A powder for laser melting, a coating cladding process and a device

Abstract

The application relates to the technical field of cladding coating, and particularly provides a powder for laser melting, a coating cladding process and a device, wherein the powder for laser melting comprises a base powder and a sacrificial carrier containing reinforcing particles; the base powder is an alloy powder; the sacrificial carrier is a porous particle capable of being decomposed into a gas in a melting temperature interval of the base powder; and the reinforcing particles are particles for improving the performance of a structure formed by the base powder; compared with the prior art, the coating prepared from the powder for laser melting disclosed by the application has more uniform microstructure and a significantly reduced defect rate.

Description

Technical Field

[0001] This invention relates to the field of cladding technology, and more particularly to a laser melting powder, a cladding process, and an apparatus. Background Technology

[0002] Laser cladding technology significantly improves the wear resistance, corrosion resistance, and fatigue resistance of mechanical parts by forming a high-performance coating that is metallurgically bonded to the substrate surface. It has found wide application in aerospace, mining and metallurgy, and power energy fields. The core determining factor of coating performance lies in its microstructure, especially the size, morphology, and distribution of the reinforcing phase.

[0003] In existing cladding processes, controlling coating uniformity faces numerous challenges. For example, coating particles, due to their extremely large specific surface area and high surface energy, are prone to irreversible agglomeration during powder storage and transportation, forming agglomerates ranging in size from several micrometers to tens of micrometers. If these agglomerates are directly fed into the laser molten pool, the viscous shear force and natural convection of the melt are insufficient to completely disperse them due to the extremely short duration of the molten pool. This results in locally enriched defect clusters in the coating, disrupting the continuity of the coating structure, easily leading to stress concentration and becoming crack initiation points. To address these issues, this application proposes a powder for laser melting, a coating cladding process, and an apparatus. Summary of the Invention

[0004] The purpose of this invention is to provide a powder for laser melting, a coating cladding process, and an apparatus to solve the problem of locally enriched defect clusters generated during the preparation of current laser cladding coatings.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A powder for laser melting includes a base powder and a sacrificial carrier containing reinforcing particles. The base powder is an alloy powder for laser melting processing, the sacrificial carrier is a porous particle capable of decomposing into gas within the melting temperature range of the base powder, and the reinforcing particles are particles that improve the performance of the structure formed by the base powder.

[0006] Preferably, the sacrificial carrier is PMMA porous particles and / or PS porous particles.

[0007] Preferably, the reinforcing particles are one or more of metal, nitride, boride, carbide, or rare earth particles.

[0008] Furthermore, the present invention also discloses a coating cladding process using the aforementioned laser melting powder, the cladding process comprising the following steps: The sacrificial carrier containing reinforcing particles is mixed with the base powder in a preset ratio to obtain a mixed powder; The mixed powder is supplied to the area of ​​the substrate to be prepared, and a laser with a preset power is applied to the area to be prepared, so that the mixed powder and the surface of the substrate are locally melted and a cladding coating is formed.

[0009] Preferably, the sacrificial carrier and the base powder are premixed or mixed during the powder feeding process.

[0010] Preferably, during the powder cladding process, an ultrasonic airflow of a preset frequency is applied to the molten pool.

[0011] Furthermore, the present invention also discloses a coating cladding apparatus for implementing the above-mentioned coating cladding process, the apparatus comprising: A laser for generating a laser of a preset intensity, wherein the laser emitted by the laser irradiates a substrate; A powder feeding unit is used to feed the mixed powder into the preparation area of ​​the matrix using a carrier gas. An ultrasonic unit, connected to the powder delivery unit, is used to apply ultrasonic vibrations of a preset frequency to the ejected carrier gas.

[0012] Furthermore, the device also includes a fusion nozzle, which is connected to the laser, the powder feeding unit, and the ultrasonic unit. The fusion nozzle includes: A laser connector, which is tubular and has one end connected to a laser; A vibrating component, which has a built-in annular ultrasonic transducer, the ultrasonic transducer being sleeved on the outside of the laser connector; The device includes a manifold and an air guide, which are coaxial housing structures. Both are fitted outside the laser connector. The air guide has a conical first air guide cavity inside. The first air guide cavity is located outside the laser connector. The first air guide cavity forms an annular airflow outlet near the light-emitting end of the laser connector. The manifold has a first air inlet that communicates with the first air guide cavity.

[0013] Furthermore, the vibrating element includes: The first outer casing is a cylindrical shape with openings at both ends, and the two ends of the first outer casing are respectively fixed to the busbar and the laser connector; A piezoelectric ceramic, wherein the piezoelectric ceramic is fitted and installed inside the first housing; An amplitude tube is a cylindrical tube with openings at both ends. One end of the amplitude tube is fixedly connected to the piezoelectric ceramic. The piezoelectric ceramic and the amplitude tube are sleeved on the outside of the laser connector. The end of the amplitude tube away from the piezoelectric ceramic is located inside the manifold. When the amplitude tube vibrates, it applies ultrasonic energy to the carrier gas.

[0014] Furthermore, at least two first air intake ports are provided. The first air intake ports are connected to the first air guide chamber through a spiral air guide channel. The first air intake ports and the spiral air guide channels correspond one-to-one. A mark indicating different air sources is provided on one side of the first air intake ports.

