Method for uniformly depositing diamond film on end surface of mechanical sealing ring

Abstract

The invention discloses a method for uniformly depositing a diamond film on the end surface of a mechanical sealing ring, which comprises the following steps of: S1, pretreating the mechanical sealing ring to coarsen the surface of the mechanical sealing ring; s2, a graphite clamp is provided, the graphite clamp is provided with at least one annular groove, the depth of the annular groove is equal to the thickness of the mechanical sealing ring, and the width of the annular groove is slightly larger than that of the mechanical sealing ring; and S3, the mechanical sealing ring is placed in a graphite clamp in the state that the working face faces upwards, the inner side wall and the outer side wall of the mechanical sealing ring are close to the graphite clamp, the working face of the mechanical sealing ring is flush with the upper surface of the graphite clamp, and uniform deposition of the diamond film on the working face of the mechanical sealing ring is achieved through a hot filament CVD method. According to the method, the height difference of the surface of the diamond coating is greatly reduced, the subsequent grinding and polishing time is greatly shortened, meanwhile, the quality of the diamond coating is improved, the working life is greatly prolonged, and the method has important significance for stabilizing the preparation process of the diamond coating mechanical sealing ring.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical seal components, and in particular to a method for uniformly depositing a diamond film on the end surface of a mechanical seal ring. Background Art

[0002] Mechanical seal is a commonly used shaft sealing device for rotating machinery. It is widely used in mechanical equipment (such as pumps, compressors, reactors, etc.) in process industries such as chemical, papermaking, pharmaceutical, and food. Its sealing mechanism is to prevent leakage by maintaining contact and relative sliding of at least one pair of end faces perpendicular to the axis under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism and the cooperation of auxiliary seals.

[0003] With the development of science and technology and industry, under high parameter conditions, the probability of end face wear of friction pair materials used in traditional mechanical seals, such as graphite, cemented carbide, and engineering ceramics, has greatly increased, resulting in the life of mechanical seals failing to meet design requirements. In order to improve the wear performance of the end face of the mechanical seal ring, a diamond coating material with higher hardness and wear resistance is selected.

[0004] Hot wire chemical vapor deposition (HFCVD) is the earliest method used to grow diamond film. It has low production cost, simple equipment, easy to control the production process, and good product film quality. It is one of the most effective methods for the industrial development and application of diamond film. However, in the preparation process of diamond coated mechanical seal rings, due to the influence of the seal ring's own structure, there is heat accumulation in the edge area, resulting in uneven film thickness of the diamond film on the end face of the seal ring. In view of the high hardness and strong wear resistance of the diamond film, the time cost required for the flattening and polishing of the prepared diamond film is greatly increased. Generally, the time required for grinding and polishing is 10-18 hours, and the coating quality is also uneven, which directly affects the industrial application of diamond coated mechanical seal rings.

[0005] In order to solve the problem of uneven diamond film thickness caused by uneven temperature field, a large number of studies have been conducted to optimize the process parameters of diamond deposition on mechanical seal rings through simulation in order to achieve the purpose of uniform temperature field. However, there are relatively few studies on substrate structure optimization and on the addition of fixtures on mechanical seal rings to deposit diamond films. Summary of the invention

[0006] The purpose of the present invention is to provide a method for uniformly depositing a diamond film on the end face of a mechanical seal ring, so as to solve the problems of uneven film thickness, low life and long polishing time of the diamond film of the mechanical seal ring in the prior art.

[0007] In order to solve the above problems, the present invention adopts the following technical solutions:

[0008] A method for uniformly depositing a diamond film on the end face of a mechanical seal ring is provided, comprising the following steps: S1, pre-treating the mechanical seal ring to roughen its surface; S2, providing a graphite fixture, wherein the graphite fixture has at least one annular groove, the depth of the annular groove is equal to the thickness of the mechanical seal ring, and the width of the annular groove is slightly larger than the width of the mechanical seal ring; S3, placing the mechanical seal ring into the graphite fixture with its working surface facing upward, so that the inner and outer side walls of the mechanical seal ring are respectively adjacent to the graphite fixture, the working surface of the mechanical seal ring is flush with the upper surface of the graphite fixture, and hot wire chemical vapor deposition is used to achieve uniform deposition of the diamond film on the working surface of the mechanical seal ring.

[0009] Preferably, in step S1, the mechanical sealing ring is made of silicon carbide ceramic material.

