In-situ formed ceramic-based diffusion barrier platinum-aluminum coating and preparation method and application thereof

Abstract

The invention discloses an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating and a preparation method and application thereof, and belongs to the technical field of platinum-aluminum coating series diffusion coatings. The coating sequentially comprises an outer platinum-aluminum coating, an in-situ generated HfO2 / Al2O3 ceramic-based diffusion barrier region and a mutual diffusion layer from outside to inside. The preparation method comprises the following steps: sequentially introducing a Ni-HfO2-Hf layer or a Ni-HfO2 layer and a Pt layer or a Pt-Hf layer on a substrate; and then vacuum diffusion annealing treatment and gas-phase aluminizing treatment are sequentially carried out. The in-situ generated HfO2 / Al2O3 ceramic-based diffusion barrier platinum-aluminum coating provided by the invention has excellent performance in the aspect of hindering mutual diffusion of elements, and also has excellent service reliability. The coating is applied to hot-end components of aero-engines and airspace engines, the service life of the hot-end components can be remarkably prolonged, and the coating has important significance in guaranteeing long-term stable operation of the aero-space engines and improving the overall performance of equipment.

Description

Technical Field

[0001] This invention belongs to the field of platinum-aluminum coating series diffusion coating technology, specifically relating to an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating, its preparation method and application. Background Technology

[0002] β-(Ni,Pt)Al coatings, due to their excellent high-temperature oxidation resistance and corrosion resistance, are widely used in critical hot-end components of aero-engines, such as turbine blades, and have become one of the most mainstream high-temperature protective coatings. The introduction of Pt into this coating significantly enhances the adhesion of the alumina film and improves overall oxidation resistance; simultaneously, Pt effectively inhibits the high-speed diffusion of Al and Ni within the coating, thereby reducing the risk of topologically dense (TCP) phase formation. However, with the further increase in engine thrust-to-weight ratio and the continuous rise in the service temperature of hot-end components, the interdiffusion phenomenon between the β-(Ni,Pt)Al coating and the substrate has become increasingly severe, becoming a key factor limiting its long-term service life.

[0003] Due to the significant difference in composition between the coating and the substrate, interdiffusion inevitably occurs under high-temperature conditions. Firstly, Al diffusion into the substrate leads to the transformation of the β phase into the γ'-Ni3Al phase, weakening the coating's oxidation resistance and causing morphological degradation. Secondly, Ni diffusion into the coating disrupts the coherent γ / γ' structure of the substrate, generating secondary reaction zones (SRZs), which severely impair the substrate's mechanical properties. To suppress interdiffusion, current research mainly employs metal-based or ceramic-based diffusion barrier layers (DBs). Among these, ceramic-based DBs (such as Al2O3, AlN, and YSZ) exhibit good diffusion barrier effects and structural stability. However, the preparation of β-(Ni,Pt)Al diffusion coatings relies on the outward diffusion of substrate elements and their reaction with the diffusion agent to maintain growth. The pre-applied ceramic-based diffusion barrier hinders the growth of the β-(Ni,Pt)Al coating, making it unsuitable for diffusion-type aluminizing processes. Metal-based DBs (such as Ni-Re, Ni-W, Hf, etc.) can be generated in situ during the coating preparation process, possessing both good toughness and thermal stability, and can alleviate interfacial stress. However, they suffer from the common degradation problem of element diffusion and gradual disappearance of the layer structure under long-term high temperature. Their barrier performance and stability are still difficult to meet the stringent service requirements. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating, wherein the coating comprises, from the outside to the inside, an outer platinum-aluminum coating, an in-situ formed HfO2 / Al2O3 ceramic-based diffusion barrier region, and an interdiffusion layer (IDZ).

[0006] As a preferred embodiment of the present invention, the coating components are distributed in a gradient from the outside to the inside, and the phase structure gradually transitions from high aluminum phase and medium aluminum phase to low aluminum phase from the outside to the inside.

[0007] The present invention also provides a method for preparing an in-situ ceramic-based diffusion barrier platinum-aluminum coating according to the above-described method, comprising the following steps: introducing a Ni-HfO2-Hf layer or a Ni-HfO2 layer on a substrate, and then introducing a Pt layer or a Pt-Hf layer on the Ni-HfO2-Hf layer or the Ni-HfO2 layer; subsequently, subjecting the obtained composite coating to vacuum diffusion annealing and vapor phase aluminizing treatment in sequence to obtain the in-situ ceramic-based diffusion barrier platinum-aluminum coating.

[0008] The Ni-HfO2-Hf or Ni-HfO2 composite coating provides the Ni source required for coating growth during the aluminizing process, while the Pt or Pt-Hf layer provides the Pt source. At the same time, the Hf element diffuses outward into the platinum-aluminum coating, realizing the Hf modification of the (Ni,Pt)Al coating and generating the HfO2 phase in situ in the diffusion barrier region.

[0009] HfO2 / Al2O3 ceramic-based diffusion barriers can significantly reduce the oxidation rate of coatings and enhance the adhesion of thermally grown oxide films in high-temperature oxidizing environments. At the same time, diffusion barriers can effectively inhibit the bidirectional diffusion of Al and Ta elements, enhance the structural stability of coatings, and ensure the mechanical properties of the substrate.

[0010] As a preferred embodiment of the present invention, the substrate is a high-temperature alloy substrate, including a nickel-based single-crystal high-temperature alloy; the introduction of the Ni-HfO2-Hf layer, Ni-HfO2 layer, Pt layer and Pt-Hf layer includes electroplating, sputtering or ion implantation; the thickness of the Ni-HfO2-Hf layer or Ni-HfO2 layer is 12 to 18 μm, and the thickness of the Pt layer or Pt-Hf layer is 3 to 7 μm.

