Titanium alloy heavy load drilling special composite coating tool and its manufacturing method and application

Abstract

The present application relates to the technical field of drilling tools, and particularly relates to a special composite coating tool for heavy load drilling of titanium alloy, a manufacturing method and application thereof; the base material of the tool is ultra-fine grain cemented carbide, and the working surface of the base is divided into three zones with differentiated functions; the first zone is the inner zone of the chisel edge and the main cutting edge, and the first zone is provided with bionic scale micro-texture; the second zone is the chip removal curved surface zone, and the second zone is provided with dendritic fractal micro-texture; the third zone is the outer peripheral surface zone, and the third zone is provided with bionic cicada wing capillary network micro-texture; the surfaces of the above three zones are all deposited with high-entropy composite nitride coating. The present application can solve the problem that the tool is prone to failure when heavy load drilling of titanium alloy is performed in the prior art. The manufacturing method of the present application is fully compatible with the existing industrialized production line of high-end cemented carbide tools, and has great popularization value and conversion value. The present application can fundamentally solve the pain points of short service life of titanium alloy machining tools and unstable hole forming quality.

Description

Technical Field

[0001] This invention relates to the field of drilling tool technology, and in particular to a composite coated tool for heavy-duty drilling of titanium alloy, its manufacturing method and application. Background Technology

[0002] Deep-hole heavy-duty drilling of large titanium alloy core load-bearing components such as compressor disks and casings for aero engines has always been a challenge in the industry. Due to the extremely low thermal conductivity of titanium alloys, cutting heat easily accumulates in the outer edge turning point region of the tool, causing the instantaneous temperature in the outer edge turning point region to approach 1000℃. In addition, the chisel edge region of the tool is subjected to extreme axial compressive forces; furthermore, the main cutting edge region of the tool faces intense shearing and friction. These factors result in different thermal loads on different areas of the tool, requiring the tool to cope with severe anisotropic thermal loads.

[0003] Currently, there are three main directions for optimizing cutting tools for heavy-duty drilling of titanium alloys, but all of them have obvious limitations:

[0004] One is the tool substrate optimization technology. For example, using K55UF ultra-fine grain cemented carbide as the substrate can improve hardness and wear resistance. However, under the extremely high axial force and high temperature of heavy-duty drilling, the Co binder phase in the substrate and the Ti element in the titanium alloy undergo violent interdiffusion, forming a TiCo intermetallic compound diffusion layer at the interface. This leads to severe adhesive wear and built-up edge phenomenon. The bonded titanium alloy deposit layer will periodically peel off, which not only accelerates the wear of the substrate, but also leads to the deterioration of the hole wall surface quality.

[0005] Secondly, there is the issue of tool surface coating technology. Existing technologies mostly employ PVD-deposited nitride coatings, which can construct a chemically inert barrier on the tool surface. However, this still faces the problem of easy peeling. Faced with the extreme heat accumulation at the outer edge turning point of nearly 1000°C, conventional coatings lack a high-temperature adaptive solid lubrication mechanism. Under the coupling effect of alternating thermal stress and mechanical impact, the coating is prone to cracking and large-area peeling. Furthermore, although the coefficient of friction of the coating surface is low, it cannot effectively resolve the severe extrusion friction of chips on the hole wall in deep holes. Titanium alloy chips can still form a large area of ​​tight adhesion to the coating surface under high temperature and pressure, thereby damaging the coating.

[0006] Thirdly, there is the issue of microtexturing technology on the tool surface. Existing laser microtexturing tools reduce friction by machining periodic micro-dimples or grooves on the working surface. However, existing microtextures adopt a "globally uniform etching" strategy, resulting in identical microtexture structures in all regions without considering the differences in working conditions between the transverse cutting edge region, the main cutting edge region, and the outer edge turning point region. Secondly, existing microtextures lack multi-level capillary conduction capabilities, making them prone to clogging by fine chips and unable to meet the deep penetration and extreme heat dissipation requirements of cooling media in heavy-duty cutting. Furthermore, an unreasonable structure and distribution of microtextures can actually reduce the strength of critical areas of the tool, making the tool more susceptible to damage.

[0007] In summary, existing technologies cannot synergistically solve the multi-factor coupled failure problem of "anisotropic force and thermal load - high temperature and heavy load tool sticking - coating peeling - matrix strength reduction due to microtexture". The tool is prone to failure, which seriously restricts the efficient and stable batch processing of titanium alloy structural parts. Summary of the Invention

[0008] The purpose of this invention is to provide a composite-coated cutting tool specifically for heavy-duty drilling of titanium alloys, aiming to solve the problem that cutting tools are prone to failure when performing heavy-duty drilling of titanium alloys in the prior art.

