Metal-ceramic high-temperature anti-oxidation composite coating

Abstract

A metal-ceramic high-temperature antioxidant composite coating comprises a topcoat and a bottomcoat; the topcoat is a silica sol-type coating or a coating combining silica sol and metal oxide; the bottomcoat is a coating combining silica sol and metal-chromium-aluminum-yttrium alloy powder. The preparation method comprises the steps of preparing a silane hydrolyzate, preparing a silica sol-type coating, mixing the silica sol with metal-chromium-aluminum-yttrium alloy powder to form a coating containing metal-chromium-aluminum-yttrium alloy powder, spraying and curing the coating to form a bottomcoat; mixing the silica sol coating or silica sol with metal oxide to form a coating containing metal oxide, curing the topcoat, and the like. The present invention has good high-temperature oxidation resistance, high strength, and good process performance. Low-temperature curing and high-temperature application are achieved, meeting the thermal process requirements of the powder high-temperature alloy substrate.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a metal-ceramic high-temperature oxidation-resistant composite coating, which is used for resisting high-temperature thermal oxidation on the surface of powder high-temperature alloy components working at 650-750°C. Background Art

[0002] The turbine disk rims and inter-disk seal grate rims of long-life gas turbine engines are required to operate for thousands of hours in a high-temperature environment of 650°C. Existing turbine disks and seal grate disks are manufactured using powder superalloying. Due to the high alloying degree and complex composition of precipitation-strengthened nickel-based powder superalloys, the chromium content of these alloys is reduced from 20% to approximately 12% compared to nickel-based deformable superalloys to ensure microstructure stability and avoid the presence of detrimental topologically close-packed phases. This reduction in chromium, an antioxidant, results in a corresponding decrease in the powder superalloy's resistance to high-temperature thermal oxidation.

[0003] The existing solution is to use aluminum powder, phosphate, and chromate metal ceramics as anti-corrosion coatings. However, high temperature environments will cause aluminum elements to diffuse into the high-temperature alloy matrix, thereby affecting the stability of the structure. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a metal-ceramic high-temperature anti-oxidation composite coating to solve the problems in the prior art.

[0005] The present invention is achieved through the following technical solutions: The technical key points of the metal-ceramic high-temperature anti-oxidation composite coating are:

[0006] including topcoat and basecoat;

[0007] The top coating is prepared by uniformly mixing silica sol or a composition of silica sol and metal oxide in a mass ratio of 10:2.5-25, filtering through a 200-mesh sieve, and curing at room temperature and at a high temperature of 220°C-260°C for 1-2 hours respectively;

[0008] The primer layer is formed by curing a metal-chromium-aluminum-yttrium alloy powder and a silica sol composition in a mass ratio of 10:4.0-6.0 at room temperature and at a high temperature of 220-260°C for 1-2 hours respectively.

[0009] Silica sol is made by mixing and modifying JN-30 alkaline silica sol and silane hydrolyzate in equal mass ratios;

[0010] The metallization powder has an average particle size of less than 500 mesh and is selected from one of h-BN (hexagonal boron nitride), Cr2O3 (chromium oxide), or ZrO2 (zirconium oxide);

[0011] The metal-chromium aluminum yttrium alloy powder has an average particle size of less than 500 mesh and is prepared by mixing the following components in a weight ratio:

[0012] Co balance

[0013] Ni 31.0~33wt%

[0014] Cr 20.0~23.0wt%

[0015] Al 7.0~9.0wt%

[0016] Y 0.4~0.7wt%

[0017] Fe 0~0.2wt% (excluding 0 point)

[0018] Si 0~0.1wt% (excluding 0 point)

[0019] or

[0020] Co 21.0~25wt%

[0021] Ni Residue

[0022] Cr 15.0~19.0wt%

[0023] Al 10.0~15.0wt%

[0024] Y 0.3~1.0wt%

[0025] Fe 0~0.2wt% (excluding 0 point)

[0026] Si 0~0.1wt% (excluding 0 point)

[0027] or

[0028] Ni Residue

[0029] Cr 24.0~26.0wt%

[0030] Al 4.0~6.0wt%

[0031] Y 0.3~0.7wt%

[0032] Fe 0~0.2wt% (excluding 0 point)

[0033] Si 0~0.1wt% (excluding 0 point).

