A full-face PDC drill bit and a method of manufacturing the same

Abstract

The application provides a full-edge PDC drill bit and a preparation method thereof, and relates to the technical field of drill bits for oil and gas drilling. The full-edge PDC drill bit comprises a rotating body and a fixed cavity, the rotating body is installed in the fixed cavity and filled with a lubricant, the rotating body comprises a tooth head and a positioning block, the tooth head and the positioning block are connected through threads, the tooth head diamond part is composed of a wear-resistant ring and a core part with different materials, a hard alloy part is spliced by two segments of alloys with different Co contents, the tooth head and the positioning block are mechanically assembled in a sleeve ring, and a bottom sealing piece is installed in the sleeve ring through a cold assembly interference fit process. Compared with a traditional product, the application has the characteristics of high wear resistance, high impact resistance, long service life, fast drilling speed and the like, can significantly improve drilling efficiency and reduce drilling cost.

Description

Technical Field

[0001] This invention relates to the field of drill bit technology for oil and gas drilling, specifically to a full-edge PDC drill bit and its preparation method. Background Technology

[0002] PDC (diamond composite) boasts a range of advantages, including extremely high wear resistance, excellent impact resistance, good thermal stability, high thermal conductivity, ease of processing, and convenient use. One of the most important applications of PDC is as drill bits—the primary load-bearing and wear-resistant component—in geological exploration and coalfield / oil and gas development. Currently, PDC drill bits account for over 90% of total drilling footage worldwide.

[0003] Currently, traditional PDC drill bits are typically welded to the drill bit body and remain fixed in the same position throughout use, with the encased portion often accounting for over 60% of the total volume. Based on current usage experience, the cutting edge only occupies about one-third of the entire circumference. This means that when the product fails, a significant portion remains unused, resulting in substantial material waste and increasing the operating cost of PDC drill bits.

[0004] Simultaneously, the limited operating area also leads to a relatively shortened product lifespan, resulting in frequent tripping during actual drilling. In current drilling environments, especially in ultra-deep wells, the cost of tripping in and out of the well already accounts for 30-50% of the total cost of drilling a single well. The frequent tripping in and out of traditional PDC drill bits significantly reduces drilling speed and prolongs the drilling cycle, resulting in substantial cost losses for the drill bit user. Furthermore, considering the current distribution of oil and gas resources both domestically and internationally, deep and ultra-deep wells already account for over 50%, this constraint on drilling urgently needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to provide a full-edge PDC drill bit that addresses the shortcomings of current traditional products, such as low cutting edge efficiency, short product lifespan, and frequent tripping in and out of the drill string. This invention provides a PDC drill bit that can be used across the entire cutting edge, exhibits significantly improved wear resistance and impact resistance, greatly extends its lifespan, and can significantly improve drilling efficiency and reduce drilling costs. This invention also provides a method for preparing the aforementioned PDC drill bit.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A full-edge PDC drill bit includes a rotating body and a fixed cavity. The rotating body is installed in the fixed cavity. The rotating body includes a tooth head and a positioning block. The tooth head and the positioning block are connected by threads. The bottom of the positioning block has a blind hole for installation. The tooth head has a T-shaped cylindrical structure. The upper part is made of diamond and the lower part is made of cemented carbide. The two mating surfaces are either planar or non-planar. The fixed cavity consists of an outer ring and a bottom sealing member. The inner diameter of the outer ring is divided into two sections with a difference of 2-5 mm between the two sections. Lubricant is filled between the rotating body and the fixed cavity.

[0008] Specifically, the diamond layer is divided into a frustum-shaped core and an outer wear-resistant ring. The width d of the wear-resistant ring is 1 to 5 mm and the thickness h is 1 to 3 mm. The mating surface between the wear-resistant ring and the core includes, but is not limited to, an arc surface and a vertical surface.

