An anisometric ternary rare earth double-silicate environmental barrier coating and a high-energy plasma preparation method thereof

Abstract

The present application relates to the field of environmental barrier coatings or thermal barrier / environmental barrier integrated protective coatings, and discloses a non-eutectic ternary rare earth double-silicate environmental barrier coating and a high-energy plasma preparation method thereof. The present application aims at the current situation that the single-rare earth main element double-silicate environmental barrier coating has poor water vapor corrosion resistance, and uses an axial powder feeding high-energy plasma spraying system to prepare a non-eutectic ternary rare earth double-silicate coating which has excellent high-temperature water vapor corrosion resistance, so that the service life of SiC f / SiC material in a high-temperature water vapor environment can be effectively improved. The specific process is that rare earth oxides and silicon oxides are used as raw materials, and mechanical mixing, pressureless sintering, spray drying, high-energy plasma spraying and high-temperature heat treatment are sequentially performed to prepare the non-eutectic ternary rare earth double-silicate environmental barrier coating which has a dense interior, low porosity and excellent high-temperature water vapor corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of environmental barrier coatings or integrated thermal barrier / environmental barrier protective coatings. Specifically, it relates to a non-uniform ternary rare earth dual silicate environmental barrier coating with a dense structure, low porosity, and excellent resistance to high-temperature water vapor corrosion on the surface of continuous SiC fiber reinforced SiC matrix composites, and its high-energy plasma preparation method. Background Technology

[0002] With the pursuit of higher thrust-to-weight ratio and higher efficiency in aero engines, increasing the turbine inlet temperature has become a key measure to achieve this goal. Continuous SiC fiber-reinforced SiC matrix composites (SiC...) f SiC (SiC) possesses characteristics such as low density, excellent high-temperature oxidation resistance, and superior high-temperature strength, and has gradually become one of the most promising candidate materials for hot-section components of aero-engines, recognized internationally. However, the operating environment of aero-engines contains a large amount of water vapor generated by fuel combustion, and its combined action with oxygen can cause SiC to degrade. f After forming thermal oxides (TGO), SiC materials rapidly transform into gaseous products (Si(OH)4) and volatilize, leaving pores on the material surface, leading to performance degradation or even failure, and affecting the service life of aero-engines. Currently, the most common solution is to... f Applying an environmental barrier coating (EBC) to the surface of SiC materials provides high-temperature resistance, wear resistance, and excellent high-temperature mechanical properties. This effectively blocks high-temperature water vapor in the service environment, thereby improving the performance of SiC. f Stability of SiC materials in service environment.

[0003] Currently, the internationally recognized preferred system for environmental barrier materials is rare earth disilicate materials, among which Yb₂Si₂O₇ material is favored due to its high-temperature stability and low coefficient of thermal expansion (~4.0×10⁻⁶). -6 K -1 ) and SiC f The excellent chemical compatibility of SiC materials has made them one of the most widely studied environmental barrier coating materials. Bakan et al. prepared a Si / Yb₂Si₂O₇ coating system using atmospheric plasma spraying and subjected it to corrosion in a water vapor environment. The results showed that the Yb₂Si₂O₇ surface layer reacted with water vapor and decomposed, forming a porous Yb₂SiO₅ layer with a thickness of approximately 23 μm. The generated Yb₂SiO₅ exhibited a large coefficient of thermal expansion (6.7–7.4 × 10⁻⁶). -6 K -1This can easily lead to significant thermal stress within the coating during service, causing cracking upon stress release and affecting the coating's service life. Furthermore, the porous surface layer cannot further prevent water vapor erosion, resulting in continuous damage to the coating and eventual failure and peeling. Therefore, to ensure the SiC... f The efficient operation of SiC materials requires the exploration of new material systems.

[0004] Atmospheric Plasma Spray (APS) is a widely used thermal spraying process. It utilizes a plasma arc to spray molten powder onto the surface of another material, operating at temperatures exceeding 10,000 °C, and producing high-quality, highly repeatable coatings. This invention employs an axially fed high-energy plasma spraying system, where powder is directly fed axially into the plasma jet via a powder feeding pipeline. The powder is then heated and accelerated through a nozzle to reach the substrate. This system offers advantages such as high deposition efficiency and high powder feed rate, and can spray various raw materials ranging from powders to ceramics. It can also spray ultrafine powders smaller than 10 µm, resulting in a uniform and dense coating.