[0009] To achieve the above objectives, this invention provides a composite-coated cutting tool specifically designed for heavy-duty drilling with titanium alloy. The tool's substrate material is K55UF ultra-fine grain cemented carbide. The working surface of the substrate is divided into three functionally differentiated zones, each etched with a different microtexture. The first zone is the inner side of the transverse cutting edge and main cutting edge, featuring a biomimetic scale-like microtexture. This includes a first groove with a depth-to-width ratio of 0.1-0.2. The first groove divides the surface into honeycomb-arranged hexagonal scales, constructing a hexagonal topological grid within the first zone. The second zone is a chip-removing curved surface, featuring a tree-like fractal microtexture. This includes a primary main channel spirally extending along the chip-removing curved surface axis and multiple secondary branch channels extending from the primary main channel to both sides. The width and depth of the primary main channel are greater than the width and depth of the secondary branch channels, respectively. The ends of the secondary branch channels are located 20-30 mm from the edge of the chip-removing curved surface. The flow terminates smoothly at μm, with the direction from the working part of the tool towards the shank as the positive direction. The angle ∠1 between the secondary flow channel and the primary flow channel is 50-70°. The third region is the outer peripheral surface region, which is equipped with a biomimetic cicada wing capillary microtexture. It includes a primary vein groove extending along the geometric center line of the outer peripheral surface, multiple secondary vein grooves extending from the primary vein grooves to both sides, and a tertiary capillary network set in the region between the primary and secondary vein grooves. The tertiary capillary network divides the region between the primary and secondary vein grooves into horizontally and vertically arranged rhomboid pieces and constructs a rhomboid topological grid. The width and depth of the primary vein groove, secondary vein groove and tertiary capillary network decrease sequentially. With the direction from the working part of the tool towards the shank as the positive direction, the angle ∠2 between the secondary vein groove and the primary vein groove is 120-150°. The surfaces of the above three regions are all coated with a (AlCrTiVMo)N high-entropy composite nitride coating.

[0010] Furthermore, the first groove has a depth of 3-5 μm and a width of 15-25 μm, and the side length of each hexagonal scale in the hexagonal topological mesh is 15-25 μm.

[0011] Furthermore, the width of the primary main channel is 70-100μm and the depth is 35-50μm, while the width of the secondary branch channel is 23-35μm and the depth is 13-25μm.

[0012] Furthermore, along the length of the primary main channel, the spacing between adjacent secondary branch channels on the same side is 230-350 μm, and the angle ∠1 between the secondary branch channel and the primary main channel is 60°.

[0013] Furthermore, the width of the primary vein groove is 45-55 μm and the depth is 23-27 μm, the width of the secondary vein groove is 13-17 μm and the depth is 9-11 μm, the width of the tertiary capillary network is 4-8 μm and the depth is 3-8 μm, and the side length of each rhomboid piece in the rhomboid topological mesh is 15-25 μm.

[0014] Furthermore, along the length of the primary vein groove, the spacing between adjacent secondary vein grooves on the same side is 230-350 μm, and the included angle ∠2 between the secondary vein groove and the primary vein groove is 135°.

[0015] Furthermore, the thickness of the (AlCrTiVMo)N high-entropy composite nitride coating is 2-3 μm.

[0016] Furthermore, the K55UF ultrafine grain cemented carbide has a WC grain size of 0.2-0.4μm, a Co content of 6%-8%, a hardness ≥94.0HRA, and a bending strength ≥3500MPa.

[0017] This invention also provides a method for manufacturing the aforementioned composite-coated tool for heavy-duty drilling of titanium alloys, comprising the following steps: blank preparation, using a K55UF ultra-fine grain cemented carbide twist drill blank, finely grinding the working surface of the tool to achieve a surface roughness Ra≤0.2μm, followed by ultrasonic cleaning to remove surface oil and impurities; laser etching, using an ultraviolet nanosecond laser to etch the tool surface area by area, with etching process parameters of wavelength 355nm, pulse width 15ns, repetition frequency 100kHz, laser power 5W, and scanning speed 800mm / s; coating deposition, using a multi-arc ion plating PVD equipment to deposit an (AlCrTiVMo)N coating on the surface of three zones, using an equiatomic ratio AlCrTiVMo high-entropy alloy target, working gas N2, deposition temperature 450°C, and bias voltage -90V; after deposition, the aforementioned composite-coated tool for heavy-duty drilling of titanium alloys is obtained.

