Cobalt-based brazing filler metal for brazing service-damaged area of hot end component of high-temperature alloy with surface oxide film and preparation method thereof

Abstract

This invention belongs to the field of brazing technology and relates to a cobalt-based brazing filler metal for brazing service-damaged areas of high-temperature alloy hot-end components with oxide films on their surfaces. The filler metal has the following weight percentage composition: Cr 17.0–18.5%, Ni 15.0–16.5%, W 8.0–10.0%, Ti 7.0–9.0%, B 1.0–2.0%, Zr 1.0–2.0%, C 0.4–0.5%, with Co as the balance. It can be prepared as a powder for use. By adding appropriate amounts of the active elements Ti and Zr, the filler metal of this invention possesses good activity without significantly reducing the oxidation resistance of the filler metal matrix. During brazing, it can react with various oxides to achieve wetting and gap filling. It can be directly used for brazing repair of service-damaged areas of high-temperature alloy hot-end components with oxide films on their surfaces, effectively reducing the surface treatment requirements of service-damaged areas, improving the adaptability of the brazing repair process, and significantly reducing repair costs.

Description

Technical Field

[0001] This invention belongs to the field of brazing technology and relates to a cobalt-based active brazing filler metal and its preparation method for brazing repair of service damage areas of high-temperature alloy hot-end components with oxide films on the surface. Background Technology

[0002] Cobalt-based brazing filler metals possess superior high-temperature performance compared to nickel-based brazing filler metals, making them suitable for brazing high-temperature components. Table 1 lists the composition of cobalt-based brazing filler metals specified in aviation standards (Cobalt-based brazing filler metal specifications, HB 20453-2018). These filler metals are suitable for high-performance brazing of various high-temperature alloys and other materials, and are currently widely used in aviation, aerospace, and other fields. Based on the characteristics of these filler metals, they are all rich in Co-Cr-Ni-W, differing only in the composition and content of the reducing elements. K465 alloy brazed with B-Co45NiCrWB filler metal achieved 85% of the room temperature tensile strength and 50% of the high-temperature creep rupture performance of the base metal (Microstructure and properties of K465 high-temperature alloy joints brazed with different filler metals. Mao Wei, Zhou Yuan, Ye Lei, et al. Spot Welding Machine, vol.38 No.9, 2008). The tensile strength of DD5 single-crystal alloy joints brazed with Co-Cr(18~20)-Ni(15~17)-W(4~5)-Si(7~9)-B(2~3) (wt%) reached over 80% of that of the base metal (Microstructure and Mechanical Properties Analysis of Brazed Joints of DD5 Single-Crystal High-Temperature Alloy. Sun Yuan, Hou Xingyu, Jin Tao, et al. Welding Journal, vol.38No.1, 2017). From the application of cobalt-based brazing filler metals, high-performance horizontal joints can be obtained. However, based on the composition characteristics of these filler metals, the cleanliness of the surface of the high-temperature alloy being welded is very important. If the cleanliness of the welded surface is insufficient, the wettability and filling ability of the filler metal will be affected, ultimately leading to defects such as incomplete welding in the brazed joint.

[0003] Table 1. Composition of cobalt-based brazing filler metal specified in navigation marks.

[0004]

[0005]

[0006] For damage such as cracks and ablation that occur in engine hot-end components after service, such as cast high-temperature alloy blades (e.g.) Figure 1 As shown in the figure, brazing is required for repair. Currently, the main brazing filler metals available for repair are the cobalt-based filler metals listed in Table 1. These filler metals cannot react with the oxide film. The oxide film will prevent the filler metal from wetting the high-temperature alloy surface to be brazed. Therefore, the oxide film needs to be thoroughly removed before brazing repair, otherwise it will affect the filler metal filling. The oxide film is extremely difficult to clean and the cleaning cost is high.

[0007] Based on the above problems, in order to achieve brazing repair of service damage areas in high-temperature alloy hot-end components with oxide films or oxide films that cannot be completely removed, it is urgent to improve the wettability of brazing filler metals on high-temperature alloy surfaces with oxide films. Therefore, this invention designs a new composition brazing filler metal, which will find widespread application in the field of service damage repair of high-temperature alloy hot-end components. Summary of the Invention

[0008] The objective of this invention is to provide a cobalt-based active brazing filler metal and its preparation method for brazing repair of service-damaged areas of high-temperature alloy hot-end components with oxide films on their surfaces. Utilizing the high reactivity of Ti and Zr elements in the filler metal, even when an oxide film exists on the surface of the service-damaged area of ​​the high-temperature alloy hot-end component, the liquid filler metal can wet the base material, promoting wetting and filling of the gaps, and ensuring the formation of the brazed joint.

