Gradient functional material monolithic drill bit and preparation method thereof

Abstract

The application discloses a gradient functional material integrated drill bit and a preparation method thereof. The drill bit mainly comprises a steel body and a drill crown connected with the steel body. The drill crown is an integrated structure formed by at least three kinds of powder materials through a gradient sintering process and does not contain any assembled cutting element. The material composition of the drill crown continuously changes from the top of the crown to the connecting interface with the steel body. The top of the crown is rich in superhard wear-resistant phase, and the hardness is not less than HRA92. The connecting interface area is rich in metal bonding phase, and the bending strength is not less than 1500MPa. The working surface of the drill crown is provided with a main chip groove and an auxiliary crushing structure. The auxiliary crushing structure is a continuous protrusion formed on the top surface of the crown and consistent with the composition of the drill body.

Description

Technical Field

[0001] This invention relates to the field of drill bit and drill bit manufacturing technology, and more particularly to a monolithic drill bit made of graded functional materials and its manufacturing method. Background Technology

[0002] Drilling tools are core equipment in resource exploration, geological engineering, and oil and gas extraction, and their performance directly affects operational efficiency and cost. Traditional drill bits mostly use polycrystalline diamond composite (PDC) or cemented carbide teeth as cutting units, which are fixed to the drill bit matrix by brazing or sintering. Although such structures have a certain degree of high hardness and wear resistance, they still have significant drawbacks: First, the interface between the cemented material and the matrix is ​​a weak point in mechanical properties, and failures such as composite chipping and tooth breakage are prone to occur in the high-load, high-impact downhole environment; second, the abrupt change in material properties at the interface leads to significant stress concentration, especially under thermo-mechanical coupling conditions, where the mismatch in thermal expansion coefficients can cause crack initiation and propagation; in addition, the cooling of traditional drill bits relies on external flow channels, which has limited cooling efficiency and makes it difficult to effectively suppress the temperature rise of the drill bit crown, seriously affecting its red hardness and service life. Although some studies have attempted to improve performance by optimizing brazing materials or improving tooth structure, none of them have fundamentally solved the systemic problem of integrated material-structure-function design. Therefore, there is an urgent need to develop a new type of drill bit technology that can achieve continuous and gradual changes in material composition and properties, and integrated structure and function, thereby breaking through the performance bottleneck of traditional drill bits. Summary of the Invention

[0003] The purpose of this invention is to provide a monolithic drill bit made of graded functional materials and its preparation method to solve the technical problems mentioned in the background.

[0004] The main objective of this application is to provide a gradient functional material integral drill bit, including a steel body and a drill bit crown connected to the steel body. The drill bit crown is an integral structure formed by a gradient sintering process of at least three powder materials, without any post-assembled cutting elements.

[0005] The material composition of the drill bit crown varies continuously from the crown top to the interface with the steel body.

[0006] The crown region is rich in an ultra-hard wear-resistant phase with a hardness of not less than HRA92; the connecting interface region is rich in a metallic binder phase with a bending strength of not less than 1500MPa.

[0007] The working surface of the drill bit crown is provided with a main chip removal groove and an auxiliary crushing structure. The auxiliary crushing structure is a continuous protrusion formed by sintering on the crown top surface, which is consistent with the composition of the drill bit body.

[0008] Furthermore, the ultrahard wear-resistant phase is one or a mixture of two of micron or nano-sized polycrystalline diamond particles and cubic boron nitride particles, with a volume fraction of 85% to 95% in the crown region, and decreasing gradually along the direction towards the steel body.

[0009] Furthermore, the metal binder phase is a mixed powder of cobalt, nickel, and tungsten carbide, with a volume fraction of 60% to 80% in the interface region, decreasing gradually towards the crown.

[0010] Furthermore, the auxiliary crushing structure is a spiral, corrugated, or honeycomb-shaped network of protrusions with a height of 0.5-2 mm and a width of 1-3 mm.

[0011] Furthermore, the drill bit crown is provided with a three-dimensional interconnected micro-cooling channel. The micro-cooling channel is formed by inserting a spacer material to decompose the material during the sintering process. Its inlet is connected to the inner cavity of the steel body, and its outlet leads to the main chip removal groove or the outer wall of the drill bit.

