AlCoCrNi high-entropy alloy powder for marine corrosion resistant coating as well as preparation method and application of AlCoCrNi high-entropy alloy powder

Abstract

The invention discloses AlCoCrNi high-entropy alloy powder for a marine corrosion resistant coating, which comprises the following elements in percentage by weight: 15-35% of Al, 15-35% of Cr, 15-35% of Co and 15-35% of Ni, is prepared by a gas atomization method, and has the particle size of 15-53 mu m; the preparation raw materials of the high-entropy alloy powder are metal simple substances Al, Cr, Co and Ni, and the purity of the metal simple substances Al, Cr, Co and Ni is higher than 99.9 wt%. The AlCoCrNi high-entropy alloy powder is prepared through a gas atomization method, and the AlCoCrNi high-entropy alloy powder is good in performance, wide in application range and low in cost. Meanwhile, the invention further discloses a preparation method of the coating, and the preparation method comprises the following specific steps: carrying out vacuum drying treatment on the AlCoCrNii high-entropy alloy powder, polishing the surface of the matrix, carrying out sand blasting on the surface of the matrix, preheating the matrix, spraying HVOF on the surface of the matrix to prepare the high-entropy alloy coating, and carrying out remelting treatment on the matrix. The coating provided by the invention has strong binding force with a matrix and excellent seawater corrosion resistance, and can meet the long-term use of the material in the ocean.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of high-entropy alloy materials, and particularly relates to a high-entropy alloy coating resistant to marine corrosion and a preparation method thereof. Background Art

[0002] Due to its unique physical and chemical properties, the marine environment has become one of the most severe corrosion environments faced by industrial equipment. According to the "Global Corrosion Costs Report" released by the National Association of Corrosion Engineers (NACE) in 2024, the direct economic losses caused by marine corrosion account for 3.4% of the global GDP, and the failure of metal structures such as ships, offshore platforms, and cross-sea bridges accounts for as high as 70%. The root cause of this phenomenon lies in the complex corrosion mechanism triggered by the synergistic action of multiple factors in the marine environment, including electrochemical corrosion, chemical erosion, mechanical wear, and biological fouling.

[0003] As a strong electrolyte solution, seawater has a chloride ion concentration as high as 19 g / L, which significantly damages the passivation film on the metal surface. Taking carbon steel parts as an example, the corrosion rate in 3.5% NaCl solution reaches 0.1 mm / year, and in the splash zone, due to sufficient oxygen, the corrosion rate surges by 5 times to 0.5 mm / year. In addition, under the deep-sea high-pressure environment (>100 MPa), the decrease in the diffusion coefficient of dissolved oxygen triggers the cathodic depolarization reaction, and the probability of local corrosion increases by 3 - 5 times; moreover, there are extreme environmental composite effects such as temperature gradients, ultraviolet radiation, and microbial erosion in the ocean, and the alternating stress (106 times / year) caused by wave loads is coupled with the corrosive medium, resulting in stress-corrosion synergistic damage and a decrease in the fatigue life of the material.

[0004] The current common strategy to extend the service life of carbon steel is to prepare a corrosion-resistant coating on its surface. However, traditional electroplated coatings have problems such as insufficient interfacial bonding performance and serious pollution in the production process, and conventional alloy coatings also have significant limitations in resisting chloride ion corrosion and microbial corrosion. AlCoCrNi-based high-entropy alloy (HEAs) materials have both excellent high strength and high toughness, and a dense composite passivation film rich in Cr2O3 and Al2O3 is easily formed on their surface. This passivation film can effectively block the penetration of seawater corrosion media and exhibits excellent corrosion resistance, and is expected to become an ideal material for extending the service life of carbon steel.

[0005] Chinese Patent CN110438385A (publication date: November 12, 2019) discloses an Al-Co-Cr-Ni quaternary high-entropy alloy system and a preparation method thereof, which have the following disadvantages: 1. The cost of preparing Al-Co-Cr-Ni high-entropy alloy workpieces by the casting method is too high, and the practical application value is relatively low; 2. The properties of cast AlCoCrNi high-entropy alloy are relatively fixed and it is difficult to match the properties of actual workpieces, resulting in a narrow application range. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide an AlCoCrNi high-entropy alloy powder for a marine corrosion-resistant coating. It is prepared by gas atomization method, has good performance, wide application range and low cost. At the same time, the present invention also provides a preparation method for the marine corrosion-resistant coating of AlCoCrNi high-entropy alloy powder. The coating has strong bonding force with the substrate and excellent seawater corrosion resistance, and can meet the long-term use of materials in the ocean.

