A method for producing a surface coating and a tungsten-tantalum alloy

Abstract

The present application belongs to the technical field of non-ferrous metal surface treatment and coating preparation, and particularly relates to a surface coating preparation method and a tungsten-tantalum alloy, which comprises the following steps: coating an inner layer slurry on a workpiece after surface treatment, drying, and vacuum sintering to obtain a workpiece with a transition layer; the inner layer slurry comprises Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder; coating an outer layer slurry on the workpiece with the transition layer, drying, and vacuum sintering to obtain an additive surface coating; the outer layer slurry comprises Si powder, SiC powder, SmO2 powder and NaF powder, and the mass ratio of the Si powder, SiC powder, SmO2 powder and NaF powder is 38-50:40-50:5-8:6-10; the present application reduces surface roughness and improves coating performance.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal surface treatment and coating preparation technology, specifically relating to a method for preparing a surface coating and a tungsten-tantalum alloy. Background Technology

[0002] Ta 10 W alloy possesses excellent high-temperature mechanical properties, chemical stability, corrosion resistance, wear resistance, and creep resistance. With a service temperature of up to 1600℃ to 1900℃, it is a high-performance refractory alloy material. In the aerospace field, it can replace traditional nickel-based high-temperature alloys in hot-end areas such as gas turbine blades and engine nozzles to improve service life and combustion efficiency.

[0003] Spacecraft often contain many complex components, Ta 10 W alloys have a melting point as high as 3080℃, and traditional processing methods are inefficient, costly, and have low yield rates. Emerging 3D printing technology enables additive manufacturing of refractory alloys, effectively improving the manufacturing efficiency and yield rate of complex components, reducing manufacturing costs and processing difficulty, and producing products with high precision.

[0004] Ta 10 The surface properties of W alloys directly affect their overall performance and service life, with the impact becoming more pronounced under high temperature, high pressure, and complex environments. While 3D printing additive manufacturing can relatively easily fabricate complex shapes of Ta alloys... 10 W alloy parts, however, experience rapid cooling and solidification during additive manufacturing, which can lead to excessively high surface roughness and microstructural defects, directly affecting the material's properties. 10 The service performance of W alloy components. Additionally, the Ta alloy components manufactured using 3D printing additive manufacturing. 10 W alloy parts still suffer from the problem of easy oxidation at high temperatures leading to failure.

[0005] For 3D printing additive manufacturing Ta 10 The surface defects of the inner wall of the flow channel in W alloy pipe fittings necessitate optimization through appropriate surface treatment techniques to improve their performance in practical applications. As the aerospace industry demands increasingly stringent precision for components, the complexity of component structures continues to rise, with components trending towards miniaturization and greater complexity. Structures such as large curved surfaces and small-aperture flow channels are becoming increasingly common. Traditional surface treatment methods are inadequate for alloy components with complex internal cavity structures. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a surface coating and a tungsten-tantalum alloy, which reduces surface roughness and improves coating performance.

[0007] This invention provides a method for preparing a surface coating, comprising the following steps: The surface-treated workpiece is coated with an inner layer slurry, dried, and then vacuum sintered to obtain a workpiece with a transition layer. The inner layer slurry comprises Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder, with a mass ratio of Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder of 60-70:4-5:3-6:10-25. In the Gd2O3-Ho2O3-Yb2O3 powder, the mass ratio of Gd2O3, Ho2O3, and Yb2O3 is 0.8-1.2:0.8-1.2:0.8-1.2. The workpiece with the transition layer is coated with an outer slurry, dried, and vacuum sintered to obtain an additive surface coating; the outer slurry includes Si powder, SiC powder, SmO2 powder and NaF powder, and the mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder is 38-50:40-50:5-8:6-10.

[0008] Preferably, the material of the workpiece is additively manufactured Ta. 10 W alloy.

[0009] Preferably, the mass ratio of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder is 70:4:5:21, and the mass ratio of Gd2O3, Ho2O3 and Yb2O3 in the Gd2O3-Ho2O3-Yb2O3 powder is 1:1:1.

[0010] Preferably, the mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder is 38:46:7:9.

[0011] Preferably, the solvent for the inner layer slurry is anhydrous ethanol, and it also includes a binder; the solvent for the outer layer slurry is anhydrous ethanol.

