A boron-free nickel-based wear-resistant coating and a preparation method and application thereof

Abstract

This invention belongs to the field of material surface strengthening technology, and proposes a boron-free nickel-based wear-resistant coating, its preparation method, and its application. The invention uses a mixed powder as raw material, heats the substrate with a hot plate, and performs laser cladding on the raw material through synchronous powder feeding to form a wear-resistant coating on the substrate surface. The mixed powder consists of the following components: 35.0-65.0% zirconium carbide powder and 35.0-65.0% nickel-based alloy powder. The nickel-based alloy powder comprises, by mass percentage: 28.0-31.5% chromium, 8.5-10.0% iron, 0-0.1% carbon, and 58.4-63.5% nickel. Compared with existing technologies, the coating obtained by this invention can achieve a hardness of over 40 HRC and exhibits excellent wear resistance at both room temperature and high temperature, ensuring its application in the field of strengthening bearings in control rod drive mechanisms.

Description

Technical Field

[0001] This invention relates to the field of material surface strengthening technology, and in particular to a boron-free nickel-based wear-resistant coating, its preparation method, and its application. Background Technology

[0002] The control rod drive mechanism is a core component of a nuclear reactor, driving the control rod assemblies within the core to regulate reactor power and, in emergencies, safely shut down the reactor, ensuring its safe and normal operation. The bearings of the control rod drive mechanism operate under high temperature, high humidity, and high radiation conditions, frequently experiencing excessive wear and even cracking, severely impacting the normal operation of the nuclear power plant. Traditional bearing surface strengthening methods utilize welding to create a Stellite6 cobalt-based alloy weld overlay. This process offers advantages such as high hardness and good wear resistance, but it also results in high heat input, significant thermal deformation of the workpiece, and the poor thermal conductivity of Stellite6, leading to numerous internal defects in the weld overlay. Wear debris from the Stellite6 weld overlay is transported to the core region via the primary coolant circulation. 59 Co is easily transformed into radioactive isotopes upon thermal neutron bombardment. 60 Co, 60 Co decays and releases gamma photons, which can harm surrounding equipment and workers.

[0003] Therefore, there is an urgent need for a coating that can enhance the wear resistance of the substrate surface. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems by providing a boron-free nickel-based wear-resistant coating, its preparation method and application, and to propose a nickel-based coating and its preparation method that can ensure the radiation resistance of the coating while having high wear resistance and high corrosion resistance.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The first objective of this invention is to provide a boron-free nickel-based wear-resistant coating, wherein the boron-free nickel-based wear-resistant coating is made from a mixed powder, the mixed powder comprising the following components by weight percentage:

[0007] Zirconium carbide powder 35-65%, with a particle size of 10-60μm; nickel-based alloy powder 35-65%, with a particle size of 53-109μm;

[0008] The nickel-based alloy powder comprises the following components by mass percentage: 28.0-31.5% chromium, 8.5-10.0% iron, 0-0.1% carbon, and 58.4-63.5% nickel.

[0009] More preferably, the mass percentage content of each component in the nickel-based alloy powder is: chromium 28.0-31.5%, iron 8.5-10.0%, carbon 0-0.1%, and nickel 58.4-63.5%.

[0010] Furthermore, the thickness of the boron-free nickel-based wear-resistant coating is adjustable between 0.7 and 1.3 mm, and the hardness of the boron-free nickel-based wear-resistant coating is greater than 40 HRC.

[0011] Furthermore, under normal temperature conditions, a friction and wear test was conducted using tungsten carbide grinding balls with a diameter of 5 mm, a friction radius of 10 mm, a rotational speed of 200 rpm, a load of 30 N, and a test time of 1 hour. The wear volume of the boron-free nickel-based wear-resistant coating at room temperature was less than 10 mm. 3 .

[0012] Furthermore, under high temperature conditions of 300℃, a high-temperature friction and wear test was conducted using tungsten carbide grinding balls with a diameter of 9.25mm. The friction radius was 10mm, the rotation speed was 200rpm, the load was 30N, and the test time was 1h. The high-temperature wear volume of the boron-free nickel-based wear-resistant coating was less than 1mm. 3 .

