Laser cladding layer staggered additive manufacturing method based on alternating pulse timing control

Abstract

The application relates to a laser cladding layer staggered additive manufacturing method based on an alternating pulse timing control, and solves the problems existing in the traditional laser cladding technology in thin-walled part repair. The method comprises the following steps: 1) a powder feeding device is turned on, a mechanical arm drives a laser cladding head to move in one direction along an additive path; a first layer of the substrate surface leaves intermittent additive areas; 2) when the laser cladding head moves to the end point in the direction, the laser cladding head is cooled; then, the mechanical arm drives the laser cladding head to move horizontally to the starting point direction, and the laser on-off timing is opposite to that in the previous moving direction; 4) when the second layer is cladded, the movement and laser pulse control process of the first layer are repeated, but the laser on-off timing is just opposite to that of the first layer; 5) steps 1) to 4) are repeatedly performed to complete the whole laser cladding additive manufacturing process. The application reduces the heat input amount in unit time, and guarantees the size precision and use performance of the repaired thin-walled part.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, specifically relating to a laser cladding additive manufacturing method, and more particularly to a laser cladding layer staggered additive manufacturing method based on alternating pulse timing control, which is applied to the repair of thin-walled parts of aero-engines. Background Technology

[0002] Laser cladding is a surface modification technology that uses a laser beam to rapidly melt and solidify metal powder onto a substrate surface to form a cladding layer with specific properties. It is widely used in material surface repair and additive manufacturing. However, in traditional laser cladding processes, the highly concentrated and continuous input of laser energy in time and space generates significant thermal stress, leading to deformation and cracking of the clad parts. This severely affects the quality and lifespan of the clad parts, limiting the scope of laser cladding technology.

[0003] Especially for the repair of high and low pressure compressor blades in aero-engines, due to their complex structure and high dimensional requirements, traditional laser cladding technology is prone to defects such as undercut, melt pool collapse, excessive deformation, and hot cracking during cladding due to excessive heat input. These defects result in repaired parts that fail to meet usage requirements, limiting the further application of laser cladding technology in the repair of thin-walled parts. Therefore, there is an urgent need for a laser cladding technology that can effectively reduce stress deformation and improve forming quality. Summary of the Invention

[0004] This invention aims to provide a laser cladding layer staggered additive manufacturing method based on alternating pulse timing control. By optimizing the pulse control and motion mode in the laser cladding process, the stress deformation during the cladding process is reduced, the bonding strength of the additive area is improved, the forming effect of laser cladding repair of thin-walled parts is improved, and the problems existing in the traditional laser cladding technology in the repair of thin-walled parts are solved.

[0005] This invention is achieved through the following technical solutions:

[0006] A laser cladding layer staggered additive manufacturing method based on alternating pulse timing control includes the following steps:

[0007] 1) When laser cladding begins, the powder feeding device is turned on, and the motion device robotic arm drives the laser cladding head to move in one direction along the additive path; at the same time, the laser is controlled to pulse at a switching frequency of 1-20Hz, leaving an intermittent additive area on the first layer of the substrate surface.

[0008] 2) When the laser cladding head moves to the end point in this direction, it stays for a cooling period to allow the cladding area to cool down initially. Then, the robotic arm drives the laser cladding head to move horizontally towards the starting point. At this time, the laser still maintains the same switching pulse frequency as before, but the timing of switching the laser is opposite to the previous movement direction, so that the cladding area can cover the blank uncladding area left in the previous movement, thus achieving the staggered arrangement of cladding areas in the first layer.

[0009] 3) After completing the first layer of bidirectional cladding, the laser cladding head is raised in the Z direction to the thickness of the cladding layer;

[0010] 4) When performing the second cladding layer, the motion and laser pulse control process of the first layer are repeated, but the laser switching timing is exactly the opposite of the first layer, so that the direction of each small segment of the second layer is opposite to the direction of the corresponding small segment of the first layer; in this way, the cladding areas between layers and between passes can be staggered and superimposed; the third layer is the opposite of the second layer, alternating and cycling.