[0007] An AlCoCrNi high-entropy alloy powder for a marine corrosion-resistant coating according to the present invention, the percentage content of each element is: Al 15% - 35%, Cr 15% - 35%, Co 15% - 35%, Ni 15% - 35%. It is prepared by gas atomization method, and the powder particle size is 15 - 53μm. The raw materials for preparing the high-entropy alloy powder are metal elements Al, Cr, Co and Ni, and the purity of the metal elements Al, Cr, Co and Ni is higher than 99.9wt%.

[0008] Preferably, the percentage content of each element in the AlCoCrNi high-entropy alloy powder is: Al 25% - 35%, Cr 20% - 30%, Co 20% - 30%, Ni 20% - 30%.

[0009] Preferably, the percentage content of each element in the AlCoCrNi high-entropy alloy powder is: 25% Al, 25% Cr, 25% Co, 25% Ni.

[0010] Preferably, the percentage content of each element in the AlCoCrNi high-entropy alloy powder is: 35% Al, 25% Cr, 20% Co, 20% Ni.

[0011] A preparation method for a marine corrosion-resistant coating according to the present invention, the specific steps are as follows: ①. Vacuum dry the AlCoCrNi high-entropy alloy powder at 110 - 130°C; ②. Grind, clean and dry the surface of the substrate (duplex stainless steel); ③. Sandblast the surface of the substrate with white corundum sand, and the sandblasting roughness Ra is 5 - 7μm; ④. Preheat the substrate, and the preheating temperature is 80 - 120°C; ⑤. Use HVOF spraying to prepare a high-entropy alloy coating on the surface of the substrate; ⑥. Remelt the substrate using a vacuum heat treatment furnace.

[0012] Among them, in step ③: Use 46# white corundum sand for sandblasting, and the sandblasting process parameters are: spray gun angle 85 - 95°, air pressure 5 - 6kg / cm 2 , nozzle diameter 20 - 25mm, working distance 300 - 350mm, moving speed 200 - 250mm / s.

[0013] Among them, step ⑤: The spraying process parameters are as follows: oxygen flow rate 1800 - 2000 SCFH, kerosene flow rate 5 - 7 Gal / h, powder feeding rate 80 - 100 g / min, working distance 300 - 380 mm, spraying speed 400 - 700 mm / s, and number of spraying passes 6 - 10 times.

[0014] Among them, step ⑥: The substrate is heat-insulated at 1000 - 1200 °C for 2 - 6 h.

[0015] The advantages of the AlCoCrNi high-entropy alloy powder and its preparation method for a marine corrosion-resistant coating of the present invention are as follows: First, the AlCoCrNi high-entropy alloy powder is prepared by gas atomization method, so its cost is relatively low and its practical application value is relatively high; at the same time, the powder prepared by gas atomization method has good performance and can match substrates such as carbon steel and duplex stainless steel, and has a wide application range; Second, the Al content in the AlCoCrNi high-entropy alloy is relatively high, and the cost is significantly reduced compared with other AlCoCrNi materials; Third, under the severe plastic deformation of HVOF spraying, a large number of refined grains can be formed in the coating of the AlCoCrNi high-entropy alloy powder, and a dense composite passivation film rich in Al2O3 and Cr2O3 can be rapidly generated, and has a certain surface self-repairing ability, that is, it can be rapidly re-passivated after the passivation film is corroded and penetrated, and then the passivation film is repaired, so as to effectively hinder the corrosion penetration of seawater, that is, it has excellent corrosion resistance; Fourth, by limiting the composition and content of the material prepared by gas atomization method of the present invention and adapting to the appropriate process parameters in HVOF spraying, the coating has a high bonding strength exceeding 70 MPa, a low porosity, and excellent seawater corrosion resistance, which is 2.2 times higher than that of the duplex stainless steel substrate; Fifth, spraying an AlCoCrNi alloy coating with a thickness of about 0.1 mm on the surface of the workpiece by HVOF spraying can achieve the protection effect, which has high practicality. Description of the Drawings

