Rare earth modified brazing filler metal and brazing method thereof

Abstract

The invention discloses nickel-based brazing filler metal doped with rare earth Tm and a brazed diamond thereof, and belongs to the technical field of brazing. The brazing filler metal is obtained through vacuum arc melting of element particles of Ni, Cr, B, Si, Fe and Tm under argon protection, the brazing filler metal comprises, by weight, 76.0%-82.0% of Ni, 9.0%-13% of Cr, 2.0%-4.0% of B, 3.0%-5.0% of Si, 2.0%-5.0% of Fe and 0-2% of Tm, and the brazing diamond is obtained through heating under the conditions that the vacuum degree is smaller than 2.0 * 10 <-3 > Pa, the brazing temperature is 1080 DEG C and the heat preservation time is 5 min. Results show that Tm doping can optimize the structure of the brazing filler metal, improve the mechanical property of brazing filler metal alloy, effectively improve the holding strength of the diamond in the brazing process and effectively inhibit thermal damage of the diamond after welding, so that the diamond can maintain the original performance to a large extent, and has better wear resistance in the service process.

Description

Technical Field

[0001] The present invention belongs to the technical field of brazing, and particularly relates to a rare earth modified brazing filler metal and a brazing method thereof. Technical Background

[0002] Due to its excellent hardness and wear resistance, diamond is determined to be the most suitable abrasive for manufacturing production tools such as ceramics, glass, rock and ore. Natural diamond has excellent processing performance, but its small storage quantity and high price limit its application in the industrial field. Synthetic diamond not only has excellent properties comparable to natural diamond, but also has the characteristics of easy preparation and low price, making it widely used in fields such as cutting, grinding, and drilling. For diamond tools prepared by traditional preparation technologies such as hot pressing sintering and electroplating, the holding strength of the matrix for diamond is small, and diamond is easy to fall off. In contrast, for diamond tools prepared by the brazing method, the brazing filler metal and diamond are metallurgically combined, with high connection strength, high utilization efficiency, long service life, and better grinding performance.

[0003] At present, the brazing filler metals for brazing diamond mainly include three categories: Ag-based, Cu-based, and Ni-based. Ag-based brazing filler metals have advantages such as low melting point and excellent wettability, but their high cost limits their use; Cu-based brazing filler metals are widely used, but have poor wear resistance; Ni-based brazing filler metals have high hardness, excellent wear resistance, and high bonding strength with diamond, which can effectively improve the processing performance of diamond tools and are currently the most widely used brazing filler metals. However, their brazing temperature is relatively high, the graphitization degree of diamond is relatively high, and the main element Ni as a catalyst element exacerbates the thermal corrosion of diamond, resulting in a reduction in its performance. Therefore, it is necessary to modify the brazing filler metal to reduce the weakening of the post-brazing performance of diamond.

[0004] Rare earth elements have active chemical properties and can form relatively stable metal compounds with most metals. Due to their unique electron arrangement, they have strong spin-orbit coupling characteristics and have great advantages in the field of metal modification. Therefore, it is feasible to modify Ni-based brazing filler metals by adding trace rare earth elements. Compared with other rare earth elements, rare earth Tm has the smallest atomic radius, making it have stronger electronegativity and be able to form ionic compounds more easily. After melting into the Ni-based brazing filler metal, it can not only change its processing performance, but also consume part of the catalyst element Ni, thereby improving the degree of thermal damage of diamond.

[0005] Chinese Invention Patent CN 202410706341.4 published "A Brazing Method for Rare Earth Modified High-Performance Brazing Filler Metal". This method refines the grains of the brazing filler metal, reduces the graphitization degree of brazed diamond, and improves the grinding performance of brazed diamond tools. However, there are still a small number of cracks at the brazed joint, which affects the machining performance of the brazed diamond specimens. Chinese Invention Patent CN 202210705036.4 discloses "A Preparation Method and Brazing Method of a Multielement Nickel-Based Alloy Brazing Filler Metal Doped with Y". This method modifies the brazing filler metal by adding rare earth Y, refines the structure of the brazing filler metal, improves the holding force of the brazing filler metal to diamond, and effectively improves the grinding performance of the brazed diamond specimens. However, in this method, the heating method of high-frequency induction has the problem of inaccurate temperature control, and the brazing temperature is relatively high, which is extremely easy to cause the graphitization of diamond and reduce the quality of the brazed diamond specimens. Chinese Invention Patent CN 202410706413.5 discloses "A Brazing Method of a Scandium-Containing Nickel-Based Brazing Filler Metal". This method greatly increases the hardness of the brazing filler metal and reduces the tendency of brazed diamond to transform into graphite in a high-temperature environment. However, the too high hardness may lead to poor toughness of the brazed joint and affect the service performance of the tool. Moreover, there is a metal brazing filler metal structure on the surface of the diamond brazed by this method, and the smoothness is poor, which affects the grinding performance of the brazed diamond.

