A composite coating for the surface of high-speed steel cutting tools and its preparation method

Abstract

This invention discloses a composite coating for the surface of high-speed steel cutting tools and its preparation method, belonging to the field of surface treatment technology for cemented carbide cutting tools. The composite coating of this invention, from the outer surface to the substrate direction, sequentially comprises a CrAlN sealing layer, a laser-textured layer, a nano-functional layer, and a substrate strengthening layer. The laser-textured layer has periodic grooves; the bottom of the grooves has nano-ripples, and the cross-section of the grooves has an asymmetrical trapezoidal structure; the inclination angles of the first and second sidewalls of the asymmetrical trapezoidal structure are unequal; the nano-functional layer comprises alternating hard layers and lubricating layers deposited on the substrate strengthening layer; the substrate strengthening layer contains nitrogen, and the nitrogen content in the substrate strengthening layer decreases from the outer surface of the substrate strengthening layer to the interior of the substrate. The coating system of this invention has high adhesion and excellent high-temperature stability, suitable for various scenarios such as gear machining, drilling, and milling, solving the problem of insufficient high-temperature wear resistance of high-speed steel cutting tools.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for cemented carbide cutting tools, and relates to a composite coating for the surface of high-speed steel cutting tools and its preparation method. Background Technology

[0002] High-speed steel cutting tools, as core tools in gear machining, have their surface coatings that directly determine their cutting performance and service life. Current mainstream coating materials face three major challenges: First, insufficient film-substrate adhesion. Traditional CrAlN coatings have low critical load capacities, are prone to interfacial spalling due to thermal expansion mismatch, and internal stress limits coating thickness. Second, high-temperature performance degradation. The formation of the Al2O3 weakening phase leads to decreased hardness at high temperatures, significant oxidation and weight gain, accelerating tool failure. Third, an imbalance between wear resistance and anti-adhesion. Traditional laser micro-dimples are large, increasing the chipping rate, and the lack of a high-temperature lubricating phase causes a rapid increase in the friction coefficient during titanium alloy machining.

[0003] Existing improvement solutions also have some inherent defects: single-layer transition coatings have limited ability to improve adhesion, while homogeneous alloying coatings such as CrAlSiN will significantly reduce impact toughness due to Si segregation. The mismatch between fixed texture parameters and cutting edge curvature will lead to a surge in chip clogging rate. In particular, the machining of gears for new energy vehicles requires tool life > 4000 meters, while the actual machining life of existing tools is < 2200 meters, which cannot meet the requirements.

[0004] For example, Chinese patent application CN112779495A discloses a composite textured PVD coated cutting tool. This method improves the lubrication performance of the composite texture by creating pits and grooves in the tool-chip contact area and coating the textured surface with a thin hard coating, thereby increasing the tool's wear resistance. However, in this method, the pits and grooves are directly designed on the tool surface without considering the mismatch in thermal expansion coefficients between the substrate and the coating. This results in limited interfacial bonding strength, and under high-temperature cutting conditions, the single hard coating lacks sufficient resistance to high-temperature red hardness and lubrication performance, failing to effectively suppress the initiation of interfacial cracks, thus having a limited effect on improving tool life.

[0005] Therefore, it is urgent to break through the technical barriers of existing coatings for high-speed steel cutting tools. Summary of the Invention

[0006] To address the problems of coating peeling, high-temperature softening, and adhesive wear that exist in existing high-speed steel cutting tools during cutting, the first objective of this invention is to provide a composite coating for the surface of high-speed steel cutting tools. This coating, through the synergistic effect of the nitrogen concentration gradient distribution of the matrix reinforcement layer, the setting of the nano-functional layer, and the asymmetric trapezoidal groove texture, can simultaneously achieve high adhesion, high thermal stability, and long-term anti-adhesion, significantly improving the service life of the cutting tool under extreme working conditions.

[0007] The second objective of this invention is to provide a method for preparing a composite coating for the surface of high-speed steel cutting tools. This method controls the nitrogen ion concentration by adjusting the voltage of the nitrogen ion implantation energy and the nitrogen implantation dose, and coordinates with dynamic focusing femtosecond laser to make the coating of this invention have a special asymmetric trapezoidal periodic groove texture and elemental gradient distribution.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a composite coating for the surface of high-speed steel cutting tools. This composite coating, from the outer surface towards the substrate, sequentially comprises a CrAlN sealing layer, a laser-textured layer, a nano-functional layer, and a substrate strengthening layer. The laser-textured layer has periodic grooves; the bottom of the grooves has nano-ripples, and the cross-section of the grooves is an asymmetrical trapezoidal structure. The inclination angles of the first and second sidewalls of the asymmetrical trapezoidal structure are unequal. The nano-functional layer comprises alternating hard layers and lubricating layers deposited sequentially on the substrate strengthening layer, and both the hard layer and the lubricating layer are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from the substrate strengthening layer towards the outer surface of the nano-functional layer. The substrate strengthening layer contains nitrogen, and the nitrogen content in the substrate strengthening layer decreases from the outer surface of the substrate strengthening layer towards the interior of the substrate.

[0009] In this invention, the substrate reinforcement layer forms a compositional gradient transition zone through a nitrogen concentration gradient, effectively mitigating the thermal expansion coefficient mismatch effect between the high-speed steel substrate and the coating, while simultaneously enhancing interfacial adhesion and suppressing interfacial crack initiation. The hard layer in the nanofunctional layer exhibits an increasing boron content from the substrate reinforcement layer towards the outer surface of the nanofunctional layer, effectively improving the high-temperature red hardness of the coating. A continuous Cr2B transition layer is formed between the alternately deposited hard and lubricating layers. The elastic modulus of the Cr2B transition layer is between that of the hard and lubricating layers, coordinating interlayer deformation and reducing interfacial stress. Simultaneously, the alternately deposited hard and lubricating layers effectively guide crack deflection, reduce interfacial delamination, improve coating stability, and effectively support the laser-textured layer. Furthermore, the laser-textured layer with periodic grooves on the outer surface of the functional layer effectively guides the directional flow of chips, reduces the friction coefficient, and decreases the adhesion area during metal processing. Finally, the CrAlN sealing layer deposited on the surface of the laser-textured layer protects the integrity of the texture.

[0010] Furthermore, experiments have shown that the asymmetric trapezoidal groove structure and nano-ripples at the bottom of the groove adopted in this invention can not only serve as a micro-oil reservoir to reduce frictional shear force compared to symmetrical grooves, but its asymmetric profile can also guide the cutting fluid and grinding debris to be discharged in one direction. The groove structure increases the mechanical interlocking area with the overlying CrAlN sealing layer, thereby further improving the overall structural stability and extending the life of high-speed steel tools by combining the high hardness and high-temperature oxidation resistance of the CrAlN sealing layer itself.

[0011] The substrate in this invention refers to a high-speed steel cutting tool substrate.

[0012] As a preferred embodiment, the width of a single groove in the periodic groove is 500~700nm, and the depth of a single groove is 80~120nm.

[0013] As a preferred embodiment, the arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 150-200 grooves / mm on the rake face and 50-80 grooves / mm on the flank face. This differential distribution of groove density (denser at the front and sparser at the back) further enhances the guidance of chip flow, reduces the coefficient of friction, and decreases the adhesion area in metal processing.

[0014] As a preferred embodiment, the angle α between the first sidewall and the vertical plane of the asymmetrical trapezoidal structure is 15~20°, and the angle β between the second sidewall and the vertical plane is 5~10°. The relatively large angle α significantly reduces chip flow resistance and cutting force fluctuations, and prevents premature chip breakage; while the small angle β ensures sufficient oil storage space and lubrication release capability for the tool, and avoids secondary chip contact and stress concentration.

