A high-CuNi content, low-melting-point, high-entropy alloy brazing material and brazing diamond thereof

Abstract

A high-entropy alloy brazing material with a high CuNi content and a low melting point, and its use for brazing diamonds, is disclosed. The chemical composition of the high-entropy alloy brazing material is as follows: Cu: 33%-35%, Ni: 33%-35%, Fe: 8%-10%, Cr: 8%-10%, and Sn: 8%-10%. The alloy is prepared by vacuum arc melting. Upon cooling, the high-entropy alloy forms a FeCrNi-rich FCC phase, a Cu-rich phase, and a Sn-rich phase. It has a hardness of 330 HV and a melting point of 935°C, enabling diamond brazing at relatively low temperatures below 1000°C. Compared to conventional nickel-based brazing materials, which require higher temperatures above 1050°C for diamond brazing, the high-entropy alloy brazing material significantly reduces diamond brazing temperatures and post-weld thermal damage. The diamond surface morphology remains intact after brazing, with high abrasive grain exposure and no significant cracks, corrosion pits, or graphitization. At the same time, the high entropy effect and hysteresis diffusion effect reduce the formation of brittle phase in the brazing seam, ensure the mechanical properties of the joint, have higher holding force and wettability on diamond, and have better wear resistance after brazing.

Description

Technical Field

[0001] The invention belongs to the technical field of brazing, and in particular relates to a high-CuNi content, low-melting-point, high-entropy alloy brazing material and a method for brazing diamonds thereof. Background Art

[0002] Brazed diamond tools are often used to process hard and brittle materials due to their high strength, hardness, and wear resistance. Currently, the main brazing fillers used for brazing diamond tools are Ag-based, Ni-based, and Cu-based. Ag-based fillers wet diamond well, but are prohibitively expensive. Ni-based fillers offer high wear resistance and bonding strength, but they also have a high melting point. After high-temperature brazing, brittle compounds easily form on the diamond surface, leading to thermal damage such as graphitization. Cu-based fillers have a low melting point, good wettability for diamond, and a relatively low cost for the Cu element, making them a widely used filler material for diamond brazing in industrial applications. The main copper-based fillers include Cu-Sn, Cu-Mn, and Cu-Fe. However, Cu-based fillers have low hardness and strength, generally below 200 HV, resulting in low wear resistance of the brazing layer and low bonding strength with diamond. This can lead to premature shedding of diamond grains during high-speed grinding.

[0003] High-entropy alloys (HEAs), a rapidly developing new alloy, have attracted significant attention due to their exceptional mechanical properties, including high strength, high toughness, chemical stability, and corrosion resistance. In particular, their "high entropy effect" and "delayed diffusion effect" can significantly reduce excessive diffusion between the filler metal and the base material, as well as the formation of large amounts of brittle compounds. Furthermore, utilizing a "cocktail effect" of ingredients, reactive elements can be added to improve the wettability of the filler metal on the base material surface, demonstrating significant advantages in brazing high-melting-point dissimilar metals or hard ceramics. However, most HEAs have high melting points, making it difficult to avoid the thermal damage that can occur during high-temperature brazing of diamond tools. The present invention provides a high-CuNi content, low-melting-point HEAs brazing filler metal. Its high Cu / Ni content combines the advantages of both Cu- and Ni-based fillers. The addition of Sn lowers its melting point to 935°C, enabling diamond brazing at temperatures below 1000°C. Supersaturated solid solution strengthening significantly improves the filler metal's hardness and wear resistance compared to Cu-based fillers, while significantly reducing thermal damage issues such as complex brittle phases at the brazed joint and graphitization of the diamond surface compared to Ni-based fillers. Summary of the Invention

[0004] The present invention provides a high-CuNi content, low-melting-point high-entropy alloy brazing material, a preparation method, and diamond brazing methods. The high-entropy alloy brazing material of the present invention has a low melting point, improving the thermal damage problems of conventional Ni-based brazing materials, such as the formation of complex brittle phases and graphitization of the diamond surface caused by high brazing temperatures. Furthermore, its mechanical properties, such as hardness and wear resistance, significantly surpass those of existing copper-based brazing materials, significantly improving the processing performance and service life of brazed diamond tools.

[0005] To achieve the above objectives, the present invention discloses a high-CuNi content, low-melting-point, high-entropy alloy solder comprising the following atomic percentages: Cu: 33%-35%, Ni: 33%-35%, Fe: 8%-10%, Cr: 8%-10%, and Sn: 8%-10%. The solder alloy consists of an FeCrNi-rich FCC phase, a Cu-rich phase, and a Sn-rich solid solution phase, achieving a hardness of 330 HV.

[0006] The invention discloses a high-CuNi content, low-melting-point, high-entropy alloy solder with a melting point of 935°C. Diamond brazing can be achieved below 1000°C. The solder has good wettability with diamond during high-temperature brazing.

