A rare earth Lu-doped solder alloy, preparation method and application thereof

Abstract

The present invention belongs to the field of welding materials technology, specifically relating to a rare earth (Lu)-doped solder alloy, its preparation method, and its application. The raw material components of the Lu-doped solder alloy, by mass percentage, include 10-12% Cr, 3-4% B, 3-4% Si, 4-5% Fe, 0.5-2% Lu, and the balance Ni. The Lu-doped solder alloy exhibits a uniform microstructure and excellent mechanical properties. The exposed height of diamond particles after brazing using the Lu-doped solder alloy reaches up to 55.3% of their original height.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a rare earth Lu-doped brazing alloy, its preparation method, and its application. Background Technology

[0002] The brazing filler metal is a crucial component in the brazing process, playing a vital role in material bonding. The selection of the filler metal requires consideration of its bonding ability with the matrix, ensuring a stable bond between them. Brazing temperature is also an important factor; excessively high temperatures can degrade the performance of diamond particles. In addition to meeting these conditions, the chosen filler metal must also be economical, offering good brazing performance while being suitable for large-scale application. Currently, among the active filler metal alloys commonly used for brazing diamond, silver-based filler metals have a low melting point and strong wetting ability for diamond particles, but the price of precious metal silver is very high; copper-based filler metals have a lower melting point and do not contain precious metals, but their wear resistance is poor; filler metal alloys offer the advantages of high hardness and strong bonding with diamond particles, while also being economical, and are widely used in the diamond tool brazing industry. Summary of the Invention

[0003] This invention discloses a method for preparing rare-earth Lu-doped solder alloys, comprising the following steps:

[0004] Step (1): Weigh the metal ingots of each component raw material Ni, Cr, B, Si, Fe and Lu, and clean them to remove impurities;

[0005] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace, evacuate, and melt to obtain the molten brazing alloy ingot.

[0006] Step (3): Cut the smelted brazing alloy ingot to obtain brazing alloy sheets. After polishing, the brazing alloy sheets are obtained as sheet-like rare earth Lu-doped brazing alloy.

[0007] Preferably, in step (1), the raw materials of each component are, by mass percentage: 10~12% Cr, 3~4% B, 3~4% Si, 4~5% Fe, 0.5~2% Lu and the balance Ni.

[0008] Preferably, in step (2), the vacuuming process includes:

[0009] First, the atmosphere pressure inside the vacuum arc melting furnace chamber is evacuated to a vacuum level <20 Pa using a mechanical pump. Argon gas is then introduced to bring the atmosphere pressure to -0.05 MPa. Next, the atmosphere pressure is evacuated to a vacuum level <20 Pa using a mechanical pump. Finally, the atmosphere pressure is evacuated to 5 × 10⁻⁶ Pa using a molecular pump. -3 Below Pa.

[0010] Preferably, in step (2), the smelting process specifically includes: smelting the metal ingots of each component raw material under a current of 180~220A until the metal ingots of each component raw material are completely melted, and then stopping the power supply.

[0011] Preferably, the smelting process needs to be repeated 3-4 times to ensure that the composition of the smelted brazing alloy ingot is uniform.

[0012] Preferably, step (3) specifically includes: cutting the smelted brazing alloy ingot with diamond wire to obtain brazing alloy sheets, and polishing the brazing alloy sheets sequentially with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-like rare earth Lu-doped brazing alloy.

[0013] The present invention also discloses a rare earth Lu-doped solder alloy prepared by the method described above for preparing rare earth Lu-doped solder alloy.

[0014] The present invention also discloses an application of the rare earth Lu-doped brazing alloy as described above, the application including brazing diamond using the rare earth Lu-doped brazing alloy.

[0015] The method for brazing diamond using a rare-earth Lu-doped brazing alloy includes the following steps:

[0016] Step S1: Select diamond particles, clean and dry them; select a steel substrate, grind the brazing surface, clean and dry it.

[0017] Step S2: After bonding the diamond, the sheet-like rare earth Lu-doped brazing alloy, and the steel substrate, place them in a vacuum molybdenum wire brazing furnace for brazing.

[0018] Preferably, in step S1, the diamond particles have a particle size of 425 μm, and the steel matrix is ​​made of 45... # The steel substrate measures 15mm × 10mm × 6mm.

[0019] Preferably, in step S2, the bonding process of diamond, flake-shaped rare-earth Lu-doped brazing alloy, and steel substrate includes: applying an adhesive to the brazing surface of the steel substrate, spreading the flake-shaped rare-earth Lu-doped brazing alloy flat on the brazing surface coated with adhesive, applying adhesive to the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy, and orderly arranging diamond particles on the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy, so that diamond, flake-shaped rare-earth Lu-doped brazing alloy, and steel substrate are placed in a sandwich structure from top to bottom.

[0020] Preferably, in step S2, the brazing process specifically includes: maintaining the vacuum level inside the vacuum molybdenum wire brazing furnace at 5 × 10⁻⁶.-3 Below Pa, the temperature is increased to 1080℃ at a heating rate of 10℃ / min, held at 1080℃ for 5 min, and then decreased to 500℃ at a heating rate of 10℃ / min. After furnace cooling, brazed diamond is obtained.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) In the rare earth Lu-doped solder alloy, the rare earth element Lu is mainly distributed at the grain boundary, which hinders grain growth and provides heterogeneous nucleation sites to achieve the purpose of grain refinement. In addition, the Lu element reacts with the Ni element in the solder alloy to generate the NiLu phase. The grain refinement and the generation of new phase together improve the microhardness of the solder alloy.

[0023] (2) Rare earth Lu-doped brazing alloy can effectively improve the quality of brazed joints. By combining with Ni elements around diamond particles, it reduces the erosion of diamond by Ni at high temperatures and increases the exposure height of brazed diamond particles.

[0024] (3) The Lu element in the rare earth Lu-doped solder alloy affects the formation of carbides at the interface between diamond particles and solder alloy. The carbides change from ordered long strips to short rods, which improves the problem of mismatch between the thermal expansion coefficients of diamond particles and solder alloy, reduces the number of cracks in the carbide layer, and improves the holding force of solder alloy on diamond particles.

