of the substrate can
exceed 300°C and the thermal balance time has a big improvement of 240 s, more than 50%,
than the traditional TBCs structure. Compared with the TBCs structure without microstructure,
the designed microstructure can significantly improve the insulation temperature of more than
110°C.Thermal spray coatings (TSCs) have complex microstructures and they often operate in
demanding environments. Plasma sprayed (PS) thermal barrier coating (TBC) is one such
ceramic layer that is applied onto metallic components where a low macroscopic stiffness
favors stability by limiting the stresses from differential thermal contraction. In this paper, the

Young’s modulus of TBC top coat, measured using different techniques, such as four-point
bending, indentation and impulse excitation is reported, along with a brief description of how
the techniques probe different length scales. Zirconia-based TBC top coats were found to have
a much lower global stiffness than that of dense zirconia. A typical value for the as-sprayed
Young’s modulus was ~23 GPa, determined by beam bending. Indentation, probing a local
area, gave significantly higher values. The difference between the two stiffness values is
thought to explain the wide range of TBC top coat Young’s modulus values reported in the
literature. On exposure to high temperature, due to the sintering process, detached top coats
exhibit an increase in stiffness. This increase in stiffness caused by the sintering of fine-scale
porosity has significant impact on the strain tolerance of the TBC. The paper discusses the
different techniques for measuring the Young’s modulus of the TBC top coats and implications
of the measured values.
New methods in the fabrication of top coat and bond coat have been introduced
to improve the efficiency and performance of advanced thermal barrier coatings (TBCs).
2.1 Top coat.
Thick yttria-stabilized-zirconia (YSZ) coatings (300-400 μm) have been fabricated by using
electrophoretic deposition (EPD) method. The EPD coatings have more favorable
microstructures with uniformly distributed porosity and stronger bonding, in comparison with
conventional air-plasma spray (APS) coatings.
2.2 .Bond coat.
Pt-diffused single γ’-phase bond coat has been fabricated by applying selective etching
prior to the electroplating of Pt on CMSX-4 single crystal superalloys. The concern on the
compromised scale adhesion caused by the depletion of Pt is effectively avoided, as Pt remains
stable in a coherent γ’-phase layer after long-term diffusion and oxidation. Considerable cost of
Pt could also be reduced.
Commercial TBCs, comprising an electron beam physical vapour deposition (EBPVD)
top coat, a Pt-enriched intermetallic bond coat and a CMSX-4 single crystal superalloy, have
also been investigated focusing on the failures that typically occurred at the scale/alloy
interface. Advanced characterization techniques have been used to study the chemical factors
(Al, Pt, S, Hf, etc.) that determine the durability of TBCs. Mechanisms have been discussed
that control the TBCs behaviours of diffusion, oxidation, and adhesion.

2.3 Diffusion.
A depletion of Pt near the scale/alloy interface inevitably occurs at high
temperatures, which significantly weakens the scale adhesion. Mechanisms controlling the
diffusion of Pt in Ni-based single crystal superalloys at high temperatures have been
investigated focusing on the evolution of phase, microstructure, and composition. It was found
that Pt has negative chemical interactions with Al, Ti and Ta, all of which could stabilize Pt in
β- and γ’-phases, and therefore avoid the depletion of Pt.
2.4 Oxidation
Selective oxidation behaviour of Ni-based superalloys has been studied by using
thermodynamic calculations, which is mainly affected by alloy compositions, oxygen partial
pressures and temperatures. It was found that the formation of a protective α-Al2O3 scale is
more favoured under lower oxygen partial pressures and higher temperatures. The additions of
Al and Pt in Ni-based superalloys could also promote the formation of Al2O3 and the
exclusion of NiO and spinel. The additions of reactive elements (RE), however, are less
effective and may even cause severe internal oxidations due to a competitive oxidation
between Al and RE.
2.5.Adhesion.
Sulphur effect in TBCs mainly refers to a segregation of sulphur at the scale/alloy
interface,which significantly deteriorates the scale adhesion to alloys. High resolution
secondary ion mass spectrometry (Nano-SIMS) was employed to trace sulphur in commercial
TBCs. The undesired “sulphur effect” on scale adhesion was suggested to be caused by the
formation of residual sulphides beneath the scale with weaker ionic bonding to alloy cations,
rather than a segregation of sulphur atoms. Possible solutions have been suggested to alleviate
the sulphur effect in TBCs.