[0011] As a preferred embodiment of the present invention, the Ni-HfO2-Hf layer or Ni-HfO2 layer, Pt layer or Pt-Hf layer is introduced by electroplating. The specific electroplating conditions for the Ni-HfO2-Hf layer or Ni-HfO2 layer are: electroplating temperature 40-50℃, current density 4.8 mA / cm². 2 The pH value is 3-4, and the electroplating time is 2 hours. The specific electroplating conditions for Pt or Pt-Hf layers are: electroplating temperature 70-80℃, current density 7 mA / cm². 2 The pH value is 10.0–11.0, and the electroplating time is 1 hour.

[0012] By adjusting the composite electroplating process parameters (such as current density, plating solution concentration, stirring speed, etc.), the coating thickness and Hf element content can be flexibly adjusted, thereby making the preparation process highly flexible to adapt to the coating performance requirements of different application scenarios.

[0013] As a preferred embodiment of the present invention, the vacuum degree of the vacuum diffusion annealing treatment is less than 1×10⁻⁶. -3 Pa, heating rate of 5-10 ℃ / min, annealing temperature of 1000-1080 ℃, holding time of 1-4 h.

[0014] As a preferred embodiment of the present invention, the annealing process further includes a heat treatment at 600 °C for 3 h to remove residual hydrogen in the coating.

[0015] As a preferred embodiment of the present invention, the vapor phase aluminizing treatment is carried out at 1020-1080 °C for 6 h. Ar gas is introduced as a protective gas during the aluminizing process. The aluminizing agent is composed of iron-aluminum mixed powder and activator NH4Cl, wherein the NH4Cl content is 1-4 wt%; the iron-aluminum mixed powder contains 49 wt% iron powder and the remainder is aluminum powder.

[0016] This invention also provides an application of the ceramic-based diffusion barrier platinum-aluminum coating formed in situ according to the above description in the aerospace field.

[0017] As a preferred embodiment of the present invention, the in-situ formed ceramic-based diffusion barrier platinum-aluminum coating is used in protective coatings for aerospace engine components.

[0018] The in-situ generated HfO2 / Al2O3 ceramic-based diffusion barrier significantly improves the coating's oxidation resistance and element diffusion inhibition performance. At 1100 °C, the oxidation rate is significantly reduced, the adhesion of the thermally grown oxide film is enhanced, and the surface roughness is decreased. Simultaneously, this diffusion barrier effectively inhibits the interdiffusion behavior of Al and refractory elements such as Ta, thereby maintaining the microstructural stability of the coating and preventing the degradation of the matrix's mechanical properties due to element diffusion. This invention ensures the structural integrity and performance reliability of the coating under long-term high-temperature service conditions, and has significant engineering application value. It can maximize the preservation of the mechanical properties of the high-temperature alloy matrix.

[0019] This invention introduces a Ni-HfO2-Hf layer or a Ni-HfO2 layer and a Pt layer or a Pt-Hf layer on the surface of a substrate using a composite electroplating technique. The concentration distribution of Pt, Hf and Ni elements in the coating is controlled by vacuum annealing. Subsequently, an in-situ HfO2 / Al2O3 ceramic-based diffusion barrier platinum-aluminum coating is prepared using a vapor phase aluminizing process.

[0020] This invention innovatively incorporates a composite electroplated Ni-HfO2-Hf layer or Ni-HfO2 layer transition layer between the substrate and the Pt plating layer. This transition layer possesses three core functions: (1) The Ni-HfO2-Hf or Ni-HfO2 composite coating provides the required Ni element for the growth of NiAl coating during the aluminizing process, thereby reducing the outward diffusion of Ni element in the substrate, maximizing the protection of the γ / γ' coherent structure of the substrate, inhibiting the interdiffusion of elements between the coating and the substrate, and avoiding the formation of secondary reaction zones. (2) Ni-HfO2-Hf or Ni-HfO2 composite coating releases Hf atoms during the aluminizing process, thereby obtaining Hf-modified (Ni,Pt)Al coating under the same preparation conditions. This can effectively enhance the adhesion of the oxide film and inhibit the wrinkling phenomenon of the oxide film, which is beneficial to reduce the surface undulation deformation during the oxidation process of the coating. (3) During the aluminizing process, the HfO2 in the Ni-HfO2-Hf or Ni-HfO2 composite coating can react with internally diffused Al atoms to generate Al2O3, while Hf reacts with O atoms to generate HfO2, ultimately forming an in-situ HfO2 / Al2O3 ceramic-based diffusion barrier. This diffusion barrier effectively hinders the interdiffusion of Al and Ta elements, effectively blocking their interdiffusion behavior. On the one hand, it ensures sufficient Al content in the coating to continuously generate a protective Al2O3 film, thereby extending the service life of the coating; on the other hand, it reduces the tendency of Ta elements to diffuse into the coating, ensuring the stability of the coating structure and maintaining the mechanical properties of the substrate. This, in turn, ensures the stability of the coating structure and its service reliability.

[0021] This invention achieves significant optimization in coating performance: In a high-temperature oxidation environment, the modification effect of Hf element can effectively reduce the overall oxidation rate of the coating and significantly enhance the adhesion between the thermally grown oxide film and the coating substrate, preventing the oxide film from cracking or peeling due to insufficient adhesion; In addition, the HfO2 / Al2O3 ceramic matrix diffusion barrier generated in situ in the coating system can effectively block the interdiffusion behavior of Al and Ta elements, thereby ensuring the long-term stability of the coating microstructure, avoiding the decline in the mechanical properties of the substrate due to element diffusion, and ensuring the performance reliability of the coating under high-temperature service conditions.

