Coated components including boron-doped

Abstract

The invention relates to a coated ceramic composite component having a silicon carbide substrate, a bond coating overlying the substrate, and a barrier coating overlying the bond coating, where the bond coating comprises boron-doped silicon.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to a process for forming coatings by chemical vapor deposition (CVD), especially for protecting ceramic substrates from corrosive environments. Background Technology

[0002] Ceramic matrix composites (CMCs), particularly those based on carbides (often denoted as SiC / SiC), have been proposed for numerous applications, especially for the production of gas (turbo) turbine components such as blades and nozzles. More specifically, these materials, through their heat resistance, can reduce or even eliminate the cooling commonly used in nickel-based and / or cobalt-based metal turbine components by increasing operating temperatures.

[0003] However, in the corrosive environment of turbines, SiC / SiC CMC oxidizes, forming silicon oxide, which then volatilizes in the presence of water vapor. Therefore, for applications in oxygen-rich and water-vapor-rich environments at temperatures above 1000°C, it is recommended to apply a protective coating to the ceramic matrix composite components.

[0004] Since the protective coating will be subjected to particularly harsh thermomechanical and chemical environments, it should preferably have a coefficient of thermal expansion compatible with the substrate, low permeability to corrosive substances (which have low molecular diffusion directly related to the physical parameters of airtightness, and low ionic diffusion of superoxide ions and hydroxide ions, which are inherent characteristics of rare earth silicates), and thermomechanical stability at temperatures above 800°C (e.g., those temperatures commonly found in gas (turbo) turbines).

[0005] For this purpose, protective coatings typically include barrier coatings or environmental barrier coatings (EBCs), such as rare-earth silicate-based coatings, and adhesive coatings, such as silicon-based coatings, between the substrate and the barrier coating to ensure adhesion between the barrier coating and the substrate. Furthermore, the oxidation of silicon in the adhesive coating can form an intermediate silica layer between the adhesive coating and the barrier coating, known as thermally grown oxide (TGO).

[0006] In addition, although the formation of thermally grown oxide interlayers can help protect silicon carbide-containing substrates from corrosion, it may also produce thermomechanical effects, such as generating mechanical stress between the adhesive coating and the barrier coating.

[0007] These stresses can be caused by a variety of factors. At moderate temperatures (800°C to 1000°C), silicon oxidizes to form silicon dioxide. This allotropic transformation of silicon is accompanied by an increase in volume, and the molar volume of silicon dioxide is approximately 1.2 times that of silicon. Therefore, as it oxidizes, the thickness of the adhesive coating increases, placing stress on the barrier coating. When a critical thickness is exceeded, the mechanical stress causes the dome to crack, eventually leading to partial or complete peeling of the barrier coating, thus losing its anti-corrosion function.

[0008] Furthermore, at high temperatures (above 1000°C), EBC tends to creep. When the component is rotating, centrifugal force can cause the EBC to creep in this manner, resulting in very significant deformation. This is known as EBC centrifugation. In this case, the EBC may partially lose its coating, thus losing its anti-corrosion function.

[0009] Therefore, improvements are needed to EBCs that are at least partially free of the aforementioned drawbacks. Summary of the Invention

[0010] This disclosure relates to a coated ceramic composite component having a silicon carbide substrate, an adhesive coating covering the substrate, and a barrier coating covering the adhesive coating, wherein the adhesive coating comprises boron-doped silicon.

[0011] Compared to known adhesive coatings, boron-doped adhesive coatings exhibit significant creep at moderate temperatures (between 800°C and 1000°C). Therefore, boron doping enables the adhesive coating to more effectively relax stress, particularly when silicon in the adhesive coating oxidizes to form thermally grown oxides. Consequently, this adhesive coating is less likely to deteriorate due to phenomena such as "dome cracking." In other words, the coating can relax localized stresses that may occur at the interface between the barrier coating and the adhesive coating through the creep of the adhesive coating.

[0012] Furthermore, compared to known adhesive coatings, boron-doped adhesive coatings exhibit less significant creep at high temperatures (above 1000°C). Therefore, this adhesive coating is unlikely to deteriorate due to centrifugal forces.