[0016] Figure 1 It is the bonding strength spectrum of the AlCoCrNi high-entropy alloy coating obtained in Example 2;

[0017] Figure 2 It is the corrosion resistance comparison spectrum of the AlCoCrNi high-entropy alloy coating obtained in Example 2;

[0018] Figure 3 It is the composition proportion spectrum of the dynamic surface passivation film of the AlCoCrNi high-entropy alloy coating obtained in Example 2. Detailed Embodiments

[0019] The following further describes the present invention in detail with specific embodiments.

[0020] Example 1

[0021] The substrate selected in this embodiment is duplex stainless steel, and the preparation method of the coating is as follows:

[0022] ①. Vacuum dry the AlCoCrNi powder at 110 °C.

[0023] ②. Grind, clean, and dry the surface of the substrate.

[0024] ③. Sandblast the surface of the substrate with white corundum sand, and the sandblasting roughness Ra is 5 - 7 μm.

[0025] ④. Preheat the substrate, and the preheating temperature is 110 °C.

[0026] ⑤. Use HVOF spraying to prepare a high-entropy alloy coating on the surface of the substrate.

[0027] ⑥. Remelt the substrate using a vacuum heat treatment furnace.

[0028] In step ①: The percentage contents of each element in the AlCoCrNi high-entropy alloy powder are: Al content 25 at.%, Co content 25 at.%, Cr content 25 at.%, Ni content 25 at.%, and the powder particle size is 15 - 53 μm.

[0029] In step ③: 46# white corundum sand is used for sandblasting, and the sandblasting process parameters are: spray gun angle 86°, air pressure 5.5 kg / cm 2 , nozzle diameter 20 mm, working distance 300 - 320 mm, moving speed 220 mm / s.

[0030] In step ⑤: The spraying process parameters are: oxygen flow rate 1900 SCFH, kerosene flow rate 6 Gal / h, powder feeding rate 95 g / min, working distance 350 - 380 mm, spraying speed 600 mm / s, and number of spraying passes 8.

[0031] In step ⑥: The substrate is kept at 1200 °C for 2 h.

[0032] Example 2

[0033] The substrate selected in this embodiment is duplex stainless steel, and the preparation method of the coating is as follows:

[0034] ①. Vacuum dry the AlCoCrNi powder at 120 °C.

[0035] ②. Grind, clean, and dry the surface of the substrate.

[0036] ③. Sandblast the surface of the substrate with white corundum sand, and the sandblasting roughness Ra is 5 - 7 μm.

[0037] ④. Preheat the substrate, and the preheating temperature is 100 °C.

[0038] ⑤. Use HVOF spraying to prepare a high-entropy alloy coating on the substrate surface.

[0039] ⑥. Use a vacuum heat treatment furnace to remelt the substrate.

[0040] In step ①: The percentage contents of each element in the AlCoCrNi high-entropy alloy powder are as follows: the Al content is 25 at.%, the Co content is 25 at.%, the Cr content is 25 at.%, the Ni content is 25 at.%, and the powder particle size is 15 - 53 μm.

[0041] In step ③: 46# white fused alumina sand is used for sandblasting, and the sandblasting process parameters are: the spray gun angle is 82°, the air pressure is 5.5 kg / cm 2 , the nozzle diameter is 25 mm, the working distance is 320 - 350 mm, and the moving speed is 240 mm / s.

[0042] In step ⑤: The spraying process parameters are: the oxygen flow rate is 2000 SCFH, the kerosene flow rate is 6.5 Gal / h, the powder feeding rate is 95 g / min, the working distance is 350 - 380 mm, the spraying speed is 600 mm / s, and the number of spraying passes is 8.

[0043] In step ⑥: The substrate is kept at 1200 °C for 4 h.