[0022] To address the technical bottleneck of existing diffusion barriers that struggle to balance structural stability and fabrication process adaptability, this invention combines the superior structural stability of ceramic-based diffusion barriers with the in-situ generation advantage of metal-based diffusion barriers, providing a novel design scheme based on in-situ generation of ceramic-based diffusion barriers. By screening active elements with high oxygen affinity, low diffusion coefficients, and the ability to enhance the coating's oxidation resistance, Hf is preferentially selected as a key additive element. During the aluminizing process of the (Ni,Pt)Al coating, an oxide ceramic-based diffusion barrier is generated in-situ through oxidation. This in-situ generated ceramic diffusion barrier not only effectively blocks the bidirectional interdiffusion of Al and Ni, significantly delaying the degradation from the β phase to the γ' phase, but also enhances the adhesion and structural integrity of the thermally grown oxide film (TGO), suppressing coating wrinkling, oxide film cracking, and peeling from the source. This invention requires no additional prefabrication process and is directly compatible with existing (Ni,Pt)Al diffusion coating fabrication processes, achieving a balance between the structural stability of the ceramic diffusion barrier and the in-situ generation of the diffusion coating. This provides a novel technical path for improving the high-temperature, long-term service reliability of hot-end components in aero-engines.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention has outstanding innovation in the design concept and structure construction of the coating system: by accurately constructing the functional layer, on the one hand, HfO2 / Al2O3 ceramic-based diffusion barrier is generated in situ inside the coating, which effectively avoids the problem that the traditional pre-placed ceramic diffusion layer will hinder the growth of β-(Ni,Pt)Al coating; on the other hand, the introduction of two key functional elements, Pt and Hf, is realized, which ensures that the coating has excellent anti-oxidation and anti-surface fluctuation performance from the material system level.

[0024] (2) The ceramic-based diffusion barrier generated by the present invention has excellent diffusion resistance and structural stability. Compared with metal diffusion barriers, it can maintain structural integrity under high temperature and long-term service conditions, thereby effectively delaying coating degradation and improving reliability.

[0025] (3) The in-situ generated HfO2 / Al2O3 ceramic-based diffusion barrier platinum-aluminum coating provided by this invention has a simple and efficient preparation process, and the preparation process does not damage the properties of the substrate. This ceramic-based diffusion barrier coating performs excellently in hindering element interdiffusion and also has excellent service reliability. Applying this coating to the hot-end components of aero-engines and space engines can significantly extend the service life of the hot-end components, which is of great significance for ensuring the long-term stable operation of aero-engines and improving the overall performance of the equipment. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The images show the surface and cross-sectional morphology of the (Ni,Pt)Al coating and the CDB-(Ni,Pt)Al coating prepared in Example 1, where (a) and (b) are the surface and cross-sectional morphology of the (Ni,Pt)Al coating, and (c) and (d) are the surface and cross-sectional morphology of the CDB-(Ni,Pt)Al coating. Figure 2 In the middle (a) to (d), respectively, are the cross-sectional morphology, XRD pattern, morphology and phase composition diagram of the HfO2 / Al2O3 diffusion barrier of the CDB-(Ni,Pt)Al coating prepared in Example 1; Figure 3 The mass change curves of (Ni,Pt)Al and CDB-(Ni,Pt)Al coatings during the oxidation process are shown. Figure 4 The images show the surface and cross-sectional morphology of (Ni,Pt)Al and CDB-(Ni,Pt)Al coatings after 600 oxidation cycles. (a) and (b) are the surface and cross-sectional morphology of the (Ni,Pt)Al coating after 600 oxidation cycles, respectively, and (c) and (d) are the surface and cross-sectional morphology of the CDB-(Ni,Pt)Al coating after 600 oxidation cycles, respectively. Figure 5 In the middle (a) and (b), the elemental distribution diagrams of (Ni,Pt)Al and CDB-(Ni,Pt)Al coatings after 600 cycles of oxidation are respectively. Figure 6 The following are surface and cross-sectional morphology diagrams of the aluminized coating in Example 2: (a) and (b) are surface and cross-sectional morphology diagrams of 5CDB-(Ni,Pt)Al, (c) and (d) are surface and cross-sectional morphology diagrams of 10CDB-(Ni,Pt)Al, and (e) and (f) are surface and cross-sectional morphology diagrams of 20CDB-(Ni,Pt)Al. Figure 7 In the figures, (a) and (b) represent the diffusion barrier morphology and phase content of the 5CDB-(Ni,Pt)Al coating, (c) and (d) represent the diffusion barrier morphology and phase content of the 10CDB-(Ni,Pt)Al coating, and (e) and (f) represent the diffusion barrier morphology and phase content of the 20CDB-(Ni,Pt)Al coating. Figure 8The mass change curves of three diffusion barrier coatings, 5CDB-(Ni,Pt)Al, 10CDB-(Ni,Pt)Al and 20CDB-(Ni,Pt)Al, during the cyclic oxidation process are shown. Figure 9 The surface and cross-sectional morphologies of three coating groups—5CDB-(Ni,Pt)Al, 10CDB-(Ni,Pt)Al, and 20CDB-(Ni,Pt)Al—after 600 oxidation cycles are shown. (a) and (b) are the surface and cross-sectional morphologies of 5CDB-(Ni,Pt)Al, (c) and (d) are the surface and cross-sectional morphologies of 10CDB-(Ni,Pt)Al, and (e) and (f) are the surface and cross-sectional morphologies of 20CDB-(Ni,Pt)Al. Figure 10 In the middle (a) to (c), the elemental distribution diagrams of the three coatings 5CDB-(Ni,Pt)Al, 10CDB-(Ni,Pt)Al, and 20CDB-(Ni,Pt)Al after 600 cycles of oxidation are shown respectively. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0029] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0032] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0033] The raw materials used in the following examples are all commercially available and conventional, and are not particularly limited. They will not be described again below.

