DLC (Diamond Like Carbon) coating with gradient composite structure and surface microstructure and preparation method of DLC coating

Abstract

The invention discloses a DLC coating with a gradient composite structure and a surface microstructure and a preparation method of the DLC coating, and belongs to the technical field of hard alloy tool surface treatment. The coating comprises a transition layer, a DLC gradient layer and a laser microstructure layer arranged on the outer surface of a DLC main coating, the transition layer is composed of Cr layers and CrN layers which are alternately stacked; the sp3 bond content of the DLC gradient layer is gradually increased in the direction from the transition layer to the outer surface of the DLC gradient layer, and the W element content in the DLC gradient layer is gradually decreased in the direction from the transition layer to the outer surface of the DLC gradient layer; the laser micro-texture layer is composed of a hexagonal honeycomb-shaped densely-arranged pit array. The coating system has the characteristics of high interface bonding strength and ultralow friction, and the service life of the hard alloy cutter can be remarkably prolonged when the coating system is applied to the surface of the hard alloy cutter.

Description

Technical Field

[0001] The invention belongs to the technical field of surface treatment of cemented carbide cutting tools, and relates to a DLC coating with a gradient composite structure and surface microtexture and a preparation method thereof. Background Art

[0002] Diamond-like carbon (DLC) is a metastable carbon-based functional coating composed of a blend of sp³-bonded diamond and sp²-bonded graphite. Its structure features sp³ / sp² hybrid bonds crosslinked in a three-dimensional random network. This coating combines the mechanical properties of diamond with the tribological advantages of graphite, exhibiting ultrahigh hardness (15-40 GPa), ultra-low coefficient of friction (0.05-0.15), excellent thermal conductivity (500-1200 W / m·K), and exceptional chemical inertness. It holds significant application value in precision machinery and biomedical applications.

[0003] However, the industrial application of DLC coatings faces two bottlenecks: first, due to the poor matching between the DLC film and the substrate material and the large internal stress generated in the film during the deposition process, the bonding strength between the DLC film and the substrate is not high, which makes it easy for the film to crack and peel off, and it is difficult to prepare a thick film; second, when the temperature rises, the carbon atoms will move to the sp 2 Hybridization transition, that is, graphitization of the film, leads to film failure. The above defects seriously restrict its long-term service in extreme environments such as aerospace.

[0004] One way to improve the internal stress of DLC coatings is to introduce a buffer transition layer to improve the interface bonding strength by improving the difference in thermal expansion coefficients and structural mismatch between the interfaces. Conventional transition layers generally use transition metal target materials such as Ti, Si, and Cr. However, these single-layer transition layers have limited ability to coordinate the overall deformation of the film base. At the same time, the weak interface bonding between the metal transition layer and the top DLC layer causes cracks to initiate and propagate upward, causing the DLC film to peel off prematurely. In addition, the traditional DLC coating lacks an active lubricating phase, resulting in a discontinuous transfer film and a time-dependent deterioration of the friction coefficient in high-speed cutting of titanium alloys. In the initial stage of processing, the friction coefficient increased from 0.18 to 0.27 within 5 minutes. When the cutting temperature is >600°C, the sp³ bond content drops sharply from 75% to 50%, the friction coefficient rises to 0.35, and abrasive wear is intensified.

[0005] Therefore, it is urgent to design a new coating structure to solve the above problems. Summary of the Invention

[0006] In response to the dual bottlenecks of easy peeling and lubrication failure of DLC coatings in the cutting process of difficult-to-machine materials (such as titanium alloys and high-temperature alloys) in the existing technology, the first purpose of the present invention is to provide a DLC coating with a gradient composite structure and surface microtexture. This coating system has both high interfacial bonding strength and ultra-low friction characteristics. Applying it to the surface of cemented carbide tools can significantly improve their service life.

[0007] The second object of the present invention is to provide a method for preparing a DLC coating with a gradient composite structure and surface microtexture, which is efficient, low-consumption, and environmentally friendly. By regulating the acetylene flow in the magnetron sputtering and ion beam composite process and coordinating the laser microtexturing processing process control, the coating of the present invention has a special surface morphology and sp 3 Key gradient content.

[0008] In order to achieve the above technical objectives, the present invention provides a DLC coating with a gradient composite structure and surface micro-texture, the coating comprises a transition layer, a DLC gradient layer and a laser micro-texture layer arranged on the outer surface of the DLC gradient layer; the transition layer is composed of an alternately stacked Cr layer and a CrN layer; the sp 3 The bond content increases from the transition layer to the outer surface of the DLC gradient layer, and the W element content in the DLC gradient layer decreases from the transition layer to the outer surface of the DLC gradient layer; the laser micro-textured layer is composed of a hexagonal honeycomb close-packed pit array.

