A Yb and Tb co-doped alloy solder, its preparation method and brazing process

Abstract

This invention relates to the field of brazing technology, and discloses a Yb and Tb co-doped alloy brazing filler metal, its preparation method, and brazing process. The mass percentage of each component in the Yb and Tb co-doped alloy brazing filler metal is: 12-13% chromium, 3-4% boron, 3-4% silicon, 4-5% iron, 0.5-2% terbium, 0.5-1.5% ytterbium, with the balance being nickel. Yb and Tb co-doping effectively suppresses dendrite growth, and rare earth elements readily accumulate at grain boundaries, forming a fine equiaxed crystal structure. The prepared Yb and Tb co-doped alloy brazing filler metal results in less thermal damage when brazing diamond, a smoother brazed surface without accumulation, and significantly reduced wrinkles and pores. Rare earth co-doping improves the wettability of the brazing filler metal, and the brazing filler metal undergoes intense chemical metallurgy with diamond, increasing the interfacial bonding strength between the filler metal and diamond, thereby improving the machining performance of diamond tools.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, specifically to a Yb and Tb co-doped alloy brazing filler metal, its preparation method, and brazing process. Background Technology

[0002] Diamond, with its ultra-high hardness, excellent wear resistance, and thermal conductivity, is widely used in cutting, grinding, and mining drilling. However, effectively improving the overall performance of brazed diamond tools, especially enhancing the bonding strength between diamond and brazing filler metal to suppress thermal damage, remains a current research hotspot and challenge. Rare earth elements, due to their unique physicochemical properties (such as high surface activity, strong reducing properties, and extremely low solubility), have been widely used in metal matrix composites. Rare earth elements can not only significantly improve the wettability of brazing filler metals but also improve the microstructure and mechanical properties of brazed diamond joints through interfacial reactions.

[0003] Currently, research on the doping effects and modification mechanisms of heavy rare earth elements in the field of diamond brazing is lacking, particularly regarding the interfacial reaction process between the brazing filler metal and diamond after heavy rare earth element doping. Single rare earth doping improves the microstructure of Ni-Cr brazing filler metal to some extent, effectively refining the grains and mitigating thermal damage to diamond. However, while research on single rare earth doping is relatively comprehensive, research on co-doping of two rare earth elements remains a gap, and co-doping of two rare earth elements will be a key focus for further research. Addressing the technical challenges of brazing diamond with Ni-Cr brazing filler metal, there is an urgent need to design a high-performance rare earth-doped Ni-Cr brazing filler metal for diamond brazing. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a Yb and Tb co-doped alloy solder, its preparation method, and brazing process. Yb and Tb co-doping effectively suppresses dendrite growth, and rare earth elements readily accumulate at grain boundaries, acting as heterogeneous nucleation sites to hinder the growth of other phases, thus forming a fine equiaxed crystal structure. The Yb and Tb co-doped alloy solder results in less thermal damage when brazing diamond, and the brazed surface is smoother without accumulation, greatly reducing wrinkles and voids. Rare earth co-doping improves the wettability of the solder, and the intense chemical metallurgy between the solder and diamond enhances the interfacial bonding strength, thereby improving the machining performance of diamond tools.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a Yb and Tb co-doped alloy solder includes the following steps:

[0007] Step (1): Grind, ultrasonically treat, remove, and dry the nickel, chromium, boron, silicon, iron, terbium, and ytterbium to obtain pre-dried alloy raw materials;

[0008] Step (2): Place the pre-dried alloy raw material in the crucible of the melting furnace, melt the alloy, and after melting, cool it with the furnace and take it out to obtain the brazing filler ingot;

[0009] Step (3): Cut the brazing ingot to obtain sheet alloy brazing, grind and dry to obtain Yb and Tb co-doped alloy brazing.

[0010] Preferably, in step (1), the ultrasonic treatment operation includes: in an ultrasonic cleaner, ultrasonically oscillating and cleaning in acetone for 10-15 minutes, then transferring to ethanol for further ultrasonic treatment for 5-10 minutes.

[0011] Preferably, in step (2), the order of adding the pre-dried alloy raw materials is as follows: they are placed in the copper crucible of the smelting furnace according to the element melting point gradient distribution.

[0012] Furthermore, in step (2), the order of adding the pre-dried alloy raw materials is as follows: they are placed in the copper crucible of the smelting furnace in the order of ytterbium, terbium, silicon, nickel, iron, chromium, and boron.

[0013] Preferably, in step (2), the conditions for melting the alloy are: using a mechanical pump to draw a low vacuum to 1×10⁻⁶. -1 Pa, then use a molecular pump to evacuate to a high vacuum of 3 × 10 Pa. -3 Pa, the molecular pump is turned off, and the alloy is melted in an Ar atmosphere at a pressure of -0.05 MPa.

[0014] Preferably, in step (2): the smelting operation is as follows: turn on the smelting power supply heating switch to make the voltage between 60-80 V, and then perform high-frequency arc ignition control to make the heating current in the smelting furnace 250-280 A, and repeatedly turn the alloy ingot over and remelt it 3-4 times to make its composition uniform.

[0015] Preferably, in step (3), the specifications of the sheet alloy brazing filler metal are: length 12-15 mm and thickness 150-180 μm.

[0016] Preferably, in step (3): the mass percentage of each component in the Yb and Tb co-doped alloy solder is: 12-13% chromium, 3-4% boron, 3-4% silicon, 4-5% iron, 0.5-2% terbium, 0.5-1.5% ytterbium, and the balance is nickel.

[0017] Preferably, a Yb and Tb co-doped alloy solder is prepared using the Yb and Tb co-doped alloy solder preparation method described above.

