Cutter and method of making

Abstract

The application discloses a cutter and a preparation method, and relates to the technical field of drilling cutters.The application combines an ultrafine nanocrystalline cemented carbide base body with a functionally gradient composite coating, the bottom layer made of CrAlN material in the composite coating is firmly combined with the tungsten carbide cutter base body, the top layer made of TiSiCN has hardness and lubricity, cutting force and cutting heat are reduced, the intermediate layer made of AlCrSiN material provides core ultra-high hardness and thermal stability, the long service life of the cutter is ensured, a transition layer with gradient change in silicon content is further arranged between the bottom layer and the intermediate layer, stress between the bottom layer and the intermediate layer can be effectively buffered, the base body toughness, coating bonding strength, overall wear resistance and surface lubricity of the cutting cutter, especially the drill bit, are comprehensively improved, and the application has extremely high market value.

Description

Technical Field

[0001] This invention relates to the field of drilling tool technology, and in particular to a cutting tool and its manufacturing method. Background Technology

[0002] Printed circuit board (PCB) processing presents significant challenges. Ordinary micro PCB cutting tools experience rapid and extensive wear during machining, resulting in short tool life. Furthermore, chips easily clog the chip vents of the cutting tools, severely degrading the hole wall quality of the PCB. Related technologies primarily utilize micron-sized cemented carbide, such as tungsten carbide, as the substrate material for micro drills. After grinding, the cutting edge area often consists of a small number or even a single WC particle. This dot-like particle structure is prone to structural instability. Therefore, the industry typically applies a high-hardness coating to the substrate surface. TiSiN coatings, due to their excellent hardness and superior heat oxidation resistance, have become the preferred surface coating for high-end micro drills. However, TiSiN coatings are prone to residual stress during deposition, easily leading to cracks and peeling, limiting their thickness and widespread application. Additionally, the high coefficient of friction of TiSiN coatings increases tool wear during drilling, resulting in reduced hole accuracy and shortened tool life. Summary of the Invention

[0003] The main objective of this invention is to design a cutting tool with high hardness, high toughness, low coefficient of friction, and strong adhesion between the coating and the tool substrate.

[0004] To achieve the above objectives, the present invention proposes a cutting tool, comprising a tool substrate and a composite coating deposited on the surface of the tool substrate. The composite coating comprises a bottom layer, a transition layer, an intermediate layer, and a top layer stacked sequentially. The bottom layer is attached to the tool substrate. The bottom layer comprises CrAlN. The intermediate layer comprises Cr, Al, Si, and N. The transition layer is disposed between the bottom layer and the intermediate layer, and the silicon content of the transition layer increases from the end closer to the bottom layer to the end closer to the intermediate layer. The top layer comprises TiSiCN.

[0005] In one embodiment, the transition layer comprises CrAlN and CrAlSiN.

[0006] In one embodiment, the intermediate layer comprises AlCrSiN.

[0007] In one embodiment, the molar percentages of each element in the bottom layer include: Cr: 20 at.%~30 at.%; Al: 15 at.%~25 at.%; N: 45 at.%~55 at.%; and / or, the molar percentages of each element in the intermediate layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 5 at.%~15 at.%; N: 45 at.%~55 at.%;

[0008] And / or, the molar percentages of each element in the transition layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 2 at.%~10 at.%; N: 45 at.%~55 at.%; And / or, the molar percentages of each element in the top layer include: Ti: 20 at.%~35 at.%; Si: 5 at.%~15 at.%; C: 5 at.%~15 at.%; N: 45 at.%~55 at.%; and the sum of the atomic percentages of C and N in the top layer is 45 at.%~55 at.%.

[0009] In one embodiment, the thickness of the bottom layer is 100nm~500nm.

[0010] In one embodiment, the thickness of the transition layer is 100nm~300nm.

[0011] In one embodiment, the thickness of the intermediate layer is 300nm~1000nm.

[0012] In one embodiment, the thickness of the top layer is 200nm~500nm.

[0013] In one embodiment, the hardness of the intermediate layer is not less than 35 GPa; and / or, the hardness of the top layer is not less than 38 GPa.

[0014] In one embodiment, the raw materials of the tool matrix include: tungsten carbide: 85wt%~94wt%; Co: 5wt%~10wt%; additives: 0.5wt%~5wt%; wherein the additives include at least one of Cr3C2, VC, and Y2O3.

[0015] In one embodiment, the average grain size of the tungsten carbide phase in the tool substrate is 150 nm to 250 nm.

[0016] The present invention also proposes a method for preparing the aforementioned cutting tool, comprising the following steps: S1. The powder used to prepare the tool substrate is mixed and ball-milled, pressed into shape and then isostatically sintered to obtain the tool substrate. S2. The tool substrate obtained in step S1 is cleaned and etched sequentially; then, the bottom layer, transition layer, intermediate layer and top layer are deposited sequentially by multi-target magnetron sputtering or arc ion plating to complete the preparation of the tool.

