Preparation method of hard alloy diamond compact and hard alloy diamond compact

Abstract

The invention discloses a preparation method of a hard alloy diamond compact and the hard alloy diamond compact. A two-time ultra-high-temperature and high-pressure sintering process is adopted. Compared with the problem that WC can migrate upwards along with Co in the one-step method sintering process in the prior art, sintering of the diamond layer and combination of the composite layer are completely separated physically, the problem of tungsten carbide pollution of the working layer is solved fundamentally, the working layer of the hard alloy diamond compact prepared through the method cannot contain WC, and therefore the hard alloy diamond compact is not prone to being damaged. Only the connecting layer contains a small amount of WC; and meanwhile, the porous framework manufactured through the chemical treatment step between the two ultrahigh-temperature and high-pressure sintering steps forms a mechanical interlocking / metallurgical bonding area, and the bonding force problem of the hard alloy matrix and the diamond wafer in the second ultrahigh-temperature and high-pressure sintering process is solved. The heat resistance of the prepared hard alloy diamond compact is improved, and the service life is effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of superhard materials technology, and in particular to a method for preparing a cemented carbide-diamond composite sheet and the cemented carbide-diamond composite sheet prepared by the method. Background Technology

[0002] The cemented carbide-diamond composite sheet consists of a diamond layer and a cemented carbide matrix. The diamond layer is formed by sintering numerous diamond particles under high pressure and high temperature conditions through the catalytic action of a metal catalyst, Co. The cemented carbide-diamond composite sheet involved in this invention is used in oil and gas drilling. The diamond layer thickness of the cemented carbide-diamond composite sheet used in this industry is 3mm. The diamond composite sheet combines the high hardness and super wear resistance of diamond with the high impact resistance of cemented carbide. Simultaneously, cemented carbide provides good weldability, allowing for the secure welding of the diamond composite sheet to the diamond drill bit body in engineering applications. As oil and gas drilling continues to extend deeper into the earth, the deeper the depth, the more complex the geological environment, and the more demanding the hardness, abrasiveness, and impact resistance of the formations become. These factors place higher requirements on the various performance indicators of the diamond composite sheet.

[0003] In the preparation of diamond composite sheets, diamond powder and a cemented carbide matrix are first loaded into a high-temperature resistant metal cup, then assembled into a sintered block, and placed in a six-sided press for high-pressure, high-temperature sintering, sintering the diamond and cemented carbide into a single unit. Finally, the product is processed into a diamond composite sheet that meets market demands. This method, commonly known as the "one-step method," can be referenced in Chinese patents CN116330801B and CN111906319B, where diamond particles and the cemented carbide matrix are simultaneously loaded into the cup and sintered in one step under high temperature and high pressure. While some existing methods also involve "two-stage high-temperature, high-pressure" processes (refer to Chinese patent CN116330751A), the entire sintering process occurs within the same press cycle. First, impurities are removed under low temperature and low pressure, then high-temperature, high-pressure sintering is completed. The matrix used for sintering is always present within the high-pressure chamber, which can be considered an improvement on the "one-step method."

[0004] It is evident that high-pressure sintering is a conventional method for preparing cemented carbide-diamond composite sheets, as it yields strong bonding (DD bonds) between diamond particles. In this process, the catalyst—metallic Co—primarily originates from the cemented carbide matrix. The Co, molten at high temperature, migrates to the diamond layer above the cemented carbide under high pressure, and the gaps between diamond particles in the diamond layer become migration channels for the liquid-phase Co. The cemented carbide matrix is ​​composed of tungsten carbide (WC) and Co, with a weight ratio of approximately 84%–89% WC + 11%–16% Co. The average particle size of WC is approximately 1.0–1.8 μm, containing some fine WC particles of 0.2–0.8 μm. These fine WC particles infiltrate into the diamond layer along with the liquid-phase Co and remain as impurities, negatively impacting the heat resistance of the entire composite sheet and reducing its lifespan. The residual WC in the diamond layer is positively correlated with the pressure applied during the preparation of the diamond composite sheet; higher pressure results in more residual WC and a greater negative impact on the diamond composite sheet.

