Cemented carbide cutter tooth with continuous gradient structure and preparation method thereof

Abstract

The invention discloses a hard alloy cutter tooth of a continuous gradient structure and a preparation method of the hard alloy cutter tooth, the hard alloy cutter tooth is divided into a hard alloy inner core layer, a hard alloy gradient structure middle transition layer and a hard alloy surface working layer from inside to outside, in the hard alloy cutter tooth, the Co content is gradually reduced from inside to outside, and the Co content is gradually reduced from inside to outside. In the middle transition layer of the hard alloy gradient structure, the content of the carbide and the hard alloy grain inhibitor is gradually increased, and in the middle transition layer of the hard alloy gradient structure, the content of Co is linearly and continuously decreased from inside to outside, and the content of the carbide and the hard alloy grain inhibitor is linearly and continuously increased from inside to outside; the hard alloy cutter tooth of the continuous gradient structure is of a hard alloy inhibitor component gradient distribution structure with controllable components, the physical structure that the inner portion is thick and the outer portion is thin is achieved, the physical and mechanical characteristics that the outer portion is hard and the inner portion is tough are achieved according to the functional gradient structure principle, and the abrasion resistance and impact toughness of the cutter tooth are remarkably improved. And the service life and the working efficiency of the tunneling tool are improved.

Description

Technical Field

[0001] This invention belongs to the field of engineering machinery, specifically relating to a cemented carbide cutting tooth with a continuous gradient structure and its preparation method. Background Technology

[0002] Cemented carbide, due to its high hardness, excellent heat and wear resistance, high compressive strength, good chemical stability, and economic benefits, is widely used in various industrial fields, such as cutting tools, abrasives, molds, and other demanding applications. Carbide grain size is a key microstructural parameter determining the overall performance of cemented carbide. According to the Hall-Page effect, grain refinement can simultaneously improve the hardness and strength of the material, while improving toughness by increasing the tortuosity of crack propagation paths. However, reducing grain size shortens the mean free path of the binder phase, creating an inherent trade-off between extremely high hardness and impact toughness. Therefore, coarse-grained alloys (1.5-5.0µm) are suitable for heavy-duty applications such as mining tools due to their excellent impact resistance, while fine-grained (0.5-0.8µm) and ultrafine-grained (<0.5µm) alloys are widely used in precision tools and micro-tools due to their ultra-high hardness, wear resistance, and cutting edge stability. Precise control of grain size has become a core means of optimizing cemented carbide performance.

[0003] In heavy engineering equipment such as tunnel boring machine cutters, traditional cutters are generally made of a single material, cemented carbide. This homogeneous material structure makes it difficult to simultaneously achieve a synergistic optimization of high hardness, high impact resistance, and high toughness, thus failing to meet the comprehensive performance requirements of cutters in the complex, variable, and heterogeneous rock formations of future underground engineering projects. When facing uneven geological conditions with alternating soft and hard surfaces and significant strength differences, traditional cemented carbide cutters often exhibit uneven wear distribution and insufficient service life, leading to frequent cutter replacements. This not only significantly increases construction costs but also severely restricts engineering efficiency.

[0004] By adding varying amounts of cemented carbide inhibitors from the inside out, a tough core region is formed within the cemented carbide through coarser carbide grains and a relatively sufficient distribution of cobalt phase. This endows the material with excellent impact resistance and fracture toughness, effectively inhibiting crack initiation and propagation. On the surface of the cemented carbide material, fine carbide grains construct a high-strength, high-hardness wear-resistant working layer, significantly improving the material's wear resistance and lifespan. This "tough inside, hard outside" gradient structure allows cemented carbide to simultaneously meet the dual requirements of withstanding high internal stress and resisting severe external wear, making it particularly suitable for complex working conditions such as tunnel boring machine cutters and mining drilling tools that must withstand strong impact loads and face severe wear.

[0005] By replacing the traditional layered structure with a continuous gradient structure, and constructing a gradient transition zone with continuously changing physical properties, the thermal and mechanical stress concentrations caused by abrupt changes in material properties in traditional layered or coated cutting tools are eliminated. This significantly reduces the risk of stress concentration and crack propagation, effectively suppressing crack initiation and rapid propagation at the interface, and improving the service reliability of the cutting tools under high-impact conditions. Simultaneously, by utilizing additive manufacturing to precisely control powder ratios and forming paths, programmable design of gradient direction, gradient amplitude, and gradient function form is achieved. This allows the material properties of the cutting tools to match actual service conditions, overcoming the limitations of poor controllability and low repeatability of gradient structures in traditional powder metallurgy processes, and providing a new direction for the design and development of next-generation high-performance cemented carbides. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a cemented carbide cutting tooth with a continuous gradient structure. This continuous gradient structure has a gradient distribution structure of cemented carbide inhibitor components with controllable composition, realizing a physical structure of "coarse inside and fine outside" cemented carbide carbides. It utilizes the principle of functional gradient structure to achieve the physical and mechanical properties of "hard outside and tough inside", significantly increasing the wear resistance and impact toughness of the cutting tooth, and improving the service life and working efficiency of tunneling tools.