[0018] A brazing process for a Yb and Tb co-doped alloy solder, comprising the following steps:

[0019] Take a No. 45 steel block, apply an adhesive to the brazing surface of the steel block, spread the Yb and Tb co-doped alloy brazing filler metal prepared above on the brazing surface coated with adhesive, and then arrange diamond abrasive grains in an orderly manner on the upper surface of the sheet alloy brazing filler metal, so that the steel block, sheet alloy brazing filler metal and diamond abrasive grains are placed from bottom to top, dried, brazed, heat-preserved, cooled, cooled with the furnace, and taken out to obtain Yb and Tb co-doped alloy brazing filler metal brazed with diamond.

[0020] Preferably, the No. 45 steel block has dimensions of 15 mm × 10 mm × 6 mm, and the amount of adhesive applied is 3-8 mg.

[0021] Preferably, the heat preservation conditions are: under a vacuum degree of 4×10 -4 Under the condition of Pa, the temperature is increased to 1080℃ at a heating rate of 10℃ / min and held for 5-8 minutes.

[0022] Preferably, the cooling condition is: cooling to 500°C at a cooling rate of 5°C / min.

[0023] Preferably, a brazing process using Yb and Tb co-doped alloy brazing filler metal prepared as described above is used to braze diamond.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The Ni-Cr-B-Si-Fe brazing filler metal used in this invention is the most mainstream brazing filler metal for diamond welding, possessing advantages such as low cost, excellent wear resistance, and high bonding strength, making it the first choice for brazing diamond tools. The choice of matrix material for brazing diamond tools determines the wear resistance and thermal conductivity of the diamond tool during processing, and is a crucial factor affecting processing performance. The 45# steel used in this invention has good weldability and excellent thermal conductivity. 45# steel also has a certain degree of corrosion resistance, effectively preventing oxidation and corrosion. Moreover, 45# steel is a common medium carbon steel with a relatively low price, suitable for large-scale production and application.

[0026] The vacuum arc melting method employed in this invention effectively avoids contamination from oxidation, inclusions, and other impurities during the preparation of brazing filler metal, significantly improving alloy purity. It facilitates thorough mixing of all components, ensuring compositional uniformity and providing a solid foundation for subsequent processing. Furthermore, the quality of the brazing filler metal can be further enhanced through multiple melting processes. When preparing the brazing filler metal using vacuum arc melting, the raw materials are placed in the copper crucible in order of increasing melting point. This ensures that high-melting-point elements melt preferentially and fully in the initial stage, while placing low-melting-point elements in the lower layer effectively prevents potential volatilization loss at high temperatures, contributing to precise composition control. Moreover, this layered loading method allows high-melting-point elements to melt first near the arc, followed by low-melting-point elements melting through heat transfer. Compared to random loading, this promotes thorough mixing of elements during the melting process, improving alloy uniformity and ensuring the stability of the melting process and the final alloy quality.

[0027] 2. In this invention, regarding the preparation of the brazing filler metal, Yb effectively improves the wettability of the filler metal and enhances the chemical metallurgical bonding between the filler metal and diamond, while Tb increases the hardness of the filler metal and promotes the uniformity and stability of the interfacial reaction. In terms of application performance, rare earth co-doping can form a denser and more continuous reaction layer at the brazed joint interface, enhancing the bonding strength of the brazed joint and significantly improving the thermal stability and mechanical properties of the joint. Therefore, this invention, through the synergistic effect of Yb and Tb rare earth co-doping, has significant advantages in improving brazing quality, extending product lifespan, and expanding application environments.

[0028] 3. Co-doping with rare earth elements Yb and Tb can effectively refine grains and suppress dendrite growth. After co-doping, four rare earth phases, NiTb, Tb3Ni, Ni7Yb2, and NiYb3, are generated in the solder, and changes in the co-doping content do not lead to changes in the rare earth phases.

[0029] 4. The brazing filler metal co-doped with rare earth elements Yb and Tb exhibits better fluidity, significantly reducing wrinkles and pores. Furthermore, the diamond crystal structure remains relatively intact after brazing, and the combined effect of Yb and Tb reduces the chemical corrosion of diamond by the catalyst element Ni.

[0030] 5. Rare earth co-doping improves the wettability of Ni-Cr solder, allowing the solder to climb along the side of the diamond abrasive grains to a greater height. When Yb and Tb co-doped alloy solders are used to braze diamond, the diamond exhibits better mechanical properties.

[0031] 6. Rare earth co-doping forms relatively dense carbides, which to some extent reduces stress concentration and crack formation, thereby significantly improving the thermal stability and mechanical properties of the joint, and improving the wear resistance and processing performance of the diamond sample. Attached Figure Description

[0032] Figure 1 These are microstructure diagrams of the Yb and Tb co-doped alloy solders prepared in Examples 1-6;

[0033] Figure 2 The microstructure diagrams are of the Ni-Cr solders prepared in Comparative Examples 1-3.

[0034] Figure 3 This is a scanned image of the microstructure of the Ni-Cr CFA2 solder prepared in Example 2;

[0035] Figure 4 These are XRD patterns of the Yb and Tb co-doped alloy solders prepared in Examples 1-6;

[0036] Figure 5 These are bar charts showing the microhardness of the Yb and Tb co-doped alloy solders prepared in Examples 1-6;

[0037] Figure 6 These are morphological images of diamond brazed with Yb and Tb co-doped alloy solder prepared in Example 7;

[0038] Figure 7 The image shows the morphology of diamond brazed with Ni-Cr solder prepared in Comparative Example 4.

[0039] Figure 8 This is an EDS surface scan of the diamond surface brazed with Ni-Cr CFA2 solder prepared in Example 7;

[0040] Figure 9 This is a diagram showing the diamond exposure of the Yb and Tb co-doped alloy brazing filler metal prepared in Example 7.