[0034] Furthermore, the topcoat layer further comprises a composition of silica sol and further comprises 2 wt % to 4 wt % of the total mixture of an aqueous aluminum paste having a concentration of 70 wt % of flake aluminum.

[0035] Furthermore, the dry film thickness of the top coating is 15 μm to 20 μm, and the dry film thickness of the base coating is 30 μm to 60 μm.

[0036] The present invention also provides a method for preparing the above-mentioned metal-ceramic high-temperature anti-oxidation composite coating, the technical key points of which are as follows:

[0037] Step S1, preparing a silane hydrolyzate: the silane hydrolyzate is prepared by mixing the following components in parts by volume: 180-220 parts of a silane coupling agent, 90-110 parts of ethanol, 1.2-1.5 parts of acetic acid, and 560-580 parts of deionized water;

[0038] Step S2, mixing equal amounts of JN-30 alkaline silica sol and silane hydrolyzate to prepare a silica sol coating for later use;

[0039] Step S3, mixing the silica sol coating obtained in step S2 with the alloy powder, spraying the mixture onto the workpiece surface, and curing the mixture at room temperature and at a high temperature of 220°C to 260°C for 1 to 2 hours respectively to form a primer layer;

[0040] Step S4, preparing a coating containing metal oxide by mixing silica sol coating or silica sol coating with metal oxide, spraying the coating onto the base coating as a top coating, and curing the coating at room temperature and at a high temperature of 220° C. to 260° C. for 1 to 2 hours, respectively, to form a metal-ceramic high-temperature antioxidant composite coating of the base coating and the top coating;

[0041] The metal-chromium aluminum yttrium alloy powder has an average particle size of less than 500 mesh and is prepared by mixing the following components in a weight ratio:

[0042] Co balance

[0043] Ni 31.0~33wt%

[0044] Cr 20.0~23.0wt%

[0045] Al 7.0~9.0wt%

[0046] Y 0.4~0.7wt%

[0047] Fe 0~0.2wt% (excluding 0 point)

[0048] Si 0~0.1wt% (excluding 0 point)

[0049] or

[0050] Co 21.0~25wt%

[0051] Ni Residue

[0052] Cr 15.0~19.0wt%

[0053] Al 10.0~15.0wt%

[0054] Y 0.3~1.0wt%

[0055] Fe 0~0.2wt% (excluding 0 point)

[0056] Si 0~0.1wt% (excluding 0 point)

[0057] or

[0058] Ni Residue

[0059] Cr 24.0~26.0wt%

[0060] Al 4.0~6.0wt%

[0061] Y 0.3~0.7wt%

[0062] Fe 0~0.2wt% (excluding 0 point)

[0063] Si 0~0.1wt% (excluding 0 point).

[0064] Beneficial effects of the present invention: In terms of the overall technical solution, the composite coating of the present invention can remain intact for more than five times under thermal shock test conditions after being cooled suddenly to 20°C after being heated to 650°C to 750°C. The composite coating forms a high-concentration silica sol as a binding medium for the M-CrAlY ultrafine powder through the hydrolysis of high-temperature resistant silane, forming a high-temperature thermal oxidation resistant coating with good thermal oxidation resistance, effectively avoiding the problem of aluminum elements diffusing into the high-temperature alloy substrate. A small amount of aluminum powder is added to the topcoat to effectively solve the problem of micro cracks easily formed when the coating solidifies and shrinks. The combination of the coating and the powder high-temperature alloy substrate is free of pores, and the bonding strength is higher than that of the thermal spraying process, realizing low-temperature curing and high-temperature application. In addition, there are no high-temperature unstable elements in the coating, which meets the working conditions of the turbine disk rim and the inter-disk sealing comb disk rim of the long-life gas turbine engine that need to work for a long time at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Comparison of the results of the primer test piece prepared by the present invention.

[0066] Figure 2 These are the SEM morphology images of coating No. 1 at magnifications of 500x, 1000x, 2000x, and 5000x.

[0067] Figure 2a for Figure 2 SEM image of CoNiCrAlY powder size distribution at 2000x magnification.