[0007] The second objective of this invention is to provide a method for preparing cemented carbide cutting teeth with a continuous gradient structure. This invention, through continuous control of the feeding ratio of multiple sets of cemented carbide printing filaments during the 3D printing process, forms a gradient region with continuously changing material composition and microstructure in three-dimensional space. This effectively solves the problems of extremely high difficulty in powder laying, uniformity, cost, and manufacturing precision control in conventional methods. The preparation method of this invention is low in cost and high in precision.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0009] This invention provides a cemented carbide cutting tooth with a continuous gradient structure, wherein the cemented carbide cutting tooth is divided into an internal cemented carbide core layer, an intermediate transition layer of the cemented carbide gradient structure, and a surface working layer of cemented carbide from the inside out.

[0010] The core layer, intermediate transition layer of the cemented carbide gradient structure, and working layer on the surface of the cemented carbide are all composed of Co, carbides, and cemented carbide grain inhibitors.

[0011] In the cemented carbide cutting tool, the content of Co gradually decreases from the inside to the outside, while the content of carbides and cemented carbide grain inhibitors gradually increases. In the intermediate transition layer of the cemented carbide gradient structure, the content of Co decreases linearly and continuously from the inside to the outside, while the content of carbides and cemented carbide grain inhibitors increases linearly and continuously from the inside to the outside.

[0012] The carbide cutting teeth provided by this invention, according to the composition of this invention, have a core layer with high toughness, moderate hardness and wear resistance, capable of withstanding large impact loads, providing structural support and strength for the cutting tool; the surface working layer of the carbide has high hardness and excellent wear resistance, suitable for use under extreme wear conditions, thus increasing the cutting performance and wear resistance of the cutting tool; and the connecting layer has a gradient structure, so that the performance of the carbide changes with the composition of the carbide, gradually transitioning from strong wear resistance on the surface to strong toughness and impact resistance inside the tooth body, effectively inhibiting crack initiation and propagation while improving the drilling speed, wear resistance and life of the cutting teeth.

[0013] In a preferred embodiment, in the core layer of the cemented carbide, the volume ratio of Co: cemented carbide grain inhibitor: carbide is (25~30): (0.2~0.5): (69.5~74.8); in the working layer of the cemented carbide surface, the volume ratio of Co: cemented carbide grain inhibitor: carbide is (3~5): (1.8~2): (93~95.2); and in the intermediate transition layer of the cemented carbide gradient structure, the Co content decreases linearly from 24~28% to 3.5~6% by volume percentage, and the cemented carbide grain inhibitor content increases linearly from 0.3~0.6% to 1.4~1.6%.

[0014] In this invention, a smaller amount of cemented carbide grain inhibitor is added to the interior of the cemented carbide to form coarser carbide grains, and a relatively sufficient cobalt phase distribution forms a tough core region, endowing the material with excellent impact resistance and fracture toughness, effectively inhibiting crack initiation and propagation. On the surface of the cemented carbide material, a larger amount of cemented carbide grain inhibitor is added to form finer carbide grains, thus constructing a high-strength, high-hardness wear-resistant working layer, avoiding the problem of not being able to achieve both hardness and toughness, and significantly improving the material's wear resistance and lifespan. In this invention, the coarseness of carbides in the cemented carbide is controlled by the cemented carbide grain inhibitor, and the interior and exterior of the cemented carbide each have their optimal performance, thereby avoiding the performance defects of traditional cutting tools under high impact and high wear conditions.

[0015] Furthermore, by employing a continuously distributed gradient connection layer, there is no clear compositional abrupt interface between adjacent voxel units, enabling a smooth spatial transition of the material's mechanical and thermophysical properties. This effectively reduces stress concentration and thermal stress levels, inhibits the initiation and propagation of cracks within the material, thereby improving the structural stability, fracture resistance, and overall service reliability of the cutting teeth under impact loads and high-temperature conditions.

