A low-diffusion pt-al2o3 modified nanocrystalline coating for single crystal superalloy protection and a preparation method thereof

Abstract

The application discloses a low-diffusion Pt-Al2O3 modified nanocrystalline coating for single-crystal high-temperature alloy protection and a preparation method thereof, and belongs to the technical field of single-crystal high-temperature alloy protection coating. The coating comprises a Pt-doped gamma'-Ni3Al phase and a nanometer-scale Al2O3 phase; and the Pt-doped gamma'-Ni3Al phase is a nanocrystalline structure. The gamma' phase similar to main phases of the single-crystal high-temperature alloy is used as a main phase, main grain structures of the coating are prepared into nanocrystalline structures, and the gamma' phase coating structure is modified by means of the Pt element and the nanometer-scale Al2O3, so as to stabilize the gamma' phase coating structure with the nanocrystalline structure; these improvements can make the nanocrystalline structure maintain for a long time at high temperature, and further make the coating maintain the surface to form a single alumina film for a long time in a high-temperature environment, so as to protect the coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of single crystal superalloy protective coating, and particularly relates to a low-diffusion Pt-Al2O3 modified nanocrystalline coating for single crystal superalloy protection and a preparation method thereof. BACKGROUND

[0002] Single crystal superalloy and advanced coating technology are the core technologies of aviation / ship turbine engines. As a hot end component, single crystal superalloy not only needs to withstand complex mechanical loads, but also needs to withstand oxidation and corrosion under harsh environments, and therefore needs to be coated with a protective coating. High-temperature oxidation / corrosion resistant coating can be used as a protective coating alone or as a bonding layer to connect high-temperature alloy and ceramic thermal barrier layer. At present, high-temperature protective coatings mainly include MCrAlY type (M represents Ni, Co, Fe or a combination thereof) coating and modified aluminide coating (such as NiPtAl coating). Due to the need for oxidation resistance and corrosion resistance, the content of aluminum (aluminide coating) or chromium (MCrAlY type coating) in the two types of coatings will far exceed the content of the two elements in the high-temperature alloy substrate. The above situation leads to a large difference in chemical composition and microstructure between the coating and the high-temperature alloy substrate, and serious interdiffusion occurs between the high-temperature protective coating and the alloy during high-temperature service. Interdiffusion not only accelerates the loss of oxidation-resistant elements such as aluminum and chromium in the coating, but also forms a large amount of TCP phase on the alloy side, which damages the mechanical properties of the high-temperature alloy. Studies have shown that due to the influence of interfacial element interdiffusion, the high-temperature creep life of the fourth generation single crystal alloy TMS-138 is shortened by 86%, which will seriously affect the reliability and durability of the high-temperature alloy component. Therefore, it is urgent to develop a new type of high-temperature oxidation-resistant coating with low diffusion and oxidation resistance.

[0003] The nickel-based single crystal superalloy mainly has a γ / γ' two-phase structure, in which the γ-Ni phase is the parent phase and the γ'-Ni3Al phase is the precipitated strengthening phase. The aluminide coating mainly has a β-NiAl phase, and the high aluminum activity in the coating will cause interdiffusion with the substrate at high temperature, causing the substrate near the coating side to change from a γ / γ' two-phase structure to a β phase or a β+γ' phase structure, and TCP phases appear in the interdiffusion zone. The chromium content in the MCrAlY coating is high, and the diffusion of chromium elements into the alloy will gather with refractory elements to form spherical TCP phases.

[0004] If the coating structure and phase composition are similar to those of the high-temperature alloy substrate, the interdiffusion phenomenon will be greatly alleviated. To be similar to the alloy structure, the coating needs to maintain a γ / γ' two-phase or γ' single-phase structure. However, after removing the chromium element, the coating with a γ / γ' two-phase structure or a single-phase γ' is difficult to form a single alumina protective film at high temperature, and the coating does not have excellent high-temperature oxidation resistance.

