Double-layer ceramic thermal barrier coating with different porosities
By optimizing the design of a double-layer ceramic thermal barrier coating with matching porosity and thickness, the problem of interface failure caused by thermal transients in gas turbine engines was solved, and the coating life and stability were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SIEMENS ENERGY GLOBAL GMBH & CO KG
- Filing Date
- 2024-09-30
- Publication Date
- 2026-06-19
Smart Images
Figure CN122249589A_ABST
Abstract
Description
[0001] This invention relates generally to the field of thermal barrier coatings (TBCs), and particularly to ceramic thermal barrier coatings for protecting metal components in extremely high-temperature applications such as gas turbine engines.
[0002] TBCs are exposed to high-temperature environments during gas turbine operation, and also experience rapid thermal transients during engine start-up and shutdown.
[0003] These transient thermal loads can cause coating failure, necessitating component replacement before the end of their expected lifespan. In layered TBC systems, failure can occur at the interface between the adhesive coating and the TBC, or at the interfaces between the individual TBC layers.
[0004] Therefore, the purpose of this invention is to optimize the hierarchical TBC system to improve the cycle life of the TBC and minimize the occurrence of TBC failure at the interface.
[0005] This problem is solved by the TBC as described in claim 1.
[0006] Further advantages are listed in the further dependent claims, and these advantages can be combined with each other in any advantageous manner to produce further advantages.
[0007] Figure 1 , Figure 2 An example of the present invention is shown.
[0008] The description and accompanying drawings are merely examples of the present invention.
[0009] Our aim is to address this issue by improving the porosity distribution of TBC between layers and the thickness of the TBC system.
[0010] This invention addresses the problem through two different strategies designed to reduce stress levels at the interfaces between ceramic layers and between the bottom TBC layer and the bonding coating on a metal substrate, such as a nickel-based or cobalt-based superalloy.
[0011] The first strategy is to optimize the porosity of each TBC layer to minimize stress and strain at all interfaces. To do this, the porosity of each TBC layer must match that of its adjacent layers. The layer closest to the adhesive coating has a porosity lower than or similar to that of its adjacent outer layer.
[0012] One example is a two-layer TBC system, in which the bottom ceramic layer (close to the adhesive coating) has an average porosity of 15% and the top layer (in contact with hot gas or the outermost layer) has a porosity of 20%.
[0013] In this context, a "layer" refers to a layer that has the same properties (such as porosity, composition, microstructure, etc.) in the vertical direction along its thickness. It should not be used in combination with several nozzles (surpasses) of a spray gun to produce such a single layer.
[0014] For some feasible systems with porosity (average target porosity, with the range of permissible porosity at any location within the layer measured at 100x magnification), where the layers are: TBC Layer 1 (Innermost Layer) TBC Layer 2 (Outermost TBC Layer) TBC layer 3 / Wearable layer: System 1: Innermost layer: 17% (12%-22%) — Outermost layer: 19% (14%-24%) System 2: Innermost layer: 17% (12%-22%) — Outermost layer: 22% (17%-27%) System 3: Innermost layer: 17% (12%-22%) — Outermost layer: 22% (17%-27%) — Wearable layer: 30% (25%-35%) System 4: Innermost layer: 17% (12%-22%) — Outermost layer: 25% (20%-30%) — Wearable layer: 35% (30%-40%) System 5: Innermost layer: 17% (12%-22%) — Outermost layer: 19% (14%-24%) — Wearable layer: 25% (20%-30%).
[0015] The porosity of TBC layer 2 (outermost layer) should be at least 2% higher than that of TBC layer 1 (innermost layer) at any location.
[0016] The porosity of TBC layer 3 (wearable layer) should be at least 2% higher than that of TBC layer 2 (outermost layer) at any location.
[0017] The second strategy aims to reduce stress at the interface by optimizing the coating thickness.
[0018] Due to the thermal expansion mismatch between the ceramic layers (innermost layer – outermost layer – wearable layer) and the metal substrate, the compressive stress in the TBC is highest at the adhesive coating-TBC interface under cold conditions, while it may be tensile stress at the TBC surface. Based on the understanding of the thermal mismatch between the substrate material and the TBC layer, and between the adhesive coating and the TBC surface temperature, the following rules are used to optimize the relative thickness of the TBC layer: The interface between the two ceramic layers should be in the compressive stress region under cold conditions. If possible, the compressive strain at the interface of the outer layer should be between 0.05% and 0.2%. • The surface temperature of partially stabilized zirconia should be kept below the temperature at which a large amount of monoclinic zirconia phase will form. For 8YSZ, this limit depends on the target lifetime of the coating and will be between 1523 K (1250 °C) and 1623 K (1350 °C).
[0019] The thickness of the partially stabilized zirconia (PSZ) layer, as the innermost layer, should be maximized while taking into account manufacturing tolerances.
[0020] One example is a double-layer 8YSZ / Gd2Zr2O7 (GZO) coating with a total thickness of 1.0 mm, wherein the manufacturing tolerance is ±100 µm, the bonding coating temperature is 1173 K (900 °C), and the TBC surface temperature is 1673 K (1400 °C).
