Inner hole laser cladding composite powder material and preparation method thereof

Abstract

The application belongs to the technical field of additive manufacturing, and particularly relates to an inner hole laser cladding composite powder material and a preparation method thereof. In order to solve the problems of poor uniformity and flowability of the inner hole laser cladding composite powder material in the prior art and the limitations in hardness, wear resistance and corrosion resistance, the application provides an inner hole laser cladding composite powder material and a preparation method thereof. The material comprises tungsten carbide powder, NiCr alloy powder, silver and a mixed crystal of calcium fluoride and barium fluoride, is mixed and ball milled, is pre-sintered and then ball milled again, is then subjected to gas atomization treatment and laser pretreatment, and finally a nickel plating layer is formed on the surface of the powder through chemical plating. The composite powder material has high hardness, high wear resistance, good corrosion resistance and high temperature stability, is suitable for inner hole laser cladding, and significantly improves the service life and performance of a workpiece.

Description

Technical Field

[0001] This application belongs to the field of additive manufacturing technology, and specifically relates to an internal hole laser cladding composite powder material and its preparation method. Background Technology

[0002] Laser cladding composite powder materials are composite materials in which a coating with specific properties is formed on the surface of a metal or alloy substrate through laser cladding technology. This technology uses a high-energy laser beam as a heat source to melt and rapidly solidify pre-prepared powder materials onto the substrate surface, thereby forming a coating with excellent physicochemical properties. This coating can significantly improve the wear resistance, corrosion resistance, fatigue resistance, and other properties of the substrate material.

[0003] The main function of laser cladding composite powder materials is to improve the surface properties of materials, including enhancing wear resistance, corrosion resistance, high-temperature stability, and repairing and strengthening worn or damaged components. In the aerospace field, this material is commonly used in the manufacture and repair of critical components such as engine blades and turbine disks; in the energy industry, it is suitable for high-temperature components in gas turbines and nuclear power equipment; in the machinery manufacturing field, it can be used for parts in various mechanical equipment that withstand high loads and high temperatures; in the automotive industry, components such as engine pistons and cylinder liners can be strengthened using laser cladding technology; and in the chemical industry, components such as pumps and valves operating in corrosive environments can also benefit from this technology.

[0004] Laser cladding composite powder materials are mainly divided into two categories: metal matrix composites and ceramic matrix composites. Each type can be further subdivided into several subcategories according to different needs. Metal matrix composites, such as nickel-based, cobalt-based, and iron-based composites, usually have hard phases such as carbides and borides added to improve the material's hardness and wear resistance. Ceramic matrix composites, such as alumina and silicon carbide, have extremely high hardness and corrosion resistance, making them suitable for applications under extreme working conditions.

[0005] Internal hole laser cladding is used to treat the surface of holes or cavities inside workpieces. The geometry and size of the internal hole limit the delivery path of the laser beam and powder, requiring special equipment and techniques to ensure that the laser beam and powder can accurately reach the surface of the internal hole. Poor uniformity and flowability of the powder greatly affect the cladding effect. Furthermore, existing cladding materials are prone to defects such as pores and cracks during the cladding process, affecting the integrity and performance of the coating. Insufficient bonding strength between the substrate and the coating is also a common problem, especially under high stress conditions, where peeling may occur between the coating and the substrate. Finally, although some existing composite powder materials perform well in certain aspects, their hardness, corrosion resistance, and high-temperature stability still need further optimization. Summary of the Invention

[0006] To address the limitations of existing laser cladding composite powder materials for internal holes, such as poor uniformity and flowability, as well as limitations in hardness, wear resistance, and corrosion resistance, this application provides a laser cladding composite powder material for internal holes and its preparation method. The material comprises tungsten carbide powder, NiCr alloy powder, silver, and a mixed crystal of calcium fluoride and barium fluoride. The mixture is ball-milled, pre-sintered, and then ball-milled again. Following this, it undergoes gas atomization and laser pretreatment, and finally, a nickel plating layer is formed on the powder surface through chemical plating. This composite powder material exhibits high hardness, high wear resistance, good corrosion resistance, and high-temperature stability, making it suitable for laser cladding of internal holes and significantly improving the service life and performance of workpieces.