[0015] In summary, the present invention has the following advantages compared with the prior art: The laser melting powder disclosed in this invention adds a sacrificial carrier to a base powder. The porous structure of the sacrificial carrier supports reinforcing particles, and the sacrificial carrier rapidly decomposes into a gaseous state within the melting temperature range. The resulting microbubbles create localized disturbances in the molten pool, making the coating more uniform and dense, while simultaneously ensuring that the reinforcing particles are uniformly dispersed in the coating matrix. Compared with existing technologies, the coating prepared by the laser melting powder disclosed in this invention has a more uniform microstructure and a significantly reduced defect rate. Attached Figure Description

[0016] Figure 1 This is a flowchart of the coating cladding process disclosed in an embodiment of the present invention.

[0017] Figure 2 These are electron microscope (EM) images of the coatings prepared in the experimental group in this embodiment of the invention, where a1 is an EEM image of the top of the coating at a scale of 50 μm, and a2 is an EEM image of the middle position of the coating at a scale of 50 μm.

[0018] Figure 3 The images shown are electron microscope (EM) images of the coating prepared in control group 1 in this embodiment of the invention. B1 is an EEM image of the top of the coating at a scale of 50 μm, and B2 is an EEM image of the middle position of the coating at a scale of 50 μm.

[0019] Figure 4 The images shown are electron microscope (EM) images of the coating prepared in control group two in this embodiment of the invention. C1 is an EEM image of the top of the coating at a scale of 50 μm, and C2 is an EEM image of the middle position of the coating at a scale of 50 μm.

[0020] Figure 5 This is a comparison chart of wear data of the coatings prepared in the experimental group, control group 1, and control group 2 in the embodiments of the present invention. In the chart, a represents the wear curve of the coating prepared in the experimental group, b represents the wear curve of the coating prepared in control group 1, and c represents the wear curve of the coating prepared in control group 2.

[0021] Figure 6 This is a comparison chart of the hardness of the coatings prepared in the experimental group, control group 1, and control group 2 in the embodiments of the present invention. In the chart, a represents the hardness curve of the coating prepared in the experimental group, b represents the hardness curve of the coating prepared in control group 1, and c represents the hardness curve of the coating prepared in control group 2.

[0022] Figure 7This is a schematic diagram of the overall structure of the fusion nozzle in the coating cladding device disclosed in Embodiment 3 of the present invention.

[0023] Figure 8 This is a front view of the fusion nozzle in the coating cladding apparatus disclosed in Embodiment 3 of the present invention.

[0024] Figure 9 for Figure 8 Sectional view of AA.

[0025] Figure 10 This is an exploded view of the fusion nozzle in the coating cladding device disclosed in Embodiment 3 of the present invention.

[0026] Figure 11 for Figure 7 A schematic diagram of the amplitude tube in the publicly disclosed fusion nozzle.

[0027] Figure 12 for Figure 7 A schematic diagram of the manifold structure in a publicly disclosed fusion nozzle.

[0028] Figure 13 for Figure 7 A fully sectional view of the manifold in the publicly available fusion nozzle.

[0029] Figure 14 for Figure 7 A fully sectional view of the air guide component in the publicly available fusion nozzle.

[0030] Figure 15 for Figure 7 A schematic diagram of the protective gas component in the publicly disclosed fusion nozzle.

[0031] Figure label: Laser connector; 101, fiber optic connector; 102, mounting flange; 103, retraction section; 200, vibrating component; 210, first outer shell; 220, piezoelectric ceramic; 230, amplitude tube; 231, limiting ring; 240, fixing ring; 241, first disassembly / assembly hole; 250, amplitude transformer; 260, isolation sleeve; 270, elastic component; 300, manifold; 301, first air inlet; 302, air guide groove; 303, marking; 304, vibration chamber; 400, air guide component; 401, mixing chamber; 402, first air guide chamber; 403, connecting section; 404, mixing section; 405, first air guide section; 500, protective gas shell; 501, second air guide chamber; 502, air inlet; 503, second air guide section. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Example 1: An embodiment of the present invention provides a method comprising a base powder and a sacrificial carrier containing reinforcing particles. The base powder is an alloy powder, the sacrificial carrier is a porous particle capable of decomposing into gas within the melting temperature range of the base powder, and the reinforcing particles are particles that improve the performance of the structure formed by the base powder.

[0034] The base powder is an alloy powder in the prior art, such as iron-based alloy powder or nickel-based alloy powder. In the verification experiment of this embodiment, the base powder is FeCrCoNiTi alloy particles.

