A method of laser cladding to repair an APU turbine blade tip

Abstract

The application discloses a kind of methods for laser cladding to repair APU turbine blade tip, to blade defect area executes cleaning pretreatment;Utilize scanning equipment to obtain the thickness distribution model of blade and generate processing path;Blade is installed to attitude adjustment component, based on thickness distribution model real-time adjustment cladding process parameters, so that laser power is proportional to blade cross section thickness, scanning speed is inversely proportional to cross section thickness;Utilize powder feeding system and gas path system to transport alloy powder and protective gas, form local protective atmosphere above molten pool;Utilize translation mechanism to drive laser cladding head according to path layer by layer cladding, by built-in acousto-optic deflector and electro-optic deflector real-time adjustment spot geometric size and energy density distribution;Finally, execute cooling, stress relief and quality detection;The application realizes the high-quality repair of blade tip by precise dynamic regulation and control to laser parameter and spot form.

Description

Technical Field

[0001] This invention relates to the field of laser cladding technology, and specifically to a method for repairing the tip of an APU turbine blade using laser cladding. Background Technology

[0002] As a key component of aero-engines, APU turbine blades are used in extreme environments of high temperature, high pressure, and high-speed airflow for a long time. Their tips are prone to defects such as wear, pitting, and microcracks, which reduce the aerodynamic performance of the blades, increase the sealing gap, and in severe cases, cause engine shutdown failure.

[0003] Existing technologies typically utilize laser cladding to repair turbine blades. However, this method employs a single parameter for uniform cladding at the blade tip. For example, scanning the inlet and outlet edges of the blade with a laser of the same power can lead to several issues. Because the inlet edge is thicker, the heat carried by the laser is rapidly conducted away by the substrate material. This can result in the laser failing to heat the substrate surface to its melting point, preventing the molten powder from forming a metallurgical bond. Consequently, the repair layer on the inlet edge is prone to peeling off during subsequent use. Conversely, the outlet edge is thinner, and the heat from the same power laser may have nowhere to dissipate, causing the temperature on the outlet edge to rise sharply, potentially exceeding the melting point of the substrate material and leading to melting and deformation of the blade edge. Therefore, existing technologies result in poor repair quality for turbine blades. Summary of the Invention

[0004] This invention provides a method for laser cladding repair of APU turbine blade tips to solve the problem of poor quality in existing laser cladding repair of turbine blades.

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

[0006] A method for laser cladding repair of APU turbine blade tips includes the following steps:

[0007] S10. Perform cleaning pretreatment on the defective areas of the blade to make the surface roughness of the blade less than the threshold.

[0008] S20. The blade is scanned using a scanning device to obtain a thickness distribution model of the blade; the control system generates the processing path of the laser cladding head based on the thickness distribution model.

[0009] S30. Install the blade onto the attitude adjustment assembly; based on the thickness distribution model, use the control system to adjust the cladding process parameters of the laser cladding head in real time, so that the power of the laser cladding head is proportional to the cross-sectional thickness of the blade, and the scanning speed of the laser cladding head is inversely proportional to the cross-sectional thickness of the blade.

[0010] S40. The alloy powder is fed to the laser cladding head using a powder feeding system; at the same time, a protective gas is supplied to the laser cladding head using a gas path system; simultaneously, an inert protective gas is supplied to the output end of the laser cladding head using a gas path system to form a local protective atmosphere above the molten pool.

[0011] S50. The laser cladding head is driven by a translation mechanism to clad the blade layer by layer according to the processing path; wherein, the laser cladding head is equipped with an acousto-optic deflector and an electro-optic deflector; the control system controls the acousto-optic deflector to adjust the geometric size of the light spot in real time according to the thickness distribution model, and controls the electro-optic deflector to adjust the energy density distribution inside the light spot.

[0012] S60. After the blade cladding is completed, the blade is subjected to cooling treatment, stress relief and quality inspection.

