Composite diffusion barrier and preparation method thereof

Abstract

The invention provides a composite diffusion barrier and a preparation method thereof, and relates to the technical field of high-temperature alloys and thermal barrier coatings. The composite diffusion barrier is composed of a nano Al2O3 layer and a dispersed nano carbide (MxCy) layer and is used for stabilizing a coating / Ni3Al-based single-crystal high-temperature alloy matrix interface under the high-temperature condition. The preparation method comprises the following steps: firstly, carrying out pretreatment on the surface of the single-crystal high-temperature alloy, then carrying out gas-phase carburization, and controlling the diffusion speed of Al and C by adjusting the atmosphere in the carburization process to obtain the nano Al2O3 layer and dispersed nano carbide (MxCy) composite diffusion barrier. According to the method, diffusion paths of aluminum, titanium, molybdenum and the like of the matrix can be effectively limited, the diffusion rate of the aluminum, the titanium, the molybdenum and the like can be reduced, and finally the mutual diffusion degree of elements between the coating and the matrix under the service condition is slowed down, so that the high-temperature oxidation resistance and the corrosion resistance of the alloy are improved, and the stability of a coating / alloy interface is enhanced. In addition, the method provided by the invention is simple in process, low in cost, high in repeatability and beneficial to popularization and engineering application.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy materials and thermal barrier coating technology, specifically to a composite diffusion barrier and its preparation method. Background Technology

[0002] As aero-engines develop towards higher thrust-to-weight ratios and higher efficiency, the operating temperatures of hot-end components such as turbine blades are approaching the temperature limits of materials. Single-crystal superalloys, film cooling, and thermal barrier coatings are three key technologies for aero-engines, all aimed at improving the operating temperature of aero-engine turbine blades. The coating / single-crystal alloy interface stabilization design, which reduces the impact of element diffusion on the microstructure stability and service performance of single-crystal superalloys, is one of the core technologies for developing long-life, high-performance thermal barrier coatings. However, with the advancement of single-crystal alloy generations, the use of refractory elements such as Re, Ru, W, Ta, and Mo increases to enhance high-temperature strength. Under the combined effects of high temperatures and complex multi-phase compositions, element diffusion at the coating interface intensifies, leading to more severe degradation of the alloy's mechanical properties. For IC series alloys with high Re, W, Ta, and Mo content, traditional coatings exhibit poor oxidation resistance at 1150 °C and above, and severe interdiffusion between the coating and the matrix occurs. For example, Al diffuses into the matrix, causing coating degradation; Re, W, and Ta enrichment induces brittle TCP phases; and Mo migrates outward, forming volatile oxides, exacerbating matrix instability. Especially in thin-walled components under ultra-high temperature and high-stress conditions, interdiffusion reduces the load-bearing cross-section of the matrix, significantly decreasing the effective load-bearing area and causing stress concentration. Therefore, preventing the internal diffusion of Al and the external diffusion of refractory elements become crucial.

[0003] Aside from the diffusion barriers of precious metals like Re and Ru, which suffer from insufficient high-temperature stability, research on diffusion barriers for high-generation single-crystal superalloys with high W / Ta / Mo content mainly focuses on carbide diffusion-blocking preparation methods. For example, patents CN111621735A and CN101845609A describe carbide preparation methods using vacuum carburizing, which is complex and costly. The carbide morphology exhibits a "nano-submicron" composite size; examples show that most carbides are submicron in size, which is detrimental to the alloy's mechanical properties. Patent CN110468384B uses atmospheric pressure carburizing, obtaining a graphene / carbide layer / alloy sample. The graphene and carbide work together to block diffusion; however, graphene has a layered structure, and during the preparation of the MCrAlY coating on its surface, weak bonding strength is a common problem. Al2O3 is also a commonly used diffusion barrier, effectively preventing the internal diffusion of Al elements caused by chemical potential gradients, but its weak bonding strength is also a significant issue.

