A ta-n enhanced high-entropy alloy spray layer and a preparation method thereof

Abstract

This invention provides a TaN-reinforced high-entropy alloy spray-welded layer and its preparation method, belonging to the field of material surface modification technology. The invention comprises 0.1%–5% TaN and 95%–99.9% high-entropy alloy matrix FeCoNiCrMo, and is prepared using in-situ or non-in-situ synthesis methods. The corrosion current density of the alloy spray-welded layer of this invention is 1.472 × 10⁻⁶. ‑7 ~2.131×10 ‑7 Acm 2 The self-corrosion potential is -0.132 to -0.104 V. SCE The pitting potential is 0.548–0.972 V. SCE It has a high corrosion potential and low corrosion current density. Experimental results show that its corrosion resistance, microhardness and wear resistance are significantly improved compared with the original high-entropy alloy matrix. At the same time, Ta refines the grains and enhances the comprehensive mechanical properties. Moreover, the preparation process is simple and highly repeatable.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and in particular to a TaN-reinforced high-entropy alloy spray coating and its preparation method. Background Technology

[0002] High-entropy alloys are unique metallic alloys produced by combining five or more metals in equimolar or near-equimolar ratios at high concentrations. Under high configurational entropy conditions, they form a single-phase solid solution structure and exhibit superior properties compared to conventional alloys in terms of corrosion resistance, wear resistance, high hardness, and superplasticity. They can demonstrate excellent performance in the preparation of composite sprayed welding layers while ensuring economic practicality and have great development potential.

[0003] Current research and applications of high-entropy alloys mainly focus on the formation of new alloy systems through different metal combinations, the influence of element content on system performance, and preparation methods. Due to the high cost of high-entropy alloy bulk materials, their application in spray-welded layers as a surface modification technology has significant practical implications. Adding Ta as a reinforcing phase to high-entropy alloy spray-welded layers can greatly improve their corrosion resistance, and the in-situ synthesis reaction can effectively enhance the overall mechanical properties of the composite spray-welded layer. Summary of the Invention

[0004] The purpose of this invention is to provide a TaN-reinforced high-entropy alloy spray coating and its preparation method, which can further improve corrosion resistance, protect materials and extend their service life and performance, and the preparation process is simple and highly repeatable.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a TaN-reinforced high-entropy alloy spray coating, comprising the following steps:

[0007] 1) Preheat the metal substrate, remove the oxide layer, and then clean it;

[0008] 2) Weigh the metal powder, vacuum melt it, refine it, and cast it to obtain high-entropy alloy rods. Then, vacuum atomize the high-entropy alloy rods to make powder, sieve it, and dry it to obtain high-entropy alloy matrix powder.

[0009] 3) Put the high-entropy alloy matrix powder Ta powder into a mixer and mix evenly, then dry to obtain a high-entropy alloy spray welding mixture;

[0010] 4) High-entropy alloy spray welding mixture is sprayed onto a preheated metal substrate using plasma spray welding equipment to obtain a TaN-reinforced high-entropy alloy spray welding layer.

[0011] Preferably, the mass percentage of TaN in the TaN-reinforced high-entropy alloy spray coating is 0.1% to 5.0%, and the mass percentage of the high-entropy alloy matrix is ​​95% to 99.9%.

[0012] Preferably, the TaN-reinforced high-entropy alloy spray coating is prepared by in-situ synthesis or non-in-situ synthesis.

[0013] Preferably, the metal substrate in step 1) is 3Cr2Mo mold steel; the preheating temperature is 300-400℃.

[0014] Preferably, the metal powder in step 2) is Fe, Co, Ni, Cr, and Mo metal powder, and the mass percentage of the metal powder is: Fe 15.0-20.0%; Co 15.0-20.0%; Ni 18.0-23.0%; Cr 14.0-19.0%; Mo 25.0-30.0%, and the sum of the mass percentages of each metal powder is 100%.

[0015] Preferably, in step 2), the vacuum degree of the vacuum melting is ≤100Pa, and the vacuum melting time is 3-5h; the refining temperature is 1500-1600℃, the number of times is 2-5, and the refining time for each time is 2-5h; the vacuum atomizing inert gas is argon or nitrogen, the vacuum degree is ≤0.1Pa, the power is 25-40kw, the atomization pressure is 4-8MPa, and the bar rotation speed is 15-25rpm; the drying temperature is 90-150℃, the drying time is 4-6h, and the bar is turned over every 2h.

[0016] Preferably, the high-entropy alloy powder in step 2) has a purity of over 99% and a particle size of 150-325 mesh.

