Method and apparatus for field assisted infiltration sintering of high temperature alloy hot end component coatings

Abstract

A method and device for sintering high-temperature alloy hot end part coating by magnetic field assisted infiltration, the device comprising a water pump (1), a high-frequency power supply (3), a vacuum furnace (5), a diffusion vacuum pump (2) and a temperature control and protection device (4). The method surrounds the surface of the pre-processed workpiece with a layer of enclosure, and lays the prepared wear-resistant coating powder inside the enclosure; the pre-processed workpiece is placed on the support platform in the vacuum furnace, the furnace cover is closed, the vacuum system and the power supply are started, and when the temperature reaches the infiltration sintering temperature, the temperature is kept for 30-60 min; after the heat preservation is finished, the heating is stopped; after the workpiece is cooled to room temperature, the workpiece is taken out, the coating surface is treated, and the high-temperature alloy hot end part wear-resistant coating is obtained. The present application changes the eddy current while melting the metal filler by the induction heating device, effectively reduces the internal pores of the coating, improves the coating density, and further enhances the bonding strength and wear resistance of the coating.

Description

Technical Field

[0001] This invention relates to a method and apparatus for magnetic field-assisted melting and sintering of coatings on hot-end components of high-temperature alloys, belonging to the field of high-temperature alloy coating technology. Background Technology

[0002] In high-end equipment such as aero engines and gas turbines, high-temperature alloy hot-end components (such as turbine blade tips) are subjected to harsh conditions of high-speed operation, high temperature, high load and complex media erosion for a long time, which makes them prone to wear failure and seriously affects the operating efficiency and service life of the equipment.

[0003] To extend the service life of hot-end components of high-temperature alloys, wear-resistant coatings are typically prepared on the friction surfaces. Melt infiltration sintering technology is a relatively advanced method for preparing such coatings after several iterations. It can overcome the shortcomings of other traditional methods, such as laser cladding (high equipment and operating costs, low efficiency, strict requirements on workpiece shape and size, difficulty in processing complex curved surfaces and large components, and susceptibility to thermal deformation); and thermal spraying (weak bonding strength between the coating and the substrate, porosity, insufficient density, and inability to meet the high-performance requirements of high-end equipment for high-temperature wear and corrosion resistance).

[0004] Meanwhile, during the conventional heating and melting process, the melt is prone to upward eddy currents in the edge region, which further exacerbates the problems of uneven coating composition and unstable performance, thus restricting the development and application of coating preparation technology for hot-end components of high-temperature alloys. Summary of the Invention

[0005] The purpose of this invention is to address the problems of insufficient brazing filler metal flow, high coating porosity, and edge melt eddy current effect in the preparation of wear-resistant coatings for high-temperature alloy hot-end components using existing melt infiltration sintering technology. This invention proposes a method and apparatus for magnetic field-assisted melt infiltration sintering of coatings for high-temperature alloy hot-end components.

[0006] The technical solution of this invention is as follows: a device for magnetic field-assisted melting and sintering of coatings on hot-end components of high-temperature alloys, comprising a water pump, a high-frequency power supply, a vacuum furnace, a diffusion vacuum pump, and a temperature control and protection device. The water pump is connected to the diffusion vacuum pump and the vacuum furnace via water pipes, providing cooling water to both. The diffusion vacuum pump is connected to the vacuum pump interface of the vacuum furnace via a pipe. The high-frequency power supply is connected to the vacuum pump via a high-voltage line. The temperature control and protection device is connected to both the high-frequency power supply and the vacuum furnace, controlling the operation of the high-frequency power supply and the vacuum furnace based on the vacuum furnace temperature information transmitted by thermocouples.

[0007] The vacuum furnace contains an induction coil and a support platform, and is equipped with a vacuum monitoring and control module and a temperature monitoring and control module. The induction coil is wound with 5-9 turns of oxygen-free copper tubing (Φ3-4mm, 1mm wall thickness), with each turn spaced 2-3mm apart. The coil is wound according to the outline of the workpiece, spaced 2-4mm from the workpiece's outer surface. Two water-cooling channels, passing through the furnace wall and entering the furnace, are connected to both ends of the induction coil. The water-cooling channel interfaces are equipped with detachable devices for replacing the coil with one compatible with the workpiece. The temperature control and protection device consists of a PID controller, a solid-state relay (SSR), and a thermocouple. The thermocouple transmits the detected temperature signal to the PID controller in real time, and outputs a pulse width modulation signal to the solid-state relay based on the deviation between the signal and the set value, thereby controlling the output current of the high-frequency power supply and achieving temperature control and protection. The support platform is made of stainless steel and is used to place the sample workpiece. The support platform is equipped with horizontal and vertical slide bars to allow for free adjustment of the platform, so as to adjust and fix the position of the sample workpiece and insert it into the predetermined position inside the induction coil. A vacuum pump interface is installed on the furnace wall above the support platform. The thermocouple wires connecting the induction coil are led out through the furnace wall. The top of the vacuum furnace is equipped with a vacuum furnace cover.

