Boron-free nickel-based wear-resistant coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of material surface strengthening, and provides a boron-free nickel-based wear-resistant coating as well as a preparation method and application thereof. Mixed powder serves as a raw material, a base body is heated through an electric heating plate, the raw material is subjected to laser cladding through synchronous powder feeding, and a wear-resistant coating is formed on the surface of the base body; the mixed powder is prepared from the following components: 35.0 to 65.0 percent of zirconium carbide powder and 35.0 to 65.0 percent of nickel-based alloy powder; the nickel-based alloy powder comprises the following components in percentage by mass: 28.0 to 31.5 percent of chromium, 8.5 to 10.0 percent of iron, 0 to 0.1 percent of carbon and 58.4 to 63.5 percent of nickel. Compared with the prior art, the hardness of the obtained coating can reach 40 HRC or above, good normal-temperature and high-temperature wear resistance is achieved, and application of the coating in the field of control rod drive mechanism bearing strengthening is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of material surface strengthening, and in particular to a boron-free nickel-based wear-resistant coating and a preparation method and application thereof. Background Art

[0002] The control rod drive mechanism is the core component of a nuclear reactor. It can drive the control rod assembly to move in the core, adjust the power of the reactor, and control the safe shutdown of the reactor in an emergency to ensure the safe and normal operation of the reactor. The bearings of the control rod drive mechanism have been working in a high temperature, high humidity, and high radiation environment for a long time, and often suffer from excessive wear and even cracking, which seriously affects the normal operation of the nuclear power plant. The traditional method of bearing surface strengthening is to use surfacing technology to prepare a layer of Stellite6 cobalt-based alloy surfacing layer. The advantage of this process is that the generated surfacing layer has high hardness and good wear resistance, but the surfacing process has a large heat input, the thermal deformation of the workpiece is large, and the thermal conductivity of Stellite6 is poor, resulting in many internal defects in the surfacing layer. The wear debris of the Stellite6 surfacing layer moves to the core area with the first-circuit water circulation, 59 Co is easily transformed into radioactive isotopes by thermal neutron bombardment 60 Co, 60 Co decays and releases gamma photons, which can cause harm to surrounding equipment and production 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 the present invention is to provide a boron-free nickel-based wear-resistant coating and its preparation method and application in order to solve the above problems, and to propose a nickel-based coating and preparation method that can ensure the radiation resistance of the coating while having high wear resistance and high corrosion resistance.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The first object of the present invention is to provide a boron-free nickel-based wear-resistant coating, wherein the boron-free nickel-based wear-resistant coating is made of mixed powder as a raw material, and the mixed powder comprises the following components by mass percentage:

[0007] Zirconium carbide powder 35-65%, zirconium carbide powder particle size 10-60μm, nickel-based alloy powder 35-65%, nickel-based alloy powder particle size 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] Further preferably, the mass percentage content of each component of 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 carried out using a tungsten carbide grinding ball with a diameter of 5 mm, a friction radius of 10 mm, a rotation speed of 200 rpm, a load of 30 N, and an experimental time of 1 h. 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°C, a high temperature friction and wear test was carried out using a tungsten steel grinding ball with a diameter of 9.25 mm, a friction radius of 10 mm, a rotation speed of 200 rpm, a load of 30 N, and an experimental time of 1 h. The high temperature wear volume of the boron-free nickel-based wear-resistant coating was less than 1 mm 3 .

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

[0014] Pretreatment of the substrate to be clad: polishing and cleaning the surface of the substrate to be clad to obtain the substrate to be clad;

[0015] Mixing of cladding powder: ball-milling zirconium carbide powder and nickel-based alloy powder according to mass ratio to prepare mixed powder;

[0016] Drying of mixed powder: heating and drying the mixed powder;

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

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

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

[0020] S2. Mixing of cladding powders: The zirconium carbide powder and the nickel-based alloy powder were uniformly mixed by a planetary ball mill to form a mixed powder according to a mass ratio;

[0021] S3. Drying of the mixed powder: The mixed powder is heated and dried by a heating 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 the condition of protective gas to form a laser cladding layer on the surface of the substrate to be clad. The obtained laser cladding layer is the boron-free nickel-based wear-resistant coating.

