An apparatus and process for in-situ pulse current assisted laser cladding of fiber-reinforced composite coatings

Abstract

An apparatus and process for in-situ pulsed current-assisted laser cladding of a fiber-reinforced composite coating comprises a substrate, a plurality of refractory metal wires, a refractory metal wire fixture, a laser cladding structure, and a pulsed current structure. The substrate is a metal part requiring surface reinforcement, and has thick insulating members disposed at both ends of the substrate. The plurality of refractory metal wires, used for coating the fiber-reinforced substrate surface, are laid transversely and parallel to the substrate to be reinforced, with both ends extending from the substrate's upper surface. The refractory metal wire fixture is used to secure the plurality of refractory metal wires. The laser cladding structure is used to laser-clad the substrate and the plurality of refractory metal wires. The pulsed current structure is used to synchronously deliver pulsed current to the substrate and the plurality of refractory metal wires. The present invention utilizes the refractory metal wires as pulsed current conductors, directing the majority of the current into the molten pool during the laser cladding process. This improves the utilization rate of the pulsed current while enabling the production of a low-defect, high-performance fiber-reinforced composite coating.

Description

Technical Field

[0001] The present invention relates to the technical field of laser surface engineering, and in particular to a device and a process method for in-situ pulse current assisted laser cladding of a fiber-reinforced composite coating. Background Art

[0002] Laser cladding technology is used to create coatings that meet the requirements of components under varying operating conditions, significantly extending their service life. The localized heating and rapid solidification characteristics of laser cladding result in high thermal and residual stress levels in the coating, making it susceptible to cracking. This phenomenon is particularly pronounced during the laser cladding of high-hardness coatings. To improve the quality of the laser cladding process, technologies such as induction heating, ultrasonic vibration, and electromagnetic induction are being combined with laser cladding. Through thermal, force, and electromagnetic fields, the physical and chemical processes of heat and mass transfer within the molten pool are manipulated to reduce thermal stress, lower coating cracking susceptibility, eliminate defects such as porosity and shrinkage, and refine grains, thereby improving the overall performance of laser cladding coatings. Among these, electric pulse metal treatment involves applying pulsed current directly to metal materials or to metal materials during solidification. Applying pulsed current to solidified or unsolidified metal materials can promote crack healing, atomic diffusion, and recrystallization, refine the material's microstructure, and reduce residual stresses generated during the laser cladding process.

[0003] Generally speaking, electric pulse technology processing requires a high pulse current density (the size of the pulse current passing through a unit area) to achieve microstructure control and crack self-healing effects. For example, the Chinese invention patent with the announcement number CN 103602977 B discloses a device for realizing a method for refining the solidification structure of laser cladding metal coatings with pulse current. The device applies an electrode directly to the workpiece to be clad for pulse-assisted laser cladding. Since the cross-sectional area of ​​the workpiece is larger than the coating area, most of the current does not pass through the coating and returns to the negative electrode. The requirements for the pulse current generating device are too high, and the size of the workpiece to be clad is also limited. At the same time, since the pulse current is applied to the entire cladding workpiece, the pulse current density passing through the cladding layer is also low, resulting in poor effects of the pulse current in terms of grain refinement, crack healing, and stress release, and the current utilization rate is very low. Summary of the Invention

[0004] Technical problem to be solved: In response to the defects caused by low pulse current density and low current utilization in the existing technology, the present invention provides an apparatus and process method for in-situ pulse current-assisted laser cladding of fiber-reinforced composite coatings, which can improve the utilization rate of pulse current and at the same time prepare low-defect and high-performance fiber-reinforced composite coatings.

[0005] Technical solution: An in-situ pulse current assisted laser cladding fiber reinforced composite coating device, including a substrate, a plurality of refractory metal wires, a refractory metal wire fixture, a laser cladding structure and a pulse current structure.

[0006] The substrate is a metal part that needs to be surface-strengthened, and insulating parts with a certain thickness (0.5-1 mm) are provided at both ends of the substrate.