[0041] Figure 10 This is a diagram showing the carbide morphology on the surface of diamond brazed with the Yb and Tb co-doped alloy brazing filler prepared in Example 7;

[0042] Figure 11 This is a diagram showing the morphology of carbides on the surface of diamond brazed with Ni-Cr solder prepared in Comparative Example 4.

[0043] Figure 12 This is the diamond Raman spectrum of the Yb and Tb co-doped alloy brazing filler prepared in Example 7;

[0044] Figure 13 The image shows the results of diamond Raman testing on Ni-Cr solder prepared in Comparative Example 4.

[0045] Figure 14 This is a bar chart showing the hydrostatic strength of Yb and Tb co-doped alloy brazing alloys for diamond welding prepared in Example 7.

[0046] Figure 15These are images showing the wear morphology of diamond brazing with Yb and Tb co-doped alloy brazing filler metal prepared in Example 7;

[0047] Figure 16 The graph shows the coefficient of friction curve for brazing diamond with the Yb and Tb co-doped alloy brazing filler metal prepared in Example 7, and the bar graph shows the amount of alumina ceramic removed.

[0048] Figure 17 This is an EDS surface scan image of the interface between the Ni-Cr CFA1 brazing filler metal and the diamond prepared in Example 7.

[0049] Figure 18 This is an EDS line scan image of the interface between the Ni-Cr CFA1 brazing filler metal and the diamond prepared in Example 7.

[0050] Figure 19 This is an EDS surface scan image of the interface between the Ni-Cr CFA2 solder and the diamond prepared in Example 7.

[0051] Figure 20 This is an EDS line scan image of the interface between the Ni-Cr CFA2 solder and the diamond prepared in Example 7.

[0052] Figure 21 This is an EDS surface scan image of the interface between the Ni-Cr CFA3 solder and the diamond prepared in Example 7.

[0053] Figure 22 This is an EDS line scan image of the interface between the Ni-Cr CFA3 solder and diamond prepared in Example 7.

[0054] Figure 23 This is an EDS surface scan image of the interface between the Ni-Cr CFA4 solder and the diamond prepared in Example 7.

[0055] Figure 24 This is an EDS line scan image of the interface between the Ni-Cr CFA4 solder and diamond prepared in Example 7.

[0056] Figure 25 This is an EDS surface scan image of the interface between the Ni-Cr CFA5 solder and the diamond prepared in Example 7.

[0057] Figure 26 This is an EDS line scan image of the interface between the Ni-Cr CFA5 solder and diamond prepared in Example 7.

[0058] Figure 27This is an EDS surface scan image of the interface between the Ni-Cr CFA6 solder and diamond prepared in Example 7.

[0059] Figure 28 This is an EDS line scan image of the interface between the Ni-Cr CFA6 solder and diamond prepared in Example 7.

[0060] In the picture:

[0061] Figure 1 (a) is Ni-Cr CFA1 prepared in Example 1, with the left image being a SEM image at a 10 μm scale and the right image being a SEM image at a 3 μm scale; (b) is Ni-Cr CFA2 prepared in Example 2, with the left image being a SEM image at a 10 μm scale and the right image being a SEM image at a 3 μm scale; (c) is Ni-Cr CFA3 prepared in Example 3, with the left image being a SEM image at a 10 μm scale and the right image being a SEM image at a 3 μm scale; (d) is Ni-Cr CFA4 prepared in Example 4, with the left image being a SEM image at a 10 μm scale and the right image being a SEM image at a 3 μm scale; (e) is Ni-Cr CFA5 prepared in Example 5, with the left image being a SEM image at a 10 μm scale and the right image being a SEM image at a 3 μm scale; (f) is Ni-Cr CFA5 prepared in Example 6. CFA6, the left image is the SEM image under a 10μm scale, and the right image is the SEM image under a 3μm scale;

[0062] Figure 2 In the examples, (a) is Ni-Cr 1 prepared in Comparative Example 1; (b) is Ni-Cr 2 prepared in Comparative Example 2; and (c) is Ni-Cr 3 prepared in Comparative Example 3.

[0063] Figure 3 A, B, and C in the diagram are the points selected during EDS point scanning;

[0064] Figure 6(a) shows the Ni-Cr CFA1 brazed diamond prepared in Example 7, with the left image being a SEM image at a 100 μm scale and the right image being a SEM image at a 30 μm scale; (b) shows the Ni-Cr CFA2 brazed diamond prepared in Example 7, with the left image being a SEM image at a 100 μm scale and the right image being a SEM image at a 30 μm scale; (c) shows the Ni-Cr CFA3 brazed diamond prepared in Example 7, with the left image being a SEM image at a 100 μm scale and the right image being a SEM image at a 30 μm scale; (d) shows the Ni-Cr CFA4 brazed diamond prepared in Example 7, with the left image being a SEM image at a 100 μm scale and the right image being a SEM image at a 30 μm scale; (e) shows the Ni-Cr... CFA5 solder brazing diamond, the left image is a SEM image under a 100 μm scale, and the right image is a SEM image under a 30 μm scale; (f) is Ni-Cr CFA6 solder brazing diamond prepared in Example 7, the left image is a SEM image under a 100 μm scale, and the right image is a SEM image under a 30 μm scale.

[0065] Figure 7 (a) is the Ni-Cr1 brazed diamond prepared in Comparative Example 1; (b) is the Ni-Cr2 brazed diamond prepared in Comparative Example 2; and (c) is the Ni-Cr3 brazed diamond prepared in Comparative Example 3.

[0066] Figure 11 (a) is the Ni-Cr1 brazing alloy used for brazing diamond prepared in Comparative Example 4; (b) is the Ni-Cr2 brazing alloy used for brazing diamond prepared in Comparative Example 4; and (c) is the Ni-Cr3 brazing alloy used for brazing diamond prepared in Comparative Example 4.

