A cobalt-based alloy sand, preparation method and optimization of the surface of the damaged area

Abstract

This invention discloses a cobalt-based alloy sand, a method for preparing and optimizing the surface of the damaged area, relating to the field of alloy repair. The cobalt-based alloy sand includes Cr, Ni, Mo, Ti, Ta, B, and Y, with the remainder being Co and / or unavoidable impurity elements. The method for optimizing the surface of the damaged area mainly involves sandblasting the surface of the damaged area twice. This invention can sandblast the damaged area surface to achieve the purpose of surface modification, thereby inhibiting the aggregation of Si-rich and B-rich brittle eutectic phases at the interface during powder metallurgy and improving the interfacial bonding strength of the repair joint.

Description

Technical Field

[0001] This invention relates to the field of repairing cobalt-based high-temperature alloy thermal components, and in particular to a method for preparing and optimizing the surface of a damaged area using cobalt-based alloy sand. Background Technology

[0002] Above 1000℃, cobalt-based superalloys exhibit superior high-temperature performance compared to nickel-based superalloys (higher resistance to hot corrosion, higher thermal conductivity, lower coefficient of thermal expansion, longer service life, and better thermal fatigue resistance), making them ideal for manufacturing high-temperature components such as turbine blades and combustor nozzles for aero-engines, industrial gas turbines, and marine gas turbines. Due to prolonged operation in ultra-high temperature environments or under extremely complex stress conditions, these high-temperature components may experience structural integrity failure (ablation, material reduction, and cracking). Repairing damaged parts of components using appropriate and effective methods can significantly reduce the unit's operation and maintenance costs.

[0003] For cobalt-based superalloy hot components with complex shapes and multiple thin-walled structures (such as turbine blades), fusion welding is highly prone to causing thin-walled melt-through and blockage of internal flow channels when repairing defects. Therefore, powder metallurgy is usually used for repair. This repair process has many advantages, such as high repair efficiency, simple process, and low repair cost. The repair material used is composed of a low-melting-point alloy powder (i.e., activator) and a high-melting-point alloy powder (i.e., curing agent). At high temperature, the activator melts to form a liquid phase, which wets and fills the gap between the substrate and the curing agent, and then solidifies isothermally to form a metallurgical joint. The activator usually contains a high concentration of active elements (such as silicon and boron) to lower the melting point of the alloy, such as commercial grades AMDRY788 (Co-21Ni-22Cr-14W-2Si-2B) and AMS4783 (Co-17Ni-19Cr-4W-8Si-0.8B).

[0004] However, when using powder metallurgy materials with silicon and boron as melting point inhibitors to repair damaged areas of workpieces, a large amount of brittle eutectic phases rich in Si and boron are often generated at the substrate-repair zone interface, resulting in low interfacial bonding strength. This is mainly because the substrate and the spherical curing agent powder have point contact with larger gaps, making it easier for the super-liquid phase to aggregate; furthermore, the small specific surface area of ​​the repair zone interface is unfavorable for the diffusion of active elements. The combination of these two factors leads to the formation of brittle eutectic phases rich in Si and boron. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a cobalt-based alloy sand, a method for preparing and optimizing the surface of the damaged area, and by sandblasting the damaged area to achieve surface modification, thereby inhibiting the aggregation of Si- and B-rich brittle eutectic phases at the interface during powder metallurgy and improving the interfacial bonding strength of the repair joint.

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

[0007] Cr: 22.1%-27.3%, Ni: 4.1%-8.9%, Mo: 8.7%-13.5%, Ti: 6.1%-9.3%, Ta: 0%-1.8%, B: 1.4%-2.2%, Y: 0.01wt%-0.05wt%, with the remainder being Co 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 cobalt-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 22.1wt%-27.3wt% of Cr to ensure that the in-situ sand inclusion area has excellent oxidation resistance and hot corrosion resistance.

[0010] Add 4.1wt%-8.9wt% Ni to stabilize the face-centered cubic matrix in the in-situ sand inclusion zone.

[0011] Adding 8.7wt%-13.5wt% of Mo increases the hardness of the cobalt-based alloy sand of the present invention and stabilizes the in-situ sand inclusions and the B element in the activator.

[0012] Adding 8.1 wt%-12.3 wt% Ti can both weakly suppress the melting point of the cobalt-based alloy sand of the present invention and stabilize the in-situ sand inclusions and the B element in the activator.

[0013] Adding 0-1.8 wt% Ta can achieve solid solution strengthening in the in-situ sand inclusion area;

[0014] Adding 1.4wt%-2.2wt% of B effectively further suppresses the melting point of the cobalt-based alloy sand of the present invention.