[0005] Based on this, the present invention utilizes the axial powder feeding high-energy plasma spraying system to prepare a non-uniform ternary rare-earth dual-silicate environmental barrier coating resistant to high-temperature water vapor corrosion. Its morphology and high-temperature water vapor corrosion performance were studied, confirming that the coating prepared by the present invention not only has a dense structure and low porosity, but also exhibits excellent resistance to high-temperature water vapor corrosion, which is beneficial for improving the SiC... f Service life of / SiC materials. Summary of the Invention

[0006] The purpose of this invention is to provide a non-uniform ternary rare-earth dual-silicate environmental barrier coating and its high-energy plasma preparation method. This coating exhibits resistance to high-temperature water vapor corrosion, thereby solving the problem of SiC... f The challenges faced by SiC materials under water vapor conditions.

[0007] This invention provides a non-uniform ternary rare earth disilicate environmental barrier coating, the coating being composed of non-uniform ternary rare earth disilicate (RE) Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 It consists of a 2Si2O7 surface layer and a Si bonding layer; (RE) Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4In 2Si2O7, RE can be any two rare earth elements selected from Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu; the Si binder can be either molten and crushed silicon or spherical silicon powder; the coating is prepared using an axial powder feeding high-energy plasma spraying system. The axial powder feeding method ensures that the feed material is fully melted during the spraying process, resulting in a coating with low porosity and high density, exhibiting excellent resistance to high-temperature water vapor corrosion.

[0008] The present invention provides a non-uniform ternary rare earth dual silicate environmental barrier coating, wherein the (RE) Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 The thickness of the 2Si2O7 surface layer is 120~360 μm, and the thickness of the Si adhesive layer is 50~200 μm.

[0009] This invention also provides a high-energy plasma preparation method for non-uniform ternary rare-earth dual silicate environmental barrier coatings, the steps of which are as follows:

[0010] (1) Using rare earth oxides (RE2O3), Yb2O3 and silicon oxide (SiO2) as raw materials, non-uniform ternary rare earth double silicate powder was prepared by grinding, mixing and pressureless sintering;

[0011] (2) The powder obtained in the above steps is mixed with the dispersion medium, binder and defoamer to form a slurry with uniform composition. The powder with smooth surface and good sphericity is obtained by spray drying technology. Then, the organic reagent is removed by heat treatment. The powder is then sieved through sieves of different mesh sizes to obtain a spray feed that meets the particle size distribution requirements.

[0012] (3) Using an axial powder feeding high-energy plasma spraying system, a Si bonding layer and a non-uniform ternary rare earth double silicate surface layer are sprayed onto the substrate to obtain a double-layer environmental barrier coating.

[0013] (4) The coating after spraying is annealed to obtain a non-uniform ternary rare earth double silicate environmental barrier coating that is resistant to high temperature water vapor corrosion.

[0014] The present invention provides a high-energy plasma preparation method for non-uniform ternary rare earth dual silicate environmental barrier coatings, wherein the RE2O3 is any two powders selected from Y2O3, Sc2O3, La2O3, Ce2O3, Pr2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, and Lu2O3.

[0015] The present invention provides a high-energy plasma preparation method for a non-uniform ternary rare-earth dual-silicate environmental barrier coating, wherein step (1) is performed by grinding and mixing in accordance with (a1) or (a2): (a1) rare-earth oxide RE2O3 powder, Yb2O3 and silicon oxide SiO2 powder are mixed in accordance with RE... Ⅰ 2O3:Yb2O3:RE Ⅱ The molar ratio of 2O3:SiO2 = 1:2:1:4 is used for mixing, wherein SiO2 powder can be in excess, and the mass fraction of excess SiO2 powder is 0.01 wt%~10.0 wt%; (a2) Rare earth oxide RE2O3 powder, Yb2O3 and silicon oxide SiO2 powder are first mixed with RE Ⅰ 2O3:Yb2O3:RE Ⅱ A mixture of O3 and SiO2 in a molar ratio of 1:2:1:2 yields rare earth monosilicates (RE). Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 )2SiO5 powder, and then mix the above powder and SiO2 powder in a molar ratio of 1:1, wherein SiO2 powder can be in excess, and the mass fraction of excess SiO2 powder is 0.01 wt%~10.0 wt%.

[0016] The high-energy plasma preparation method for non-uniform ternary rare-earth dual silicate environmental barrier coatings provided by this invention includes a grinding and mixing process in step (1), which can be carried out by high-speed shear mixing, three-dimensional motion mixing, ball milling, pneumatic conveying mixing, turbine stirring mixing, etc. Taking ball milling as an example, the ball milling solvent used is anhydrous ethanol, wherein the mass ratio of raw material powder to anhydrous ethanol is 1:2 to 2:1; the ball-to-material ratio is 1:2 to 4:1; the ball milling speed is 120 to 350 rpm; and the mixing and ball milling time is 2 to 24 h. Subsequently, pressureless sintering is carried out in a muffle furnace at a temperature of 1200 to 1600 ℃ and a holding time of 2 to 24 h.