[0025] (4) Rare earth Lu-doped brazing alloy can effectively improve the post-weld mechanical properties of brazed diamond samples. The brazed samples have excellent stability during grinding. The diamond particles can maintain most of their integrity after the wear test and have a high removal capacity for alumina ceramics. Attached Figure Description

[0026] Figure 1 SEM images of the morphology of the solder alloy samples prepared in Examples 1-4 and Comparative Example 1 of this invention.

[0027] Figure 2 These are EDS surface scan images of the brazing alloy samples prepared in Example 3 and Comparative Example 1 of the present invention.

[0028] Figure 3 The XRD patterns are of the solder alloy samples prepared in Examples 1-4 and Comparative Example 1 of this invention.

[0029] Figure 4 The hardness test results of the brazing alloy samples prepared in Examples 1-4 and Comparative Example 1 of this invention are shown in the figure.

[0030] Figure 5 SEM images of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention.

[0031] Figure 6 EDS surface scan images of the bonding interface of the brazed diamond samples prepared in Example 7 and Comparative Example 2 of the present invention.

[0032] Figure 7 EDS line scan images of the bonding interface of the brazed diamond samples prepared in Example 7 and Comparative Example 2 of this invention.

[0033] Figure 8 The Raman spectra of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention are shown.

[0034] Figure 9 The image shows the height of diamond particles exposed in the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention, obtained using an ultra-depth-of-field microscope.

[0035] Figure 10 This is a schematic diagram illustrating the effect of rare earth Lu doping on the diamond particle exposure of the present invention.

[0036] Figure 11 The XRD patterns of carbides on the surface of diamond particles are shown for the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention.

[0037] Figure 12 SEM images of the carbide morphology on the surface of diamond particles after etching of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention.

[0038] Figure 13 The diagram shows the test results of the compressive strength of the diamond particles after etching of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 of this invention.

[0039] Figure 14 The diagram shows the interface hardness test results of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2.

[0040] Figure 15 SEM images of the diamond particle morphology of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 after wear tests.

[0041] Figure 16 The graph shows the test results of the friction coefficient of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2.

[0042] Figure 17 The graph shows the test results of the amount of alumina ceramic removed by the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2. Detailed Implementation

[0043] By referring to the accompanying drawings and in conjunction with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be further explained. The purpose is to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0044] like Figures 1 to 17 As shown, this invention discloses a rare-earth Lu-doped solder alloy, its preparation method, and its application. The raw material composition of the rare-earth Lu-doped solder alloy, by mass percentage, includes 10-12% Cr, 3-4% B, 3-4% Si, 4-5% Fe, 0.5-2% Lu, and the balance Ni. The rare-earth Lu-doped solder alloy is prepared under a vacuum of 5 × 10⁻⁶. -3 Below Pa, diamond is brazed in a vacuum molybdenum wire brazing furnace. The resulting brazed diamond has good surface integrity. The doping of rare earth element Lu can promote the formation of Cr7C3 at the interface between diamond and brazing alloy, reduce the cracks in the interface carbide layer, effectively improve the holding force of brazing alloy on diamond, and enhance the grinding performance of brazed diamond samples.

[0045] Example 1

[0046] This embodiment discloses a method for preparing a rare-earth Lu-doped solder alloy, including the following steps:

[0047] Step (1): Weigh the metal ingots of Ni, Cr, B, Si, Fe and Lu after sanding, with Ni 77.5g, Cr 12g, B 3g, Si 3g, Fe 4g and Lu 0.5g, place them in acetone, clean them in an ultrasonic cleaner for 15 minutes, and then place them in ethanol and clean them in an ultrasonic cleaner for 5 minutes to remove impurities.

[0048] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace. Before melting, perform vacuuming, including: first, using a mechanical pump to evacuate the atmosphere pressure inside the vacuum arc melting furnace cavity to a vacuum degree <20 Pa, then introducing argon gas to bring the atmosphere pressure to -0.05 MPa, then using a mechanical pump to evacuate the atmosphere pressure to a vacuum degree <20 Pa, and finally using a molecular pump to evacuate the atmosphere pressure to 5 × 10⁻⁶ Pa. -3 Below Pa, after vacuuming, the metal ingots of each component raw material are melted under a current of 220A until the metal ingots of each component raw material are completely melted. Then the current is stopped. The melting process needs to be repeated 4 times to obtain the melted brazing alloy ingot.

[0049] Step (3): Cut the smelted brazing alloy ingot with diamond wire to obtain brazing alloy flakes. The brazing alloy flakes are then polished with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-like rare earth Lu-doped brazing alloy with a thickness of 0.15 mm.

[0050] Example 2

[0051] This embodiment discloses a method for preparing a rare-earth Lu-doped solder alloy, including the following steps:

[0052] Step (1): Weigh the metal ingots of Ni, Cr, B, Si, Fe and Lu after sanding, with Ni 77g, Cr 12g, B 3g, Si 3g, Fe 4g and Lu 1g. Place them in acetone and clean them in an ultrasonic cleaner for 15 minutes. Then place them in ethanol and clean them in an ultrasonic cleaner for 5 minutes to remove impurities.

[0053] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace. Before melting, perform vacuuming, including: first, using a mechanical pump to evacuate the atmosphere pressure inside the vacuum arc melting furnace cavity to a vacuum degree <20 Pa, then introducing argon gas to bring the atmosphere pressure to -0.05 MPa, then using a mechanical pump to evacuate the atmosphere pressure to a vacuum degree <20 Pa, and finally using a molecular pump to evacuate the atmosphere pressure to 5 × 10⁻⁶ Pa. -3 Below Pa, after vacuuming, the metal ingots of each component raw material are melted under a current of 220A until the metal ingots of each component raw material are completely melted. Then the current is stopped. The melting process needs to be repeated 4 times to obtain the melted brazing alloy ingot.