[0011] 5) Repeat steps 1)-4) continuously until the predetermined additive height and width are reached, thus completing the entire laser cladding additive manufacturing process.

[0012] The thickness of the cladding layer is generally set to 0.5 mm.

[0013] The robotic arm's movement speed is adjusted according to the actual cladding requirements.

[0014] Throughout the process, the heat input and forming effect per unit time can be further precisely adjusted by controlling the movement speed of the robotic arm, the laser switching frequency, the laser power, and the amount of metal powder fed, so as to adapt to the cladding additive manufacturing requirements of different materials and part structures.

[0015] The beneficial effects of this invention are:

[0016] 1. Reduced stress deformation: By controlling the laser switching through alternating pulses, the continuous input of laser energy is reduced, thereby lowering the thermal stress during the cladding process and effectively preventing deformation of the clad parts due to excessive stress.

[0017] 2. Improved bonding strength: The staggered arrangement of cladding areas and the alternating reverse cladding method between layers make the stress distribution of the additive area more uniform in all directions, thereby enhancing the bonding strength between the additive area and the matrix, as well as between layers.

[0018] 3. Reduced crack initiation and propagation: Reduced thermal stress and uniform stress distribution decrease the probability of cracks in the additive manufacturing area during operation and effectively inhibit further crack propagation, thereby improving the reliability and service life of the clad parts.

[0019] 4. Suitable for repairing thin-walled parts: For thin-walled parts such as blade tips of high and low pressure compressors in aero-engines, this invention reduces the heat input per unit time, avoiding forming defects such as undercut and melt pool collapse commonly found in traditional laser cladding, thus achieving high-quality repair and ensuring the dimensional accuracy and performance of the repaired thin-walled parts. Attached Figure Description

[0020] Figure 1 Overall structural diagram;

[0021] Figure 2 Schematic diagram of the first cladding layer;

[0022] Figure 3 Schematic diagram of the second cladding layer;

[0023] Figure 4 Schematic diagram of continuous multi-layer cladding;

[0024] Figure 5 Macroscopic view of the cladding layer;

[0025] Figure 6 .Schematic diagram of cladding direction. Detailed Implementation

[0026] like Figure 1-6 This invention is a laser cladding layer staggered additive manufacturing method based on alternating pulse timing control, comprising the following steps:

[0027] (I) Implementation Preparation

[0028] 1. Prepare the thin-walled parts to be repaired, such as high-pressure or low-pressure compressor blades of aircraft engines. Clean the surface of the area to be repaired to remove oil, scale and impurities to ensure good bonding between the cladding layer and the substrate.

[0029] 2. Select a suitable metal powder as the cladding material. Determine the type and particle size of the metal powder based on the usage requirements and performance needs of the parts.

[0030] 3. Debug the laser cladding equipment, including the laser generator, powder feeding device, robotic arm, water chiller, etc., to ensure normal operation. Set the pulse frequency to 1-20Hz, adjust the robotic arm's movement speed according to the actual cladding requirements, and set the Z-axis lifting height as the height of a single cladding layer.

[0031] (II) Specific cladding process

[0032] 1. Turn on the powder feeding device to deliver metal powder to the laser cladding head. At the same time, the robotic arm drives the laser cladding head to start moving along the predetermined path starting point. The laser starts to turn on and off at a frequency of 1-20Hz, leaving a discontinuous additive area in the first layer of the thin-walled part to be repaired.

[0033] 2. When the laser cladding head reaches the end point in this direction, control the robotic arm to stop moving, turn off the laser, and let the laser cladding head stay for a period of time (depending on the material) to wait for cooling, so as to avoid continuous operation that would cause the temperature of the cladding area to rise continuously, resulting in thermal deformation and changes in process conditions.

