A DLC coating with gradient composite structure and surface microtexture and its preparation method.

Abstract

This invention discloses a DLC coating with a gradient composite structure and surface microtexture, and its preparation method, belonging to the field of surface treatment technology for cemented carbide cutting tools. The coating includes a transition layer, a DLC gradient layer, and a laser microtexture layer disposed on the outer surface of the main DLC coating; the transition layer consists of alternating stacked Cr layers and CrN layers; the DLC gradient layer... 3 The bond content increases from the transition layer towards the outer surface of the DLC gradient layer, while the W element content in the DLC gradient layer decreases from the transition layer towards the outer surface of the DLC gradient layer. The laser microtexture layer is composed of a hexagonal honeycomb-shaped densely packed pit array. The coating system of this invention combines high interfacial bonding strength and ultra-low friction characteristics, and its application to the surface of cemented carbide cutting tools can significantly improve their service life.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for cemented carbide cutting tools, and relates to a DLC coating with a gradient composite structure and surface microtexture and its preparation method. Background Technology

[0002] Diamond-like carbon (DLC) coatings are metastable carbon-based functional coatings formed by blending sp³-bonded diamond and sp²-bonded graphite phases, with sp³ / sp² hybrid bonds cross-linked in a three-dimensional random network. This coating combines the mechanical properties of diamond with the tribological advantages of graphite, exhibiting ultra-high hardness (15–40 GPa), ultra-low coefficient of friction (0.05–0.15), excellent thermal conductivity (500–1200 W / m·K), and outstanding chemical inertness, making it valuable for applications in precision machinery and biomedicine.

[0003] However, the industrial application of DLC coatings faces two major bottlenecks: First, due to the poor compatibility between the DLC film and the substrate material, and the large internal stress generated within the film during deposition, the bonding strength between the DLC film and the substrate is low, leading to cracking and peeling, and making it difficult to prepare thick films. Second, as the temperature rises, carbon atoms will... 2 Hybridization transition, i.e. graphitization of the thin film, leads to film failure. These defects severely limit its long-term service life in extreme environments such as aerospace.

[0004] One method to improve the internal stress of DLC coatings is to introduce a buffer transition layer, which enhances interfacial bonding strength by mitigating the difference in thermal expansion coefficients and structural mismatch between interfaces. Conventional transition layers typically use transition metal targets such as Ti, Si, and Cr. However, these single-layer transition layers have limited ability to coordinate the overall deformation of the film substrate. Furthermore, the weak interfacial bonding between the metal transition layer and the top DLC layer leads to crack initiation and upward propagation, causing premature brittle spalling of the DLC film. In addition, the lack of an active lubricating phase in traditional DLC coatings results in discontinuous transfer films, exhibiting a deterioration in the friction coefficient over time during high-speed cutting of titanium alloys. Initially, the friction coefficient increases from 0.18 to 0.27 within 5 minutes. When the cutting temperature exceeds 600℃, the sp³ bond content drops sharply from 75% to 50%, and the friction coefficient rises to 0.35, exacerbating abrasive wear.

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

[0006] To address the dual bottlenecks of easy peeling and lubrication failure in the cutting of difficult-to-machine materials (such as titanium alloys and high-temperature alloys) in the existing technology, the first objective of this 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, and its application to the surface of cemented carbide tools can significantly improve their service life.

[0007] The second objective of this invention is to provide a method for preparing a DLC coating with a gradient composite structure and surface microtexture. This method is efficient, low-consumption, and environmentally friendly. By controlling the acetylene flow rate in the magnetron sputtering and ion beam composite process in conjunction with the laser microtexturing process, the coating of this invention exhibits a unique surface morphology and sp... 3 Bond gradient content.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a DLC coating with a gradient composite structure and surface microtexture. The coating includes a transition layer, a DLC gradient layer, and a laser microtexture layer disposed on the outer surface of the DLC gradient layer. The transition layer is composed of alternately stacked Cr layers and CrN layers. The DLC gradient layer... 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 microtexture layer is composed of a hexagonal honeycomb-shaped densely packed pit array.