[0005] Diamond composite sheet manufacturers face a dilemma: on the one hand, they want to increase the sintering pressure as much as possible to obtain stronger inter-particle bonds in diamond; on the other hand, higher sintering pressure will result in more residual WC in the diamond layer, thereby reducing the performance of the diamond composite sheet. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing cemented carbide diamond composite sheets and the cemented carbide diamond composite sheets themselves.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a cemented carbide-diamond composite sheet includes the following steps: Step S1: Place diamond micro powder into a high-temperature resistant metal cup and sinter it in a high-pressure chamber. The pressure in the sintering chamber is greater than 7.5 GPa, the temperature is 1490℃~1530℃, the sintering time is 8-12 min, and the sintered product is a diamond disc that does not contain tungsten carbide (WC). Step S2: Remove the diamond disc from the high-pressure chamber and perform acid washing on any one of its planes to remove the Co element in that plane and a certain depth range, and form a hole in situ to obtain a porous skeleton. Step S3: Encapsulate the base formed by the cemented carbide substrate and the diamond disc treated by acid pickling in step S2 in a high-temperature resistant metal cup, and place it again in a high-pressure chamber for sintering. The pressure in the sintering chamber is 70%-80% of the pressure in the chamber in step S1, the temperature is 1450℃~1510℃, and the sintering time is 3-6 minutes. The holes are filled by Co back-permeation of the cemented carbide substrate, so that the diamond disc and the cemented carbide substrate are sintered into one piece to produce a cemented carbide diamond composite sheet blank.

[0008] Preferably, before step S1, a step of surface purification treatment of diamond micro powder is included, for example, soaking the diamond micro powder in acid or alkali to remove surface impurities, and then repeatedly washing it with high-purity water.

[0009] Before step S3, a step of surface cleaning treatment of the cemented carbide substrate is also included, such as sandblasting cleaning treatment of the surface of the cemented carbide base.

[0010] Preferably, the pressure inside the sintering chamber in step S1 is 7.5-9 GPa.

[0011] Preferably, the depth range in step S2 is 0.5mm to 1.5mm.

[0012] Preferably, the depth range in step S2 is 1 mm.

[0013] Preferably, the acid liquid used in step S2 is one or more liquid mixtures of nitric acid, sulfuric acid, hydrofluoric acid, oxalic acid, ferric chloride, and hydrogen peroxide, the acid treatment temperature is 50~80℃, and the acid soaking time is 8~16 days.

[0014] The present invention also discloses a cemented carbide diamond composite sheet, which is prepared by any of the preparation methods described above, comprising a cemented carbide substrate as a base and a diamond layer thereon.

[0015] Preferably, the thickness of the diamond layer is 3 mm.

[0016] Preferably, the diamond layer is divided into a connecting layer in contact with the cemented carbide substrate and a working layer located above the connecting layer. The thickness of the connecting layer is 1 mm, the thickness of the working layer is 2 mm, and the WC particles exist only in the connecting layer.

[0017] The beneficial effects of this invention are mainly reflected in: 1. Compared with the problem that WC migrates upward with Co during the "one-step" sintering process of the existing technology, the present invention solves the problem of tungsten carbide (WC) contamination in the working layer by physically separating the sintering of the diamond layer from the bonding of the composite layer. The working layer (top 2mm) of the cemented carbide diamond composite sheet prepared by the method of the present invention cannot contain WC, and only the bonding layer (bottom 1mm) contains a small amount of WC. 2. Since the ultra-high pressure and high temperature sintering in step S1 is only performed on the diamond layer and the cemented carbide matrix does not participate in the sintering of this step, the heat resistance of the cemented carbide diamond composite sheet is improved and its service life is effectively extended, while obtaining extremely strong DD bonds and completely eliminating WC contamination. 3. The porous skeleton manufactured by the pickling process in step S2 forms a "mechanical interlocking / metallurgical bonding" region, which solves the bonding force problem between the cemented carbide matrix and the diamond disc during the sintering process in step S3. 4. The pressure ratio in steps S1 and S3 is set to meet the sintering conditions for high-quality diamond composite sheets, so that the diamond particles in the diamond layer can achieve a strong bond, while protecting the formed porous skeleton to adapt to the deformation of the matrix. Attached Figure Description

