An aluminide coating formed without a zone of interdiffusion and a method of making the same

Abstract

The present application belongs to the technical field of high-temperature protective coating, and relates to an aluminized coating without interdiffusion zone, which comprises layer-connected alpha-Al2O3 layer, gamma'-Ni3Al layer and beta-NiAl layer. The preparation method is also disclosed, which comprises the following steps: performing surface ultrasonic cleaning on a high-temperature alloy substrate; depositing an alpha-Al2O3 layer on the surface of the high-temperature alloy substrate; depositing a nickel layer on the surface of the alpha-Al2O3 layer; performing aluminizing treatment on the nickel layer, so that the originally continuous alpha-Al2O3 layer is converted into discontinuously distributed alpha-Al2O3 particles, the nickel layer in contact with the alpha-Al2O3 layer is converted into a gamma'-Ni3Al layer, and the nickel layer in the remaining area is converted into a beta-NiAl layer; the gamma'-Ni3Al layer is locally in contact with the high-temperature alloy substrate, thereby forming the aluminized coating without interdiffusion zone. The problem of forming an interdiffusion zone in the preparation process of the diffusion nickel-aluminum coating is solved.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature protective coating technology, specifically relating to an aluminizing coating without interdiffusion regions and its preparation method. Background Technology

[0002] High-temperature alloy matrices are the most critical components of aero-engines and gas turbines. Currently, aero-engines and gas turbines are developing towards lightweight, high-thrust, and long-life designs, which heavily rely on increasing gas combustion temperature. However, these higher gas combustion temperatures pose a significant challenge to the high-temperature resistance of the materials used in the matrix. To address this challenge, high-temperature alloy materials with excellent high-temperature thermomechanical properties must be employed. Currently, high-temperature alloy materials have evolved from polycrystalline to directional and even single-crystal directions, approaching their ultimate operating temperatures. Further increasing gas combustion temperature requires cooling or insulation treatment of the high-temperature alloys. The most widely used cooling and insulation technologies are film cooling (FSC) and thermal barrier coatings (TBCs). Driven by the development of FSC and TBC technologies, engine operating temperatures have now reached 2000K. While FSC and TBCs allow the high-temperature alloy matrix to operate in combustion gases exceeding its melting point, the matrix's service temperature also approaches its melting point. Under high-temperature conditions, the high-temperature alloy matrix is ​​highly susceptible to severe oxidation and corrosion damage. Therefore, in order to improve the safety and stability of engines and gas turbines, it is urgent to take measures to improve the oxidation resistance and corrosion resistance of high-temperature alloy matrices.

[0003] Currently, the commonly used method to improve the oxidation and corrosion resistance of high-temperature alloy substrates is to prepare an anti-oxidation and corrosion resistant coating on the surface of the high-temperature alloy substrate, such as a diffused nickel-aluminum coating or a cladding coating.

[0004] The coating is typically an MCrAlY (M being Ni and / or Co) coating prepared by thermal spraying. The dense oxide film formed on the surface prevents further oxidation and corrosion damage to the high-temperature alloy substrate from high-temperature combustion gases. Typically, the Al content in the MCrAlY coating is 5–10 wt.%. During high-temperature service, the alumina film formed on the coating surface gradually grows and thickens, leading to a significant consumption of the protective Al element within the coating, resulting in insufficient Al supply. When the Al supply in the coating is insufficient, other alloying elements will be oxidized, leading to the formation of non-alumina oxides. Since the growth rate of non-alumina oxides is much higher than that of alumina, their growth can cause rapid degradation or even failure of the coating performance.

