A method for preparing a three-dimensional cross-linked interface-toughened diamond film-based system

Abstract

The present invention discloses a method for preparing a three-dimensional cross-linked interface toughened diamond film-based system, which includes the following steps: ultrashort pulse laser processing of three-dimensional micro-nano structures on a cemented carbide substrate and de-Co; ultrasonic crystal planting of the three-dimensional micro-nano structures on the substrate surface; growth of diamond coating, using chemical vapor deposition technology (CVD) to grow a micron-crystalline diamond coating with a thickness of about 1 μm on the surface of the cemented carbide; and control of the three-dimensional cross-linked interface structure by regulating the height of the diamond cone and the multilayer film modulation period. The beneficial effect of the present invention is that the three-dimensional cross-linked interface formed by the micro-nano structure on the substrate surface, the diamond cone, and the micro-nano alternating diamond coating effectively inhibits the crack propagation inside the coating and at the film-based interface, generates a crack shielding effect at the interface, reduces the merging phenomenon of microcracks, and inhibits the generation of through cracks, so as to achieve the purpose of improving the toughness of the coating and the fracture toughness of the film-based interface.

Description

Technical Field

[0001] The invention relates to a method for preparing a three-dimensional cross-linked interface toughened diamond film-based system, belonging to the technical field of surface engineering. Background Art

[0002] CVD diamond coatings are often prepared on cemented carbide surfaces to improve the surface properties of workpieces, but crack initiation and propagation at the film-substrate interface and within the coating are the main causes of fracture and spalling of diamond coatings. In order to effectively inhibit the initiation and propagation of cracks in the film-substrate system, it is proposed to create a three-dimensional cross-linked interface through a micro-nanocrystalline multilayer structure diamond coating, diamond cones, and surface microstructures. The crack shielding effect at the interface inhibits the multi-directional propagation of cracks, produces a toughened diamond film-substrate system, and achieves the purpose of inhibiting the fracture and spalling of diamond coatings. Summary of the invention

[0003] The present invention aims at the problems of short service life and unstable operation of diamond coated tools caused by fracture and peeling of diamond coating on the surface of cutting tools and molds in engineering applications in the prior art, and provides a method for preparing a diamond film-based system with three-dimensional cross-linked interface toughening.

[0004] A method for preparing a three-dimensional cross-linked interface-toughened diamond film-based system, characterized in that it comprises the following steps:

[0005] S1: Ultrashort pulse laser processing of three-dimensional micro-nano structures on cemented carbide substrates and de-Co removal;

[0006] S2: Ultrasonic crystal planting of three-dimensional micro-nano structures on the substrate surface;

[0007] S3: Diamond coating growth, using chemical vapor deposition technology (CVD) to grow a micron-crystalline diamond coating with a thickness of about 1 μm on the surface of cemented carbide;

[0008] S4: Reactive ion etching of diamond coating, negative bias is applied to the cemented carbide substrate, positive bias is applied above the hot wire, and etching gases such as CH4 and H2 are introduced into the cavity of the CVD equipment. The heat source of the CVD equipment decomposes the gas into methyl ions and hydrogen ions. Under the action of positive and negative bias, the diamond coating is etched to form diamond cones;

[0009] S5: Screening diamond cones, using ultrasonic abrasive flow technology to screen diamond cones. Diamond cones with poor adhesion are removed under the impact of ultrasonic abrasive flow, and diamond cones with good adhesion are retained;

[0010] S6: Cleaning: put the diamond cone sample into acetone and clean it once. The cleaning time is 10 to 15 minutes.

[0011] S7: growing a nanocrystalline diamond coating with a thickness of 1 μm on the diamond cone;

[0012] S8: etching the nanocrystalline diamond coating again to form a diamond cone, and growing a micron-crystalline diamond coating on the nanocrystalline diamond cone, and establishing a three-dimensional cross-linked interface in the film-substrate system through repeated growth and etching of the micron-crystalline diamond coating and the diamond cone;

[0013] S9: Control of the three-dimensional cross-linked interface structure is achieved by adjusting the height of the diamond cones and the modulation period of the multilayer film.