[0012] Preferably, the binder is polyvinyl butyral, and the ratio of the total mass of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder to the mass of the binder is 1:0.005-0.02, preferably 1:0.01.

[0013] The coating method of the present invention adopts the dip-lift method, the dip time is 3-8 seconds, after dip, take out and dry, and the drying temperature is 6-80℃.

[0014] Preferably, the vacuum sintering temperature is 1680-1720℃, more preferably 1710℃, the sintering time is preferably 2h, and the heating rate is 5℃ / min.

[0015] Preferably, the surface treatment steps are as follows: The workpiece is cleaned, dried, pickled, dried again, and then surface polished using a mixed slurry. The mixed slurry comprises abrasive particles, a dispersant, and anhydrous ethanol, with the pH controlled at 7-8 (citric acid is preferred). The abrasive particles are SiC and BN particles with particle sizes of 0.6-0.7 μm, 1.4-2.8 μm, 3-3.8 μm, and 5.4-6.5 μm. The mass ratio of abrasive particles with particle sizes of 0.6-0.7 μm, 1.4-2.8 μm, 3-3.8 μm, and 5.4-6.5 μm is 4-15:10-26:20-50:38-65, preferably 5-12:10-24:20-50:45-65.

[0016] Preferably, the mass ratio of the abrasive particles with particle sizes of 0.6-0.7 μm, 1.4-2.8 μm, 3-3.8 μm, and 5.4-6.5 μm is 8:15:22:55. The mass ratio of SiC abrasive particles to BN abrasive particles is 2-4:1-3, preferably 3:2. The mass fraction of abrasive particles in the mixed slurry is preferably 45-48%.

[0017] Preferably, the acid used for pickling includes hydrochloric acid and nitric acid, and the concentrations of hydrochloric acid and nitric acid are 85-95 g·L. -1 The volume ratio of hydrochloric acid to nitric acid is 1-5:1-3, preferably 5:2, and the pickling temperature is 45-50℃.

[0018] Preferably, the dispersant is one or more of sodium polyacrylate and ammonium polyacrylate, more preferably sodium polyacrylate and ammonium polyacrylate, with a mass ratio of sodium polyacrylate to ammonium polyacrylate of 1-3:1-3, more preferably 1:1. The mass fraction of the dispersant is 0.5-1%, more preferably 0.55%.

[0019] The mixed slurry is dispersed by ultrasonic dispersion and ball milling to make it uniform. The ultrasonic dispersion time is not less than 12 minutes, the frequency is 45KHz, and the ultrasonic power is 350W. The ball milling dispersion is carried out by using a planetary ball mill for 10 hours at a speed of 250rpm.

[0020] Preferably, for tubular workpieces, the surface polishing process is carried out by feeding from both ends, with a compressive load pressure of 60-70 MPa and a polishing time of 10-20 min.

[0021] After the surface polishing process is completed, the workpiece can be cleaned and dried. Cleaning can be done by rinsing with water and / or anhydrous ethanol or by ultrasonic cleaning. Drying can be done at 100-150℃.

[0022] This invention provides a tungsten-tantalum alloy, the surface of which is a surface coating prepared by the aforementioned method. Preferably, the tungsten-tantalum alloy is obtained by additive manufacturing.

[0023] The beneficial effects of this invention are: For the prepared B4C / (Gd,Ho,Yb)2O3 / MoSi2-TaSi2-Ta5Si3 high-temperature oxidation-resistant composite ceramic coating, the slurry sintering process is mature, and all process parameters have been adjusted to their current optimal values, effectively ensuring the yield and pass rate of the coating preparation. The multi-layer composite structure design results in a gradient structure of B4C / (Gd,Ho,Yb)2O3 / MoSi2 main layer, TaSi2 diffusion layer, and Ta5Si3 transition layer. The (Gd,Ho,Yb)2O3 phase is uniformly distributed in an "island-like" pattern within the MoSi2 interstices, significantly improving the coating density. In an ultra-high temperature oxidation environment of 1800℃, the coating provides effective protection for 10.5 hours. The continuous SiO2 glass film formed during oxidation synergistically inhibits oxygen permeation with the (Gd,Ho,Yb)2Si2O7 / (Gd,Ho,Yb)2Si2O7 silicate. 3+ By stabilizing the SiO2 network structure, reducing the content of non-bridging oxygen, and enhancing the viscosity of the oxide film, the diffusion of oxygen (O) is hindered. B4C decomposes and releases boron atoms, which integrate and alter the microstructure and oxidation behavior of the coating system, forming a low-melting-point, high-flow-rate borosilicate glass phase that promotes defect repair; inhibits molybdenum volatilization and "pest oxidation"; and improves the thermal compatibility of the oxide film. This invention broadens the scope for composition design and performance optimization of ultra-high temperature protective ceramic coatings, promoting the application of tantalum-based materials in aerospace and energy fields. Attached Figure Description

