A high temperature protective coating with linearly varying composition and method of making

Abstract

The application discloses a high-temperature protective coating with linearly changed components and a preparation method thereof. The high-temperature protective coating is coated on an alloy substrate, and the content of the component elements of the high-temperature protective coating linearly changes. The component elements of the innermost layer of the high-temperature protective coating are metal elements with the minimum value of the content of the elements in the alloy substrate being greater than or equal to 4%. The component elements of the outermost layer of the high-temperature protective coating are only protective elements. The content of the protective elements in the high-temperature protective coating gradually increases from inside to outside to 100%, and the content of other elements gradually decreases from inside to outside to 0%. The high-temperature protective coating with linearly changed components is deposited on the alloy substrate by gradiently adjusting the sputtering power of each target material. The application overcomes the problems of interdiffusion and internal stress caused by large component change of the traditional high-temperature protective coating, and has a predictable huge economic value.

Description

Technical Field

[0001] This invention relates to the fields of metal materials science and the design and application technology of high-temperature protective coatings, specifically to a high-temperature protective coating with linearly varying composition and its preparation method. Background Technology

[0002] In existing technologies, aero-engines generally operate in high-temperature and high-pressure environments, and in coastal areas, they need to operate in environments containing Cl and S. These factors are destructive to aero-engines. Therefore, the materials used to manufacture aero-engines not only require high high-temperature strength but also good creep resistance and high-temperature performance. Furthermore, for every 100°C increase in turbine inlet temperature, thrust can increase by 20%. To pursue higher engine thrust-to-weight ratio and thermal efficiency, turbine inlet temperature also needs to be further increased, which places higher demands on the alloys used in the engine. However, the high-temperature resistance of traditional high-temperature alloys has approached its performance limit. To meet the requirements of high-temperature alloys operating in more severe environments, high-temperature protective coatings need to be prepared on the alloy surface.

[0003] High-temperature protective coatings refer to a series of coatings that can be used at high temperatures and provide good resistance to oxidation and hot corrosion, preventing the rapid consumption of the base alloy due to the formation of non-protective oxides. Their protective effect mainly comes from the slowly growing oxide film on their surface, including Al₂O₃, Cr₂O₃, and SiO₂. Taking Al as an example, it is a key element for the alloy's resistance to high-temperature oxidation. Alloys with a certain Al content can form a protective oxide film during oxidation. This oxide film has low cation vacancies and provides protection against hot corrosion above 1000℃ and type I (800-950℃). However, excessively high Al content will cause the alloy to become brittle and have poor mechanical properties. To meet the requirements of practical applications, high-temperature protective coatings are usually applied to the surface of alloys that meet high-temperature mechanical properties to satisfy the alloy's resistance to high-temperature oxidation. However, preparing a high-Al content metal coating on the surface of a high-temperature alloy will lead to a significant elemental gradient at its transition interface, resulting in elemental diffusion, affecting the mechanical properties of the base material and the bonding performance of the coating. This significantly reduces the theoretical service life in actual use.

[0004] In the prior art, CN114277350A discloses a structurally stable nano-high-temperature protective coating and its preparation method. The coating is doped with non-metallic elements, and the content of other elements is consistent with that of the alloy. Although the coating composition is basically consistent with the alloy, slowing down the interdiffusion between the coating and the alloying elements in the substrate, the protective effect on the substrate material in high-temperature environments is not significantly improved because the content of protective elements is not significantly increased. CN114293147B discloses a nickel-based high-temperature alloy material and its preparation method. The protective coating includes an anti-diffusion bonding layer and a multi-layer gradient coating from the substrate to the surface. The anti-diffusion bonding layer is a high-entropy FeCoNiCrSiB alloy coating. The multi-layer gradient coating consists of a CrCeN coating, an AlCrN coating, an AlCrSiN coating, and an AlCrSiCeN coating, sequentially from the inside out. The content and types of alloying elements between the layers in the above coating still have significant differences, failing to solve the problem of significant interdiffusion between elements in the coatings.