[0010] Preferably, in step S1, the pretreatment method of the mechanical sealing ring includes: 1) immersing the working surface of the mechanical sealing ring in an acetone solution for ultrasonic cleaning to remove impurities and dirt on the working surface of the sealing ring; 2) immersing the mechanical sealing ring in a mixed solution made of diamond grinding powder and isopropyl alcohol for ultrasonic pretreatment to roughen the surface of the sealing ring; 3) using deionized water and acetone to ultrasonically clean the mechanical sealing ring again to remove the residual diamond grinding powder and impurities on the working surface, and putting it into a drying oven for drying.

[0011] Preferably, in the pretreatment method, the size of the diamond grinding powder is 2.5-12 μm, and the ratio is 10 g diamond powder: 100 mL isopropyl ketone.

[0012] Preferably, in step S1, the dimensions of the mechanical sealing ring are an outer diameter of Φ40-150 mm, an inner diameter of Φ30-120 mm, a thickness of 8-18 mm, and a working surface width of 2-30 mm.

[0013] Preferably, in step S2, the graphite fixture has a plurality of annular grooves, including a large annular groove for a large-sized mechanical seal ring and a plurality of small annular grooves for a small-sized mechanical seal ring, wherein the large annular groove is centrally arranged and the plurality of small annular grooves are evenly arranged along the circumference. This arrangement can reduce production costs and improve production efficiency.

[0014] Preferably, in step S3, when the mechanical seal ring is placed in the annular groove of the graphite fixture, a gap of 0.2 mm to 1.2 mm is maintained between the inner side wall and the outer side wall of the mechanical seal ring and the inner wall of the annular groove. For ease of installation, more preferably, a gap of 1 mm is left between the graphite fixture and the mechanical seal ring placed therein.

[0015] Preferably, in step S3, the diameter of the hot wire is 0.5-0.6 mm, the hot wire spacing is 10-25 mm, the number of hot wires is 12-32, the number of sealing rings is 1-8, and each mechanical sealing ring is placed in a corresponding annular groove.

[0016] Preferably, in step S3, the hot wire power for depositing the diamond film is 12-17 kW, the reaction gas is a mixture of a carbon source and hydrogen, the reaction gas pressure is 20-30 Torr, the carbon source concentration is 1-4%, the substrate temperature is 800-900°C, the bias current is 3.0-5.0A, and the deposition time is 10-17 hours.

[0017] Preferably, the method further includes the step: S4, polishing the working surface of the mechanical sealing ring on a grinding and polishing machine to obtain a high-quality diamond coating, the grinding liquid is a mixture of diamond grinding paste with a particle size of 10 to 20 μm, the grinding liquid flow rate is 2 to 4 mL / min, the grinding disc speed is 40 to 60 r / min, and the polishing time is 1 to 4 hours.

[0018] According to the method for uniformly depositing a diamond film on the end face of a mechanical seal ring provided by the present invention, the key invention point is that, by specially designing a graphite fixture, when the mechanical seal ring is installed in the graphite fixture, the inner and outer side walls of the mechanical seal ring are respectively adjacent to the graphite fixture, and the working surface of the mechanical seal ring is flush with the upper surface of the graphite fixture. Therefore, when the hot wire chemical vapor deposition process is performed, the heat at the edge of the mechanical seal ring can be gathered and transferred to the graphite fixture, thereby effectively reducing the temperature at the edge of the seal ring, so that the working surface of the mechanical seal ring has a more uniform temperature distribution, and the diamond film of the mechanical seal ring prepared in this way is also more uniform, and the coating life and quality are also significantly improved, and the subsequent polishing and grinding time is greatly shortened. However, the prior art before the present invention has never disclosed a similar report on improving the quality of diamond coating by adding such a graphite fixture.

[0019] It should be understood that according to the method of the present invention, before depositing the diamond film on the working surface of the mechanical seal ring, the surface of the substrate is roughened to form a potential low point that is easy for diamond nucleation and growth, while enhancing the mechanical bite between the diamond particles and the substrate particles and improving the bonding force of the diamond coating.