[0006] In addition, some metals contain other metal impurities. In order to improve the metal purity, reaction agents need to be added during the heating and melting process of the metal to react and eliminate the impurities. However, the structure of the existing vacuum melting furnace is relatively simple. During the process of adding the reaction agent, the furnace body needs to be opened for addition, resulting in the influence of the internal temperature and vacuum effect of the furnace body, and interfering with the metal processing efficiency.

[0007] Based on the above problems, it is urgent to develop an alloy brazing filler metal that can effectively improve the comprehensive performance of brazed diamond, and a new type of vacuum melting furnace is needed to improve the melting quality of the brazing filler metal alloy. Summary of the Invention

[0008] To achieve the above object, the present invention discloses a rare earth modified brazing filler metal, which is obtained by vacuum arc melting Ni, Cr, B, Si, Fe and Tm element particles under argon protection. Its composition and weight percentage are: 76.0% - 82.0% of Ni, 9.0% - 13% of Cr, 2.0% - 4.0% of B, 3.0% - 5.0% of Si, 2.0% - 5.0% of Fe and 0 - 2% of Tm.

[0009] A brazing method, the method uses the rare earth modified brazing filler metal, and includes the following steps:

[0010] S1: Prepare alloy ingots

[0011] Weigh each component of the filler metal with a purity of not less than 99.5% by mass percentage, ultrasonically clean it in acetone solution for 15 minutes, then ultrasonically clean it in ethanol solution for 5 minutes. After drying, put it into a vacuum melting furnace in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as the protective gas, adjust the heating current, and melt it repeatedly 4 - 5 times. Take out the alloy ingot after it cools down with the furnace.

[0012] S2: Process the alloy ingot

[0013] Cut the alloy ingot obtained in step S1 into filler metal thin slices with a thickness of 200 μm using a diamond wire cutting machine, mechanically polish its surface with 400# and 800# sandpapers, then put it into acetone and ethanol solutions for ultrasonic cleaning, and then dry it;

[0014] S3: Prepare the sample

[0015] Select a No. 45 steel substrate, polish the surface of the No. 45 steel substrate with sandpaper to remove the surface oxide layer and impurities, put the No. 45 steel substrate and diamond into acetone solution and alcohol solution respectively for ultrasonic cleaning and drying. Then combine diamond with the filler metal sheet and the filler metal sheet with the steel substrate through an organic carrier. From top to bottom, it is diamond, filler metal thin sheet, and steel substrate to obtain the sample;

[0016] S4: Brazing

[0017] Put the sample into a vacuum molybdenum strip sintering furnace for brazing, keep the vacuum degree at 2.0×10 -3 -5.0×10 -3 Pa, heat it to 1050 - 1080 °C and hold for 5 minutes, take out the sample after it cools down with the furnace to room temperature.

[0018] Preferably, in step S1, the heating current of the vacuum melting furnace is 180 - 220 A.

[0019] Preferably, in step S2, the diamond wire cutting speed is 260 μm / min.

[0020] Preferably, in step S2, the size of the filler metal sheet is 15 mm × 6 mm.

[0021] Preferably, in step S3, the size of the steel substrate is 15 mm × 10 mm × 6 mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the brazing of diamond with rare earth Tm-doped nickel-based filler metal proposed by the present invention, the addition of Tm effectively reduces the grain size of the filler metal alloy, transforms the coarse dendrites in the original filler metal into more uniform and finer equiaxed grains, optimizes the element distribution, and Tm can react with Ni element to form new compounds NiTm and Ni 3 Tm. These new phases can not only consume part of the Ni element, reduce the thermal corrosion of Ni on diamond, but also improve the microhardness of the filler metal, making the hardness of the filler metal alloy reach 715.8 HV 0.2 , which is much higher than the microhardness of the original filler metal.