[0054] Step (3): Cut the smelted brazing alloy ingot with diamond wire to obtain brazing alloy flakes. The brazing alloy flakes are then polished with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-like rare earth Lu-doped brazing alloy with a thickness of 0.15 mm.

[0055] Example 3

[0056] This embodiment discloses a method for preparing a rare-earth Lu-doped solder alloy, including the following steps:

[0057] Step (1): Weigh the metal ingots of Ni, Cr, B, Si, Fe and Lu after sanding, with Ni 76.5g, Cr 12g, B 3g, Si 3g, Fe 4g and Lu 1.5g, place them in acetone, clean them in an ultrasonic cleaner for 15 minutes, and then place them in ethanol and clean them in an ultrasonic cleaner for 5 minutes to remove impurities.

[0058] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace. Before melting, perform vacuuming, including: first, using a mechanical pump to evacuate the atmosphere pressure inside the vacuum arc melting furnace cavity to a vacuum degree <20 Pa, then introducing argon gas to bring the atmosphere pressure to -0.05 MPa, then using a mechanical pump to evacuate the atmosphere pressure to a vacuum degree <20 Pa, and finally using a molecular pump to evacuate the atmosphere pressure to 5 × 10⁻⁶ Pa. -3 Below Pa, after vacuuming, the metal ingots of each component raw material are melted under a current of 220A until the metal ingots of each component raw material are completely melted. Then the current is stopped. The melting process needs to be repeated 4 times to obtain the melted brazing alloy ingot.

[0059] Step (3): Cut the smelted brazing alloy ingot with diamond wire to obtain brazing alloy flakes. The brazing alloy flakes are then polished with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-like rare earth Lu-doped brazing alloy with a thickness of 0.15 mm.

[0060] Example 4

[0061] This embodiment discloses a method for preparing a rare-earth Lu-doped solder alloy, including the following steps:

[0062] Step (1): Weigh the metal ingots of Ni, Cr, B, Si, Fe and Lu after sanding, with Ni 76g, Cr 12g, B 3g, Si 3g, Fe 4g and Lu 2g. Place them in acetone and clean them in an ultrasonic cleaner for 15 minutes. Then place them in ethanol and clean them in an ultrasonic cleaner for 5 minutes to remove impurities.

[0063] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace. Before melting, perform vacuuming, including: first, using a mechanical pump to evacuate the atmosphere pressure inside the vacuum arc melting furnace cavity to a vacuum degree <20 Pa, then introducing argon gas to bring the atmosphere pressure to -0.05 MPa, then using a mechanical pump to evacuate the atmosphere pressure to a vacuum degree <20 Pa, and finally using a molecular pump to evacuate the atmosphere pressure to 5 × 10⁻⁶ Pa. -3 Below Pa, after vacuuming, the metal ingots of each component raw material are melted under a current of 220A until the metal ingots of each component raw material are completely melted. Then the current is stopped. The melting process needs to be repeated 4 times to obtain the melted brazing alloy ingot.

[0064] Step (3): Cut the smelted brazing alloy ingot with diamond wire to obtain brazing alloy flakes. The brazing alloy flakes are then polished with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-like rare earth Lu-doped brazing alloy with a thickness of 0.15 mm.

[0065] Comparative Example 1

[0066] This embodiment discloses a method for preparing a brazing filler alloy, including the following steps:

[0067] Step (1): Weigh the metal ingots of Ni, Cr, B, Si and Fe after sanding. Place 78g of Ni, 12g of Cr, 3g of B, 3g of Si and 4g of Fe in acetone and clean them in an ultrasonic cleaner for 15 minutes. Then place them in ethanol and clean them in an ultrasonic cleaner for 5 minutes to remove impurities.

[0068] Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace. Before melting, perform vacuuming, including: first, using a mechanical pump to evacuate the atmosphere pressure inside the vacuum arc melting furnace cavity to a vacuum degree <20 Pa, then introducing argon gas to bring the atmosphere pressure to -0.05 MPa, then using a mechanical pump to evacuate the atmosphere pressure to a vacuum degree <20 Pa, and finally using a molecular pump to evacuate the atmosphere pressure to 5 × 10⁻⁶ Pa. -3 Below Pa, after vacuuming, the metal ingots of each component raw material are melted under a current of 220A until the metal ingots of each component raw material are completely melted. Then the current is stopped. The melting process needs to be repeated 4 times to obtain the melted brazing alloy ingot.

[0069] Step (3): Cut the molten brazing alloy ingot with diamond wire to obtain brazing alloy sheet. The brazing alloy sheet is then polished with 320-mesh, 600-mesh and 1000-mesh sandpaper to obtain sheet-shaped brazing alloy with a thickness of 0.15 mm.

[0070] Example 5

[0071] This embodiment discloses a method for brazing diamond using the rare-earth Lu-doped brazing alloy prepared in Example 1, comprising the following steps:

[0072] Step S1: Select diamond particles with a particle size of 425 μm, first place them in acetone, clean them in an ultrasonic cleaner for 15 minutes, then place them in ethanol, clean them in an ultrasonic cleaner for 5 minutes, and dry them; select 15 mm × 10 mm × 6 mm diamond particles with a particle size of 425 μm. #Using steel as the base material, the brazing surface of the steel base material is polished sequentially with 320-grit, 600-grit, and 1000-grit sandpaper. After that, it is first placed in acetone and cleaned in an ultrasonic cleaner for 15 minutes. Then, it is placed in ethanol and cleaned in an ultrasonic cleaner for 5 minutes. Finally, it is dried.

[0073] Step S2: After bonding the diamond, the sheet-like rare-earth Lu-doped brazing alloy, and the steel substrate, place them in a vacuum molybdenum wire brazing furnace for brazing. During the brazing process, the vacuum level inside the furnace is maintained at 5 × 10⁻⁶. -3 Below Pa, the temperature is increased to 1080℃ at a heating rate of 10℃ / min, held at this temperature for 5min, and then decreased to 500℃ at a rate of 10℃ / min. After furnace cooling, brazed diamond is obtained.