[0024] Figure 1 This refers to the 3D printing additive manufacturing of Ta before and after abrasive flow polishing in Embodiment 1 of the present invention. 10 Endoscopic images of the flow channel of W alloy pipe fittings. (a) is the endoscopic image before polishing, and (b) is the endoscopic image after polishing.

[0025] Figure 2 This is the 3D printing additive manufacturing of Ta before and after abrasive flow polishing in Embodiment 1 of the present invention. 10 Surface roughness results of the inner wall of the flow channel in the middle section of W alloy pipe fittings. (a) is the surface roughness result before polishing, and (b) is the surface roughness result after polishing.

[0026] Figure 3 This is a cross-sectional view of the coated sample after the slurry sintering process in Embodiment 1 of the present invention, without high-temperature oxidation test.

[0027] Figure 4 This is a cross-sectional view of the coated sample after high-temperature oxidation test in Embodiment 1 of the present invention, after the slurry sintering process.

[0028] Figure 5These are cross-sectional views of the coated sample after the slurry sintering process in Example 1 of the present invention, after the room temperature-1800℃ thermal shock cycle test, where (a), (b), and (c) are cross-sectional views at different scales. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0031] Example 1 A 3D printing additive manufacturing method 10 Surface treatment methods for the inner wall of W alloy flow channels, for additive manufacturing Ta 10 The flow channel of the W alloy tubular sample underwent abrasive flow polishing, including the following steps: I. Preparation of abrasive slurry 1. Initial test of Ta 10 The average surface roughness of the flow channel in the W alloy pipe sample was 28.14 μm. This was achieved using additively manufactured Ta... 10 Six W alloy pipe samples (70×Φ4mm, wall thickness 1mm) were placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes. The ultrasonic frequency was controlled at 45KHz and the power at 350W to remove impurities and oil stains adhering to the surface of the pipe samples.

[0032] 2. After ultrasonic cleaning, dry the sample and then immerse it in a mixed acid solution at 48°C (the mixed acid solution includes hydrochloric acid and nitric acid, both with a concentration of 90 g·L⁻¹). -1 The sample was acid-washed in a solution of hydrochloric acid and nitric acid in a volume ratio of 5:2 for 9 minutes to remove the oxide layer on the surface of the pipe fitting, until the surface turned slightly black and produced dense bubbles, exposing the fresh substrate surface. After completion, vacuum drying was performed in preparation for subsequent abrasive flow polishing of the inner wall of the pipe fitting flow channel.

[0033] 3. SiC+BN abrasive particles with particle sizes of 0.6-0.7μm, 1.4-2.8μm, 3-3.8μm, and 5.4-6.5μm (SiC to BN abrasive particles in a mass ratio of 3:2) were mixed in deionized water at a mass ratio of 8:15:22:55. Then, 0.55% (w / w) of sodium polyacrylate and ammonium polyacrylate (sodium polyacrylate to ammonium polyacrylate in a mass ratio of 1:1, with water as the solvent) were added as a dispersant to prevent the mixed abrasive particles from agglomerating. After thorough mixing, 0.35% (w / w) of citric acid solution was added to adjust the pH to 7-8. Subsequently, an appropriate amount of anhydrous ethanol was added to obtain a mixed slurry of the abrasive particles. In the above reagents, the dispersant solution accounted for 0.2% (w / w) of the final mixed slurry, and the anhydrous ethanol accounted for 3% (w / w) of the mixed slurry.