CHAPTER 03
MATERIALS FOR THERMAL BARRIER COATING
The selection of thermal barrier coating materials is restricted by some basic require-
ments. They are high melting point, no phase transformation between room temperature and
operation temperature, low thermal conductivity, chemical inertness, thermal expansion match
with the metallic substrate, good adherence to the metallic substrate and low sintering rate of
the porous microstructure. So far, only a few materials have been found to basically satisfy
these requirements. There are some ceramics which are used for thermal barrier coating below.
3.1 Zirconates
The main advantages of zirconates are their low sintering activity, low thermal conductivity,
high thermal expansion coefficient and good thermal cycling resistance. The main problem is
the high thermal expansion coefficient which results in residual stress in the coating, and this
can cause coating delamination.
3.2 Yi ttria Stabilized Zirconia
%7-8 yittria stabilized zirconia has high thermal expansion coefficient, low thermal
conductivity and high thermal shock resistance. Disadvantages of yittria stabilized zirconia are
sintering above 1473 K, phase transformation at 1443 K, corrosion and oxygen transparent.
3.3 Mullite
Mullite is an important ceramic material because of its low density, high thermal stability,
stability in severe chemical environments, low thermal conductivity and favorable strength and
creep behavior. Compared with yittria stabilized zirconia, mullite has a much lower thermal
expansion coefficient and higher thermal conductivity, and is much more oxygen-resistant than
yittria stabilized zirconia. The low thermal expansion coefficient of mullite is an advantage relative
to yittria stabilized zirconia in high thermal gradients and under thermal shock conditions.
However, the large mismatch in thermal expansion coefficient with metallic substrate leads to poor
adhesion. The other disadvantage of mullite is crystallization at 1023-1273 K.
3.4 Alumina
It has very high hardness and chemical inertness. Alumina has relatively high thermal conductivity
and low thermal expansion coefficient compared with yittria stabilized zirconia. Even though alumina
alone is not a good thermal barrier coating candidate, its addition to yittria stabilized zirconia can
increase the hardness of the coating and improve the oxidation resis-tance of the substrate. The
disadvantages of alumina are phase transformation at 1273K, high thermal conductivity and very low
thermal expansion coefficient.

3.4 Spinel
Although spinel has very good high temperature and chemical properties, its thermal
expansion coefficient prevents its
3.5 .Forsterite
The high thermal expansion coefficient of forsterite permits a good match with the
substrate. At thicknesses of some hundred microns, it shows a very good thermal shock
resistance.

CHAPTER 04
PRINCIPLE OF DESIGN.
The schematic ideal Otto cycle of a petrol engine is as shown in figure 1. The area 1-2-3-
4-1 represents the work done by engine during one complete cycle.
Figure 1. Schematic Representation of Ideal Otto cycle TS Diagram
However, in the actual case, the Otto Cycle is as shown in the figure 2. It can be seen that
due to various reasons, the process 1-2 and 3-4 deviate from the ideal cycle as 1-2` and 3-4`
respectively. The net result is decreased work output when compared with ideal cycle, which is
represented by the shaded area in figure 2. In order to overcome it, we use TBC which make the
cycle reject lesser heat through IC engine walls during the process 3-4 (refer process 3-4`` in
figure 3). Thus the net work output from the IC engine can be increased by increasing its thermal
efficiency.
Figure 2. Schematic Representation of Actual Otto cycle in Current IC Engine.
Figure 3. Schematic Representation Otto cycle With the Use of TBC in IC Engine.

CHAPTER 05
THERMAL BARRIER COATING.
Thermal barrier coatings (TBCs) have been successfullyapplied to the internal
combustion engine, in particular the combustion chamber, to simulate adiabatic engines. The
objectives are not only for reduced in-cylinder heat rejection and thermal fatigue protection of
underlying metallic surfaces, but also for possible reduction of engine emissions. The
application of TBC reduces the heat loss to the engine coolingjacket through the surfaces
exposed to the heat transfer such as cylinder head, liner, piston crown and piston rings. The
insulation of the combustion chamber with ceramic coating affects the combustion process and
hence the performance andexhaust emissions characteristics of the engines Thermal barrier
coatings are duplex systems, consisting of a ceramic topcoat and a metallic intermediate bond
coat. The topcoat consists of ceramic material whose function is to reduce the temperature of
the underlying, less heat resistant metal part. The bond coat is designed to protect the metallic
substrate from oxidation and corrosion and promote the ceramic topcoat adherence. A thermal
barrier application is shown in figure
Figure 4. Thermal barrier coating consisting of metallic bond coat on the substrate and ceramic top
coat on the bond coat.
In a diesel engine almost %30 of the fuel energy is wasted due to heat losses through
combustion chamber components. For that reason, lots of research activity has focused on
applying thermal barrier coatings to diesel engines. Figure 2 shows a cross-sectional view of the
diesel engine combustion chamber and points out the components that might be effectively coated
with thermal barrier coatings.