[0067] Figure 9 , Figure 10 , Figure 15 In this example, (a) is the Ni-Cr CFA1 brazed diamond prepared in Example 7; (b) is the Ni-Cr CFA2 brazed diamond prepared in Example 7; (c) is the Ni-Cr CFA3 brazed diamond prepared in Example 7; (d) is the Ni-Cr CFA4 brazed diamond prepared in Example 7; (e) is the Ni-Cr CFA5 brazed diamond prepared in Example 7; and (f) is the Ni-Cr CFA6 brazed diamond prepared in Example 7.

[0068] Figure 16 In the figure, (a) is the friction coefficient curve and (b) is the bar chart of alumina ceramic removal amount. Detailed Implementation

[0069] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0070] Example 1

[0071] This embodiment discloses a method for preparing a Yb and Tb co-doped alloy solder, including the following steps:

[0072] Step (1): Use sandpaper to polish nickel, chromium, boron, silicon, iron, terbium and ytterbium to remove the oxide film and impurities on the surface, place them in an ultrasonic cleaner, ultrasonically vibrate and clean them in acetone for 10 min, then transfer them to ethanol and continue ultrasonic treatment for 5 min, take them out, dry them, and obtain the pre-dried alloy raw materials.

[0073] Step (2): Place the pre-dried alloy raw materials in the copper crucible of the melting furnace in the order of ytterbium, terbium, silicon, nickel, iron, chromium, and boron. First, use a mechanical pump to evacuate to a low vacuum of 1×10⁻⁶. -1 Pa, then use a molecular pump to evacuate to a high vacuum of 3 × 10 Pa. -3 Pa, the molecular pump is turned off, and the alloy is melted in an Ar atmosphere at a pressure of -0.05 MPa. After melting, the alloy is cooled in the furnace and removed to obtain a brazing filler ingot.

[0074] The smelting operation is as follows: turn on the smelting power supply heating switch to make the voltage between 60-80 V, then use high frequency arc ignition to control the heating current in the smelting furnace to 260 A, and repeatedly turn the alloy ingot over and remelt it 3 times to make its composition uniform.

[0075] Step (3): Cut the brazing ingot with a diamond wire cutter to obtain a sheet alloy brazing material with a length of 15 mm and a thickness of 150 μm. Polish the surface of the sheet alloy brazing material with a metallographic polishing machine and dry it at 50°C to obtain a Yb and Tb co-doped alloy brazing material, denoted as Ni-Cr CFA1.

[0076] In the Yb and Tb co-doped alloy solder, the mass percentage of each component is as follows: 76% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 1.5% terbium (Tb), and 0.5% ytterbium (Yb).

[0077] Example 2

[0078] The difference from Example 1 is that the mass percentage of each component in the Yb and Tb co-doped alloy solder is changed to: 75.5% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 1.5% terbium (Tb), and 1% ytterbium (Yb), denoted as Ni-Cr CFA2; other parameters and conditions are the same as in Example 1.

[0079] Example 3

[0080] The difference from Example 1 is that the mass percentage of each component in the Yb and Tb co-doped alloy solder is changed to: 75% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 1.5% terbium (Tb), and 1.5% ytterbium (Yb), denoted as Ni-Cr CFA3; other parameters and conditions are the same as in Example 1.

[0081] Example 4

[0082] The difference from Example 1 is that the mass percentage of each component in the Yb and Tb co-doped alloy solder is changed to: 76.5% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 0.5% terbium (Tb), and 1% ytterbium (Yb), denoted as Ni-Cr CFA4; other parameters and conditions are the same as in Example 1.

[0083] Example 5

[0084] The difference from Example 1 is that the mass percentage of each component in the Yb and Tb co-doped alloy solder is changed to: 76% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 1% terbium (Tb), and 1% ytterbium (Yb), denoted as Ni-Cr CFA5; other parameters and conditions are the same as in Example 1.

[0085] Example 6

[0086] The difference from Example 1 is that the mass percentage of each component in the Yb and Tb co-doped alloy solder is changed to: 75% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), 2% terbium (Tb), and 1% ytterbium (Yb), denoted as Ni-Cr CFA6; other parameters and conditions are the same as in Example 1.

[0087] Example 7

[0088] This embodiment discloses a brazing process for a Yb and Tb co-doped alloy solder, including the following steps:

[0089] Take a No. 45 steel block with dimensions of 15 mm × 10 mm × 6 mm. Apply 5 mg of adhesive to the brazing surface of the steel block. Spread the Yb and Tb co-doped alloy brazing filler metals prepared in Examples 1-6 on the adhesive-coated brazing surface. Then, arrange diamond abrasive grains in an orderly manner on the upper surface of the sheet alloy brazing filler metal, placing the steel block, sheet alloy brazing filler metal, and diamond abrasive grains in sequence from bottom to top. Dry at 50°C. After drying, place in a high-vacuum molybdenum strip brazing furnace for brazing connection at a vacuum degree of 4 × 10⁻⁶ mm. -4 Under the condition of Pa, the temperature was increased to 1080℃ at a heating rate of 10℃ / min and held for 5 min, then decreased to 500℃ at a cooling rate of 5℃ / min. The temperature was then cooled to room temperature in the furnace and removed to obtain Yb and Tb co-doped alloy brazing diamonds, which were designated as Ni-Cr CFA1 brazing diamond, Ni-Cr CFA2 brazing diamond, Ni-Cr CFA3 brazing diamond, Ni-Cr CFA4 brazing diamond, Ni-Cr CFA5 brazing diamond, and Ni-Cr CFA6 brazing diamond, respectively.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that the mass percentage of each component in the Ni-Cr solder is changed to: 78% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), and 4% iron (Fe), denoted as Ni-Cr1; other parameters and conditions are the same as in Example 1.

