_________________________________________________________________

SLURRY SPRAYED THERMAL

BARRIER COATINGS FOR

AEROSPACE APPLICATIONS

_________________________________________________________________

Phuc Nguyen

A thesis submitted in fulfilment of requirements

for degree of Doctor of Philosophy

School of Mechanical Engineering

The University of Adelaide

May 2010

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191

APPENDICES

Appendices

192

Appendix A

Investigation of Thermo-Mechanical Properties of Slurry based Thermal Barrier Coatings under Repeated Thermal

Shock Phuc Nguyena, Andrei Kotousovb, Sook-Ying Hoc and

Stuart Wildyd

School of Mechanical Engineering, the University of Adelaide, SA 5005 Australia aphuc.nguyen@adelaide.edu.au, bandrei.kotousov@adelaide.edu.au,

csookying.ho@adelaide.edu.au, dstuart.wildy@adelaide.edu.au

Keywords: thermal barrier coating, repeated thermal shock loading, thermo-mechanical properties, adhesion strength, thermal shock resistance, thermal stresses

Abstract. Thermal Barrier Coatings have existed for over 40 years, and within the last 15 years their use in industrial applications has dramatically increased. Thermal Barrier Coatings (TBCs) are currently used in gas turbines, diesel engines, throughout aerospace and nuclear power industries. The purpose of TBC is to reduce temperature and thermal stresses, and, as a result, increase the reliability and life of load-bearing components subjected to high temperature or temperature flux. However, TBCs often fail under thermal cyclic loading with reliability still being the major issue impeding their wide-spread applications.

The focus of this work is on experimental investigations of zirconia/nickel graded TBC system, subject to thermal shock loading. The graded TBC systems were fabricated utilising a recently developed slurry spray manufacturing technique. This is a robust technique, and is able to cover large and curved surfaces at low cost, and provides many advantages in comparison with its alternatives. This paper describes the developed technique and presents selected results of thermo-mechanical and fracture testing of the TBCs including graded coatings fabricated using this new technique.

Introduction Thermal Barrier Coatings (TBCs) represent a relatively thin layer of a material with high insulating properties, such as ceramics, that is bonded to a substrate, which is usually metal, to protect the metal load carrying structure during temperature excursions. The application of TBCs can significantly increase the operating temperatures up to 1400-1500ºC, increase efficiency and improve the durability of the components. There are many applications, which have benefited from adopting TBCs. These include the aeronautical, aerospace, automotive and nuclear industries and heavy-duty utilities such as diesel trucks [1].

Appendices

193

The development of TBCs has centred mostly on Partially Stabilised Zirconia (PSZ) due to its unique physico-mechanical properties and has been led by its use in aircraft-engine combustion-path components [2]. The significant advance in the development of an effective protective coating was associated with the development of Functionally Graded (FG) TBCs. FG-TBCs are multiphase composite materials that are engineered to a have a spatial variation of material constituencies. Using FG TBCs, as an alternative to joining directly together two dissimilar materials such as ceramics and metal, carries several advantages including: much lower thermal stress distribution across the thickness; minimisation of stress concentrations; and an increase in bonding strength. First, the new developed technique will be briefly outlined. The technique is also suitable for producing the FG-Coating. Examples of the FG-Coatings will be given in the paper. Experimental results on thermal cycling, adhesion strength, investigation of microstructure and effect of various manufacturing parameters on the quality, fracture and durability of the coating will be discussed. The paper will be concluded with a summary of major outcomes of the current experimental study and suggestions on future work.

Slurry Spray Technique The Slurry Spray Technique for manufacturing TBCs utilises traditional wet powder spraying methods to deposit sinterable coating materials onto target substrates to produce a functional coating. The process involves suspending the coating material within a fluid to form a slurry mixture that can be applied to a surface using common gravity fed spray guns. Successive layers are then sprayed onto the Inconel substrate and dried using varying slurry compositions. The optimal thickness of the layers to deter surface cracking during the drying process is approximately 100 µm (which can be seen in Fig. 1) and the drying time is approximately an hour, depending on ambient conditions. After the desirable number of layers of the TBC is deposited the multi-layered coating is loaded in a compression chamber to form a densified layer before being sintered with an acetylene torch or furnace. The applied pressure varies depending on the number of coating layers, typically between 10 and 40 MPa. Details of this technique can be found in [3] and [4].

Examples of Slurry based Thermal barrier coatings Below we describe several examples of TBC fabricated using the developed manufacturing technique, which can be seen in Fig. 1.

Appendices

194

(a) MonoLayer Coating 1 (b) MonoLayer Coating 2 (c) FG – Multilayered Coating

Figure 1. Cross-sectional view of a Slurry Sprayed TBC’s

An example of a monolayer coating, fabricated utilising the Slurry Spray Technique, can be seen in Fig. 1(a, b). The composition of the monolayered coating is 50% ZrO2 – 50% Ni, which can be distinguished by the different grain structure. The nickel substrate can be seen on the left hand side of Fig. 1(b, c), and the epoxy resin on the right hand side of the image; the epoxy resin was used to set the TBC specimens for SEM investigations. In Fig. 1(c) an example of a FG – Multilayered TBC can be seen. This coating consists of 2 layers, with the initial layer of the FG-TBC composition consisting of 50% ZrO2 – 50% Ni, and the top layer of the FG-TBC consisting of 100% ZrO2 – 0% Ni. In Fig. 2(c), the layer is more pronounce than the monolayer coating seen in Fig. 2(b), this is due to the mechanical densification of the coating during the fabrication of the FG-TBC [5].

Experimental Results Adhesion Test. Adhesion tests of the adhesion strength of the various TBC compositions were carried out with the PosiTest pull off adhesion tester. The results showed that FG-TBC were a 100% improvement from the monolayered TBC with 100% of ZrO2 and 25% improvement from the monolayered TBC with 50% ZrO2 - 50% Ni (Fig. 2). The maximum adhesion strength obtained through the experiment, for the FG-Coating was approximately 11 MPa. However in comparison with existing coating techniques such as the flame spray method, with adhesion strength of approximately 21 MPa, the adhesion strength of the FG-Coating produced is 50% lower than the flame spray method [6].

Substrate Ni Epoxy

MonoLayered TBC

Substrate Ni

MultiLayered TBC

Epoxy

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195

Figure 2. Adhesion strength range for various types of coatings

Thermal Cycling Test. The purpose of the thermal cycling tests was to give an indication of thermal fatigue behaviour of the Slurry based TBC [7]. The maximum temperature reached was 900°C, with a 30 minute heating/cooling cycle. The monolayered TBC with 100% of ZrO2, 50% ZrO2 – 50% Ni and FG-Coating with two layers of and 50% ZrO2 – 50% Ni and 100% ZrO2 were subjected to the thermal cycling.

The experimental study showed that the majority of the failures occur during the first few cycles (see Fig. 3). If the coating survived the first 4-5 thermal cycles, the coating integrity is preserved throughout the following thermal cycle. Fig. 3 demonstrates that FG-Coatings are normally much more durable and better resistant to the thermal cycling. The effect of the first few cycles can be explained by the manufacturing defects, which lead to the almost immediate failure of the coating. The FG-Coating has much lower probability of failure during the thermal cycling, which can be explained by the lower mismatch in material properties and the lower level of thermal stresses during the sintering of the TBC.

Figure 3. Ratio of the survived TBC to the total number of tested samples for FG-Coating and Monolayered Coatings

The results obtained through the experiment coincide with theoretical analysis presented in literature reviews where TBCs are expected to perform better in real life application if manufactured in a controlled sintering and cooling environment. Firstly, by applying constant heat flow, uniform heat expansion, and ideal boundary grain growth between particles is achieved thus reducing thermal stress induced

0

4

8

σad, MPa

50% ZrO2 – 50% Ni

100% ZrO2

50% ZrO2 – 50% Ni

100% ZrO2Delamination cracking

F F

TBC

0

0.5

1

0 5 10 15 20 N of cycles

Functionally graded coating

Monolayered

Appendices

196

during the thermal expansion process. Secondly, a slow cooling rate after sintering effectively reduces the strain and stress associated with rapid cooling. Thirdly, introduction of FG-Coating induces a temperature gradient across the coating hence minimising thermal mismatch due to cooling and the resulting residual stresses.

(a) (b) (c) Figure 4. Microstructure of TBC after fabrication (a), 10 thermal cycles (b)

and 20 thermalcycles (c), magnitification – 500x.

From SEM images taken after the fabrication, 10 and 20 thermal cycles (see Fig.4), it can be seen that the increase of porosity with the number of thermal cycles and formation of crack damage, eventually propagates through the thickness and lead to the failure of the coating.

Conclusion This paper presents results of an experimental study on the thermo-mechanical properties of TBCs fabricated using a new method based upon the Slurry based TBC technique. The main advantages of this technique are the low costs and the ability to cover large and curved surfaces, which are critical for a number of important practical applications. This technique allows the fabrication of the multilayered FG-TBC’s, which can significantly reduce the thermal stresses and, and as a rule, have higher durability and lower failure rates in comparison with monolayered TBCs.

