A Pt-Hf co-modified aluminide coating and its preparation process

Abstract

The present invention discloses a Pt-Hf co-modified aluminide coating and a preparation method thereof, and belongs to the technical field of preparing high-temperature protective coatings on high-temperature alloy substrates. The method first deposits a Ni-Hf layer + a Pt layer + a Ni-Hf layer on a substrate by an electroplating method; then vacuum annealing is performed to obtain a Ni / Pt-Hf layer; then a pure Al layer is deposited; finally, the Ni / Pt-Hf layer + the pure Al layer are vacuum annealed to obtain a Pt-Hf co-modified aluminide coating. By adjusting the thickness of the electroplated layer and the thickness of the arc ion plating deposited layer, the content of Ni, Pt and Al in the coating can be adjusted, thereby preparing Pt-Hf co-modified aluminide coatings of various compositions. The advantages of the present invention are: simple preparation process and low cost; Pt and Hf elements are added to the coating by an electroplating method; the composition of the coating can be adjusted arbitrarily, and it has strong universality.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing high-temperature protective coatings on high-temperature alloy substrates, and in particular to a Pt-Hf co-modified aluminide coating and a preparation method thereof. Background Art

[0002] Nickel-based superalloys are widely used in turbine blades and other hot-end components in aircraft engines and industrial gas turbines due to their excellent high-temperature mechanical properties. However, as engine thrust and weight ratios increase, turbine inlet temperatures continue to rise, requiring the high-temperature mechanical properties of nickel-based superalloys used in these components to be continuously improved. Consequently, researchers have been optimizing the composition and processing of nickel-based superalloys. The evolution of nickel-based superalloys from polycrystalline casting and directionally solidified to single crystals has eliminated the detrimental effects of grain boundaries on performance and improved the heat-resistant capabilities of nickel-based superalloys. To further enhance the heat-resistant capabilities of nickel-based single crystal superalloys, the content of refractory elements (such as W, Ta, Re, and Ru) has been gradually increased. These refractory elements can dissolve in the γ / γ′ phase, providing excellent solid-solution strengthening and enhancing the material's high-temperature mechanical properties. However, higher Al contents reduce the alloy's plasticity, so the Al content in nickel-based single crystal superalloys has been maintained at 5.0-6.0 wt.%. When nickel-based superalloys are used at high temperatures, severe oxidation occurs because the aluminum content falls below the critical value for selective oxidation of Al. This consumes a large amount of alloying elements, which in turn reduces the material's high-temperature mechanical properties. To ensure that nickel-based superalloys maintain excellent high-temperature oxidation and hot corrosion resistance at service temperatures, it is common practice to apply one or more layers of high-temperature protective coatings to the alloy surface.

[0003] High-temperature protective coatings generally include simple aluminide coatings, modified aluminide coatings, MCrAlY cladding coatings, and thermal barrier coatings. Modified aluminide coatings exhibit excellent high-temperature oxidation resistance due to their high aluminum content and the addition of active elements. The aluminum content in aluminide coatings is approximately 30 wt.%, which is much higher than the aluminum content in nickel-based single-crystal superalloys (5.0-6.0 wt.%). During service, Al from the coating diffuses into the substrate, leading to the precipitation of a topologically close-packed phase (TCP) within the substrate beneath the coating. Numerous studies have shown that the precipitation of TCP phases degrades the mechanical properties of the substrate. Therefore, some researchers have proposed electroplating a layer of Pt on the substrate, followed by diffusion annealing to obtain a Pt-modified γ / γ' coating. However, the coating composition cannot be adjusted. Therefore, the present invention aims to propose a preparation process that can regulate the Ni, Pt, and Al contents in the coating to produce Pt-Hf co-modified aluminide coatings of various compositions. Summary of the Invention

[0004] The present invention aims to provide a Pt-Hf co-modified aluminide coating and a preparation method thereof, namely, a process combining electroplating, arc ion plating technology and vacuum heat treatment annealing to prepare an aluminide coating containing Pt and Hf. The process of the present invention can effectively control the content of various elements in the coating, thereby obtaining modified aluminide coatings of various compositions.