[0018] This invention also provides the application of the above-mentioned composite coated tool for heavy-duty drilling of titanium alloys, used for drilling titanium alloy forgings; the drilling method adopts deep hole peck drilling, the spindle speed is 1000 r / min, and the feed rate is 0.10 mm / r; the coolant is h-BN nanofluid, which is composed of 98.0% water-based semi-synthetic emulsion, 1.5% h-BN nanoparticles with a particle size of 80 nm, 0.3% polyvinylpyrrolidone dispersant, and 0.2% sodium dodecyl sulfate surfactant.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The present invention sets up a biomimetic scale microtexture in the inner area of ​​the transverse cutting edge and the main cutting edge, and combined with a high-entropy composite nitride coating. With an extremely low groove depth-to-width ratio, it effectively disperses and dissipates extreme axial compressive stress while fully preserving the compressive rigidity of the K55UF ultra-fine grain cemented carbide matrix, thus preventing microscopic plastic deformation of the matrix. At the same time, the biomimetic scale, as a strong mechanical node, combined with the flexibility of the high-entropy composite nitride coating, enables the coating bonding force Lc2 ≥ 75N.

[0021] (2) The tree-like fractal microtexture in the chip removal curved surface area of ​​the present invention can effectively guide fine chips in a graded manner and transform the contact between chips and the chip removal curved surface into line contact, avoiding chip blockage in the deep hole blind area; more importantly, this graded topology greatly optimizes the fluid velocity gradient distribution, allowing the coolant to dive deep into the core drilling area along the two-stage flow channels, rapidly absorbing the heat generated during cutting, and effectively suppressing the grain growth and phase transformation of titanium alloy. At the same time, after the (AlCrTiVMo)N high-entropy composite nitride coating is cured, the surface hardness of the tool reaches 3850~3920 HV, which completely compensates for the mechanical loss caused by the microtexture on the surface and breaks the industry's technical prejudice that the strength of microtextured tools is reduced.

[0022] (3) The present invention achieves active adaptive lubrication by using a (AlCrTiVMo)N high-entropy composite nitride coating in conjunction with a biomimetic cicada wing capillary microtexture in the third region: On the one hand, the extremely distorted lattice of the high-entropy composite nitride coating produces a significant hysteresis diffusion effect, which constructs a dense thermal diffusion barrier between the tool and the titanium alloy chip. The diffusion depth of Co and Ti elements at the interface is reduced by more than 95% compared with the uncoated cemented carbide. On the other hand, the liquid / glassy Magnellian phase lubricant generated in situ by V and Mo elements on the coating surface at high temperature is firmly locked by the three-level capillary network in the third region near the outer edge turning point. The rhombic topological network provides excellent isotropic capillary resistance in the two-dimensional spanning direction. No matter how the chip extrusion or drainage direction changes, the liquid lubricant can be effectively spread evenly, constructing an extremely stable and uniform dynamic liquid thermal barrier membrane, which significantly reduces the dry friction area.

[0023] (4) The manufacturing method provided by this invention is fully compatible with the existing industrial production line of high-end cemented carbide tools. The three-zone differential laser etching can be precisely controlled by the digital program of a commercial industrial-grade ultraviolet nanosecond laser. The deposition of the (AlCrTiVMo)N high-entropy composite nitride coating is also based on the mature multi-arc ion plating PVD mass production process. The entire production process of the tool does not require unconventional equipment modification. The process cost and yield are controllable, and it has great promotion and transformation value for the high-end manufacturing field of aerospace. Attached Figure Description

[0024] Figure 1This is a schematic diagram of the structure of the titanium alloy heavy-duty drilling composite coated tool of the present invention;

[0025] Figure 2 This is a schematic diagram of the biomimetic scale-like microtexture in the first zone;

[0026] Figure 3 This is a schematic diagram of the tree-like fractal microtexture in the second region;

[0027] Figure 4 This is a schematic diagram of the biomimetic cicada wing capillary microtexture structure in the third region.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Inner region of the transverse cutting edge and main cutting edge; 11. Bionic scale-like microtexture; 12. First groove; 13. Hexagonal topological mesh;

[0030] 2. Chip removal curved surface area; 21. Tree-like fractal microtexture; 22. Primary main channel; 23. Secondary branch channel;

[0031] 3. Outer peripheral surface area; 31. Bionic cicada wing capillary microtexture; 32. Primary vein groove; 33. Secondary vein groove; 34. Tertiary capillary network; 35. Rhomboid topological mesh. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below.

[0033] In this embodiment, unless otherwise explicitly specified and limited, terms such as "set in," "connected," and "linked" 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 direct connection or a connection through one or more intermediate media. Those skilled in the art can understand the specific meaning of these terms in this embodiment based on the specific circumstances. The directional terms appearing in this embodiment are for the purpose of better describing the characteristics of the features and the relationships between them. It should be understood that when the placement direction of this embodiment changes, the direction of the characteristics of the features and the relationships between them also changes accordingly. Therefore, directional terms do not constitute an absolute limitation on the characteristics of the features and the relationships between them in space, but only a relative limitation.

