Machining process for surface coating of metal rotating part based on laser cladding

Abstract

The invention discloses a laser-cladding-based processing technology for a surface coating of a metal rotating member, which comprises the following steps: step 1, firstly, cladding powder is put into a drying oven to be baked and heated, and the heated powder is cooled to room temperature; 2, the surface of a workpiece to be machined is subjected to pretreatment operation such as cleaning and polishing, impurities such as oil stains and oxide skin on the surface are removed, the size of the workpiece is detected, and the base material workpiece is stably grabbed and clamped in a lathe through a three-jaw chuck, a center frame and a tailstock; and 3, a powder cylinder in the powder feeder is cleaned up, then the powder cooled to the room temperature is sieved, and the sieved powder is loaded into the powder cylinder. According to the method, the machining process is standardized, various parameters during machining are reasonably controlled, the machining precision of laser cladding is improved, and the stability of the quality of a cladding coating is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding, in particular to a processing technology for a surface coating of a metal rotating part based on laser cladding. Background Art

[0002] Laser cladding, as an advanced surface modification technology, significantly improves the hardness, wear resistance, and corrosion resistance of rotating metal parts by rapidly fusing a cladding material with specific properties to the substrate surface, forming a dense coating that is metallurgically bonded to the substrate. However, existing laser cladding processes for coating the surface of rotating metal parts suffer from issues such as non-standardized processing procedures and irrational parameter control. For example, improper powder pretreatment can affect the quality of the cladding layer, unstable workpiece clamping can lead to reduced processing accuracy and unstable coating quality, and a lack of systematic equipment commissioning and parameter setting can easily lead to energy waste and low production efficiency. Summary of the Invention

[0003] The present invention aims to provide a process for coating the surface of a rotating metal part using laser cladding. By standardizing the processing flow and rationally controlling various processing parameters, the present invention improves the processing accuracy of laser cladding and ensures the stability of the cladding coating quality.

[0004] The technical solution of the present invention is a process for processing a surface coating of a metal rotating part based on laser cladding, comprising the following steps:

[0005] Step 1: First, place the cladding powder in an oven for baking and heating, and then cool the heated powder to room temperature;

[0006] Step 2: Pre-treat the surface of the workpiece to be processed, remove surface impurities, check the workpiece size, and stably clamp the base workpiece in the lathe using a three-jaw chuck, center rest, and tailstock;

[0007] Step 3: Clean the powder barrel in the powder feeder, sieve the powder cooled to room temperature, and put the sieved powder into the powder barrel;

[0008] Step 4: Check the integrity of the protective lens inside the laser cladding head, then check the water level in the water tank of the water cooler used to cool the laser, start the laser, turn on the protective gas used to protect the lens, and start the powder feeder;

[0009] Step 5: Adjust the distance between the laser cladding head and the workpiece surface, compile the machine tool program, set the laser cladding head movement path, cladding rate, overlap rate parameters, and check the movement of the cladding head;

[0010] Step 6: Start the shielding gas switch, powder feeding switch, and machine tool motion program in sequence. After the laser cladding head moves stably, start the laser switch again to achieve cladding on the surface of the workpiece. If cladding processing is required on the inner wall of the workpiece, adjust the servo movement mechanism and use the extension component to allow the laser cladding head to penetrate deeper into the workpiece.

[0011] Step 7: Turn off the laser cladding head's light output signal, stop the machine tool's motion program, turn off the powder feeder and shielding gas switches, and then turn off the powder feeder, laser, water cooler, machine tool, and gas cylinder valves in sequence.

[0012] In the above-mentioned processing technology of the surface coating of the metal rotating part based on laser cladding, in step 1, the heating temperature range of the oven is between 70 degrees and 120 degrees. After the powder heating is completed, the powder is kept warm and then cooled to room temperature.

[0013] In the aforementioned processing technology of surface coating of metal rotating parts based on laser cladding, in step 2, when clamping the workpiece, a center stand and tailstock are used to support the extra-long workpiece, and the support height of the center stand is adjusted by the height adjustment component in the center stand so that the center stand can fit the metal rotating part to be processed, and the top of the tailstock touches the end center of the workpiece.

[0014] In the aforementioned laser cladding-based surface coating process for metal rotating parts, in step 3, the powder feeder adopts a single-barrel powder feeder, and the corresponding parameters of the powder feeder are set, including the powder tray speed, carrier gas type, powder feeding gas flow rate, and shielding gas flow rate.

[0015] In the aforementioned processing technology of surface coating of metal rotating parts based on laser cladding, in step 4, when the water tank of the water cooler is on, the laser circuit breaker is turned on, the water cooler is started, and it is ensured that the water pressure is positive, the fan operates normally, and there is no water leakage in the water tank pipe.