[0005] Diffusion nickel-aluminum coating technology is an anti-oxidation and corrosion-resistant coating deposition technique. It involves the dissociation of aluminum-containing media on the surface of a high-temperature alloy, releasing Al elements and allowing them to penetrate to a certain depth within the workpiece, thus forming an Al-rich nickel-aluminum coating (Al content greater than 20 wt.%). The high Al content in the nickel-aluminum coating can maintain the Al required for the growth of the surface alumina film during high-temperature service, effectively inhibiting the formation of non-alumina oxides and improving the oxidation and corrosion resistance of the high-temperature alloy substrate. However, due to the difference in the types and contents of alloying elements between the prepared nickel-aluminum coating and the high-temperature alloy substrate, directly preparing the nickel-aluminum coating on the surface of the high-temperature alloy substrate leads to interdiffusion of elements between the coating and the substrate, forming an interdiffusion zone rich in topologically packed phases (TCP phase). The formation of the interdiffusion zone consumes solid solution strengthening elements in the substrate alloy, and the TCP phase is a brittle phase, a root cause of fatigue cracks. Therefore, the formation of the interdiffusion zone reduces the creep fracture life of the high-temperature alloy substrate, affecting its service life and posing serious safety hazards. Therefore, an important problem in preparing diffused nickel-aluminum infiltration layers is to suppress the formation of interdiffusion zones as much as possible. Summary of the Invention

[0006] The purpose of this invention is to provide an aluminized coating without interdiffusion region formation and its preparation method, thereby solving the problem of interdiffusion region formation during the preparation of diffused nickel-aluminum coatings.

[0007] This invention is achieved through the following technical solution:

[0008] This invention discloses an aluminizing coating without interdiffusion regions, comprising an α-Al2O3 layer, a γ'-Ni3Al layer, and a β-NiAl layer, wherein the α-Al2O3 layer is located at the bottom layer, the γ'-Ni3Al layer is located at the middle layer, and the β-NiAl layer is located at the outermost layer.

[0009] Furthermore, the α-Al2O3 layer consists of discontinuous elliptical α-Al2O3 particles distributed on the high-temperature alloy matrix.

[0010] Furthermore, the high-temperature alloy matrix is ​​an iron-based, nickel-based, or cobalt-based high-temperature alloy matrix.

[0011] Furthermore, the γ'-Ni3Al layer is located between adjacent α-Al2O3 particles and on the α-Al2O3 layer.

[0012] Furthermore, the β-NiAl layer is a dense single-phase β-NiAl layer; the γ'-Ni3Al layer is a dense single-phase γ'-Ni3Al layer.

[0013] This invention also discloses a method for preparing an aluminized coating without interdiffusion regions, comprising the following steps:

[0014] S1. Perform ultrasonic cleaning on the surface of the high-temperature alloy substrate;

[0015] S2. Deposit an α-Al2O3 layer on the surface of a high-temperature alloy substrate;

[0016] S3. Deposit a nickel layer on the surface of the α-Al2O3 layer;

[0017] S4. Aluminizing treatment is performed on the nickel layer;

[0018] After S4 treatment, the original continuous α-Al2O3 layer is transformed into discontinuously distributed α-Al2O3 particles. The nickel layer in contact with the α-Al2O3 layer is transformed into a γ'-Ni3Al layer, and the nickel layer in the remaining area is transformed into a β-NiAl layer. The γ'-Ni3Al layer makes local contact with the high-temperature alloy substrate, forming a metallurgical bond, and finally forming an aluminized coating without interdiffusion zones.

[0019] Furthermore, in S1, deionized water and acetone are used for ultrasonic cleaning.

[0020] Furthermore, in S2, the deposition methods for the α-Al2O3 layer include high-temperature oxidation growth, physical vapor deposition, and chemical vapor deposition.

[0021] Furthermore, in S3, the nickel layer deposition method employs chemical plating, thermal spraying, physical vapor deposition, and chemical vapor deposition.