[0005] Studies have shown that nanocrystalline coating can greatly improve the high-temperature oxidation resistance of the γ / γ' coating, but the nanocrystalline structure is difficult to maintain for a long time at high temperature, and how to stabilize the nanocrystalline γ / γ' or γ' coating becomes the key to improving the high-temperature oxidation service performance of the coating. SUMMARY

[0006] The purpose of the present application is to provide a high-temperature protective coating suitable for the protection of nickel-based single crystal superalloy blades and a preparation method thereof, so as to solve the problems existing in the prior art. The coating has a nanocrystalline Pt-γ'(Pt-doped γ'-Ni3Al phase) single-phase structure and is doped with nanometer alumina to stabilize the coating structure. The coating has excellent high-temperature oxidation resistance, is suitable for nickel-based single crystal superalloy blades, and can significantly slow down the interdiffusion behavior between the coating and the superalloy, avoid the formation of a secondary reaction zone on the alloy side, and ensure that the mechanical properties of the alloy are not affected.

[0007] To achieve the above purpose, the present application provides the following scheme:

[0008] One of the technical solutions of the present application is a low-diffusion Pt-Al2O3 modified nanocrystalline coating, which comprises a Pt-doped γ'-Ni3Al phase and an Al2O3 phase; the Pt-doped γ'-Ni3Al phase is in a nanocrystalline structure.

[0009] The Pt-doped γ'-Ni3Al phase is the main phase organization of the coating, and the Pt-doped γ'-Ni3Al phase refers to a solid solution formed by doping Pt atoms into the γ'-Ni3Al lattice; the nanometer-scale Al2O3 phase is uniformly dispersed in the coating; the grain size of the nanometer-scale Al2O3 phase is 5-50 nm.

[0010] The nanocrystalline structure can provide a large number of fast diffusion channels for element diffusion, which is beneficial to the diffusion of Al elements in the coating to the top of the coating to maintain the formation and growth of the oxide film.

[0011] Further, the low-diffusion Pt-Al2O3 modified nanocrystalline coating contains elements including Ni, Al, Y, Hf, O and Pt.

[0012] Further, the axial size of the nanocrystalline is less than 50 nm.

[0013] Further, the content of each element in the coating layer, i.e. the chemical composition of the coating layer, ranges, in percentage by mass, as follows: Al: 7-12 wt%, Y: 0.05-0.6 wt%, Hf: 0.01-0.5 wt%, O: 0.5-3 wt%, Pt: 4-20 wt%, and the balance being Ni; the content of each element is the average content of the element in the coating layer. The introduction of Y element can inhibit the formation of holes at the interface between the oxide film and the coating layer and the segregation of S element to enhance the binding force of the oxide film; the introduction of Hf element can segregate at the grain boundary of the oxide film, promote the transformation of the oxide film structure from equiaxed structure to columnar structure, and slow down the growth rate of the oxide film.

[0014] The second technical solution of the present application is a preparation method of the above-mentioned low-diffusion Pt-Al2O3 modified nanocrystalline coating, comprising the following steps:

[0015] The pre-coating layer is deposited on the surface of the alloy substrate, then a Pt layer is electroplated on the surface of the pre-coating layer, and then vacuum diffusion annealing is performed to obtain the low-diffusion Pt-Al2O3 modified nanocrystalline coating; the pre-coating layer is an Al2O3-Ni3AlHfY coating layer.

[0016] Further, the deposition of the pre-coating layer on the surface of the alloy substrate comprises: depositing the pre-coating layer by magnetron sputtering, and the deposition conditions are as follows: base vacuum degree < 6 × 10 -3 Pa; power 1-3 kW; argon partial pressure 0.1-0.2 Pa; oxygen partial pressure 0.02-0.1 Pa; deposition temperature 180-220 °C; and pre-coating layer deposition thickness 20-100 μm.

[0017] Further, the chemical composition of the target material used for depositing the pre-coating layer by magnetron sputtering ranges, in percentage by mass, as follows: Al: 9-12 wt%, Y: 0.05-0.6 wt%, Hf: 0.01-0.5 wt%, and the balance being Ni.

[0018] Further, the main phase structure of the pre-coating layer is γ'-Ni3Al phase structure, and the γ'-Ni3Al phase is nanocrystalline structure; and the Al2O3 phase is uniformly dispersed in the pre-coating layer.