[0005] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0006] A method for preparing a Pt-Hf co-modified aluminide coating comprises the following steps:

[0007] 1) Substrate pretreatment process: polish the substrate with 150#, 240#, 400#, 600#, and 800# SiC sandpaper respectively, then wet-sandblast the substrate surface with 200-mesh alumina pellets, and finally ultrasonically clean the substrate with deionized water, acetone, and alcohol for 10-20 minutes in sequence;

[0008] (2) Matrix pretreatment process: first, the matrix is degreased with NaOH solution, and then the matrix is activated with HCl solution;

[0009] (3) A Ni / Pt-Hf layer is prepared by combining electroplating and vacuum heat treatment: a Ni-Hf layer, a Pt layer, and a Ni-Hf layer are sequentially deposited on the surface of the pretreated substrate; and then vacuum annealing is performed to obtain the Ni / Pt-Hf layer;

[0010] (4) Arc ion plating technology is used to deposit a pure Al layer: Arc ion plating is used to deposit a pure Al layer on the Ni / Pt-Hf layer;

[0011] (5) Vacuum heat treatment to obtain a Pt-Hf co-modified aluminide coating: The sample deposited with Ni / Pt-Hf layer and pure Al layer was annealed in a vacuum annealing furnace to obtain a Pt-Hf co-modified aluminide coating.

[0012] In the above step (1), the substrate is a nickel-based single crystal high temperature alloy; the alloy is cut into A disc-shaped specimen is cut 1 mm from the edge of the specimen. The small hole is convenient for hanging samples during electroplating and arc ion plating.

[0013] In the above step (2), the degreasing process is as follows: in a 5-15g / L NaOH solution, the substrate is used as the cathode, the stainless steel plate is used as the anode, and the current density is 2-15A / dm 2 , the degreasing time is 1-10min; the activation treatment process is: under room temperature, the sample is immersed in 10-30vol.% hydrochloric acid for 1-5min.

[0014] In the above step (3), the plating solution used for electroplating the Ni-Hf layer is composed of: nickel sulfate 0.1-0.4 mol / L, citric acid 0.1-0.6 mol / L, Hf powder 5-30 g / L, ammonia water in appropriate amount, and the rest is deionized water; wherein the Hf powder particle size is 0.5-2 μm, the pH of the plating solution is adjusted to 8-9 by the amount of ammonia water, the temperature is 40-60 ° C, and the current density is 2-6 A / dm 2 , the electroplating time is 10-50min; the thickness of the obtained Ni-Hf layer is 10-45μm.

[0015] In the above step (3), the plating solution used for electroplating the Pt layer is composed of: [Pt(NH3)4]HPO4 3-8g / L, Na2HPO4 2-7g / L, an appropriate amount of NaOH, and the rest is deionized water; the pH value of the plating solution is adjusted to 9-11 by the amount of NaOH, the temperature is 90-95°C, and the current density is 0.2-0.6A / dm 2 , the electroplating time is 60-180 min; the thickness of the obtained Pt layer is 3-10 μm.

[0016] In the above step (3), the vacuum annealing treatment is to place the sample in a vacuum annealing furnace, heat the annealing furnace to 700-1000°C at a heating rate of 3-7°C / min, keep it at this temperature for 3-10 hours, and then cool it to room temperature with the furnace.

[0017] In the above step (4), during the arc ion plating process of depositing pure Al: the target material is a pure Al target, the arc current is 60-90A, the arc voltage is 20-30V, and the deposition time is 20-110min; the thickness of the obtained pure Al layer is 3-18μm.

[0018] In the above step (5), the annealing treatment is to place the sample in a vacuum annealing furnace, heat the annealing furnace to 950-1100°C at a heating rate of 5-10°C / min, keep it at this temperature for 1-4 hours, and then cool it to room temperature with the furnace.

[0019] Using the above method, a Pt-Hf co-modified aluminide coating was prepared on a nickel-based superalloy surface. Hf was dissolved into the coating and uniformly distributed. The interdiffusion zone between the coating and the substrate was small. Varying Ni, Pt, and Al contents could be achieved by adjusting the deposition time, depending on the desired coating phase composition. This Pt-Hf co-modified aluminide coating is used for surface protection of gas turbine blades.

[0020] The present invention has the following advantages:

[0021] 1. The Pt-Hf co-modified aluminide coating prepared by the present invention has an interdiffusion zone thickness of less than 20 μm between the coating and the substrate and has excellent high-temperature oxidation resistance.

[0022] 2. The present invention can control the chemical composition of the coating and adjust the phase composition of the coating by adjusting the electroplating deposition time and the arc ion plating deposition time.