[0020] It should also be understood that in order to prevent leakage during the use of the mechanical seal ring, the working surface of the mechanical seal ring needs to have excellent surface flatness and finish. The surface flatness and finish of the diamond film prepared by the method of the present invention meet the industry standards and can meet industrial applications. The present invention can obtain a higher quality diamond coating by further polishing the working surface of the mechanical seal ring on a grinding and polishing machine after the diamond film is deposited.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) Through simulation and experimental verification, the diamond-coated mechanical seal ring prepared according to the method of the present invention can greatly improve the uniformity of the diamond film and the coating quality, thereby reducing the wear rate of the contact end face, and its service life is significantly improved compared with the mechanical seal ring prepared without installing the fixture.

[0023] 2) Since the maximum film thickness difference on the working surface of the sealing ring can be reduced to 1 μm after the fixture is installed, the time for subsequent mechanical polishing to smooth the surface can be effectively shortened, thereby reducing production costs.

[0024] In summary, the present invention adopts a method of adding a graphite fixture to uniformly deposit a layer of diamond film on the working surface of the mechanical seal ring through hot wire chemical vapor deposition. According to the method of the present invention, the surface height difference of the diamond coating can be greatly reduced to reduce the surface roughness of the diamond coating, greatly shorten the subsequent grinding and polishing time, and improve the quality of the diamond coating. Its working life is greatly improved compared with the general coated mechanical seal ring, which is of great significance to the preparation process of the stable diamond coated mechanical seal ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of a mechanical seal ring;

[0026] Figure 2 This is a schematic diagram of the fixture installation;

[0027] Figure 3 A diagram showing the arrangement of a mechanical seal ring according to a preferred embodiment of the present invention;

[0028] Figure 4 Schematic diagram of diamond coating thickness before and after the fixture is installed;

[0029] Figure 5 Schematic diagram of film thickness under different fixture conditions, where (a) is the cross-sectional morphology of the coating at different positions on the end face of the sealing ring under the condition of fixture, and (b) is the cross-sectional morphology of the coating at different positions on the end face of the sealing ring under the condition of no fixture;

[0030] Figure 6 This is a comparison of the temperature field distribution on the end face of the sealing ring before and after the fixture is installed. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional operations in the art, or according to the experimental methods recommended by the instrument and equipment manufacturers. The reagents and materials used in the examples can be obtained from commercial sources unless otherwise specified.

[0032] Example 1

[0033] The mechanical seal ring in this embodiment is directly applied to the standard 100-hour seal ring performance test and is prepared by the following method:

[0034] 1) Provide a mechanical seal ring 10 made of silicon carbide material, the seal ring base structure is as follows Figure 1 As shown, the outer dimensions are Φ70mm×10mm, the working surface 11 is annular, with an inner diameter of 30mm and an outer diameter of 70mm. Then, the working surface 11 is ultrasonically roughened using a diamond grinding liquid with a particle size of 7μm;

[0035] 2) Prepare a graphite fixture 20, combined with Figure 2 , Figure 3 As shown, the graphite fixture 20 has a plurality of annular grooves 21, including a large annular groove and seven small annular grooves, which are respectively used to place a large-sized mechanical sealing ring and a small-sized mechanical sealing ring. The depth of the annular groove 21 is equal to the thickness of the corresponding mechanical sealing ring 10, and the width of the annular groove 21 is slightly larger than the width of the corresponding mechanical sealing ring 10.

[0036] S3, such as Figure 3 As shown, the mechanical seal ring 10 is placed in the graphite fixture 20 with the working surface facing upward, so that the inner and outer side walls of the mechanical seal ring 10 are respectively adjacent to the graphite fixture 20, and the working surface 11 of the mechanical seal ring 10 is flush with the upper surface 22 of the graphite fixture 20, and the hot wire CVD method is used to achieve uniform deposition of the diamond film 30 on the working surface of the mechanical seal ring. For easy installation, a 1mm gap is left between the graphite fixture 20 and the mechanical seal ring 10 placed therein.

[0037] Specifically, 12 hot wires were arranged in parallel, and six silicon carbide mechanical seal rings were placed in a corresponding fixture to deposit diamond films on their working surfaces for 20 hours. After the film was formed, the experiment was carried out directly without plane polishing.