[0015] As a preferred embodiment, the CrAlN capping layer has a thickness of 100-150 nm, an Al content of 40-50 at.%, and a thickness not exceeding 1.2 times the depth of the periodic grooves. The CrAlN capping layer thickness of this invention falls within the ultra-thin range, thus protecting the integrity of the texture without covering the laser texture layer. Limiting its thickness to no more than 1.2 times the depth of the periodic grooves prevents capping layer failure.

[0016] As a preferred embodiment, the thickness of the nanofunctional layer is 2~4μm, and the B content of the hard layer in the nanofunctional layer increases from 5~5.5at.% to 6.5~7at.% from the matrix reinforcement layer toward the outer surface of the nanofunctional layer.

[0017] As a preferred embodiment, the hard layer is a (CrAlBMo)N layer with a single layer thickness of 20~50nm, wherein the B content is 5~7 at.% and the Mo content is ≤1 at.%.

[0018] As a preferred embodiment, the lubricating layer is a (CrAlMoB)N layer with a single layer thickness of 5~10nm, and the Mo content in the single layer is 7~12 at.%, and the B content is ≤1 at.%.

[0019] In this invention, controlling the thickness of the hard layer and the lubricating layer within a preferred range can further balance the overall performance of the coating in terms of hardness, toughness, and coefficient of friction. However, experiments have shown that when the boron content in the hard layer is too low, it leads to insufficient solid solution strengthening, while when the content is too high, it leads to a decrease in hardness. Similarly, when the molybdenum (Mo) content in the lubricating layer is too low, its lubrication effect is not obvious, while when the content is too high, it leads to oversaturation and increased fluctuations in the coefficient of friction.

[0020] As a preferred embodiment, the interface between the alternately deposited hard layer and lubricating layer has a continuous Cr2B transition layer with a thickness of 3-5 nm. The relatively thin continuous Cr2B transition layer is beneficial for connecting the hard layer and the lubricating layer and for coordinating interlayer deformation.

[0021] As a preferred embodiment, the nitrogen concentration in the substrate reinforcement layer decreases from 30-35 at.% to 5-8 at.% from the outer surface of the substrate reinforcement layer towards the interior of the substrate. Within the further preferred nitrogen concentration gradient range of the present invention, the thermal expansion coefficient mismatch effect between the high-speed steel substrate and the coating can be effectively mitigated, while improving the interfacial adhesion.

[0022] This invention also provides a method for preparing a composite coating for the surface of high-speed steel cutting tools, comprising the following steps:

[0023] S1 prepares a matrix reinforcement layer by nitrogen ion implantation on the surface of a high-speed steel tool substrate, and then prepares a nanofunctional layer by alternating deposition using a dual-arc target, resulting in a matrix reinforcement layer-nanofunctional layer. The nitrogen ion implantation treatment controls the nitrogen ion concentration by adjusting the voltage and dosage of the nitrogen ion implantation energy, and the boron content of the hard layer in the nanofunctional layer is controlled by adjusting the power of the dual-arc target. The dual-arc target is composed of a CrAlMo composite target and a CrB composite target.

[0024] S2 uses a femtosecond laser to perform surface processing on the substrate reinforcement layer-nanofunctional layer, forming periodic grooves on the outer surface of the nanofunctional layer to obtain the substrate reinforcement layer-nanofunctional layer-laser textured layer.

[0025] S3 is obtained by sealing the surface of the matrix reinforcement layer-nanofunctional layer-laser textured layer with CrAlN.

[0026] The preparation method of this invention mainly controls the nitrogen ion concentration by controlling the voltage and dosage of nitrogen ion implantation energy. The nitrogen ion implantation depth is positively correlated with the implantation voltage. By gradually decreasing the implantation energy from high to low voltage, combined with the control of the nitrogen ion implantation dosage, a gradually decreasing nitrogen concentration distribution can be formed from the surface to the interior of the substrate. The boron content in the hard layer is mainly achieved by adjusting the power of the dual-arc target. A high boron content in the hard layer is achieved by increasing the arc current of the CrB composite target and correspondingly decreasing the arc current of the CrAlMo target, increasing the current ratio between the two targets, and thus increasing the proportion of boron atoms in the plasma from the CrB target. Simultaneously, the deposition time of the hard layer is controlled to ensure sufficient boron incorporation. Furthermore, by employing femtosecond laser lithography with a specific laser beam and scanning path, the periodic grooves of the asymmetric trapezoidal structure required by this invention can be formed. In addition, the entire preparation process of the composite coating of this invention needs to be carried out in a nitrogen atmosphere to facilitate bonding with the composite target.

[0027] As a preferred embodiment, in S1, the nitrogen ion implantation is divided into three stages: the first stage has a voltage of 20-25 kV and a duration of 30-50 min; the second stage has a voltage of 10-15 kV and a duration of 15-30 min; and the third stage has a voltage of 4-5 kV and a duration of 5-15 min. The total implantation dose is (1-3) × 10⁻⁶. 17 ions / cm 2 By using a three-stage decreasing injection voltage, combined with a nitrogen ion implantation dose that increases sequentially from the first to the third stage, the nitrogen ion concentration can be reduced from 30-35 at.% to 5-8 at.% from the outer surface of the substrate reinforcement layer to the interior of the substrate.

[0028] As a preferred embodiment, the CrAlMo composite target is composed of 45 at.%Cr, 40 at.%Al and 15 at.%Mo; the CrB composite target is composed of 80 at.%Cr and 20 at.%B.

[0029] As a preferred embodiment, the parameters for the alternating deposition of the dual-arc targets are as follows: under a nitrogen atmosphere, the target current of the CrAlMo composite target is 60-80 A, the target current of the CrB composite target is 40-50 A, the pulse bias voltage is -100 to -150 V, and the deposition temperature is 400-500 °C. During the deposition of the hard layer, both the CrAlMo and CrB composite targets are simultaneously activated. The CrAlMo target provides Cr, Al, and Mo, while the CrB target provides Cr and B, ensuring that the B content of the hard layer meets the set value. After the hard layer deposition is complete, the CrAlMo target is turned off, and only the CrB target is kept active for several seconds to tens of seconds to deposit a pure Cr-B layer with a thickness of 3-5 nm, and an in-situ reaction to generate a Cr2B transition layer. Subsequently, during the deposition of the lubricating layer, both targets are activated simultaneously again. The CrB target provides Cr and B, while the CrAlMo target provides the background Al, Cr, and Mo, ensuring that the Mo content of the lubricating layer meets the set value. This alternating cycle achieves stable fabrication of multilayer structures.

[0030] As a preferred embodiment, the nanofunctional layer is achieved by periodically rotating a workpiece holder at a rotation speed of 3-5 rpm. The deposition time for a single layer of the hard layer is 100-250 s, and the deposition time for a single layer of the lubricating layer is 28-60 s. The number of deposition cycles is 20-80. This invention achieves alternating deposition of the hard and lubricating layers through periodic rotation of the workpiece holder. The thickness of a single layer can be controlled by adjusting the deposition time, and the total number of nanofunctional layers can be controlled by adjusting the number of cycles.