Figure 5. Potential thermal barrier coated components in a diesel engine combustion chamber.
In figure 2, 1 indicates piston head, 2 indicates cylinder liner, 3 indicates seating of intake
valve, 4 indicates seating of exhaust valve, 5 indicates cylinder head, 6 indicates intake valve and
7 indicates exhaust valve..
. Thermal barrier coatings (TBCs), with low thermal conduct-ivity and very low
temperature sensitivity, are initially and widely used in turbine blades of aeronautical
aircraft.Currently, they are widely used in many industry areas, where part of the working
component operates in an extremely high temperature environment. For example, the sprayed
layer of ceramic.
TBCs on the equipment of high-temperature corrosion parts in the petrochemical industry, can
significantly improve the ser-vice life of the equipment. The temperature of the reaction zone in
the oxidation furnace is far beyond the melting point of the alloy. The sprayed TBCs on the heat-
resistant alloy can dramatically help improve the ability of high temperature resist-ant for the
alloy structure.
Increasing the thrust-to-weight ratio is one of the main re-search directions of the aircraft
engine. To achieve this, the inlet temperature of the engine turbine needs to be increased, and it is
believed that the inlet temperature will reach 1930°C soon. Such a high operating temperature is
far beyond the operat-ing temperature of the current existing super-alloy. There-fore, to meet the
higher engine inlet temperature requirement, seeking new material or structure is an important
direction for the fabrication and development of TBCs. To obtain an ideal TBCs structure, one of
the promising directions is to design a TBCs structure with lower thermal conductivity.
Recent studies have shown that the rare earth zirconates is one of the most promising
surface ceramic material in TBCs, ow-ing to its good thermal physical properties, like lower
thermal conductivity, high coefficient of thermal expansion, and high temperature phase stability

up to 2300°C. Many scholars have added other chemical element into the ceramic coat to re-duce
the thermal conductivity and improve its phase stability.
There are many ways to obtain a TBCs structure with lower thermal conductivity, one of
which making microstructure on the TBCs structure is considered to be a possible and important
way. Scholars have put forward this new method to enhance the thermal performance of ceramics
through fabricating nano-structure into the ceramic. The proposed new method can help the
insensitive ceramics withstand thermal shocks until its melting temperature, in which there is
nano-structure on the ceramic surface. When the structure is heated and heat conduc-tion occurs,
the temperature drops rapidly near the nano-struc-ture, indicating nano-structure has a good
insulation effect.
In this study, a TBCs structure with lower thermal conductiv-ity and enhanced thermal
insulation effect was obtained through fabricating the designed microstructure in the substrate or
bonding coat and filling hollow ceramic microspheres into the interspace. The size parameters of
the designed microstructure were optimized. Compared with the traditional TBCs structure
without microstructure, the designed microstructure can signi-ficantly improve the insulation
temperature of more than 110°C and the thermal balance time have a big improvement of 240 s,
more than 50% of the balance time than that in the traditional TBCs structure.
Figure 6. Cutaway view of Engine Trent 800 from Rolls-Royce on the Boeing 777; photographs of high-
pressure turbine blades with internal cooling holes and thermal barrier coatings (TBCs); and temperature
profiles on the cross-section of TBCs which consist of an electron beam physical vapour deposited (EBPVD) 7
wt% yttria-stablized zirconia (YSZ) top coat, a thermal grown oxide (TGO) mainly consisting of α-alumina, a
platinum enriched γ/γ’-phase bond coat and a CMSX-4 single crystal