[0034] This embodiment provides a composite-coated cutting tool specifically designed for heavy-duty drilling of titanium alloys, such as... Figures 1 to 4 As shown.

[0035] The base material of this tool is K55UF ultrafine grain cemented carbide. The selected K55UF ultrafine grain cemented carbide has a WC grain size of 0.2-0.4μm, a Co content of 6%-8%, a hardness of ≥94.0HRA, and a bending strength of ≥3500MPa, which can ensure that the base has sufficient strength and provide a high-density, low-defect base platform for the subsequent microtexturing in the three zones.

[0036] The working surface of the substrate is divided into three regions with differentiated functions. Each region is etched with a different microtexture, and a (AlCrTiVMo)N high-entropy composite nitride coating is deposited on the surface of all three regions. Preferably, the thickness of the (AlCrTiVMo)N high-entropy composite nitride coating is 2-3 μm. In this embodiment, the three regions are first differentiated and weakened to form microtextures, and then the high-entropy composite nitride coating is used as a compensating medium to embed and fill the microtextures, anchoring and strengthening the surface mechanical properties, improving strength, and achieving in-situ lubrication reinforcement. This adapts to the severe anisotropic force and thermal loads that different regions need to face during heavy-duty drilling of titanium alloys.

[0037] The first region is the inner region 1 of the transverse cutting edge and the main cutting edge. This first region is equipped with a biomimetic scale-like microtexture 11, which includes a first groove 12 with a depth-to-width ratio of 0.1-0.2. The first groove 12 divides the surface into hexagonal scale-like plates arranged in a honeycomb pattern, constructing a hexagonal topological grid 13 within the first region. By employing grooves with a low depth-to-width ratio and forming a hexagonal scale-like array, the microscopic plastic deformation slip path is altered. The honeycomb-arranged scale-like microtexture 11 divides the continuously stressed surface into multiple independent load-bearing units, causing a redistribution of axial loads at the groove edges, changing the stress transmission path, distributing and dissipating extreme axial compressive stress, preventing plastic deformation of the substrate, and providing strong mechanical anchoring nodes for the high-entropy composite nitride coating to prevent coating extrusion and peeling.

[0038] The second zone is the chip removal curved surface zone 2, which is equipped with a tree-like fractal microtexture 21. This includes a primary main channel 22 extending spirally along the axial direction of the chip removal curved surface and multiple secondary branch channels 23 extending from the primary main channel 22 to both sides. The width and depth of the primary main channel 22 are both greater than the width and depth of the secondary branch channels 23. The ends of the secondary branch channels 23 smoothly terminate 20-30 μm from the edge of the chip removal curved surface. With the working part of the tool towards the shank as the positive direction, the angle ∠1 between the secondary branch channels 23 and the primary main channel 22 is 50-70°. By setting the main channel and branch channels in accordance with the chip outflow direction, the surface contact between the chip and the chip removal curved surface is transformed into line contact or bridging contact, achieving the effect of chip breaking and anti-sticking, and providing a deep-diving channel for the internal cooling medium in the opposite direction of chip discharge.

[0039] The third region is the outer peripheral surface region 3, which is equipped with a biomimetic cicada wing capillary microtexture 31. It includes a primary vein groove 32 extending along the geometric center line of the outer peripheral surface, multiple secondary vein grooves 33 extending from the primary vein groove 32 to both sides, and a tertiary capillary network 34 set in the region between the primary vein groove 32 and the secondary vein groove 33. The tertiary capillary network 34 divides the region between the primary vein groove 32 and the secondary vein groove 33 into horizontally and vertically arranged rhomboid pieces and constructs a rhomboid topological mesh 35. The width and depth of the primary vein groove 32, the secondary vein groove 33 and the tertiary capillary network 34 decrease sequentially. With the direction from the working part of the tool to the shank as the positive direction, the included angle ∠2 between the secondary vein groove 33 and the primary vein groove 32 is 120-150°. The three-tiered progressive troughs significantly enlarge the heat dissipation surface area. The micro-nano capillary effect generated by the three-tiered capillary network 34 not only forces the coolant to undergo extreme convective heat transfer, but also acts as a "miniature oil reservoir" to firmly lock in the liquid lubricating phase generated in situ by the high-entropy composite nitride coating at high temperatures. The extremely distorted lattice of the high-entropy composite nitride coating constructs an excellent thermal diffusion barrier, completely blocking the interdiffusion channels of Co-Ti elements. V and Mo elements in the surface of the high-entropy composite nitride coating react with trace amounts of oxygen in situ at extreme high temperatures of 800~1000°C to generate Magnellie-phase amorphous oxides such as V2O5 and MoO3. These liquid / glassy lubricants are firmly stored and locked by the three-tiered capillary network 34 in the third region, constructing a dynamic liquid thermal barrier membrane and achieving true self-adaptive zero adhesion.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) The present invention provides a biomimetic scale microtexture 11 in the inner area 1 of the transverse cutting edge and the main cutting edge, and in combination with a high-entropy composite nitride coating. With an extremely low groove depth-to-width ratio, the extreme axial compressive stress is effectively dispersed and dissipated while fully preserving the compressive rigidity of the K55UF ultra-fine grain cemented carbide substrate, thus preventing microscopic plastic deformation of the substrate. At the same time, the biomimetic scale, as a strong mechanical node, combined with the flexibility of the high-entropy composite nitride coating, enables the coating bonding force Lc2 ≥ 75N.