[0012] A method for preparing a monolithic drill bit made of the graded functional material includes the following steps:

[0013] Step 1): The superhard wear-resistant phase powder and the metallic binder phase powder are laid layer by layer in the mold according to the designed gradient composition ratio, forming a powder bed with continuously changing composition.

[0014] Step 2): Place the spacer material wire or mesh at the preset position to form micro-cooling channels;

[0015] Step 3): Place the prepared powder bed and the steel body into the mold together, and sinter them in one go using spark plasma sintering or ultra-high pressure sintering processes. During the sintering process, the spacer material decomposes and volatilizes to form micro-cooling channels.

[0016] Step 4): After sintering, the drill bit crown working surface is cooled, demolded, cleaned, and polished.

[0017] Further, in step 1), polycrystalline diamond powder or cubic boron nitride powder with an average particle size of 5-20 μm is selected as the main superhard phase; it is ultrasonically dispersed in anhydrous ethanol for 30 minutes and then dried for later use to prevent agglomeration;

[0018] Cobalt powder, nickel powder, and tungsten carbide powder with an average particle size of 10-50μm are selected and premixed according to the required composition of the interface. The mixture is then mixed for 4-6 hours using a V-type mixer to ensure uniform mixing.

[0019] Further, in step 1), based on the preset gradient composition curve, a computer-aided design model is used to calculate the target composition ratio of each layer from the crown to the connecting interface. The superhard phase powder and the metallic binder phase powder are precisely weighed by the control system and mixed using dry or wet methods to prepare a mixed powder with continuously changing composition; each layer of mixed powder is stored separately for later use.

[0020] Further, in step 2), the method for implanting the spacer material includes:

[0021] Install the cleaned graphite mold for forming the crown cavity of the drill bit on the base of the sintering equipment; insert the connecting end of the pre-treated drill bit steel body into the corresponding positioning groove in the mold to ensure that its position is accurately fixed;

[0022] Pre-woven water-soluble fiber filaments or low-melting-point metal wires with a three-dimensional mesh structure are used as placeholder materials and placed in predetermined positions in the mold cavity according to the designed three-dimensional configuration of the micro-cooling channels; this material will be removed in the subsequent sintering process to form the channels.

[0023] Furthermore, in step 3), a digital gradient powder spreading method is adopted: an automated powder spreading system is used, which spreads powder layer by layer according to the gradient model calculated in step 1);

[0024] 31): A first layer is laid at the bottom of the mold, which is a mixed powder with the highest content of ultrahard phase;

[0025] 32): When laying the second layer, the content of the superhard phase is reduced proportionally, and the content of the metallic binder phase is increased accordingly;

[0026] 33): Repeat this process layer by layer until the interface layer that connects with the steel body is reached. This layer is a mixed powder with the highest content of metallic binder phase.

[0027] 34): After each layer is laid, use a scraper to level it and apply slight pre-pressure to ensure that the powder layer density is uniform and to avoid obvious boundaries between layers.

[0028] This application has the following beneficial effects:

[0029] 1. This invention utilizes gradient functional materials and integrated sintering technology. The drill bit crown exhibits a continuous gradient in composition from the superhard phase-rich crown top to the metallic binder-rich base, with no physical interfaces present. This means that material properties such as hardness, toughness, and coefficient of thermal expansion are smoothly transitioned, effectively avoiding stress concentration. Its mechanical properties are isotropically optimized; the crown top region withstands cutting impacts, while the connecting areas effectively buffer stress and transmit torque, forming a truly "whole" structure. This interface-free structural design significantly improves the drill bit's impact resistance and fatigue resistance under extreme downhole conditions, completely solving the most common failure modes of traditional drill bits, such as tooth breakage and weld failure, thus significantly enhancing reliability.

[0030] 2. This invention employs a graded functional material design concept, using a computer-aided design model to design the composition and properties of any location on the drill bit crown. An 85%-95% superhard phase is set in the crown region, with a hardness HRA≥92 sufficient to easily penetrate the hardest rock formations, ensuring extremely high drilling efficiency. Meanwhile, a 60%-80% metallic binder phase is set in the interface region connecting to the steel body, with a bending strength ≥1500MPa, providing sufficient toughness to absorb vibration and impact loads, preventing overall brittle fracture.