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

[0016] Furthermore, the cobalt-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] Furthermore, the melting temperature of the cobalt-based alloy sand is controlled at 1150℃-1180℃. When performing powder metallurgy sintering in the damaged area, the cobalt-based alloy sand is ensured to melt at the temperature of the powder metallurgy sintering process to avoid surface sand inclusions that would cause a decrease in the performance of the bonding surface.

[0018] A preparation method for preparing the cobalt-based alloy sand includes the following steps:

[0019] A: Material preparation: Prepare elemental metals or intermediate alloys containing relevant elements according to the element ratio;

[0020] B: Melting, the elemental metal or intermediate alloy prepared in step A is melted in a vacuum environment to form an alloy ingot;

[0021] C: Crushing, crushing the alloy ingot obtained in step B;

[0022] D: Screening, separating cobalt-based alloy sand into two specifications with particle sizes of 60-100 mesh and 200-280 mesh.

[0023] A method for optimizing the surface of a damaged area, using the aforementioned cobalt-based alloy sand, includes the following steps:

[0024] S1: Preparation, using the preparation method described above, prepare cobalt-based alloy sand with two particle sizes: 60-100 mesh and 200-280 mesh;

[0025] S2: Grinding and cleaning, grinding and cleaning the damaged surface of the hot end component of cobalt-based superalloy;

[0026] S3: First sandblasting, the damaged area is sandblasted for the first time, the sand particles are cobalt-based alloy sand, the particle size is 60-100 mesh; the main purpose of the first sandblasting is to roughen the substrate surface, refine the surface grains of the substrate, and modify the surface structure of the substrate.

[0027] S4: Second sandblasting, the damaged area that has been sandblasted in step S3 is sandblasted a second time. The sand particles are cobalt-based alloy sand with a particle size of 200-280 mesh. The main purpose of the second sandblasting is to roughen the surface of the crater after the first sandblasting and remove the large sand particles left on the substrate surface after the first sandblasting.

[0028] Furthermore, the substrate of the cobalt-based high-temperature alloy hot end component in step S2 is any one or more of FSX414, X40, X45, Mar-M509, Mar-M332, HS25, HS27 and AR213.

[0029] Furthermore, in step S3, the sandblasting gun head of the first sandblasting is perpendicular to the surface being sprayed, and the sandblasting pressure is 0.3MPa-0.7MPa.

[0030] Furthermore, in step S4, the sandblasting gun head of the second sandblasting is at an angle of 30°-50° to the surface being sandblasted, and the sandblasting pressure is 0.2MPa-0.4MPa.

[0031] Furthermore, after the first and second sandblasting, the crater coverage of the blasted surface 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. The cobalt-based alloy sand (blasting material) of the present invention is simple to prepare and 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, and is applicable to most sandblasting machine models.

[0034] 2. Regarding sandblasting materials, compared with traditional sandblasting materials (common traditional sandblasting materials include quartz sand, iron sand, corundum, etc.), the cobalt-based alloy sand provided by this invention, when used as a sandblasting material, allows the sand inclusions on the surface of the damaged area (area to be repaired) to melt at the powder metallurgy sintering process temperature after sand blasting, thus preventing a decrease in the performance of the connecting surface due to surface sand inclusions.

[0035] 3. After the surface of the damaged area is sandblasted with the cobalt-based alloy sand provided by this invention, the surface of the damaged area (the area to be repaired) is roughened due to the formation of craters, the specific surface area increases, the length of the two-dimensional connection boundary is extended, and the area of ​​the shape reshaping area (the area after the damaged area is repaired by powder metallurgy) and the metallurgical interface of the substrate is significantly increased; and the large specific surface area effectively increases the diffusion sites of active elements silicon and boron into the substrate, which is conducive to the diffusion of melting point inhibiting elements into the matrix, thereby effectively inhibiting the formation of eutectic phase at the interface.

[0036] 4. After the surface of the damaged area is sandblasted with the cobalt-based alloy sand provided by this invention, the crater formed on the surface of the damaged area (the area to be repaired) is very conducive to the occupancy of spherical curing agent powder, shortens the diffusion distance of melting point inhibiting elements, effectively avoids the formation of eutectic phase at the interface, can reduce the gap size between the curing agent powder and the substrate interface, avoids the aggregation of liquid phase generated after the activator melts, and prevents brittle compounds from continuously precipitating in sheets at the interface.

[0037] 5. After the surface of the damaged area is sandblasted with the cobalt-based alloy sand provided by this invention, the surface grains of the damaged area (the area to be repaired) are refined. The large number of grain boundaries generated promotes the formation of a large number of high-density dislocations, stacking faults and twins in 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 active elements silicon and boron into 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 image shows the morphology of the cobalt-based alloy sand disclosed in Example 1.

[0040] Figure 2 The surface morphology of the repaired area in the test case of Example 3;

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

[0042] Figure 4 This is the interface morphology of the repair area in the control example in Example 3. Detailed Implementation

[0043] 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.

[0044] 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.