[0019] By controlling the parameters of magnetron sputtering, the γ'-Ni3Al phase in the obtained pre-coating layer can be nanocrystalline structure; and by controlling the oxygen partial pressure, the nanoscale Al2O3 phase can be uniformly dispersed in the pre-coating layer.

[0020] Further, the electroplating of the Pt layer on the surface of the pre-coating layer comprises: electroplating with pure platinum or platinum mesh as anode; plating solution pH value is 7-11; electroplating temperature is 60-90 °C; current density is 1-5 A / dm 2 ; and the thickness of the electroplated Pt layer is 2-6 μm.

[0021] Further, the plating solution has the following components: 7-15 g / L of di-nitroso-diamine platinum, 6-12 g / L of sodium nitrite, 10-20 g / L of sodium citrate, 5-10 g / L of sodium acetate, and the rest is water.

[0022] Further, the vacuum diffusion annealing includes: first heating to 400-700 DEG C for 2-4 h (to remove the residual hydrogen in the plating layer), and then continuing to heat to 1050-1200 DEG C for 1-5 h (to diffuse the Pt element into the pre-coating layer, to dope the Pt atoms into the gamma'-Ni3Al lattice, and to form a solid solution).

[0023] Further, the overall thickness of the coating after the vacuum diffusion annealing is 20-105 mu m (during the vacuum diffusion annealing, the Pt layer diffuses into the pre-coating layer to form an overall coating, and the thickness is reduced compared with the pre-coating layer+Pt layer before the vacuum diffusion annealing).

[0024] Further, the alloy substrate is a nickel-based single crystal superalloy, including: a second-generation nickel-based single crystal alloy, a third-generation nickel-based single crystal alloy, or a single crystal intermetallic compound.

[0025] The third technical scheme of the application is: application of the above-mentioned low-diffusion Pt-Al2O3 modified nanocrystalline coating in the protection of single crystal superalloys.

[0026] Further, the low-diffusion Pt-Al2O3 modified nanocrystalline coating is used as a high-temperature oxidation / corrosion resistant protective coating or a thermal barrier coating bonding layer of a single crystal superalloy blade.

[0027] The high-temperature oxidation / corrosion resistant protective coating refers to a coating that has both high-temperature oxidation resistance and corrosion resistance.

[0028] Further, the single crystal superalloy is a nickel-based single crystal superalloy, including: a second-generation nickel-based single crystal alloy, a third-generation nickel-based single crystal alloy, or a single crystal intermetallic compound.

[0029] The application has the following technical effects:

[0030] (1) The present application takes the gamma prime phase similar to the main phase of single crystal superalloy as the main phase, and prepares the main grain structure of the coating as a nanocrystalline structure, which can form a single alumina at a low aluminum content, and can greatly improve the high-temperature oxidation resistance of the coating. However, the nanocrystalline structure is difficult to maintain for a long time at high temperature, therefore, the present application also modifies the gamma prime phase coating structure with Pt element and nanoscale Al2O3 to stabilize the gamma prime phase coating structure with nanocrystalline structure. The addition of Pt element into the coating can promote the formation of an alpha-Al2O3 film on the surface of the coating, reducing the consumption of aluminum elements in the coating. At the same time, the Pt element can inhibit the sulfur segregation behavior at the interface between the oxidation film and the coating, and enhance the bonding force of the oxidation film. The nanoscale alumina plays a role in pinning the nanocrystalline grain boundary of the coating, hindering the rapid diffusion behavior of atoms at the grain boundary and subgrain boundary, thereby inhibiting the rapid growth behavior of the grain, and stabilizing the nanocrystalline structure. These improvements can make the nanocrystalline structure maintain for a long time at high temperature, and further promote the coating to maintain a single alumina film on the surface for a long time in a high-temperature environment to protect the coating. On the other hand, since the gamma prime phase is similar to the matrix alloy phase, the interdiffusion phenomenon will be greatly inhibited, so that the coating has excellent alumina film forming ability and avoids interdiffusion between the coating and the matrix, avoiding the formation of TCP phase, achieving the effect of protecting the high-temperature oxidation and mechanical properties of the alloy.

