A ceramic thermal barrier coating with high bonding strength on a nickel-based alloy surface and a preparation method thereof

Abstract

This invention discloses a high-bonding-strength ceramic thermal barrier coating for nickel-based alloy surfaces and its preparation method. The ceramic thermal barrier coating, from bottom to top, comprises a dense metal bonding layer, a dense oxygen barrier layer, a low-porosity composite transition layer, and a high-porosity insulation layer; the bonding strength between the ceramic thermal barrier coating and the nickel-based alloy substrate is greater than 50 MPa. The dense metal bonding layer is made of NiCrAlY, with a thickness of 80-100 μm and a porosity of less than 2%; the dense oxygen barrier layer is made of RETaO4, with a thickness of 50-80 μm and a porosity of less than 2%; the low-porosity composite transition layer is a composite ceramic composed of RETaO4 and RE3TaO7, wherein the mass fraction of RETaO4 is 56-78%, its coating thickness is 70-100 μm, and its porosity is 3-8%; the high-porosity insulation layer is made of RE3TaO7 ceramic, with the RE element being the same as in the composite ceramic, its thickness is 50-1000 μm, and its porosity is 15-30%. The coating prepared by this invention has the characteristics of high bonding strength, strong oxygen barrier and high heat insulation.

Description

Technical Field

[0001] This invention belongs to the field of ceramic coating technology, specifically relating to a high-bonding-strength ceramic thermal barrier coating for nickel-based alloy surfaces and its preparation method. Background Technology

[0002] Ceramic thermal barrier coatings are widely used on the surfaces of high-temperature components in the combustion chambers of gas turbines, aero engines, and hypersonic vehicles to provide thermal insulation and cooling. Most of these high-temperature alloy parts are made of nickel-based alloys, and ceramic thermal barrier coatings are applied to their surfaces via atmospheric plasma spraying to increase their operating temperature. However, due to the weak bonding strength between the ceramic layer and the nickel-based alloy substrate (less than 10 MPa), the ceramic thermal barrier coating is prone to peeling and failure during service. Preparing an adhesive layer between the ceramic layer and the substrate can improve the bonding strength (reaching 20-40 MPa). However, with the increase in combustion chamber operating temperature and blade rotation speed, even higher requirements are placed on the bonding strength of the ceramic coating. The bonding strength between the ceramic coating and the nickel-based alloy substrate directly affects its service life. Therefore, improving the bonding strength of ceramic thermal barrier coatings on nickel-based alloy surfaces is a key focus of current research. Summary of the Invention

[0003] The first objective of this invention is to provide a high-bonding-strength ceramic thermal barrier coating on the surface of a nickel-based alloy, and the second objective of this invention is to provide a method for preparing the high-bonding-strength ceramic thermal barrier coating on the surface of the nickel-based alloy.

[0004] The first objective of this invention is achieved as follows: a high-bonding-strength ceramic thermal barrier coating for a nickel-based alloy surface, comprising, from bottom to top, a dense metal bonding layer, a dense oxygen barrier layer, a low-porosity composite transition layer, and a high-porosity thermal insulation layer; wherein the bonding strength between the ceramic thermal barrier coating and the nickel-based alloy substrate is greater than 50 MPa.

[0005] The dense metal bonding layer material is NiCrAlY, with a thickness of 80~100μm and a porosity of less than 2%;

[0006] The dense oxygen barrier layer material is RETaO4, with a thickness of 50~80μm and a porosity of less than 2%;

[0007] The low-porosity composite transition layer material is a composite ceramic composed of RETaO4 and RE3TaO7, wherein the mass fraction of RETaO4 is 56-78%, the coating thickness is 70-100 μm, and the porosity is 3-8%.

[0008] The high-porosity thermal insulation layer material is RE3TaO7 ceramic, with RE element consistent with that in composite ceramics, a thickness of 50~1000μm, and a porosity of 15~30%;

[0009] RE can be one or more of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, and Y.

[0010] The second objective of this invention is achieved by the following steps in the preparation method of the high-bonding-strength ceramic thermal barrier coating on the nickel-based alloy surface:

[0011] 1) Use sandpaper to directly scratch the surface of the nickel-based alloy, and then apply a metal bonding layer to the surface of the nickel-based alloy by atmospheric plasma spraying. The process parameters for atmospheric plasma spraying are: spray gun power of 35~42kW, spray gun distance of 100~200mm, argon and hydrogen flow rates of 30 / 10 and 35 / 15slpm respectively, feed rate of 30~50g / min, spray gun speed of 500~600mm / s, and spraying time of 1~3 min.

