A nickel-based alloy sand and a method of optimizing the surface of a damaged area thereof

Abstract

The application discloses a nickel-based alloy sand and a method for optimizing a damaged area surface, relates to the field of nickel-based high-temperature alloy repairing, and the nickel-based alloy sand comprises Cr, Co, Al, Mo, Nb, Hf and Sc, and the rest is Ni or / and inevitable impurity elements; the method for optimizing the damaged area surface mainly adopts the mode of twice sand blasting on the damaged area surface. The application can perform sand blasting treatment on the damaged area surface, achieves the purpose of modifying the damaged area surface, promotes the diffusion of melting point inhibiting elements to the base body, and improves the bonding strength of the connecting interface between the shape and property remodeling area and the base material.

Description

Technical Field

[0001] This invention relates to the field of nickel-based superalloy repair, and in particular to a nickel-based alloy sand and a method for optimizing the surface of the damaged area. Background Technology

[0002] Heavy-duty gas turbine hot components (turbine blades, combustors, and turbine discs) are core components made of high-value nickel-based superalloys. Due to their long-term operation under extreme conditions such as high temperature, high pressure, high stress, and hot corrosion, coupled with unit start-up and shutdown and peak load changes, they are prone to microstructural degradation and surface integrity damage, threatening the safe and stable operation of the unit. Repairing damaged parts of these components using reasonable and effective methods can significantly reduce the unit's operation and maintenance costs. In the field of reshaping high-temperature hot components of heavy-duty gas turbines, powder metallurgy is a commonly used repair method, highly suitable for repairing large-area surface damage and material reduction of hot components. It enables batch repair of complex, irregularly shaped high-temperature components, offering advantages of high efficiency and low cost.

[0003] Powder metallurgy repair technology involves mixing a binder, one or more activator powders, and one or more curing agent powders in a specific mass ratio to create a plastic paste. This paste is then applied to the damaged area and placed in a vacuum furnace for heat preservation within a temperature range higher than the melting point of the activator powders but lower than the melting point of the curing agent powders. During this heat preservation process, the activator powders with lower melting points liquefy and fill the gaps between the curing agent powders and between the curing agent powders and the substrate. Simultaneously, highly diffusive demelting elements in the liquid phase (such as boron, silicon, zirconium, etc.) diffuse into the substrate and the curing agent powders. As the concentration of these highly diffusive demelting elements in the liquid phase decreases, the liquid phase undergoes isothermal solidification, achieving shape reshaping of the damaged area.

[0004] Since then, in order to improve the performance of the shape remodeling zone, researchers have conducted a lot of research on activator materials and developed a variety of high-performance repair materials, such as those described in patents CN1056645A, CN1800425A, CN101306494A, CN101780610A, CN101780604A, CN101780612A, CN103894599B, ​​CN109909641A. Although these repair materials can achieve high-performance remodeling of the shape of the damaged area, the interface between the shape remodeling zone and the substrate is a weak area, and failure often occurs from this. Analysis of a large number of failed samples revealed that the harmful phase precipitated along the interface is the main reason for the decrease in interfacial bonding strength. More importantly, at high temperatures, these harmful phases will exacerbate the decline in interfacial bonding strength. The main reasons for the precipitation of these harmful phases are as follows: (1) Interfacial oxidation. The main cause is the incomplete grinding and cleaning of the substrate before applying the plastic paste, leaving oxides and oil residues on the surface. (2) A continuous layer of brittle compounds precipitates at the interface. This is mainly due to the combination of elements such as carbon, chromium, molybdenum, and tungsten in the matrix with elements such as titanium, boron, and silicon in the liquid phase during the heat preservation stage, resulting in the precipitation of brittle compounds such as carbides, borides, and silicides along the straight interface. (3) Large areas of brittle eutectic phase precipitate at the interface. This is mainly due to the insufficient diffusion of active elements during the heat preservation stage, resulting in the liquid phase at the interface failing to solidify completely isothermally. Therefore, a solution is urgently needed in this field to address the above-mentioned problems. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a nickel-based alloy sand and a method for optimizing the surface of the damaged area. This method involves pre-treating the surface of the damaged area of ​​the substrate by surface sandblasting, thereby improving the bonding strength between the reshaped area and the substrate interface.

[0006] The technical solution adopted in this invention is as follows: A nickel-based alloy sand, comprising the following elements by mass percentage:

[0007] Cr (5.3%-10.8%), Co (7.1%-12.7%), Al (2.5%-5.3%), Mo (18.6%-22.9%), Nb (2.5%-6.8%), Hf (0.5%-1.1%), Sc (0.01%-0.05%), with the remainder being Ni and / or unavoidable impurity elements.