[0024] (2) In the brazing of diamond with rare earth Tm-doped nickel-based filler metal proposed by the present invention, the addition of Tm improves the surface quality of the brazed diamond, reduces the number and area of thermal corrosion pits of diamond, reduces the graphitization degree of diamond, ensures the integrity of the cutting edge of the brazed diamond, and enables the diamond to maintain its original complete morphology to a large extent.

[0025] (3) In the brazing of diamond with rare earth Tm-doped nickel-based filler metal proposed by the present invention, the addition of Tm promotes the element diffusion at the brazing interface. Compared with the brazed diamond without Tm addition, the cracks at the interface disappear, the carbide size at the interface decreases, and it changes from the original relatively orderly state to crisscross, releasing the thermal stress during the brazing process to a large extent and improving the bonding strength of the brazed diamond.

[0026] (4) In the brazing of diamond with rare earth Tm-doped nickel-based filler metal proposed by the present invention, the addition of Tm can effectively reduce the friction coefficient of diamond, significantly increase the removal amount of the ground specimen, and can retain the cutting edge of diamond to a large extent, enabling the diamond tool to have better grinding performance and increasing its service life.

[0027] (5) For this vacuum melting furnace, by setting the movable box, when it is necessary to add reactant to the crucible, under the action of the jacking spring, the lifting plate rises to the top. At the same time, the transmission sleeve located above is sleeved with the first connecting block, and then the transmission sleeve is driven to rotate by the driving motor. Then the first transmission shaft drives the first bevel gear to rotate, then the threaded sleeve rotates, and then drives the threaded rod and the gate to move, so that the reactant can be put into the feed pipe through the feed hopper. Then the stop valve is closed by reversing the driving motor, so that the reactant is located inside the feed pipe. Then the vacuum pump is started, and the inside of the feed pipe is evacuated through the exhaust port. Then the stop valve located inside the vacuum box is opened to send the reactant into the crucible, saving the operation steps of opening the vacuum box for adding during the process of adding reactant, avoiding the influence on the internal temperature and vacuum effect of the furnace body, and improving the metal processing efficiency.

[0028] (6) The vacuum melting furnace is provided with a second transmission shaft. After the vacuum pump evacuates the inside of the feed pipe, the air inside the movable box is evacuated through the connecting pipe, thereby causing the piston plate to move downward, making the first connecting block disengage from the transmission sleeve. As the lifting plate descends, the lower transmission sleeve is sleeved with the second connecting block, causing the second transmission shaft to rotate, and then controlling the opening of the stop valve located inside the vacuum chamber. Description of the Drawings

[0029] Figure 1 is the SEM image of Ni-Cr-Tm filler metal;

[0030] Figure 2 is the microhardness diagram of Ni-Cr-Tm filler metal;

[0031] Figure 3 is the XRD diagram of Ni-Cr-Tm filler metal;

[0032] Figure 4 is the morphology and Raman test diagram of diamond brazed with rare earth Tm-doped nickel-based filler metal;

[0033] Figure 5 is the morphology and surface scan of the diamond brazed joint with rare earth Tm-doped nickel-based filler metal;

[0034] Figure 6 is the line scan of the diamond brazed joint with rare earth Tm-doped nickel-based filler metal;

[0035] Figure 7 is the morphology diagram of the carbide of diamond brazed with rare earth Tm-doped nickel-based filler metal;

[0036] Figure 8 is the micro-area XRD diagram of diamond brazed with nickel-based filler metal doped with different contents of rare earth Tm;

[0037] Figure 9 is the friction coefficient of diamond brazed with Ni-Cr-Tm filler metal;

[0038] Figure 10 is the removal amount of the worn sample of diamond brazed with Ni-Cr-Tm filler metal;

[0039] Figure 11 is the micro-morphology of diamond abrasive grains after friction and wear under different Tm contents;

[0040] Figure 12 is the overall structure schematic diagram of the present invention;

[0041] Figure 13 is the structure schematic diagram of the vacuum chamber of the present invention;

[0042] Figure 14 is the structure schematic diagram of the feed pipe of the present invention;

[0043] Figure 15 Schematic structural diagram of the vacuum pump of the present invention;

[0044] Figure 16 Of the present invention Figure 15 Enlarged view at position A in;

[0045] Figure 17 Schematic structural diagram of the connecting conduit of the present invention;

[0046] Figure 18 Partial structural schematic diagram of the movable box of the present invention;

[0047] Figure 19 Of the present invention Figure 18 Enlarged view at position B in;

[0048] Figure 20 Schematic structural diagram of the stop valve of the present invention. Specific embodiments