[0031] 3. This invention employs spacer material technology to form a three-dimensional interconnected micro-cooling channel network in situ during manufacturing. These microchannels, like capillaries inside the drill bit, can directly guide the coolant transported within the steel body cavity to the heat-generating core region closest to the crown cutting point. Their enormous specific surface area makes the heat exchange efficiency far exceed that of any external macroscopic channel. This active, internal cooling method can extremely effectively suppress the rise in drill bit operating temperature, thereby 1) maintaining the high-temperature hardness of the superhard phase material; 2) reducing cracks caused by thermal stress; and 3) preventing softening of the brazing filler metal (in traditional drill bits).

[0032] 4. This invention integrates digital material design, additive manufacturing, and advanced sintering technology. This process is a near-net-shape integrated manufacturing process. Through a digital powder spreading system, precise distribution of material components in three-dimensional space is achieved. Utilizing the material placement method, complex three-dimensional internal microchannels that are impossible to achieve with traditional machining are directly sculpted within the sintered body. Spark plasma sintering technology, at relatively low temperatures and pressures, achieves rapid densification sintering of these high-performance, high-melting-point materials through plasma activation, while ensuring metallurgical bonding with the steel body.

[0033] 5. The seamless, one-piece structure of this drill bit provides excellent impact resistance, enabling stable operation even in fractured and heterogeneous formations, reducing the frequency of drill bit replacements due to impact failure. The extremely high hardness and wear resistance of the crown ensure high drilling rates and long cuts in abrasive formations. An internal micro-cooling system maintains continuous high-efficiency cutting capability, preventing efficiency degradation due to overheating. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the drill bit structure of the present invention;

[0035] Figure 2 This is a layout diagram of one form of gradient functional material in this invention. Detailed Implementation

[0036] 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.

[0037] Reference Figure 1 and Figure 2 The main objective of this application is to provide a monolithic drill bit made of graded functional materials, comprising a steel body and a drill bit crown 200 connected to the steel body 100.

[0038] The drill bit crown 200 is an integral structure formed by a gradient sintering process of at least three powder materials, without any post-assembled cutting elements;

[0039] The material composition of the drill bit crown 200, from the crown top 201 to the connection interface 202 with the steel body 100, exhibits a continuous gradient change.

[0040] The crown 201 region is rich in an ultra-hard wear-resistant phase with a hardness of not less than HRA92; the connecting interface 202 region is rich in a metallic bonding phase with a bending strength of not less than 1500MPa.

[0041] The working surface of the drill bit crown 200 is provided with a main chip removal groove 203 and an auxiliary crushing structure 204. The auxiliary crushing structure 204 is a continuous protrusion formed by sintering on the surface of the crown top 201, which is consistent with the composition of the drill bit body.

[0042] The fatal weakness of traditional drill bits lies in the mechanical or brazed interface between the hard cutting units, such as the PDC blade and the metal matrix. This interface exhibits abrupt changes in chemical composition, crystal structure, and mechanical properties, making it highly susceptible to crack initiation and propagation under high-frequency impact and alternating thermal stress, leading to the complete detachment of the composite blade or matrix cracking. This invention fundamentally overturns this structure through gradient functional materials and integrated sintering technology. The drill bit crown exhibits a continuous gradient in composition from the superhard phase-rich crown top to the metallic binder-rich base, with no physical interfaces present. This means that material properties such as hardness, toughness, and coefficient of thermal expansion are smoothly transitioned, effectively avoiding stress concentration. Its mechanical properties are isotropically optimized; the crown top region withstands cutting impacts, while the connecting area effectively buffers stress and transmits torque, forming a truly "whole" structure. This interface-free structural design significantly improves the drill bit's impact resistance and fatigue resistance under extreme downhole conditions, completely solving the most common failure modes of traditional drill bits, such as tooth breakage and weld failure, resulting in significantly enhanced reliability.

[0043] In some embodiments, the superhard wear-resistant phase is one or a mixture of two of micron or nano-sized polycrystalline diamond particles and cubic boron nitride particles, with a volume fraction of 85% to 95% in the crown region and decreasing gradually along the direction toward the steel body 100.

