A method for simultaneously improving the mechanical properties and thickness of ta-c coatings

Abstract

The application belongs to the technical field of substrate surface modification, and discloses a method for simultaneously improving the mechanical property and thickness of a ta-C coating, wherein the coating structure is (metal layer / ta-C layer) n The thickness ratio of the metal layer and the ta-C layer is 1:2-4, the thickness of the ta-C layer is 180-220 nm, the ta-C layer is deposited by a PVD method in multiple stages, and vacuum in-situ cooling is performed after each deposition. The application can release stress by depositing a multilayer coating and using an intermediate metal layer, thereby improving the overall thickness of the coating. In addition, by selecting a suitable metal layer, a suitable cycle period and a thickness ratio of the metal layer to the multi-stage ta-C layer, the internal stress of the ta-C layer can be released, thereby improving the overall thickness of the coating, prolonging the service life of the workpiece, and further being suitable for different application environments.

Description

Technical Field

[0001] This invention belongs to the field of substrate surface modification technology, specifically relating to a method for simultaneously improving the mechanical properties and thickness of ta-C coatings. Background Technology

[0002] Tetrahedral amorphous carbon (ta-C) film is a type of hydrogen-free diamond-like carbon (DLC) film. It has high hardness, good chemical stability, low coefficient of friction and excellent wear resistance. It is often used as a wear-resistant coating and is widely applied to the surfaces of tools, molds and precision engineering parts.

[0003] As a wear-resistant coating, its service life is not only closely related to its mechanical properties, but its thickness is also a crucial factor affecting its lifespan. However, excellent mechanical properties and high thickness are contradictory. This is because the hardness and other mechanical properties of the ta-C coating are related to the SP... 3 Related to bond content, sp 3 The higher the sp bond content, the better its mechanical properties such as hardness; however, high sp... 3 Hybrid bonds result in a relatively high average coordination number of carbon atoms in the film, which in turn leads to excessive constraint on the three-dimensional network structure of the ta-C coating, resulting in large internal stress. When the coating thickness exceeds a certain value, the ta-C coating will develop cracks, wrinkles, or even peel off.

[0004] Therefore, how to provide a method to simultaneously improve the mechanical properties and thickness of ta-C coating for its long-life wear-resistant application is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for simultaneously improving the mechanical properties and thickness of ta-C coatings. Through the structure and preparation method of this invention, the thickness can be increased while ensuring mechanical properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for simultaneously improving the mechanical properties and thickness of a ta-C coating, wherein the coating has a structure of (metal layer / ta-C layer). n Multi-layer coating;

[0008] Where n is 2-6, and the thickness ratio of the metal layer to the ta-C layer is 1:2-4.

[0009] If the cycle time is too short, the overall thickness of the coating will be low; if the cycle time is too long, the coating will peel off.

[0010] If the metal layer is too thick, it will reduce the overall hardness of the coating; if the ta-C layer is too thick, the coating will peel off due to excessive internal stress. Therefore, the thickness ratio of the metal layer to the ta-C layer should be appropriate.

[0011] Preferably, the thickness of the ta-C layer is 180-220 nm.

[0012] Preferably, the metal layer and the ta-C layer are prepared by physical vapor deposition.

[0013] Preferably, the ta-C layer is deposited in stages and multiple times using physical vapor deposition.

[0014] A multi-stage ta-C coating was obtained by in-situ vacuum cooling, which reduced the deposition temperature of the ta-C coating and improved the sp... 3 The bond content is increased, thereby improving mechanical properties such as hardness and wear resistance.

[0015] Preferably, the deposition is performed 2-4 times.

[0016] Preferably, vacuum in-situ cooling is performed after each deposition during the deposition process.

[0017] This invention employs a PVD method to deposit ta-C coatings in stages and multiple times, with vacuum in-situ cooling after each deposition. This cooling process keeps the ta-C coating deposition temperature below 80°C, preventing graphitization transformation and thus improving the coating's sp. 3 The bond content is reduced, thereby improving mechanical properties such as hardness and wear resistance; at the same time, vacuum in-situ cooling does not increase the movement of the sample or exposure to the atmospheric environment during the process, resulting in low process cost, ease of operation, and high reliability.