[0005] Therefore, there is an urgent need for a high-temperature protective coating with linearly varying composition, which can provide good mechanical properties without cracking due to stress. Summary of the Invention

[0006] To address the aforementioned limitations of existing technologies, the present invention aims to provide a high-temperature protective coating with linearly varying composition and its preparation method. This invention utilizes magnetron sputtering technology to prepare a high-temperature protective coating. The composition of this coating is based on the matrix alloy composition and exhibits a linear variation from the inside out, with the innermost coating layer having a composition close to that of the matrix alloy, and the outermost layer being a protective element layer. The high-temperature protective coating with linearly varying composition obtained by this invention effectively overcomes the problems of decreased mechanical properties caused by interfacial interdiffusion between the alloy matrix and the coating; stress caused by phase transformation resulting from the reaction of aluminum-rich (chromium) layers and nickel-rich (iron, cobalt, etc.) layers, leading to cracking; and internal stress caused by excessive chemical element gradients, resulting in a short coating service life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a high-temperature protective coating with linearly varying composition, wherein the high-temperature protective coating with linearly varying composition is applied to an alloy substrate, and the content of its constituent elements varies linearly from the inside to the outside of the alloy substrate; wherein,

[0009] The innermost layer of the high-temperature protective coating with linear composition variation consists of metallic elements whose minimum content range in the alloy matrix is ​​≥4%. The content of the innermost layer constituent elements is determined by the following values: (excluding the main element in the alloy matrix) the content of other constituent elements is taken as the percentage of that element in the alloy matrix. ofMinimum value, balance is the main element in the alloy matrix;

[0010] The outermost layer of the high-temperature protective coating with linearly varying composition consists only of protective elements.

[0011] In the high-temperature protective coating with linearly varying composition, the content of protective elements gradually increases to 100% from the inside out, while the content of other elements gradually decreases to 0% from the inside out.

[0012] The protective element is Al or Cr.

[0013] Preferably, the alloy matrix is ​​a nickel-based superalloy, a cobalt-based superalloy, an iron-based superalloy, or a titanium alloy.

[0014] Preferably, the thickness of the high-temperature protective coating with linearly varying composition is 20-50 μm.

[0015] A second aspect of the present invention provides a method for preparing a high-temperature protective coating with linearly varying composition, comprising the following steps:

[0016] By employing magnetron sputtering or multi-arc ion plating, a corresponding target material is selected based on the elemental composition of the high-temperature protective coating, and deposited on the surface of the alloy substrate to obtain a high-temperature protective coating with linearly varying composition.

[0017] Preferably, the specific operation of applying a high-temperature protective coating with linearly varying composition to the surface of the alloy substrate using magnetron sputtering is as follows:

[0018] After surface pretreatment of the alloy substrate, a high-temperature protective coating is deposited by adjusting the power of each target material by magnetron sputtering.

[0019] Preferably, the target material is a pure metal target.

[0020] Further preferably, each element is the same as the constituent element of the high-temperature protective coating, and is used as an element of the pure metal target.

[0021] Preferably, the power of each target material in magnetron sputtering is 0-1000W, and the deposition time is 4-12h.

[0022] Preferably, during magnetron sputtering, the change in power of each target material within a unit deposition time is the same as the change in element content of the corresponding element in the high-temperature protective coating with linear composition change within a unit deposition time, and the sum of the power of each target material is equal to the total power of the magnetron sputtering target.

[0023] The total power of the magnetron sputtering target is 1000W.

[0024] More preferably, the change in element content per unit deposition time is calculated using the following formula:

[0025] K Ⅰ = Formula (I)

[0026] In equation (I), K I 1 represents the change in element content per unit deposition time, expressed as % / hour; a represents the content of a certain element in the outermost layer of the high-temperature protective coating, expressed as %; b represents the content of the same element in the innermost layer of the high-temperature protective coating, expressed as %; t represents the deposition time, expressed as hours.

[0027] Preferably, the surface pretreatment operation of the alloy substrate is as follows: after grinding the alloy substrate, it is ultrasonically cleaned in a mixture of acetone and ethanol for 8-12 minutes, and then dried at 80-100℃ for 10-15 minutes.

[0028] More preferably, the volume fraction of both acetone and ethanol in the mixture is 50%.

[0029] Preferably, the parameters for depositing the high-temperature protective layer are: the distance between the target and the alloy substrate is 10-20 cm; during the bias cleaning process, the vacuum degree is 3×10⁻⁶. -3 The temperature is 300℃, the bias voltage is -400V, and the cleaning time is 5min; during sputtering, argon gas is introduced to a vacuum of 0.2Pa, the temperature is 200℃, and the sputtering time is 4-12h.

[0030] The beneficial effects of this invention are:

[0031] The alloy element content of the high-temperature protective coating prepared by this invention varies from the inside to the outside of the alloy matrix; the innermost layer consists of metallic elements with an element content ≥4% in the alloy matrix, while the outermost layer consists only of protective elements. Because the composition and content of the innermost layer of the high-temperature protective coating are similar to those of the alloy matrix, the problem of decreased mechanical properties caused by interfacial interdiffusion is overcome. Simultaneously, it overcomes the stress caused by phase transformation resulting from the reaction between aluminum-rich (chromium) layers and nickel-rich (iron, cobalt, etc.) layers, thus preventing cracking.