[0034] 3. After cooling is complete, the robotic arm drives the laser cladding head to move along the path it came from in the direction of the starting point. At this time, the pulse frequency of the laser is kept unchanged, but the timing of the laser's on and off is adjusted so that it is opposite to the on and off timing of the previous movement direction. This ensures that the cladding can cover the previous blank area, complete the first layer of bidirectional cladding, and realize the staggered arrangement of the cladding areas.

[0035] 4. After completing the first layer of bidirectional cladding, the laser is turned off, the robotic arm is allowed to cool down, and then the robotic arm lifts the cladding head 0.5mm (the thickness of a single cladding layer) in the Z direction to reach the starting position of the second layer.

[0036] 5. Begin the second cladding layer, repeating the motion and laser pulse control process of the first layer, but adjusting the laser switching timing to be opposite to that of the first layer, so that the direction of each segment in the second layer is opposite to the corresponding direction of the first layer. The third layer is the opposite of the second layer, and the process alternates.

[0037] 6. Repeat the above steps continuously, layer by layer, until the predetermined additive height is reached, completing the laser cladding repair process for the entire thin-walled part.

[0038] (III) Quality Inspection

[0039] After cladding is completed, the repaired parts undergo quality inspection, including checking for defects such as cracks, pores, and lack of fusion that exceed allowable values ​​inside the cladding layer using non-destructive testing techniques (such as ultrasonic testing and X-ray testing); metallographic analysis to detect the bonding interface between the cladding layer and the substrate, as well as the microstructure of the cladding layer; and mechanical property testing (such as tensile testing and hardness testing) to evaluate the mechanical properties of the cladding layer, ensuring that the repaired parts meet the usage requirements.

[0040] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein. For example, for ease of demonstration, this specification only shows single-pass multilayer linear cladding, but this method can also be used for multi-pass multilayer non-linear cladding. This should not be considered as an exclusion of other embodiments, but rather applicable to various other combinations, modifications, and environments. Modifications can be made within the scope of the concept described herein through the above teachings or related field techniques or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A laser cladding layer staggered additive manufacturing method based on alternating pulse timing control, characterized in that: Includes the following steps: 1) When laser cladding begins, the powder feeding device is turned on, and the motion device robotic arm drives the laser cladding head to move in one direction along the additive path; at the same time, the laser is controlled to pulse at a switching frequency of 1-20Hz, leaving an intermittent additive area on the first layer of the substrate surface. 2) When the laser cladding head moves to the end point in this direction, it pauses for a cooling period to allow the cladding area to cool down initially. Then, the robotic arm drives the laser cladding head to move horizontally towards the starting point. At this time, the laser still maintains the same switching pulse frequency as before, but the timing of switching the laser is opposite to the previous movement direction, so that the cladding area can cover the blank uncladding area left in the previous movement, thus achieving the staggered arrangement of cladding areas in the first layer. 3) After completing the first layer of bidirectional cladding, the laser cladding head is raised in the Z direction to the thickness of the cladding layer; 4) When performing the second cladding layer, the motion and laser pulse control process of the first layer are repeated, but the laser switching timing is exactly the opposite of the first layer, so that the direction of each small segment of the second layer is opposite to the direction of the corresponding small segment of the first layer; in this way, the cladding areas between layers and between passes can be staggered and superimposed; the third layer is the opposite of the second layer, alternating and cycling. 5) Repeat steps 1)-4) until the predetermined additive height and width are reached, thus completing the entire laser cladding additive manufacturing process.

2. The laser cladding layer staggered additive manufacturing method based on alternating pulse timing control according to claim 1, characterized in that: The thickness and height of the cladding layer are set to 0.5 mm.

3. The laser cladding layer staggered additive manufacturing method based on alternating pulse timing control according to claim 1, characterized in that: The robotic arm's movement speed is adjusted according to the actual cladding requirements.

Images