[0017] In one embodiment, in step S1, the particle size of the powder used to prepare the tool substrate is 0.1 μm to 0.2 μm; in another embodiment, in step S1, the pressure is controlled at 50 MPa to 80 MPa during the isostatic pressing sintering process.

[0018] In one embodiment, step S2 involves sequentially depositing the bottom layer, transition layer, intermediate layer, and top layer using arc ion plating, specifically including the following steps: P1. Place the tool substrate in the coating device, introduce nitrogen gas, turn on the CrAl target, and deposit a CrAlN bottom layer. P2. Keep the CrAl target in the on state, and simultaneously turn on the CrAlSi target. Gradually increase the power of the CrAlSi target during the deposition process to deposit a CrAlN / CrAlSiN transition layer. P3. Turn off the CrAl target and the CrAlSi target, turn on the AlCrSi target, and deposit the AlCrSiN intermediate layer. P4. Turn off the AlCrSi target and stop the nitrogen gas supply, turn on the TiSi target and introduce a mixture of nitrogen and acetylene gas to deposit the TiSiCN top layer.

[0019] The technical solution of this invention combines an ultrafine nanocrystalline cemented carbide substrate with a functionally graded composite coating. In the composite coating, the CrAlN bottom layer is firmly bonded to the tungsten carbide tool substrate; the TiSiCN top layer combines hardness and lubricity, reducing cutting force and heat; the AlCrSiN intermediate layer provides core ultra-high hardness and thermal stability, ensuring a long tool life; and a transition layer with a gradient silicon content is provided between the bottom and intermediate layers, effectively buffering stress between them. In summary, the tool substrate and composite coating in this invention synergistically enhance each other, achieving a comprehensive improvement in the substrate toughness, coating bonding strength, overall wear resistance, and surface lubricity of cutting tools, especially micron-sized cemented carbide tools such as drill bits, resulting in extremely high market value. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the composite coating structure of a cutting tool according to an embodiment of the present invention.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] The technical problem this application addresses is that PCB cutting tools experience rapid and significant wear during the processing of printed circuit boards, resulting in short tool life. Furthermore, chips easily clog the chip removal grooves of the PCB cutting tool, severely degrading the hole wall quality of the printed circuit board. Existing technologies typically use micron-sized cemented carbide, such as tungsten carbide, as the base material for micro-drills. After grinding, the cutting edge area often consists of a small number or even a single WC particle, which is prone to structural instability and subsequent detachment during cutting.

[0027] In related technologies, TiSiN coatings are used as hard coatings. However, TiSiN coatings are prone to residual stress during deposition, which can easily lead to cracks and peeling, limiting their thickness and wide application. In addition, TiSiN coatings have a high coefficient of friction. During drilling, friction increases the wear rate of the tool, resulting in reduced hole diameter accuracy and shortened tool life.

[0028] Therefore, micron-sized cemented carbide tools still suffer from problems such as insufficient stability of the tool matrix and surface particle structure, large fluctuations in interface stress, difficulty in stress control of high-hardness coatings, and rapid wear and short life due to high friction coefficients in high-speed precision machining. There is an urgent need to innovate manufacturing processes and structural designs to comprehensively improve the microstructure and coating design to obtain high-performance micro-drilling tools.

[0029] To address the aforementioned technical problems, this invention proposes a cutting tool, comprising a tool substrate and a composite coating deposited on the surface of the tool substrate; the composite coating comprises a bottom layer, a transition layer, an intermediate layer, and a top layer stacked sequentially, the bottom layer being adhered to the tool substrate; the bottom layer comprises CrAlN; the intermediate layer comprises Cr, Al, Si, and N; the transition layer is disposed between the bottom layer and the intermediate layer, the silicon content of the transition layer increasing from the end closer to the bottom layer to the end closer to the intermediate layer; the top layer comprises TiSiCN.

[0030] Specifically, the Cr and Al nitrides in the bottom layer have excellent adhesion strength and thermal stability. Their coefficient of thermal expansion is between that of the tool substrate and the transition layer, which can alleviate stress concentration caused by thermal mismatch. In addition, CrAlN has high hardness and high density, which can effectively prevent cutting heat from being transferred to the substrate, reduce the thermal softening of the substrate, and provide a smooth and stable bonding interface for subsequent coatings.

[0031] The silicon content in the transition layer gradually increases from the bottom layer to the middle layer. This compositional gradient design avoids a sudden increase in interfacial stress caused by abrupt material changes, allowing for continuous stress distribution between the interfaces. The gradient introduction of silicon promotes the formation of amorphous phases, thereby effectively dispersing stress and improving the interlayer bonding strength and anti-peeling ability of the coating.