[0031] As a preferred embodiment, the laser focus of the femtosecond laser moves synchronously along the cutting edge direction of the tool, with a moving speed to scanning speed ratio of 1:(50~100). The laser beam is linearly polarized, with the polarization direction perpendicular to the groove extension direction. The femtosecond laser beam is modulated using a vortex phase plate to form a ring-shaped energy distribution. By controlling the ratio of the synchronous moving speed to the scanning speed, as well as the laser beam direction, an asymmetric trapezoidal groove profile with α of 15~20° and β of 5~10° can be obtained. Furthermore, by using a vortex phase plate to modulate the ring-shaped energy distribution, nano-ripples with a width of 50~80nm can be formed at the bottom of the groove. Specifically, with a fixed pulse energy and spot diameter, a faster scanning speed increases the spacing between adjacent pulses, resulting in a corresponding increase in groove width; conversely, a slower scanning speed decreases the groove width.

[0032] As a preferred embodiment, the surface processing conditions are: wavelength of 1010~1050nm, pulse width of 300~500fs, and energy density of 1.8~2.5J / cm². 2The scanning speed is 400~600 mm / s. This invention controls surface processing conditions primarily to regulate the width, depth, bottom nano-ripples, and heat-affected zone of the periodic grooves in the laser-textured layer. Wavelength and scanning speed together determine the groove width; energy density and pulse width affect the ablation depth and the formation quality of the bottom nano-ripples; too low an energy density results in an unclear structure, while too high an energy density increases thermal damage; femtosecond-level short pulses can significantly reduce the heat-affected zone, preventing graphitization or phase transition of the coating.

[0033] As a preferred embodiment, in S3, the conditions for the CrAlN capping layer are as follows: under a nitrogen atmosphere, using a CrAl composite target composed of 45~55 wt.% Cr and 55~45 wt.% Al, at a deposition rate of 0.1~0.3 μm / h, and a bias voltage of -80V~-120V. Under the preferred deposition conditions of this invention, an ultrathin and uniformly thick CrAlN capping layer can be obtained.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention achieves high bonding force, high thermal stability and long-term anti-adhesion by means of the nitrogen concentration gradient distribution of the matrix reinforcement layer, the setting of the nano functional layer and the synergistic effect of the asymmetric trapezoidal groove texture on the high-speed steel cutting tool, which significantly improves the service life of the cutting tool under extreme working conditions.

[0036] (2) The asymmetric trapezoidal groove structure and the nano-wave design of the groove bottom of the present invention can guide the cutting fluid and grinding chips to be discharged in one direction. The groove structure increases the mechanical interlocking area with the CrAlN sealing layer, thereby further improving the stability of the overall structure and extending the life of high-speed steel tools by combining the high hardness and high temperature oxidation resistance of the CrAlN sealing layer itself.

[0037] (3) In the nanofunctional layer of the present invention, the alternating hard layer and lubricating layer, and the B content in the hard layer increase from the matrix reinforcement layer to the outer surface of the nanofunctional layer. Combined with the amorphous reinforcement of B and the self-lubricating effect of Mo, the high-temperature stability of the coating is significantly improved and the friction coefficient is reduced. At the same time, a continuous Cr2B transition layer can be formed between the alternating hard layer and lubricating layer. The elastic modulus of the Cr2B transition layer is between that of the hard layer and the lubricating layer, which can coordinate interlayer deformation and reduce interfacial stress.

[0038] (4) By limiting the thickness of the CrAlN sealing layer to ≤ 1.2 times the depth of the periodic groove, the present invention avoids the loss of the functionality of the laser textured layer, and at the same time prevents stress cracking caused by excessively thick sealing layer, thus ensuring cutting life. Attached Figure Description

[0039] Figure 1This is a schematic cross-sectional view of the composite coating on the surface of the high-speed steel cutting tool according to Embodiment 1 of the present invention.

[0040] Figure 2 The images show cross-sectional SEM images of the high-speed steel matrix and the gradient nitrogen matrix reinforcement layer of the present invention.

[0041] Wherein, 1-matrix reinforcement layer; 2-nano functional layer; 3-laser textured layer; 4-CrAlN sealing layer; 5-high-speed steel matrix; 6-nano corrugations; 7-first sidewall; 8-second sidewall; α-angle between the first sidewall of the asymmetric trapezoidal structure and the vertical plane; β-angle between the second sidewall and the vertical plane. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0043] Example 1

[0044] A composite coating for the surface of high-speed steel cutting tools, the schematic diagram of the surface microtexture morphology is shown below. Figure 1 As shown, it consists of a substrate reinforcement layer 1, a nanofunctional layer 2, a laser textured layer 3 disposed on the outer surface of the nanofunctional layer, a CrAlN sealing layer 4, a high-speed steel substrate 5, and nano-corrugations 6. The total thickness of the substrate reinforcement layer is 150 nm, and the N concentration in the substrate reinforcement layer decreases from 32 at.% at the outer surface of the substrate reinforcement layer to 7 at.% at the interior of the substrate.

[0045] The nanofunctional layer has a thickness of 3 μm and consists of alternating hard and lubricating layers deposited sequentially on a substrate reinforcement layer. Both the hard and lubricating layers are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from 5.5 at.% to 6.5 at.% towards the outer surface of the nanofunctional layer from the substrate reinforcement layer, while the Mo content in the lubricating layer increases from 7 at.% to 12 at.% towards the outer surface of the nanofunctional layer from the substrate reinforcement layer. The hard layer is a (CrAlBMo)N layer with a single-layer thickness of 30 nm and a Mo content ≤1 at.%, while the lubricating layer is a (CrAlMoB)N layer with a single-layer thickness of 8 nm and a B content ≤1 at.%. A continuous Cr2B transition layer with a thickness of 4 nm is present at the interface between the alternating hard and lubricating layers.

[0046] The laser-textured layer has periodic grooves with 65nm wide nano-ripples at the bottom and an asymmetric trapezoidal cross-section. The width of a single groove is 600nm and the depth is 100nm. The asymmetric trapezoidal structure has an α of 18° and an β of 8°. The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 180 grooves / mm on the rake face and 65 grooves / mm on the flank face.

[0047] The CrAlN capping layer has a thickness of 120 nm and an Al content of 45 at.% on the surface.

[0048] A method for preparing a composite coating for the surface of high-speed steel cutting tools includes the following steps:

[0049] (1) Matrix strengthening treatment: The high-speed steel hobbing cutter matrix used is M42, and the total nitrogen injection dosage is 2×10 17 ions / cm 2 Nitrogen ion implantation is divided into three stages. The first stage has a voltage of 25 kV and an implantation dose of 4 × 10⁻⁶ kV. 16 ions / cm 2 The time was 40 minutes, the voltage of the second stage was 15 kV, and the injection dose was 6 × 10⁻⁶. 16 ions / cm 2 The time was 20 minutes, the voltage in the third stage was 5 kV, and the injection dose was 1 × 10⁻⁶. 17 ions / cm 2 The time is 10 minutes.