[0042] (2) The tree-like fractal microtexture 21 in the chip removal curved surface area 2 of the present invention can effectively guide fine chips in a graded manner and transform the contact between the chips and the chip removal curved surface into a line contact, avoiding chip blockage in the deep hole blind area; more importantly, this graded topology greatly optimizes the fluid velocity gradient distribution, allowing the coolant to dive deep into the core drilling area along the two-stage flow channel, quickly absorbing the heat generated during cutting, and effectively suppressing the grain growth and phase transformation of titanium alloy. At the same time, after the (AlCrTiVMo)N high-entropy composite nitride coating is cured, the surface hardness of the tool reaches 3850~3920 HV, which completely makes up for the mechanical loss caused by the microtexture on the surface and breaks the industry's technical prejudice that the strength of microtextured tools is reduced.

[0043] (3) The present invention achieves active adaptive lubrication by using a (AlCrTiVMo)N high-entropy composite nitride coating in conjunction with a biomimetic cicada wing capillary microtexture 31 in the third region: On the one hand, the extremely distorted lattice of the high-entropy composite nitride coating produces a significant hysteresis diffusion effect, which constructs a dense thermal diffusion barrier between the tool and the titanium alloy chip. The diffusion depth of Co and Ti elements at the interface is reduced by more than 95% compared with the uncoated cemented carbide. On the other hand, the liquid / glassy Magnellian phase lubricant generated in situ by V and Mo elements on the coating surface at high temperature is firmly locked by the third-level capillary network 34 in the third region near the outer edge turning point. The rhombic topological network provides excellent isotropic capillary resistance in the two-dimensional spanning direction. No matter how the chip extrusion or drainage direction changes, the liquid lubricant can be effectively spread evenly, constructing an extremely stable and uniform dynamic liquid thermal barrier membrane, which significantly reduces the dry friction area.

[0044] The following description uses K55UF ultrafine grain cemented carbide twist drill blank with a diameter of 8mm to further illustrate this embodiment. It should be noted that the depth and width of the microtexture in each region of the present invention are absolute values ​​and do not scale with the diameter of the drill bit.

[0045] Preferably, the depth of the first groove 12 is 3-5 μm and the width is 15-25 μm, and the side length of each hexagonal scale in the hexagonal topological mesh 13 is 15-25 μm. More preferably, the depth of the first groove 12 is controlled to be extremely shallow at 3 μm and the width is 15 μm, with a width-to-depth ratio of 0.2, and the side length of each hexagonal scale is 25 μm.

[0046] Preferably, the width of the primary main channel 22 is 70-100 μm and the depth is 35-50 μm, and the width of the secondary branch channel 23 is 23-35 μm and the depth is 13-25 μm. Along the length of the primary main channel 22, the spacing between adjacent secondary branch channels 23 on the same side is 230-350 μm, and the angle ∠1 between the secondary branch channel 23 and the primary main channel 22 is 60°. Based on the geometry of an 8 mm diameter drill bit, the axial helical extension length of the chip removal surface area 2 is set to 45000 μm, and the effective width of the transverse groove is 3000~3500 μm. The primary main channel 22 is precisely positioned at the center of the geometric baseline of the entire helical chip removal surface, and is continuously distributed in a helical streamline shape in accordance with the chip discharge direction, extending throughout the entire 45000 μm chip removal stroke. More preferably, the primary main channel 22 has a width of 80 μm and a depth of 40 μm, serving as the main channel for high-flow-rate, low-resistance fluid transport; the secondary branch channel 23 extends divergently from both sides of the primary main channel 22, with a width of 25 μm and a depth of 15 μm; taking the direction from the working part of the tool towards the shank as positive, the angle between the secondary branch channel 23 and the primary main channel 22 is set to 60°; the spacing between the stagnation points of adjacent secondary vein grooves 33 on the same side on the primary vein groove 32 is set to 250 μm to ensure the axial torsional rigidity of the tool. The physical extension length of the secondary vein groove 33 on one side is 1500~1700 μm, extending outward from the primary main channel 22 to a smooth termination at 25 μm at the edge of the chip removal surface (i.e., at the secondary cutting edge), preserving the unetched matrix skeleton and ensuring the strength at the edge of the chip removal surface. During the chip removal process, this structure continuously pumps the cooling medium to the entire chip-groove friction pair interface through two-stage troughs, achieving low-friction coefficient chip transport.