[0013] A second objective of this invention is to provide a method for preparing a boron-free nickel-based wear-resistant coating, the method comprising the following steps:

[0014] Pretreatment of the substrate to be clad: Polish the surface of the substrate to be clad to a smooth finish and clean it to obtain the substrate to be clad;

[0015] Mixing of cladding powders: Zirconium carbide powder and nickel-based alloy powder are ball-milled and mixed in a mass ratio to prepare a mixed powder;

[0016] Drying of the mixed powder: The mixed powder is dried by heating;

[0017] Laser cladding: The substrate to be clad is heated, and the mixed powder is laser clad under protective gas conditions to form a laser cladding layer on the surface of the substrate. The resulting laser cladding layer is the boron-free nickel-based wear-resistant coating.

[0018] Furthermore, the preparation method includes the following steps:

[0019] S1. Pretreatment of the substrate to be clad: The surface of the substrate to be clad is polished smooth with a grinding wheel and cleaned to obtain the substrate to be clad;

[0020] S2. Mixing of cladding powder: Zirconium carbide powder and nickel-based alloy powder are uniformly mixed in a planetary ball mill according to the mass ratio to prepare a mixed powder;

[0021] S3. Drying of the mixed powder: The mixed powder is dried by heating in a furnace;

[0022] S4. Laser cladding: The substrate to be clad is heated by an electric heating plate, and the mixed powder is laser clad under protective gas conditions to form a laser cladding layer on the surface of the substrate. The resulting laser cladding layer is the boron-free nickel-based wear-resistant coating.

[0023] Furthermore, in step S1, the substrate to be clad is a 304 stainless steel substrate.

[0024] Furthermore, in step S2, the planetary ball mill has a mixing time of 2-3 hours and a rotation speed of 250-300 rpm.

[0025] Furthermore, in step S3, the heating and drying time is 2-3 hours, and the temperature is 80-110°C.

[0026] More preferably, in step S3, the heating and drying time is 2 hours and the temperature is 100°C.

[0027] Further, in step S4, the protective gas is argon; in step S4, the temperature parameter of the heating plate is 150℃; in step S4, the process parameters of the laser cladding are: laser power of 1200-1400W, scanning speed of 1800-2000mm / min, overlap rate of 50%, powder feeding speed of 8-12g / min, and spot diameter of 1.3mm.

[0028] A third objective of this invention is to provide an application of a boron-free nickel-based wear-resistant coating for use in the control rod drive mechanism of a nuclear reactor.

[0029] Furthermore, the boron-free nickel-based wear-resistant coating is used to strengthen the bearings of the control rod drive mechanism.

[0030] Furthermore, a boron-free nickel-based wear-resistant coating is used as the cladding layer for the bearings of the control rod drive mechanism. The cladding layer has good radiation resistance and can work for a long time in the nuclear power plant environment.

[0031] Furthermore, a boron-free nickel-based wear-resistant coating is used as the cladding layer for the bearing of the control rod drive mechanism. The cladding layer has high hardness and excellent wear resistance.

[0032] The technical principles and concepts of this invention are as follows:

[0033] To address the problems of traditional bearing surface strengthening methods, laser cladding technology is used to prepare nickel-based wear-resistant coatings, enhancing the wear resistance of the substrate surface. Laser cladding technology uses a high-energy laser beam as a heat source to melt cladding powder sprayed simultaneously above the substrate. The substrate surface absorbs a small amount of heat to form a molten pool, and the molten cladding powder then falls into the pool, forming a metallurgical bond with the substrate. After cooling, a cladding layer is formed, thereby altering the substrate's surface properties. Compared to welding, laser cladding technology uses a higher laser energy density, resulting in less total heat input to the substrate, less thermal deformation during processing, a lower dilution rate, and a smoother surface. The internal grains of the cladding layer are finer, the structure is denser, the internal microstructure is more uniform, and there are fewer defects, giving the cladding layer better hardness, wear resistance, and corrosion resistance than the weld layer.

