A method for preparing a nickel platinum aluminum coating by co-deposition of nickel and aluminum in an ionic liquid

Abstract

The application belongs to the field of thermal barrier coatings, and particularly relates to a method for preparing a nickel platinum aluminum coating by co-deposition of nickel and aluminum in an ionic liquid. The method comprises the following steps: surface treatment of a metal substrate; electrodepositing at least one layer of platinum or platinum-containing alloy on the metal substrate after the surface treatment; annealing the platinum or platinum-containing alloy layer; preparing an ionic liquid and dissolving nickel and aluminum salts in the ionic liquid to form an electroplating solution for co-deposition; co-depositing a nickel aluminum alloy on the platinum or platinum-containing alloy layer by electrodepositing in the electroplating solution; and heat treating the co-deposited nickel aluminum alloy layer to form a coating with oxidation resistance and mechanical properties; the heat treatment temperature is lower than a temperature at which the metal substrate is significantly degraded; in order to overcome the decrease in mechanical properties caused by element interdiffusion during high-temperature oxidation, the method of co-deposition of nickel and aluminum in an ionic liquid combined with low-temperature heat treatment is used to realize a single beta-(Ni, Pt) Al phase without an interdiffusion zone, and the oxidation resistance and mechanical properties of the platinum aluminum coating are improved.

Description

Technical Field

[0001] This invention belongs to the field of thermal barrier coating technology, specifically relating to a method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid. Background Technology

[0002] Platinum-aluminum coatings are currently a common thermal barrier coating adhesive layer system, and their preparation methods mainly include electroplating of platinum layers and vapor-phase aluminizing (such as embedding aluminizing and chemical vapor deposition). Regardless of the aluminizing method, based on the different diffusion mechanisms during the preparation process, they can be divided into low-temperature high-activity aluminizing (inward growth type) and high-temperature low-activity aluminizing (outward growth type). In the preparation process of inward growth type coatings, the coating formation mechanism is through the inward diffusion of aluminum atoms and their reaction with nickel atoms in the substrate.

[0003] Generally, the coating consists of three layers: an outer and middle layer composed of β-NiAl, with the outer layer containing numerous fine precipitates and the middle layer being the precipitated phase; and an inner interdiffusion region containing numerous complex precipitates of the β matrix phase. In the preparation of outward-growing coatings, the coating formation mechanism involves outward growth from the substrate alloy surface as the initial interface. The coating consists of two layers: an outer layer composed of β-NiAl, and an inner interdiffusion region with a composition similar to that of an inward-growing coating. Regardless of the aluminizing method, in addition to obtaining the outermost β-(Ni,Pt)Al layer, an interdiffusion region is also formed, which is determined by the phase diagram of nickel and aluminum (see Appendix). Figure 1 It is determined by the process. Before β-NiAl is produced by thermal diffusion, β-NiAl3 and γ-Ni2Al3 are inevitably formed.

[0004] Studies have shown that a large amount of residual NiAl3 and Ni2Al3 remain in the interdiffusion region, while aluminum diffuses very rapidly in Ni2Al3. Aluminum diffusion in the nickel-aluminum intermetallic compound follows the Kirkendall effect, where the separation boundary between the two different phases coincides with the Kirkendall plane. Since the Kirkendall plane is significantly farther from the NiAl layer, the intrinsic diffusion coefficient of aluminum in Ni2Al3 is significantly greater than that of nickel in Ni2Al3, making aluminum a key diffusing element leading to the formation of Ni2Al3. During high-temperature oxidation, aluminum diffusion causes the coating to transform from aluminum-rich β-NiAl to aluminum-poor γ'-Ni3Al, until it becomes the oxidation-resistant γ-Ni phase. With the continuous consumption of aluminum, the coating undergoes severe degradation. The β-to-γ' transformation produces volume shrinkage, and the areas where phase transformation occurs first at the grain boundaries form depressions, while the surrounding areas bulge, forming wrinkles. Furthermore, refractory elements precipitated in the matrix also diffuse outwards, forming volatile oxides such as MoO3 on the coating surface. These oxides can damage the adhesion of the thermally grown layer, causing cracking or even peeling.