[0032] The intermediate layer forms a coating structure with a constant composition of four elements: Cr, Al, Si, and N, based on the transition layer. Cr and Al form nanocrystalline nitrides embedded in an amorphous silicon nitride network. Due to the pinning effect, the grains are further refined, and the amorphous phase hinders dislocation movement, giving the intermediate layer both high hardness and good toughness. Furthermore, silicon promotes the formation of a silicon oxide lubricating film on the surface, resulting in a low coefficient of friction and excellent high-temperature stability, maintaining the integrity of the cutting edge under high-speed machining.

[0033] The top layer employs a TiSiCN coating, with TiC and TiN as the hard phases. The introduction of carbon generates a friction-reducing carbon phase, significantly lowering the coating's friction coefficient; silicon enhances the coating's oxidation resistance and thermal stability. The resulting top layer combines high hardness, low friction coefficient, and good chemical stability, effectively extending tool life and ensuring hole wall smoothness.

[0034] By adopting the above technical solution, the composite coating of the cutting tool in this invention is systematically optimized from multiple dimensions such as interface bonding, stress control, mechanical properties and surface lubricity through the synergistic effect of different layer structures.

[0035] In one embodiment, such as Figure 1 As shown, the transition layer includes CrAlN and CrAlSiN; specifically, the side of the transition layer near the bottom layer is composed of CrAlN, and the side of the transition layer near the middle layer is composed of CrAlSiN. It should be noted that during the deposition of the transition layer, by controlling the arc current and voltage of the alloy target to change with an increasing or decreasing trend, CrAlN and CrAlSiN layers are deposited alternately, forming a layered structure in the transition layer where CrAlN and CrAlSiN layers alternate. Macroscopically, as the arc current and voltage of the alloy target change with an increasing or decreasing trend, the side of the transition layer near the bottom layer is composed of CrAlN, the side near the middle layer is mainly composed of CrAlSiN, and the side near the bottom layer is composed of CrAlN. The transition layer starts from the bottom layer of CrAlN, and during the growth towards the middle layer, CrAlN and CrAlSiN layers alternate, with the thickness of the CrAlN layer decreasing and the thickness of the CrAlSiN layer increasing. Silicon is continuously and gradually introduced, causing its composition to gradually evolve into CrAlSiN. This allows for a smooth transition in lattice constant, elastic modulus, and coefficient of thermal expansion; and the gradual infiltration of silicon promotes the formation of amorphous phases, which can suppress the risk of stress-induced crack initiation and interface peeling during coating deposition and use.

[0036] In one embodiment, the intermediate layer comprises AlCrSiN.

[0037] It should be noted that the aluminum content in the intermediate layer is significantly higher than that in the transition layer and the bottom layer, which can significantly improve the coating's oxidation resistance and high-temperature hardness. The coating surface can form a dense and stable alumina protective film more quickly, protecting the internal structure from oxidation and maintaining the sharpness and stability of the cutting edge.

[0038] In one embodiment, the molar percentages of each element in the bottom layer include: Cr: 20 at.%~30 at.%; Al: 15 at.%~25 at.%; N: 45 at.%~55 at.%.

[0039] In one embodiment, the molar percentages of each element in the intermediate layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 5 at.%~15 at.%; N: 45 at.%~55 at.%.

[0040] In one embodiment, the molar percentages of each element in the transition layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 2 at.%~10 at.%; N: 45 at.%~55 at.%.

[0041] In one embodiment, the molar percentages of each element in the top layer include: Ti: 20 at.%~35 at.%; Si: 5 at.%~15 at.%; C: 5 at.%~15 at.%; N: 45 at.%~55 at.%; and the sum of the atomic percentages of C and N in the top layer is 45 at.%~55 at.%.

[0042] In one embodiment, the thickness of the bottom layer is 100nm~500nm; and / or, the thickness of the transition layer is 100nm~300nm; and / or, the thickness of the intermediate layer is 300nm~1000nm; and / or, the thickness of the top layer is 200nm~500nm.

[0043] It's important to note that the 500nm upper limit for the bottom layer is primarily based on stress control. An excessively thick pure CrAlN layer may accumulate significant internal stress, weakening the bonding strength. The relatively thin thickness of the transition layer requires a smooth gradient change in silicon content over a short distance in the manufacturing process, avoiding excessive thickness that would compress the design space of the intermediate layer responsible for wear resistance. The intermediate layer is the thickest layer in the entire composite coating, providing sufficient thickness to resist wear failure during prolonged cutting, which is crucial for extending tool life. The top layer's thickness is limited to 500nm for the sake of the tool's (micro-drill's) cutting edge sharpness. An excessively thick top layer would produce a "rounding effect," dulling the cutting edge and hindering entry and chip breaking in PCB micro-hole machining.

