A high-entropy alloy coating material and a method for preparing a wear-resistant coating by plasma cladding

Abstract

The present invention provides a high-entropy alloy coating material, comprising: FeCoCrNiAl high-entropy alloy powder and yttrium powder; the weight of the yttrium powder is 0.5-1.0 wt.% of the weight of the FeCoCrNiAl high-entropy alloy powder. A method for preparing a wear-resistant coating by plasma cladding is also provided. By using the plasma cladding process with the high-entropy alloy-based coating material, a FeCoCrNiAl coating with a single BCC structure can be directly prepared on the surface of a substrate without further heat treatment, and a high-performance wear-resistant coating can be obtained while effectively reducing costs.

Description

Technical Field

[0001] The present invention belongs to the field of high-entropy alloy coatings, and particularly relates to a high-entropy alloy coating material and a method for preparing a wear-resistant coating by plasma cladding. Background Art

[0002] High-entropy alloys (HEAs) generally consist of four or more elements in equimolar or near-equimolar ratios, with the mass fraction of each element being 5% - 35%. The high mixing entropy formed among multi-component atoms inhibits the formation of intermetallic compounds and promotes the formation of solid solutions with simple crystal structures. Under the combined action of unique high-entropy effect, lattice distortion effect, atomic delayed diffusion effect and cocktail effect, HEAs often have more excellent mechanical and chemical properties than other alloys, such as high strength, high hardness, excellent wear resistance, good corrosion resistance and thermal stability. Therefore, HEAs have great application potential to break through the performance bottleneck of existing materials.

[0003] The problem of friction and wear has always been a major challenge in the application process of engineering materials. Some HEAs with excellent friction and wear properties can be used in the form of coatings to make up for the deficiency of poor wear resistance of traditional materials. At present, the preparation technologies of HEA coatings mainly include laser cladding, plasma cladding, cold spraying, electric spark deposition, etc. Among them, due to the moderate energy density, plasma cladding can not only fully melt the coating material during the cladding process, but also control the thermal deformation of the substrate within a small range, enabling good bonding between the coating and the substrate. In addition, plasma cladding has the characteristics of low production cost and high efficiency, and has obvious advantages in the cladding of large-size component coverage.

[0004] Research shows that the FeCoCrNiAl high-entropy alloy composed of a single BCC phase has excellent wear resistance. However, during the plasma cladding process, the BCC structure is easily damaged and transformed into the FCC structure or σ phase. The FCC phase has relatively high ductility but low strength, seriously affecting the wear resistance of the coating. Appropriate annealing heat treatment after cladding can make the coating reform into a single BCC structure and improve its wear resistance. However, the heat treatment process in production will reduce production efficiency and increase production costs. Therefore, there is an urgent need to propose a method for directly preparing a FeCoCrNiAl coating with a single BCC structure by plasma cladding. Summary of the Invention

[0005] Based on the above technical problems, the present invention proposes a high-entropy alloy coating material, which is obtained by modifying the composition of FeCoCrNiAl alloy with a certain amount of rare earth. The high-entropy alloy coating material is applicable to the plasma cladding process and can directly obtain a FeCoCrNiAl coating with a single BCC structure on the surface of the substrate.

[0006] The specific solution of the present invention is as follows:

[0007] One of the objectives of the present invention is to provide a high-entropy alloy coating material, including: FeCoCrNiAl high-entropy alloy powder and yttrium powder; the weight of the yttrium powder is 0.5-1.0 wt.% of the weight of the FeCoCrNiAl high-entropy alloy powder.

[0008] Aiming at the technical problem that during the rapid cooling process of the FeCoCrNiAl high-entropy alloy coating in plasma cladding, an unstable Fe-Cr phase will precipitate, which has an FCC structure and has an adverse effect on the hardness and wear resistance of the coating. The present invention adds rare earth yttrium to FeCoCrNiAl and strictly controls the content of yttrium within a specific range, which can not only effectively inhibit the precipitation of the Fe-Cr phase, but also avoid the formation of the Ni-Y phase formed by excessive addition of yttrium and Ni in the FeCoCrNiAl high-entropy alloy. A Cr-rich region and an Fe-Co region will be formed around the Ni-Y phase, which promote each other's growth, and finally a large amount of Al-depleted FeCoCrNi phase (FCC structure) will be generated, so that the cladded coating still has a typical high-entropy effect, realizing its characteristics of high hardness and high wear resistance.