[0008] Considering that sandblasting can create sand inclusions on the substrate surface, the selection principle for the composition of the nickel-based alloy sand in this invention is based on the following considerations to ensure that the sand inclusions do not damage the substrate's properties:

[0009] Add 5.3wt%-10.8wt% of Cr to ensure that the in-situ sand inclusion area has excellent oxidation resistance and hot corrosion resistance.

[0010] Adding 7.1wt%-12.7wt% of Co can provide solid solution strengthening to the in-situ sand inclusions and reduce the matrix stacking fault energy.

[0011] Adding 2.5wt%-5.3wt% Al can induce the precipitation of γ' strengthening phase in the in-situ sand inclusion zone.

[0012] Adding 8.7wt%-13.5wt% of Mo serves two purposes: firstly, it strengthens the in-situ sand inclusions through solid solution, and secondly, it stabilizes the B element in the activator.

[0013] Adding 2.5wt%-6.8wt% of Nb can change the composition of the γ' phase in the in-situ sand-bearing zone, increase the amount of γ' phase, and improve the stability of the γ' phase.

[0014] Adding 0.5-1.1 wt% Hf can strengthen the γ' phase in the in-situ sand inclusion region, improve grain boundary strength, and enhance creep strength.

[0015] Adding 0.01wt%-0.05wt% of Sc can desulfurize and deoxidize, reducing the harmful effects of oxygen and sulfur on the interface of the in-situ sand inclusion zone.

[0016] Furthermore, the nickel-based alloy sand has at least two specifications, one of which has a particle size of 60-100 mesh, and the other of which has a particle size of 200-280 mesh.

[0017] A method for optimizing the surface of a damaged area, using the aforementioned nickel-based alloy sand, includes the following steps:

[0018] S1: Preparation of sandblasting abrasive; the abrasive is nickel-based alloy sand, and there are two specifications of nickel-based alloy sand with a particle size of 60-100 mesh and 200-280 mesh.

[0019] S2: Grinding and cleaning; Grinding and cleaning the damaged area of ​​the nickel-based superalloy substrate, and drying it after cleaning;

[0020] S3: First sandblasting; The damaged area surface after step S2 is subjected to the first sandblasting treatment. The sand used for sandblasting is nickel-based alloy sand with 60-100 mesh particles as in step S1.

[0021] S4: Second sandblasting; A second sandblasting treatment is performed on the damaged area surface after the first sandblasting in step S3. The sand used in step S1 is nickel-based alloy sand with a particle size of 200-280 mesh.

[0022] Further, in step S1, the steps for obtaining nickel-based alloy sand are as follows:

[0023] S11: Prepare elemental metals or intermediate alloys containing relevant elements according to the elemental proportions;

[0024] S12: Melt the elemental metal or intermediate alloy prepared in step S11 in a vacuum environment to form an alloy ingot;

[0025] S13: Crush the alloy ingot obtained in step S12;

[0026] S14: Screened out nickel-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh.

[0027] Further, the nickel-based superalloy in step S2 is any one or more of the following: Mar-M247 alloy, IN738LC alloy, IN939 alloy, MGA2400 alloy, GTD111 alloy, and GTD222 alloy.

[0028] Furthermore, in step S2, the nickel-based superalloy substrate should be cleaned using an alcohol or acetone solution and by ultrasonic cleaning.

[0029] Furthermore, the sandblasting pressure in the first sandblasting in step S3 is between 0.4 MPa and 0.6 MPa.

[0030] Furthermore, in step S4, the sandblasting pressure for the second sandblasting is between 0.2 MPa and 0.4 MPa.

[0031] Furthermore, the crater coverage of the sprayed surface in the first sandblasting in step S3 and the second sandblasting in step S4 must reach 100%.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. Regarding sandblasting materials, compared with traditional sandblasting materials (common traditional sandblasting materials include quartz sand, iron sand, corundum, etc.), the nickel-based alloy sand provided by this invention is a sandblasting material containing strengthening elements in nickel-based high-temperature alloys. This effectively avoids the introduction of impurity elements due to sand inclusions on the substrate surface during the sandblasting process. The surface sand inclusions can act as a stabilizer for melting point inhibiting element B, effectively inhibiting the formation of brittle eutectic phases at the interface and preventing performance degradation of the bonding surface due to surface sand inclusions.