[0016] In the aforementioned processing technology for the surface coating of a metal rotating part based on laser cladding, in step 4, when the laser is turned on, turn on the key switch, confirm that the emergency stop button of the laser is not pressed, and after the screen starts up, select the control mode, set the laser power, and check the three-way laser output.

[0017] In the aforementioned process for processing the surface coating of a metal rotating part based on laser cladding, in step 5, the distance between the laser cladding head and the workpiece surface ranges from 10 mm to 15 mm.

[0018] In the aforementioned process for processing the surface coating of a metal rotating part based on laser cladding, in step 7, after the protective gas switch is turned off, the laser cladding head is sealed with masking paper to prevent dust from entering the laser cladding head.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. In the present invention, the powder is heated in an oven to completely remove the adsorbed water and surface oxides in the cladding powder, thereby reducing the moisture content of the powder. This avoids the pores and oxidation inclusions caused by moisture in the powder during the cladding process from the source, ensures the density and metallurgical bonding strength of the coating, and realizes the standardization of powder pretreatment. The combination of a three-jaw chuck, a center rest, and a tailstock is used to clamp the workpiece, stably control the radial runout error of the workpiece, and ensure clamping accuracy and processing consistency.

[0021] 2. Through the cooperation of the servo moving mechanism and the extension component, the laser cladding head can achieve stable processing deep into the workpiece, and the laser cladding processing of the inner and outer surfaces of the workpiece is realized, which expands the processing range and avoids the secondary clamping error caused by the inability to reach the inner wall in traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0023] Figure 2 Schematic diagram of the laser cladding machine.

[0024] Explanation of the marks in the accompanying drawings: 1-bed, 2-three-jaw chuck, 3-center frame, 4-tailstock, 5-servo movement system, 6-powder feeder, 7-laser cladding head. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0026] Example: A process for processing a surface coating of a metal rotating part based on laser cladding comprises the following steps:

[0027] Step 1, baking powder: first, place the cladding powder in an oven for baking and heating, and cool the heated powder to room temperature; the heating temperature range of the oven is between 70 degrees and 120 degrees. After the powder is heated, the powder is kept warm and then cooled to room temperature.

[0028] Step 2, substrate processing and clamping: the surface of the workpiece to be processed is cleaned, polished and other pre-processing operations are carried out to remove impurities such as oil, oxide scale and so on on the surface, the workpiece surface is cleaned with alcohol, and the surface of the substrate workpiece is polished with a grinding wheel until it is flat and free of oxide scale; the workpiece size is detected, and the substrate workpiece is stably clamped in the lathe by a three-jaw chuck, a center frame and a tailstock; the processing technology of the surface coating of the metal rotating parts is mainly realized by the laser cladding machine tool, which mainly includes a bed 1, a three-jaw chuck 2, a center frame 3, a tailstock 4 and a servo movement system 5, as shown in the attached figure. Figure 2As shown, a powder feeder 6 and a laser cladding head 7 are provided on the servo motion system 5. When clamping the workpiece, a center frame and a tailstock are used for support. The support height of the center frame is adjusted by a height adjustment assembly in the center frame so that the center frame can fit the metal rotating part to be processed and the top of the tailstock touches the end center of the workpiece.

[0029] Step 3, powder loading: clean the powder barrel in the powder feeder, sieve the powder cooled to room temperature, load the sieved powder into the powder barrel, open the barrel cover on the upper end of the powder barrel, pour the powder into the powder barrel and tighten the barrel cover; the powder feeder adopts a single-barrel powder feeder, and a scraper structure is used in the powder feeder to achieve uniform powder discharge. Then set the corresponding parameters of the powder feeder, including the powder pan speed, carrier gas type, powder feeding gas flow rate and protective gas flow rate. The capacity of the powder feeder is 5 liters, the maximum speed of the powder pan is 8 revolutions per minute, the carrier gas type can be nitrogen or argon, the powder feeding gas flow rate adjustment range is between 0.5 liters and 25 liters per minute, and the protective gas flow rate adjustment range is between 1 liter and 50 liters per minute. The powder feeder can also support powder preheating.

[0030] Step 4. Prepare the cladding system: Check the integrity of the protective lens in the laser cladding head, then check the water level in the water tank of the water cooler used to cool the laser, start the laser, open the gas cylinder for protecting the lens, and start the powder feeder; when the water cooler water tank is open, turn on the laser circuit breaker, start the water cooler, ensure that the water pressure is positive, the fan is operating normally, and there is no water leakage in the water tank pipe; when the laser is turned on, turn on the key switch, confirm that the laser's emergency stop button is not pressed, and after the screen starts up, select the control mode, set the laser power, and check the three-way laser output.