CHAPTER 06
PROBLEMS OF TBCS
With high barriers to enter, gas turbine engine industry is still occupied by three main
companies – General Electrics (GE) Aviation, Pratt & Whitney and Rolls-Royce, coupled with a
few joint venture partnerships that deal with specific engine programmes. High production cost
and extremely strict control on productive process of TBCs on turbine blades is one of the main
reasons for such a monopolistic situation.
For TBCs only, a state-of-art equipment of electron beam physical vapour deposition
(EBPVD) normally costs £10-20 million depending on the machine capacity. A facility for
platinum aluminide diffusion coating process normally costs between £2 million and £4 million in
total, which consists of a platinum plating line, vacuum heat treatment furnaces, and a chemical
vapour deposition (CVD) furnace or a vapour phase aluminizing (VPA) furnace. Another major
concern is the high materials cost. For example, the cost of yttria-stablized zirconia (YSZ)
ceramic powder is £20 to £50 per kg, and the cost of MCrAlY powder is £30 to £70 per kg.
However, the price for 1 kg of platinum is above £27,000, and the price for platinum salt (Q salt,
[Pt(NH3)4]HPO4, 0.5% w/w) containing the equivalent amount of platinum is even two or three
times higher, which is above £90,000. The weight usage of platinum on each turbine blade is one
sixth to one third of YSZ powder (if we assume the platinum layer is 10 μm thick while the YSZ
layer is 100-200 μm thick. The density of platinum and YSZ is 21.4 g/cm3 and 6.10 g/cm3,
respectively). Therefore, it is quite clear that platinum takes a considerable proportion in the
overall cost of each TBCs coated turbine blade. Unfortunately, the current technique is not able to
reduce the usage of platinum in commercial TBCs as it will put the turbine engines at risks. The
high cost of platinum remains to be a critical issue unless a cheaper bond coat system is invented
with an adequate replacement of platinum.
In addition, it is always essential to consider TBCs as a complex, multi-layered,
interrelated, and evolving materials system, consisting of a ceramic top coat, a TGO ceramic
layer, an intermetallic bond coat and the underlying superalloy components. The durability of
TBCs for prolonged service times is still an overriding concern. One typical example of TBCs
failure on a serviced turbine blade is shown in Figure 1.2. A spallation failure during high
temperature operation could directly expose the metallic components to the hot gases, which
would accelerate the failures of turbine blades and endanger the whole engine. Therefore, studies
on the failure mechanism of TBCs should be an ongoing task aiming to have a complete

knowledge of TBCs, which will be helpful for the design of next-generation advanced gas turbine
engines with improved performances
Figure 7. Typical photograph shows the failure of TBCs on a serviced turbine blade.
Detachment occurred at the interface between TGO and bond coat.

CHAPTER 07
CONCEPT OF FGM
Ceramic-metal FGM have been attracting a great deal of attention as thermal barrier
coatings (TBC) for aerospace structures, gas turbines and aircraft engines, working under super
high temperatures and thermal gradients. FGM is a relatively new concept involving tailoring the
internal microstructure of composite materials to specific applications, producing a microstructure
with continuously varying thermal and mechanical properties at the continuum or bulk level. It
has continuous variation of material properties from one surface to another and thus alleviates the
stress discontinuities. Hence, they are ideal for applications involving severe thermo fatigue
loadings.
Functionally graded thermal barrier coating (FTBC) introduces more reliability and
reduces interfacial thermal stress between metallic and ceramic layers. FTBC provides less inter-
layer thermal stress since the gradient will vary smoothly across the coating thickness as shown in
figure 3. It also effectively reduces the discontinuities in thermal expansion coefficients between
the bond coat and substrate. Each FTBC layers will act as a TBC layers with various material
compositions thereby it gives more spallation life cycles than that of TBC layers of same
thickness under the same loading. With this conceptual of graded coating, the bond strength will
be increased by almost twice time per mm coating thickness. The main sticky situation with this
type coating is cohesive failure pattern within the structure and may take anywhere within the
coatings where as in TBC, the failure mostly occurred at the interface layers (Thermally Grown
Oxide).
The present study considers FTBC layers composed of bond coat typically used as NiCrAlY
metal and Yttrium Stabilized Zirconia oxide (YSZ) ceramic with five layers of different
compositions. The spallation life model is used for predicting life, with the available strain value
obtained from finite elelysis.
1600
1400
1200
1000
800
600
400
200
0 -11.6 -11.1 -10.6 -10.1 Radius (mm)
Figure 8: Details of the tempera ture difference between TBC and FTBC across the thickness of the same
substrate.
HotGaS