[0009] Specifically, the No. 1 powder used in the wear-resistant ring comprises 10-15 wt.% W3.5 diamond micro powder, 20-30 wt.% W5 diamond micro powder, 45-60 wt.% W28 diamond micro powder, 0-5 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, 0.5-1 wt.% 10-20 μm Fe powder, and 2-4 wt.% 20-30 μm SiC powder; the No. 2 powder used in the core 1102 comprises 45-60 wt.% W28 diamond micro powder, 35-45 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, and 2-5 wt.% 10-20 μm Ti3SiC2 powder.

[0010] Specifically, the cemented carbide portion is a multi-segment heterogeneous alloy, wherein one end near the diamond layer is a low-Co content alloy with a Co content of 5-8 wt.%, and the other end is a high-Co content alloy with a Co content of 13-16 wt.%.

[0011] A method for preparing a full-edge PDC drill tooth, the specific steps of which are as follows:

[0012] 1) Place powder No. 1 into a metal cup mold and press it into a ring shape. Then place powder No. 2 into the mold and smooth the surface of the powder.

[0013] 2) Immerse the side of the low-Co alloy that is in contact with diamond in the prepared acid solution for cobalt reduction treatment. After treatment, grind and polish the other side. Also polish the side of the high-Co alloy that is in contact with diamond.

[0014] 3) The low-Co content alloy and the high-Co content alloy are placed into the metal cup mold in sequence, and then auxiliary materials such as salt tubes, carbon tubes, and pyrophyllite are put on the outside. They are then synthesized into a blank under high temperature and high pressure.

[0015] 4) The blank is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to a semi-finished product.

[0016] 5) After removing cobalt from the semi-finished diamond layer, the lower alloy end is machined to the required shape and threaded to form a tooth.

[0017] 6) Insert the outer rings into the toothed head and the fixing block at both ends and tighten them;

[0018] 7) Fill the outer ring with lubricant from the side with the larger diameter;

[0019] 8) The bottom sealing component is installed into the large diameter side of the outer ring using an interference fit process, and the outer edge of the bottom circle of the outer ring is chamfered to obtain the finished PDC drill teeth.

[0020] Specifically, both types of diamond layer powders are mixed using a composite mixing process of dry mixing in a three-dimensional mixer and wet mixing in a roller ball mill. The dry mixing speed is 60-90 r / min and the time is 1-3 h; the wet mixing speed is 100-150 r / min and the time is 2-10 h. The medium includes, but is not limited to, acetone, anhydrous ethanol, and purified water.

[0021] Specifically, before use, the side of the low-Co alloy closest to the diamond layer must undergo cobalt reduction treatment, while both low-Co and high-Co alloys require polishing before use.

[0022] Specifically, the cemented carbide is treated by acid leaching. The acid solution is prepared by mixing concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid in a volume ratio of 1:0.5-0.8:1.5-2.5. The acid leaching temperature is 10-30℃ and the acid leaching time is 1-3 hours.

[0023] Specifically, first, put No. 1 powder into the mold, dry press it into the required ring shape, then put in No. 2 powder, level it, and then put in the two matrix sections of low Co content alloy and high Co content alloy in sequence.

[0024] Specifically, after inserting the toothed head into the outer ring from the smaller diameter end, insert the positioning block from the other end, and tighten the two together using a special tool.

[0025] Specifically, the bottom cover and the outer ring are assembled using an interference fit and a cold assembly process.

[0026] Compared with existing technologies, this new type of full-edge PDC drill tooth has the following advantages:

[0027] 1. This type of full-edge PDC drill bit adopts a rotating body design, which enables the diamond layer of the PDC drill bit to work on the full edge. With the total amount of material remaining unchanged, it can greatly improve the service life of the product, thereby increasing the single drilling depth, greatly improving drilling efficiency, and reducing drilling costs.