The test results demonstrate a satisfactory adhesive strength of the coating, which is comparable with the adhesive strength of other coatings, fabricated using traditional techniques such as the Flame Spray method. The outcomes of the experimental study also showed that the FG-TBC fabricated using the Slurry Spray technique are able to survive low-cycle thermal excursions, when the temperature increases up to 1000°C. Further work will focus on real-life applications, such as high temperature burner tests and leading edge of scramjet propulsion systems.

Acknowledgments The authors acknowledge, with thanks, the financial support from the U.S Air

Force, without their support this research would not have been possible.

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197

References

[1] Koizumi, M. (1997), Composites Part B; Engineering, 28(1-2), 1-4. [2] Martena, M., Botto, D., Fino P., Sabbadini S., Gola M.M., Badini C. (2006), Engineering Failure Analysis, 13 (3), 409-426. [3] Nguyen, P., Harding, S., Ho, S-Y. (2007) ACAM, 1, 545-550. [4] Ho, S-Y., Kotousov, A., Nguyen, P., Harding, S., Codrington, J., Tsukamoto, H., (2007) Scientific and Technical Information Network, Defense Technical Information Centre. [5] Dahl, P., Kaus, I., Zhao, Z., Johnsson, M., Nygren, M., Wiik, K., Grande, T. & Einarsrud, M.A. (2007) Ceramics International, 33, 1603-1610. [6] Davis, J. R. (2004) Handbook of Thermal Spray Technology, Thermal Spray Society and ASM International, United States of America. [7] Zhu, D., Choi, S.R., Miller, R. A. (2004) Surface and Coatings Technology, 188-189, 146-152.

Appendices

198

Appendix B

Induction heating apparatus for high temperature testing of thermo-mechanical properties

by J. Codrington*, P. Nguyen, S.Y. Ho, and A. Kotousov

School of Mechanical Engineering

The University of Adelaide, SA 5005, Australia

*Tel: +61 – 8 – 83033177; Fax: +61 – 8 – 83034367 E-mail: john.codrington@adelaide.edu.au

ABSTRACT— A low cost high temperature test facility designed and built for

the purpose of thermo-mechanical testing is described. An induction heater

provides variable heating rates, simple operation and easy access for

temperature and strain measurement. Specially designed high temperature

specimen grips with water-cooling allow for testing over long periods of time.

Contact temperature and strain measurements are utilised to provide

accurate and reliable results. Detail is given on the experimental procedure

including calibration of the thermocouple temperature measurement. A

validation study of the thermal expansion and tensile Young’s Modulus of

carbon steel 1020 at temperatures up to 850°C prove s the accuracy of the

test set-up and procedure. Results are given for the stress-strain curves of

aluminium alloy 7000 T4 at various temperatures to further demonstrate the

capabilities of the test facility. The measured thermo-mechanical properties

Appendices

199

of these materials were used to develop high temperature constitutive

models for implementation in finite element thermal-structural analysis of

hypersonic structures.

KEY WORDS— High temperature, Mechanical test, Thermo-mechanical

properties, Induction heating

1 Introduction

Advanced applications are emerging that require high temperature materials and

structures that are able to withstand conditions above 1000°C. These applications

include hypersonic and supersonic aircraft, anti-terrorist measures, welding

technologies, the mining industry and many others. At elevated temperatures

significant changes occur in the thermal and mechanical properties of materials.

These properties are the basis of thermo-structural design calculations and allow for

development of accurate finite element (FE) models. High temperature material

properties that are suitable for development of constitutive models in FE analysis are

not readily available in the literature. The primary motivation for the present study is

to develop a relatively low cost, simple and reliable method to measure thermo-

mechanical properties in the high temperature regime for use in thermal-structural

analysis of hypersonic structures.

The main constraints placed on high temperature mechanical test facilities are

usually based on the high cost and limited availability of test material. As a result

small test specimens are favoured. However, at high temperatures external forces that

are usually considered negligible can greatly affect the mechanical behaviour of

small specimens. For example, contact forces from temperature or strain

measurement equipment, such as thermocouples or mechanical extensometers, can

produce large stress concentrations. Additionally, the loads required to hold the

sensors against the specimen surface are often sufficient enough to cause distortion

or bending of the specimen. This places restrictions on the chosen test equipment in

Appendices

200

particular the temperature and strain measurement techniques. A review of various

high temperature mechanical test methods was presented by V�lkl and Fischer [1].

Details were also included of their own specially designed facilities [1,2] for testing

metallic materials at temperatures up to 3000°C using non-contact temperature and

strain measurement. A further review and summary of current techniques is provided

in this paper.

An important requirement of the test facility is to be able to provide a

controllable heat distribution over the test specimen gauge length, while still

allowing access for temperature and strain measurement. A means of gripping and

applying loads to the high temperature specimen is also necessary. The grips must

not affect the specimen’s mechanical behaviour and should also prevent heat damage

to any load equipment. The main methods of heating the specimen include single and

multi-zone furnaces, induction heating and ohmic heating. Reppich et al. [3]. used a

single zone furnace with the specimen grips placed inside the heated zone. The grips

were made from alumina (Al2O3) and experienced temperatures up to 1400°C. On

the other hand, Ho and MacEwen [4] utilised a three-zone furnace, which allowed for

low cost stainless steel grips to be used without creating significant temperature

gradients over the specimen gauge length. As an alternative to furnaces, induction

heating and ohmic heating both provide localised heating within the test specimen

and allow for fast heating and cooling rates. Policella and Pacou [5] made use of an

induction heater for tension and torsion testing of metals at temperatures of up to

1000°C. However, Ohmic heating was chosen by V�lkl and Fischer [1] for its

simplicity and for full access to the specimen gauge length. The localised heating

also meant that low cost copper grips could be used.

Both contact and non-contact temperature measurement techniques are

commonly used in high temperature test facilities. Contact temperature methods

include thermocouples and resistance temperature detectors (RTD). Lee et al. [6]

used thermocouples located at the top and bottom of the steel tensile specimens for

temperatures of up to 800°C. A platinum resistance thermometer was chosen by Aria

and Yamazawa [7] for high stability control of their furnace to temperatures up to

1000°C.

Appendices

201

For precise temperature measurement intimate contact is required with the

specimen throughout testing. This can affect the temperature distribution and

mechanical behaviour of the test specimen. Non-contact temperature measurement

techniques avoid these problems and include radiation thermometers and optical

pyrometers. Temperature measurement can also be made indirectly by using

thermocouples, for example, to measure environmental conditions such as the air

temperature in a furnace. V�lkl and Fischer [1] used an infrared pyrometer operating

at wavelengths of 0.7 to 1.1 �m for temperature measurement between 750 to

3000°C. For accurate radiation temperature measurement spectral emissivity data is

required as function of temperature for the materials to be tested. This problem was

overcome by Potdar and Zehnder [8] who calibrated an infrared detector against

thermocouples spot welded to a test specimen’s surface. Calibration can also be

achieved by using a reference material of known spectral emissivity. Neuer and

Jaroma-Weiland [9] recommended the use of various Pt/Rh alloys for which they

measured the total and spectral emissivity at temperatures of up to 1350°C.

Contact strain measurement techniques include the use of strain gauges and

mechanical extensometers. Lei et al. [10] compared the use of resistance strain

gauges and PdCr wire strain gauges, along with various attachment methods, at

temperatures up to 800°C. Alternatively, mechanical extensometers allow strain

measurement at temperatures of up to around 1500°C by using extension rods to

remove the displacement sensor from the heated specimen. Cooling of the sensor can

provide a further increase in the range of operation. Reppich et al. [3] used an axial

extensometer with Al2O3 extension rods and an inductive linear position sensor for

tensile tests at temperatures up to 1400°C. A low cost method of modifying room

temperature extensometers was offered by Quesnel and Tsou [11] for use at

temperatures up to 500°C. Lee et al. [6] also used a modified room temperature

extensometer for tensile tests of steel at temperatures up to 800°C. Contact strain

measurement techniques can be utilised as non-contact methods by measuring

displacement outside of the heated gauge length. This however requires knowledge

of the mechanical behaviour of the entire region between the measurement points.

Ho and MacEwen [4] measured displacement by attaching an extensometer at the

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202

shoulders of a heated tensile specimen under the assumption that the total measured

deformation is mainly due to the significant plastic flow within the gauge length.