[0044] In some embodiments, the metal binder phase is a mixed powder of cobalt, nickel, and tungsten carbide, with a volume fraction of 60% to 80% in the region of the interface 202, decreasing gradually towards the crown 201, wherein the weight ratio of cobalt:nickel:tungsten carbide is 50:20:30.

[0045] In some embodiments, the auxiliary crushing structure 204 is a spiral, corrugated, or honeycomb-shaped network of protrusions with a height of 0.5-2 mm and a width of 1-3 mm.

[0046] In some embodiments, the drill bit crown 200 is provided with a three-dimensional interconnected micro-cooling channel 205. The micro-cooling channel 205 is formed by inserting a spacer material to decompose the material during the sintering process. Its inlet is connected to the inner cavity of the steel body 100, and its outlet leads to the main chip removal groove 203 or the outer wall of the drill bit.

[0047] A method for preparing a monolithic drill bit made of the graded functional material includes the following steps:

[0048] Step 1): The superhard wear-resistant phase powder and the metallic binder phase powder are laid layer by layer in the mold according to the designed gradient composition ratio, forming a powder bed with continuously changing composition.

[0049] Step 2): Place the spacer material wire or mesh at the preset position to form the micro-cooling channel 205;

[0050] Step 3): Place the filled powder bed and steel body 100 into the mold together, and sinter them in one go using spark plasma sintering or ultra-high pressure sintering process. During the sintering process, the spacer material decomposes and volatilizes to form micro-cooling channels 205.

[0051] Step 4): After sintering, the drill bit crown is cooled, demolded, cleaned, and polished.

[0052] In some embodiments, in step 1), polycrystalline diamond powder or cubic boron nitride powder with an average particle size of 5-20 μm is selected as the main superhard phase; it is ultrasonically dispersed in anhydrous ethanol for 30 minutes and then dried for later use to prevent agglomeration.

[0053] Cobalt powder, nickel powder, and tungsten carbide powder with an average particle size of 10-50μm are selected and premixed according to the required composition of the interface. The mixture is then mixed for 4-6 hours using a V-type mixer to ensure uniform mixing.

[0054] In some embodiments, in step 1), the target component ratio of each layer from the crown to the interface is calculated using a computer-aided design model based on a preset gradient component curve. The superhard phase powder and the metallic binder phase powder are precisely weighed by the control system and mixed using dry or wet methods to prepare a mixed powder with continuously varying composition; each layer of mixed powder is stored separately for later use. Traditional drill bit material selection often involves compromise: superhard materials (such as diamond) chosen to increase crown hardness inevitably result in brittleness, while the metallic binder phase used to ensure matrix toughness lacks sufficient hardness. The gradient functional materials design concept adopted in this invention allows engineers to proactively and precisely design the composition and performance of any location on the drill bit crown, much like writing a program. The optimal performance gradient curve can be calculated using a computer-aided design model. In the crown region (85%-95% superhard phase), its hardness (HRA ≥ 92) is sufficient to easily gnaw through the hardest rock formations, ensuring extremely high drilling efficiency. Meanwhile, in the interface region connecting with the steel body (60%-80% metallic bonding phase), its bending strength (≥1500 MPa) provides sufficient toughness to absorb vibration and impact loads, preventing overall brittle fracture. This continuous change from "superhard" to "super tough" is something that no homogeneous material or simple composite material can achieve. It perfectly solves the core contradiction of drill bits needing both hardness and toughness, enabling customizable and optimized performance.

[0055] In some embodiments, the method for implanting the spacer material in step 2) includes:

[0056] Install the cleaned graphite mold for forming the crown cavity of the drill bit on the base of the sintering equipment; insert the connecting end of the pre-treated drill bit steel body 100 into the corresponding positioning groove in the mold to ensure that its position is accurately fixed.

[0057] Pre-woven water-soluble fiber filaments or low-melting-point metal wires with a three-dimensional mesh structure are used as placeholder materials and placed in predetermined positions in the mold cavity according to the three-dimensional configuration of the designed micro-cooling channel 205; this material will be removed in the subsequent sintering process to form the channel.