[0028] 2. This type of full-edge PDC drill bit features a wear-resistant ring structure within the diamond layer, offering enhanced wear resistance and chipping resistance. This ensures that the cutting edge does not become excessively large in the early stages of use, preventing rapid wear at the cutting edge due to jamming and subsequent product failure. The multi-segment alloy construction combined with a cobalt reduction process avoids excessive diffusion of Co from the alloy into the diamond layer, thus preventing performance degradation. It also ensures that the Co content in the lower alloy section meets subsequent machining requirements. After polishing the two substrate sections, they can self-join under a diffusion-like welding principle during the high-temperature synthesis stage, exhibiting high joint strength.

[0029] 3. This type of full-edge PDC drill bit uses outer rings with different hole diameters as the walls of the fixed cavity, which reduces the difficulty of manufacturing the fixed cavity and can be produced through existing normal processes; the fixed cavity bottom is sealed by a cold-fitting process, avoiding the adverse effects of high-temperature heating on the diamond layer and maximizing the original excellent performance of the diamond layer; the composite mixing process avoids unevenness or segregation of powders with different particle sizes during mixing, thereby greatly improving the uniformity of materials in the diamond layer, thus ensuring uniform performance and uniform cutting edge grinding.

[0030] 4. The rotation of the tooth head of this full-edge PDC drill bit can convert part of the impact force into rotational force during the drilling process, thereby improving the impact resistance of the product and further increasing its service life. At the same time, the required drilling pressure is also greatly reduced at the same drilling speed, which can save energy consumption. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the drill teeth described in this invention.

[0032] Figure 2 yes Figure 1 A magnified view of a portion of the image.

[0033] Figure 3 This is a schematic diagram of a cemented carbide assembly.

[0034] Figure 4 This is a cross-sectional view of a semi-finished drill bit.

[0035] Figure 5 This is a schematic diagram of the cross-section of another type of semi-finished drill bit.

[0036] Figure 6 This is a schematic diagram of the cross-section of the solid of revolution.

[0037] Figure 7 This is a top view of the outer ring.

[0038] The components are: 1. Tooth head; 11. Diamond layer; 12. Hard alloy; 1101. Wear-resistant ring; 1102. Core; 1201. Low Co content alloy; 1202. High Co content alloy; 2. Positioning block; 3. Outer ring; 4. Sealing bottom component; 5. Lubricant. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that in the description of the present invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] like Figure 1-7As shown, this invention provides a full-edge PDC drill bit, including a rotating body and a fixed cavity. The rotating body is installed in the fixed cavity. The rotating body includes a tooth head 1 and a positioning block 2. The tooth head 1 and the positioning block 2 are connected by threads. The bottom of the positioning block 2 has a blind hole for installation. The tooth head 1 has a T-shaped cylindrical structure. The upper part is made of diamond layer 11, and the lower part is made of cemented carbide 12. The two mating surfaces are either planar or non-planar. The fixed cavity consists of an outer ring 3 and a bottom sealing member 4. The inner diameter of the outer ring 3 is divided into two sections with a difference of 2-5 mm between the two sections, using different hole diameters. The outer ring serves as the wall of the fixed cavity, reducing the manufacturing difficulty of the fixed cavity and allowing it to be produced using existing normal processes. Lubricant 5 is filled between the rotating body and the fixed cavity. The material of lubricant 5 includes, but is not limited to, graphite, hexagonal boron nitride, molybdenum disulfide, etc., enabling the use of various lubricating materials and improving the applicability of the tool. The rotating body design allows the diamond layer of the PDC drill teeth to achieve full-edge operation. With the total amount of material remaining unchanged, the service life of the product can be greatly improved, thereby increasing the single drilling depth, greatly improving drilling efficiency, and reducing drilling costs.

[0042] Furthermore, the diamond layer 11 is divided into a frustum-shaped core 1102 and an outer wear-resistant ring 1101. The width d of the wear-resistant ring 1101 is 1-5 mm and the thickness h is 1-3 mm. The mating surface between the wear-resistant ring 1101 and the core includes, but is not limited to, curved surfaces and vertical surfaces. By setting a wear-resistant ring structure with better wear resistance and anti-breakage performance, it can ensure that the product does not develop a large cutting edge in the early stage of use, thereby avoiding the situation where the cutting edge is stuck and the cutting edge wears quickly, leading to product failure.