[0013] Preferably, in step S20, the processing path is constructed through the following steps:

[0014] S210. Establish a polar coordinate system with the geometric center or centroid of the blade section as the origin, and set the initial radius according to the maximum radial dimension of the blade profile. The initial circular trajectory constructed by the initial radius can completely cover the area to be repaired.

[0015] S220, Set the polar angle that increases with the processing progress. Establish information regarding the number of cladding layers. l and the polar angle polar radius function ;in,

[0016] = ;

[0017] in, k The preset attenuation rate; It is the spiral expansion factor;

[0018] S230, according to the polar angle and through the polar radius function Calculated polar diameter Generate the planar coordinates of the processing path points ,in, , .

[0019] Preferably, in step S30, the attitude adjustment assembly includes a first base, a second base, a first drive motor, a second drive motor, a mounting platform, and a clamp.

[0020] The first drive motor is mounted on the first base and is used to drive the second base to rotate around the Y-axis; the second drive motor is mounted on the second base and is used to drive the mounting platform to rotate around the X-axis; the clamp is mounted on the mounting platform and is used to clamp the blade so that the long axis of the blade is parallel to the plane XOZ.

[0021] Preferably, the power of the laser cladding head... Satisfy the following formula:

[0022] ;

[0023] The scanning speed of the laser cladding head Satisfy the following formula:

[0024] ;

[0025] in, x This represents the displacement distance from the starting point of the blade's air intake edge to the current machining position. L This is the total path length from the intake side to the exhaust side; The preset power of the laser cladding head at the air inlet edge of the blade; The preset power of the laser cladding head at the blade exhaust edge; The scanning speed of the laser cladding head at the air inlet edge of the blade; The scanning speed of the laser cladding head at the exhaust edge of the blade; wherein, > ; < .

[0026] Preferably, in step S40, the powder feeding system can deliver at least two types of alloy powders to the laser cladding head. The powder feeding system adjusts the proportion of alloy powders in different components in real time through a flow controller, and delivers the corresponding alloy powders to the laser cladding head according to the real-time position of the laser cladding head.

[0027] Preferably, the alloy powder conveyed by the powder feeding system includes at least a first powder and a second powder, wherein the first powder contains a component for improving the blade's erosion resistance, and the second powder contains a component for improving the blade's oxidation resistance; the ratio of the first powder to the second powder... Satisfy the following formula:

[0028] = ;

[0029] in, x This represents the displacement distance from the starting point of the blade's air intake edge to the current machining position. LThis is the total path length from the intake side to the exhaust side; The proportion of the first powder at the air inlet edge of the blade when the laser cladding head is used; The proportion of the first powder when the laser cladding head is at the blade exhaust edge.

[0030] Preferably, the laser cladding head includes the following components arranged sequentially along the laser transmission optical axis:

[0031] Laser input interface for introducing high-power laser beams;

[0032] Collimating lenses are used to convert an introduced laser beam into parallel light;

[0033] The beam shaping module, including the acousto-optic deflector and the electro-optic deflector, is used to geometrically stretch and modulate the energy distribution of parallel light to obtain a first laser beam;

[0034] A diffractive optical element group is used to perform preliminary auxiliary modification of the first laser beam with a preset contour to obtain a second laser beam;

[0035] A focusing lens group is used to focus the second laser beam onto the processing area on the blade surface, and the focusing lens group has an adjustable focal length structure;

[0036] A protective output window is provided to allow the second laser beam to pass through while physically isolating processing spatter.

[0037] Preferably, the laser cladding head is provided with a powder channel for spraying alloy powder. The powder channel surrounds the outside of the protective output window and is in the shape of a rectangular ring. The inner wall of the powder channel on the outer diameter side is made of a flexible metal sheet. A micro pressure actuator is integrated on the back of the flexible metal sheet. The micro pressure actuator is electrically connected to the control system. The micro pressure actuator can generate radial displacement according to the voltage to drive the flexible metal sheet to change the opening size of the powder channel outlet.