Non-contact strain measurement techniques include laser speckle, laser

extensometers and computer-vision systems such as digital-image correlation (DIC)

or video extensometers. Lyons et al. [12] utilised DIC by coating test specimens with

BN or alumina to create black speckles on the surface. Strain was then measured at

temperatures of up to 650°C by comparing images of the specimen’s surface. The

performance of DIC methods can be affected by various factors such as image

distortion, increased illumination and changes in the specimen surface. These

decorrelation effects were reduced by Anwander et al. [13] who combined both DIC

and laser speckle techniques. Two laser diode beams created speckle patterns on the

specimen surface and the displacement of these patterns was measured. This allowed

strain to be measured at temperatures up to 1200°C. V�lkl and Fischer [1] measured

strain with a digital camera and the computer software SuperCreep [1] at

temperatures of up to 3000°C. The software determined the distance between

physical markers on the test specimen to provide a strain measurement. Optical fibre

sensors provide another means of strain measurement that combines both contact and

non-contact methods, and can also be used for temperature measurement. Elster et al.

[14] used Fabry-Perot sensor elements to measure strain during fatigue tests at

temperatures of up to 1100°C.

The design constraints placed on high temperature test facilities are usually in

contradiction with the desired characteristics of low cost and versatility. High

precision and reliability generally means expensive and specialised test equipment. A

balance between the requirements placed on test equipment, including cost, accurate

results, and simple set-up and operation therefore needs to be found.

This paper describes a low cost high temperature test rig that was developed in

this investigation. The versatile facility can be used for a range of thermo-mechanical

tests and is simple to set-up and operate. Details of an experimental validation study

are given for the thermo-mechanical properties of carbon steel 1020 at elevated

temperatures up to 850°C. This study includes a comparison of the experimental

results obtained with already published data to verify the test setup. An experimental

Appendices

203

study of aluminium alloy 7000 T4, a material used in aerospace applications, is also

presented to further prove the reliability of the test rig. This material is tested at

temperatures of 260°C and 480°C and demonstrates the rapid deterioration in

mechanical properties with temperature. The thermo-mechanical properties

determined in both experimental studies are the linear coefficient of thermal

expansion and the tensile modulus of elasticity, yield strength and ultimate strength.

These properties are used to develop high temperature constitutive models for

thermal-structural analysis of hypersonic structures.

2 Description of the Apparatus

A low cost test rig has been designed and built for the investigation of high

temperature thermo-mechanical properties. The test rig consists primarily of an

induction heater, high temperature specimen grips and a control system. Loading of

the test specimens is via an Instron (1342) test machine, although the design of the

high temperature grips allows the use of any standard test machine. Strain is

measured by a high temperature mechanical extensometer with ceramic extension

rods. The test specimen temperature is measured by multiple type K thermocouples,

which provide the feedback signal for a PID temperature controller. The test rig is

shown in Fig. 1 and is described in further detail in the following sections.

Appendices

204

Fig. 1. Test rig

2.1 Induction Heater

A 3 kW induction heater provides an effective method of heating the test

specimen to temperatures up to around 1500°C, depending on the material and

specimen size. Induction heating allows for rapid heating and cooling rates and can

be used with a range of specimen designs and materials. Metallic materials can be

heated directly, while ceramics and other materials can be heated indirectly using a

metal radiation tube, or similar device. The design of the induction heating coil

ensures localised and uniform heating over the specimen gauge length and provides

access to the specimen for temperature and strain measurement. Induction heating

Mechanical Extensometer

Thermocouples

Extensometer - Displacement Sensor

High Temperature Grip

Test Specimen in Heating Coil

High Temperature Grip Extensometer - Extension

Appendices

205

was also chosen for its ease of operation. The test specimen is heated in air with the

heating rate and temperature controlled by a feedback control system.

2.2 High Temperature Specimen Grips

Heat transfer from the heated specimen to the Instron test machine is prevented

by specially designed high temperature grips (shown in Fig. 2). Using an induction

heater means only the specimen is directly heated with the grips experiencing a lower

temperature then at the specimen gauge length. The grips therefore consist of a low

cost stainless steel main body with pull rods for connection to the test machine. A

small section of higher cost Inconel 601, a nickel-chromium alloy with a low thermal

conductivity of 11.2 Wm-1K-1, reduces the initial heat transfer from the specimen.

Excess heat is removed from the grips by water circulation through the main body

via a pump and cooling unit. The combination of a low thermal conductivity section

and water-cooling allows the grips to be used for testing over long periods of time.

The Inconel section of each grip is made up of two removable pieces to allow for

attachment of the specimen by a variety of methods, e.g. threaded end piece, wedge

blocks. A range of specimen shapes and sizes can therefore be tested without the cost

of having to remanufacture the grips.

Appendices

206

Fig.2. High Temperature Grip

2.3 Test Specimens

The test specimens used for these investigations were round tensile specimens in

accordance with ASTM E21 [15] and E8M. [16] A diameter of 6 mm and gauge

length of 30 mm was chosen as a compromise between the limited amount of test

material and the increased specimen size requirements for contact strain

measurement. Round specimens were used for simplicity to manufacture and to

ensure uniform heat distribution from the heating coil. A threaded end section was

used to attach the specimens to the high temperature grips.

2.4 Measurement and Control

Temperature is measured by three type K thermocouples along the length of the

specimen reduced section (Fig. 1). Thermocouples were chosen over optical methods

based on low cost and simplicity of use. Furthermore, the use of thermocouples

means that spectral emissivity data for the test materials need not be determined.

Temperature measurements are taken from the specimen surface and are calibrated

against measurements from a thermocouple placed inside a test specimen. A further

discussion of this is provided in section 3.1. This method allows specimen

temperatures of around 1700°C to be measured, depending on the material being

tested, with the thermocouples only reaching temperatures of up to 1300°C. Multiple

thermocouples along the specimen length ensure a uniform and steady heat

distribution throughout testing.

Strain is measured by a high temperature mechanical extensometer with high

purity Al2O3 (99.7%) ceramic extension rods and a strain gauge based displacement

sensor (see Fig. 1). The extensometer has a gauge length of 30 mm with a 50%

displacement range for tension and can be left in place throughout specimen failure.

For temperatures up to 1200°C the extensometer can be used uncooled and with

Appendices

207

cooling can be used at temperatures above this value. A mechanical extensometer

was chosen due to low cost and straightforward operation, enabling strain

measurement in real-time without the need for complex software. However, being a

contact measurement method limitations are placed on the size of the specimens that

can be tested.

A laptop computer and 16-bit microcontroller are used to monitor and control all

test equipment. The microcontroller runs a C based code written by the authors and

interfaced through the computer. A PID feedback control system is included in the

code to control the induction heater and hence specimen temperature and heating

rates. For these investigations a sample rate of 100 Hz was used to ensure that the

digital PID implemented with the microcontroller best emulated the analogue PID

used for its design. All test variables and measurements are output from the

microcontroller to the computer for data logging. The Instron test machine used for

these investigations has its own control computer and software which allows for both

strain and load control. The output from the load cell, however was data logged

through the microcontroller.

3 Experimental Procedure

3.1 Thermocouple calibration

Temperature is determined by the measuring junctions of the thermocouples

being held against the specimen’s surface. The thermocouples apply only a minimal

contact force and are free to move with the strained specimens. This is to ensure that

any affect on the specimen’s mechanical behaviour will be negligible. Heat is then

transferred to the thermocouples mainly via conduction and radiation, depending on

the material being tested. At the same time heat is lost from the thermocouples due to

radiation and convection to the surroundings. Heat is also lost by the non-perfect

contact between the thermocouples and the test specimen. A theoretical study of the

heat transfer to the specimen and to the thermocouple and heat loss to the

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208

surroundings was performed by finite element (FE) transient thermal analysis of a

3D model of the specimen with a thermocouple on the surface (Fig. 3a). A heat flux

of 4.8 x 105 W/m2K from the induction heater was used for the initial analysis and

was varied by a factor of 0.5 - 2 to investigate the effect of heating rate. The results

from the FEA confirmed that the steady state temperature was achieved very quickly,

because of the rapid heating rate, and the temperature distribution across the

specimen was fairly uniform (see Figure 3b). The heat loss from the thermocouple to

the surroundings by radiation and convection was quite significant and can result in a

lower reading than the actual temperature on the specimen surface. Figure 4 shows

the theoretical temperatures, from the FEA, at the surface and centre of the specimen

and at the surface of the thermocouple. The temperature of the thermocouple at the

surface of the specimen was 100 – 250 degrees lower than the actual temperature of

the specimen surface. The thermocouple placed inside the centre of specimen,

however, would have much better contact with the specimen and heat loss by

convection is expected to be minimal.

