Corrosion-resistant medium-entropy alloy coating and preparation method thereof

Abstract

The invention discloses a corrosion-resistant medium-entropy alloy coating and a preparation method thereof, and belongs to the technical field of engineering materials. The chemical formula of the corrosion-resistant medium-entropy alloy coating is Fe < 1 + y > CrNi < 1-y > Si < x >, and the molar ratio of all elements in the corrosion-resistant medium-entropy alloy coating is Fe: Cr: Ni: Si = 1 + y: 1: 1-y: x, x is less than or equal to 0.4, 0lt; y is smaller than or equal to 0.3, iron elementary substances, chromium elementary substances, nickel elementary substances and silicon elementary substances are put into a vacuum arc furnace according to the proportion, vacuumizing is carried out, the vacuum degree is adjusted, smelting is carried out under the argon protective atmosphere, a master alloy ingot is obtained and then put into a quartz crucible of a gas atomization preparation device, the vacuum degree is adjusted, the master alloy ingot is melted, powder spraying is carried out, and room-temperature medium-entropy alloy powder is obtained and then sieved; a laser cladding method is adopted, and synchronous powder feeding is combined, so that the corrosion-resistant medium-entropy alloy coating is obtained. According to the preparation method provided by the invention, a defect-free and high-quality coating can be obtained, and the coating has high corrosion resistance, so that a long-term anti-corrosion effect on a key component is realized, and the service life of the component is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of engineering materials, and in particular to a corrosion-resistant medium-entropy alloy coating and a preparation method thereof. Background Art

[0002] The fields of marine industry, aerospace, rail transportation, etc. are developing rapidly, and the more severe and complex service environment has put forward higher performance requirements for materials. Marine corrosion, as a typical harsh working condition, poses a serious threat to the service performance and life of marine ships and equipment. Coating technology is currently the most widely used and most effective means to improve the corrosion resistance of components. It greatly improves the service performance and life of components by improving the surface properties of components.

[0003] At present, commonly used coating materials include iron-based coatings, nickel-based coatings, metal-ceramic composite coatings, etc., and coating preparation techniques include laser cladding, plasma cladding, thermal spraying, etc. However, the long-term anti-corrosion effect of existing coating technologies and coating material systems on marine equipment needs to be improved. As a new material that has attracted much attention in recent years, medium / high entropy alloys are different from traditional single-principal alloys and exhibit the characteristics of multiple principal elements. Therefore, they can synergistically exert the effects of multiple corrosion-resistant elements, that is, the "cocktail" effect, and exhibit excellent corrosion resistance, such as CoCrFeMnNi, CoCrNi, FeCrNi and other medium / high entropy alloy systems. However, these medium / high entropy alloys are currently facing several problems in industrial applications: First, the alloy contains a high content of precious metal elements, and the alloy cost is high, which hinders widespread industrial application; second, it is difficult to effectively avoid grain boundary corrosion, which poses a challenge to long-term corrosion resistance; third, how to effectively improve the quality of medium / high entropy alloy coatings and reduce defects to improve service performance such as corrosion resistance.

[0004] In summary, there is an urgent need to develop low-cost, corrosion-resistant medium / high-entropy alloy compositions, as well as related alloy powder and coating preparation technologies. Summary of the invention

[0005] The purpose of the present invention is to provide a corrosion-resistant medium-entropy alloy coating and a preparation method thereof, which can obtain a defect-free, high-quality coating with strong corrosion resistance to achieve a long-term anti-corrosion effect on key components and improve the service life of the components.

[0006] To achieve the above object, the present invention provides a corrosion-resistant medium entropy alloy coating, the chemical formula of which is Fe 1+y CrNi 1-y Si x The molar ratio of each element in the corrosion-resistant medium entropy alloy coating is Fe:Cr:Ni:Si=1+y:1:1-y:x, where 0 <x≤0.4,0<y≤0.3。

[0007] The present invention also provides a method for preparing a corrosion-resistant medium-entropy alloy coating as claimed in claim 1, comprising the following steps: S1. Putting iron, chromium, nickel and silicon into a vacuum arc furnace in proportion, evacuating the furnace, adjusting the vacuum degree, and smelting the furnace under an argon protective atmosphere to obtain a master alloy ingot; S2, placing the master alloy ingot into a quartz crucible of a gas atomization preparation device, then evacuating and adjusting the vacuum degree, melting the master alloy ingot and spraying powder, obtaining the room temperature entropy alloy powder and sieving it, the particle size of the room temperature entropy alloy powder after sieving is 15-80 μm; S3. Using laser cladding method and synchronous powder feeding, the room temperature medium entropy alloy powder is melted on the cladding substrate to obtain a corrosion-resistant medium entropy alloy coating.