[0016] In a preferred embodiment, the thickness of the intermediate transition layer in the cemented carbide gradient structure is 50~200μm, and the thickness of the cemented carbide surface working layer is 5~50μm. The inventors have discovered that the thicknesses of the intermediate transition layer and the surface working layer need to be effectively controlled. If the surface working layer is too thin, the wear-resistant layer will be quickly depleted, exposing the poor-performing internal material and leading to accelerated failure. If the surface working layer is too thick, excessive residual stress will cause it to peel off.

[0017] In a preferred embodiment, the carbide is selected from one of WC, TiC, and TaC.

[0018] In a preferred embodiment, the cemented carbide grain inhibitor is selected from at least one of chromium carbide (Cr3C2), vanadium carbide (VC), tantalum carbide (TaC), niobium carbide (NbC), and molybdenum carbide (Mo2C).

[0019] In a further preferred embodiment, the cemented carbide grain inhibitor used in the core layer of the cemented carbide is composed of vanadium carbide and chromium carbide in a mass ratio of 1~2:1~3, and the cemented carbide grain inhibitor used in the working layer on the surface of the cemented carbide is composed of vanadium carbide and chromium carbide in a mass ratio of 4~7:6~8.

[0020] The inventors discovered that the composite addition of cemented carbide grain inhibitors can work synergistically to balance various properties, providing good overall inhibition and corrosion resistance while providing strong grain refinement. The combination of the two can obtain a fine-grained alloy with uniform structure and excellent performance. The performance is optimal when the above-mentioned proportions of vanadium carbide and chromium carbide are used in the internal core layer and the cemented carbide surface working layer, respectively.

[0021] In a preferred embodiment, the carbide cutting teeth are selected from one of the following: ball teeth, bevel teeth, arc teeth, wedge teeth, and axe teeth.

[0022] This invention also provides a method for preparing a cemented carbide cutting edge with a continuous gradient structure. Based on the composition of the cemented carbide internal core layer, Co powder, carbide powder, cemented carbide grain inhibitor powder, and binder are mixed to prepare a cemented carbide internal core layer filament. Based on the composition of the cemented carbide surface working layer, Co powder, carbide powder, cemented carbide grain inhibitor powder, and binder are mixed to prepare a cemented carbide surface working layer filament. The cemented carbide internal core layer filament and the cemented carbide surface working layer filament are placed in two feed ports of a 3D printing device. Based on the model of the cemented carbide cutting edge, the feeding speed of the two filaments is controlled by the feeding system, allowing the two filaments to enter the mixing chamber continuously, either individually or in different proportions. Then, the filaments are extruded and deposited through a nozzle to obtain a cemented carbide cutting edge green blank. The green blank is then successively cold-pressed or pre-pressed and sintered to form a cemented carbide cutting edge compact. Finally, the green blank is obtained by high-temperature and high-pressure sintering.

[0023] The printing process of the cemented carbide cutting edge green blank is as follows: First, only the cemented carbide internal core layer wire is fed into the mixing chamber through the feed port, and then extruded through the nozzle to form the cemented carbide internal core layer green blank. Then, according to the composition of the intermediate transition layer of the cemented carbide gradient structure, the proportion of the cemented carbide internal core layer wire entering the mixing chamber is uniformly decreased, and the proportion of the cemented carbide surface working layer entering the mixing chamber is uniformly increased. After continuous mixing in the mixing chamber, it is extruded through the nozzle and printed on the basis of the cemented carbide internal core layer green blank to form the cemented carbide gradient structure intermediate transition layer green blank. Finally, only the cemented carbide surface working layer wire is fed into the mixing chamber and extruded through the nozzle and printed on the basis of the cemented carbide gradient structure intermediate transition layer green blank to form the cemented carbide surface working layer green blank.

[0024] In a preferred embodiment, the Co powder has a particle size of 1~15μm, the cemented carbide grain inhibitor powder has a particle size of 0.1~0.8μm, and the carbide powder has a particle size of 5~15μm.

[0025] The inventors discovered that controlling the particle diameter within the aforementioned range yields optimal printing accuracy and product quality.

[0026] In a preferred embodiment, the adhesive comprises 70-85% by mass of deionized water, 15-25% by mass of polyvinyl alcohol, and 3-8% by mass of glycerin.