[0022] Furthermore, in S4, the aluminizing treatment methods employed include embedding, physical vapor deposition, and chemical vapor deposition.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] This invention discloses an aluminizing coating without interdiffusion zones, comprising an α-Al₂O₃ layer, a γ'-Ni₃Al layer, and a β-NiAl layer. The α-Al₂O₃ layer is in contact with the surface of a high-temperature alloy substrate, and the β-NiAl layer is located as the outermost layer. The α-Al₂O₃ layer is composed of discontinuous elliptical α-Al₂O₃ particles distributed along the surface of the high-temperature alloy. The γ'-Ni₃Al layer is disposed between adjacent α-Al₂O₃ particles and on the α-Al₂O₃ layer. The α-Al₂O₃ layer and the nickel layer can suppress the formation of interdiffusion zones between the high-temperature alloy substrate and the aluminizing coating when the aluminizing coating is prepared by direct aluminizing on the surface of the high-temperature alloy substrate. The γ'-Ni₃Al layer can suppress the diffusion of alloying elements from the high-temperature alloy substrate into the aluminizing coating, and suppress the degradation of mechanical properties of the high-temperature alloy caused by element diffusion. The discontinuously distributed α-Al₂O₃ particles can enable the γ'-Ni₃Al layer to make local contact with the high-temperature alloy substrate, thereby forming a metallurgical bond at high temperature, improving the bonding strength of the coating, and preventing the coating from peeling off and failing during use.

[0025] This invention also discloses a method for preparing an aluminized coating without interdiffusion regions. The preparation process is simple. After high-temperature aluminizing treatment, the originally continuous α-Al2O3 layer is partially or completely transformed into discontinuously distributed α-Al2O3 particles, which makes the γ'-Ni3Al layer make local contact with the high-temperature alloy matrix to form a metallurgical bond, thereby improving the bonding strength. The β-NiAl layer is a dense single-phase β-NiAl layer, and the γ'-Ni3Al layer is a dense single-phase γ'-Ni3Al layer. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an aluminizing coating without interdiffusion regions according to the present invention.

[0027] Figure 2 An image showing the effect of depositing α-Al2O3 and nickel layers on the surface of a high-temperature alloy substrate;

[0028] Figure 3 The image shows the effect of the aluminized coating prepared in Example 1;

[0029] Figure 4 This image shows the effect of the α-Al2O3 layer breaking into α-Al2O3 particles after aluminizing treatment.

[0030] Figure 5 The image shows the effect of the aluminized coating prepared in Example 2;

[0031] Figure 6 The image shows the effect of the aluminized coating prepared in Example 3;

[0032] In this model, 1 represents the high-temperature alloy matrix, 2 represents the α-Al2O3 layer, 3 represents the γ'-Ni3Al layer, and 4 represents the NiAl layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0034] The implementation method of the present invention will be further described below with reference to specific embodiments.

[0035] This invention relates to the preparation of a nickel-aluminum coating on a nickel-based superalloy substrate. The chemical composition of the nickel-based superalloy used is as follows (mass percentage): Cr: 8.4%, Co: 10.0%, W: 10.0%, Al: 5.5%, Ta: 3.0%, Ti: 1.0%, Hf: 1.0%, Mo: 0.7%, C: 0.15%, Zr: 0.05%, B: 0.015%, Ni: balance.

[0036] Example 1

[0037] This invention discloses a method for preparing an aluminized coating without interdiffusion regions, comprising the following steps:

[0038] S1. Before preparing the diffusion layer, the ingot is first cut into a long strip sample of 20×10×2mm (length×width×height) using electrical discharge cutting and milling. A 2mm diameter hole is drilled at one end to facilitate the suspension of the sample when preparing the nickel-aluminum layer by chemical vapor deposition.

[0039] Before preparing the α-Al2O3 layer, the sample was ultrasonically cleaned with deionized water and acetone in sequence to remove residual oil on the sample surface.

[0040] S2. An α-Al2O3 layer is grown on the surface of a nickel-based superalloy using a high-temperature oxidation growth method. The specific operation steps are as follows:

[0041] 2.1 First, place the sample in a corundum crucible and send it into the furnace chamber of a vacuum heat treatment furnace;

[0042] 2.2 Then, close the furnace door and turn on the vacuum pump to evacuate the pressure inside the furnace to 1×10⁻⁶. -3 Pa;

[0043] 2.3. Subsequently, the sample was heated to 1100℃ at a heating rate of 4℃ / min;

[0044] 2.4 Finally, the furnace was filled with 100 Pa of high-purity oxygen (O2 ≥ 99.999%). The sample was heat-treated for 4 hours in this low-oxygen atmosphere at 1100℃, which caused the surface of the high-temperature alloy to oxidize and form an α-Al2O3 layer with a thickness of about 1 μm.