[0008] A method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melt infiltration sintering, comprising the following steps: (1) Grind, degrease and derust the surface of the workpiece to be coated to remove the surface oxide layer and impurities.

[0009] (2) Wrap a barrier around the surface of the workpiece to be coated, then spread the prepared wear-resistant coating powder evenly on the surface of the workpiece to be coated inside the barrier, and then put in a pressure block to fix each layer of powder.

[0010] (3) Place the pretreated workpiece into the support platform inside the vacuum furnace, adjust the platform so that the part of the workpiece to be coated is inserted into the induction coil and reaches the predetermined position, and then fix it to ensure that the distance between the coil and the outer contour surface of the workpiece is uniform; close the furnace cover, start the vacuum system, and evacuate to ≤3×10 -3 Pa; Set the temperature and power parameters according to the composition of the metal brazing filler metal, start the power supply to heat up, and when the temperature reaches the melting and infiltration sintering temperature, hold for 30~60 minutes.

[0011] (4) After the heat preservation is completed, reduce the induced current at a rate of 3~8A / min and stop heating; after the workpiece cools to room temperature, open the furnace cover and take out the workpiece, grind and polish the coating surface to remove excess residue on the surface, and obtain the wear-resistant coating of high temperature alloy hot end parts.

[0012] The enclosure is made of high-temperature ceramic adhesive and is molded into a groove shape according to the outer contour of the workpiece, with a groove depth of 6~10mm.

[0013] The shape of the bottom of the pressing block is designed according to the shape of the surface to be coated, and it is made of stainless steel using laser additive manufacturing method. Its weight is 20~80g.

[0014] The workpiece to be coated is located 4-8 mm below half the height of the induction coil; the power supply parameters are set as follows: frequency 18-22KHz, current 100-400A; sintering temperature 1000-1200℃.

[0015] The wear-resistant coating powder comprises a high-melting-point alloy mixed powder, wear-resistant particles, and brazing filler metal. The high-melting-point alloy mixed powder is composed of a mixture of high-melting-point alloy powder and ceramic particles, with a thickness of 200-500 μm. The high-melting-point alloy powder accounts for 60-80 wt.% of the high-melting-point alloy mixed powder, with a particle size of 45-150 μm. The ceramic particles account for 20-40 wt.% of the high-melting-point alloy mixed powder, with a particle size of 1-50 μm. The wear-resistant particles have an irregular shape, a particle size of 150-300 μm, and are embedded on the surface of the high-melting-point alloy mixed powder layer, with an exposed height of 30-60% of the particle size. The brazing filler metal has a particle size of 45-150 μm and a thickness of 200-300 μm.

[0016] The wear-resistant coating powder is laid in the following order from bottom to top: high melting point alloy mixed powder, wear-resistant particles, and brazing filler metal.

[0017] The beneficial effects of this invention are as follows: By using an induction heating device to melt the metal brazing filler metal while simultaneously altering the eddy currents, and by adjusting the position of the workpiece and the coil, the magnetic field at the workpiece gradually weakens from top to bottom, thereby generating a repulsive force pointing in the direction of magnetic field weakening. This repulsive force applies compressive stress to the brazing filler metal, promoting its infiltration into the gaps between the wear-resistant hard phase particles, effectively reducing internal porosity of the coating, increasing coating density, and thus enhancing the coating's bonding strength and wear resistance. This invention employs a multi-degree-of-freedom workpiece positioning mechanism to adapt to different types of workpieces, achieving precise alignment between the coating area and the heating coil, ensuring uniform magnetic field action, and further improving coating quality stability. The current and frequency parameters of the induction heating device used in this invention are flexibly adjustable, adaptable to various brazing filler metals, and have a wide range of applications, meeting the preparation requirements of wear-resistant coatings for various high-end equipment. Attached Figure Description