[0034] Nickel (Ni) has a small neutron absorption cross section and good radiation resistance, making nickel-based superalloys widely used in nuclear power as heat transfer tube materials. Nickel-based alloys exhibit good wettability with stainless steel, and the cladding layer prepared from nickel-based cladding powder bonds strongly to the substrate, also possessing excellent high-temperature resistance. Currently, most commercially available wear-resistant nickel-based cladding powders contain boron (B). Boron has a large neutron absorption cross section and readily undergoes an (n, α) reaction in nuclear facilities, generating Li atoms and helium gas, leading to defects within the cladding layer and affecting the service life of the wear-resistant coating. Therefore, it is necessary to explore a boron-free nickel-based alloy powder that can create a nickel-based coating with good radiation resistance, as well as excellent hardness and wear resistance.

[0035] In practical applications in the nuclear power industry, high-temperature nickel-based alloys frequently experience stress corrosion cracking. This is because during the cooling and solidification process of the molten nickel-based alloy, chromium (Cr) forms carbides that precipitate from the grain boundaries, leading to a decrease in the Cr content in the matrix and the formation of Cr-depleted zones. This reduces the corrosion resistance of the matrix, and stress corrosion cracking becomes severe when the Cr content of the nickel-based alloy is already low. Therefore, it is necessary to add a higher Cr content to the nickel-based alloy to reduce stress corrosion cracking.

[0036] A small amount of iron (Fe) is usually added to high-temperature nickel-based alloys. This iron acts as a solid solution strengthener in the matrix, increasing the alloy's hardness while reducing its cost. The addition of Fe can also improve the alloy's resistance to concentrated sulfuric acid corrosion. However, excessive Fe content can reduce the alloy's corrosion resistance in pure water environments, adversely affecting its performance.

[0037] Cobalt readily absorbs neutrons to form cobalt-60 in the operating environment of nuclear power plants. 60 Cobalt-60 decays and releases gamma photons, making it unsuitable for use in nuclear power plant environments.

[0038] Zirconium carbide (ZrC) exhibits superior radiation resistance compared to other hard ceramics used in nuclear facilities. It maintains its crystal structure even under high radiation flux and reduces the diffusion rate of fission products, thus resisting nuclear fission product impact. In cladding layers, zirconium carbide can refine metal grains, reduce dislocation density, and improve the tensile strength and microhardness of the cladding layer. With its extremely high melting point and excellent high-temperature resistance, zirconium carbide is suitable as a reinforcing phase in high-temperature nickel-based alloy coatings, increasing the hardness of the cladding layer and thus improving its wear resistance.

[0039] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0040] 1) This invention provides a boron-free nickel-based wear-resistant coating, using a nickel-based alloy as the matrix with the following mass percentages: chromium 28.0-31.5%, iron 8.5-10.0%, carbon 0-0.1%, and nickel 58.4-63.5%. The high Cr content ensures that even after Cr-rich compounds precipitate in the cladding layer, a high Cr content remains in the matrix, effectively reducing the stress corrosion cracking susceptibility of the cladding layer; it also alters the pitting potential, improving the corrosion resistance of the cladding layer; and Cr can form chromium oxide during the cladding process, enhancing the high-temperature wear resistance of the cladding layer. A small amount of Fe provides solid solution strengthening while ensuring good corrosion resistance. Trace amounts of C form carbides with metallic elements, which act as pinning agents, increasing grain boundary migration energy, improving the deformation resistance of the cladding layer, and thus enhancing its strength.

[0041] 2) This invention provides a boron-free nickel-based wear-resistant coating. Zirconium carbide powder is selected as the reinforcing phase and mixed with nickel-based alloy powder. After cladding, a wear-resistant coating is formed. Zirconium carbide has a very low neutron absorption cross section. Under the premise of having high hardness and high temperature resistance, it does not have the defect of existing wear-resistant nickel-based coatings that are prone to performance degradation in high radiation environments. Zirconium carbide plays a role in hard reinforcement and grain refinement in the cladding layer, which can effectively improve the hardness of the cladding layer, so that the cladding layer has excellent wear resistance.