[0034] The mixed abrasive slurry was ultrasonically dispersed for 15 minutes at a frequency of 45 kHz and a power of 350 W. Then, it was ball-milled in a planetary ball mill at 250 rpm for 10 hours to obtain a SiC+BN abrasive slurry with a mass fraction of 46%.

[0035] The abrasive slurry prepared by the method in this embodiment has a good density (3.1 g·cm³). -3 ), viscosity (9.4 mPa·s) state.

[0036] II. Abrasive Flow Surface Polishing This 3D printed additive manufacturing piece 10 W alloy pipe fittings are fixed with special clamps. The abrasive mixture slurry is fed into the pipe fitting channel for abrasive flow surface polishing using a double-end feeding method (both the inlet and outlet ends are fed). The processing time is 15 minutes and the load pressure applied during feeding is 65 MPa.

[0037] The roughness of the inner wall of the flow channel was measured after polishing using a Wyko-NT9100 optical profilometer, and the results are as follows: Figure 1-2 As shown, the surface roughness of the middle section of the 3D-printed additively manufactured Ta10W alloy pipe was significantly reduced from 28.14 μm to 3.22 μm. Additionally, the surface roughness of the inner wall of the feed section was 3.39 μm, and the surface roughness of the inner wall of the discharge section was 3.18 μm. The roughness of the polished inner wall of the pipe is relatively uniform and reaches a machining level of Ra3.2. The good and uniform surface roughness distribution and unobstructed pipe flow after machining meet the requirements of practical applications.

[0038] For abrasive flow surface polishing, a specific concentration of hydrochloric acid is used to precisely control the acid washing degree. This effectively removes the oxide layer from the sample surface while avoiding excessive corrosion, exposing the pure substrate and providing favorable conditions for subsequent abrasive flow polishing. Specifying SiC+BN abrasives according to a certain particle size and corresponding mass ratio improves the precision of abrasive flow polishing while preventing sedimentation due to excessively large abrasives or agglomeration and sedimentation due to excessively small abrasives with excessive specific surface area. Compared to single-size abrasives or improperly proportioned mixed abrasives, this method allows for action on the inner wall surface at different scales during polishing, resulting in a more uniform polishing effect. Furthermore, among the four particle sizes, smaller abrasives can aid flow to larger abrasives, thereby reducing slurry viscosity and ensuring the overall fluidity of the slurry during operation. In the dispersion stage, this invention employs a combination of ultrasonic dispersion at 350W power and 45KHz frequency for ≥12 minutes and ball mill dispersion at 250rpm for 10 hours. This combination ensures more uniform and thorough dispersion of the abrasive particles, improving abrasive activity and polishing efficiency. The abrasive flow processing method using two-end feeding avoids the problem of inconsistent cutting amounts and polishing effects between the feed and discharge sections, which is present in single-end feeding processing. Through this abrasive flow processing technology, the roughness of the inner wall of the pipe channel decreased from Ra28.14 to Ra3.2, resulting in excellent processing results.

[0039] For 3D additive manufacturing Ta 10 To address the issue of W alloys being prone to oxidation at high temperatures, Example 1 provides a method for preparing a B4C-(Gd,Ho,Yb)2O3 composite-modified MoSi2 high-temperature oxidation-resistant ceramic coating, comprising the following steps: 1) The 3D additive manufacturing process Ta after the above abrasive flow surface polishing treatment 10 The W alloy pipe samples were cleaned by rinsing with deionized water and dried at 120°C. The samples were then placed in a beaker containing anhydrous ethanol for ultrasonic cleaning to thoroughly remove any residual polishing liquid and impurities from the surface. The samples were then vacuum dried at 70°C for 12 hours with a vacuum degree of ≤133Pa.