[0009] Preferably, the atomic ratio of Fe, Co, Cr, Ni, and Al in the FeCoCrNiAl high-entropy alloy powder is 0.8-1:0.8-1:0.8-1:0.8-1:0.8-1.

[0010] Preferably, the particle size of the FeCoCrNiAl high-entropy alloy powder is 53-105 μm; the particle size of the yttrium powder is 200-400 mesh.

[0011] Preferably, its preparation method includes: mixing the FeCoCrNiAl high-entropy alloy powder and the yttrium powder in proportion, and then drying under the protection of an inert atmosphere.

[0012] Preferably, in the preparation method, the drying temperature is 100-200 °C and the drying time is 1-4 h.

[0013] Preferably, the inert atmosphere is argon or nitrogen.

[0014] Another objective of the present invention is to provide a method for preparing a wear-resistant coating by plasma cladding, using the high-entropy alloy coating material described in any one of the above to prepare a wear-resistant coating on the surface of a substrate by plasma cladding.

[0015] Preferably, the plasma cladding process parameters include: cladding current 180-200 A, ion gas flow rate 2.0-2.5 L / min, cladding speed 100-150 cm / min, and cladding layer overlap rate 40%-60%.

[0016] Preferably, the substrate is preheated to 180-220 °C before plasma cladding; preferably, the preheating method is selected from any one of resistance heating, flame heating, and induction heating.

[0017] Before preheating the substrate, surface pretreatment of the substrate is also included. The pretreatment method is a conventional method in the art, including but not limited to: grinding and polishing the substrate, removing surface oxide layers, oil stains and other contaminants, and then cleaning with solutions such as alcohol or acetone solution and waiting for use.

[0018] It also includes a post-treatment step after plasma cladding. The post-treatment method is a conventional method in the art, including but not limited to: removing rough areas on the surface by means of grinding debris, turning and milling after cladding to obtain a bright and clean cladding coating surface.

[0019] Preferably, the substrate is a ferrous material; preferably, the substrate is selected from any one of 45 steel, Q235 steel, and 316 stainless steel.

[0020] The beneficial effects of the present invention are as follows:

[0021] Aiming at the problem of reduced wear resistance of the coating caused by the destruction of the single BCC structure during the plasma cladding of FeCoCrNiAl high-entropy alloy, the present invention modifies the FeCoCrNiAl high-entropy alloy with a certain amount of yttrium powder to obtain a high-entropy alloy coating material suitable for the plasma cladding process. Using this coating material, a FeCoCrNiAl coating with a single BCC structure can be directly obtained by the plasma cladding process without subsequent heat treatment processes, which can effectively reduce production costs.

[0022] Furthermore, by optimizing the plasma cladding process, a FeCoCrNiAl wear-resistant coating with high hardness and high density can be obtained. Description of the Drawings

[0023] Figure 1 It is the surface morphology diagram of the wear-resistant coatings obtained in Examples 1-2 and Comparative Example 1;

[0024] Figure 2 It is the cross-sectional morphology diagram of the wear-resistant coatings obtained in Examples 1-2 and Comparative Example 1;

[0025] Figure 3 It is the XRD diagram of the wear-resistant coatings obtained in Examples 1-2 and Comparative Examples 2-3;

[0026] Figure 4 It is the backscattering diagram of the wear-resistant coatings obtained in Examples 1-2 and Comparative Examples 2-3;

[0027] Figure 5 It is the hardness distribution diagram of the wear-resistant coatings obtained in Examples 1-2 and Comparative Examples 2-3; DETAILED DESCRIPTION

[0028] The technical solutions of the present invention are described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0029] Example 1