[0007] A plurality of refractory metal wires are used for coating the surface of the fiber-reinforced substrate, are laid transversely and parallelly on the substrate to be reinforced, and have both ends extending from the upper surface of the substrate;

[0008] The refractory metal wire clamp is used to fix a plurality of refractory metal wires, connect the two ends of the plurality of refractory metal wires respectively and tighten them, and the refractory metal wire clamp includes a clamp body, a limiting structure, a pressing structure and a fixing structure, wherein the clamp body is an "I"-shaped frame suspended at the bottom of the middle connecting beam, the limiting structure is provided at one end of the clamp body close to the base, the pressing structure is provided at the middle connecting beam, and the fixing structure is provided at the other end of the clamp body, the pressing structure is height-adjustable, and the bottom end is lower than the limiting structure, and a plurality of refractory metal wires pass through the limiting structure, the bottom of the pressing structure and the top of the fixing structure in sequence, are limited by the limiting structure, fixed by the fixing structure, and pressed by the pressing structure;

[0009] The laser cladding structure is used to perform laser cladding on a substrate and a plurality of refractory metal wires, and includes a fixing seat arranged above the substrate, a laser head connected to the fixing seat, and a coaxial powder feeding head arranged at the bottom of the laser head;

[0010] The pulse current structure is used to synchronously transmit pulse current to the substrate and several refractory metal wires, including a pulse power supply and a pulse current connecting device, wherein the pulse current connecting device includes a fixed arm, two lateral moving devices, positive and negative electrodes and two electrode blocks, wherein the fixed arm is horizontally sleeved on the outside of the laser head, the two lateral moving devices are respectively arranged at both ends of the fixed arm and can move horizontally, the positive and negative electrodes are respectively movably connected to the bottom ends of the two lateral moving devices, the two electrode blocks are respectively movably connected to the bottom ends of the positive and negative electrodes, and the bottom surfaces of the electrode blocks are arranged on several refractory metal wires, and the two positive / negative poles of the pulse power supply are respectively connected to the positive and negative electrodes through wires; the non-electrically connected parts of the refractory metal wire clamp and the pulse current structure are insulated.

[0011] Preferably, the limiting structure is a refractory metal wire limiting plate having a plurality of circular hole-shaped limiting slots transversely defined in the middle of the refractory metal wire limiting plate, the diameter of the limiting slots being larger than the diameter of the refractory metal wire. The refractory metal wire limiting plate provides positioning to prevent uneven coating structure caused by non-parallel arrangement of the molybdenum wires during cladding.

[0012] Preferably, the clamp body has a plurality of sets of threaded holes symmetrically and vertically arranged on the two side surfaces of the clamp body near the substrate. The two ends of the refractory metal wire stopper plate are movably connected to any of the sets of threaded holes on the two side surfaces of the clamp body near the substrate via bolts. In this way, the refractory metal wire stopper plate can be moved up and down to meet the needs of laser cladding on substrates at different heights.

[0013] Preferably, the clamping structure includes a tightening bolt, a through hole is provided in the center of the middle connecting beam of the clamp body, a thread corresponding to the tightening bolt is provided on the inside of the through hole, the height of the tightening bolt is higher than the thickness of the through hole, when tightening is not required, the tightening bolt is screwed out upward, and the bottom does not contact the several refractory metal wires; when tightening is required, the tightening bolt is tightened downward, and the bottom extends out of the through hole to tighten the several refractory metal wires; a handle is provided on the top of the tightening bolt for easy rotation.

[0014] Preferably, the clamping structure includes a tightening bolt and a tensioning device connected to the bottom of the tightening bolt, the tensioning device includes two side slide grooves and a clamping block that can slide in the slide grooves, a through hole is provided in the center of the middle connecting beam of the clamp body, and a thread corresponding to the tightening bolt is provided on the inner side of the through hole, the slide grooves on both sides are provided on the side walls of the clamp body and the bottom of the middle connecting beam, the top of the clamping block is movably connected to the bottom of the tightening bolt, when tightening is not needed, the tightening bolt is screwed out upward, and the clamping block moves upward as the tightening bolt rotates, when tightening is needed, the tightening bolt is tightened downward, and the clamping block moves downward as the tightening bolt rotates, thereby achieving the tightening of several refractory metal wires; a handle is provided on the top of the tightening bolt for easy rotation.

[0015] Furthermore, a plurality of evenly distributed grooves are provided below the pressing block for fixing the refractory metal wire, and the refractory metal wire is pressed into the pressing cavity, thereby tightening the refractory metal wire.

[0016] Preferably, the fixing structure includes a base, a fixing bolt and a refractory metal wire connector. The refractory metal wire connector is rotatably connected to the base via the fixing bolt, and the connecting end is connected to the ends of several refractory metal wires. When the refractory metal wire connector is rotated, the several refractory metal wires are tightened.