[0068] Figure 2b for Figure 2a SEM images of the coating cross section at 1000x and 2000x magnifications show that the CoNiCrAlY powder is bonded together by the silica sol colloid.

[0069] Figure 2c for Figure 2 SEM image of the distribution of various elements in the initial state of the coating.

[0070] Figure 2d for Figure 2c SEM image of the distribution of various elements in the cross section of the initial state of the coating.

[0071] Figure 3 These are the SEM morphology images of coating No. 2 (coating No. 1 after five thermal shocks at 760°C and water quenching) at magnifications of 500x, 1000x, 2000x, and 5000x.

[0072] Figure 3a for Figure 3 SEM image of CoNiCrAlY powder size distribution at 2000x magnification.

[0073] Figure 3b for Figure 3a The SEM image of the coating cross section at a magnification of 2000 times shows that the silica sol colloid completely covers the CoNiCrAlY particles.

[0074] Figure 3c for Figure 3c SEM image of the distribution of elements in the coating.

[0075] Figure 3d for Figure 3 SEM image of the distribution of various elements in the cross section of the coating.

[0076] Figure 4 These are the SEM morphology images of No. 3 at magnifications of 500 times, 2000 times, and 5000 times.

[0077] Figure 4a for Figure 4 SEM image of CoNiCrAlY powder size distribution at 1000x magnification.

[0078] Figure 4b for Figure 4a The SEM image of the coating cross section at a magnification of 2000 times shows that the flaky aluminum powder in the closed coating is arranged horizontally and evenly.

[0079] Figure 4c for Figure 4 SEM image of the distribution of various elements in the initial state of the composite coating.

[0080] Figure 4d for Figure 4c SEM image of the distribution of various elements in the cross section of the composite coating in its initial state. The binder of the closed coating is silica sol colloid;

[0081] The fillers are hexagonal boron nitride and flake aluminum powder.

[0082] Figure 5 These are the SEM morphology images of coating No. 4 (coating No. 3 after five thermal shocks at 760°C and water quenching) at magnifications of 500x, 1000x, 2000x, and 5000x.

[0083] Figure 5a for Figure 5 SEM image of CoNiCrAlY powder size distribution at 2000x magnification.

[0084] Figure 5b for Figure 5 SEM image of the distribution of elements in the composite coating.

[0085] Figure 5c for Figure 5b The SEM image of the distribution of various elements in the cross section of the middle coating shows that the silica colloidal layer of the closed coating is complete; the boron nitride is evenly distributed; and the aluminum powder is discontinuously distributed.

[0086] Figure 6 Comparison of SEM results of coatings numbered 1 to 4. Implementation Method

[0087] The following combination Figures 1 to 6 The specific content of the present invention is described in detail through specific embodiments. The preparation method of each embodiment comprises the following steps:

[0088] Step S1, preparing a silane hydrolyzate: mixing 180-220 ml of a silane coupling agent (such as commercially available KH-550, KH-560, or KH-570), 90-110 ml of commercially available industrial ethanol, 1.2-1.5 ml of commercially available industrial acetic acid, 1.3-1.6 g of potassium chloride, and 560-580 ml of deionized water to obtain a silane hydrolyzate for later use.

[0089] Step S2: Mix commercially available JN-30 alkaline silica sol and silane hydrolyzate in equal quantities to prepare a silica sol coating for use. The parameters of the commercially available JN-30 alkaline silica sol are: SiO2 20wt% to 30wt%, Na2O ≤ 0.3wt%, pH 9 to 10, average particle size 8 to 15nm, and density 1.2 g / cm 3 .

[0090] Step S3, mixing the silica sol coating obtained in step S2 with the alloy powder, spraying the mixture onto the workpiece surface, and curing the mixture at room temperature and at a high temperature of 220°C to 260°C for 1 to 2 hours respectively to form a primer layer, and determining the curing endpoint when the mass no longer decreases;

[0091] Step S4: Silica sol and metal oxide in the corresponding amounts for each example in Table 2 are mixed to form a coating containing metal oxide (Example 2 uses only silica sol, without adding metal oxide powder). This coating is sprayed onto the base coat as a top coat and then cured at room temperature and then at a high temperature of 220°C to 260°C for 1 to 2 hours, respectively. The curing endpoint is determined when the mass no longer decreases, thereby forming a metal-ceramic high-temperature antioxidant composite coating comprising the base coat and top coat. (This step is not included in Example 1.)