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209

(a)

Appendices

210

(b)

Fig. 3 — 3D Finite element thermal analysis: (a) 3D model and (b)

Temperature distribution across the specimen

Appendices

211

0

500

1000

1500

0 500 1000 1500

SurfaceThermocouple

Temperature (°C)

Cen

tre

Tem

pera

ture

(°C

)

Fig. 4 — Comparison of the theoretical specimen temperature and

thermocouple measurement

Calibration was achieved by comparison of the surface temperature readings with

that of a centre temperature measurement. The centre thermocouples were placed

inside a 30 cm deep hole drilled along the specimen centreline. Any direct heating

affects of the induction heater on the thermocouples were neglected as the resulting

temperature levels were well below that of the actual specimen and surface

temperature measurements. Fig. 5 shows the calibration data for carbon steel 1020

with a third-order best-fit curve to allow for extrapolation above the centre

thermocouple’s operational limit. A similar overall trend can be seen to that of the

theoretical curve presented in Fig. 4. The differences in the curve shapes below

approximately 800°C can be partially explained by the non-linear heating effects of

the induction heating process, which were not considered in the FE analysis. The test

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212

results were also used to calibrate the induction heater power level for use in the PID

control system. Over time oxidation of the thermocouple and specimen surfaces can

lead to small changes in calibration. Average measurements over extended test

periods were therefore used to account for any variations with time.

0

250

500

750

1000

1250

1500

0 200 400 600 800 1000

experimental databest-fit curve

Surface Measurement (°C)

Cen

tre

Mea

sure

men

t (°C

)

Fig. 5—Thermocouple calibration curve for carbon steel 1020

Thermocouple calibration was verified by experimentally determining the Curie

and melting temperatures for carbon steel 1020. The Curie temperature was found

during heating the specimen by the point at which magnetic heating affects, or

hysteresis, ceased. A Curie temperature of 790°C was determined compared to a

value of 760°C given by Smithells [17]. The Curie point can also be observed in Fig.

5 where the calibration curve changes shape. A melting temperature of 1420°C was

determined compared to a value of 1455°C given by the material’s manufacturer

Onesteel [18]. This gives an error of ±4% in the temperature measurement compared

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213

to the published values. Taking into account inherent differences of the magnetic and

thermal properties between the various carbon steel 1020 specimens; this level of

accuracy was considered to be very good.

3.1 Test Procedure

The described high temperature test rig was used for thermal expansion and

tensile testing of metals. Although, it can also be used for a range of other

mechanical tests such as compression, fatigue and creep. The general test procedure

involves preparation of the test specimen, placement of the specimen in the high

temperature grips and set-up of the heating and measurement equipment. The desired

test temperature is set with the PID controller and the specimen is heated until at

steady state. For these investigations a heating rate of approximately 10°Cs-1 was

used with a total heating time of 3 mins to ensure uniform temperature distribution

through the specimen thickness and over the gauge length.

The high heating rate from the induction method is appropriate to that seen in

hypersonic flights where the heat flux from stagnation heating, shock/boundary layer

interaction, etc. can be of the order of 106 – 109 W/m2K. Faster, or slower, heating

rates are also possible using the induction method. The affect that the heating rate has

on the mechanical properties was not investigated in this study. Instead the same

heating rate was employed for each of the specimens and the final tests were carried

out once the temperature distribution was uniform in the gauge section. However, the

effect of heating rate is not expected to be significant because the induction method

rapidly heats up the specimen and FEA shows that a near uniform temperature

distribution is reached within 20-60 s. Finite element heat transfer analysis of the

specimen showed that a heating time of 3 mins was sufficient for uniform

temperature distribution through the specimen thickness and gauge length. This is

also supported by temperature measurements at various positions in the specimen

during the induction heating. For this study a temperature variation of 50ºC over the

specimen gauge length was considered acceptable, although a lower temperature

Appendices

214

variation is achievable.

Procedure for the thermal expansion tests was based on ASTM E831 [19] and for

the tensile tests on ASTM E21 [15] and E8M [16]. Thermal expansion tests were

undertaken with no applied load and the thermal strain was measured once

temperature was at steady state. During heating the specimens for tensile testing

thermal expansion was allowed by using load control set at zero load. Load control

was also used to apply a small tensile load at a constant load rate for the

determination of the modulus of elasticity. Displacement control was used for the

tensile failure tests to apply a large displacement to the specimen at a constant strain

rate. All measurements and test data were recorded by the computer for post-

processing.

3.3 Validation Study

To verify the test rig the linear coefficient of thermal expansion and tensile modulus

of elasticity were determined as functions of temperature for carbon steel 1020 (Fig.

6). Tests were undertaken at temperatures up to 850°C and compared with literature

data [17,20]. Room temperature of 25°C was used as reference for the thermal

expansion coefficient calculations and the elastic tensile tests were performed at a

constant load rate of 5 MPa s-1. The experimental values obtained are within ±4%

and ±5% of the literature data for the expansion coefficient and elastic modulus,

respectively. At temperatures above 850°C the limitations of contact strain

measurement were experienced with the contact forces from the extensometer

affecting the small test specimens.

Appendices

215

10

11

12

13

14

15

0 150 300 450 600 750 900

according to Smithells

Temperature (°C)

Line

ar C

oeffi

cien

t of T

herm

al E

xpan

sion

(�m

/m °C

-1)

experimental resultswith error bars of ±4%

(a)

60

110

160

210

260

0 150 300 450 600 750 900

according to Ashby and Waterman

Temperature (°C)

Mod

ulus

of E

last

icity

(GPa

)

experimental resultswith error bars of ±5%

(b)

Appendices

216

Fig. 6—Carbon steel 1020 experimental results for the temperature

dependence of (a) the linear coefficient of thermal expansion compared to

literature data according to Smithells [17]; and (b) the tensile modulus of

elasticity compared to literature data according to Ashby and Waterman [20]

4 Selected Results

Tensile test were undertaken for aluminium alloy 7000 T4 to determine the

stress-strain curves at temperatures of 260°C and 480°C (Fig. 7). A constant strain

rate of 10-3s-1 was used throughout all tests. The lower temperature specimen

underwent a moderately ductile failure with regions of both strain hardening and

necking before the final sudden fracture. An elastic modulus of 63 GPa, 0.2% yield

strength of 180 MPa, ultimate strength of 233 MPa and a fracture strain of 27% were

determined. The higher temperature specimen experienced a highly ductile failure

with no sudden fracture. An elastic modulus of 37 GPa, 0.2% yield strength of 68

MPa, ultimate strength of 73 MPa and a fracture strain of 44% were determined.

Appendices

217

0

50

100

150

200

250

Engineering Strain (m/m)

Engi

neer

ing

Stre

ss (M

Pa)

480 °C

260°C

0.0 0.1 0.2 0.3 0.4 0.5

Fig. 7—Experimental results for the tensile stress-strain curves obtained at

temperatures of 260°C and 480°C for aluminum alloy 7000 T4

5 High Temperature Constitutive Models

The results of thermal expansion coefficient (CTE), modulus of elasticity and

stress-strain behaviour as functions of temperature were used to develop high

temperature constitutive models, in a form that can be implemented in finite element

analysis (FEA). At a given temperature, the constitutive equation has the form

( ) ( ) mTET εσ '= (1)

where σ is the stress, ε is the strain (calculated from the temperature dependent

CTE values), E’ is the modulus of elasticity, m is the strain exponent respectively

and T is the temperature. The constitutive models developed in this study were

Appendices

218

utilised in the thermal-structural analysis of the HyCause Scramjet engine for flight

test [21].

6 Conclusion

Various test methods and equipment for high temperature thermo-mechanical

testing have been reviewed. Based on these findings; the low cost high temperature

test rig designed and built for these investigations was then described. An induction

heater provides fast heating and cooling rates, simple operation and access to the test

specimen for temperature and strain measurement. Specially designed high

temperature specimen grips with water-cooling allow for testing over long periods of

time. Thermocouples measure temperature and provide a feedback signal for PID

control of the induction heater. Strain is measured by a mechanical extensometer

with ceramic extension rods. A microcontroller and laptop computer allow for

complete control and monitoring of all equipment and test parameters.

Calibration of the thermocouples made temperature measurement of the test

specimen possible to within ±4%. A validation study of the linear coefficient of

thermal expansion and tensile Young’s modulus of carbon steel 1020 verified the test

rig. Results for the thermal expansion coefficient and elastic modulus were obtained

within ±4% and ±5% of literature data, respectively. Tensile tests to failure of the

aerospace material aluminium alloy 7000 T4 further verified the reliability of the test

set-up.

Limitations were found with the use of contact strain measurement due to the

small size of the test specimens. At the higher temperatures contact forces from the

mechanical extensometer were sufficient to buckle the test specimens. With further

expense improvements could be made with the test rig, such as the use of non-

contact temperature and strain measurement. The capability could also be extended

to measure Poisson’s ratio.

The test rig developed for these investigations allowed for accurate and reliable

experimental results. Test equipment was chosen based on the ability to provide

Appendices

219

accurate results as well as low cost and simplicity in design and operation. The

ability for the test rig to be used for a range of thermo-mechanical tests was also an

important factor. The measured thermo-mechanical properties have enabled the

development of high temperature constitutive models for structural design

calculations and the thermal-structural analysis of a hypersonic vehicle for flight test.

Acknowledgements

This work was completed with the financial support of the Defence Science and

Technology Organisation (DSTO) of Australia.

Appendices

220

References

[1] R. V�lkl, B. Fischer, Mechanical Testing of Ultra-High Temperature Alloys,

Experimental Mechanics 44 (2) (2004) 121-127.