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

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

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

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

[0027] Furthermore, in step S4, the protective gas is argon; in step S4, the temperature parameter of the electric heating plate is 150°C; in step S4, the process parameters of the laser cladding are: 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.

[0028] A third object of the present invention is to provide an application of a boron-free nickel-based wear-resistant coating, wherein the boron-free nickel-based wear-resistant coating is used in a control rod drive mechanism of a nuclear reactor.

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

[0030] Furthermore, the boron-free nickel-based wear-resistant coating is used as a 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 a nuclear power plant environment.

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

[0032] The technical principle and concept of the present invention are as follows:

[0033] In order to solve the problems existing in traditional bearing surface strengthening methods, laser cladding technology is used to prepare nickel-based wear-resistant coatings to enhance the wear resistance of the substrate surface. Laser cladding technology uses a high-energy laser beam as a heat source to melt the cladding powder ejected synchronously above the substrate. The substrate surface absorbs a small amount of heat to form a molten pool, and then the melted cladding powder falls into the molten pool, forming a metallurgical bond with the substrate, and forms a cladding layer after cooling, thereby changing the surface properties of the substrate. Compared with the surfacing process, the laser cladding technology uses a higher laser energy density, a smaller total heat input to the substrate, and a smaller thermal deformation of the processed substrate. The dilution rate of the cladding layer is lower than that of the surfacing layer, and the surface of the cladding layer is smoother than that of the surfacing layer. The internal grains of the cladding layer are finer than those of the surfacing layer, the structure is denser, the internal organization distribution is more uniform, and there are fewer defects, which makes the cladding layer have better hardness, wear resistance and corrosion resistance than the surfacing layer.

[0034] The nickel (Ni) element itself has a small neutron absorption cross section and good radiation resistance. Nickel-based high-temperature alloys have been widely used as heat transfer tube materials in the nuclear power field. Nickel-based alloys have good wettability on stainless steel. The cladding layer prepared from nickel-based cladding powder is very firmly bonded to the substrate and has good high temperature resistance. At present, most of the wear-resistant nickel-based cladding powders on the market contain boron (B) elements. The B element has a large neutron absorption cross section and is prone to (n, α) reactions in nuclear facilities to generate Li atoms and helium, resulting in defects inside the cladding layer and affecting the service life of the wear-resistant coating. Therefore, it is necessary to explore a nickel-based alloy powder that does not contain B, so that the formed nickel-based coating has good radiation resistance while having good hardness and wear resistance.

[0035] In practical applications in the field of nuclear power, stress corrosion cracking often occurs in high-temperature nickel-based alloys. This is because during the cooling and solidification of the molten pool, the internal chromium (Cr) element of the high-temperature nickel-based alloy will form carbides and precipitate from the grain boundaries, resulting in a decrease in the Cr content in the matrix to form a Cr-poor zone, which reduces the corrosion resistance of the matrix. When the Cr content of the nickel-based alloy itself is low, stress corrosion cracking will be very serious. Therefore, a high content of Cr should be added to the nickel-based alloy to reduce the stress corrosion cracking of the nickel-based alloy.

[0036] A small amount of iron (Fe) is usually added to high-temperature nickel-based alloys, which can play a role in solid solution strengthening in the matrix, improve the hardness of the alloy and reduce the alloy cost. The addition of Fe can also improve the alloy's ability to withstand concentrated sulfuric acid corrosion, but if the amount of Fe added is too high, it will reduce the alloy's corrosion resistance in a pure water environment and have an adverse effect on the alloy's performance.

[0037] Cobalt easily absorbs neutrons to form cobalt 60 ( 60 Cobalt 60 will decay and release gamma photons, and is not suitable for use in nuclear power plant working environments.

[0038] Zirconium carbide (ZrC) has better radiation resistance than other hard ceramics used in nuclear facilities. It can still maintain its crystal structure under high radiation flux, reduce the diffusion rate of fission products, and resist the impact of nuclear fission products. Zirconium carbide can refine metal grains, reduce dislocation density, and improve the tensile strength and microhardness of the cladding layer in the cladding layer. Zirconium carbide has an extremely high melting point and good high temperature resistance. It is suitable as a reinforcing phase for high-temperature nickel-based alloy coatings to improve the hardness of the cladding layer and improve the wear resistance of the cladding layer.