[0049] In order to better understand the technical solutions provided by the present invention, the following further describes the content of the present invention in conjunction with the accompanying drawings and implementation cases:

[0050] Embodiment 1

[0051] A method for brazing diamond with a nickel-based filler metal doped with rare earth Tm, comprising the following steps:

[0052] S1: Prepare alloy ingots

[0053] Weigh 15.5 g of Ni, 2.4 g of Cr, 0.6 g of B, 0.8 g of Fe, 0.6 g of Si and 0.1 g of Tm, ultrasonically clean in acetone solution for 15 min, then ultrasonically clean in ethanol solution for 5 min, and after drying, put them into the vacuum melting furnace in Example 5 in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as the protective gas, adjust the heating current to 180 A, and melt repeatedly 4-5 times. Take out the alloy ingot after cooling with the furnace.

[0054] S2: Treat the alloy ingot

[0055] Cut the alloy ingot obtained in step S1 into filler metal sheets with a thickness of 200 μm using a diamond wire cutting machine, mechanically polish its surface with 400# and 800# sandpapers, then put it into acetone and ethanol solutions for ultrasonic cleaning, and then dry it;

[0056] S3: Prepare samples

[0057] Select a 45# steel substrate, sand the surface of the 45# steel substrate to remove the surface oxide layer and impurities, and ultrasonically clean and dry the 45# steel substrate and diamond in acetone solution and alcohol solution respectively. Then, combine diamond with the solder sheet and the solder sheet with the steel substrate through an organic carrier. From top to bottom, they are diamond, solder thin sheet, and steel substrate to obtain a sample;

[0058] S4: Brazing

[0059] Put the sample into a vacuum molybdenum belt sintering furnace for brazing, keep the vacuum degree at 2.0×10 -3 Pa, heat it to 1080 °C and keep it warm for 5 min, take out the sample after cooling with the furnace to room temperature.

[0060] Example 2

[0061] A method for brazing diamond with a nickel-based filler metal doped with rare earth Tm, comprising the following steps:

[0062] S1: Prepare alloy ingot

[0063] Weigh 15.4 g of Ni, 2.4 g of Cr, 0.6 g of B, 0.8 g of Fe, 0.6 g of Si and 0.2 g of Tm, ultrasonically clean them in acetone solution for 15 min, then ultrasonically clean them in ethanol solution for 5 min, dry them and put them into a vacuum melting furnace in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as a protective gas, adjust the heating current to 200 A, and melt repeatedly for 4 - 5 times. Take out the alloy ingot after it cools with the furnace.

[0064] S2 - S4 are the same as in Example 1.

[0065] Example 3

[0066] A method for brazing diamond with a nickel-based filler metal doped with rare earth Tm, comprising the following steps:

[0067] S1: Prepare alloy ingot

[0068] Weigh 15.3 g of Ni, 2.4 g of Cr, 0.6 g of B, 0.8 g of Fe, 0.6 g of Si and 0.3 g of Tm, ultrasonically clean them in acetone solution for 15 min, then ultrasonically clean them in ethanol solution for 5 min, dry them and put them into a vacuum melting furnace in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as a protective gas, adjust the heating current to 220 A, and melt repeatedly for 4 - 5 times. Take out the alloy ingot after it cools with the furnace.

[0069] S2 - S4 are the same as in Example 1.

[0070] Example 4

[0071] A method for brazing diamond with a nickel-based filler metal doped with rare earth Tm, comprising the following steps:

[0072] S1: Prepare an alloy ingot

[0073] Weigh 15.2 g of Ni, 2.4 g of Cr, 0.6 g of B, 0.8 g of Fe, 0.6 g of Si and 0.4 g of Tm, ultrasonically clean in an acetone solution for 15 min, then ultrasonically clean in an ethanol solution for 5 min. After drying, place them in a vacuum melting furnace in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as the protective gas, adjust the heating current to 220 A, and melt repeatedly 4 - 5 times. After the alloy ingot cools with the furnace, take it out.

[0074] S2 - S4 are the same as in Example 1.