[0012] 2) A dense oxygen barrier layer is applied to the surface of the metal bonding layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 40~46kW, spray gun distance is 120~200 mm, argon and hydrogen flow rates are 40 / 10 and 50 / 10 slpm respectively, feed rate is 30~50g / min, spray gun speed is 200~300mm / s, and spraying time is 1~5 min.

[0013] 3) A low-porosity composite transition layer is applied to the surface of the dense oxygen barrier layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power: 38~50 kW, spray gun distance: 300~500 mm, argon and hydrogen flow rates: 40 / 10 and 50 / 10 slpm, respectively, feed rate: 30~45 g / min, spray gun speed: 200~300 mm / s, and spraying time: 1~5 min.

[0014] 4) A high-porosity heat insulation layer is applied to the surface of the low-porosity composite transition layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 32~38 kW, spray gun distance is 130~300 mm, argon and hydrogen flow rates are 43 / 12 and 41 / 13 slpm respectively, feed rate is 20~42 g / min, spray gun speed is 300~500 mm / s, and spraying time is 2~6 min.

[0015] The beneficial effects of this invention are as follows:

[0016] 1) This invention improves the surface roughness of nickel-based alloys by rubbing the surface with sandpaper, eliminating the need for commonly used sandblasting treatment, and ultimately improving the bonding strength between the adhesive layer and the nickel-based alloy;

[0017] 2) The dense oxygen barrier layer of the ceramic thermal barrier coating of the present invention is RETaO4 (RE is one or more of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Y), and its thickness is 50-80 micrometers. The RETaO4 prepared from the above rare earth elements has a high coefficient of thermal expansion (greater than 10 × 10⁻⁶). -6 K -1 It features extremely low oxygen ion transport efficiency (one-thousandth to one-ten-thousandth of that of current YSZ and rare earth zirconates), high thermal expansion coefficient can improve the bonding strength between the coating and the adhesive layer, and low oxygen ion transport efficiency can provide excellent oxygen barrier function, delay the oxidation of the alloy adhesive layer and thus extend its service life.

[0018] 3) The low porosity composite transition layer of the ceramic thermal barrier coating of the present invention is composed of RETaO4+RE3TaO7, wherein the mass fraction of RETaO4 is 56~78%, the porosity is 3~8%, and RETaO4 and RE3TaO7 have the same rare earth elements. This can ensure that the two phases of the composite coating have excellent high-temperature chemical compatibility and will not cause mutual diffusion leading to coating failure.

[0019] 4) The coefficients of thermal expansion of RETaO4 and RE3TaO7 in the ceramic thermal barrier coating of this invention are 10~12×10⁻⁶. -6 K -1 The coefficient of thermal expansion of the NiCrAlY bonding layer is 14~16×10⁻⁶. -6 K -1 The coefficient of thermal expansion of nickel-based alloys is 14~16×10⁻⁶. -6 K -1 Therefore, using NiCrAlY as the bonding layer can eliminate the thermal expansion coefficient mismatch between the nickel-based alloy substrate and the bonding layer, improving the bonding strength between them. Using dense RETaO4 as the oxygen barrier layer can increase the contact area between them, achieving high bonding strength and strong oxygen barrier properties. The thermal expansion coefficient changes gradually from the bottom alloy substrate to the top high-porosity insulation layer, which can mitigate the thermal expansion coefficient mismatch between traditional three-layer thermal barrier coatings, thereby improving the bonding strength. The high-porosity insulation layer, low-porosity composite transition layer, and dense oxygen barrier layer of the ceramic thermal barrier coating of this invention have the same RE element, which is beneficial to improving the bonding strength between the three layers and suppressing element diffusion between layers, thereby ensuring the thermal stability and service life of the coating under high-temperature service conditions.

[0020] 5) The porosity of each layer of the ceramic thermal barrier coating of this invention decreases progressively from the top high-porosity insulation layer to the bottom dense alloy bonding layer. This is beneficial for gradually increasing the contact area between layers, improving the bonding strength between each layer, and allowing each layer to play its respective role. Specifically, the high-porosity insulation layer has extremely low thermal conductivity, providing a higher thermal insulation and cooling gradient; the dense oxygen barrier layer has excellent oxygen barrier properties, thus improving its oxygen barrier performance; and the dense metal bonding layer can improve the bonding area and bonding strength between the ceramic layer and the alloy substrate. The final coating has high bonding strength (above 50 MPa), strong oxygen barrier, and high thermal insulation properties. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the high bonding strength ceramic thermal barrier coating on the surface of the nickel-based alloy of the present invention, wherein 1—nickel alloy substrate, 2—dense metal bonding layer, 3—dense oxygen barrier layer, 4—low porosity composite transition layer, and 5—high porosity thermal insulation layer.