[0045] S3. A nickel layer is deposited on the surface of the α-Al2O3 layer using a chemical plating method:

[0046] The nickel plating solution containing the sample was kept in a water bath at 100°C for 3 hours. Figure 2As shown, after this treatment, a nickel layer with a thickness of 20 μm can be deposited on the surface of the α-Al₂O₃ layer. The nickel plating solution used is formulated as follows: 75 g of lactic acid, 9 g of sodium carbonate, 129 g of nickel sulfate, 75 g of sodium hypophosphite, 27 mL of ammonia, and 4.5 g of boric acid are added to 3 L of deionized water.

[0047] S4. High-temperature aluminizing treatment of the nickel layer is performed using chemical vapor deposition aluminizing:

[0048] Aluminum powder was used as the aluminizing source, and HCl gas was used as the activator. The sample was aluminized for 4 hours at a temperature of 1050℃, a gas flow rate of 24 L / min, and a low pressure of 30 kPa. Figure 3 As shown, an aluminized coating is obtained after aluminizing the surface of a high-temperature alloy.

[0049] After aluminizing, the outer nickel layer is completely transformed into a β-NiAl layer, while the inner nickel layer in contact with the α-Al2O3 layer is completely transformed into a γ'-Ni3Al layer.

[0050] like Figure 4 As shown, the originally continuous α-Al2O3 layer is partially or completely transformed into discontinuously distributed α-Al2O3 particles, which causes the γ'-Ni3Al layer to make local contact with the high-temperature alloy matrix, forming a metallurgical bond to improve the bonding strength.

[0051] Example 2

[0052] This invention discloses a method for preparing an aluminized coating without interdiffusion regions, comprising the following steps:

[0053] S1. Before preparing the diffusion layer, the ingot is first cut into a long strip sample of 20×10×2mm (length×width×height) using electrical discharge cutting and milling. A 2mm diameter hole is drilled at one end to facilitate the suspension of the sample when preparing the nickel-aluminum layer by chemical vapor deposition.

[0054] Before preparing the α-Al2O3 layer, the sample was ultrasonically cleaned with deionized water and acetone in sequence to remove residual oil on the sample surface.

[0055] S2. An α-Al2O3 layer is grown on the surface of a nickel-based superalloy using a high-temperature oxidation growth method. The specific operation steps are as follows:

[0056] 2.1 First, place the sample in a corundum crucible and send it into the furnace chamber of a vacuum heat treatment furnace;

[0057] 2.2 Then, close the furnace door and turn on the vacuum pump to evacuate the pressure inside the furnace to 1×10⁻⁶. -3 Pa;

[0058] 2.3. Subsequently, the sample was heated to 1100℃ at a heating rate of 4℃ / min;

[0059] 2.4 Finally, the furnace was filled with 100 Pa of high-purity oxygen (O2 ≥ 99.999%). The sample was heat-treated for 4 hours in this low-oxygen atmosphere at 1100℃, which caused the surface of the high-temperature alloy to oxidize and form an α-Al2O3 layer with a thickness of about 5 μm.

[0060] S3. A nickel layer is deposited on the surface of the α-Al2O3 layer using a chemical plating method:

[0061] The nickel plating solution containing the sample was kept in a water bath at 100°C for 3 hours. Figure 2 As shown, after this treatment, a nickel layer with a thickness of 20 μm can be deposited on the surface of the α-Al₂O₃ layer. The nickel plating solution used is formulated as follows: 75 g of lactic acid, 9 g of sodium carbonate, 129 g of nickel sulfate, 75 g of sodium hypophosphite, 27 mL of ammonia, and 4.5 g of boric acid are added to 3 L of deionized water.