[0035] The sacrificial carrier is a porous particle, and the reinforcing particles are attached to the inner walls and surface of the pores of the sacrificial carrier, forming a composite structure of the sacrificial carrier and the reinforcing particles. The method for preparing the sacrificial carrier is existing technology. In this embodiment, the sacrificial carrier is a mixture of PMMA (polymethyl methacrylate) porous particles and PS (polystyrene) porous particles. The PMMA porous particles and the PS porous particles are prepared by suspension polymerization using existing technology. Taking PMMA porous particles as an example, firstly, deionized water (the mass ratio of the aqueous phase to the subsequent oil phase is controlled at 3:1 to 10:1) and a dispersant (polyvinyl alcohol, degree of alcoholysis 88%) at a mass of 1 / 667 to 1 / 333 of the MMA monomer mass are added to the reactor, stirred and heated to 60°C to dissolve, and then deoxygenated with high-purity nitrogen for 15 to 30 minutes to obtain an aqueous suspension. Then, methyl methacrylate (MMA) monomer, a crosslinking agent (divinylbenzene) at a mass of 1 / 100 to 1 / 20 of the monomer mass, and a porogen (at least one of toluene, liquid paraffin, or n-heptane) at a mass of 2 / 3 to 3 / 2 of the MMA monomer mass are added. An oil-soluble initiator (azobisisobutyronitrile) of 1 / 200 to 1 / 100 of the MMA monomer mass is stirred until completely dissolved to form an oil phase solution. The oil phase solution is slowly added to the aqueous phase, and while stirring at 300–500 rpm, the oil phase solution is dispersed into droplets suspended in the water. A nitrogen positive pressure atmosphere is maintained, and the temperature is slowly increased to 75–85°C at a rate of 1–3°C / min. The reaction is held at this temperature for 4–6 hours, then the temperature is increased to 90–95°C and the reaction is held at this temperature for another 1–2 hours. The microspheres were aged at high temperature for 24-36 hours after polymerization. After polymerization, the microspheres were separated by filtration and extracted with acetone by Soxhlet extraction for 24-36 hours to completely remove the porogen and residual monomers. Then, they were vacuum dried at 50-70℃ to constant weight. After sieving, porous PMMA particles with a particle size range of 45-150μm, three-dimensional interconnected channels (average pore size 50-500nm, channel connectivity ≥90%), porosity of 60%-85%, and specific surface area of ​​50-200m² / g were obtained.

[0036] The preparation method for PS porous particles is the same as above, except that the monomer is replaced by styrene instead of MMA.

[0037] Preferably, to improve the bonding force between the particles and the pore walls, the porous PMMA microspheres are first subjected to surface hydroxylation pretreatment: the porous particles are placed in a plasma treatment instrument, and the treatment time is 8 minutes at 100W under an oxygen atmosphere; then, a silane coupling agent hydrolysate is prepared: anhydrous ethanol and deionized water are mixed at a volume ratio of 9:1, the pH is adjusted to 4.5 with glacial acetic acid, and 0.6% KH-550 is added. The mixture is stirred and hydrolyzed at room temperature for 30 minutes; the hydroxylated porous particles are added to the above hydrolysate at a solid-liquid ratio of 1g:20mL, and the mixture is stirred and reacted at 50℃ for 5 hours; after the reaction, the porous particles are separated by filtration, washed three times with anhydrous ethanol (10 minutes each time), and vacuum dried at 45℃ for 6 hours for later use.

[0038] The PMMA porous particles and PS porous particles are mixed in a mass ratio of PMMA:PS = 1:0 to 0:1. In this embodiment, the PMMA porous particles and PS porous particles are mixed in a ratio range of PS:PMMA = 7:3 to 4:1 to obtain a mixed sacrificial carrier.

[0039] Preferably, the reinforcing particles are one or more of metal, nitride, boride, carbide, or rare earth particles. In this embodiment, the reinforcing particles are FeCrCoNiTi alloy particles with a particle size of 1-200 μm. In other embodiments, tungsten carbide, titanium nitride, zirconium oxide, silicon carbide, etc., may also be used depending on the coating requirements. The performance of the structure refers to physical, chemical, or mechanical properties such as wear resistance, bending resistance, strength, and elasticity.

[0040] The reinforcing particles (FeCrCoNiTi alloy particles) to be added are added to anhydrous ethanol or isopropanol and dispersed for 15 to 30 minutes under ultrasonic assistance of 100 to 300 W to form a suspension with a particle mass concentration of 5% to 30%. Polyvinylpyrrolidone (PVP, K30) at a mass of 0.1% to 0.5% of the particles is added as a dispersion stabilizer. The mixed sacrificial carrier is added to the above suspension and placed in a vacuum-sealed container. It is immersed for 30 to 60 minutes under a negative pressure of -0.08 MPa to -0.095 MPa while stirring at a speed of 50 to 100 r / min to allow the suspension to carry the particles to fully penetrate into the three-dimensional through-pores of the carrier microspheres.

[0041] After impregnation, the pressure is restored to normal, and the wet composite powder is obtained by vacuum filtration. The wet composite powder is dried at 60-80℃ and vacuum degree ≤-0.09MPa for 4-8 hours. After drying, it is passed through a 200-mesh standard sieve to remove surface floating powder or large agglomerates, thus obtaining the "sacrificial carrier / reinforcing particle" composite powder.

[0042] The above composite powder and base powder are mixed in a preset ratio (3% to 10%) to obtain a mixed powder.

[0043] The composite powder and the base powder can be mixed in a mixing device or during the powder feeding process. In this embodiment, the composite powder and the base powder are pre-mixed manually in the verification experiment.

[0044] It should be noted that the sacrificial carrier scheme disclosed in this embodiment aims to improve the uniformity of the formed structure. Therefore, it can be applied not only in the field of coating cladding (the field to which embodiments 2 and 3 of this application belong), but also in other fields similar to laser cladding, such as laser processing using additive manufacturing methods, specifically, in the field of metal additive manufacturing using lasers and metal powders, and in the field of laser welding using lasers and powders. When used in metal additive manufacturing, it can promote the formation of a uniform microstructure from the powder, thereby improving the strength of the manufactured parts.

