CoCrNi medium-entropy alloy composite coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of CoCrNi medium-entropy alloy composite coatings, in particular to a CoCrNi medium-entropy alloy composite coating and a preparation method and application thereof. The invention provides a preparation method of a CoCrNi medium-entropy alloy composite coating, which comprises the following steps: mixing CoCrNi medium-entropy alloy and niobium carbide to obtain cladding powder; the mass percentage content of the niobium carbide in the cladding powder is 10-20%; and after the cladding powder is laid on the surface of a base body, an obtained cladding powder layer is subjected to laser cladding, and the CoCrNi medium-entropy alloy composite coating is obtained. The CoCrNi medium-entropy alloy composite coating prepared by the preparation method has excellent wear resistance and corrosion resistance, and can meet the extreme requirements of ocean engineering and aerospace on the coating performance.

Description

Technical Field

[0001] The present invention relates to the technical field of CoCrNi medium-entropy alloy composite coatings, and in particular to a CoCrNi medium-entropy alloy composite coating and a preparation method and application thereof. Background Art

[0002] The stacking failure capability of CoCrNi medium-entropy alloy membrane electrode is low, so it has a stable FCC structure and excellent mechanical properties. These properties make it widely used in marine engineering and aerospace. However, in actual application scenarios, due to the combined action of friction and shear stress, the coating is often very susceptible to corrosion and wear, which shortens the service life of the material and even causes engineering disasters. Although CoCrNi medium-entropy alloy has better mechanical properties and corrosion resistance than traditional materials, a single CoCrNi medium-entropy alloy still does not meet the extreme requirements of marine engineering and aerospace for coating performance. Therefore, there is an urgent need for effective methods to improve the overall performance of CoCrNi coatings. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a CoCrNi medium-entropy alloy composite coating and its preparation method and application. The CoCrNi medium-entropy alloy composite coating prepared by the preparation method has excellent wear resistance and corrosion resistance, which can meet the extreme requirements of marine engineering and aerospace for coating performance.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a CoCrNi medium-entropy alloy composite coating, comprising the following steps:

[0006] Mixing a CoCrNi medium entropy alloy and niobium carbide to obtain a cladding powder; wherein the mass percentage of the niobium carbide in the cladding powder is 10 to 20%;

[0007] After the cladding powder is laid on the surface of the substrate, the obtained cladding powder layer is subjected to laser cladding to obtain the CoCrNi medium entropy alloy composite coating.

[0008] Preferably, the particle size of the CoCrNi mesentropy alloy is 10 to 100 μm.

[0009] Preferably, the mass ratio of Co, Cr and Ni in the CoCrNi medium entropy alloy is (33.2-36.2): ​​(29.2-32.2): (33.1-36.1).

[0010] Preferably, the particle size of the niobium carbide is 1 to 5 μm.

[0011] Preferably, the thickness of the cladding powder layer is 2.5±0.5 mm.

[0012] Preferably, the laser cladding is performed in a protective atmosphere;

[0013] The laser power of the laser cladding is 1000-1400W; the scanning rate is 300-600mm / min; the defocus rate is +(4-6)mm; the overlap rate is 40-60%; the spot diameter is 2.2-2.8mm; the track spacing is 1-1.3mm; and the flow rate is 5-10L / min.

[0014] Preferably, the protective atmosphere comprises an argon atmosphere;

[0015] The laser power of the laser cladding is 1000W; the scanning rate is 500mm / min; the defocus rate is +5mm; the overlap rate is 50%; the spot diameter is 2.5mm; the track spacing is 1.3mm; and the flow rate is 6L / min.

[0016] Preferably, the substrate is a Q235B low carbon steel substrate.

[0017] The present invention also provides a CoCrNi medium-entropy alloy composite coating prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides the application of the CoCrNi medium entropy alloy composite coating described in the above technical solution in the fields of marine engineering or aerospace.