[0018] Preferably, the specific cooling steps are as follows: close the gas passage, and at 7×10 -3 Vacuum in-situ cooling is performed at a vacuum level below Pa until the coating temperature drops below 80°C.

[0019] Preferably, the physical vapor deposition method is an arc ion plating technique.

[0020] The arc ion plating technology used in this invention has advantages such as good ion diffraction and good uniformity of the deposited film. It also has high controllability of process parameters, enabling the preparation of coatings with high density, high adhesion and excellent comprehensive mechanical properties.

[0021] Preferably, the metal layer is any one of Ti, Cr, TiAl, and CrAl.

[0022] Preferably, the coating preparation method specifically includes the following steps:

[0023] (1) Under vacuum conditions, the cleaned substrate is subjected to Ar+ bombardment etching to remove impurities on the substrate surface and set aside for later use.

[0024] (2) Depositing a metal layer: Ar gas is introduced, the pure metal target is turned on, and an arc ion plating technique is used to deposit a metal layer on the substrate.

[0025] (3) Depositing a ta-C coating: A ta-C coating is deposited on the substrate prepared in step (2) using an arc ion plating technique;

[0026] (4) Cooling: The substrate obtained in step (3) is cooled in situ under vacuum until the coating temperature drops below 80°C;

[0027] (5) Repeat steps (3) and (4) to obtain a multi-stage ta-C coating;

[0028] (6) After the ta-C coating is prepared in step (5), repeat steps (2)-(5) to obtain a multilayer coating of (metal layer / ta-C layer)n.

[0029] Preferably, after the (metal layer / ta-C layer)n multilayer coating is deposited, the gas channel is closed and the furnace temperature is cooled to below 100°C before sampling.

[0030] Preferably, the substrate is a WC-Co cemented carbide.

[0031] Preferably, the cleaning step in step (1) is as follows: ultrasonically clean the substrate with ultrapure water, acetone and alcohol for 15-20 minutes, and then dry it with nitrogen.

[0032] The etching process parameters are: Ar gas flow rate of 20-40 sccm, negative bias voltage of 100-110V, and etching time of 2100s.

[0033] The process parameters for depositing the metal layer in step (2) are: Ar gas flow rate of 10-40 sccm, negative bias voltage of 40-60V, arc current of 60-80A, pure metal target, and deposition time of 600s.

[0034] The process parameters for depositing the ta-C coating in step (3) are: Ar gas flow rate of 10-20 sccm, negative bias voltage of 100-110V, target current of 40-50A, and deposition time of 600s.

[0035] Preferably, the cleaning step in step (1) is as follows: ultrasonically clean the substrate with ultrapure water, acetone and alcohol for 15 minutes, and then dry it with nitrogen.

[0036] The etching process parameters are: Ar gas flow rate of 40 sccm, negative bias voltage of 100V, and etching time of 2100s.

[0037] Ar + Etching can remove surface contaminants and large particles, thereby improving the adhesion between the film and the substrate.

[0038] The process parameters for depositing the metal layer in step (2) are: Ar gas flow rate of 40 sccm, negative bias voltage of 60 V, arc current of 80 A, pure metal target, and deposition time of 600 s.

[0039] The process parameters for depositing the ta-C coating in step (3) are: Ar gas flow rate of 20 sccm, negative bias voltage of 110 V, target current of 40 A, and deposition time of 600 s.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] This invention improves the overall thickness of the coating by depositing a multi-layer coating and releasing stress through an intermediate metal layer. By selecting appropriate metal layers, such as Ti, Cr, TiAl, and CrAl alloys (whose coefficient of thermal expansion is similar to that of cemented carbide substrates), a suitable cycle period, and a thickness ratio between the metal layer and the multi-stage ta-C layer, the internal stress of the ta-C layer can be released through the metal layer, thereby improving the overall thickness of the coating, extending the service life of the workpiece, and making it suitable for different application environments. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0043] Figure 1 SEM images of the coatings were prepared for Example 1 and Comparative Examples 1-2 of this invention;