[0045] Example 2: Figure 1 As shown, one embodiment of the present invention provides a coating cladding process, the cladding process including the following steps: Step S1: Mix the sacrificial carrier containing reinforcing particles with the base powder in a preset ratio to obtain a mixed powder. The sacrificial carrier is a porous particle that can decompose into gas within the melting temperature range of the base powder, and the reinforcing particles are particles that improve the performance of the structure formed by the base powder.

[0046] Specifically, in this embodiment, the mixed powder is prepared in the manner described in Example 1.

[0047] Step S2: The mixed powder is supplied to the area to be prepared on the substrate, and a laser with a preset power is applied to the area to be prepared, so that the mixed powder and the surface of the substrate are locally melted and a cladding coating is formed.

[0048] Specifically, in this step, for the pre-mixed powder, a traditional powder feeder is used with an inert gas (argon) as the carrier gas to deliver the mixed powder to the laser cladding head. The laser beam is then focused onto the substrate surface to melt the base powder in the area to be prepared on the substrate, forming a uniform and dense metallurgical bonding layer. In this embodiment, the delivery flow rate and laser power are set according to the process requirements, and no specific requirements are made in this embodiment. For example, in some examples, the delivery flow rate of the carrier gas is 15-25 L / min, the laser power is set to 1800-3200 W, the scanning speed is controlled at 6-12 mm / s, the spot diameter is 2-3 mm, and argon gas is introduced simultaneously for protection during the cladding process.

[0049] Preferably, during the powder cladding process, an ultrasonic airflow of a preset frequency is applied to the molten pool. Specifically, ultrasonic energy is applied to the ejected carrier gas inside the laser cladding head, causing the composite powder carried by the carrier gas to generate ultrasonic vibrations along its direction of motion before entering the molten pool. When the airflow is sprayed onto the surface of the molten pool, high-frequency capillary waves are excited at the gas-liquid interface. The capillary waves resonate and couple with the acoustic pressure field within the volume of the molten pool, injecting ultrasonic energy into the molten pool, establishing acoustic flow circulation and acoustic cavitation field, significantly promoting the uniform dispersion and interface wetting of reinforcing particles in the molten pool, thereby effectively inhibiting particle agglomeration and floating, and improving the spatial distribution uniformity and interface bonding strength of the particles in the coating matrix.

[0050] This invention uses porous particles (polymethyl methacrylate PMMA and / or polystyrene PS) made of organic polymers that can be completely thermally decomposed within the powder melting temperature range and whose products are mainly gaseous as a sacrificial carrier. The reinforcing particles are pre-loaded into the internal channels of the sacrificial carrier to form a composite powder. After the composite powder enters the laser molten pool, the carrier rapidly decomposes and vaporizes in the molten pool (within 5 to 20 milliseconds), releasing the particles into the melt. The microbubbles generated by the decomposition produce a micro-area stirring effect on the surrounding melt during expansion and escape, achieving initial pre-dispersion of the particles. At the same time, the substances generated by decomposition and vaporization expand violently in all directions, forming impact disturbances and turbulence effects in local areas, pushing the reinforcing particles into the surrounding melt, completing the initial physical dispersion. The ultrasonic action in the molten pool forms acoustic flow and acoustic cavitation effects, which can promote the breakage, migration, merging and escape of bubbles, thereby reducing the probability of the formation of pore defects. The impact energy generated by gas expansion is converted into an orderly and uniform stirring force, and its range of action is extended from local to the entire molten pool, dispersing the reinforcing particles throughout the entire molten pool. This synergistic mechanism ensures uniform particle distribution throughout the molten pool before solidification. Simultaneously, micro-area stirring homogenizes the temperature and composition fields within the molten pool, suppressing segregation and improving the density and mechanical properties of the coating. Furthermore, as ultrasound propagates through the molten metal, it generates periodic alternations of positive and negative pressure. During the negative pressure half-cycle, the melt is stretched, and dissolved gases or tiny bubbles grow as cavitation nuclei. During the positive pressure half-cycle, these bubbles are compressed and collapse. In this repeated cavitation process, tiny bubbles collide, aggregate, and merge into larger bubbles. When the bubble size reaches a certain level, its buoyancy exceeds the viscous resistance of the melt, causing it to rapidly rise and escape from the molten pool surface. The acoustic flow circulation established by ultrasound within the molten pool is a macroscopically ordered convection covering the entire volume of the molten pool. This strong convection continuously transports bubbles from inside the molten pool to the surface, accelerating their rise and escape.

[0051] Meanwhile, the gas generated by the decomposition of the carrier is not only a physical stirring medium. By selecting porous PMMA particles and porous PS particles and mixing them in different proportions, the carbon potential of the decomposition gas can be controlled: a higher PS content results in a relatively higher carbon potential, which is conducive to promoting the formation of carbide interface phases (such as Cr3C2 and TiC) at the bubble-melt interface; a higher PMMA content results in a relatively lower carbon potential, which is conducive to promoting the formation of intermetallic compounds or amorphous interface phases.