[0042] 3) This invention provides a method for preparing a boron-free nickel-based wear-resistant coating. The substrate to be clad is heated, the process parameters of laser cladding are adjusted, and the height and depth of the cladding layer are controlled so that the dilution rate of the cladding layer is kept at a good level, ensuring that the cladding layer and the substrate to be clad form a good metallurgical bond, and also avoiding cracking caused by excessively fast cooling rate of laser cladding, so that the cladding layer has a good morphology and wear resistance.

[0043] 4) This invention provides a boron-free nickel-based wear-resistant coating. The resulting coating has a hardness of over 40 HRC and exhibits excellent wear resistance at both room temperature and high temperature, ensuring its application in the field of strengthening bearings for control rod drive mechanisms. Attached Figure Description

[0044] Figure 1 Microstructure images of the cladding layers in Comparative Examples 2-3 and Examples 1-2;

[0045] Figure 2 This is an EDS surface scan result of the cladding layer cross section in Example 1;

[0046] Figure 3 The hardness curves of the cladding layer are shown for Comparative Examples 1-3 and Examples 1-2;

[0047] Figure 4 Microscopic images of wear marks in Comparative Examples 2-3 and Examples 1-2;

[0048] Figure 5 The wear figures are from the friction and wear experiments of Comparative Examples 1-3 and Examples 1-2.

[0049] Figure 1 In the diagram, the scale corresponds to a length of 50 μm. a is the microstructure of Comparative Example 2; b is the microstructure of Comparative Example 3; c is the microstructure of Example 1; d is the microstructure of Example 2.

[0050] Figure 2 In the diagram, the scale bar corresponds to a length of 250 μm. a is the microscopic morphology of the surface scan area, b is the distribution map of Cr, c is the distribution map of Zr, d is the distribution map of Ni, e is the distribution map of Fe, and f is the distribution map of C.

[0051] Figure 4 In the diagram, the length corresponding to the scale is 200 μm. a is a microscopic image of the wear track at room temperature in Comparative Example 2; b is a microscopic image of the wear track at room temperature in Comparative Example 3; c is a microscopic image of the wear track at room temperature in Example 1; d is a microscopic image of the wear track at room temperature in Example 2; e is a microscopic image of the wear track at high temperature (300℃) in Comparative Example 2; f is a microscopic image of the wear track at high temperature (300℃) in Comparative Example 3; g is a microscopic image of the wear track at high temperature (300℃) in Example 1; and h is a microscopic image of the wear track at high temperature (300℃) in Example 2. Detailed Implementation

[0052] The present invention will now be described in detail with reference to specific embodiments, but this is by no means a limitation thereof. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0053] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0054] Example 1:

[0055] This embodiment provides a boron-free nickel-based wear-resistant coating. The wear-resistant coating uses a cladding material (i.e., mixed powder) with the following mass ratio: 40% zirconium carbide powder with a particle size of 10-60 μm; 60% nickel-based alloy powder with a particle size of 53-109 μm; and the mass percentage content of each component of the nickel-based alloy powder is: 29.5% chromium, 9.0% iron, 0.02% carbon, and 61.48% nickel.

[0056] This embodiment provides a method for preparing a boron-free nickel-based wear-resistant coating, including the following steps: S1. Pretreatment of the substrate to be clad. The surface of the substrate to be clad is polished smooth using a grinding wheel, cleaned with ethanol, and then dried for later use.

[0057] S2. Mixing of cladding powders. Zirconium carbide powder and nickel-based alloy powder are mixed in a planetary ball mill at a mass ratio for 3 hours at a speed of 300 rpm to produce a uniform mixed powder.

[0058] S3. Drying of the mixed powder. Place the mixed powder in a heating furnace and dry it at 100°C for 2 hours.

[0059] S4. Laser Cladding. The temperature of the graphite heating plate is set to 300℃ to heat the substrate to be clad. The mixed powder is placed into the powder feeder of the synchronous powder feeding laser cladding device, using argon as the powder feeding gas. Laser cladding is performed using a fiber laser under the protection of the argon atmosphere. The process parameters are: laser power of 1200W, scanning speed of 1800mm / min, overlap rate of 50%, powder feeding speed of 12g / min, spot diameter of 1.3mm, and cladding layer thickness of 700-1000μm, to obtain the clad sample.