[0062] S4. High-temperature aluminizing treatment of the nickel layer is performed using chemical vapor deposition aluminizing:

[0063] Aluminum powder was used as the aluminizing source, and HCl gas was used as the activator. The sample was aluminized for 4 hours at a temperature of 950℃, a gas flow rate of 24 L / min, and a low pressure of 30 kPa. Figure 5 As shown, an aluminized coating is obtained after aluminizing the surface of a high-temperature alloy.

[0064] After aluminizing, the outer nickel layer is completely transformed into a β-NiAl layer, while the inner nickel layer in contact with the α-Al2O3 layer is completely transformed into a γ'-Ni3Al layer.

[0065] like Figure 4 As shown, the originally continuous α-Al2O3 layer is partially or completely transformed into discontinuously distributed α-Al2O3 particles, which causes the γ'-Ni3Al layer to make local contact with the high-temperature alloy matrix, forming a metallurgical bond to improve the bonding strength.

[0066] Example 3

[0067] This invention discloses a method for preparing an aluminized coating without interdiffusion regions, comprising the following steps:

[0068] S1. Before preparing the diffusion layer, the ingot is first cut into a long strip sample of 20×10×2mm (length×width×height) using electrical discharge cutting and milling. A 2mm diameter hole is drilled at one end to facilitate the suspension of the sample when preparing the nickel-aluminum layer by chemical vapor deposition.

[0069] Before preparing the α-Al2O3 layer, the sample was ultrasonically cleaned with deionized water and acetone in sequence to remove residual oil on the sample surface.

[0070] S2. An α-Al2O3 layer is grown on the surface of a nickel-based superalloy using a high-temperature oxidation growth method. The specific operation steps are as follows:

[0071] 2.1 First, place the sample in a corundum crucible and send it into the furnace chamber of a vacuum heat treatment furnace;

[0072] 2.2 Then, close the furnace door and turn on the vacuum pump to evacuate the pressure inside the furnace to 1×10⁻⁶. -3 Pa;

[0073] 2.3. Subsequently, the sample was heated to 1100℃ at a heating rate of 4℃ / min;

[0074] 2.4 Finally, the furnace was filled with 100 Pa of high-purity oxygen (O2 ≥ 99.999%). The sample was heat-treated for 4 hours in this low-oxygen atmosphere at 1100℃, which caused the surface of the high-temperature alloy to oxidize and form an α-Al2O3 layer with a thickness of about 1 μm.

[0075] S3. A nickel layer is deposited on the surface of the α-Al2O3 layer using a chemical plating method:

[0076] The nickel plating solution containing the sample was kept in a water bath at 100°C for 3 hours. Figure 2 As shown, after this treatment, a nickel layer with a thickness of 20 μm can be deposited on the surface of the α-Al₂O₃ layer. The nickel plating solution used is formulated as follows: 75 g of lactic acid, 9 g of sodium carbonate, 129 g of nickel sulfate, 75 g of sodium hypophosphite, 27 mL of ammonia, and 4.5 g of boric acid are added to 3 L of deionized water.

[0077] S4. High-temperature aluminizing treatment of the nickel layer is performed using chemical vapor deposition aluminizing:

[0078] Aluminum powder was used as the aluminizing source, and HCl gas was used as the activator. The sample was aluminized for 4 hours at a temperature of 850℃, a gas flow rate of 24 L / min, and a low pressure of 30 kPa. Figure 6 As shown, an aluminized coating is obtained after aluminizing the surface of a high-temperature alloy.

[0079] After aluminizing, the outer nickel layer is completely transformed into a β-NiAl layer, while the inner nickel layer in contact with the α-Al2O3 layer is completely transformed into a γ'-Ni3Al layer.

[0080] like Figure 4As shown, the originally continuous α-Al2O3 layer is partially or completely transformed into discontinuously distributed α-Al2O3 particles, which causes the γ'-Ni3Al layer to make local contact with the high-temperature alloy matrix, forming a metallurgical bond to improve the bonding strength.