[0040] 2) A two-step slurry sintering method was adopted in Ta 10 A composite coating was prepared on the surface of the W alloy pipe sample and the inner wall of the flow channel: 2.1 First Step Slurry Sintering: Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder were mixed in a mass ratio of 70:4:5:21; the mass ratio of Gd2O3, Ho2O3, and Yb2O3 in the Gd2O3-Ho2O3-Yb2O3 powder was 1:1:1. Anhydrous ethanol was used as the solvent system, and the total mass ratio of Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder to the volume ratio of anhydrous ethanol was 1 g:1 ml. Polyvinyl butyral was added as a binder (the total mass ratio of Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder to the binder was 1:0.01). The mixture was mixed for 10 hours at 250 rpm using a planetary ball mill. The Ta powder was then pretreated in step 1) using an impregnation-coating method (one dip coating, 5-8 seconds drying). 10 The W alloy sample surface and inner surface of the flow channel were uniformly coated with a slurry and dried in a vacuum drying oven at 70°C. After drying, the sample was placed in a vacuum tungsten mesh sintering furnace for high-temperature sintering for 2 hours, with the vacuum level of the tungsten mesh sintering furnace guaranteed to be ≤10. -3 Pa, sintering temperature 1710℃, heating rate 5℃ / min, finally forming a Mo-B4C-(Gd,Ho,Yb)2O3 pre-sintered transition layer; 2.2 Second step slurry sintering: A composite powder was prepared using high-purity Si powder, SiC powder, SmO2 powder, and NaF powder in a mass ratio of 38:46:7:9. Anhydrous ethanol was used as the solvent (the total mass of Si powder, SiC powder, SmO2 powder, and NaF powder to the volume ratio of anhydrous ethanol was 1 g:3 ml). The mixture was then ground in a planetary ball mill at 250 rpm for 10 h. The same impregnation-coating method was then used to coat and dry the sample. The sample obtained in step 2.1 was placed in a vacuum tungsten mesh sintering furnace for reactive melting and infiltration. A diffusion-controlled process (sintering temperature 1710℃, heating rate 5℃ / min) was used to promote the penetration of Si elements into the pre-sintered layer, ultimately resulting in Si in the Ta... 10 A B4C / (Gd,Ho,Yb)2O3 / MoSi2-TaSi2-Ta5Si3 composite ceramic coating with a gradient structure was formed on the surface of the W alloy sample, with a coating thickness of approximately 65 μm. Morphological characterization confirmed that the B4C powder and Gd2O3-Ho2O3-Yb2O3 powder-doped composite ceramic coating exhibits a three-layer structure from the outside to the inside, with the main phase being B4C / (Gd,Ho,Yb)2O3 / MoSi2-TaSi2-Ta5Si3, and Yb2O3 being dispersedly distributed in the outer layer of MoSi2.

[0041] The cross-sectional morphology of the final prepared sample was observed before the high-temperature oxidation test. It is evident that the coating is tightly bonded to the substrate material. The coating thickness is approximately 65 μm.

[0042] The ultra-high temperature oxidation resistance of ceramic coatings was studied using an oxidation testing device. The temperature was rapidly increased to 1400℃ by applying a high current and held for 30 min. Then, the temperature was increased to 1450℃ at a rate of 10℃ / min and held for 5 min, while the coating condition was observed simultaneously to ensure no failure occurred during each heating and holding phase. If no failure occurred during the holding period, this process was repeated until 1800℃. The oxidation life of the coating was then calculated until obvious failure symptoms appeared (black spots, excessive white smoke, and coating peeling). The results are as follows: Figure 3-5 As shown in the figure. After the above tests, it was determined that the static oxidation resistance life of the ceramic coating at 1800℃ is 10.5h, and the coating can withstand 577 cycles in the thermal shock cycle from room temperature to 1800℃, which shows that its performance is excellent.

[0043] Example 2 The difference from Example 1 is as follows: The mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder used in the second sintering step of Example 1 is 40:46:5:9.

[0044] The rest is the same as in Example 1, and will not be repeated here.

[0045] After the above tests, it was determined that the static oxidation resistance life of the ceramic coating at 1800℃ is 9.0h, and the coating can withstand 486 cycles in the thermal shock cycle from room temperature to 1800℃, which shows that its performance is excellent.

[0046] Example 3 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the mass ratios of the four particle size levels of SiC+BN mixed abrasive particles (0.6-0.7μm, 1.4-2.8μm, 3-3.8μm, and 5.4-6.5μm) are 5:10:25:65, respectively. The rest is the same as in Example 1 and will not be repeated.

[0047] Example 4 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the mass ratios of the four particle size levels of SiC+BN mixed abrasive particles (0.6-0.7μm, 1.4-2.8μm, 3-3.8μm, and 5.4-6.5μm) are 12:24:26:38, respectively. The rest is the same as in Example 1 and will not be repeated.