[0031] (2) The low-diffusion Pt-Al2O3 modified nanocrystalline NiAlHfY coating of the present application has the following advantages: 1) excellent oxidation resistance, the high-temperature oxidation resistance of the coating of the present application is comparable to that of NiPtAl coating; 2) the interdiffusion between the coating of the present application and the matrix is limited, which will not form a secondary reaction zone between the NiPtAl coating and the single crystal matrix, and the influence on the mechanical properties of the alloy is limited; 3) the coating of the present application has a nanocrystalline structure, which has obvious anti-wrinkling and anti-peeling ability in a thermal fatigue environment, so that the high-temperature service life of the coating is greatly prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 The electron microscope pictures of the pre-coating Al2O3-Ni3Al-0.5Hf-0.1Y prepared on the second generation single crystal alloy N5 matrix of the present application 1, wherein (a) is the cross-sectional SEM picture of the pre-coating, and (b) is the surface TEM picture of the pre-coating;

[0034] Figure 2 SEM picture (a) and energy spectrum analysis result (b) of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application after annealing;

[0035] Figure 3 XRD pattern of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application after vacuum annealing at 1050°C;

[0036] Figure 4 Surface pictures of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application after isothermal oxidation test at 1050°C for 100h, wherein the upper picture is a photo of the surface of the sample and the lower picture is an SEM picture of the surface of the sample;

[0037] Figure 5 Oxidation weight gain curve of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application during isothermal oxidation test at 1050°C for 200h;

[0038] Figure 6 Cross-section SEM picture of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application after isothermal oxidation test at 1050°C for 100h;

[0039] Figure 7 STEM picture of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 1 of the present application after isothermal oxidation test at 1050°C for 100h;

[0040] Figure 8 SEM picture of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 2 of the present application after annealing;

[0041] Figure 9 XRD picture of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 2 of the present application after vacuum annealing at 1050°C;

[0042] Figure 10 Weight change curve of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 2 of the present application after isothermal oxidation test at 1100°C for 24h;

[0043] Figure 11 Cross-section SEM picture of the low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared in Example 2 of the present application after high-temperature oxidation at 1100°C for 24h. DETAILED DESCRIPTION

[0044] The following detailed description of various example embodiments of the application will not be considered limiting of the application, but rather as a description of certain aspects, features and embodiments of the application. Modifications and variations are possible in light of the above detailed description.

[0045] It should be understood that the terms used herein are for the purpose of describing particular embodiments and are not intended to limit the application. Additionally, for numerical ranges that are expressed in a range format, it is intended that any numerical value, which is within the recited range, is also specifically contemplated. For example, a range of "1 to 10" is intended to include any number from 1 to 10, including the integers 1 and 10. Any numerical range described herein is intended to include each and every value and sub-range within the range. These ranges are intended to perform as slide rules, guiding a person of ordinary skill in the art by marking the boundaries of what can be claimed.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application.

[0047] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof. Other implementations of this application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The examples and embodiments described herein are exemplary and are not intended to be limiting.

[0048] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0049] Example 1

[0050] Preparation of Pt-Al2O3 modified nanocrystalline Ni3Al-0.5Hf-0.1Y coating

[0051] (1) A target material for sputtering Al2O3-Ni3Al-0.5Hf-0.1Y pre-coating layer was prepared by vacuum melting method. The chemical composition of the target material was 11wt% Al, 0.5wt% Hf, 0.1wt% Y, and the balance of Ni in terms of mass percentage. Then the processed target material was installed on a sputtering instrument.

[0052] (2) The substrate sample pretreatment: before preparing the pre-coating, the alloy substrate sample (second generation N5 single crystal superalloy) was polished to 2000# sandpaper, and then cleaned with acetone and alcohol respectively, and dried.

[0053] (3) The Al2O3-doped nanocrystalline Ni3Al-0.5Hf-0.1Y (Al2O3-Ni3AlHfY) pre-coating was prepared on the alloy surface by magnetron sputtering, and the specific parameters were as follows:

[0054] Background vacuum: P < 6 × 10 -3 Pa

[0055] Power: 2000W

[0056] Argon partial pressure: 0.3Pa

[0057] Oxygen partial pressure: 0.1Pa

[0058] Deposition current: 7A

[0059] Current duty cycle: 80%

[0060] Frequency: 40KHz

[0061] Alloy substrate temperature: 200℃

[0062] Deposition time: 7 hours in total.