[0060] After cladding, the samples underwent wire cutting, mounting, grinding, polishing, and metallographic etching (all conventional techniques in this field). The microstructure of the cladding layer (a boron-free nickel-based wear-resistant coating) was observed using an optical microscope, and its composition was analyzed using energy dispersive spectroscopy (EDS). The hardness of the cladding layer was tested using a Vickers hardness tester, and the average hardness of the obtained samples reached 495.9 HV. 0.2A friction and wear test was conducted using a friction and wear testing machine with tungsten carbide grinding balls of 5 mm diameter at room temperature. The friction radius was 10 mm, the rotational speed was 200 rpm, the load was 30 N, and the test time was 1 hour. The wear cross-sectional area of ​​the sample was observed using a super depth-of-field microscope, and the wear volume at room temperature was calculated to be 5.6312 mm². 3 A high-temperature rotary friction and wear test was conducted at 300℃ using a friction and wear testing machine with tungsten carbide grinding balls of 9.25 mm diameter. The friction radius was 10 mm, the rotational speed was 200 rpm, the load was 30 N, and the test time was 1 hour. The wear cross-section of the sample was observed using a super depth-of-field microscope to obtain the cross-sectional area of ​​the wear track, and the high-temperature wear volume was calculated to be 0.9076 mm². 3 .

[0061] Example 2:

[0062] This embodiment provides a boron-free nickel-based wear-resistant coating. The wear-resistant coating uses a cladding material (i.e., mixed powder) with the following mass ratio: 60% zirconium carbide powder with a particle size of 10-60 μm; and 40% nickel-based alloy powder with a particle size of 53-109 μm. The mass percentage content of each component of the nickel-based alloy powder is: 29.0% chromium, 9.5% iron, 0.05% carbon, and 61.45% nickel.

[0063] This embodiment provides a method for preparing a boron-free nickel-based wear-resistant coating, comprising the following steps:

[0064] S1. Pretreatment of the substrate to be clad. Grind the surface of the substrate to be clad with a grinding wheel until smooth, clean it with ethanol, and then blow it dry for later use.

[0065] S2. Mixing of cladding powder. Zirconium carbide powder and nickel-based alloy powder are mixed in a planetary ball mill at a mass ratio for 3 hours at a speed of 300 rpm to produce a uniform mixed powder.

[0066] S3. Drying of the mixed powder. Place the mixed powder in a heating furnace and dry it at 100°C for 2 hours.

[0067] S4. Laser Cladding. The temperature of the graphite heating plate is set to 300℃ to heat the substrate to be clad. The mixed powder is placed into the powder feeder of the synchronous powder feeding laser cladding device, using argon as the powder feeding gas. Laser cladding is performed using a fiber laser under the protection of the argon atmosphere. The process parameters are: laser power of 1200W, scanning speed of 1500mm / min, overlap rate of 50%, powder feeding speed of 10g / min, spot diameter of 1.3mm, and cladding layer thickness of 700-1000μm, to obtain the clad sample.

[0068] After cladding, the samples underwent wire cutting, mounting, grinding, polishing, and metallographic etching. The microstructure of the cladding layer cross-section was observed using an optical microscope. The hardness of the cladding layer was tested using a Vickers hardness tester, and the average hardness of the obtained samples reached 507.7 HV. 0.2 Friction and wear tests were conducted using a friction and wear testing machine with tungsten carbide grinding balls of 5 mm diameter at room temperature. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 hour. The wear cross-sectional area of ​​the sample was observed using a super depth-of-field microscope, and the wear volume at room temperature was calculated to be 0.6272 mm². 3 A high-temperature friction and wear test was conducted at 300℃ using a tungsten carbide grinding ball with a diameter of 9.25 mm on a friction and wear testing machine. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 hour. The wear cross-sectional area of ​​the sample was observed using a super depth-of-field microscope, and the high-temperature wear volume was calculated to be 0.4294 mm². 3 .