[0074] The bonding process of diamond, flake-shaped rare-earth Lu-doped brazing alloy, and steel substrate is as follows: an adhesive is applied to the brazing surface of the steel substrate, the flake-shaped rare-earth Lu-doped brazing alloy is laid flat on the brazing surface with the adhesive, and then an adhesive is applied to the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy. Diamond particles are arranged in an orderly manner on the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy, so that the diamond, the flake-shaped rare-earth Lu-doped brazing alloy, and the steel substrate are placed in a sandwich structure from top to bottom.

[0075] Example 6

[0076] This embodiment discloses a method for brazing diamond using a rare earth Lu-doped brazing alloy prepared in Example 2. The brazing method is the same as in Example 5.

[0077] Example 7

[0078] This embodiment discloses a method for brazing diamond using a rare earth Lu-doped brazing alloy prepared in Example 3. The brazing method is the same as in Example 5.

[0079] Example 8

[0080] This embodiment discloses a method for brazing diamond using a rare earth Lu-doped brazing alloy prepared in Embodiment 4. The brazing method is the same as in Embodiment 5.

[0081] Comparative Example 2

[0082] This comparative example discloses a method for brazing diamond using the brazing alloy prepared in Comparative Example 1, and the brazing method is the same as in Example 5.

[0083] Characterization tests:

[0084] (1) The microstructure of the brazing alloy samples prepared in Examples 1-4 and Comparative Example 1 was observed by scanning electron microscopy (SEM). The results are as follows: Figure 1 As shown. Figure 1 In the examples, (a) is the solder alloy sample prepared in Comparative Example 1 (i.e., the solder alloy without rare earth Lu doping), (b) is the solder alloy sample prepared in Example 1 with rare earth Lu doping (i.e., the solder alloy doped with 0.5 wt.% rare earth Lu), (c) is the solder alloy sample prepared in Example 2 with rare earth Lu doping (i.e., the solder alloy doped with 1.0 wt.% rare earth Lu), (d) is the solder alloy sample prepared in Example 3 with rare earth Lu doping (i.e., the solder alloy doped with 1.5 wt.% rare earth Lu), and (e) is the solder alloy sample prepared in Example 4 with rare earth Lu doping (i.e., the solder alloy doped with 2.0 wt.% rare earth Lu). Figure 1 It can be seen that in the solder alloy sample without rare earth Lu doping, a large number of coarse dendrites are neatly arranged, indicating that elemental segregation occurs during solidification. In the solder alloy sample doped with 0.5 wt.% rare earth Lu, the number and size of dendrites are significantly reduced. In the solder alloy sample doped with 1.5 wt.% rare earth Lu, the solder mainly consists of relatively coarse intergranular structures.

[0085] (2) The brazing alloys prepared in Example 3 and Comparative Example 1 were subjected to EDS surface scanning, and the results are as follows: Figure 2 As shown. Figure 2 In the examples, (a) is the solder alloy sample prepared in Comparative Example 1 (i.e., the solder alloy without rare earth Lu doping), and (b) is the rare earth Lu-doped solder alloy sample prepared in Example 3 (i.e., the solder alloy doped with 1.5 wt.% rare earth Lu). Figure 2 It can be seen that the dendritic structure of the undoped Lu solder alloy sample is mainly composed of Ni. The solute element Cr separates from Si and is locally enriched in the solder structure, precipitating in large quantities in the interdendritic region. The Ni content is low in the Cr-rich regions, and the Si-rich regions overlap with the Ni-rich regions, indicating the possible presence of a Ni-Si phase in the solder. The Lu-doped solder alloy sample shows a higher energy dispersive spectral response at the grain boundaries, indicating that Lu is mainly present at the grain boundaries in the solder.

[0086] (3) The brazing alloy samples prepared in Examples 1-4 and Comparative Example 1 were tested and analyzed using an X-ray diffractometer (XRD). The results are as follows: Figure 3 As shown. Figure 3 In the diagram, curve 0 wt.% Lu corresponds to the solder alloy sample prepared in Comparative Example 1, curve 0.5 wt.% Lu corresponds to the solder alloy sample prepared in Example 1, curve 1.0 wt.% Lu corresponds to the solder alloy sample prepared in Example 2, curve 1.5 wt.% Lu corresponds to the solder alloy sample prepared in Example 3, and curve 2.0 wt.% Lu corresponds to the solder alloy sample prepared in Example 4. Figure 3 It can be seen that the rare earth Lu-doped solder alloy sample produced the intermetallic compound NiLu phase, and hard particle phases such as CrB, FeB and Ni3Si were detected in the solder.

[0087] (4) The hardness of the brazing alloy samples prepared in Examples 1-4 and Comparative Example 1 was tested, and the results are as follows: Figure 4 As shown. Figure 4 In the diagram, the horizontal axis "0.0" corresponds to the solder alloy sample prepared in Comparative Example 1 (i.e., the solder alloy without rare earth Lu doping), the horizontal axis "0.5" corresponds to the solder alloy sample prepared in Example 1 (i.e., the solder alloy doped with 0.5 wt.% rare earth Lu), the horizontal axis "1.0" corresponds to the solder alloy sample prepared in Example 2 (i.e., the solder alloy doped with 1.0 wt.% rare earth Lu), the horizontal axis "1.5" corresponds to the solder alloy sample prepared in Example 3 (i.e., the solder alloy doped with 1.5 wt.% rare earth Lu), and the horizontal axis "2.0" corresponds to the solder alloy sample prepared in Example 4 (i.e., the solder alloy doped with 2.0 wt.% rare earth Lu). Figure 4 It can be seen that the brazing alloy sample without rare earth Lu has the lowest Vickers hardness, which is 576.8HV0.1. As the doping amount of rare earth Lu increases, the Vickers hardness of the brazing alloy sample first increases and then decreases. When the doping amount of rare earth Lu is 1.5wt.%, the Vickers hardness increases by 14.5% compared with the brazing alloy sample without rare earth Lu.