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

[0040] 1) The present invention provides a boron-free nickel-based wear-resistant coating, with a nickel-based alloy as the matrix, in which the mass percentages of the components are: 28.0-31.5% chromium, 8.5-10.0% iron, 0-0.1% carbon, and 58.4-63.5% nickel. Among them, the high content of Cr element allows a high content of Cr element to remain in the matrix after the Cr-rich compound in the cladding layer is precipitated, which can effectively reduce the stress corrosion cracking sensitivity of the cladding layer; it can change the pitting potential and improve the corrosion resistance of the cladding layer; the Cr element can also form chromium oxide during the cladding process, which plays a role in enhancing the high-temperature wear resistance of the cladding layer. A small amount of Fe element can play a role in solid solution strengthening, while ensuring that the cladding layer has good corrosion resistance. The carbides formed by trace C elements and metal elements will play a pinning role, increase the grain boundary migration energy, improve the deformation resistance of the cladding layer, and play a role in enhancing the strength of the cladding layer.

[0041] 2) The present invention provides a boron-free nickel-based wear-resistant coating, which selects zirconium carbide powder as a reinforcing phase, is mixed with nickel-based alloy powder, and is clad to form a wear-resistant coating. Zirconium carbide has a very low neutron absorption cross section. On the premise that it has high hardness and high temperature resistance, it does not have the defect of the existing wear-resistant nickel-based coating that its performance is easily deteriorated in a high radiation environment. 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 good wear resistance.

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

[0043] 4) The present invention provides a boron-free nickel-based wear-resistant coating, the hardness of the obtained coating can reach above 40HRC, and it has good wear resistance at room temperature and high temperature, ensuring its application in the field of control rod drive mechanism bearing strengthening. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The microscopic metallographic images of the cladding layers of Comparative Example 2-3 and Example 1-2;

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

[0046] Figure 3 It is a hardness curve diagram of the cladding layer of comparative example 1-3 and embodiment 1-2;

[0047] Figure 4 The wear scar micrographs of Comparative Example 2-3 and Example 1-2;

[0048] Figure 5 The wear amount diagram of the friction and wear experiment of Comparative Examples 1-3 and Examples 1-2;

[0049] Figure 1 In the figure, the length corresponding to the scale is 50 μm, a is the microscopic metallographic image of comparative example 2; b is the microscopic metallographic image of comparative example 3; c is the microscopic metallographic image of embodiment 1; d is the microscopic metallographic image of embodiment 2;

[0050] Figure 2 In the figure, the length corresponding to the scale is 250 μm, a is the microscopic morphology of the surface scanned part, b is the distribution diagram of the Cr element, c is the distribution diagram of the Zr element, d is the distribution diagram of the Ni element, e is the distribution diagram of the Fe element, and f is the distribution diagram of the C element;

[0051] Figure 4 , the length corresponding to the scale is 200 μm, a is the wear scar micrograph of comparative example 2 at room temperature; b is the wear scar micrograph of comparative example 3 at room temperature; c is the wear scar micrograph of embodiment 1 at room temperature; d is the wear scar micrograph of embodiment 2 at room temperature; e is the wear scar micrograph of comparative example 2 at high temperature (300°C); f is the wear scar micrograph of comparative example 3 at high temperature (300°C); g is the wear scar micrograph of embodiment 1 at high temperature (300°C); h is the wear scar micrograph of embodiment 2 at high temperature (300°C). DETAILED DESCRIPTION

[0052] The present invention is described in detail below in conjunction with specific embodiments, but is by no means intended to limit the present invention. Features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

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

[0054] Embodiment 1:

[0055] The present embodiment provides a boron-free nickel-based wear-resistant coating, wherein the mass ratio of the cladding material (i.e., mixed powder) used in the wear-resistant coating is: 40% zirconium carbide powder with a particle size of 10-60μm; 60% nickel-based alloy powder with a particle size of 53-109μm; 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, comprising the following steps: S1. Pretreatment of the substrate to be clad. Use a grinding wheel to polish the surface of the substrate to be clad, clean it with ethanol, and blow it dry for later use.