[0004] Therefore, this invention proposes a composite diffusion barrier and its preparation method, which involves in-situ generation of a nano-Al2O3 film + dispersed nano-carbide (Mx C y By combining a diffusion barrier and a gradient bonding layer design, a triple protection mechanism of "physical-kinetic-thermodynamic" is constructed. In-situ nano-Al2O3 film is prepared on the IC51 substrate surface as a diffusion barrier to physically block the interdiffusion path of Al / Mo and alleviate the loss of load-bearing area. By carburizing, dispersed nano-TaC, HfC and other carbides are prepared to pin refractory elements and slow down the migration rate of refractory elements. Furthermore, the γ / γ' structure is stabilized by carbide interface segregation, which improves the high-temperature strength of the coating to cope with large stress loads. This strategy is expected to break through the bottleneck of single technology and achieve synergistic suppression of interdiffusion behaviors such as Al migration, Mo volatilization and TCP phase formation at the IC51 alloy / coating interface. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a composite diffusion barrier and its preparation method, which can effectively restrict the diffusion paths of substrates such as aluminum, titanium, and molybdenum, reduce their diffusion rates, and ultimately slow down the interdiffusion of elements between the coating and the substrate under service conditions. This improves the alloy's resistance to high-temperature oxidation and corrosion, and enhances the stability of the coating / alloy interface. Furthermore, the method provided by this invention is simple, low-cost, and highly repeatable, making it particularly suitable for substrate materials with complex shapes, thus facilitating its widespread engineering applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite diffusion barrier, characterized in that: the composite diffusion barrier consists of a nano-Al2O3 layer and dispersed nano-carbide (M x C y Composed of multiple layers, this composite diffusion barrier is used to stabilize the interface between the anti-oxidation coating and the Ni3Al-based single-crystal superalloy matrix under high-temperature conditions. The preparation method of this composite diffusion barrier is as follows: Step 1: Pre-treatment is performed on the surface of the single-crystal high-temperature alloy to control the residual stress and dislocation density of the surface and subsurface layers; Step 2: Place the sample obtained in Step 1 into the carburizing furnace, then seal the carburizing furnace and use a vacuum pump to evacuate the environment until the vacuum level drops to 0.1 MPa or below. Step 3: Turn off the vacuum pump, introduce high-purity argon gas into the formation environment, and perform gas washing. Repeat this process at least 3 times until the final environmental pressure is balanced with atmospheric pressure. Step 4: In the state of step 3, continue to introduce gas 1 and start heating at the same time to raise the temperature inside the carburizing furnace to 900~1100 ℃; Step 5: At a temperature of 900~1100 ℃, gas 1 is turned off, gas 2 is introduced, and the temperature is maintained for 0~1h to initially form a nano Al2O3 layer and a shallow C layer. Step 6: At a temperature of 900~1100 ℃, shut off gas 2, introduce gas 3, and maintain the temperature for 1~5 hours to perform carburizing treatment, controlling the formation of dispersed nano-carbide (M) of different thicknesses. x C y )layer.

[0007] Step 7: Perform surface treatment on the sample obtained in Step 6, followed by cleaning.

[0008] Step 8: Place the sample obtained in Step 7 into a multi-arc ion plating equipment, raise the substrate to 900~1000 ℃, introduce gas 4, and keep it at that temperature for 15min~45min; Step 9: Next, an arc ion plating method is used to prepare a metal bonding layer on the surface; Furthermore: the composite diffusion barrier is composed of continuous or discontinuous Al2O3 nanoparticles with a thickness of 0.5~3μm; the dispersed nanocarbide (M x C y The thickness is 20~80 μm.

[0009] Furthermore, in step 1, the surface pretreatment can be carried out by dry sandblasting, wet sandblasting or sandpaper polishing, etc. The air pressure range of the sandblasting process is 0.1~0.4 MPa, and it can be used with corundum sand of different particle sizes.

[0010] Further: In step 4, gas 1 is a mixture of H2, CH4 and Ar / N2, wherein the H2 content is 0% to 90%, the CH4 content is 0% to 10%, and the Ar or N2 content is 5% to 90%, all of which are mass percentages.

[0011] Further: In step 5, gas 2 is a mixture of CH4 and Ar / N2, wherein the CH4 content is 0% to 10% and the Ar / N2 content is 90% to 100%, all of which are mass percentages.

[0012] Further: In step 6, gas 3 is a mixture of CH4, Ar and O2, wherein the CH4 content is 0% to 20%, the Ar / N2 content is 80% to 90%, and the O2 content is 0% to 0.1%, all of which are mass percentages.

[0013] Furthermore, step 7 involves sample cleaning via wet sandblasting followed by ion cleaning.