[0017] The high-energy plasma preparation method for non-uniform ternary rare earth dual silicate environmental barrier coating provided by the present invention, wherein the slurry in step (2) is prepared by using raw material powder, deionized water, binder and defoamer, and its solid content is 40~60 wt%; wherein the binder is one or a combination of polyvinyl alcohol, polyethylene glycol, polyacrylate, carboxypropyl methylcellulose, styrene-butadiene rubber emulsion, polyvinylpyrrolidone or aluminum dihydrogen phosphate, and its function is to enhance the bonding force between powders and improve fluidity, and its addition amount is 0.1 wt%~5.0 wt%; wherein the defoamer is selected from one or a combination of polypropylene glycol, n-octanol, polyether modified organosilicon or polydimethylsiloxane, and is mainly used to eliminate bubbles generated during the mixing process, and its addition amount is 0.01~1.0 wt%.

[0018] The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings provided by this invention includes the following process parameters for spray drying in step (2): inlet air temperature of 150~350 ℃, outlet air temperature of 100~250 ℃, peristaltic pump speed of 5~15 rpm, atomizer speed of 8000~15000 rpm, and negative pressure in the cavity of -1.0~-0.1 kPa. These process parameters can be modified according to the characteristics of the powder being produced and actual needs, as long as granulated powder with good sphericity, no agglomeration, and satisfactory flowability can be obtained.

[0019] The high-energy plasma preparation method for non-uniform ternary rare earth dual silicate environmental barrier coatings provided by this invention, wherein the heat treatment temperature in step (2) is 1200~1600 °C and the holding time is 2~24 h. The purpose of heat treatment, in addition to removing organic reagents, is to sinter the granulated powder to make the internal and surface particles more compact, thereby improving fluidity and bulk density.

[0020] The high-energy plasma preparation method for non-uniform ternary rare earth dual silicate environmental barrier coatings provided by this invention involves a sieving process in step (2) using a 180-500 mesh sieve to obtain spherical powder below the sieve; the median particle size D50 of the obtained spherical powder is 25-80 μm. As long as the sprayed powder has good flowability and does not clog the powder feeder pipeline, sieves of other mesh sizes can also be used.

[0021] The high-energy plasma preparation method for non-uniform ternary rare-earth dual silicate environmental barrier coatings provided by this invention, in step (3), the substrate is selected from graphite, SiC substrate, Si3N4 substrate, C f / C composite matrix, C f / SiC composite matrix and SiC f At least one of the following: / SiC composite matrix; before spraying, the surface of the matrix must be roughened by sandblasting pretreatment. The sandblasting medium is quartz sand, corundum or a combination of the two, as long as the surface roughness after sandblasting is 2~5 μm.

[0022] The high-energy plasma preparation method for non-uniform ternary rare-earth double silicate environmental barrier coating provided by this invention includes the following parameters for spraying the Si bonding layer in step (3): plasma gas H2: 20~80 L / min; plasma gas Ar: 80~150 L / min; plasma gas N2: 30~90 L / min; carrier gas Ar: 1~12 L / min; spraying distance: 80~300 mm; spraying current: 100~250 A; spraying power: 50~150 kW; powder feeding rate: 5~20 r / min; number of spraying passes: 2~12. The parameters for spraying the non-uniform ternary rare-earth double silicate surface layer are: plasma gas H2: 10~60 L / min; plasma gas N2: 90~160 L / min; carrier gas Ar: 1~12 L / min; spraying distance: 80~300 mm; spraying current: 100~250 A. A; Spraying power: 70~180 kW; Powder feeding rate: 1~10 r / min; Number of spraying passes: 2~12. As long as the coating and substrate can be well bonded and the expected coating thickness can be achieved, the above parameters can be adjusted accordingly based on the coating structure or morphology requirements.

[0023] The non-equiproportional ternary rare earth double silicate environmental barrier coating and its high-energy plasma preparation method provided by the present invention, in step (4), the annealing temperature is 1100~1400 ℃, the holding time is 5~25 h, the heat treatment process is carried out under Ar gas protection, the annealing operation is to make the amorphous phase in the coating fully crystallize, and the Ar gas protection is to avoid the Si bonding layer being oxidized.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) This invention uses rare earth oxides and silicon oxide as raw materials to successfully prepare stable non-uniform ternary rare earth double silicate powder, in which the elements are evenly distributed and there is no segregation.