[0027] In this invention, the intermediate transition layer is formed by extruding an internal core layer filament and a surface working layer filament mixed in a specific ratio within the mixing chamber of the printhead. Both filaments use the same or similar binder systems. Under printing temperature conditions, the binder softens or melts, forming a continuous polymer flow phase. Co particles, carbide particles, and cemented carbide grain inhibitor particles are uniformly dispersed in this phase as a solid phase, thus forming a high-solids-content particle-polymer composite fluid system. Simultaneously, the two filaments exhibit similar melt viscosity and shear-thinning characteristics at the printing temperature. Under the shearing and turbulence effects within the mixing chamber, the material viscosity decreases with increasing shear rate, improving material flowability and promoting uniform mixing and stable flow of the two materials in a short time. When the viscosity difference between the two filaments is small, stratification or relative slippage during the flow process can be effectively avoided. Furthermore, both filaments are primarily composed of Co and carbides, differing only in the content of the binder phase or the content of the cemented carbide grain inhibitor, thus exhibiting good interfacial compatibility in the molten state. During the extrusion process, the two materials can form a stable composite flow structure in the mixing chamber and be continuously and stably extruded through the nozzle, thereby realizing the continuous change of material composition along the printing direction and forming an intermediate transition layer structure.

[0028] In the binder of this invention, deionized water serves as the base solvent for the entire binder system, responsible for dissolving organic components such as PEG to form a homogeneous solution. Polyvinyl alcohol, as a water-soluble polymer binder, enhances the physical bonding between powder particles through molecular bridging, improving the strength and structural stability of the green body. It also possesses excellent wetting and penetration properties and mild, controllable degreasing characteristics, playing a crucial role in the forming and complete sintering of complex gradient structures. Glycerin is added as a plasticizer; its small molecules can insert between the long polymer chains of PEG, weakening the inter-chain interactions and thus increasing the flexibility of the green body. This effectively prevents cracking of the green body due to internal stress during handling or the initial degreasing stage. Furthermore, glycerin is a highly hygroscopic polyol that can absorb moisture from the air, preventing the printhead from drying out and better controlling the curing process.

[0029] In a preferred embodiment, the mixing chamber has an inner diameter of 6-12 mm, preferably 8-10 mm, a length of 20-50 mm, preferably 25-40 mm, and an effective volume of 0.5-5 ml, preferably 1-3 ml.

[0030] In the preferred embodiment, during the process of forming the intermediate transition layer of the cemented carbide gradient structure on the core layer green body through nozzle extrusion printing, the temperature of the mixing chamber is controlled at 160~220℃, preferably 170~200℃; and stirring is applied in the mixing chamber, with the stirring speed controlled at 50~300rpm.

[0031] In this invention, when printing the core layer inside the cemented carbide and the working layer on the surface of the cemented carbide separately, the mixing chamber only serves as a channel for the filaments and does not require heating or stirring. However, when printing the intermediate transition layer, the temperature of the mixing chamber is controlled at 160~220°C, and by stirring, the two filaments form a stable composite flow structure under the shearing and turbulence action in the mixing chamber.

[0032] In the preferred embodiment, when printing to form both the inner core layer green blank and the surface working layer green blank of cemented carbide, the nozzle diameter is controlled to be 0.6~1.0mm, the layer height to be 0.2~0.4mm, the extrusion rate to be 50~200mm / s, and the extrusion flow rate to be 100~150%.

[0033] When printing the intermediate transition layer of the cemented carbide gradient structure, the nozzle diameter is controlled to be 0.6~1.0mm, the layer height to be 0.3~0.5mm, the extrusion rate to be 5~100mm / s, and the extrusion flow rate to be 80~120%.

[0034] In this invention, the carbide cutting tooth blank, dried to constant weight, is placed in a high-temperature and high-pressure resistant metal mold for preliminary compaction to ensure the accuracy and uniformity of the carbide cutting tooth.

[0035] In the preferred embodiment, the cold pressing pressure is 50~300MPa; the pre-pressing sintering temperature is 300~1500℃ and the pressure is 100~1500MPa; the high-temperature and high-pressure sintering pressure is 20~100MPa, the high-temperature and high-pressure sintering temperature is 1350~1600℃, and the high-temperature and high-pressure sintering time is 5~70min.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] This invention provides a cemented carbide cutting tooth that achieves a "coarse inside and fine outside" physical structure of cemented carbide carbides by controlling the gradient distribution structure of cemented carbide inhibitor components. It utilizes the functional gradient structure principle to achieve "hard outside and tough inside" physical and mechanical properties, taking into account both the toughness and wear resistance of cemented carbide, significantly increasing the wear resistance and impact toughness of the cutting tooth, and improving the service life and working efficiency of tunneling tools.

[0038] This invention provides a process for preparing cemented carbide cutting teeth. By continuously controlling the feed ratio of multiple sets of printing filaments during the 3D printing process, a continuous gradient transition zone without obvious compositional abrupt changes is formed in three-dimensional space, achieving a continuous and smooth performance gradient. From the core to the surface, the WC grain size and cobalt content can change steplessly, effectively avoiding the stress concentration, spalling, and early failure problems caused by abrupt changes in interface properties in traditional layered loading or diffusion sintering processes.