[0092] In each embodiment, the metal-chromium-aluminum-yttrium alloy powder using ultrasonic gas atomization has an average particle size of less than 500 mesh, and is made by mixing the metal powders in corresponding proportions. The specific weight proportions are shown in Table 3.

[0093] Table 1 Film thickness of each example

[0094]

[0095] Table 2 Preparation ingredients of topcoat and primer in each example

[0096]

[0097] In Example 4, based on the topcoat preparation formula of Example 3, 70 wt % (calculated as aluminum flakes) of aqueous aluminum paste, which accounts for 3 wt % of the total mixture, was added.

[0098] The content of the M-CrAlY alloy powder in the embodiment is as follows according to the weight ratio.

[0099] Table 3 Metal-chromium aluminum yttrium composition ratio in various examples (weight percentage)

[0100]

[0101] In Example 1, only a primer layer was prepared for testing, and in Examples 2 to 9, composite coatings of a primer layer and a top layer were used for testing. In Example 2, the top layer was prepared using only silica sol.

[0102] The composite coating was applied on a test piece of 40×70×3 mm made of powdered high-temperature alloy according to the coating method of the present invention.

[0103] After keeping at 650℃ for 10min, the samples were directly quenched in a water bath at 25℃ and repeated 5 times.

[0104] After holding at 750℃ for 10 minutes, the test piece was directly quenched in a water bath at 25℃ and repeated 5 times. The composite coating on the test piece was inspected and the coating was in good condition without cracks or shedding.

[0105] The coatings of Example 1 and Example 5 were used to conduct water quenching thermal shock tests, and 304 stainless steel was selected as the base material. Figure 1 As shown, the coatings for each number are as follows.

[0106] No. 1: The original cured state of the primer test piece prepared by the formulation of Example 1; the primer thickness is 40 μm, and the coating morphology and thickness are as follows Figure 2 shown.

[0107] No. 2: After the coating specimen of No. 1 was kept at 760℃ for 10 minutes and water quenched five times, the coating morphology and thickness were as follows: Figure 3 shown.

[0108] No. 3: The primer and topcoat (half coated) prepared in Example 5 were sequentially coated and cured to form a composite coating test piece. The primer thickness was 40 μm and the topcoat thickness was 20 μm. The morphology and thickness of the composite coating were as follows: Figure 4 shown.

[0109] No. 4: After the composite coating specimen of No. 3 was heated at 760℃ and air-cooled for five cycles, the morphology and thickness of the composite coating were as follows: Figure 5 shown.

[0110] The coating inspection test mainly includes water quenching thermal shock test, adhesion test, oxidation weight gain and heat corrosion resistance test. The specific steps of each test are as follows.

[0111] A composite coating was applied using the coating method described herein to a 25.4×5 mm Φ test piece made of FGH95 powdered superalloy. Testing according to aviation standard HB 5476-1991, "Test Method for Bond Strength of Thermal Spray Coatings," showed adhesion between the basecoat and the substrate to be greater than 50 MPa, while adhesion between the topcoat and the basecoat to be greater than 20 MPa.

[0112] The composite coating was applied according to the coating method of the present invention to a 25.4×5 mm Φ test piece made of FGH95 high-temperature alloy. Testing was conducted in accordance with aviation standard HB 5258-2000, "Test Methods for Determination of Oxidation Resistance of Steel and High-Temperature Alloys." After the test piece was heated to 750°C for 100 hours, a weight gain of less than 0.1% was observed.

[0113] like Figure 6 As shown, the coatings or composite coatings No. 1 and 3 were subjected to water quenching thermal shock test, and the results are shown in the test pieces No. 2 and 4. Figure 6The morphology SEM images of No. 1 to No. 4 are shown in Tables 5 and 6. The weight percentages of the elements in the images are shown in Tables 5 and 6. No obvious oxidation loss was observed in the (composite) coatings No. 2 and 4, and the silica colloidal coating on the surface of each CoNiCrAlY powder particle still existed.