[0008] Preferably, in step S1, the purity of the iron element, the chromium element, the nickel element and the silicon element by mass percentage is not less than 99.9%.

[0009] Preferably, in step S1, the vacuum degree in the vacuum arc furnace is 5×10 -3 Pa, and the argon pressure is 0.01-0.05MPa.

[0010] Preferably, in step S2, in the quartz crucible, the diameter of the quartz tube nozzle is 1-4 mm, and the vacuum degree of the atomization chamber is 10 -1 Pa, the injection gas pressure is 6-10 MPa, the gas pressure in the chamber is below 0.1 MPa, and both the protective gas and the injection gas are argon.

[0011] Preferably, in step S3, the cladding substrate is made of alloy steel or carbon steel, and the cladding substrate is polished with sandpaper of 800 mesh or above before use.

[0012] Preferably, in step S3, the cladding parameters are: scanning speed 0.36-50 m / min, powder feeding speed 10-20 g / min, spot diameter 1.5-4 mm, laser power 1-2.5 kW, overlap rate 50-70%; argon protection is used during the cladding process, and the gas flow rate is 8-15 L / min.

[0013] Preferably, in step S3, the thickness of the corrosion-resistant medium entropy alloy coating is 300-800 μm, the porosity is less than or equal to 0.5%, it is metallurgically bonded to the substrate, the coating elements Cr and Ni are evenly distributed, but the grain boundaries are rich in Si and poor in Fe.

[0014] Therefore, the present invention adopts the above-mentioned corrosion-resistant medium-entropy alloy coating and preparation method thereof, which has the following beneficial effects: 1) The typical FeCrNi medium entropy alloy contains a high content of Ni element, the alloy cost is high, and the alloy melt viscosity is high, which easily causes defects such as pores and cracks in the laser cladding coating. The method of the present invention reduces the Ni content and increases the Fe content. First, it can reduce the stacking fault energy of the alloy, so as to effectively improve the hardness of the coating and comprehensively improve the service performance of the coating. Second, it can reduce the alloy cost and make its engineering application range wider.

[0015] 2) The addition of Si element proposed in the present invention also has two functions. One is to improve the fluidity of the alloy melt, which is conducive to the preparation of powders with higher sphericity and defect-free, good-quality coatings; the other is to cause greater lattice distortion, increase the hardness of the coating, and comprehensively improve the service performance of the coating.

[0016] 3) Although the typical FeCrNi medium entropy alloy also has relatively excellent corrosion resistance, it still suffers from intergranular corrosion, making it difficult to ensure long-term anti-corrosion effect. The present invention, by adjusting the Fe and Ni content and appropriately adding Si elements, enriches Si elements at the grain boundaries through element redistribution, which can effectively reduce the potential difference between the grain boundaries and the grains of the medium entropy alloy coating, slow down intergranular corrosion, and form a denser and more stable oxide film, thereby greatly improving the corrosion resistance of the coating and providing better protection for key components.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a characterization diagram of the sample prepared in Example 1, Figure 1 (a) is Fe 1.2 CrNi 0.8 Si 0.2 XRD pattern of corrosion resistant medium entropy alloy powder, Figure 1 (b) is Fe 1.2 CrNi 0.8 Si 0.2 SEM images of corrosion-resistant medium entropy alloy powders. Figure 1 (c) is Fe 1.2 CrNi 0.8 Si 0.2 XRD pattern of corrosion-resistant medium entropy alloy coating, Figure 1 (d) is Fe 1.2 CrNi 0.8 Si 0.2 Cross-sectional view of the corrosion-resistant medium entropy alloy coating; Figure 2 Sample Fe was prepared for Example 1 1.2 CrNi 0.8 Si 0.2Surface morphology and element distribution of corrosion-resistant medium entropy alloy coating, where: Figure 2 (a) shows the surface morphology of the coating. Figure 2 (b) is the distribution diagram of iron element. Figure 2 (c) is the distribution diagram of nickel element. Figure 2 (d) is the distribution diagram of chromium element. Figure 2 Middle (e) is the silicon element distribution diagram; Figure 3 Fe prepared in Example 1 1.2 CrNi 0.8 Si 0.2 Polarization curves of corrosion-resistant medium entropy alloy coating and Q235 steel substrate in 3.5wt.% NaCl solution. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0020] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0021] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0022] The present invention provides a corrosion-resistant medium entropy alloy coating, the chemical formula of which is Fe 1+y CrNi 1- y Si x The molar ratio of each element in the corrosion-resistant medium entropy alloy coating is Fe:Cr:Ni:Si=1+y:1:1-y:x, where 0 <x≤0.4,0<y≤0.3。