[0045] Example 1

[0046] like Figure 1 As shown, a cobalt-based alloy sand, in a mass percentage ratio, contains the following elements:

[0047] Cr: 22.1%-27.3%, Ni: 4.1%-8.9%, Mo: 8.7%-13.5%, Ti: 6.1%-9.3%, Ta: 0%-1.8%, B: 1.4%-2.2%, Y: 0.01wt%-0.05wt%, with the remainder being Co and / or unavoidable impurity elements.

[0048] In this embodiment, the cobalt-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.

[0049] 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.

[0050] Table 1. Implementation methods of cobalt-based alloy sand

[0051]

[0052] As can be seen from the melting points of DFS-A alloy sand, DFS-O alloy sand, DFS-D alloy sand and DFS-I alloy sand in Table 1, the melting temperature of the cobalt-based alloy sand is controlled between 1150℃ and 1173℃. When performing powder metallurgy sintering in the damaged area, it is ensured that the cobalt-based alloy sand can melt at the temperature of the powder metallurgy sintering repair process in the damaged area of ​​the cobalt-based high-temperature alloy, so as to avoid the situation of surface sand inclusion causing a decrease in the performance of the bonding surface.

[0053] Example 2

[0054] A preparation method for preparing the cobalt-based alloy sand described in Example 1, taking the preparation of DFS-A alloy sand in Example 1 as an example, includes the following steps:

[0055] A: Material preparation: Prepare elemental metals or intermediate alloys of Co, Cr, Ni, Mo, Ti, Ta, B and Y with a purity of 99.99% according to the element ratio. Elemental metals are preferred, and the introduction of impurities should be minimized.

[0056] B: Melting. The material prepared in step A is placed in a vacuum environment for melting to form an alloy ingot. The vacuum environment is provided by a vacuum arc melting furnace, and 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, and the liquid phase solidifies. The above steps are repeated 8 times to obtain an alloy ingot with uniform composition and thorough mixing.

[0057] C: Crushing. The alloy ingots obtained in step B are mechanically crushed using an alloy crusher.

[0058] D: Screening, separating cobalt-based alloy sand into two specifications with particle sizes of 60-100 mesh and 200-280 mesh.

[0059] It should be noted that, in this embodiment, the cobalt-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 blasting machine models.

[0060] Example 3

[0061] A method for optimizing the surface of a damaged area, using cobalt-based alloy sand provided in any embodiment of Example 1, taking DFS-A alloy sand in Example 1 as an example, applied to a substrate of any one or more of FSX414, X40, X45, Mar-M509, Mar-M332, HS25, HS27, and AR213, taking the application to a substrate made of FSX414 cobalt-based superalloy as an example; wherein, the nominal chemical composition of FSX414 cobalt-based superalloy is:

[0062] Co-29wt%Cr-10wt%Ni-7.5wt%W-1wt%Fe-0.25wt%C-0.01wt%B,

[0063] It can be used to manufacture guide vanes for high-power gas turbines.

[0064] A method for optimizing the surface of a damaged area includes the following steps:

[0065] S1: Preparation: Using the preparation method described in Example 2, cobalt-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh was prepared.

[0066] S2: Grinding and cleaning. Grinding and cleaning are performed on the surface of the damaged area (area to be repaired) of the substrate. Grinding can be done by mechanical grinding to remove the oxide layer on the surface of the damaged area. Cleaning can be done with anhydrous ethanol, which can completely dissolve the organic matter attached to the damaged area of ​​the substrate. It is also easy to volatilize during drying and will not leave any residue, effectively avoiding the impact of organic matter or other impurities on the repair quality of the repair area. After cleaning, the area is dried for later use.

[0067] S3: First sandblasting: The damaged area is sandblasted for the first time. The sand particles are cobalt-based alloy sand with a particle size of 60-100 mesh. The sandblasting gun head is perpendicular to the surface to be sprayed, and the sandblasting pressure is 0.3MPa-0.7MPa, preferably 0.6MPa. The crater coverage of the surface to be sprayed is 100%.

[0068] S4: Second sandblasting. The damaged area that has undergone the first sandblasting in step S3 is sandblasted a second time. The sand particles are cobalt-based alloy sand with a particle size of 200-280 mesh. The sandblasting gun head is at an angle of 30° to 50° to the surface being sandblasted. The sandblasting pressure is 0.2MPa-0.4MPa, preferably 0.3MPa. The crater coverage of the surface being sandblasted is 100%.

[0069] In this embodiment, as Figure 2 As shown, the surface morphology of the damaged area of ​​the FSX414 cobalt-based superalloy substrate after a second sandblasting process has a roughness of 2.9 μm and a surface area of ​​1.3 cm² per unit size of 1 cm × 1 cm. 2 .