[0009] The DLC coating of the present invention forms a diffusion bond between the Cr and CrN layers in the transition layer, significantly enhancing the interlayer diffusion bonding strength of the coating and the substrate surface while minimizing toughness loss, resolving the "high bonding strength-high toughness" dilemma. The alternating deposition method leverages the plastic buffering properties of Cr and the complementary rigidity of CrN to disperse internal stress layer by layer, avoiding stress concentration caused by excessively thick single layers and achieving stress gradient control. The DLC gradient layer above the transition layer utilizes a dual gradient control of sp³ bond content and W element content. The high W content (1.0-1.2 wt%) near the substrate inhibits interfacial crack propagation through a pinning effect and reduces thermal expansion coefficient mismatch. The high sp³ bond content (≥80%) on the surface provides ultrahard wear resistance, while the low W content (≤0.8 wt%) reduces the formation of brittle carbides (such as WC), preventing friction coefficient fluctuations, and comprehensively improving the coating's bonding strength and tribological stability. Finally, by introducing a laser micro-textured layer with a hexagonal honeycomb-shaped densely packed pit array on the outer surface of the DLC gradient layer, the arrangement of the honeycomb morphology is fully utilized to maximize the pit density, extend the lubricant retention time, and improve the oil storage efficiency. The symmetry of the hexagon can make the stress distribution uniform, and the Y-shaped channel between the pits guides the chips to be discharged in a specific direction, reducing the contact area between the chips and the tool, lowering the friction coefficient and reducing the cutting force fluctuation, significantly improving the processing surface quality, and preventing the accumulation of chips and increasing the friction coefficient of the coating, causing the lubrication performance to fail.

[0010] As a preferred solution, the DLC coating with a gradient composite structure and surface microtexture of the present invention is deposited on the surface of a substrate, and the substrate is selected from cemented carbide.

[0011] As a preferred solution, the thickness of a single Cr layer is 50-100 nm, the thickness of a single CrN layer is 80-150 nm, and the total number of layers is 10-16.

[0012] As a preferred embodiment, the thickness ratio of the Cr layer to the CrN layer is 1:(1.2-1.8). In the present invention, each Cr layer forms a diffusion bond with the CrN layer through argon ion bombardment of the interface. Furthermore, by setting the thickness of the CrN layer to be greater than that of the Cr layer, the thicker CrN layer, due to its greater hardness than the Cr layer, disperses the external load of the composite coating and buffers the interfacial stress.

[0013] As a preferred embodiment, the pit diameter of the laser microtexturing layer is 10-50 μm, the depth is less than half the thickness of the DLC gradient layer, and the pit area accounts for 15%-30% of the surface area of the DLC gradient layer. By limiting the laser microtexturing depth, the present invention prevents high laser energy or multiple scans, which can trigger localized graphitization (sp³ to sp² bond conversion) of the DLC coating, thereby affecting coating hardness. This also prevents excessively deep pits from causing lubricant loss or chip accumulation, which increases the coating's friction coefficient and leads to lubrication failure. By controlling the pit area as a percentage of the surface area of the DLC gradient layer, the oil storage effect and chip guidance function can be utilized to reduce friction and minimize cutting force fluctuations. However, the pit area percentage of the DLC gradient layer's surface area should not be too large, otherwise it will reduce the effective contact area between the tool and the workpiece, leading to excessively high local pressure and accelerated coating wear. Furthermore, the interconnected pits form a capillary network, which can rapidly drain lubricant and cause a rebound in the friction coefficient.

[0014] As a preferred solution, the thickness ratio of the transition layer to the DLC gradient layer is (0.8-1.5):(3-5).

[0015] As a preferred solution, the sp of the DLC gradient layer 3 The bond content increases from 60-70wt% to 73-85wt% from the transition layer to the outer surface of the DLC gradient layer, and the W element content in the DLC gradient layer decreases from 0.9-1.2wt% to 0.5-0.8wt% from the transition layer to the outer surface of the DLC gradient layer. 3 The hardness of the DLC gradient layer can be comprehensively controlled within the range of bond content and W element content to 25~35GPa.

[0016] As a preferred solution, the center-to-center distance between adjacent hexagonal close-packed dimples is 1.2 to 1.5 times the dimple diameter, and the dimple sidewall angle is 30° to 60°. In the present invention, too small a center-to-center distance between adjacent dimples increases the risk of material bridges breaking between the dimples; while too large a sidewall angle makes it difficult for chips to be embedded in the dimples and removed, leading to increased friction temperatures.