[0030] A high entropy alloy coating material comprises: FeCoCrNiAl high entropy alloy powder and rare earth yttrium powder; the weight of the yttrium powder is 0.5wt.% of the weight of the FeCoCrNiAl high entropy alloy powder; wherein: (1) the atomic ratio of Fe, Co, Cr, Ni and Al in the FeCoCrNiAl high entropy alloy is 1:1:1:1:1; the particle size range of the FeCoCrNiAl high entropy alloy powder is 53-105μm, and the powder particle size distribution conforms to the normal distribution law; (2) the particle size of the yttrium powder is 200 mesh. The preparation method thereof is: FeCoCrNiAl high entropy alloy powder and yttrium powder are weighed in proportion and placed in a three-dimensional powder mixer with vacuum protection, after being fully mixed for 3h, taken out, placed under argon protection and dried at 160°C for 2h to obtain the obtained material.

[0031] The high entropy alloy coating material described in this embodiment is used as the wear-resistant layer material, and a plasma cladding process is used to prepare a wear-resistant coating on the surface of a 45 steel substrate. The specific parameters include: preheating temperature 200°C, cladding current 180A, ion gas flow rate 2.0L / min, cladding speed 100cm / min, and cladding layer overlap rate 40%.

[0032] The surface morphology of the wear-resistant coating obtained in this embodiment is shown in FIG. Figure 1 (a) is shown; the cross-sectional morphology is shown Figure 2 (a) as shown; XRD pattern as shown Figure 3 (0.5wt.%Y) as shown; the backscattering diagram is as Figure 4 As shown in (b), it can be seen that the main structure of the coating is composed of a single BCC phase. The coating has good surface quality, a density of more than 99%, and a hardness of up to 525 HV.

[0033] Example 2

[0034] A high entropy alloy coating material comprises: FeCoCrNiAl high entropy alloy powder and rare earth yttrium powder; the weight of the yttrium powder is 1.0wt.% of the weight of the FeCoCrNiAl high entropy alloy powder; wherein: (1) the atomic ratio of Fe, Co, Cr, Ni and Al in the FeCoCrNiAl high entropy alloy is 1:1:1:1:1; the particle size range of the FeCoCrNiAl high entropy alloy powder is 53-105μm, and the powder particle size distribution conforms to the normal distribution law; (2) the particle size of the yttrium powder is 400 mesh. The preparation method thereof is: FeCoCrNiAl high entropy alloy powder and yttrium powder are weighed in proportion and placed in a three-dimensional powder mixer with vacuum protection, after being fully mixed for 3 hours, taken out, placed under argon protection and dried at 160°C for 2 hours to obtain the obtained material.

[0035] The high entropy alloy coating material described in this embodiment is used as the wear-resistant layer material, and a plasma cladding process is used to prepare a wear-resistant coating on the surface of a 45 steel substrate. The specific parameters include: preheating temperature 200°C, cladding current 200A, ion gas flow rate 2.5L / min, cladding speed 150cm / min, and cladding layer overlap rate 60%.

[0036] The surface morphology of the wear-resistant coating obtained in this embodiment is shown in FIG. Figure 1 (b) as shown; the cross-sectional morphology is shown Figure 2 (b) as shown; XRD pattern as Figure 3 (1.0wt.%Y) as shown; the backscattering diagram is as Figure 4 As shown in (c), it can be seen that the main structure of the coating is still composed of BCC phase, but there is a small amount of FCC phase, indicating that the high entropy effect of the FeCoCrNiAl coating can still be retained, but the yttrium addition of 1.0wt.% is already the upper limit. The coating has good surface quality, a density of more than 99%, and a hardness of up to 535HV.

[0037] Comparative Example 1

[0038] The high entropy alloy coating material described in Example 1 was used to prepare a wear-resistant coating on the surface of a 45 steel substrate using a plasma cladding process. The specific parameters included: preheating temperature of 200°C, cladding current of 150A, ion gas flow rate of 1.5L / min, cladding speed of 100cm / min, and cladding layer overlap rate of 50%.