[0014] The method further comprises step S1: the size of the substrate micro-texture prepared by laser is in the same order of magnitude as the size of the diamond cone;

[0015] Wherein, the S2 used in the substrate micro-texture ultrasonic crystal planting is a nano powder with a particle size of ≤800nm;

[0016] Wherein, the S3 first grows a 1 μm thick micron-crystalline diamond coating;

[0017] Among them, the ratio of etching gas introduced into the chamber of the CVD equipment in S4 is CH4:H2=0.02-0.2, and the diamond cone after etching forms an island shape, part of the cemented carbide substrate is exposed, and the exposed area is ≤30%. The graphite points of the exposed cemented carbide substrate in reactive ion etching are removed by hydrogen ions, forming a CoC layer to inhibit Co diffusion and form an excellent diamond nucleation environment.

[0018] Among them, there are defects such as pores and graphite at the interface between the diamond coating film and the substrate in the S5, which leads to different adhesion of the diamond cone. The diamond cone with poor adhesion is removed by ultrasonic abrasive flow technology, and the diamond cone with good adhesion is left as a seed crystal. The abrasive particles in the diamond cone abrasive flow are micro powders with a particle size greater than 0.5μm and less than 2μm, and the carrying medium is water.

[0019] Wherein, the thickness of the secondary grown diamond in S7 is about 1 μm, and the secondary grown diamond coating is a nano-diamond coating.

[0020] The ratio of the etching gas introduced into the chamber of the CVD equipment in S8 is CH4:H2=0.02-0.2.

[0021] The beneficial effects of the present invention are:

[0022] The present invention obtains seed crystals with strong adhesion through screening of diamond cones, and H ions etch graphite points at the interface between the film and the substrate, CH3 +The carbon-containing ions form CoC with Co, which inhibits the diffusion of C atoms. The three-dimensional cross-linked interface formed by the micro-nano structure on the substrate surface, diamond cones, and micro-nano alternating diamond coatings effectively inhibits the crack propagation inside the coating and at the film-substrate interface, and a crack shielding effect is generated at the interface, "trapping" the cracks in the closed units divided by the three-dimensional cross-linked interface, reducing the merging of microcracks and inhibiting the generation of through cracks, thereby achieving the purpose of improving the toughness of the coating and the fracture toughness of the film-substrate interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Preparation method of diamond film-based system with three-dimensional cross-linked interface toughening

[0024] Figure 2 Diamond film-based system and interface improvement methods

[0025] Figure 3 Ultrasonic abrasive flow screening diamond cone and diamond cone

[0026] Figure 4 Three-dimensional cross-linked interface-toughened diamond film-based system DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and examples.

[0028] Firstly, a short pulse laser is used to process micro-nanostructures on the surface of cemented carbide. The size of the microstructures is at the same order of magnitude as that of the diamond cone, and the Co element on the surface is removed by a de-Co treatment method.

[0029] Ultrasonic cleaning of cemented carbide samples after pulse laser processing, placing the samples in CVD equipment, passing gases such as CH4 and H2, and using CVD technology to grow diamond coatings. In order to eliminate the influence of micropores and graphite, reactive ion etching was used to etch diamond coatings. The etching rate was regulated by positive bias, negative bias and gas composition, and the etching depth was adjusted by etching time. When part of the cemented carbide was exposed and the exposed area reached 30%, etching was stopped to form an island-like diamond cone. The graphite phase at the exposed cemented carbide interface was etched by H ions, and Co reacted with methyl to form CoC, which inhibited the diffusion of Co, modified the interface nucleation environment, and increased the nucleation rate. The diamond cone showed an island distribution. The sample was implanted in a diamond suspension, and the abrasive particle size was greater than 0.5μm and less than 2μm. The diamond cone with poor adhesion was removed by ultrasonic abrasive flow method, and the sample was taken out and cleaned once with acetone. The diamond coating is grown based on the diamond cone seed with good adhesion, and the diamond coating is regrown in the area where the diamond cone is removed, which greatly improves the bonding performance of the diamond coating and cemented carbide.