[0017] Preferably, the mass percentage of Ta powder in step 3) is 0.1% to 5%; the purity of the Ta powder is above 99% and the particle size of the powder is 150 to 325 mesh; the drying temperature is 90 to 150°C and the drying time is 4 to 6 hours, with the powder being turned over once every 2 hours.

[0018] Preferably, the parameters of the plasma spraying equipment in step 4) are: transfer arc voltage 15-18V; transfer arc current 130-150A; scanning speed 25-30mm / min; plasma arc length 20-22mm; plasma gas flow rate 9-10L / min; shielding gas flow rate 2.0-2.5L / min; welding torch vertical swing amplitude: 30-60mm; spray distance: 8-10mm; nitrogen is used for the ion gas, shielding gas, and powder feeding gas in the plasma spraying process.

[0019] The present invention also provides a TaN-reinforced high-entropy alloy spray coating prepared by the above preparation method.

[0020] The selection of the reinforcing phase and the actual elemental content are fundamental guarantees for the excellent performance of high-entropy alloy spray-welded layers. The main objective of this invention is to obtain a spray-welded layer with good corrosion resistance. Therefore, a FeCoNiCrMo-based high-entropy alloy with good corrosion resistance is selected as the matrix. Simultaneously, Ta is added to generate TaN in situ at high temperature using nitrogen as a protective gas. When exposed to a corrosive environment, TaN forms a stable, thin, dense, and pinhole-free surface oxide layer with strong chemical bonds, slowing down the corrosion rate. It can also self-cures when the surface layer is damaged. At the same time, Ta inhibits grain growth, and the alloy grain size decreases regularly with increasing Ta content, refining the grains and significantly altering the microstructure of the matrix, thus playing a role in particle reinforcement and effectively improving the overall performance of the spray-welded layer.

[0021] The corrosion current density range of the TaN-reinforced high-entropy alloy spray-welded layer provided by this invention is 1.472 × 10⁻⁶. -7 ~2.131×10 -7 Acm 2 The self-corrosion potential is lower than that of the original FeCoNiCrMo high-entropy alloy matrix; the self-corrosion potential is -0.132 to -0.104 V. SCE Pitting potential: 0.548–0.972 V SCE Both are higher than the original FeCoNiCrMo high-entropy alloy matrix. According to the neutral salt spray test, the unit area mass change of the high-entropy alloy sprayed layer sample in this invention is 0.287g, which is significantly reduced compared with the original sprayed layer. This indicates that the high-entropy alloy sprayed layer of this invention has excellent corrosion resistance and can further improve corrosion resistance. At the same time, Ta refines the grains, strengthens the comprehensive mechanical properties, and significantly improves the microhardness and wear resistance compared with the substrate. It can protect the material and extend its service life and performance. Moreover, the preparation process is simple and highly repeatable. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for preparing the TaN-reinforced high-entropy alloy spray coating of the present invention;

[0023] Figure 2 The images show the microstructure of the (FeCoNiCrMo)100-x(TaN)x high-entropy alloy spray-welded layers from Examples 1 to 3 in Example 4, where (a) is the microstructure without TaN, (b) is the microstructure with 0.5% TaN added in Example 1, (c) is the microstructure with 1% TaN added in Example 2, and (d) is the microstructure with 1.5% TaN added in Example 3.

[0024] Figure 3This describes the change in mass per unit area of ​​the substrate of the (FeCoNiCrMo)100-x(TaN)x high-entropy alloy in Examples 1-3 of Example 4 before and after the neutral salt spray test. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. These embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0026] Example 1

[0027] A TaN-reinforced high-entropy alloy spray coating: its composition is 99.5% Fe. 17 Co 19 Ni 20 Cr 16 Mo 28 0.5% TaN was added to the matrix in situ. Fe, Co, Ni, Cr, Mo metal powders and 325-mesh Ta powder were weighed according to the composition of the TaN-reinforced high-entropy alloy spray coating.

[0028] like Figure 1 As shown, the method for preparing the TaN-reinforced high-entropy alloy spray-welded layer in this embodiment is as follows:

[0029] 1) Cut the 3Cr2Mo mold steel plate into plates with a thickness of 10mm, a width of 50mm, and a length of 100mm; then use a milling machine to cut and grind the surface of the steel plate to remove the surface oxide layer until the metal luster is exposed; then use potassium hydroxide degreasing agent and cleaning aid organic complexing agent to degrease and clean the steel plate at a cleaning temperature of about 25℃. After cleaning, rinse with clean water, and finally wipe the surface of the steel plate with anhydrous ethanol and dry it for later use.

