A method for producing a high wear resistant tungstoboron coating

Abstract

The application relates to a preparation method of a high-wear-resistance tungsten boride coating and belongs to the technical field of wear-resistant material preparation. By using a chemical vapor deposition technology, a pure tungsten coating with a thickness of about 29.1 microns is first prepared on a tungsten base, then a low-temperature solid-phase boronizing technology is used to convert part of the pure tungsten coating into a tungsten boride coating, and thus the surface hardness and wear resistance of the material are improved. Compared with direct chemical vapor deposition of tungsten boride on a metal surface, the method can avoid using the high-risk boron trichloride gas, and can effectively control the coating thickness and the microstructure. The coating preparation process can be applied to the surface strengthening modification of various metal materials, and has strong practical application value.

Description

Technical Field

[0001] The invention relates to a method for preparing a metal boride coating with wear-resistant performance, and belongs to the technical field of wear-resistant material preparation. Background Art

[0002] Wear is a major cause of metal material loss and energy consumption, primarily occurring on the surface of the material. Preparing a highly wear-resistant coating on the surface can significantly improve the material's performance, thereby reducing wear. As we all know, ceramic materials have attracted much attention due to their excellent wear resistance, especially transition metal borides, which possess both metal-like and ceramic-like properties and have been widely used in the medical, aerospace, chemical, and other fields. Among them, WB, as a coating reinforcement phase material, is expected to significantly improve the wear resistance of the material surface.

[0003] There are many methods for preparing WB coatings, one of which is to prepare them directly on the surface by physical vapor deposition. However, the coatings prepared by this method usually have large internal stress, resulting in a thin coating (<1μm), which is difficult to meet the requirements of use. Another method is chemical vapor deposition, but it requires the use of boron trichloride gas, which is dangerous, and the deposition process is difficult to control, and it is difficult to regulate the thickness and structure. Therefore, it is necessary to develop a new preparation method to prepare highly wear-resistant WB coatings simply, quickly and efficiently.

[0004] After extensive research, we discovered that first using chemical vapor deposition to create a columnar ultrafine-grained tungsten coating, followed by solid-phase boronization, can effectively introduce boron atoms. The columnar ultrafine-grained tungsten coating provides a diffusion path for the boron atoms, lowering the boronization temperature and significantly improving efficiency. This method allows for low-temperature deposition (>300°C), avoiding the effects of high temperatures on the substrate material, while ensuring a coating with controllable thickness, high purity, and good density. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a wear-resistant tungsten boride coating and a preparation method thereof.

[0006] The method of the present invention is based on chemical vapor deposition technology, and deposits an ultrafine columnar crystal structure tungsten coating with a controllable thickness, such as about 29.1 μm, on the surface of a pure tungsten substrate. On this basis, a chemical heat treatment solid phase boronizing method is adopted to prepare a metal ceramic composite coating with good wear resistance.

[0007] In the present invention, the ultrafine columnar crystal structure tungsten coating serves as a transition layer, and its presence can provide a B atom diffusion channel, thereby reducing the subsequent solid phase boriding temperature; the tungsten boride coating can significantly improve the wear resistance.

[0008] The method has a simple process, and the thickness of the ultrafine columnar crystal structure tungsten coating and the tungsten boride coating is easy to control and can be set according to actual needs, thus having high practical application value.

[0009] In order to achieve the above technical objectives, the technical solutions of the present invention are as follows:

[0010] 1) Sandpaper the wire-cut rolled pure tungsten substrate to 1000#, then use alcohol ultrasonic cleaning and dry it for later use;

[0011] 2) Sand the deposition table of the chemical vapor deposition equipment until it is smooth and check the safety of the equipment;

[0012] 3) Open the argon flow needle valve and introduce protective argon gas for 3 to 5 minutes, and then exhaust the air from the reaction chamber and all pipelines. After the reaction chamber and all pipelines are exhausted, test the air tightness of the equipment;

[0013] 4) Introduce hydrogen and ignite the tail gas discharged from the reaction chamber, then close the argon flow needle valve;

[0014] 5) Heat the reaction chamber by electric current, and keep the substrate at the set temperature for 15 minutes;

[0015] 6) Turn on the alkali pump of the tail gas treatment system and introduce the heated and vaporized WF6 mixed with H2 into the reaction chamber. WF6 and H2 undergo a hydrogen reduction reaction to generate W atoms that are deposited on the substrate surface to form a tungsten coating. After the set process reaction time is reached, turn off the reaction gas and heating power supply to cool the reaction chamber. When the reaction chamber temperature drops below 100°C, remove the deposited sample and the chemical vapor deposition experiment is completed.