[0034] Example 1 Comparison of ceramic-based diffusion barrier coatings and ordinary coatings 1. Ordinary platinum-aluminum coating preparation process: Electroplating of Ni and Pt layers onto the surface of second-generation nickel-based single-crystal high-temperature alloys, followed by vacuum annealing and vapor-phase aluminizing. (1) Matrix pretreatment: The matrix was a second-generation nickel-based single-crystal high-temperature alloy. The sample size was Φ15mm×2mm. The sample was polished with 600#, 1000#, 1500# and 2000# SiC sandpaper in sequence, and then wet sandblasted with quartz sand particles. After sandblasting, the sample was degreased in 50 g / L boiling sodium hydroxide aqueous solution for 10 min, and then ultrasonically cleaned with alcohol and deionized water for 30 min respectively to remove surface contaminants and ensure surface cleanliness.

[0035] (2) Electrodeposition of Ni layer: Watt's nickel plating solution was used as the electroplating solution. The pretreated sample was suspended in the electroplating tank with copper wire, with the sample as the cathode and the nickel mesh as the anode. The water temperature was maintained at 45 ℃ and the current density at 4.8 mA / cm in the water bath. 2 Electroplating was performed for 2 hours at a pH of 3. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried.

[0036] (3) Electrodeposition of Pt layer: In alkaline plating solution, the sample with deposited Ni layer is suspended in the electroplating tank by copper wire, with the sample as cathode and platinum mesh as anode; the water temperature is maintained at 80 ℃ and the current density is 7 mA / cm² in the water bath. 2 Electroplating was performed for 1 hour at a pH of 10. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried.

[0037] (4) Vacuum annealing: The electroplated sample is placed in a vacuum tube furnace and annealed under a vacuum of 1000 kJ / m². -3 Under the conditions of Pa and a heating rate of 10 ℃ / min, the coating is first held at 600 ℃ for 3 h to remove residual hydrogen and prevent defects such as bulging; then the temperature is raised to 1050 ℃ and held for 2 h to eliminate hydrogen introduced during the preparation process, reduce coating stress, and promote the full dissolution of Pt in the alloy matrix; after annealing, the coating is cooled to room temperature in the furnace.

[0038] (5) Vapor phase aluminizing treatment: The annealed sample was placed in a chemical vapor deposition vacuum furnace and held at 1050 °C for 6 h at a heating rate of 10 °C / min. Ar gas was introduced as a protective gas during the aluminizing process. The aluminizing agent consisted of iron-aluminum mixed powder (97 wt.%) and activator NH4Cl (3 wt.%). The iron-aluminum mixed powder contained 49 wt% iron powder and 51 wt% aluminum powder. After aluminizing, the sample was cooled to room temperature with the furnace and then removed. The coating was named (Ni,Pt)Al coating.

[0039] Figure 1 In Figures (a) and (b), the surface and cross-sectional morphology of the coating prepared by the above method are shown respectively. It can be seen that the surface is composed of equiaxed grains, and the cross-section includes a NiAl layer and an interdiffused layer (IDZ) structure.

[0040] 2. Ceramic-based diffusion barrier coating preparation process: composite electroplating of Ni-Hf-HfO2 layer and Pt-Hf layer on the surface of second-generation nickel-based single-crystal high-temperature alloy, vacuum annealing and vapor-phase aluminizing. (1) Matrix pretreatment: The matrix was a second-generation nickel-based single-crystal high-temperature alloy. The sample size was Φ15mm×2mm. The sample was polished with 600#, 1000#, 1500# and 2000# SiC sandpaper in sequence, and then wet sandblasted with quartz sand particles. After sandblasting, the sample was degreased in 50 g / L boiling sodium hydroxide aqueous solution for 10 min, and then ultrasonically cleaned with alcohol and deionized water for 30 min respectively to remove surface contaminants and oxide layer and ensure surface cleanliness.

[0041] (2) Composite electroplating of Ni-Hf-HfO2 layer: Hf powder with a particle size of 300~500 nm was added to Watt's nickel plating solution at a mass concentration of 60 g / L, followed by HfO2 powder with a particle size of 100~200 nm at a mass concentration of 60 g / L. The mixture was then magnetically stirred to ensure uniform dispersion of the powder. The pretreated sample was suspended in the electroplating tank with copper wire, with the sample as the cathode and the nickel mesh as the anode. Electroplating was carried out in a water bath at a temperature of 45 ℃, a current density of 4.8 mA / cm², and a pH of 4 for 2 h. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried. The thickness of the obtained Ni-Hf-HfO2 layer was 15 μm.

[0042] (3) Composite electroplating of Pt-Hf layers: Hf powder with a particle size of 300~500 nm was added to an alkaline plating solution at a mass concentration of 30 g / L, and magnetic stirring was performed to ensure uniform dispersion of the powder; the sample with deposited Ni-Hf-HfO2 layers was suspended in the electroplating bath with copper wire, with the sample as the cathode and the platinum mesh as the anode; the water temperature was maintained at 80 ℃ and the current density at 7 mA / cm in the water bath. 2 Electroplating was performed for 1 hour at a pH of 10. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried. The thickness of the obtained Pt-Hf layer was 5 μm.

[0043] (4) Vacuum annealing: The electroplated sample is placed in a vacuum tube furnace and annealed under a vacuum of 1000 kJ / m². -3 Under the conditions of Pa and a heating rate of 10 ℃ / min, the coating is first held at 600 ℃ for 3 h to remove residual hydrogen and prevent defects such as bulging; then the temperature is raised to 1050 ℃ and held for 2 h to eliminate hydrogen introduced during the preparation process, reduce coating stress, and promote the full dissolution of Pt in the alloy matrix; after annealing, the coating is cooled to room temperature in the furnace.

[0044] (5) Vapor phase aluminizing treatment: The annealed sample was placed in a chemical vapor deposition vacuum furnace and kept at 1050 °C for 6 h with a heating rate of 10 °C / min. Ar gas was introduced as a protective gas during the aluminizing process. The aluminizing agent was composed of iron-aluminum mixed powder (97 wt.%) and activator NH4Cl (3 wt.%). In the iron-aluminum mixed powder, the iron powder content was 49 wt% and the aluminum powder content was 51 wt%. After the aluminizing was completed, the sample was cooled to room temperature with the furnace and taken out. The coating was named CDB-(Ni,Pt)Al coating.