[0030] The high brittleness and low toughness of diamond coatings are also one of the reasons for the fracture and peeling of the coating. Multilayer micro-nano alternating diamond coatings are prepared by adjusting the methane content and the cavity pressure. Multilayer coatings can effectively improve the toughness of diamond coatings, especially inhibit cracks perpendicular to the interface. However, cracks parallel to the interface or extending within the layer are prone to appear in the layer. Diamond cones are formed by reactive ion etching of each layer of diamond, and the interface configuration is changed to form a three-dimensional cross-linked interface diamond coating. The shielding and toughening effect of the crack tip is used to inhibit the expansion and merging of cracks, thereby improving the toughness of the diamond coating. In order to improve the fracture and peeling resistance of the diamond coating and extend the service life of the diamond coated tool.

[0031] like Figure 1 As shown in the figure, the surface of cemented carbide is treated by two-step acid-base method to remove Co, and micropores exist at the interface after treatment. The micropores are discretely distributed at the interface. After ultrasonic cleaning with acetone, the diamond coating is grown on the surface of cemented carbide by CVD method, CH4:H2=0.02-0.05, pressure is 400-3500Pa, temperature is 1950℃-2300℃. Due to the vacuum and high temperature environment of CVD, Co diffuses and reacts with diamond, and a graphite phase is generated at the interface. The presence of micropores and graphite phase greatly weakens the adhesion of the diamond coating.

[0032] like Figure 2 As shown, in order to eliminate the influence of interface pores and graphite points, the flow ratio of CH4 to H2 is adjusted, the CH4 content is appropriately increased, and the etching gas is CH4:H2=0.02-0.2. A negative bias power supply of 50V-300V is added to the bottom of the sample, and the sample stage rotation speed is 6-60rd / min. CH4 and H2 are decomposed by the heat source to form CH3 + and H + , ion bombardment and reaction etching of diamond coating under positive bias and negative bias (50-300V). By controlling bias and time, the height of the etched diamond cone is controlled until the exposed area of ​​cemented carbide reaches more than 30% and the diamond cone is in the shape of an island. H ions etch graphite points at the film-substrate interface under the action of bias, CH3 + The carbon-containing ions form CoC with Co under the action of bias, and CoC inhibits the diffusion of Co.

[0033] like Figure 3 As shown in the figure, the seed crystal is screened by ultrasonic abrasive flow technology, and the diamond cone sample is placed in the abrasive flow field. The carrier of the abrasive flow is a medium such as pure water, ethanol or acetone, and the particle size of the abrasive is greater than 0.5μm and less than 2μm. Under the impact of the abrasive caused by ultrasound, the diamond cone with poor adhesion is removed, and the diamond cone with good adhesion is retained.

[0034] like Figure 4As shown, the sample is placed in an ultrasonic cleaning agent for one cleaning, the cleaning time is 10-15 minutes, and the sample is taken out and blown dry with nitrogen. The sample is placed in a CVD device to re-grow a diamond coating. Based on the strong adhesion of the diamond seed crystal and the modified interface, the adhesion of the secondary growth diamond coating is greatly improved.

[0035] The methyl ions and hydrogen ions decomposed by the heat source gather at the heat source. The positive bias voltage is applied to the heat source and the negative bias voltage on the substrate attracts the positively charged ions to bombard and etch the diamond coating. The rotation speed of the sample stage is 6-60rd / min. The height of the micro-nano diamond cone is controlled by controlling the reaction etching time and adjusting the methane content. The multi-layer micro-nano alternating diamond coating is prepared by adjusting the methane content. Each layer of diamond forms a diamond cone through reactive ion etching of diamond, changes the interface configuration to form a jagged diamond coating, and improves the toughness of the diamond coating according to the crack tip shielding toughening mechanism.

