A composite magnetic field assisted ultra-high speed laser cladding processing method

Abstract

The present invention provides a composite magnetic field assisted ultra-high speed laser cladding processing method, comprising: providing a metal workpiece to be clad; loading the clad metal powder into a powder feeder; mounting the metal workpiece on an ultra-high speed laser cladding processing device and fixing it; turning on a transverse magnetic field generating device to generate a transverse magnetic field perpendicular to the axial direction of the laser beam; turning on a longitudinal magnetic field generating device to generate a longitudinal magnetic field along the axial direction of the laser beam; turning on the ultra-high speed laser cladding processing device, and completing the cladding processing process under the coordination of the transverse magnetic field and the longitudinal magnetic field. The present invention utilizes the force effect and thermal effect of the magnetic field to provide a composite energy field in the ultra-high speed laser manufacturing process so that the surface of the material is subjected to thermal and mechanical synergy, and can control or even eliminate manufacturing defects such as cracks and pores in the cladding layer, thereby optimizing the coating surface quality and comprehensive performance of the ultra-high speed laser cladding layer.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high-speed laser cladding, and in particular to a processing method of ultra-high-speed laser cladding assisted by a composite magnetic field. Background Art

[0002] At this stage, laser cladding technology is mainly used to form a functional coating on the metal surface that is different from the base material. It can effectively improve and enhance the surface properties of the base material, and comprehensively improve the surface hardness, wear resistance and corrosion resistance of parts, and has broad application prospects.

[0003] Shaft components such as hydraulic supports and offshore platform columns in the coal machinery industry have been serving in harsh working conditions for a long time. The surface of the workpiece is easily damaged by corrosion under the influence of the corrosive environment, which leads to the scrapping and failure of the entire shaft component, greatly wasting materials and increasing production costs. In industrial production, in order to save costs and increase the working time of parts, surface modification is usually used to improve the service performance of parts. Existing surface treatment methods mainly include laser cladding, electroplating and thermal spraying. Among them, laser cladding technology can produce metallurgical bonding between the cladding material and the base material compared to thermal spraying technology, and has a greater advantage in coating bonding strength. Compared with electroplating, laser cladding technology does not produce waste liquid or other harmful substances, which can greatly reduce pollution to the environment.

[0004] As an emerging surface modification technology, ultra-high-speed laser cladding has an ultra-high cladding line speed, which makes the cooling rate and coating structure during the coating preparation process significantly different from those of traditional laser cladding technology. The cladding line speed of ultra-high-speed laser cladding technology can reach 15 to 200 m / min, which is much higher than the cladding line speed of 0.1 to 7 m / min of traditional laser cladding. Based on the ultra-high cladding line speed, the laser directly heats the powder above the surface of the part, so that the powder melts in space and then falls onto the surface of the part. The heat input of the coating can be as low as 2.2 J / mm, and the coating preparation efficiency can be as high as 1.2 m / min. 2 / min or more. Its processing efficiency is 2 to 3 times higher than that of conventional laser cladding technology, and the utilization rate of powder is greatly improved to more than 90%. Since the powder absorbs most of the energy of the laser, the substrate obtains less energy. While ensuring the formation of a shallow and thin molten pool, the dilution rate of the ultra-high-speed laser cladding coating is extremely small, only less than 1%. Therefore, ultra-thin and high-quality protective coatings can be prepared by ultra-high-speed laser cladding technology. By adjusting the process parameters such as cladding line speed and powder feeding speed, the thickness of the ultra-high-speed laser cladding coating can be basically controlled between 25 and 200 μm, and the coating surface has a good finish (Rz <10). In practical applications, only simple grinding and polishing are required to put it into use. At present, ultra-high-speed laser cladding is considered to be the best alternative technology for electroplating process and has received widespread attention. However, the ultra-thin cladding layer produced by ultra-high-speed cladding is prone to overlap marks and pores and cracks. Therefore, it is necessary to further improve the processing method of ultra-high-speed laser cladding. Summary of the invention

[0005] In view of the problem that the ultra-thin cladding layer produced by ultra-high-speed cladding is prone to overlap marks, pores and cracks, the purpose of the present invention is to provide a composite magnetic field assisted ultra-high-speed laser cladding processing method, which can effectively improve the performance and accuracy of the cladding layer prepared by ultra-high-speed laser cladding.