[0038] Preferably, in step S30, the attitude adjustment assembly further includes a first heat-conducting element, a second heat-conducting element, a cooling water circulation unit, a mounting base, and a universal bracket; both the first heat-conducting element and the second heat-conducting element are disposed on the mounting base, the first heat-conducting element is used to abut against the air inlet side of the blade, and the second heat-conducting element is used to abut against the air outlet side of the blade; a heat-insulating gasket is provided between the first heat-conducting element and the blade; the second heat-conducting element is made of a high thermal conductivity metal material, and the second heat-conducting element is connected to the cooling water circulation unit; the mounting base is disposed on the universal bracket.

[0039] Preferably, the laser cladding head is equipped with a monitoring system electrically connected to the control system, the monitoring system comprising:

[0040] Infrared thermometers are used to collect instantaneous temperature signals on the surface of the molten pool in real time.

[0041] Industrial cameras are used to capture images of the geometric shape of the molten pool and extract the width and aspect ratio data of the molten pool through image recognition algorithms;

[0042] A laser displacement sensor is used to monitor the real-time stacking height of the cladding layer along the blade length.

[0043] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0044] The defective areas of the blade undergo cleaning pretreatment to reduce the surface roughness to below a threshold. The blade is then scanned using a scanning device to obtain its thickness distribution model. The control system generates the processing path for the laser cladding head based on this model. The blade is then installed onto the attitude adjustment assembly. Based on the thickness distribution model, the control system adjusts the cladding process parameters of the laser cladding head in real time, ensuring that the power of the laser cladding head is directly proportional to the cross-sectional thickness of the blade, and the scanning speed is inversely proportional to the cross-sectional thickness. Alloy powder is fed to the laser cladding head using a powder feeding system. Simultaneously, a protective gas is supplied to the laser cladding head via a gas path system. The gas path system delivers inert protective gas to the output end of the laser cladding head to form a local protective atmosphere above the molten pool. A translation mechanism drives the laser cladding head to clad the blade layer by layer along the processing path. The laser cladding head is equipped with an acousto-optic deflector and an electro-optic deflector. The control system, based on a thickness distribution model, controls the acousto-optic deflector in real time to adjust the geometric size of the laser spot, and controls the electro-optic deflector to adjust the energy density distribution within the laser spot. After the blade cladding is completed, cooling, stress relief, and quality inspection are performed on the blade. This invention achieves high-quality repair of the blade tip through precise dynamic control of laser parameters and laser spot morphology. Attached Figure Description

[0045] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 This is a flowchart illustrating a specific embodiment of the method for laser cladding repair of APU turbine blade tips according to the present invention;

[0047] Figure 2 This is a schematic diagram of the structure of the laser cladding repair device according to a specific embodiment of the present invention;

[0048] Figure 3 This is a diagram showing the internal structure of the laser cladding head according to a specific embodiment of the present invention;

[0049] Figure 4This is a schematic diagram of the powder feeding system according to a specific embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram of the asymmetric heat-conducting structure according to a specific embodiment of the present invention;

[0051] Figure 6 This is a schematic diagram of the posture adjustment component according to a specific embodiment of the present invention;

[0052] Figure 7 This is a schematic diagram of the clamping structure in a specific embodiment of the present invention.