[0016] 7) placing a commercial boronizing agent in a ceramic crucible and drying the crucible together with the ceramic crucible in an oven;

[0017] 8) burying the substrate having the ultrafine columnar tungsten coating after the chemical vapor deposition experiment in a dried boronizing agent and sealing it in a ceramic crucible using a sealant;

[0018] 9) placing the sealed crucible into a box-type high-temperature furnace for solid phase boronizing treatment;

[0019] 10) After the sample cools down in the furnace, take out the boronized sample;

[0020] 11) Use 3000# sandpaper to lightly grind away the boronizing agent remaining on the surface of the sample, and ultrasonically rinse the sample with alcohol. After drying, seal and store it to obtain a tungsten-tungsten-boron composite coating metal ceramic material with wear resistance.

[0021] The substrate used is rolled pure tungsten, wherein the sample size can be controlled according to needs, such as a sample of Ф15×2mm.

[0022] In the step (3), the argon flow rate is 25 mm.

[0023] In the step (4), the hydrogen flow rate is 25 mm.

[0024] In the step (5), the deposition temperature is 600° C., and the deposition time is 50-70 min, preferably 60 min.

[0025] The ultrasonic cleaning time in steps (1) and (11) is 10 minutes.

[0026] In step (7), the drying temperature of the boronizing agent is 150° C. and the drying time is 120 min. In step (7), the boronizing agent is a commercial solid powder boronizing agent (eg, the boronizing agent includes components: boron carbide, silicon carbide, potassium fluoroborate, and aluminum powder).

[0027] In the step (9), the solid phase boronizing temperature is 850° C. and the boronizing time is 120 min.

[0028] The beneficial effects of the present invention are:

[0029] Chemical vapor deposition of an ultrafine columnar tungsten coating on the surface of the rolled tungsten-based material provides diffusion channels for boron atoms, lowering the boronizing temperature and enabling low-temperature boronizing. Further treatment using the solid-phase boronizing process within chemical heat treatment technology enhances the wear resistance of the tungsten-based material.

[0030] The rolled tungsten substrate was maintained at a deposition temperature of 600°C for 60 minutes, resulting in a coating approximately 29.1 μm thick. This coating exhibited a regularly arranged columnar structure, with a relatively flat, silvery-white macroscopic surface. A tungsten boride coating with a thickness of 3-4 μm was obtained by treating the tungsten coating with a boriding temperature of 850°C for 120 minutes. Friction and wear performance tests revealed a wear rate of only 5.4×10 -6 mm 3 / N·m, which is one order of magnitude lower than that of tungsten coating. The composite metal ceramic material prepared by the present invention has the advantage of easy control of the thickness of the boronized layer and has good application prospects in the wear resistance field. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD patterns of the CVD-W coating and WB / CVD-W coating prepared in Example;

[0032] Figure 2 The microstructure SEM images of the CVD-W coating and the WB / CVD-W composite coating prepared in the examples;

[0033] Figure 3 This is the EDS result of the WB / CVD-W composite coating prepared in Example;

[0034] Figure 4 The room temperature friction coefficient curves of the WB / CVD-W composite coating and the CVD-W coating in the embodiment;

[0035] Figure 5 The surface morphology of the CVD-W coating in the embodiment after rubbing for 30 minutes;

[0036] Figure 6 This is the surface morphology of the WB / CVD-W composite coating in the embodiment after rubbing for 30 minutes.

[0037] Figure 7 The wear rate histogram of the CVD-W coating and the WB / CVD-W composite coating in the examples; DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.

[0039] Example 1: This example uses a rolled pure tungsten substrate

[0040] First, the rolled pure tungsten substrate was pretreated. The treatment process included polishing the pure tungsten substrate with 400-1000# sandpaper until the surface wire cutting marks were completely removed. After cleaning the surface with deionized water, it was placed in a beaker containing alcohol, ultrasonically cleaned for 10 minutes, and then dried. It was then wrapped and sealed with dust-free paper and stored in a sample bag for use.