[0009] To solve this technical problem, the technical solution of the present invention is as follows:

[0010] On the one hand, a cobalt-based active brazing filler metal is provided for brazing repair of service damage areas of high-temperature alloy hot-end components with oxide films on the surface. The brazing filler metal is characterized by the following composition and mass percentage (wt%): Cr 17.0~18.5, Ni 15.0~16.5, W 8.0~10.0, Ti 7.0~9.0, B 1.0~2.0, Zr 1.0~2.0, C 0.4~0.5, and Co balance.

[0011] The strengthening elements and their corresponding mass percentages in the cobalt-based active solder are: Cr 17.5–17.8, Ni 15.5, W 8.5–8.8. Preferably, Cr 17.5, Ni 15.5, W 8.8.

[0012] The active element composition and mass percentage of the cobalt-based active solder are: Ti 8.0-8.8, Zr 1.5-1.8. Preferably, Ti 8.0, Zr 1.5.

[0013] The cobalt-based active solder has the following composition and mass percentage of elements that reduce melting point: B 1.2-1.4, C 0.46-0.48. Preferably, B 1.4, C 0.46.

[0014] On the other hand, a method for preparing a cobalt-based active brazing filler metal for brazing repair of service damage zones in high-temperature alloy hot-end components with an oxide film on the surface is provided, the method being as follows:

[0015] Step 1: Prepare the ingredients according to the composition of the cobalt-based brazing filler metal; Step 2: Melt the brazing filler metal alloy ingot, and repeat the melting process at least 3 times; Step 3: Prepare the brazing filler metal alloy ingot into powder, and then sieve it; Step 4: Mix acetone and neutral resin to prepare a solution, and then mix it with the brazing filler metal powder to prepare solder paste.

[0016] In step one, Co, W, Ti, and Zr are all-element, B is a Ni-B master alloy, C is a Cr-C master alloy, Ni is all-element and a Ni-B master alloy, and Cr is all-element and a Cr-C master alloy, and the proportions are made according to the design composition.

[0017] In step two, the mixed raw materials are placed in a crucible and melted using induction melting or electric arc melting to prepare a brazing alloy ingot.

[0018] In step three, the brazing alloy ingot is prepared into powder by argon atomization, or the brazing alloy ingot is prepared into foil by vacuum argon-filled rapid quenching equipment and then mechanically crushed to obtain powder.

[0019] In step four, acetone is mixed with neutral resin at a volume ratio of 45-55:1 to prepare a solution. After precipitation and filtration, the solution is mixed with brazing powder at a volume ratio of 1.5:1 to prepare a solder paste. When used, the paste is placed in a syringe and added to the brazing area of ​​the part.

[0020] The brazing filler metal using the composition of this invention can braze high-temperature alloys with oxide films such as Ti-O, Al-O, and Cr-O on the surface to be brazed at a temperature of 1180–1220°C and a holding time of 5–60 min.

[0021] The beneficial effects of this invention are:

[0022] (1) In order to achieve good wetting and filling of the service damage area of ​​high-temperature alloy hot-end components with oxide film, active elements must be added to the brazing filler metal matrix. The active elements are usually selected such as Ti, Zr, and Hf. These active elements have strong bonding force with Ni, but relatively weak bonding force with Co. Therefore, in this invention, the brazing filler metal is designed with Co as the matrix, the Ni content is controlled at a relatively low level, and 7.0 to 9.0 (wt%) Ti and 1.0 to 2.0 (wt%) Zr are added. The brazing filler metal can exhibit good activity, achieve wetting of the surface of high-temperature alloy with oxide film, and obtain a high-performance high-temperature alloy brazed joint.

[0023] (2) Currently, there are two main methods for removing oxide films from the damaged surfaces of hot-end components such as high-temperature alloy blades with high Al and Ti content after service: one is to completely remove the damaged area using an electrical discharge machining (EDM) method, which is suitable for small-sized defects with good accessibility, but not for large-sized defects with poor accessibility; the other is to remove the oxide film using a fluoride ion cleaning method, which is widely applicable as the location of the oxide film removed is not limited, but domestic manufacturers lack mature manufacturing capabilities for fluoride ion cleaning equipment, resulting in scarce equipment resources and high operating costs. In order to meet the repair needs of all service-damaged parts of high-temperature alloy hot-end components and reduce the cost of oxide film removal, this invention directly provides a high-temperature active brazing filler metal that bypasses the oxide film removal process in the service-damaged area and directly repairs the damage, resulting in a simple process and a significant reduction in repair costs. Attached Figure Description

[0024] To more clearly illustrate the technical solutions implemented in this invention, the accompanying drawings used in the embodiments of this invention will be briefly explained below. Obviously, the drawings described below are merely some embodiments of this invention. Those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0025] Figure 1 Image of a crack near the exhaust slot at the trailing edge of a guide vane;

[0026] Figure 2 This is a diagram of a crack in the rim plate of a guide vane. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. 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.