[0045] Figure 1 (c) and (d) show the surface and cross-sectional morphology of the coating prepared by the above method, respectively. It can be seen that the surface is composed of equiaxed grains, and the cross-section includes a three-layer structure of NiAl layer, HfO2 / Al2O3 diffusion barrier layer and interdiffusion layer (IDZ).

[0046] The composition of the nickel plating solution, electroplating parameters, and composition of the plating solution, electroplating parameters, and the plating parameters of the plating plating solution during the preparation of (Ni,Pt)Al coating and CDB-(Ni,Pt)Al coating are shown in Table 1 and Table 2, respectively.

[0047] Table 1. Composition and electroplating parameters of nickel plating solution

[0048] Table 2 Composition and Electroplating Parameters of Platinum Plating Solution

[0049] Comparison of the performance of ceramic diffusion barrier coatings and ordinary coatings After diffusion annealing and vapor-phase aluminizing treatment, two groups of samples were obtained with (Ni,Pt)Al coating and ceramic CDB-(Ni,Pt)Al coating, respectively. Their surface and cross-sectional morphologies are as follows. Figure 1 As shown, the two coatings have similar surface morphologies, both consisting of grains separated by grain boundary ridges. However, the CDB-(Ni,Pt)Al coating has a finer grain size because the oxide particles doped in its coating inhibit grain growth during the aluminizing process.

[0050] Cross-sectional morphology reveals that both coatings consist of a uniform NiAl outer layer (outer zone OZ) and an interdiffused zone (IDZ) rich in precipitated phases. Specifically, the CDB-(Ni,Pt)Al coating contains an additional region between the (Ni,Pt)Al phase region and the IDZ region. This additional region, composed of bright white and black particles, has a thickness of approximately 14.6 μm. The sum of the thickness of this additional region and the thickness of the (Ni,Pt)Al phase region is comparable to the thickness of the (Ni,Pt)Al phase region in the (Ni,Pt)Al coating.

[0051] The Hf and HfO2 particles in the CDB-(Ni,Pt)Al coating not only did not hinder the coating preparation process, but also significantly reduced the thickness of the interdiffusion zone (IDZ). Figure 1 As shown in Figure (d), the precipitates in the IDZ of the CDB-(Ni,Pt)Al coating mainly exist in the form of dispersed particles. In contrast, the IDZ of the (Ni,Pt)Al coating contains a large number of blocky precipitates. In terms of thickness, as shown in Table 3, the IDZ thickness of the CDB-(Ni,Pt)Al coating is 4.3 μm less than that of the (Ni,Pt)Al coating.

[0052] To further investigate the phase composition of the HfO2 / Al2O3 diffusion barrier in the CDB-(Ni,Pt)Al coating, the (Ni,Pt)Al region on the outer layer of the coating was removed by grinding. The resulting cross-sectional morphology is shown in the figure below. Figure 2 As shown in Figure (a), the phase composition of this region was analyzed using XRD, and the results are as follows. Figure 2As shown in Figure (b). XRD results show that this region is mainly composed of Al2O3, HfO2, NiAl and γ / γ'. It can be seen that the metal Hf in the original coating has been completely converted into HfO2, while the HfO2 in the coating reacts with Al to form Al2O3 in situ, as shown in Equation (1). The diffusion barrier's diffusion-blocking effect is also related to the density of the diffusion-blocking particles. In order to quantitatively evaluate the content of the two particles in the diffusion barrier layer, we used ImageJ software to stain and analyze the Al2O3 and HfO2 phases. The area fraction of the Al2O3 phase was measured to be 14.7%, and the area fraction of the HfO2 phase was 5.9%. The morphology and phase composition diagram of this region are shown in Figures (b). Figure 2 As shown in Figures (c) and (d), the particles are composed of bright white and black elliptical particles, which are made of black Al2O3 and white HfO2, respectively.

[0053]

[0054] Table 3 Thickness of each zone of the two coatings after aluminizing

[0055] Figure 3 The mass change curves of the two coatings after 600 cycles of oxidation at 1100 °C (one cycle consisting of 50 min at 1100 °C followed by 10 min cooling to room temperature) are shown. These curves reflect the dynamic relationship between the mass gain caused by high-temperature oxidation and the mass loss due to oxide scale peeling. In the first 20 cycles, both coatings showed significant mass gains due to the rapid formation of transient surface oxides. The mass gain of the CDB-(Ni,Pt)Al coating was higher than that of the (Ni,Pt)Al coating, mainly due to the longer duration of θ-Al₂O₃ on the CDB-(Ni,Pt)Al coating surface. As the θ-Al₂O₃ in the CDB-(Ni,Pt)Al coating transitioned to α-Al₂O₃, the rate of mass gain decreased rapidly. By the 28th cycle, the total mass gain of the CDB-(Ni,Pt)Al coating began to fall below that of the (Ni,Pt)Al coating. After 70 cycles, the (Ni,Pt)Al coating began to show sustained mass loss. In contrast, the CDB-(Ni,Pt)Al coating maintained steady mass growth over 600 cycles without significant peeling loss, indicating that the CDB-(Ni,Pt)Al coating has better resistance to oxide film peeling.