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

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

[0059] S4. Laser cladding. Set the temperature of the graphite heating plate to 300°C to heat the substrate to be clad, put the mixed powder into the powder feeder of the synchronous powder feeding laser cladding device, use argon as the powder feeding gas, and use a fiber laser for laser cladding under the protection of an 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, cladding layer thickness of 700-1000μm, and obtain the clad sample.

[0060] After the samples after cladding were subjected to wire cutting, inlaying, grinding, polishing, and metallographic etching (wire cutting, inlaying, grinding, polishing, and metallographic etching are all conventional technical means in this field), the microstructure of the cross section of the cladding layer (the cladding layer is a boron-free nickel-based wear-resistant coating) was observed using an optical microscope, and the composition of the cross section of the cladding layer was analyzed using an energy dispersive spectrometer (EDS); the hardness of the cladding layer was tested using a Vickers hardness tester, and the average hardness of the obtained sample could reach 495.9HV 0.2; A friction and wear tester was used to carry out a rotational friction and wear test at room temperature using a tungsten carbide grinding ball with a diameter of 5 mm. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 h. The wear cross-sectional area of ​​the sample was observed using an ultra-depth of field microscope, and the wear volume at room temperature was calculated to be 5.6312 mm 3 ; A high-temperature rotational friction and wear test was conducted at 300°C using a friction and wear tester with a tungsten steel grinding ball with a diameter of 9.25 mm. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 h. The wear section of the sample was observed using an ultra-depth of field microscope to obtain the wear scar cross-sectional area, and the high-temperature wear volume was calculated to be 0.9076 mm 3 .

[0061] Embodiment 2:

[0062] The present embodiment provides a boron-free nickel-based wear-resistant coating, and the mass ratio of the cladding material (i.e., mixed powder) used in the wear-resistant coating is: 60% zirconium carbide powder with a particle size of 10-60μm; 40% nickel-based alloy powder with a particle size of 53-109μm, and 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. Use a grinding wheel to polish the surface of the substrate to be clad, clean it with ethanol, and blow it dry for later use.

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

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

[0067] S4. Laser cladding. Set the temperature of the graphite heating plate to 300°C to heat the substrate to be clad, put the mixed powder into the powder feeder of the synchronous powder feeding laser cladding device, use argon as the powder feeding gas, and use a fiber laser for laser cladding under the protection of an 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, cladding layer thickness of 700-1000μm, and obtain the clad sample.

[0068] After the cladding samples were cut by wire, inlaid, ground, polished, and metallographically etched, the microstructure of the cross section of the cladding layer 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 could reach 507.7HV. 0.2 The friction and wear test was carried out at room temperature using a tungsten carbide grinding ball with a diameter of 5 mm. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 h. The wear cross-sectional area of ​​the sample was observed using an ultra-depth of field microscope, and the wear volume at room temperature was calculated to be 0.6272 mm. 3 ; A high-temperature friction and wear test was conducted at 300°C using a tungsten steel grinding ball with a diameter of 9.25 mm using a friction and wear tester. The friction radius was 10 mm, the rotation speed was 200 rpm, the load was 30 N, and the test time was 1 h. The wear cross-sectional area of ​​the sample was observed using an ultra-depth of field microscope, and the high-temperature wear volume was calculated to be 0.4294 mm 3 .

[0069] Comparative Example 1

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

[0071] Comparative Example 2

[0072] This comparative example provides a boron-free nickel-based coating. The other conditions are the same as those in Example 1, except that the mass ratio of the cladding material is: 10% zirconium carbide powder, with a particle size of 10-60μm; 90% nickel-based alloy powder, with a particle size of 53-109μm. 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. The average hardness of the obtained sample is only 285.7HV 0.2 The wear volume at room temperature is 17.6033mm 3 , the high temperature wear volume is 6.1642mm 3 .

[0073] Comparative Example 3

[0074] This comparative example provides a boron-free nickel-based coating. Other conditions are the same as those in Example 1, except that the mass ratio of the cladding material is: 30% zirconium carbide powder with a particle size of 10-60μm; 70% nickel-based alloy powder with a particle size of 53-109μm. 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. The average hardness of the obtained sample is 452.2HV 0.2 The wear volume at room temperature is 10.6747 mm 3 , high temperature wear volume is 2.017mm 3 .

