A nickel-based single crystal superalloy brazing repair material and method

Abstract

A nickel-based single crystal superalloy brazing repair material comprises a first brazing filler metal and a second brazing filler metal, wherein the first brazing filler metal comprises a brazing powder, and the second brazing filler metal comprises a mixture of the brazing powder and a base metal powder which is the same as the material of the part to be repaired; wherein the brazing powder comprises 8-18% of Cr, 3-12% of Co, 1-6% of W, 1-6% of Ta, 2-6% of Al, 1-5% of B, not more than 4% of Mo, not more than 5% of Hf, not more than 3% of Re, and the balance of Ni and inevitable impurities; and the weight ratio of the brazing powder in the second brazing filler metal is 5-50%. The repair material can effectively braze repair large-size gaps of more than 0.25 mm. The application also provides a nickel-based single crystal superalloy brazing repair method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of welding, and particularly relates to a nickel-based single-crystal high-temperature alloy brazing repair material and a repair method. BACKGROUND

[0002] The nickel-based single-crystal high-temperature alloy has good corrosion resistance and mechanical properties under high-temperature service conditions due to the elimination of grain boundaries, and in particular has good high-temperature creep properties. Therefore, current hot end components of an aero-engine, such as high-pressure turbine working blades or guide vanes, are widely manufactured using nickel-based single-crystal alloys. During long-term service, the turbine blades periodically bear impact and corrosion, and it is difficult to avoid damage such as ablation, cracks, and wear. Brazing repair of damaged nickel-based single-crystal high-temperature alloy parts is an important issue for aero-engine maintenance and maintenance. The existing brazing repair process mostly utilizes capillary phenomenon formed by narrow cracks to promote uniform flow of molten filler metal in the gap. Once the crack gap has developed to a large size, the capillary phenomenon disappears, making it difficult to repair damaged parts by brazing, increasing the maintenance cost of nickel-based single-crystal alloy parts, and limiting the service life of nickel-based single-crystal alloy parts. SUMMARY

[0003] The purpose of the present application is to provide a nickel-based single-crystal high-temperature alloy brazing repair material that can effectively repair large-size cracks by brazing. The present application also provides a nickel-based single-crystal high-temperature alloy brazing repair method.

[0004] According to an embodiment of one aspect of the present application, a nickel-based single-crystal high-temperature alloy brazing repair material is provided, which includes a first filler metal, the first filler metal including uniformly mixed brazing powder and base material powder of the same composition as the nickel-based single-crystal high-temperature alloy to be repaired; wherein the brazing powder includes the following components by weight ratio: 8%-18% Cr, 3%-12% Co, 1%-6% W, 1%-6% Ta, 2%-6% Al, 1%-5% B, not more than 4% Mo, not more than 5% Hf, not more than 3% Re, and the balance of Ni and unavoidable impurities; the weight ratio of the brazing powder in the first filler metal is 5%-50%.

[0005] The Cr, Co, W, Mo elements in the brazing repair material can be solid-solved in the weld seam matrix after brazing, improving the weld seam strength, and improving the high-temperature oxidation resistance and corrosion resistance of the weld seam. The Al element can participate in the formation of γ' phase, improving the weld seam strength and oxidation resistance. The Ta element and the Re element can improve the stability of the γ' phase, thereby improving the service temperature of the welded joint; but when Ta is excessive, it will precipitate in the form of a compound and is difficult to eliminate in the subsequent processing process, which has an adverse effect on the weld seam strength. The B element can lower the melting point of the filler metal and improve the wettability of the filler metal melt. The Hf element can lower the melting point of the filler metal and improve the strength and plasticity of the weld seam structure. The C element and the Si element are easy to form harmful precipitates in the weld seam area, so they need to be controlled as impurity elements, so that their content does not exceed the upper limit of the solid solubility of C and Si in the alloy matrix, so that the brazed repair structure has better mechanical properties. Further, mixing the brazing powder and the base material powder in the first filler metal can improve the wettability of the first filler metal and the weld seam, improve the uniformity of the structure of the brazing repair of large-size cracks, and improve the strength of the repaired part.

[0006] Further, in some embodiments, the weight ratio of the brazing powder in the first filler metal is 10%-40%. The base material component has a higher melting point than the brazing powder, and controlling the proportion of the base material powder can improve the high-temperature mechanical properties of the weld seam structure. The base material does not melt during welding, and acts as a skeleton connecting the base material of the part during weld repair.