[0044] In summary, the total thickness of the composite coating on the cutting tool in this invention is approximately 0.7μm to 2.3μm, which is perfectly matched to the size of micron-level PCB cutting tools such as micro drills. An excessively thick coating would weaken the toughness of the substrate and alter the mechanical properties of the cutting edge; an excessively thin coating would fail to demonstrate the advantages of a multi-layer design.

[0045] In a preferred embodiment, the thickness of the bottom layer is 200 nm; the thickness of the transition layer is 300 nm; the thickness of the intermediate layer is 800 nm; and the thickness of the top layer is 500 nm.

[0046] In one embodiment, the hardness of the intermediate layer is not less than 35 GPa; in another embodiment, the hardness of the top layer is not less than 38 GPa.

[0047] Specifically, the tool features a high-hardness intermediate layer and an even harder top layer. As a consumable component, the top layer's slightly higher initial hardness ensures optimal surface protection and lubrication during the initial stages of service. As it gradually wears down, the slightly lower but still extremely hard intermediate layer is exposed, continuing to provide strong wear resistance and ensuring a smooth decline in tool performance throughout its lifespan. Furthermore, the intermediate layer effectively buffers stress from the top layer, preventing spalling caused by excessive stress.

[0048] In one embodiment, the raw materials of the tool matrix include: tungsten carbide: 85wt%~94wt%; Co: 5wt%~10wt%; additives: 0.5wt%~5wt%; wherein the additives include at least one of Cr3C2, VC, and Y2O3.

[0049] It is understood that the present invention obtains an ultrafine nanocrystalline cemented carbide through the above-mentioned proportions, wherein the tungsten carbide has a uniform particle size distribution and small grain size. The uniform and dense fine-grained structure makes the cutting edge collectively supported by countless small and firmly bonded WC grains at the microscopic level, which greatly improves the structural integrity and anti-chipping ability of the cutting edge, and provides a stable and reliable foundation for coating deposition.

[0050] Specifically, additives such as VC can act as grain growth inhibitors and be uniformly dispersed in the matrix to suppress abnormal growth of WC grains during sintering.

[0051] In a preferred embodiment, the average grain size of the tungsten carbide phase in the tool matrix is ​​150 nm to 250 nm.

[0052] Specifically, within the aforementioned grain size range, when subjected to the impact of high-speed cutting, stress is uniformly distributed across a vast number of fine grains, preventing the initiation and propagation of microcracks caused by stress concentration. Secondly, the substrate at this grain size, after precision grinding, yields a substrate surface with extremely low surface roughness and very few defects, providing an ideal deposition interface.

[0053] Furthermore, the hardness of the tool matrix is ​​not less than Hv1800, and the fracture strength is not less than 110 MPa·m. 1 / 2 It has a bending strength of not less than 3500MPa and good toughness and structural stability.

[0054] The present invention also proposes a method for preparing the aforementioned cutting tool, comprising the following steps: S1. The powder used to prepare the tool substrate is mixed and ball-milled, pressed into shape and then isostatically sintered to obtain the tool substrate. S2. The tool substrate obtained in step S1 is cleaned and etched sequentially; then, the bottom layer, transition layer, intermediate layer and top layer are deposited sequentially by multi-target magnetron sputtering or arc ion plating to complete the preparation of the tool.

[0055] Specifically, in step S1, the particle size of the powder used to prepare the tool substrate is 0.1 μm to 0.2 μm. By using submicron-sized raw material powder, extremely high surface energy and sintering driving force are ensured at the sintering initiation point, which is beneficial for achieving complete densification at relatively low temperatures and pressures, and also facilitates the function of grain growth inhibitors.

[0056] Specifically, in step S1, the pressure is controlled at 50MPa~80MPa during the isostatic pressing sintering process.

[0057] In one embodiment, step S2 involves sequentially depositing the bottom layer, transition layer, intermediate layer, and top layer using arc ion plating, specifically including the following steps: P1. Place the tool substrate in the coating device, introduce nitrogen gas, turn on the CrAl target, and deposit a CrAlN bottom layer. P2. Keep the CrAl target in the on state, and simultaneously turn on the CrAlSi target. Gradually increase the power of the CrAlSi target during the deposition process to deposit a CrAlN / CrAlSiN transition layer. P3. Turn off the CrAl target and the CrAlSi target, turn on the AlCrSi target, and deposit the AlCrSiN intermediate layer. P4. Turn off the AlCrSi target and stop the nitrogen gas supply, turn on the TiSi target and introduce a mixture of nitrogen and acetylene gas to deposit the TiSiCN top layer.

[0058] The present invention will be further illustrated below through specific embodiments: All raw materials used in the embodiments of this invention are commercially available, and this invention does not impose any restrictions on the source of raw materials.

[0059] Example 1 The raw materials for the tool substrate in Example 1 include: WC powder: 93.1 wt%; Co powder: 6 wt%; VC powder: 0.9 wt%; the particle size of the above powders is 0.1 μm to 0.2 μm.