[0009] In the DLC coating of this invention, a diffusion bond is formed between the Cr and CrN layers in the transition layer, significantly improving the interlayer diffusion bonding force and the bonding force with the substrate surface, while reducing toughness loss and resolving the contradiction between "high bonding force and high toughness". The alternating deposition method comprehensively utilizes the plastic buffer of Cr and the rigidity complementarity of Cr, dispersing internal stress layer by layer and avoiding stress concentration caused by excessive single-layer thickness, thus achieving stress gradient control. In the DLC gradient layer set above the transition layer, the content of sp³ bonds and W elements are controlled by a dual gradient. The high content of W elements (1.0~1.2wt%) near the substrate inhibits the propagation of interfacial cracks through the pinning effect and reduces the mismatch of thermal expansion coefficients; the high sp³ bond content (≥80%) on the surface provides ultra-hard wear resistance, while the low W content (≤0.8wt%) can reduce the formation of brittle carbides (such as WC) and avoid friction coefficient fluctuations, thus comprehensively improving the coating's bonding force and tribological stability. Finally, by introducing a laser microtextured layer with a hexagonal honeycomb-shaped densely packed pit array on the outer surface of the DLC gradient layer, the honeycomb morphology is fully utilized to maximize pit density, prolong lubricant residence time, and improve oil storage efficiency. The symmetry of the hexagon can make the stress distribution uniform, while the Y-shaped channels between the pits guide the chips to be discharged in a specific direction, reducing the contact area between the chips and the tool, reducing the coefficient of friction and reducing cutting force fluctuations, significantly improving the surface quality of the machined surface. At the same time, it can prevent chip accumulation from increasing the coefficient of friction of the coating and causing lubrication performance failure.

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

[0011] As a preferred embodiment, the thickness of a single Cr layer is 50~100nm, the thickness of a single CrN layer is 80~150nm, 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 this invention, each Cr layer and CrN layer are diffusely bonded to each other through argon ion bombardment of the interface. Simultaneously, by setting the thickness of the CrN layer to be greater than that of the Cr layer, the thicker CrN layer, with its greater hardness than the Cr layer, disperses the external load on the composite coating and buffers the interfacial stress.

[0013] As a preferred embodiment, the diameter of the pits in the laser microtextured 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 outer surface area of ​​the DLC gradient layer. In this invention, limiting the depth of the laser microtexturation avoids high-energy laser scanning or multiple scans, which could induce localized graphitization (sp³→sp² bond conversion) in the DLC coating, thus affecting the coating hardness. Simultaneously, it prevents excessively deep pits from causing lubricant loss or chip accumulation, increasing the coating's friction coefficient and leading to lubrication failure. By controlling the proportion of the pit area to the outer surface area of ​​the DLC gradient layer, the oil storage effect and chip guiding function can be utilized to reduce the friction coefficient and decrease cutting force fluctuations. However, the proportion of the pit area to the outer surface area of ​​the DLC gradient layer 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 accelerating coating wear. Furthermore, interconnected pits forming a capillary network will cause rapid lubricant loss and a rebound in the friction coefficient.

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

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

[0016] As a preferred embodiment, the center-to-center distance between adjacent hexagonal recesses is 1.2 to 1.5 times the recess diameter, and the sidewall inclination angle is 30° to 60°. In this invention, an excessively small center-to-center distance between adjacent recesses increases the risk of material bridge breakage between recesses; while an excessively large sidewall inclination angle makes it difficult for chips to be embedded in the recesses and thus increases the friction temperature.

[0017] This invention also provides a method for preparing a DLC coating with a gradient composite structure and surface microtexture. The method involves sequentially and alternately depositing Cr and CrN layers on a pretreated substrate surface, followed by depositing a DLC gradient layer using 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, while the W content in the DLC gradient layer is controlled by adjusting the tungsten target power, using a tungsten target as the target material, to obtain a transition layer-DLC gradient layer. A laser is then used to microtexture the transition layer-DLC gradient layer, forming a hexagonal honeycomb-shaped densely packed pit array on the outer surface of the DLC gradient layer, thus obtaining the final product.

[0018] The preparation method of this invention mainly uses magnetron sputtering combined with ion beam technology and laser to control the distribution of W content and sp³ bond content in the gradient layer, as well as a special hexagonal honeycomb array. The acetylene flux is negatively correlated with the sp³ bond content, while the W target power is positively correlated with the W content. This invention employs femtosecond laser interference lithography, generating a hexagonal grating pattern through dual-beam interference, combined with a honeycomb scanning path, to ensure consistent pit morphology, thereby effectively forming a hexagonal honeycomb densely packed pit array.

[0019] As a preferred embodiment, the pretreatment of the substrate involves argon ion bombardment cleaning of the substrate surface at a bombardment voltage of 800~1200V for 20~30min, resulting in a surface roughness Ra<0.05μm.

