Assembly structure and preparation method of polycrystalline diamond

Abstract

The invention relates to the field of manufacturing of superhard materials, in particular to a polycrystalline diamond assembly structure and a preparation method thereof.The polycrystalline diamond assembly structure comprises a metal cup, a cobalt tube used for containing diamond powder is arranged in the metal cup in a sleeved mode, the metal cup and the cobalt tube are the same in height, and a metal cup cover made of the same material as the metal cup is arranged at the top of the metal cup; the outer side of the metal cup is sleeved with a salt pipe, salt pieces making contact with the end of the metal cup are arranged at the upper end and the lower end in the salt pipe, the sum of the height of the metal cup and the height of the two salt pieces is equal to the height of the salt pipe, and the outer side of the salt pipe is sleeved with a dolomite pipe with the same height as the salt pipe. The outer side of the dolomite tube is sleeved with a heating carbon tube as high as the dolomite tube, and heating carbon sheets are placed at the upper end and the lower end of the heating carbon tube; the device is simple in structure and process, polycrystalline diamond with the length-diameter ratio can be prepared, and polycrystalline fracture is avoided.

Description

Technical Field

[0001] The invention relates to the field of superhard material manufacturing, and in particular to an assembly structure and a preparation method of polycrystalline diamond. Background Art

[0002] Polycrystalline diamond (PCD) refers to a diamond material made of graphite using a special processing technology. Compared with single crystal diamond, PCD has advantages such as good durability, good wear resistance, high hardness, and high impact strength. It has broad application prospects in many fields such as precision cutting, hard rock mining, mechanical processing, and mold manufacturing. With the promotion and application of PCD in the field of micro-drilling, the demand for high aspect ratio PCD materials is increasing. Traditional assembly methods such as Figure 2 As shown, polycrystalline diamond with an aspect ratio of less than 1.5 can be produced. When the polycrystalline aspect ratio is greater than 1.5, conventional preparation methods will cause problems such as cracks and intermediate fractures. At the same time, in the traditional preparation of polycrystalline diamond, diamond powder and binder need to be premixed, which is cumbersome and inefficient. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an assembly structure and preparation method of polycrystalline diamond. The present invention has a simple structure and a simple process, and can prepare polycrystalline diamond with a high aspect ratio and avoid the occurrence of polycrystalline fracture.

[0004] The objective of the present invention is achieved through the following measures: an assembly structure of polycrystalline diamond, comprising a metal cup, a cobalt tube for containing diamond powder is installed inside the metal cup, the metal cup is at the same height as the cobalt tube, a metal cup cover made of the same material as the metal cup is arranged on the top of the metal cup, a salt tube is installed outside the metal cup, salt sheets in contact with the ends of the metal cup are placed at both the upper and lower ends of the salt tube, the sum of the heights of the metal cup and the two salt sheets is equal to the height of the salt tube, a dolomite tube with the same height as the salt tube is installed outside the salt tube, a heating carbon tube with the same height as the dolomite tube is installed outside the dolomite tube, and heating carbon sheets are placed at the upper and lower ends of the heating carbon tube.

[0005] In the above-mentioned polycrystalline diamond assembly structure, the aspect ratio of the metal cup is greater than 2.

[0006] In the above-mentioned polycrystalline diamond assembly structure, the aspect ratio of the cobalt tube is greater than 2.

[0007] In the above-mentioned polycrystalline diamond assembly structure, the thickness of the cobalt tube is 0.05-1.0 mm.

[0008] In the above-mentioned polycrystalline diamond assembly structure, the material of the metal cup is one or a combination of niobium, tantalum, molybdenum and zirconium.

[0009] The method for preparing polycrystalline diamond using the above-mentioned polycrystalline diamond assembly structure comprises the following steps:

[0010] S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2;

[0011] S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material;

[0012] S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube.

[0013] S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe;

[0014] S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom;

[0015] S6: placing the graphite tube in a pyrophyllite block and sintering it in a six-sided top press at a sintering temperature of 1500-1600°C for 5-10 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

[0016] The cobalt tube in the present invention can replace the traditional cobalt powder to provide a polycrystalline diamond binder and reduce the mixing process. Cobalt is a binder for polycrystalline materials. During the sintering process, the cobalt tube will melt into the diamond powder and react with the diamond to sinter into a polycrystalline diamond material.