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a cemented carbide-diamond composite sheet prepared by conventional methods; Figure 2 This is a schematic diagram of the assembly of the diamond disc sintered in step S1; Figure 3 This is a schematic diagram of the acid washing process performed on the diamond disc in step S2. Figure 4 This is a schematic diagram of the assembly of the cemented carbide-diamond composite sheet sintered in step S3; Figure 5 This is a schematic diagram of the cemented carbide-diamond composite sheet prepared according to the present invention; Figure 6 This is a thermal stability test performance diagram of a cemented carbide-diamond composite sheet prepared using conventional methods; Figure 7 This is a thermal stability test performance diagram of the cemented carbide-diamond composite sheet prepared by the method of this invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments are not limited to the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0020] Figure 1 This is a schematic diagram of a cemented carbide-diamond composite sheet prepared by conventional methods. In the diagram, 11 is the diamond layer, 12 is the diamond particles, 13 is the catalyst metal Co in the diamond layer, 14 is the WC fine particles in the diamond layer, 15 is the inter-particle bond of the diamond particles, 16 is the cemented carbide matrix, 17 is the WC particles in the cemented carbide matrix, 18 is the binder metal Co in the cemented carbide, and 19 is the bonding interface between the diamond layer and the cemented carbide matrix.

[0021] Figure 5 This is a schematic diagram of the cemented carbide-diamond composite sheet prepared according to the present invention. In the diagram, 51 is the diamond layer, 52 is the diamond particles, 53 is the catalyst metal Co in the diamond layer, 54 is the WC fine particles in the connecting part of the diamond layer (near the cemented carbide matrix), there is no WC in the upper working part of the diamond layer, 55 is the inter-bonding of diamond particles, 56 is the cemented carbide matrix, 57 is the WC particles in the cemented carbide matrix, and 58 is the binder metal Co in the cemented carbide.

[0022] The main difference between the two lies in the fact that the cemented carbide diamond layer composite sheet prepared by conventional methods contains residual WC throughout the entire diamond layer. This residual WC has a significant negative impact on the heat resistance of the cemented carbide diamond composite sheet. Figure 5 The cemented carbide-diamond composite sheet prepared according to the present invention shown has no WC residue in its working part, with only a small amount of WC residue within 1 mm in height near the interface with the cemented carbide substrate. Therefore, the diamond composite sheet prepared by the present invention has higher heat resistance and better performance.

[0023] The fundamental reason for the above differences lies in the fact that this invention discloses a method for preparing cemented carbide-diamond composite sheets, which changes the conventional "one-step" sintering process of cemented carbide-diamond composite sheets to a two-step sintering process, specifically including the following steps: Step S1: Place diamond micro powder into a high-temperature resistant metal cup and sinter it in a high-pressure chamber. The pressure in the sintering chamber is 7.5-9 Gpa, the temperature is 1490℃~1530℃, and the sintering time is 8-12 min, preferably 10 min. The sintered product is a diamond disc, which does not contain tungsten carbide (WC). Step S2: Remove the diamond disc from the high-pressure chamber and perform acid pickling on any one of its planes, so that the Co element in the plane and the depth range of 0.5mm to 1.5mm is precipitated and removed, and pores are formed in situ to obtain a porous skeleton. The acid liquid used in this step is one or more liquid mixtures of nitric acid, sulfuric acid, hydrofluoric acid, oxalic acid, ferric chloride, and hydrogen peroxide. The acid treatment temperature is 50 to 80°C, the acid immersion time is 8 to 16 days, and the acid pickling depth (1mm) is controlled as the bonding layer.

[0024] Step S3: Encapsulate the base formed by the cemented carbide substrate and the diamond disc treated by acid pickling in step S2 in a high-temperature resistant metal cup, and place it again in a high-pressure chamber for sintering. The pressure in the sintering chamber is 70%-80% of the pressure in the chamber in step S1, the temperature is 1450℃~1510℃, and the sintering time is 3-6 minutes, preferably 5 minutes. The holes are filled by the Co back-permeation of the cemented carbide substrate, so that the diamond disc and the cemented carbide substrate are sintered into one piece to produce a cemented carbide diamond composite sheet blank.

[0025] The following is a detailed description with reference to the accompanying drawings.

[0026] Figure 2 This is a schematic diagram of the assembly of the sintered diamond disc in step S1, where 21 is a pyrophyllite block, 22 is a conductive steel ring, 23 is a high-temperature resistant metal Mo sheet, 24 is a heat-insulating graphite sheet, 25 is a graphite tube, 26 is a NaCl tube, 27 is a diamond powder and metal Co component, 27a is a high-temperature resistant metal cup containing diamond powder and Co, and 28 is a ceramic block.