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

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

[0022] As a preferred embodiment, the conditions for laser microtexturing processing are as follows: a femtosecond laser is used 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 15%~25% for the laser scanning path, and 3~5 laser pulses are applied to each pit.

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

[0024] (1) This invention solves the contradiction of “high bonding strength - high toughness” by alternating deposition of Cr / CrN transition layers through interlayer diffusion bonding and stress gradient regulation.

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

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

[0027] (4) By limiting the depth of laser microtexturing, this invention avoids high-energy or multiple laser scans that could induce local graphitization (sp³→sp² bond conversion) in the DLC coating, thereby affecting the coating hardness. At the same time, it can prevent excessively deep pits from causing lubricant loss or chip accumulation, which would increase the coating's coefficient of friction and lead to 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 requirements of high-speed cutting and is conducive to large-scale industrial application. Attached Figure Description

[0029] Figure 1 This is a planar schematic diagram of the hexagonal honeycomb-shaped densely packed pit array of the surface laser microtexture layer of the DLC coating of the present invention. Wherein, 1-surface laser microtexture; 2-DLC gradient layer.

[0030] Figure 2 This is a schematic cross-sectional view of the DLC coating with gradient composite structure and surface microtexture of the present invention. Wherein, 2-DLC gradient layer; 3-laser microtexture layer; 4-Cr / CrN alternating transition layer.

[0031] Figure 3 This is a SEM image of the transition layer of the DLC coating prepared in Example 1 of the present invention. Detailed Implementation

[0032] 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.

[0033] Example 1

[0034] A DLC coating with a gradient composite structure and surface microtexture, the surface microtexture morphology is shown in the schematic diagram. Figure 1 As shown in the diagram, the structural distribution 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 0.65 μm, the thickness of the DLC gradient layer is 3.0 μm, and the hardness is 28 GPa. The depth of the laser microtextured layer 3 is 1.5 μm.

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

[0036] In this implementation, the sp³ bond content of the DLC gradient layer increased from 60wt% to 80wt%, while the W content decreased from 1.2wt% to 0.5wt%.

[0037] In this implementation, the pits on the microtexture have a diameter of 10 μm, a depth of 1 / 2 the thickness of the DLC gradient layer, a center-to-center distance of 12 μm, an area of ​​15% of the outer surface area of ​​the DLC gradient layer, and a sidewall inclination angle of 45°.

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

[0039] (1) Pretreatment of the substrate: The substrate of the solid carbide end mill 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. The target current was 8A, the temperature was 280℃, and the bias voltage was -80V when depositing the CrN layer. The N2 flow rate was 60sccm, the pressure was 0.4Pa, and the bias voltage was -100V when depositing the CrN layer.

[0041] (3) DLC gradient layer deposition: C target current is 4A, Ar / C2H2 flow ratio is 4:1, and deposition rate is 0.7μm / h; acetylene flow rate is linearly reduced from the initial value of 30sccm to 15sccm at 0.06sccm / min. W target is turned on simultaneously, and W target power is linearly reduced from the initial 100W to 50W at 0.19W / min, so that W content decreases from 1.2wt% to 0.5wt%; bias voltage is -120V.

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

[0043] In this embodiment, the SEM detection result of the transition layer shows 5 alternating layers of Cr / CrN. Figure 3 As shown, the thickness is 650 nm, and the sp³ bond content of the DLC main coating increased from 60 wt% to 80 wt% according to 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, and the remaining steps and conditions are the same as those in Example 1.

[0046] A comparative experiment was conducted on the DLC-coated tool A prepared in Example 1 and control 1 to continuously mill aluminum alloy (6063). The results of the comparative experiment are shown in Table 1 below.

[0047]

[0048] As shown in Table 1, under the same tool substrate and model, the same process conditions, and the same test conditions, only the transition layer is changed from a single Cr layer to a Cr / CrN multilayer structure (with the same total thickness). The DLC coating with alternating Cr / CrN transition layers of the present invention can significantly improve the interfacial bonding force and stress distribution. The impact on the performance of the coating is greater than that of a single transition layer. Its bonding force, tool life, cutting force fluctuation performance, and surface roughness performance are all better than the general DLC coating of control product 1.

[0049] Example 2

[0050] A DLC coating with a gradient composite structure and surface microtexture, the surface microtexture morphology is shown in the schematic diagram. Figure 1 As shown in the diagram, the structural distribution 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 1.2 μm, the thickness of the DLC gradient layer is 4.0 μm, and the hardness is 32 GPa. The depth of the laser microtextured layer 3 is 2 μm.

