Cavitation-erosion-resistant Fe-based medium-entropy alloy coating and preparation method thereof

Abstract

The invention relates to the technical field of surface strengthening, in particular to an anti-cavitation Fe-based medium-entropy alloy coating and a preparation method thereof. Although the Fe2CrNi medium-entropy alloy with the FCC phase structure shows excellent plasticity, the hardness of the Fe2CrNi medium-entropy alloy is relatively low, in order to improve the cavitation erosion resistance of the coating, the medium-entropy alloy coating with the FCC and HCP dual-phase structure is prepared by adding Nb element into Fe2CrNi and utilizing laser cladding, so that the alloy realizes high-strength-plastic combination, and the cavitation erosion damage is effectively reduced. In addition, laser cladding can enhance combination between the coating and a matrix, and meanwhile, by optimizing process parameters, the prepared coating is refined in grain and uniform in structure and has good forming quality.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology, specifically to an anti-cavitation Fe-based medium-entropy alloy coating and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] When flow-through components such as turbines, propellers, and pumps move at high speeds in a liquid, the surrounding liquid pressure changes drastically. This triggers the nucleation, growth, and collapse of numerous micron-sized cavitation bubbles, generating high-speed, high-pressure shock waves or microjets. Under repeated impacts, the material surface develops honeycomb-like damage, and in severe cases, it can even lead to component puncture or breakage—a phenomenon known as cavitation erosion. Cavitation erosion is widespread on the surfaces of flow-through components in hydraulic machinery, shipbuilding, and other fields, causing significant economic losses and posing serious risks to the safe operation of equipment.

[0004] Since cavitation erosion only occurs on the surface of equipment, and coating protection technology is an important means of protecting material surfaces from damage and improving their surface properties, applying anti-cavitation coating materials to the surface of flow components to improve their cavitation resistance and extend their service life is currently a mature and cost-effective approach. Common anti-cavitation coatings mainly include alloy coatings, ceramic coatings, and organic coatings. However, different types of protective coatings still have their own advantages and disadvantages. For example, iron-based alloy coatings are relatively inexpensive, but their cavitation resistance is generally low; ceramic coatings (including oxide and carbide ceramic coatings) have high hardness and good cavitation resistance, but their plasticity is poor and they are susceptible to porosity and brittle failure of the hard phase; organic coatings (including low surface energy antifouling coatings, biomimetic antifouling coatings, etc.) have good toughness, but their preparation process is relatively complex, and their hardness is relatively low, resulting in poor cavitation resistance. They also suffer from weak adhesion to the substrate and are prone to peeling. Therefore, there is an urgent need to develop an anti-cavitation coating with superior overall performance. Summary of the Invention

[0005] To overcome the above problems, the present invention provides an anti-cavitation Fe-based medium-entropy alloy coating and its preparation method.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a cavitation-resistant Fe-based medium-entropy alloy coating, wherein the chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.4 to 1.0; Fe-based medium-entropy alloy coatings contain a dual-phase microstructure with face-centered cubic (FCC) phase and hexagonal close-packed (HCP) phase.

[0007] In one or more embodiments, the thickness of the cavitation erosion resistant Fe-based entropy alloy coating is 1-2 mm.

[0008] A second aspect of the present invention provides a method for preparing the cavitation erosion resistant Fe-based medium-entropy alloy coating described in the first aspect, comprising the following steps: (1) According to the atomic ratio of the chemical formula of Fe-based medium entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder are mixed evenly to obtain cladding powder; (2) After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser cladding to obtain the cavitation erosion-resistant Fe-based medium entropy alloy coating.

[0009] In one or more embodiments, in step (1), the particle size of the Fe powder, Cr powder, Ni powder and Nb powder is 40~50 μm.

[0010] In one or more embodiments, in step (1), the method for achieving uniform mixing is ball milling; Preferably, the ball milling is a wet ball milling process; More preferably, ethanol is added as a ball milling aid.

[0011] More preferably, the ball-to-powder ratio during wet ball milling is (45~55):(2.8~3.2), preferably 50:3; the ball milling speed is 18~30 rpm, preferably 20 rpm; and the ball milling time is 20~30 h, preferably 24 h.

[0012] More preferably, the clad powder is obtained by wet ball milling followed by drying; More preferably, the drying conditions are vacuum drying at 55~65 °C for 7~9 h.

[0013] In one or more embodiments, in step (2), laser cladding is performed in an atmosphere of nitrogen or an inert gas.

[0014] In one or more embodiments, the laser cladding process parameters in step (2) include: The laser power is 800~2000 W, the spot diameter is 2~6 mm, the scanning speed is 8~12 mm / s, the overlap rate is 40%, and the pre-layer thickness is 1~2 mm, preferably 1.5 mm.