[0034] 2. The sandblasting material (nickel-based alloy sand) of the present invention is simple to prepare. It can be directly prepared by conventional vacuum melting of alloy ingots and mechanical crushing of alloy ingots. It is not easily oxidized at room temperature, can be stored, and is suitable for most sandblasting machine models.

[0035] 3. Sandblasting can achieve secondary cleaning of the surfaces to be joined. After the surface of the damaged area (the area to be repaired) of the nickel-based superalloy is sandblasted with the abrasive provided by this invention, the resulting craters increase the specific surface area of ​​the damaged area per unit size, extend the length of the two-dimensional connection boundary, and significantly increase the area of ​​the shape-remodeling area (the area after the damaged area has been repaired by powder metallurgy) and the metallurgical interface of the substrate. In addition, the large specific surface area can provide more diffusion sites, which is conducive to the diffusion of melting point inhibiting elements (such as Si, B, Zr, Hf, etc.) into the matrix, thereby effectively inhibiting the formation of eutectic phase at the interface.

[0036] 4. After the surface of the damaged area (area to be repaired) of the nickel-based high-temperature alloy is sandblasted with the abrasive provided by this invention, the craters formed on its surface are conducive to the placement of the curing agent powder, reducing the gap between the curing agent powder and the substrate, shortening the diffusion distance of the melting point inhibiting element, and effectively avoiding the formation of eutectic phase at the interface; in addition, the uneven interface can also effectively prevent brittle compounds from continuously precipitating in sheets on the interface.

[0037] 5. After the surface of the damaged area (the area to be repaired) of the nickel-based superalloy is sandblasted with the abrasive provided by this invention, the compressive stress generated during the process can refine the surface grains of the substrate, generate a large number of grain boundaries, and promote the formation of a large number of high-density dislocations, stacking faults and twins and other microstructures inside the grains. The generated grain boundaries and crystal defects can serve as fast channels for the diffusion of melting point inhibiting elements, accelerate the diffusion of melting point inhibiting elements to the substrate during the powder metallurgy repair process, promote the isothermal solidification of the liquid phase at the interface, and inhibit the formation of brittle eutectic phase. Attached Figure Description

[0038] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0039] Figure 1 The morphology of the nickel-based alloy sand disclosed in Example 1;

[0040] Figure 2 The surface morphology of the damaged area of ​​the substrate in Example 2 after secondary sandblasting treatment;

[0041] Figure 3 The interface morphology of the repair area in the test case of Example 2;

[0042] Figure 4 The fracture morphology of the tensile specimen in the test example of Example 2;

[0043] Figure 5 The interface morphology of the repair area in the control example in Example 2;

[0044] Figure 6 The fracture morphology of the tensile specimen in the control example of Example 2 is shown. Detailed Implementation

[0045] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0046] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0047] Example 1

[0048] like Figure 1 As shown, a nickel-based alloy sand contains the following elements by mass percentage:

[0049] Cr (5.3%–10.8%), Co (7.1%–12.7%), Al (2.5%–5.3%), Mo (18.6%–22.9%), Nb (2.5%–6.8%), Hf (0.5%–1.1%), Sc (0.01%–0.05%), with the remainder being Ni and / or unavoidable impurity elements.

[0050] In this embodiment, the nickel-based alloy sand has two specifications, one of which has a particle size of 60-100 mesh, and the other of which has a particle size of 200-280 mesh.

[0051] In this embodiment, in order to further illustrate and explain the technical solution of the present invention, the following non-limiting implementation methods are provided. The element content data below are all mass percentage data, as detailed in Table 1.

[0052] Table 1. Implementation methods of nickel-based alloy sand

[0053]

[0054]

[0055] Example 2

[0056] A method for optimizing the surface of a damaged area, using the nickel-based alloy sand described in the examples, taking the DFS-S alloy sand in Example 1 as an example, is applied to the surface of the damaged area of ​​any one or more nickel-based superalloy substrates selected from Mar-M247 alloy, IN738LC alloy, IN939 alloy, MGA2400 alloy, GTD111 alloy, and GTD222 alloy, with the application to the damaged area of ​​the Mar-M247 nickel-based superalloy substrate as an example; wherein:

[0057] The nominal chemical composition of Mar-M247 nickel-based superalloy is:

[0058] Ni - 8wt% Cr - 10wt% Co - 10wt% W - 5.5wt% Al - 1wt% Ti - 3wt% Ta - 1.5wt% Hf - 0.6wt% Mo - 0.15wt% C - 0.015wt% B - 0.03wt% Zr; can be used to manufacture hot components for heavy-duty gas turbines.