[0007] This application provides an internal hole laser cladding powder material, comprising the following components: 40-60 wt% tungsten carbide, 37-57 wt% NiCr, 0.5-1.5 wt% silver, and 1-3 wt% calcium fluoride-barium fluoride mixed crystals.

[0008] This application also provides a method for preparing an internal hole laser cladding powder material, comprising the following steps:

[0009] S1. After mixing tungsten carbide powder with cobalt and vanadium carbide, the mixture is ball-milled for 10-12 hours. After removing the mixture, it is sintered at 500-600℃ for 1-2 hours, then heated to 1450-1500℃ for 0.5-1 hours. After removing the mixture and cooling it to room temperature, it is sieved for later use.

[0010] S2. Mix the tungsten carbide powder, NiCr alloy powder, silver and calcium fluoride-barium fluoride mixed crystals obtained in step S1, and then ball mill them using a high-energy ball mill for 10-12 hours.

[0011] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a pressure of 1.5-2.0 MPa;

[0012] S4. Pre-treat the powder obtained in S3 using a high-power direct diode laser for 30-50 minutes.

[0013] S5. Dissolve nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate, and sodium dodecyl sulfate in water and mix thoroughly. Then heat the mixture to 85-95℃. Add the powder obtained in S4, stir, and soak for 0.5-1h. Remove the powder, clean, and dry it to obtain the laser cladding powder material with internal pores.

[0014] Furthermore, in step S2, the ball milling speed is 1000-2000 rpm and the ball-to-material ratio is 8-10:1.

[0015] Furthermore, in step S1, the tungsten carbide powder has a particle size range of 40-160 μm, the amount of cobalt added is 6-12% of the mass of the tungsten carbide powder, and the amount of vanadium carbide added is 0.5-1% of the mass of the tungsten carbide powder.

[0016] Furthermore, in step S4, the laser wavelength is 980-1060nm, the laser power is 1.2kW, the laser spot size is 5mm×1mm, the scanning speed is 1500mm / min, the working distance is 15mm, and the protective gas is argon with a flow rate of 3.4L / min.

[0017] Furthermore, in step S5, the mass ratio of nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate, and sodium dodecyl sulfate is 10-15:2-3:2-3:1:0.02-0.05, and water is added to adjust the pH to 4.5-5.0.

[0018] This application involves ball milling and sintering a mixture of tungsten carbide powder with cobalt and vanadium carbide. This process not only promotes tight bonding between tungsten carbide particles but also effectively improves the toughness of the tungsten carbide through the addition of cobalt and vanadium carbide, preventing brittle fracture during subsequent processing. During sintering, the low-temperature stage helps remove adsorbed water and organic impurities from the powder, while high-temperature sintering promotes diffusion bonding between particles, enhancing the material's density—a crucial step in improving the material's mechanical properties. Next, the treated tungsten carbide powder is mixed with NiCr alloy powder, silver, and a calcium fluoride-barium fluoride mixed crystal, and then ball-milled for an extended period using a high-energy ball mill. This step achieves uniform dispersion of the components through the impact and friction generated by the high-energy ball milling. Simultaneously, the mechanical activation effect generated during ball milling activates the powder surface, promoting subsequent reactions. The addition of silver improves the material's conductivity and oxidation resistance, while the calcium fluoride-barium fluoride mixed crystal acts as a flux, lowering the melting temperature and helping to reduce heat input during cladding, preventing substrate deformation and cracking. The synergistic effect of these components significantly enhances the overall performance of the composite powder material. Gas atomization, using high-pressure nitrogen, atomizes the powder into fine particles. This process not only increases the specific surface area of ​​the powder but also improves its flowability and filling density, which is particularly important for applications like internal hole laser cladding, where strict requirements for powder uniformity and flowability are necessary. The atomized powder then undergoes laser pretreatment, where the laser partially melts the powder surface, forming tiny spherical particles. These particles spread more easily into a continuous coating during cladding, reducing porosity and crack formation, and improving coating quality and the bonding strength between the substrate and the coating. Finally, a nickel plating layer is formed on the powder surface through a chemical plating process. This nickel layer not only strengthens the connection between powder particles and improves the overall integrity of the coating but also further enhances the corrosion resistance and high-temperature stability of the composite material due to nickel's inherent corrosion resistance and good thermal stability. Furthermore, the nickel plating layer can act as a wetting agent in subsequent cladding processes, promoting metallurgical bonding between the cladding material and the substrate, which is crucial for improving coating adhesion. Detailed Implementation

[0019] The following specific embodiments further illustrate the technical solution and effects of the present invention. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0020] The equipment used in the preparation method of this invention can all be equipment known in the art. Unless otherwise specified, all raw materials used in this invention are commercially available.