[0026] (2) The spherical feed prepared by the spray drying process of the present invention has high sphericity, good fluidity and good thermal stability, which can better meet the needs of subsequent spraying technology.

[0027] (3) The high-energy plasma spraying system used in this invention adopts an axial powder feeding method, which allows the feed to be fully heated and melted, resulting in fast spraying speed, high deposition efficiency, and low porosity of the prepared coating, making it more uniform and dense.

[0028] (4) The non-equiproportional ternary rare earth double silicate environmental barrier coating prepared by the present invention has excellent resistance to water vapor corrosion, which can effectively protect the substrate from corrosion and ensure structural integrity after long-term service. Attached Figure Description

[0029] Figure 1 The image shows the SEM morphology of Example 1 after heat treatment at 1300 °C; where (a) is the surface and (b) is the cross-section.

[0030] Figure 2 The image shows the SEM morphology of Example 2 after heat treatment at 1300 °C; where (a) is the surface and (b) is the cross-section.

[0031] Figure 3 The image shows the SEM morphology of Example 3 after heat treatment at 1300 °C; where (a) is the surface and (b) is the cross-section.

[0032] Figure 4 The cross-sectional morphology of Example 1 after 200 h of water vapor corrosion at 1350 °C is shown in (a) after 50 h of corrosion, (b) after 100 h of corrosion, and (c) after 200 h of corrosion.

[0033] Figure 5 The cross-sectional morphology of Example 2 after 200 h of water vapor corrosion at 1350 °C is shown in (a) after 50 h of corrosion, (b) after 100 h of corrosion, and (c) after 200 h of corrosion.

[0034] Figure 6 The cross-sectional morphology of Comparative Example 1 after 200 h of water vapor corrosion at 1350 °C is shown; (a) after 50 h of corrosion, (b) after 100 h of corrosion, and (c) after 200 h of corrosion.

[0035] Figure 7 The curves show the change in TGO layer thickness over time after 200 h of water vapor corrosion at 1350 °C for Examples 1, 2 and Comparative Example 1. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. The specific process parameters, etc., in the following examples are only examples within a suitable range, that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0037] The performance test information in the following examples is as follows:

[0038] The surface and cross-sectional morphology of the heat-treated coating and the cross-sectional morphology of the etched coating were observed using field emission scanning electron microscopy (Clara, Tescan, Czech Republic).

[0039] The thickness of the TGO layer formed within the coating after corrosion was determined using image analysis software (Mipar, Mipar Software LLC, USA).

[0040] Example 1

[0041] Using silicon dioxide (SiO2) and rare earth oxides Er2O3, Yb2O3, and Lu2O3 as raw materials, the raw materials were weighed according to a molar ratio of Er2O3:Yb2O3:Lu2O3:SiO2 = 1:2:1:4, with SiO2 powder in excess (5.0 wt%). The weighed powder was then placed in a ball mill jar, and anhydrous ethanol was added at a mass ratio of 1:1 (powder to anhydrous ethanol). The ball-to-powder ratio was 1:1, the ball milling speed was 160 rpm, and the mixing and milling time was 24 h. The ball-milled raw material was dried at 80 °C and sieved to obtain a uniformly mixed oxide raw material. Subsequently, it was sintered in a muffle furnace without pressure at 1550 °C for 20 h.

[0042] For the prepared (Er 1 / 4 Yb 1 / 2 Lu 1 / 4 Spherical feeding was used to prepare 2Si2O7 non-uniform ternary rare earth disilicate powder. First, the raw materials were prepared into a slurry with a solid content of 50 wt%; the binder was polyvinyl alcohol, added at 0.8 wt%; and the defoamer was n-octanol, added at 0.05 wt%. The ball-to-powder mass ratio was 1:2, the ball milling speed was 160 rpm, and the mixing and milling time was 30 min. The spray drying process parameters were: inlet air temperature 250 ℃, outlet air temperature 120 ℃, peristaltic pump speed 9 rpm, atomizer speed 14000 rpm, and negative pressure in the chamber -0.6 kPa. The subsequent heat treatment temperature was 1550°C, and the holding time was 10 h. Then, the obtained spherical powder was sieved through a 250-mesh sieve, and the spherical powder below the sieve was collected. The median particle size D50 of the obtained spherical powder was 45.09 μm.