[0019] The present invention provides a method for preparing a CoCrNi medium-entropy alloy composite coating, comprising the following steps: mixing a CoCrNi medium-entropy alloy and niobium carbide to obtain a cladding powder; the niobium carbide content of the cladding powder is 10-20% by weight; applying the cladding powder on a substrate surface, and then laser cladding the resulting cladding powder layer to obtain the CoCrNi medium-entropy alloy composite coating. The preparation method utilizes niobium carbide (NbC) due to its high melting point (3873°C), high hardness (19.6 GPa), and excellent chemical stability. By mixing it into the CoCrNi medium-entropy alloy, the coating significantly improves its overall performance. NbC acts as a heterogeneous nucleation site, increasing the nucleation rate and refining the grains, achieving fine grain strengthening. Furthermore, the significant difference in atomic radius between NbC and the matrix elements (Co, Cr, Ni) creates a solid solution strengthening effect in the coating. Furthermore, the dispersion strengthening mechanism initiated by NbC as a hard phase can further enhance the material's hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the laser cladding process according to an embodiment of the present invention;

[0021] Figure 2 The wear depth (a) and wear rate (b) of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1;

[0022] Figure 3 The electrochemical impedance spectroscopy diagrams of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1 are shown;

[0023] Figure 4 The Tafel polarization curves of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1 were tested in a scanning range of -0.5V to 1.5V and a scanning speed of 0.01V / s. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing a CoCrNi medium-entropy alloy composite coating, comprising the following steps:

[0025] Mixing a CoCrNi medium entropy alloy and niobium carbide to obtain a cladding powder; wherein the mass percentage of the niobium carbide in the cladding powder is 10 to 20%;

[0026] After the cladding powder is laid on the surface of the substrate, the obtained cladding powder layer is subjected to laser cladding to obtain the CoCrNi medium entropy alloy composite coating.

[0027] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0028] The present invention mixes a CoCrNi medium entropy alloy and niobium carbide to obtain cladding powder; the mass percentage of the niobium carbide in the cladding powder is 10-20%.

[0029] In the present invention, the particle size of the CoCrNi medium-entropy alloy is preferably 10 to 100 μm, more preferably 15 to 53 μm. In the present invention, the mass ratio of Co, Cr, and Ni in the CoCrNi medium-entropy alloy is preferably (33.2 to 36.2): ​​(29.2 to 32.2): (33.1 to 36.1), more preferably (34 to 35): (30 to 31): (34 to 35). In an embodiment of the present invention, the mass ratio of Co, Cr, and Ni can be 34.7:30.5:34.7.

[0030] In the present invention, the particle size of the niobium carbide is preferably 1 to 5 μm.

[0031] In the present invention, the particle sizes of the CoCrNi medium-entropy alloy and niobium carbide are controlled within the aforementioned ranges. The niobium carbide is smaller than the CoCrNi medium-entropy alloy, ensuring that the niobium carbide easily blends into the CoCrNi medium-entropy alloy, forming a finer alloy coating. Specifically, smaller additive powders disperse more evenly within the main powder, improving mixing uniformity and ensuring a more uniform distribution of the additives within the coating, avoiding localized enrichment or defects. During the cladding process, the fine additive powders contribute to the formation of finer grains or microstructures, thereby improving the hardness and strength of the coating.

[0032] In the present invention, the mass percentage of the niobium carbide in the cladding powder is 10-20%, preferably 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%. In an embodiment of the present invention, the mass percentage of the niobium carbide in the cladding powder may be 10%.

[0033] The present invention does not have any special limitation on the mixing process, and the mixing process may be carried out using a process well known to those skilled in the art.

[0034] After obtaining the cladding powder, the present invention lays the cladding powder on the surface of the substrate and then performs laser cladding on the obtained cladding powder layer to obtain the CoCrNi medium entropy alloy composite coating.

[0035] In the present invention, the substrate is preferably a Q235B low carbon steel substrate.