[0053] Reference numerals: 10. Blade; 11. Inlet side; 12. Exhaust side; 20. Laser cladding head; 21. Housing; 211. Powder channel; 212. Flexible metal sheet; 213. Micro-pressure actuator; 214. Gas delivery channel; 22. Laser input interface; 23. Collimating lens; 24. Acousto-optic deflector; 25. Electro-optic deflector; 26. Diffractive optical element group; 27. Focusing lens group; 28. Protective output window; 29. ​​Copper base; 31. Powder storage tank; 32. First gas source; 33. Delivery pipe; 34. Mixing tank; 41. First base; 42. 43. Second base; 44. First drive motor; 45. Second drive motor; 46. Mounting platform; 461. Connecting seat; 462. Clamping motor; 463. Lead screw; 464. Clamping block; 465. Rubber pad; 47. First heat-conducting component; 471. First limiting block; 48. Second heat-conducting component; 481. Second limiting block; 49. Mounting base; 410. Universal bracket; 411. Heat insulation pad; 412. Compression spring; 51. Worktable; 52. Frame; 53. Slide; 54. First lead screw mechanism; 55. Second lead screw mechanism; 56. Third lead screw mechanism. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are for explaining the invention only and are not intended to limit the invention. In the description of this application, it should be understood that terms such as "left," "right," "upper," "lower," "vertical," "horizontal," "high," "lower," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application.

[0055] Example 1:

[0056] refer to Figures 1-7A method for laser cladding repair of APU turbine blade tips includes the following steps:

[0057] S10. Perform cleaning pretreatment on the defective areas of the blade to make the surface roughness of the blade less than the threshold.

[0058] The pre-treatment cleaning process includes mechanical polishing and chemical cleaning. First, mechanical cleaning removes oxide scale, fatigue layer, and crack propagation zones from the blade tip surface, achieving a surface roughness Ra ≤ 0.8 μm, creating a smooth surface for cladding. After polishing the blade surface, the area to be repaired is wiped clean with anhydrous ethanol or alcohol. Following cleaning, a visual inspection system is used to preliminarily assess the extent and depth of the damage.

[0059] S20. Use a scanning device to scan the blade and obtain the thickness distribution model of the blade; the control system generates the processing path of the laser cladding head based on the thickness distribution model.

[0060] The scanning equipment can employ a laser profilometer or a structured light 3D scanner to perform high-precision scanning of the profile from the inlet edge to the exhaust edge along the blade's length, acquiring point cloud data of the blade tip. The control system processes the point cloud data, for example, using point cloud data processing software Geomagic, to reconstruct the blade's thickness distribution model. This model can accurately identify the geometrical differences between the inlet and exhaust edges, showing that the inlet edge of the blade is thicker than the exhaust edge, and the blade's cross-section is wing-shaped.

[0061] The control system generates the processing path of the laser cladding head based on the thickness distribution model. The processing path can be a reciprocating scanning path or a spiral scanning path to ensure that the cladding layer can completely cover the area to be repaired and that the overlap rate is reasonable.

[0062] In this embodiment, the processing path can be constructed through the following steps:

[0063] S210. Establish a polar coordinate system with the geometric center or centroid of the blade section as the origin, and set the initial radius according to the maximum radial dimension of the blade profile. Initial radius The initial circumferential trajectory constructed by the initial radius should be determined based on the actual geometric dimensions of the blade tip so that it can completely cover the area to be repaired, allowing the first layer of cladding to completely cover the worn surface.

[0064] S220, Set the polar angle that increases with the processing progress. Establish information regarding the number of cladding layers. l and polar angle polar radius function ;in,

[0065] = ;

[0066] in, k The preset attenuation rate, k It can be 0.1, meaning that the cladding layer gradually decreases by 10% from bottom to top; It is the spiral expansion factor. The value can be between 0.1 and 0.5. Determined based on the curvature of the blades; number of cladding layers l Starting from 0, increment by 1 for each layer; polar angle The value starts from 0 degrees and increases by an increment of 0. .

[0067] Polar radius function By simulating tapering through exponential decay, the number of cladding layers is determined at the thicker parts of the blade. l Smaller, polar diameter Larger; in the thinner parts of the blade, the number of cladding layers is greater. l Larger, polar diameter Smaller.

[0068] S230, according to polar angle And through the polar radius function Calculated polar diameter Generate the planar coordinates of the processing path points ,in, , .

[0069] The machining path is offset according to the profile of the blade cross section.