[0013] It should be understood that boron-doped adhesive coatings are more resistant to failure modes such as dome cracking and centrifugal force. Therefore, at turbine operating temperatures, coated components are more robust than known coated components. In this case, the service life of the coated components is increased.

[0014] In some embodiments, the doping level of the silicon in the adhesive coating is from 0.05% to 0.5 atoms.

[0015] In some embodiments, the doping level of the silicon in the adhesive coating is 0.1% to 0.2 atoms.

[0016] Boron doping within the aforementioned range provides improved performance for the adhesive coating. In particular, these preferred doping ranges ensure a good trade-off in the adhesive coating's performance. More specifically, the adhesive coating exhibits adequate creep at approximately 800°C and low creep above 1000°C.

[0017] In some embodiments, the adhesive coating is deposited on the substrate by chemical vapor deposition.

[0018] The CVD method allows for easier control of doping in adhesive coatings. Furthermore, this method is easily industrialized. More specifically, it is suitable for complex geometries and is therefore more conducive to industrialization, especially for complex parts that are difficult to obtain using simpler methods.

[0019] In some implementations, the barrier coating is deposited onto the adhesive coating via electrophoretic deposition.

[0020] This method offers a good trade-off between cost, ease of implementation, and the performance of the resulting barrier coating. Furthermore, electrophoresis can produce highly sealed coatings. Other methods, such as thermal spraying or physical vapor deposition, can also be considered.

[0021] In some embodiments, the adhesive coating includes alternating first and second intermediate layers, the first intermediate layer comprising boron-doped silicon and the second intermediate layer being made of pure silicon or silicon carbide.

[0022] This multi-layer adhesive coating can further reduce the creep of the adhesive coating at high temperatures. Therefore, the corrosion resistance of the coated part is improved.

[0023] The above features and advantages, as well as other features and advantages, will become apparent after reading the following detailed description of exemplary embodiments of the proposed apparatus and method. This detailed description refers to the accompanying drawings.

[0024] Brief description of the attached figures

[0025] The accompanying drawings are schematic diagrams and are primarily intended to illustrate the principles of this disclosure.

[0026] [ Figure 1 ] Figure 1 The diagram schematically illustrates a coated composite material component according to a first embodiment of the present invention.

[0027] [ Figure 2A ] Figure 2A The creep curves of various components with different adhesive coatings at 800°C are compared.

[0028] [ Figure 2B ] Figure 2B The creep curves of various components with different adhesive coatings at 1000°C are compared.

[0029] [ Figure 3 ] Figure 3 The diagram schematically shows a detailed view of the adhesive coating of a coated composite material component according to a second embodiment of the present invention.

[0030] Description of implementation methods

[0031] To make this disclosure more specific, examples of the apparatus are described in detail below with reference to the accompanying drawings. It should be noted that the invention is not limited to these examples.

[0032] Figure 1 The diagram schematically illustrates a coated composite material component 10 according to a first embodiment of the present invention. Component 10 includes a substrate 105 typically made of silicon carbide, an adhesive coating 103 covering at least a portion of the substrate, and a barrier coating 101 covering at least a portion of the adhesive coating 103.

[0033] According to one example, an adhesive coating 103 is obtained using a chemical vapor deposition (CVD) process.

[0034] Substrate 105 is introduced into a suitable reactor. Chemical vapor deposition is performed by introducing a precursor mixture into the reactor, as shown in the table below.

[0035] [Table 1]

[0036] chemical substances <![CDATA[H2]]> <![CDATA[SiHCl3]]> <![CDATA[BCl3]]> <![CDATA[Flow velocity( sccm )]]> 330 66 1

[0037] It should be noted that the unit "sccm" refers to the flow rate expressed in "standard cubic centimeters per minute". It measures the flow rate of fluids flowing under standard temperature and pressure conditions, expressed in cubic centimeters per minute.

[0038] Deposition on the substrate was carried out in a reactor at a pressure of 5 kPa and a temperature of 1011 °C.

[0039] This yields a boron-doped silicon adhesive coating 103. Under current conditions, the doping rate is 0.14 atomic%. This doping rate can be changed by adjusting the flow rate of BCl3. The higher the flow rate of BCl3, the higher the doping rate of the adhesive coating 103.