[0088] (5) Since the thermal damage suffered by diamond particles during brazing directly affects their processing performance, the thermal damage includes graphitization and residual stress, specifically manifested as the destruction of the surface morphology of the diamond particles. The microstructure of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 was observed by scanning electron microscopy, and the results are as follows: Figure 5 As shown. Figure 5 In the examples, (a) is the brazed diamond sample obtained in Comparative Example 2 (i.e., brazed diamond using a brazing alloy without rare earth Lu doping), (b) is the brazed diamond sample obtained in Example 5 (i.e., brazed diamond using a brazing alloy with 0.5 wt.% rare earth Lu doping), (c) is the brazed diamond sample obtained in Example 6 (i.e., brazed diamond using a brazing alloy with 1.0 wt.% rare earth Lu doping), (d) is the brazed diamond sample obtained in Example 7 (i.e., brazed diamond using a brazing alloy with 1.5 wt.% rare earth Lu doping), and (e) is the brazed diamond sample obtained in Example 8 (i.e., brazed diamond using a brazing alloy with 2.0 wt.% rare earth Lu doping). Figure 5It is known that when brazing diamond using a solder alloy without rare earth Lu doping, the integrity of the brazed diamond particles is compromised, with small fragments breaking off on the surface and the cutting edge becoming incomplete. When brazing diamond using a solder alloy doped with 0.5 wt.% rare earth Lu, large pits were found at the junction of the diamond particles and the solder alloy. This is because the diamond is affected by high temperatures during brazing and eroded by the catalyst elements Ni and Fe, causing some sp3 hybrid orbitals to transform into sp2 orbitals, resulting in graphitization on the diamond particle surface. The graphitized carbon atoms dissolve in the molten solder alloy, forming pits. When the rare earth Lu doping content in the solder alloy is increased to 1.5 wt.% (i.e., the brazed diamond sample obtained in Example 7), the diamond particles remain intact after brazing, without surface breakage or pitting. This is because rare earth Lu combines with excess Ni atoms around the diamond during brazing, reducing the corrosive effect of the catalyst element Ni on the diamond particles at high temperatures.

[0089] (6) EDS surface scanning and EDS line scanning were performed on the bonding interface of the brazed diamond samples prepared in Example 7 and Comparative Example 2, and the results are as follows: Figure 6 and Figure 7 As shown. Figure 6 In the examples, (a) shows a brazed diamond sample obtained in Comparative Example 2 using a brazing alloy without rare earth Lu doping, and (b) shows a brazed diamond sample obtained in Example 7 using a brazing alloy doped with 1.5 wt.% rare earth Lu. Figure 6 It is known that when brazing diamond with a solder alloy without rare earth Lu, the Cr element appears as dispersed strips at the interface between the diamond particles and the solder alloy, forming discontinuous and uneven strips at the interface between the diamond particles and the solder alloy. Figure 7 In the examples, (a) shows a brazed diamond sample obtained in Comparative Example 2 using a brazing alloy without rare earth Lu doping, and (b) shows a brazed diamond sample obtained in Example 7 using a brazing alloy doped with 1.5 wt.% rare earth Lu. Figure 7 The elemental line scan results at the interface show that the thickness of the overlapping region of Cr and C is 2.6 μm. When brazing diamond with a solder alloy doped with 1.5 wt.% rare earth Lu, at the interface between the diamond particles and the solder alloy, Cr exhibits a continuous and uniform chromium-rich band that intersects with the element band formed by C, indicating that Cr reacts with C atoms at the interface, and the resulting uniform carbide layer has a thickness of 5.1 μm.

[0090] (7) During the brazing process, diamond is affected by the high temperature of brazing and the combined influence of the catalyst elements Fe and Ni, resulting in graphitization on the diamond surface and reducing the mechanical properties of the diamond particles. Raman spectroscopy tests were performed on the brazed diamonds prepared in Examples 5-8 and Comparative Example 2, and the results are as follows: Figure 8 As shown, the figures are located at 1332cm. -1 Nearby and 3122cm -1 Mount Raman, located at 1332cm -1 Raman Peak is the Diamond Peak (D), located at 3122cm. -1 The Raman peak is the graphite peak (G), and the degree of graphitization on the surface of diamond particles is determined based on the intensity of the peak. Figure 8 In the diagram, curve 0 wt.% Lu corresponds to the brazed diamond prepared in Comparative Example 2, curve 0.5 wt.% Lu corresponds to the brazed diamond prepared in Example 5, curve 1.0 wt.% Lu corresponds to the brazed diamond prepared in Example 6, curve 1.5 wt.% Lu corresponds to the brazed diamond prepared in Example 7, and curve 2.0 wt.% Lu corresponds to the brazed diamond prepared in Example 8. Figure 8 It can be seen that the graphite peak (G) intensity of the brazed diamond using a solder alloy without rare earth Lu (i.e., the brazed diamond sample obtained in Comparative Example 2) is significantly higher than that of the brazed diamond using a solder alloy doped with rare earth Lu. When brazing diamond particles using a solder alloy doped with rare earth element Lu, the graphite peak is significantly weakened. When brazing diamond using a solder alloy with a rare earth Lu doping content of 1.5 wt.%, the graphite peak on the surface of the diamond particles is extremely low.

[0091] (8) The exposed height of diamond particles after brazing affects the machinability of the brazed samples. Its significance lies not only in the exposure height of the cutting edge but also in its impact on chip handling and removal. The exposed height of diamond particles in the brazed diamonds prepared in Examples 5-8 and Comparative Example 2 was tested using a super depth-of-field microscope. The results are as follows: Figure 9 As shown. Figure 9 In the examples, (a) is the brazed diamond sample obtained in Comparative Example 2 (i.e., brazed diamond using a brazing alloy without rare earth Lu doping), (b) is the brazed diamond sample obtained in Example 5 (i.e., brazed diamond using a brazing alloy with 0.5 wt.% rare earth Lu doping), (c) is the brazed diamond sample obtained in Example 6 (i.e., brazed diamond using a brazing alloy with 1.0 wt.% rare earth Lu doping), (d) is the brazed diamond sample obtained in Example 7 (i.e., brazed diamond using a brazing alloy with 1.5 wt.% rare earth Lu doping), and (e) is the brazed diamond sample obtained in Example 8 (i.e., brazed diamond using a brazing alloy with 2.0 wt.% rare earth Lu doping). Figure 9It is evident that when brazing diamond samples using a solder alloy without rare-earth Lu doping, the diamond particles are almost completely covered, and the diamond cutting edge is barely exposed. Furthermore, due to the excessively high rise of the solder alloy, the chip containment and removal space around the diamond particles is reduced, significantly impacting the machinability of the diamond samples. In contrast, when brazing diamond samples using a solder alloy doped with rare-earth Lu, the exposure height of the diamond particles is significantly improved. The highest exposure height, reaching 55.3% of the diamond particle's height, is achieved when brazing diamond with a solder alloy containing 1.5 wt.% rare-earth Lu doping.