[0017] The present invention also provides a method for preparing a DLC coating having a gradient composite structure and surface microtexture, wherein a Cr layer and a CrN layer are alternately deposited on a pretreated substrate surface, and then a DLC gradient layer is deposited by a magnetron sputtering and ion beam composite process, the sp³ bond content in the DLC gradient layer is controlled by adjusting the acetylene flow rate, and a tungsten target is used as a target material, and the W content in the DLC gradient layer is controlled by adjusting the tungsten target power to obtain a transition layer-DLC gradient layer; and the transition layer-DLC gradient layer is microtextured by laser to form a hexagonal honeycomb-shaped close-packed pit array on the outer surface of the DLC gradient layer.

[0018] The preparation method of the present invention primarily utilizes a combined magnetron sputtering and ion beam process, along with lasers, to control the distribution of W content and sp³ bond content in the graded layer, creating a unique hexagonal honeycomb array. The acetylene flow rate is negatively correlated with the sp³ bond content, while the W target power is positively correlated with the W content. The present invention utilizes femtosecond laser interference lithography, generating a hexagonal grating pattern through dual-beam interference. This, combined with a honeycomb scanning path, ensures consistent pit morphology, effectively forming a hexagonal honeycomb close-packed pit array.

[0019] As a preferred solution, the substrate is pretreated by argon ion bombardment to clean the substrate surface, with a bombardment voltage of 800-1200V and a time of 20-30 minutes to obtain a surface roughness Ra<0.05μm.

[0020] As a preferred solution, when the Cr layer and the CrN layer are alternately deposited on the substrate surface, the parameters for depositing the Cr layer are: using a pure Cr target, a target current of 6~10A, a substrate temperature of 250~300°C, and a bias voltage of -60V~-100V; the parameters for depositing the CrN layer are: a nitrogen flow rate of 50~80sccm, a deposition pressure of 0.3~0.6Pa, and a bias voltage of -80V~-120V.

[0021] As a preferred solution, the parameters for the magnetron sputtering and ion beam hybrid process are as follows: a carbon target current of 3-5A, an argon to acetylene flow ratio of (3-5):1, a deposition rate of 0.5-1μm / h, and a controlled acetylene flow rate that is linearly reduced from an initial value of 30sccm to 14-20sccm at a rate of 0.03-0.1sccm / min. The tungsten target power is linearly reduced from 85-100W to 50-60W at a rate of 0.1-0.2W / min, and the bias voltage is -100V to -150V. During magnetron sputtering of the DLC layer, the W target is simultaneously activated, and the W content is controlled by regulating the W target power.

[0022] As a preferred solution, the conditions for the laser microtexturing processing are: using a femtosecond laser with a wavelength of 1030~1064nm, a pulse energy of 0.5~1.2mJ, a scanning speed of 200~500mm / s, an overlap rate of the laser scanning path of 15%~25%, and the number of laser pulses for each pit is 3~5 times.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention alternately deposits Cr / CrN transition layers through interlayer diffusion bonding and stress gradient regulation, thereby improving the interface bonding strength and reducing the toughness loss, thus solving the "high bonding strength-high toughness" contradiction.

[0025] (2) The present invention designs a dual-gradient DLC coating with sp³ bond content and W element, combining the pinning effect of W element and sp³ bond network strengthening to simultaneously improve high temperature stability and wear resistance.

[0026] (3) The present invention introduces hexagonal close-packed laser microtexturing, which reduces the friction coefficient and the cutting force fluctuation through the oil storage effect and chip guiding function, and significantly improves the processing surface quality.

[0027] (4) By limiting the depth of laser microtexturing, the present invention avoids high laser energy or multiple scans, which can cause local graphitization (sp³→sp² bond conversion) of the DLC coating and thus affect the coating hardness. It also prevents excessively deep pits from causing lubricant loss or chip accumulation, which increases the coating friction coefficient and causes lubrication failure.

[0028] (5) The preparation method of the present invention is efficient, low-consumption, and environmentally friendly. The prepared coated tool can meet the needs of high-speed cutting and is conducive to large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic plan view of a hexagonal honeycomb close-packed pit array in the surface laser microtexturing layer of the DLC coating of the present invention. Here, 1 is the surface laser microtexturing; 2 is the DLC gradient layer.

[0030] Figure 2 The schematic diagram of the cross-section of the DLC coating with gradient composite structure and surface micro-texture of the present invention is shown in FIG2 , wherein: 2 is the DLC gradient layer; 3 is the laser micro-texture layer; and 4 is the Cr / CrN alternating transition layer.

[0031] Figure 3 This is the SEM detection spectrum of the transition layer of the DLC coating prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0033] Example 1

[0034] A DLC coating with a gradient composite structure and surface micro-texture, the surface micro-texture morphology is shown in the figure Figure 1 As shown, the structural distribution diagram is as follows Figure 2 As shown, it consists of a transition layer 1, a DLC graded layer 2, and a laser microtextured layer 3. The total thickness of the transition layer 1 is 0.65 μm, the DLC graded layer is 3.0 μm thick, and has a hardness of 28 GPa. The depth of the laser microtextured layer 3 is 1.5 μm.