[0017] Preferably, the lateral moving device includes a spring, and the positive and negative electrodes include an internal spring. The spring is arranged inside the lateral moving device, one end is connected to the top of the lateral moving device, and the other end is connected to the positive and negative electrodes. The internal spring is arranged inside the positive and negative electrodes, one end is connected to the top of the positive and negative electrodes, and the other end is connected to the top of the electrode block. The top of the electrode block extends into the positive and negative electrodes, and the bottom is embedded in the outside of the positive and negative electrodes. When the electrode block is in a suspended state, the internal spring is in a stretched state. When the electrode block contacts the upper surface of the refractory metal wire, the internal spring is in a compressed state. When the bottom of the electrode block is under pressure, the internal spring is further tightened; the fixed arm includes two semicircular clamps, bolts and nuts corresponding to the bolts. Bolt holes corresponding to the bolts are provided on both sides of the semicircular clamps. The two semicircular clamps are movably connected to the outside of the laser head through bolts and nuts.

[0018] Furthermore, the substrate needs to be polished and cleaned before cladding to remove the surface oxide layer.

[0019] The process method of the above-mentioned in-situ pulse current assisted laser cladding fiber reinforced composite coating device comprises the following steps:

[0020] Step 1: Use a refractory metal wire clamp to fix the two ends of several refractory metal wires. First, fix one end of several refractory metal wires to the fixed structure on one side, then straighten them and pass them through the limiting structure on one side, lay them parallel to the substrate to be reinforced, and extend their two ends from the upper surface of the substrate. Due to the presence of the insulating member on the upper surface of the substrate, a gap is left between the several refractory metal wires and the upper surface of the substrate to ensure that the refractory metal wires do not contact the substrate, thereby increasing the pulse current density. Then, pass them through the limiting structure on the other side and fix the other ends of the several refractory metal wires to the fixed structure on the other side.

[0021] Step 2: After fixing several refractory metal wires, use the compression structures on both sides to compress them;

[0022] Step 3: Adjust the positions of the laser cladding structure, the pulse current structure, and the substrate to be reinforced so that the bottom surface of the electrode block of the pulse current structure contacts the upper surfaces of the plurality of refractory metal wires, and the molten pool and the coaxial powder feeding head of the laser cladding structure are located on the upper surfaces of the plurality of refractory metal wires;

[0023] Step 4: Set the laser cladding process parameters and pulse current process parameters, and start the pulse power supply to preheat the refractory metal wires and the substrate after power is turned on;

[0024] Step 5: Start the power supply and perform pulse current assisted laser cladding operation on the sample to obtain the product.

[0025] Preferably, the refractory metal wire is a molybdenum wire with a diameter of 0.2-0.6 mm, and the powder of the coaxial powder feeding head is a high entropy alloy CoCrFeMnNi with a particle size of 75-105 μm.

[0026] Preferably, the laser cladding process parameters in step 4 are: spot diameter of 2 mm; laser power of 1400-1600 W; scanning speed of 3 mm / s; powder feeding rate of 20 g / min; argon gas is used for gas protection of the molten pool, and the carrier gas volume is 5 L / min; the process parameters of the pulse current are: the pulse current is a unidirectional square wave, the peak current is 300 A, the pulse frequency is 500 Hz, the pulse width is 1000 μs, and the duty cycle is 50%.

[0027] The process method of the present invention utilizes refractory metal wire as a conductor of pulsed current, and introduces most of the current into the molten pool during the laser cladding process, thereby improving the current utilization rate and the refractory metal wire can also play a fiber reinforcement effect. The principle of the present invention is that the molding quality and performance improvement of the composite coating in the present invention are achieved by the introduction of refractory metal wire reinforcement and the electrothermal effect of pulsed current. Since the refractory metal wire has a high melting point and laser cladding has the characteristics of rapid cooling, the refractory metal wire remains in an unmelted state during the laser cladding process, and thus exists as a filamentous structure in the solidified structure, achieving the fiber reinforcement effect. During laser cladding, a pulsed current is applied through the refractory metal wire, and the current is also conducted into the molten pool. Therefore, during the solidification process, the pulsed current will play a role in disturbing the molten pool and achieving grain refinement. For microcracks generated during solidification, due to the existence of the interface resistance of the microcracks, the pulsed current bypasses the crack tip, thereby generating a large local thermal effect. The local melting and thermal stress at the crack tip will inhibit the growth of the crack and even heal the microcracks. Compared to manipulating the material's microstructure, crack healing relies primarily on the heat generated by pulsed current at the crack site, requiring a relatively high pulse current density. This method directs current into the molten pool via a molybdenum wire. Compared to applying current directly to the substrate, the pulsed current has a higher current utilization rate and can effectively heal cracks in the coating.