[0114] Table 4 Composition ratio of FGH95 (weight percentage)

[0115]

[0116] Table 5 Comparison of the content of each element in the coating of specimens No. 1 and No. 2

[0117]

[0118] Table 6 Comparison of the content of each element in the coating of specimens No. 3 and No. 4

[0119]

[0120] Unless otherwise specified, the high temperature environment in this article mainly refers to above 650℃.

Claims

1. A metal-ceramic high-temperature anti-oxidation composite coating, characterized by: including topcoat and basecoat; The topcoat is prepared by uniformly mixing a composition of silica sol and metal oxide in a mass ratio of 10:2.5-25.0, filtering through a 200-mesh sieve, and curing at room temperature and at a high temperature of 220°C-260°C for 1-2 hours respectively. The primer layer is formed by curing a silica sol and a metal-chromium aluminum yttrium alloy powder composition at a mass ratio of 10:4.0-6.0 at room temperature and at a high temperature of 220-260°C for 1-2 hours respectively. Silica sol is made by mixing and modifying JN-30 alkaline silica sol and silane hydrolyzate in equal mass ratios; The metal oxide powder has an average particle size of less than 500 mesh and is selected from one of Cr2O3 and ZrO2; The metal-chromium aluminum yttrium alloy powder has an average particle size of less than 500 mesh and is prepared by mixing the following components in a weight ratio: Co balance Ni 31.0~33wt% Cr 20.0~23.0wt% Al 7.0~9.0wt% Y 0.4~0.7wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point; or Co 21.0~25wt% Ni Residue Cr 15.0~19.0wt% Al 10.0~15.0wt% Y 0.3~1.0wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point; or Ni Residue Cr 24.0~26.0wt% Al 4.0~6.0wt% Y 0.3~0.7wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point.

2. The metal-ceramic high-temperature anti-oxidation composite coating according to claim 1, characterized in that: The topcoat layer further contains 2 wt% to 4 wt% of the total topcoat layer mixture, and the concentration of the aqueous aluminum paste is 70 wt% based on the aluminum flakes.

3. The metal-ceramic high-temperature anti-oxidation composite coating according to claim 1, characterized in that: The dry film thickness of the topcoat is 15μm~20μm, and the dry film thickness of the basecoat is 30μm~60μm.

4. A method for preparing a metal-ceramic high-temperature anti-oxidation composite coating, characterized in that: The steps include: Step S1, preparing a silane hydrolyzate: The silane hydrolyzate is prepared by mixing the following components in parts by volume: 180-220 parts of a silane coupling agent, 90-110 parts of ethanol, 1.2-1.5 parts of acetic acid, and 560-580 parts of deionized water; Step S2, mixing equal amounts of JN-30 alkaline silica sol and silane hydrolyzate to prepare a silica sol coating for later use; Step S3, mixing the silica sol coating obtained in step S2 with metal-chromium aluminum yttrium alloy powder, spraying the mixture onto the workpiece surface, and curing the mixture at room temperature and 220-260° C. for 1-2 hours respectively to form a primer layer; Step S4, mixing silica sol and metal oxide to form a coating containing metal oxide, spraying the coating onto the base coat as a top coat, and curing at room temperature and 220-260° C. for 1-2 hours, respectively, to form a metal-ceramic high-temperature antioxidant composite coating of the base coat and the top coat; The metal oxide is selected from one of Cr2O3 and ZrO2; The metal-chromium aluminum yttrium alloy powder has an average particle size of less than 500 mesh and is prepared by mixing the following components in a weight ratio: Co balance Ni 31.0~33wt% Cr 20.0~23.0wt% Al 7.0~9.0wt% Y 0.4~0.7wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point; or Co 21.0~25wt% Ni Residue Cr 15.0~19.0wt% Al 10.0~15.0wt% Y 0.3~1.0wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point; or Ni Residue Cr 24.0~26.0wt% Al 4.0~6.0wt% Y 0.3~0.7wt% Fe 0~0.2wt%, excluding 0 point; Si 0~0.1wt%, excluding 0 point.

Images