[0043] First, the SiC substrate was pretreated by sandblasting with corundum as the sandblasting medium, resulting in a surface roughness of 3.3 ± 0.5 μm. Next, a Si binder layer was sprayed with the following parameters: total gas flow rate 250 L / min, plasma gas H2: 50 L / min, plasma gas Ar: 125 L / min, plasma gas N2: 75 L / min; carrier gas Ar: 8 L / min; spraying distance: 170 mm; spraying current: 180 A; spraying power: 93 kW; powder feed rate: 12 r / min; 4 spray passes; spraying (Er 1 / 4 Yb 1 / 2 Lu1 / 4 The parameters for the non-uniform ternary rare-earth dual-silicate surface layer of 2Si2O7 are as follows: total gas flow rate: 150 L / min; plasma gas H2: 37.5 L / min; plasma gas N2: 112.5 L / min; carrier gas Ar: 5 L / min; spraying distance: 170 mm; spraying current: 220 A; spraying power: 107 kW; powder feed rate: 6 r / min; and 6 spray passes. Finally, the non-uniform ternary rare-earth dual-silicate environmental barrier coating was annealed at 1300 ℃ for 20 h under Ar gas protection.

[0044] like Figure 1 The image shown is of the (Er) prepared in this embodiment. 1 / 4 Yb 1 / 2 Lu 1 / 4 The surface and cross-sectional morphology of the 2Si2O7 non-uniform ternary rare earth dual silicate environmental barrier coating after heat treatment at 1300 ℃ were examined. Although cracks were observed on the surface, they were largely healed, with a small number of pores appearing. Analysis of the cross-sectional morphology showed that the coating had good internal bonding, with no longitudinal cracks observed. Image analysis software determined that the porosity of the coating was only 0.71±0.19%, indicating a very dense coating structure.

[0045] Example 2

[0046] Using silicon dioxide (SiO2) and rare earth oxides (Ho2O3, Er2O3, and Yb2O3) as raw materials, the raw materials were weighed according to a molar ratio of Ho2O3:Er2O3:Yb2O3:SiO2 = 1:1:2:4, with SiO2 powder in excess (5.0 wt%). The weighed powder was then placed in a ball mill jar, and anhydrous ethanol was added at a mass ratio of 1:1 (powder to anhydrous ethanol). The ball-to-powder ratio was 1:1, the ball milling speed was 160 rpm, and the mixing and milling time was 24 h. The ball-milled raw material was dried at 80 °C and sieved to obtain a uniformly mixed oxide raw material. Subsequently, it was sintered in a muffle furnace under pressureless conditions at 1550 °C for 20 h.

[0047] The prepared (Ho) 1 / 4 Er 1 / 4 Yb 1 / 2Spherical feeding was used to prepare 2Si2O7 non-uniform ternary rare earth disilicate powder. First, the raw materials were prepared into a slurry with a solid content of 50 wt%; polyvinyl alcohol was added as a binder at 0.8 wt%; and n-octanol was added as a defoamer at 0.05 wt%. The ball-to-powder mass ratio was 1:2, the ball milling speed was 160 rpm, and the mixing and milling time was 30 min. The spray drying process parameters were: inlet air temperature 250 ℃, outlet air temperature 120 ℃, peristaltic pump speed 9 rpm, atomizer speed 14000 rpm, and negative pressure in the chamber -0.6 kPa. The subsequent heat treatment temperature was 1550°C, and the holding time was 10 h. Then, the obtained spherical powder was sieved through a 250-mesh sieve, and the spherical powder below the sieve was collected. The median particle size D50 of the obtained spherical powder was 45.95 μm.

[0048] First, the SiC substrate was pretreated by sandblasting with corundum as the sandblasting medium, resulting in a surface roughness of 3.3 ± 0.5 μm. Next, a Si binder layer was sprayed with the following parameters: total gas flow rate 250 L / min, plasma gas H2: 50 L / min, plasma gas Ar: 125 L / min, plasma gas N2: 75 L / min; carrier gas Ar: 8 L / min; spraying distance: 170 mm; spraying current: 180 A; spraying power: 93 kW; powder feed rate: 12 r / min; 4 spray passes; spraying (Ho) 1 / 4 Er 1 / 4 Yb 1 / 2 The parameters for the non-uniform ternary rare-earth dual-silicate surface layer of 2Si2O7 are as follows: total gas flow rate: 150 L / min; plasma gas H2: 37.5 L / min; plasma gas N2: 112.5 L / min; carrier gas Ar: 5 L / min; spraying distance: 170 mm; spraying current: 220 A; spraying power: 99 kW; powder feed rate: 6 r / min; and 6 spray passes. Finally, the non-uniform ternary rare-earth dual-silicate environmental barrier coating was annealed at 1300 ℃ for 20 h under Ar atmosphere protection.