[0006] According to one aspect of the present invention, a composite magnetic field assisted ultra-high speed laser cladding processing method is provided, comprising:

[0007] Providing a metal workpiece to be clad;

[0008] Loading the cladding metal powder into a powder feeder;

[0009] The metal workpiece is mounted on an ultra-high-speed laser cladding processing device and fixed;

[0010] Turning on the transverse magnetic field generating device to generate a transverse magnetic field perpendicular to the axial direction of the laser beam;

[0011] Turning on the longitudinal magnetic field generating device to generate a longitudinal magnetic field along the axial direction of the laser beam;

[0012] The ultra-high-speed laser cladding processing equipment is turned on to complete the cladding processing process under the cooperation of the transverse magnetic field and the longitudinal magnetic field.

[0013] Furthermore, the metal workpiece is a rotating body.

[0014] Furthermore, the clad metal powder is loaded into a powder feeder, wherein the metal powder is any one of iron-based powder, nickel-based powder and cobalt-based powder; the particle size of the metal powder is 20-50 μm, and the sphericity is not less than 90%.

[0015] Furthermore, the metal workpiece is mounted on and fixed in an ultra-high-speed laser cladding processing device, wherein the ultra-high-speed laser cladding processing device comprises a four-axis CNC machine tool, the metal workpiece is fixed on the CNC machine tool, and the CNC machine tool can drive the metal workpiece to move in a preset direction and speed.

[0016] Furthermore, the transverse magnetic field generating device is turned on to generate a transverse magnetic field perpendicular to the axis of the laser beam, including: adjusting the current size to 100-500A, the output frequency to 30-100kHz, and the output magnetic field strength to 10-100mT.

[0017] Furthermore, the longitudinal magnetic field generating device is turned on to generate a longitudinal magnetic field along the axis of the laser beam, including: adjusting the current size to 10-30A, the output frequency to 1-10kHz, and the magnetic field strength to 10-40mT.

[0018] Further, the cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including:

[0019] Setting the rotation speed of the metal workpiece to 30-300 m / min;

[0020] The laser and the powder feeder are turned on, and the laser beam and the powder flow are moved along the axial direction of the metal workpiece. The laser beam melts the surface of the metal workpiece substrate and the metal powder used for filling, and cladding is performed on the surface of the metal workpiece.

[0021] Furthermore, the cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: using a coaxial powder feeding method, adjusting the focus of the laser beam to 1-10 mm above the surface of the metal workpiece, and adjusting the powder feeding nozzle of the powder feeder to 1-2 mm above the surface of the metal workpiece.

[0022] Furthermore, the cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: the powder feeding speed of the powder feeder is 20 to 160 g / min, and the conveying distance is 1.5 to 6 m.

[0023] Furthermore, the cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: using a gas supply nozzle to deliver inert gas to protect the molten pool during the cladding process.

[0024] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0025] The present invention cooperates with an electromagnetic assist system and an ultra-high-speed laser manufacturing system, utilizes the force effect and thermal effect of a magnetic field to provide a composite energy field in the ultra-high-speed laser manufacturing process to subject the material surface to a thermal-mechanical synergistic effect, utilizes a longitudinal magnetic field to regulate the organizational morphology and grain size, thereby eliminating defects such as pores and cracks in the cladding layer, and obtaining a uniform, dense, high-performance manufacturing surface; utilizes a transverse magnetic field to exert a Lorentz force on the powder flow and molten metal, controls the splashing of powder and liquid metal, and simultaneously preheats the metal workpiece substrate to further reduce the temperature gradient in the ultra-high-speed laser manufacturing process, and significantly improves the powder utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0027] Figure 1 A schematic diagram of a composite magnetic field assisted ultra-high speed laser cladding processing method according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of surface morphology comparison of cladding layers in embodiments of the present invention, (a) represents no magnetic field applied, (b) represents a longitudinal magnetic field applied;

[0029] Figure 3 Schematic diagram of microstructure comparison of cladding layers in embodiments of the present invention, (a) represents no magnetic field applied, (b) represents longitudinal magnetic field applied;

[0030] Figure 4 A schematic diagram showing a comparison of mechanical properties of an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of grain morphology of each layer of a five-layer sample formed by single-pass melting assisted by alternating magnetic field form and frequency according to an embodiment of the present invention, (a) represents the first layer, ordinary melting without external magnetic field; (b) represents the second layer, 200Hz longitudinal alternating magnetic field assisted melting; (c) represents the third layer, 10Hz longitudinal alternating magnetic field assisted melting; (d) represents the fourth layer, 40Hz longitudinal alternating magnetic field assisted melting; (e) represents the fifth layer, 40Hz transverse alternating magnetic field assisted melting.