[0075] Example 5

[0076] Please refer to Figures 12 to 20 , the vacuum melting furnace, including a fixed base 1, a vacuum chamber 2 is fixedly installed on the top of the fixed base 1, a sealing cover 4 is slidably arranged on the top of the fixed base 1 on one side of the vacuum chamber 2, a crucible 30 is arranged on the side of the sealing cover 4 facing the vacuum chamber 2, a connecting pipe 3 connected to the vacuum system is arranged on the other side of the vacuum chamber 2, a feed pipe 5 is fixedly installed through the top of the vacuum chamber 2 directly above the crucible 30, a vacuum pump 9 is fixedly installed on the top of the vacuum chamber 2 on one side of the feed pipe 5, a fixing frame 8 is fixedly installed on the top of the vacuum chamber 2 on the other side of the feed pipe 5, a stop valve 6 is arranged at the top of the feed pipe 5, another stop valve 6 is fixedly installed at the bottom of the feed pipe 5 inside the vacuum chamber 2, a feed hopper 7 is fixedly installed at the top of the stop valve 6 outside the vacuum chamber 2, one side of the stop valve 6 outside the vacuum chamber 2 is fixedly installed with the top of the fixing frame 8, an exhaust pipe 10 is arranged at the top on one side of the feed pipe 5, and the intake port of the vacuum pump 9 is fixedly installed with the exhaust pipe 10.

[0077] As an implementation manner of the present invention, a connecting conduit 11 is fixedly installed at the top on the other side of the feed pipe 5, a movable box 12 is fixedly installed inside the fixing frame 8, a piston plate 14 is slidably connected inside the movable box 12, the other end of the connecting conduit 11 is fixedly installed at the bottom on one side of the movable box 12, a connecting column 15 is fixedly installed at the top of the piston plate 14, the connecting column 15 penetrates and slides through the top of the movable box 12, and a lifting plate 16 slidably connected inside the fixing frame 8 is fixedly installed at the top of the connecting column 15.

[0078] As an implementation manner of the present invention, a transmission column 18 is rotatably connected through the end of the lifting plate 16. A driving motor 17 is fixedly installed through the lifting plate 16 on one side of the transmission column 18. The output end of the driving motor 17 is in transmission connection with the transmission column 18. Transmission sleeves 19 are fixedly installed at the top and bottom of the transmission column 18.

[0079] As an implementation manner of the present invention, a fixed bracket 20 is fixedly installed at the top of one side of the fixed frame 8 above the driving motor 17. A first rotating shaft 21 is rotatably connected through the end of the fixed bracket 20. A first bevel gear 22 is fixedly installed at the top of the first rotating shaft 21 above the fixed bracket 20. A first connecting block 23 is fixedly installed at the bottom of the first rotating shaft 21 directly above the transmission sleeve 19. The first bevel gear 22 is in transmission connection with the stop valve 6 located outside the vacuum chamber 2. By providing the movable box 12, when it is necessary to add a reactant to the crucible 30, under the action of the jacking spring 13, the lifting plate 16 rises to the top. At the same time, the transmission sleeve 19 located above is sleeved with the first connecting block 23. Then, the driving motor 17 drives the transmission sleeve 19 to rotate, thereby causing the first transmission shaft to drive the first bevel gear 22 to rotate, further causing the threaded sleeve 606 to rotate, and then driving the threaded rod 605 and the gate plate 604 to move, so that the reactant can be put into the feed pipe 5 through the feed hopper 7. Then, the driving motor 17 is reversed to close the stop valve 6, so that the reactant is located inside the feed pipe 5. Then, the vacuum pump 9 is started, and the inside of the feed pipe 5 is evacuated through the exhaust port. Then, by opening the stop valve 6 located inside the vacuum chamber 2, the reactant is sent into the crucible 30, saving the operation steps of opening the vacuum chamber 2 for adding during the process of adding the reactant, avoiding the influence on the internal temperature and vacuum effect of the furnace body, and improving the metal processing efficiency.

[0080] As an implementation manner of the present invention, a second transmission shaft 24 is rotatably connected through the top of the vacuum chamber 2 directly below the transmission column 18. A second connecting block 25 is fixedly installed at the top of the second transmission shaft 24 directly below the transmission sleeve 19. A second bevel gear 26 is fixedly installed at the bottom of the second transmission shaft 24 inside the vacuum chamber 2. The second bevel gear 26 is in transmission connection with the stop valve 6 located inside the vacuum chamber 2.

[0081] As an implementation manner of the present invention, the stop valve 6 includes a valve housing 601 fixedly installed with the feed pipe 5. A connecting frame 602 is fixedly installed on one side of the valve housing 601. A connecting seat 603 is slidably arranged inside the connecting frame 602. A gate plate 604 located inside the valve housing 601 is fixedly installed on one side of the connecting seat 603. A threaded rod 605 is fixedly installed on the other side of the connecting seat 603. A threaded sleeve 606 is rotatably connected through the other end of the connecting seat 603. A third bevel gear 607 is fixedly installed on one side of the threaded sleeve 606.