[0049] like Figure 2 The image shown is of (Ho) prepared in this embodiment. 1 / 4 Er 1 / 4 Yb 1 / 2The surface and cross-sectional morphology of the 2Si2O7 non-uniform ternary rare earth double silicate environmental barrier coating after heat treatment at 1300 °C were shown. The surface crack healing behavior was also obvious, and a small number of pores appeared on the surface. The porosity of the coating was determined to be 1.07±0.18% by image analysis software, which is slightly increased compared with Example 1, but the internal structure is also very dense. No cracks were found, and the bonding between the surface layer and the adhesive layer, and between the adhesive layer and the substrate, was good.

[0050] Example 3

[0051] (Ho) was prepared according to the method in Example 2. 1 / 4 Er 1 / 4 Yb 1 / 2 The difference between the 2Si2O7 non-uniform ternary rare earth dual silicate environmental barrier coating and the 2Si2O7 non-uniform ternary rare earth dual silicate coating is:

[0052] Spraying (Ho) 1 / 4 Er 1 / 4 Yb 1 / 2 The parameters for the non-uniform ternary rare-earth dual-silicate surface layer of 2Si2O7 are as follows: total gas flow rate: 150 L / min; plasma gas H2: 22.5 L / min; plasma gas N2: 127.5 L / min; carrier gas Ar: 5 L / min; spraying distance: 170 mm; spraying current: 140 A; spraying power: 81 kW; powder feed rate: 6 r / min; spraying passes: 7. Finally, the non-uniform ternary rare-earth dual-silicate environmental barrier coating was annealed at 1300 ℃ for 20 h under Ar gas protection.

[0053] like Figure 3 The image shown is of (Ho) prepared in this embodiment. 1 / 4 Er 1 / 4 Yb 1 / 2 The surface and cross-sectional morphology of the 2Si2O7 non-uniform ternary rare earth dual silicate environmental barrier coating after heat treatment at 1300 °C were shown. The surface exhibited few pores, and crack healing was observed. Image analysis software determined the coating's porosity to be 0.98 ± 0.09%, which is essentially the same as in Example 2. The internal structure was intact and dense, with no cracks found, and good bonding between layers.

[0054] Comparative Example 1

[0055] Using silicon dioxide (SiO2) and rare earth oxide (Yb2O3) as raw materials, the raw materials were weighed according to a molar ratio of Yb2O3:SiO2 = 1:2, with SiO2 powder in excess (3.0 wt%). The weighed powder was then placed in a ball mill jar, and anhydrous ethanol was added at a mass ratio of 1:1 (powder to anhydrous ethanol). The ball-to-powder ratio was 1:1, the ball milling speed was 160 rpm, and the mixing and milling time was 24 h. The ball-milled raw material was dried at 80 °C and sieved to obtain a uniformly mixed oxide raw material. Subsequently, it was subjected to pressureless sintering in a muffle furnace at 1550 °C for 20 h.

[0056] The prepared Yb₂Si₂O₇ disilicate powder was processed using spherical feeding. First, the raw materials were prepared into a slurry with a solid content of 50 wt%; polyvinyl alcohol was added as a binder at 1.0 wt%; and n-octanol was added as a defoamer at 0.05 wt%. The ball-to-powder mass ratio was 1:2, the ball milling speed was 160 rpm, and the mixing and milling time was 30 min. The spray drying process parameters were: inlet air temperature 240 °C, outlet air temperature 130 °C, peristaltic pump speed 9 rpm, atomizer speed 14000 rpm, and negative pressure in the chamber -0.6 kPa. The subsequent heat treatment temperature was 1550 °C, and the holding time was 10 h. Then, the obtained spherical powder was sieved through a 250-mesh sieve, and the spherical powder below the sieve was collected. The median particle size D50 of the obtained spherical powder was 50.80 μm.

[0057] First, the SiC substrate was pretreated by sandblasting with corundum as the sandblasting medium. The surface roughness after pretreatment was 3.3±0.5 μm. Next, the Si bonding layer was sprayed with the following parameters: total gas flow rate of 250 L / min, plasma gas H2 of 50 L / min, plasma gas Ar of 125 L / min, plasma gas N2 of 75 L / min; carrier gas Ar of 8 L / min; spraying distance of 170 mm; spraying current of 180 A; spraying power of 93 kW; powder feed rate of 12 r / min; and 4 spraying passes. The parameters for spraying the Yb2Si2O7 double silicate topcoat were as follows: total gas flow rate of 150 L / min, plasma gas H2 of 37.5 L / min, plasma gas N2 of 112.5 L / min; carrier gas Ar of 5 L / min; spraying distance of 170 mm; spraying current of 220 A; spraying power of 103 kW; powder feed rate of 6 r / min; and 6 spraying passes. Finally, the bissilicate environmental barrier coating was annealed at 1300 ℃ for 20 h under Ar atmosphere protection.