[0032] In the figure: 1 is a laser beam, 2 is a powder flow, 3 is a molten pool, 4 is a cladding coating, 5 is a working surface of a metal workpiece, 6 is a transverse magnetic field generating device, and 7 is a longitudinal magnetic field generating device. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention. In the description of the embodiments of the present invention, it should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0034] The embodiment of the present invention provides a composite magnetic field assisted ultra-high speed laser cladding processing method, referring to Figure 1 , the method comprising:

[0035] S1. Provide a metal workpiece to be clad.

[0036] In some specific implementations, the metal workpiece is a rotating body, and the centers of all cross sections are on the same straight line. Since the rotating body has a relatively high linear speed, a thin cladding layer can be formed quickly and evenly.

[0037] S2. Load the cladding metal powder into the powder feeder.

[0038] In some specific embodiments, the cladding metal powder is loaded into a powder feeder, wherein the material composition, sphericity, particle size, loose density, etc. of the metal powder are determined. Preferably, the metal powder is any one of an iron-based powder, a nickel-based powder and a cobalt-based powder. Since the ultra-high-speed cladding technology has very high requirements on powder properties, inappropriate particle size will affect the cladding quality, and poor sphericity will easily cause pores and inclusions in the cladding layer. Preferably, the particle size of the metal powder is 20 to 50 μm, and the sphericity is not less than 90%.

[0039] S3. Install the metal workpiece on the ultra-high-speed laser cladding processing equipment and fix it with a chuck.

[0040] In some specific embodiments, the metal workpiece is mounted and fixed on an ultra-high-speed laser cladding processing device, wherein the ultra-high-speed laser cladding processing device includes a four-axis linkage CNC machine tool, and the metal workpiece is fixed on the CNC machine tool using a manual three-jaw chuck, and the CNC machine tool can drive the metal workpiece to move in a preset direction and speed.

[0041] S4. Turn on the transverse magnetic field generating device to generate a transverse magnetic field perpendicular to the axis of the laser beam.

[0042] In some specific embodiments, the transverse magnetic field generating device can use a coil, and turning on the transverse magnetic field generating device can generate a transverse magnetic field perpendicular to the axis of the laser beam, including: adjusting the current size to 100-500A, the output frequency to 30-100kHz, and the output magnetic field strength to 10-100mT.

[0043] S5. Turn on the longitudinal magnetic field generating device to generate a longitudinal magnetic field along the axis of the laser beam.

[0044] In some specific embodiments, the longitudinal magnetic field generating device can use a coil, and turning on the longitudinal magnetic field generating device to generate a longitudinal magnetic field along the axis of the laser beam includes: adjusting the current size to 10-30A, the output frequency to 1-10kHz, and the magnetic field strength to 10-40mT.

[0045] S6. Turn on the ultra-high-speed laser cladding processing equipment to complete the cladding processing process under the coordination of the transverse magnetic field and the longitudinal magnetic field.

[0046] Continue to refer to Figure 1 In some specific embodiments, the cladding process is completed under the coordination of the transverse magnetic field generated by the transverse magnetic field generating device 6 and the longitudinal magnetic field generated by the longitudinal magnetic field generating device 7, specifically including: setting the rotation linear speed of the metal workpiece to 30-300 m / min to provide a higher surface moving speed and form a uniform ultra-thin cladding layer; turning on the laser and the powder feeder, moving the laser beam 1 and the powder flow 2 along the axial direction of the metal workpiece, the laser beam 1 melts the surface of the metal workpiece substrate (working surface 5) and the metal powder used for filling, forming a molten pool 3 on the working surface 5 of the metal workpiece, cladding the surface of the metal workpiece, and forming a cladding coating 4. In order to improve the cladding effect, a coaxial powder feeding method is adopted, and the focus of the laser beam 1 is adjusted to 1-10 mm above the surface of the metal workpiece, and the powder feeding nozzle of the powder feeder is adjusted to 1-2 mm above the surface of the metal workpiece. The powder feeding speed determines the cladding efficiency and quality, and the conveying distance determines the focus position and also determines the cladding quality. Preferably, the powder feeding speed of the powder feeder is 20-160 g / min, and the conveying distance is 1.5-6 m. In addition, during the cladding process, a gas delivery nozzle is used to deliver argon to protect the molten pool. Of course, in some other embodiments, other types of inert gases such as helium, neon, etc. can also be used to protect the molten pool, which is not specifically limited in the embodiment of the present invention.