[0032] The high-temperature protective coating prepared by this invention exhibits a linear variation in element content from the inside out, with the content of protective elements gradually increasing to 100% from the inside out. This ensures that the outermost layer of the high-temperature protective coating is entirely composed of protective elements, meeting the coating's high-temperature resistance requirements. Simultaneously, the gradient change in element content from the inside out reduces the internal stress of the coating and extends its service life. Attached Figure Description

[0033] Figure 1 (a) Surface SEM image of the high-temperature protective coating obtained in Example 1; (b) Cross-sectional SEM image of the high-temperature protective coating obtained in Example 1;

[0034] Figure 2 SEM images of the cross-sections of the coatings prepared in Example 1 and Comparative Example 1 after isothermal oxidation at 1000℃.

[0035] Figure 3 Oxidation weight gain kinetics curves of the coatings prepared in Example 1 and Comparative Example 1 at 1000°C;

[0036] Figure 4 Example 1: Fracture morphology of the high-temperature protective coating obtained;

[0037] Figure 5 Fracture morphology of the high-temperature protective coating prepared in Comparative Example 1;

[0038] Figure 6 Example 4: Oxidation weight gain kinetics curve of the high-temperature protective coating at 1000℃;

[0039] Figure 7 Example 1: Elemental distribution diagram of the cross-section of the high-temperature protective coating;

[0040] Figure 8 Example 4: Elemental distribution diagram of the cross-section of the high-temperature protective coating;

[0041] Figure 9 (a) Surface SEM image of the high-temperature protective coating obtained in Example 4; (b) Cross-sectional SEM image of the high-temperature protective coating obtained in Example 4;

[0042] Figure 10 Example 2: Cross-sectional elemental distribution of the high-temperature protective coating. Detailed Implementation

[0043] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.

[0044] As described in the background art, in the prior art, Al, Cr and Si are elements that have good protective properties in high-temperature service environments. However, their single-element coatings on alloy substrates have drawbacks such as large coefficient of thermal expansion, low adhesion, high stress, element interdiffusion, and poor overall mechanical properties, making them unsuitable for harsh service environments during use.

[0045] Based on this, the present invention takes the alloy matrix elements as the starting point and adopts a linear transition method to make the outermost layer of the coating a pure Al or pure Cr layer. Specifically, the high-temperature protective coating is applied to the alloy matrix, and the content of its constituent elements changes linearly from the inside to the outside of the alloy matrix; the innermost constituent element of the high-temperature protective coating is a metallic element whose minimum content range in the alloy matrix is ​​≥4%, and the content of the innermost constituent element of the high-temperature protective coating is: except for the main element in the alloy matrix, the content of other constituent elements is the minimum content range of that element in the alloy matrix, and the remainder is the main element in the alloy matrix; the outermost constituent element of the high-temperature protective coating is only a protective element; the content of the protective element in the high-temperature protective coating gradually increases to 100% from the inside to the outside, and the content of other elements gradually decreases to 0% from the inside to the outside; the protective element is Al or Cr.

[0046] Meanwhile, this invention selects either magnetron sputtering or multi-arc ion plating, choosing the corresponding target material based on the elemental composition of the high-temperature protective coating, and depositing it on the surface of the alloy substrate to obtain the high-temperature protective coating. Specifically, when using magnetron sputtering to coat the high-temperature protective coating onto the surface of the alloy substrate, the process involves: after surface pretreatment of the alloy substrate, adjusting the power of each magnetron sputtering target by gradient to deposit the high-temperature protective coating.

[0047] In magnetron sputtering, sputtering power affects the sputtering content of the target material; higher power results in a higher content of sputtered elements. Therefore, the content of sputtered components can be controlled by adjusting the power of each target. By controlling the power of each target, the content of each element in the high-temperature protective coating can be controlled to vary linearly from the inside out, ensuring that the sputtering amount of each target meets the expected requirements and changes according to the anticipated pattern.

[0048] The main element is the most abundant element in the alloy matrix.

[0049] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0050] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0051] Example 1: Preparation of a high-temperature protective coating with linear composition variation on a K403 nickel-based superalloy substrate

[0052] The constituent elements and contents of the K403 nickel-based superalloy are shown in Table 1:

[0053] Table 1. Composition elements and content of K403 nickel-based superalloy

[0054]

[0055] 1. Composition:

[0056] The high-temperature protective coating with linearly varying composition exhibits a linear change in elemental content from the inside to the outside of the alloy substrate, and its thickness is 50 μm.