[0017] The main function of the salt tube is to provide a uniform pressure field. The salt is in a molten liquid state under sintering temperature conditions.

[0018] Dolomite tubes release gas at high temperatures to increase the pressure around the cavity, avoiding the problem of polycrystalline fracture caused by high pressure in the upper and lower directions.

[0019] The heated carbon tubes and carbon sheets are both heating elements that provide heat to the sintered polycrystals.

[0020] Beneficial effects of the present invention: In view of the problems of cracks and intermediate fractures in traditional assembly of polycrystalline diamond with high aspect ratio structure, the present invention provides a high aspect ratio assembly structure, utilizes a cobalt tube to provide a polycrystalline sintering binder, reduces the mixing process of diamond and cobalt powder, and simultaneously adds a dolomite tube outside the salt tube to release gas at high temperature to increase the pressure around the cavity, thereby avoiding the problem of polycrystalline fracture caused by high pressure in the upper and lower directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the assembly structure of polycrystalline diamond in the present invention;

[0022] Figure 2 Schematic diagram of the assembly structure of traditional polycrystalline diamond.

[0023] In the figure: 1-heated carbon tube, 2-dolomite tube, 3-salt tube, 4-metal cup, 5-cobalt tube, 6-diamond powder, 7-heated carbon sheet, 8-salt sheet. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1: Figure 1 As shown, a polycrystalline diamond assembly structure includes a metal cup 4, a cobalt tube 5 is mounted inside the metal cup 4, and the cobalt tube 5 is used to contain diamond powder 6, that is, the diamond powder is placed in the metal cup with the cobalt tube, and the cobalt tube is used to replace the cobalt powder to provide a polycrystalline sintering binder. The metal cup 4 is the same height as the cobalt tube 5, the aspect ratio of the metal cup is greater than 2, and the aspect ratio of the cobalt tube is greater than 2, thereby a polycrystalline diamond with an aspect ratio greater than 2 can be produced, the thickness of the cobalt tube is 0.05-1.0mm, and the material of the metal cup is a high-temperature metal, such as one or more combinations of niobium, tantalum, molybdenum, and zirconium. The metal cup can play a shielding and protective role to prevent external impurities from entering the polycrystalline material during the synthesis process, and at the same time plays an important role in the diffusion of cobalt and the growth and bonding of diamond powder. Selecting a suitable metal material is of great significance to the quality of polycrystalline diamond production.

[0026] A metal cup cover made of the same material as the metal cup is arranged on the top of the metal cup 4, a salt tube 3 is mounted on the outside of the metal cup, and salt sheets 8 are placed at both ends of the salt tube to contact the ends of the metal cup, and the sum of the heights of the metal cup and the two salt sheets is equal to the height of the salt tube. A dolomite tube 2 with the same height as the salt tube is mounted on the outside of the salt tube 3, and the dolomite tube releases gas at high temperature to increase the pressure around the cavity, thereby avoiding the problem of polycrystalline fracture caused by high pressure in the upper and lower directions.

[0027] A heating carbon tube 1 having the same height as the dolomite tube is sleeved on the outside of the dolomite tube 2, and heating carbon sheets 7 are placed at the upper and lower ends of the heating carbon tube.

[0028] The method for preparing polycrystalline diamond using the above-mentioned polycrystalline diamond assembly structure comprises the following steps:

[0029] S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2;

[0030] S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material;

[0031] S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube.

[0032] S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe;

[0033] S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom;

[0034] S6: Place the graphite tube in a pyrophyllite block and sinter it in a six-sided top press at a sintering temperature of 1500°C for 5 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

[0035] In this embodiment, the above method can be used to prepare polycrystalline diamond with a height of 15 mm and a diameter of 6 mm, and an aspect ratio of 2.5.

[0036] Example 2: The assembly structure of the polycrystalline diamond in this example is the same as that in Example 1, and will not be repeated here.

[0037] A method for preparing polycrystalline diamond using an assembled structure of polycrystalline diamond comprises the following steps:

[0038] S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2;

[0039] S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material;

[0040] S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube.