[0035] In this embodiment, the transition layer specifically includes 5 alternating layers of Cr layer (50 nm) / CrN layer (80 nm), for a total of 10 layers, with a Cr / CrN thickness ratio of 1:1.6.

[0036] In this embodiment, the sp³ bond content of the DLC gradient layer increases from 60wt% to 80wt%, and the W content decreases from 1.2wt% to 0.5wt%.

[0037] In this embodiment, the diameter of the pits on the micro-texture is 10 μm, the depth is 1 / 2 of the thickness of the DLC gradient layer, the center distance of the pits is 12 μm, the pit area accounts for 15% of the surface area of the DLC gradient layer, and the pit sidewall inclination angle is 45°.

[0038] A method for preparing a DLC coating having a gradient composite structure and surface microtexture comprises the following steps:

[0039] (1) Matrix pretreatment: The matrix of the cemented carbide integral milling cutter used is WC-Co6wt%, model D6×100×3F, argon ion bombardment voltage 1000V, time 25min, Ra=0.03μm.

[0040] (2) Transition layer deposition: The transition layer was deposited using a Cr target by magnetron sputtering. When depositing the Cr layer, the target current was 8 A, the temperature was 280 °C, and the bias voltage was -80 V. When depositing the CrN layer, the N2 flow rate was 60 sccm, the pressure was 0.4 Pa, and the bias voltage was -100 V.

[0041] (3) Deposition of a graded DLC layer: The C target current was 4 A, the Ar / C2H2 flow ratio was 4:1, and the deposition rate was 0.7 μm / h. The acetylene flow rate was linearly decreased from an initial value of 30 sccm to 15 sccm at a rate of 0.06 sccm / min. The W target power was simultaneously turned on, and the W target power was linearly decreased from an initial value of 100 W to 50 W at a rate of 0.19 W / min, causing the W content to decrease from 1.2 wt% to 0.5 wt%. The bias voltage was -120 V.

[0042] (4) Laser processing: Femtosecond laser interference lithography technology is used to generate a hexagonal grating pattern through double-beam interference. The wavelength of the femtosecond laser is 1040 nm, the pulse energy is 0.8 mJ, the scanning speed is 300 mm / s, the overlap rate of the laser scanning path is 20%, and each pit has 3 pulses.

[0043] In this embodiment, the SEM test results of the transition layer show that there are five layers of Cr / CrN alternating. Figure 3 As shown in Figure 2, the thickness is 650 nm and the sp³ bond content of the DLC primary coating increases from 60 wt% to 80 wt% as measured by Raman spectroscopy.

[0044] Control experiment 1

[0045] The tool transition layer of reference product 1 is a single Cr layer with a thickness of 650 nm. The remaining steps and conditions are consistent with those of Example 1.

[0046] The DLC-coated tool A prepared in Example 1 and the control product 1 were subjected to a comparative experiment for continuous milling of aluminum alloy (6063). The comparative test results are shown in Table 1 below.

[0047]

[0048] As can be seen from Table 1, under the same tool substrate and model, the same process conditions, and the same test conditions, the DLC coating of the present invention with alternating Cr / CrN transition layers can significantly improve the interfacial bonding strength and stress distribution, and has a greater impact on the coating's performance than a single-layer transition layer. Its bonding strength, tool life, cutting force fluctuation performance, and surface roughness performance are all superior to the general DLC coating of reference product 1.

[0049] Example 2

[0050] A DLC coating with a gradient composite structure and surface micro-texture, the surface micro-texture morphology is shown in the figure Figure 1 As shown, the structural distribution diagram is as follows Figure 2 As shown, it consists of a transition layer 1, a DLC graded layer 2, and a laser microtextured layer 3. The transition layer 1 has a total thickness of 1.2 μm, the DLC graded layer is 4.0 μm thick, and has a hardness of 32 GPa. The laser microtextured layer 3 is 2 μm deep.

[0051] In this embodiment, the transition layer specifically includes 6 alternating layers of Cr layer (80 nm) / CrN layer (120 nm), for a total of 12 layers, with a Cr / CrN thickness ratio of 1:1.5.

[0052] In this embodiment, the sp³ bond content of the DLC gradient layer increases from 60wt% to 78wt%, and the W content decreases from 1.1wt% to 0.6wt%.

[0053] In this embodiment, the diameter of the pits on the micro-texture is 30 μm, the depth is 2 μm, the pit center distance is 36 μm, the pit area accounts for 25% of the surface area of the DLC gradient layer, and the pit sidewall inclination angle is 50°.