[0028] Beneficial effects:

[0029] 1. The refractory metal wires in this invention provide fiber reinforcement for the coating. After laser cladding, the coating contains unmelted refractory metal wires that extend throughout the coating, improving its impact and bending resistance. In high-temperature environments, the metal fibers also provide additional support, reducing internal stress caused by temperature fluctuations.

[0030] 2. The refractory metal wire through which pulse current is passed in the present invention utilizes the electrothermal effect of current to suppress and heal microcracks generated in the coating due to thermal stress, thereby improving the molding quality of the coating and reducing the scrap rate.

[0031] 3. The molten pool disturbance effect of the pulse current in the present invention achieves grain refinement of the coating.

[0032] 4. When current is applied to the refractory metal wire, it heats up, causing the surface of the wire to melt more rapidly during laser cladding, making it easier to form a metallurgical bond with the coating and less likely to separate. Furthermore, the refractory metal elements dissolve into the coating, improving its wear resistance.

[0033] 5. The present invention offers high processing flexibility, adapting to diverse operating conditions. The pulse-assisted laser cladding process allows for flexible control of coating thickness, shape, and distribution of metal filaments within the coating. The pulse current connection mechanism moves synchronously with the laser head, enabling flexible adjustment of position in the X / Y axes and a limited range in the Z axis. This makes it suitable for cladding coating applications on three-dimensional surfaces.

[0034] 6. In the design of the present invention, a pulse current is applied to a molybdenum wire with an extremely small diameter through a pulse current connection device. Compared with directly applying the pulse current to both ends of the substrate, this method significantly increases the pulse current density in the molten pool during the cladding process, thereby greatly improving the utilization efficiency of the pulse current. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The assembly diagram of the target device structure of the present invention, (a) front view; (b) top view;

[0036] Figure 2 Schematic diagram of the refractory metal wire clamp used in the present invention, (a) AA sectional view; (b) left view; (c) top view; (d) three-dimensional view Figure 1 ; (e) is a three-dimensional Figure 2 ; (f) is a cross-sectional view of a portion of (c) along the AA direction;

[0037] Figure 3 Schematic diagram of the pulse current connection device used in the present invention, (a) BB cross-sectional view; (b) left side view; (c) top view.

[0038] In the figure, the accompanying drawings are marked as follows:

[0039] 1- Refractory metal wire fixture, 2- Laser head, 3- Coaxial powder feeding head, 4- Refractory metal wire, 5- Substrate, 6- Pulse current connecting device, 7- Insulator, 8- Handle, 9- Refractory metal wire limiting plate, 10- Clamp body, 11- Tensioning device, 12- Refractory metal wire connector, 13- Lateral moving device, 14- Spring, 15- Fixed arm, 16- Positive and negative electrodes, 17- Internal spring, 18- Electrode block, 19- Bolt, 20- Nut. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] In the embodiment of this specification, the refractory metal wire 4 is a molybdenum wire with a diameter of 0.2-0.6 mm (0.6 mm in this embodiment), and the number of molybdenum wires is 50. The powder of the coaxial powder feeder 3 is a high entropy alloy CoCrFeMnNi with a particle size of 75-105 μm.

[0042] During laser cladding, an SMD-500 pulse power supply is used to provide pulse current.

[0043] Example 1

[0044] A device for in-situ pulse current assisted laser cladding of fiber reinforced composite coatings, such as Figure 1 As shown, the laser cladding system comprises a substrate 5, several refractory metal wires 4, a refractory metal wire fixture 1, a laser cladding structure, and a pulse current structure. The substrate 5 is a metal part requiring surface hardening. Insulators 7 with a thickness of 0.5-1 mm are provided at both ends of the substrate 5 to prevent contact between the molybdenum wires and the substrate 5 during the laser cladding process. In this embodiment, the insulating members 7 are 0.5 mm thick rubber sheets.

[0045] The refractory metal wire 4 is used for coating the surface of the fiber-reinforced matrix 5 , is laid transversely and parallelly on the matrix 5 to be reinforced, and has both ends extending from the upper surface of the matrix 5 .

[0046] The refractory metal wire clamp 1 is used to fix a plurality of refractory metal wires 4 , and connects two ends of the plurality of refractory metal wires 4 respectively and tightens them.