[0022] Figure 2 The image shows a scanning electron microscope (SEM) image of the high-bonding-strength ceramic thermal barrier coating on the surface of the nickel-based alloy prepared in Example 3; wherein, 2—dense metal bonding layer, 3—dense oxygen barrier layer, 4—low porosity composite transition layer, and 5—high porosity thermal insulation layer.

[0023] Figure 3 Comparison of oxide film thickness between dense metal bonding layer and dense oxygen barrier layer for coatings prepared in Example 1 (left) and Comparative Example 3 (right). Detailed Implementation

[0024] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications made based on the present invention are within the scope of protection of the present invention.

[0025] This invention discloses a high-bonding-strength ceramic thermal barrier coating for nickel-based alloy surfaces, which, from bottom to top, consists of a dense metal bonding layer, a dense oxygen barrier layer, a low-porosity composite transition layer, and a high-porosity thermal insulation layer; the bonding strength between the ceramic thermal barrier coating and the nickel-based alloy substrate is greater than 50 MPa.

[0026] The dense metal bonding layer material is NiCrAlY, with a thickness of 80~100μm and a porosity of less than 2%;

[0027] The dense oxygen barrier layer material is RETaO4, with a thickness of 50~80μm and a porosity of less than 2%;

[0028] The low-porosity composite transition layer material is a composite ceramic composed of RETaO4 and RE3TaO7, wherein the mass fraction of RETaO4 is 56-78%, the coating thickness is 70-100 μm, and the porosity is 3-8%.

[0029] The high-porosity thermal insulation layer material is RE3TaO7 ceramic, with RE element consistent with that in composite ceramics, a thickness of 50~1000μm, and a porosity of 15~30%;

[0030] RE can be one or more of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, and Y.

[0031] The mass ratio of RETaO4 to RE3TaO7 in the low porosity composite transition layer is 5-8:2-5.

[0032] This invention also provides a method for preparing a high-bonding-strength ceramic thermal barrier coating on the surface of the nickel-based alloy, which is implemented according to the following steps:

[0033] 1) Use sandpaper to directly scratch the surface of the nickel-based alloy, and then apply a metal bonding layer to the surface of the nickel-based alloy by atmospheric plasma spraying. The process parameters for atmospheric plasma spraying are: spray gun power of 35~42kW, spray gun distance of 100~200mm, argon and hydrogen flow rates of 30 / 10 and 35 / 15slpm respectively, feed rate of 30~50g / min, spray gun speed of 500~600mm / s, and spraying time of 1~3 min.

[0034] 2) A dense oxygen barrier layer is applied to the surface of the metal bonding layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 40~46kW, spray gun distance is 120~200 mm, argon and hydrogen flow rates are 40 / 10 and 50 / 10 slpm respectively, feed rate is 30~50g / min, spray gun speed is 200~300mm / s, and spraying time is 1~5 min.

[0035] 3) A low-porosity composite transition layer is applied to the surface of the dense oxygen barrier layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power: 38~50 kW, spray gun distance: 300~500 mm, argon and hydrogen flow rates: 40 / 10 and 50 / 10 slpm, respectively, feed rate: 30~45 g / min, spray gun speed: 200~300 mm / s, and spraying time: 1~5 min.

[0036] 4) A high-porosity heat insulation layer is applied to the surface of the low-porosity composite transition layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 32~38 kW, spray gun distance is 130~300 mm, argon and hydrogen flow rates are 43 / 12 and 41 / 13 slpm respectively, feed rate is 20~42 g / min, spray gun speed is 300~500 mm / s, and spraying time is 2~6 min.

[0037] Example 1

[0038] 1) The surface of the nickel-based alloy is directly scratched with sandpaper, and a metal bonding layer is applied to the surface of the nickel-based alloy by atmospheric plasma spraying. The process parameters for atmospheric plasma spraying are: spray gun power of 40kW, spray gun distance of 100mm, argon and hydrogen flow rates of 30 / 10 and 35 / 15 slpm respectively, feed rate of 50g / min, spray gun speed of 600mm / s, and spraying time of 1min.

[0039] 2) A dense oxygen barrier layer is sprayed onto the surface of the metal bonding layer by atmospheric plasma spraying; the process parameters are: spray gun power of 46kW, spray gun distance of 120mm, argon and hydrogen flow rates of 40 / 10 and 50 / 10 slpm respectively, feed rate of 50g / min, spray gun speed of 300mm / s, and spraying time of 1min.