[0039] This invention provides a process for manufacturing carbide cutting teeth, which utilizes the moldless manufacturing characteristics of 3D printing to produce cutting teeth of any complex shape, such as ball teeth, bevel teeth, arc teeth, wedge teeth, axe teeth and other irregular teeth. At the same time, it greatly shortens the development cycle of new products and is particularly suitable for small-batch, customized high-performance cutting tool production, which is conducive to industrial production. Detailed Implementation

[0040] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the protection scope of this invention.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0042] Example 1

[0043] This example provides a continuously gradient structure cemented carbide cutting tool with a tapered tooth shape, using WC powder, Co powder, and cemented carbide grain inhibitors as cemented carbide raw materials. In the core layer of the cemented carbide, WC powder accounts for 72% of the volume, Co powder accounts for 27.6% of the volume, and the cemented carbide grain inhibitor powder is composed of vanadium carbide and chromium carbide (mass fraction ratio of 1:2), accounting for 0.4% of the volume. In the working layer on the surface of the cemented carbide, WC powder accounts for 94% of the volume, Co powder accounts for 4.2% of the volume, and the cemented carbide grain inhibitor powder is composed of vanadium carbide and chromium carbide (mass fraction ratio of 4:7), accounting for 1.8% of the volume. In the gradient transition region, the volume percentage of Co powder continuously increases from 6% to 26% from the inside to the outside, while the corresponding volume percentage of cemented carbide grain inhibitor powder continuously decreases from 0.6% to 1.6%, with the remainder being WC powder.

[0044] The thickness of the intermediate transition layer in the cemented carbide gradient structure is 120 μm, the thickness of the cemented carbide surface working layer is 30 μm, and the rest are the internal core layers of cemented carbide.

[0045] Its manufacturing process is as follows:

[0046] (1) Take appropriate amounts of Co powder, cemented carbide grain inhibitor powder and WC powder, wherein the particle size of Co powder is 1 μm, the particle size of cemented carbide grain inhibitor powder is 0.2 μm, and the particle size of WC powder is 10 μm.

[0047] (2) Co powder, cemented carbide grain inhibitor powder, and WC powder are mixed according to their respective distribution gradient requirements and then added to a special binder (the binder consists of 75 vol% deionized water, 20 vol% polyvinyl alcohol, and 5 vol% glycerol). The mixture is then kneaded, granulated, and drawn into filaments to obtain the filaments.

[0048] (3) Use computer 3D modeling software to build the core layer model of cemented carbide, the intermediate transition layer model of cemented carbide gradient structure and the working layer model of cemented carbide surface. Store the model files in STL format, and then use slicing software to cut these files so that the thickness of each layer is machinable. Import the final slice files into the corresponding extrusion molding 3D printing equipment.

[0049] (4) Then, only the core layer wire of the cemented carbide is fed into the mixing chamber through the feed inlet (without heating or stirring), and then extruded through the nozzle to form a green blank of the core layer of cemented carbide. During the printing process, the nozzle diameter is controlled to be 1.0 mm, the layer height to be 0.3 mm, the extrusion rate to be 80 mm / s, and the extrusion flow rate to be 120%. Then, according to the composition design of the transition layer, the proportion of the core layer wire of cemented carbide entering the mixing chamber decreases uniformly, and the proportion of the working layer of cemented carbide entering the mixing chamber increases uniformly. The mixture is continuously mixed in the mixing chamber, and the temperature of the mixing chamber is controlled to be 180°C. The stirring speed of the mixing chamber is 300 rpm. The cemented carbide gradient structure intermediate transition layer is then formed by extrusion printing through a nozzle onto the core layer of the cemented carbide preform. During the printing process, the nozzle diameter is controlled at 1.0 mm, the layer height at 0.4 mm, the extrusion rate at 45 mm / s, and the extrusion flow rate at 80%. Finally, only the cemented carbide surface working layer filament is introduced into the mixing chamber (without heating or stirring), and then extruded through a nozzle onto the intermediate transition layer of the cemented carbide gradient structure preform to form the surface working layer preform. During the printing process, the nozzle diameter is controlled at 1.0 mm, the layer height at 0.4 mm, the extrusion rate at 50 mm / s, and the extrusion flow rate at 100%.