[0023] The present invention also provides a method for preparing a corrosion-resistant medium-entropy alloy coating, comprising the following steps: S1. Putting iron, chromium, nickel and silicon into a vacuum arc furnace in proportion, evacuating the furnace, adjusting the vacuum degree, and smelting the furnace under an argon protective atmosphere to obtain a master alloy ingot; S2, placing the master alloy ingot into a quartz crucible of a gas atomization preparation device, then evacuating and adjusting the vacuum degree, melting the master alloy ingot and spraying powder, obtaining the room temperature entropy alloy powder and sieving it, the particle size of the room temperature entropy alloy powder after sieving is 15-80 μm; S3. Using laser cladding method and synchronous powder feeding, the room temperature medium entropy alloy powder is melted on the cladding substrate to obtain a corrosion-resistant medium entropy alloy coating.

[0024] In step S1, the purity of the iron element, the chromium element, the nickel element and the silicon element by mass percentage is not less than 99.9%.

[0025] In step S1, the vacuum degree in the vacuum arc furnace is 5×10 -3 Pa, and the argon pressure is 0.01-0.05 MPa.

[0026] In step S2, in the quartz crucible, the diameter of the quartz tube nozzle is 1-4 mm, and the vacuum degree of the atomization chamber is 10 -1 Pa, the injection gas pressure is 6-10 MPa, the gas pressure in the chamber is below 0.1 MPa, and both the protective gas and the injection gas are argon.

[0027] In step S3, the cladding substrate is made of alloy steel or carbon steel, and the cladding substrate is polished with sandpaper of 800 mesh or above before use.

[0028] In step S3, the cladding parameters are: scanning speed 0.36-50 m / min, powder feeding speed 10-20 g / min, spot diameter 1.5-4 mm, laser power 1-2.5 kW, overlap rate 50-70%; argon gas protection is used during the cladding process, and the gas flow rate is 8-15 L / min.

[0029] In step S3, the thickness of the corrosion-resistant medium-entropy alloy coating is 300-800 μm, the porosity is less than or equal to 0.5%, the alloy coating is metallurgically bonded to the substrate, the coating elements Cr and Ni are evenly distributed, but the grain boundaries are rich in Si and poor in Fe.

[0030] The present invention is further described below by way of examples.

[0031] Embodiment 1: The present invention provides a corrosion-resistant medium entropy alloy coating, the chemical formula of which is: Fe 1.2 CrNi 0.8 Si 0.2 The alloying element ratio of the entropy alloy is Fe:Cr:Ni:Si=1.2:1:0.8:0.2. According to the proportion of the alloying elements, iron, chromium, nickel and silicon are mixed, and the mass percentage purity of each element is not less than 99.9%.

[0032] The single element in the smelting raw material is placed in a vacuum arc furnace, and then vacuumed and the vacuum degree is adjusted to 4.5×10 -3Pa, argon protection was adopted, the argon pressure was 0.02 MPa, and the alloy was evenly smelted for 5 times to obtain the master alloy ingot.

[0033] The master alloy ingot was placed in a quartz crucible of the gas atomization preparation device, and the diameter of the quartz crucible nozzle was 1 mm. Then the vacuum was evacuated and the vacuum degree was adjusted to 10 -1 Pa, powder spraying is carried out after melting the alloy, the spraying gas is argon and the gas pressure is 8 MPa, and the gas pressure in the cavity is 0.1 MPa.