[0063] After the deposition was completed and the sample was cooled, the sample was taken out. The electron microscope image of the deposited pre-coating is shown in Figure 1 , wherein (a) is the cross-sectional SEM image of the pre-coating, and (b) is the surface TEM image of the pre-coating. Figure 1 As can be seen from (a), the overall thickness of the coating is 30μm, and there is an obvious interface between the alloy substrate and the pre-coating, and the two are well combined; as can be seen from Figure 1 (b), the pre-coating has a nanocrystalline structure and nanometer aluminum oxide particles, and the grain size of the pre-coating is about 5-50nm.

[0064] (4) Pt layer was electroplated on the surface of the sputtered pre-coating, and the composition of the electroplating solution was (g / L):

[0065] Dinitrosoplatinum diammine: 10

[0066] Sodium nitrite: 10

[0067] Sodium citrate: 10

[0068] Sodium acetate: 8

[0069] Balance: water

[0070] The pH value of the plating solution is adjusted to 11. The plating is performed using an alternating current power source, and the plating is performed in a magnetic stirrer at a stirring speed of 10 r / min. The entire plating process is performed under constant temperature, and the temperature is controlled at 80°C and the current density is controlled at 3 A / dm 2 2 during plating. The pH value of the plating solution is maintained in the range of 9-11 during the entire plating process, and the thickness of the plated Pt layer is 2 μm.

[0071] (5) Vacuum diffusion annealing: The composite coating after plating is subjected to vacuum diffusion annealing in a tube-type annealing furnace. The gas pressure of the vacuum annealing furnace is 9 x 10 -3 Pa during annealing. The temperature is first raised to 500°C for 2 h to remove the residual hydrogen in the plated layer during plating, so as to prevent the occurrence of phenomena such as blistering. Then, the temperature is continuously raised to 1100°C for 5 h, so as to diffuse the plated layer with the preformed coating (so as to diffuse the Pt element into the preformed coating, and to dope the Pt atoms into the γ'-Ni3Al crystal lattice), to obtain a Pt-Al2O3 modified nanocrystalline Ni3Al-0.5Hf-0.1Y coating. The SEM picture (interface) of the coating after annealing is shown in Figure 2 (a), and it can be seen from Figure 2 (a) that the overall thickness of the coating is 30 μm. It can be seen from the energy spectrum analysis (as shown in Figure 2 (b)) that the element composition of the coating is Ni-9Al-6Pt-0.48Hf-0.08Y-0.9O.

[0072] The phase composition of the coating after annealing is analyzed using XRD, and the XRD diagram is shown in Figure 3 . The results show that the main phase of the Pt-Al2O3 modified nanocrystalline coating is the γ'-Ni3Al phase.

[0073] (6) The Pt-Al2O3 modified nanocrystalline Ni3Al-0.5Hf-0.1Y coating sample is subjected to isothermal oxidation test at 1050°C. The sample surface after 100 h of oxidation test is shown in Figure 4 . The upper diagram is a photo of the sample surface, and the lower diagram is an SEM diagram of the sample surface. It can be seen from Figure 4 that a continuous oxide film is formed on the sample surface and there is no obvious peeling. The oxidation weight gain curve of the coating during the isothermal oxidation test for 200 h is shown in Figure 5 . It can be seen from Figure 5 that the weight gain per unit area of the coating after isothermal oxidation for 200 h is only 0.72 mg / cm 2, and the coating weight increased continuously without weight loss during the isothermal oxidation process, showing good high-temperature oxidation resistance. The Pt-γ' / γ coating without nanocrystalline structure (prepared by electroplating a 2-μm-thick Pt layer on a polished N5 high-temperature alloy surface and then vacuum diffusion annealing treatment, with the same vacuum annealing treatment process as step (5)) has a γ' / γ coherent structure and is a single crystal. The Pt element is solid-solved in the γ' and γ lattices by thermal diffusion of the electroplated Pt layer to the alloy interior, forming a Pt-γ' / γ diffusion coating without nanocrystalline structure. The Pt-γ' / γ coating without nanocrystalline structure started to lose weight after 100 h in the late oxidation stage, meaning that peeling occurred on the coating surface. Cross-sectional anatomical analysis was performed on the oxidized coating sample (in order to protect the oxidation film on the sample surface, a layer of nickel plating was prepared on the outside of the oxidation film before the cross-sectional sample was prepared), and the cross-sectional SEM image is shown in Figure 6 It was found that no TCP phase or secondary reaction zone was generated at the interface between the coating and the single-crystal substrate, indicating that the coating with the main phase of γ'-Ni3Al phase effectively slowed down the element interdiffusion behavior between the coating and the substrate. The grain structure (STEM image) in the coating after 100 h of oxidation is shown in Figure 7 It can be seen from Figure 7 that the grain structure in the coating is still less than 500 nm after long-term high-temperature exposure.