[2] R. V�lkl, D. Freund, B. Fischer, Economic Creep Testing of Ultra-High

Temperature Alloys, Journal of Testing and Evaluation 31 (1) (2003) 35-43.

[3] B. Reppich, F. Brungs, G. Hümmer, H. Schmidt, Modelling of the Creep

Behaviour of ODS Platinum-Based Alloys, in: R.W. Evans, B. Witshire (eds),

Proceedings of the 4th International Conference on Creep Fracture of Engineering

Materials and Structures, The Institute of Metals, Swansea, (1990) 142-158.

[4] E.T.C. Ho, S.R. MacEwen, A Facility for Precise Measurement of

Mechanical Properties at Elevated Temperatures, Journal of Metals 35 (2) (1983) 25-

29.

[5] H. Policella, D. Pacou, High Temperature Tension-Torsion Testing Machine,

La Recherche Aerospatiale (English Edition), (5) (1988) 39-49.

[6] J.H. Lee, M. Mahendran, P. Makelainen, Prediction of Mechanical Properties

of Light Gauge Steels at Elevated Temperatures, Journal of Construction Steel

Research 59 (12) (2003) 1517-1532.

[7] M. Aria, K. Yamazawa, High-Temperature Furnace Controlled by a Platinum

Resistance Thermometer, in: Proceedings of the SICE Annual Conference, The

Society of Instrumentation and Control Engineers, Sapporo, (2004) 1543-1546.

[8] Y.K. Potdar, A.T. Zehnder, Temperature and Deformation Measurements in

Transient Metal Cutting, Experimental Mechanics 44 (1) (2004) 1-9.

[9] G. Neuer, G. Jaroma-Weiland, Spectral and Total Emissivity of High

Temperature Materials, International Journal of Thermophysics 19 (3) (1998) 917-

929.

[10] J.F. Lei, M.G. Castelli, D. Androjna, C. Blue, R. Blue, R.Y. Lin,

Comparison Testings between two High-Temperature Strain Measurement Systems,

Experimental Mechanics 36 (4) (1996) 430-435.

[11] D.J. Quesnel, J.C. Tsou, Extensometer Extender for Conversion of Room-

Appendices

221

Temperature Extensometers for High-Temperature Applications, Review of

Scientific Instruments 54 (2) (1983) 226-228.

[12] J.S. Lyons, J. Liu, M.A. Sutton, High-Temperature Deformation

Measurements Using Digital-Image Correlation, Experimental Mechanics 36 (1)

(1996) 64-70.

[13] B.G. Anwander, B. Zagar, B. Weiss, H. Weiss, Non-Contacting Strain

Measurements at High Temperatures by the Digital Laser Speckle Technique,

Experimental Mechanics 40 (1) (2000) 98-105.

[14] J.K. Elster, T.A. Tran, A.E. Barnes, J.E. Coate, M.F. Gunther, R.G. May,

R.O. Claus, High-Temperature Fiber Optic Strain Sensors in Fatigue-Loading

Conditions, in: Proceedings of SPIE – The International Society of Optical

Engineering, 2718 (1996) 20-26.

[15] American Society for Testing and Materials (ASTM ), E21 Standard Test

Methods for Elevated Tension Tests of Metallic Materials, 2005.

[16] American Society for Testing and Materials (ASTM ), E8M Standard Test

Methods for Tension Testing of Metallic Materials [Metric], 2004.

[17] C. Smithells, Metals Reference Book, Butterworths, London 1967.

[18] OneSteel Market Mills, OneSteel Martin Bright Technical Handbook – Issue

2,” Mayfield, Australia, 2003.

[19] American Society for Testing and Materials (ASTM ), E831Standard Test

Method for Linear Thermal Expansion of Solid Materials Thermomechanical

Analysis, 2005.

[20] M. Ashby, N. Waterman, The Materials Selector, Chapman & Hall, London

1997.

[21]. S.Y. Ho, Thermal-Structural Analysis of the DARPA HyCause Engine for

Flight Test, in: Proceedings of the 14th AIAA/AHI International Space Planes and

Hypersonic Systems and Technologies Conference, AIAA paper no 2006-8070

(2006).

Appendices

222

Appendix C

Porosity Measurements

Figures were taken from ASTM E2109-01 standard.

Figure 1: 0.5 % Porosity

Figure 2: 1.0 % Porosity

a1172507Text Box NOTE: Appendix C is included in the print copy of the thesis held in the University of Adelaide Library.

References

227

REFERENCES

References

228

Abdul-Aziz, A., Tong, M. T. and Kaufman, A. F. [1989]. 'Thermal finite-element analysis of space shuttle main engine turbine blade', Finite Elements in Analysis and Design, 5(4): 337-348. Ahmaniemi, S., Vuoristo, P., Mäntylä, T., Gualco, C., Bonadei, A. and Di Maggio, R. [2005]. 'Thermal cycling resistance of modified thick thermal barrier coatings', Surface and Coatings Technology, 190(2-3): 378-387. Alhama, F. and Campo, A. [2003]. 'Network simulation of the rapid temperature changes in the composite nozzle wall of an experimental rocket engine during a ground firing test', Applied Thermal Engineering, 23(1): 37-47. Antou, G., Hlawka, F., Cornet, A., Montavon, G., Coddet, C. and Machi, F. [2004]. 'Processing of yttria partially stabilized zirconia thermal barrier coatings implementing a high-power laser diode', Journal of Thermal Spray Technology, 13(3): 381-389.

Bansal, N. P. and Zhu, D. [2008]. 'Thermal properties of oxides with magnetoplumbite structure for advanced thermal barrier coatings', Surface and Coatings Technology, 202(12): 2698-2703. Basu, D., Funke, C. and Steinbrech, R. W. [1999]. 'Effect of heat treatment on elastic properties of separated thermal barrier coatings', Journal of Materials Research, 14(12): 4643-4650.

Beele, W., Marijnissen, G. and van Lieshout, A. [1999]. 'The evolution of thermal barrier coatings - status and upcoming solutions for today's key issues', Surface and Coatings Technology, 120-121: 61-67. Bergant, Z. and Grum, J. [2009]. 'Quality Improvement of Flame Sprayed, Heat Treated, and Remelted NiCrBSi Coatings', Journal of Thermal Spray Technology, 18(3): 380-391.

Bernard-Granger, G., Monchalin, N. and Guizard, C. [2007]. 'Sintering of ceramic powders: Determination of the densification and grain growth mechanisms from the "grain size/relative density" trajectory', Scripta Materialia, 57(2): 137-140. Bernard-Granger, G., Monchalin, N. and Guizard, C. [2008]. 'Comparisons of grain size-density trajectory during spark plasma sintering and hot-pressing of zirconia', Materials Letters, 62(30): 4555-4558. Berndt, C. C. and Lenling, W. J. [2004]. Handbook of Thermal Spray Technology. USA, ASM.

Bialas, M. [2008]. 'Finite element analysis of stress distribution in thermal barrier coatings', Surface and Coatings Technology, 202(24): 6002-6010. Bolcavage, A., Feuerstein, A., Foster, J. and Moore, P. [2004]. 'Thermal shock testing of thermal barrier coating/bondcoat systems', Journal of Materials Engineering and Performance, 13: 389-397. Bolelli, G., Lusvarghi, L., Varis, T., Turunen, E., Leoni, M., Scardi, P., Azanza-Ricardo, C. L. and Barletta, M. [2008]. 'Residual stresses in HVOF-sprayed ceramic

References

229

coatings', Surface and Coatings Technology, 202(19): 4810-4819. Bordeaux, F., Saint Jacques, R. G. and Moreau, C. [1991]. 'Study of surface preparation for enhanced resistance to thermal shocks of plasma-sprayed TiC coatings', Surface and Coatings Technology, 49(1-3): 50-56. Bouzakis, K.-D., Lontos, A., Michailidis, N., Knotek, O., Lugscheider, E., Bobzin, K. and Etzkorn, A. [2003]. 'Determination of mechanical properties of electron beam-physical vapor deposition-thermal barrier coatings (EB-PVD-TBCs) by means of nanoindentation and impact testing', Surface and Coatings Technology, 163-164: 75-80.

Braun, R., Leyens, C. and Fröhlich, M. [2005]. 'Performance of thermal barrier coatings on gamma-TiAl', Materials and Corrosion, 56(12): 930-936. Brinson, L. C. and Lin, W. S. [1998]. 'Comparison of micromechanics methods for effective properties of multiphase viscoelastic composites', Composite Structures, 41(3-4): 353-367.