[0007] Further, in some embodiments, the particle size of the brazing powder and the base material powder is not more than 110 μm. Smaller particle size is beneficial to accelerate the melting of the filler metal during brazing, and improve the uniformity of the welded structure.

[0008] Further, in some embodiments, the particles of the brazing powder and the base material powder are spherical or near-spherical. Spherical or near-spherical base material powder can be prepared by vacuum air atomization and the like, can be fully mixed, and can quickly melt during brazing.

[0009] Further, in some embodiments, the brazing repair material further comprises a second filler metal, which is the brazing powder, for coating on the surface of the first filler metal. The second filler metal composed of low-melting-point brazing powder is coated on the surface of the first filler metal, and the second filler metal area melts first and forms a liquid phase during brazing, improving the uniformity of the liquid phase distribution in the weld seam, and avoiding defects such as pores and gaps in the weld seam structure after solidification.

[0010] Further, in some embodiments, the nickel-based single crystal superalloy is DD4, DD6 or CMSX-4 alloy.

[0011] According to another aspect of the embodiments of the present application, a nickel-based single crystal superalloy brazing repair method is provided, which uses the nickel-based single crystal superalloy brazing repair material of any of the preceding embodiments, and comprises the following steps: providing a part to be repaired having a crack, filling the first filler in the crack; coating the brazing powder on the surface of the first filler filled in the crack until the first filler is completely covered; vacuum heating the part to be repaired at a temperature of 1150-1230°C for 20-180 min to complete the brazing repair. By using this method, the weld joint formed in the brazing repair process is fully welded and has no pore, inclusion or crack defects, and has good high-temperature mechanical properties and high-temperature durability.

[0012] Further, in some embodiments, the maximum width of the crack of the part to be repaired is not less than 0.25 mm. This method can effectively repair cracks with a maximum width of not less than 0.25 mm.

[0013] Further, in some embodiments, the first filler filled in the crack is flush with the surface of the part to be repaired.

[0014] Further, in some embodiments, the part repaired by brazing has a strength of not less than 60% of the base material at 1000°C under high-temperature tension. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 An electron microscope photo of the brazing powder in one embodiment;

[0016] Figure 2 An electron microscope photo of the mixed brazing powder and base material powder in one embodiment;

[0017] Figure 3 A schematic diagram of the brazing filler arrangement position in one embodiment;

[0018] Figure 4 A weld joint metallographic structure photo in one embodiment;

[0019] Figure 5 A weld joint metallographic structure photo in another embodiment;

[0020] Figure 6 A weld joint metallographic structure photo in yet another embodiment;

[0021] Figure 7 A weld joint metallographic structure photo in a comparative example.

[0022] The purpose of the above drawings is to make a detailed description of the present application so that those skilled in the art can understand the technical concept of the present application, and is not intended to limit the present application. DETAILED DESCRIPTION

[0023] The application will be further described in detail below with reference to the accompanying drawings.

[0024] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art will recognize that the embodiments herein can be combined with other embodiments.

[0025] In the description herein, the terms "first", "second", and the like are used only to distinguish different objects, and cannot be understood as indicating relative importance or limiting the number, specific order, or primary and secondary relationship of the technical features described. In the description herein, "a plurality of" means at least two.

[0026] In an embodiment of one aspect of the application, a nickel-based single crystal superalloy brazing repair material is provided to realize brazing repair of a nickel-based single crystal superalloy part with a large gap crack.

[0027] In one embodiment, two pieces of DD6 alloy sample pieces are used to simulate the nickel-based single crystal superalloy part to be repaired. The brazing alloy is prepared according to the following proportions: 9.6% Cr, 10.7% Co, 1.5% W, 4.3% Ta, 3.7% Al, 2.5% B, and the balance of Ni and unavoidable impurities by weight. The brazing alloy is processed by a vacuum air atomization method to obtain brazing powder with a particle size of ≤110 μm, and the scanning electron microscope (SEM) photograph is as shown in FIG. 1. The DD6 base material alloy is also processed by a vacuum air atomization method to obtain base material powder with a particle size of ≤110 μm. Part of the brazing powder is uniformly mixed with the base material powder at a weight ratio of 1:4, and the morphology of the mixed powder under the SEM photograph is as shown in FIG. 2. The brazing powder and the base material powder are both fine spherical or near-spherical particles. Figure 1 Figure 2 The brazing powder is mixed with a binder to obtain a paste-like second brazing filler metal, and the mixed powder of the brazing powder and the base material powder is mixed with a binder to obtain a paste-like first brazing filler metal. In different embodiments, the binder can be an organic binder such as polystyrene or polymethyl methacrylate that can completely vaporize at high temperature.