[0027] like Figure 2 As shown, the sintering assembly block used in the first step of ultra-high pressure high temperature sintering (8GPa, 1490℃~1530℃) is pressured by a six-sided press and transmitted into the high-pressure chamber through pyrophyllite block 21. The conductive steel ring 22 introduces the heating current from the outside, which is transmitted to the graphite tube 25 to heat the sintering chamber through high-temperature resistant metal Mo sheet 23 and heat-insulating graphite sheet 24. NaCl tube 26 is used for pressure transmission. The diamond powder to be sintered and the catalyst metal Co component 27 are placed in a high-temperature resistant metal cup 27a. The high-temperature resistant metal cup is made of Zr, or Mo, or Nb, or Ta. The ceramic block 28 for pressurization is made of Zr2O3, or Al2O3, or MgO, or SiC, or Si3N4.

[0028] Under ultra-high pressure and high temperature conditions, diamond powder forms diamond crystal-to-diamond crystal bonds (called DD bonds) between diamond particles under the catalytic action of metallic Co. The stronger these DD bonds become with increasing pressure, the better the performance of the diamond composite sheet. Therefore, the first sintering step employs the most effective ultra-high pressure technology currently available in the industry, achieving a sintering chamber pressure of 8 GPa. No hard alloy matrix is ​​added during the sintering process in step S1 of this invention; a purely physical isolation method is used to avoid introducing WC.

[0029] Figure 3This is a schematic diagram of step S2, which involves acid etching of the diamond wafer. The diamond wafer obtained from the first sintering step is flattened and then subjected to appropriate treatment. This process precipitates and removes metallic Co from the surface and a certain depth within any plane of the diamond wafer, leaving some pores in the diamond composite sheet. The appropriate treatment refers to using a specially formulated acid solution to precipitate and remove metallic Co from designated areas of the diamond wafer. The specific process is as follows: Generally, a mixture of several acids can be used to effectively precipitate Co. This acid mixture can be a combination of several substances selected from nitric acid, sulfuric acid, hydrofluoric acid, oxalic acid, ferric chloride, hydrogen peroxide, etc. Of course, as those skilled in the art know, using only one acidic solution is also possible.

[0030] The acid treatment temperature is 50~80℃, and the acid soaking time is 8~16 days, depending on the treatment temperature and the pressure used in the first sintering step S1. The higher the acid treatment temperature, the shorter the acid soaking time, and vice versa. The higher the pressure used in the first sintering step S1, the longer the acid soaking time, and vice versa.

[0031] In this invention, under a constant acid treatment temperature, the depth of Co removal is determined by combining the acid immersion time with X-ray detection. Since the acid treatment time is as long as 8-16 days, the depth of the Co-removed layer is easily controlled.

[0032] To ensure that metallic Co can successfully penetrate into the pores between diamond particles during the second sintering step S3, the pores left after Co removal must be extremely clean, free of any residual acid or waste liquid. Therefore, the acid-treated diamond wafers must be subjected to high-temperature boiling and ultrasonic vibration cleaning, respectively. The specific methods are as follows: (1) Boil for 30 minutes with pure water and steam at a temperature ≥100℃; (2) After cooling, rinse with pure water 3 to 5 times until the pH value of the rinsing water reaches 7; (3) Then put the diamond disc into an ultrasonic cleaner and ultrasonically clean it with pure water for 20 minutes; (4) Take out the diamond disc and place it in a drying oven and dry it at 100~110℃ for 2 hours.

[0033] Figure 4 This is a schematic diagram of the assembly of the sintered cemented carbide diamond composite sheet in step S3, where 41 is a pyrophyllite block, 42 ​​is a conductive steel ring, 43 is a high-temperature resistant metal Mo sheet, 44 is a graphite sheet, 45 is a graphite tube, 46 is a NaCl tube, 47 is an acid-treated diamond disc, 48 is a cemented carbide substrate, and 49 is a high-temperature resistant metal cup that holds the diamond disc and the cemented carbide substrate.

[0034] The principle of this step is... Figure 2 They are basically the same, the differences are: The high-temperature resistant metal cup 49 contains a properly treated diamond disc 47 and a cemented carbide substrate 48, rather than... Figure 2 Diamond powder and Co metal components 27. The pressure used is 6 GPa, which is higher than... Figure 2 The ultra-high pressure used is 8 GPa, which is 25% lower.

[0035] During the sintering process in this step, the surface of the diamond wafer with the removed Co metal comes into contact with the cemented carbide. Since the diamond wafer was sintered under ultra-high pressure of 8 GPa in the first step, the framework formed by its diamond particles is very strong. During the second step of sintering under high pressure of 6 GPa, this framework does not collapse, and the pores left in the diamond layer after the Co removal process remain. The high temperature melts the Co in the cemented carbide matrix and diffuses towards the diamond wafer under high pressure. Co, carrying a small amount of WC, enters the pores of the diamond wafer. After cooling, the diamond layer and the cemented carbide matrix are bonded together.