[0074] Example 2

[0075] Preparation of Pt-Al2O3 modified nanocrystalline Ni3Al-0.2Hf-0.5Y (0.2 and 0.5 represent the content of the element in the target material) coating

[0076] (1) A target material for sputtering Al2O3-Ni3Al-0.2Hf-0.5Y pre-coating was prepared by vacuum melting, and the chemical composition of the target material was 10wt% Al, 0.2wt% Hf, 0.5wt% Y, and the balance was Ni in terms of mass percentage. Then the processed target material was installed on the sputtering instrument.

[0077] (2) The substrate sample was pretreated: a nickel-based single-crystal intermetallic compound IC21 was used as the substrate alloy, the alloy was cut and then polished with 150#, 240#, and 400# sandpaper in sequence, and then subjected to alumina sandblasting treatment, followed by ultrasonic cleaning with alcohol and acetone, and then dried for use.

[0078] (3) An Al2O3-doped nanocrystalline Ni3Al-0.2Hf-0.5Y (Al2O3-Ni3AlHfY) pre-coating was prepared on the surface of the alloy substrate by magnetron sputtering, and the specific parameters were as follows:

[0079] Vacuum degree: P < 6 × 10-3 Pa

[0080] Power: 1500W

[0081] Argon partial pressure: 0.2 Pa

[0082] Oxygen partial pressure: 0.05 Pa

[0083] Deposition current: 6 A

[0084] Current duty cycle: 80%

[0085] Frequency: 40 kHz

[0086] Alloy substrate temperature: 200°C

[0087] Deposition time: 8 hours in total.

[0088] After the deposition is completed and the sample is cooled, the sample is taken out. It is detected that the overall thickness of the pre-coating layer is 30 μm, there is a clear interface between the alloy substrate and the pre-coating layer, and the two are well combined. The pre-coating layer has a nanocrystalline structure and nano-aluminum oxide particles, and the grain size of the pre-coating layer is about 5-50 nm.

[0089] (4) Electroplating a Pt layer on the surface of the sputtered pre-coating layer, the composition of the electroplating solution is (g / L):

[0090] Dinitrosoplatinum diammine: 9

[0091] Sodium nitrite: 12

[0092] Sodium citrate: 15

[0093] Sodium acetate: 8

[0094] Balance: water

[0095] The pH value of the electroplating solution is adjusted to 11. The electroplating is carried out using an alternating current power source, and the electroplating is carried out in a magnetic stirrer with a stirring speed of 10 r / min. The entire electroplating process is carried out at a constant temperature, and the temperature is controlled at 85°C and the current density is controlled at 2 A / dm 2 2 during electroplating. The pH value of the electroplating solution is maintained in the range of 9-11 during the entire electroplating process, and the thickness of the electroplated Pt layer is 2 μm.

[0096] (5) Vacuum diffusion annealing: The composite coating after electroplating is subjected to vacuum diffusion annealing treatment in a tubular annealing furnace, and the gas pressure of the vacuum annealing furnace during annealing is 9 x 10 -3First, the plating layer is heated to 500℃ and held for 2 hours to remove residual hydrogen gas from the plating layer during electroplating, preventing blistering and other phenomena. Then, it is heated to 1050℃ and held for 3 hours to allow diffusion between the electroplated layer and the pre-coated layer (allowing Pt elements to diffuse into the interior of the pre-coated layer, and Pt atoms to dope into the γ'-Ni3Al lattice), resulting in a Pt-Al2O3 modified nanocrystalline Ni3Al-0.2Hf-0.5Y coating. The SEM image after annealing is shown below. Figure 8 As shown. By Figure 8 It can be seen that the overall thickness of the coating is 30 μm. Energy dispersive spectroscopy analysis shows that the elemental composition of the coating is Ni-9.2Al-5.0Pt-0.15Hf-0.4Y-0.6O.