[0050] (2) Nanofunctional layer deposition: Nanofunctional layers were prepared on the above-mentioned substrate reinforcement layer by alternating deposition using dual arc targets under nitrogen atmosphere. The target current of the CrAlMo composite target (composition 45Cr-40Al-15Mo) was 75A, the target current of the CrB composite target (80Cr-20B) was 45A, the pulse bias voltage was -120V, the temperature was 450℃, the workpiece holder rotation speed was 4rpm, the deposition time of a single layer of (CrAlBMo)N hard layer was 150s, and the deposition time of a single layer of (CrAlMoB)N lubricating layer was 45s. A total of 71 deposition cycles were performed. One cycle refers to the deposition of a (CrAlBMo)N hard layer, a continuous Cr2B transition layer and a (CrAlMoB)N lubricating layer. The composition gradient is achieved by adjusting the target power. In each deposition cycle, the CrAlMo composite target and the CrB composite target are turned on first to deposit a (CrAlBMo)N hard layer. After that, the CrAlMo target is turned off and the CrB target is turned on alone with a constant power of 4.0kW for 10s to form a pure Cr-B layer with a thickness of about 4nm and generate a continuous Cr2B transition layer in situ. Then the dual targets are turned on again and a (CrAlMoB)N lubricating layer is deposited by periodically rotating the workpiece holder. This process is repeated for 71 cycles. Over 71 cycles, a (CrAlBMo)N hard layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 6.0 kW and the target power for CrB was 1.2 kW. The target power for CrAlMo decreased by 0.003 kW and the target power for CrB increased by 0.011 kW per cycle until the 71st cycle. The single-layer deposition time for the hard layer was 150 s, allowing the B content to gradually increase from 5 at.% to 7 at.% towards the outer surface of the nanofunctional layer, while the Mo content remained ≤1 at.%. Conversely, a (CrAlMoB)N lubricating layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 1.0 kW and the target power for CrB was 6.0 kW. The target power for CrAlMo increased by 0.014 kW and the target power for CrB decreased by 0.007 kW per cycle until the 71st cycle. The single-layer deposition time for the lubricating layer was 45 s, allowing the Mo content to gradually increase from 7 at.% to 12 at.% and the B content remained ≤1 at.%.

[0051] (3) Laser texturing: Femtosecond laser dynamic focusing technology is used for processing. The laser focus of the femtosecond laser moves synchronously along the cutting edge of the tool. The ratio of the moving speed to the scanning speed is 1:80. The laser beam is linearly polarized, and the polarization direction is perpendicular to the groove extension direction, so that the groove cross-section has an asymmetric trapezoidal structure with α = 18° and β = 8°. The femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution, so that a nano-ripple with a width of 65nm is formed at the bottom of the groove. The femtosecond laser wavelength is 1030nm, the pulse width is 400fs, and the energy density is 2.2J / cm. 2 The scanning speed is 500 mm / s.

[0052] (4) Plasma cleaning: Ar / H2 mixed gas (volume ratio 4:1), gas pressure 1.0 Pa; radio frequency power 270 W, cleaning time 7 min.

[0053] (5) CrAlN sealing: Under nitrogen atmosphere, a CrAl composite target composed of 50 wt.% Cr and 50 wt.% Al was used. The CrAlN deposition rate was 0.25 μm / h, and the bias voltage was controlled in three stages: initial stage (0~30 nm) bias voltage -80V, intermediate stage (greater than 30 and less than or equal to 100 nm) bias voltage -100V, and final stage (greater than 100 and less than or equal to 120 nm) bias voltage -120V. Finally, a high-speed steel tool A with a composite coating was obtained.

[0054] Comparative Example 1

[0055] In Comparative Example 1, the tool substrate reinforcement layer was obtained by homogeneous nitrogen implantation with a constant energy of 15 kV, a constant N content of 20 at.%, and a thickness of 150 nm. All other steps and conditions were the same as in Example 1.

[0056] The composite coated tool A prepared in Example 1 and Comparative Example 1 were compared in a gear machining life test. The results of the comparison test are shown in Table 1 below.

[0057] Table 1. Comparative experimental results of the composite coated high-speed steel cutting tool A in Example 1 and Comparative Example 1.

[0058]

[0059] As shown in Table 1, under the same tool substrate and model, the same process conditions, and the same test conditions, only the substrate reinforcement layer was changed to gradient nitrogen ion implantation (with the same total thickness). The composite coating with gradient nitrogen ion distribution in Example 1 can significantly improve the interfacial bonding force, reduce coating peeling, and has a greater impact on the performance of the coating than the homogeneous nitrogen ion reinforced substrate. Its bonding force and tool life are better than the composite coating of Comparative Example 1.

[0060] Example 2

[0061] A composite coating for the surface of high-speed steel cutting tools, with the same surface microtexture morphology as in Example 1, wherein the total thickness of the substrate reinforcement layer is 120 nm, and the N concentration in the substrate reinforcement layer decreases from 34 at.% at the surface to 6 at.% at the interior of the substrate.

[0062] The nanofunctional layer has a thickness of 3.2 μm and consists of alternating hard and lubricating layers deposited sequentially on a substrate reinforcement layer. Both the hard and lubricating layers are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from 5 at.% to 7 at.% from the substrate reinforcement layer toward the outer surface of the nanofunctional layer, while the Mo content in the lubricating layer increases from 7 at.% to 12 at.% from the substrate reinforcement layer toward the outer surface of the nanofunctional layer. The hard layer is a (CrAlBMo)N layer with a single-layer thickness of 30 nm and a Mo content ≤1 at.%, while the lubricating layer is a (CrAlMoB)N layer with a single-layer thickness of 8 nm and a B content ≤1 at.%. A continuous Cr2B transition layer with a thickness of 4 nm is present at the interface between the alternating hard and lubricating layers.

[0063] The laser-textured layer has periodic grooves with 60 nm wide nano-ripples at the bottom and an asymmetric trapezoidal cross-section. The width of a single groove is 550 nm and the depth is 90 nm. The asymmetric trapezoidal structure has an α of 20° and an β of 8°. The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 200 grooves / mm on the rake face and 70 grooves / mm on the flank face.

[0064] The CrAlN capping layer has a thickness of 110 nm and an Al content of 48 at.% on the surface.

[0065] A method for preparing a composite coating for the surface of high-speed steel cutting tools includes the following steps:

[0066] (1) Matrix strengthening treatment: The high-speed steel hobbing cutter matrix used is M42, and the total nitrogen injection dosage is 2×10 17 ions / cm 2 Nitrogen ion implantation is divided into three stages. The first stage has a voltage of 25 kV and an implantation dose of 4 × 10⁻⁶ kV. 16 ions / cm 2 The time was 32 minutes, the voltage of the second stage was 15 kV, and the injection dose was 6 × 10⁻⁶. 16 ions / cm 2 The time was 16 minutes, the voltage in the third stage was 5 kV, and the injection dose was 1 × 10⁻⁶. 17 ions / cm 2 The time is 8 minutes.

[0067] (2) Nanofunctional layer deposition: Nanofunctional layers were prepared on the above-mentioned substrate reinforcement layer by alternating deposition using dual arc targets under nitrogen atmosphere. The target current of the CrAlMo composite target (composition 45Cr-40Al-15Mo) was 75A, the target current of the CrB composite target (80Cr-20B) was 45A, the pulse bias voltage was -130V, the temperature was 480℃, the workpiece holder rotation speed was 4rpm, the deposition time of a single layer of (CrAlBMo)N hard layer was 140s, and the deposition time of a single layer of (CrAlMoB)N lubricating layer was 40s. A total of 76 deposition cycles were performed. One cycle refers to the deposition of a (CrAlBMo)N hard layer, a continuous Cr2B transition layer and a (CrAlMoB)N lubricating layer. The composition gradient is achieved by adjusting the target power. In each deposition cycle, the CrAlMo composite target and the CrB composite target are turned on first to deposit a (CrAlBMo)N hard layer. After that, the CrAlMo target is turned off and the CrB target is turned on alone with a constant power of 4.0kW for 10s to form a pure Cr-B layer with a thickness of about 4nm and generate a continuous Cr2B transition layer in situ. Then the dual targets are turned on again and a (CrAlMoB)N lubricating layer is deposited by periodically rotating the workpiece holder. This process is repeated for 76 cycles. Over 76 cycles, a (CrAlBMo)N hard layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 6.0 kW and the target power for CrB was 1.2 kW. The target power for CrAlMo decreased by 0.003 kW and the target power for CrB increased by 0.011 kW per cycle until the 76th cycle. The single-layer deposition time for the hard layer was 140 s, allowing the B content to gradually increase from 5 at.% to 7 at.% towards the outer surface of the nanofunctional layer, while the Mo content remained ≤1 at.%. Conversely, a (CrAlMoB)N lubricating layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 1.0 kW and the target power for CrB was 6.0 kW. The target power for CrAlMo increased by 0.013 kW and the target power for CrB decreased by 0.007 kW per cycle until the 76th cycle. The single-layer deposition time for the lubricating layer was 40 s, allowing the Mo content to gradually increase from 7 at.% to 12 at.% and the B content remained ≤1 at.%.