[0047] When performing ultra-high-speed cladding processing, the embodiment of the present invention applies longitudinal (along the axial direction of the laser beam) and transverse (perpendicular to the axial direction of the laser beam) magnetic fields to cooperate with each other to realize the ultra-high-speed cladding process. The ultra-high-speed laser cladding process is assisted by two magnetic fields of different directions and frequencies obtained by an electromagnetic generating device, which can control or even eliminate manufacturing defects such as cracks and pores in the cladding layer, thereby optimizing the coating surface quality and comprehensive performance of the ultra-high-speed laser cladding layer.

[0048] The processing method of composite magnetic field assisted ultra-high speed laser cladding in the embodiment of the present invention is described in more detail with a specific embodiment.

[0049] S1. Grind, polish, clean with alcohol, and blow dry the metal workpiece to be clad for standby use. The metal workpiece is a rotating body, and the centers of all cross sections are on the same straight line;

[0050] S2. Screening and drying the clad metal powder and then loading it into a powder feeder. The metal powder is one of iron-based powder, nickel-based powder and cobalt-based powder. The particle size of the metal powder is in the range of 20 to 50 μm and the sphericity is ≥ 90%;

[0051] S3. Install the metal workpiece on the ultra-high-speed laser cladding processing equipment and clamp it with a chuck and an ejector pin; the ultra-high-speed laser cladding processing equipment includes a four-axis linkage CNC machine tool, the maximum working stroke of the X-axis is 2000mm, the moving speed is 0-10000mm / min, and the repeat positioning accuracy is 0.025mm; the spindle servo speed of the C-axis is 0-300r / min, the chuck is a manual three-jaw chuck, and the chuck diameter is Ф600mm;

[0052] S4. Turn on the power of the transverse magnetic field coil, adjust the current to 100-500A, the output frequency to 30-100kHz, and the output magnetic field strength to 10-100mT;

[0053] S5. Turn on the power of the longitudinal magnetic field coil, adjust the current to 10-30A, the output frequency to 1-10kHz, and the magnetic field strength to 10-40mT;

[0054] S6. Turn on the ultra-high-speed laser cladding processing equipment, control the movement of the metal workpiece through the CNC machine tool, and complete the cladding processing process under the coordination of the transverse magnetic field and the longitudinal magnetic field; during the processing, use the gas nozzle to deliver argon to protect the molten pool; use a coaxial powder feeding method, the powder feeding speed of the coaxial powder feeder is 20-160g / min, the feeding distance is 1.5-6m, adjust the laser beam focus to 1-10mm above the surface of the metal workpiece, and adjust the powder feeding nozzle to 1-2mm above the surface of the metal workpiece; set the metal workpiece rotation linear speed to 30-300m / min, turn on the laser and powder feeder, move the laser beam and powder flow along the axial direction of the metal workpiece, the laser beam melts the surface of the metal workpiece substrate and the filling powder, and clads the surface of the metal workpiece.

[0055] The embodiment of the present invention uses composite alternating magnetic fields in different directions to assist in the preparation of an ultra-high-speed laser cladding layer, cooperates an electromagnetic assistance system with an ultra-high-speed laser manufacturing system, utilizes the force effect and thermal effect of the magnetic field to provide a composite energy field in the ultra-high-speed laser manufacturing process so that the surface of the material is subjected to thermal synergy, utilizes the longitudinal magnetic field to regulate the organizational morphology and grain size, thereby eliminating defects such as pores and cracks in the cladding layer, and obtaining a uniform and dense high-performance manufacturing surface; utilizes the transverse magnetic field to apply Lorentz force to the powder flow and molten metal, controls the splashing of powder and liquid metal, and simultaneously preheats the metal workpiece substrate to further reduce the temperature gradient in the ultra-high-speed laser manufacturing process, and significantly improves the powder utilization rate.

