Author Contributions
Conceptualization, K.D.; methodology, L.W.; software, L.W.; validation, Z.W. and T.Z.; formal analysis, J.Y.; investigation, L.W.; writing—original draft preparation, T.Z.; writing—review and editing, K.D.; visualization, Z.W.; supervision, K.D.; project administration, K.D.; funding acquisition, L.W. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Coating structure and thermal cycling process: (a) coating structure and (b) thermal cycle process.
Figure 1.
Coating structure and thermal cycling process: (a) coating structure and (b) thermal cycle process.
Figure 2.
Interface morphology after different sandblasting treatments: (a) No.1 (24 mesh) (b) No.2 (36 mesh) (c) No.3 (60 mesh) (d) No.4 (96 mesh).
Figure 2.
Interface morphology after different sandblasting treatments: (a) No.1 (24 mesh) (b) No.2 (36 mesh) (c) No.3 (60 mesh) (d) No.4 (96 mesh).
Figure 3.
3D morphology of the bonding coating surface: (a) No.1 (24 mesh) (b) No.2 (36 mesh) (c) No.3 (60 mesh) (d) No.4 (96 mesh).
Figure 3.
3D morphology of the bonding coating surface: (a) No.1 (24 mesh) (b) No.2 (36 mesh) (c) No.3 (60 mesh) (d) No.4 (96 mesh).
Figure 4.
Schematic diagram of interface morphology.
Figure 4.
Schematic diagram of interface morphology.
Figure 5.
Morphology and elements of coatings under thermal cycling: (a) 0 cycles (b) 10 cycles (c) 60 cycles (d) 200 cycles (e) 340 cycles and (f) 390 cycles.
Figure 5.
Morphology and elements of coatings under thermal cycling: (a) 0 cycles (b) 10 cycles (c) 60 cycles (d) 200 cycles (e) 340 cycles and (f) 390 cycles.
Figure 6.
Oxide thickness at different interface curvatures: No.1 (24 mesh); No.2 (36 mesh); No.3 (60 mesh); No.4 (96 mesh).
Figure 6.
Oxide thickness at different interface curvatures: No.1 (24 mesh); No.2 (36 mesh); No.3 (60 mesh); No.4 (96 mesh).
Figure 7.
Model of thermal barrier coating: (a) shape under SEM (b) physical model (c) local models and TGO growth directions (d) thermal loads and constraints.
Figure 7.
Model of thermal barrier coating: (a) shape under SEM (b) physical model (c) local models and TGO growth directions (d) thermal loads and constraints.
Figure 8.
Growth model of oxide layer: (a) C = 0, (b) C = 2, (c) C = 4, (d) C = 7, (e) C = 10, and (f) C = 13.
Figure 8.
Growth model of oxide layer: (a) C = 0, (b) C = 2, (c) C = 4, (d) C = 7, (e) C = 10, and (f) C = 13.
Figure 9.
TGO ultimate growth morphology at other interface curvatures: (a) No. 2, (b) No. 3, (c) No. 4.
Figure 9.
TGO ultimate growth morphology at other interface curvatures: (a) No. 2, (b) No. 3, (c) No. 4.
Figure 10.
Typical areas within the TGO.
Figure 10.
Typical areas within the TGO.
Figure 11.
Test area diagram using PLPS.
Figure 11.
Test area diagram using PLPS.
Figure 12.
Typical PLPS spectra inside the oxide layer.
Figure 12.
Typical PLPS spectra inside the oxide layer.
Figure 13.
TGO Residual Stress Evolution in Thermal Cycles under Cooling Phase.
Figure 13.
TGO Residual Stress Evolution in Thermal Cycles under Cooling Phase.
Figure 14.
(a–d) Stress diagram of the coating in the initial state.
Figure 14.
(a–d) Stress diagram of the coating in the initial state.
Figure 15.
(a–d) Stress diagram of TGO layer with a dense Al2O3 layer.
Figure 15.
(a–d) Stress diagram of TGO layer with a dense Al2O3 layer.
Figure 16.
(a–d) Stress diagram of oxide layer under Al2O3 growth.
Figure 16.
(a–d) Stress diagram of oxide layer under Al2O3 growth.
Figure 17.
(a–d) Stress diagram of TGO layer under MO initiating stage.
Figure 17.
(a–d) Stress diagram of TGO layer under MO initiating stage.
Figure 18.
(a–d) Stress diagram of rapid growth process of mixed oxides.
Figure 18.
(a–d) Stress diagram of rapid growth process of mixed oxides.
Figure 19.
Effect of thermal cycling cycles on the stress evolution in typical regions of the TGO layer: (a) No.1 (b) No.2 (c) No.3 (d) No.4.
Figure 19.
Effect of thermal cycling cycles on the stress evolution in typical regions of the TGO layer: (a) No.1 (b) No.2 (c) No.3 (d) No.4.
Figure 20.
TGO/BC Interface Cracking and Propagation (a) Crack initiation at small roughness (b) Crack propagation at small roughness (c) Crack initiation at large roughness (d) Crack propagation at large roughness.
Figure 20.
TGO/BC Interface Cracking and Propagation (a) Crack initiation at small roughness (b) Crack propagation at small roughness (c) Crack initiation at large roughness (d) Crack propagation at large roughness.
Table 1.
Deposition parameters of thermal barrier coatings.
Table 1.
Deposition parameters of thermal barrier coatings.
Spraying Process | Spraying Voltage/V | Spraying Current/A | Powder Feeding Amount/r·min−1 | Spraying Distance/mm | Spray Gun Rate/mm·s−1 |
---|
Surface layer | 39 | 850 | 3.5 | 85 | 250 |
Bonding layer | 38 | 750 | 2.5 | 85 | 450 |
Table 2.