CHAPTER 08
COATING SYSTEM
8.1 The Plasma Spraying Process:
Fig.9 Schematic diagram of Plasma spray gun
Figure shows a schematic of the plasma spray gun, with thethoriated tungsten cathode
inside the water-cooled copper anode. A gas, commonly a mixture of argon and hydrogen, is
injected into the annular space between the two. To start the process, a DC electric arc is stuck
between the two electrodes. The electric arc produces gas ionisation, i.e. gas atoms lose electrons
and become positive ions. Electrons move with high velocity to the anode, while ions move to the
cathode. On their way, electrons and atoms collide with neutral gas atomsand molecules. Hence,
the electric arc continuously converts
the gas into a plasma (a mixture of ions and electron of high energy).
The plasma is on average, electrically neutral and characterized by a very high
temperature. The kinetic energyof the plasma (mostly carried by free electrons) is converted into
thermal energy during collisions between ions, electrons and atoms. In this way, the plasma is
capable of producing temperatures up to approximately 104K. The hot gas exits the nozzle of the
gun with high velocity. Powder material is fed into the plasma plume. The powder particles are
melted and propelled by the hot gas onto the surface of the substrate. When individual molten
particles hit the substrate surface, they form splats by spreading, coolingand solidifying. These
splats then incrementally build the coating.
Plasma plumes exhibit radial temperature gradients. Whereas particles that pass through
the central core of the plasma tend to be melted, superheated or even vapourised, particles that
flow near the periphery may not melt at all. This will affect the final structure of the coating,
which may contain partially molten or unmelted particles. Voids, oxidised particles andunmelted
particles can appear in the coating. These effects may be desirable, or they may be unwanted,
depending on the requirements of the coating.

CHAPTER 09
MECHANICAL PROPERTIES OF TBC
9.1 Porosity
Pores of the spherical shape are characterized by porosity-relative volume of
pores contained in a respective volume V: P=1/V ∑V (K) Where V(K) are the volumes of
individual pores and k is kth pore. Porosity is a typical coating feature of plasma spray and
can be viewed generally as the absence of material within coating. It is found that either
surface connected or totally enclosed. The pores can be observed nominally disk-like and lie
between the splats formed during rapid deposition and solidification process. This process
may leads to highly defective microstructures. Dr.Weis found, the effect on residual stresses
of porosity in MgO–ZrO2 coatings on Al–Si alloy substrate, and the coatings were
characterized by means of optical microscopy and environmental scanning electron
microscopy (Fig1.). Finite element calculations (Fig 2.) demonstrated that the highest thermal
shock resistance was reached in the coating system with 7.5% small size sphere shape and
uniformly distributed porosity. It was also found that the coating with above 7.5% porosity
had maximum values in radial, axial and shear stresses. Anand Kulkarni found that the
influence of feedstock characteristics on particle state in the plasma and the resultant coating
properties. Result shows that higher substrate temperatures and low particle velocity lead to
lower porosity and improved inter-splat contact and, thus, enhanced coating properties.
Sintering during thermal cycling reduces porosity and increases thermal conductivity and
modulus. A key consideration is the dependency of porosity on spray ambient environment
powder characteristics and plasma sprayed parameters.
Figure 10.1 SEM micrograph of MgO–ZrO2/Al–Si
material coating. Figure 10.2(a) Radial, (b) axial and
(c) shear stresses of MgO–ZrO2with
0, 2.5, 5, 7.5 10, 12.5, 15, 17.5 and 20%
(porosity).

In many engineering cases a plasma coating of 0.5 mm is sufficient to protect the
surface.Wanes Sampath investigated that the surface roughness, as important factor of
tribological durability of the materials. He investigated that the surface roughness parameters
for two groups of plasma sprayed coatings with different composition of yttrium stabilized
zirconia – 5.2 wt% and 10 wt% – 15 wt%. The results of surface roughness measurements
shows, that the content of yttria does not have a great influence on the surface roughness
parameters. Data of roughness indicated in the Table 1 shows that YSZ-2 coatings are slightly
smoother than the coatings deposited using precursor with less content of yttria (YSZ-1).
Table 1: Surface roughness parameters and microhardness values of plasma sprayed
zirconias
Bond strength in the plasma sprayed TBCis the degree to which Bond and top layers
linked to substrate on which they are deposited. M.Yoshiba et.al investigated that for the YSZ-
TBC system, increased chromium content in bond coat results in decreased damage depth, both
in high temperature oxidation and in hot corrosion. Stecura also reported that the spilling
resistance of the top coat in the YSZ-TBC system depends strongly on the chromium content in
the NiCrAlY bond coat. G.Goller investigated the effect of bond coat on mechanical properties
of plasma sprayed bioglass-titanium coatings and found that it is possible to coat bioglass on
titanium substrate by utilizing similar conditions used for hydroxyapatite. Application of bond
coat layer in the plasma spraying of bioglass on titanium substrate has increased the bonding
strength about three times and there is a uniform coating layer with a thickness of 110 and 80
μm depending on coating type with a little amount of porosity. The effect of spraying power on
microstructure and bonding strength of MoSi2-based coatings prepared by supersonic plasma
spraying shows that coatings become more and more compact and the bonding strength
increases when the spraying power increases from 40 kW to 50 kW. At the power of 50 kW, the
coatings were dense and the bonding strength reached a maximum value of 14.5 MPa.