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

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

[0053] In this implementation case, the pits on the microtexture have a diameter of 30μm, a depth of 2μm, a center-to-center distance of 36μm, and the area of ​​the pits accounts for 25% of the outer surface area of ​​the DLC gradient layer. The sidewall inclination angle of the pits is 50°.

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

[0055] (1) Pretreatment of the substrate: The substrate of the solid carbide end mill 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. The target current was 7A, the temperature was 260℃, and the bias voltage was -70V when depositing the CrN layer. The N2 flow rate was 70sccm, the pressure was 0.5Pa, and the bias voltage was -110V when depositing the CrN layer.

[0057] (3) DLC gradient layer deposition: C target current is 3.5A, Ar / C2H2 flow ratio is 3:1, and deposition rate is 0.6μm / h; acetylene flow rate is linearly reduced from 30sccm to 16sccm at 0.035sccm / min. W target is turned on simultaneously, and W target power is linearly reduced from the initial 95W to 55W at 0.1W / min, so that W content decreases from 1.1wt% to 0.6wt%; bias voltage is -120V.

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

[0059] In this embodiment, the SEM detection results of the transition layer show that there are 6 alternating Cr / CrN layers with a thickness of 1.2 μm, and the sp³ bond content of the DLC gradient layer increases from 60 wt% to 78 wt% according to Raman spectroscopy.

[0060] Control Experiment 2

[0061] The tool substrate and pretreatment process of control sample 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 the same as those of Example 2.

[0062] A comparative experiment was conducted on the DLC-coated tool B prepared in Example 2 and control sample 2 to continuously mill aluminum alloy (6063). The results of the comparative experiment are shown in Table 2 below.

[0063]

[0064] As shown in Table 2, under the same tool substrate and model, consistent transition layer and main coating process conditions, and identical test conditions, by simply changing the surface microtexture pits to a random distribution, the DLC coating with a closely packed hexagonal pit structure of the present invention significantly improves the coating lubrication performance, reduces the coating friction coefficient and cutting temperature, and simultaneously reduces chip residue. Its impact on coating performance is superior to that of the randomly distributed microtexture pits. Its tool life, cutting temperature control, chip residue, and average friction coefficient are all superior to the randomly distributed pit DLC coating of control 2.

[0065] Example 3

[0066] A DLC coating with a gradient composite structure and surface microtexture, the surface microtexture morphology is shown in the schematic diagram. Figure 1 As shown in the diagram, the structural distribution 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 1.19 μm, the thickness of the DLC gradient 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 implementation example, the transition layer consists of 7 alternating Cr layers (70nm) and CrN layers (100nm), for a total of 14 layers, with a Cr / CrN thickness ratio of 1:1.4.

[0068] In this implementation case, the DLC main coating sp 3 The bond content gradient increased from 60 wt% to 73 wt%, while the W content decreased from 1.0 wt% to 0.7 wt%.

[0069] In this implementation case, the pits on the microtexture have a diameter of 40μm, a depth of 2.5μm, a center-to-center distance of 48μm, an area ratio of 28%, and a sidewall inclination angle of 55°.

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

[0071] (1) Pretreatment of the substrate: The substrate of the solid carbide end mill 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. The target current was 9A, the temperature was 290℃, and the bias voltage was -90V when depositing the CrN layer. The N2 flow rate was 75sccm, the pressure was 0.45Pa, and the bias voltage was -105V when depositing the CrN layer.

[0073] (3) DLC gradient layer deposition: C target current is 4.5A, Ar / C2H2 flow ratio is 5:1, and deposition rate is 0.9μm / h; acetylene flow rate is linearly reduced from 30sccm to 18sccm at 0.035sccm / min. W target is turned on simultaneously, and W target power is linearly reduced from the initial 90W to 60W at 0.1W / min, so that W content decreases from 1.0wt% to 0.7wt%; bias voltage is -120V.

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

[0075] In this embodiment, the SEM detection result of the transition layer is 7 alternating Cr / CrN layers with a thickness of 1.19 μm. The content of sp³ bonds in the DLC main coating increased from 60 wt% to 73 wt% according to Raman spectroscopy.

[0076] Control Experiment 3

[0077] During the deposition of the DLC gradient layer in the tool of control product 3, the acetylene flow rate was kept constant at 30 sccm, and the remaining steps and conditions were the same as in Example 3.