[0047] See also Figure 2 The refractory metal wire clamp 1 includes a clamping body 10, a limiting structure, a pressing structure and a fixing structure, wherein the clamping body 10 is an "I"-shaped frame suspended at the bottom of the middle connecting beam, the limiting structure is arranged at one end of the clamping body 10 close to the base 5, the pressing structure is arranged at the middle connecting beam, and the fixing structure is arranged at the other end of the clamping body 10. The pressing structure is height-adjustable, and the bottom end is lower than the limiting structure. Several refractory metal wires 4 pass through the limiting structure, the bottom of the pressing structure and the top of the fixed structure in turn, and are limited by the limiting structure, fixed by the fixed structure, and pressed by the pressing structure.

[0048] Specifically, the limiting structure is a refractory metal wire limiting plate 9, which has 50 circular hole-shaped limiting grooves with a hole diameter of 0.6 mm in the middle, and the interval between two limiting grooves is 1 mm (the distance between the centers of the two limiting grooves).

[0049] The clamp body 10 has a plurality of symmetrical and vertically arranged sets of threaded holes on its two side surfaces near the end of the base 5. The two side ends of the refractory metal wire limiting plate 9 are movably connected to any set of threaded holes on the two side surfaces of the clamp body 10 near the end of the base 5 by bolts. In this way, the position of the refractory metal wire limiting plate 9 can be moved up and down to meet the needs of laser cladding on substrates of different heights.

[0050] The clamping structure includes a tightening bolt and a tensioning device 11 connected to the bottom of the tightening bolt. The tensioning device 11 includes two side slide grooves and a clamping block that can slide in the slide groove. A through hole is provided in the center of the middle connecting beam of the clamping body 10, and a thread corresponding to the tightening bolt is provided on the inner side of the through hole. The slide grooves on both sides are provided on the side walls of the clamping body 10 and the bottom of the middle connecting beam. The top of the clamping block is movably connected to the bottom of the tightening bolt (when the tightening bolt is rotated, the clamping block does not rotate with it, but moves up with the tightening bolt). When tightening is not needed, the tightening bolt is unscrewed upward, and the clamping block moves upward during the rotation of the tightening bolt. When tightening is needed, the tightening bolt is tightened downward, and the clamping block moves downward during the rotation of the tightening bolt, thereby achieving the tightening of several refractory metal wires 4; a handle 8 is provided on the top of the tightening bolt for easy rotation.

[0051] The fixing structure includes a base, fixing bolts and a refractory metal wire connector 12. The refractory metal wire connector 12 is rotatably connected to the base through the fixing bolts, and the connecting end is connected to the ends of several refractory metal wires 4. When the refractory metal wire connector 12 is rotated, the several refractory metal wires 4 are tightened.

[0052] See also Figure 1 The laser cladding structure is used to laser clad a substrate 5 and a plurality of refractory metal wires 4, and includes a fixing seat arranged above the substrate 5, a laser head 2 connected to the fixing seat, and a coaxial powder feeding head 3 arranged at the bottom of the laser head 2.

[0053] The pulse current structure is used to synchronously transmit pulse current to the substrate 5 and the plurality of refractory metal wires 4, including a pulse power supply and a pulse current connecting device 6, wherein, Figure 3 The pulse current connection device 6 includes a fixed arm 15, two lateral moving devices 13, positive and negative electrodes 16 and two electrode blocks 18, wherein the fixed arm 15 is horizontally sleeved on the outside of the laser head 2, and the two lateral moving devices 13 are respectively provided at both ends of the fixed arm 15 and can move horizontally (slide grooves for moving the lateral moving devices are provided on both sides of the fixed arm), the positive and negative electrodes 16 are respectively movably connected to the bottom ends of the two lateral moving devices 13, and the two electrode blocks 18 are respectively movably connected to the bottom ends of the positive and negative electrodes 16, and the bottom surfaces of the electrode blocks 18 are provided on several refractory metal wires 4, and the two positive / negative poles of the pulse power supply are respectively connected to the positive and negative electrodes 16 through wires; the refractory metal wire clamp 1 and the non-electrically connected parts of the pulse current structure are insulated.

[0054] Furthermore, the lateral moving device 13 includes a spring 14, and the positive and negative electrodes 16 include an internal spring 17. The spring 14 is arranged inside the lateral moving device 13, one end of which is connected to the top of the lateral moving device 13, and the other end is connected to the positive and negative electrodes 16. The internal spring 17 is arranged inside the positive and negative electrodes 16, one end of which is connected to the top of the positive and negative electrodes 16, and the other end of which is connected to the top of the electrode block 18. The top of the electrode block 18 extends into the positive and negative electrodes 16, and the bottom is embedded in the outside of the positive and negative electrodes 16. When the electrode block 18 is in a suspended state, the deadweight of the electrode block 18 pulls the internal spring 17 into a stretched state. When the electrode block 18 contacts the upper surface of the refractory metal wire 4, the internal spring 17 is in a compressed state. When the bottom of the electrode block 18 is under pressure, the internal spring 17 is further tightened; the fixed arm 15 includes two semicircular clamps, bolts 19 and nuts 20 corresponding to the bolts. Bolt holes corresponding to the bolts 19 are provided on both sides of the semicircular clamps. The two semicircular clamps are movably connected to the outside of the laser head 2 through the bolts 19 and the nuts.