[0014] Further: In step 8, gas 4 is a mixture of Ar and O2, wherein the Ar content is 90% to 99.99% and the O2 content is 0.01% to 10%, all of which are mass percentages.

[0015] This invention provides a composite diffusion barrier and its preparation method. It has the following beneficial effects: 1. This invention provides a composite diffusion barrier and its preparation method. The composite diffusion barrier consists of a nano-Al2O3 layer and dispersed nano-carbide (M... x C y The coating consists of multiple layers, with the nano-Al2O3 layer effectively preventing the internal diffusion of Al elements within the coating and dispersing nano-carbide (M) layers. x C y The layer can prevent the outward diffusion of refractory elements. The two effects work synergistically to prevent the precipitation of the TCP phase by alloying elements and the formation of secondary reaction zones. In-situ generation of nano-Al2O3 can effectively reduce interlayer stress and improve the bonding strength of the coating.

[0016] 2. This invention provides a composite diffusion barrier and its preparation method, wherein the diffusion barrier consists of a nano-Al2O3 layer and dispersed nano-carbide (M x C y The novel anti-diffusion layer can precisely control the depth and size of carbides through the competitive diffusion mechanism of Al and C.

[0017] 3. This invention provides a composite diffusion barrier and its preparation method, which is simple, low-cost, highly repeatable, and highly designable, especially suitable for matrix materials with complex shapes, and is conducive to promoting engineering applications. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the composite diffusion barrier layer of the present invention; Figure 2 This is a comparison diagram showing the effects of the composite diffusion barrier of the present invention and the traditional process.

[0019] Figure 2 middle: (ac) Cross-sectional morphology of prepared samples: MCrAlY / IC51, MCrAlY / Al2O3 / IC51, MCrAlY / Al2O3-M x C y Cross-sectional morphology of samples / IC51, (a1-c1) after oxidation at 1150℃ for 100h: MCrAlY / IC51, MCrAlY / Al2O3 / IC51, MCrAlY / Al2O3-M x C y / IC51. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0021] like Figure 1-2 As shown, this invention provides a composite diffusion barrier and its preparation method. The composite diffusion barrier consists of a nano-Al2O3 layer and dispersed nano-carbide (M... x C y Composed of multiple layers, this composite diffusion barrier is used to stabilize the interface between the anti-oxidation coating and the Ni3Al-based single-crystal superalloy matrix under high-temperature conditions. The preparation method of this composite diffusion barrier is as follows: Step 1: Dry sandblasting treatment of single crystal high temperature alloy surface. The sandblasting process air pressure range is ~0.3 MPa, and 60~120 mesh corundum sand can be used. Step 2: Place the sample obtained in Step 1 into the carburizing furnace, then seal the carburizing furnace and use a vacuum pump to evacuate the environment until the vacuum level drops to 0.1 MPa or below. Step 3: Turn off the vacuum pump, introduce high-purity argon gas into the formation environment, and perform gas washing. Repeat this process at least 3 times until the final environmental pressure is balanced with atmospheric pressure. Step 4: Under the conditions of Step 3, continue to introduce Gas 1 and start heating at the same time to raise the temperature inside the carburizing furnace to 900~1100 ℃; the H2 content in Gas 1 is ~85%, the CH4 content is ~0.35%, and the Ar content is ~14.65%.

[0022] Step 5: At a temperature of 900~1100 ℃, gas 1 is turned off and gas 2 is introduced. The temperature is maintained for 0~5h to form a nano Al2O3 layer; the CH4 content in gas 2 is ~2% and the Ar content is ~98%.

[0023] Step 6: At a temperature of 900~1100 ℃, turn off gas 2, introduce gas 3, and maintain the temperature for 2 hours to perform carburizing treatment, controlling the formation of dispersed nano-carbide (M) of different thicknesses. x C y ) layer, dispersed nano-carbide (M x C y The gas contains ~4% CH4, ~95.9% Ar, and ~0.1% O2.

[0024] Step 7: Perform wet sandblasting on the coating obtained in Step 6 at a pressure of 0.3 MPa, and then clean it with alcohol.