[0047] Preferably, the width of the primary capillary groove 32 is 45-55 μm and the depth is 23-27 μm, the width of the secondary capillary groove 33 is 13-17 μm and the depth is 9-11 μm, the width of the tertiary capillary network 34 is 4-8 μm and the depth is 3-8 μm, and the side length of each rhomboid piece in the rhomboid topological mesh 35 is 15-25 μm. Along the length of the primary capillary groove 32, the spacing between adjacent secondary capillary grooves 33 on the same side is 230-350 μm, and the included angle ∠2 between the secondary capillary groove 33 and the primary capillary groove 32 is 135°. Based on the geometry of an 8mm diameter drill bit, the axial helical extension length of the outer peripheral surface region 3 is 45,000 μm, and the effective lateral width is 3,000~3,500 μm. The primary groove 32 is positioned at the geometric center line of this helical outer peripheral surface region 3, and is continuously distributed in a streamlined shape following the helix angle, extending throughout the entire 45,000 μm friction stroke. More preferably, the width of the primary groove 32 is set to 50 μm and the depth to 25 μm, serving as the main channel for cooling and lubrication media. The secondary groove 33 extends outwards from both sides of the primary groove 32 at a 135° angle, with a width of 15 μm and a depth of 10 μm. The spacing between adjacent secondary grooves 33 on the same side is 300 μm. The secondary grooves 33 extend smoothly from the primary grooves 32 to 25 μm from the edge of the outer peripheral surface region 3 (i.e., at the secondary cutting edge), retaining the unetched portion. The matrix skeleton ensures the strength at the edge of the chip removal surface; the three-level capillary network 34 is obtained by full-coverage cross etching on the left and right sides of the first-level capillary groove 32 respectively. A rhomboid topological mesh 35 is divided in the area enclosed by the first-level capillary groove 32 and the second-level capillary groove 33. The width of the three-level capillary network 34 is 5μm and the depth is 4μm. In order to balance the liquid storage rate and the compressive rigidity of the matrix, the single side length of the rhomboid is set to 20μm. The denser the rhomboid, the more lubricating phase is stored, and the better the effect; the intersection of the various levels of capillary grooves is smoothly transitioned by arc. After a 2μm thick (AlCrTiVMo)N high-entropy composite nitride coating is deposited, the tertiary capillary network 34 still retains residual rhomboid capillary channels with a width of 1.0~2.0μm and a depth of 1.0~2.0μm. Under the extreme high temperature and pressure of deep hole drilling, this network of residual rhomboid capillary channels, distributed along its entire length, can firmly lock the Magnelli phase solid lubricant generated in situ by the high-entropy composite nitride coating with its extremely small hydraulic diameter, and perfectly receive the coolant guided by the upper-level network grooves. This creates an extremely difficult-to-break isolation film between the outer peripheral surface of the tool and the hole wall, avoiding frictional burn-off or seizing interference between the outer peripheral surface and the hole wall.

[0048] This embodiment also provides a method for manufacturing the aforementioned titanium alloy heavy-duty drilling composite coated tool, which includes the following steps: blank preparation: a K55UF ultra-fine grain cemented carbide twist drill blank is selected, and the working surface of the tool is pre-treated by fine grinding to achieve a surface roughness Ra≤0.2μm. Then, ultrasonic cleaning is used to remove surface oil and impurities. Laser etching: an ultraviolet nanosecond laser is used to etch the tool surface area by area. The etching process parameters are: wavelength 355nm, pulse width 15ns, repetition frequency 100kHz, laser power 5W, and scanning speed 800mm / s. Coating deposition: a multi-arc ion plating PVD equipment is used to deposit an (AlCrTiVMo)N coating on the surface of three zones. The target material is an equiatomic ratio AlCrTiVMo high-entropy alloy target, the working gas is N2, the deposition temperature is 450°C, the bias voltage is -90V, and the coating thickness is 2μm. After deposition, the titanium alloy heavy-duty drilling composite coated tool is obtained. The microhardness of the tool surface reaches 3850HV, and the coating-substrate adhesion Lc2 is [not specified]. ≥75 N. In another manufacturing method, the deposition temperature is changed to 480°C, the coating thickness is changed to 3μm, the microhardness of the tool surface reaches 3920HV, and the coating-substrate adhesion Lc2 ≥80N.