[0060] like Figure 1 As shown, the composite coating for the cutting tool in Example 1 comprises layers sequentially stacked from the cutting tool substrate: The bottom layer is 0.2μm thick and made of CrAlN material, with the specific elemental composition including Cr: 25 at.%; Al: 20 at.%; N: 55 at.%; A 0.3μm thick transition layer made of CrAlN / CrAlSiN material is used. The side of the transition layer near the bottom layer does not contain Si and has the same elemental composition as the bottom layer. The Si content increases from the bottom layer to the middle layer. The side of the transition layer near the middle layer does not contain Si and has the same elemental composition as the middle layer. The intermediate layer, with a thickness of 0.8 μm, is made of AlCrSiN and has the following elemental composition: Cr: 25 at.%; Al: 15 at.%; Si: 10 at.%; N: 50 at.%; The top layer is made of TiSiCN with a thickness of 0.5μm and the elemental composition includes Ti: 30 at.%; Si: 10 at.%; C: 10 at.%; N: 40 at.%.

[0061] The preparation method of the composite coating for the cutting tool in Example 1 includes the following steps: S1. Carbide, Co, and additive powders with a particle size of 0.1μm~0.2μm were mixed and wet-milled at a ball-to-particle ratio of 5:1, a milling speed of 200 rpm, and a milling time of 24 hours. After milling, the mixture was vacuum-dried at 60℃. The mixture was then pressed into shape and densified using a spark plasma sintering process. During sintering, the heating rate was controlled at 100℃ / min, the sintering temperature was 900℃, and the sintering pressure was 40MPa for 5 minutes to obtain the tool substrate. Testing showed that the average WC grain size was 180nm and the hardness was 1850 HV30. S2. The tool substrate obtained in step S1 is sequentially cleaned and etched; then, the bottom layer, transition layer, intermediate layer and top layer are sequentially deposited using arc ion plating. Specific steps include: P1. Place the tool substrate in the coating apparatus, introduce nitrogen gas, and maintain the total pressure in the chamber at 3.0 Pa. Turn on the CrAl target, and deposit for about 6 minutes at a target current of 80 A, a bias voltage of (-60) V, and a substrate temperature of 450°C to obtain a 0.2 μm thick CrAlN underlayer. P2. Keep the CrAl target in the open state, and simultaneously turn on the CrAlSi target. Maintain constant chamber pressure and substrate temperature. During deposition, linearly increase the current of the CrAlSi alloy target from 0A to 80A, and increase the substrate bias voltage to [value missing]. At 100V, deposition was carried out for about 8 minutes, resulting in a 0.3μm thick CrAlN / CrAlSiN transition layer. P3. Close the CrAl target, maintain the chamber pressure at 3.0 Pa, the substrate temperature at 450 °C, set the target current to 80 A, and further increase the substrate bias voltage to [value missing]. At 140V, deposition was carried out for about 20 minutes to obtain an AlCrSiN interlayer with a thickness of 0.8μm. P4. Turn off the AlCrSi target, turn on the TiSi target and introduce a mixture of nitrogen and acetylene gas with a ratio of 10:1. Maintain the total pressure in the chamber at 2.5 Pa. Deposit for about 15 minutes under the conditions of target current of 70A and substrate bias voltage of -50V to obtain a 0.5μm thick TiSiCN top layer.

[0062] Example 2 The raw materials for the tool substrate in Example 2 include: WC powder: 91.5wt%; Co powder: 7wt%; VC powder: 1.5wt%; the particle size of the above powders is 0.1μm~0.2μm.

[0063] like Figure 1 As shown, the tool composite coating in Example 2 comprises layers sequentially stacked from the tool substrate: The bottom layer is 0.25μm thick and made of CrAlN material, with the specific elemental composition including Cr: 30 at.%; Al: 18 at.%; N: 52 at.%; A 0.25μm thick transition layer made of CrAlN / CrAlSiN material is used. The side of the transition layer near the bottom layer does not contain Si and has the same elemental composition as the bottom layer. The Si content increases from the bottom layer to the middle layer. The side of the transition layer near the middle layer does not contain Si and has the same elemental composition as the middle layer. The intermediate layer, with a thickness of 0.9 μm, is made of AlCrSiN and has the following elemental composition: Cr: 15 at.%; Al: 30 at.%; Si: 7 at.%; N: 48 at.%; The top layer is made of TiSiCN with a thickness of 0.4μm and the elemental composition includes Ti: 25 at.%; Si: 8 at.%; C: 10 at.%; N: 47 at.%.