[0092] Comparative Example 2

[0093] The difference from Example 1 is that the mass percentage of each component in the Ni-Cr solder is changed to: 77% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), and 1% ytterbium (Yb), denoted as Ni-Cr2; other parameters and conditions are the same as in Example 1.

[0094] Comparative Example 3

[0095] The difference from Example 1 is that the mass percentage of each component in the Ni-Cr solder is changed to: 76.5% nickel (Ni), 12% chromium (Cr), 3% boron (B), 3% silicon (Si), 4% iron (Fe), and 1.5% terbium (Tb), denoted as Ni-Cr3; other parameters and conditions are the same as in Example 1.

[0096] Comparative Example 4

[0097] The difference from Example 7 is that the Ni-Cr brazing filler metal used is the same as that prepared in Comparative Examples 1-3; other parameters and conditions are the same as in Example 7, and the resulting Ni-Cr brazing filler metal brazed diamonds are respectively denoted as Ni-Cr1 brazing filler metal brazed diamond, Ni-Cr2 brazing filler metal brazed diamond, and Ni-Cr3 brazing filler metal brazed diamond.

[0098] In the above embodiments and comparative examples: the raw materials of nickel (99.9%), chromium (99.9%), boron (99.9%), silicon (99.9%), iron (99.9%), terbium (99.9%), and ytterbium (99.9%) were provided by Chengshuo Metal Materials Co., Ltd. and were in granular form; the binder was provided by Yantai Guguang Co., Ltd. and was of type ZT-W02.

[0099] Experimental data characterization and performance testing

[0100] like Figure 1 As shown, the solders prepared in Examples 1-6 and Comparative Examples 1-3 were subjected to scanning electron microscopy tests, respectively.

[0101] according to Figure 1 The test results show that the microstructure of the Ni-Cr CFA1 solder prepared in Example 1 is mainly cellular crystals, with equiaxed crystals forming in some local areas; the Ni-Cr CFA2 solder prepared in Example 2 is co-doped with the optimal doping amounts of Yb and Tb, and its microstructure is mainly composed of fine equiaxed crystals; as the Yb doping amount increases, the Ni-Cr CFA3 solder prepared in Example 3 begins to show the formation of secondary dendrites, with larger grain sizes. This is mainly because the total rare earth doping amount is large, which reduces the supercooling of the solder and slows down the cooling rate, resulting in weakened grain refinement and increased grain size, which contributes to the formation of dendrites. According to... Figure 2 The test results show that the microstructure of the Ni-Cr 1 solder prepared in Comparative Example 1 is mainly composed of coarse dendrites and large-spaced secondary dendrites; the microstructure of the Ni-Cr 2 solder prepared in Comparative Example 2 is refined, but it still exhibits a clear dendritic structure, with dendrite dissolution in some dendrites and local cellular structures; the size of the dendrites in the microstructure of the Ni-Cr 3 solder prepared in Comparative Example 3 is slightly reduced, but it is still dominated by a clear dendritic structure.

[0102] In summary, when the optimal doping amount of Yb is fixed and the doping amount of Tb is varied, the microstructure of the solder does not exhibit equiaxed crystals but is mainly composed of cellular and columnar crystals, all of which show better grain refinement than the traditional Ni-Cr solder without rare earth doping. The microstructure of the solder shows that the grain refinement effect is most significant when Yb and Tb are co-doped at their optimal doping amounts.

[0103] Since the Ni-CrCFA2 solder prepared in Example 2 showed a significant improvement in microstructure refinement, an EDS surface scan was performed on the Ni-CrCFA2 solder prepared in Example 2. Figure 3 As shown;

[0104] according to Figure 3 The test results show that rare earth elements Yb and Tb tend to accumulate at grain boundaries, hindering the growth of other phases and thus refining the grains. Studies indicate that the formed rare earth phases are relatively small and can act as heterogeneous nucleation sites, promoting grain nucleation and growth at these sites, increasing the nucleation rate, and thus acting as nucleating agents. However, the rare earth content should not be too high, which is also related to… Figure 3 This is consistent with the findings of the study.

[0105] To investigate the possible phases that may be generated in the solder, as shown in Table 1, EDS point scanning was performed on the Ni-enriched region, Cr-enriched region and rare earth-enriched region of the Ni-Cr CFA2 solder prepared in Example 2.

[0106] Table 1

[0107]

[0108] The test results in Table 1 show that rare earth compounds are generated at the grain boundaries, indicating that rare earth elements are easily enriched at the grain boundaries, effectively inhibiting grain growth and thus obtaining a refined solder structure.

[0109] like Figure 4 As shown, XRD tests were performed on the solders prepared in Examples 1-6, respectively.

[0110] according to Figure 4 The test results show that the Yb and Tb co-doped alloy solders prepared in Examples 1-6 mainly consist of γ-Ni, Ni3Fe, CrB, and Ni3Si2 phases, as well as rare earth phases such as NiYb3, Ni7Yb2, Tb3Ni, and NiTb, verifying the results in Table 1. Furthermore, the rare earth phases formed by Yb and Tb co-doping with Ni are the same as those formed by single doping, indicating that co-doping does not affect the formation of rare earth phases in the solder.

[0111] like Figure 5 As shown, the brazing filler metals prepared in Examples 1-6 and Comparative Example 1 were subjected to microhardness tests, respectively.