[0054] A method for preparing a DLC coating having a gradient composite structure and surface microtexture comprises the following steps:

[0055] (1) Matrix pretreatment: The matrix of the cemented carbide integral milling cutter used is WC-Co6wt%, model D6×100×3F, argon ion bombardment voltage 1100V, time 28min, Ra=0.04μm.

[0056] (2) Transition layer deposition: The transition layer was deposited using a Cr target by magnetron sputtering. When depositing the Cr layer, the target current was 7 A, the temperature was 260 °C, and the bias voltage was -70 V. When depositing the CrN layer, the N2 flow rate was 70 sccm, the pressure was 0.5 Pa, and the bias voltage was -110 V.

[0057] (3) Deposition of a graded DLC layer: The C target current was 3.5 A, the Ar / C2H2 flow ratio was 3:1, and the deposition rate was 0.6 μm / h. The acetylene flow rate was linearly decreased from 30 sccm to 16 sccm at a rate of 0.035 sccm / min. The W target power was simultaneously turned on, and the W target power was linearly decreased from an initial 95 W to 55 W at a rate of 0.1 W / min, reducing the W content from 1.1 wt% to 0.6 wt%. The bias voltage was -120 V.

[0058] (4) Laser processing: Femtosecond laser interference lithography technology is used to generate a hexagonal grating pattern through dual-beam interference. The wavelength of the femtosecond laser is 1050 nm, the pulse energy is 1.0 mJ, the scanning speed is 400 mm / s, the overlap rate of the laser scanning path is 18%, and each pit has 4 pulses.

[0059] In this embodiment, the SEM test results of the transition layer show that it has 6 alternating layers of Cr / CrN with a thickness of 1.2 μm. The sp³ bond content of the DLC gradient layer measured by Raman spectroscopy increases from 60wt% to 78wt%.

[0060] Control experiment 2

[0061] The tool substrate and pretreatment process of control product 2 are the same as those of Example 2, except that the surface laser processing scanning path is disordered and the micro-texture pits are randomly distributed. The remaining steps and conditions are consistent with those of Example 2.

[0062] The DLC-coated tool B prepared in Example 2 and the control product 2 were subjected to a comparative experiment for continuous milling of aluminum alloy (6063). The comparative test results are shown in Table 2 below.

[0063]

[0064] As shown in Table 2, given the same tool substrate and model, identical transition layer and main coating process conditions, and identical testing conditions, the DLC coating with a close-packed hexagonal pit structure, when modified to a random distribution of surface micro-texture pits, significantly improves the coating's lubricity, reduces the coating's friction coefficient and cutting temperature, and also reduces chip residue. Its performance impact is superior to that of a DLC coating with a random distribution of micro-texture pits. Tool life, cutting temperature control, chip residue, and average friction coefficient are all superior to those of the DLC coating with a random distribution of pits, as in Reference 2.

[0065] Example 3

[0066] A DLC coating with a gradient composite structure and surface micro-texture, the surface micro-texture morphology is shown in the figure Figure 1 As shown, the structural distribution diagram is as follows Figure 2 As shown, it consists of a transition layer 1, a DLC graded layer 2, and a laser microtextured layer 3. The total thickness of the transition layer 1 is 1.19 μm, the thickness of the DLC graded layer is 5.0 μm, and the hardness is 34 GPa. The depth of the laser microtextured layer 3 is 2.5 μm.

[0067] In this embodiment, the transition layer specifically includes 7 alternating layers of Cr layer (70 nm) / CrN layer (100 nm), for a total of 14 layers, with a Cr / CrN thickness ratio of 1:1.4.

[0068] In this embodiment, the DLC main coating sp 3 The bond content gradient increases from 60wt% to 73wt%, and the W content decreases from 1.0wt% to 0.7wt%.

[0069] In this embodiment, the diameter of the pits on the micro texture is 40 μm, the depth is 2.5 μm, the pit center distance is 48 μm, the area accounts for 28%, and the side wall inclination angle is 55°.

[0070] A method for preparing a DLC coating having a gradient composite structure and surface microtexture comprises the following steps:

[0071] (1) Matrix pretreatment: The matrix of the cemented carbide integral milling cutter used is WC-Co6wt%, model D6×100×3F, argon ion bombardment voltage 900V, time 22min, Ra=0.02μm.

[0072] (2) Transition layer deposition: The transition layer was deposited using a Cr target by magnetron sputtering. When depositing the Cr layer, the target current was 9 A, the temperature was 290 °C, and the bias voltage was -90 V. When depositing the CrN layer, the N2 flow rate was 75 sccm, the pressure was 0.45 Pa, and the bias voltage was -105 V.