[0041] S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe;

[0042] S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom;

[0043] S6: placing the graphite tube in a pyrophyllite block and sintering it in a six-sided top press at a sintering temperature of 1600°C for 10 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

[0044] In this embodiment, the above method can be used to prepare polycrystalline diamond with a height of 12 mm and a diameter of 4 mm, and an aspect ratio of 3.0.

[0045] Embodiment 3:

[0046] The assembly structure of the polycrystalline diamond in this embodiment is the same as that in Embodiment 1 and will not be described again here.

[0047] A method for preparing polycrystalline diamond using an assembled structure of polycrystalline diamond comprises the following steps:

[0048] S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2;

[0049] S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material;

[0050] S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube.

[0051] S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe;

[0052] S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom;

[0053] S6: Place the graphite tube in a pyrophyllite block and sinter it in a six-sided top press at a sintering temperature of 1550°C for 8 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

[0054] In this embodiment, the above method can be used to prepare polycrystalline diamond with a height of 15 mm and a diameter of 6 mm, and an aspect ratio of 2.5.

[0055] Example 4: The assembly structure of the polycrystalline diamond in this example is the same as that in Example 1, and will not be described again here.

[0056] A method for preparing polycrystalline diamond using an assembled structure of polycrystalline diamond comprises the following steps:

[0057] S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2;

[0058] S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material;

[0059] S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube.

[0060] S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe;

[0061] S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom;

[0062] S6: placing the graphite tube in a pyrophyllite block and sintering it in a six-sided top press at a sintering temperature of 1500°C for 10 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

[0063] In this embodiment, the above method can be used to prepare polycrystalline diamond with a height of 12 mm and a diameter of 4 mm, and an aspect ratio of 3.0.

[0064] The common traditional preparation method can only produce polycrystalline diamond with a height of 10mm and a diameter of 8mm, with an aspect ratio of only 1.25, which cannot meet the demand. At the same time, the traditional production process is also complicated and inefficient.

[0065] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polycrystalline diamond assembly structure, characterized in that: It comprises a metal cup, wherein a cobalt tube for containing diamond powder is mounted inside the metal cup, the metal cup is of the same height as the cobalt tube, a metal cup cover made of the same material as the metal cup is arranged on the top of the metal cup, a salt tube is mounted outside the metal cup, salt sheets in contact with the ends of the metal cup are placed at both the upper and lower ends of the salt tube, the sum of the heights of the metal cup and the two salt sheets is equal to the height of the salt tube, a dolomite tube of the same height as the salt tube is mounted outside the salt tube, a heating carbon tube of the same height as the dolomite tube is mounted outside the dolomite tube, and heating carbon sheets are placed at the upper and lower ends of the heating carbon tube.

2. The polycrystalline diamond assembly structure according to claim 1, characterized in that: The aspect ratio of the metal cup is greater than 2.

3. The polycrystalline diamond assembly structure according to claim 2, characterized in that: The aspect ratio of the cobalt tube is greater than 2.

4. The polycrystalline diamond assembly structure according to claim 3, characterized in that: The thickness of the cobalt tube is 0.05-1.0 mm.

5. The polycrystalline diamond assembly structure according to claim 2, characterized in that: The metal cup is made of one or more combinations of niobium, tantalum, molybdenum and zirconium.

6. A method for preparing polycrystalline diamond using the polycrystalline diamond assembly structure according to claim 1, characterized in that: The steps include: S1: Put the cobalt tube into the metal cup, the length-to-diameter ratio of the cobalt tube is greater than 2, and the length-to-diameter ratio of the metal cup is greater than 2; S2: Put diamond powder into a metal cup with a cobalt tube and cover it with a metal cup lid made of the same material; S3: Place a metal cup with a lid in the salt tube, and place salt flakes in the salt tube. The sum of the height of the salt flakes and the height of the metal cup is the same as the height of the salt tube. S4: Place the salt pipe inside the dolomite pipe, and the height of the dolomite pipe is the same as that of the salt pipe; S5: Place the dolomite tube in the heated carbon tube, and place heated carbon sheets on top and bottom; S6: placing all the structures assembled in step S5 in a pyrophyllite block and sintering them in a six-sided top press at a sintering temperature of 1500-1600°C for 5-10 minutes. After the assembled structure is taken out from the six-sided top press and cracked, the material inside the metal cup is the obtained high aspect ratio polycrystalline diamond.

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