[0057] The innermost layer of the high-temperature protective coating with linearly varying composition consists of 10% Cr, 4.5% Co, 4.8% W, 5.3% Al, and Ni as the balance; the outermost layer consists of 100% Al, i.e., Al is the protective element in this embodiment; the Al content in the high-temperature protective coating gradually increases to 100% from the inside out, while the content of other elements gradually decreases to 0% from the inside out.

[0058] The linear variation range of each element and its corresponding percentage content in the high-temperature protective coating with linear composition from the inside to the outside is as follows: Al: 5.3%-100%, Cr: 10%-0%, Co: 4.5%-0%, W: 4.8%-0%, Ni: 75.4%-0%.

[0059] 2. Preparation method:

[0060] (1) Based on the composition of the high-temperature protective coating, select pure Ni target, pure Al target, pure Co target, pure Cr target, and pure W target;

[0061] (2) K403 nickel-based alloy was wire-cut into thin sheets of 12mm×10mm×20mm as the alloy substrate. The surface of the alloy was first polished with 100#, 200#, 400#, 800# and 1000# sandpaper. Then it was ultrasonically cleaned with a mixture of 50% acetone and 50% ethanol for 10 minutes. Finally, it was placed in a 90℃ drying oven and dried for 13 minutes to obtain the alloy substrate after surface pretreatment.

[0062] The pretreated alloy substrate was placed in a magnetron sputtering vacuum chamber. The distance between each target and the alloy substrate in the vacuum chamber was adjusted to 15 cm, and the vacuum was evacuated to a vacuum level of 3 × 10⁻⁶. -3 Pa, set the temperature in the vacuum chamber to 300℃, and set the bias voltage to -400 V to perform bias cleaning on the alloy substrate for 5 minutes to further remove contaminants from the surface of the alloy substrate;

[0063] (3) After the bias cleaning is completed, argon gas is introduced to a vacuum of 0.2 Pa, and the magnetron sputtering power is adjusted by gradient at 200°C for 10 hours to obtain a high-temperature protective coating.

[0064] The method for gradient-adjusted magnetron sputtering power specifically involves determining the change in element content K of a corresponding element per unit deposition time based on the change in element content from the inside to the outside of the alloy matrix. I Specifically:

[0065] Change in Ni content per unit deposition time (% / hour): K Ni =-7.54;

[0066] Change in elemental content of Al per unit deposition time (% / hour): K Al =9.47;

[0067] Change in elemental concentration of Co per unit deposition time (% / hour): K Co =-0.45;

[0068] Change in Cr content per unit deposition time (% / hour): K Cr =-1;

[0069] Change in element content of element W per unit deposition time (% / hour): K W =-0.48.

[0070] Therefore, the sputtering power and gradient changes of each target material can be obtained as follows:

[0071] The sputtering power of the Ni target gradually decreased from 754 W to 0 W over 10 hours. The change in power per unit time corresponds to the change in Ni element content per unit time, K. Ni Consistent;

[0072] The sputtering power of the Al target gradually increased from 53W to 1000W over 10 hours. The change in power per unit time corresponds to the change in Al element content per unit time, K. Al Consistent;

[0073] The sputtering power of the Co target gradually decreased from 45W to 0W over 10 hours. The change in power per unit time corresponds to the change in Co element content per unit time, K. Co Consistent;

[0074] The sputtering power of the Cr target gradually decreased from 100W to 0W over 10 hours. The change in power per unit time corresponds to the change in Cr element content per unit time, K. Cr Consistent;

[0075] The sputtering power of the W target gradually decreased from 48W to 0W over 10 hours. The change in power per unit time of the target is related to the change in W element content per unit time, K.W Consistent.

[0076] The elemental distribution of the cross-section of the high-temperature protective coating obtained in this embodiment is as follows: Figure 7 As shown in the figure. The surface and cross-sectional SEM morphology of the high-temperature protective coating obtained in this embodiment are as follows. Figure 1 As shown, by Figure 1 It can be seen that the coating has a typical columnar crystal structure, with a spherical cap-shaped surface, and the high-temperature protective coating is continuous and dense, without defects such as cracks or voids.

[0077] Example 2: Preparation of a high-temperature protective coating with linear composition variation on a K403 nickel-based superalloy substrate

[0078] In this embodiment, the elemental composition and mass fraction of the K403 nickel-based superalloy matrix are the same as in Example 1.

