A Pt-Al coating and preparation method thereof

Abstract

The present invention belongs to the technical field of high-temperature coatings, and specifically relates to a Pt-Al coating and a preparation method thereof. The present invention uses nickel grit for sandblasting, which is difficult to embed into the substrate during the sandblasting process, thereby preventing it from becoming a source of fatigue cracks and reducing the fatigue performance of the coating, while also ensuring the continuity of the coating as a whole. Furthermore, the composition of the nickel grit is identical to the main element composition of the nickel-based high-temperature alloy. Even if a small amount of nickel grit remains, it can diffuse into the substrate during the subsequent coating heat treatment process and will not remain as a heterogeneous phase that destroys the continuity of the substrate, thereby preventing the coating from degrading its antioxidant properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature coatings, and in particular relates to a Pt-Al coating and a preparation method thereof. Background Art

[0002] High-temperature alloys, the most commonly used materials for aircraft engine blades, are exposed to extremely high temperatures during service. To protect these alloys from oxidation during use, a high-Al content, anti-oxidation coating, also known as a metal bond coat, is often applied to their surface. This coating forms a dense aluminum oxide film at high temperatures to protect the underlying material. Currently, Pt-Al coatings within these anti-oxidation coatings are a key research area in the field of high-temperature protective coatings.

[0003] Preparing a Pt-Al coating on a high-temperature alloy substrate requires sandblasting before Pt electroplating. Since electroplating relies on metal cations receiving electrons on the substrate surface to form a metallic element, which then mechanically bonds to the substrate, the substrate surface must not only have good conductivity but also a certain degree of roughness to bond with the coating. Excessive roughness results in uneven coating deposition and numerous pores between the coating and the substrate. Insufficient roughness weakens the coating's bond to the substrate and makes it susceptible to flaking due to accumulated internal stress during deposition. Therefore, selecting an appropriate roughness for electroplating is crucial.

[0004] Traditional sandblasting processes usually use corundum sand as the sandblasting raw material. Although corundum sand has the advantage of low cost, since the hardness of corundum sand is higher than that of the high-temperature alloy substrate, it will be embedded in the substrate during the sandblasting process. The residual corundum sand has a different composition from the coating. As a heterogeneous phase, it will destroy the overall continuity of the electroplated coating and thus reduce the coating's antioxidant properties. Moreover, the residual corundum sand, as a hard phase, will become the source of fatigue crack initiation and have a harmful effect on the fatigue performance of the coating. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a Pt-Al coating. The method provided by the present invention can further improve the oxidation resistance of the Pt-Al coating and extend the fatigue life of the Pt-Al coating.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a Pt-Al coating, comprising the following steps:

[0008] After polishing the nickel-based high-temperature alloy, sandblasting is performed to obtain a pre-treated substrate; the medium used in the sandblasting is nickel sand;

[0009] Electroplating and depositing a Pt layer on the surface of the pretreated substrate, and sequentially performing dehydrogenation and vacuum annealing to obtain a substrate with a Pt layer deposited thereon;

[0010] The surface of the substrate on which the Pt layer is deposited is subjected to aluminizing treatment to obtain the Pt-Al coating.

[0011] Preferably, the particle size of the nickel sand is 120-240 meshes.

[0012] Preferably, the sandblasting air flow pressure during the sandblasting process is ≥0.5 MPa.

[0013] Preferably, the sandblasting treatment lasts for 1 to 3 minutes.

[0014] Preferably, the conditions for electroplating the Pt layer are: temperature of 80-90°C, current density of 1-5 A / dm 2 , the electroplating time is 1 to 60 minutes.

[0015] Preferably, the dehydrogenation temperature is 500-700° C., the heating rate to the dehydrogenation temperature is 5-10° C. / min, and the holding time is 5-7 h.

[0016] Preferably, the vacuum annealing temperature is 1000-1100° C., the heating rate to the vacuum annealing temperature is 5-10° C. / min, and the holding time is 2-4 h.

[0017] Preferably, the temperature of the aluminizing treatment is 800-1000° C., and the holding time is 3-5 hours.

[0018] The present invention also provides a Pt-Al coating prepared by the preparation method described in the above technical solution, wherein the thickness of the Pt-Al coating is 45 to 50 μm.

[0019] Preferably, the mass content of the Pt element in the Pt-Al coating is 20-25%; the mass content of the Al element is 25-30%.