[0070] By importing the sequence of processing path points into the control system, a continuous trajectory can be generated. The total number of turns of the processing path is determined according to the size of the blade.

[0071] S30. Install the blade onto the attitude adjustment assembly; based on the thickness distribution model, use the control system to adjust the cladding process parameters of the laser cladding head in real time, so that the power of the laser cladding head is proportional to the cross-sectional thickness of the blade, and the scanning speed of the laser cladding head is inversely proportional to the cross-sectional thickness of the blade.

[0072] During laser cladding, the laser cladding head 20 moves from the air inlet edge 11 to the air outlet edge 12 of the blade. At the air inlet edge 11, the laser cladding head 20 operates with higher power and a lower scanning speed to ensure complete melting. At the air outlet edge 12, the laser cladding head 20 operates with lower power and a higher scanning speed to prevent heat accumulation and burn-out. In this embodiment, the power of the laser cladding head 20 can be 160W~220W, and the scanning speed can be 1.5mm / s~3mm / s. For example, at the air inlet edge 11, the laser cladding head 20 can operate with 200W power and a scanning speed of 2mm / s; at the air outlet edge 12, the laser cladding head 20 can operate with 180W power and a scanning speed of 2.5mm / s.

[0073] Power of laser cladding head Satisfy the following formula:

[0074] ;

[0075] Scanning speed of laser cladding head Satisfy the following formula:

[0076] ;

[0077] in, x This represents the displacement distance from the starting point of the blade's air intake edge to the current machining position. L This is the total path length from the intake side to the exhaust side; The preset power of the laser cladding head at the air inlet edge of the blade; The preset power of the laser cladding head at the blade exhaust edge; The scanning speed of the laser cladding head on the inlet edge of the blade; denoted as , where is the scanning speed of the laser cladding head at the exhaust edge of the blade; > ; < .

[0078] laser power Depending on the cladding position x The power of the laser cladding head 20 decreases linearly with the increase of the air intake edge 11 to the exhaust edge 12 of the blade; that is, the power of the laser cladding head 20 gradually decreases from the air intake edge 11 to the exhaust edge 12. Depending on the cladding position x The scanning speed increases linearly with the increase of laser power, that is, from the inlet edge 11 to the exhaust edge 12 of the blade, the scanning speed gradually increases. Through the coordinated gradual change of laser power and scanning speed, continuous and smooth adjustment of heat input is achieved, avoiding the transition zone defects caused by abrupt parameter changes in the traditional segmented cladding method.

[0079] In terms of control implementation, the control system determines the boundary positions of the inlet edge 11 and the exhaust edge 12 based on the blade thickness distribution model and calculates the total path length. L During the cladding process, the control system monitors the current position of the laser cladding head 20 in real time. x Through the above formula ( and The system calculates the required power and scanning speed values ​​in real time. Laser power is adjusted by regulating the laser's output current, and scanning speed is adjusted by controlling the movement speed of the translation mechanism.

[0080] S40. The alloy powder is delivered to the laser cladding head 20 using the powder feeding system; at the same time, the protective gas is delivered to the laser cladding head 20 using the gas path system; and at the same time, the gas path system delivers an inert protective gas, such as argon or nitrogen, to the output end of the laser cladding head 20 to form a local protective atmosphere above the molten pool.

[0081] In step S40, the powder feeding system can deliver at least two types of alloy powders to the laser cladding head 20. The powder feeding system adjusts the proportion of alloy powders in different components in real time through a flow controller, and delivers the corresponding alloy powders to the laser cladding head 20 according to the real-time position of the laser cladding head 20.

[0082] In this embodiment, the powder feeding system may include two powder storage tanks 31, a first air source 32, a conveying pipe 33, and a mixing tank 34; the flow controller may consist of the first air source 32, the conveying pipe 33, and the mixing tank 34. A flow meter may be installed on each conveying pipe 33 to provide feedback to the control system on the powder flow rate conveyed by each conveying pipe 33, thereby accurately controlling the output of each type of powder.