[0058] In some embodiments, in step 3), a digital gradient powder spreading method is used: an automated powder spreading system is used, which spreads powder layer by layer according to the gradient model calculated in step 1);

[0059] 31): A first layer is laid at the bottom of the mold, which is a mixed powder with the highest content of ultrahard phase;

[0060] 32): When laying the second layer, the content of the superhard phase is reduced proportionally, and the content of the metallic binder phase is increased accordingly;

[0061] 33): Repeat this process layer by layer until the interface layer that connects with the steel body is reached. This layer is a mixed powder with the highest content of metallic binder phase.

[0062] 34): After each layer is laid, use a scraper to level it and apply slight pre-pressure to ensure that the powder layer density is uniform and to avoid obvious boundaries between layers.

[0063] Step 4: After the integrated powder filling of the spark plasma sintering molding is completed, install the graphite pressure head of the SPS system and seal the entire mold.

[0064] Start the SPS sintering process:

[0065] Vacuuming: The vacuum level in the sintering chamber is ≤10Pa to avoid oxidation of the material at high temperatures.

[0066] Apply pressure: First apply a small axial pressure (e.g., 10-20 MPa) to allow the powder particles to initially contact each other.

[0067] Heating and sintering: The temperature is rapidly increased to the sintering temperature at a rate of 100-200°C / min, typically between 1000-1300°C depending on the binder phase composition. During the heating process, when the temperature reaches 300-500°C, the site material (PVA fiber) decomposes, carbonizes, and is discharged by the vacuum system with the airflow, leaving behind pre-defined three-dimensional interconnected micro-cooling channels 205. After reaching the maximum sintering temperature, the temperature is held for 3-10 minutes while the pressure is increased to the final sintering pressure of 30-50 MPa. During this period, pulsed direct current passes through the mold and powder to generate plasma, cleaning the powder surface and greatly promoting the densification process, achieving rapid sintering of the powder and metallurgical bonding with the steel body 100.

[0068] Cooling: After the heat preservation is completed, stop heating and cool the furnace to below 300°C while maintaining pressure. Then release the pressure and remove the mold.

[0069] Post-processing includes: Demolding and cleaning: Remove the sintered drill bit from the graphite mold and clean any graphite paper or dust adhering to the surface using sandblasting or light grinding. Channel unblocking and inspection: Use high-pressure airflow or an ultrasonic cleaner to ensure that the micro-cooling channel 205 is completely unobstructed. Working surface finishing: Use a diamond grinding wheel to grind and polish the working surface of the drill bit crown 200, precisely shape the main chip removal groove 203, and ensure that the dimensions and shape of the auxiliary crushing structure 204 meet the design requirements to form the final product.

[0070] In the above, the main functions of the computer-aided design model are as follows: Define the material composition ratio at each point from the crown top (201) to the connection interface (202) of the drill bit crown. The engineer will first set the target performance of the crown top (e.g., hardness ≥ HRA92) and the target performance of the connection interface (bending strength ≥ 1500MPa). The computer will back-calculate the required composition ratio (e.g., superhard phase volume fraction 85-95%) based on the material database (containing performance parameters of powder materials such as diamond, Co, Ni, WC, etc.) and the theoretical model, and generate a continuous gradient composition curve. Micro-cooling channel topology optimization: Design the most efficient three-dimensional interconnected micro-cooling channel (205) network. Based on thermodynamic simulation, the computer model will analyze the distribution of the main heat sources and the heat transfer path when the drill bit is working. Through the topology optimization algorithm, the channel configuration that can transport the coolant to the hottest area with the shortest path and the largest surface area is automatically generated, thereby achieving the best cooling efficiency. The designed material gradient model and channel model are converted into instructions that can be executed by the automated equipment. The model "slices" the entire drill bit crown along the Z-axis (height direction), specifying the powder formula and spreading path for each layer. This "digital formula" directly drives the digitally controlled spreading system to spread the powder layer by layer.

[0071] Performance testing and results analysis:

[0072] The prepared drill bit and the brand APDC drill bit were subjected to performance tests under the same conditions.

[0073] Test 1: Mechanical performance test, sampling at the drill bit crown.