[0097] The phase composition of the annealed coating was analyzed using XRD, and its XRD pattern is shown below. Figure 9 As shown, the results indicate that the main phase of the coating is the γ'-Ni3Al phase, with Pt elements dissolved into the Ni3Al phase.

[0098] (6) The Pt-Al2O3 modified nanocrystalline Ni3Al-0.2Hf-0.5Y coating sample was subjected to an isothermal oxidation test at 1100℃. The oxidation weight gain curve of the coating during the 24-hour isothermal oxidation test is shown in the figure. Figure 10 As shown, by Figure 10 It can be seen that the coating weight gain was 0.29 mg / cm³ after 24 hours of oxidation testing. 2 The oxidation kinetics follow a parabolic law. Cross-sectional dissection analysis was performed on the oxidized coated sample (to protect the oxide film on the sample surface, a nickel plating layer was first prepared on the outside of the oxide film using electroless nickel plating before preparing the cross-sectional sample). The cross-sectional SEM images are shown below. Figure 11 As shown, no TCP phase or secondary reaction zone was found to form at the interface between the coating and the single-crystal substrate, indicating that the coating, whose main phase is Pt-doped γ'-Ni3Al, effectively mitigates the interdiffusion behavior between the coating and the substrate. A continuous oxide film was also found to form on the coating surface, exhibiting excellent resistance to high-temperature oxidation.

[0099] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing a low-diffusion Pt-Al2O3 modified nanocrystalline coating, characterized in that, The method comprises the following steps: The low-diffusion Pt-Al2O3 modified nanocrystalline coating is prepared by the following steps: depositing a pre-coating on the surface of an alloy substrate, electroplating a Pt layer on the surface of the pre-coating, and then performing vacuum diffusion annealing. The deposition of the pre-coating on the surface of the alloy substrate comprises: depositing the pre-coating by magnetron sputtering, the deposition conditions being: base vacuum < 6×10 -3 Pa; power 1-3 kW; argon partial pressure 0.1-0.2 Pa; oxygen partial pressure 0.02-0.1 Pa; deposition temperature 180-220 °C; pre-coating deposition thickness 20-100 μm; The chemical composition of the target material for depositing the pre-coating by magnetron sputtering is: Al: 9-12 wt%, Y: 0.05-0.6 wt%, Hf: 0.01-0.5 wt%, and the balance is Ni. The vacuum diffusion annealing comprises the following steps: heating to 400-700 ℃ first and keeping for 2-4 h, and then continuously heating to 1050-1200 ℃ and keeping for 1-5 h.

2. The method of claim 1, wherein the low-diffusion Pt-Al2O3 modified nanocrystalline coating is prepared by, The surface of the pre-coating layer is plated with Pt layer, including: using pure Pt or Pt mesh as anode for plating; pH value of plating solution is 7-11; plating temperature is 60-90℃; current density is 1-5A / dm 2 ; thickness of the plated Pt layer is 2-6μm.

3. The method of claim 2, wherein the low-diffusivity Pt-Al2O3 modified nanocrystalline coating is prepared by, The composition of the plating solution is: 7-15 g / L of dinitrosoplatinum diammine, 6-12 g / L of sodium nitrite, 10-20 g / L of sodium citrate, 5-10 g / L of sodium acetate, and the balance is water.

4. A low-diffusion Pt-Al2O3 modified nanocrystalline coating prepared by the method according to any one of claims 1-3.

5. The low-diffusion Pt-Al2O3 modified nanocrystalline coating according to claim 4 is used for the protection of single-crystal superalloys.

6. Use according to claim 5, wherein The low-diffusion Pt-Al2O3 modified nanocrystalline coating is used as a high-temperature oxidation / corrosion resistant protective coating or a thermal barrier coating bonding layer for single-crystal superalloy blades.

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