[0052] To verify the above preparation method, this embodiment was conducted in the laboratory. An experimental group was set up, and the process was as follows: FeCrCoNiTi high-entropy alloy was used as the base powder, FeCrCoNiTi alloy particles were used as reinforcing particles, and PMMA / PS mixed porous particles were selected as the sacrificial carrier. Composite powder was prepared at a mass ratio of PMMA:PS=3:1. The composite powder was mixed with 5% of the base powder. A binder was added to the mixed powder. Multiple rectangular grooves were made on the experimental body (pre-designed substrate), with a groove depth of 2mm, a width of 10mm, and a length of 3mm. 0mm, the mixed powder is pre-spread evenly inside the rectangular groove. After drying, the mixed powder is bonded to the rectangular groove by the binder. The laser is adjusted to 1000W and irradiates the base powder. The modified protective gas nozzle (with an integrated ultrasonic transducer) is used to apply ultrasonic vibration to the protective gas, thereby simulating the carrier gas with ultrasonic vibration. The ultrasonic vibration continuously injects high-frequency energy into the molten pool through the protective gas flow. The working frequency of the ultrasonic transducer is set to 20kHz, the amplitude is controlled at 15μm, and the ultrasonic power is 50W. After the molten pool cools, the coating parameters are measured.

[0053] Preferably, in this embodiment, control group one and control group two are also set up. The experimental group uses a mixture of sacrificial carrier and base powder, and ultrasonic vibration is applied to the protective gas. The difference between control group one and the experimental group is that ultrasonic vibration is not applied to the protective gas. The difference between control group two and the experimental group is that a sacrificial carrier is not used, and ultrasonic vibration is not applied to the protective gas. Other parameters are the same for all three experimental groups. The electron micrographs and tribological properties of the coatings are analyzed to obtain the following results: Figures 2 to 6 The experimental results are shown.

[0054] analyze Figures 2 to 4 It can be seen that at a microscopic scale of 50 μm, the analysis Figure 2 a1 and a2 in Figure 3 b1 and b2 in Figure 4 In the figures c1 and c2, the uniformity and density of the top of the coating are a1 > b1 > c1, and the uniformity and density of the middle of the coating are a2 > b2 > c2. It can be seen that using a sacrificial carrier helps to improve the uniformity and density of the coating. After applying ultrasonic vibration to the protective gas, the uniformity and density of the coating are further improved.

[0055] The friction and wear test was conducted at room temperature using an HT-1000 high-temperature friction and wear testing machine. During the test, the sample was placed on the bottom disc of the machine and secured with four bolts. The sample moved in a periodic circular motion with the disc. The friction pair was fixed above the sample, and the friction coefficient was recorded in real time by a sensor. The abrasive material selected was 6mm diameter Si3N4 ceramic balls that are insensitive to temperature changes. After the abrasive material was properly placed, the abrasive pair with a counterweight was placed above the sample. The friction and wear testing machine was started according to the operating procedure, causing the abrasive material and the sample to rotate relative to each other at a specified speed. The specific experimental parameters were: test force 15N, spindle speed 318r / min, test time 1800s, test revolutions 9540 rpm, and test temperature room temperature.

[0056] Depend on Figure 5 It can be seen that the friction coefficients of the three groups of samples all showed a trend of first increasing and then fluctuating and stabilizing with the increase of test time, but the friction response of the coatings under different process conditions was significantly different. The friction coefficient of the coating in the experimental group increased rapidly in the initial stage, and then gradually entered the stable wear stage, stabilizing at 0.70-0.80 with relatively small fluctuations. This indicates that ultrasonic vibration and the sacrificial carrier can improve the uniformity of the coating structure, refine the grains, and reduce local defects, so that the coating exhibits good stability and low frictional resistance during friction. The friction coefficient of the coating in control group 1 was higher than that in the experimental group, and the stable stage was about 0.80-0.90. This indicates that the sacrificial carrier has a certain improving effect on the coating performance, but its frictional stability is not as good as the combination of ultrasonic vibration and sacrificial carrier. The friction coefficient of the coating in control group 2 was the highest, reaching above 1.0 in the later stage, and the curve fluctuated more significantly, indicating that its surface structure may be rough or have more defects, which can easily generate greater resistance and unstable wear during friction.

[0057] This experiment used a microhardness tester to test the hardness of three types of coated samples. The test direction was from the coating surface towards the substrate, and the test load was 0.2 kgf. The hardness results are expressed in HV. 0.2 It means that by Figure 6 It can be seen that the hardness of the three groups of samples all exhibits a variation pattern of "high hardness in the coating area, decreasing hardness in the heat-affected zone, and lowest hardness in the substrate area". Within the coating area, the experimental group showed the highest overall microhardness of the coating, with the hardness mostly remaining at 600 HV. 0.2 The above, with a maximum of approximately 650 HV. 0.2 This indicates that ultrasonic vibration and the sacrificial carrier help refine grains, improve the uniformity of the molten pool structure, and promote the dispersed distribution of strengthening phases, thereby increasing the coating hardness; the coating hardness of control group one is the second lowest, with an overall hardness of approximately 560–610 HV. 0.2This indicates that sacrificing the carrier alone can improve the coating microstructure and hardness, but not as effectively as adding ultrasonic vibration. The coating hardness of control group two fluctuated significantly, with some areas showing higher hardness, but its overall stability was inferior to the experimental group and control group one. Upon entering the heat-affected zone, the hardness of all three groups of samples decreased significantly, indicating that this region was affected by thermal cycling, causing some softening of the microstructure. This was especially evident in the area near the substrate, where the hardness rapidly decreased to 200–230 HV. 0.2 It is around the same level as the matrix hardness.