[0015] The beneficial effects of this invention are as follows: (1) Although the Fe2CrNi medium-entropy alloy with FCC phase structure exhibits excellent plasticity, its hardness is relatively low. In order to improve the cavitation erosion resistance of the coating, Nb element was added to Fe2CrNi, and a medium-entropy alloy coating with FCC and HCP dual phase structure was prepared by laser cladding. This enabled the alloy to achieve a high strength-plasticity bond, thereby effectively reducing cavitation erosion damage. In addition, laser cladding can enhance the bonding between the coating and the substrate. At the same time, by optimizing the process parameters, the prepared coating grains are refined, the structure is uniform, and it has good forming quality.

[0016] (2) The present invention uses wet ball milling to form an alloy-like powder from elemental metal powder. Compared with ordinary mixing, thorough ball milling can make the powder mix more uniform. Under the thermal effect of laser, the powder melts more fully, has a higher absorption rate, and the coating forming quality is better.

[0017] (3) The method for preparing the anti-cavitation Fe-based medium-entropy alloy coating provided in this invention has the characteristics of low cost, simple process and excellent performance, and can be industrialized. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 The process flow for anti-cavitation Fe-based medium-entropy alloy coating; Figure 2 X-ray diffraction (XRD) patterns of the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4, the Fe-based medium-entropy alloy coatings prepared in Comparative Example 1, and the Fe-based alloy coatings prepared in Comparative Example 2. Figure 3 The images show the hardness curves of the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4, the Fe-based medium-entropy alloy coatings prepared in Comparative Example 1, and the Fe-based alloy coatings prepared in Comparative Example 2 to the substrate. Figure 4 The images shown are scanning electron microscope (SEM) images and EDS spectra of the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4 and the Fe-based alloy coating prepared in Comparative Example 2; wherein, a is the SEM image of the Fe-based alloy coating prepared in Comparative Example 2, b-e are the SEM images of the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4 respectively, and f is the EDS spectra of the cavitation erosion resistant Fe-based medium-entropy alloy coating prepared in Example 4. Figure 5The cumulative weight loss curves for cavitation erosion of the Fe-based medium-entropy alloy coatings prepared in Examples 1-4, the Fe-based medium-entropy alloy coatings prepared in Comparative Example 1, the Fe-based alloy coatings prepared in Comparative Example 2, and the 316L stainless steel substrate are shown. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0023] Example 1 Figure 1 For the process flow of Fe-based medium-entropy alloy coatings for cavitation erosion resistance, refer to Figure 1 Synthesize Fe-based medium-entropy alloy coatings resistant to cavitation erosion.

[0024] Preparation of Fe-based medium-entropy alloy coatings for cavitation erosion resistance: (1) The chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.4; according to the atomic ratio of the chemical formula of Fe-based entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain cladding powder.

[0025] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. An anti-cavitation Fe-based medium-entropy alloy coating is obtained.

[0026] Example 2 Preparation of Fe-based medium-entropy alloy coatings for cavitation erosion resistance: (1) The chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.6; according to the atomic ratio of the chemical formula of Fe-based entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain clad powder.

[0027] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. An anti-cavitation Fe-based medium-entropy alloy coating is obtained.

[0028] Example 3 Preparation of Fe-based medium-entropy alloy coatings for cavitation erosion resistance: (1) The chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.8; according to the atomic ratio of the chemical formula of Fe-based entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain cladding powder.

[0029] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. An anti-cavitation Fe-based medium-entropy alloy coating is obtained.

[0030] Example 4 Preparation of Fe-based medium-entropy alloy coatings for cavitation erosion resistance: (1) The chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 1.0; according to the atomic ratio of the chemical formula of Fe-based entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain cladding powder.

[0031] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. An anti-cavitation Fe-based medium-entropy alloy coating is obtained.

[0032] Comparative Example 1 Preparation of Fe-based medium-entropy alloy coatings: (1) The chemical formula of the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.2; according to the atomic ratio of the chemical formula of Fe-based entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain clad powder.

[0033] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. Fe-based medium-entropy alloy coating is obtained.

[0034] Comparative Example 2 Preparation of Fe-based alloy coatings: (1) The chemical formula of the Fe-based alloy coating is: Fe2CrNi; according to the atomic ratio of the chemical formula of the Fe-based medium entropy alloy, Fe powder, Cr powder and Ni powder (total 30 g) were put into a ball mill jar, and 15 mL of anhydrous ethanol was added as a ball milling aid for wet ball milling. The ball-to-powder ratio during wet ball milling was 50:3, the ball milling speed was 20 rpm, and the ball milling time was 24 h. After ball milling, the slurry was placed in a drying oven at 60 ℃ for drying to obtain cladding powder.