[0092] Furthermore, diamond surfaces possess significant surface energy, preventing brazing alloys from directly wetting their surfaces. This can be achieved through methods such as... Figure 10 The schematic diagram shown illustrates the effect of rare earth Lu doping on the exposure height of diamond particles in brazed diamond samples. Figure 10 In the diagram, (a) shows the wetting effect of the undoped Lu brazing alloy on diamond, and (b) shows the wetting effect of the Lu doped brazing alloy on diamond. In (a) and (b), I, II, III, and IV represent the four stages of brazing diamond using brazing alloy. Stage I is the assembled diamond sample to be brazed; in Stage II, as the temperature increases, graphitization occurs on the diamond surface, and the brazing alloy adheres to the diamond surface; in Stage III, the temperature further increases, and the adhered brazing alloy promotes further graphitization of the diamond and climbs along the surface carbide layer; Stage IV is the brazed diamond sample. During brazing, carbon atoms on the surface of diamond particles undergo graphitization. Cr atoms in the brazing alloy react with the graphitized carbon atoms to form Cr-C compounds in situ, allowing Cr atoms to wet the diamond particle surface. Simultaneously, Ni atoms gradually encapsulate the diamond by adhering to carbides with lower surface energy. The adhesion of Ni and Fe promotes graphitization on the diamond surface, further reacting Cr with the graphitized carbon atoms, ultimately completely encapsulating the diamond particle. In brazing alloys doped with rare earth element Lu, Lu atoms combine with Ni atoms surrounding the diamond to form compounds, reducing the Ni atom concentration around the diamond. Because less brazing alloy adheres to the exposed diamond surface, the promoting effect of Ni and Fe on diamond surface graphitization is reduced, allowing the brazed diamond particles to retain a larger exposed height.

[0093] (9) The phase composition of the carbides on the surface of diamond particles in the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 was studied using micro-area XRD (MA-XRD). The results are as follows: Figure 11 As shown. Figure 11In the diagram, curve 0 wt.% Lu corresponds to the brazed diamond prepared in Comparative Example 2, curve 0.5 wt.% Lu corresponds to the brazed diamond prepared in Example 5, curve 1.0 wt.% Lu corresponds to the brazed diamond prepared in Example 6, curve 1.5 wt.% Lu corresponds to the brazed diamond prepared in Example 7, and curve 2.0 wt.% Lu corresponds to the brazed diamond prepared in Example 8. Figure 11 It is known that two types of carbides, Cr7C3 and Cr3C2, exist on the diamond surface. During the brazing process of Ni-Cr composite solder alloy, the morphology of the carbides on the diamond surface is affected by the solubility of C atoms in Ni. Cr atoms first react with the graphitized carbon atoms on the diamond particle surface, forming a dense Cr3C2 layer parallel to the diamond particle surface. The carbide layer continues to absorb carbon atoms dissolved from the diamond particle surface, forming fine, short rod-shaped Cr7C3 in a direction different from the orientation of the Cr3C2 layer. The growth of carbides on the diamond surface can be described by the following formula:

[0094]

[0095] (10) The brazed diamond samples obtained in Examples 5-8 and Comparative Example 2 were subjected to etching treatment: the brazed diamond samples were etched with aqua regia to obtain diamond particles without brazing alloy. The etched diamond particles were cleaned with alcohol and dried in a constant temperature oven. The surface carbide morphology was studied by SEM observation. The results are as follows: Figure 12 As shown. Figure 12In the images, (a) and (f) are SEM images and partial magnified images of the surface carbides of the brazed diamond prepared in Comparative Example 1; (b) and (g) are SEM images and partial magnified images of the surface carbides of the brazed diamond prepared in Example 5; (c) and (h) are SEM images and partial magnified images of the surface carbides of the brazed diamond prepared in Example 6; (d) and (i) are SEM images and partial magnified images of the surface carbides of the brazed diamond prepared in Example 7; and (e) and (j) are SEM images and partial magnified images of the surface carbides of the brazed diamond prepared in Example 8. As shown in (a) and (c), when brazing diamond using a solder alloy without rare earth doping (Lu), the surface carbides of the diamond particles exhibit ordered elongated compounds. Cracks appear in the carbide layer, and the carbide layer detaches from the observed diamond particle surface. Pitfalls caused by the dissolution of C atoms are also observed. The doping of rare earth element Lu affects the morphology of carbides on the surface of diamond particles, causing the carbides to gradually transform into short rod-like shapes. When brazing diamond with a solder alloy containing 1.5 wt% rare earth Lu, as shown in (d) and (i), no cracks were observed on the surface of the carbide layer, and the morphology of the carbides changed from short rod-like to granular. The reduction in cracks may be due to the fact that rare earth Lu improves the difference in the coefficient of thermal expansion between the solder alloy and the diamond particles, effectively reducing the residual stress on the diamond particles after welding.