[0040] 3) A low-porosity composite transition layer is applied to the surface of the dense oxygen barrier layer by atmospheric plasma spraying; the process parameters are as follows: spray gun power is 38kW, spray gun distance is 120mm, argon and hydrogen flow rates are 40 / 10 and 50 / 10 slpm respectively, feed rate is 50g / min, spray gun speed is 300mm / s, and spraying time is 1min.

[0041] 4) A high-porosity heat insulation layer was applied to the surface of the low-porosity composite transition layer by atmospheric plasma spraying. The process parameters were as follows: spray gun power of 32kW, spray gun distance of 130mm, argon and hydrogen flow rates of 43 / 12 and 41 / 13 slpm respectively, feed rate of 42g / min, spray gun speed of 300mm / s, and spraying time of 2min.

[0042] The difference between the preparation process of Examples 2-6 and Example 1 lies in the use of different spraying process parameters within the set range, thereby obtaining coatings with different porosities. In addition, the thickness of each coating layer, the RE element of the dense oxygen barrier layer, the low porosity composite transition layer and the high porosity heat insulation layer, as well as the mass fraction of RETaO4 and RE3TaO7 in the low porosity composite transition layer are also different, as shown in Tables 1-2.

[0043] Scanning electron microscope (SEM) image of the high-bonding-strength ceramic thermal barrier coating on the nickel-based alloy surface prepared in Example 3 is shown below. Figure 2 As shown.

[0044] Table 1. Coating thickness and RETaO4 mass fraction of the transition layer in Examples 1-6 and Comparative Examples 1-4

[0045]

[0046] The adhesion strength, oxidation resistance, and thermal erosion resistance of the coatings prepared in Examples 1-6 and Comparative Examples 1-4 were tested.

[0047] 1. Determination of the bonding performance of the coatings of Examples 1-6 and Comparative Examples 1-4

[0048] Test method: The coated nickel alloy substrate was bonded to the upper and lower ends of the tensile testing machine with strong adhesive. The tensile force was continuously increased. The ratio of the tensile force required to completely separate and peel off the entire coating from the substrate to the area of ​​the nickel alloy substrate is the bonding strength of the coating.

[0049] Table 2. Porosity, coefficient of thermal expansion, and bonding strength of each coating thickness in Examples 1-6 and Comparative Examples 1-4.

[0050]

[0051] As shown in Table 2, the coating materials prepared in Examples 1-6 exhibit high bonding strength. In Comparative Example 1, compared to Example 1, the transition layer was entirely made of RETaO4, leading to interdiffusion between the transition layer and the insulation layer during use. This structural failure between the two resulted in coating peeling. In Comparative Example 2, the transition layer thickness was 10 μm compared to Example 1. This thin transition layer failed to provide adequate buffering during spraying, resulting in a mismatch in the thermal expansion coefficients between the dense oxygen barrier layer and the insulation layer, causing premature peeling failure of the insulation coating. In Comparative Example 3, the dense oxygen barrier layer thickness was only 10 μm compared to Example 1, exhibiting weak oxygen barrier properties. During service, the adhesive layer was oxidized by external high-temperature oxygen, forming an oxide layer and causing coating peeling failure. In Comparative Example 4, the dense oxygen barrier layer had a porosity of 5%, allowing high-temperature air to directly oxidize the adhesive layer through the pores, forming oxides and leading to coating peeling failure.

[0052] 2. Determination of the oxidation resistance, thermal erosion resistance, thermal fatigue resistance, and thermal insulation cooling gradient of the coatings in Examples 1-6 and Comparative Examples 1-4.

[0053] After preparing the above coating on the surface of a 25 mm diameter nickel-based alloy disc, its performance was tested. The coating surface was heated to 1300 °C within 20 s using an acetylene + oxygen torch, and the surface temperature was measured using an infrared thermometer (T1 = 1300 °C). The coating was held at 1300 °C for 20 s, then the torch was removed, and the surface was cooled with compressed air for 20 s, constituting one thermal erosion performance test. The coating was considered to have failed when the area of ​​peeling off the nickel-based alloy surface exceeded 10% of the total area. During the 1300 °C holding period, the back temperature of the nickel-based alloy (T2) was simultaneously measured using a thermocouple. The difference between T1 and T2 is the thermal insulation cooling gradient of the coating (ΔT = T1 - T2). Each sample coating was tested for 20 seconds. Before failure, the mass W1 and W2 before and after testing are measured. The ratio of the difference between the two to W1 is the oxidation weight gain rate (W% = 100% * (W2 - W1) / W1). The larger the oxidation weight gain rate, the worse its antioxidant performance (oxygen barrier properties). Additionally, from... Figure 3 It can be seen that the thickness of the oxide film in the gray area of ​​Comparative Example 3 (1~2 micrometers) is significantly greater than that of Example 1 (less than 0.5 micrometers), which also indicates that Example 1 has stronger oxygen barrier properties.