[0050] (5) The green blank dried to constant weight is placed in a metal conical cup resistant to high temperature and high pressure and compacted into shape. It is then placed in a vacuum sintering hot isostatic pressing furnace for pre-pressing sintering. The pre-pressing sintering temperature is 1050℃ and the pressure is 250MPa to obtain a conical tooth compact. Then, it is subjected to high temperature and high pressure sintering. The pressure of high temperature and high pressure sintering is 6MPa, the temperature of high temperature and high pressure sintering is 1450℃, and the time of high temperature and high pressure sintering is 30min to obtain a continuous gradient structure cemented carbide cutting tooth.

[0051] The hardness of the fabricated continuous gradient cemented carbide cutting teeth was measured to be 1790 HV using a Vickers hardness tester. The impact toughness of the distributed gradient cemented carbide cutting teeth was evaluated using an impact testing machine, and was found to be 18.4 J / cm². 2 A hydraulic press was used to test the compressive strength of the cutting teeth under pressure, and the deformation or failure of the cutting teeth was measured. The compressive strength of the cemented carbide cutting teeth was 4270 MPa. These properties are all improved compared to traditional cemented carbide cutting teeth, indicating that the continuous gradient structure cemented carbide cutting teeth prepared by this invention effectively balance the toughness and wear resistance of cemented carbide.

[0052] Example 2

[0053] This example provides a continuously gradient structure cemented carbide cutting tool with a spherical tooth shape, using WC powder, Co powder, and cemented carbide grain inhibitors as cemented carbide raw materials. In the core layer of the cemented carbide, WC powder accounts for 70% of the volume, Co powder accounts for 29.8% of the volume, and the cemented carbide grain inhibitor powder is composed of vanadium carbide and chromium carbide (mass fraction ratio of 1:1), accounting for 0.2% of the volume. In the working layer on the surface of the cemented carbide, WC powder accounts for 95% of the volume, Co powder accounts for 3% of the volume, and the cemented carbide grain inhibitor powder is composed of vanadium carbide and chromium carbide (mass fraction ratio of 5:6), accounting for 2% of the volume. In the gradient transition region, the volume percentage of Co powder continuously increases from 6% to 27% from the inside to the outside, while the corresponding cemented carbide grain inhibitor powder continuously decreases from 0.4%, 0.6% to 1.8%, with the remainder being WC powder.

[0054] The thickness of the intermediate transition layer in the cemented carbide gradient structure is 120 μm, the thickness of the cemented carbide surface working layer is 50 μm, and the rest are the internal core layers of cemented carbide.

[0055] Its manufacturing process is as follows:

[0056] (1) Take appropriate amounts of Co powder, cemented carbide grain inhibitor powder and WC powder, wherein the particle size of Co powder is 5 μm, the particle size of cemented carbide grain inhibitor powder is 0.1 μm and the particle size of WC powder is 12 μm.

[0057] (2) Co powder, cemented carbide grain inhibitor powder, and WC powder are mixed according to the requirements of each distribution gradient and then added to a special binder (the binder consists of 78 vol% deionized water, 18 vol% polyvinyl alcohol, and 4 vol% glycerol). The mixture is then kneaded, granulated, and drawn into wire to obtain filaments.

[0058] (3) Use computer 3D modeling software to build the core layer model of cemented carbide, the intermediate transition layer model of cemented carbide gradient structure and the working layer model of cemented carbide surface. Store the model files in STL format, and then use slicing software to cut these files so that the thickness of each layer is machinable. Import the final slice files into the corresponding extrusion molding 3D printing equipment.

[0059] (4) Then, only the core layer wire of the cemented carbide is fed into the mixing chamber through the feed port (without heating or stirring), and then extruded through the nozzle to form a green blank of the core layer of cemented carbide. During the printing process, the nozzle diameter is 0.8 mm, the layer height is 0.2 mm, the extrusion rate is 120 mm / s, and the extrusion flow rate is 130%. Then, according to the composition design of the transition layer, the proportion of the core layer wire of cemented carbide entering the mixing chamber decreases uniformly, and the proportion of the working layer of cemented carbide entering the mixing chamber increases uniformly. The mixture is continuously mixed in the mixing chamber, and the temperature of the mixing chamber is controlled at 200°C. The stirring speed of the mixing chamber is 200 rpm. To form a cemented carbide gradient structure intermediate transition layer preform by extrusion printing onto the core layer preform within the cemented carbide structure, the nozzle diameter was controlled at 0.8 mm, the layer height at 0.4 mm, the extrusion rate at 80 mm / s, and the extrusion flow rate at 100% during the printing process. Finally, only the cemented carbide surface working layer filament was introduced into the mixing chamber (without heating or stirring) and extruded onto the intermediate transition layer preform of the cemented carbide gradient structure to form the cemented carbide surface working layer preform. During this process, the nozzle diameter was 0.8 mm, the layer height at 0.3 mm, the extrusion rate at 100 mm / s, and the extrusion flow rate at 110%.