[0096] (11) After brazing, the structure of the diamond is damaged to a certain extent, resulting in a decrease in mechanical properties and consequently a decrease in the machinability of diamond tools. Therefore, this study uses a compressive strength test to characterize the mechanical properties of the brazed diamond and to study the performance loss of the diamond particles after brazing. To verify the mechanical properties of the diamond particles after brazing, the compressive strength of the brazed diamond particles in Examples 5-8 and Comparative Example 2 was tested using a compressive strength tester. This included: etching the brazed diamond samples with aqua regia to obtain diamond particles without brazing alloy; cleaning the etched diamond particles with alcohol and drying them in a constant temperature oven to obtain etched single diamond particles. The compressive strength of the etched single diamond particles was tested using an HP603 compressive strength tester. The test force was slowly applied until the diamond particles broke, and the test force value was recorded. Each experiment was repeated 30 times to reduce experimental error. The formula for calculating the compressive strength of diamond particles is:

[0097]

[0098] in, σ (MPa) represents compressive strength. P (N) represents the static pressure test force. d (mm) represents the average diameter of the diamond particle. d =0.425mm. The test results for compressive strength are as follows: Figure 13 As shown. Figure 13In the diagram, the horizontal axis "0.0" corresponds to the brazed diamond prepared in Comparative Example 2, the horizontal axis "0.5" corresponds to the brazed diamond prepared in Example 5, the horizontal axis "1.0" corresponds to the brazed diamond prepared in Example 6, the horizontal axis "1.5" corresponds to the brazed diamond prepared in Example 7, and the horizontal axis "2.0" corresponds to the brazed diamond prepared in Example 8. Figure 13 It can be seen that the average compressive strength of the brazed diamond particles prepared in Comparative Example 2 is 1481.27 MPa, which is much lower than that of the brazed diamond sample prepared in Example 7. The reduction in the mechanical properties of the diamond is due to the combined effects of graphitization and internal stress. The compressive strength of the brazed diamond sample prepared in Example 7 reached 3058.59 MPa, indicating that the diamond particles experienced the least loss of mechanical properties in the experiment. This is because the use of rare-earth Lu-doped brazing alloy results in less Ni erosion of the diamond particles during brazing, and the carbide layer formed on the surface of the diamond particles facilitates stress release. Therefore, rare-earth Lu-doped brazing alloy can effectively reduce the loss of mechanical properties of diamond particles during the brazing process.

[0099] (12) During the brazing process, complex element diffusion phenomena occur between the brazing alloy and the steel substrate, affecting the hardness of the brazing interface. To study the interfacial bonding strength between the rare-earth Lu-doped brazing alloy and the steel substrate, the interface hardness of the brazed diamond samples prepared in Examples 5-8 and Comparative Example 2 was tested using a Vickers hardness tester. The test results are as follows: Figure 14 As shown. Figure 14 In the diagram, curve 0Lu corresponds to the brazed diamond prepared in Comparative Example 2, curve 0.5Lu corresponds to the brazed diamond prepared in Example 5, curve 1.0Lu corresponds to the brazed diamond prepared in Example 6, curve 1.5Lu corresponds to the brazed diamond prepared in Example 7, and curve 2.0Lu corresponds to the brazed diamond prepared in Example 8. Figure 14 It can be seen that the microhardness from the steel matrix to the brazing alloy region exhibits a trend of first increasing and then decreasing, reaching its maximum at the interface. This phenomenon may be related to element diffusion and phase transformation in the interface region, where high-hardness intermetallic compounds or solid solutions are formed. The brazing interface without rare-earth Lu exhibits the lowest microhardness, indicating that Lu doping has a significant effect on improving interface hardness. With increasing Lu doping concentration, the microhardness of the brazing interface gradually increases, reaching its maximum when the Lu doping concentration is 1.5 wt.%. Lu doping may promote a more uniform element distribution and a denser microstructure at the interface, thereby improving the mechanical properties of the interface.

[0100] (13) To study the effect of rare earth Lu doping on the wear characteristics of brazed diamond samples, the brazed diamond samples were tested using a friction and wear testing machine. The diamond particles after the wear test were as follows: Figure 15 As shown. Figure 15 In the figures, (a) shows the morphology of the diamond particles after the wear test of the brazed diamond prepared in Comparative Example 2; (b) shows the morphology of the diamond particles after the wear test of the brazed diamond prepared in Example 5; (c) shows the morphology of the diamond particles after the wear test of the brazed diamond prepared in Example 6; (d) shows the morphology of the diamond particles after the wear test of the brazed diamond prepared in Example 7; and (e) shows the morphology of the diamond particles after the wear test of the brazed diamond prepared in Example 8. Figure 15 It can be seen that the diamond particles all exhibited varying degrees of damage on their surfaces. In (a), the diamond particles showed cleavage fracture, with the fracture location occurring at the interface between the diamond and the brazing alloy. This is because the internal stress experienced by the diamond particles at this location is the greatest. With the increase of rare earth Lu doping, the diamond particles exhibited different morphologies after wear. As shown in (b), (c), and (e), the brazed diamond samples prepared in Examples 5, 6, and 8 showed a large fragmented morphology after wear, which greatly affected the service life and stability of the brazed diamond tools. As shown in (d), the brazed diamond sample prepared in Example 7 showed small fragments after wear. The research results indicate that the doping of rare earth Lu reduced the loss of mechanical properties of diamond particles during the brazing process. When the rare earth Lu doping content was 1.0 wt.%, the brazed diamond sample achieved relatively optimal wear resistance and processing stability.

[0101] Furthermore, 99% alumina ceramic was used as the grinding partner for the brazed diamond sample. Wear tests were conducted on a tribometer (MM-W1B) with a pin-disc type, a test force of 100 N, a test time of 1800 s, and a rotation speed of 200 r / min. The amount of alumina ceramic removed before and after the test was weighed using an analytical balance, and the friction coefficient after the test was recorded.