[0044] For the coating obtained in Example 2, the following experiments were conducted: 1. Use a microcomputer-controlled electronic universal testing machine to conduct a tensile test on the coating. The specific results are as Figure 1 shown. Its bonding strength is 76.51 MPa, far higher than 70 MPa in the standard; 2. Use a programmable salt spray testing machine to conduct a copper-accelerated acetic acid salt spray test according to the standard of GB / T 10125-2021. The specific test results are as Figure 2 shown. Corrosion marks on the AlCoCrNi high-entropy alloy coating appeared after 55 days; under the same experimental conditions, obvious corrosion marks on the duplex stainless steel appeared after 25 days. Therefore, the corrosion resistance of the coating of the present invention is 2.2 times that of the duplex stainless steel; 3. Analyze the composition of the passive film in the coating. The specific results are as Figure 3 shown. The contents of Al2O3 and Cr2O3 in the passive film are relatively high, making this coating have excellent corrosion resistance.

[0045] Example 3

[0046] The substrate selected in this example is duplex stainless steel, and the preparation method of the coating is as follows:

[0047] ①. Vacuum-dry the AlCoCrNi powder at 125 °C.

[0048] ②. Grind, clean, and dry the surface of the substrate.

[0049] ③. Blast the surface of the substrate with white fused alumina sand, and the blast roughness Ra is 5 - 7 μm.

[0050] ④. Preheat the substrate, and the preheating temperature is 90°C.

[0051] ⑤. Use HVOF spraying to prepare a high-entropy alloy coating on the surface of the substrate.

[0052] ⑥. Remelt the substrate using a vacuum heat treatment furnace.

[0053] In step ①: The percentage contents of each element in the AlCoCrNi high-entropy alloy powder are as follows: the Al content is 35 at.%, the Co content is 25 at.%, the Cr content is 20 at.%, the Ni content is 20 at.%, and the powder particle size is 15 - 53 μm.

[0054] In step ③: Use 46# white fused alumina sand for blasting, and the blasting process parameters are: spray gun angle 88°, air pressure 6 kg / cm 2 , nozzle diameter 25 mm, working distance 320 - 350 mm, moving speed 220 mm / s.

[0055] In step ⑤: The spraying process parameters are: oxygen flow rate 1900 SCFH, kerosene flow rate 6 Gal / h, powder feeding rate 95 g / min, working distance 350 - 380 mm, spraying speed 600 mm / s, and number of spraying passes 8 times.

[0056] In step ⑥: The heat treatment process parameters are holding at 1200°C for 2 h.

[0057] The coating of the present invention is not limited to the substrate being duplex stainless steel, and it can be prepared on the surfaces of substrates such as carbon steel and stainless steel materials.

[0058] The advantages of the AlCoCrNi high-entropy alloy powder and its preparation method for a marine corrosion-resistant coating of the present invention are as follows: First, the AlCoCrNi high-entropy alloy powder is prepared by gas atomization, so its cost is low and its practical application value is high; at the same time, the powder prepared by gas atomization has good properties and can match substrates such as carbon steel and duplex stainless steel, with a wide range of applications. Second, the Al content in the AlCoCrNi high-entropy alloy is relatively high, significantly reducing the cost compared to other AlCoCrNi materials. Third, under the severe plastic deformation of HVOF spraying, the coating can form a large number of refined grains, and can quickly generate a dense composite passivation film rich in Al2O3 and Cr2O3, and has a certain surface self-repair ability, that is, it can be quickly re-passivated after the passivation film is corroded and broken through, and then repair the passivation film, thereby effectively hindering the corrosion penetration of seawater, that is, it has excellent corrosion resistance. Fourth, the present invention limits the composition and content of the material prepared by gas atomization and adapts to the appropriate process parameters in HVOF spraying, so that the coating has a high bonding strength exceeding 70 MPa, a low porosity, and excellent seawater corrosion resistance, which is 2.2 times higher than that of the duplex stainless steel substrate. Fifth, spraying an AlCoCrNi alloy coating with a thickness of about 0.1 mm on the surface of the workpiece by HVOF spraying can achieve the protection effect, which has high practicality.

[0059] In summary, the present invention obtains an AlCoCrNi alloy with specific composition and content by gas atomization, and prepares a coating on the surface of substrates such as carbon steel and duplex stainless steel by HVOF spraying. The severe plastic deformation brought by the HVOF process significantly improves the mechanical properties and wear resistance of the coating, greatly improving the seawater corrosion resistance of the coating, thereby extending the service life of the substrate parts.