[0112] according to Figure 5The test results show that the rare-earth co-doped Ni-Cr solders prepared in Examples 1-6 all have higher microhardness than the undoped Ni-Cr solder prepared in Comparative Example 1. The Ni-Cr CFA1 solder prepared in Example 1 and the Ni-Cr CFA2 solder prepared in Example 2 have relatively higher microhardness, which is due to the fixed optimal Tb doping amount of 1.5 wt.% and the relatively low total rare-earth content. The Ni-Cr CFA2 solder prepared in Example 2 has the highest microhardness, reaching 717.64 HV. 0.2 Compared to the Ni-Cr1 solder without rare earth doping in Comparative Example 1, which has a microhardness of 597.73 HV, this figure is significantly higher. 0.2 The hardness was increased by about 20%, which is due to the formation of fine intermetallic compounds between rare earth elements and Ni elements, which is a second-phase strengthening process that increases the microhardness of the solder.

[0113] like Figure 6 , Figure 7 As shown, the microstructure of the brazed diamonds prepared in Example 7 and Comparative Example 4 was tested.

[0114] Diamonds suffer thermal damage during brazing, primarily including surface corrosion pits, graphitization, and residual stress in the brazed joint. A favorable diamond morphology is crucial for the mechanical properties of the diamond sample. According to... Figure 6 The test results show that after brazing diamonds using a Yb and Tb co-doped alloy solder, the diamond crystal structure remained relatively intact, with no obvious large-area corrosion pits appearing. This indicates that during the brazing process, the two rare earth elements work together, reacting chemically with Ni to form a rare earth phase, reducing the catalytic effect of Ni in the solder on the diamond. This effectively mitigates the weakening of the bonding force of carbon atoms on the diamond surface by Ni, preventing C atoms from dissolving into the solder and thus forming corrosion pits. Figure 7 The test results show that the surface of the diamond brazed with Ni-Cr1 brazing filler metal has large corrosion pits and the diamond is severely eroded by heat, resulting in low diamond exposure. The crystal structure of the diamond brazed with Ni-Cr2 brazing filler metal is relatively complete, but defects such as obvious cracks and holes appear on the brazed side. The surface of the diamond brazed with Ni-Cr3 brazing filler metal has large corrosion pits and corrosion marks, low diamond exposure, and a rough brazed surface, resulting in poor brazing effect.

[0115] In summary, the brazing effect of rare earth co-doping is better than that of undoped and single-doped brazing. The combined effect of the two rare earth elements effectively reduces the weakening of the bonding force of carbon atoms on the diamond surface by Ni, prevents C atoms from dissolving into the brazing filler metal, reduces the formation of corrosion pits, and thus allows the diamond to maintain its complete crystal structure. The more cutting edges are more conducive to the grinding effect of diamond abrasive grains.

[0116] like Figure 8 As shown, EDS surface scanning was performed on the Ni-Cr CFA2 solder used for brazing diamond prepared in Example 7.

[0117] according to Figure 8 The test results show that the solder spreads freely on the substrate surface, and there is no obvious enrichment of Ni, Cr, Si, Fe, Yb and Tb elements. The elements are nearly uniformly distributed, indicating that there is no obvious large-area accumulation of solder. After rare earth co-doping, the solder has good fluidity, the brazing surface is relatively smooth, and there are no wrinkles, holes or defects.

[0118] like Figure 9 As shown, the exposure height of diamond abrasive grains in the brazed diamond prepared in Example 7 was tested using an ultra-depth-of-field microscope.

[0119] according to Figure 9 The test results show that the solder climbs along the side of the diamond abrasive grains, and the height of the climb is relatively high, indicating that the Ni-Cr solder has good wettability after rare earth co-doping. Even... Figure 9 As shown in (e), a significant climb of the solder on the diamond side is clearly observed, resulting in a lower diamond exposure. Figure 9 In (b), the diamond exposure was the highest when brazed with Ni-Cr CFA2 solder, which was about 40% of the diamond's own height.

[0120] like Figure 17-28 As shown, EDS surface scanning and EDS line scanning were performed on the interface between the brazing filler metal and diamond in the brazing filler metal prepared in Example 7.

[0121] according to Figure 17-28 The test results show that Cr and Si elements exhibit distinct bright enrichment bands at the interface between the diamond and the solder, corresponding to the enrichment of C. It is preliminarily inferred that a carbide layer may form at this location. Ni elements surrounding the diamond erode the diamond abrasive grains, causing more C elements to diffuse from the diamond into the solder alloy. Cr has a strong affinity for C, thus attracting Cr elements in the solder to diffuse towards the diamond side and accumulate around it, forming a Cr-enriched region. The varying widths of the enriched bands indicate that the thickness of the carbide layer may differ. A small amount of nickel rises to the diamond surface and accumulates, likely related to the wettability of the solder. Furthermore, line scanning perpendicular to the solder-diamond interface revealed significant fluctuations in C and Cr elements. The width of these fluctuations indicates the thickness of the carbide layer; a thicker carbide layer indicates better wettability of the solder to the diamond. However, an excessively thick carbide layer can exacerbate the chemical corrosion of diamond by the catalytic elements in the solder, damaging the diamond's own carbon atomic structure and reducing its mechanical properties. Finally, combined with Figure 9 The exposure of diamond in medium-sized diamonds proves that co-doping with Yb and Tb can improve the wettability of Ni-Cr solder to diamond and promote the interfacial reaction between the solder and diamond. However, excessive co-doping may reduce the exposure of diamond and make the carbide layer too thick, which will aggravate the chemical corrosion of the solder.

[0122] like Figure 10 , Figure 11 As shown, the brazing diamonds prepared in Example 7 and Comparative Example 4 were etched with aqua regia, and the microstructure of the carbide morphology on the diamond surface was tested.

[0123] The experimental steps of aqua regia etching are as follows: the diamond-matrix part of the brazed diamond is placed in the aqua regia solution for etching until the matrix and the brazing filler layer surrounding the diamond are removed, so that the carbide layer is completely exposed on the diamond surface.