[0059] A method for optimizing the surface of a damaged area includes the following steps:

[0060] S1: Prepare sandblasting material; the sand is nickel-based alloy sand, and there are two specifications of nickel-based alloy sand with a particle size of 60-100 mesh and 200-280 mesh; see steps S11-S14 for details.

[0061] S11: Prepare elemental metals or intermediate alloys containing Cr, Co, Al, Mo, Nb, Hf and Sc according to the elemental ratio, preferably elemental metals with a purity of 99.99% to reduce the introduction of impurities;

[0062] S12: Melt the elemental metal or intermediate alloy prepared in step S11 in a vacuum environment to form an alloy ingot; wherein, the vacuum environment is provided by a vacuum arc melting furnace, and the melting is carried out in a high-purity Ar protective atmosphere. After melting, once all the metals have been fully liquefied, the power is turned off, the liquid phase solidifies, and the above actions are repeated 8 times to obtain an alloy ingot with uniform composition and sufficient mixing.

[0063] S13: The alloy ingot obtained in step S12 is mechanically crushed using an alloy crusher;

[0064] S14: Screening yields nickel-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh.

[0065] It should be noted that, in this embodiment, nickel-based alloy sand (blasting material) can be prepared by conventional vacuum melting of alloy ingots and mechanical crushing of alloy ingots. It is not easily oxidized at room temperature, has high hardness, can be stored for later use, and is applicable to most sandblasting machine models.

[0066] S2: Grinding and cleaning; Grinding and cleaning the damaged area of ​​the nickel-based superalloy substrate, followed by drying; Specifically, mechanical grinding removes the oxide layer on the surface of the substrate alloy, then ultrasonically cleaning it in alcohol or acetone solution for 60 minutes, and finally drying it in a 60-degree Celsius drying oven for later use; Among these methods, cleaning with alcohol or acetone solution can completely dissolve the organic matter adhering to the damaged area of ​​the substrate, and the organic matter is easily volatilized during drying, leaving no residue, effectively preventing the repair area from being affected by organic matter or other impurities and thus affecting the repair quality.

[0067] S3: First sandblasting; The damaged area surface after step S2 is subjected to the first sandblasting treatment. The sand used for sandblasting is nickel-based alloy sand with 60-100 mesh particles as in step S1. The sandblasting pressure is between 0.4MPa and 0.6MPa, preferably 0.6MPa. The coverage rate of the crater on the sprayed surface is 100% to ensure complete coverage.

[0068] S4: Second sandblasting; A second sandblasting treatment is performed on the damaged area surface after the first sandblasting in step S3. The sand used for sandblasting is nickel-based alloy sand with 200-280 mesh particles as in step S1. The sandblasting pressure is between 0.2MPa and 0.4MPa, preferably 0.3MPa, and the coverage rate of the crater on the sprayed surface is 100% to ensure complete coverage.

[0069] In this embodiment, as Figure 2 As shown, the surface morphology of the damaged area of ​​the Mar-M247 nickel-based superalloy matrix after a second sandblasting is as follows: its roughness is 1.53 μm, and the surface area within a 1 cm × 1 cm unit size reaches 1.31 cm². 2 .

[0070] Therefore, the main purpose of the first sandblasting is to roughen the surface of the substrate in the damaged area and apply compressive stress to the surface of the substrate in the damaged area to achieve the purpose of refining grains and modifying the structure. The main purpose of the second sandblasting is to roughen the surface of the crater left by the first sandblasting and remove the large sand particles left on the substrate surface by the first sandblasting. The two sandblastings can increase the specific surface area of ​​the damaged area, which can increase the area of ​​the metallurgical interface between the shape remodeling area (the area of ​​the damaged area after powder metallurgy repair) and the substrate, and provide more diffusion sites and occupancy sites for the curing agent powder. This is conducive to the diffusion of melting point inhibiting elements (such as Si, B, Zr, Hf, etc.) into the matrix, thereby effectively inhibiting the formation of eutectic phase at the interface. The generated grain boundaries and crystal defects can serve as fast channels for the diffusion of melting point inhibiting elements, accelerating the diffusion of melting point inhibiting elements into the substrate during the powder metallurgy repair process, promoting isothermal solidification of the liquid phase at the interface, and inhibiting the formation of brittle eutectic phase.