[0054] Table 3 shows the oxidation resistance, thermal erosion resistance, and thermal insulation cooling gradient data of the coatings in Examples 1-6 and Comparative Examples 1-4.

[0055] Oxidative weight gain (%) Heat scouring resistance times Thermal insulation cooling gradient (°C) Example 1 3 146 120 Example 2 2 150 266 Example 3 1.6 233 183 Example 4 3.3 304 190 Example 5 4.0 151 139 Example 6 2.2 163 228 Comparative Example 1 10 33 135 Comparative Example 2 26 45 110 Comparative Example 3 12 60 94 Comparative Example 4 18 77 128

[0056] As shown in Table 3, the coating materials prepared in Examples 1 to 6 have the characteristics of high bonding strength, resistance to gas thermal shock and strong oxygen barrier.

Claims

1. A high-bonding-strength ceramic thermal barrier coating for nickel-based alloy surfaces, characterized in that, The ceramic thermal barrier coating consists of a dense metal bonding layer, a dense oxygen barrier layer, a low porosity composite transition layer, and a high porosity thermal insulation layer, from bottom to top. The dense oxygen barrier layer, the low porosity composite transition layer, and the high porosity thermal insulation layer all have the same RE element. The bonding strength between the ceramic thermal barrier coating and the nickel-based alloy substrate is greater than 50 MPa. The dense metal bonding layer material is NiCrAlY, with a thickness of 80~100μm and a porosity of less than 2%; The dense oxygen barrier layer material is RETaO4, with a thickness of 50~80μm and a porosity of less than 2%; The low-porosity composite transition layer material is a composite ceramic composed of RETaO4 and RE3TaO7, and RETaO4 and RE3TaO7 have the same rare earth elements. The mass fraction of RETaO4 is 56-78%, the coating thickness is 70-100 μm, and the porosity is 3-8%. The high-porosity thermal insulation layer material is RE3TaO7 ceramic, with a thickness of 50~1000μm and a porosity of 15~30%; RE can be one or more of Y, Nd, Sm, Eu, Gd, Ho, and Er.

2. The high-bonding-strength ceramic thermal barrier coating on the nickel-based alloy surface according to claim 1, characterized in that, The mass ratio of RETaO4 to RE3TaO7 in the low porosity composite transition layer is 5~8:2~5.

3. A method for preparing a high-bonding-strength ceramic thermal barrier coating on the surface of a nickel-based alloy as described in claim 1, characterized in that, Follow these steps to achieve the following: 1) Use sandpaper to directly scratch the surface of the nickel-based alloy, and then apply a metal bonding layer to the surface of the nickel-based alloy by atmospheric plasma spraying. The process parameters for atmospheric plasma spraying are: spray gun power of 35~42kW, spray gun distance of 100~200mm, argon and hydrogen flow rates of 30 / 10 and 35 / 15slpm respectively, feed rate of 30~50g / min, spray gun speed of 500~600mm / s, and spraying time of 1~3min. 2) A dense oxygen barrier layer is applied to the surface of the metal bonding layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 40~46kW, spray gun distance is 120~200mm, argon and hydrogen flow rates are 40 / 10 and 50 / 10 slpm respectively, feed rate is 30~50g / min, spray gun speed is 200~300mm / s, and spraying time is 1~5min. 3) A low-porosity composite transition layer is applied to the surface of the dense oxygen barrier layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power: 38~50kW, spray gun distance: 300~500mm, argon and hydrogen flow rates: 40 / 10 and 50 / 10 slpm, respectively, feed rate: 30~45g / min, spray gun speed: 200~300mm / s, and spraying time: 1~5min. 4) A high-porosity heat insulation layer is applied to the surface of the low-porosity composite transition layer by atmospheric plasma spraying. The atmospheric plasma spraying process parameters are as follows: spray gun power is 32~38kW, spray gun distance is 130~300mm, argon and hydrogen flow rates are 43 / 12 and 41 / 13 slpm respectively, feed rate is 20~42g / min, spray gun speed is 300~500mm / s, and spraying time is 2~6min.

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