[0069] Comparative Example 1

[0070] This embodiment provides a boron-free nickel-based coating. All other conditions are the same as in Example 1, except that the cladding powder (cladding material) is a nickel-based alloy powder with a particle size of 53-109 μm. The mass percentages of the components are: chromium 29.5%, iron 9.0%, carbon 0.02%, and nickel 61.48%. The resulting sample has an average hardness of only 220 HV. 0.2 The wear volume at room temperature is 16.6971 mm. 3 The high-temperature wear volume is 5.4432 mm. 3 .

[0071] Comparative Example 2

[0072] This comparative example provides a boron-free nickel-based coating, with other conditions identical to Example 1, except that the mass ratio of the cladding material is: 10% zirconium carbide powder with a particle size of 10-60 μm; 90% nickel-based alloy powder with a particle size of 53-109 μm. The mass percentage content of each component in the nickel-based alloy powder is: 29.5% chromium, 9.0% iron, 0.02% carbon, and 61.48% nickel. The resulting sample has an average hardness of only 285.7 HV. 0.2 The wear volume at room temperature is 17.6033 mm. 3 The high-temperature wear volume is 6.1642 mm. 3 .

[0073] Comparative Example 3

[0074] This comparative example provides a boron-free nickel-based coating, with other conditions identical to Example 1, except that the mass ratio of the cladding material is: 30% zirconium carbide powder with a particle size of 10-60 μm; 70% nickel-based alloy powder with a particle size of 53-109 μm. The mass percentage content of each component in the nickel-based alloy powder is: 29.5% chromium, 9.0% iron, 0.02% carbon, and 61.48% nickel. The average hardness of the obtained sample is 452.2 HV. 0.2 The wear volume at room temperature is 10.6747 mm. 3 The high-temperature wear volume is 2.017 mm. 3 .

[0075] Comparative Example 4

[0076] This comparative example provides a boron-free nickel-based coating, with all other conditions the same as in Example 1, except that:

[0077] The mass ratio of the cladding material is: zirconium carbide powder accounts for more than 65%. In this comparative example, the cladding layer cracks during laser cladding.

[0078] Depend on Figure 1 It can be seen that the hard phase inside Examples 1 and 2 is greater than that in Comparative Examples 2 and 3. Because the amount of hard ceramic phase added to the cladding powder in Examples 1 and 2 is greater, there are more nucleation centers inside the molten pool during the cladding process, resulting in finer grain size inside Examples 1 and 2.

[0079] Depend on Figure 2 It can be seen that the internal particulate phase of Example 1 is mainly composed of Zr and C elements. Zirconium carbide in the mixed powder was successfully added to the cladding layer, forming a zirconium carbide hard phase.

[0080] Depend on Figure 3 It can be seen that the hardness of Examples 1 and 2 is higher than that of Comparative Examples 1-3, and the hardness of the top of the cladding layer is also higher. This is because Examples 1 and 2 have a higher zirconium carbide content, more hard phase inside the cladding layer, and finer grain size. The hardening and grain refining effects inside the cladding layer are stronger, so cladding layers 1 and 2 have higher hardness. During the cladding process, the liquid-solid interface undergoes repulsion and convection, causing zirconium carbide particles to float to the surface, resulting in a concentrated distribution of zirconium carbide in the upper region of the cladding layer, leading to higher hardness.

[0081] Depend on Figure 4It can be seen that after the friction and wear test, the wear marks of Comparative Examples 2 and 3 were more severe than those of Examples 1 and 2. Comparative Examples 2 and 3 showed more spalling pits and wear debris on their wear marks, while Examples 1 and 2 only showed shallow furrows. This is because Comparative Examples 2 and 3 had lower hardness and lower resistance to plastic deformation of the cladding layer. During the experiment, the grinding ball caused greater deformation to the cladding layer. During the friction between the grinding ball and the cladding layer, under high-speed contact and pressure, the temperature increased, causing oxidation of the cladding layer surface. After the oxides peeled off, a large number of fragments were generated. These oxide fragments do not have a self-lubricating effect, and the wear mechanism was mainly adhesive wear. In contrast, Examples 1 and 2 had higher hardness, less deformation during the wear process, and the wear mechanism was mainly abrasive wear, with almost no spalling.