[0079] 1. Composition

[0080] The high-temperature protective coating with linearly varying composition exhibits a linear change in elemental content from the inside to the outside of the alloy substrate, and its thickness is 20 μm.

[0081] The innermost layer of the high-temperature protective coating with linearly varying composition consists of the following elements and their contents: 10% Cr, 4.5% Co, 4.8% W, 5.3% Al, and 75.4% Ni; the outermost layer consists of the following elements and their contents: 100% Cr, i.e., Cr is the protective element in this embodiment; the Cr content in the high-temperature protective coating gradually increases to 100% from the inside out, while the contents of other elements gradually decrease to 0% from the inside out.

[0082] The linear variation range of each component in the high-temperature protective coating and its corresponding percentage content in the coating from the inside to the outside is as follows: Cr: 10%-100%, Al: 5.3%-0%, Co: 4.5%-0%, W: 4.8%-0%, Ni: 75.4%-0%.

[0083] 2. Preparation method:

[0084] (1) Based on the composition of the high-temperature protective coating, select pure Ni target, pure Al target, pure Co target, pure Cr target, and pure W target;

[0085] (2) K403 nickel-based alloy was wire-cut into thin sheets of 12mm×10mm×20mm as the alloy substrate. The surface of the alloy was first polished with 100#, 200#, 400#, 800# and 1000# sandpaper. Then it was ultrasonically cleaned with a mixture of 50% acetone and 50% ethanol for 8 minutes. Finally, it was placed in an 80℃ drying oven and dried for 10 minutes to obtain the alloy substrate after surface pretreatment.

[0086] The pretreated alloy substrate was placed in a magnetron sputtering vacuum chamber, and the distance between each target and the alloy substrate in the chamber was adjusted to 10 cm. The vacuum was then evacuated to a vacuum level of 3 × 10⁻⁶. -3 Pa, set the temperature in the vacuum chamber to 300℃, and set the bias voltage to -400V to perform bias cleaning on the alloy substrate for 5 minutes to further remove contaminants from the surface of the alloy substrate;

[0087] (3) After the bias cleaning is completed, argon gas is introduced to a vacuum of 0.2 Pa, and the magnetron sputtering power is adjusted by gradient at 200°C for 4 hours to obtain a high-temperature protective coating.

[0088] The specific method for gradient-adjusted magnetron sputtering power is as follows:

[0089] Based on the change in elemental content from the inside to the outside of the alloy matrix, determine the change in elemental content K of the corresponding element per unit deposition time. I Specifically:

[0090] Change in Ni content per unit deposition time (% / hour): K Ni =-18.85;

[0091] Change in elemental content of Al per unit deposition time (% / hour): K Al =-1.325;

[0092] Change in elemental concentration of Co per unit deposition time (% / hour): K Co =-1.125;

[0093] Change in Cr content per unit deposition time (% / hour): K Cr =22.5;

[0094] Change in element content of element W per unit deposition time (% / hour): K W =-1.2;

[0095] Therefore, the sputtering power and gradient changes of each target material can be obtained as follows:

[0096] The sputtering power of the Ni target gradually decreased from 754 W to 0 W over 10 hours. The change in power per unit time corresponds to the change in Ni element content per unit time, K. Ni Consistent;

[0097] The sputtering power of the Al target gradually decreased from 53W to 0W over 10 hours. The change in power per unit time corresponds to the change in Al element content per unit time, K. Al Consistent;

[0098] The sputtering power of the Co target gradually decreased from 45W to 0W over 10 hours. The change in power per unit time corresponds to the change in Co element content per unit time, K. Co Consistent;

[0099] The sputtering power of the Cr target gradually decreased from 100W to 1000W over 10 hours. The change in power per unit time corresponds to the change in Cr element content per unit time, K. Cr Consistent;

[0100] The sputtering power of the W target gradually decreased from 48W to 0W over 10 hours. The change in power per unit time and the change in W content per unit time are related by K. W Consistent;

[0101] Example 3: Preparation of a high-temperature protective coating with linear composition variation on a K403 nickel-based superalloy substrate

[0102] In this embodiment, the elemental composition and mass fraction of the K403 nickel-based superalloy matrix are the same as in Example 1.

[0103] 1. Composition

[0104] The high-temperature protective coating with linearly varying composition exhibits a linear change in elemental content from the inside to the outside of the alloy substrate, and its thickness is 50 μm.