Briscoe, B. J., Khan, A. U. and Luckham, P. F. [1998]. 'Optimising the dispersion on an alumina suspension using commercial polyvalent electrolyte dispersants', Journal of the European Ceramic Society, 18(14): 2141-2147. Brunauer, G., Frey, F., Boysen, H. and Schneider, H. [2001]. 'High temperature thermal expansion of mullite: an in situ neutron diffraction study up to 1600°C', Journal of the European Ceramic Society, 21(14): 2563-2567. Brunner, M. H., Rose, M. G., Mühlbauer, K. and Abhari, R. S. [2008]. 'In-situ heat transfer measurements on coated and uncoated turbine blades of a full-scale turbine', Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 222(3): 331-338. Cannon, J., Alkam, M. and Butler, P. [2008]. 'Efficiency of Pulsed Detonation Thermal Spraying', Journal of Thermal Spray Technology, 17(4): 456-464. Cao, X., Li, J., Zhong, X., Zhang, J., Zhang, Y., Vassen, R. and Stoever, D. [2008]. 'La2(Zr0.7Ce0.3)2O7 - A new oxide ceramic material with high sintering-resistance', Materials Letters, 62(17-18): 2667-2669. Cao, X., Vassen, R., Tietz, F., Jungen, W. and Stoever, D. [2001]. 'Thermal stability of lanthanum zirconate plasma-sprayed coating', Journal of the American Ceramic Society, 84(9): 2086-2090. Cao, X. Q., Vassen, R. and Stoever, D. [2004]. 'Ceramic materials for thermal barrier coatings', Journal of the European Ceramic Society, 24(1): 1-10. Choi, S. R., Zhu, D. and Miller, R. A. [2005]. 'Effect of Sintering on Mechanical Properties of Plasma-Sprayed Zirconia-Based Thermal Barrier Coatings', Journal of the American Ceramic Society, 88(10): 2859-2867. Choy, K. L. [2003]. 'Chemical vapour deposition of coatings', Progress in Materials Science, 48(2): 57-170. Clarke, D. R. and Phillpot, S. R. [2005]. 'Thermal barrier coating materials',

References

230

Materials Today, 8(6): 22-29. Dahl, P., Kaus, I., Zhao, Z., Johnsson, M., Nygren, M., Wiik, K., Grande, T. and Einarsrud, M.-A. [2007]. 'Densification and properties of zirconia prepared by three different sintering techniques', Ceramics International, 33(8): 1603-1610. Degarmo, E. P., Black, J. T. and Kohser, R. A. [2003]. Materials and Processes in Manufacturing. USA.

Degueldre, C. [2007]. 'Zirconia inert matrix for plutonium utilisation and minor actinides disposition in reactors', Journal of Alloys and Compounds, 444-445: 36-41. Dobbins, T. A., Knight, R. and Mayo, M. J. [2003]. 'HVOF thermal spray deposited Y2O3-stabilized ZrO2 coatings for thermal barrier applications', Journal of Thermal Spray Technology, 12: 214-225. Duvall, D. S. and Ruckle, D. L. [1982]. 'Ceramic Thermal Barrier Coatings for Turbine Engine Components', ASME Paper, 82(GT): 332. Eroglu, S. and Gallois, B. [1991]. 'Design and chemical vapor deposition of graded TiN/TiC coatings', Surface and Coatings Technology, 49(1-3): 275-278. Feuerstein, A., Knapp, J., Taylor, T., Ashary, A., Bolcavage, A. and Hitchman, N. [2008]. 'Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review', Journal of Thermal Spray Technology, 17(2): 199-213. Gatto, A. [2006]. 'Critical evaluation of indentation fracture toughness measurements with Vickers indenter on ceramic matrix composite tools', Journal of Materials Processing Technology, 174(1-3): 67-73. Gilbert, A., Kokini, K. and Sankarasubramanian, S. [2008]. 'Thermal fracture of zirconia-mullite composite thermal barrier coatings under thermal shock: An experimental study', Surface and Coatings Technology, 202(10): 2152-2161. Greenwood, R. and Kendall, K. [1999]. 'Selection of Suitable Dispersants for Aqueous Suspensions of Zirconia and Titania Powders using Acoustophoresis', Journal of the European Ceramic Society, 19(4): 479-488. Guo, H., Kuroda, S. and Murakami, H. [2006]. 'Microstructures and Properties of Plasma-Sprayed Segmented Thermal Barrier Coatings.' Journal of the American Ceramic Society, 89(4): 1432-1439. Gurrappa, I. and Sambasiva, A. R. [2006]. 'Thermal barrier coatings for enhanced efficiency of gas turbine engines', Surface and Coatings Technology, 201(6): 3016-3029.

Hasan, M., Stokes, J., Looney, L. and Hashmi, M. S. J. [2008]. 'Design and optimisation of a multi-powder feed system for the HVOF deposition process', Surface and Coatings Technology, 202(14): 3215-3220. He, B., Li, F., Zhou, H., Dai, Y. and Sun, B. [2007]. 'Microstructure and thermal cycling behavior of thermal barrier coating on near-α titanium alloy', Journal of Coatings Technology and Research, 4(3): 335-340.

References

231

Hejwowski, T. and Weronski, A. [2002]. 'The effect of thermal barrier coatings on diesel engine performance', Vacuum, 65(3-4): 427-432. Hirvonen, A., Nowak, R., Yamamoto, Y., Sekino, T. and Niihara, K. [2006]. 'Fabrication, structure, mechanical and thermal properties of zirconia-based ceramic nanocomposites', Journal of the European Ceramic Society, 26(8): 1497-1505. Hvizdos, P., Jonsson, D., Anglada, M., Anné, G. and Van Der Biest, O. [2007]. 'Mechanical properties and thermal shock behaviour of an alumina/zirconia functionally graded material prepared by electrophoretic deposition', Journal of the European Ceramic Society, 27(2-3): 1365-1371. Jin, G., Takeuchi, M., Honda, S., Nishikawa, T. and Awaji, H. [2005]. 'Properties of multilayered mullite/Mo functionally graded materials fabricated by powder metallurgy processing', Materials Chemistry and Physics, 89(2-3): 238-243. Kakuda, T. R., Limarga, A. M., Bennett, T. D. and Clarke, D. R. [2009]. 'Evolution of thermal properties of EB-PVD 7YSZ thermal barrier coatings with thermal cycling', Acta Materialia, 57(8): 2583-2591. Kawamura, M., Okado, H., Nishio, K. and Suzuki, K. [2004]. 'Effect of interface roughness on internal stress of ceramic thermal barrier coating', Zairyo/Journal of the Society of Materials Science, Japan, 53(9): 1019-1023. Ke, P. L., Wu, Y. N., Wang, Q. M., Gong, J., Sun, C. and Wen, L. S. [2005]. 'Study on thermal barrier coatings deposited by detonation gun spraying', Surface and Coatings Technology, 200(7): 2271-2276. Kepets, M., Lu, T. and Dowling, A. [2007]. 'Mechanical characterization of the role of defects in sintered FeCrAlY foams', Acta Mechanica Sinica, 23(4): 383-398. Khan, A. U., Briscoe, B. J. and Luckham, P. F. [2000]. 'Interaction of binders with dispersant stabilised alumina suspensions', Colloids and Surfaces A: Physicochemical and Engineering Aspects, 161(2): 243-257. Khor, K. A., Dong, Z. L. and Gu, Y. W. [1999]. 'Plasma sprayed functionally graded thermal barrier coatings', Materials Letters, 38(6): 437-444. Khor, K. A. and Gu, Y. W. [2000]. 'Effects of residual stress on the performance of plasma sprayed functionally graded ZrO2/NiCoCrAlY coatings', Materials Science and Engineering A, 277(1-2): 64-76. Khor, K. A. and Gu, Y. W. [2000]. 'Thermal properties of plasma-sprayed functionally graded thermal barrier coatings', Thin Solid Films, 372(1-2): 104-113. Kieback, B., Neubrand, A. and Riedel, H. [2003]. 'Processing techniques for functionally graded materials', Materials Science and Engineering A: Papers from the German Priority Programme (Functionally Graded Materials), 362(1-2): 81-106.

Kim, H.-J. and Kweon, Y.-G. [1999]. 'Elastic modulus of plasma-sprayed coatings determined by indentation and bend tests', Thin Solid Films, 342(1-2): 201-206. Koizumi, M. [1997]. 'FGM activities in Japan', Composites Part B: Engineering: Use

References

232

of Composites Multi-Phased and Functionally Graded Materials, 28(1-2): 1-4. Kokini, K., Takeuchi, Y. R. and Choules, B. D. [1996]. 'Surface thermal cracking of thermal barrier coatings owing to stress relaxation: zirconia vs. mullite', Surface and Coatings Technology, 82(1-2): 77-82. Konyashin, I. [2001]. 'A technique for fabrication of coated TiCN-based cermets with functionally graded structure', International Journal of Refractory Metals and Hard Materials, 19(4-6): 523-526. Kreye, H. and Stoltenhoff, T., [2000], 'Cold Spraying-A Study of Process and Coating Characteristics', Proceedings of the International Thermal Spray Conference. Lackey, W. J., Stinton, D. P., Cerny, G. A., Schaffhauser, A. C. and Fehrenbacher, L. L. [1987]. 'Ceramic coatings for advanced heat engines - A review and projection', Advanced Ceramic Materials: Pages: 24-34. Lan, W. and Xiao, P. [2007]. 'Drying stress of yttria-stabilized-zirconia slurry on a metal substrate', Journal of the European Ceramic Society, 27(10): 3117-3125. Lee, K. N., Miller, R. A. and Jacobson, N. S. [1995]. 'New Generation of Plasma-Sprayed Mullite Coatings on Silicon Carbide', Journal of the American Ceramic Society, 78(3): 705-710. Leushake, U., Winter, A. N., Rabin, B. H. and Corff, B. A. [1999]. 'General aspects of FGM fabrication by powder stacking', Materials Science Forum (Switzerland),308-311: 13-18.