[0064] The preparation method of the composite coating for the cutting tool in Example 2 includes the following steps: S1. Carbide, Co, and additive powders with a particle size of 0.1μm~0.2μm were mixed and wet-milled at a ball-to-particle ratio of 6:1, a milling speed of 220 rpm, and a milling time of 30 h. After milling, the mixture was vacuum-dried at 65℃. The mixture was then pressed into shape and densified using a spark plasma sintering process. During sintering, the heating rate was controlled at 120℃ / min, the sintering temperature was 920℃, and the sintering pressure was 45 MPa for 4 minutes to obtain the tool substrate. S2. The tool substrate obtained in step S1 is sequentially cleaned and etched; then, the bottom layer, transition layer, intermediate layer and top layer are sequentially deposited using arc ion plating. Specific steps include: P1. Place the tool substrate in the coating apparatus, introduce nitrogen gas, and maintain the total pressure in the chamber at 3.2 Pa. Turn on the CrAl target, and deposit the CrAlN underlayer at a target current of 85 A, a bias voltage of (-70) V, and a substrate temperature of 460°C. P2. Keep the CrAl target in the open state, and simultaneously turn on the CrAlSi target. Maintain constant chamber pressure and substrate temperature. During deposition, linearly increase the current of the CrAlSi alloy target from 0A to 75A, and increase the substrate bias voltage to [value missing]. 110V, deposit CrAlN / CrAlSiN transition layer; P3. Turn off the CrAl target, with the target current at 85A and the substrate bias voltage at [value missing]. An AlCrSiN intermediate layer was deposited at 140V. P4. Turn off the AlCrSi target, turn on the TiSi target and introduce a mixture of nitrogen and acetylene gas with a ratio of 8:1. Maintain the total pressure in the chamber at 2.6 Pa. Under the conditions of target current of 75 A and substrate bias of -60 V, deposit the TiSiCN top layer.

[0065] Example 3 The raw materials for the tool substrate in Example 3 include: WC powder: 89wt%; Co powder: 9wt%; Cr3C2 powder: 1.5wt%; The particle size of the above powders is 0.1μm~0.2μm.

[0066] like Figure 1 As shown, the composite coating for the cutting tool in Example 3 comprises layers sequentially stacked from the cutting tool substrate: The bottom layer is 0.15μm thick and made of CrAlN material, with the specific elemental composition including Cr: 28 at.%; Al: 22 at.%; N: 50 at.%; A 0.35μm thick transition layer made of CrAlN / CrAlSiN material is used. The side of the transition layer near the bottom layer does not contain Si and has the same elemental composition as the bottom layer. The Si content increases from the bottom layer to the middle layer. The side of the transition layer near the middle layer does not contain Si and has the same elemental composition as the middle layer. The intermediate layer, with a thickness of 0.7 μm, is made of AlCrSiN and has the following elemental composition: Cr: 12 at.%; Al: 33 at.%; Si: 6 at.%; N: 49 at.%; The top layer is made of TiSiCN with a thickness of 0.45μm and the elemental composition includes Ti: 28 at.%; Si: 6 at.%; C: 12 at.%; N: 44 at.%.

[0067] The preparation method of the composite coating for the cutting tool in Example 3 includes the following steps: S1. Carbide, Co, and additive powders with a particle size of 0.1μm~0.2μm were mixed and wet-milled at a ball-to-particle ratio of 5:1, a milling speed of 180 rpm, and a milling time of 28 h. After milling, the mixture was vacuum-dried at 65℃. The mixture was then pressed into shape and densified using a spark plasma sintering process. During sintering, the heating rate was controlled at 90℃ / min, the sintering temperature was 880℃, and the sintering pressure was 38 MPa for 6 minutes to obtain the tool substrate. S2. The tool substrate obtained in step S1 is sequentially cleaned and etched; then, the bottom layer, transition layer, intermediate layer and top layer are sequentially deposited using arc ion plating. Specific steps include: P1. Place the tool substrate in the coating apparatus, introduce nitrogen gas, and maintain the total pressure in the chamber at 2.8 Pa. Turn on the CrAl target, and deposit the CrAlN underlayer at a target current of 75 A, a bias voltage of (-50) V, and a substrate temperature of 460°C. P2. Keep the CrAl target in the open state, and simultaneously turn on the CrAlSi target. Maintain constant chamber pressure and substrate temperature. During deposition, increase the bias voltage of the CrAlSi alloy target substrate to [value missing]. 90V, deposit CrAlN / CrAlSiN transition layer; P3. Turn off the CrAl target, with the target current at 75A and the substrate bias voltage at [value missing]. An AlCrSiN intermediate layer was deposited under a 130V condition; P4. Turn off the AlCrSi target, turn on the TiSi target and introduce a mixture of nitrogen and acetylene gas with a ratio of 12:1. Maintain the total pressure in the chamber at 2.4 Pa. Under the conditions of target current of 65 A and substrate bias voltage of -60 V, deposit the TiSiCN top layer.