[0058] Water vapor corrosion performance test

[0059] The coating samples prepared in Examples 1 and 2 and Comparative Example 1 were subjected to steam corrosion at 1350 °C for 200 h in a vertical tube furnace. The corrosion atmosphere was 90 vol% H₂O - 10 vol% air at a flow rate of 80 cm / s. The mixed gas was introduced into the furnace tube through a steam generator, and the temperature of the heating cable was set to 120 °C to prevent condensation and liquefaction of the introduced steam. The heating and cooling rate of the tube furnace was 5 °C / min. Samples were taken out at 50 h, 100 h, and 200 h for characterization. The cross-sectional morphology of the coating samples after steam corrosion was observed using a field emission scanning electron microscope.

[0060] Figure 4 The image shows the cross-sectional morphology of Example 1 after 200 hours of water vapor corrosion. It can be seen that the internal structure of the coating did not change significantly with prolonged corrosion time, and the layers remained tightly bonded. However, after 100 hours of corrosion, cracks appeared in the surface layer, but these cracks did not penetrate the entire surface layer; instead, they terminated internally, effectively inhibiting the diffusion of the oxidizing medium. A TGO layer was found at the interface between the surface layer and the adhesive layer, and its thickness increased significantly with time. After 200 hours of corrosion, the average thickness of the generated TGO layer was 7.00 ± 1.68 μm.

[0061] Figure 5 The image shows the cross-sectional morphology of Example 2 after 200 hours of water vapor corrosion. It can be seen that more pores were formed internally than in Example 1, and many cracks appeared inside after 200 hours of corrosion due to stress release within the coating. Because the surface layer contains a light gray RE2SiO5 phase and a gray RE2Si2O7 phase, which have different coefficients of thermal expansion, stress accumulated within the coating during heating and cooling, eventually leading to stress release and crack formation. These cracks became diffusion channels for the corrosive medium, resulting in Example 2 forming a thicker TGO layer than Example 1 after 200 hours of corrosion, with an average thickness of 7.73 ± 2.07 μm.

[0062] Figure 6 The cross-sectional morphology of Comparative Example 1 after 200 h of water vapor corrosion is shown. Cracks appeared in the coating after 50 h of corrosion, which resulted in a TGO layer thickness (5.72 μm) that was much greater than that of Examples 1 and 2 (1.95 μm and 1.37 μm). Furthermore, the thickness of the TGO layer formed at the interface increased with the extension of corrosion time. Finally, after 200 h of corrosion, a TGO layer of 10.81 ± 2.87 μm was formed at the interface.

[0063] Figure 7The graph shows the TGO layer thickness as a function of time during the 200-h corrosion process of Examples 1, 2 and Comparative Example 1. As can be seen from the graph, the TGO layer thickness generated in Comparative Example 1 was always greater than that of the two examples throughout the entire corrosion process; while the TGO layer thickness generated in Example 2 was smaller in the early stage, and then suddenly increased after 200 h, which corresponds to the appearance of cracks in the coating.

[0064] The above embodiments demonstrate that the non-uniform ternary rare-earth disilicate environmental barrier coating and its high-energy plasma preparation method provided by this invention can prepare coatings with excellent resistance to water vapor corrosion. Its performance is significantly improved compared to ytterbium disilicate coatings. Furthermore, the coating prepared by this invention exhibits high melting degree, dense structure, and low porosity, further enhancing its performance. The technology provided by this invention offers a new approach to the future production and preparation of environmental barrier coatings, and is expected to achieve even higher coating performance.

[0065] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely one specific embodiment of the present invention and are not limited to the scope of protection of the present invention. The present invention can be embodied in various forms without departing from its essential characteristics. Therefore, the embodiments described herein are for illustrative purposes only and not for limitation. Since the scope of the present invention is defined by the claims rather than the specification, all changes falling within the scope defined by the claims, or their equivalents, should be understood to be included in the claims. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-uniform ternary rare earth dual silicate environmental barrier coating, characterized in that, The coating consists of a non-eutectic ternary rare earth double silicate (RE Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 )2Si2O7 surface layer and a Si adhesive layer; The (RE) Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 The surface layer of 2Si2O7 is (Er) 1 / 4 Yb 1 / 2 Lu 1 / 4 )2Si2O7 surface layer; The Si bonding layer is made of molten and broken silicon or spherical silicon powder; The aforementioned (RE) Ⅰ 1 / 4 Yb 1 / 2 RE Ⅱ 1 / 4 The thickness of the 2Si2O7 surface layer is 120~360 μm, and the thickness of the Si adhesive layer is 50~200 μm.