[0044] Figure 2 This invention (Ti layer / multi-stage cooling ta-C layer) n Multilayer coating structure diagram, where 1 is the substrate, 2 is the metal Ti layer, and 3 is the ta-C coating;

[0045] Figure 3 SEM images of the coating were prepared for Example 2 of the present invention;

[0046] Figure 4 SEM images of the coating were prepared for Example 3 of the present invention. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] This invention provides a method for simultaneously improving the mechanical properties and thickness of a ta-C coating, the method being to deposit a multilayer coating (Ti layer / multi-stage cooled ta-C layer) on a cemented carbide substrate;

[0050] The preparation method includes the following specific steps:

[0051] (1) Substrate cleaning: The WC-Co cemented carbide substrate was ultrasonically cleaned for 15 minutes in sequence with ultrapure water, acetone, and alcohol, and then dried with nitrogen. It was then magnetically fixed on the workpiece holder and finally loaded into the furnace, i.e., into the arc ion plating equipment, and the vacuum was evacuated to 7×10. -3 Pa; then proceed with Ar + Bombardment etching is used to remove impurities from the substrate surface. Etching process parameters: Ar gas flow rate is 40 sccm, negative bias voltage is 100V, etching time is 2100s.

[0052] (2) Deposition of pure metal Ti layer: Ar gas is introduced, the pure metal target is turned on, and the metal Ti layer is deposited on the substrate using arc ion plating technology. The thickness of the pure metal Ti layer is 90nm. The process parameters are: Ar gas flow rate is 40sccm, negative bias voltage is 60V, arc current is 80A, and deposition time is 600s.

[0053] (3) Deposition of ta-C coating: A ta-C coating is deposited on the substrate prepared in step (2) using arc ion plating technology. The process parameters are: Ar gas flow rate is 20 sccm, negative bias voltage is 110 V, target current is 40 A, and deposition time is 600 s.

[0054] (4) In-situ cooling under vacuum: Close the gas passage and cool at 7×10 -3 The substrate obtained in step (3) is subjected to vacuum in-situ cooling at a vacuum level of Pa or below until the coating temperature drops below 80°C;

[0055] (5) Repeat steps (3) and (4) three times to obtain a multi-stage ta-C coating with a thickness of 195 nm.

[0056] (6) After the ta-C coating is prepared in step (5), repeat steps (2), (3), (4), and (5) three times. After the (Ti layer / multi-stage cooled ta-C layer) 4 multilayer coating is deposited, close the gas channel and cool the furnace temperature to below 100°C before taking a sample.

[0057] The prepared (Ti layer / multi-stage cooled ta-C layer) 4 multilayer coating has the following structure: Figure 1 (a) and Figure 2 Its thickness can reach 1.14μm, and its micro Vickers hardness is as high as 4823.8HV. 0.025 The coefficient of friction is 0.08, I D / I G =0.66 (usually I) D / I G The value indirectly reflects sp 3 The lower the sp bond content, the lower the sp bond content. 3 (The higher the bond content).

[0058] Example 2

[0059] In step (6): After the ta-C coating preparation described in step (5) is completed, steps (2), (3), (4), and (5) are repeated once, and the rest is exactly the same as in Example 1;

[0060] The prepared (Ti / multi-stage cooled ta-C)2 multilayer coating has the following structure: Figure 3 and Figure 2 Its thickness can reach 570nm, and its micro Vickers hardness is as high as 3822.36HV. 0.025 The coefficient of friction is 0.08, I D / I G =0.59.

[0061] Example 3

[0062] In step (6): After the ta-C coating preparation described in step (5) is completed, steps (2), (3), (4), and (5) are repeated twice, and the rest is exactly the same as in Example 1;

[0063] The prepared (Ti / multi-stage cooled ta-C)3 multilayer coating has the following structure: Figure 4 and Figure 2 Its thickness can reach 855nm, and its micro Vickers hardness is as high as 4245.5HV. 0.025 The coefficient of friction is 0.085, I D / I G =0.61.