[0043] Furthermore, the No. 1 powder used in the wear-resistant ring 1101 comprises 10-15 wt.% W3.5 diamond micro powder, 20-30 wt.% W5 diamond micro powder, 45-60 wt.% W28 diamond micro powder, 0-5 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, 0.5-1 wt.% 10-20 μm Fe powder, and 2-4 wt.% 20-30 μm SiC powder; the No. 2 powder used in the core 1102 comprises 45-60 wt.% W28 diamond micro powder, 35-45 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, and 2-5 wt.% 10-20 μm Ti3SiC2 powder.

[0044] Furthermore, the cemented carbide 12 part is a multi-segment heterogeneous alloy, with one end near the diamond layer 11 being a low-Co content alloy 1201 with a Co content of 5-8 wt.%, and the other end being a high-Co content alloy 1202 with a Co content of 13-16 wt.%. The use of multi-segment alloys combined with cobalt reduction process not only avoids the large-scale diffusion of Co elements from the alloy into the diamond layer, which would lead to performance degradation, but also ensures that the Co content in the lower alloy is suitable for subsequent machining requirements.

[0045] This invention provides a method for preparing full-edge PDC drill teeth, the specific steps of which are as follows:

[0046] 1) Place powder No. 1 into a metal cup mold and press it into a ring shape. Then place powder No. 2 into the mold and smooth the surface of the powder.

[0047] 2) Immerse the side of the low-Co alloy that is in contact with diamond in the prepared acid solution for cobalt reduction treatment. After treatment, grind and polish the other side. Also polish the side of the high-Co alloy 1202 that is in contact with diamond.

[0048] 3) The low-Co content alloy and the high-Co content alloy are placed into the metal cup mold in sequence, and then auxiliary materials such as salt tubes, carbon tubes, and pyrophyllite are put on the outside. They are then synthesized into a blank under high temperature and high pressure.

[0049] 4) The blank is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to a semi-finished product.

[0050] 5) After removing cobalt from the semi-finished diamond layer, the lower alloy end is machined to the required shape and threaded to form a tooth.

[0051] 6) Insert the outer rings into the toothed head and the fixing block at both ends and tighten them;

[0052] 7) Fill the outer ring with lubricant from the side with the larger diameter;

[0053] 8) The bottom sealing component is installed into the large diameter side of the outer ring using an interference fit process, and the outer edge of the bottom circle of the outer ring is chamfered to obtain the finished PDC drill teeth.

[0054] Furthermore, both types of diamond layer powders were mixed using a composite mixing process of dry mixing in a three-dimensional mixer and wet mixing in a drum ball mill. The dry mixing speed was 60–90 r / min and the time was 1–3 h; the wet mixing speed was 100–150 r / min and the time was 2–10 h. The medium included, but was not limited to, acetone, anhydrous ethanol, and purified water. This composite mixing process avoided unevenness or segregation of powders with different particle sizes during mixing, thereby greatly improving the uniformity of materials in the diamond layer and ensuring uniform performance and edge grinding.

[0055] Furthermore, before use, the low-Co content alloy must undergo cobalt reduction treatment on the side near the diamond layer. Both the low-Co content alloy and the high-Co content alloy need to be polished before use. After polishing the two substrate sections, they can be spliced ​​together on their own under the diffusion-like welding principle during the high-temperature synthesis stage, and at the same time have high splicing strength.

[0056] Furthermore, the cemented carbide is treated by acid leaching. The acid solution is prepared by mixing concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid in a volume ratio of 1:0.5-0.8:1.5-2.5. The acid leaching temperature is 10-30℃ and the acid leaching time is 1-3 hours.

[0057] Further, first put No. 1 powder into the mold, dry press it into the required ring shape, then put in No. 2 powder, level it, and then put in the two matrix sections of low Co content alloy and high Co content alloy in sequence.