[0105] The innermost layer of the linearly varying high-temperature protective coating consists of the following elements and their contents: 10% Cr, 4.5% Co, 4.8% W, 5.3% Al, and 75.4% Ni. The outermost layer consists of the following elements and their contents: 100% Al, i.e., Al is the protective element in this embodiment. The Al content in the linearly varying high-temperature protective coating gradually increases to 100% from the inside out, while the contents of other elements gradually decrease to 0% from the inside out.

[0106] The linear variation range of each component in the high-temperature protective coating and its corresponding percentage content in the coating from the inside to the outside is as follows: Al: 5.3%-100%, Cr: 10%-0%, Co: 4.5%-0%, W: 4.8%-0%, Ni: 75.4%-0%.

[0107] 2. Preparation method:

[0108] (1) Based on the composition of the high-temperature protective coating, select pure Ni target, pure Al target, pure Co target, pure Cr target, and pure W target;

[0109] (2) K403 nickel-based alloy was wire-cut into thin sheets of 12mm×10mm×20mm as the alloy substrate. The surface of the alloy was first polished with 100#, 200#, 400#, 800# and 1000# sandpaper. Then it was ultrasonically cleaned with a mixture of 50% acetone and 50% ethanol for 12 minutes. Finally, it was placed in a 100℃ drying oven and dried for 15 minutes to obtain the alloy substrate after surface pretreatment.

[0110] The pretreated alloy substrate was placed in a magnetron sputtering vacuum chamber. The distance between each target and the alloy substrate in the chamber was adjusted to 20 cm, and the vacuum was evacuated to a vacuum level of 3 × 10⁻⁶. -3 Pa, set the temperature in the vacuum chamber to 300℃, and set the bias voltage to -400V to perform bias cleaning on the alloy substrate for 5 minutes to further remove contaminants from the surface of the alloy substrate;

[0111] (3) After the bias cleaning is completed, argon gas is introduced to a vacuum of 0.2 Pa, and the magnetron sputtering power is adjusted by gradient at 200°C for 12 hours to obtain a high-temperature protective coating.

[0112] The specific method for gradient-adjusted magnetron sputtering power is as follows:

[0113] Based on the change in elemental content from the inside to the outside of the alloy matrix, determine the change in elemental content K of the corresponding element per unit deposition time. I Specifically:

[0114] Change in Ni content per unit deposition time (% / hour): K Ni =-6.28;

[0115] Change in elemental content of Al per unit deposition time (% / hour): K Al =7.89;

[0116] Change in elemental concentration of Co per unit deposition time (% / hour): K Co =-0.83;

[0117] Change in Cr content per unit deposition time (% / hour): K Cr =-0.375;

[0118] Change in element content of element W per unit deposition time (% / hour): K W =-0.4.

[0119] Therefore, the sputtering power and gradient changes of each target material can be obtained as follows:

[0120] The sputtering power of the Ni target gradually decreased from 754 W to 0 W over 10 hours. The change in power per unit time corresponds to the change in Ni element content per unit time, K. Ni Consistent;

[0121] The sputtering power of the Al target gradually increased from 53W to 1000W over 10 hours. The change in power per unit time corresponds to the change in Al element content per unit time, K. Al Consistent;

[0122] The sputtering power of the Co target gradually decreased from 45W to 0W over 10 hours. The change in power per unit time corresponds to the change in Co element content per unit time, K. Co Consistent;

[0123] The sputtering power of the Cr target gradually decreased from 100W to 0W over 10 hours. The change in power per unit time corresponds to the change in Cr element content per unit time, K. Cr Consistent;

[0124] The sputtering power of the W target gradually decreased from 48W to 0W over 10 hours. The change in power per unit time of the target is related to the change in W element content per unit time, K. W Consistent.

[0125] Example 4: Preparation of a high-temperature protective coating with linear composition variation on TC4 titanium alloy

[0126] The main constituent elements and their contents of the TC4 titanium alloy are shown in Table 2:

[0127] Table 2. Main constituent elements and content of TC4 titanium alloy

[0128] Element Al V Ti Content (%) 5.5-6.8 3.5-4.5 Balance

[0129] 1. Composition:

[0130] The high-temperature protective coating with linearly varying composition exhibits a linear variation in elemental content from the inside out of the alloy substrate, and its thickness is 21 μm.

[0131] The innermost layer of the linearly varying high-temperature protective coating consists of 5.5% Al and 94.5% Ti, while the outermost layer consists of 100% Al. In this embodiment, the protective element is Al. The Al content in the linearly varying high-temperature protective coating gradually increases to 100% from the inside out, while the content of other elements gradually decreases to 0% from the inside out.

[0132] The linear variation range of each component in the high-temperature protective coating and its corresponding percentage content in the coating from the inside to the outside is as follows: Al: 5.5%-100%, Ti: 94.5%-0%.