[0007] The present invention also discloses a method for preparing the high entropy alloy solder, comprising the following steps:

[0008] (1) Weigh the corresponding metal element raw materials according to mass percentage, put them into alcohol and acetone solution, clean them with ultrasonic waves for 10 minutes, and then dry them;

[0009] (2) The raw materials in step (1) are placed in a vacuum arc melting furnace in the order of melting point from low to high, and the vacuum degree is 5×10 -3 MPa, with argon as the protective gas, the alloy was smelted repeatedly for 5 times, and after cooling with the furnace, it was taken out from the furnace to obtain a high entropy alloy ingot.

[0010] Preferably, the purity of the elemental Fe, Cr, Ni, Cu, and Sn in the low-melting-point high-entropy alloy in step (1) is greater than 99.9%; and the pulse arc heating current during smelting in step (2) is in the range of 50 to 100 A.

[0011] The present invention also discloses a method for brazing diamond tools with the high entropy alloy brazing material, comprising the following steps:

[0012] (1) Cut the high entropy alloy ingot into thin sheets by wire cutting, place it in an acetone alcohol solution, clean it with ultrasonic waves for 10 minutes, and dry it;

[0013] (2) Polish the surface of the No. 45 steel block with 400# and 600# sandpaper, place the No. 45 steel block and diamond abrasive in acetone and alcohol solution for ultrasonic cleaning, and then dry;

[0014] (3) The sheet brazing material is spread on the surface of the 45 steel block, and the diamond abrasive is spread on the surface of the brazing material layer, and then placed in a vacuum hot pressing furnace for brazing. The vacuum degree is 5.0×10 -3 MPa, keep warm at 970℃~1000℃ for 8min, and take out the sample after cooling to room temperature.

[0015] Preferably, in step (1), the solder thickness is 0.15 mm and the size is 15 mm×6 mm; in step (2), the substrate size is 15 mm×10 mm×6 mm; and in step (3), the heating rate is 10°C / min.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The high-CuNi content, low-melting-point, high-entropy alloy of the present invention forms a FeCrNi-rich-FCC phase, a Cu-rich phase, and a Sn-rich solid solution phase after solidification. The low-melting-point Sn-rich phase first melts at 836°C, and the alloy finally melts completely into a liquid phase at 935°C. This allows the alloy brazing material to achieve high-strength bonding between diamond and the brazing alloy at a relatively low brazing temperature below 1000°C. Compared with traditional nickel-based brazing materials that require higher brazing temperatures above 1050°C, high-temperature thermal damage to diamond after brazing is significantly reduced.

[0018] (2) In the high CuNi content, low melting point high entropy alloy described in the present invention, the solid solution strengthening effect of the high hardness Fe, Cr, Ni elements in the FeCrNi-rich FCC reinforcing phase and the Cu-rich and Sn-rich phases makes the hardness of the high entropy alloy solder reach 330HV, which is higher than the microhardness of traditional Cu-based solder below 200HV.

[0019] (3) In the high CuNi content, low melting point, high entropy alloy described in the present invention, it was found that the equimolar addition of Ni and Cu elements increased the system entropy of the brazing alloy. Moreover, due to the infinite solid solution of Cu and Ni, the catalytic effect of the catalyst element Ni on the graphitization of diamond was weakened, and no thermal damage such as graphitization occurred on the diamond surface after brazing. Sn has a low melting point and can significantly reduce the melting point of the alloy and improve its wettability to diamond. The addition of Fe and the strong carbide-forming element Cr further increases the mixing entropy of the alloy and has the effect of improving the high-strength bonding between the brazing filler metal and diamond.

[0020] (4) Due to the thermodynamic high entropy effect and hysteresis diffusion effect, the high CuNi content, low melting point high entropy alloy of the present invention does not form complex brittle intermetallic compounds at the brazing seam, which significantly improves the mechanical properties and service life of the brazed diamond tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 X-ray phase analysis of the low melting point high entropy alloy solder according to the embodiment of the present invention;

[0022] Figure 2 This is the SEM solidification structure of the low melting point high entropy alloy solder according to the embodiment of the present invention;

[0023] Figure 3 This is the DSC curve of the low melting point high entropy alloy solder according to the embodiment of the present invention;

[0024] Figure 4 The surface morphology of diamond after brazing with high entropy alloy solder according to an embodiment of the present invention;

[0025] Figure 5 This is the Raman spectrum of the diamond surface after brazing with high entropy alloy according to the embodiment of the present invention;

[0026] Figure 6 is the wetting angle between the high entropy alloy solder and diamond during brazing according to the embodiment of the present invention;

[0027] Figure 7 These are the friction and wear results after brazing diamond at different temperatures according to the embodiments of the present invention. DETAILED DESCRIPTION

[0028] In order to better understand the technical solution provided by the present invention, the present invention is further described below with reference to the accompanying drawings and examples.