[0005] Platinum-aluminum coatings prepared by diffusion all have interdiffusion regions. During the subsequent high-temperature oxidation process, a secondary reaction region containing needle-like TCP phases will be generated below the interdiffusion region. The needle-like structure will cause local stress concentration, resulting in a significant decrease in the high-temperature mechanical properties of the substrate (especially high-temperature deformation and fatigue). Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] This invention addresses the above-mentioned problems by proposing a method for preparing nickel-platinum-aluminum coatings by nickel-aluminum co-deposition in ionic liquids. The aim is to overcome the decrease in mechanical properties caused by element interdiffusion during high-temperature oxidation.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides a method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid, comprising the following steps:

[0010] Surface treatment of the metal substrate;

[0011] At least one layer of platinum or a platinum-containing alloy is electrodeposited on a metal substrate after surface treatment;

[0012] Anneal the platinum or platinum-containing alloy layer;

[0013] An ionic liquid was prepared, and nickel and aluminum salts were dissolved in it to form an electroplating solution for co-deposition.

[0014] In the electroplating solution, a nickel-aluminum alloy is co-deposited on a platinum or platinum-containing alloy layer by electrodeposition.

[0015] The co-deposited nickel-aluminum alloy layer is heat-treated to form a coating with oxidation resistance and mechanical properties;

[0016] The heat treatment temperature is lower than the temperature at which the metal matrix will significantly degrade.

[0017] Furthermore, the surface treatment steps are selected from one or more combinations of mechanical grinding, chemical soaking, electrolytic polishing, and ultrasonic cleaning.

[0018] Furthermore, mechanical polishing includes polishing sequentially with gauze paper of different grit sizes, including 120#, 200#, 400#, 800#, and 1200# gauze paper; ultrasonic cleaning includes ultrasonic cleaning in a 60℃ NaOH aqueous solution and a propanol solution, wherein the concentration of the NaOH aqueous solution in the cleaning step is 5-15 g / L.

[0019] Furthermore, the plating solution used in the plating plating step is tetraamine hydrogen phosphate platinum alloy, containing 5 g / L of platinum. The solution has a pH of 7.5-8 at 20°C. During electroplating, the pH is adjusted and the solution is heated to 92-95°C. The pH of the plating solution in the plating plating step is adjusted to 10.0-10.6 by adding 10% NaOH. The electroplating current ranges from 0.2-0.7 A / dm³. 2 .

[0020] Furthermore, the annealing conditions in the annealing process are: a vacuum degree of 10... -6 The process involves maintaining a temperature of 1100℃ for 3-5 hours and a pressure of mbar.

[0021] Further, the steps for preparing the ionic liquid include: slowly adding anhydrous AlCl3 to EMI C in small amounts multiple times, with a molar ratio of AlCl3 to EMI C of 2:1, while continuously stirring; after the AlCl3 is completely dissolved, adding 99.99% high-purity aluminum wire to remove impurities, and letting it stand for more than 24 hours to obtain the AlCl3-EMI C ionic liquid; and adding anhydrous NiCl2 to it to a concentration of 12-15 mol / L for use in nickel-aluminum co-deposition. All reagents in the ionic liquid preparation steps must be dried in an environment with a water and oxygen content of less than 0.1 ppm, and the preparation and use processes must be completed in a glove box. The AlCl3-EMI C ionic liquid is a relatively mature ionic liquid system with advantages such as adjustable Lewis acidity, a wide electrochemical window, and high conductivity, and has been widely studied in the field of electrodeposition.

[0022] Furthermore, the nickel-aluminum co-deposition step is carried out under inert gas atmosphere, waterproof and oxidation-resistant operating conditions.

[0023] Furthermore, the nickel-aluminum co-deposition step includes: heating an ionic liquid containing NiCl2 to completely dissolve NiCl2 under a dry argon atmosphere at a pressure of 5-20 mbar, then cooling it to 65±5℃, using a cathode current density of 6-8 mA / cm². 2 Nickel-aluminum co-deposition was performed for 30-60 minutes.

[0024] Furthermore, the coating obtained by heat treatment is a β-(Ni,Pt)Al phase.

[0025] Furthermore, the temperature in the heat treatment step is 400°C.

[0026] (III) Beneficial Effects

[0027] The present invention provides a method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid, which has the following beneficial effects:

[0028] 1. Elimination of interdiffusion zones in platinum-aluminum coatings: Traditional methods for preparing platinum-aluminum coatings generate interdiffusion zones, mainly composed of β-NiAl3 and γ-Ni2Al3. Aluminum diffuses rapidly within these zones, eventually causing the coating to transform into the non-oxidizing γ-Ni phase. With continuous aluminum consumption, the coating undergoes severe degradation. The β-to-γ' phase transition causes volume shrinkage, resulting in depressions at the grain boundaries where the phase transition occurs first, followed by bulging and wrinkling in the surrounding areas, ultimately leading to coating system failure. However, coatings prepared via nickel-aluminum co-deposition in ionic liquids fundamentally eliminate the formation of β-NiAl3 and γ-Ni2Al3, reducing the aluminum diffusion rate and extending the coating's lifespan.