[0035] (2) The surface of the 316L stainless steel substrate to be clad is pretreated. The pre-clad surface is polished with 60-grit sandpaper to remove surface defects and oxide layer. Finally, the substrate is ultrasonically cleaned in anhydrous ethanol solution and then dried for later use. After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser clad. The specific cladding process parameters are: laser power of 1000 W, spot size of 3 mm, scanning speed of 10 mm / s, overlap rate of 40%, and pre-layer thickness of 1.5 mm. Fe-based alloy coating is obtained.

[0036] Figure 2 The powder diffraction (XRD) patterns are shown for the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4, the Fe-based medium-entropy alloy coating prepared in Comparative Example 1, and the Fe-based alloy coating prepared in Comparative Example 2. Figure 2 As can be seen, adding a limited amount of Nb to Fe2CrNi will form an HCP phase, which in turn forms a medium-entropy alloy coating with a dual-phase structure of FCC and HCP, enabling the alloy to achieve a high-strength-plasticity bond and effectively reducing cavitation erosion damage. When Nb is not doped or the doping amount is low, the HCP phase cannot be formed.

[0037] Figure 3 The hardness curves of the Fe-based medium-entropy alloy coatings prepared in Examples 1-4, Comparative Example 1, and Comparative Example 2 to the substrate show that, compared with the Fe2CrNi coating, the Fe2CrNiNb coating has higher hardness to the substrate. 0.4~1.0The hardness of the medium-entropy alloy coating increases rapidly with the increase of the x value.

[0038] Figure 4 The images are scanning electron microscope (SEM) images and EDS spectra of the cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4 and the Fe-based alloy coating prepared in Comparative Example 2. Figure 4 As the Nb content increases, the microstructure gradually transforms from equiaxed crystals to dendritic crystals, accompanied by the HCP phase evolving from a small amount of dispersed precipitation to a continuous network within the dendrites. EDS confirms that Nb is enriched in the HCP phase region between dendrites, while Fe, Cr, and Ni mainly enter the FCC matrix, forming a typical FCC+HCP dual-phase structure.

[0039] Figure 5 The cumulative weight loss curves of cavitation erosion resistant Fe-based medium-entropy alloy coatings prepared in Examples 1-4, Fe-based medium-entropy alloy coatings prepared in Comparative Example 1, Fe-based alloy coatings prepared in Comparative Example 2, and 316L stainless steel substrates are shown. It can be found that, compared to the Fe2CrNi coating, Fe2CrNiNb... 0.4~1.0 The cumulative weight loss of the medium-entropy alloy coating over 12 hours is much smaller than that of the Fe2CrNi coating, therefore Fe2CrNiNb 0.4~1.0 The cavitation resistance of the medium-entropy alloy coating is greatly enhanced.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Fe-based medium-entropy alloy coating resistant to cavitation erosion, characterized in that, The chemical formula for the Fe-based medium-entropy alloy coating is: Fe2CrNiNb x Where x is 0.4 to 1.0; Fe-based medium-entropy alloy coatings contain a dual-phase microstructure with face-centered cubic (FCC) phase and hexagonal close-packed (HCP) phase.

2. The method for preparing the cavitation erosion resistant Fe-based medium-entropy alloy coating according to claim 1, characterized in that, Includes the following steps: (1) According to the atomic ratio of the chemical formula of Fe-based medium entropy alloy, Fe powder, Cr powder, Ni powder and Nb powder are mixed evenly to obtain cladding powder; (2) After the cladding powder is laid on the substrate surface, the obtained cladding powder layer is laser cladding to obtain the cavitation erosion-resistant Fe-based medium entropy alloy coating.

3. The preparation method as described in claim 2, characterized in that, In step (1), the particle size of the Fe powder, Cr powder, Ni powder and Nb powder is 40~50 μm.

4. The preparation method as described in claim 2, characterized in that, In step (1), the method for uniform mixing is ball milling; preferably, the ball milling is wet ball milling.

5. The preparation method as described in claim 4, characterized in that, Ethanol was added as a ball milling aid.

6. The preparation method as described in claim 4, characterized in that, During wet ball milling, the ball-to-powder ratio is (45~55):(2.8~3.2), preferably 50:3; the ball milling speed is 18~30 rpm, preferably 20 rpm; and the ball milling time is 20~30 h, preferably 24 h.

7. The preparation method as described in claim 4, characterized in that, The clad powder is obtained by wet ball milling followed by drying.

8. The preparation method as described in claim 7, characterized in that, The drying conditions are vacuum drying at 55~65 ℃ for 7~9 h.

9. The preparation method as described in claim 2, characterized in that, In step (2), laser cladding is performed in an atmosphere of nitrogen or inert gas.

10. The preparation method as described in claim 2, characterized in that, In step (2), the process parameters for laser cladding include: The laser power is 800~2000 W, the spot diameter is 2~6 mm, the scanning speed is 8~12 mm / s, the overlap rate is 40%, and the pre-layer thickness is 1~2 mm, preferably 1.5 mm.

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