[0068] (3) Laser texturing: Femtosecond laser dynamic focusing technology is used for processing. The laser focus of the femtosecond laser moves synchronously along the cutting edge of the tool. The ratio of the moving speed to the scanning speed is 1:60. The laser beam is linearly polarized, and the polarization direction is perpendicular to the groove extension direction, so that the groove cross-section has an asymmetric trapezoidal structure with α = 20° and β = 8°. The femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution, so that a nano-ripple with a width of 60nm is formed at the bottom of the groove. The femtosecond laser wavelength is 1020nm, the pulse width is 400fs, and the energy density is 2.4J / cm. 2 The scanning speed is 550 mm / s.

[0069] (4) Plasma cleaning: Ar / H2 mixed gas (volume ratio 4:1), gas pressure 1.0 Pa; radio frequency power 270 W, cleaning time 7 min.

[0070] (5) CrAlN sealing: Under nitrogen atmosphere, a CrAl composite target composed of 50 wt.% Cr and 50 wt.% Al was used. The CrAlN deposition rate was 0.25 μm / h, and the bias voltage was controlled in three stages: initial stage (0~30 nm) bias voltage -80V, intermediate stage (greater than 30 and less than or equal to 100 nm) bias voltage -100V, and final stage (greater than 100 and less than or equal to 110 nm) bias voltage -120V. Finally, a high-speed steel tool B with a composite coating was obtained.

[0071] Comparative Example 2

[0072] In Comparative Example 2, the nano-functional layer of the tool composite coating had a constant Mo content of 10 at.%, a target current of 75 A (CrAlMo target, composition 50Cr-40Al-10Mo, at.%), and 45 A (CrB target), a pulse bias of -130 V, a temperature of 480 °C, a workpiece holder rotation speed of 4 rpm, a hard layer deposition time of 140 s, a lubricant layer deposition time of 40 s, and a total deposition cycle of 76 cycles. All other steps and conditions were the same as in Example 2.

[0073] The composite coated tool B prepared in Example 2 and Comparative Example 2 were compared in a gear machining life test. The results of the comparison test are shown in Table 2 below.

[0074] Table 2 Comparison of experimental results between the composite coated tool B of Example 2 and Comparative Example 2

[0075]

[0076] As shown in Table 2, under the same tool substrate and model, the same process conditions, and the same test conditions, by simply changing the nano-functional layer to a constant Mo element distribution, the composite coating with gradient Mo element distribution of the present invention can significantly improve the high-temperature oxidation resistance and thermal stability of the tool, reduce the friction coefficient between the coating and the workpiece, and its high-temperature performance, workpiece surface roughness, and tool life are all superior to the composite coating of Comparative Example 2.

[0077] Example 3

[0078] A composite coating for the surface of high-speed steel cutting tools, with the same surface microtexture morphology as in Example 1. The total thickness of the substrate reinforcement layer is 150 nm, and the nitrogen concentration in the substrate reinforcement layer decreases from 32 at.% at the surface to 7 at.% at the interior of the substrate.

[0079] The thickness of the nano-multilayer functional layer is 2 μm. The nano-functional layer consists of alternating hard and lubricating layers deposited sequentially on a substrate reinforcement layer. Both the hard and lubricating layers are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from 5 at.% to 7 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer, while the average Mo content in the lubricating layer increases from 7 at.% to 12 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer. The hard layer is a (CrAlBMo)N layer with a single-layer thickness of 20 nm and a Mo content ≤1 at.%, while the lubricating layer is a (CrAlMoB)N layer with a single-layer thickness of 5 nm and a B content ≤1 at.%. A continuous Cr2B transition layer with a thickness of 4 nm is present at the interface between the alternating hard and lubricating layers.

[0080] The laser-textured layer has periodic grooves with 65nm wide nano-ripples at the bottom and an asymmetric trapezoidal cross-section. The width of a single groove is 600nm and the depth is 100nm. The asymmetric trapezoidal structure has an α of 20° and an β of 8°. The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 180 grooves / mm on the rake face and 60 grooves / mm on the flank face.

[0081] The CrAlN capping layer has a thickness of 120 nm and an Al content of 45 at.% on the surface.

[0082] A method for preparing a composite coating for the surface of high-speed steel cutting tools includes the following steps:

[0083] (1) Matrix strengthening treatment: The high-speed steel hobbing cutter matrix used is M42, and the total nitrogen injection dosage is 2×10 17 ions / cm 2 Nitrogen ion implantation is divided into three stages. The first stage has a voltage of 25 kV and an implantation dose of 4 × 10⁻⁶ kV. 16 ions / cm 2 The time was 40 minutes, the voltage of the second stage was 15 kV, and the injection dose was 6 × 10⁻⁶. 16 ions / cm 2 The time was 20 minutes, the voltage in the third stage was 5 kV, and the injection dose was 1 × 10⁻⁶. 17 ions / cm 2 The time is 10 minutes.

[0084] (2) Nanofunctional layer deposition: Nanofunctional layers were prepared on the above-mentioned substrate reinforcement layer by alternating deposition using dual arc targets under nitrogen atmosphere. The target current of the CrAlMo composite target (composition 45Cr-40Al-15Mo) was 75A, the target current of the CrB composite target (80Cr-20B) was 45A, the pulse bias voltage was -120V, the temperature was 450℃, the workpiece holder rotation speed was 4rpm, the deposition time of a single layer of (CrAlBMo)N hard layer was 100s, and the deposition time of a single layer of (CrAlMoB)N lubricating layer was 28s. A total of 69 deposition cycles were performed. One cycle refers to the deposition of a hard layer, a continuous Cr2B transition layer and a lubricating layer. The composition gradient is achieved by adjusting the target power. In each deposition cycle, the CrAlMo composite target and the CrB composite target are turned on first to deposit a (CrAlBMo)N hard layer. After that, the CrAlMo target is turned off and the CrB target is turned on alone with a constant power of 4.0kW for 10s to form a pure Cr-B layer with a thickness of about 4nm and generate a continuous Cr2B transition layer in situ. Then the dual targets are turned on again and a (CrAlMoB)N lubricating layer is deposited by periodically rotating the workpiece holder. This process is repeated for 69 cycles. Over 69 cycles, a hard layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 6.0 kW and the target power for CrB was 1.2 kW. The target power for CrAlMo decreased by 0.003 kW and the target power for CrB increased by 0.012 kW per cycle until the 69th cycle. The single-layer deposition time for the hard layer was 100 s, allowing the B content to gradually increase from 5 at.% to 7 at.% towards the outer surface of the nanofunctional layer, while the Mo content remained ≤1 at.%. Similarly, a lubricating layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 1.0 kW and the target power for CrB was 6.0 kW. The target power for CrAlMo increased by 0.015 kW and the target power for CrB decreased by 0.007 kW per cycle until the 69th cycle. The single-layer deposition time for the lubricating layer was 28 s, allowing the average Mo content to gradually increase from 7 at.% to 12 at.% and the B content remained ≤1 at.%.