[0078] The DLC-coated tool C prepared in Example 3 and the control sample 3 were subjected to a comparative experiment of continuous milling of aluminum alloy (6063). The results of the comparative experiment 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 identical test conditions, by simply changing the acetylene flow rate to a constant 30 sccm, the DLC coating with a gradient variation in sp³ bond content of this invention can significantly improve coating life, reduce surface roughness, and enhance high-temperature stability. Its performance impact is superior to that without sp³ bonds. 3 DLC coatings with varying bond content.

[0081] Example 4

[0082] A DLC coating with a gradient composite structure and surface microtexture, the surface microtexture morphology is shown in the schematic diagram. Figure 1 As shown in the diagram, the structural distribution 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 implementation example, the transition layer consists of 8 alternating Cr layers (100nm) and CrN layers (150nm), for a total of 16 layers, with a Cr / CrN thickness ratio of 1:1.5.

[0084] In this implementation example, the DLC gradient layer sp 3 The bond content gradient increased from 60 wt% to 80 wt%, while the W content decreased from 1.2 wt% to 0.5 wt%.

[0085] In this implementation case, the pits on the microtexture have a diameter of 20μm, a depth of 1.8μm, a center-to-center distance of 24μm, and the area of ​​the pits accounts for 20% of the outer surface area of ​​the DLC gradient layer. The sidewall inclination angle of the pits is 40°.

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

[0087] (1) Matrix pretreatment: The cemented carbide solid end mill matrix 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. The target current was 6A, the temperature was 250℃, and the bias voltage was -60V when depositing the CrN layer. The N2 flow rate was 80sccm, the pressure was 0.6Pa, and the bias voltage was -120V when depositing the CrN layer.

[0089] (3) DLC gradient layer deposition: C target current is 5A, Ar / C2H2 flow ratio is 4:1, and deposition rate is 1.0μm / h; acetylene flow rate is linearly reduced from 30sccm to 14sccm at 0.06sccm / min. W target is turned on simultaneously, and W target power is linearly reduced from the initial 100W to 50W at 0.19W / min, so that W content decreases from 1.2wt% to 0.5wt%; bias voltage is -120V.

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

[0091] In this embodiment, the SEM detection result of the transition layer is 8 alternating Cr / CrN layers with a thickness of 2.0 μm. The content of sp³ bonds in the DLC main coating increased from 60 wt% to 80 wt% according to Raman spectroscopy.

[0092] Control Experiment 4

[0093] The surface microtexture thickness of control sample 4 exceeded half the total thickness of the DLC gradient layer, reaching 3 μm. The remaining steps and conditions were the same as in Example 4.

[0094] A comparative experiment was conducted on the DLC-coated tool D prepared in Example 4 and the control sample 4 to continuously mill aluminum alloy (6063). The results of the comparative experiment are shown in Table 4 below.

[0095]

[0096] As shown in Table 4, under the same tool substrate and model, the same process conditions for the transition layer and the main coating, and the same test conditions, only the surface microtexture depth was changed to 3μm, which is more than 1 / 2 of the total thickness of the DLC coating. The DLC coating with gradient composite structure and surface microtexture of the present invention can balance lubrication performance and coating structure integrity, optimize stress distribution, significantly improve coating life, reduce surface roughness, and reduce lubricant consumption. Its performance effect on the coating is better than that of the control product 4, whose 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 microtexture, the surface microtexture morphology is shown in the schematic diagram. Figure 1 As shown in the diagram, the structural distribution 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 implementation example, the transition layer consists of 5 alternating Cr layers (60nm) and CrN layers (80nm), for a total of 10 layers, with a Cr / CrN thickness ratio of 1:1.3.

[0100] In this implementation case, the DLC main coating sp 3 The bond content gradient increased from 60 wt% to 80 wt%, while the W content decreased from 1.0 wt% to 0.6 wt%.

[0101] In this implementation case, the pits on the microtexture have a diameter of 15μm, a depth of 1.0μm, a center-to-center distance of 18μm, an area ratio of 18%, and a sidewall inclination angle of 35°.

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

[0103] (1) Pretreatment of the substrate: The substrate of the solid carbide end mill 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. The target current was 7.5A, the temperature was 270℃, and the bias voltage was -75V when depositing the CrN layer. The N2 flow rate was 55sccm, the pressure was 0.35Pa, and the bias voltage was -85V when depositing the CrN layer.