[0049] The manufacturing method provided by this invention is fully compatible with existing industrial production lines for high-end cemented carbide cutting tools. The three-zone differentiated laser etching can be precisely controlled by a digital program of a commercial industrial-grade ultraviolet nanosecond laser. The deposition of the (AlCrTiVMo)N high-entropy composite nitride coating is also based on the mature multi-arc ion plating PVD mass production process. The entire production process of the tool does not require unconventional equipment modifications, and the process cost and yield are controllable. It has great promotion and transformation value for the high-end manufacturing field of aerospace.

[0050] This embodiment also provides the application of the above-mentioned composite coated tool for heavy-duty drilling of titanium alloys, used for drilling titanium alloy forgings; the drilling method adopts deep hole peck drilling, the spindle speed is 1000 r / min, and the feed rate is 0.10 mm / r; the coolant is h-BN nanofluid, which is composed of 98.0% water-based semi-synthetic emulsion, 1.5% h-BN nanoparticles with a particle size of 80 nm, 0.3% polyvinylpyrrolidone dispersant, and 0.2% sodium dodecyl sulfate surfactant. This coolant can have excellent thermal conductivity, lubrication performance, and suspension stability. h-BN nanofluid is directly delivered to the cutting zone through an internal cooling channel. Utilizing the excellent thermal conductivity and solid self-lubricating properties of h-BN nanoparticles, combined with the liquid storage and conduction capabilities of the biomimetic cicada-wing capillary microtexture 31 in the third zone, the nanofluid can rapidly spread to the tertiary capillary network 34 and the tool-chip interface under capillary force, achieving continuous transport and circulation of coolant. Simultaneously, h-BN nanoparticles continuously deposit at the cutting interface, forming a stable boundary lubrication film, effectively reducing the friction coefficient between the tool and chips, minimizing cutting heat accumulation, improving heat dissipation efficiency in the cutting zone, and inhibiting tool wear. Furthermore, the (AlCrTiVMo)N high-entropy composite nitride coating possesses excellent high-temperature stability and wear resistance, forming a synergistic friction-reducing effect with the h-BN nanoparticles, improving the stability and sustainability of the lubrication film, and constructing a closed-loop cooling and lubrication system of "fractal capillary conduction—high-efficiency nanofluid cooling—continuous friction reduction by the boundary lubrication film—wear-resistant protection by the high-entropy coating." Drilling tests show that, under the same cutting parameters, the continuous drilling life of the titanium alloy heavy-duty drilling-specific composite coated tool of this invention is more than 120% higher than that of commercial high-performance carbide drill bits. The surface roughness Ra value of the assembly hole wall is stably reduced from the conventional 3.2μm to below 1.2μm. The hole diameter tolerance is strictly controlled at IT7 level, and no microscopic tearing defects are observed on the surface. This fundamentally solves the engineering pain points of short tool life and unstable hole quality in the machining of high-stress assembly holes for key aerospace load-bearing components.

[0051] In summary, the present invention can solve the problem of tool failure during heavy-duty drilling of titanium alloys in the prior art.

[0052] Where there is no conflict, the above embodiments and features can be combined with each other.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the preferred technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the present invention.

Claims

1. A composite-coated cutting tool for heavy-duty drilling of titanium alloys, characterized in that: The base material of this tool is K55UF ultra-fine grain cemented carbide. The working surface of the base is divided into three regions with different functions, and each region is etched with different microtextures. The first region is the inner region of the transverse blade and the main cutting edge (1). The first region is provided with a biomimetic scale microtexture (11), which includes a first groove (12). The depth-to-width ratio of the first groove (12) is 0.1-0.