[0038] The standard 100-hour sealing ring performance test experiment was used to compare the durability of diamond-coated silicon carbide sealing rings with and without fixtures after the fixture was installed. Four sealing rings with and without fixtures from the same batch were tested respectively. The thickness of the diamond film is 10 microns. The medium is water, the temperature is 120-150°C, the pressure is 0.8-1.03Mpa, and the speed is 6000r / min. After 100 hours of standard mechanical seal test experiments, the diamond-coated sealing rings prepared with fixtures showed no obvious wear, and the leakage was 2-5mL / h, while the working surface of the diamond-coated mechanical sealing rings prepared without fixtures had coating peeling, and the leakage was 10-30mL / h.

[0039] Example 2

[0040] The diamond-coated mechanical seal ring of this embodiment is used in a high-pressure pump. The conveying medium is viscous cement slurry. The seal ring base material is silicon nitride. The outer dimensions are Φ45mm×15mm. The working surface is annular with an inner diameter of 30mm and an outer diameter of 40mm.

[0041] The specific preparation method of the sealing ring is as follows: first, the working surface of the sealing ring is ultrasonically roughened with a 10μm coarse diamond grinding liquid, and then the workpiece is cleaned with acetone. Secondly, 12 hot wires are arranged in parallel, and 12 silicon carbide mechanical sealing rings are placed in the corresponding fixture and a diamond film is deposited on their working surface. The heat source is 8mm away from the deposition surface, the total power of the hot wire is 21kw, the substrate temperature is 800-900℃, and the deposition time is 21 hours. Finally, a flat polishing machine is used to level the working surface.

[0042] A company ordered 24 such sealing rings. After adding the fixture, 12 were prepared and polished in 2 hours. Without the fixture, 12 were prepared and polished in 10 hours. After adding the fixture, the polishing time was shortened by 80%. The mechanical sealing rings prepared by adding the fixture greatly improved the company's production efficiency.

[0043] In the subsequent use of the company, the service life of the 12 mechanical seal rings prepared by adding a fixture was an average of 6 to 8 months; the service life of the 12 mechanical seal rings prepared without adding a fixture was an average of 2 to 3 months. Usually, the maintenance of high-pressure pump machines is relatively frequent. The silicon carbide mechanical seal rings prepared by adding a fixture can greatly reduce the subsequent maintenance costs of the machine, ensure a longer working cycle of the machine, and reduce the number of downtimes.

[0044] Example 3

[0045] The diamond-coated mechanical seal ring of this embodiment is used in high-pressure ceramic powder transmission equipment. The seal ring base material is silicon carbide, the outer dimensions are Φ66mm×20mm, the working surface is annular, the inner diameter is 50mm, and the outer diameter is 55mm.

[0046] The preparation method of the sealing ring is as follows: first, the working surface is ultrasonically roughened using a 12μm coarse diamond grinding liquid, and then the sealing ring is mechanically ground with 2.5μm diamond powder. Subsequently, 13 hot wires are arranged in parallel, and 6 silicon carbide mechanical sealing rings are placed in a corresponding fixture to deposit a diamond film on their surface. The hot wire power is 17kw, the reaction gas pressure is 28Torr, and the carbon source concentration is 1%. Finally, a flat polishing machine is used to flatten the surface of the diamond film for 3 hours.

[0047] The prepared mechanical seal ring was cut radially and the cross section of the diamond coating was observed using a scanning electron microscope. Figure 5 As shown, compared with the mechanical sealing ring prepared without the fixture, the diamond coating prepared after adding the fixture is obviously more uniform, and the thickness difference between the edge and the middle area is only 0.8μm. Compared with the mechanical sealing ring obtained without the fixture, the thickness difference between the edge and the middle area is reduced by 3.1μm.

[0048] Example 4

[0049] In this example, Fluent simulation software is used to simulate the surface temperature field of the mechanical seal ring when the diamond film is prepared by the HFCVD method. Two cases with and without the fixture are studied. The sealing ring substrate is made of silicon carbide, with an outer dimension of Φ155mm×15mm, and a ring-shaped working surface with an inner diameter of 140mm and an outer diameter of 155mm.

[0050] The simulation settings are as follows: the hot wire diameter d = 0.6mm, the length L = 340mm, the hot wire spacing S = 25mm, and the distance from the hot wire to the surface of the mechanical seal ring H = 10mm. The reaction gas is set to hydrogen, the gas flow rate is 300sccm, the hot wire temperature is set to 2000℃, the ambient temperature and the initial temperature of the cooling water are set to 26℃, and the reaction chamber pressure is set to 1000pa.