[0020] The present invention provides a method for preparing a Pt-Al coating, comprising the following steps: polishing a nickel-based high-temperature alloy and then sandblasting it to obtain a pretreated substrate; the medium used in the sandblasting is nickel sand; electroplating and depositing a Pt layer on the surface of the pretreated substrate, sequentially performing dehydrogenation and vacuum annealing to obtain a substrate deposited with the Pt layer; and aluminizing the surface of the substrate deposited with the Pt layer to obtain the Pt-Al coating. The present invention uses nickel sand for sandblasting, which is difficult to embed into the substrate during the sandblasting process, thereby preventing it from becoming a source of fatigue crack initiation and reducing the fatigue performance of the coating, and also ensuring the continuity of the entire coating. Furthermore, the composition of the nickel sand is the same as the main element composition of the nickel-based high-temperature alloy. Even if a small amount of nickel sand remains, it can diffuse into the substrate during the subsequent coating heat treatment process and will not remain as a heterogeneous phase that destroys the continuity of the substrate, thereby preventing the coating from degrading its antioxidant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a SEM image of the cross section of the Pt-Al coating obtained in Example 1;

[0022] Figure 2 is a SEM image of the cross section of the Pt-Al coating obtained in Comparative Example 1;

[0023] Figure 3 These are the oxidation resistance test curves of the Pt-Al coatings obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing a Pt-Al coating, comprising the following steps:

[0025] After polishing the nickel-based high-temperature alloy, sandblasting is performed to obtain a pre-treated substrate; the medium used in the sandblasting is nickel sand;

[0026] Electroplating and depositing a Pt layer on the surface of the pretreated substrate, and performing vacuum annealing to obtain a substrate with a Pt layer deposited thereon;

[0027] The surface of the substrate on which the Pt layer is deposited is subjected to aluminizing treatment to obtain the Pt-Al coating.

[0028] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0029] The present invention grinds the nickel-based high-temperature alloy and then performs sandblasting to obtain a pretreated substrate; the medium used in the sandblasting is nickel sand.

[0030] The present invention does not specifically limit the type of nickel-based superalloy; any alloy known to those skilled in the art may be used. In a specific embodiment of the present invention, the nickel-based superalloy is preferably an IC21 alloy; in terms of mass percentage, the IC21 alloy preferably comprises 6.5-8.2% Al, 1.0-4.5% Ta, 7-11% Mo, 0.8-1.8% Re, 1.3-3.2% Cr, and the balance Ni.

[0031] In the present invention, the polishing process is preferably: polishing is performed using 60#, 240#, 600#, and 1000# sandpaper in sequence; the polishing time for each type of sandpaper is preferably 3 to 5 minutes; and the total polishing time is preferably 12 to 20 minutes. During the polishing process, the present invention also preferably includes chamfering the edges of the nickel-based high-temperature alloy. The present invention does not specifically limit the chamfering process; it can be performed using methods well known to those skilled in the art. In the present invention, polishing can remove the non-conductive surface oxide film, making the surface roughness uniform.

[0032] In the present invention, the particle size of the nickel sand is preferably 120-240 mesh. In the present invention, the airflow pressure during the sandblasting process is preferably ≥0.5 MPa, more preferably 0.5-1 MPa. In the present invention, the sandblasting time is preferably 1-3 minutes. In the present invention, by controlling the airflow pressure during the sandblasting process, the surface roughness of the nickel-based high-temperature alloy is ensured to ensure a strong bond between the coating and the substrate.

[0033] After the sandblasting, the present invention also preferably includes ultrasonically washing the obtained substrate; the ultrasonic washing time is preferably 10 to 15 minutes. In the present invention, ultrasonic washing can remove residual sand particles on the surface to prevent the sand particles from affecting subsequent electroplating.

[0034] In the present invention, the surface roughness of the pretreated substrate is preferably 3 to 5 μm.

[0035] After obtaining the pretreated substrate, the present invention deposits a Pt layer on the surface of the pretreated substrate by electroplating, and performs vacuum annealing to obtain a substrate with the Pt layer deposited thereon.

[0036] In the present invention, the conditions for electroplating the Pt layer preferably include: a temperature of 80 to 90°C, a current density of 1 to 5 A / dm 2 , the electroplating time is 1 to 60 minutes.

[0037] In the present invention, the process of electroplating and depositing the Pt layer preferably includes: using the platinum titanium mesh as the anode to connect the positive electrode of the constant current voltage source, using the pretreated substrate as the cathode to connect the negative electrode, placing the pretreated substrate in the electroplating solution parallel to the platinum titanium mesh and maintaining a certain distance, and performing electroplating after setting the electroplating parameters.