[0021] Example 1

[0022] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 10-12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 200:12:1. After being taken out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After being taken out and cooled to room temperature, it is sieved for later use.

[0023] S2. Mix 45wt% of tungsten carbide powder obtained in step S1, 50.5wt% of NiCr alloy powder, 1.5wt% of silver and 3wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 1000 rpm and a ball-to-material ratio of 10:1.

[0024] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 2.0 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0025] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0026] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 10:2:2:1:0.02 to adjust the pH to 4.5. After mixing evenly, heat to 85°C. Then, put the powder obtained in S4 into the mixture, stir and soak for 0.5 hours. After removing, clean and dry to obtain the internal pore laser cladding powder material.

[0027] Example 2

[0028] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 100:12:1. After taking it out, it is sintered at 600℃ for 2 hours and then heated to 1500℃ for 1 hour. After taking it out and cooling it to room temperature, it is sieved for later use.

[0029] S2. Mix 60wt% of tungsten carbide powder obtained in step S1, 37wt% of NiCr alloy powder, 0.5wt% of silver and 2.5wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0030] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0031] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0032] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 15:3:3:1:0.05 to adjust the pH to 5.0. After mixing evenly, heat to 95℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0033] Example 3

[0034] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 11 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 10:1:0.07. After taking it out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After taking it out and cooling it to room temperature, it is sieved for later use.

[0035] S2. Mix 40wt% of tungsten carbide powder obtained in step S1, 57wt% of NiCr alloy powder, 1wt% of silver and 2wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0036] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0037] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0038] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 12:2:2:1:0.03 to adjust the pH to 5.0. After mixing evenly, heat to 90℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0039] Example 4

[0040] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 11 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 10:1:0.07. After taking it out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After taking it out and cooling it to room temperature, it is sieved for later use.

[0041] S2. Mix 56wt% of tungsten carbide powder obtained in step S1, 40wt% of NiCr alloy powder, 1.5wt% of silver and 2.5wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0042] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0043] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0044] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 12:2:2:1:0.03 to adjust the pH to 5.0. After mixing evenly, heat to 90℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0045] Comparative Example 1

[0046] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 11 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 10:1:0.07. After taking it out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After taking it out and cooling it to room temperature, it is sieved for later use.

[0047] S2. Mix 40wt% of tungsten carbide powder obtained in step S1, 57wt% of NiCr alloy powder, 1wt% of silver and 2wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0048] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0049] S4. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 12:2:2:1:0.03 to adjust the pH to 5.0. After mixing evenly, heat to 90℃. Then put the powder obtained in S3 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0050] Comparative Example 2

[0051] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 11 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 10:1:0.07. After taking it out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After taking it out and cooling it to room temperature, it is sieved for later use.

[0052] S2. Mix 40wt% of tungsten carbide powder obtained in step S1, 57wt% of NiCr alloy powder, 1wt% of silver and 2wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0053] S3. The powder obtained in S2 is pretreated using a high-power direct diode laser for 30 min. The laser wavelength is 1060 nm, the laser power is 1.2 kW, the laser spot size is 5 mm × 1 mm, the scanning speed is 1500 mm / min, the working distance is 15 mm, and the protective gas is argon with a flow rate of 3.4 L / min.

[0054] S4. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 12:2:2:1:0.03 to adjust the pH to 5.0. After mixing evenly, heat to 90℃. Then put the powder obtained in S3 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0055] Comparative Example 3

[0056] S1. Mix 40wt% tungsten carbide powder, 57wt% NiCr alloy powder, 1wt% silver and 2wt% calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0057] S2. Place the powder obtained in step S1 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0058] S3. The powder obtained in S2 is pretreated using a high-power direct diode laser for 30 min. The laser wavelength is 1060 nm, the laser power is 1.2 kW, the laser spot size is 5 mm × 1 mm, the scanning speed is 1500 mm / min, the working distance is 15 mm, and the protective gas is argon with a flow rate of 3.4 L / min.