[0064] Comparative Example 1

[0065] A four-layer (Ti / ta-C) coating was deposited on a WC-Co cemented carbide substrate. Compared with Example 1, Comparative Example 1 did not undergo in-situ vacuum cooling, but all other processes were the same. The four-layer (Ti / ta-C) coating prepared in Comparative Example 1 has the following structure. Figure 1 (b) has a thickness of up to 1.14 μm and a micro Vickers hardness of 4532.6 HV. 0.025 The coefficient of friction is 0.1, I D / I G =0.80, with almost the same thickness as Example 1, but different hardness, coefficient of friction, and sp. 3 The bond content decreased.

[0066] Comparative Example 2

[0067] A Ti / (multi-stage ta-C layer) 3 multilayer coating was deposited on a WC-Co cemented carbide substrate. Compared with Example 1, the deposition time of the multi-stage ta-C coating was increased, but no multilayer structure was prepared. That is, steps (3) and (4) were repeated 8 times, step (6) was canceled, and other processes were the same. The Ti / (multi-stage ta-C layer) 3 multilayer coating prepared in Comparative Example 2 has the following structure. Figure 1 (c) has a thickness of 675 nm and a hardness of 3829.8 HV. 0.025 The coefficient of friction is 0.08, I D / I G =0.48, the coating peeled off due to excessive internal stress.

[0068] The various embodiments are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between the various embodiments can be referred to each other.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simultaneously improving the mechanical properties and thickness of a ta-C coating, characterized in that, The coating is a multilayer coating consisting of alternating metal layers and ta-C layers cyclically n times. Where n is 2-6, and the thickness ratio of the metal layer to the ta-C layer is 1:2-4; The ta-C layer is deposited in stages and multiple times using physical vapor deposition. During the deposition process, vacuum in-situ cooling is performed after each deposition. The deposition is performed 2-4 times.

2. The method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to claim 1, characterized in that, The thickness of the ta-C layer is 180-220 nm.

3. The method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to claim 1, characterized in that, The metal layer was prepared using physical vapor deposition.

4. The method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to claim 3, characterized in that, The physical vapor deposition method is an arc ion plating technique.

5. The method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to claim 1, characterized in that, The metal layer is any one of Ti, Cr, TiAl, and CrAl.

6. A method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to any one of claims 1-5, characterized in that, The coating preparation method specifically includes the following steps: (1) Under vacuum conditions, the cleaned substrate is subjected to Ar reaction. + Bombardment etching is used to remove impurities from the substrate surface, for later use; (2) Depositing a metal layer: Ar gas is introduced, the pure metal target is turned on, and an arc ion plating technique is used to deposit a metal layer on the substrate; (3) Deposition of ta-C coating: A ta-C coating is deposited on the substrate prepared in step (2) using arc ion plating technology; (4) Cooling: The substrate obtained in step (3) is cooled in situ under vacuum until the coating temperature drops below 80°C; (5) Repeat steps (3) and (4) to obtain a multi-stage ta-C coating; (6) After the ta-C coating is prepared in step (5), repeat steps (2)-(5) to obtain (metal layer / ta-C layer). n Multi-layer coating.

7. A method for simultaneously improving the mechanical properties and thickness of a ta-C coating according to claim 6, characterized in that, The cleaning steps described in step (1) are as follows: ultrasonically clean the substrate with ultrapure water, acetone, and alcohol for 15-20 minutes, and then dry it with nitrogen gas; The etching process parameters are: Ar gas flow rate of 20-40 sccm, negative bias voltage of 100-110V, and etching time of 2100s. The process parameters for depositing the metal layer in step (2) are: Ar gas flow rate of 10-40 sccm, negative bias voltage of 40-60V, arc current of 60-80A, pure metal target, and deposition time of 600s. The process parameters for depositing the ta-C coating in step (3) are: Ar gas flow rate of 10-20 sccm, negative bias voltage of 100-110V, target current of 40-50A, and deposition time of 600s.

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