[0029] 2. Improved high-temperature oxidation resistance of high-temperature alloy systems with nickel-platinum-aluminum bonding layers: High-temperature cyclic oxidation tests show that platinum-aluminum coatings without interdiffusion zones exhibit more than 50% better thermal cycling performance than platinum-aluminum coatings with interdiffusion zones prepared using conventional methods. For example, during high-temperature oxidation cycling at 1100°C, the conventional chemical vapor deposition coating showed an oxidation weight gain of 1.62 mg / cm³ after 800 hours. 2 The coating prepared by ionic liquid electroplating showed a weight gain of only 0.78 mg / cm³ under the same conditions. 2 .

[0030] 3. Improves the low aluminum source utilization rate in traditional aluminizing methods: Compared with traditional aluminizing methods (such as embedding aluminizing and chemical vapor deposition), ionic liquid electroplating has a high aluminum source utilization rate. Ionic liquids can be reused; more than 90% of the aluminum in AlCl3 is deposited on the platinum surface in the form of NiAl, with a small portion existing in the ionic liquid as complexes. In contrast, the aluminum utilization rate of embedding aluminizing is only 10-20%, and methods such as chemical vapor deposition are slightly higher, but rarely exceed 50%. Most of the aluminum is mixed with unreacted gases and treated as exhaust gas, resulting in waste. Attached Figure Description

[0031] Figure 1 This is a nickel-aluminum binary phase diagram disclosed in the background art of this application.

[0032] Figure 2 The images show the XRD patterns of the three coatings obtained in the embodiments of this application.

[0033] Figure 3 This is a cross-sectional schematic diagram of a coating obtained according to Embodiment 1 of this application.

[0034] Figure 4 This is a cross-sectional schematic diagram of a coating obtained according to Embodiment 2 of this application.

[0035] Figure 5 This is a cross-sectional schematic diagram of a coating obtained according to Embodiment 3 of this application. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] 1) Pretreatment: The test pieces were polished on 120#, 200#, 400#, 800# and 1200# gauze paper in sequence, and then ultrasonically cleaned in 12g / L NaOH aqueous solution and propanol solution at 60℃ for 10 minutes in sequence.

[0039] 2) Platinum plating: The plating solution used for platinum plating is tetraamine hydrogen phosphate platinum, containing 5 g / L of platinum, with a pH of 7.5 at 20°C. During platinum plating, the solution needs to be heated to 95°C, and the pH is adjusted to 10.5 using 10% NaOH. The plating current is 0.5 A / dm³. 2 .

[0040] 3) Annealing homogenization: The specimens with the platinum layer need to be vacuum annealed at a vacuum degree of 10. -6 mbar, temperature maintained at 1100℃ for 3.5 hours.

[0041] 4) Preparation of ionic liquids: All reagents required in the experiment needed to be dried for at least 24 hours in an environment with an oxygen content of less than 0.1 ppm. The preparation and use of the reagents were all performed in a glove box. During preparation, anhydrous AlCl3 was slowly added to EMIC (1-methyl-3-ethylimidazole chloride, 99% purity) in small, repeated additions, with a molar ratio of AlCl3 to EMIC of 2:1, while continuously stirring. After the AlCl3 was completely dissolved, high-purity aluminum wire (99.99%) was added to remove impurities, and the solution was left to stand for at least 24 hours to obtain a slightly yellow, oily liquid. For electrodeposition of nickel-aluminum alloys, anhydrous NiCl2 was added to the prepared solution and stirred until dissolved. The concentration of NiCl2 added was 13 mol / L.

[0042] 4) Nickel-aluminum co-deposition: Deposition still needs to be carried out in a glove box. The gas environment is dry argon gas at a pressure of 15 mbar. After repeated circulation of argon gas, the water and oxygen content in the glove box environment is ensured to be less than 0.1 ppm.

[0043] Before electroplating, the ionic liquid needs to be heated to 80℃ to completely dissolve the NiCl2, and then the liquid is cooled. The electroplating temperature is 65±5℃, and the power supply used is a KEYSIGHT N5745A. The cathode current density is 6mA / cm². 2 The deposition time was 30 minutes. After electrodeposition, the sample was quickly removed, cleaned with ethanol, and dried with nitrogen.