Average roughness (Ra), amplitude (A), wave length (λ), and peak curvature (Kp) at the interface.
Table 2.
Average roughness (Ra), amplitude (A), wave length (λ), and peak curvature (Kp) at the interface.
Grouping of Samples | Ra/μm | A/μm | Average/μm | λ/μm | Average/μm | Kp/μm−1 | Average/μm−1 |
---|
No.1 | 7.526 ± 0.836 | 10.381 | 10.276 ± 1.361 | 54.348 | 51.868 ± 5.952 | 0.188 | 0.192 ± 0.041 |
9.016 | 43.341 | 0.242 |
11.431 | 57.914 | 0.146 |
No.2 | 5.941 ± 0.775 | 8.862 | 8.289 ± 1.527 | 43.393 | 41.527 ± 5.149 | 0.253 | 0.243 ± 0.029 |
6.994 | 35.358 | 0.274 |
9.012 | 45.831 | 0.202 |
No.3 | 4.542 ± 0.709 | 6.536 | 6.159 ± 1.178 | 33.465 | 31.942 ± 4.739 | 0.353 | 0.319 ± 0.027 |
5.040 | 27.369 | 0.292 |
6.901 | 34.992 | 0.312 |
No.4 | 3.541 ± 0.684 | 4.466 | 4.295 ± 0.757 | 25.358 | 23.517 ± 4.463 | 0.498 | 0.480 ± 0.021 |
3.821 | 18.358 | 0.474 |
4.597 | 26.836 | 0.468 |
Table 3.
Growth rates of TGO (Al2O3 and MO) regions at different roughness levels.
Table 3.
Growth rates of TGO (Al2O3 and MO) regions at different roughness levels.
No. | Phase I Components | KPeak (μm·s−0.5) | KOther (μm·s−0.5) | Phase II Components | KPeak (μm·s−0.5) | KOther (μm·s−0.5) |
---|
1 | Al2O3 | 4.242 × 10−5 | 3.179 × 10−5 | MO | 7.177 × 10−5 | 4.337 × 10−5 |
2 | Al2O3 | 4.063 × 10−5 | 2.923 × 10−5 | MO | 6.498 × 10−5 | 4.265 × 10−5 |
3 | Al2O3 | 3.543 × 10−5 | 2.917 × 10−5 | MO | 5.235 × 10−5 | 4.198 × 10−5 |
4 | Al2O3 | 3.000 × 10−5 | 2.857 × 10−5 | MO | 4.728 × 10−5 | 4.198 × 10−5 |
Table 4.
Material parameters of 8YSZ coatings.
Table 4.
Material parameters of 8YSZ coatings.
Type of Material Physical Parameters | TC | MO | Al2O3 | BC | SUB |
---|
Temperature range (°C) | 20–1100 | 20–1100 | 20–1100 | 20–1100 | 20–1100 |
Elastic modulus (GPa) | 48–22 | 100 | 400–320 | 200–110 | 220–120 |
Poisson’s ratio | 0.1–0.12 | 0.3 | 0.23–0.25 | 0.3–0.33 | 0.31–0.35 |
Coefficient of thermal expansion (10−6/°C) | 9–12.2 | 5–8 | 8–9.6 | 13.6–17.6 | 11.8–18.7 |
Table 5.
Creep effect parameters of 8YSZ coatings.
Table 5.
Creep effect parameters of 8YSZ coatings.
Material | B (s−1 MPa−n) | n | T (°C) |
---|
TC | 1.8 × 10−7 | 1 | 1000 |
Al2O3 | 7.3 × 10−10 | 1 | 1000 |
MO | 5 × 10−10 | 1 | 1000 |
BC | 6.54 × 10−19 | 4.57 | 600 |
2.2 × 10−12 | 2.99 | 700 |
1.84 × 10−7 | 1.55 | 800 |
2.15 × 10−8 | 2.45 | 850 |
SUB | 4.85 × 10−36 | 1 | 20 |
2.25 × 10−9 | 3 | 1200 |
Table 6.
Relationship between the number of cycles, interfacial curvature, stress, and crack length under thermal cycling.
Table 6.
Relationship between the number of cycles, interfacial curvature, stress, and crack length under thermal cycling.
Interface Curvature/μm−1: 0.198 | Interface Curvature/μm−1: 0.257 |
Cycles | Maximum Tension Stress/MPa | /μm | Maximum Tension Stress/MPa | /μm |
0 | 153 | 0 ± 0.11 | 150 | 0 ± 0.12 |
10 | 189 | 0.34 ± 0.14 | 185 | 0.46 ± 0.17 |
60 | 224 | 1.06 ± 0.25 | 229 | 1.11 ± 0.25 |
200 | 441 | 4.61 ± 0.74 | 465 | 6.53 ± 0.95 |
340 | 628 | 18.76 ± 3.72 | 831 | 21.48 ± 5.24 |
390 | 562 | 34.31 ± 5.21 | 690 | 38.17 ± 8.11 |
Interface curvature/μm−1: 0.372 | Interface curvature/μm−1: 0.499 |
Cycles | Maximum tension stress/MPa | /μm | Maximum tension stress/MPa | /μm |
0 | 149 | 0 ± 0.10 | 150 | 0 ± 0.11 |
10 | 205 | 0.49 ± 0.13 | 228 | 0.53 ± 0.12 |
60 | 225 | 1.38 ± 0.42 | 230 | 1.71 ± 0.37 |
200 | 482 | 9.85 ± 2.52 | 579 | 15.51 ± 2.96 |
340 | 1045 | 28.17 ± 4.72 | 1239 | 39.43 ± 6.01 |
390 | 800 | 49.42 ± 7.85 | 860 | 64.82 ± 10.45 |