[0036] Prior to laying, the present invention also preferably includes pre-treating the substrate, preferably including sequential polishing and cleaning. In the present invention, the polishing is preferably performed using sandpaper with a mesh size of 100 to 1000. The present invention does not impose any particular restrictions on the polishing process, and the process may be performed using a process well known to those skilled in the art. In the present invention, the cleaning agent used for cleaning is preferably anhydrous ethanol. The present invention does not impose any particular restrictions on the cleaning process, and the process may be performed using a process well known to those skilled in the art.

[0037] The present invention does not have any special limitation on the paving process, and the paving process may be carried out using a process well known to those skilled in the art.

[0038] In the present invention, the thickness of the cladding powder layer is preferably 2.5±0.5 mm. In an embodiment of the present invention, the thickness of the cladding powder layer can be 2.5 mm.

[0039] In the present invention, the laser cladding is preferably performed in a protective atmosphere, and the protective atmosphere is preferably an argon atmosphere, a nitrogen atmosphere or a helium atmosphere. In an embodiment of the present invention, the protective atmosphere can be an argon atmosphere.

[0040] In the present invention, the protective atmosphere is preferably provided by introducing a protective gas, and the flow rate of the protective gas is preferably 3 to 9 L / min, more preferably 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min or 9 L / min. In an embodiment of the present invention, the flow rate of the protective gas can be 5 L / min.

[0041] In the present invention, the laser power of the laser cladding is preferably 1000-1400W, more preferably 1000W, 1050W, 1100W, 1150W, 1200W, 1250W, 1300W, 1350W or 1400W; the scanning rate is preferably 300-600mm / min, more preferably 300mm / min, 350mm / min, 400mm / min, 450mm / min, 500mm / min, 550mm / min or 600mm / min; the defocus rate is preferably +(4-6)mm, more preferably +4mm, +5mm or +6mm; the overlap rate is preferably The optical fiber density is preferably 40-60%, more preferably 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% or 60%; the spot diameter is preferably 2.2-2.8mm, more preferably 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm or 2.8mm; the track spacing is preferably 1-1.3mm, more preferably 1mm, 1.1mm, 1.2mm or 1.3mm; the flow rate is preferably 5-10L / min, more preferably 5L / min, 6L / min, 7L / min, 8L / min, 9L / min or 10L / min. In an embodiment of the present invention, the laser power of the laser cladding can be 1000W; the scanning rate can be 500mm / min; the defocus rate can be +5mm; the overlap rate can be 50%; the spot diameter can be 2.5mm; the track spacing can be 1.3mm; and the flow rate can be 6L / min.

[0042] In the present invention, the advantage of controlling the laser cladding parameters within the above range is that the coating surface has a good microstructure without obvious defects such as cracks and pores.

[0043] The present invention also provides a CoCrNi medium-entropy alloy composite coating prepared by the preparation method described in the above technical solution.

[0044] The present invention also provides the application of the CoCrNi medium entropy alloy composite coating described in the above technical solution in the fields of marine engineering and aerospace. In the present invention, the application is preferably used for turbine blades in the field of aerospace or for ship decks or propellers in marine engineering.

[0045] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, Q235B low carbon steel is used as a metal substrate, the Q235B low carbon steel is polished with sandpaper having a mesh size of 100 to 1000, and then cleaned with anhydrous ethanol to obtain pretreated Q235B low carbon steel;

[0048] Nb carbide powder with a particle size of 1 to 5 μm and CoCrNi medium entropy alloy powder with a particle size of 10 to 100 μm (the mass ratio of Co, Cr and Ni is 34.7:30.5:34.7) are mixed in a mass ratio of 1:9 to obtain a cladding powder;

[0049] Laying the cladding powder on the surface of the pretreated Q235B low-carbon steel to obtain a cladding powder layer with a thickness of 2.5 mm;

[0050] The cladding powder layer was subjected to laser cladding treatment (the laser power of the laser cladding treatment was 1000 W, the scanning rate was 500 mm / min, the defocus rate was +5 mm, the overlap rate was 50%, the spot diameter was 2.5 mm, the track pitch was 1.3 mm, the flow rate was 6 L / min, and argon gas was introduced at a rate of 5 L / min to provide a protective atmosphere) to obtain a CoCrNi medium-entropy alloy composite coating (denoted as CoCrNi+10 wt.% NbC).