[0040] Therefore, by varying the flow rate of BCl3 between 0.5 and 3 sccm, the doping rate of the adhesive coating 103 can be varied between 0.05% and 0.5 atomic%.

[0041] The thickness of the adhesive coating 103 is between 2 μm and 30 μm, preferably between 2 μm and 10 μm.

[0042] Furthermore, without being bound by arbitrary theories, the inventors have noted that the doping level affects the surface roughness of doped silicon. More specifically, the higher the doping level, the higher the surface roughness.

[0043] The barrier coating 101 is a rare-earth silicate. In this example, the barrier coating is RE2Si2O7. The barrier coating 101 can be deposited on the adhesive coating 103 by thermal spraying. Other deposition methods can be considered, such as physical vapor deposition (PVD), particularly electron beam physical vapor deposition (eb-PVD), or electrophoresis.

[0044] Figure 2A The creep curves of various components with different adhesive coatings at 800°C are compared. Figure 2B The creep curves of various components with different adhesive coatings at 1000°C are compared. The curves are shown in the table below.

[0045] [Table 2]

[0046] Adhesive coating Boron doping (atomic %) M1, M2, M3, M4 0 M4_0.14%B 0.14 M4_0.21%B 0.21 VPS 0

[0047] The various designations M1, M2, M3, and M4 refer to test adhesive coatings containing pure silicon with different microstructures. These designations are consistent with other designations: in other words, M4 and M4_0.14%B have the same silicon microstructure. VPS refers to an adhesive coating according to the prior art.

[0048] Figure 2 shows that at 800°C, the creep of the boron-containing adhesive coatings is greater than that of the VPS reference. Conversely, it can be seen that at 1000°C, the creep of these boron-containing adhesive coatings is less than that of the VPS reference.

[0049] Therefore, the use of boron-doped adhesive coatings offers a dual advantage over known coatings, as its creep performance at 800°C limits the "dome cracking" phenomenon, while its creep resistance at 1000°C limits centrifugal phenomena.

[0050] Figure 3 A schematic view of the adhesive coating 103 of a coated composite material component according to a second embodiment of the present invention is shown in detail.

[0051] In this embodiment, the adhesive coating 103 includes alternating first intermediate layers 1031 and second intermediate layers 1032. The first intermediate layer 1031 comprises boron-doped silicon. The first intermediate layer 1031 can be obtained by the CVD process described above.

[0052] The second intermediate layer 1032 is made of pure silicon or silicon carbide and can be obtained by a CVD process. Advantageously, the alternation of the first and second intermediate layers 1031, 1032 can be obtained by a single CVD deposition.

[0053] While the invention has been described with reference to specific exemplary embodiments, it will be apparent that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Specifically, individual features shown or mentioned in different embodiments may be combined in other embodiments. Therefore, the specification and drawings should be considered illustrative rather than limiting.

[0054] It is equally evident that all features described in the reference method can be individually or in combination transferred to the apparatus, and conversely, all features described in the reference apparatus can be individually or in combination transferred to the method.

Claims

1. A coated ceramic composite material component, comprising: Silicon carbide substrate, Adhesive coating covering the substrate, Barrier coating covering the adhesive coating, in, The adhesive coating contains boron-doped silicon.

2. The component as claimed in claim 1, wherein, The doping level of the silicon in the adhesive coating is from 0.05% to 0.5 atoms.

3. The component as claimed in claim 2, wherein, The doping level of the silicon in the adhesive coating is 0.1% to 0.2 atoms.

4. The component as claimed in any one of claims 1 to 3, wherein, The adhesive coating is deposited on the substrate by chemical vapor deposition.

5. The component as claimed in any one of claims 1 to 4, wherein, The barrier coating is deposited onto the adhesive coating via electrophoretic deposition.

6. The component as claimed in any one of claims 1 to 5, wherein, The adhesive coating comprises alternating first and second intermediate layers, the first intermediate layer comprising boron-doped silicon and the second intermediate layer being made of pure silicon or silicon carbide.

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