[0025] Step 8: Place the sample obtained in Step 7 into the multi-arc ion plating equipment, heat the substrate to 1000 ℃, introduce gas 4, and keep it at that temperature for 15 min. Gas 4 is a mixture of Ar and O2, with Ar content of 99.99% and O2 content of 0.01%.

[0026] Step 9: Prepare an MCrAlY layer on the surface using arc ion plating at a temperature of 450℃, a negative bias of 35V, an arc source current of 185A, and a plating time of 1.5h.

[0027] The coated samples obtained in step 9 were subjected to interdiffusion experiments at 1150 °C for 100 h. The control group samples were those without diffusion barriers, such as... Figure 2 As shown, the secondary reaction zone is not obvious, which effectively slows down the migration rate of refractory elements and stabilizes the γ / γ' structure through segregation at the carbide interface, thus helping to improve its high-temperature strength.

[0028] The following points should be noted in this article: 1. The accompanying drawings of the embodiments disclosed herein only relate to the structures involved in the embodiments disclosed herein; other structures can be referred to in general design.

[0029] 2. Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0030] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite diffusion barrier, characterized in that: The composite diffusion barrier consists of a nano-Al2O3 layer and dispersed nano-carbide (M). x C y Composed of multiple layers, this composite diffusion barrier is used to stabilize the interface between the anti-oxidation coating and the Ni3Al-based single-crystal superalloy matrix under high-temperature conditions. The preparation method of this composite diffusion barrier is as follows: Step 1: Pre-treatment is performed on the surface of the single-crystal high-temperature alloy to control the residual stress and dislocation density of the surface and subsurface layers; Step 2: Place the sample obtained in Step 1 into the carburizing furnace, then seal the carburizing furnace and use a vacuum pump to evacuate the environment until the vacuum level drops to 0.1 MPa or below. Step 3: Turn off the vacuum pump, introduce high-purity argon gas into the formation environment, and perform gas washing. Repeat this process at least 3 times until the final environmental pressure is balanced with atmospheric pressure. Step 4: In the state of step 3, continue to introduce gas 1 and start heating at the same time to raise the temperature inside the carburizing furnace to 900~1100 ℃; Step 5: At a temperature of 900~1100 ℃, gas 1 is turned off, gas 2 is introduced, and the temperature is maintained for 0~1h to initially form a nano Al2O3 layer and a shallow C layer. Step 6: At a temperature of 900~1100 ℃, shut off gas 2, introduce gas 3, and maintain the temperature for 1~5 hours to perform carburizing treatment, controlling the formation of dispersed nano-carbide (M) of different thicknesses. x C y )layer; Step 7: Perform surface treatment on the sample obtained in Step 6, followed by cleaning; Step 8: Place the sample obtained in Step 7 into a multi-arc ion plating equipment, raise the substrate to 900~1000 ℃, introduce gas 4, and keep it at that temperature for 15min~45min; Step 9: Next, an arc ion plating method is used to prepare a metal bonding layer on the surface.

2. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: The nano-Al2O3 layer is composed of continuous or discontinuous Al2O3, with a thickness of 0.5~3 μm; the dispersed nano-carbide (M x C y The layer thickness is 20~80 μm.

3. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: In step 1, the surface pretreatment can be carried out by dry sandblasting, wet sandblasting or sandpaper polishing, etc. The air pressure range of the sandblasting process is 0.1~0.4MPa, and it can be used with corundum sand of different particle sizes.

4. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: In step 4, gas 1 is a mixture of H2, CH4 and Ar / N2, wherein the H2 content is 0%~90%, the CH4 content is 0%~10%, and the Ar or N2 content is 5%~90%, all of which are mass percentages.

5. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: In step 5, gas 2 is a mixture of CH4 and Ar / N2, wherein the CH4 content is 0% to 10% and the Ar / N2 content is 90% to 100%, all of which are mass percentages.

6. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: In step 6, gas 3 is a mixture of CH4, Ar and O2, wherein the CH4 content is 0% to 20%, the Ar / N2 content is 80% to 90%, and the O2 content is 0% to 0.1%, all of which are mass percentages.

7. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: The sample cleaning method in step 7 is wet sandblasting, followed by ion cleaning.

8. The method for preparing a composite diffusion barrier according to claim 1, characterized in that: In step 8, gas 4 is a mixture of Ar and O2, wherein the Ar content is 90% to 99.99% and the O2 content is 0.01% to 10%.

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