[0051] Example 2

[0052] like Figure 1 As shown, Q235B low carbon steel is used as a metal substrate, the Q235B low carbon steel is polished with sandpaper having a mesh size of 100 to 1000, and then cleaned with anhydrous ethanol to obtain pretreated Q235B low carbon steel;

[0053] Nb carbide powder with a particle size of 1 to 5 μm and CoCrNi medium entropy alloy powder with a particle size of 10 to 100 μm (the mass ratio of Co, Cr and Ni is 34.7:30.5:34.7) are mixed in a mass ratio of 1.5:8.5 to obtain a cladding powder;

[0054] Laying the cladding powder on the surface of the pretreated Q235B low-carbon steel to obtain a cladding powder layer with a thickness of 2.5 mm;

[0055] The cladding powder layer was subjected to laser cladding treatment (the laser power of the laser cladding treatment was 1000 W, the scanning rate was 500 mm / min, the defocus rate was +5 mm, the overlap rate was 50%, the spot diameter was 2.5 mm, the track pitch was 1.3 mm, the flow rate was 6 L / min, and argon gas was introduced at a rate of 5 L / min to provide a protective atmosphere) to obtain a CoCrNi medium entropy alloy composite coating (denoted as CoCrNi+15wt.%NbC).

[0056] Comparative Example 1

[0057] Refer to Example 1, except that no niobium carbide powder is added, and a CoCrNi medium entropy alloy coating is obtained.

[0058] Test Case

[0059] A pin-on-disc friction and wear tester (Model: SFT-2M, Manufacturer: Lanzhou Zhongke Technology Development Co., Ltd., Lanzhou, China) equipped with a displacement sensor was used at room temperature using a 4 mm GCr15 steel ball as the friction counterpart of the coating surface to measure the wear depth and subsequently calculate the wear rate. The test parameters were: load 25 N, rotation radius 2 mm, rotation speed 200 r / min, and test duration 30 min; the test results are shown in Figure 2. Figure 2 As shown in Table 1, Figure 2 The wear depth (a) and wear rate (b) of the CoCrNi medium entropy alloy composite coatings described in Examples 1 and 2 and the CoCrNi medium entropy alloy coating described in Comparative Example 1;

[0060] Table 1 Wear depth and wear rate of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1

[0061] Test samples Wear depth <![CDATA[Wear rate (10 -4 mm 3 ·N -1 ·m -1 )]]> Comprehensive judgment Example 1 Shallow (32μm) 1.2145 good Comparative Example 1 Deeper (131μm) 6.2121 generally Example 2 Shallow (40μm) 1.4914 good

[0062] Depend on Figure 2 As can be seen from Table 1, the introduction of NbC has an undeniable effect on the wear resistance of the coating. The high-hardness NbC particles formed in the coating can effectively resist the micro-cutting of the friction pair, thereby significantly enhancing the wear resistance of the coating.

[0063] An electrochemical workstation (model CS350M, Corrtest, Wuhan, China) was used at room temperature using the three-electrode method (working electrode: coating, reference electrode: saturated mercury electrode, auxiliary electrode: platinum sheet). A 3.5 wt% NaCl solution was used for the experiment. Before the test, each sample was prepared to a standard size of 1 mm × 1 mm and then immersed in the 3.5 wt% NaCl solution for 10 h to stabilize the self-corrosion potential. -1 ~10 5 The sample was tested at a frequency of Hz to obtain the electrochemical impedance spectroscopy (EIS). The test results are as follows: Figure 3 As shown in Table 2, Figure 3 The electrochemical impedance spectroscopy of the CoCrNi medium-entropy alloy composite coating of Example 1 and the CoCrNi medium-entropy alloy coating of Comparative Example 1 is shown, wherein (a) is the Nyquist plot, (b) is the Bode modulus plot, (c) is the Bode phase angle plot, and (d) is the equivalent circuit model. Figure 3 It can be seen that the addition of NbC makes the CoCrNi medium entropy alloy coating exhibit a larger arc radius, higher impedance modulus and larger phase angle. This shows that NbC can effectively reduce the charge accumulation on the surface of the CoCrNi medium entropy alloy coating, thereby slowing down the corrosion of the coating;