[0082] As an implementation manner of the present invention, a synchronous pulley 27 is fixedly installed at the output end of the driving motor 17 and is located below the lifting plate 16. Another synchronous pulley 27 is fixedly installed in the middle of the transmission column 18 and is located below the lifting plate 16. The two synchronous pulleys 27 are connected by a synchronous belt 28.

[0083] As an implementation manner of the present invention, a jacking spring 13 is arranged inside the movable box 12 and is located below the piston plate 14. The top of the jacking spring 13 is in tight contact with the bottom of the piston plate 14. The bottom of the jacking spring 13 is fixedly installed on the bottom inside the movable box 12. A limiting frame 29 is fixedly installed inside the movable box 12 and is located below the piston plate 14. The limiting frame 29 is located above the connection between the movable box 12 and the connecting conduit 11. By arranging the second transmission shaft 24, after the vacuum pump 9 evacuates the inside of the feed pipe 5, the air inside the movable box 12 is evacuated through the connecting pipe 3, so that the piston plate 14 moves downward, causing the first connecting block 23 to become loose from the transmission sleeve 19. As the lifting plate 16 descends, the transmission sleeve 19 located below is sleeved with the second connecting block 25, causing the second transmission shaft 24 to rotate, thereby controlling the opening of the stop valve 6 located inside the vacuum box 2.

[0084] As an implementation manner of the present invention, the first bevel gear 22 meshes with the third transmission gear in the stop valve 6 outside the vacuum box 2, and the second bevel gear 26 meshes with the third transmission gear in the stop valve 6 inside the vacuum box 2.

[0085] As an implementation manner of the present invention, an electric push rod 31 is fixedly installed at the top of the fixed base 1 and is located below the vacuum box 2. The movable end of the electric push rod 31 is fixedly installed with a movable frame 34. The sealing cover 4 is fixedly installed on the top of the movable frame 34. A guide rail 32 is fixedly installed at the top of the fixed base 1 and is located on one side of the electric push rod 31. The bottom of the movable frame 34 is provided with rollers 33, and the rollers 33 are in rolling contact with the guide rail 32.

[0086] It should be noted that during use, after moving the crucible 30 into the vacuum chamber 2, the sealing cover 4 is tightly sealed with the vacuum chamber 2. Then, the inside of the vacuum chamber 2 is evacuated through the connecting pipe 3, and the raw materials in the crucible 30 are heated. When a reactant needs to be added to the crucible 30 after heating for a period of time, under the action of the jacking spring 13, the lifting plate 16 rises to the top. At the same time, the driving sleeve 19 located above is sleeved with the first connecting block 23. Then, the driving motor 17 drives the driving sleeve 19 to rotate, which in turn causes the first transmission shaft to drive the first bevel gear 22 to rotate, further causing the threaded sleeve 606 to rotate, and then driving the threaded rod 605 and the gate plate 604 to move, so that the reactant can be put into the feed pipe 5 through the feed hopper 7. Then, the cut-off valve 6 is closed by reversing the driving motor 17, so that the reactant is located inside the feed pipe 5. Then, the vacuum pump 9 is started, and the inside of the feed pipe 5 is evacuated through the exhaust port. After the vacuum pump 9 evacuates the inside of the feed pipe 5, the air inside the movable box 12 is evacuated through the connecting pipe 3, which in turn causes the piston plate 14 to move downward, so that the first connecting block 23 is disengaged from the driving sleeve 19. As the lifting plate 16 descends, the driving sleeve 19 located below is sleeved with the second connecting block 25, causing the second transmission shaft 24 to rotate, and then controlling the cut-off valve 6 located inside the vacuum chamber 2 to open, and sending the reactant into the crucible 30, saving the operation steps of opening the vacuum chamber 2 for adding during the process of adding the reactant, avoiding the influence on the internal temperature and vacuum effect of the furnace body, and improving the metal processing efficiency.

