1

Seminar Presentationon

Thermal Barrier Coating

Presented by:Bharat Chhabria

2

ContentsIntroductionStructure of Thermal Protection

SystemMaterial SelectionTBC FailureTBC Deposition MethodsTBC on Turbine Blades and EnginesConclusion

3

Introduction TBCs are refractory-oxide ceramic coatings applied to

the surfaces of hot metallic parts.

TBCs perform the important function of insulating components operating at elevated temperature.

Coatings can allow higher operating temperatures beyond the limiting temperature of metal parts.

TBC not only consist of oxide ceramic coating (topcoat) itself but also the underlying superalloy engine part, and two other layers in between.

4

5

Structure of Thermal Protection System

Thermal Protection System

Top Coat/TBC

Thermally Grown Oxide

(TGO)

Bond Coat

Superalloy Substrate

6

7

Material SelectionMaterial selected for TBC should have following properties:-

Low Thermal Conductivity.

High Thermal Expansion Coefficient.

Good Erosion Resistance.

Therefore we use Porous Zirconia (ZrO2) partially stabilized with yttria (Y2O3) popularly known as YSZ.

8

9

TBC FailureSpallation: It is a process by which the TBC peels off of the substrate; and naturally, after the coating has spalled, the continuous thermal protection layer no longer exists.

Thermal cycle is the main cause of TBC failure due to Thermal mismatch.

10

TBC Deposition Methods

EBPVD APS

ESAVD Direct Vapour Deposition

TBCProductio

n

11

EBPVD Electron Beam Physical Vapour Deposition or EBPVD is a

form of physical vapour deposition in which a target anode is bombarded with an electron beam which causes atoms from the target to transform into the gaseous phase.

These atoms then precipitate into solid form, coating everything in the vacuum chamber (within line of sight) with a thin layer of the anode material.

12

APS(Air Plasma Spray)

In plasma spraying process, the material to be deposited (feedstock) is introduced into the plasma jet, emanating from a plasma torch.

In the jet, where the temperature is of the order of 10,000 K, the material is melted and propelled towards a substrate.

There, the molten droplets flatten, rapidly solidify and form a deposit.

13

TBC on Turbine Blades and Engines

Aircraft Gas Turbine:-

As we know that increase in turbine inlet temperature results in increased thermal efficiency.

TBC can be applied on both Turbine blades and combustion chambers.

Earlier calcia and magnesia stabilized zirconia were used for coating (less durable).

Various tests were done at NASA on Turbine blades for various temperature and all coated blade were in good conditions.

14

15

Diesel Engines:-

TBC can allow higher working temperature which increase efficiency and decrease CO and NOx emission.

Increase in engine power by 8% and decrease in fuel consumption by 15-20% is noted by applying TBC.

Although not yet met with wide success.

16

ConclusionTBC is a very useful technique and has a wide application in industries as well as in automobile manufacturing.

Detailed analysis of coating stresses and controlled process, plasma spray technology has significantly improved the reliability of TBC turbines, diesel engines and other heat engines.

Thermal barrier coating allows engineers to improve product and performance, reduce maintenance time, cost, save energy and reduce production cost.

Application of TBC on Turbine blades made dramatic change in increasing efficiency of Engine.

17

ReferencesMaterials Research Society (MRS) Bulletin, Thermal Barrier Coatings for more efficient Gas Turbine Engines; October 2012 Vol. 37 No. 10.

Thermal Barrier Coating, http://en.wikipedia.org/wiki/Thermal_barrier_coating

Plasma Spray, http://en.wikipedia.org/wiki/Plasma_Spray

A.G. Evans, D.R. Mumm, J.W. Hutchinson, G.H. Meier, F.S. Pettit. Mechanism controlling the durability of Thermal Barrier Coatings: Progress in Material Science 46 (2001) 505-553.

Carlos G. Levi. Emerging materials and processes for thermal barrier systems: Current Opinion in Solid State and Materials Science 8 (2004) 77–91.

18

Thank You