[0058] A comprehensive comparison shows that the coatings treated with ultrasonic vibration and those using a sacrificial carrier exhibit the highest hardness and best stability. Sacrificial carrier treatment alone can also improve coating performance, while the hardness distribution of coatings without a sacrificial carrier and those treated with ultrasonic vibration is relatively uneven. Therefore, the hardness performance of the coatings under the three processes is ranked as follows: Experimental Group > Control Group 1 > Control Group 2.

[0059] Example 3: As another embodiment of the present invention, this embodiment also discloses a coating cladding device, the device including a laser, a powder feeding unit and an ultrasonic unit, the laser being used to generate a laser of a preset intensity, the laser emitted by the laser irradiating the substrate; the powder feeding unit feeding mixed powder into the preparation area through a carrier gas; the ultrasonic unit being connected to the powder feeding unit and used to apply ultrasonic vibration of a preset frequency to the sprayed carrier gas.

[0060] In this embodiment, the device includes a fusion nozzle, the light-emitting end of the laser is fixedly connected to the fusion nozzle, the powder feeding unit is connected to the fusion nozzle and is used to feed carrier gas into the fusion nozzle. When the carrier gas is ejected from the gas outlet of the fusion nozzle, it carries the base powder. The ultrasonic unit is integrated inside the fusion nozzle, and its transducer applies ultrasonic vibration along the airflow direction. The vibration energy is transferred to the powder and molten pool interface with the airflow, thereby refining the grains, inhibiting the formation of pores and improving the density of the coating.

[0061] Specifically, in this embodiment, such as Figures 7 to 10As shown, the fusion nozzle includes a laser connector 100, a vibrating element 200, a manifold 300, a gas guide 400, and a protective gas shell 500. The laser connector 100 is tubular, with one end connected to a laser and the other end coaxially nested with and passing through the vibrating element 200. The vibrating element 200 houses an ultrasonic transducer, which is a ring structure. The ultrasonic transducer is sleeved on the outside of the laser connector 100 and coaxially arranged with it. The laser connector 100 and the vibrating element 200... The laser connector 100 is fixedly connected by threads. The manifold 300 and the gas guide 400 are coaxial housing structures. Both the manifold 300 and the gas guide 400 are sleeved on the outside of the laser connector 100. The gas guide 400 has a mixing cavity 401 and a first gas guide cavity 402 that are interconnected. Both the mixing cavity 401 and the first gas guide cavity 402 are located on the outside of the laser connector 100. The first gas guide cavity 402 forms an annular airflow outlet near the light-emitting end of the laser connector 100. 402 is a conical air passage. The carrier gas ejected from the first air guide cavity 402 and the laser emitted from the laser connector 100 converge at the molten pool. The manifold 300 is provided with a first air inlet 301, which is used to connect the carrier gas. The first air inlet 301 is connected to the mixing chamber 401. The carrier gas enters the mixing chamber 401 through the first air inlet 301 and is ejected from the first air guide cavity 402. The output end of the ultrasonic transducer is located inside the mixing chamber 401. The protective gas shell 500 is disposed in the first air guide cavity 402. At one end of the gas component 400 away from the manifold 300, a second gas guiding cavity 501 is provided between the inner side of the protective gas shell 500 and the outer side of the gas guiding component 400. The second gas guiding cavity 501 forms an annular opening with the gas guiding component 400 at the end of the gas guiding component 400 away from the manifold 300. An air inlet 502 is also provided on the outside of the protective gas shell 500. The air inlet 502 is a through hole structure that penetrates the inner and outer sides of the protective gas shell 500. The air inlet 502 communicates with the second gas guiding cavity 501 and is used to introduce protective gas.The first air inlet 301 is connected to the powder feeding unit, and the second air guide cavity 501 is connected to the protective gas source. The light-emitting end of the laser unit is fixed to the laser connector 100. When preparing the coating, the laser is transmitted axially along the inside of the laser connector 100 to the molten pool. The carrier gas carries the base powder into the mixing cavity 401 through the first air inlet 301, and then is ejected from the first air guide cavity 402 in the form of a conical airflow, which intersects with the laser beam above the molten pool. After the protective gas enters the second air guide cavity 501 through the air inlet 502, it uniformly wraps the molten pool area from the annular opening to form an inert gas protective atmosphere. The ultrasonic transducer continuously applies high-frequency vibration to the carrier gas, so that the carrier gas transmits ultrasonic energy to the molten pool.

[0062] The laser connector 100 is a cylindrical tube structure. An optical fiber connector 101 is provided at one end of the laser connector 100 away from the gas guide 400. The optical fiber connector 101 is a threaded hole, and the light-emitting end of the laser is fixed to the optical fiber connector 101 via a threaded structure. A mounting flange 102 is provided near the optical fiber connector 101 on the laser connector 100. The mounting flange 102 is a flange structure used to fix the fusion nozzle to a spatially movable structure such as a robotic arm. A constriction section 103 is provided at the laser connector 100 away from the optical fiber connector 101. The constriction section 103 is conical and used to guide the carrier gas to be ejected in a conical shape.