[0083] The control system pre-calculates the powder delivery delay time based on the length of the powder delivery pipeline and the powder delivery airflow speed, and adjusts the opening of the solenoid valve in advance to ensure that the powder ratio change is synchronized with the spatial position of the laser head.

[0084] Two powder storage bins 31 are used to load the first powder and the second powder, respectively. The first powder can be a wear-resistant reinforcing powder containing tungsten carbide (WC) particles, and the second powder can be a high-temperature resistant nickel oxide-based powder containing rare earth elements, such as yttrium and cerium.

[0085] The powder storage tank 31 is connected to the mixing tank 34 through the conveying pipe 33. The discharge port of the powder storage tank 31 is equipped with a solenoid valve that is electrically connected to the control system. The solenoid valve can adjust the outlet opening with a response speed of milliseconds. One end of the mixing tank 34 is connected to the first air source 32, and the other end of the mixing tank 34 is connected to the powder channel 211 of the laser cladding head 20 through the conveying pipe 33.

[0086] The powder storage tank 31 conveys different amounts of powder to the mixing tank 34 via the conveying pipe 33. The first gas source 32 fills the mixing tank 34 with high-pressure inert gas. The high-pressure gas drives the first powder and the second powder to mix within the mixing tank 34, and then the mixture is conveyed to the laser cladding head 20 via the conveying pipe 33 and discharged. It should be noted that when the first powder and the second powder are mixed in the mixing tank 34, the volume of the cavity inside the mixing tank 34, excluding the powder, is much larger than the volume of the powder. At this time, the high-pressure gas filling the mixing tank 34 can fully mix the first powder and the second powder. The discharge port of the mixing tank 34 can also be equipped with a solenoid valve.

[0087] During the laser cladding operation, when the laser cladding head 20 is located at the air inlet edge 11 of the blade, it is necessary to focus on improving the erosion resistance of the blade 10, so the proportion of the first powder is increased; at the exhaust edge 12 of the blade, it is necessary to focus on improving the oxidation resistance of the blade 10, so the proportion of the second powder is increased; the solenoid valve on the control system conveying pipe 33 sends a command to adjust the powder output flow rate of the two powder storage tanks 31 respectively, so that the proportion of the mixed powder meets the current requirements.

[0088] The alloy powder conveyed by the powder feeding system includes at least a first powder and a second powder. The first powder contains components for improving the erosion resistance of the blade 10, and the second powder contains components for improving the oxidation resistance of the blade 10; the ratio of the first powder to the second powder... Satisfy the following formula:

[0089] = ;

[0090] in, x This is the displacement distance from the starting point of the air intake edge 11 of the blade 10 to the current machining position; L This is the total path length from intake side 11 to exhaust side 12; The proportion of the first powder when the laser cladding head 20 is at the air inlet edge 11 of the blade; The proportion of the first powder at the exhaust edge 12 of the blade when the laser cladding head is in the exhaust.

[0091] Mixing ratio Depending on the cladding position x The proportion of the first powder gradually decreases and the proportion of the second powder gradually increases as the intake side 11 increases to the exhaust side 12. It is easy to control and can ensure a continuous and smooth transition of the powder proportion, avoiding interface defects caused by abrupt changes in composition.

[0092] S50. The laser cladding head 20 is driven by the translation mechanism to clad the blade 10 layer by layer according to the processing path. The laser cladding head 20 is equipped with an acousto-optic deflector 24 and an electro-optic deflector 25. The control system controls the acousto-optic deflector 24 to adjust the geometric size of the light spot in real time according to the thickness distribution model, and controls the electro-optic deflector 25 to adjust the energy density distribution inside the light spot.