[0070] Therefore, the main purpose of the first sandblasting is to roughen the surface of the damaged area of ​​the substrate, refine the surface grains of the damaged area, and modify the surface structure. The main purpose of the second sandblasting is to roughen the surface of the crater after the first sandblasting and remove the large sand particles left on the surface after the first sandblasting. After the two sandblasting treatments, the surface of the damaged area (the area to be repaired) is roughened, the specific surface area is greatly increased, and the sites for the diffusion of active elements silicon and boron into the substrate are significantly increased.

[0071] Furthermore, a set of experimental examples is provided, in which the damaged area of ​​a secondary sandblasted FSX414 cobalt-based superalloy substrate was repaired using powder metallurgy with the commercially available activator AMDRY788 (Co-21Ni-22Cr-14W-2Si-2B). After repair, the microstructure of the repaired area (the area after repair) was observed under a microscope, such as... Figure 3 As shown, no Si- or B-rich brittle intermetallic compounds were found at the interface. Tensile properties of the repaired area were tested at 870℃, yielding a yield strength of 315 MPa and a tensile strength of 338 MPa.

[0072] In this embodiment, a set of control examples is provided, namely, after grinding and cleaning the surface of FSX414 nickel-based superalloy, powder metallurgy repair is directly performed using the commercially available activator AMDRY788. The repair process is consistent with the above-mentioned experimental examples. After the powder metallurgy repair is completed, the microstructure of the repaired area section is observed, such as... Figure 4 As shown, a large area of ​​Si- and B-rich brittle intermetallic compounds precipitated along the interface; tensile properties of the repaired area were tested at a high temperature of 870°C, and no yield strength was measured, and the sample underwent brittle fracture; the tensile strength was 281 MPa, which was significantly lower than the tensile strength obtained in the test example in Example 3.

[0073] In summary, after the surface of the damaged area is sandblasted with the cobalt-based alloy sand provided by this invention, the craters formed on the surface of the damaged area (the area to be repaired) are very conducive to the occupancy of spherical curing agent powder, which can reduce the gap size between the curing agent powder and the substrate interface and prevent the aggregation of liquid phase generated after the activator melts; the surface grains of the damaged area (the area to be repaired) are refined, and the large number of grain boundaries generated can serve as fast channels to accelerate the diffusion of active elements silicon and boron into the substrate and inhibit the formation of brittle eutectic phase.

[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 cobalt-based alloy grit, characterized by: According to the mass percentage, the cobalt-based alloy sand comprises the following elements: Cr: 22.1%-27.3%, Ni: 4.1%-8.9%, Mo: 8.7%-13.5%, Ti: 6.1%-9.3%, Ta: 0%-1.8%, B: 1.4%-2.2%, Y: 0.01%-0.05%, and the rest is Co and inevitable impurity elements; the cobalt-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.

2. The cobalt-based alloy grit according to claim 1, characterized in that: The melting temperature of the cobalt-based alloy sand is controlled at 1150-1180°C.

3. A production method for producing the cobalt-based alloy sand according to any one of claims 1 to 2, characterized by: The method comprises the following steps: A: preparation, preparing elemental metals or intermediate alloys containing relevant elements according to the element ratio; B: smelting, smelting the elemental metals or intermediate alloys prepared in step A in a vacuum environment to form an alloy ingot; C: crushing, crushing the alloy ingot obtained in step B; D: screening, screening out cobalt-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh.

4. A method for optimizing the surface of a damaged area using the cobalt-based alloy sand according to any one of claims 1 to 2, characterized by: The method comprises the following steps: S1: preparation, applying the preparation method of claim 3 to prepare cobalt-based alloy sand with particle sizes of 60-100 mesh and 200-280 mesh; S2: polishing and cleaning, polishing and cleaning the surface of the damaged area of the cobalt-based superalloy substrate; S3: first sandblasting, first sandblasting the damaged area, and the sand particles are cobalt-based alloy sand with a particle size of 60-100 mesh; S4: second sandblasting, second sandblasting the damaged area that has been subjected to the first sandblasting in step S3, and the sand particles are cobalt-based alloy sand with a particle size of 200-280 mesh.

5. The method of claim 4, wherein: The cobalt-based superalloy substrate in step S2 is any one or more of FSX414, X40, X45, Mar-M509, Mar-M332, HS25, HS27, and AR213.

6. The method of claim 4, wherein: In step S3, the sandblasting gun head is perpendicular to the sprayed surface during the first sandblasting, and the sandblasting pressure is 0.3-0.7 MPa.

7. The method of claim 4, wherein: In step S4, the angle between the sandblasting gun head and the sprayed surface during the second sandblasting is 30-50°, and the sandblasting pressure is 0.2-0.4 MPa.

8. The method according to any one of claims 4-7, characterized by: After the first sandblasting and the second sandblasting, the crater coverage rate of the sprayed surface needs to reach 100%.

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