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INTRODUCTION

HISTORY

STRUCTURE OF THERMAL BARRIER COATING

PROCESS

COATING MATERIAL PROPERTIES

APPLICATIONS

ADVANTAGE AND DISADVANTAGE

CONCLUSION

REFERENCE

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AfterBefore

IntroductionThermal barrier coatings (TBC) are layer systems deposited on thermally

highly loaded metallic components by utilizing insulating material.

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Pratt & Whitney first introduced TBC on burner can in JT8D engine in 1963

Turbo fan engine Burner can

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COATING LAYERS

Typical structure of TBC Schematic representation of TBC withtemperature gradient

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Initially

After some time

Schematic representation of Pack cementation

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In industry , thermal barrier coatings are produced in anumber of ways:

* Electron Beam Physical Vapor Deposition: EBPVD

* Air Plasma Spray: APS

* Electrostatic Spray Assisted Vapor Deposition: ESAVD

* Direct Vapor Deposition

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Plasma spray method

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Hardness

Erosion resistance

Adhesion strength

Thermal conductivity

Coating material properties

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Application :

Some of products incorporating TBC:-

Turbine blades

Cutting tool inserts

Aero engine parts

Gas turbine parts such as combustion liners, nozzles or blades

IC engine parts

Rocket nozzles and valve bodies

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Schematic representation of Turbine blade

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Some Representative Engine Applications for TBC

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ADVANTAGES:

Low temperature deposition for super alloy turbine engine

components.

Low thermal conductivity.

Increase considerably the creep life of the blade while

maintaining level of blade cooling.

The coating itself is harder and more wear resistant, and the

stress that can sometimes occur in the top coat (ceramic coat)

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DISADVANTAGES:

TBCs produced with plasma spray lack reproducibility asporosity is introduced when the molten particles splat

down

TBCs deposited by electron beam evaporation arereported to generally fail on cooling by spreading and

separation occurs at the interface with the bond coat.

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The thermal barrier coating performs the function of insulatingcomponents.

Due to the good corrosion resistance and wear resistance these will

improve the mechanical behavior .

The TBCs are suitable for low temperature deposition for super

alloy turbine engine components due to their low thermal

conductivity.

Because of these properties the thermal barrier coatings are widely

used in jet engines, turbine blades, aero engine parts , gas turbines.

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R.Krishnan, R. Keshavamurthy, C. Babu rao, surface modification

and characterization of air plasma sprayed alumina coatings, Surf.,Coat., Technology

C. Batista, A. Portinha, Surface laser glazing of plasma sprayed

thermal barrier coatings, Applied Surface Science,

T.W. Clyne, C.J. Humphreys, Improvements in plasma sprayed TBCfor Use in Advanced Gas Turbines, Department of Material Science

and Metrology, University of Cambridge, Cambridge.

WEBSITES

http://dauskardt.stanford.edu/joanna_mroz/Thermal.html

http://en.wikipedia.org/wiki/Thermal_barrier_coating

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