[0048] Example 5 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the mass ratios of the four particle size levels of SiC+BN mixed abrasive particles (0.6-0.7μm, 1.4-2.8μm, 3-3.8μm, and 5.4-6.5μm) are 4:26:20:50, respectively. The rest is the same as in Example 1 and will not be repeated.

[0049] Example 6 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the mass ratios of the four particle size levels of SiC+BN mixed abrasive particles (0.6-0.7μm, 1.4-2.8μm, 3-3.8μm, and 5.4-6.5μm) are 15:25:20:40, respectively. The rest is the same as in Example 1 and will not be repeated.

[0050] Example 7 In this embodiment, in step 3 of preparing the abrasive mixture slurry, the mass ratio of SiC abrasive particles to BN abrasive particles is 1:1, and the rest is the same as in Example 1, so it will not be repeated here.

[0051] Example 8 In this embodiment, in step 3 of preparing the abrasive mixture slurry, the mass ratio of SiC abrasive particles to BN abrasive particles is 2:3, and the rest is the same as in Example 1, so it will not be repeated here.

[0052] Example 9 In this embodiment, in step 2 of preparing the abrasive mixture slurry, the volume ratio of hydrochloric acid to nitric acid is 1:1, and the rest is the same as in Example 1, so it will not be repeated here.

[0053] Example 10 In this embodiment, in step 2 of preparing the abrasive mixture slurry, the volume ratio of hydrochloric acid to nitric acid is 5:3, and the rest is the same as in Example 1, so it will not be repeated here.

[0054] Example 11 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the weight ratio of sodium polyacrylate to ammonium polyacrylate is 3:2, and the rest is the same as in Example 1, so it will not be repeated here.

[0055] Example 12 In this embodiment, in step 3 of preparing the abrasive mixture slurry in step one, the weight ratio of sodium polyacrylate to ammonium polyacrylate is 2:3, and the rest is the same as in Example 1, so it will not be repeated here.

[0056] Comparative Example 1 The difference from Example 1 is as follows: In step 2 of preparing the abrasive slurry, the mixed acid (hydrochloric acid + nitric acid) solution contains 70 g·L⁻¹ -1 .

[0057] The rest is the same as in Example 1, and will not be repeated here.

[0058] Comparative Example 2 The difference from Example 1 is as follows: In step 2 of preparing the abrasive slurry, the mixed acid (hydrochloric acid + nitric acid) solution contains 100 g·L⁻¹ -1 .

[0059] The rest is the same as in Example 1, and will not be repeated here.

[0060] In relation to Ta 10 When pickling the surface of W alloy pipe fittings, the content of the mixed acid (hydrochloric acid + nitric acid) solution used in Comparative Example 1 was insufficiently removed under the above conditions. In Comparative Example 2, the content of the mixed acid (hydrochloric acid + nitric acid) solution completely removed the oxide layer under the above conditions, but the surface of the sample showed severe unevenness due to corrosion caused by the strong acidity, which was detrimental to subsequent polishing. Therefore, this invention ultimately selected a mixed acid (hydrochloric acid + nitric acid) solution content of 90 g·L⁻¹ for pickling. -1 .

[0061] Comparative Example 3 The difference from Example 1 is as follows: In the prepared SiC+BN abrasive slurry, the total mass fractions of SiC and BN were 40% and 43%, respectively.

[0062] The rest is the same as in Example 1, and will not be repeated here.

[0063] Comparative Example 4 The difference from Example 1 is as follows: The total mass fractions of SiC and BN in the prepared SiC+BN abrasive slurry were 49% and 52%, respectively.

[0064] The rest is the same as in Example 1, and will not be repeated here.

[0065] In relation to Ta 10 When performing abrasive flow polishing on the internal flow channel surface of W alloy pipe fittings, the SiC+BN mixed abrasive slurry prepared in Comparative Example 3 showed poor polishing effect on the flow channel surface under the above conditions; the SiC+BN mixed abrasive slurry prepared in Comparative Example 4, under the above conditions, caused accumulation and blockage at the outlet end due to the slurry's high viscosity. See Table 1 for details.

[0066] Table 1. Flow channel polishing conditions corresponding to different mass fractions of SiC+BN mixed abrasive slurries.

