Thermal barrier coating surface engineering

1. Seminar Presentation
on
Thermal barrier coating
(TBC)
Presented by:
CHANDRASHEKARACHARI M
ENG16ME0015

2. Contents
Introduction
Structure of Thermal Protection System
Material Selection
TBC Deposition Methods
TBC on Turbine Blades and Engines
TBC Failure
Conclusion

3. Introduction
• The combination of mechanical stresses and
high temperatures is highly destructive to
metallic parts, and could lead to various type of
failure such as,thermal fatigue, hot corrosion,
creep, erosion.
• High motivation to improve performance of
engineered
parts at elevated temperatures:
• Life cycle
• Efficiency
• Reliability
• Gasturbine blades, combustor chamber, cutting
tool.

4. • Thermal Barrier Coatings are highly advanced material systems
applied to metallic surfaces,
operating at elevated temperatures.
• Multi-layer structure with thermal isolation ceramic top-coat, that
provide good resistanceto erosion, wear and corrosion.
• Substrate – NickelCobalt super alloys
• Bond coat – usually NiCoCrAlY, promote adhesion of ceramic
layer, prevent oxidation of substrate
• Top-coat – ceramic layer (YSZ–
Ytria-stabilized Zirconia), high
hardness, low thermal conductivity.
Multi-layer structure of
TBC[1]

5. Structure of Thermal
Protection System

6. Material Selection
Material 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. TBC Deposition Methods
1. Electron Beam Physical Vapour Deposition or
EBPVD
2. APS(Air Plasma Spray)
3. Thermal spray

9. 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.

10. 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.

11. 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.

13. 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.

14. TBC Failure
Thermal cycle is the main cause of TBC failure due to Thermal mismatch.
Spallation: 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.

15. Conclusion
TBC 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.

16. Thank You