[0081] In S1, the high-temperature alloy matrix is ​​not limited to a nickel-based high-temperature alloy matrix, but can also be an iron-based or cobalt-based high-temperature alloy matrix.

[0082] In S2, in addition to high-temperature oxidation growth, physical vapor deposition and chemical vapor deposition can also be used to deposit the α-Al2O3 layer.

[0083] In S3, in addition to chemical plating, nickel layer deposition methods can also include thermal spraying, physical vapor deposition, and chemical vapor deposition.

[0084] In S4, in addition to chemical vapor deposition, aluminizing methods can also include encapsulation and physical vapor deposition.

[0085] The above embodiments prepare an aluminizing coating without interdiffusion regions, such as Figure 1 As shown, it includes an α-Al2O3 layer, a γ'-Ni3Al layer, and a β-NiAl layer. The α-Al2O3 layer is located at the bottom layer, the γ'-Ni3Al layer is located in the middle layer, and the β-NiAl layer is located at the outermost layer.

[0086] The α-Al₂O₃ layer consists of discontinuous elliptical α-Al₂O₃ particles distributed on the high-temperature alloy matrix. The γ'-Ni₃Al layer is located between adjacent α-Al₂O₃ particles and on the α-Al₂O₃ layer.

[0087] The β-NiAl layer is a dense single-phase β-NiAl layer; the γ'-Ni3Al layer is a dense single-phase γ'-Ni3Al layer.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An aluminizing coating without interdiffusion regions, characterized in that, It includes an α-Al2O3 layer, a γ'-Ni3Al layer and a β-NiAl layer, with the α-Al2O3 layer at the bottom, the γ'-Ni3Al layer in the middle layer and the β-NiAl layer at the outermost layer. The α-Al2O3 layer consists of discontinuous elliptical α-Al2O3 particles distributed on the high-temperature alloy matrix; The γ'-Ni3Al layer is located between adjacent α-Al2O3 particles and on the α-Al2O3 layer.

2. The aluminizing coating without interdiffusion regions according to claim 1, characterized in that, The high-temperature alloy matrix is ​​an iron-based, nickel-based, or cobalt-based high-temperature alloy matrix.

3. The aluminizing coating without interdiffusion regions according to claim 1, characterized in that, The β-NiAl layer is a dense single-phase β-NiAl layer; the γ'-Ni3Al layer is a dense single-phase γ'-Ni3Al layer.

4. A method for preparing an aluminized coating without interdiffusion regions as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Perform ultrasonic cleaning on the surface of the high-temperature alloy substrate; S2. Deposit an α-Al2O3 layer on the surface of a high-temperature alloy substrate; S3. Deposit a nickel layer on the surface of the α-Al2O3 layer; S4. Aluminizing treatment is performed on the nickel layer; After S4 treatment, the original continuous α-Al2O3 layer is transformed into discontinuously distributed α-Al2O3 particles. The nickel layer in contact with the α-Al2O3 layer is transformed into a γ'-Ni3Al layer, and the nickel layer in the remaining area is transformed into a β-NiAl layer. The γ'-Ni3Al layer makes local contact with the high-temperature alloy substrate, forming a metallurgical bond, and finally forming an aluminized coating without interdiffusion zones.

5. The method for preparing an aluminized coating without interdiffusion regions according to claim 4, characterized in that, In S1, deionized water and acetone are used for ultrasonic cleaning.

6. The method for preparing an aluminized coating without interdiffusion regions according to claim 4, characterized in that, In S2, the deposition methods for the α-Al2O3 layer include high-temperature oxidation growth, physical vapor deposition, and chemical vapor deposition.

7. The method for preparing an aluminized coating without interdiffusion regions according to claim 4, characterized in that, In S3, the nickel layer deposition methods include chemical plating, thermal spraying, physical vapor deposition, and chemical vapor deposition.

8. The method for preparing an aluminized coating without interdiffusion regions according to claim 4, characterized in that, In S4, the aluminizing treatment methods include embedding, physical vapor deposition, and chemical vapor deposition.

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