[0031] Step 5: Set the cladding path: Adjust the distance between the laser cladding head and the workpiece surface, compile a machine program, set the laser cladding head motion path, cladding rate, and overlap rate parameters, and check the cladding head motion. The distance between the laser cladding head and the workpiece surface ranges from 10 mm to 15 mm. In this embodiment, the laser cladding head is an inner wall reflection side-axis pin cladding head. It changes the transmission direction of the laser beam by reflecting it off the inner wall, allowing the laser beam to be more accurately focused on a specific location on the inner wall of the workpiece. This adapts to the inner wall cladding requirements of workpieces of different shapes and sizes, and can achieve excellent cladding effects, especially for workpieces with complex internal cavities.

[0032] Step 6. Start cladding: Start the shielding gas switch, powder feeding switch, and machine tool motion program in sequence. After the laser cladding head moves stably, start the laser switch again to achieve cladding on the surface of the workpiece. If cladding processing is required on the inner wall of the workpiece, adjust the servo movement mechanism and use the extension component to allow the laser cladding head to penetrate deep into the workpiece. During the processing, it is necessary to observe the powder discharge, powder feeding, and cladding conditions at any time. If any abnormality is found, immediately turn off the light signal and stop cladding.

[0033] Step 7, end cladding: turn off the laser cladding head's light signal, stop the machine tool's motion program, turn off the powder feed switch and the protective gas switch, and then turn off the powder feeder, laser, water cooler, machine tool, and gas cylinder valve in sequence; after the protective gas switch is turned off, seal the laser cladding head with masking paper to prevent dust from entering the laser cladding head. The specific laser cladding process flow for metal rotating parts is shown in the attached figure. Figure 1 shown.

[0034] Furthermore, this embodiment specifically describes the solution of the present invention for a cast iron automobile engine cylinder liner with a diameter of 80 mm and a length of 150 mm, and prepares a Ni-based alloy wear-resistant coating on its inner wall by laser cladding to improve the wear resistance:

[0035] Step 1: Pretreatment of cladding powder baking. The powder type used is Ni60A alloy powder with a particle size range of 50-150 mesh. The baking equipment used to heat the powder is SX2-4-10 box-type resistance furnace. The heating temperature is set to 80℃ and the temperature is gradually increased to the target temperature to avoid powder agglomeration. The holding time is 60 minutes to ensure that the adsorbed water is fully volatilized. Then the powder is cooled to room temperature with the furnace to prevent the powder from absorbing moisture.

[0036] Step 2: Substrate preparation and clamping: First, ultrasonically clean the inner wall of the cylinder liner with anhydrous ethanol for 30 minutes to remove oil stains. Then, mechanically polish the inner wall with 80-grit sandpaper to control the roughness to below Ra1.6μm, revealing a metallic luster. The workpiece is clamped on a CL-600 laser cladding lathe. The outer diameter of one end of the cylinder liner is fixed with a three-jaw chuck, and the center stand supports the middle of the cylinder liner through a height adjustment assembly to ensure radial runout ≤0.05mm. The tailstock's top touches the center hole at the other end of the cylinder liner, forming a three-point support.

[0037] Step 3: Powder loading: Use a single-barrel powder feeder model SF-5L, wipe the inner wall of the powder barrel with acetone, dry it, and then load the sieved (100 mesh) Ni60A powder; set the parameters of the powder feeder, set the powder tray speed to 5 rpm, the powder output to a stable level of 15 g / min, use argon as the carrier gas, with a flow rate of 10 liters / minute, and set the shielding gas flow rate to 15 liters / minute;

[0038] Step 4: Preparation of the cladding system: Use a fiber laser model IPG-YLR-2000 with a maximum output power of 2000W. Before use, perform a pre-startup inspection of all components, including the protective lens and water cooling system. The protective lens must be free of cracks and stains during visual inspection, and the transmittance must be ≥95%. Start the water cooler (model CW-5200), with a water pressure of 0.3MPa, a water tank temperature of 25°C, and no water leakage in the pipes. Then start the laser, turn on the key switch, release the emergency stop button, and after the control system screen starts, select "continuous mode", set the laser power to 1200W, and check the three-way output.

[0039] Step 5: Cladding path planning and parameter setting: Set the cladding head parameters. Use an inner wall reflection side-axis needle cladding head with a distance of 12 mm from the workpiece (adjusted by the Z-axis servo motor). The cladding motion path is a spiral line scan (pitch 0.8 mm), cladding layer by layer from the bottom of the cylinder liner to the open end. The cladding rate is 500 mm / min, and the overlap rate is set to 40% (to ensure uniform coating coverage). Then, perform a test run and dry run the machine to confirm that there is no interference in the cladding head motion trajectory and the positioning accuracy is ±0.02 mm.