[0041] The chemical vapor deposition deposition table was polished with sandpaper until smooth, and the deposition table was cleaned. The pre-treated substrate was centered on the deposition table and sealed.

[0042] Open the argon flow needle valve and introduce protective gas argon for 3 to 5 minutes. The argon flow rate is 25mm. Empty the air from the reaction chamber and all pipelines. After the reaction chamber and all pipelines are emptied, test the air tightness of the equipment.

[0043] Introduce hydrogen and ignite the tail gas discharged from the reaction chamber to test its purity. The hydrogen flow rate is 25 mm, and then close the argon flow needle valve.

[0044] The deposition reaction chamber is heated by electric current. When the deposition substrate reaches the set temperature, it is kept warm for 15 minutes. The deposition temperature is 600°C and the deposition time is 60 minutes.

[0045] The alkali pump of the tail gas treatment system is turned on and the heated and vaporized WF6 is mixed with H2 and then introduced into the reaction chamber. WF6 and H2 undergo hydrogen reduction reaction to generate W atoms which are deposited on the substrate surface to obtain an ultrafine columnar crystal structure tungsten coating.

[0046] After the set reaction time, turn off the reaction gas and heating power to cool the reaction chamber. When the reaction chamber temperature drops below 100°C, remove the deposited sample and immediately wrap it in dust-free paper for later use.

[0047] The crucible was cleaned with deionized water and alcohol. After the crucible was dried, a commercial boronizing agent was placed in the crucible. The boronizing agent and the crucible were placed in a vacuum drying oven and dried at 150°C for 120 min.

[0048] The material after chemical vapor deposition tungsten coating was buried in a boronizing agent and sealed in a ceramic crucible with a sealant. The sealed crucible was placed in a box furnace and subjected to a boronizing treatment at a temperature of 850° C. for 120 minutes.

[0049] After the sample cools down to room temperature in the furnace, it can be taken out. Use 3000# sandpaper to gently grind off the boronizing agent remaining on the surface of the sample.

[0050] The sample was rinsed with deionized water and alcohol to further remove the boronizing agent and other impurities remaining on the surface to obtain a composite metal-ceramic coating material with a certain wear-resistant effect.

[0051] The WB / CVD-W composite coating and CVD-W coating were analyzed by X-ray diffractometer (XRD). Figure 1 shown.

[0052] XRD results show that the surface phase composition of the WB / CVD-W composite coating is WB, and the surface phase composition of the CVD-W coating is W.

[0053] The WB / CVD-W composite coating and CVD-W coating samples of this embodiment were respectively subjected to fracture cross-section sample preparation, and the structure of the samples was characterized by scanning electron microscopy (SEM). The SEM morphology of the fracture cross-section is shown in FIG. Figure 2 shown.

[0054] SEM results Figure 2 (a) shows that the CVD-W coating has uniform microstructure distribution, good growth condition, columnar crystal structure, clear interface with pure tungsten substrate, and the coating thickness is about 29.1μm. Figure 2 (b) shows that the WB / CVD-W composite coating has good stratification, and the top 3.7μm dense structure, the middle columnar structure and the rolled pure tungsten morphology at the bottom are clearly observed.

[0055] The WB / CVD-W composite coating was analyzed for element types and atomic ratios in micro-areas by X-ray energy dispersive spectroscopy (EDS). The micro-area analysis results are as follows: Figure 3 shown.

[0056] EDS results show that Figure 2The phase composition of the top dense layer in (b) is WB, and the phase composition of the middle columnar layer and pure tungsten matrix is ​​W.

[0057] The friction and wear of the samples were analyzed by a friction and wear tester. At room temperature and 18.0% relative humidity, the loading load was set to 10N, the test time was 30min, the running speed was 200r / m, and the grinding pair was GCr15 steel ball.

[0058] The friction coefficient curve of the CVD-W coating sample fluctuates greatly, showing a gradual upward trend, and finally reaches 1.3, at which point the sample surface has been damaged to a considerable extent. The friction coefficient of the WB / CVD-W composite coating sample first increases and then decreases, and finally stabilizes at around 1.0. Figure 4 shown.