[0030] 2) Weighed Fe, Co, Ni, Cr, and Mo metal powders were mixed and melted in a vacuum induction furnace for 4 hours. During the process, the furnace was pressurized to a vacuum level ≤100 Pa. The mixture was then refined three times in a crucible at 1500℃ for 2 hours each time. Afterward, the mixture was poured into a mold to obtain a high-entropy alloy rod for vacuum atomization. The high-entropy alloy rod was installed in an electrode induction gas atomization powder-making device, and a vacuum of 8×10⁻⁶ was applied. -3 After Pa, argon gas is injected into the atomization chamber for melting. The power is 28kw and the bar rotation speed is 15rpm. When the molten material drips, high-pressure argon gas is used to atomize the molten material. The atomization pressure is 4MPa. The powder with a sieve particle size of 150-325 mesh is dried at 90℃ for 6h and turned over once every 2h to obtain high-entropy alloy matrix powder.

[0031] 3) Mix the high-entropy alloy matrix powder and the weighed Ta powder in a mixer until uniform, dry at 120°C for five hours, turning it over every 2 hours to obtain the high-entropy alloy spray welding mixture.

[0032] 4) Load the high-entropy alloy spray welding mixture into the powder feeding tank of the instrument, preheat the 3Cr2Mo mold steel plate treated in step 1) to 300°C, and spray it onto the preheated 3Cr2Mo mold steel plate in a nitrogen atmosphere using a plasma spray welding device to obtain a TaN-reinforced high-entropy alloy spray welding layer.

[0033] The specific parameters of the plasma spraying equipment are set as follows: transfer arc voltage 15V; transfer arc current 130A; scanning speed 25mm / min; plasma arc length 20mm; plasma gas flow rate 9L / min; shielding gas flow rate 2.0L / min; welding torch vertical swing amplitude: 30mm; spray distance: 8mm.

[0034] Electrochemical testing results showed that the corrosion current density of the coating in a 3.5% NaCl solution was 2.131 × 10⁻⁶. - 7 Acm 2 The self-corrosion potential is -0.132VSCE.

[0035] Example 2

[0036] A TaN-reinforced high-entropy alloy spray coating, the composition of which is 99% Fe. 17 Co 19 Ni 20 Cr 16 Mo 28 1% TaN was added to the matrix in situ. Fe, Co, Ni, Cr, Mo metal powders and 200-mesh Ta powder were weighed according to the composition of the TaN-reinforced high-entropy alloy spray coating.

[0037] The method of Example 1 was adopted, with the following differences from the preparation method of Example 1: refining temperature 1550℃, vacuum atomization power of high-entropy alloy bar 35kw, bar rotation speed 20rpm, atomization pressure 6MPa, drying temperature 130℃, drying for 5h; step 1) the treated 3Cr2Mo mold steel plate was preheated to 350℃; step 2) the specific parameters of the plasma spraying equipment were set as follows: transfer arc voltage 16V; transfer arc current 140A; scanning speed 26mm / min; plasma arc length 21mm; plasma gas flow rate 9.5L / min; shielding gas flow rate 2.3L / min; welding torch vertical swing amplitude: 40mm; spray distance: 9mm.

[0038] Electrochemical test results show that the corrosion current density of this coating is 1.472 × 10⁻⁶ in a 3.5% NaCl solution. - 7 Acm 2 The self-corrosion potential is -0.104VSCE.

[0039] Example 3

[0040] A TaN-reinforced high-entropy alloy spray coating, the composition of which is 98.5% Fe. 17 Co 19 Ni 20 Cr 16 Mo 28 And 1.5% TaN, the TaN is added to the matrix in situ synthesis, and Fe, Co, Ni, Cr, Mo metal powder and 150 mesh Ta powder are weighed according to the composition of TaN-reinforced high-entropy alloy spray welding layer.

[0041] The method of Example 1 was adopted, with the following differences from the preparation method of Example 1: refining temperature 1600℃, vacuum atomization power of high-entropy alloy bar 40kw, bar rotation speed 25rpm, atomization pressure 8MPa, drying temperature 150℃, drying for 4h; step 1) the treated 3Cr2Mo mold steel plate was preheated to 400℃; step 2) the specific parameters of the plasma spraying equipment were set as follows: transfer arc voltage 18V; transfer arc current 150A; scanning speed 30mm / min; plasma arc length 22mm; plasma gas flow rate 10L / min; shielding gas flow rate 2.5L / min; welding torch vertical swing amplitude: 50mm; spray distance: 10mm.

[0042] Electrochemical test results show that the corrosion current density of this coating is 1.725 × 10⁻⁶ in a 3.5% NaCl solution. - 7 Acm 2 The self-corrosion potential is -0.119VSCE.