2. The high-energy plasma preparation method for the non-uniform ternary rare-earth dual-silicate environmental barrier coating according to claim 1, characterized in that: The steps of this method are as follows: (1) Using Er2O3, Lu2O3, Yb2O3 and SiO2 as raw materials, non-uniform ternary rare earth double silicate powder was prepared by grinding, mixing and pressureless sintering; (2) The powder obtained in the above steps is mixed with the dispersion medium, binder and defoamer to form a slurry with uniform composition. The powder with smooth surface and good sphericity is obtained by spray drying technology. Then, the organic reagent is removed by heat treatment. The powder is then sieved through a sieve with a specific mesh size to obtain a spray feed that meets the particle size distribution requirements. (3) Using an axial powder feeding high-energy plasma spraying system, a Si bonding layer and a non-uniform ternary rare earth double silicate surface layer are sprayed onto the substrate to obtain a double-layer environmental barrier coating. (4) The coating after spraying is annealed at a temperature of 1100~1400 ℃ and a holding time of 5~25h. The heat treatment process is carried out under Ar gas protection to obtain a non-uniform ternary rare earth double silicate environmental barrier coating resistant to high temperature water vapor corrosion.

3. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: The grinding and mixing in step (1) are carried out in the following manner: Er2O3, Yb2O3, Lu2O3 and SiO2 are mixed in a molar ratio of Er2O3:Yb2O3:Lu2O3:SiO2 = 1:2:1:4, wherein the mass fraction of SiO2 is 0.01 wt% to 10.0 wt%.

4. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: The grinding and mixing methods used in step (1) are high-speed shear mixing, three-dimensional motion mixing, ball milling mixing, pneumatic conveying mixing, and turbine stirring mixing; The pressureless sintering temperature is 1200~1600 ℃, and the holding time is 2~24 h.

5. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: The grinding and mixing is ball milling. In ball milling, the ball milling solvent is anhydrous ethanol, and the mass ratio of raw material powder to anhydrous ethanol is 1:2 to 2:1; the ball-to-material ratio is 1:2 to 4:1; and the ball milling time is 2 to 24 hours.

6. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: The solid content of the slurry in step (2) is 40~60 wt%; The dispersion medium is deionized water; The binder is one or a combination of several of the following: polyvinyl alcohol, polyethylene glycol, polyacrylate, carboxypropyl methylcellulose, styrene-butadiene rubber latex, polyvinylpyrrolidone, or aluminum dihydrogen phosphate, and its addition amount is 0.1 wt% to 5.0 wt%. The defoamer is selected from one or more of polypropylene glycol, n-octanol, polyether-modified organosilicon or polydimethylsiloxane, and its addition amount is 0.01~1.0 wt%.

7. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: In step (2), the heat treatment temperature is 1200~1600 °C and the holding time is 2~24 h; the sieving process uses a 180~500 mesh sieve to obtain spherical powder below the sieve; the median particle size D50 of the obtained spherical powder is 25~80 μm.

8. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: In step (3), the matrix is ​​selected from graphite, SiC matrix, Si3N4 matrix, C f / C composite matrix, C f / SiC composite matrix and SiC f At least one of the following: / SiC composite matrix; prior to spraying, the matrix surface must undergo surface roughening pretreatment by sandblasting, with the sandblasting medium being quartz sand, corundum, or a combination of both.

9. The high-energy plasma preparation method for non-uniform ternary rare-earth dual-silicate environmental barrier coatings according to claim 2, characterized in that: The parameters for spraying the Si adhesive layer in step (3) are as follows: plasma gas H2: 20~80 L / min; plasma gas Ar: 80~150 L / min; plasma gas N2: 30~90 L / min; carrier gas Ar: 1~12 L / min; spraying distance: 80~300 mm; spraying current: 100~250 A; spraying power: 50~150 kW; powder feeding rate: 5~20 r / min; number of spraying passes: 2~12. Parameters for spraying non-uniform ternary rare earth double silicate surface layer: plasma gas H2: 10~60 L / min; plasma gas N2: 90~160 L / min; carrier gas Ar: 1~12 L / min; spraying distance: 80~300 mm; spraying current: 100~250 A; spraying power: 70~180 kW; powder feeding rate: 1~10 r / min; number of spraying passes: 2~12.

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