9.2 Microhardness
Ozkan Sarikaya investigated the effect of some parameters on microstructure and hardness
of alumina coatings. The results indicated that the parameters such as the spraying distance,
substrate temperature, coating thickness and substrate roughness were fairly effected the
hardness, porosity and surface roughness of Al2O3 coatings. It also found that the increases of
coating thickness were lowered the hardness and enhanced the porosity and the coating
roughness. Hao.Huang Chen investigated the effect of plasma Spraying conditions on
microhardness TiO2 coating and it was noticed that a relationship exists between the
microstructure and microhardness of TiO2 coating. The lower the porosity is, higher the
microhardness. It was found that an increase in porosity content decreases the microhardness of
TiO2 coatings. As porosity of the TiO2 coating depends on spraying power and distance (Fig.
4), the two parameters can influence microhardness of TiO2 coating. The coating deposited
with the higher spraying power and shorter spraying distance has a higher microhardness.
Figure 11 : Influence of spraying power (a) and distance (b) on microhardness of plasma sprayed
TiO2 coatings

9.3 Wear
It is well known that the evolution of wear process, resulting from two moving structural
parts in contact, is largely dependent on the mechanical and microstructural properties of the
material involved. Results from laboratory studies indicate that coating processed by laser meet
more of the requirements for a wear resistance coating obtained by conventional technique
Y.Wang studied the Abrasive wear characteristics of plasma sprayed nanostructured
alumina/titania coatings and found that the abrasive wear resistance of the coatings produced
using the nanostructured Al2O3/TiO2 powders is greatly improved compared with the coating
produced using the conventional Al2O3/TiO2 powder (Metco 130). DZ.Guo studied the effects of
post-coating processing by means of flame, laser and vacuum furnace on heating structure.
Erosive wear characteristics of flame and plasma spray coatings were also studied. Results shows
that post-coating processing can modify the microstructure, reduce its porosity, increase its
plasticity and toughness and also improve the metallurgical bonding to the substrate.

CHAPTER 10
CURRENT MATERIALS FOR IC ENGINE
The most widely used materials for construction of IC Engines are Grey Cast Iron,
Aluminium alloys and steels in some parts. Close-grained cast iron is the material most
commonly used for liner construction. Some liners are plated on the wearing surface with porous
chromium, because chromium has greater wear-resistant qualities than other materials.
Table 2. Commonly Used Materials for Construction of IC Engines

CHAPTER 11
PROPOSED TBC MATERIALS FOR IC ENGINE.
In seeking potential new TBC materials, it makes sense to explore other refractory
materials. However, since there are numerous crystal structures known to the mineralogical and
crystal-chemistry communities, and each can be formed from several different elements, there are
literally thousands of possible compounds to search. Among the most useful thermal barrier
coating materials developed, we intend to use the following two materials based on their
properties;
I. BaLa2Ti3O10 (BLT) with Ruddlesden–Popper structure
II. Perovskite Type Strontium Zirconate
Table 3. Properties of TBC materials considered.
11.1. Properties of Coating Materials:
Low thermal conductivity.
High thermal stability.
High wear resistance.
Highly hardness.
Good adhesive property.

CHAPTER 12
EXPERIMENTAL SETUP
A Honda GK 200 engine was tested with brake drum load. The engine tests were conducted
in single cylinder, air cooled spark ignition engine at constant speed of 2500 rpm. Two types of
test were conducted namely base line test and coated pistontest by the following procedure. The
load was given as 20%, 40%, 60%, and 80% and full load and the readings were taken. For each
load the time taken for 10CC of fuel was measured. The exhaust emission and smoke parameter
was measured by exhaust gas analyzer and smoke meter. Initially readings were taken normal
(uncoated) piston. After taking the readings, the engine parts were dismantled. Cylinder heads,
piston, wallswere coated with YSZ. Same procedure was repeated to predict the performance of
the engine with the coating. Fig. shows the schematic diagram of the experimental setup.
Fig.12 Schematic diagram of the experimental setup