[0133] 2. Preparation method:

[0134] (1) Based on the composition of the high-temperature protective coating, select pure Al target and pure Ti target;

[0135] (2) The TC4 titanium alloy was wire-cut into a thin sheet of 2mm×10mm×20mm as the alloy substrate. The alloy substrate was subjected to surface pretreatment, and the surface pretreatment operation was the same as in Example 1.

[0136] The pretreated alloy substrate was placed in a magnetron sputtering vacuum chamber and subjected to bias cleaning, the same as in Example 1.

[0137] After the bias cleaning is completed, argon gas is introduced into the vacuum chamber to a vacuum level of 0.2 Pa, and the magnetron sputtering power is adjusted by gradient at 200°C for 10 hours to obtain a high-temperature protective coating.

[0138] The specific method for gradient-adjusted magnetron sputtering power is as follows:

[0139] Based on the change in elemental content from the inside to the outside of the alloy matrix, determine the change in elemental content K of the corresponding element per unit deposition time. I Specifically:

[0140] Change in elemental content of Al per unit deposition time (% / hour): K Al =9.45;

[0141] Change in elemental content of Ti per unit deposition time (% / hour): K Ti =-0.55;

[0142] Therefore, the sputtering power and gradient changes of each target material can be obtained as follows:

[0143] Over 10 hours, the sputtering power of the Al target gradually increased from 55W to 1000W, while the sputtering power of the Ti target gradually decreased from 945W to 0W. The change in power per unit time for the Al target corresponds to the change in element content per unit time, K. Al Consistent, the change in power of the Ti target per unit time is related to the change in the element content K of the corresponding element per unit time. Ti Consistent.

[0144] The elemental distribution of the cross-section of the high-temperature protective coating obtained in this embodiment is shown in the figure below. Figure 8 As shown in Figure 9, the surface and cross-sectional SEM images of the high-temperature protective coating are presented.Figure 9 It can be seen that the high-temperature protective coating is continuous and dense, without defects such as cracks or voids.

[0145] Comparative Example 1:

[0146] 1. Composition:

[0147] The high-temperature protective coating consists of the following elements and their contents: 35% Cr, 8% Al and 57% Ni.

[0148] The thickness of the high-temperature protective coating is 50 μm.

[0149] 2. Preparation method:

[0150] (1) K403 nickel-based alloy was wire-cut into thin sheets of 10mm×20mm×20mm as the alloy substrate. The alloy substrate was subjected to surface pretreatment, and the surface pretreatment operation was the same as in Example 1.

[0151] The pretreated alloy substrate was placed in a magnetron sputtering vacuum chamber and subjected to bias cleaning, the same as in Example 1.

[0152] (2) After the bias cleaning is completed, argon gas is introduced into the vacuum chamber to a vacuum degree of 0.2 Pa, and magnetron sputtering is performed on an alloy target at 200 °C for 10 hours to obtain a high-temperature protective coating.

[0153] The alloy target is composed of 35% Cr, 8% Al and 57% Ni.

[0154] Experimental Example 1:

[0155] The coatings prepared in Example 1 and Comparative Example 1 were subjected to constant temperature oxidation at 1000℃ for 10 hours, and the coating prepared in Example 4 was subjected to constant temperature oxidation at 800℃ for 300 hours. After the oxidation was completed, the cross-section, oxidation weight gain, phase transformation and fracture surface of the coatings were analyzed.

[0156] The high-temperature protective coating with linear composition variation prepared by this invention can effectively overcome the problems of decreased mechanical properties caused by interfacial interdiffusion between the alloy substrate and the coating; the stress caused by phase transformation due to the reaction between aluminum-rich (chromium) layer and nickel-rich (iron, cobalt, etc.) layer, which leads to cracking; and the internal stress caused by excessive chemical element composition gradient, which results in a short service life of the coating.

[0157] like Figure 2As shown, the high-temperature protective coating prepared in the prior art (Comparative Example 1) forms a three-layer structure through interdiffusion with the substrate after oxidation, and cracks can be observed. However, the high-temperature protective coating prepared in Example 1 of this invention does not exhibit interdiffusion in a high-temperature environment, and no cracks are generated. Therefore, it can be seen that the high-temperature protective coating with linear composition variation prepared by this invention can effectively overcome the interfacial interdiffusion problem between the alloy substrate and the coating.