[0056] The high-frequency magnetic field generated by the transverse steady-state electromagnetic generator can generate electromagnetic force perpendicular to the plane. Therefore, applying a steady-state magnetic field perpendicular to the paper surface in the outward or inward direction can generate electromagnetic force pointing to the direction of the cladding layer or away from the cladding layer, thereby "pulling" the liquid molten metal to fly backward, so that the laser directly irradiates the front area of ​​the workpiece to produce a preheating effect. At the same time, it helps to transport the molten metal backward and more directly flush the solid-liquid crystallization surface of the previously formed cladding layer, increasing the supercooling of the front component of the dendrite.

[0057] The longitudinal magnetic field applied by the magnetic coil during the ultra-high-speed laser cladding process, such as Figure 2 The experimental results of the surface morphology comparison of the cladding layer shown in the figure show that the longitudinal steady-state magnetic field helps to improve the overlap accuracy and the overall surface accuracy of the cladding layer. Figure 3 The microstructure comparison shown in the figure shows that the longitudinal steady-state magnetic field assisted cladding has a certain grain refinement effect, and has better grain uniformity and consistency than ordinary cladding, and can also reduce metallurgical defects in the weld. Figure 4 The mechanical properties comparison shown in the figure indicates that the longitudinal steady-state magnetic field assisted melting helps to improve the mechanical properties of the formed specimens and reduce anisotropy.

[0058] like Figure 5 The microstructure of the longitudinal and transverse alternating magnetic field assisted deposition forming samples shown in the figure shows that a lower frequency alternating magnetic field is conducive to grain refinement, especially the transverse alternating magnetic field directly scours the crystal surface, which has a better grain refinement effect, while an excessively large magnetic field frequency makes the grains coarsened. The external magnetic field can effectively control the ultra-high-speed laser cladding process, and reasonable matching of process parameters and magnetic field parameters can be used as an effective means to control the performance of ultra-high-speed laser cladding.

[0059] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A composite magnetic field assisted ultra-high speed laser cladding processing method, characterized in that: include: Providing a metal workpiece to be clad; Loading the cladding metal powder into a powder feeder; The metal workpiece is mounted on an ultra-high-speed laser cladding processing device and fixed; Turn on the transverse magnetic field generating device to generate a transverse magnetic field perpendicular to the axis of the laser beam. The current of the transverse magnetic field is 100-500A and the output frequency is 30-100kHz. Turn on the longitudinal magnetic field generating device to generate a longitudinal magnetic field along the axis of the laser beam, the current of the longitudinal magnetic field is 10-30A, and the output frequency is 1-10kHz; The powder flow is formed by coaxial powder feeding outside the light, and the ultra-high-speed laser cladding processing equipment is turned on to complete the cladding processing process under the cooperation of the transverse magnetic field and the longitudinal magnetic field.

2. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The metal workpiece is a rotating body.

3. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The clad metal powder is loaded into a powder feeder, wherein the metal powder is any one of iron-based powder, nickel-based powder and cobalt-based powder; the particle size of the metal powder is 20-50 μm, and the sphericity is not less than 90%.

4. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The metal workpiece is mounted on and fixed in an ultra-high-speed laser cladding processing device, wherein the ultra-high-speed laser cladding processing device comprises a four-axis CNC machine tool, the metal workpiece is fixed on the CNC machine tool, and the CNC machine tool can drive the metal workpiece to move in a preset direction and speed.

5. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The transverse magnetic field generating device is turned on to generate a transverse magnetic field perpendicular to the axis of the laser beam, including: the output magnetic field intensity is 10-100mT.

6. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The longitudinal magnetic field generating device is turned on to generate a longitudinal magnetic field along the axis of the laser beam, including: a magnetic field intensity of 10-40 mT.

7. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, comprising: Setting the rotation speed of the metal workpiece to 30-300 m / min; The laser and the powder feeder are turned on, and the laser beam and the powder flow are moved along the axial direction of the metal workpiece. The laser beam melts the surface of the metal workpiece substrate and the metal powder used for filling, and cladding is performed on the surface of the metal workpiece.

8. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: adjusting the focus of the laser beam to be 1-10 mm above the surface of the metal workpiece, and adjusting the powder feeding nozzle of the powder feeder to be 1-2 mm above the surface of the metal workpiece.

9. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: the powder feeding speed of the powder feeder is 20 to 160 g / min, and the conveying distance is 1.5 to 6 m.

10. The composite magnetic field assisted ultra-high speed laser cladding processing method according to claim 1, characterized in that: The cladding process is completed under the cooperation of the transverse magnetic field and the longitudinal magnetic field, including: using a gas supply nozzle to transport inert gas to protect the molten pool during the cladding process.

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