[0085] (3) Laser texturing: Femtosecond laser dynamic focusing technology is used for processing. The laser focus of the femtosecond laser moves synchronously along the cutting edge of the tool. The ratio of the moving speed to the scanning speed is 1:60. The laser beam is linearly polarized, and the polarization direction is perpendicular to the groove extension direction, so that the groove cross-section has an asymmetric trapezoidal structure with α = 20° and β = 8°. The femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution, so that a nano-ripple with a width of 70nm is formed at the bottom of the groove. The femtosecond laser wavelength is 1030nm, the pulse width is 400fs, and the energy density is 2.0J / cm. 2 The scanning speed is 500 mm / s.

[0086] (4) Plasma cleaning: Ar / H2 mixed gas (volume ratio 4:1), gas pressure 1.0 Pa; radio frequency power 270 W, cleaning time 7 min.

[0087] (5) CrAlN sealing: Under nitrogen atmosphere, a CrAl composite target composed of 50 wt.% Cr and 50 wt.% Al was used. The CrAlN deposition rate was 0.25 μm / h, and the bias voltage was controlled in three stages: initial stage (0~30 nm) bias voltage -80V, intermediate stage (greater than 30 and less than or equal to 100 nm) bias voltage -100V, and final stage (greater than 100 and less than or equal to 120 nm) bias voltage -120V. Finally, a high-speed steel tool C with a composite coating was obtained.

[0088] Comparative Example 3

[0089] In Comparative Example 3, the laser textured layer of the tool was changed to a symmetrical trapezoidal groove, α equals β, and the arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool was set to be greater on the rake face than on the flank face, with 180 grooves / mm on the rake face and 60 grooves / mm on the flank face. The remaining steps and conditions were the same as in Example 3.

[0090] The composite coated tool C prepared in Example 3 and Comparative Example 3 were compared in a gear machining life test. The results of the comparison test are shown in Table 3 below.

[0091] Table 3 Comparison of experimental results between the composite coated cutting tool C of Example 3 and Comparative Example 3

[0092]

[0093] As shown in Table 3, under the same tool substrate and model, the same process conditions, and the same test conditions, by simply changing the laser texture layer to a symmetrical trapezoidal groove, the composite coating of the present invention with an asymmetrical trapezoidal groove texture can reduce material sticking and chip clogging during the cutting process, significantly reduce the surface roughness of the workpiece, and its anti-adhesion performance and chip removal ability are superior to the general composite coating of Comparative Example 3.

[0094] Example 4

[0095] A composite coating for the surface of high-speed steel cutting tools, with the same surface microtexture morphology as in Example 1. The total thickness of the substrate reinforcement layer is 150 nm, and the nitrogen concentration in the substrate reinforcement layer decreases from 32 at.% at the surface to 7 at.% at the interior of the substrate.

[0096] The thickness of the nano-multilayer functional layer is 4 μm. The nano-functional layer consists of alternating hard and lubricating layers deposited sequentially on a substrate reinforcement layer. Both the hard and lubricating layers are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from 5 at.% to 7 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer, and the Mo content in the lubricating layer increases from 7 at.% to 12 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer. The hard layer is a (CrAlBMo)N layer with a single-layer thickness of 50 nm and a Mo content ≤1 at.%, and the lubricating layer is a (CrAlMoB)N layer with a single-layer thickness of 10 nm and a B content ≤1 at.%. A continuous Cr2B transition layer with a thickness of 4 nm is present at the interface of the alternating hard and lubricating layers.

[0097] The laser-textured layer has periodic grooves with 65nm wide nano-ripples at the bottom and an asymmetric trapezoidal cross-section. The width of a single groove is 600nm and the depth is 105nm. The asymmetric trapezoidal structure has an α of 18° and an β of 8°. The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 180 grooves / mm on the rake face and 65 grooves / mm on the flank face.

[0098] The CrAlN capping layer has a thickness of 126 nm and an Al content of 45 at.% on the surface.

[0099] A method for preparing a composite coating for the surface of high-speed steel cutting tools includes the following steps:

[0100] (1) Matrix strengthening treatment: The high-speed steel hobbing cutter matrix used is M42, and the total nitrogen injection dosage is 2×10 17 ions / cm 2 Nitrogen ion implantation is divided into three stages. The first stage has a voltage of 25 kV and an implantation dose of 4 × 10⁻⁶ kV. 16 ions / cm 2 The time was 40 minutes, the voltage of the second stage was 15 kV, and the injection dose was 6 × 10⁻⁶. 16 ions / cm 2 The time was 20 minutes, the voltage in the third stage was 5 kV, and the injection dose was 1 × 10⁻⁶. 17 ions / cm 2 The time is 10 minutes.

[0101] (2) Nanofunctional layer deposition: Nanofunctional layers were prepared on the above-mentioned substrate reinforcement layer by alternating deposition using dual arc targets under nitrogen atmosphere. The target current of the CrAlMo composite target (composition 45Cr-40Al-15Mo) was 75A, the target current of the CrB composite target (80Cr-20B) was 45A, the pulse bias voltage was -120V, the temperature was 450℃, the workpiece holder rotation speed was 4rpm, the deposition time of a single layer of (CrAlBMo)N hard layer was 250s, and the deposition time of a single layer of (CrAlMoB)N lubricating layer was 56s. A total of 62 deposition cycles were performed. One cycle refers to the deposition of a hard layer, a continuous Cr2B transition layer and a lubricating layer. The composition gradient is achieved by adjusting the target power: In each deposition cycle, the CrAlMo composite target and the CrB composite target are first turned on to deposit a (CrAlBMo)N hard layer. After that, the CrAlMo target is turned off, and only the CrB target is turned on with a constant power of 4.0kW to deposit a pure Cr-B layer with a thickness of about 4nm and generate a continuous Cr2B transition layer in situ. Then the dual targets are turned on again, and a (CrAlMoB)N lubricating layer is deposited by periodically rotating the workpiece holder. This process is repeated for 62 cycles. Over 62 cycles, a hard layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 6.0 kW and the target power for CrB was 1.2 kW. The target power for CrAlMo decreased by 0.003 kW and the target power for CrB increased by 0.013 kW per cycle until the 62nd cycle. The single-layer deposition time for the hard layer was 250 s, allowing the B content to gradually increase from 5 at.% to 7 at.% towards the outer surface of the nanofunctional layer, while the Mo content remained ≤1 at.%. Similarly, a lubricating layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 1.0 kW and the target power for CrB was 6.0 kW. The target power for CrAlMo increased by 0.016 kW and the target power for CrB decreased by 0.008 kW per cycle until the 62nd cycle. The single-layer deposition time for the lubricating layer was 56 s, allowing the Mo content to gradually increase from 7 at.% to 12 at.% and the B content remained ≤1 at.%.

[0102] (3) Laser texturing: Femtosecond laser dynamic focusing technology is used for processing. The laser focus of the femtosecond laser moves synchronously along the cutting edge of the tool. The ratio of the moving speed to the scanning speed is 1:80. The laser beam is linearly polarized, and the polarization direction is perpendicular to the groove extension direction, so that the groove cross-section has an asymmetric trapezoidal structure with α = 18° and β = 8°. The femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution, so that a nano-ripple with a width of 65nm is formed at the bottom of the groove. The femtosecond laser wavelength is 1030nm, the pulse width is 400fs, and the energy density is 2.2J / cm. 2 The scanning speed is 500 mm / s.