[0056] Figure 4The surface and cross-sectional morphologies of two coatings after 600 oxidation cycles at 1100 °C are shown. (a) and (b) are the surface and cross-sectional morphologies of the (Ni,Pt)Al coating after 600 oxidation cycles, respectively; (c) and (d) are the surface and cross-sectional morphologies of the CDB-(Ni,Pt)Al coating after 600 oxidation cycles, respectively. Table 4 shows... Figure 4 Corresponding morphological composition analysis diagrams. In the (Ni,Pt)Al coating, after 600 cycles, large areas of the oxide layer peeled off, and large cracks were visible in the peeled areas, such as... Figure 4 As shown in (a). EDS analysis of the exfoliated area confirmed that the newly formed oxide was entirely composed of aluminum oxide. Slight localized exfoliation of the CDB-(Ni,Pt)Al coating was also observed, but no cracks were found, as shown in (a). Figure 4 As shown in (c), bright white oxides are present along the original ridge structure on the coating surface in the exfoliated areas. EDS results (marked points 1 and 2) indicate that these white oxides contain Hf, suggesting that Hf in the diffusion barrier layer preferentially migrates through the coating ridge structure and enters the oxide layer with increasing oxidation time. The difference in PBR between hafnium oxide (PBR≈1.62) and alumina (PBR≈1.28) leads to significant local stress in these areas, resulting in preferential exfoliation of the upper alumina layer. Cross-sectional analysis after 600 cycles shows that both coatings exhibit a significant amount of γ'-Ni3Al degradation phase beneath the oxide layer, and the total thickness of the interfacial diffusion zone (IDZ) and surface reaction zone (SRZ) extends further into the matrix. The total thickness of the IDZ and SRZ of the (Ni,Pt)Al coating is 137.5 μm, while that of the ceramic-based diffusion barrier (Ni,Pt)Al coating is 82.8 μm. Although the interfacial diffusion zone in the ceramic-based diffusion barrier (Ni,Pt)Al coating also increases with prolonged exposure time, its total thickness is still significantly lower than that of the (Ni,Pt)Al coating. Furthermore, the SRZ in the CBD-(Ni,Pt)Al coating mainly consists of elliptical precipitates, with very little needle-like TCP phase. The (Ni,Pt)Al coating exhibits severe surface wrinkling and a large area of ​​oxide layer peeling, while the ceramic-based diffusion barrier (Ni,Pt)Al coating maintains a relatively smooth surface with limited peeling. EDS point analysis (marked point 3) also detected bright white HfO2 particles in the oxide layer of the ceramic-based diffusion barrier (Ni,Pt)Al coating.

[0057] Table 4 Figure 4 EDS results (at. %) of the marked points

[0058] Figure 5(a) and (b) are the elemental distribution diagrams of the (Ni,Pt)Al and CDB-(Ni,Pt)Al coatings after 600 oxidation cycles, respectively. It can be seen that the (Ni,Pt)Al coating exhibits a large number of needle-like Cr, Re, Mo, Ta, and W precipitates beneath the substrate. These elements are the main components of the TCP phase and will reduce the mechanical properties of the substrate. Furthermore, Al in the (Ni,Pt)Al coating is largely consumed during oxidation, resulting in the formation of a large amount of the degraded phase γ'-Ni3Al beneath the oxide film. Al diffuses into the substrate, leading to a continuous Al-depleted region at the bottom of the coating. Ta diffuses dramatically into the coating, and a large amount of Ta is detected in the coating.

[0059] In contrast, W, Mo, Re, Cr, and Ta precipitates were also observed in the CDB-(Ni,Pt)Al coating, but they were smaller and had lower densities. Furthermore, sufficient Al was still present beneath the coating, with no large-area degraded phase γ'-Ni3Al formed, and fewer aluminum-depleted regions. Regarding Ta diffusion, it was observed that Ta was primarily distributed below the coating interface and did not diffuse into the coating itself. This indicates that the CDB-(Ni,Pt)Al coating has a good diffusion-blocking effect on Ta and Al.

[0060] Example 2 Comparison of ceramic-based diffusion barrier coatings with different Hf contents Preparation process of ceramic-based diffusion barrier coatings with different Hf contents: composite electroplating of Ni-Hf-HfO2 layers and Pt-Hf layers with different Hf contents on the surface of second-generation nickel-based single-crystal superalloys, vacuum annealing and vapor phase aluminizing. (1) Matrix pretreatment: The matrix was a second-generation nickel-based single-crystal high-temperature alloy. The sample size was Φ15mm×2mm. The sample was polished with 600#, 1000#, 1500# and 2000# SiC sandpaper in sequence, and then wet sandblasted with quartz sand particles. After sandblasting, the sample was degreased in 50 g / L boiling sodium hydroxide aqueous solution for 10 min, and then ultrasonically cleaned with alcohol and deionized water for 30 min respectively to remove surface contaminants and oxide layer and ensure surface cleanliness.

[0061] (2) Composite electroplating of Ni-Hf-HfO2 layers: To obtain diffusion barrier coatings with different contents, different contents of Hf powder with a particle size of 300~500 nm and HfO2 powder with a particle size of 100~200 nm were added to the Watt nickel plating solution, and magnetic stirring was performed to ensure uniform dispersion of the powder. The pretreated sample was suspended in the electroplating tank with copper wire, with the sample as the cathode and the nickel mesh as the anode. The water temperature was maintained at 45 ℃ and the current density at 4.8 mA / cm² in the water bath. 2Electroplating was performed for 2 hours at a pH of 3. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried. The composition of the plating solution and the electroplating parameters are shown in Table 5. Based on the different particle contents, the three ceramic-based diffusion barrier coatings were named 5CBD-(Ni,Pt)Al, 10CBD-(Ni,Pt)Al, and 20CBD-(Ni,Pt)Al, respectively.

[0062] Table 5. Composition and electroplating parameters of nickel plating solution

[0063] (3) Composite electroplating of Pt-Hf layers: Hf powder with a particle size of 300~500 nm was added to an alkaline plating solution at a mass concentration of 30 g / L, and magnetic stirring was performed to ensure uniform dispersion of the powder. The sample with the electroplated Ni-Hf-HfO2 layer was suspended in the electroplating bath by copper wire, with the sample as the cathode and the platinum mesh as the anode. The water temperature was maintained at 80 ℃ and the current density at 7 mA / cm² in the water bath. 2 Electroplating was performed for 1 hour at a pH of 10. The specific composition and parameters of the plating solution are shown in Table 2. After electroplating, the sample was rinsed with deionized water, ultrasonically cleaned with alcohol, and then dried.