[0075] Comparative Example 4

[0076] This comparative example provides a boron-free nickel-based coating, and other conditions are consistent with those of Example 1, except that:

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

[0078] Depend on Figure 1 It can be seen that the internal hard phases of Examples 1 and 2 are greater than those of Comparative Examples 2 and 3. Since 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, making the grain size inside Examples 1 and 2 finer.

[0079] Depend on Figure 2 It can be seen that the internal particle phase of Example 1 is mainly composed of Zr elements and C elements, and the zirconium carbide in the mixed powder is successfully added into the cladding layer to form 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 higher. This is because the zirconium carbide content in Examples 1 and 2 is higher, the hard phase inside the cladding layer is more, the grain size is finer, and the hardness strengthening and grain refinement inside the cladding layer are stronger, so the cladding layers 1 and 2 have higher hardness. During the cladding process, repulsion and convection occur at the liquid-solid interface, causing the zirconium carbide particles to float, resulting in concentrated distribution of zirconium carbide in the middle and upper regions of the cladding layer, and higher hardness.

[0081] Depend on Figure 4It can be seen that after the friction and wear test, the wear scars of Comparative Examples 2 and 3 are more severely peeled than those of Examples 1 and 2. There are more peeling pits and wear debris on the wear scar surfaces of Comparative Examples 2 and 3, while only shallow furrows appear on the wear scar surfaces of Examples 1 and 2. This is because the hardness of Comparative Examples 2 and 3 is relatively low, the resistance to plastic deformation of the cladding layer is low, and the deformation of the cladding layer caused by the grinding ball during the experiment is relatively large. During the friction between the grinding ball and the cladding layer, under the action of high-speed contact and pressure, the temperature rises, causing the surface of the cladding layer to oxidize, and a large number of fragments are generated after the oxides peel off. The oxide fragments do not have a self-lubricating effect, and the wear mechanism is mainly adhesive wear. However, the hardness of Examples 1 and 2 is higher, the deformation during the wear process is small, and the wear mechanism is mainly abrasive wear, and almost no peeling occurs.

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

[0083] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection 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 is made of mixed powder as a raw material, and the mixed powder includes the following components by mass percentage: Zirconium carbide powder 35-65%, zirconium carbide powder particle size 10-60μm, nickel-based alloy powder 35-65%, nickel-based alloy powder particle size 53-109μm; 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.

2. A 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 wear volume of the boron-free nickel-based wear-resistant coating at room temperature is less than 10 mm 3 , high temperature wear volume is less than 1mm 3 .

4. A method for preparing a boron-free nickel-based wear-resistant coating according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Pretreatment of the substrate to be clad: polishing and cleaning the surface of the substrate to be clad to obtain the substrate to be clad; Mixing of cladding powder: ball-milling zirconium carbide powder and nickel-based alloy powder according to mass ratio to prepare mixed powder; Drying of mixed powder: heating and drying the mixed powder; Laser cladding: The substrate to be clad is heated, and the mixed powder is laser clad under the condition of protective gas to form a laser cladding layer on the surface of the substrate to be clad. The obtained 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 processed and 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 comprises the following steps: S1. Pretreatment of the substrate to be clad: The surface of the substrate to be clad is polished with a grinding wheel and cleaned to obtain a substrate to be clad; S2. Mixing of cladding powders: The zirconium carbide powder and the nickel-based alloy powder were uniformly mixed by a planetary ball mill to form a mixed powder according to a mass ratio; S3. Drying of the mixed powder: The mixed powder is heated and dried by a heating furnace; S4. Laser cladding: The substrate to be clad is heated by an electric heating plate, and the mixed powder is laser clad under the condition of protective gas to form a laser cladding layer on the surface of the substrate to be clad. The obtained 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 mixing time of the planetary ball mill is 2-3 hours, and the rotation speed is 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 to 3 hours, and the temperature is 80 to 110°C.

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 electric heating plate is 150°C; In step S4, the process parameters of the laser cladding are: laser power of 1200-1400 W, scanning speed of 1800-2000 mm / min, overlap rate of 50%, powder feeding speed of 8-12 g / min, and spot diameter of 1.3 mm.

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

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