[0067] Comparative Example 5 The difference from Example 1 is as follows: Change the feed pressure to 40MPa or 55MPa.

[0068] The rest is the same as in Example 1, and will not be repeated here.

[0069] Comparative Example 6 The difference from Example 1 is as follows: Change the feed pressure to 71MPa or 80MPa.

[0070] The rest is the same as in Example 1, and will not be repeated here.

[0071] Comparative Example 7 The difference from Example 1 is as follows: Change the feeding method to single-end feeding.

[0072] The rest is the same as in Example 1, and will not be repeated here.

[0073] Test results after polishing at a feed pressure below 60 MPa showed that, under the same processing conditions, the reduction in surface roughness inside the pipe was small at low-pressure feed, with a final roughness Ra > 8 μm; while at pressures above 70 MPa, severe cutting occurred on the pipe surface. Therefore, a feed pressure of 60-70 MPa was ultimately selected. Furthermore, with other parameters remaining constant, single-end feeding resulted in material accumulation at the pipe port, while double-end feeding ensured smooth pipe flow; therefore, double-end feeding was ultimately chosen. The results are shown in Table 2.

[0074] Table 2. Polishing of flow channels corresponding to different feeding methods and feeding pressures.

[0075] Comparative Example 8 The difference from Example 1 is as follows: During sintering of the slurry, vacuum tungsten mesh sintering is carried out at a high-temperature melting temperature of 1650℃ (i.e., the sintering temperature in the first and second steps of slurry sintering); the melting time is 2 hours and the heating rate is 5℃ / min.

[0076] The rest is the same as in Example 1, and will not be repeated here.

[0077] Comparative Example 9 The difference from Example 1 is as follows: During sintering of the slurry, vacuum tungsten mesh sintering is carried out at a high-temperature melting temperature of 1750℃ (i.e., the sintering temperature in the first and second steps of slurry sintering); the melting time is 2 hours and the heating rate is 5℃ / min.

[0078] The rest is the same as in Example 1, and will not be repeated here.

[0079] Compared to Example 1, the vacuum sintering temperatures in Comparative Examples 8 and 9 were either too high or too low, both of which resulted in poor bonding between the final coating and the substrate material. Furthermore, at lower temperatures, the coating structure was not dense enough. Therefore, a high-temperature sintering temperature of 1710°C was ultimately chosen for vacuum tungsten mesh sintering during slurry sintering.

[0080] Comparative Example 10 The difference from Example 1 is as follows: In Example 1, the modified element Gd2O3-Ho2O3-Yb2O3 powder used in the first step of slurry sintering was replaced with Ho2O3.

[0081] The rest is the same as in Example 1, and will not be repeated here.

[0082] Comparative Example 11 The difference from Example 1 is as follows: In Example 1, the modified element Gd2O3-Ho2O3-Yb2O3 powder used in the first step of slurry sintering was replaced with Y2O3.

[0083] The rest is the same as in Example 1, and will not be repeated here.

[0084] Comparative Example 12 The difference from Example 1 is as follows: In Example 1, the modified element Gd2O3-Ho2O3-Yb2O3 powder used in the first step of slurry sintering was replaced with La2O3.

[0085] The rest is the same as in Example 1, and will not be repeated here.

[0086] Comparative Example 13 The difference from Example 1 is as follows: In Example 1, the modified element Gd2O3-Ho2O3-Yb2O3 powder used in the first step of slurry sintering was replaced with Ga2O3.

[0087] The rest is the same as in Example 1, and will not be repeated here.

[0088] Compared with Example 1, the modified elements introduced into the modified coatings in Comparative Examples 10-13 are different and relatively singular. Their properties are measured as shown in Table 3.

[0089] Table 3 High-temperature test results for different coatings

[0090] Comparative Example 14 The difference from Example 1 is as follows: In Example 1, the mass ratio of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder used in the first sintering step was 74:4:1:21, and the mass fraction of B4C powder was 1%.

[0091] The rest is the same as in Example 1, and will not be repeated here.

[0092] Comparative Example 15 The difference from Example 1 is as follows: In Example 1, the mass ratio of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder used in the first sintering step was 72:4:3:21, and the mass fraction of B4C powder was 3%.

[0093] The rest is the same as in Example 1, and will not be repeated here.