[0087] Comparative Example 1

[0088] A method for brazing diamond with a nickel-based filler metal includes the following steps:

[0089] S1: Prepare an alloy ingot

[0090] Weigh 15.6 g of metallic elemental raw materials of Ni, 2.4 g of Cr, 0.6 g of B, 0.8 g of Fe, and 0.6 g of Si, ultrasonically clean them in an acetone solution for 15 min, then ultrasonically clean them in an ethanol solution for 5 min, and after drying, put them into a vacuum melting furnace in ascending order of melting point, evacuate to 0.1 Pa, introduce Ar gas as a protective gas, adjust the heating current to 180 A, and melt repeatedly for 4 - 5 times. After the alloy ingot cools with the furnace, take it out.

[0091] S2: Process the alloy ingot

[0092] Cut the alloy ingot obtained in step S1 into filler metal sheets with a thickness of 200 μm using a diamond wire cutting machine, mechanically polish its surface with 400# and 800# sandpapers, then put it into an acetone solution and ultrasonically clean it for 15 min, clean it in an ethanol solution for 5 min, and then dry it;

[0093] S3: Prepare samples

[0094] Select a 45 steel matrix, and polish its surface with sandpaper to remove the oxide layer and impurities. Place the 45 steel matrix and diamond in acetone solution and alcohol solution respectively for ultrasonic cleaning and drying. Then, combine diamond with the solder sheet and the solder sheet with the steel matrix through an organic carrier. From top to bottom, they are diamond, solder thin sheet, and steel matrix to obtain a sample;

[0095] S4: Brazing

[0096] Put the sample into a vacuum molybdenum strip sintering furnace for brazing. The vacuum degree is maintained at 4.0×10 -3 Pa, heat it to 1080 °C and hold for 5 min, and take out the sample after cooling to room temperature with the furnace.

[0097] Figure 1 For the scanning electron microscope images of the solder microstructure of Case 1-4 and Comparative Case 1, it can be seen that the microstructure of the solder alloy with 0 rare earth addition is mainly composed of coarse dendrites, and the microstructure distribution is uneven; after adding rare earth Tm, due to the small atomic radius of Tm and its solid solution strengthening effect and alloying effect, the grain size of the solder gradually becomes smaller, and the microstructure gradually becomes more uniform. When the addition amount is 1.5 wt%, the grain refinement is the most significant, and the number of dendrites is the least, replaced by some small equiaxed grains. When the addition amount reaches 2.0 wt.%, due to the weakening of the alloying performance, the number of solder dendrites increases.

[0098] Figure 2 For the microhardness diagrams of nickel-based solders doped with different contents of rare earth Tm, it is found by comparison that the addition of rare earth Tm can significantly improve the microhardness of the alloy solder, and with the increase of the content of rare earth Tm, the microhardness of the solder shows a trend of first increasing and then decreasing. When the addition amount is 1.5 wt.%, the hardness reaches the maximum value of 715.8 HV 0.2 , which is 17.8% higher than the solder without adding rare earth Tm.

[0099] Figure 3 For the X-ray phase analysis of the solders of Case 1-4 and Comparative Case 1, it can be seen that the addition of rare earth Tm promotes the formation of two new phases, NiTm and Ni 3 Tm, consumes Ni element and thus reduces the thermal damage of diamond.

[0100] Figure 4 By comparing the brazed diamond morphology and Raman spectrum of Case 3 and Comparative Case 1, it can be found that there are relatively serious thermal etching pits on the surface of the brazed specimen without adding rare earth Tm, and the diamond graphitization is relatively serious. While for the brazed specimen added with 1.5 wt.% Tm, the diamond surface remains intact, and the graphitization is significantly inhibited, effectively ensuring the processing performance of diamond.

[0101] Figure 5 and Figure 6 Figs. and

[0101] are the morphology and surface scan images of the brazed diamond joints for Case 3 and Comparative Case 1. It can be seen that large cracks appeared in the brazed joints without the addition of rare earth Tm. This may be because the difference in the thermal expansion coefficients between diamond and the filler metal is relatively large, resulting in significant residual stress during the cooling process. After adding 1.5 wt.% Tm, the brazed joints became smooth and flat, and no obvious cracks were found. Energy spectrum analysis revealed that Cr elements were enriched at the interface with an obvious gradient change, and there was also an obvious transition trend for C elements. Moreover, there was partial overlap in the concentration change regions of the two elements, indicating obvious diffusion of the two elements at the interface. After adding Tm, some Tm elements also appeared at the interface, consuming some Ni elements and reducing the corrosion of diamond abrasives.