[0124] according to Figure 10 The test results show that after etching with aqua regia, a dense carbide layer was formed on the diamond surface. This carbide was formed by Cr atoms diffusing to the diamond surface after the solder melts and reacting with graphitized C atoms. Chromium-carbon compounds act as a bridge, and their formation can reduce the mismatch in thermal expansion coefficients between the diamond and the solder. Rare earth co-doping formed a relatively dense carbide, which to some extent alleviated stress concentration and crack formation. In particular, the carbide surface after brazing with the Ni-Cr CFA2 solder prepared in Example 2 showed no obvious cracks, and the carbide size was relatively small. The uniform distribution of carbides at the brazed joint provided a certain buffering effect. With the continuous increase of co-doping content... Figure 10 In (c) and (f), the size of the carbides continuously increases, and the length and number of cracks also increase. This may be because the solder has high wettability, forming coarse carbides. Due to the presence of residual stress, the cracks extend to the entire carbide layer. According to Figure 11 The test results show that the carbide morphology on the surface of diamond brazed with Ni-Cr1 brazing filler metal is mainly composed of coarse lath-shaped carbides, and the carbide surface has wide microcracks that extend to the entire carbide layer; the carbide morphology on the surface of diamond brazed with Ni-Cr2 brazing filler metal is refined, but the number of microcracks on the carbide surface is relatively large; the surface cracks of the carbide morphology on the surface of diamond brazed with Ni-Cr3 brazing filler metal are relatively long, which is caused by the large residual stress between the diamond abrasive grains and the brazing filler metal alloy. The cracks in the carbide are prone to further cracking, causing the brazing filler metal alloy to lose its ability to hold the diamond abrasive grains.

[0125] In summary, the carbides on the surface of diamond without rare earth elements and with single doping exhibit coarse, lath-like structures, and the microcracks on the carbide surface are long and numerous. Rare earth co-doping effectively improves the size of the carbides; the finer carbides can effectively alleviate the residual stress in the brazed joint, thereby effectively reducing the degree of cracking in the carbide layer and improving the bonding strength between the brazing filler metal and the diamond abrasive grains.

[0126] like Figure 12 , Figure 13 As shown, Raman spectroscopy tests were performed on the brazing diamonds prepared in Example 7 and Comparative Example 4, respectively.

[0127] according to Figure 12 The test results show that Ni-Cr CFA2 solder produces diamonds with the lowest degree of graphitization. The carbon element structure in the diamond crystal is stable, mainly composed of sp. 3 Hybrid bonding, with no significant sp. 3 To sp 2 The hybridization transition indicates that the hardness and wear resistance of diamond brazed with Ni-Cr CFA2 solder are maintained. All diamonds brazed after rare-earth co-doping exhibit scattering peaks (G peaks) of graphite structure. This may be because rare-earth co-doping improves the wettability of the solder, allowing it to climb to a greater height on the diamond surface. Furthermore, the Ni and Fe elements in the solder act as catalysts, accelerating the sp-span transition. 3 To sp 2 Hybridization transitions resulted in varying degrees of graphite structural characteristic scattering peaks appearing in the detection results. According to... Figure 13 The test results show that the graphite peak G-peak intensity of Ni-Cr1 brazed diamond is relatively high, indicating that the diamond has undergone severe graphitization and suffered significant thermal damage. Ni-Cr2 brazed diamond still exhibits a high tendency to graphitize, and graphitization severely weakens the mechanical properties of the diamond. Ni-Cr3 brazed diamond has a lower graphite peak intensity, but it is still quite pronounced, indicating that the internal atomic structure of the diamond has changed from sp... 3 Hybrid structures gradually shift towards sp 2 The transformation of the hybrid structure led to graphitization in diamond.

[0128] In summary, rare earth co-doping, compared to undoped and single-doped materials, can effectively mitigate the catalytic effect of catalyst elements in solder on diamond graphitization. The combined action of rare earth elements Yb and Tb with Ni slows down the deposition of carbon atoms on the diamond surface from sp(s)... 3 To sp 2 Hybridization greatly reduces the graphitization of diamond and preserves its mechanical properties.

[0129] like Figure 14As shown, the hydrostatic strength of the Yb and Tb co-doped alloy brazing diamond prepared in Example 7 and the Ni-Cr1 brazing diamond prepared in Comparative Example 4 were tested.

[0130] according to Figure 14 The test results show that the static compressive strength of the undoped rare-earth Ni-Cr1 brazed diamond prepared in Comparative Example 4 is 2014.3 MPa. The static compressive strengths of the Ni-CrCFA1, Ni-CrCFA2, and Ni-CrCFA3 brazed diamonds are all above 3000 MPa, reaching 73% of the original diamond, indicating good mechanical properties. Among these, the static compressive strength of the diamonds brazed with Ni-CrCFA3 and Ni-CrCFA6 brazed diamonds is lower. These two brazed diamonds have a higher degree of graphitization, where the carbon-carbon covalent bonds in the diamond structure change from three-dimensional sp³ bonds to two-dimensional sp² planar layered structures. The sp² bonds in the graphite structure are weaker, and the interatomic bonding force is much weaker than that in diamond. This damages the integrity of the crystal structure, making the diamond more fragile and leading to a decrease in static compressive strength.

[0131] In summary, the static compressive strength of diamond brazed with rare earth co-doped brazing filler metal is about 50% higher than that of diamond brazed with undoped rare earth brazing filler metal. This shows that rare earth co-doping reduces thermal damage to diamond while preserving its mechanical properties.

[0132] like Figure 15 As shown, the wear resistance of the brazed diamond alloys prepared in Example 7 and the comparative example was tested using an MM-W1B vertical universal friction and wear testing machine. The load was 100 N, the rotation speed was 200 r / min, and the grinding time was 30 min.