[0028] The surfaces of the two pieces of DD6 alloy sample pieces are polished and cleaned with alcohol to remove surface oil stains to meet the surface composite cleanliness requirements. The gap between the two pieces of DD6 alloy sample pieces is controlled to be about 0.3 mm by using a clamp to simulate the state of a part with a large size crack. The brazing filler metal is applied to the gap between the two pieces of DD6 alloy sample pieces as shown in FIG. 3, and the brazing is carried out in a vacuum furnace at a temperature of 1150°C for 2 hours. After the brazing, the brazing filler metal is cooled to room temperature, and the brazing joint is obtained as shown in FIG. 4.

[0029] The surfaces of the two pieces of DD6 alloy sample pieces are polished and cleaned with alcohol to remove surface oil stains to meet the surface composite cleanliness requirements. The gap between the two pieces of DD6 alloy sample pieces is controlled to be about 0.3 mm by using a clamp to simulate the state of a part with a large size crack. The brazing filler metal is applied to the gap between the two pieces of DD6 alloy sample pieces as shown in FIG. 3, and the brazing is carried out in a vacuum furnace at a temperature of 1150°C for 2 hours. After the brazing, the brazing filler metal is cooled to room temperature, and the brazing joint is obtained as shown in FIG. 4.​Figure 3 The solder is coated in the form shown. The first solder 1 is filled into the gap 4 and the surface is scraped flat so that the surface of the first solder 1 is flush with the surface of the sample 3. After filling the first solder 1, a second solder 2 is coated on its surface so that the first solder 1 is completely covered.

[0030] Next, the DD6 alloy sample was placed in a vacuum furnace for brazing. The vacuum furnace was evacuated until the internal pressure was below 4 × 10⁻⁶. -2 Pa, then heating began, reaching 1190℃ and holding for 2 hours, then cooling to 80℃ before removing from the furnace to complete brazing. The parts were then subjected to aging treatment, holding at 1120℃ for 4 hours and then cooling to 870℃ and holding for 32 hours.

[0031] Metallographic analysis was performed on the brazed samples, such as... Figure 4 As shown, the microstructure within weld 5 is uniform and tightly bonded to the matrix of sample 3, without any gaps, voids, or incomplete welds. Tensile property testing of the weld was conducted on standard samples; the high-temperature tensile strength at 1000℃ was approximately 433 MPa, reaching 60% of the base material's properties.

[0032] In another embodiment, two DD6 alloy samples were used to simulate the nickel-based single-crystal superalloy part to be repaired. The brazing alloy was prepared according to the following proportions by weight: 15.3% Cr, 5.5% Co, 4.3% W, 1.3% Ta, 2.2% Al, 0.9% Mo, 2.9% B, 4.5% Hf, 2.1% Re, with the balance being Ni and unavoidable impurities. The brazing alloy and the base alloy were separately processed using vacuum atomization to prepare powders. A portion of the brazing powder was uniformly mixed with the base powder at a weight ratio of 1:3. The brazing powder was mixed with a binder to obtain a paste-like second brazing filler metal; the mixture of brazing powder and base powder was mixed with a binder to obtain a paste-like first brazing filler metal.

[0033] The surfaces of the two DD6 alloy samples were polished and cleaned with alcohol to remove surface oil and dirt, in order to determine the required surface cleanliness. A fixture was used to maintain a gap of approximately 0.3 mm between the two DD6 alloy samples to simulate the condition of a part with a large-sized crack. Figure 3 The solder is applied in the manner shown. First solder 1 is filled into gap 4, and the surface is smoothed so that the surface of first solder 1 is flush with the surface of sample 3. After filling with first solder 1, a second solder 2 is applied to its surface, completely covering the first solder 1. In a preferred embodiment, the coverage area of ​​the second solder 2 is slightly larger than the width of gap 4, and the surface formed by the coating of the second solder 2 forms a naturally transitioning arc shape.