[0064] (4) Vacuum annealing treatment: The three electroplated samples were placed in a vacuum tube furnace and annealed under a vacuum of 1000 kJ / m². -3 Under the conditions of Pa and a heating rate of 10 °C / min, the coating was first held at 600 °C for 3 h to remove residual hydrogen and prevent defects such as bulging. Then, the temperature was raised to 1050 °C and held for 2 h to eliminate hydrogen introduced during the preparation process, reduce coating stress, and promote the full dissolution of Pt in the alloy matrix. After annealing, the coating was cooled to room temperature in the furnace.

[0065] (5) Vapor phase aluminizing treatment: The annealed sample was placed in a chemical vapor deposition vacuum furnace and held at 1050 °C for 6 h at a heating rate of 10 °C / min. Ar gas was introduced as a protective gas during the aluminizing process. The aluminizing agent consisted of iron-aluminum mixed powder (97 wt.%) and activator NH4Cl (3 wt.%). The iron-aluminum mixed powder contained 49 wt% iron powder and 51 wt% aluminum powder. After aluminizing, the sample was cooled to room temperature with the furnace and then removed. (Ni,Pt)Al coatings with different Hf contents were obtained, namely 5CBD-(Ni,Pt)Al, 10CBD-(Ni,Pt)Al and 20CBD-(Ni,Pt)Al.

[0066] Comparison of the performance of ceramic-based diffusion barrier coatings with different Hf contents After diffusion annealing and vapor phase aluminizing treatments, the surface and cross-sectional morphologies of the three samples are as follows: Figure 6 As shown, (a) and (b) are surface and cross-sectional morphology diagrams of 5CDB-(Ni,Pt)Al, (c) and (d) are surface and cross-sectional morphology diagrams of 10CDB-(Ni,Pt)Al, and (e) and (f) are surface and cross-sectional morphology diagrams of 20CDB-(Ni,Pt)Al. From the surface morphology, it can be seen that all three coatings exhibit an equiaxed grain structure separated by grain boundary ridges, showing similar surface characteristics. However, with the increase of Hf content, the grain size on the coating surface gradually decreases, with the 20CDB-(Ni,Pt)Al coating exhibiting the finest grain size, indicating that the increase of Hf content significantly inhibits grain growth during aluminizing.

[0067] Cross-sectional morphology reveals that all three coatings consist of a NiAl region, a diffusion barrier region (DB), and an interdiffusion zone (IDZ), the thicknesses of which are listed in Table 6. With increasing Hf content, the thickness of the diffusion barrier region gradually increases, while the thickness of the interdiffusion zone gradually decreases. The 20CBD-(Ni,Pt)Al coating exhibits the largest diffusion barrier region thickness, reaching 16.7 μm, while its interdiffusion zone thickness is the smallest, at only 10.2 μm. This phenomenon indicates that the addition of a ceramic-based diffusion barrier not only does not hinder the coating formation process but also effectively suppresses the diffusion of matrix elements to the surface, protecting the mechanical properties of the matrix.

[0068] Table 6 Thickness of each zone of the three coatings after aluminizing

[0069] Figure 7 In the figures (a) and (b), the diffusion barrier morphology and phase content of the 5CDB-(Ni,Pt)Al coating are shown; (c) and (d) represent the diffusion barrier morphology and phase content of the 10CDB-(Ni,Pt)Al coating; and (e) and (f) represent the diffusion barrier morphology and phase content of the 20CDB-(Ni,Pt)Al coating.

[0070] ImageJ software was used to stain the diffusion barrier regions of the three coatings, and the area percentage of each phase was calculated. For the 5CBD-(Ni,Pt)Al coating, the area fraction of Al2O3 was 3.3%, and HfO2 was 0.4%; in the 10CBD-(Ni,Pt)Al coating, the area fraction of Al2O3 was 14.7%, and HfO2 was 5.9%; and in the 20CBD-(Ni,Pt)Al coating, the area fraction of Al2O3 was 16.3%, and HfO2 was 6.7%. It can be seen that with the increase of Hf content in the coating, the contents of Al2O3 and HfO2 in the diffusion barrier region increase synchronously, indicating that the amount of ceramic phase formed is positively correlated with the initial amount of Hf added.

[0071] Figure 8 The mass change curves of three coatings—5CDB-(Ni,Pt)Al, 10CDB-(Ni,Pt)Al, and 20CDB-(Ni,Pt)Al—after 600 cycles of oxidation at 1100℃ (one cycle consisting of 50 min at 1100℃ followed by 10 min cooling to room temperature) are shown. In the initial oxidation phase (the first 20 cycles), all three coatings showed significant weight gain due to the rapid growth of transient oxides. With increasing cycle count, the 5CBD-(Ni,Pt)Al coating began to show a continuous mass decrease after approximately 380 cycles, indicating that its surface oxide film had peeled off. In contrast, the 10CBD-(Ni,Pt)Al and 20CBD-(Ni,Pt)Al coatings maintained a continuous weight gain trend throughout the entire 600 cycles, without significant oxide scale peeling. Among them, the 20CBD-(Ni,Pt)Al coating showed the least weight gain, with only 0.38 mg / cm² after 600 cycles of oxidation, demonstrating the best cyclic antioxidant performance.