[0059] Scanning electron microscopy (SEM) was used to characterize the morphology of the wear scar on the sample surface. The wear scar on the CVD-W coating sample surface was wide, up to 541.0 μm, with many wear chips and furrows. The wear mechanism was abrasive wear. Figure 5 As shown in the figure, the wear scar on the surface of the WB / CVD-W composite coating sample is narrowed to 450.2μm in width, the wear debris is significantly reduced, and a glaze layer is formed. The wear mechanism is adhesive wear. Figure 6 shown.

[0060] The surface wear volume of the sample was further measured by surface profilometer to calculate the wear rate. The wear rate of the CVD-W coating sample was 1.3×10 -5 mm 3 / N·m, and the wear rate of the WB / CVD-W composite coating sample is 5.4×10 -6 mm 3 / N·m, showing excellent wear resistance. Figure 7 shown.

Claims

1. A method for preparing a highly wear-resistant tungsten boride coating, characterized in that: The following steps are involved: (1) Sandpaper polishing the wire-cut rolled pure tungsten substrate to 1000#, then ultrasonically clean it with alcohol and dry it for later use; (2) Sand the deposition table of the chemical vapor deposition equipment until it is smooth and check the safety of the equipment; (3) Open the argon flow needle valve and introduce protective gas argon for 3 to 5 minutes, and then exhaust the air from the reaction chamber and all pipelines. After the reaction chamber and all pipelines are exhausted, test the air tightness of the equipment; (4) Introduce hydrogen and ignite the tail gas discharged from the reaction chamber, then close the argon flow needle valve; (5) Heat the reaction chamber by electric current, and keep the substrate at the set temperature for 15 minutes; (6) Turn on the alkali pump of the tail gas treatment system and mix the heated and vaporized WF6 with H2 and introduce it into the reaction chamber. WF6 and H2 undergo hydrogen reduction reaction to generate W atoms which are deposited on the substrate surface to obtain a tungsten coating. After the set reaction time is reached, turn off the reaction gas and heating power supply to cool the reaction chamber. When the reaction chamber temperature drops below 100 °C, remove the deposited sample and the chemical vapor deposition experiment ends. (7) Place the commercial boronizing agent in a ceramic crucible and place it in an oven together with the ceramic crucible for drying; (8) The substrate with the ultrafine columnar tungsten coating after the chemical vapor deposition experiment is buried in the dried boronizing agent and sealed in a ceramic crucible with a sealant; (9) Place the sealed crucible into a box-type high-temperature furnace for solid phase boronizing treatment; (10) After the sample cools down in the furnace, take out the boronized sample; (11) Use 3000# sandpaper to lightly grind away the boronizing agent remaining on the surface of the sample, and rinse the sample with alcohol ultrasonically. After drying, seal and store it to obtain a tungsten-tungsten-boron composite coating metal ceramic material with wear resistance; In the step (9), the solid phase boronizing temperature is 850°C and the boronizing time is 120 min.

2. The method according to claim 1, characterized in that The substrate used is rolled pure tungsten.

3. The method according to claim 1, characterized in that In the step (3), the argon flow rate is 25 mm; in the step (4), the hydrogen flow rate is 25 mm.

4. The method according to claim 1, characterized in that In the step (5), the deposition temperature is 600°C and the deposition time is 50-70 min.

5. The method according to claim 4, characterized in that In the step (5), the deposition time is 60 min.

6. The method according to claim 1, characterized in that The ultrasonic cleaning time in steps (1) and (11) is 10 minutes.

7. The method according to claim 1, characterized in that In the step (7), the drying temperature of the boronizing agent is 150° C., and the drying time is 120 min.

8. The method according to claim 1, characterized in that In the step (7), the boronizing agent is a commercial solid powder boronizing agent.

9. A high wear-resistant tungsten boride coating prepared according to the method according to any one of claims 1 to 8.

10. A high wear-resistant tungsten boride coating prepared by the method according to any one of claims 1 to 8, characterized in that: The rolled tungsten substrate was kept at a deposition temperature of 600°C for 60 minutes to grow a 29.1 μm thick coating with a regularly arranged columnar crystal structure. The tungsten coating was treated at a boriding temperature of 850°C for 120 minutes to obtain a tungsten boride coating with a thickness in the range of 3-4 μm. According to the friction and wear performance test, the wear rate of the tungsten boride coating is 5.4×10 -6 mm 3 / N·m.

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