[0034] Next, the DD6 alloy sample pieces are sent into a vacuum furnace for brazing, the vacuum furnace is evacuated to a pressure lower than 4x10 -2 Pa, then heating is started and the temperature is raised to 1220°C and held for 1 h, and then the furnace is cooled to 80°C and the brazing is completed. Then the part is aged at 1120°C for 4 h and cooled to 870°C for 32 h.

[0035] The brazed sample is analyzed by metallography, as shown in FIG. 5, the microstructure in the weld 5 is uniform and tightly combined with the base material of the sample 3, without defects such as gaps, holes and incomplete welding. The standard sample is cut for tensile test of the weld, the high temperature tensile strength at 1000°C is about 595 MPa, reaching 80% of the base material performance. Figure 5

[0036] In another embodiment, two piece DD6 alloy sample pieces are used to simulate a nickel-based single crystal superalloy part to be repaired. The brazing alloy is prepared according to the following proportions: 14.3% Cr, 10.5% Co, 1.2% W, 3.5% Ta, 2.5% Al, 3.8% Mo, 3.2% B, 2.9% Hf, 0.7% Re, and the balance of Ni and unavoidable impurities. The brazing alloy and the base material alloy are processed into powders by vacuum gas atomization. Part of the brazing powder is mixed with the base material powder at a weight ratio of 2:3. The brazing powder is mixed with a binder to prepare a paste-like second brazing material; the mixed powder of the brazing powder and the base material powder is mixed with a binder to prepare a paste-like first brazing material.

[0037] The surfaces of the two piece DD6 alloy sample pieces are polished and cleaned with alcohol to remove surface oil and meet the surface composite cleanliness requirements. The two piece DD6 alloy sample pieces are controlled by a jig to maintain a gap of about 0.3 mm to simulate a part with a large size crack. The brazing material is applied as shown in FIG. 4, the first brazing material 1 is filled into the gap 4 and the surface is scraped flat so that the surface of the first brazing material 1 is flush with the surface of the sample 3; after the first brazing material 1 is filled, a layer of the second brazing material 2 is applied on the surface to completely cover the first brazing material 1. Figure 3

[0038] Next, the DD6 alloy sample pieces are sent into a vacuum furnace for brazing, the vacuum furnace is evacuated to a pressure lower than 4x10 -2 Pa, then heating is started and the temperature is raised to 1220°C and held for 1 h, and then the furnace is cooled to 80°C and the brazing is completed. Then the part is aged at 1120°C for 4 h and cooled to 870°C for 32 h.

[0039] The brazed sample is analyzed by metallography, as shown in FIG. 5, the microstructure in the weld 5 is uniform and tightly combined with the base material of the sample 3, without defects such as gaps, holes and incomplete welding. The standard sample is cut for tensile test of the weld, the high temperature tensile strength at 1000°C is about 595 MPa, reaching 80% of the base material performance. Figure 6 ​​As shown, the microstructure in the weld 5 is uniform and closely combined with the base of the sample 3, without defects such as gaps, holes and incomplete welding. The standard sample is cut for tensile test of the weld, and the high-temperature tensile strength at 1000℃ is about 581MPa, reaching 80% of the performance of the base material.

[0040] In some embodiments, the wedge-shaped cracks in the actual parts are brazed, and the narrower part of the wedge-shaped cracks, such as the area with a width less than 0.25mm, can be directly filled with brazing powder, and for the area with a width greater than 0.25mm, the brazing repair material provided in the above embodiments can be used to achieve effective brazing repair of the wedge-shaped cracks. In other embodiments, the above brazing repair material and brazing repair method can also be applied to other grades of nickel-based single crystal superalloys such as DD4 alloy or CMSX-4 alloy. In different embodiments, the mixing ratio of the brazing powder and the base material powder in the first brazing filler metal can be reasonably adjusted according to factors such as the gap width and the melting point of the base material. In some embodiments, the gap width is narrow or the melting point of the base material is low, and the proportion of the brazing powder can be appropriately increased; when the gap width is wide or the melting point of the base material is high, the proportion of the brazing powder can be appropriately reduced.