[0028] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention.

[0029] In the various accompanying drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the invention.

[0030] The present invention provides a cobalt-based active brazing filler metal for brazing repair of service damage areas of high-temperature alloy hot-end components with oxide film on the surface. Typical components are shown in Table 1.

[0031] Table 1

[0032]

[0033]

[0034] Example 1:

[0035] Step 1: Design the solder composition (wt%) as follows: Cr 17.5, Ni 15.5, W 8.8, Ti 8.0, B 1.4, Zr 1.5, C 0.46, Co balance;

[0036] Step 2: Weigh the metals or intermediate alloys according to the designed composition, and then mix them;

[0037] Step 3: Melt the mixture using vacuum induction melting method, repeating the melting process at least 3 times;

[0038] Step 4: Prepare brazing filler metal powder using argon atomization, and sieve the powder through a 100-mesh sieve to select the undersize material;

[0039] Step 5: Mix acetone with neutral resin at a volume ratio of 50:1 to prepare a solution. After precipitation and filtration, mix the solution with brazing powder at a volume ratio of 1.5:1 to prepare a solder paste. Apply the paste to the brazing area of ​​the clean, oxidized K465 plate sample. The oxide film on the K465 surface is mainly composed of Ti-O, Al-O, and Cr-O, with a thickness of approximately 20 μm.

[0040] Step 6: Place the assembled sample in a vacuum furnace and heat it to 1200°C at a rate of 8°C per minute. Hold the temperature for 30 minutes, and then cool it with the furnace.

[0041] Step 7: After the samples are machined, room temperature tensile strength tests are performed. The average tensile strength of the clean surface samples is 684 MPa, and the average tensile strength of the surface-oxidized samples is 669 MPa. The strength levels of the two types of joints are comparable.

[0042] Example 2:

[0043] Step 1: Design the solder composition (wt%) as follows: Cr 17.8, Ni 15.0, W 8.5, Ti 7.9, B 1.8, Zr 1.6, C 0.46, Co balance;

[0044] Step 2: Weigh the metals or intermediate alloys according to the designed composition, and then mix them;

[0045] Step 3: Melt the mixture using vacuum induction melting method, repeating the melting process at least 3 times;

[0046] Step 4: Prepare brazing filler metal powder using argon atomization, and sieve the powder through a 100-mesh sieve to select the undersize material;

[0047] Step 5: Mix acetone with neutral resin at a volume ratio of 50:1 to prepare a solution. After precipitation and filtration, mix the solution with brazing powder to prepare a solder paste. Apply the paste to the brazing area of ​​the clean, oxidized GH3536 high-temperature alloy plate sample. The oxide film on the surface of GH3536 is mainly composed of Cr-O and Ni-O, with a thickness of about 25μm.

[0048] Step 6: Place the assembled sample in a vacuum furnace and heat it to 1210°C at a rate of 10°C per minute. Hold the temperature for 20 minutes, and then cool it with the furnace.

[0049] Step 7: After the samples are machined, room temperature tensile strength tests are performed. The average tensile strength of the clean surface samples is 435 MPa, and the average tensile strength of the surface-oxidized samples is 422 MPa. The strength levels of the two types of joints are comparable.

[0050] Example 3:

[0051] Step 1: Design the solder composition (wt%) as follows: Cr 18.2, Ni 16.2, W 9.8, Ti 9.0, B 1.6, Zr 2.0, C 0.50, Co balance;

[0052] Step 2: Weigh the metals or intermediate alloys according to the designed composition, and then mix them;

[0053] Step 3: Melt the mixture using vacuum induction melting method, repeating the melting process at least 3 times;

[0054] Step 4: Prepare brazing filler metal powder using argon atomization, and sieve the powder through a 100-mesh sieve to select the undersize material;

[0055] Step 5: Mix acetone with neutral resin at a volume ratio of 50:1 to prepare a solution. After precipitation and filtration, mix the solution with brazing powder to prepare a solder paste. Apply the paste to the brazing area of ​​the clean, oxidized K465 plate sample. The oxide film on the K465 surface is mainly composed of Ti-O, Al-O, and Cr-O, with a thickness of about 20 μm.

[0056] Step 6: Place the assembled sample in a vacuum furnace and heat it to 1180°C at a rate of 9°C per minute. Hold it at that temperature for 60 minutes, and then cool it with the furnace.

[0057] Step 7: After the samples are machined, room temperature tensile strength tests are performed. The average tensile strength of the clean surface samples is 665 MPa, and the average tensile strength of the surface-oxidized samples is 647 MPa. The strength levels of the two types of joints are comparable.