[0073] (3) Deposition of a graded DLC layer: The C target current was 4.5 A, the Ar / C2H2 flow ratio was 5:1, and the deposition rate was 0.9 μm / h. The acetylene flow rate was linearly decreased from 30 sccm to 18 sccm at 0.035 sccm / min. The W target power was simultaneously turned on, and the W target power was linearly decreased from an initial 90 W to 60 W at 0.1 W / min, reducing the W content from 1.0 wt% to 0.7 wt%. The bias voltage was -120 V.

[0074] (4) Laser processing: Femtosecond laser interference lithography technology is used to generate a hexagonal grating pattern through dual-beam interference. The wavelength of the femtosecond laser is 1064 nm, the pulse energy is 1.1 mJ, the scanning speed is 450 mm / s, the overlap rate of the laser scanning path is 22%, and each pit has 5 pulses.

[0075] In this embodiment, the SEM test results of the transition layer showed that it had 7 alternating layers of Cr / CrN with a thickness of 1.19 μm. The sp³ bond content of the DLC main coating increased from 60wt% to 73wt% according to Raman spectroscopy.

[0076] Control experiment 3

[0077] During the deposition of the DLC gradient layer on the tool of reference product 3, the acetylene flow rate was constant at 30 sccm, and the remaining steps and conditions were consistent with those of Example 3.

[0078] The DLC-coated tool C prepared in Example 3 and the control product 3 were subjected to a comparative experiment in continuous milling of aluminum alloy (6063). The comparative test results are shown in Table 3 below.

[0079]

[0080] As shown in Table 3, under the same tool substrate and model, consistent transition layer and surface microtexture process conditions, and the same test conditions, only the acetylene flow rate is changed to a constant 30 sccm. The DLC coating with a gradient change in sp³ bond content of the present invention can significantly improve the coating life, reduce surface roughness, and improve high-temperature stability. Its performance is better than that of the coating without sp³ bond content. 3 Typical DLC coatings with varying bond contents.

[0081] Example 4

[0082] A DLC coating with a gradient composite structure and surface micro-texture, the surface micro-texture morphology is shown in the figure Figure 1 As shown, the structural distribution diagram is as follows Figure 2 As shown, it consists of a transition layer 1, a DLC gradient layer 2 and a laser microtextured layer 3. The total thickness of the transition layer 1 is 2.0 μm, the thickness of the DLC gradient layer is 4.5 μm, the hardness is 30 GPa, and the depth of the laser microtextured layer 3 is 1.8 μm.

[0083] In this embodiment, the transition layer specifically includes 8 alternating layers of Cr layer (100 nm) / CrN layer (150 nm), for a total of 16 layers, with a Cr / CrN thickness ratio of 1:1.5.

[0084] In this embodiment, the DLC gradient layer sp 3 The bond content gradient increases from 60wt% to 80wt%, and the W content decreases from 1.2wt% to 0.5wt%.

[0085] In this embodiment, the diameter of the pits on the micro-texture is 20 μm, the depth is 1.8 μm, the pit center distance is 24 μm, the pit area accounts for 20% of the surface area of the DLC gradient layer, and the pit sidewall inclination angle is 40°.

[0086] A method for preparing a DLC coating having a gradient composite structure and surface microtexture comprises the following steps:

[0087] (1) Matrix pretreatment: The matrix of the cemented carbide integral milling cutter used is WC-Co6wt%, model D6×100×3F, argon ion bombardment voltage 1200V, time 30min, Ra=0.05μm.

[0088] (2) Transition layer deposition: The transition layer was deposited using a Cr target by magnetron sputtering. When depositing the Cr layer, the target current was 6 A, the temperature was 250 °C, and the bias voltage was -60 V. When depositing the CrN layer, the N2 flow rate was 80 sccm, the pressure was 0.6 Pa, and the bias voltage was -120 V.

[0089] (3) Deposition of a graded DLC layer: The C target current was 5 A, the Ar / C2H2 flow ratio was 4:1, and the deposition rate was 1.0 μm / h. The acetylene flow rate was linearly decreased from 30 sccm to 14 sccm at a rate of 0.06 sccm / min. The W target was simultaneously turned on, and the W target power was linearly decreased from an initial 100 W to 50 W at a rate of 0.19 W / min, causing the W content to decrease from 1.2 wt% to 0.5 wt%. The bias voltage was -120 V.

[0090] (4) Laser processing: Femtosecond laser interference lithography technology is used to generate a hexagonal grating pattern through double-beam interference. The wavelength of the femtosecond laser is 1030 nm, the pulse energy is 0.6 mJ, the scanning speed is 250 mm / s, the overlap rate of the laser scanning path is 25%, and each pit has 3 pulses.