[0038] In the present invention, the electroplating solution preferably comprises a diammonium nitrite platinum salt solution; the concentration of the diammonium nitrite platinum salt solution is preferably 8 to 10 g / L. In the present invention, the distance between the pretreated substrate and the platinum titanium mesh is preferably 20 to 30 mm.

[0039] In the present invention, the temperature of the vacuum annealing is preferably 1000-1100°C, the heating rate to the vacuum annealing temperature is preferably 5-10°C / min; the time is preferably 2-4h; the vacuum degree is preferably 1.0×10 -4 ~1.0×10 - 3 After the vacuum annealing, the present invention further preferably includes cooling the obtained substrate to room temperature in a furnace. In the present invention, the vacuum annealing is preferably performed in a vacuum heat treatment furnace.

[0040] In the present invention, the thickness of the Pt layer is preferably 3 to 5 μm.

[0041] After obtaining the substrate with the Pt layer deposited thereon, the present invention performs aluminizing treatment on the surface of the substrate with the Pt layer deposited thereon to obtain the Pt-Al coating.

[0042] In the present invention, the conditions of the aluminizing treatment preferably include: an aluminizing temperature of 800 to 1000°C, a heating rate of 5 to 10°C / min to the aluminizing temperature, an aluminizing time of 3 to 5 hours, a vacuum degree of 1.0×10 -4 ~1.0×10 - 3 Pa.

[0043] The present invention has no particular limitation on the aluminizing process, and any method known to those skilled in the art may be used.

[0044] The present invention also provides a Pt-Al coating prepared by the preparation method described in the above technical solution, wherein the Pt-Al coating has a thickness of 45 to 50 μm. In the present invention, the Pt-Al coating preferably has a Pt content of 20 to 25% by weight and an Al content of 25 to 30% by weight.

[0045] To further illustrate the present invention, a Pt-Al coating provided by the present invention, its preparation method and application are described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] A nickel-based high-temperature alloy of grade IC21 is selected, which comprises, by mass percentage, 8.0% Al, 2.0% Ta, 7.0% Mo, 1.0% Re, 3.0% Cr and the balance Ni;

[0048] The nickel-based high-temperature alloy was polished with 60#, 240#, 600#, and 1000# sandpaper in sequence for a total of 20 minutes. The polished substrate was then sandblasted with 120-mesh nickel sand at a blasting pressure of 0.5 MPa for 2 minutes. The substrate was then ultrasonically washed for 10 minutes to obtain a pretreated substrate with a surface roughness of 3 μm.

[0049] The platinum titanium mesh was used as the anode to connect to the positive electrode of the constant current voltage source, and the pretreated substrate was used as the cathode to connect to the negative electrode. The pretreated substrate was placed in a 10 g / L nitrite diammonium platinum salt solution parallel to the platinum titanium mesh and kept 30 mm apart. The current was 1 A / dm 2 The electroplating treatment was carried out under the conditions of 90 ° C for 20 min on both sides; the electroplated substrate was then placed in a vacuum heat treatment furnace at a vacuum degree of 1.0×10 -3 Pa, the temperature was raised to 1040°C at a heating rate of 10°C / min for vacuum annealing, the holding time was 2 hours, and then the substrate was cooled to room temperature to obtain a substrate with a Pt layer deposited thereon, wherein the Pt layer had a thickness of 3 μm;

[0050] The substrate with the Pt layer deposited was subjected to aluminizing treatment. The specific process was as follows: chemical vapor deposition aluminizing with a vacuum degree of 1.0×10 -3 Pa, the aluminizing temperature is 960°C, the heating rate is 10°C / min, and the aluminizing time is 4h to obtain the Pt-Al coating. The thickness of the Pt-Al coating is 45μm, wherein the mass content of the Pt element is 23.0%; the mass content of the Al element is 28.0%.

[0051] Comparative Example 1

[0052] A Pt-Al coating was prepared in the same manner as in Example 1, except that corundum sand was used instead of nickel sand for sand blasting.