2. The first groove (12) divides the hexagonal scale plates arranged in a honeycomb pattern and constructs a hexagonal topological grid (13) in the first region. The second zone is the chip removal curved surface zone (2). The second zone is provided with a tree-like fractal microtexture (21), which includes a primary main channel (22) that extends spirally along the chip removal curved surface axis and multiple secondary branch channels (23) that extend from the primary main channel (22) to both sides. The width and depth of the primary main channel (22) are greater than the width and depth of the secondary branch channels (23), respectively. The end of the secondary branch channel (23) terminates smoothly at a distance of 20-30μm from the edge of the chip removal curved surface. The direction from the working part of the tool to the shank is taken as the positive direction. The angle ∠1 between the secondary branch channel (23) and the primary main channel (22) is 50-70°. The third region is the outer peripheral surface region (3). The third region is provided with a biomimetic cicada wing capillary microtexture (31), which includes a primary vein groove (32) extending along the geometric center line of the outer peripheral surface, multiple secondary vein grooves (33) extending from the primary vein groove (32) to both sides, and a tertiary capillary network (34) set in the region between the primary vein groove (32) and the secondary vein groove (33). The tertiary capillary network (34) divides the region between the primary vein groove (32) and the secondary vein groove (33) into horizontally and vertically arranged rhomboid pieces and constructs a rhomboid topological grid (35). The width and depth of the primary vein groove (32), the secondary vein groove (33) and the tertiary capillary network (34) decrease sequentially. With the working part of the tool towards the shank as the positive direction, the included angle ∠2 between the secondary vein groove (33) and the primary vein groove (32) is 120-150°. The surfaces of all three regions are coated with a (AlCrTiVMo)N high-entropy composite nitride coating.

2. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 1, characterized in that: The first groove (12) has a depth of 3-5 μm and a width of 15-25 μm, and the side length of each hexagonal scale in the hexagonal topological mesh (13) is 15-25 μm.

3. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 1, characterized in that: The width of the primary main channel (22) is 70-100μm and the depth is 35-50μm, and the width of the secondary branch channel (23) is 23-35μm and the depth is 13-25μm.

4. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 3, characterized in that: Along the length of the primary main channel (22), the spacing between adjacent secondary branch channels (23) on the same side is 230-350 μm, and the angle ∠1 between the secondary branch channel (23) and the primary main channel (22) is 60°.

5. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 1, characterized in that: The width of the primary vein groove (32) is 45-55 μm and the depth is 23-27 μm, the width of the secondary vein groove (33) is 13-17 μm and the depth is 9-11 μm, the width of the tertiary capillary network (34) is 4-8 μm and the depth is 3-8 μm, and the side length of each rhomboid piece in the rhomboid topological mesh (35) is 15-25 μm.

6. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 5, characterized in that: Along the length of the primary vein groove (32), the spacing between adjacent secondary vein grooves (33) on the same side is 230-350μm, and the included angle ∠2 between the secondary vein groove (33) and the primary vein groove (32) is 135°.

7. The composite-coated cutting tool for heavy-duty drilling of titanium alloys according to claim 1, characterized in that: The thickness of the (AlCrTiVMo)N high-entropy composite nitride coating is 2-3 μm.

8. The titanium alloy heavy-duty drilling composite coated tool according to any one of claims 1 to 7, characterized in that: The K55UF ultrafine grain cemented carbide has a WC grain size of 0.2-0.4μm, a Co content of 6%-8%, a hardness ≥94.0HRA, and a bending strength ≥3500MPa.

9. A method for manufacturing a titanium alloy heavy-duty drilling composite coated tool as described in any one of claims 1 to 8, characterized in that, Includes the following steps: For blank preparation, K55UF ultra-fine grain cemented carbide twist drill blanks are selected. The working surface of the tool is finely ground to make the surface roughness Ra≤0.2μm. Then, ultrasonic cleaning is used to remove surface oil and impurities. Laser etching uses an ultraviolet nanosecond laser to etch corresponding microtextures on the surface of the tool area by area. The wavelength is 355nm, the pulse width is 15ns, the repetition frequency is 100kHz, the laser power is 5W, and the scanning speed is 800mm / s. The coating deposition was performed using a multi-arc ion plating PVD equipment to deposit a (AlCrTiVMo)N high-entropy composite nitride coating on the surface of three zones. The target material was an AlCrTiVMo high-entropy alloy target with an equiatomic ratio. The working gas was N2, the deposition temperature was 450°C, and the bias voltage was -90V. After deposition, the titanium alloy heavy-duty drilling special composite coated tool was obtained.

10. The application of the titanium alloy heavy-duty drilling composite coated tool according to any one of claims 1 to 8, characterized in that: Drilling for titanium alloy forgings; The drilling method adopts deep hole peck drilling, with a spindle speed of 1000 r / min and a feed rate of 0.10 mm / r; The coolant is an h-BN nanofluid, which consists of 98.0% water-based semi-synthetic emulsion, 1.5% h-BN nanoparticles with a particle size of 80 nm, 0.3% polyvinylpyrrolidone dispersant, and 0.2% sodium dodecyl sulfate surfactant.

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