[0058] Example 4:

[0059] Step 1: Design the solder composition (wt%) as follows: Cr 17.3, Ni 15.0, W 9.5, Ti 8.5, B 1.5, Zr 1.5, C 0.42, Co balance;

[0060] Step 2: Weigh the metals or intermediate alloys according to the designed composition, and then mix them;

[0061] Step 3: Melt the mixture using vacuum induction melting method, repeating the melting process at least 3 times;

[0062] Step 4: Prepare brazing filler metal powder using argon atomization, and sieve the powder through a 100-mesh sieve to select the undersize material;

[0063] Step 5: Mix acetone with neutral resin at a volume ratio of 50:1 to prepare a solution. After precipitation and filtration, mix the solution with brazing powder to prepare a solder paste. Apply the paste to the brazing area of ​​the clean, oxidized K465 plate sample. The oxide film on the K465 surface is mainly composed of Ti-O, Al-O, and Cr-O, with a thickness of about 20 μm.

[0064] Step 6: Place the assembled sample in a vacuum furnace and heat it to 1220°C at a rate of 10°C per minute. Hold the temperature for 40 minutes, and then cool it with the furnace.

[0065] Step 7: After the samples are machined, room temperature tensile strength tests are performed. The average tensile strength of the clean surface samples is 462 MPa, and the average tensile strength of the surface-oxidized samples is 454 MPa. The strength levels of the two types of joints are comparable.

[0066] Compared to existing technologies, the tensile strength of the repaired sample after oxide film removal and repair using the brazing filler metal of this invention is comparable to that of the sample with a clean surface. Specifically, the tensile strength achieved in the various embodiments is 97.8%, 97%, 97.3%, and 98.3% of that of the sample with a clean surface, respectively. This represents a significant improvement in strength compared to the 85% and 80% (background art) of existing technologies. The brazing filler metal of this invention exhibits excellent activity, enabling wetting of high-temperature alloy surfaces with oxide films and producing high-performance brazed joints, demonstrating significant technical advantages.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A cobalt-based brazing filler metal for brazing service-damaged areas of high-temperature alloy hot-end components with an oxide film on the surface, characterized in that, The brazing filler metal has the following composition and mass percentage (wt%): Cr 17.0–18.5, Ni 15.5–16.5, W 8.0–10.0, Ti 8.5–9.0, B 1.0–2.0, Zr 1.0–2.0, C 0.4–0.5, and Co balance. The brazing filler metal can braze high-temperature alloys with Ti-O, Al-O, and Cr-O oxide films on the surface to be welded at 1180–1220℃ for 5–60 min. The oxide film thickness is 20 or 25 μm, and the tensile strength of the joint after brazing reaches more than 97% of the tensile strength of the clean sample.

2. The brazing filler metal as described in claim 1, characterized in that, The reinforcing elements and their corresponding mass percentages in the cobalt-based active solder are: Cr 17.5~17.8, Ni 15.5, W 8.5~8.

8.

3. The brazing filler metal as described in claim 1, characterized in that, The active element composition and mass percentage of the cobalt-based active solder are: Ti 8.5~8.8, Zr 1.5~1.

8.

4. The brazing filler metal as described in claim 1, characterized in that, The melting point reducing element composition and mass percentage of cobalt-based active solder are: B 1.2~1.4, C 0.46~0.

48.

5. A method for preparing the solder as described in claim 1, characterized in that, The preparation method is as follows: Step 1: Prepare the ingredients according to the composition of the cobalt-based brazing filler metal; Step 2: Melt the brazing filler metal alloy ingot, and repeat the melting process at least 3 times; Step 3: Prepare the brazing filler metal alloy ingot into powder, and then sieve it; Step 4: Mix acetone and neutral resin to prepare a solution, and then mix it with the brazing filler metal powder to prepare solder paste.

6. The preparation method according to claim 5, characterized in that, In step one, Co, W, Ti, and Zr are all-element, B is a Ni-B master alloy, C is a Cr-C master alloy, Ni is all-element and a Ni-B master alloy, and Cr is all-element and a Cr-C master alloy, and the proportions are made according to the design composition.

7. The preparation method according to claim 5, characterized in that, In step two, the mixed raw materials are placed in a crucible and melted using induction melting or electric arc melting to prepare a brazing alloy ingot.

8. The preparation method according to claim 5, characterized in that, In step three, the brazing alloy ingot is prepared into powder by argon atomization, or the brazing alloy ingot is prepared into foil by vacuum argon-filled rapid quenching equipment and then mechanically crushed to obtain powder.

9. The preparation method according to claim 5, characterized in that, In step four, acetone is mixed with neutral resin at a volume ratio of 45-55:1 to prepare a solution. After precipitation and filtration, the solution is mixed with brazing powder at a volume ratio of 1.5:1 to prepare a solder paste. When used, the paste is placed in a syringe and added to the brazing area of ​​the part.

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