[0044] 5) Low-temperature heat treatment: Heat treatment at 400℃ in a vacuum for 2 hours forms a uniform NiAl phase.

[0045] The resulting coating is as follows Figure 2 As shown, the coating is a single-phase β-(Ni,Pt)Al with a thickness of 16-20 μm, and the cross-section is as follows. Figure 3 As shown.

[0046] Example 2

[0047] 1) Pretreatment: The test pieces were polished on 120#, 200#, 400#, 800# and 1200# gauze paper in sequence, and then ultrasonically cleaned in 12g / L NaOH aqueous solution and propanol solution at 60℃ for 10 minutes in sequence.

[0048] 2) Platinum plating: The plating solution used for platinum plating is tetraamine hydrogen phosphate platinum, containing 5 g / L of platinum, with a pH of 7.5 at 20°C. During platinum plating, the solution needs to be heated to 95°C, and the pH is adjusted to 10.5 using 10% NaOH. The plating current is 0.5 A / dm³. 2 .

[0049] 3) Annealing homogenization: The specimens with the platinum layer need to be vacuum annealed at a vacuum degree of 10. -6 mbar, temperature maintained at 1100℃ for 3.5 hours.

[0050] 4) Preparation of ionic liquids: All reagents required in the experiment needed to be dried for at least 24 hours in an environment with an oxygen content of less than 0.1 ppm. The preparation and use of the reagents were all performed in a glove box. During preparation, anhydrous AlCl3 was slowly added to EMIC (1-methyl-3-ethylimidazole chloride, 99% purity) in small, repeated additions, with a molar ratio of AlCl3 to EMIC of 2:1, while continuously stirring. After the AlCl3 was completely dissolved, high-purity aluminum wire (99.99%) was added to remove impurities, and the solution was left to stand for at least 24 hours to obtain a slightly yellow, oily liquid. For electrodeposition of nickel-aluminum alloys, anhydrous NiCl2 was added to the prepared solution and stirred until dissolved. The concentration of NiCl2 added was 13 mol / L.

[0051] 4) Nickel-aluminum co-deposition: Deposition still needs to be carried out in a glove box. The gas environment is dry argon gas at a pressure of 5 mbar. After repeated circulation of argon gas, the water and oxygen content in the glove box environment is ensured to be less than 0.1 ppm.

[0052] Before electroplating, the ionic liquid needs to be heated to 80℃ to completely dissolve the NiCl2, and then the liquid is cooled. The electroplating temperature is 65±5℃, and the power supply used is a KEYSIGHT N5745A. The cathode current density is 6mA / cm². 2 The deposition time was 40 minutes. After electrodeposition, the sample was quickly removed, cleaned with ethanol, and dried with nitrogen.

[0053] 5) Low-temperature heat treatment: Heat treatment at 400℃ in a vacuum for 2.5 hours forms a uniform NiAl phase.

[0054] The resulting coating is as follows Figure 2 As shown, the coating is a single-phase β-(Ni,Pt)Al with a thickness of 22-25 μm, and the cross-section is as follows. Figure 4 As shown.

[0055] Example 3

[0056] 1) Pretreatment: The test pieces were polished on 120#, 200#, 400#, 800# and 1200# gauze paper in sequence, and then ultrasonically cleaned in 12g / L NaOH aqueous solution and propanol solution at 60℃ for 10 minutes in sequence.

[0057] 2) Platinum plating: The plating solution used for platinum plating is tetraamine hydrogen phosphate platinum, containing 5 g / L of platinum, with a pH of 7.5 at 20°C. During platinum plating, the solution needs to be heated to 95°C, and the pH is adjusted to 10.5 using 10% NaOH. The plating current is 0.5 A / dm³. 2 .

[0058] 3) Annealing homogenization: The specimens with the platinum layer need to be vacuum annealed at a vacuum degree of 10. -6 mbar, temperature maintained at 1100℃ for 3.5 hours.

[0059] 4) Preparation of ionic liquids: All reagents required in the experiment needed to be dried for at least 24 hours in an environment with an oxygen content of less than 0.1 ppm. The preparation and use of the reagents were all performed in a glove box. During preparation, anhydrous AlCl3 was slowly added to EMIC (1-methyl-3-ethylimidazole chloride, 99% purity) in small, repeated additions, with a molar ratio of AlCl3 to EMIC of 2:1, while continuously stirring. After the AlCl3 was completely dissolved, high-purity aluminum wire (99.99%) was added to remove impurities, and the solution was left to stand for at least 24 hours to obtain a slightly yellow, oily liquid. For electrodeposition of nickel-aluminum alloys, anhydrous NiCl2 was added to the prepared solution and stirred until dissolved. The concentration of NiCl2 added was 13 mol / L.