[0059] S4. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 12:2:2:1:0.03 to adjust the pH to 5.0. After mixing evenly, heat to 90℃. Then put the powder obtained in S3 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0060] Comparative Example 4

[0061] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 11 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 10:1:0.07. After taking it out, it is sintered at 500℃ for 1 hour and then heated to 1450℃ for 0.5 hours. After taking it out and cooling it to room temperature, it is sieved for later use.

[0062] S2. Mix 40wt% of tungsten carbide powder obtained in step S1, 57wt% of NiCr alloy powder, 1wt% of silver and 2wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0063] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0064] S4. The powder obtained in S3 is pretreated using a high-power direct diode laser for 30 min. The laser wavelength is 1060 nm, the laser power is 1.2 kW, the laser spot size is 5 mm × 1 mm, the scanning speed is 1500 mm / min, the working distance is 15 mm, the protective gas is argon, and the flow rate is 3.4 L / min. The resulting powder material is laser-clad with internal pores.

[0065] Comparative Example 5

[0066] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 100:12:1. After taking it out, it is sintered at 600℃ for 2 hours and then heated to 1500℃ for 1 hour. After taking it out and cooling it to room temperature, it is sieved for later use.

[0067] S2. Mix 60wt% of tungsten carbide powder obtained in step S1, 39.5wt% of NiCr alloy powder and 0.5wt% of silver, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0068] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0069] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0070] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 15:3:3:1:0.05 to adjust the pH to 5.0. After mixing evenly, heat to 95℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0071] Comparative Example 6

[0072] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 100:12:1. After taking it out, it is sintered at 600℃ for 2 hours and then heated to 1500℃ for 1 hour. After taking it out and cooling it to room temperature, it is sieved for later use.

[0073] S2. Mix 60wt% of tungsten carbide powder obtained in step S1, 37.5wt% of NiCr alloy powder and 2.5wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0074] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0075] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0076] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 15:3:3:1:0.05 to adjust the pH to 5.0. After mixing evenly, heat to 95℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0077] Comparative Example 7

[0078] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 100:12:1. After taking it out, it is sintered at 600℃ for 2 hours and then heated to 1500℃ for 1 hour. After taking it out and cooling it to room temperature, it is sieved for later use.

[0079] S2. Mix 60wt% of tungsten carbide powder obtained in step S1, 34.5wt% of NiCr alloy powder, 3wt% of silver and 2.5wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0080] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0081] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0082] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate and sodium dodecyl sulfate in a mass ratio of 15:3:3:1:0.05 to adjust the pH to 5.0. After mixing evenly, heat to 95℃. Then put the powder obtained in S4 into the mixture, stir and soak for 1 hour. After taking it out, wash and dry it to obtain the internal pore laser cladding powder material.

[0083] Comparative Example 8

[0084] S1. Tungsten carbide powder is mixed with cobalt and vanadium carbide and then ball-milled for 12 hours. The mass ratio of tungsten carbide powder, cobalt and vanadium carbide is 100:12:1. After taking it out, it is sintered at 600℃ for 2 hours and then heated to 1500℃ for 1 hour. After taking it out and cooling it to room temperature, it is sieved for later use.

[0085] S2. Mix 60wt% of tungsten carbide powder obtained in step S1, 34.5wt% of NiCr alloy powder, 0.5wt% of silver and 5wt% of calcium fluoride-barium fluoride mixed crystals, and ball mill them using a high-energy ball mill for 10 hours at a speed of 2000 rpm and a ball-to-material ratio of 8:1.

[0086] S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a gas pressure of 1.5 MPa, and a cyclone separator as the collector with a collector temperature of room temperature.

[0087] S4. The powder obtained in S3 was pretreated using a high-power direct diode laser for 30 min. The laser wavelength was 1060 nm, the laser power was 1.2 kW, the laser spot size was 5 mm × 1 mm, the scanning speed was 1500 mm / min, the working distance was 15 mm, and the protective gas was argon with a flow rate of 3.4 L / min.

[0088] S5. Add water to nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate, and sodium dodecyl sulfate in a mass ratio of 15:3:3:1:0.05 to adjust the pH to 5.0. After mixing evenly, heat to 95°C. Then, add the powder obtained in S4, stir, and soak for 1 hour. Remove, wash, and dry to obtain the internal pore laser cladding powder material. Laser cladding samples were obtained by laser cladding the materials obtained in the examples and comparative examples on a high-manganese steel substrate. The substrate was preheated to 200°C for laser cladding. The laser power was 1000W, the scanning speed was 0.5m / min, the powder delivery rate was 10g / min, and the laser spot diameter was 2mm.