[0058] Furthermore, after the toothed head is inserted into the outer ring from one end of the small diameter hole, the positioning block is inserted from the other end, and the two are tightened using a special tool. The bottom sealing part and the outer ring are assembled using an interference fit and a cold assembly process. The cold assembly process for sealing the bottom of the fixing cavity avoids the adverse effects of high-temperature heating on the diamond layer and can maximize the original excellent performance of the diamond layer.

[0059] Example 1:

[0060] The PDC drill bit in this embodiment is prepared by the following steps:

[0061] 1) Prepare powder No. 1 by using 10 wt.% W3.5 diamond micro powder, 30 wt.% W5 diamond micro powder, 45 wt.% W28 diamond micro powder, 2.5 wt.% 3-5 μm Co powder, 0.5 wt.% 10-20 μm Fe powder, and 2 wt.% 20-30 μm SiC powder; prepare powder No. 2 by using 52 wt.% W28 diamond micro powder, 45 wt.% W40 diamond micro powder, 1 wt.% 3-5 μm Co powder, and 2 wt.% 10-20 μm Ti3SiC2 powder.

[0062] 2) The two powders mentioned above are mixed using a composite mixing process of dry mixing with a three-dimensional mixer and wet mixing with a drum ball mill. The dry mixing speed is 70 r / min and the time is 1 h; the wet mixing speed is 120 r / min and the time is 6 h. The medium is pure water.

[0063] 3) Place the mixed No. 1 powder into the mold and press it into a ring shape, then put in No. 2 powder and smooth the surface.

[0064] 4) Prepare an acid solution with a volume ratio of concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid of 1:0.6:1.9. Immerse the side of the cemented carbide with a Co content of 8% in contact with the diamond layer in the acid solution at 15°C for 1 hour.

[0065] 5) Sequentially add cemented carbide with a Co content of 8% and cemented carbide with a Co content of 13%, wherein the contact surface between the alloy and the diamond layer is non-planar;

[0066] 6) After the above-mentioned composite is coated with salt tubes, carbon tubes and pyrophyllite, it is subjected to high temperature and high pressure synthesis to obtain a blank PDC;

[0067] 7) The blank PDC is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to form a semi-finished product. Then the composite layer is subjected to cobalt removal treatment.

[0068] 8) The cobalt-free PDC semi-finished product is processed into tooth heads and assembled with the positioning block in the outer ring, wherein the difference in inner diameter between the two ends of the outer ring is 3mm;

[0069] 9) Fill the outer ring with graphite lubricant, and then use a cold fitting interference fit process to install the bottom part into the outer ring to obtain the finished PDC drill teeth.

[0070] A batch of PDC drill bits was prepared using this method. Five bits were randomly selected for performance testing. The wear resistance, service life, and drilling efficiency of the diamond composite sheet were tested using stone turning and simulated micro-drilling methods. The results were compared with those of conventional PDC drill bits under the same conditions. The comparison results are as follows:

[0071]

[0072] Example 2:

[0073] The PDC drill bit in this embodiment is prepared by the following steps:

[0074] 1) Prepare powder No. 1 by using 12wt.% W3.5 diamond micro powder, 23wt.% W5 diamond micro powder, 55wt.% W28 diamond micro powder, 5wt.% W40 diamond micro powder, 1.5wt.% 3-5μm Co powder, 0.5wt.% 10-20μm Fe powder, and 3wt.% 20-30μm SiC powder; Prepare powder No. 2 by using 57wt.% W28 diamond micro powder, 37wt.% W40 diamond micro powder, 2wt.% 3-5μm Co powder, and 5wt.% 10-20μm Ti3SiC2 powder.

[0075] 2) The two powders mentioned above are mixed using a composite mixing process of dry mixing with a three-dimensional mixer and wet mixing with a drum ball mill. The dry mixing speed is 60 r / min and the time is 2 h; the wet mixing speed is 140 r / min and the time is 8 h.