Levy, A. and Macadam, S. [1987]. 'The behavior of ceramic thermal barrier coatings on diesel engine combustion zone components', Surface and Coatings Technology, 30(1): 51-61.

Li, M., Sun, X., Hu, W. and Guan, H. [2007]. 'Thermal shock behavior of EB-PVD thermal barrier coatings', Surface and Coatings Technology, 201(16-17): 7387-7391. Lima, C. and Trevisan, R. [1999]. 'Temperature measurements and adhesion properties of plasma sprayed thermal barrier coatings', Journal of Thermal Spray Technology, 8: 323-327. Lima, C. R. C. and Guilemany, J. M. [2007]. 'Adhesion improvements of Thermal Barrier Coatings with HVOF thermally sprayed bond coats', Surface and Coatings Technology, 201(8): 4694-4701. Lima, R. S., Kucuk, A. and Berndt, C. C. [2001]. 'Evaluation of microhardness and elastic modulus of thermally sprayed nanostructured zirconia coatings', Surface and Coatings Technology, 135(2-3): 166-172. Limarga, A. M., Widjaja, S. and Yip, T. H. [2005]. 'Mechanical properties and oxidation resistance of plasma-sprayed multilayered Al2O3/ZrO2 thermal barrier coatings', Surface and Coatings Technology, 197(1): 93-102. Liu, G. R. [1997]. 'A step-by-step method of rule-of-mixture of fiber- and particle-reinforced composite materials', Composite Structures, 40(3-4): 313-322.

References

233

Liu, Y., Gao, Y. F., Tao, S. Y., Zhou, X. M. and Luo, H. J. [2009]. 'La2O3-modified YSZ coatings: High-temperature stability and improved thermal barrier properties', Surface and Coatings Technology, 203(8): 1014-1019. Ma, X., Wu, F., Roth, J., Gell, M. and Jordan, E. H. [2006]. 'Low thermal conductivity thermal barrier coating deposited by the solution plasma spray process', Surface and Coatings Technology, 201(7): 4447-4452. Mahdjoub, H., Roy, P., Filiatre, C., Bertrand, G. and Coddet, C. [2003]. 'The effect of the slurry formulation upon the morphology of spray-dried yttria stabilised zirconia particles', Journal of the European Ceramic Society, 23(10): 1637-1648. Majumdar, A. and Jana, S. [2000]. 'Yttria doped zirconia in glassy matrix useful for thermal barrier coating', Materials Letters, 44(3-4): 197-202. Mao, W., Dai, C., Yang, L. and Zhou, Y. [2008]. 'Interfacial fracture characteristic and crack propagation of thermal barrier coatings under tensile conditions at elevated temperatures', International Journal of Fracture, 151(2): 107-120. Markocsan, N., Nylen, P., Wigren, J., Li, X.-H. and Tricoire, A. [2009]. 'Effect of Thermal Aging on Microstructure and Functional Properties of Zirconia-Base Thermal Barrier Coatings', Journal of Thermal Spray Technology, 18(2): 201-208. Martena, M., Botto, D., Fino, P., Sabbadini, S., Gola, M. M. and Badini, C. [2006]. 'Modelling of TBC system failure: Stress distribution as a function of TGO Thickness and thermal expansion mismatch', Engineering Failure Analysis, 13(3): 409-426.

Medwell, R., Paul., Chan, Q. N., Kalt, P., A, M. , Zeyad, T., Alwahabi., Dally, B., Bassam. and Nathan, J., Graham. [2010]. 'Instantaneous Temperature Imaging of Diffusion Flames Using Two-Line Atomic Fluorescence', Applied Optics, 64. Medwell, R. P., Chan, Q. N., Kalt, P. A. M., Zeyad, T. A., Dally, B., B. and Nathan, J. G. [2009]. 'Development of temperature imaging using two-line atomic fluorescence', Applied Optics, 48(6): 1237-1248. Meier, S. M. and Gupta, D. V. [1994]. 'The Evolution of Thermal Barrier Coatings in Gas Turbine Engine Applications', Journal of Engineering for Gas Turbines and Power, 116(n1): 250-257. Menvie Bekale, V., Legros, C., Haut, C., Sattonnay, G. and Huntz, A. M. [2006]. 'Processing and microstructure characterization of ceria-doped yttria-stabilized zirconia powder and ceramics', Solid State Ionics, 177(37-38): 3339-3347. Mesrati, N., Ajhrourh, H., Du, N. and Treheux, D. [2000]. 'Thermal spraying and adhesion of oxides onto graphite', Journal of Thermal Spray Technology, 9(1): 95-99.

Miller, R. A., Leissler, G. W. and Jobe, J. M. [1993]. Characterization and durability testing of plasma-sprayed zirconia-yttria and hafnia-yttria thermal barrier coatings. United States: Pages: (34 p). Mills, A., F. [1999]. Heat Transfer, Prentice Hall Inc.

References

234

Miyamoto, Y., Kaysser, W. A., Rabin, B. H., Kawasaki, A. and Ford, R. G. [1999]. Functionally Graded Materials: Design, Processing and Applications. London, Kluwer Academic Publishers.

Moriya, S., Kuroda, Y., Sato, M., Tadano, M., Moro, A. and Nino, M. [1999]. 'Research on the application of PSZ/Ni FGM thermal barrier coating to the combustion chamber (damage conditions of TBC and its mechanism)', Materials Science Forum, 308-311: 410-415. Movchan, B. A. and Yakovchuk, K. Y., [2004], 'Graded thermal barrier coatings, deposited by EB-PVD', Proceedings of the 31st International Conference on Metallurgical Coatings and Thin Films. Narita, T., Hébraud, P. and Lequeux, F. [2005]. 'Effects of the rate of evaporation and film thickness on nonuniform drying of film-forming concentrated colloidal suspensions', The European Physical Journal E: Soft Matter and Biological Physics, 17(1): 69-76.

Nesbitt, J. A. [1990]. 'Thermal response of various thermal barrier coatings in a high heat flux rocket engine', Surface and Coatings Technology, 43-44(Part 1): 458-469. Nesbitt, J. A. [2000]. 'Thermal modeling of various thermal barrier coatings in a high heat flux rocket engine', Surface and Coatings Technology, 130(2-3): 141-151. Nicholls, J. R. [1991]. 'High temperature coatings for gas turbines', Metals and materials Bury St Edmunds, 7(3): 156. Niino, M., Hirai, T. and Watanabe, R. [1987]. 'The functionally graded material', Japan Society Composite Material, 13: 257-264. Osyka, A. S., Rybnikov, A. I., Leontiev, S. A., Nikitin, N. V. and Malashenko, I. S. [1995]. 'Experience with metal/ceramic coating in stationary gas turbines', Surface and Coatings Technology, 76-77(Part 1): 86-94. Padture, N. P., Gell, M. and Jordan, E. H. [2002]. 'Thermal Barrier Coatings for Gas - Turbine Engine Applications', Science.296: 280-284. Padture, N. P., Gell, M. and Jordan, E. H. [2002]. 'Thermal Barrier Coatings for Gas-Turbine Engine Applications

10.1126/science.1068609', Science, 296(5566): 280-284. Padture, N. P. and Klemens, P. G. [1997]. 'Low Thermal Conductivity in Garnets', Journal of the American Ceramic Society, 80(4): 1018-1020. Papyrin, A. [2001]. 'Cold spray technology', Advanced Materials and Processes, 159(9): 49-51.

Peters, M., Leyens, C., Schulz, U. and Kaysser, W. A. [2001]. 'EB-PVD Thermal Barrier Coatings for Aeroengines and Gas Turbines', Advanced Engineering Materials, 3(4): 193-204. Pichon, T., Lacoste, M., Barreteau, R. and Glass, D. E., [2006], 'Integrated thermal protection systems and heat resistant structures', AIAA 57th International Astronautical Congress.