[0055] When the internal spring 17 is in a compressed state, it drives the positive and negative electrodes 16 to further compress the spring 14 to ensure that the laser head can move freely to perform a complex path cladding process.

[0056] As the laser head moves up and down, the positive and negative electrodes compress and stretch the springs, enabling coordinated movement with the laser head on the Z axis. The springs 17 inside the positive and negative electrodes are compressed, exerting a certain amount of pressure on the electrode block 18, ensuring that the bottom surface of the electrode block (10mm*10mm) is always in contact with the molybdenum wire during the laser cladding process.

[0057] The process method of the above-mentioned in-situ pulse current assisted laser cladding fiber reinforced composite coating device comprises the following steps:

[0058] Step 1: Before cladding, the surface of the substrate 5 is polished and cleaned to remove the surface oxide layer; a refractory metal wire clamp 1 is used to fix the two ends of several refractory metal wires 4. First, one end of several refractory metal wires 4 is fixed to the fixed structure on one side, and then it is straightened and passed through the limiting structure on one side, and laid parallel to the substrate 5 to be reinforced with both ends extending from the upper surface of the substrate 5. Due to the presence of the insulating part on the upper surface of the substrate 5, a gap of 0.5 mm is left between the several refractory metal wires 4 and the upper surface of the substrate 5 to ensure that the refractory metal wires do not contact the substrate and increase the pulse current density. Then, the refractory metal wires 4 are passed through the limiting structure on the other side and the other ends are fixed to the fixed structure on the other side. Before laser cladding, the molybdenum wire is passed through the refractory metal wire limiting plate 9 for limiting, so as to avoid uneven coating structure caused by non-parallel arrangement of the molybdenum wires during cladding;

[0059] Step 2: After fixing a plurality of refractory metal wires 4, use the compression structures on both sides to compress them;

[0060] Step 3: Adjust the positions of the laser cladding structure, the pulse current structure, and the substrate 5 to be reinforced so that the bottom surface of the electrode block 18 of the pulse current structure contacts the upper surfaces of the plurality of refractory metal wires 4, and the molten pool of the laser cladding structure and the coaxial powder feeding head 3 are located on the upper surfaces of the plurality of refractory metal wires 4;

[0061] Step 4. Set the laser cladding process parameters and pulse current process parameters. The laser cladding process parameters are: spot diameter of 2 mm; laser power of 1500 W; scanning speed of 3 mm / s; powder feeding rate of 20 g / min; argon gas is used for gas protection of the molten pool, and the carrier gas volume is 5 L / min; the process parameters of the pulse current are: pulse current is unidirectional square wave, peak current of 300 A, pulse frequency of 500 Hz, pulse width of 1000 μs, duty cycle of 50%, and start the pulse power supply. After power is turned on, preheat the several refractory metal wires 4 and the substrate 5 for 30 minutes to prevent cracks from occurring during the cladding process. At the same time, the refractory metal wires 4 are deformed under the action of tension to have a certain wire texture, which can better enhance the coating performance.

[0062] Step 5: After preheating for 30 minutes, the sample is subjected to a pulse current-assisted laser cladding operation to obtain a coating with a thickness of 2 mm.