[0023] 3. The Pt-Hf co-modified aluminide coating of the present invention can effectively alleviate the interdiffusion between the coating and the substrate during high-temperature oxidation, and reduce the thickness of the interdiffusion zone and the secondary reaction zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The cross-sectional morphology of the Ni / Pt-Hf layer.

[0025] Figure 2 This is the XRD pattern of the Pt-Hf co-modified γ / γ′ aluminide coating.

[0026] Figure 3 The cross-sectional morphology of the Pt-Hf co-modified γ / γ′ aluminide coating. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] The chemical composition of the nickel-based high-temperature alloy matrix is as follows (wt.%): Cr: 4.0%, Co: 12.0%, W: 6.0%, Al: 6.0%, Nb: 0.15%, Mo: 1.0%, Ta: 8%, Re: 5.0%, Ru: 3.0%, and the rest is Ni. The high-temperature alloy is cut into A disc-shaped specimen is cut 1 mm from one end of the specimen. Small holes for hanging specimens.

[0030] The specimens were surface treated by first grinding and chamfering them using 150#, 240#, 400#, 600#, and 800# SiC sandpaper. They were then wet-sandblasted with 200-mesh alumina pellets. Finally, the specimens were ultrasonically cleaned in deionized water, acetone, and alcohol for 15 minutes each.

[0031] The sample was pretreated by electrochemical degreasing and then activation treatment. The electrochemical degreasing process is as follows: in 5g / L NaOH solution, the substrate is used as cathode and the stainless steel plate is used as anode, and the current density is 8A / dm 2 , degreasing for 1 minute; activation process: soak the sample in 20 vol.% hydrochloric acid for 1 minute at room temperature.

[0032] The pre-treated sample is placed in the electroplating solution for Ni-Hf electroplating. The composition of the plating solution is: nickel sulfate 0.1-0.4 mol / L, citric acid 0.1-0.6 mol / L, Hf powder 5-30 g / L, ammonia water in appropriate amount, and the rest is deionized water. Among them, the particle size of Hf powder is 1-5 μm. The electroplating process is: adjust the pH of the plating solution to 9 with ammonia water, the temperature is 50 ° C, and the current density is 4A / dm 2 The thickness of the Ni-Hf layer obtained by electroplating for 20 minutes is about 17μm. Subsequently, a Pt layer is deposited on the Ni-Hf layer by electroplating. The composition of the plating solution is: [Pt(NH3)4]HPO4 is 3-8g / L, Na2HPO4 is 2-7g / L, NaOH is appropriate, and the rest is deionized water. The electroplating process is: pH 10.5, temperature 92℃, current density 0.4A / dm 2 The sample was electroplated for 120 minutes, resulting in a Pt layer with a thickness of 6 μm. The sample was then annealed in a vacuum annealing furnace. The annealing process involved heating to 800°C at a rate of 5°C / min and holding for 5 hours. This resulted in a Ni / Pt-Hf layer.

[0033] Arc ion plating was used to deposit an Al layer on the Ni / Pt-Hf layer. The Al layer had a thickness of 5 μm. The detailed arc ion plating process is shown in Table 1.

[0034] Table 1 Arc ion plating deposition process of Al layer

[0035]

[0036]

[0037] The sample with the deposited Al layer was placed in a vacuum annealing furnace, heated to 1050°C for 2 hours, and then cooled in the furnace at a heating rate of 10°C / min.

[0038] In this embodiment. Figure 1 The cross-sectional morphology of the Ni / Pt-Hf layer after annealing is shown. It can be seen that the thickness of the Ni / Pt-Hf layer is approximately 20 μm, and white Hf particles are distributed at the interface between the Ni / Pt-Hf layer and the substrate.

[0039] Figure 2 Figure 2 is the XRD pattern of the Pt-Hf co-modified γ / γ′ aluminide coating. It can be seen that the coating is composed of a γ / γ′ dual phase.

[0040] Figure 3This figure shows the cross-sectional morphology of a Pt-Hf co-modified γ / γ′ aluminide coating. The interdiffusion zone between the coating and the substrate is small, approximately 10 μm, and no TCP phase precipitation occurs. Combined with EDS results, the coating's chemical composition is 8.0% Al, 43.4% Ni, 46.0% Pt, 1.6% Co, 0.7% Cr, and 0.3% Hf (wt.%).