[0076] 3) Place the mixed No. 1 powder into the mold and press it into a ring shape, then put in No. 2 powder and smooth the surface.

[0077] 4) Prepare an acid solution with a volume ratio of concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid of 1:0.5:2.5. Immerse the side of the cemented carbide with a Co content of 8% in contact with the diamond layer in the acid solution at 25°C for 1 hour.

[0078] 5) Sequentially add cemented carbide with a Co content of 8% and cemented carbide with a Co content of 16%, wherein the contact surface between the alloy and the diamond layer is non-planar;

[0079] 6) After the above-mentioned composite is coated with salt tubes, carbon tubes and pyrophyllite, it is subjected to high temperature and high pressure synthesis to obtain a blank PDC;

[0080] 7) The blank PDC is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to form a semi-finished product. Then the composite layer is subjected to cobalt removal treatment.

[0081] 8) The cobalt-free PDC semi-finished product is processed into tooth heads and assembled with the positioning block in the outer ring, wherein the difference in inner diameter between the two ends of the outer ring is 2mm;

[0082] 9) Fill the outer ring with hexagonal boron nitride lubricant, and then use a cold fitting interference fit process to install the bottom part into the outer ring to obtain the finished PDC drill teeth.

[0083] A batch of PDC drill bits was prepared using this method. Five bits were randomly selected for performance testing. The wear resistance, service life, and drilling efficiency of the diamond composite sheet were tested using stone turning and simulated micro-drilling methods. The results were compared with those of conventional PDC drill bits under the same conditions. The comparison results are as follows:

[0084]

[0085] Example 3:

[0086] The PDC drill bit in this embodiment is prepared by the following steps:

[0087] 1) Prepare powder No. 1 by using 15wt.% W3.5 diamond micro powder, 30wt.% W5 diamond micro powder, 45wt.% W28 diamond micro powder, 5wt.% W40 diamond micro powder, 1wt.% 3-5μm Co powder, 1wt.% 10-20μm Fe powder, and 3wt.% 20-30μm SiC powder; prepare powder No. 2 by using 57wt.% W28 diamond micro powder, 40wt.% W40 diamond micro powder, 1wt.% 3-5μm Co powder, and 2wt.% 10-20μm Ti3SiC2 powder.

[0088] 2) The two powders mentioned above are mixed using a composite mixing process of dry mixing with a three-dimensional mixer and wet mixing with a drum ball mill. The dry mixing speed is 90 r / min and the time is 2 h; the wet mixing speed is 120-150 r / min and the time is 8 h.

[0089] 3) Place the mixed No. 1 powder into the mold and press it into a ring shape, then put in No. 2 powder and smooth the surface.

[0090] 4) Prepare an acid solution with a volume ratio of concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid of 1:0.6:1.5. Immerse the side of the cemented carbide with a Co content of 5% in contact with the diamond layer in the acid solution at 10-30°C for 1-3 hours.

[0091] 5) Sequentially add cemented carbide with a Co content of 5% and cemented carbide with a Co content of 16%, wherein the contact surface between the alloy and the diamond layer is non-planar;

[0092] 6) After the above-mentioned composite is coated with salt tubes, carbon tubes and pyrophyllite, it is subjected to high temperature and high pressure synthesis to obtain a blank PDC;

[0093] 7) The blank PDC is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to form a semi-finished product. Then the composite layer is subjected to cobalt removal treatment.

[0094] 8) The cobalt-free PDC semi-finished product is processed into tooth heads and assembled with the positioning block in the outer ring, wherein the difference in inner diameter between the two ends of the outer ring is 5mm;

[0095] 9) Fill the outer ring with molybdenum disulfide lubricant, and then use a cold fitting interference fit process to install the bottom part into the outer ring to obtain the finished PDC drill teeth.