[0051] The entire simulation process lasted 10 hours and converged after about 2000 steps. The simulation results are as follows Figure 6 As shown in the figure. After the fixture is installed, the overall temperature of the mechanical seal ring surface shows a downward trend. It can be seen from the figure that the radial temperature of the seal ring end face without the fixture shows a trend of high temperature at both ends and low temperature in the middle. After adding the graphite fixture, the radial average temperature drops significantly, and the high temperature points at the corners on both sides are significantly improved.

[0052] Compared with the case without the fixture, after installing the fixture, the average temperature of the end face of the mechanical seal ring dropped from 755.3℃ to 739.18℃, and the maximum temperature range can be reduced to 6℃.

[0053] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiments of the present invention can also be modified in various ways. All simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for uniformly depositing a diamond film on the end surface of a mechanical seal ring, characterized in that: The following steps are involved: S1, pre-treating the mechanical seal ring to roughen its surface; S2, providing a graphite fixture, wherein the graphite fixture has at least one annular groove, the depth of the annular groove is equal to the thickness of the mechanical sealing ring, and the width of the annular groove is slightly larger than the width of the mechanical sealing ring; S3, placing the mechanical sealing ring into the graphite fixture with its working surface facing upward, so that the inner and outer side walls of the mechanical sealing ring are respectively adjacent to the graphite fixture, and the working surface of the mechanical sealing ring is flush with the upper surface of the graphite fixture, and hot wire chemical vapor deposition method can be used to achieve uniform deposition of diamond film on the working surface of the mechanical sealing ring.

2. The method according to claim 1, characterized in that In step S1, the mechanical sealing ring is made of silicon carbide ceramic material.

3. The method according to claim 1, characterized in that In step S1, the pretreatment method of the mechanical seal ring includes: 1) Immerse the working surface of the mechanical seal ring in an acetone solution for ultrasonic cleaning to remove impurities and dirt on the working surface of the seal ring; 2) Immerse the mechanical seal ring in a mixture of diamond abrasive powder and isopropyl alcohol for ultrasonic pretreatment to roughen the working surface of the seal ring; 3) Use deionized water and acetone to ultrasonically clean the mechanical seal ring again to remove the diamond grinding powder and impurities remaining on the working surface, and put it in an oven for drying.

4. The method according to claim 3, characterized in that: In the pretreatment method, the size of the diamond grinding powder is 2.5-12 μm, and the ratio is 10 g diamond powder: 100 mL isopropyl ketone.

5. The method according to claim 1, characterized in that In step S1, the dimensions of the mechanical sealing ring are an outer diameter of Φ40 to 150 mm, an inner diameter of Φ30 to 120 mm, a thickness of 8 to 18 mm, and a working surface width of 2 to 30 mm.

6. The method according to claim 1, characterized in that In step S2, the graphite fixture has multiple annular grooves, including a large annular groove for a large-sized mechanical sealing ring and multiple small annular grooves for a small-sized mechanical sealing ring. The large annular groove is centrally arranged, and the multiple small annular grooves are evenly arranged along the circumference.

7. The method according to claim 1, characterized in that In step S3, when the mechanical sealing ring is placed in the annular groove of the graphite fixture, a gap of 0.2 mm to 1.2 mm is maintained between the inner side wall and the outer side wall of the mechanical sealing ring and the inner wall of the annular groove respectively.

8. The method according to claim 1, characterized in that In step S3, the diameter of the hot wire is 0.5-0.6 mm, the hot wire spacing is 10-25 mm, the number of hot wires is 12-32, the number of sealing rings is 1-8, and each mechanical sealing ring is placed in a corresponding annular groove.

9. The method according to claim 1, characterized in that: In step S3, the hot wire power for depositing the diamond film is 12-17 kW, the reaction gas is a mixture of a carbon source and hydrogen, the reaction gas pressure is 20-30 Torr, the carbon source concentration is 1-4%, the substrate temperature is 800-900°C, the bias current is 3.0-5.0A, and the deposition time is 10-17 hours.

10. The method according to claim 1, characterized in that The method further comprises the steps of: S4, polishing the working surface of the mechanical seal ring on a grinding and polishing machine to obtain a high-quality diamond coating, the grinding liquid is a mixture of diamond grinding paste with a particle size of 10 to 20 μm, the grinding liquid flow rate is 2 to 4 mL / min, the grinding disc speed is 40 to 60 r / min, and the polishing time is 1 to 4 hours.

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