[0102] Figure 7 Fig. Figure 5 is the morphology image of the brazed diamond carbide for Case 3 and Comparative Case 1. The size of the brazed diamond carbide without the addition of rare earth Tm was relatively large, and many long cracks appeared on its surface. After adding 1.5 wt.% Tm, there were basically no cracks on the carbide surface, and the growth directions of the carbides intersected vertically and horizontally, which could more effectively release the residual stress of the brazed diamond and ensure the brazing quality.

[0103] Figure 9 、 10 Figs. Figure 6 , , and

[0102] are the friction coefficient, the removal amount of the sample being ground, and the morphology image of the diamond after wear of the diamond brazed with Ni-Cr-Tm filler metal, respectively. It can be seen that the diamond brazed with Ni-Cr filler metal without the addition of rare earth Tm had a relatively large friction coefficient, a small removal amount of the sample being ground, and large-area damage to the diamond. After adding Tm, the friction coefficient of the diamond decreased, the removal amount of the sample being ground increased significantly, and the wear degree of the diamond decreased. When the addition amount was 1.5 wt.%, the diamond tool had the best grinding performance.

Claims

1. A rare earth modified solder, characterized in that: The solder is obtained by vacuum arc melting of Ni, Cr, B, Si, Fe and Tm element particles under argon protection, and its composition and weight percentage are: 76.0% to 82.0% Ni, 9.0% to 13% Cr, 2.0% to 4.0% B, 3.0% to 5.0% Si, 2.0% to 5.0% Fe and 0 to 2% Tm.

2. A brazing method, the method using the rare earth modified brazing filler metal according to claim 1, characterized in that: The following steps are involved: S1: Preparation of alloy ingots Weigh each component of the solder with a purity of not less than 99.5% by mass percentage, ultrasonically clean it in an acetone solution for 15 minutes, then ultrasonically clean it in an ethanol solution for 5 minutes, and after drying, put it into a vacuum melting furnace in ascending order of melting point, evacuate to 0.1Pa, introduce Ar gas as a protective gas, adjust the heating current, and repeatedly melt for 4-5 times, and take out the alloy ingot after it cools down with the furnace; S2: Processing alloy ingots The alloy ingot obtained in step S1 is cut into solder sheets with a thickness of 200 μm using a diamond wire cutting machine, and its surface is mechanically polished with 400# and 800# sandpapers, and then it is ultrasonically cleaned in acetone and ethanol solutions, and then dried; S3: Sample preparation A No. 45 steel substrate was selected, and the surface of the No. 45 steel substrate was polished with sandpaper to remove the oxide layer and impurities on the surface. The No. 45 steel substrate and the diamond were respectively placed in an acetone solution and an alcohol solution for ultrasonic cleaning and drying; then, the diamond was combined with the brazing sheet, and the brazing sheet was combined with the steel substrate through an organic carrier, and from top to bottom, the diamond, the brazing sheet, and the steel substrate were combined to obtain a sample; S4: Brazing The sample was placed in a vacuum molybdenum strip sintering furnace for brazing, and the vacuum degree was maintained at 2.0×10 -3 -5.0×10 -3 Pa, heated to 1050-1080℃ and kept warm for 5min, cooled with the furnace to room temperature and then took out the sample.

3. A vacuum melting furnace, characterized in that: The invention comprises a fixed base (1), a vacuum box (2) is fixedly installed on the top of the fixed base (1), a sealing cover (4) is slidably provided on the top of the fixed base (1) and is located on one side of the vacuum box (2), a crucible (30) is provided on the side of the sealing cover (4) facing the vacuum box (2), a connecting pipe (3) connected to a vacuum system is provided on the other side of the vacuum box (2), a feeding pipe (5) located directly above the crucible (30) is fixedly installed through the top of the vacuum box (2), a vacuum pump (9) is fixedly installed on the top of the vacuum box (2) and is located on one side of the feeding pipe (5), and the vacuum box (2 ) is fixedly mounted on the top of a fixing frame (8) located on the other side of a feed pipe (5), a stop valve (6) is arranged on the top of the feed pipe (5), another stop valve (6) located inside the vacuum box (2) is fixedly mounted on the bottom of the feed pipe (5), a feed hopper (7) is fixedly mounted on the top of the stop valve (6) located outside the vacuum box (2), one side of the stop valve (6) located outside the vacuum box (2) is fixedly mounted on the top of the fixing frame (8), an exhaust pipe (10) is arranged on the top of one side of the feed pipe (5), and an air inlet of a vacuum pump (9) is fixedly mounted on the exhaust pipe (10).

Images