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

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

[0107] In this embodiment, the SEM detection result of the transition layer shows five alternating Cr / CrN layers with a thickness of 0.7 μm. The sp content of the DLC gradient layer was measured by Raman spectroscopy. 3 The bond content increased from 60wt% to 80wt%.

[0108] Control Experiment 5

[0109] The cutting tool transition layer of reference product 5 has a Cr / CrN thickness ratio of 1:1, wherein the thickness of each Cr layer and CrN layer is 80 nm. The remaining steps and conditions are the same as those in Example 5.

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

[0111]

[0112] As shown in 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 was changed to 1:1. The DLC coating with a transition layer Cr / CrN thickness ratio of 1:1.3 in Example 5 can improve cross-sectional adhesion, optimize stress distribution, suppress crack propagation, and improve cutting stability. Its performance effect 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 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 DLC coating with a gradient composite structure and surface microtexture, characterized in that: It includes a transition layer, a DLC gradient layer, and a laser microtextured layer disposed on the outer surface of the DLC gradient layer; the transition layer consists of alternating stacked Cr layers and CrN layers; the DLC gradient layer... 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 microtexture layer is composed of a hexagonal honeycomb-shaped densely packed pit array. The preparation process of the DLC coating is as follows: Cr layers and CrN layers are sequentially and alternately deposited on the pretreated substrate surface. 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, the W content in the DLC gradient layer is controlled by adjusting the tungsten target power using a tungsten target as the target material, thus obtaining a transition layer-DLC gradient layer. The transition layer-DLC gradient layer is then microtextured using a laser to form a hexagonal honeycomb-shaped densely packed pit array on the outer surface of the DLC gradient layer, thus obtaining the final product. The thickness ratio of the Cr layer to the CrN layer is 1:(1.2~1.8). The DLC gradient layer sp 3 The bond content increases from 60-70 wt% to 73-85 wt% from the transition layer to the outer surface of the DLC gradient layer, and the W content in the DLC gradient layer decreases from 0.9-1.2 wt% to 0.5-0.8 wt% from the transition layer to the outer surface of the DLC gradient layer.

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

3. The DLC coating with a gradient composite structure and surface microtexture according to claim 1, characterized in that: The diameter of the pits in the laser microtextured layer is 10~50μm, the depth is less than or equal to 1 / 2 of the thickness of the DLC gradient layer, and the area of ​​the pits accounts for 15%~30% of the outer surface area of ​​the DLC gradient layer.

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

5. A method for preparing a DLC coating with a gradient composite structure and surface microtexture as described in any one of claims 1 to 4, characterized in that: Cr and CrN layers are sequentially and alternately deposited on the pretreated substrate surface. Then, a DLC gradient layer is deposited using 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. Simultaneously, the W content in the DLC gradient layer is controlled by adjusting the tungsten target power, using a tungsten target as the target material, to obtain a transition layer-DLC gradient layer. The transition layer-DLC gradient layer is then microtextured using a laser to form a hexagonal honeycomb-shaped densely packed pit array on the outer surface of the DLC gradient layer, thus obtaining the final product.

6. The method for preparing a DLC coating with a gradient composite structure and surface microtexture according to claim 5, characterized in that: When Cr and CrN layers are deposited alternately on the substrate surface, the parameters for depositing the Cr layer are as follows: using a pure Cr target, target current of 6~10A, substrate temperature of 250~300℃, and bias voltage of -60V~-100V; the parameters for depositing the CrN layer are as follows: nitrogen flow rate of 50~80sccm, deposition pressure of 0.3~0.6Pa, and bias voltage of -80V~-120V.

7. The method for preparing a DLC coating with a gradient composite structure and surface microtexture according to claim 6, characterized in that: The parameters of the magnetron sputtering and ion beam composite process are as follows: carbon target current 3~5A, argon to acetylene flow rate ratio (3~5):1, deposition rate 0.5~1μm / h, acetylene flow rate linearly reduced from the initial value of 30sccm to 14~20sccm at 0.03~0.1sccm / min; tungsten target power linearly reduced from 85~100W to 50~60W at 0.1~0.2W / min, bias voltage -100V~-150V.

8. A method for preparing a DLC coating with a gradient composite structure and surface microtexture according to claim 6 or 7, characterized in that: The conditions for laser microtexturing processing are as follows: a femtosecond laser is used 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 15%~25% for the laser scanning path, and 3~5 laser pulses are applied to each pit.

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