References

235

Polanco, R., Miranzo, P. and Osendi, M. I. [2006]. 'Fabrication and microstructure of a ZrO2-Ni functionally graded bonding interlayer using the airbrush spraying method', Acta Materialia, 54(8): 2215-2222. Portinha, A., Teixeira, V., Carneiro, J., Martins, J., Costa, M. F., Vassen, R. and Stoever, D. [2005]. 'Characterization of thermal barrier coatings with a gradient in porosity', Surface and Coatings Technology, 195(2-3): 245-251. Rätzer-Scheibe, H.-J., Schulz, U. and Krell, T. [2006]. 'The effect of coating thickness on the thermal conductivity of EB-PVD PYSZ thermal barrier coatings', Surface and Coatings Technology, 200(18-19): 5636-5644. Rendtorff, N. M., Garrido, L. B. and Aglietti, E. F. [2008]. 'Thermal shock behavior of dense mullite-zirconia composites obtained by two processing routes', Ceramics International, 34(8): 2017-2024. Rogé, B., Fahr, A., Giguère, J. S. R. and McRae, K. I. [2003]. 'Nondestructive measurement of porosity in thermal barrier coatings', Journal of Thermal Spray Technology, 12(4): 530-535. Roy, P., Bertrand, G. and Coddet, C. [2005]. 'Spray drying and sintering of zirconia based hollow powders', Powder Technology: 4th French Meeting on Powder Science and Technology, 157(1-3): 20-26. Ruder, A., Buchkremer, H. P., Jansen, H., Malléner, W. and Stöver, D. [1992]. 'Wet powder spraying - A process for the production of coatings', Surface and Coatings Technology, 53(1): 71-74. Sahin, A. and Erdogan, F. [2004]. 'On debonding of graded thermal barrier coatings', International Journal of Fracture, 129(4): 341-359. Sampath, S., Herman, H., Shimoda, N. and Saito, T. [1995]. 'Thermal spray processing of FGMs', MRS bulletin (0883-7694), 20(1): 27. Schulz, U., Rätzer-Scheibe, H.-J., Saruhan, B. and Renteria, A. F. [2007]. 'Thermal conductivity issues of EB-PVD thermal barrier coatings', Materialwissenschaft und Werkstofftechnik, 38(9): 659-666. Song, Y.-S., Lee, I.-G., Lee, D. Y., Kim, D.-J., Kim, S. and Lee, K. [2002]. 'High-temperature properties of plasma-sprayed coatings of YSZ NiCrAlY on Inconel substrate', Materials Science and Engineering A, 332(1-2): 129-133. Stöver, D. and Funke, C. [1999]. 'Directions of the development of thermal barrier coatings in energy applications', Journal of Materials Processing Technology, 92-93: 195-202.

Sumirat, I., Ando, Y. and Shimamura, S. [2006]. 'Theoretical consideration of the effect of porosity on thermal conductivity of porous materials', Journal of Porous Materials, 13(3): 439-443. Sweet, J., Roth, E. and Moss, M. [1987]. 'Thermal conductivity of Inconel 718 and 304 stainless steel', International Journal of Thermophysics, 8(5): 593-606. Takeuchi, Y. R. and Kokini, K. [1994]. 'Thermal Fracture of Multilayer Ceramic

References

236

Thermal Barrier Coatings', Journal of Engineering for Gas Turbines and Power, 116(1): 266-271.

Tamura, M., Takahashi, M., Ishii, J., Suzuki, K., Sato, M. and Shimomura, K. [1999]. 'Multilayered thermal barrier coating for land-based gas turbines', Journal of Thermal Spray Technology, 8(1): 68-72. Tanaka, S., Pin, C. C. and Uematsu, K. [2006]. 'Effect of Organic Binder Segregation on Sintered Strength of Dry-Pressed Alumina', Journal of the American Ceramic Society, 89(6): 1903-1907. Taymaz, I. [2007]. 'The effect of thermal barrier coatings on diesel engine performance', Surface and Coatings Technology, 201(9-11): 5249-5252. Taymaz, I., [2007], 'The effect of thermal barrier coatings on diesel engine performance', Proceedings of the Fifth Asian-European International Conference on Plasma Surface Engineering - AEPSE 2005. Teixeira, V. [2001]. 'Numerical analysis of the influence of coating porosity and substrate elastic properties on the residual stresses in high temperature graded coatings', Surface and Coatings Technology, 146-147: 79-84. Teixeira, V., Andritschky, M., Fischer, W., Buchkremer, H. P. and Stöver, D. [1999]. 'Analysis of residual stresses in thermal barrier coatings', Journal of Materials Processing Technology, 92-93: 209-216. Thiery, P.-Y., Poulain, M., Dupeux, M. and Braccini, M. [2009]. 'Spallation of two thermal barrier coating systems: experimental study of adhesion and energetic approach to lifetime during cyclic oxidation', Journal of Materials Science, 44(7): 1726-1733.

Thomé, L. and Garrido, F. [2001]. 'Application of ion beams to nuclear waste issues: evaluation of nuclear ceramics', Vacuum, 63(4): 619-626. Toriz, F. C., Thakker, A. B. and Gupta, S. K. [1989]. 'Flight service evaluation of thermal barrier coatings by physical vapor deposition at 5200 H', Surface and Coatings Technology, 39-40(Part 1): 161-172. Torrecillas, R., Calderón, J. M., Moya, J. S., Reece, M. J., Davies, C. K. L., Olagnon, C. and Fantozzi, G. [1999]. 'Suitability of mullite for high temperature applications', Journal of the European Ceramic Society, 19(13-14): 2519-2527. Troczynski, T., Cockcroft, S. and Wong, H. [1996]. 'Thermal barrier coatings for heat engines', Key Engineering Materials, v 122-124: 451-462. Trunova, O., Beck, T., Herzog, R., Steinbrech, R. W. and Singheiser, L. [2008]. 'Damage mechanisms and lifetime behavior of plasma sprayed thermal barrier coating systems for gas turbines - Part I: Experiments', Surface and Coatings Technology, 202(20): 5027-5032. Uzun, A., Çevik, I. and Akçil, M. [1999]. 'Effects of thermal barrier coating on a turbocharged diesel engine performance', Surface and Coatings Technology, 116-119: 505-507.

References

237

Vargas Garcia, J. R. and Goto, T. S. [2003]. 'Thermal barrier coatings produced by chemical vapor deposition', Science and Technology of Advanced Materials, 4(4): 397-402.

Vassen, R. [2000]. 'Zirconates as new materials for thermal barrier coatings', Journal of the American Ceramic Society, 83(8): 2023-2029. Vaßen, R., Kaßner, H., Stuke, A., Hauler, F., Hathiramani, D. and Stöver, D. [2008]. 'Advanced thermal spray technologies for applications in energy systems', Surface and Coatings Technology. Vassen, R., Stuke, A. and Stöver, D. [2009]. 'Recent Developments in the Field of Thermal Barrier Coatings', Journal of Thermal Spray Technology, 18(2): 181-186. Wakamatsu, Y., Saito, T., Ono, F., Ishia, K., Matsuzaki, T., Hamamura, O., Sohoda, Y. and Kude, Y., [1997], 'Evaluation Test of C/C composites coated with SiC/C FGM under simulated condition for aerospace application', The 4th International Symposium on Functionally Graded Materials, Takuba, Japan. Wakashima, K. and Tsukamoto, H. [1992]. 'A Unified Micromechanical Approach toward Thermomechanical Tailoring of Metal Matrix Composites', ISIJ International, 32(2): 883-892. Waki, H. and Kobayashi, A. [2008]. 'Influence of the mechanical properties of CoNiCrAlY under-coating on the high temperature fatigue life of YSZ thermal-barrier-coating system', Vacuum, 83(1): 171-174. Watanabe, R. [1995]. 'Powder processing of functionally gradient materials', Composites and Functionally Graded Materials, 20(1): 32. Zhang, Q., Li, C.-J., Li, Y., Zhang, S.-L., Wang, X.-R., Yang, G.-J. and Li, C.-X. [2008]. 'Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold-Sprayed Nanostructured NiCrAlY Bond Coat', Journal of Thermal Spray Technology, 17(5): 838-845. Zhang, X. C., Xu, B. S., Wang, H. D., Jiang, Y. and Wu, Y. X. [2006]. 'Modeling of thermal residual stresses in multilayer coatings with graded properties and compositions', Thin Solid Films, 497(1-2): 223-231. Zhang, Y., Han, J., Zhang, X., He, X., Li, Z. and Du, S. [2001]. 'Rapid prototyping and combustion synthesis of TiC/Ni functionally gradient materials', Materials Science and Engineering, 299(1-2): 218-224. Zhou, H., Li, F., He, B., Wang, J. and Sun, B. [2008]. 'Effect of Plasma Spraying Process on Microstructure and Microhardness of Titanium Alloy Substrate', Journal of Thermal Spray Technology, 17(2): 284-288. Zhu, D. and Miller, R. A. [2000]. 'Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions', Journal of Thermal Spray Technology, 9(2): 175-180.

TITLE: SLURRY SPRAYED THERMAL BARRIER COATINGS FOR AEROSPACE APPLICATIONSAPPENDICESAppendix AAppendix BAppendix C

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