CHAPTER 13
THERMAL ANALYSIS OF CONVENTIONAL IC ENGINE
MODELS
Firstly, thermal analysis on uncoated conventional IC Engines is performed in order to
visualize the thermal distribution throughout the body. The two materials considered here are
Grey Cast Iron (GCI) ASTM GRADE 40 and Aluminum Silicon alloy.
13.1 Thermal Analysis On Aluminum Silicon Alloy Engine
Aluminum Silicon Alloy is the material which is increasingly being used in the
construction of modern IC Engines. The entire IC Engine is considered to be made of Aluminum
Silicon alloy material except the cylinder liner which is made of Grey Cast Iron (ASTM Grade
40). The thermal analysis is performed for a period of 30 seconds in steps of one second. The
state of temperature distribution in the internal combustion engine at the end of 30 seconds is as
shown in figure 6.
Figure 13.1 Temperature Distribution in an IC ENGINE Made Of Al Si Alloy.

13.2 Thermal Analysis On Grey Cast Iron Engine.
Another widely used material for the body of internal combustion engine is Grey Cast
Iron. In this case, the aluminium Silicon alloy is replaced with Grey Cast Iron completely.
Thermal analysis is performed for the same time of 30 seconds and in steps of one second as in
the previous case; without changing the mesh quality and test conditions. Figure 7. Represents the
heat distribution in the IC Engine body made completely of Grey Cast Iron (ASTM Grade 40)
material.
Figure 13.2 Temperature Distribution In An Ic Enginemade Of Grey Cast Iron

CHAPTER 14
THERMAL ANALYSIS OF PROPOSED IC ENGINE WITH
TBCS.
Now, thermal analysis is performed on the internal combustion engines made of Grey Cast
sIron material with a coating of TBC material on the inner side of the combustion chamber walls.
The thickness of each coating is 1000 microns (1 mm).
14.1 Thermal Analysis On Strontium Zirconatecoated Engine
A well-established thermal barrier coating is Strontium Zirconate which has a higher
thermal stability of up to 1573K. The Grey Cast Iron IC Engine is coated with Strontium
Zirconate on its combustion chamber walls completely and thermal analysis is carried out as
before. At the end of 30 seconds of thermal simulation over the strontium Zirconate coated IC
Engine, the heat distribution is observed as shown in the figure 8.
Figure 14.1 Temperature Distribution In An Ic Engine Made Of Grey Cast Iron Coated Internally
With Strontium Zirconate Tbc

14.2 Thermal Analysis On Blt Coated Engine
Barium Lanthanum Titanate (BLT) is relatively a new found thermal barrier coating
material which has approximately 25% more thermal stability than Strontium Zirconate. It can
resist phase transition up to 1773K with thermal conductivity of 0.7 W/mK which is an added
advantage in terms of reliability of engine operation in the event of sudden surge in temperature
during combustion. The conditions of thermal simulations are maintained the same. The
temperature distribution is observed to be as shown in figure 9.
Figure 14.2 Temperature Distribution in an IC ENGINE Made Of GREY CAST IRON Coated
Internally With BLT TBC

CHAPTER 15
ADVANTAGES OF THERMAL BARRIER COATING.
1) Increased effective efficiency and thermal efficiency.
2) The ignition delay of the fuel is considerably reduced.
3) The faster vaporization and the better mixing of the fuel.
4) Reduced specific fuel consumption.
5) Reduced specific fuel consumption.
6) Improved reliability
Some advantages of thermal barrier coatings on diesel engines are below
7) Improvements occurs at emissions except NOx
8) Waste exhaust gases are used to produce useful shaft work,
9) Increased effective efficiency,
10)Increased thermal efficiency,
11)Using lower-quality fuels within a wider distillation range,
12)The ignition delay of the fuel is considerably reduced,
13)The faster vaporization and the better mixing of the fuel,
14)Reduced specific fuel consumption,
15)Multi-Fuel capability,
16)Improved reliability,
17)Smaller size,
18)Lighter weight,
19)Decreased the heat removed by the cooling system,
20)The first start of engine on cold days will be easier,
21)Decreasing knocking and noise caused by combustion.
22) Availability and Reliability
 Corrosion / Erosion resistance
 Lower metal temperature
 Lower transient thermal stress
23) Efficiency
 Reduce coolant flow
 Increase the turbine inlet temperature
24) Capital cost
 Easily cast super alloy & simplified colling.

CHAPTER 16
DISADVANTAGES OF THERMAL BARRIER COATING
17.1 Thermal spray coating
1) Disguises the substrate – as thermal spray coatings are so efficient in many cases it is
impossible to tell what material the substrate was made of after the coating process, unless
stringent records are kept.
2) Cannot precisely evaluate effectiveness – once the thermal spray coating has been applied it
is often difficult to tell exactly how well the coating has gone on, other than by a visual
assessment.
3) Costly set up – some of the methods of thermal spray coatings require very expensive
apparatus, which can result in a high initial set up cost.