[0133] according to Figure 15 The test results show that Figure 15 (a) The diamond abrasive grains showed small-area breakage. This breakage had little impact on the diamond abrasive grains, and most of the cutting edge of the diamond sample was preserved, so it can continue to perform grinding. Figure 15 (b) and (e) The diamond abrasive grains are basically intact because the diamond is subjected to less thermal damage, which greatly preserves the mechanical properties of the diamond, so that the diamond does not break or shatter over a large area while performing grinding. Figure 15 (d) The fracture mode is plowing, which is the appearance of interlaced grooves and grooves in the fracture area by diamond abrasive grains. Figure 15(c) and (f) represent intergranular fracture, caused by the diamond abrasive grains being subjected to high impact and high stress during grinding, as well as residual stress within the grains. The cracks propagate along the interface between the diamond and the brazing filler metal. In this case, the diamond abrasive grains essentially lose their grinding function, significantly impacting the processing efficiency and service life of the diamond.

[0134] Figure 16 The results show the friction coefficient of diamond abrasive grains and the amount of alumina ceramic removed. In the initial grinding stage, the cutting edges of the diamond abrasive grains are sharp, resulting in a small contact area with the alumina ceramic sample. As grinding progresses, localized wear and crack propagation lead to an increase in contact area and localized roughness, thereby increasing frictional resistance and raising the friction coefficient. With further grinding, factors such as diamond wear, interface temperature, and chip generation and shedding reach a dynamic equilibrium, at which point the friction coefficient begins to decrease and eventually stabilizes. The average friction coefficient during the stable phase after a grinding time of 300 s was statistically analyzed. Figure 16 The test results show that the Ni-Cr CF2 brazed diamond has the lowest average friction coefficient (approximately 0.092) and the flattest friction curve, indicating excellent wear resistance. Similarly, the amount of alumina removed from the alumina ceramic was statistically analyzed, which indirectly reflects the mechanical properties of the diamond. The Ni-Cr CF2 brazed diamond exhibits low graphitization and excellent mechanical properties, thus demonstrating superior processing performance when grinding alumina ceramics, with a maximum removal rate of up to 45.8 mg.

[0135] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Yb and Tb co-doped alloy solder, characterized in that, Includes the following steps: Step (1): Grind, ultrasonically treat, remove, and dry the nickel, chromium, boron, silicon, iron, terbium, and ytterbium to obtain pre-dried alloy raw materials; Step (2): Melt the pre-dried alloy raw material, cool it with the furnace after melting, and take it out to obtain the brazing filler ingot; The smelting conditions include: using a mechanical pump to create a low vacuum of 1×10⁻⁶. -1 Pa, then use a molecular pump to evacuate to a high vacuum of 3 × 10 Pa. -3 Pa, turn off the molecular pump, and melt the alloy in an Ar atmosphere at a pressure of -0.05 MPa. The melting operation is as follows: turn on the melting power supply heating switch to make the voltage between 60-80 V, then use high frequency arc ignition to control the heating current in the melting furnace to 250-280 A, and repeatedly turn the alloy ingot over and remelt it 3-4 times to make its composition uniform. Step (3): Cut the brazing filler ingot to obtain sheet-like alloy brazing filler, grind and dry to obtain Yb and Tb co-doped alloy brazing filler; In the Yb and Tb co-doped alloy solder, the mass percentage of each component is: 12% chromium, 3% boron, 3% silicon, 4% iron, 1.5% terbium, 1% ytterbium, and the balance is nickel.

2. The method for preparing a Yb and Tb co-doped alloy solder according to claim 1, characterized in that, In step (1), the ultrasonic treatment operation includes: in an ultrasonic cleaner, ultrasonically oscillating and cleaning in acetone for 10-15 minutes, then transferring to ethanol for further ultrasonic treatment for 5-10 minutes.

3. The method for preparing a Yb and Tb co-doped alloy solder according to claim 1, characterized in that, In step (2), the order of adding the pre-dried alloy raw materials is as follows: they are placed in the copper crucible of the smelting furnace according to the element melting point gradient distribution.

4. The method for preparing a Yb and Tb co-doped alloy solder according to claim 1, characterized in that, In step (3), the specifications of the sheet alloy brazing filler metal are: length 12-15 mm and thickness 150-180 μm.

5. A Yb and Tb co-doped alloy solder prepared by the method described in any one of claims 1-4.

6. A brazing process for a Yb and Tb co-doped alloy solder, characterized in that, The brazing process includes the following steps: Take a No. 45 steel block, apply an adhesive to the brazing surface of the steel block, spread the Yb and Tb co-doped alloy brazing filler metal as described in claim 5 on the brazing surface coated with adhesive, and then arrange diamond abrasive grains in an orderly manner on the upper surface of the sheet alloy brazing filler metal, so that the steel block, sheet alloy brazing filler metal and diamond abrasive grains are placed in sequence from bottom to top, dried, brazed, heat-preserved, cooled, cooled with the furnace, and taken out to obtain Yb and Tb co-doped alloy brazing filler metal brazed diamond.

7. The brazing process of a Yb and Tb co-doped alloy solder according to claim 6, characterized in that, The insulation conditions are: under a vacuum degree of 4×10⁻⁶. -4 Under the condition of Pa, the temperature is increased to 1080℃ at a heating rate of 10℃ / min and held for 5-8 minutes.

8. The brazing process of a Yb and Tb co-doped alloy solder according to claim 6, characterized in that, The cooling conditions are as follows: cooling to 500℃ at a cooling rate of 5℃ / min.

9. A brazing diamond made with Yb and Tb co-doped alloy brazing filler metal prepared by the brazing process described in any one of claims 6-8.

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