[0036] The key to improving the service life of diamond coated tools is to improve the toughness of the diamond coating and the interface bonding strength between the diamond coating and cemented carbide. This patent provides an effective way to break through the bottleneck of the use of diamond coated tools.

[0037] The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

Claims

1. A method for preparing a three-dimensional cross-linked interface toughened diamond film-based system, characterized in that: The following steps are involved: S1: Ultrashort pulse laser processing of three-dimensional micro-nano structures on cemented carbide substrates and de-Co removal; S2: Ultrasonic crystal planting of three-dimensional micro-nano structures on the substrate surface; S3: Diamond coating growth, using chemical vapor deposition (CVD) technology to grow micron-crystalline diamond coating on the surface of cemented carbide; S4: Reactive ion etching of diamond coating, negative bias is applied to the cemented carbide substrate, positive bias is applied above the hot wire, and etching gases such as CH4 and H2 are introduced into the cavity of the CVD equipment. The heat source of the CVD equipment decomposes the gas into methyl ions and hydrogen ions. Under the action of positive and negative bias, the diamond coating is etched to form diamond cones; S5: Screen diamond cones, use ultrasonic abrasive flow technology to remove diamond cones with poor adhesion, and retain diamond cones with good adhesion; S6: Cleaning: put the diamond cone sample into acetone and clean it once. The cleaning time is 10-15 minutes. S7: Growth of nanocrystalline diamond coating on diamond cone base; S8: etching the nanocrystalline diamond coating again to form a diamond cone, and growing a micron-crystalline diamond coating on the nanocrystalline diamond cone, and realizing three-dimensional cross-linking of the interface of the micron-crystalline diamond coating and the nanocrystalline diamond coating in the film-substrate system through repeated growth and etching of the micron-crystalline diamond coating and the diamond cone; S9: Achieve structural controllability of the three-dimensional cross-linked interface by changing the etching process; Through the above preparation process, the three-dimensional cross-linked interface structure formed by the micro-nano structure on the substrate surface, diamond cones, and micro-nano alternating diamond coating constitutes a closed unit, which produces a crack tip shielding effect, improves the toughness of the coating and the fracture toughness of the film-substrate interface.

2. The method for preparing a three-dimensional cross-linked interface toughened diamond film-based system according to claim 1, characterized in that: A diamond coating with a thickness of 1 μm is grown on the cemented carbide substrate treated for de-Co in S3, and then ion etching is performed.

3. The method for preparing a three-dimensional cross-linked interface toughened diamond film-based system according to claim 1, characterized in that: In the S4, the diamond cones etched by reactive ion etching form isolated islands, and part of the cemented carbide substrate is exposed, and the exposed area is ≤30%.

4. The method for preparing a three-dimensional cross-linked interface toughened diamond film-based system according to claim 1, characterized in that: In the S5, the ultrasonic abrasive flow technology is used to screen the seed abrasive particles, the particle size of which is greater than 0.5 μm and less than 2 μm, and the carrier is pure water.

5. The method for preparing a three-dimensional cross-linked interface toughened diamond film-based system according to claim 1, characterized in that: In S8, the surface of the micron diamond coating is reactively ion etched with diamond cones, and nanocrystalline diamond coating is regrown on the diamond cones. S7 and S8 are repeatedly performed to form a three-dimensional cross-linked interface structure.

6. The three-dimensional cross-linked interface structure formed by the substrate surface micro-nano structure, diamond cones, and micro-nano alternating diamond coating according to claim 1, characterized in that: The height of the etched diamond cone is greater than or equal to the thickness of a single layer of diamond and less than the thickness of two layers of diamond, so that the interface between the layers is cross-linked.

7. The method for preparing a three-dimensional cross-linked interface toughened diamond film-based system according to claim 1, characterized in that: The controllable three-dimensional cross-linked interface structure in S9 is adjusted by the modulation period of the multilayer film and the height of the diamond cone.

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