[0053] Performance Testing

[0054] Test Example 1

[0055] The cross sections of the Pt-Al coatings obtained in Example 1 and Comparative Example 1 were examined by scanning electron microscopy. Figures 1-2 As shown, Figure 1 For Example 1, Figure 2 For comparative example 1, Figures 1-2 It can be seen that the internal defects of the Pt-Al coating obtained by using nickel sand as the sandblasting raw material are far less than those of the Pt-Al coating obtained by using corundum sand as the sandblasting raw material. Since the hardness of corundum sand is higher than that of the high-temperature alloy substrate, it will be embedded in the substrate during the sandblasting process. The residual corundum sand has a different composition from that of the coating. As a heterogeneous phase, it will destroy the overall continuity of the electroplated coating. The use of nickel sand as the sandblasting raw material has the following reasons: first, the hardness of nickel sand is softer than that of the high-temperature alloy substrate, and it is difficult to embed into the substrate during the sandblasting process, which can ensure the continuity of the overall coating; second, the composition of nickel sand is the same as the main element composition of nickel-based high-temperature alloy. Even if a small amount of nickel sand remains, it can diffuse into the substrate during the subsequent coating heat treatment process, and will not remain as a heterogeneous phase to destroy the continuity of the substrate.

[0056] Test Example 2

[0057] The oxidation resistance of the Pt-Al coatings obtained in Example 1 and Comparative Example 1 was tested according to the test standard HB5258-2000. The unit area oxidation weight gain curve of the samples after 100 hours of oxidation resistance test was shown in FIG. Figure 3 As shown, Coating / Ni represents Example 1, Coating / Al2O3 represents Comparative Example 1, and the test results are shown in Table 1;

[0058] Table 1 Test results of the oxidation resistance of the Pt-Al coatings obtained in Example 1 and Comparative Example 1

[0059] <![CDATA[Example 1 (mg / cm 2 )]]> <![CDATA[Comparative Example 1 (mg / cm 2 )]]> 0h 0 0 20h 0.292 0.324 40h 0.399 0.443 60h 0.471 0.522 80h 0.539 0.599 100h 0.597 0.663

[0060] from Figure 3 As can be seen from Table 1, the Pt-Al coating obtained by using nickel sand as the spraying medium has less oxidation weight gain per unit area and better oxidation resistance.

[0061] Test Example 3

[0062] High cycle fatigue tests were performed on the Pt-Al coatings obtained in Example 1 and Comparative Example 1 under different temperature / stress conditions;

[0063] The test standard is HB5153-1996, the environment is air, the test machine is QBWP-10000 rotary bending fatigue testing machine, the specimen type Kt=1, the test speed is 5000r / min, and the number of cycles is more than 10 7 The experiment was then stopped;

[0064] The high temperature high cycle fatigue test parameters are designed as follows: 700℃ / 425Mpa. The experimental results are as follows: the high cycle fatigue life of the test sample of comparative example 1 is 3.06×10 6 The high cycle fatigue life of the test sample of Example 1 is 3.37×10 6 The fatigue life of the Pt-Al coating obtained by the preparation method provided by the present invention is improved by about 10% compared with the coating sample prepared by using corundum sand as the sandblasting raw material for pre-treatment.

[0065] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Pt-Al coating, characterized in that: The steps are: After polishing the nickel-based high-temperature alloy, sandblasting is performed to obtain a pretreated substrate; the medium used in the sandblasting is nickel sand; the sandblasting airflow pressure during the sandblasting process is ≥0.5 MPa; A Pt layer is electroplated on the surface of the pretreated substrate, and dehydrogenation and vacuum annealing are sequentially performed to obtain a substrate with a Pt layer deposited thereon; the dehydrogenation temperature is 500-700° C., the heating rate to the dehydrogenation temperature is 5-10° C. / min, and the holding time is 5-7 hours; the vacuum annealing temperature is 1000-1100° C., the heating rate to the vacuum annealing temperature is 5-10° C. / min, and the holding time is 2-4 hours; The surface of the substrate on which the Pt layer is deposited is subjected to aluminizing treatment to obtain the Pt-Al coating.

2. The preparation method according to claim 1, characterized in that The particle size of the nickel sand is 120-240 meshes.

3. The preparation method according to claim 1, characterized in that The sandblasting treatment takes 1 to 3 minutes.

4. The preparation method according to claim 1, characterized in that The conditions for electroplating the Pt layer are: temperature of 80-90°C, current density of 1-5A / dm 2 , the electroplating time is 1 to 60 minutes.

5. The preparation method according to claim 1, characterized in that The temperature of the aluminizing treatment is 800-1000° C., and the holding time is 3-5 hours.

6. The Pt-Al coating prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The thickness of the Pt-Al coating is 45-50 μm.

7. The Pt-Al coating according to claim 6, characterized in that The mass content of the Pt element in the Pt-Al coating is 20-25%; the mass content of the Al element is 25-30%.

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