[0029] The atomic percentages of the high entropy alloy brazing material (Cu: 33%-35%, Ni: 33%-35%, Fe: 8%-10%, Cr: 8%-10%, Sn: 8%-10%) were converted into mass percentages, and elemental iron, chromium, copper, iron, nickel, and tin were weighed. The weighed raw materials were ultrasonically cleaned in an alcohol and acetone solution for 10 minutes, and then dried. The prepared raw materials were placed in a vacuum arc melting furnace in order of melting point from low to high, and the melting was repeated 5 times to obtain an alloy ingot. During the melting process, the vacuum degree was maintained at 5.0×10 -3 MPa, the pulse arc heating current range is 50-100A, and high-purity argon is used as the shielding gas. The melted high-entropy alloy ingot is cut into thin sheets with a thickness of 0.15mm and a size of 15mm×6mm using wire cutting. The sheets are then placed in an alcohol-acetone solution for cleaning for 10 minutes and then dried. In this embodiment, the substrate is 45# steel with a size of 15mm×10mm×6mm. The surface of the 45# steel substrate is polished using 400# and 600# sandpaper to remove the oxide on the substrate surface. The diamond abrasive grains and 45# steel are ultrasonically cleaned in an acetone and alcohol solution for 10 minutes and then dried. The sheet brazing material is spread flat on the surface of the 45# steel substrate, and the diamond abrasive grains are neatly spread on the surface of the brazing material layer. The sheet is placed in a vacuum hot press furnace and brazed in a vacuum environment at 970℃-1060℃ for 8 minutes. The sample is removed after cooling to room temperature.

[0030] Figure 1 This is the XRD pattern of the low melting point high entropy alloy in this embodiment. It can be seen that the alloy is mainly composed of FeCrNi-FCC-rich phase, Cu-rich phase and Sn-rich solid solution phase, without complex brittle phase. Figure 2Table 1 shows the EDS spectrum analysis of three typical areas in the figure, where area A is the FeCrNi-rich FCC phase, area B is the Cu-rich phase, and area C is the Sn-rich phase.

[0031] Table 1 Figure 2 EDS spectrum analysis of three typical tissue areas (at.%)

[0032]

[0033] Figure 3 This is the DSC curve of the low melting point high entropy alloy in this embodiment. It can be seen from the figure that the Sn-rich phase first melts at 836°C, and the melting point of the alloy is completely melted at 935°C. Figure 4 This is the surface morphology of the high-entropy alloy brazed diamond in this embodiment. It can be seen that the diamond is firmly bonded to the substrate, the diamond surface morphology is complete, has a high exposure, and there are no defects such as cracks and pits on the surface. Figure 5 This is the Raman spectrum of the diamond surface after brazing with the low melting point high entropy alloy in this embodiment. In the figure, only the 1332 cm -1 There is no obvious graphite peak at the diamond peak, indicating that there is no obvious thermal damage such as graphitization on the surface of the diamond after brazing. Figure 6 The wetting angle between the high entropy alloy brazing material and diamond during brazing is only 11°, which shows good wettability. Figure 7 The friction and wear results of diamond brazed with a low-melting-point high-entropy alloy at different temperatures in this example are shown. It can be seen that at a brazing temperature of 1000°C, the removal of the grinding material tile reached its highest level, reaching 68 mg. In contrast, under the same friction and wear experimental conditions, the conventional Ni-Cr-B-Si-Fe brazing filler metal used in the present invention for diamond brazing only achieved a tile removal rate of 36 mg. This demonstrates that the high-entropy alloy brazing filler metal disclosed in this invention not only exhibits optimal brazing performance at 1000°C, but also exhibits significantly higher wear resistance than the Ni-based brazing filler metals currently widely used in industry.

Claims

1. A high CuNi content, low melting point, high entropy alloy solder, characterized in that The high-entropy alloy solder consists of an FeCrNi-rich FCC phase, a Cu-rich phase and a Sn-rich solid solution phase, has no complex brittle phase, and has the following chemical compositions in atomic percentage: Cu: 35%, Ni: 35%, Fe: 10%, Cr: 10%, and Sn: 10%.

2. A high CuNi content low melting point high entropy alloy solder according to claim 1, characterized in that The melting point of the high entropy alloy brazing material is 935°C, and diamond can be brazed at 970-1000°C with a brazing vacuum of 5.0×10 -3 MPa, the holding time is 8 min, the heating rate is 10℃ / min, there is no graphitization damage on the diamond surface after welding, and it has good bonding strength with the brazing filler metal.

3. A high CuNi content low melting point high entropy alloy solder according to claim 1, characterized in that The hardness and wear resistance of the high-entropy alloy brazing material after brazing diamond are higher than those of Cu-based and Ni-based brazing materials, and the complex brittle phase and diamond thermal damage problems at the brazed joint are significantly better than those of Ni-based brazing materials. The high-entropy alloy brazing material can be applied to the fields of grinding wheels, drill bits, and saw blades.

Images