[0074] Test Project Test Standards Drill bit (crown tip) Drill bit (interface) APDC brand drill bits (body) Vickers hardness (HV) ASTME384 6800±200 1250±50 1050±30 Bending strength (MPa) ASTMB528 - 1620±40 1450±35 Fracture toughness (MPa·m¹ / ²) ASTM E399 8.5±0.3 18.5±0.5 14.0±0.4

[0075] Data shows that the drill bit has successfully achieved a performance gradient. The crown hardness of HV6800MPa far exceeds the PDC drill bit matrix hardness of HV1050MPa, ensuring its extreme wear resistance and rock-breaking ability. The flexural strength (1620MPa) and fracture toughness (18MPa·m¹ / ²) of the interface zone are significantly higher than the comparative sample, demonstrating better impact and fracture resistance, effectively transmitting torque and buffering complex downhole loads. This ability to proactively achieve "super-hard surface and super-tough core" through material design fundamentally solves the contradiction between hardness and toughness.

[0076] Test 2: Cooling efficiency test.

[0077] Dry drilling tests (without coolant) were conducted on a dedicated test bench, and the temperature change of the center of the drill bit crown over time was monitored using an infrared thermal imager (drilling pressure 5 kN, rotation speed 300 rpm, drilling granite).

[0078] Time (minutes) The drill bit (with internal microchannels for coolant flow) APDC brand drill bits (external water tank for coolant) Drill bit (internal microchannel closed) 5 125°C 218°C 295°C 10 138°C 345°C (significant thermal degradation) 478°C (Severe thermal degradation) 15 145°C (thermal equilibrium) Failure Failure

[0079] The test results are highly convincing. With internal micro-cooling activated, the drill bit's operating temperature remained consistently below 150°C, while traditional PDC drill bits experienced a sharp performance decline after only 10 minutes due to thermal decay (temperatures exceeding 350°C). Even more remarkably, when the FGM drill bit's coolant was turned off, its temperature rise was even faster than that of traditional drill bits, demonstrating that it generated more heat internally, which was efficiently dissipated by the micro-cooling system. This active, direct-to-heat-source cooling method significantly improves the drill bit's red hardness, enabling it to withstand long-duration, high-intensity continuous drilling operations, preventing failures caused by high temperatures such as diamond graphitization and binder phase softening, thus greatly extending its lifespan.

[0080] Test 3: Actual drilling performance test. Drilling test was conducted on a granite block (compressive strength 250MPa) (drilling pressure 8kN, rotation speed 400rpm, water cooling).

[0081] Performance indicators drill APDC brand drill bits Increase ratio Average mechanical drilling speed 1.8m / h 1.5m / h +20% Total footage Even wear after 120 meters The composite sheet was severely worn after 65 meters. +84.6% Failure Mode Uniform wear PDC film detachment, tire wear Fundamental improvement

[0082] Real-world drilling tests were the final verification. The drill bit achieved a 20% increase in average mechanical drilling speed, thanks to its harder crown and superior rock-breaking efficiency. Its total footage reached 120 meters, nearly twice that of the comparison bit, and its failure mode was uniform wear, meaning it remains usable and has a predicted longer lifespan.

[0083] In the foregoing description, examples have been described with reference to specific exemplary embodiments. However, it will be apparent that various modifications and changes can be made to the specific examples without departing from the scope set forth in the appended claims, and the claims are not limited to the specific examples described above.

Claims

1. A monolithic drill bit made of graded functional materials, comprising a steel body and a drill bit crown (200) connected to the steel body (100), characterized in that: The drill bit crown (200) is an integral structure formed by a gradient sintering process of at least three powder materials, without any post-assembled cutting elements; The material composition of the drill bit crown (200) varies continuously from the crown top (201) to the connection interface (202) with the steel body (100); The crown (201) region is rich in an ultra-hard wear-resistant phase with a hardness of not less than HRA92; the connecting interface (202) region is rich in a metallic bonding phase with a bending strength of not less than 1500MPa. The working surface of the drill bit crown (200) is provided with a main chip removal groove (203) and an auxiliary crushing structure (204). The auxiliary crushing structure (204) is a continuous protrusion formed by sintering on the surface of the crown top (201) and having the same composition as the drill bit body. The ultrahard wear-resistant phase is one or a mixture of two of micron or nano-sized polycrystalline diamond particles and cubic boron nitride particles, with a volume fraction of 85% to 95% in the crown region and a gradient decreasing along the direction toward the steel body (100). The metal binder phase is a mixed powder of cobalt, nickel and tungsten carbide, with a volume fraction of 60% to 80% in the interface (202) region, decreasing gradually towards the crown (201).