[0096] A batch of PDC drill bits was prepared using this method. Five bits were randomly selected for performance testing. The wear resistance, service life, and drilling efficiency of the diamond composite sheet were tested using stone turning and simulated micro-drilling methods. The results were compared with those of conventional PDC drill bits under the same conditions. The comparison results are as follows:

[0097]

[0098] Example 4:

[0099] The PDC drill bit in this embodiment is prepared by the following steps:

[0100] 1) Prepare powder No. 1 by using 10 wt.% W3.5 diamond micro powder, 20 wt.% W5 diamond micro powder, 60 wt.% W28 diamond micro powder, 5 wt.% W40 diamond micro powder, 1.5 wt.% 3-5 μm Co powder, 0.5 wt.% 10-20 μm Fe powder, and 3 wt.% 20-30 μm SiC powder; Prepare powder No. 2 by using 60 wt.% W28 diamond micro powder, 45 wt.% W40 diamond micro powder, 3 wt.% 3-5 μm Co powder, and 2 wt.% 10-20 μm Ti3SiC2 powder.

[0101] 2) The two powders mentioned above are mixed using a composite mixing process of dry mixing with a three-dimensional mixer and wet mixing with a drum ball mill. The dry mixing speed is 60 r / min and the time is 3 h; the wet mixing speed is 150 r / min and the time is 9 h.

[0102] 3) Place the mixed No. 1 powder into the mold and press it into a ring shape, then put in No. 2 powder and smooth the surface.

[0103] 4) Prepare an acid solution with a volume ratio of concentrated hydrochloric acid, concentrated nitric acid, and concentrated sulfuric acid of 1:0.8:2.5. Immerse the side of the cemented carbide with a Co content of 8% in contact with the diamond layer in the acid solution at 20°C for 3 hours.

[0104] 5) Sequentially add cemented carbide with a Co content of 8% and cemented carbide with a Co content of 16%, wherein the contact surface between the alloy and the diamond layer is non-planar;

[0105] 6) After the above-mentioned composite is coated with salt tubes, carbon tubes and pyrophyllite, it is subjected to high temperature and high pressure synthesis to obtain a blank PDC;

[0106] 7) The blank PDC is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to form a semi-finished product. Then the composite layer is subjected to cobalt removal treatment.

[0107] 8) The cobalt-free PDC semi-finished product is processed into tooth heads and assembled with the positioning block in the outer ring, wherein the difference in inner diameter between the two ends of the outer ring is 5mm;

[0108] 9) Fill the outer ring with hexagonal boron nitride lubricant, and then use a cold fitting interference fit process to install the bottom part into the outer ring to obtain the finished PDC drill teeth.

[0109] A batch of PDC drill bits was prepared using this method. Five bits were randomly selected for performance testing. The wear resistance, service life, and drilling efficiency of the diamond composite sheet were tested using stone turning and simulated micro-drilling methods. The results were compared with those of conventional PDC drill bits under the same conditions. The comparison results are as follows:

[0110]

[0111] 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 full-edge PDC drill bit, comprising a rotating body and a fixed cavity, characterized in that: The rotating body is installed in the fixed cavity. The rotating body includes a tooth (1) and a positioning block (2). The tooth (1) and the positioning block (2) are connected by threads. The bottom of the positioning block (2) is provided with a blind hole for installation. The tooth (1) is a T-shaped cylindrical structure. The upper part is made of diamond layer (11) and the lower part is made of hard alloy (12). The two joint surfaces are either planar or non-planar. The fixed cavity is composed of an outer ring (3) and a bottom sealing part (4). The inner diameter of the outer ring (3) is divided into two sections, and the difference between the inner diameters of the two sections is 2-5 mm. The rotating body and the fixed cavity are filled with lubricant (5). The diamond layer (11) is divided into a frustum-shaped core (1102) and an outer wear-resistant ring (1101). The width d of the wear-resistant ring (1101) is 1-5 mm and the thickness h is 1-3 mm. The mating surface between the wear-resistant ring (1101) and the core includes, but is not limited to, an arc surface and a vertical surface. The No. 1 powder used in the wear-resistant ring (1101) comprises 10-15 wt.% W3.5 diamond micro powder, 20-30 wt.% W5 diamond micro powder, 45-60 wt.% W28 diamond micro powder, 0-5 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, 0.5-1 wt.% 10-20 μm Fe powder, and 2-4 wt.% 20-30 μm SiC powder; the No. 2 powder used in the core (1102) comprises 45-60 wt.% W28 diamond micro powder, 35-45 wt.% W40 diamond micro powder, 1-3 wt.% 3-5 μm Co powder, and 2-5 wt.% 10-20 μm Ti3SiC2 powder.