[0064] Table 2 Electrochemical impedance parameters of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1

[0065]

[0066]

[0067] Depend on Figure 3 As shown in Table 2, the addition of NbC increases the resistance of the coating passivation film and effectively inhibits the corrosion of the substrate by the corrosive medium;

[0068] Figure 4 The Tafel polarization curves of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1 were tested in a scanning range of -0.5V to 1.5V and a scanning speed of 0.01V / s. Table 3 shows the Tafel test results of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1;

[0069] Table 3 Tafel test results of the CoCrNi medium entropy alloy composite coating described in Example 1 and the CoCrNi medium entropy alloy coating described in Comparative Example 1

[0070] sample <![CDATA[I corr Self-corrosion current density (A·cm -2 )]]> <![CDATA[E corr Self-corrosion potential (V)]]> Comprehensive judgment Example 1 <![CDATA[8.4476×10 -8 ]]> -0.2770 good Comparative Example 1 <![CDATA[7.0568×10 -7 ]]> -0.2840 generally Example 2 <![CDATA[7.116×10 -8 ]]> -0.2608 good

[0071] Depend on Figure 4 As shown in Table 3, the doping of NbC significantly increases the self-corrosion potential of the coating, while reducing the self-corrosion current density, effectively enhancing the corrosion resistance of the coating.

[0072] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a CoCrNi medium entropy alloy composite coating, characterized in that: The following steps are involved: Mixing a CoCrNi medium entropy alloy and niobium carbide to obtain a cladding powder; wherein the mass percentage of the niobium carbide in the cladding powder is 10 to 20%; After the cladding powder is laid on the surface of the substrate, the obtained cladding powder layer is subjected to laser cladding to obtain the CoCrNi medium entropy alloy composite coating.

2. The preparation method according to claim 1, wherein The particle size of the CoCrNi medium entropy alloy is 10 to 100 μm.

3. The preparation method according to claim 1 or 2, wherein The mass ratio of Co, Cr and Ni in the CoCrNi medium entropy alloy is (33.2-36.2): ​​(29.2-32.2): (33.1-36.1).

4. The preparation method according to claim 1, wherein The particle size of the niobium carbide is 1 to 5 μm.

5. The preparation method according to claim 1, wherein The thickness of the cladding powder layer is 2.5±0.5 mm.

6. The preparation method according to claim 1, wherein The laser cladding is carried out in a protective atmosphere; The laser power of the laser cladding is 1000-1400W; the scanning rate is 300-600mm / min; the defocus rate is +(4-6)mm; the overlap rate is 40-60%; the spot diameter is 2.2-2.8mm; the track spacing is 1-1.3mm; and the flow rate is 5-10L / min.

7. The preparation method according to claim 6, wherein The protective atmosphere includes an argon atmosphere; The laser power of the laser cladding is 1000W; the scanning rate is 500mm / min; the defocus rate is +5mm; the overlap rate is 50%; the spot diameter is 2.5mm; the track spacing is 1.3mm; and the flow rate is 6L / min.

8. The preparation method according to claim 1, wherein The substrate is a Q235B low carbon steel substrate.

9. A CoCrNi medium-entropy alloy composite coating prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the CoCrNi medium entropy alloy composite coating according to claim 9 in the fields of marine engineering or aerospace.

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