[0034] The obtained alloy powder was sieved to obtain a powder with a particle size of 15-80 μm, and the room temperature medium entropy alloy powder was melted on the Q235 steel substrate by a laser cladding method with synchronous powder feeding, and the substrate was polished with 800 mesh sandpaper. The cladding parameters are as follows: scanning speed 0.36 m / min, powder feeding speed 15 g / min, spot diameter 1.5 mm, laser power 1.5 kW, overlap rate 60%. Argon protection was used during the cladding process, and the gas flow rate was 10 L / min.

[0035] Fe 1.2 CrNi 0.8 Si 0.2 Corrosion resistant medium entropy alloy powder Figure 1 As shown in (a), the powder is a face-centered cubic and body-centered cubic dual-phase structure, combined with Figure 1 From (b), it can be concluded that the fluidity of the alloy melt is significantly improved after the addition of Si, resulting in the powder having good sphericity.

[0036] Fe 1.2 CrNi 0.8 Si 0.2 Corrosion resistant medium entropy alloy coatings such as Figure 1 As shown in (c), the coating structure is a face-centered cubic single-phase structure. Figure 1 From (d), it can be concluded that the coating thickness of the corrosion-resistant medium-entropy alloy coating is about 300 μm, and it has good metallurgical bonding with the substrate, without defects such as holes and cracks, and the porosity is less than 0.5%.

[0037] Fe 1.2 CrNi 0.8 Si 0.2 The surface results of the corrosion-resistant medium entropy alloy coating are as follows Figure 2 As shown in Figure 1, Fe and Ni elements are evenly distributed, and the grain boundaries are Fe-poor but Si-rich. The polarization curves of the corrosion-resistant medium entropy alloy coating and the substrate are shown in Figure 1. Figure 3 As shown in the figure, the corrosion resistance of the corrosion-resistant medium entropy alloy coating is significantly improved compared with the substrate.

[0038] Embodiment 2: The present invention provides a corrosion-resistant medium entropy alloy coating, the chemical formula of which is Fe 1.3CrNi 0.7 Si 0.3 The alloying element ratio of the corrosion-resistant medium entropy alloy is Fe:Cr:Ni:Si=1.3:1:0.7:0.3. According to the proportion of alloying elements, iron, chromium, nickel and silicon are matched, and the mass percentage purity of each element is not less than 99.9%.

[0039] The single element in the smelting raw material is placed in a vacuum arc furnace, and then vacuumed and the vacuum degree is adjusted to 5×10 -3 Pa, argon protection was adopted, the argon pressure was 0.03 MPa, and the alloy was evenly smelted for 5 times to obtain the master alloy ingot.

[0040] The master alloy ingot was placed in a quartz crucible of the gas atomization preparation device, and the diameter of the quartz crucible nozzle was 1.5 mm. Then the vacuum was evacuated and the vacuum degree was adjusted to 8×10 -2 Pa, powder spraying is carried out after melting the alloy, the spraying gas is argon and the gas pressure is 10MPa, and the gas pressure in the cavity is 0.1MPa.

[0041] The obtained alloy powder was sieved to obtain a powder with a particle size of 15-80 μm, and the room temperature medium entropy alloy powder was melted on a 304 stainless steel substrate using a synchronous powder feeding laser cladding method, and the substrate was polished with 800 mesh sandpaper. The cladding parameters are as follows: scanning speed 40 m / min, powder feeding speed 17 g / min, spot diameter 2 mm, laser power 2 kW, overlap rate 70%. Argon protection was used during the cladding process, and the gas flow rate was 12 L / min.

[0042] Fe 1.3 CrNi 0.7 Si 0.3 The corrosion-resistant medium entropy alloy coating has no defects such as cracks, and the porosity is less than 0.5%. It has a good metallurgical bond with the substrate, and the coating thickness is about 350 μm. 1.3 CrNi 0.7 Si 0.3 The corrosion resistance of the corrosion-resistant medium entropy alloy coating is significantly improved.

[0043] Example 3 The present invention provides a corrosion-resistant medium entropy alloy coating, the chemical formula of which is: Fe 1.1 CrNi 0.9 Si 0.4 The alloying element ratio of the entropy alloy is Fe:Cr:Ni:Si=1.1:1:0.9:0.4. According to the proportion of the alloying elements, iron, chromium, nickel and silicon are mixed, and the mass percentage purity of each element is not less than 99.9%.