[0091] In this embodiment, the SEM test results of the transition layer show that it is composed of 8 alternating layers of Cr / CrN with a thickness of 2.0 μm. The sp³ bond content of the DLC main coating measured by Raman spectroscopy increases from 60wt% to 80wt%.

[0092] Control experiment 4

[0093] The thickness of the micro-texture on the tool surface of the control product 4 is 3 μm, which is more than half of the total thickness of the DLC gradient layer. The remaining steps and conditions are the same as those of Example 4.

[0094] The DLC-coated tool D prepared in Example 4 and the control product 4 were subjected to a comparative experiment of continuous milling of aluminum alloy (6063). The comparative test results are shown in Table 4 below.

[0095]

[0096] As can be seen from Table 4, under the same tool substrate and model, consistent process conditions for the transition layer and main coating, and identical test conditions, only the surface microtexture depth is changed to 3 μm, which exceeds 1 / 2 of the total thickness of the DLC coating. The DLC coating with a gradient composite structure and surface microtexture of the present invention can balance the lubrication performance and the integrity of the coating structure, optimize the stress distribution, significantly improve the coating life, reduce the surface roughness, and reduce the consumption of lubricant. The effect on the performance of the coating is better than that of the reference product 4 in which the microtexture thickness exceeds 1 / 2 of the thickness of the DLC gradient layer.

[0097] Example 5

[0098] A DLC coating with a gradient composite structure and surface micro-texture, the surface micro-texture morphology is shown in the figure Figure 1 As shown, the structural distribution diagram is as follows Figure 2 As shown, it consists of a transition layer 1, a DLC gradient layer 2 and a laser microtextured layer 3. The total thickness of the transition layer 1 is 0.7 μm, the thickness of the DLC gradient layer is 3.5 μm, the hardness is 27 GPa, and the depth of the laser microtextured layer 3 is 1.0 μm.

[0099] In this embodiment, the transition layer specifically includes 5 alternating layers of Cr layer (60 nm) / CrN layer (80 nm), for a total of 10 layers, with a Cr / CrN thickness ratio of 1:1.3.

[0100] In this embodiment, the DLC main coating sp 3 The bond content gradient increases from 60wt% to 80wt%, and the W content decreases from 1.0wt% to 0.6wt%.

[0101] In this embodiment, the diameter of the pits on the micro texture is 15 μm, the depth is 1.0 μm, the pit center distance is 18 μm, the area accounts for 18%, and the side wall inclination angle is 35°.

[0102] A method for preparing a DLC coating having a gradient composite structure and surface microtexture comprises the following steps:

[0103] (1) Matrix pretreatment: The matrix of the cemented carbide integral milling cutter used is WC-Co6wt%, model D6×100×3F, argon ion bombardment voltage 850V, time 24min, Ra=0.03μm.

[0104] (2) Transition layer deposition: The transition layer was deposited using a Cr target by magnetron sputtering. When depositing the Cr layer, the target current was 7.5 A, the temperature was 270 °C, and the bias voltage was -75 V. When depositing the CrN layer, the N2 flow rate was 55 sccm, the pressure was 0.35 Pa, and the bias voltage was -85 V.

[0105] (3) Deposition of a gradient DLC layer: The C target current was 3.8 A, the Ar / C2H2 flow ratio was 4:1, and the deposition rate was 0.8 μm / h. The acetylene flow rate was linearly decreased from 30 sccm to 17 sccm at a rate of 0.05 sccm / min. The W target power was simultaneously turned on, and the W target power was linearly decreased from an initial 90 W to 55 W at a rate of 0.11 W / min, causing the W content to decrease from 1.0 wt% to 0.6 wt%. The bias voltage was -120 V.

[0106] (4) Laser processing: Femtosecond laser interference lithography technology is used to generate a hexagonal grating pattern through dual-beam interference. The wavelength of the femtosecond laser is 1050 nm, the pulse energy is 0.7 mJ, the scanning speed is 350 mm / s, the overlap rate of the laser scanning path is 16%, and each pit has 4 pulses.

[0107] In this embodiment, the transition layer SEM test results show that there are 5 layers of Cr / CrN alternating with each other and the thickness is 0.7 μm. The DLC gradient layer is sp measured by Raman spectroscopy. 3 The bond content increased from 60wt% to 80wt%.

[0108] Control experiment 5

[0109] The tool transition layer Cr / CrN thickness ratio of reference product 5 is 1:1, wherein the single layer thickness of the Cr layer and the CrN layer are both 80 nm, and the remaining steps and conditions are consistent with those of Example 5.

[0110] The DLC-coated tool E prepared in Example 5 and the control product 5 were subjected to a comparative experiment of continuous milling of aluminum alloy (6063). The comparative test results are shown in Table 5 below.