[0043] Example 4

[0044] The microstructure of the TaN-reinforced high-entropy alloy spray-welded layers prepared in Examples 1-3 was measured, and the microstructure results are as follows: Figure 2 As shown.

[0045] The TaN-reinforced high-entropy alloy spray coatings prepared in Examples 1-3 were subjected to neutral salt spray tests, and the results are as follows: Figure 3 As shown.

[0046] Depend on Figures 2-3 It can be seen that the TaN-reinforced high-entropy alloy spray coating described in this invention can further improve corrosion resistance, with a corrosion current density range of 1.472 × 10⁻⁶.-7 ~2.131×10 -7 Acm 2 The self-corrosion potential is lower than that of the original FeCoNiCrMo high-entropy alloy matrix; the self-corrosion potential is -0.132 to -0.104 V. SCE Pitting potential: 0.548–0.972 V SCE Both are higher than the original FeCoNiCrMo high-entropy alloy matrix. According to the neutral salt spray test, the unit area mass change of the high-entropy alloy sprayed layer sample in this invention is 0.287g, which is significantly reduced compared with the original sprayed layer. This indicates that the high-entropy alloy sprayed layer of this invention has excellent corrosion resistance. At the same time, Ta refines the grains, and the microhardness and wear resistance are significantly improved compared with the substrate, thus enhancing the comprehensive mechanical properties.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a TaN-reinforced high-entropy alloy spray-welded layer, characterized in that, Includes the following steps: 1) Clean and preheat the metal substrate after removing the oxide layer; 2) Weigh the metal powder, vacuum melt it, refine it, and cast it to obtain high-entropy alloy rods. Then, vacuum atomize the high-entropy alloy rods to make powder, sieve it, and dry it to obtain high-entropy alloy matrix powder. 3) Mix the high-entropy alloy matrix powder and Ta powder in a mixer until homogeneous, then dry to obtain a high-entropy alloy spray welding composite material; 4) Using plasma spraying equipment, the high-entropy alloy spraying mixture is sprayed onto the preheated metal substrate in step 1) to obtain a TaN-reinforced high-entropy alloy spraying layer. The TaN-reinforced high-entropy alloy spray coating contains 0.1% to 5.0% TaN by mass, and the high-entropy alloy matrix contains 95% to 99.9% by mass. The TaN-reinforced high-entropy alloy spray-welded layer was prepared by in-situ synthesis. Step 2) The metal powder is Fe, Co, Ni, Cr, and Mo metal powder, and the mass percentage of the metal powder is: Fe 15.0~20.0%; Co 15.0~20.0%; Ni 18.0~23.0%; Cr 14.0~19.0%; Mo 25.0~30.0%, and the sum of the mass percentages of each metal powder is 100%. Step 4) The parameters of the plasma spraying equipment are as follows: transfer arc voltage 15~18V; transfer arc current 130~150A; scanning speed 25~30mm / min; plasma arc length 20~22mm; plasma gas flow rate 9~10L / min; shielding gas flow rate 2.0~2.5L / min; welding torch vertical swing amplitude: 30~60mm; spray distance: 8~10mm; nitrogen is used for the ion gas, shielding gas and powder feeding gas in the plasma spraying process.

2. The preparation method according to claim 1, characterized in that, Step 1) The metal substrate is 3Cr2Mo mold steel; the preheating temperature is 300~400℃.

3. The preparation method according to claim 1, characterized in that, Step 2) The vacuum degree of the vacuum melting is ≤100Pa, and the vacuum melting time is 3~5h; the refining temperature is 1500~1600℃, the number of times is 2~5, and the refining time is 2~5h each time; the inert gas for vacuum atomization is argon or nitrogen, the vacuum degree is ≤0.1Pa, the power is 25~40kw, the atomization pressure is 4~8MPa, and the bar rotation speed is 15~25rpm; the drying temperature is 90~150℃, the drying time is 4~6h, and the bar is turned over every 2h.

4. The preparation method according to claim 1, characterized in that, Step 2) The high-entropy alloy powder has a purity of over 99% and a particle size of 150~325 mesh.

5. The preparation method according to claim 1, characterized in that, Step 3) The mass percentage of Ta powder is 0.1%~5%; the purity of Ta powder is above 99% and the particle size of the powder is 150~325 mesh; the drying temperature is 90~150℃ and the drying time is 4~6h, with the powder being turned over once every 2h.

6. A TaN-reinforced high-entropy alloy spray coating prepared by the preparation method according to any one of claims 1 to 5.

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