2. The full-edge PDC drill tooth according to claim 1, characterized in that: The cemented carbide (12) is a multi-segment heterogeneous alloy, wherein one end near the diamond layer (11) is a low Co content alloy (1201) with a Co content of 5 to 8 wt.%, and the other end is a high Co content alloy (1202) with a Co content of 13 to 16 wt.%.

3. A method for preparing a full-edge PDC drill tooth according to claim 1, characterized in that: The preparation method involves the following steps: 1) Place powder No. 1 into a metal cup mold and press it into a ring shape. Then place powder No. 2 into the mold and smooth the surface of the powder. 2) The side of the low-Co content alloy (1201) in contact with diamond is immersed in the prepared acid solution for cobalt reduction treatment. After treatment, the other side is flat-ground and polished. The side of the high-Co content alloy (1202) in contact with diamond is also polished. 3) The low-Co content alloy (1201) and the high-Co content alloy (1202) are placed into the metal cup mold in sequence, and then auxiliary materials such as coils, carbon tubes, and pyrophyllite are put on the outside. They are then synthesized into a blank under high temperature and high pressure. 4) The blank is machined by grinding the surface, outer circle, bottom and upper and lower sharp edges of the composite layer to a semi-finished product. 5) After removing cobalt from the semi-finished diamond layer, the lower alloy end is machined to the required shape and threaded to form a tooth (1). 6) Insert the toothed head (1) and the fixing block into the outer rings at both ends and tighten them; 7) Fill the outer ring with lubricant from the side with the larger diameter; 8) The bottom sealing component is installed into the large diameter side of the outer ring using an interference fit process, and the outer edge of the bottom circle of the outer ring is chamfered to obtain the finished PDC drill teeth.

4. A method for preparing a full-edge PDC drill tooth according to claim 3, characterized in that: Both types of diamond layer powders are mixed using a composite mixing process of dry mixing with a three-dimensional mixer and wet mixing with a drum ball mill. The dry mixing speed is 60-90 r / min and the time is 1-3 h; the wet mixing speed is 100-150 r / min and the time is 2-10 h. The medium includes, but is not limited to, acetone, anhydrous ethanol, and purified water.

5. A method for preparing a full-edge PDC drill tooth according to claim 3, characterized in that: Before use, the side of the low Co content alloy (1201) close to the diamond layer (11) must be treated to reduce cobalt content. The low Co content alloy (1201) and the high Co content alloy (1202) must be polished before use.

6. A method for preparing a full-edge PDC drill tooth according to claim 3, characterized in that: The cemented carbide (12) was treated by acid leaching. The acid solution was prepared by a volume ratio of concentrated hydrochloric acid, concentrated nitric acid and concentrated sulfuric acid of 1:0.5~0.8:1.5~2.

5. The acid leaching temperature was 10~30℃ and the acid leaching time was 1~3h.

7. A method for preparing a full-edge PDC drill tooth according to claim 3, characterized in that: First, put No. 1 powder into the mold, dry press it into the required ring shape, then put in No. 2 powder, level it, and then put in two matrix sections in sequence: low Co content alloy (1201) and high Co content alloy (1202).

8. A method for preparing a full-edge PDC drill tooth according to claim 3, characterized in that: After the toothed head (1) is inserted into the outer ring from one end of the small diameter hole, the positioning block is inserted from the other end, and the two are tightened with a special tool. The bottom sealing part and the outer ring are fitted with an interference fit and assembled using a cold assembly process.

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