[0111]

[0112] As can be seen from Table 5, under the same tool substrate and model, consistent main coating and surface microtexture process conditions, and identical test conditions, only the transition layer Cr / CrN thickness ratio is changed to 1:1. The DLC coating of Example 5 with a transition layer Cr / CrN thickness ratio of 1:1.3 can improve cross-sectional bonding, optimize stress distribution, inhibit crack propagation, and improve cutting stability. Its effect on coating performance is better than that of the control sample 5 with a transition layer Cr / CrN thickness ratio of 1:1.

[0113] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A DLC coating having a gradient composite structure and surface microtexture, characterized in that: The laser micro-textured layer comprises a transition layer, a DLC gradient layer and a laser micro-textured layer arranged on the outer surface of the DLC gradient layer; the transition layer is composed of an alternately stacked Cr layer and a CrN layer; the sp 3 The bond content increases from the transition layer to the outer surface of the DLC gradient layer, and the W element content in the DLC gradient layer decreases from the transition layer to the outer surface of the DLC gradient layer; the laser micro-textured layer is composed of a hexagonal honeycomb close-packed pit array.

2. The DLC coating having a gradient composite structure and surface microtexture according to claim 1, characterized in that: The thickness of a single Cr layer is 50-100 nm, the thickness of a single CrN layer is 80-150 nm, and the total number of layers is 10-16.

3. The DLC coating having a gradient composite structure and surface microtexture according to claim 2, characterized in that: The thickness ratio of the Cr layer to the CrN layer is 1:(1.2-1.8).

4. The DLC coating having a gradient composite structure and surface microtexture according to claim 1, characterized in that: The pit diameter of the laser micro-textured layer is 10-50 μm, the depth is less than or equal to 1 / 2 of the thickness of the DLC gradient layer, and the pit area accounts for 15%-30% of the surface area of the DLC gradient layer.

5. The DLC coating having a gradient composite structure and surface microtexture according to any one of claims 1 to 4, characterized in that: The thickness ratio of the transition layer to the DLC gradient layer is (0.8-1.5): (3-5).

6. The DLC coating having a gradient composite structure and surface microtexture according to claim 5, characterized in that: The sp of the DLC graded layer 3 The bond content increases from 60-70wt% to 73-85wt% from the transition layer toward the outer surface of the DLC gradient layer, and the W element content in the DLC gradient layer decreases from 0.9-1.2wt% to 0.5-0.8wt% from the transition layer toward the outer surface of the DLC gradient layer.

7. The method for preparing a DLC coating having a gradient composite structure and surface microtexture according to any one of claims 1 to 6, characterized in that: Cr layers and CrN layers are alternately deposited on the surface of a pretreated substrate, and then a DLC gradient layer is deposited by a magnetron sputtering and ion beam composite process. The sp³ bond content in the DLC gradient layer is controlled by adjusting the acetylene flow rate. At the same time, a tungsten target is used as the target material and the W content in the DLC gradient layer is controlled by adjusting the tungsten target power to obtain a transition layer-DLC gradient layer. The transition layer-DLC gradient layer is micro-textured by laser to form a hexagonal honeycomb-shaped close-packed pit array on the outer surface of the DLC gradient layer.

8. The method for preparing a DLC coating having a gradient composite structure and surface microtexture according to claim 7, characterized in that: When the Cr layer and the CrN layer are alternately deposited on the substrate surface, the parameters for depositing the Cr layer are: using a pure Cr target, a target current of 6-10A, a substrate temperature of 250-300°C, and a bias voltage of -60V--100V; the parameters for depositing the CrN layer are: a nitrogen flow rate of 50-80sccm, a deposition pressure of 0.3-0.6Pa, and a bias voltage of -80V--120V.

9. The method for preparing a DLC coating having a gradient composite structure and surface microtexture according to claim 7, wherein: The parameters of the magnetron sputtering and ion beam composite process are as follows: a carbon target current of 3-5 A, an argon to acetylene flow ratio of (3-5):1, a deposition rate of 0.5-1 μm / h, and the acetylene flow rate is linearly reduced from an initial value of 30 sccm to 14-20 sccm at a rate of 0.03-0.1 sccm / min; the tungsten target power is linearly reduced from 85-100 W to 50-60 W at a rate of 0.1-0.2 W / min, and the bias voltage is -100 V to -150 V.

10. The method for preparing a DLC coating having a gradient composite structure and surface microtexture according to claim 8 or 9, characterized in that: The conditions for the laser microtexturing processing are: using a femtosecond laser with a wavelength of 1030~1064nm, a pulse energy of 0.5~1.2mJ, a scanning speed of 200~500mm / s, an overlap rate of the laser scanning path of 15%~25%, and the number of laser pulses applied to each pit is 3~5 times.

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