[0068] Example 4 The raw materials for the tool substrate in Example 4 include: WC powder: 94wt%; Co powder: 5wt%; TaC powder: 1.0wt%.%; The particle size of the above powders is 0.1μm~0.2μm.

[0069] like Figure 1 As shown, the tool composite coating in Example 4 comprises layers sequentially stacked from the tool substrate: The bottom layer is 0.3μm thick and made of CrAlN material, with the specific elemental composition including Cr: 32 at.%; Al: 18 at.%; N: 50 at.%; A 0.2μm thick transition layer made of CrAlN / CrAlSiN material is used. The side of the transition layer near the bottom layer does not contain Si, and its elemental composition is the same as that of the bottom layer. The Si content increases from the bottom layer to the middle layer. The side of the transition layer near the middle layer does not contain Si, and its elemental composition is the same as that of the middle layer. The intermediate layer, 1 μm thick, is made of AlCrSiN and has the following elemental composition: Cr: 10 at.%; Al: 35 at.%; Si: 8 at.%; N: 47 at.%; The top layer is made of TiSiCN with a thickness of 0.3μm and an elemental composition including Ti: 22 at.%; Si: 9 at.%; C: 8 at.%; N: 51 at.%.

[0070] The preparation method of the composite coating for the cutting tool in Example 4 is the same as that in Example 1.

[0071] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the particle size of WC powder in the tool matrix in Comparative Example 1 is changed to 0.4μm~0.6μm; this particle size range is the submicron level cemented carbide matrix particle size range commonly used in micro-drilling tools.

[0072] Furthermore, the tool substrate in Comparative Example 1 was prepared using a conventional vacuum sintering process with a sintering temperature of 1450℃ and a sintering time of 60 min.

[0073] The average size of the WC grains in the tool matrix was measured to be approximately 0.6 μm, and the matrix hardness was 1720 HV30. Due to the high sintering temperature and long holding time, the WC grains underwent a certain degree of growth during the sintering process.

[0074] Comparative Example 2 Comparative Example 2 is based on Example 1, except that the tool coating in Comparative Example 2 is only a single layer of AlCrSiN coating, and the elemental composition of the coating is the same as the intermediate layer of the tool composite coating in Example 1.

[0075] Accordingly, the method for preparing the tool coating in Comparative Example 2 includes the following steps: Nitrogen gas was introduced as the reactant gas to maintain a total chamber pressure of 3.0 Pa, a substrate temperature of 450 °C, an AlCrSi alloy target current of 80 A, and a substrate bias voltage of [missing value]. At 140V and a deposition time of approximately 38 minutes, the total thickness of the single-layer AlCrSiN coating reached approximately 1.3 μm, consistent with the total thickness of the composite coating for the cutting tool in Example 1.

[0076] Performance testing: (1) The performance of the tool substrates of Example 1 and Comparative Example 1 was measured, as shown in Table 1; (2) The performance of the tool coatings of Example 1 and Comparative Example 1 was determined, and the results are shown in Table 2; (3) The following processing conditions were adopted: Shengyi S1141 copper clad laminate (1.6 mm, 6 layers of copper, 10 z per layer), two boards were stacked; the rotation speed was 150 kRPM and the drilling speed was 40 mm / s. After the test, the usage of the tools described in Example 1 and Comparative Examples 1 and 2 is shown in Table 3.

[0077] Table 1

[0078] Table 2

[0079] Table 3

[0080] Analysis of Table 1 shows that the WC grain size of the tool substrate in Example 1 is significantly refined, and its hardness, bending strength, and fracture toughness are all significantly higher than those of the tool substrate prepared by conventional vacuum sintering process. This indicates that the nanocrystalline cemented carbide substrate prepared in this invention maintains high hardness while also possessing superior comprehensive mechanical properties, providing excellent substrate support for the high bonding strength and service stability of subsequent coatings.

[0081] Analysis of Table 2 shows that the residual compressive stress of the composite coating measured using the curvature method in Example 1 is significantly lower than that in Comparative Example 2. This indicates that setting a transition layer between the CrAlN bottom layer and the AlCrSiN intermediate layer can effectively alleviate the internal stress concentration caused by abrupt changes in material composition and lattice parameters; and the multilayer structure allows the release of thermal stress generated during deposition. Furthermore, the TiSiCN top layer in Example 1 significantly reduces the coefficient of friction while maintaining high hardness, enabling the coating to exhibit excellent wear resistance and processing stability during high-speed micro-drilling.

[0082] Analysis of Table 3 shows that the tool prepared in Example 1 can achieve the highest number of stable holes, and its maximum number of stable holes is significantly higher than that of Comparative Example 1 and Comparative Example 2. At the same time, the corresponding hole position accuracy (CPK) is significantly lower than that of Comparative Example 1 and 2, indicating that it has better hole position stability and service life in the process of high-speed drilling of PCB copper-clad laminates.