Claims

1. An AlCoCrNi high-entropy alloy powder for a marine corrosion-resistant coating, characterized in that: The percentage content of each element is as follows: Al 15% - 35%, Cr 15% - 35%, Co 15% - 35%, Ni 15% - 35%. It is prepared by gas atomization method, and the powder particle size is 15 - 53 μm. The raw materials for preparing the high-entropy alloy powder are metallic elements Al, Cr, Co and Ni, and the purity of metallic elements Al, Cr, Co and Ni is higher than 99.9 wt%.

2. The AlCoCrNi high-entropy alloy powder according to claim 1, characterized in that: The percentage content of each element is as follows: Al 25% - 35%, Cr 20% - 30%, Co 20% - 30%, Ni 20% - 30%.

3. The AlCoCrNi high-entropy alloy powder according to claim 2, wherein: The percentage content of each element is: 25% Al, 25% Cr, 25% Co, 25% Ni.

4. The AlCoCrNi high-entropy alloy powder according to claim 2, characterized in that: The percentage content of each element is: 35% Al, 25% Cr, 20% Co, 20% Ni.

5. A method for preparing a marine corrosion-resistant coating, the specific steps are as follows: ① Vacuum-dry the AlCoCrNi high-entropy alloy powder described in any one of claims 1 - 4 at 110 - 130 °C; ② Grind, clean and dry the surface of the substrate (duplex stainless steel); ③ Use white corundum sand to sandblast the surface of the substrate, and the sandblasting roughness Ra is 5 - 7 μm; ④ Preheat the substrate, and the preheating temperature is 80 - 120 °C; ⑤ Use HVOF spraying to prepare a high-entropy alloy coating on the surface of the substrate; ⑥ Use a vacuum heat treatment furnace to remelt the substrate.

6. According to the preparation method described in claim 5, the feature is: Step ③: Use 46# white corundum sand for sandblasting, and the sandblasting process parameters are: spray gun angle 85 - 95°, air pressure 5 - 6 kg / cm2, nozzle diameter 20 - 25 mm, working distance 300 - 350 mm, moving speed 200 - 250 mm / s.

7. According to the preparation method described in claim 5, the feature is: Step ⑤: The spraying process parameters are: oxygen flow rate 1800 - 2000 SCFH, kerosene flow rate 5 - 7 Gal / h, powder feeding rate 80 - 100 g / min, working distance 300 - 380 mm, spraying speed 400 - 700 mm / s, spraying passes 6 - 10 times.

8. The preparation method according to claim 5, characterized in that: Step ⑥: The substrate is kept at 1000 - 1200 °C for 2 - 6 h.

9. The preparation method according to claim 5, characterized in that: The substrate is duplex stainless steel, and the specific steps are as follows: ① Vacuum-dry the AlCoCrNi powder at 120 °C; The percentage content of each element in the AlCoCrNi high-entropy alloy powder is: Al content 25 at.%, Co content 25 at.%, Cr content 25 at.%, Ni content 25 at.%, and the powder particle size is 15 - 53 μm; ② Grind, clean and dry the surface of the substrate; ③. Use white fused alumina grit #46 for sandblasting. The sandblasting process parameters are: spray gun angle 82°, air pressure 5.5 kg / cm 2 , nozzle diameter 25 mm, working distance 320 - 350 mm, moving speed 240 mm / s, sandblasting roughness Ra 5 - 7 μm; ④ Preheat the substrate, and the preheating temperature is 100 °C; ⑤ Use HVOF spraying to prepare a high-entropy alloy coating on the surface of the substrate: The spraying process parameters are: oxygen flow rate 2000 SCFH, kerosene flow rate 6.5 Gal / h, powder feeding rate 95 g / min, working distance 350 - 380 mm, spraying speed 600 mm / s, spraying passes 8 times; ⑥ Use a vacuum heat treatment furnace to remelt the substrate: Keep it at 1200 °C for 4 h.

10. Use of the Al-Cr-Co-Ni high-entropy alloy coating according to any one of claims 1-9 in corrosion-resistant components.

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