[0103] (4) Plasma cleaning: Ar / H2 mixed gas (volume ratio 4:1), gas pressure 1.0 Pa; radio frequency power 270 W, cleaning time 7 min.

[0104] (5) CrAlN sealing: Under nitrogen atmosphere, a CrAl composite target composed of 50wt.%Cr and 50wt.%Al was used. The CrAlN deposition rate was 0.22μm / h. The bias voltage was controlled in three stages: initial stage (0~30nm) bias voltage -80V, intermediate stage (greater than 30nm and less than or equal to 100nm) bias voltage -100V, and final stage (greater than 100nm and less than or equal to 126nm) bias voltage -120V. Finally, a high-speed steel tool D with a composite coating was obtained.

[0105] Comparative Example 4

[0106] In Comparative Example 4, the CrAlN sealing layer thickness of the tool was 189 nm, the CrAlN deposition rate was 0.21 μm / h, and the bias voltage was controlled in segments: -80V (0~50 nm) in the initial stage, -100V (greater than 50 nm and less than or equal to 110 nm) in the middle stage, and -120V (greater than 110 nm and less than or equal to 189 nm) in the final stage. The remaining steps and conditions were the same as in Example 4.

[0107] The composite coated cutting tool D prepared in Example 4 and Comparative Example 4 were compared in a gear machining life test. The results of the comparison test are shown in Table 4 below.

[0108] Table 4. Comparison of experimental results between the composite coated cutting tool D of Example 4 and Comparative Example 4.

[0109]

[0110] As shown in Table 4, under the same tool substrate and model, the same process conditions, and the same test conditions, by simply increasing the thickness of the CrAlN sealing layer to 189 nm, the composite coating with the ultrathin CrAlN sealing layer of the present invention can retain more texture layers and reduce the internal stress of the sealing layer. Its oil storage capacity and tool life are better than the composite coating of Comparative Example 4.

[0111] Example 5

[0112] A composite coating for the surface of high-speed steel cutting tools, with the same surface microtexture as in Example 1. The total thickness of the substrate reinforcement layer is 150 nm, and the nitrogen concentration in the substrate reinforcement layer decreases from 32 at.% at the surface to 7 at.% at the interior of the substrate.

[0113] The thickness of the nano-multilayer functional layer is 2.5 μm. The nano-functional layer consists of alternating hard layers and lubricating layers deposited sequentially on a substrate reinforcement layer. Both the hard and lubricating layers are composite nitrides composed of Cr, Al, Mo, B, and N elements. The B content in the hard layer increases from 5 at.% to 7 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer, and the Mo content in the lubricating layer increases from 7 at.% to 12 at.% from the substrate reinforcement layer toward the outer surface of the nano-functional layer. The hard layer is a (CrAlBMo)N layer with a single-layer thickness of 40 nm and a Mo content ≤1 at.%, and the lubricating layer is a (CrAlMoB)N layer with a single-layer thickness of 6 nm and a B content ≤1 at.%. A continuous Cr2B transition layer with a thickness of 5 nm is present at the interface between the alternating hard and lubricating layers.

[0114] The laser-textured layer has periodic grooves with 65nm wide nano-ripples at the bottom and an asymmetric trapezoidal cross-section. The width of a single groove is 600nm and the depth is 100nm. The asymmetric trapezoidal structure has an α of 18° and an β of 8°. The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set to be greater on the rake face than on the flank face, with 200 grooves / mm on the rake face and 50 grooves / mm on the flank face.

[0115] The CrAlN capping layer has a thickness of 120 nm and an Al content of 45 at.% on the surface.

[0116] A method for preparing a composite coating for the surface of high-speed steel cutting tools includes the following steps:

[0117] (1) Matrix strengthening treatment: The high-speed steel hobbing cutter matrix used is M42, and the total nitrogen injection dosage is 2×10 17 ions / cm 2 Nitrogen ion implantation is divided into three stages. The first stage has a voltage of 25 kV and an implantation dose of 4 × 10⁻⁶ kV. 16 ions / cm 2 The time was 40 minutes, the voltage of the second stage was 15 kV, and the injection dose was 6 × 10⁻⁶. 16 ions / cm 2 The time was 20 minutes, the voltage in the third stage was 5 kV, and the injection dose was 1 × 10⁻⁶. 17 ions / cm 2 The time is 10 minutes.

[0118] (2) Nanofunctional layer deposition: Nanofunctional layers were prepared on the above-mentioned substrate reinforcement layer by alternating deposition using dual arc targets under nitrogen atmosphere. The target current of the CrAlMo composite target (45Cr-40Al-15Mo) was 75A, the target current of the CrB composite target (80Cr-20B) was 45A, the pulse bias voltage was -120V, the temperature was 450℃, the workpiece holder rotation speed was 4rpm, the deposition time of a single layer of (CrAlBMo)N hard layer was 200s, and the deposition time of a single layer of (CrAlMoB)N lubricating layer was 34s. A total of 50 cycles were deposited. One cycle refers to the deposition of a hard layer, a continuous Cr2B transition layer and a lubricating layer. The composition gradient is achieved by adjusting the target power: In each deposition cycle, the CrAlMo composite target and the CrB composite target are first turned on to deposit a (CrAlBMo)N hard layer. After that, the CrAlMo target is turned off, and only the CrB target is turned on with a constant power of 4.0kW to deposit a pure Cr-B layer with a thickness of about 5nm and generate a continuous Cr2B transition layer in situ. Then the dual targets are turned on again, and a (CrAlMoB)N lubricating layer is deposited by periodically rotating the workpiece holder. This process is repeated for 50 cycles. Over 50 cycles, a hard layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 6.0 kW and the target power for CrB was 1.2 kW. The target power for CrAlMo decreased by 0.004 kW and the target power for CrB increased by 0.016 kW per cycle until the 50th cycle. The single-layer deposition time for the hard layer was 200 s, allowing the B content to gradually increase from 5 at.% to 7 at.% towards the outer surface of the nanofunctional layer, while the Mo content remained ≤1 at.%. Similarly, a lubricating layer was deposited using a linearly graded power method: in the first cycle, the target power for CrAlMo was 1.0 kW and the target power for CrB was 6.0 kW. The target power for CrAlMo increased by 0.02 kW and the target power for CrB decreased by 0.01 kW per cycle until the 50th cycle. The single-layer deposition time for the lubricating layer was 34 s, allowing the Mo content to gradually increase from 7 at.% to 12 at.% and the B content remained ≤1 at.%.

[0119] (3) Laser texturing: Femtosecond laser dynamic focusing technology is used for processing. The laser focus of the femtosecond laser moves synchronously along the cutting edge of the tool. The ratio of the moving speed to the scanning speed is 1:100. The laser beam is linearly polarized and the polarization direction is perpendicular to the groove extension direction, so that the groove cross-section has an asymmetric trapezoidal structure with α = 18° and β = 8°. The femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution, so that a nano-ripple with a width of 65nm is formed at the bottom of the groove. The femtosecond laser wavelength is 1030nm, the pulse width is 400fs, and the energy density is 2.5J / cm. 2 The scanning speed is 600 mm / s.

[0120] (4) Plasma cleaning: Ar / H2 mixed gas (volume ratio 4:1), gas pressure 1.0 Pa; radio frequency power 270 W, cleaning time 7 min.