[0036] Figure 3 The diamond wafer, after appropriate treatment (partial Co removal), has pores at the contact point with the cemented carbide. These pores absorb Co migrating from the cemented carbide, bonding the diamond wafer and the cemented carbide matrix together upon cooling. Simultaneously with Co diffusion, WC from the cemented carbide is also carried to a small lower region of the diamond wafer. Compared to one-step ultra-high pressure high temperature sintering, the amount of WC diffusing into the diamond wafer is negligible, resulting in a limited negative impact on the performance of the diamond composite. The diamond composite prepared by this invention possesses a superior diamond working layer while reducing WC residue, improving the heat resistance and extending the service life of the diamond composite.

[0037] like Figure 6 and Figure 7 As shown, Figure 1 Hard alloy diamond composite sheets prepared using conventional methods and Figure 5 The cemented carbide-diamond composite sheets prepared using the method of this invention were subjected to uniform performance testing, including a thermal stability test. A single sheet was placed in a thermal expansion tester and heated from room temperature to approximately 1100°C. The thermal expansion deformation was recorded, and the peak value represents the temperature at which the diamond portion detaches from the alloy substrate. Comparative results show that the cemented carbide-diamond composite sheets prepared using this invention exhibit approximately 40°C improved thermal stability compared to those prepared using conventional methods.

[0038] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0039] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a cemented carbide diamond composite sheet, characterized in that, Includes the following steps: Step S1: Place diamond micro powder into a high-temperature resistant metal cup and sinter it in a high-pressure chamber. The pressure in the sintering chamber is greater than 7.5 GPa and the temperature is 1490℃~1530℃. The sintered product is a diamond disc, which does not contain tungsten carbide (WC). Step S2: Remove the diamond disc from the high-pressure chamber and perform acid washing on any one of its planes to remove the Co element in that plane and a certain depth range, and form a hole in situ to obtain a porous skeleton. Step S3: Encapsulate the base formed by the cemented carbide substrate and the diamond disc treated by acid pickling in step S2 in a high-temperature resistant metal cup, and place it again in a high-pressure chamber for sintering. The pressure in the sintering chamber is 70%-80% of the pressure in the chamber in step S1, and the temperature is 1450℃~1510℃. The holes are filled by Co back-permeation of the cemented carbide substrate, so that the diamond disc and the cemented carbide substrate are sintered into one piece to produce a cemented carbide diamond composite sheet blank.

2. The method for preparing the cemented carbide diamond composite sheet according to claim 1, characterized in that: The sintering time for step S1 is 8-12 minutes, and the sintering time for step S3 is 3-6 minutes.

3. The method for preparing the cemented carbide diamond composite sheet according to claim 1, characterized in that: Before step S1, a step of surface purification treatment of diamond micro powder is included, and before step S3, a step of surface cleaning treatment of cemented carbide substrate is included.

4. The method for preparing the cemented carbide diamond composite sheet according to claim 1, characterized in that: The pressure inside the sintering chamber in step S1 is 7.5-9 GPa.

5. The method for preparing the cemented carbide diamond composite sheet according to claim 1, characterized in that: The depth range in step S2 is 0.5mm to 1.5mm.

6. The method for preparing the cemented carbide diamond composite sheet according to claim 5, characterized in that: The depth range in step S2 is 1 mm.

7. The method for preparing the cemented carbide diamond composite sheet according to claim 6, characterized in that: The acid liquid used in step S2 is one or more liquid mixtures of nitric acid, sulfuric acid, hydrofluoric acid, oxalic acid, ferric chloride, and hydrogen peroxide. The acid treatment temperature is 50~80℃ and the acid soaking time is 8~16 days.

8. A cemented carbide diamond composite sheet, characterized in that, It is manufactured by any of the preparation methods described in claims 1-7, comprising a cemented carbide substrate as a base and a diamond layer thereon.

9. The cemented carbide diamond composite sheet according to claim 8, characterized in that: The thickness of the diamond layer is 3 mm.

10. The cemented carbide diamond composite sheet according to claim 9, characterized in that: The diamond layer is divided into a connecting layer that contacts the cemented carbide substrate and a working layer located above the connecting layer. The thickness of the connecting layer is 1 mm, and the thickness of the working layer is 2 mm. WC particles exist only in the connecting layer.

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