[0060] (5) The green blank dried to constant weight is placed in a high-temperature and high-pressure metal spherical cup and compacted. It is then placed in a vacuum sintering hot isostatic pressing furnace for pre-pressing sintering. The pre-pressing sintering temperature is 1200℃ and the pressure is 300MPa to obtain a spherical tooth compact. Then, it is subjected to high-temperature and high-pressure sintering. The high-temperature and high-pressure sintering pressure is 8MPa, the high-temperature and high-pressure sintering temperature is 1600℃, and the high-temperature and high-pressure sintering time is 50min to obtain a continuous gradient structure cemented carbide cutting tooth.

[0061] The hardness of the fabricated continuous gradient cemented carbide cutting teeth was measured to be 1970 HV using a Vickers hardness tester. The impact toughness of the distributed gradient cemented carbide cutting teeth was evaluated using an impact testing machine, and was found to be 16.2 J / cm². 2 A hydraulic press was used to test the compressive strength of the cutting teeth under pressure, and the deformation or failure of the cutting teeth was measured. The compressive strength of the cemented carbide cutting teeth was 4730 MPa. These properties are all improved compared to traditional cemented carbide cutting teeth, indicating that the continuous gradient structure cemented carbide cutting teeth prepared by this invention effectively balance the toughness and wear resistance of cemented carbide.

[0062] Comparative Example 1

[0063] All other conditions were the same as in Example 1, except that the volume ratio of the cemented carbide inhibitor powder was changed to 0% and the volume ratio of the Co powder to 28%. The resulting continuous gradient cemented carbide cutting teeth, lacking cemented carbide inhibitor, had excessively large WC powder particles, resulting in reduced toughness. Impact testing using an impact testing machine determined the impact toughness of the gradient cemented carbide cutting teeth to be 12.6 J / cm². 2 The impact resistance of these materials is similar to that of traditional cemented carbide cutting tools, but lower than that of Example 1.

[0064] Comparative Example 2

[0065] All other conditions were the same as in Example 2, the only difference being the absence of a gradient structure intermediate transition layer. Due to the lack of gradient layers, the impact load on the cutting teeth could not be effectively transferred, leading to stress concentration, accelerated tooth wear, and reduced working efficiency. The final continuously gradient structure cemented carbide cutting teeth had a Vickers hardness of 1480 HV and an impact toughness of 13.2 J / cm². 2 The Vickers hardness and impact toughness of the traditional cemented carbide cutting teeth are similar to those of Example 2, both being lower.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cemented carbide cutting insert of continuous gradient structure, characterized in that: The cemented carbide cutting teeth are divided into three layers from the inside out: an internal cemented carbide core layer, an intermediate transition layer with a cemented carbide gradient structure, and a surface working layer of cemented carbide. The core layer, intermediate transition layer of the cemented carbide gradient structure, and working layer on the surface of the cemented carbide are all composed of Co, carbides, and cemented carbide grain inhibitors. In the cemented carbide cutting tool, the content of Co gradually decreases from the inside to the outside, while the content of carbides and cemented carbide grain inhibitors gradually increases. In the intermediate transition layer of the cemented carbide gradient structure, the content of Co decreases linearly and continuously from the inside to the outside, while the content of carbides and cemented carbide grain inhibitors increases linearly and continuously from the inside to the outside.

2. The cemented carbide cutting tooth with a continuous gradient structure according to claim 1, characterized in that: In the core layer of the cemented carbide, the volume ratio of Co: cemented carbide grain inhibitor: carbide is 25~30:0.2~0.5:69.5~74.8; in the working layer on the surface of the cemented carbide, the volume ratio of Co: cemented carbide grain inhibitor: carbide is 3~5:1.8~2:93~95.2; in the intermediate transition layer of the cemented carbide gradient structure, the Co content decreases linearly from 24~28% to 3.5~6% by volume percentage, and the content of cemented carbide grain inhibitor increases linearly from 0.3~0.6% to 1.4~1.6%.

3. The cemented carbide cutting tooth with a continuous gradient structure according to claim 1, characterized in that: The thickness of the intermediate transition layer of the cemented carbide gradient structure is 50~200μm, and the thickness of the cemented carbide surface working layer is 5~50μm; The carbide is selected from one of WC, TiC and TaC; The cemented carbide grain inhibitor is selected from at least one of chromium carbide, vanadium carbide, tantalum carbide, niobium carbide, and molybdenum carbide; The cemented carbide cutting teeth are selected from one of the following: ball teeth, bevel teeth, arc teeth, wedge teeth, and axe teeth.