CHAPTER 17
APPLICATION
1. Gas turbine.
2. Jet engines.
3. Sports motor.
4. Military vehicle.
5. Aerospace application.
6. Automotive-Thermal barrier ceramic coatings are becoming more common in automotive
applications. They are specifically designed to reduce heat loss from engine exhaust
system components including exhaust manifolds, turbocharger casings,
7. exhaust headers, downpipes and tailpipes.
8. Aviation-Interest in increasing the efficiency of gas turbine engines for aviation
applications has prompted research into higher combustion temperatures.
Fig. 15 spary coating in aeroplane
Fig.16 thermal-spray-gun- coating

CHAPTER 18
CONCLUSION.
The 3D Finite Element Thermal Analysis is thus performed on five different models of IC
Engines. Upon the thermal analysis, we can see that the use of TBCs greatly reduced the heat
dissipation through engine body during combustion. The following inferences are made.
1. The use of TBCs in IC Engines will definitely improve the thermal efficiency.
2. Furthermore, BLT TBC is found to be the most viable TBC material for use in petrol
(gasoline) based IC Engine, on account of its high thermal phase stability and low thermal
conductivity.
3. Smaller engine cooling system is sufficient.
4. More intake charge may be expected in case of naturally aspirating engines which means
higher volumetric efficiency as well.
5. The liner would show lesser wear because of higher hardness of TBC materials.
6. With insulating combustion chamber compo-nents, it is available to keep combustion
tempe-ratures high. Due to high combustion tempera-tures thermal efficiency can be
increased, exhaust emissions can be improved and fuel consumption can be decreased on
diesel engines. Ceramic materials which have low thermal conductivity and high thermal
expansion coefficient are used for making combustion chamber components thermal
insulated.
7. For a successful coating thermal coating, ceramic material has a high melting point, high
oxygen resistance, high thermal expansion coe-fficient, high corrosion resistance, high
strain to-lerance, low thermal conductivity and phase sta-bility.

REFERENCES
[1] D.R. Clarke and S.R. Phillpot, Thermal Barrier Coating Materials, Mater. Today, 2005.
[2] Z. Mišković, I. Bobić, S. Tripković, A. Rac, A. Vencl, The Structure and Mechanical
Properties of an Aluminium A356 Alloy Base Composite With Al2O3 Particle Additions,
Tribology in industry, Volume 28, No. 3&4, 2006.
[3] A.C. Alkidas, Performance and emissions achievements with an uncooled heavy duty, single
cylinder diesel engine, SAE, vol. 890141, 1989.
[4] Xizhong Wang, Lei Guo, HongboGuo, Guohui Ma, Shengkai Gong, Effects of Pressure
during Preparation on the Grain Orientation of Ruddlesden-Popper Structured BaLa2Ti3O10
Ceramic, Journal of Materials Science & Technology 01/2013.
[5] Hieu Nguyen, Manufacturing Processes and Engineering Materials Used in Automotive
Engine Blocks, April 8, 2005.
[6] Yanyan Yin, Rui Qi, Hongye Zhang, Shangbin Xi, Yingbin Zhu, Zhanwei Liu, Microstructure
design to improve the efficiency of thermal barrier coatings,
https://www.researchgate.net/publication/326093788 , January 2018.
[7] Shiladitya Paul, Stiffness of Plasma Sprayed Thermal Barrier Coatings,
https://www.researchgate.net/publication/316819973 , 9 May 2017.
[8] Mingwen Bai, Fabrication and characterization of thermal barrier coatings,
https://www.researchgate.net/publication/287347007 , November 2015.
[9] Ilker TurgutYilmaz, Metin Gumus & Mehmet Akçay, thermal barrier coatings for diesel
engines, https://www.researchgate.net/publication/315457303 , November 2010
[10] Govindarajan Narayanan, Life Prediction of Functionally Graded Thermal Barrier Coatings,
https://www.researchgate.net/publication/320719084 , October 2017.
[11] Hongye Zhang, Zhanwei Liu, Microstructure design to improve the efficiency of thermal
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[12] Abhinav T, Thermal Barrier Coatings An- Overview,
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applications – review, ISSN 2278 – 0149 www.ijmerr.com , Vol. 3, No. 2, April, 2014.

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