[0018] Figure 1 A schematic diagram of the principle of a magnetic field-assisted melting and sintering device for wear-resistant coatings on hot-end components of high-temperature alloys. Figure 2 This is a schematic diagram of the vacuum furnace structure; Figure 3 A cross-sectional view of a vacuum furnace (AA). Figure 4A schematic diagram illustrating the principle of a method for longitudinal magnetic field-assisted melting and sintering of wear-resistant coatings for hot-end components of high-temperature alloys. Figure 5 Comparison of wear-resistant coating results for hot-end components of high-temperature alloys with and without magnetic field-assisted melting and sintering; In the diagram: 1 is a water pump; 2 is a diffusion vacuum pump; 3 is a high-frequency power supply; 4 is a temperature control and protection device; 5 is a vacuum furnace; 301 is high-temperature glass; 302 is an induction coil; 303 is a thermocouple; 304 is a sample workpiece; 305 is a thin rod; 306 is a support platform; 307 is a free slider; 308 is a sliding rod; 309 is a coil water cooling channel; 310 is a vacuum pump interface; 311 is a vacuum furnace cover; 411 is a pressure block; 412 is brazing filler metal; 413 is wear-resistant particles; 414 is ceramic particles; 415 is high-melting-point alloy powder; 416 is a high-temperature alloy; 417 is a wear-resistant coating; 418 is a high-temperature ceramic adhesive enclosure. Detailed Implementation

[0019] The specific embodiments of the present invention are shown in the figure. like Figure 1 As shown in the figure, this embodiment discloses an apparatus for magnetic field-assisted melting and sintering of coatings on hot-end components of high-temperature alloys, comprising a water pump 1, a high-frequency power supply 3, a vacuum furnace 5, a diffusion vacuum pump 2, and a temperature control and protection device 4. The water pump 1 is connected to the diffusion vacuum pump 2 and the vacuum furnace 5 via water pipes, providing cooling water to both. The diffusion vacuum pump 2 is connected to the vacuum pump interface of the vacuum furnace 5 via a pipe. The high-frequency power supply 3 is connected to the vacuum diffusion pump 2 via a high-voltage line. The temperature control and protection device 4 is connected to the high-frequency power supply 3 and the vacuum furnace 5, controlling the operation of the high-frequency power supply and the vacuum furnace based on the vacuum furnace temperature information transmitted by thermocouples.

[0020] like Figure 2 and Figure 3As shown, the vacuum furnace 5 contains an induction coil 302 and a support platform 306, and is equipped with a vacuum monitoring and control module and a temperature monitoring and control module. The induction coil is wound with oxygen-free copper tubing of Φ3~4mm and 1mm wall thickness, with 5~9 turns and a 2~3mm interval between each turn. The induction coil is wound according to the outline of the workpiece and is spaced 2~4mm from the outer surface of the workpiece. Two coil water-cooling channels 309, which pass through the furnace wall and enter the furnace, are respectively connected to the two ends of the induction coil 302. The interfaces of the coil water-cooling channels 309 are equipped with detachable fittings. The support platform 306, made of stainless steel, is used to place the sample workpiece. The support platform 306 is equipped with a horizontal slide bar 308 and a vertical free slider 307 to realize the free adjustment of the platform, so as to adjust and fix the position of the sample workpiece and insert it into the predetermined position inside the induction coil. A vacuum pump interface 310 is installed on the furnace wall above the support platform 306. The thermocouple 303 connecting the induction coil is led out through the furnace wall, and a heat-insulating conduit is threaded on the wire. A vacuum furnace cover is provided on the top of the vacuum furnace.

[0021] Figure 4 The diagram illustrates the principle of a longitudinal magnetic field-assisted melting and infiltration sintering method for wear-resistant coatings on hot-end components of high-temperature alloys. The magnetic field lines on the upper part of the brazing filler metal 412 are denser than those on the lower part, resulting in a stronger magnetic field on the upper part. The brazing filler metal experiences a repulsive force pointing in the direction of magnetic field weakening. By adjusting the position of the workpiece and the induction coil, the magnetic field at the workpiece gradually weakens from top to bottom, generating a repulsive force in the direction of magnetic field weakening. This repulsive force applies compressive stress to the brazing filler metal, promoting its infiltration into the gaps between the wear-resistant hard phase particles.

[0022] Example 1 In this embodiment, a GH3030 high-temperature alloy low-pressure turbine blade is selected as the substrate. The area to be coated is the solid blade tip surface, which has a twisted, variable cross-section curved surface. A 6-turn coil with a 3mm outer diameter and 1mm wall thickness is selected and wound according to the outer contour of the blade tip, leaving a 4mm gap. The blade tip is polished with 400-800-1000 grit sandpaper, ultrasonically cleaned with anhydrous ethanol to remove oil, and then dried.