[0040] Step 6: Start cladding. Start each component in sequence. First, open the protective gas cylinder with a pressure of 0.5MPa. Then start the powder feeder to confirm that the powder is conveying smoothly. Then start the machine tool motion program. The cylinder liner rotates at a speed of 100 rpm. When the cladding head reaches the starting position (10mm from the bottom of the cylinder liner), start the laser switch. Special treatment is required when cladding the inner wall. The servo movement mechanism (stroke 300mm) is used in conjunction with the extension component (length 200mm) to allow the cladding head to penetrate deep into the cylinder liner. The molten pool status is monitored in real time. If powder accumulation or molten pool splashing is found, the laser is immediately turned off and the matching of the powder feed gas flow and laser power is checked.

[0041] Step 7: Cladding is completed and the equipment is shut down: shut down each component in order. First, turn off the laser light signal and continue to feed powder for 30 seconds (to clean the residual powder in the cladding head). Then stop the machine tool movement, turn off the powder feed switch and the shielding gas, and then turn off the powder feeder, laser, and water cooler in turn. Finally, close the gas cylinder valve; seal the cladding head nozzle with masking paper to prevent dust from entering.

[0042] This coating demonstrates excellent performance, processing efficiency, and equipment wear control. Performance-wise, the coating achieves a thickness of 0.5 mm, uniformity within ±5%, and a hardness in the HRC58-62 range, significantly higher than the cast iron substrate's HRC25-30. The bond strength also meets the metallurgical bond standard of ≥400 MPa. Processing efficiency is improved, with a single cylinder liner cladding process taking only 12 minutes. Furthermore, thanks to the effective protection provided by the shielding gas, the laser cladding head lens lifespan reaches ≥500 hours.

Claims

1. A process for processing surface coating of metal rotating parts based on laser cladding, characterized by: The following steps are involved: Step 1: First, place the cladding powder in an oven for baking and heating, and then cool the heated powder to room temperature; Step 2: Pre-treat the surface of the workpiece to be processed, remove surface impurities, check the workpiece size, and stably clamp the base workpiece in the lathe using a three-jaw chuck, center rest, and tailstock; Step 3: Clean the powder barrel in the powder feeder, sieve the powder cooled to room temperature, and put the sieved powder into the powder barrel; Step 4: Check the integrity of the protective lens inside the laser cladding head, then check the water level in the water tank of the water cooler used to cool the laser, start the laser, turn on the protective gas used to protect the lens, and start the powder feeder; Step 5: Adjust the distance between the laser cladding head and the workpiece surface, compile the machine tool program, set the laser cladding head movement path, cladding rate, overlap rate parameters, and check the movement of the cladding head; Step 6: Start the shielding gas switch, powder feeding switch, and machine tool motion program in sequence. After the laser cladding head moves stably, start the laser switch again to achieve cladding on the surface of the workpiece. If cladding processing is required on the inner wall of the workpiece, adjust the servo movement mechanism and use the extension component to allow the laser cladding head to penetrate deeper into the workpiece. Step 7: Turn off the laser cladding head's light output signal, stop the machine tool's motion program, turn off the powder feeder and shielding gas switches, and then turn off the powder feeder, laser, water cooler, machine tool, and gas cylinder valves in sequence.

2. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 1, the heating temperature of the oven is in a range of 70 to 120 degrees. After the powder is heated, the powder is kept warm and then cooled to room temperature.

3. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 2, a center frame and a tailstock are used for support when clamping the workpiece, and the support height of the center frame is adjusted by a height adjustment assembly in the center frame so that the center frame can fit the metal rotating part to be processed and the top of the tailstock touches the end center of the workpiece.

4. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 3, the powder feeder adopts a single-barrel powder feeder, and the corresponding parameters of the powder feeder are set, including the powder tray speed, carrier gas type, powder feeding gas flow rate, and shielding gas flow rate.

5. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 4, when the water tank of the water cooler is on, turn on the laser circuit breaker and start the water cooler to ensure that the water pressure is positive, the fan operates normally, and there is no water leakage in the water tank pipe.

6. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 4, when the laser is turned on, turn on the key switch and confirm that the emergency stop button of the laser is not pressed. After the screen starts up, select the control mode, set the laser power, and check the three-way laser output.

7. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 5, the distance between the laser cladding head and the workpiece surface ranges from 10 mm to 15 mm.

8. The process for processing a surface coating of a metal rotating part based on laser cladding according to claim 1, characterized in that: In step 7, after the protective gas switch is turned off, the laser cladding head is sealed with masking paper to prevent dust from entering the laser cladding head.

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