[0063] Preferred, such as Figures 9 to 11 As shown, the vibrating element 200 includes a first outer shell 210, a piezoelectric ceramic 220, an amplitude tube 230, and a fixing ring 240. The first outer shell 210 is a cylindrical structure with openings at both ends. The through hole at the center of the first outer shell 210 is a countersunk hole structure. The laser connector 100 is fixed to the small hole of the first outer shell 210 by a threaded structure. The first outer shell 210 is fixedly connected to the busbar 300 by threads or interference fit. The piezoelectric ceramic 220 is fitted into the large hole of the first outer shell 210. The wire of the piezoelectric ceramic 220 passes through the first outer shell 210 and is guided to the outside of the first outer shell 210, as shown. Figure 11As shown, the amplitude tube 230 is a cylindrical structure with openings at both ends. A limiting ring 231 is provided at one end of the amplitude tube 230 that is attached to the piezoelectric ceramic 220. The limiting ring 231 and the amplitude tube 230 are integrally formed. When the piezoelectric ceramic 220 generates axial vibration, its vibration is transmitted to the amplitude tube 230 through the limiting ring 231. The connection method between the amplitude tube 230 and the limiting ring 231 is a conventional design for transducers in the technology, such as fixing them through interference fit or welding to ensure vibration transmission. The piezoelectric ceramic 220 and the amplitude tube 230 are sleeved on the outside of the laser connector 100, with the end of the amplitude tube 230 away from the piezoelectric ceramic 220 located at... Within the manifold 300, the amplitude tube 230 applies ultrasonic energy to the carrier gas during vibration, causing the airflow to oscillate at high frequency. The fixing ring 240 is a circular ring structure with external threads on its outer side. The fixing ring 240 is sleeved on the outer side of the amplitude tube 230 and is fixed to the end of the large hole of the first outer shell 210 through the threaded structure. The fixing ring 240 serves as a limiting ring 231 to prevent the amplitude tube 230 from detaching from the piezoelectric ceramic 220 during vibration. The fixing ring 240 is also provided with a first disassembly hole 241, which facilitates the disassembly of the fixing ring 240. The first disassembly hole 241 is a through hole structure.

[0064] Preferably, the vibrating element 200 further includes an amplitude transformer 250, which is fixedly connected to the end of the amplitude tube 230 away from the piezoelectric ceramic 220. The amplitude transformer 250 has a ring structure and is used to increase the end area of ​​the amplitude tube 230, thereby improving the coupling efficiency of ultrasonic energy to the carrier gas. The amplitude transformer 250 is fixedly connected to the end of the amplitude tube 230 by thread or interference fit.

[0065] Preferably, the vibrating element 200 further includes an isolation sleeve 260 and an elastic element 270. The isolation sleeve 260 is sleeved between the piezoelectric ceramic 220, the amplitude tube 230 and the laser connector 100 to reduce the mechanical friction between the piezoelectric ceramic 220 and the amplitude tube 230 and the laser connector 100 during vibration. The isolation sleeve 260 is a cylindrical flexible pad, such as a silicone tube. The elastic element 270 is a ring spring or a rubber washer. The elastic element 270 is located between the limiting ring 231 and the fixing ring 240 and is used to provide vibration space.

[0066] like Figure 12 and Figure 13As shown, the manifold 300 has an annular structure with stepped surfaces at both ends of its inner side, which are respectively connected to the first housing 210 and the amplitude transformer 250. The manifold 300 and the end of the amplitude tube 230 form a vibration cavity 304 that accommodates the amplitude transformer 250. The outer surface of the amplitude transformer 250 is clearance-fitted with the inner wall of the vibration cavity 304. The end face of the manifold 300 near the first housing 210 is a conical surface, and the opening of the first air inlet 301 is opened on this conical surface. The outer side of the manifold 300 is a platform. The manifold 300 is fixed to the air guide 400 by a threaded structure. The manifold 300 has an air guide groove 302 on its side inside the air guide 400. The air guide groove 302 and the inner wall of the air guide 400 form an air guide channel. One end of the air guide groove 302 is connected to the first air inlet 301, and the other end of the air guide groove 302 is connected to the mixing chamber 401. The carrier gas enters the interior of the air guide groove 302 through the first air inlet 301, and then enters the mixing chamber 401 through the air guide groove 302.

[0067] Preferably, at least two first air inlets 301 are provided, and the air guide grooves 302 correspond one-to-one with the first air inlets 301. In this embodiment, four first air inlets 301 are provided, and the air guide grooves 302 are spiral grooves. The air guide grooves 302 and the inner wall of the air guide component 400 form a spiral air guide channel to guide the carrier gas tangentially into the mixing chamber 401. One of the first air inlets 301 is connected to the carrier gas of the base powder, and the other is connected to the carrier gas of the sacrificial carrier. The base powder and the sacrificial carrier are mixed in the mixing chamber 401 to achieve real-time control of the configuration ratio. In this embodiment, two of the first air inlets 301 are connected to the carrier gas of the base powder, and two are connected to the carrier gas of the sacrificial carrier. The first air inlets 301 connected to the sacrificial carrier and the first air inlets 301 connected to the base powder are alternately arranged. Since there is a certain ratio between the sacrificial carrier and the base powder, the two enter the mixing chamber 401 at different rates. Through the alternating arrangement and the air guide grooves 302, the two can form a countercurrent in the mixing chamber 401, thereby achieving a uniform mixing effect.

