Thick Thermal Barrier Coatings (TTBC) Introduction of TTBC - PowerPoint PPT Presentation

Thick Thermal Barrier Coatings (TTBC) • Introduction of TTBC • Microstructure of TTBC • Test apparatus • Monotonic test • Strain hold • Future research

Ceramic 80% Ceramic- 20% Bond Coat 50% Ceramic-50% Bond Coat 20% Ceramic- 80% Bond Coat Bond Coat Substrate Figure 1. Functionally graded material (FGM).

In-plane direction In-plane direction Figure 2. Micrograph of TTBC coating (100% ceramic) parallel to substrate

In-plane direction Through thickness direction 10 µ m Figure 3. Micrograph of TTBC coating (100% ceramic) normal to substrate

In-plane direction Through thickness direction Figure 4. Micrograph of TTBC coating (50% ceramic and 50% bond coat) normal to substrate

In-plane direction Through thickness direction Figure 5. Micrograph of 100% bond coating normal to substrate.

Step 1: Press-fit and machine steel substrate Step 2: Plasma spray mid- section Step 3: Perform final machining and etch away inner steel press-fit tube Figure 6. Specimen fabrication processes.

Figure 7. Test system.

Figure 8. Extensometer.

25 Shear Stress (MPa) 800 °C 20 15 25 °C 10 5 0 0 1000 2000 3000 4000 5000 6000 Shear Strain (x10 -6 ) Figure 9. Ceria-stabilized TBC in-plane monotonic shear deformation to failure.

140 Principle Stress (MPa) 120 Compression 100 80 60 40 Torsion 20 Tension 0 0 2000 4000 6000 8000 10000 12000 Principle Strain (x10 -6 ) Figure 10. CSZ: comparison of principle stress-strain curves for monotonic test at room temperature.

Table 1. Material properties of CSZ Loading type Strength (MPa) Elastic modulus (GPa) E (G) Shear 11.9-17.9 (6-10) Tension 10.2 8 Compression 126 14.6

20 Strain -0.04 -0.02 0 Stress (MPa) 800 °C -20 20 °C -40 -60 Figure 11. 10-hour compression strain hold of CSZ at 3800 µε .

100 50 0 Stress (MPa) -4000 -3000 -2000 -1000 0 -50 -100 -150 -200 -250 -300 Strain (10 -6 ) Figure 12. 10-hour compression strain hold of bond coating at 3650 µε .

16 25 °C 12 Shear Stress (M Pa) 8 800 °C 4 0 0 500 1000 1500 2000 2500 -4 -8 Shear Strain (x10 -6 ) Figure 13. 10-hours shear strain hold test of 100% CSZ at 2000 µε .

70 60 25 °C Shear Stress (MPa) 50 40 30 20 10 0 0 500 1000 1500 2000 2500 -10 Shear Strain (x10 -6 ) Figure 14. 10 hours shear strain hold test of bond coating at 2000 µε .

Table 2. Stress relaxation during 10 hours holding Loading type Materials Stress relaxation 48.1MPa to 36.8MPa 100% CSZ (23.5%) Compression 281MPa to 267MPa Bond coating (5.0%) 12.0MPa to 10.1MPa 100% CSZ (15.8%) Shear 65.3MPa to 62.9MPa Bond coating (3.7%)

Future research: • To study and explain the phenomena of non-linear deformation in the monotonic test and stress relaxation and creep at room temperature. • To model the deformation process of TTBC. Future research: • Loading: Combined loading. • Materials: with controlled crack density.

compression shear tension combined loading Figure 15. The Mohr circle.