Claims

1. A method for preparing a Pt-Hf co-modified aluminide coating, characterized in that: The method comprises the following steps: (1) Substrate pretreatment process: The substrate was polished with 150#, 240#, 400#, 600#, and 800# SiC sandpaper respectively, and then the substrate surface was wet sandblasted with 200-mesh alumina pellets. Finally, the substrate was ultrasonically cleaned with deionized water, acetone, and alcohol for 10-20 minutes in sequence; (2) Matrix pretreatment process: first degrease the matrix with NaOH solution, then activate it with hydrochloric acid; (3) preparing a Ni / Pt-Hf layer by a process combining electroplating and vacuum heat treatment: depositing a Ni-Hf layer and a Pt layer on the surface of the pretreated substrate in sequence by electroplating; the Ni-Hf layer has a thickness of 10-45 μm, and the Pt layer has a thickness of 3-10 μm; and then performing vacuum annealing to obtain the Ni / Pt-Hf layer; (4) Arc ion plating technology is used to deposit a pure Al layer: Arc ion plating is used to deposit a pure Al layer on the Ni / Pt-Hf layer; (5) Vacuum heat treatment to obtain a Pt-Hf co-modified aluminide coating: The sample on which the Ni / Pt-Hf layer and the pure Al layer were deposited in step (4) was annealed in a vacuum annealing furnace to obtain a Pt-Hf co-modified aluminide coating.

2. The method for preparing the Pt-Hf co-modified aluminide coating according to claim 1, characterized in that: In step (1), the substrate is a nickel-based single crystal high-temperature alloy; the alloy is cut into a Φ14mm×2mm disc-shaped sample by wire cutting, and a Φ1.5mm small hole is cut 1mm away from the edge of the sample to facilitate hanging the sample during electroplating and arc ion plating.

3. The method for preparing the Pt-Hf co-modified aluminide coating according to claim 1, characterized in that: In step (2), the degreasing process is as follows: in a NaOH solution with a concentration of 5-15 g / L, the substrate is used as the cathode and the stainless steel plate is used as the anode, and the current density is 2-15 A / dm 2 , the degreasing time is 1-10min; the activation treatment process is: under room temperature, the sample is immersed in a concentration of 10-30vol.% hydrochloric acid for 1-5min.

4. The method for preparing the Pt-Hf co-modified aluminide coating according to claim 1, characterized in that: In step (3), the plating solution used for electroplating the Ni-Hf layer is composed of: 0.1-0.4 mol / L nickel sulfate, 0.1-0.6 mol / L citric acid, 5-30 g / L Hf powder, an appropriate amount of ammonia water, and the rest is deionized water; wherein the Hf powder particle size is 0.5-2 μm, the pH of the plating solution is adjusted to 8-9 by the amount of ammonia water, the electroplating temperature is 40-60 ° C, and the current density is 2-6 A / dm 2 , the plating time is 10-50min; the plating solution composition used for plating the Pt layer is: [Pt(NH3)4]HPO4 is 3-8g / L, Na2HPO4 is 2-7g / L, NaOH is appropriate, and the rest is deionized water; when electroplating the Pt layer, the pH value of the plating solution is adjusted to 9-11 by the amount of NaOH, the plating solution temperature is 90-95℃, and the current density is 0.2-0.6A / dm 2 , the electroplating time is 60-180min; the vacuum annealing treatment is to place the sample in a vacuum annealing furnace, heat the annealing furnace to 700-1000℃ at a heating rate of 3-7℃ / min, and keep it at this temperature for 3-10h, and then cool it to room temperature with the furnace.

5. The method for preparing the Pt-Hf co-modified aluminide coating according to claim 1, characterized in that: In step (4), during the arc ion plating process of depositing pure Al: the target material is a pure Al target, the arc current is 60-90A, the arc voltage is 20-30V, and the deposition time is 20-110min; the thickness of the obtained pure Al layer is 3-18μm.

6. The method for preparing the Pt-Hf co-modified aluminide coating according to claim 1, characterized in that: In step (5), the annealing treatment is to place the sample in a vacuum annealing furnace, heat the annealing furnace to 950-1100°C at a heating rate of 5-10°C / min, keep it at this temperature for 1-4 hours, and then cool it to room temperature with the furnace.

7. A Pt-Hf co-modified aluminide coating prepared by the method according to any one of claims 1 to 6, characterized in that: Different Ni, Pt, and Al contents are obtained by adjusting the deposition time according to the needs of the coating phase composition; the Pt-Hf co-modified aluminide coating is used for surface protection of gas turbine blades.

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