[0063] The pulse current process parameters of the present invention are: the pulse current is a unidirectional square wave, the peak current is 300A, the pulse frequency is 500Hz, the pulse width is 1000μs, and the duty cycle is 50%. For the present invention, the bottom surface of the electrode block is 10mm*10mm, and it contacts 10 molybdenum wires at a time. The diameter of each molybdenum wire is 0.6mm, and the cross-sectional area of ​​the 10 molybdenum wires is 2.826mm. 2 , the peak current density is 106.16 A / mm 2 , average current: 150A, average pulse current density: 53.08A / mm 2 However, if the positive and negative electrodes are in direct contact with the metal substrate, the peak current density is 5 A / mm 2 Therefore, compared with directly loading the pulse current onto the substrate, using refractory metal wire as the conductor of the pulse current can effectively improve the pulse current density and current utilization rate during the laser cladding process.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An in-situ pulse current assisted laser cladding device for fiber reinforced composite coating, characterized in that: It includes a substrate (5), a plurality of refractory metal wires (4), a refractory metal wire fixture (1), a laser cladding structure and a pulse current structure, The substrate (5) is a metal part that needs to be surface-strengthened, and insulating parts (7) with a certain thickness are provided at both lateral ends of the substrate (5); A plurality of refractory metal wires (4) are used for coating the surface of the fiber-reinforced matrix (5), are laid transversely and parallel to the matrix (5) to be reinforced, and have both ends extending from the upper surface of the matrix (5); The refractory metal wire clamp (1) is used to fix a plurality of refractory metal wires (4), respectively connect the two ends of the plurality of refractory metal wires (4) and tighten them. The refractory metal wire clamp (1) comprises a clamp body (10), a limiting structure, a pressing structure and a fixing structure, wherein the clamp body (10) is an "I"-shaped frame suspended at the bottom of the middle connecting beam, the limiting structure is provided at one end of the clamp body (10) close to the base (5), the pressing structure is provided at the middle connecting beam, and the fixing structure is provided at the other end of the clamp body (10). The pressing structure is height-adjustable, and the bottom end is lower than the limiting structure. The plurality of refractory metal wires (4) pass through the limiting structure, the bottom of the pressing structure and the top of the fixing structure in sequence, are limited by the limiting structure, fixed by the fixing structure, and pressed by the pressing structure; The laser cladding structure is used for laser cladding a substrate (5) and a plurality of refractory metal wires (4), and comprises a fixing seat arranged above the substrate (5), a laser head (2) connected to the fixing seat, and a coaxial powder feeding head (3) arranged at the bottom of the laser head (2); The pulse current structure is used to synchronously transmit pulse current to a substrate (5) and a plurality of refractory metal wires (4), and includes a pulse power supply and a pulse current connecting device (6), wherein the pulse current connecting device (6) includes a fixed arm (15), two lateral moving devices (13), positive and negative electrodes (16) and two electrode blocks (18), wherein the fixed arm (15) is horizontally sleeved on the outside of the laser head (2), the two lateral moving devices (13) are respectively arranged at both ends of the fixed arm (15) and can move horizontally, the positive and negative electrodes (16) are respectively movably connected to the bottom ends of the two lateral moving devices (13), the two electrode blocks (18) are respectively movably connected to the bottom ends of the positive and negative electrodes (16), and the bottom surface of the electrode block (18) is arranged on the plurality of refractory metal wires (4), and the two positive / negative poles of the pulse power supply are respectively connected to the positive and negative electrodes (16) through wires; the refractory metal wire clamp (1) and the non-electrically connected parts of the pulse current structure are insulated.

2. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 1, characterized in that: The limiting structure is a refractory metal wire limiting plate (9), and a plurality of circular hole-shaped limiting grooves are horizontally opened in the middle of the refractory metal wire limiting plate (9), and the diameter of the limiting grooves is not less than the diameter of the refractory metal wire (4).

3. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 2, characterized in that: The two side surfaces of the clamp body (10) close to one end of the base body (5) are symmetrical and vertically provided with a plurality of groups of threaded holes, and the two side ends of the refractory metal wire limiting plate (9) are movably connected to any one group of threaded holes on the two side surfaces of the clamp body (10) close to one end of the base body (5) through bolts.

4. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 1, characterized in that: The clamping structure includes a tightening bolt, a through hole is provided at the center of the middle connecting beam of the clamp body (10), a thread corresponding to the tightening bolt is provided on the inner side of the through hole, the height of the tightening bolt is higher than the thickness of the through hole, when tightening is not required, the tightening bolt is screwed out upward, and the bottom does not contact the plurality of refractory metal wires; when tightening is required, the tightening bolt is tightened downward, and the bottom extends out of the through hole to achieve tightening of the plurality of refractory metal wires (4); a handle (8) is provided on the top of the tightening bolt for easy rotation.

5. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 1, characterized in that: The clamping structure includes a tightening bolt and a tensioning device (11) connected to the bottom of the tightening bolt, the tensioning device (11) includes two side slides and a clamping block that can slide in the slides, a through hole is provided in the center of the middle connecting beam of the clamp body (10), and a thread corresponding to the tightening bolt is provided on the inner side of the through hole, the two side slides are provided on the side walls of the clamp body (10) and the bottom of the middle connecting beam, the top of the clamping block is movably connected to the bottom of the tightening bolt, when tightening is not required, the tightening bolt is screwed out upward, and the clamping block moves upward as the tightening bolt rotates, when tightening is required, the tightening bolt is screwed down, and the clamping block moves downward as the tightening bolt rotates, thereby achieving the tightening of the plurality of refractory metal wires (4); a handle (8) is provided on the top of the tightening bolt for easy rotation.

6. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 1, characterized in that: The fixing structure comprises a base, fixing bolts and a refractory metal wire connector (12); the refractory metal wire connector (12) is rotatably connected to the base via the fixing bolts, and the connecting end is connected to the ends of a plurality of refractory metal wires (4); when the refractory metal wire connector (12) is rotated, the plurality of refractory metal wires (4) are tightened.

7. The device for in-situ pulse current assisted laser cladding of fiber reinforced composite coating according to claim 1, characterized in that: The lateral moving device (13) includes a spring (14), and the positive and negative electrodes (16) include an internal spring (17). The spring (14) is arranged inside the lateral moving device (13), one end of which is connected to the top of the lateral moving device (13), and the other end is connected to the positive and negative electrodes (16). The internal spring (17) is arranged inside the positive and negative electrodes (16), one end of which is connected to the top of the positive and negative electrodes (16), and the other end of which is connected to the top of the electrode block (18). The top of the electrode block (18) extends into the inside of the positive and negative electrodes (16), and the bottom is embedded in the outside of the positive and negative electrodes (16). When the electrode block When (18) is in a suspended state, the internal spring (17) is in a stretched state; when the electrode block (18) contacts the upper surface of the refractory metal wire (4), the internal spring (17) is in a compressed state; when the bottom of the electrode block (18) is under pressure, the internal spring (17) is further compressed; the fixed arm (15) includes two semicircular clamps, bolts (19) and nuts (20) corresponding to the bolts, and bolt holes corresponding to the bolts (19) are provided on both sides of the semicircular clamps. The two semicircular clamps are movably connected to the outside of the laser head (2) through the bolts (19) and the nuts.

8. A process method for an in-situ pulse current assisted laser cladding fiber reinforced composite coating device according to claim 1, characterized in that: Here are the steps: Step 1: Use a refractory metal wire clamp (1) to fix the two ends of a plurality of refractory metal wires (4). First, fix one end of the plurality of refractory metal wires (4) to a fixed structure on one side, then straighten them and pass through a limiting structure on one side, lay them parallel to the substrate (5) to be reinforced, and extend the two ends from the upper surface of the substrate (5). Due to the presence of the insulating member on the upper surface of the substrate (5), a gap is left between the plurality of refractory metal wires (4) and the upper surface of the substrate (5) to ensure that the refractory metal wires do not contact the substrate and increase the pulse current density. Then, pass through the limiting structure on the other side and fix the other ends of the plurality of refractory metal wires (4) to the fixed structure on the other side. Step 2: After fixing a plurality of refractory metal wires (4), they are compressed using the compression structures on both sides; Step 3: Adjust the positions of the laser cladding structure, the pulse current structure, and the substrate to be reinforced (5), so that the bottom surface of the electrode block (18) of the pulse current structure contacts the upper surface of the plurality of refractory metal wires (4), and the molten pool of the laser cladding structure and the coaxial powder feeding head (3) are located on the upper surface of the plurality of refractory metal wires (4); Step 4: setting laser cladding process parameters and pulse current process parameters, and starting the pulse power supply to preheat the plurality of refractory metal wires (4) and the substrate (5) after power is turned on; Step 5: Start the power supply and perform pulse current assisted laser cladding operation on the sample to obtain the product.

9. The process method of the in-situ pulse current assisted laser cladding fiber reinforced composite coating device according to claim 8, characterized in that: The refractory metal wire (4) is a molybdenum wire with a diameter of 0.2-0.6 mm, and the powder of the coaxial powder feeding head (3) is a high entropy alloy CoCrFeMnNi with a particle size of 75-105 μm.

10. The process method of the in-situ pulse current assisted laser cladding fiber reinforced composite coating device according to claim 8, characterized in that: The laser cladding process parameters in step 4 are as follows: spot diameter of 2 mm; laser power of 1400-1600 W; scanning speed of 3 mm / s; powder feeding rate of 20 g / min; argon gas is used for gas protection of the molten pool, and the carrier gas volume is 5 L / min; the process parameters of the pulse current are as follows: the pulse current is a unidirectional square wave, the peak current is 300 A, the pulse frequency is 500 Hz, the pulse width is 1000 μs, and the duty cycle is 50%.

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