2. The integral drill bit made of graded functional materials according to claim 1, characterized in that, The auxiliary crushing structure (204) is a spiral, corrugated or honeycomb-shaped protrusion network with a height of 0.5-2 mm and a width of 1-3 mm.

3. The integral drill bit made of graded functional materials according to claim 1, characterized in that, The drill bit crown (200) is provided with a three-dimensional interconnected micro-cooling channel (205). The micro-cooling channel (205) is formed by inserting a spacer material to decompose the material during the sintering process. Its inlet is connected to the inner cavity of the steel body (100), and its outlet leads to the main chip removal groove (203) or the outer wall of the drill bit.

4. A method for preparing a monolithic drill bit made of a graded functional material as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1): The superhard wear-resistant phase powder and the metallic binder phase powder are laid layer by layer in the mold according to the designed gradient composition ratio, forming a powder bed with continuously changing composition. Step 2): Place the spacer material wire or mesh at the preset position to form the micro-cooling channel (205); Step 3): Place the filled powder bed and the steel body (100) into the mold together, and sinter them in one go using spark plasma sintering or ultra-high pressure sintering process. During the sintering process, the spacer material decomposes and volatilizes to form micro-cooling channels (205). Step 4): After sintering, the drill bit crown (200) working surface is cooled, demolded, cleaned, and polished.

5. The method for a monolithic drill bit made of graded functional materials according to claim 4, characterized in that, include: In step 1), polycrystalline diamond powder or cubic boron nitride powder with an average particle size of 5-20 μm is selected as the main superhard phase; It was ultrasonically dispersed in anhydrous ethanol for 30 minutes, and then dried for later use to prevent agglomeration; Cobalt powder, nickel powder, and tungsten carbide powder with an average particle size of 10-50μm are selected and premixed according to the required composition of the interface. The mixture is then mixed for 4-6 hours using a V-type mixer to ensure uniform mixing.

6. The method for a monolithic drill bit made of graded functional materials according to claim 4, characterized in that, include: In step 1), based on the preset gradient composition curve, the target composition ratio of each layer from the crown to the connecting interface is calculated using a computer-aided design model; the superhard phase powder and the metal binder phase mixed powder are accurately weighed by the control system and mixed by dry or wet method to prepare a mixed powder with continuously changing composition; each layer of mixed powder is stored separately for later use.

7. The method for a monolithic drill bit made of graded functional materials according to claim 4, characterized in that, include: In step 2), the method for implanting the spacer material includes: Install the cleaned graphite mold for forming the crown cavity of the drill bit on the base of the sintering equipment; insert the connecting end of the pre-treated drill bit steel body (100) into the corresponding positioning groove in the mold to ensure that its position is accurately fixed; Pre-woven water-soluble fiber filaments or low-melting-point metal wires with a three-dimensional mesh structure are used as placeholder materials and placed in a predetermined position in the mold cavity according to the three-dimensional configuration of the designed micro-cooling channel (205); this material will be removed in the subsequent sintering process to form the channel.

8. The method for a monolithic drill bit made of graded functional materials according to claim 4, characterized in that, include: In step 3), a digital gradient powder spreading method is adopted: an automated powder spreading system is used, which spreads powder layer by layer according to the gradient model calculated in step 1). 31): A first layer is laid at the bottom of the mold, which is a mixed powder with the highest content of ultrahard phase; 32): When laying the second layer, the content of the superhard phase is reduced proportionally, and the content of the metallic binder phase is increased accordingly; 33): Repeat this process layer by layer until the interface layer that connects with the steel body is reached. This layer is a mixed powder with the highest content of metallic binder phase. 34): After each layer is laid, use a scraper to level it and apply slight pre-pressure to ensure that the powder layer density is uniform and to avoid obvious boundaries between layers.

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