[0083] Further analysis reveals that although the tool coating in Comparative Example 2 is identical to the AlCrSiN intermediate layer in Example 1 in terms of material composition and deposition process, it lacks the interfacial bonding enhancement effect of the CrAlN underlayer on the cemented carbide tool substrate, as well as the buffering effect of the transition layer on stress. Furthermore, it does not have a TiSiCN top layer with both high hardness and low friction characteristics. During micro-drilling, the coating is more prone to stress concentration and accelerated wear in the cutting edge area, resulting in significantly lower tool life and machining stability compared to Example 1.

[0084] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A cutting tool, characterized in that, The cutting tool includes a cutting tool substrate and a composite coating deposited on the surface of the cutting tool substrate; The composite coating comprises a bottom layer, a transition layer, an intermediate layer and a top layer stacked sequentially, wherein the bottom layer is bonded to the tool substrate; The underlying layer includes CrAlN; The elemental composition of the intermediate layer includes Cr, Al, Si, and N; The transition layer is disposed between the bottom layer and the intermediate layer, and the silicon content of the transition layer increases from the end closer to the bottom layer to the end closer to the intermediate layer. The top layer includes TiSiCN.

2. The cutting tool as described in claim 1, characterized in that, The transition layer comprises CrAlN and CrAlSiN; And / or, the intermediate layer comprises AlCrSiN.

3. The cutting tool as described in claim 1, characterized in that, The molar percentages of each element in the bottom layer include: Cr: 20 at.%~30 at.%; Al: 15 at.%~25 at.%; N: 45 at.%~55 at.%; And / or, the molar percentages of each element in the intermediate layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 5 at.%~15 at.%; N: 45 at.%~55 at.%; And / or, the molar percentages of each element in the transition layer include: Cr: 15 at.%~30 at.%; Al: 10 at.%~25 at.%; Si: 2 at.%~10 at.%; N: 45 at.%~55 at.%; And / or, the molar percentages of each element in the top layer include: Ti: 20 at.%~35 at.%; Si: 5 at.%~15 at.%; C: 5 at.%~15 at.%; N: 45 at.%~55 at.%; and the sum of the atomic percentages of C and N in the top layer is 45 at.%~55 at.%.

4. The cutting tool as described in claim 1, characterized in that, The thickness of the bottom layer is 100nm~500nm; And / or, the thickness of the transition layer is 100nm~300nm; And / or, the thickness of the intermediate layer is 300nm~1000nm; And / or, the thickness of the top layer is 200nm~500nm.

5. The cutting tool as described in claim 1, characterized in that, The hardness of the intermediate layer is not less than 35 GPa; And / or, the hardness of the top layer is not less than 38 GPa.

6. The cutting tool as described in claim 1, characterized in that, The raw materials for the tool substrate include: Tungsten carbide: 85wt%~94wt%; Co: 5wt%~10wt%; Additives: 0.5wt%~5wt%; wherein the additives include at least one of Cr3C2, VC, and Y2O3.

7. The cutting tool as described in claim 6, characterized in that, In the tool matrix, the average grain size of the tungsten carbide phase is 150nm~250nm.

8. A method for preparing a cutting tool as described in any one of claims 1 to 7, characterized in that, The method for preparing the cutting tool includes the following steps: S1. The powder used to prepare the tool substrate is mixed and ball-milled, pressed into shape and then isostatically sintered to obtain the tool substrate. S2. The tool substrate obtained in step S1 is cleaned and etched sequentially; then, the bottom layer, transition layer, intermediate layer and top layer are deposited sequentially by multi-target magnetron sputtering or arc ion plating to complete the preparation of the tool.

9. The method for preparing the cutting tool as described in claim 8, characterized in that, In step S1, the particle size of the powder used to prepare the tool substrate is 0.1 μm to 0.2 μm; And / or, in step S1, during the isostatic pressing sintering process, the pressure is controlled to be 50MPa~80MPa.

10. The method for preparing the cutting tool as described in claim 8, characterized in that, In step S2, the bottom layer, transition layer, intermediate layer, and top layer are sequentially deposited using arc ion plating, specifically including the following steps: P1. Place the tool substrate in the coating device, introduce a mixed gas of nitrogen and argon, turn on the CrAl target, and deposit a CrAlN bottom layer. P2. Keep the CrAl target in the on state, and simultaneously turn on the CrAlSi target. Gradually increase the power of the CrAlSi target during the deposition process to deposit a CrAlN / CrAlSiN transition layer. P3. Turn off the CrAl target and the CrAlSi target, turn on the AlCrSi target, and deposit the AlCrSiN intermediate layer. P4. Turn off the AlCrSi target and stop the introduction of nitrogen and argon gas, turn on the TiSi target and introduce a mixed gas of nitrogen and acetylene to deposit the TiSiCN top layer.

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