[0060] 4) Nickel-aluminum co-deposition: Deposition still needs to be carried out in a glove box. The gas environment is dry argon gas at a pressure of 20 mbar. After repeated circulation of argon gas, the water and oxygen content in the glove box environment is ensured to be less than 0.1 ppm.

[0061] Before electroplating, the ionic liquid needs to be heated to 80℃ to completely dissolve the NiCl2, and then the liquid is cooled. The electroplating temperature is 65±5℃, and the power supply used is a KEYSIGHT N5745A. The cathode current density is 6mA / cm². 2 The deposition time was 50 minutes. After electrodeposition, the sample was quickly removed, cleaned with ethanol, and dried with nitrogen.

[0062] 5) Low-temperature heat treatment: Heat treatment at 400℃ in a vacuum for 3 hours forms a uniform NiAl phase.

[0063] The resulting coating is as follows Figure 2 As shown, the coating is a single-phase β-(Ni,Pt)Al with a thickness of 28-33 μm, and the cross-section is as follows. Figure 5 As shown.

[0064] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid, characterized in that, Includes the following steps: Surface treatment of the metal substrate; At least one layer of platinum or a platinum-containing alloy is electrodeposited on a metal substrate after surface treatment; Anneal the platinum or platinum-containing alloy layer; An ionic liquid was prepared, and nickel and aluminum salts were dissolved in it to form an electroplating solution for co-deposition. In the electroplating solution, a nickel-aluminum alloy is co-deposited on a platinum or platinum-containing alloy layer by electrodeposition. The co-deposited nickel-aluminum alloy layer is heat-treated to form a coating with oxidation resistance and mechanical properties; The heat treatment temperature is lower than the temperature at which the metal substrate will significantly degrade; the coating obtained by the heat treatment is a β-(Ni,Pt)Al phase; and the temperature in the heat treatment step is 400°C.

2. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 1, characterized in that, The surface treatment steps are selected from one or more combinations of mechanical grinding, chemical soaking, electrolytic polishing, and ultrasonic cleaning.

3. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 2, characterized in that, Mechanical polishing includes polishing with different grit sizes of paper, including 120#, 200#, 400#, 800#, and 1200#. Ultrasonic cleaning includes ultrasonic cleaning in a 60℃ NaOH aqueous solution and a propanol solution, wherein the concentration of the NaOH aqueous solution in the cleaning step is 5-15 g / L.

4. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 1, characterized in that, The plating solution used in the platinum plating step is tetraamine hydrogen phosphate platinum, containing 5 g / L of platinum. The pH of the solution is 7.5-8 at 20℃. During electroplating, the pH is adjusted and the solution is heated to 92-95℃. The pH of the plating solution in the platinum plating step is adjusted to 10.0-10.6 by adding 10% NaOH. The electroplating current range is 0.2-0.7 A / dm³. 2 .

5. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 1, characterized in that, The annealing conditions in the annealing process are: a vacuum degree of 10... -6 The process involves maintaining a temperature of 1100℃ for 3-5 hours and a pressure of mbar.

6. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 1, characterized in that, The steps for preparing the ionic liquid include: slowly adding anhydrous AlCl3 to EMIC in small amounts multiple times, with a molar ratio of AlCl3 to EMIC of 2:1, while continuously stirring; after the AlCl3 is completely dissolved, adding 99.99% high-purity aluminum wire to remove impurities, and letting it stand for more than 24 hours to obtain the AlCl3-EMIC ionic liquid, and then adding anhydrous NiCl2 to it to a concentration of 12-15 mol / L for use in nickel-aluminum co-deposition. All reagents in the ionic liquid preparation steps must be dried in an environment with a water and oxygen content of less than 0.1 ppm, and the preparation and use processes must be completed in a glove box.

7. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 1, characterized in that, The nickel-aluminum co-deposition step was carried out under inert gas atmosphere, waterproof and oxidation-proof operating conditions.

8. The method for preparing a nickel-platinum-aluminum coating by nickel-aluminum co-deposition in an ionic liquid according to claim 7, characterized in that, The nickel-aluminum co-deposition step includes: heating an ionic liquid containing NiCl2 to completely dissolve NiCl2 under a dry argon atmosphere at a pressure of 5-20 mbar, then cooling it to 65±5℃, using a cathode current density of 6-8 mA / cm². 2 Nickel-aluminum co-deposition was performed for 30-60 minutes.

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