[0121] (5) CrAlN sealing: Under nitrogen atmosphere, a CrAl composite target composed of 50 wt.% Cr and 50 wt.% Al was used. The CrAlN deposition rate was 0.25 μm / h, and the bias voltage was controlled in three stages: initial stage (0~30 nm) bias voltage -80V, intermediate stage (greater than 30 and less than or equal to 100 nm) bias voltage -100V, and final stage (greater than 100 and less than or equal to 120 nm) bias voltage -120V. Finally, a high-speed steel tool E with a composite coating was obtained.

[0122] Comparative Example 5

[0123] In Comparative Example 5, the laser-textured layer on the tool surface had its dynamic focusing function disabled, and the grooves were evenly distributed across the entire cutting edge at a density of 120 grooves / mm. The remaining steps and conditions were the same as in Example 5.

[0124] The composite coated tool E prepared in Example 5 and Comparative Example 5 were compared in a gear machining life test. The results of the comparison test are shown in Table 5 below.

[0125] Table 5. Comparison of experimental results between the composite coated cutting tool A of Example 5 and Comparative Example 5.

[0126]

[0127] As shown in Table 5, under the same tool substrate and model, the same process conditions, and the same test conditions, by simply changing the laser texture layer to a curvature-adaptive dynamic focusing machining method, the composite coating with asymmetric trapezoidal texture of the present invention can significantly reduce the chipping rate of the cutting edge and reduce texture breakage. Its impact on the performance of the coating is greater than that of the structure with uniform laser texture distribution, and both its performance and tool life are better than the composite coating of Comparative Example 5.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A composite coating for the surface of high-speed steel cutting tools, characterized in that: From the outer surface to the substrate direction, it consists of a CrAlN capping layer, a laser-textured layer, a nano-functional layer, and a substrate reinforcement layer. The laser-textured layer has periodic grooves; the bottom of the grooves has nano-ripples, and the cross-section of the grooves is an asymmetrical trapezoidal structure; the inclination angles of the first and second sidewalls of the asymmetrical trapezoidal structure are not equal. The nanofunctional layer comprises a hard layer and a lubricating layer deposited alternately on a substrate reinforcement layer, and both the hard layer and the lubricating layer are composite nitrides composed of Cr, Al, Mo, B and N elements. The matrix reinforcement layer contains nitrogen, and the nitrogen content in the matrix reinforcement layer decreases from the outer surface of the matrix reinforcement layer to the interior of the matrix. The hard layer is a (CrAlBMo)N layer, in which the B content increases from 5~5.5 at.% to 6.5~7 at.% from the matrix reinforcement layer toward the outer surface of the nanofunctional layer, and the Mo content is ≤1 at.%. The lubricating layer is a (CrAlMoB)N layer, in which the Mo content increases from 7 at.% to 12 at.% from the matrix reinforcement layer toward the outer surface of the nanofunctional layer, and the B content is ≤1 at.%.

2. The composite coating for the surface of high-speed steel cutting tools according to claim 1, characterized in that: The width of a single groove in the periodic groove is 500~700nm, and the depth of a single groove is 80~120nm; The arrangement density of the periodic grooves along the cutting direction of the high-speed steel tool is set such that the density on the rake face is greater than that on the flank face, with 150~200 grooves / mm on the rake face and 50~80 grooves / mm on the flank face. The angle α between the first sidewall and the vertical plane of the asymmetrical trapezoidal structure is 15~20°, and the angle β between the second sidewall and the vertical plane is 5~10°.

3. The composite coating for the surface of high-speed steel cutting tools according to claim 2, characterized in that: The CrAlN sealing layer has a thickness of 100~150nm, an Al content of 40~50 at.%, and the thickness of the CrAlN sealing layer does not exceed 1.2 times the depth of the periodic groove.

4. The composite coating for the surface of high-speed steel cutting tools according to claim 1, characterized in that: The thickness of the nanofunctional layer is 2~4μm; The thickness of a single layer of the hard layer is 20~50nm; The thickness of a single layer of the lubricating layer is 5~10nm.

5. A composite coating for the surface of high-speed steel cutting tools according to claim 4, characterized in that: The interface between the alternately deposited hard layer and the lubricating layer has a continuous Cr2B transition layer with a thickness of 3-5 nm.

6. A composite coating for the surface of high-speed steel cutting tools according to any one of claims 1 to 5, characterized in that: The nitrogen concentration in the matrix reinforcement layer decreases from 30-35 at.% to 5-8 at.% from the outer surface of the matrix reinforcement layer towards the interior of the matrix.

7. A method for preparing a composite coating for the surface of a high-speed steel cutting tool as described in any one of claims 1 to 6, characterized in that: Includes the following steps: S1 prepares a matrix reinforcement layer by nitrogen ion implantation on the surface of a high-speed steel tool substrate, and then prepares a nanofunctional layer by alternating deposition using a dual-arc target, resulting in a matrix reinforcement layer-nanofunctional layer. The nitrogen ion implantation treatment controls the nitrogen ion concentration by adjusting the voltage and dosage of the nitrogen ion implantation energy, and the boron content of the hard layer in the nanofunctional layer is controlled by adjusting the power of the dual-arc target. The dual-arc target is composed of a CrAlMo composite target and a CrB composite target. S2 uses a femtosecond laser to perform surface processing on the substrate reinforcement layer-nanofunctional layer, forming periodic grooves on the outer surface of the nanofunctional layer to obtain the substrate reinforcement layer-nanofunctional layer-laser textured layer; the laser focus of the femtosecond laser moves synchronously along the cutting edge direction of the tool, and the ratio of the moving speed to the scanning speed is 1:(50~100); the laser beam is linearly polarized, and the polarization direction is perpendicular to the groove extension direction; the femtosecond laser beam is modulated by a vortex phase plate to form a ring energy distribution; S3 is obtained by sealing the surface of the matrix reinforcement layer-nanofunctional layer-laser textured layer with CrAlN.

8. The method for preparing a composite coating for the surface of high-speed steel cutting tools according to claim 7, characterized in that: In S1, the nitrogen ion implantation is divided into three stages: the first stage has a voltage of 20-25 kV and a duration of 30-50 min; the second stage has a voltage of 10-15 kV and a duration of 15-30 min; and the third stage has a voltage of 4-5 kV and a duration of 5-15 min. The total implantation dose is (1-3) × 10⁻⁶. 17 ions / cm 2 .

9. The method for preparing a composite coating for the surface of high-speed steel cutting tools according to claim 8, characterized in that: The CrAlMo composite target is composed of 45 at.% Cr, 40 at.% Al, and 15 at.% Mo; the CrB composite target is composed of 80 at.% Cr and 20 at.% B. The parameters for alternating deposition using the dual-arc targets are: under nitrogen atmosphere, the target current for the CrAlMo composite target is 60-80 A, the target current for the CrB composite target is 40-50 A, the pulse bias voltage is -100 to -150 V, and the deposition temperature is 400-500 °C. The nanofunctional layer is achieved by periodically rotating the workpiece holder at a rotation speed of 3-5 rpm. The single-layer deposition time for the hard layer is 100-250 s, the single-layer deposition time for the lubricating layer is 28-60 s, and the number of deposition cycles is 20-80. The surface processing conditions are: wavelength 1010-1050 nm, pulse width 300-500 fs, and energy density 1.8-2.5 J / cm². 2 The scanning speed is 400~600mm / s.

10. The method for preparing a composite coating for the surface of a high-speed steel cutting tool according to claim 8 or 9, characterized in that: In S3 The conditions for the CrAlN encapsulation layer are as follows: under nitrogen atmosphere, a CrAl composite target composed of 45~55wt.%Cr and 55~45wt.%Al is used, the speed is 0.1~0.3μm / h, and the bias voltage is -80V~-120V.

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