[0071] In this embodiment, a set of experimental examples are provided, in which the damaged area of ​​a Mar-M247 nickel-based superalloy matrix after secondary sandblasting is reshaped (powder metallurgical repair) using the commercially available activator AmdryD-15; wherein, the nominal chemical composition of the commercially available activator AmdryD-15 is Ni-15.3Cr-10.3Co-3.5Al-3.5Ta-2.3B. After the reshaping is completed, the microstructure of the repaired area (the area after the reshaping of the damaged area) is observed, such as... Figure 3As shown, the interface between the repaired area and the substrate is curved, with brittle compounds dispersed on the interface and no enrichment of brittle eutectic phases observed. Tensile properties of the repaired area were tested at 900℃, yielding a yield strength of 428 MPa and a tensile strength of 493 MPa. The fracture surface of the tensile specimen from the repaired area at 900℃ was observed... Figure 4 As shown, the failure behavior occurs in the deformation remodeling zone, and the fracture surface is serrated, indicating ductile fracture.

[0072] In this embodiment, a set of control examples is provided, namely, the surface of Mar-M247 nickel-based superalloy was ground and cleaned, and then directly subjected to shape reshaping (powder metallurgy repair) using the commercially available activator AmdryD-15. The shape reshaping process was consistent with the experimental examples. After shape reshaping, the microstructure of the repaired area (the area after shape reshaping of the damaged area) was observed, such as... Figure 5 As shown, the interface between the repaired area and the substrate is straight, with linear, continuous brittle compounds precipitating along the interface, and some areas enriched with brittle eutectic phases. Tensile property tests were performed on the repaired area at 900℃; no yield strength was measured, and the specimen fractured brittlely. The tensile strength was 370 MPa, significantly lower than the strength obtained in the experimental example. Observation of the fracture surface of the tensile specimen from the repaired area at 900℃ is shown... Figure 6 As shown, the joint cracks along the interface.

[0073] The comparison between the experimental and control examples shows that surface sandblasting can effectively improve the bonding strength between the reshaped area and the substrate interface by modifying the surface of the damaged area of ​​the substrate.

[0074] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A nickel-based alloy sand, characterized in that: By weight percentage, it includes the following elements: Cr: 5.3%-10.8%, Co: 7.1%-12.7%, Al: 2.5%-5.3%, Mo: 18.6%-22.9%, Nb: 2.5%-6.8%, Hf: 0.5%-1.1%, Sc: 0.01%-0.05%, with the remainder being Ni and unavoidable impurity elements; this nickel-based alloy sand is available in two specifications, one with a particle size of 60-100 mesh and the other with a particle size of 200-280 mesh.

2. A method for optimizing the surface of a damaged area, using the nickel-based alloy sand described in claim 1, characterized in that: Includes the following steps: S1: Preparation of sandblasting abrasive; the abrasive is nickel-based alloy sand, and there are two specifications of nickel-based alloy sand with a particle size of 60-100 mesh and 200-280 mesh. S2: Grinding and cleaning; Grinding and cleaning the damaged area of ​​the nickel-based superalloy substrate, and drying it after cleaning; S3: First sandblasting; The damaged area surface after step S2 is subjected to the first sandblasting treatment. The sand used for sandblasting is nickel-based alloy sand with 60-100 mesh particles as in step S1. S4: Second sandblasting; A second sandblasting treatment is performed on the damaged area surface after the first sandblasting in step S3. The sand used in step S1 is nickel-based alloy sand with a particle size of 200-280 mesh.

3. The method according to claim 2, characterized in that: In step S1, the steps for obtaining nickel-based alloy sand are as follows: S11: Prepare elemental metals or intermediate alloys containing relevant elements according to the elemental proportions; S12: Melt the elemental metal or intermediate alloy prepared in step S11 in a vacuum environment to form an alloy ingot; S13: Crush the alloy ingot obtained in step S12; S14: Screened out nickel-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh.

4. The method according to claim 2, characterized in that: The nickel-based superalloy in step S2 is any one or more of the following: Mar-M247 alloy, IN738LC alloy, IN939 alloy, MGA2400 alloy, GTD111 alloy, and GTD222 alloy.

5. The method according to claim 2, characterized in that: In step S2, the nickel-based superalloy substrate should be cleaned using an alcohol or acetone solution and by ultrasonic cleaning.

6. The method according to claim 2, characterized in that: In step S3, the sandblasting pressure for the first sandblasting is between 0.4 MPa and 0.6 MPa.

7. The method according to claim 2, characterized in that: In step S4, the sandblasting pressure for the second sandblasting is between 0.2 MPa and 0.4 MPa.

8. The method according to claim 2, characterized in that: The crater coverage of the sprayed surface in the first sandblasting in step S3 and the second sandblasting in step S4 must reach 100%.

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