[0089] For corrosion resistance testing, the samples were placed in a salt spray corrosion chamber and exposed to a 35°C, 5% NaCl salt spray environment for 96 hours, and the mass loss was recorded. For flowability testing, a standard Hall funnel was used to measure the time required for 50g of powder to flow out of the funnel. A straight line was drawn on the surface of the cladding layer using a scratch tester, and the critical load generated during the scratching process was measured. The scratch depth was 0.2mm, and the scratching speed was 1mm / s. The adhesion strength of the coating was evaluated. The performance test results are shown in the table below:

[0090]

[0091] Comparative Example 1, which omitted the laser pretreatment step, showed a significant decrease in both coating adhesion strength and flowability. Comparative Example 2, which omitted the gas atomization treatment step, also showed a significant decrease in coating adhesion strength. Comparative Example 3, which did not pretreat tungsten carbide, showed a substantial decrease in its corrosion resistance. Comparative Example 4, which did not undergo chemical plating, showed a substantial decrease in both corrosion resistance and flowability. Comparative Example 5, which did not add calcium fluoride-barium fluoride mixed crystals, showed a significant decrease in the adhesion strength of its coating. Comparative Example 6, which did not add silver, also showed a significant decrease in the adhesion strength of its coating, indicating that the two have a synergistic effect on adhesion strength. Comparative Examples 6 and 7 increased the content of silver and calcium fluoride-barium fluoride mixed crystals, respectively, but the adhesion strength of the coating did not improve.

Claims

1. A method for preparing an internally porous laser cladding powder material, characterized in that: The internal pore laser cladding powder material comprises the following components: 40-60 wt% tungsten carbide, 37-57 wt% NiCr, 0.5-1.5 wt% silver, and 1-3 wt% calcium fluoride-barium fluoride mixed crystals. Includes the following steps: S1. After mixing tungsten carbide powder with cobalt and vanadium carbide, the mixture is ball-milled for 10-12 hours. After removing the mixture, it is sintered at 500-600℃ for 1-2 hours, then heated to 1450-1500℃ for 0.5-1 hours. After removing the mixture and cooling it to room temperature, it is sieved for later use. The tungsten carbide powder in step S1 has a particle size range of 40-160 μm, the amount of cobalt added is 6-12% of the mass of the tungsten carbide powder, and the amount of vanadium carbide added is 0.5-1% of the mass of the tungsten carbide powder. S2. Mix the tungsten carbide powder, NiCr alloy powder, silver and calcium fluoride-barium fluoride mixed crystals obtained in step S1, and then ball mill them using a high-energy ball mill for 10-12 hours. S3. Place the powder obtained in step S2 into a gas atomization device, using nitrogen as the high-pressure gas with a pressure of 1.5-2.0 MPa; S4. Pre-treat the powder obtained in S3 using a high-power direct diode laser for 30-50 minutes. S5. Dissolve nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate, and sodium dodecyl sulfate in water and mix thoroughly. Then heat the mixture to 85-95℃. Add the powder obtained in S4, stir, and soak for 0.5-1h. Remove the powder, clean, and dry it to obtain the laser cladding powder material with internal pores.

2. The method for preparing the internal hole laser cladding powder material according to claim 1, characterized in that: The ball milling speed in step S2 is 1000-2000 rpm, and the ball-to-material ratio is 8-10:

1.

3. The method for preparing the internal hole laser cladding powder material according to claim 1, characterized in that: The laser in step S4 has a wavelength of 980-1060nm, a laser power of 1.2kW, a laser spot size of 5mm×1mm, a scanning speed of 1500mm / min, a working distance of 15mm, and uses argon as the protective gas with a flow rate of 3.4L / min.

4. The method for preparing the internal hole laser cladding powder material according to claim 1, characterized in that: In step S5, the mass ratio of nickel sulfate, sodium citrate, sodium hypophosphite, sodium acetate, and sodium dodecyl sulfate is 10-15:2-3:2-3:1:0.02-0.05, and water is added to adjust the pH to 4.5-5.0.

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