[0082] Depend on Figure 5 It can be seen that Examples 1 and 2 have lower wear at room temperature and high temperature than Comparative Examples 1-3. This is because Examples 1 and 2 have higher hardness, smaller surface deformation, and almost no peeling during the wear process, resulting in lower wear and indicating that they have better wear resistance under room temperature and high temperature conditions.

[0083] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A boron-free nickel-based wear-resistant coating, characterized in that, The boron-free nickel-based wear-resistant coating uses a mixed powder as raw material, and the mixed powder is composed of the following components by mass percentage: Zirconium carbide powder 35-65%, with a particle size of 10-60μm; nickel-based alloy powder 35-65%, with a particle size of 53-109μm; The nickel-based alloy powder is composed of the following components by mass percentage: 28.0-31.5% chromium, 8.5-10.0% iron, 0.02-0.1% carbon, and 58.4-63.5% nickel.

2. The boron-free nickel-based wear-resistant coating according to claim 1, characterized in that, The thickness of the boron-free nickel-based wear-resistant coating is between 0.7 and 1.3 mm, and the hardness of the boron-free nickel-based wear-resistant coating is greater than 40 HRC.

3. The boron-free nickel-based wear-resistant coating according to claim 1, characterized in that, The boron-free nickel-based wear-resistant coating has a wear volume of less than 10 mm at room temperature. 3 High-temperature wear volume is less than 1 mm 3 .

4. A method for preparing a boron-free nickel-based wear-resistant coating as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: Pretreatment of the substrate to be clad: Polish the surface of the substrate to be clad to a smooth finish and clean it to obtain the substrate to be clad; Mixing of cladding powders: Zirconium carbide powder and nickel-based alloy powder are ball-milled and mixed in a mass ratio to prepare a mixed powder; Drying of the mixed powder: The mixed powder is dried by heating; Laser cladding: The substrate to be clad is heated, and the mixed powder is laser clad under protective gas conditions to form a laser cladding layer on the surface of the substrate. The resulting laser cladding layer is the boron-free nickel-based wear-resistant coating.

5. The method for preparing a boron-free nickel-based wear-resistant coating according to claim 4, characterized in that, The substrate to be clad is a 304 stainless steel substrate.

6. The method for preparing a boron-free nickel-based wear-resistant coating according to claim 4, characterized in that, The preparation method includes the following steps: S1. Pretreatment of the substrate to be clad: The surface of the substrate to be clad is polished smooth with a grinding wheel and cleaned to obtain the substrate to be clad; S2. Mixing of cladding powder: Zirconium carbide powder and nickel-based alloy powder are uniformly mixed in a planetary ball mill according to the mass ratio to prepare a mixed powder; S3. Drying of the mixed powder: The mixed powder is dried by heating in a furnace; S4. Laser cladding: The substrate to be clad is heated by an electric heating plate, and the mixed powder is laser clad under protective gas conditions to form a laser cladding layer on the surface of the substrate. The resulting laser cladding layer is the boron-free nickel-based wear-resistant coating.

7. The method for preparing a boron-free nickel-based wear-resistant coating according to claim 6, characterized in that, In step S2, the planetary ball mill has a mixing time of 2-3 hours and a rotation speed of 250-300 rpm.

8. The method for preparing a boron-free nickel-based wear-resistant coating according to claim 6, characterized in that, In step S3, the heating and drying time is 2-3 hours and the temperature is 80-110℃.

9. The method for preparing a boron-free nickel-based wear-resistant coating according to claim 6, characterized in that, In step S4, the protective gas is argon. In step S4, the temperature parameter of the heating plate is 150°C; In step S4, the laser cladding process parameters are as follows: laser power is 1200-1400W, scanning speed is 1800-2000mm / min, overlap rate is 50%, powder feeding speed is 8-12g / min, and spot diameter is 1.3mm.

10. An application of the boron-free nickel-based wear-resistant coating as described in any one of claims 1-3, characterized in that, The boron-free nickel-based wear-resistant coating is used in the control rod drive mechanism of a nuclear reactor.

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