[0158] Figure 3 The oxidation weight gain kinetics curves of the coatings obtained in Example 1 and Comparative Example 1 at 1000°C are shown below. Figure 3 It can be seen that the coating prepared in Comparative Example 1 showed an oxidation weight gain of 0.5 mg·cm³ after 10 hours of isothermal oxidation. -2 The coating with linear compositional variation prepared in Example 1 showed an oxidation weight gain of 0.45 mg·cm³ after 10 hours of isothermal oxidation. -2 Therefore, the high-temperature protective coating with linearly varying composition obtained by this invention has excellent protective performance.

[0159] Figure 4 and Figure 5 Fracture morphology images of the coatings obtained in Example 1 and Comparative Example 2 are shown respectively. Figure 4 It can be seen that the fracture surface exhibits numerous pores and dimples, and these dimples vary in size, ranging from 100 nanometers to several hundred nanometers, demonstrating characteristics of ductile fracture. Figure 5 It can be seen that the fracture is composed of a large number of small equiaxed grains, and the coating fractures intergranularly, which is a brittle fracture. Therefore, it can be seen that the linear compositional variation coating prepared by this invention effectively solves the problem of internal stress caused by excessive chemical elemental composition gradients, thus preventing a short coating service life.

[0160] Figure 6 The oxidation weight gain kinetics curve of the coating obtained in Example 4 at 1000℃ is obtained from... Figure 6 It can be seen that the coating obtained by the present invention greatly reduces the oxidation rate of the substrate and does not peel off during the entire experiment.

[0161] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-temperature protective coating with linearly varying composition, characterized in that, The high-temperature protective coating with linearly varying composition is applied to the alloy substrate, and the content of its constituent elements varies linearly from the inside to the outside of the alloy substrate; wherein... The innermost layer of the high-temperature protective coating with linear composition variation consists of metallic elements with a minimum content of ≥4% in the alloy matrix. The content of the innermost layer constituent elements is determined as follows: except for the main element in the alloy matrix, the content of other constituent elements is taken as the minimum value of the content range of that element in the alloy matrix, and the remainder is the main element in the alloy matrix. The outermost layer of the high-temperature protective coating with linearly varying composition consists only of protective elements. In the high-temperature protective coating with linearly varying composition, the content of protective elements gradually increases to 100% from the inside out, while the content of other elements gradually decreases to 0% from the inside out. The protective elements are Al or Cr. The high-temperature protective coating with linearly varying composition is prepared by the following method: After surface pretreatment of the alloy substrate, a high-temperature protective coating with linear composition variation is deposited by adjusting the power of each target material by magnetron sputtering in a gradient manner. The method for gradient adjustment of the power of each target material in magnetron sputtering is as follows: during the magnetron sputtering process, the change in power of each target material within a unit deposition time is ensured to be the same as the change in element content of the corresponding element in the high-temperature protective coating within a unit deposition time, and the sum of the power of each target material is equal to the total power of the magnetron sputtering target; the total power of the magnetron sputtering target is 1000W. The change in element content of each element in a high-temperature protective coating per unit deposition time is calculated using the following formula: Equation (I) In equation (I), K I 1 represents the change in element content per unit deposition time, expressed as % / hour; a represents the content of a certain element in the outermost layer of the high-temperature protective coating, expressed as %; b represents the content of the same element in the innermost layer of the high-temperature protective coating, expressed as %; t represents the deposition time, expressed as hours.

2. The high-temperature protective coating with linearly varying composition as described in claim 1, characterized in that, The alloy matrix is ​​one of nickel-based superalloys, iron-based superalloys, or titanium alloys.

3. The high-temperature protective coating with linearly varying composition as described in claim 1, characterized in that, The thickness of the high-temperature protective coating with linearly varying composition is 20-50 μm.

4. The high-temperature protective coating with linearly varying composition as described in claim 1, characterized in that, The power of each magnetron sputtering target is 0-1000W, and the deposition time is 4-12 hours.

5. The high-temperature protective coating with linearly varying composition as described in claim 1, characterized in that, The surface pretreatment of the alloy substrate is as follows: after grinding the alloy substrate, it is ultrasonically cleaned in a mixture of acetone and ethanol and then dried.

6. The high-temperature protective coating with linearly varying composition as described in claim 1, characterized in that, The parameters for depositing the high-temperature protective layer are as follows: the distance between the target and the alloy substrate is 10-20 cm; during the bias cleaning process, the vacuum degree is 3 × 10⁻⁶. - 3 The conditions are as follows: Pa, temperature 300℃, bias voltage -400V, cleaning time 5min; during sputtering, vacuum degree 0.2Pa, temperature 200℃, sputtering time 4-12 hours.

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