4. A continuous gradient cemented carbide insert according to claim 1, characterized in that: The cemented carbide grain inhibitor used in the core layer of the cemented carbide is composed of vanadium carbide and chromium carbide in a mass ratio of 1~2:1~3, and the cemented carbide grain inhibitor used in the surface working layer of the cemented carbide is composed of vanadium carbide and chromium carbide in a mass ratio of 4~7:6~8.

5. A method of producing a cemented carbide cutting insert with a continuous gradient structure according to any one of claims 1-4, characterized in that: Based on the composition of the internal core layer of cemented carbide, Co powder, carbide powder, cemented carbide grain inhibitor powder, and binder are mixed to prepare the internal core layer filament. Based on the composition of the surface working layer of cemented carbide, Co powder, carbide powder, cemented carbide grain inhibitor powder, and binder are mixed to prepare the surface working layer filament. The internal core layer filament and the surface working layer filament are placed in two feed ports of a 3D printing equipment, respectively. Based on the model of cemented carbide cutting teeth, the feeding speed of the two filaments is controlled by the feeding system so that the two filaments enter the mixing chamber continuously, either individually or in different proportions. Then, they are extruded and deposited through a nozzle to obtain a cemented carbide cutting tooth green blank. Then, they are successively cold-pressed or pre-pressed and sintered to form a cemented carbide cutting tooth compact. Finally, the cemented carbide cutting tooth is obtained by high-temperature and high-pressure sintering. The printing process of the cemented carbide cutting edge green blank is as follows: First, only the cemented carbide internal core layer wire is fed into the mixing chamber through the feed port, and then extruded through the nozzle to form the cemented carbide internal core layer green blank. Then, according to the composition of the intermediate transition layer of the cemented carbide gradient structure, the proportion of the cemented carbide internal core layer wire entering the mixing chamber is uniformly decreased, and the proportion of the cemented carbide surface working layer entering the mixing chamber is uniformly increased. After continuous mixing in the mixing chamber, it is extruded through the nozzle and printed on the basis of the cemented carbide internal core layer green blank to form the cemented carbide gradient structure intermediate transition layer green blank. Finally, only the cemented carbide surface working layer wire is fed into the mixing chamber and extruded through the nozzle and printed on the basis of the cemented carbide gradient structure intermediate transition layer green blank to form the cemented carbide surface working layer green blank.

6. The method for preparing a cemented carbide cutting tooth with a continuous gradient structure according to claim 5, characterized in that: The Co powder has a particle size of 1~15μm, the cemented carbide grain inhibitor powder has a particle size of 0.1~0.8μm, and the carbide powder has a particle size of 5~15μm.

7. The method for preparing a cemented carbide cutting tooth with a continuous gradient structure according to claim 5, characterized in that: The adhesive comprises 70-85% by mass of deionized water, 15-25% by mass of polyvinyl alcohol, and 3-8% by mass of glycerin.

8. The method for preparing a cemented carbide cutting tooth with a continuous gradient structure according to claim 5, characterized in that: The mixing chamber has an inner diameter of 6-12 mm, a length of 20-50 mm, and an effective volume of 0.5-5 ml. During the process of forming the intermediate transition layer of cemented carbide gradient structure on the core layer of the cemented carbide green blank through nozzle extrusion printing, the temperature of the mixing chamber is controlled at 160~220℃, and stirring is applied in the mixing chamber, with the stirring speed controlled at 50~300rpm.

9. A method of making a continuous gradient cemented carbide cutting insert according to claim 5, characterized in that: When printing to form the core layer green blank of cemented carbide and the working layer green blank of cemented carbide surface, the nozzle diameter is controlled to be 0.6~1.0mm, the layer height is 0.2~0.4mm, the extrusion rate is 50~200mm / s, and the extrusion flow rate is 100~150%. When printing the intermediate transition layer of the cemented carbide gradient structure, the nozzle diameter is controlled to be 0.6~1.0mm, the layer height to be 0.3~0.5mm, the extrusion rate to be 5~100mm / s, and the extrusion flow rate to be 80~120%.

10. The method for preparing a cemented carbide cutting tooth with a continuous gradient structure according to claim 5, characterized in that: The cold pressing pressure is 50~300MPa; the pre-pressing sintering temperature is 300~1500℃ and the pressure is 100~1500MPa; the high-temperature and high-pressure sintering pressure is 20~100MPa, the high-temperature and high-pressure sintering temperature is 1350~1600℃, and the high-temperature and high-pressure sintering time is 5~70min.