[0068] like Figure 14As shown, the gas guide 400 has an annular cylindrical structure with a stepped inner cavity. The inner cavity of the gas guide 400 is provided with a connecting section 403, a mixing section 404, and a first gas guide section 405. The connecting section 403 is cylindrical, the mixing section 404 is conical, and the first gas guide section 405 is conical. The cone angle of the mixing section 404 is greater than that of the first gas guide section 405. When the confluence member 300 and the gas guide 400 are connected, the inner wall of the connecting section 403 and the gas guide groove 302 form a spiral gas guide channel. The mixing section 404 and the laser connector 100 form a mixing cavity 401. The first gas guide section 405 and the laser connector 100 constitute a first gas guide cavity 402.

[0069] Preferably, a mark 303 is also provided on one side of the first air inlet 301, such as the letter "A" being printed on the side of the first air inlet 301 connected to the basic powder feeding air path, and the letter "B" being printed on the side of the first air inlet 301 connected to the sacrificial carrier feeding air path.

[0070] like Figure 15 As shown, the protective gas shell 500 is an annular shell. The protective gas shell 500 is fixed to the end of the gas guide 400 away from the manifold 300 by a threaded structure. A conical second gas guide section 503 is provided inside the protective gas shell 500. The air inlet 502 is opened on the side of the protective gas shell 500. The air inlet 502 and the second gas guide section 503 are connected. The second gas guide section 503 and the contraction section 103 form a second gas guide cavity 501.

[0071] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0072] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A powder for laser melting, comprising a base powder, wherein the base powder is an alloy powder, characterized in that, The laser melting powder also includes a sacrificial carrier containing reinforcing particles. The sacrificial carrier is a porous particle that can decompose into gas within the melting temperature range of the base powder. The reinforcing particles are particles that improve the performance of the structure formed by the base powder.

2. The powder for laser melting according to claim 1, characterized in that, The sacrificial carrier is PMMA porous particles and / or PS porous particles.

3. The powder for laser melting according to claim 1, characterized in that, The reinforcing particles are one or more of the following: metal, nitride, boride, carbide, or rare earth particles.

4. A coating cladding process, characterized in that, Using the laser melting powder according to any one of claims 1-3, the cladding process includes the following steps: The sacrificial carrier containing reinforcing particles is mixed with the base powder in a preset ratio to obtain a mixed powder; The mixed powder is supplied to the area of ​​the substrate to be prepared, and a laser with a preset power is applied to the area to be prepared, so that the mixed powder and the surface of the substrate are locally melted and a cladding coating is formed.

5. The coating cladding process according to claim 4, characterized in that, The sacrificial carrier and the base powder are premixed or mixed during the powder feeding process.

6. The coating cladding process according to claim 4, characterized in that, During the powder cladding process, an ultrasonic airflow of a preset frequency is applied to the molten pool.

7. A coating cladding apparatus for implementing the coating cladding process according to any one of claims 4-6, characterized in that, The device includes: A laser for generating a laser of a preset intensity, wherein the laser emitted by the laser irradiates a substrate; A powder feeding unit is used to feed the mixed powder into the preparation area of ​​the matrix using a carrier gas. An ultrasonic unit, connected to the powder delivery unit, is used to apply ultrasonic vibrations of a preset frequency to the ejected carrier gas.

8. The coating cladding apparatus according to claim 7, characterized in that, The device further includes a fusion nozzle, which is connected to the laser, the powder feeding unit, and the ultrasonic unit. The fusion nozzle includes: A laser connector, which is tubular and has one end connected to a laser; A vibrating component, which has a built-in annular ultrasonic transducer, the ultrasonic transducer being sleeved on the outside of the laser connector; The device includes a manifold and an air guide, which are coaxial housing structures. Both are fitted outside the laser connector. The air guide has a conical first air guide cavity inside. The first air guide cavity is located outside the laser connector. The first air guide cavity forms an annular airflow outlet near the light-emitting end of the laser connector. The manifold has a first air inlet that communicates with the first air guide cavity.

9. The coating cladding apparatus according to claim 8, characterized in that, The vibrating element includes: The first outer casing is a cylindrical shape with openings at both ends, and the two ends of the first outer casing are respectively fixed to the busbar and the laser connector; A piezoelectric ceramic, wherein the piezoelectric ceramic is fitted and installed inside the first housing; An amplitude tube is a cylindrical tube with openings at both ends. One end of the amplitude tube is fixedly connected to the piezoelectric ceramic. The piezoelectric ceramic and the amplitude tube are sleeved on the outside of the laser connector. The end of the amplitude tube away from the piezoelectric ceramic is located inside the manifold. When the amplitude tube vibrates, it applies ultrasonic energy to the carrier gas.

10. The coating cladding apparatus according to claim 8, characterized in that, At least two first air intake ports are provided. The first air intake ports are connected to the first air guide chamber through a spiral air guide channel. The first air intake ports and the spiral air guide channels correspond one-to-one. A mark indicating different air sources is provided on one side of the first air intake ports.

Images