[0044] The single element in the smelting raw material is placed in a vacuum arc furnace, and then vacuumed and the vacuum degree is adjusted to 4.0×10 -3 Pa, argon protection was adopted, the argon pressure was 0.02 MPa, and the alloy was evenly smelted for 5 times to obtain the master alloy ingot.

[0045] The master alloy ingot was placed in a quartz crucible of the gas atomization preparation device, and the diameter of the quartz crucible nozzle was 1 mm. Then the vacuum was evacuated and the vacuum degree was adjusted to 10 -1 Pa, powder spraying is carried out after melting the alloy, the spraying gas is argon and the gas pressure is 8 MPa, and the gas pressure in the cavity is 0.1 MPa.

[0046] The obtained alloy powder was sieved to obtain a powder with a particle size of 15-80 μm, and the room temperature medium entropy alloy powder was melted on the Q235 steel substrate by a laser cladding method with synchronous powder feeding, and the substrate was polished with 800 mesh sandpaper. The cladding parameters are as follows: scanning speed 0.36 m / min, powder feeding speed 15 g / min, spot diameter 1.5 mm, laser power 1.5 kW, overlap rate 60%. Argon protection was used during the cladding process, and the gas flow rate was 10 L / min.

[0047] Fe 1.1 CrNi 0.9 Si 0.4 The corrosion-resistant medium entropy alloy coating has good metallurgical bonding with the substrate, without defects such as holes and cracks, and the porosity is less than 0.5%. 1.1 CrNi 0.9 Si 0.4 The corrosion-resistant medium entropy alloy coating has good corrosion resistance.

[0048] Therefore, the present invention adopts the above-mentioned corrosion-resistant medium-entropy alloy coating and its preparation method to obtain a defect-free, high-quality coating with strong corrosion resistance to achieve long-term anti-corrosion effect on key components and improve the service life of the components.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A corrosion-resistant medium-entropy alloy coating, characterized in that: The chemical formula of the corrosion-resistant medium entropy alloy coating is Fe 1+y CrNi 1-y Si x The molar ratio of each element in the corrosion-resistant medium entropy alloy coating is Fe:Cr:Ni:Si=1+y:1:1-y:x, where 0 <x≤0.4,0<y≤0.3。 2. A method for preparing a corrosion-resistant medium-entropy alloy coating as claimed in claim 1, characterized in that: The following steps are involved: S1. Putting iron, chromium, nickel and silicon into a vacuum arc furnace in proportion, evacuating the furnace, adjusting the vacuum degree, and smelting the furnace under an argon protective atmosphere to obtain a master alloy ingot; S2, placing the master alloy ingot into a quartz crucible of a gas atomization preparation device, then evacuating and adjusting the vacuum degree, melting the master alloy ingot and spraying powder, obtaining the room temperature entropy alloy powder and sieving it, the particle size of the room temperature entropy alloy powder after sieving is 15-80 μm; S3. Using laser cladding method and synchronous powder feeding, the room temperature medium entropy alloy powder is melted on the cladding substrate to obtain a corrosion-resistant medium entropy alloy coating.

3. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S1, the purity of the iron element, the chromium element, the nickel element and the silicon element by mass percentage is not less than 99.9%.

4. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S1, the vacuum degree in the vacuum arc furnace is 5×10 -3 Pa, and the argon pressure is 0.01-0.05 MPa.

5. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S2, in the quartz crucible, the diameter of the quartz tube nozzle is 1-4 mm, and the vacuum degree of the atomization chamber is 10 -1 Pa, the injection gas pressure is 6-10MPa, the gas pressure in the cavity is below 0.1 MPa, and the protective gas and the injection gas are both argon.

6. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S3, the cladding substrate is made of alloy steel or carbon steel, and the cladding substrate is polished with sandpaper of 800 mesh or above before use.

7. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S3, the cladding parameters are: scanning speed 0.36-50 m / min, powder feeding speed 10-20 g / min, spot diameter 1.5-4 mm, laser power 1-2.5 kW, overlap rate 50-70%; argon gas protection is used during the cladding process, and the gas flow rate is 8-15 L / min.

8. The method for preparing a corrosion-resistant medium-entropy alloy coating according to claim 2, characterized in that: In step S3, the thickness of the corrosion-resistant medium entropy alloy coating is 300-800 μm, and the porosity is less than or equal to 0.5%.

Images