[0021] The CTE of the substrate is 16×10 -6 The CTE of the 8YSZ layer is 11.5 × 10⁻⁶. -6 Furthermore, GZO's CTE is 12×10 -6 .
[0022] According to the first rule, the maximum feasible thickness of the 8YSZ layer is 500µm, while according to the second rule (the limit for the 8YSZ layer is 1623K (1350℃)), it is 800µm.
[0023] In order to satisfy both rules at the same time and maximize the 8YSZ layer thickness, the maximum 8YSZ layer thickness is limited to 500µm, and the target 8YSZ layer thickness is set to 400µm.
[0024] Figure 1 The two-layer TBC system is shown.
[0025] Nickel-based or cobalt-based high-temperature alloys are preferably used as the metal substrate 4.
[0026] A metal bonding coating 7 is applied to the substrate 4.
[0027] The metal bonding coating 7 contains NiCoCrAlY alloys, such as NiCoCrAlYRe, NiCoCrAlYTa, NiCoCrAlYSi, NiCoCrAlYFeSi, NiCoCrAlYTaSi, etc.
[0028] The alloy forms a long-lasting alumina coating (TGO) during operation, thereby improving its bonding with the ceramic layer.
[0029] An innermost layer 10 exists above the metal bonding coating 7, and an outermost layer 13 is applied on top of it. The outermost layer 13 satisfies the thickness and porosity relationship requirements described above.
[0030] and Figure 1 compared to, Figure 2 A wearable layer 15 is shown on the outermost layer 13, although the TBC system can be used in sealing systems in combination with stator components.
[0031] The material of the innermost layer 10 specifically includes partially stabilized zirconia (PSZ). Especially noteworthy is the 8% by weight yttrium oxide stabilized zirconium oxide.
[0032] The outermost layer 13 contains, in particular, fully stabilized zirconium oxide (FSZ). Especially noteworthy is the 20% by weight yttrium oxide stabilized zirconium oxide.
[0033] The wearable layer is preferably made of zirconia-based ceramic material.
Claims
1. A layered ceramic system, comprising at least: Metal substrates (4), especially nickel-based high-temperature alloys, Metal bonding coating (7) on a metal substrate, which in particular comprises Ni-Co-Cr-Al-Y, Innermost ceramic layer (10). The outermost ceramic layer (13), and optional Wearable layer (15) The porosity of each ceramic layer is higher than 10%, especially higher than 12%, and The innermost layer (10) has an average porosity of 17%.
2. The layered ceramic system according to claim 1, wherein the porosity of the innermost ceramic layer (10) is between 12% and 22%.
3. The layered ceramic system according to one or both of claims 1 or 2, wherein the average porosity of the outermost ceramic layer (13) is 19%.
4. The layered ceramic system according to any one of claims 1, 2 or 3, wherein the porosity of the outermost ceramic layer (13) is between 14% and 24%.
5. The layered ceramic system according to one or both of claims 1 or 2, wherein the average porosity of the outermost ceramic layer (13) is 22%.
6. The layered ceramic system according to any one of claims 1, 2 or 5, wherein the porosity of the outermost ceramic layer (13) is between 17% and 27%.
7. The layered ceramic system according to one or both of claims 5 or 6, wherein the average porosity of the wearable layer (15) is 30%.
8. The layered ceramic system according to any one of claims 5, 6 or 7, wherein the porosity of the wearable layer (15) is between 25% and 35%.
9. The layered ceramic system according to one or both of claims 3 or 4, wherein the average porosity of the wearable layer (15) is 25%.
10. The layered ceramic system according to any one of claims 3, 4 or 9, wherein the porosity of the wearable layer (15) is between 20% and 30%.
11. The layered ceramic system according to one or both of claims 1 or 2, wherein the average porosity of the outermost ceramic layer (15) is 25%.
12. The layered ceramic system according to any one of claims 1, 2 or 11, wherein the porosity of the outermost ceramic layer (15) is between 20% and 30%.
13. The layered ceramic system according to one or both of claims 11 or 12, wherein the average porosity of the wearable layer (15) is 35%.
14. The layered ceramic system according to any one of claims 11, 12 or 13, wherein the porosity of the wearable layer (15) is between 30% and 40%.
15. The layered ceramic system according to any one of the preceding claims, wherein the thickness of the innermost layer (10) is 400µm ± 100µm.
16. The layered ceramic system according to any one of the preceding claims, wherein the outermost layer (13) has a thickness of 600µm ± 100µm.
17. The layered ceramic system according to any one of the preceding claims, wherein the innermost layer (10) comprises PSZ, particularly 8% by weight of yttrium-stabilized zirconia.
18. The layered ceramic system according to any one of the preceding claims, wherein the outermost layer (13) is FSZ, especially at least 20% by weight of yttrium-stabilized zirconium oxide.
19. The layered ceramic system according to any one of the preceding claims, wherein the wearable material is a zirconia-based ceramic material.