[0041] In a comparative example, a brazing filler metal alloy is configured with a weight ratio of 9.6% Cr, 10.7% Co, 1.5% W, 4.3% Ta, 3.7% Al, 2.5% B, and the balance of Ni, and is prepared into a powder. The brazing filler metal powder and the DD6 alloy powder are mixed in a ratio of 1:2, and a binder is added to prepare a paste. Two-piece DD6 alloy samples are used to simulate the gap to be welded, and the DD6 alloy samples are arranged at an interval of 0.3mm. The paste brazing filler metal is filled into the gap and leveled, and then a layer of paste brazing filler metal is laid on the surface of the paste brazing filler metal, so that the brazing filler metal is arranged between the samples in the same total amount and distribution as in the example. The samples are placed in a vacuum furnace, vacuumed to a pressure of less than 4×10 -2 Pa, heated to 1220℃ for 1h, cooled to 80℃ and taken out of the furnace. Then the welded sample is aged at 1120℃ for 4h, cooled to 870℃ for 32h for aging treatment. The metallographic analysis of the sample of the comparative example shows that Figure 7 As shown, there are large areas of incomplete welding defects 6 in the welding area between the samples 3.

[0042] The nickel-based single crystal superalloy brazing repair material provided in the embodiments of the present application has a first brazing filler metal filled in the weld with less low-melting-point brazing powder, which reduces the size of the large block or continuous chain of brittle intermetallic compounds that can be formed during brazing. At the same time, the second brazing filler metal with a lower melting point can form a liquid phase to effectively fill the gaps between the base material powders and between the base material powders and the part base material, effectively reducing the defects such as holes and gaps in the weld area.

[0043] The nickel-based single crystal superalloy brazing repair method provided by the above embodiments can simultaneously braze repair multiple parts, improve production efficiency, and reduce the influence of brazing structure on the structure and mechanical properties of the single crystal superalloy. In some embodiments, after brazing and twice repair welding, the performance of the single crystal part after simulated thermal cycling can still reach more than 95% of the performance of the brazed single crystal part.

[0044] The above embodiments are intended to further illustrate the present application in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present application. Within the scope of the claims of the present application, the components and method steps involved are optimized or equivalently replaced, and the embodiments in different embodiments are combined without principle conflict, which all fall within the protection scope of the present application.

Claims

1. A method for brazing repair of nickel-based single-crystal superalloys, characterized in that, The nickel-based single-crystal superalloy is DD4, DD6, or CMSX-4 alloy, and brazing repair is performed using a first filler metal and a second filler metal. in, The first brazing filler metal comprises a uniformly mixed brazing powder and a base material powder with the same composition as the nickel-based single-crystal superalloy to be repaired. The brazing powder comprises the following components by weight: 8%-18% Cr, 3%-12% Co, 1%-6% W, 1%-6% Ta, 2%-6% Al, 1%-5% B, not more than 4% Mo, not more than 5% Hf, not more than 3% Re, with the balance being Ni and unavoidable impurities. The brazing powder in the first brazing filler metal accounts for 5% to 50% by weight; The second solder is the brazing powder; And includes the following steps: A part with a crack is provided to be repaired, and the crack is filled with the first brazing filler metal; The brazing powder is coated onto the surface of the first filler metal filling the crack until the first filler metal is completely covered. The parts to be repaired are vacuum heated at a temperature of 1150℃-1230℃ for 20-180 minutes to complete the brazing repair.

2. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, characterized in that, The maximum width of the crack in the part to be repaired is not less than 0.25 mm.

3. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, characterized in that, The first brazing filler metal filling the crack is flush with the surface of the part to be repaired.

4. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, 2, or 3, characterized in that, The parts repaired by brazing are subjected to high-temperature tensile testing at 1000℃, and their strength is not less than 60% of that of the base material.

5. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, 2, or 3, characterized in that, The weight ratio of the brazing powder in the first brazing filler metal is 10%-40%.

6. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, 2, or 3, characterized in that, The particle size of the brazing powder and the base material powder does not exceed 110 μm.

7. The method for brazing repair of nickel-based single-crystal superalloys according to claim 1, 2, or 3, characterized in that, The brazing powder and the base material powder are spherical or nearly spherical in shape.

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