[0094] Comparative Example 16 The difference from Example 1 is as follows: In Example 1, the mass ratio of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder used in the first sintering step was 68:4:7:21, and the mass fraction of B4C powder was 7%.

[0095] The rest is the same as in Example 1, and will not be repeated here.

[0096] Compared to Example 1, the mass ratios introduced by the modified coating B4C in Comparative Examples 14-16 are different. The performance of each product was measured, as shown in Table 4.

[0097] Table 4. High-temperature test results for B4C coatings with different mass ratios.

[0098] Comparative Example 17 The difference from Example 1 is as follows: In the second sintering step of Example 1, the mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder used is 42:46:3:9, and the mass fraction of SmO2 powder is 3%.

[0099] The rest is the same as in Example 1, and will not be repeated here.

[0100] Comparative Example 18 The difference from Example 1 is as follows: In the second sintering step of Example 1, the mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder used is 36:46:9:9, and the mass fraction of SmO2 powder is 9%.

[0101] The rest is the same as in Example 1, and will not be repeated here.

[0102] Compared to Example 1, the mass ratio introduced by the modified SmO2 coating in Comparative Examples 17-18 was different. The performance of each product was measured and is shown in Table 5.

[0103] Table 5. High-temperature test results for SmO2 coatings with different mass ratios.

[0104] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0105] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for preparing a surface coating, characterized in that, Includes the following steps, The surface-treated workpiece is coated with an inner layer slurry, dried, and then vacuum sintered to obtain a workpiece with a transition layer. The inner layer slurry comprises Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder, with a mass ratio of Mo powder, Si powder, B4C powder, and Gd2O3-Ho2O3-Yb2O3 powder of 60-70:4-5:3-6:10-25. In the Gd2O3-Ho2O3-Yb2O3 powder, the mass ratio of Gd2O3, Ho2O3, and Yb2O3 is 0.8-1.2:0.8-1.2:0.8-1.

2. The workpiece with the transition layer is coated with an outer layer slurry, dried, and vacuum sintered to obtain an additive surface coating; the outer layer slurry includes Si powder, SiC powder, SmO2 powder and NaF powder, and the mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder is 38-50:40-50:5-8:6-10. The mass ratio of Mo powder, Si powder, B4C powder and Gd2O3-Ho2O3-Yb2O3 powder is 70:4:5:21, and the mass ratio of Gd2O3, Ho2O3 and Yb2O3 in the Gd2O3-Ho2O3-Yb2O3 powder is 1:1:

1. The mass ratio of Si powder, SiC powder, SmO2 powder and NaF powder is 38:46:7:9; The vacuum sintering temperature is 1680-1720℃; The surface treatment steps are as follows: The workpiece is cleaned, dried, pickled, dried again, and then surface polished using a mixed slurry. The mixed slurry includes abrasive particles, a dispersant, and anhydrous ethanol, with the pH controlled at 7-8. The abrasive particles are SiC and BN particles with particle sizes of 0.6-0.7 μm, 1.4-2.8 μm, 3-3.8 μm, and 5.4-6.5 μm. The mass ratio of abrasive particles with particle sizes of 0.6-0.7 μm, 1.4-2.8 μm, 3-3.8 μm, and 5.4-6.5 μm is 4-15:10-26:20-50:38-65. The acids used for pickling include hydrochloric acid and nitric acid, with concentrations of 85-95 g·L⁻¹. -1 .

2. The preparation method according to claim 1, characterized in that, The solvent for the inner layer slurry is anhydrous ethanol, and it also includes a binder; the solvent for the outer layer slurry is anhydrous ethanol.

3. The preparation method according to claim 2, characterized in that, The adhesive is polyvinyl butyral.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the abrasive grains with particle sizes of 0.6-0.7μm, 1.4-2.8μm, 3-3.8μm and 5.4-6.5μm is 8:15:22:

55.

5. The preparation method according to claim 1, characterized in that, The volume ratio of hydrochloric acid to nitric acid is 1-5:1-3; the dispersant is one or more of sodium polyacrylate and ammonium polyacrylate.

6. A tungsten-tantalum alloy, characterized in that, The surface of the tungsten-tantalum alloy is a surface coating prepared by the preparation method according to any one of claims 1-5.

Images