[0072] Figure 9In the images, (a) and (b) show the surface and cross-sectional morphology of 5CDB-(Ni,Pt)Al, (c) and (d) show the surface and cross-sectional morphology of 10CDB-(Ni,Pt)Al, and (e) and (f) show the surface and cross-sectional morphology of 20CDB-(Ni,Pt)Al after 600 oxidation cycles at 1100℃. In the 5CDB-(Ni,Pt)Al coating, after 600 cycles, the oxide layer showed multiple large-area peelings, with large cracks visible in the peeling areas, and the surface undulations were the most significant. A large amount of Ni3Al degradation phase was generated below the oxide film and at the diffusion barrier boundary, and many needle-like TCP phases appeared in the matrix. In both the 10CBD-(Ni,Pt)Al and 20CBD-(Ni,Pt)Al coatings, only small areas of oxide film peeling occurred. The 20CBD-(Ni,Pt)Al coating had a smoother surface and the least amount of Ni3Al degradation phase. Furthermore, a blocky TCP phase was observed deep within the matrix of the 10CBD-(Ni,Pt)Al coating, while an elliptical TCP phase was observed in the 20CBD-(Ni,Pt)Al coating. Comparing the thicknesses of different regions of the three coatings, as shown in Table 7, the 20CBD-(Ni,Pt)Al coating had the thinnest total thickness of the IDZ and SRZ regions, at only 69.5 μm, while its DB region was the thickest, at 24.5 μm. Additionally, bright white HfO2 particles were present in the oxide film. Figure 9 As indicated by the blue arrow in the middle.

[0073] Table 7. Thickness of each zone of the three coatings after 600 cycles

[0074] Figure 10 Images (a) to (c) show the distribution of major elements in three coatings (5CDB-(Ni,Pt)Al, 10CDB-(Ni,Pt)Al, and 20CDB-(Ni,Pt)Al) after oxidation at 1100℃ for 600 h, respectively. In the 5CDB-(Ni,Pt)Al coating, a large number of large needle-like Cr, Re, Mo, Ta, and W precipitates appear beneath the substrate. These elements are the main components of the TCP phase, and their presence reduces the mechanical properties of the substrate. Simultaneously, Al in this coating is consumed during oxidation, forming a large-area degraded phase γ'-Ni3Al beneath the oxide film. Furthermore, Al diffuses into the substrate, resulting in a continuous Al-depleted region at the bottom of the coating. Ta also diffuses slightly into the coating, and a small amount of Ta can be detected within the coating.

[0075] For both 10CBD-(Ni,Pt)Al and 20CBD-(Ni,Pt)Al coatings, precipitates of W, Mo, Re, Cr, and Ta were observed. The TCP precipitates in the 20CBD-(Ni,Pt)Al coating exhibited a diffusely distributed elliptical morphology, which better maintained the mechanical properties of the matrix. Figure 10 (b) and Figure 10 As shown in (c). Furthermore, the 20CBD-(Ni,Pt)Al coating retains sufficient Al elements beneath it, without the formation of a large-area degraded phase γ'-Ni3Al, and exhibits fewer Al-depleted regions. Regarding Ta diffusion, Ta elements are mainly distributed below the coating interface and do not diffuse into the coating interior. This indicates that the diffusion barrier effect of the CDB-(Ni,Pt)Al coating on Ta and Al elements increases with increasing Hf content.

[0076] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An in-situ formed ceramic-based diffusion barrier platinum-aluminum coating, characterized in that, The coating, from the outside to the inside, includes: an outer platinum-aluminum coating, an in-situ generated HfO2 / Al2O3 ceramic-based diffusion barrier region, and an interdiffusion layer.

2. The in-situ formed ceramic-based diffusion barrier platinum-aluminum coating according to claim 1, characterized in that, The coating composition is distributed in a gradient from the outside to the inside, and the phase structure gradually transitions from high aluminum phase and medium aluminum phase to low aluminum phase from the outside to the inside.

3. A method for preparing an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating according to claim 1 or 2, characterized in that, The process includes the following steps: introducing a Ni-HfO2-Hf layer or a Ni-HfO2 layer onto a substrate, and then introducing a Pt layer or a Pt-Hf layer onto the Ni-HfO2-Hf layer or the Ni-HfO2 layer; subsequently, performing vacuum diffusion annealing and vapor phase aluminizing treatment on the resulting composite coating to obtain the in-situ formed ceramic-based diffusion barrier platinum-aluminum coating.

4. The preparation method according to claim 3, characterized in that, The substrate comprises a nickel-based single-crystal superalloy; the introduction of the Ni-HfO2-Hf layer, Ni-HfO2 layer, Pt layer and Pt-Hf layer includes electroplating, sputtering or ion implantation; the thickness of the Ni-HfO2-Hf layer or Hf layer is 12-18 μm, and the thickness of the Pt or Pt-Hf layer is 3-7 μm.

5. The preparation method according to claim 4, characterized in that, The Ni-HfO2-Hf layer or Ni-HfO2 layer, Pt layer or Pt-Hf layer is introduced by electroplating. The specific electroplating conditions for the Ni-HfO2-Hf layer or Ni-HfO2 layer are: electroplating temperature 40-50℃, current density 4.8 mA / cm². 2 The pH value is 3-4, and the electroplating time is 2 hours. Specific electroplating conditions for the Pt or Pt-Hf layer are: electroplating temperature 70-80℃, current density 7 mA / cm². 2 The pH value is 10.0–11.0, and the electroplating time is 1 hour.

6. The preparation method according to claim 3, characterized in that, The vacuum degree of the vacuum diffusion annealing process is less than 1×10⁻⁶. -3 Pa, heating rate of 5-10 ℃ / min, annealing temperature of 1000-1080 ℃, holding time of 1-4 h.

7. The preparation method according to claim 3, characterized in that, The vapor phase aluminizing treatment was carried out at 1020–1080 °C for 6 h. Ar gas was introduced as a protective gas during the aluminizing process. The aluminizing agent was composed of iron-aluminum mixed powder and activator NH4Cl, wherein the NH4Cl content was 1–4 wt%; and the iron powder content in the iron-aluminum mixed powder was 49 wt%.

8. The application of an in-situ formed ceramic-based diffusion barrier platinum-aluminum coating according to claim 1 or 2 in the aerospace field.

9. The application according to claim 8, characterized in that, Application of the in-situ formed ceramic-based diffusion barrier platinum-aluminum coating in protective coatings for aerospace engine components.

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