[0039] The surface morphology of the wear-resistant coating obtained in this comparative example is shown in Figure 1 (c) shows the cross-sectional morphology. Figure 2 As shown in (c), it can be seen that cracks appear on the surface of the coating and a large number of holes appear in the cross section.

[0040] Comparative Example 2

[0041] Using pure FeCoCrNiAl powder (the atomic ratio of Fe, Co, Cr, Ni, and Al in the FeCoCrNiAl high-entropy alloy is 1:1:1:1:1; the particle size range is 53 - 105 μm, and the powder particle size distribution conforms to the normal distribution law) as the wear-resistant layer material, a wear-resistant coating was prepared on the surface of a 45 steel substrate by the plasma cladding process. The specific parameters include: preheating temperature 200 °C, cladding current 180 A, ion gas flow rate 2.0 L / min, cladding speed 100 cm / min, and cladding layer overlap rate 40%.

[0042] The XRD pattern of the wear-resistant coating obtained in this comparative example is as shown in Figure 3 (0Y), and the backscattered pattern is as shown in Figure 4 (a). It can be seen that it is composed of a mixture of a large number of BCC and FCC structures. The surface quality of the coating is good, the density is above 99%, and the hardness is 495 HV.

[0043] Comparative Example 3

[0044] A high-entropy alloy coating material and its preparation method are the same as those in Example 1, except that the addition amount of rare earth yttrium is 1.5 wt.% of the weight of the FeCoCrNiAl high-entropy alloy powder.

[0045] Using the high-entropy alloy coating material described in this comparative example as the wear-resistant layer material, a wear-resistant coating was prepared on the surface of a 45 steel substrate by the plasma cladding process. The specific parameters are the same as those in Example 1.

[0046] The XRD pattern of the wear-resistant coating obtained in this comparative example is as shown in Figure 3 (1.5 wt.% Y), and the backscattered pattern is as shown in Figure 4 (d). It is mainly composed of a large number of FCC structures and a small amount of BCC structures. The surface quality of the coating is good, the density is above 99%, and the hardness is 309 HV.

[0047] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a wear-resistant coating by plasma cladding, characterized in that, A wear-resistant coating is prepared on the surface of a substrate by using a high-entropy alloy coating material through a plasma cladding process; the high-entropy alloy coating material includes: FeCoCrNiAl high-entropy alloy powder and yttrium powder; the weight of the yttrium powder is 0.5-1.0 wt.% of the weight of the FeCoCrNiAl high-entropy alloy powder; the atomic ratio of Fe, Co, Cr, Ni, and Al in the FeCoCrNiAl high-entropy alloy powder is 0.8-1:0.8-1:0.8-1:0.8-1:0.8-1; The plasma cladding process parameters include: cladding current 180-200 A, ion gas flow rate 2.0-2.5 L / min, cladding speed 100-150 cm / min, cladding layer overlap rate 40%-60%; the substrate is preheated to 180-220 °C before plasma cladding.

2. The method for preparing a wear-resistant coating by plasma cladding according to claim 1, characterized in that, The particle size of the FeCoCrNiAl high-entropy alloy powder is 53-105 μm; the particle size of the yttrium powder is 200-400 mesh.

3. The method for preparing a wear-resistant coating by plasma cladding according to claim 1 or 2, characterized in that, The preparation method of the high-entropy alloy coating material includes: mixing the FeCoCrNiAl high-entropy alloy powder and the yttrium powder in proportion, and then drying under the protection of an inert atmosphere.

4. The method for preparing a wear-resistant coating by plasma cladding according to claim 3, characterized in that, In the preparation method of the high-entropy alloy coating material, the drying temperature is 100-200 °C, and the drying time is 1-4 h.

5. The method for preparing a wear-resistant coating by plasma cladding according to claim 3, characterized in that, In the preparation method of the high-entropy alloy coating material, the inert atmosphere is argon or nitrogen.

6. The method for preparing a wear-resistant coating by plasma cladding according to claim 1, wherein, The substrate is an iron-based material.

7. The method for preparing a wear-resistant coating by plasma cladding according to claim 1, wherein, The substrate is selected from any one of 45 steel, Q235 steel, and 316 stainless steel.

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