[0023] The workpiece was fixed on the support platform and its position was adjusted. A layer of high-temperature ceramic adhesive was wrapped around the outer surface of the blade tip to form a barrier, and a groove was formed according to the outer contour of the workpiece, with a groove depth of 7mm. Then, a mixed powder of NiCoCrAlYTa alloy particles (45~100μm) and TiC ceramic particles (10~50μm) was uniformly spread on the surface of the blade tip. After that, Al2O3 ceramic wear-resistant particles (130~300μm) were embedded into the NiCoCrAlYTa alloy mixed powder layer, with 30~60% of the particle size exposed, and assembled into a coating substrate. NiCrSi (45~150μm) was used as a solder and uniformly spread on the surface of the coating substrate to assemble a coating sample. The NiCoCrAlYTa alloy mixed powder layer was 400μm thick and the NiCrSi solder powder layer was 300μm thick. Then, a 60g weight block was placed in the sample and the weight was adjusted to 400g. Adjust the platform height so that the blade tip and coating are 5mm below the coil's half-height plane, maintaining a 4mm gap. Close the furnace lid, turn on the water pump and vacuum pump, and evacuate the furnace pressure to 3×10⁻⁶. -3 Pa. The frequency of the high-frequency power supply was set to 20 kHz, and the current was gradually increased from 0 to 300 A. During heating, the coating temperature was monitored using thermocouples. When the temperature reached 1200℃, the current was kept stable. After holding at this temperature for 30 min, the induced current was reduced to 0 at a rate of 5 A / min, and heating was stopped. After the workpiece cooled to room temperature, the furnace was opened, the workpiece was removed, and it was cut open using wire cutting. The cross-sectional morphology of the sample was then observed using a scanning electron microscope. The results are as follows: Figure 5 As shown, the results of sintering without magnetic field assistance are as follows: Figure 5 In comparison, the size and number of holes were significantly reduced.

[0024] Example 2 This embodiment uses IN718 high-temperature alloy gas turbine blades as the substrate. The surface to be coated is a thin-walled blade tip surface with a twisted variable cross-section and a wall thickness of 0.8~1.5mm. A 9-turn coil is selected, with a copper tube outer diameter of 3mm and a tube wall thickness of 1mm. The blade tip is polished with 400-800-1000 grit sandpaper, ultrasonically cleaned with anhydrous ethanol to remove oil, and then dried.

[0025] The blade tip workpiece is fixed on the support platform and its position is adjusted. A layer of high-temperature ceramic adhesive is applied to the outer perimeter of the blade tip surface to form a barrier, and a groove is formed according to the outer contour of the workpiece, with a depth of 9mm. Then, a mixed powder of NiCoCrAlY alloy (particle size 45~150μm) and TaC ceramic particles (particle size 10~50μm) is uniformly spread on the surface of the blade tip. Next, SiC ceramic wear-resistant particles are embedded into the NiCoCrAlY alloy powder layer according to the required arrangement, with 60~80% of the particle size exposed, to assemble a coating substrate. Then, NiCrBSi self-fluxing alloy powder (particle size 45~100μm) is uniformly spread on the surface of the coating substrate to assemble a coating sample. The NiCoCrAlYTa alloy powder layer is 300μm thick, and the NiCrBSi self-fluxing alloy powder layer is 300μm thick. A 40g weight block is placed in the sample, and the weight is adjusted to 360g. The platform height is adjusted so that the blade tip and coating are 6mm below the half-coil height plane, maintaining a 4mm gap. Close the furnace lid, turn on the water pump and vacuum pump, and evacuate the gas pressure inside the furnace to 3×10. -3 Pa. The frequency of the high-frequency power supply was set to 22 kHz, and the current was gradually increased from 0 to 200 A. During heating, the coating temperature was monitored using thermocouples. When the temperature reached 1100℃, the current was kept stable. After holding at this temperature for 30 minutes, the induced current was reduced to 0 at a rate of 5 A / min, and heating was stopped. After the workpiece cooled to room temperature, the furnace was opened, the workpiece was removed, and it was cut open using wire cutting. The cross-sectional morphology of the sample was then observed using a scanning electron microscope. The results are as follows: Figure 5 As shown, the results of sintering without magnetic field assistance are as follows: Figure 5 In comparison, the size and number of holes were significantly reduced.