[0102] The coefficient of friction indicates the stability of brazed diamond specimens in friction tests. In the initial stage of friction, the brazed specimen undergoes unstable wear with the alumina ceramic, leading to a drastic change in the coefficient of friction. As the friction time increases, the cutting edges of the diamond particles gradually penetrate the workpiece, resulting in stable wear. The results of the coefficient of friction measurement are as follows: Figure 16 As shown. Figure 16In the diagram, curve 0 wt.% Lu corresponds to the brazed diamond prepared in Comparative Example 2, curve 0.5 wt.% Lu corresponds to the brazed diamond prepared in Example 5, curve 1.0 wt.% Lu corresponds to the brazed diamond prepared in Example 6, curve 1.5 wt.% Lu corresponds to the brazed diamond prepared in Example 7, and curve 2.0 wt.% Lu corresponds to the brazed diamond prepared in Example 8. Figure 16 It can be seen that the friction coefficient of the brazed diamond sample prepared in Comparative Example 2 fluctuated during the wear process. This is because the diamond particles continuously broke during the test, causing changes in the friction area between the brazed sample and the alumina ceramic, resulting in an extremely unstable friction coefficient. In Example 7, the friction coefficient of the brazed diamond sample, after experiencing an initial unstable wear stage, reached stable wear with the workpiece after 400 seconds. At this point, the friction coefficient fluctuated little, and the wear tended to stabilize. The brazed diamond sample prepared in Example 7 had a low friction coefficient, generating less heat during the friction process and improving the service life of the brazed sample.

[0103] The test results of alumina ceramic removal amount are as follows: Figure 17 As shown. Figure 17 In the diagram, the horizontal axis "0.0" corresponds to the brazed diamond prepared in Comparative Example 2, the horizontal axis "0.5" corresponds to the brazed diamond prepared in Example 5, the horizontal axis "1.0" corresponds to the brazed diamond prepared in Example 6, the horizontal axis "1.5" corresponds to the brazed diamond prepared in Example 7, and the horizontal axis "2.0" corresponds to the brazed diamond prepared in Example 8. Figure 17 It can be seen that when brazing diamond with an undoped Lu-based solder alloy, the removal amount of alumina ceramic by the brazed diamond sample is low, only 27.9 mg. When brazing diamond with a Lu-doped solder alloy, the removal amount of alumina ceramic by the brazed diamond sample is improved. Among them, the highest removal amount of alumina ceramic is achieved when brazing diamond with a solder alloy doped with 1.5 wt.% Lu, reaching 45.4 mg. This indicates that Lu doping can effectively reduce the thermal damage to diamond particles caused by the solder alloy during brazing, while preserving the mechanical properties of the diamond particles.

[0104] 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 rare-earth Lu-doped solder alloy, characterized in that, Includes the following steps: Step (1): Weigh the metal ingots of each component raw material Ni, Cr, B, Si, Fe and Lu, and clean them to remove impurities; The raw materials, by mass percentage, are: 10-12% Cr, 3-4% B, 3-4% Si, 4-5% Fe, 0.5-2% Lu, and the balance Ni; Step (2): Place the cleaned metal ingots of each component raw material into a vacuum arc melting furnace, evacuate, and melt to obtain the molten brazing alloy ingot. Step (3): Cut the smelted brazing alloy ingot to obtain brazing alloy sheets. After polishing, the brazing alloy sheets are obtained as sheet-like rare earth Lu-doped brazing alloy.

2. The method for preparing a rare-earth Lu-doped solder alloy according to claim 1, characterized in that, In step (2), the vacuuming process includes: First, the atmosphere pressure inside the vacuum arc melting furnace chamber is evacuated to a vacuum level <20 Pa using a mechanical pump. Argon gas is then introduced to bring the atmosphere pressure to -0.05 MPa. Next, the atmosphere pressure is evacuated to a vacuum level <20 Pa using a mechanical pump. Finally, the atmosphere pressure is evacuated to 5 × 10⁻⁶ Pa using a molecular pump. -3 Below Pa.

3. The method for preparing a rare-earth Lu-doped solder alloy according to claim 1, characterized in that, In step (2), the smelting process specifically includes: smelting the metal ingots of each component raw material under a current of 180~220A until the metal ingots of each component raw material are completely melted, and then stopping the power supply. The smelting process is repeated 3-4 times.

4. The method for preparing a rare-earth Lu-doped solder alloy according to claim 1, characterized in that, The step (3) specifically includes: cutting the smelted brazing alloy ingot with diamond wire to obtain brazing alloy flakes, and polishing the brazing alloy flakes with 320-mesh, 600-mesh and 1000-mesh sandpaper in sequence to obtain sheet-like rare earth Lu-doped brazing alloy.

5. A rare earth Lu-doped solder alloy prepared by the method for preparing rare earth Lu-doped solder alloy as described in any one of claims 1-4.

6. The application of a rare-earth Lu-doped solder alloy as described in claim 5, characterized in that, The application includes brazing diamond using the rare-earth Lu-doped solder alloy; The method for brazing diamond using a rare-earth Lu-doped brazing alloy includes the following steps: Step S1: Select diamond particles, clean and dry them; select a steel substrate, grind the brazing surface, clean and dry it. Step S2: After bonding the diamond, the sheet-like rare earth Lu-doped brazing alloy, and the steel substrate, place them in a vacuum molybdenum wire brazing furnace for brazing.

7. The application of the rare-earth Lu-doped solder alloy according to claim 6, characterized in that, In step S1, the diamond particles have a diameter of 425 μm, and the steel matrix is ​​made of 45... # The steel substrate measures 15mm × 10mm × 6mm.

8. The application of the rare-earth Lu-doped solder alloy according to claim 6, characterized in that, In step S2, the bonding process of diamond, flake-shaped rare-earth Lu-doped brazing alloy, and steel substrate includes: applying an adhesive to the brazing surface of the steel substrate, spreading the flake-shaped rare-earth Lu-doped brazing alloy flat on the brazing surface coated with adhesive, applying adhesive to the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy, and orderly arranging diamond particles on the upper surface of the flake-shaped rare-earth Lu-doped brazing alloy, so that diamond, flake-shaped rare-earth Lu-doped brazing alloy, and steel substrate are placed in a sandwich structure from top to bottom.

9. The application of the rare-earth Lu-doped solder alloy according to claim 6, characterized in that, In step S2, the brazing process specifically includes: maintaining the vacuum degree in the vacuum molybdenum wire brazing furnace below 5×10-3 Pa, heating to 1080℃ at a heating rate of 10℃ / min, holding at 1080℃ for 5 min, cooling to 500℃ at a rate of 10℃ / min, and obtaining brazed diamond after furnace cooling.

Images