Claims

1. An apparatus for magnetic field-assisted melting and sintering of coatings on hot-end components of high-temperature alloys, comprising a water pump, a high-frequency power supply, a vacuum furnace, a diffusion vacuum pump, and a temperature control and protection device; characterized in that, The vacuum furnace contains an induction coil and a support platform, and is equipped with a vacuum monitoring and control module and a temperature monitoring and control module. The induction coil is wound with 5-9 turns of oxygen-free copper tubing (Φ3-4mm, 1mm wall thickness), with each turn spaced 2-3mm apart. The coil is wound according to the outline of the workpiece, spaced 2-4mm from the workpiece's outer surface. Two water-cooling channels, passing through the furnace wall and entering the furnace, are connected to both ends of the induction coil. The water-cooling channel interfaces are equipped with detachable devices for replacing coils that match the workpiece. The temperature control and protection device consists of a PID controller, a solid-state relay (SSR), and a thermocouple. The detected temperature signal is transmitted to the PID controller in real time, and a pulse width modulation signal is output to the solid-state relay based on the deviation between the signal and the set value to control the output current of the high-frequency power supply, thereby achieving temperature control and protection. The support platform is made of stainless steel and is used to place the sample workpiece. The support platform is equipped with horizontal and vertical slide bars to achieve free adjustment of the platform, so as to adjust and fix the position of the sample workpiece and insert it into the predetermined position inside the induction coil. A vacuum pump interface is installed on the furnace wall above the support platform. The thermocouple wire connecting the induction coil passes through the furnace wall and leads out. The top of the vacuum furnace is equipped with a vacuum furnace cover.

2. A method for preparing a magnetic field-assisted melting and sintering coating for a hot-end component of a high-temperature alloy using the apparatus for magnetic field-assisted melting and sintering of a coating for a high-temperature alloy as described in claim 1, characterized in that, The method steps are as follows: (1) Grind, degrease and derust the surface of the workpiece to be coated to remove the surface oxide layer and impurities; (2) Wrap a barrier around the surface of the workpiece to be coated, then spread the prepared wear-resistant coating powder evenly on the surface of the workpiece to be coated inside the barrier, and then put in a pressure block to fix each layer of powder. (3) Place the pretreated workpiece into the support platform inside the vacuum furnace, adjust the platform so that the part of the workpiece to be coated is inserted into the induction coil and fixed after reaching the predetermined position, and ensure that the distance between the coil and the outer contour surface of the workpiece is uniform; close the furnace cover, start the vacuum system, and pump to ≤3×10-3Pa; set the temperature and power parameters according to the composition of the metal brazing filler metal, and hold for 30~60 minutes when the temperature reaches the melting and infiltration sintering temperature. (4) After the heat preservation is completed, reduce the induced current at a rate of 3~8A / min and stop heating; after the workpiece cools to room temperature, open the furnace cover and take out the workpiece, grind and polish the coating surface to remove excess residue on the surface, and obtain the wear-resistant coating of high temperature alloy hot end parts.

3. The method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melting and sintering according to claim 2, characterized in that, The enclosure is made of high-temperature ceramic adhesive and is molded into a groove shape according to the outer contour of the workpiece, with a groove depth of 6~10mm.

4. The method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melting and sintering according to claim 2, characterized in that, The shape of the bottom of the pressing block is designed according to the shape of the surface to be coated, and it is made of stainless steel using laser additive manufacturing method. Its weight is 20~80g.

5. The method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melting and sintering according to claim 2, characterized in that, The workpiece to be coated is located 4-8 mm below half the height of the induction coil; the power supply parameters are set as follows: frequency 18-22KHz, current 100-400A; sintering temperature 1000-1200℃.

6. The method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melting and sintering according to claim 2, characterized in that, The wear-resistant coating powder comprises a high-melting-point alloy mixed powder, wear-resistant particles, and brazing filler metal. The high-melting-point alloy mixed powder is composed of a mixture of high-melting-point alloy powder and ceramic particles, with a thickness of 200-500 μm. The high-melting-point alloy powder accounts for 60-80 wt.% of the high-melting-point alloy mixed powder, with a particle size of 45-150 μm. The ceramic particles account for 20-40 wt.% of the high-melting-point alloy mixed powder, with a particle size of 1-50 μm. The wear-resistant particles have an irregular shape, a particle size of 150-300 μm, and are embedded on the surface of the high-melting-point alloy mixed powder layer, with an exposed height of 30-60% of the particle size. The brazing filler metal has a particle size of 45-150 μm and a thickness of 200-300 μm.

7. The method for preparing a coating for a hot-end component of a high-temperature alloy using magnetic field-assisted melting and sintering according to claim 6, characterized in that, The wear-resistant coating powder is laid in the following order from bottom to top: high melting point alloy mixed powder, wear-resistant particles, and brazing filler metal.

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