[0093] At the air intake edge 11 of the blade 10, the acousto-optic deflector 24 adjusts the light spot into a larger rectangle, and the electro-optic deflector 25 adjusts the energy distribution into a more concentrated flat-top distribution to achieve efficient melting; at the exhaust edge 12 of the blade 10, the acousto-optic deflector 24 adjusts the light spot into a smaller slender shape, and the electro-optic deflector 25 adjusts the energy distribution into a more dispersed distribution to reduce the heat input density.

[0094] The acousto-optic deflector 24 utilizes the beam deflection effect induced by high-frequency acoustic waves. By changing the frequency of its ultrasonic drive signal, it enables the laser beam to reciprocate at high speed, thereby expanding the point beam into a rectangular envelope shape in space.

[0095] The electro-optic deflector 25 utilizes the phase delay effect of light waves controlled by an electric field to adjust the energy density distribution and polarization direction inside the beam by changing the driving voltage at its electric terminals.

[0096] The control system controls the acousto-optic deflector 24 and the electro-optic deflector 25 in real time according to the thickness distribution model, so that the light spot projected on the inlet edge 11 of the blade is a first rectangular shape and the light spot projected on the exhaust edge 12 of the blade is a second rectangular shape; wherein, the width of the first rectangle is greater than the width of the second rectangle, so that the width of the light spot shrinks synchronously as the cross-sectional thickness of the blade 10 decreases; the length of the first rectangle is greater than or equal to the length of the second rectangle, so as to control the amount of heat accumulation at the edge of the exhaust edge 12; the long sides of the first rectangle and the second rectangle are both parallel to the length direction of the blade 10.

[0097] S60. After the blade 10 is clad, the blade 10 is subjected to cooling treatment, stress relief and quality inspection.

[0098] After the cladding is completed, the inert gas protection time is appropriately delayed, and the blade 10 is removed from the attitude adjustment assembly after cooling to room temperature. Stress relief annealing is then carried out within 8 hours.

[0099] Quality inspection includes: using fluorescent penetrant testing on blade 10 to ensure that there are no cracks, pores or other defects on the surface of blade 10; and conducting X-ray inspection after penetrant testing to check that there are no cracks, pores or other defects inside the cladding layer.

[0100] Before quality inspection, the repair area of ​​blade 10 needs to be precision ground to ensure the dimensional accuracy of the blade tip and that the aerodynamic profile is consistent with the original design.

[0101] In this embodiment, a laser cladding repair device is also provided, including a laser cladding head 20, an attitude adjustment component, a control system, a powder feeding system, an air path system, and a translation mechanism.

[0102] The laser cladding head 20 includes the following components arranged sequentially along the laser transmission optical axis:

[0103] Laser input interface 22 is used to introduce a high-power laser beam;

[0104] Collimating lens 23 is used to convert the introduced laser beam into parallel light; collimating lens 23 can be a biconvex lens;

[0105] The beam shaping module, including an acousto-optic deflector 24 and an electro-optic deflector 25, is used to stretch the geometry of parallel light and modulate its energy distribution to obtain a first laser beam.

[0106] The diffractive optical element group 26 is used to perform preliminary auxiliary modification of the first laser beam with a preset profile to obtain the second laser beam;

[0107] The focusing lens group 27 is used to focus the second laser beam onto the processing area on the surface of the blade 10. The focusing lens group 27 has an adjustable focal length.

[0108] The output window 28 is protected to allow the second laser beam to pass through and to physically isolate processing splashes.

[0109] The laser cladding head 20 also includes a housing 21, on which a laser input interface 22, a collimating lens 23, a beam shaping module, a diffractive optical element group 26, a focusing lens group 27, and a protective output window 28 are all mounted. The distances between the collimating lens 23, the beam shaping module, the diffractive optical element group 26, the focusing lens group 27, and the protective output window 28 can be set as needed.

[0110] A copper base 29 with a water-cooling channel can be installed inside the housing 21. The acousto-optic deflector 24 is mounted on the copper base 29. The copper base 29 has an RF signal line interface on its side, allowing the acousto-optic deflector 24 to be electrically connected to the control system through this interface. The acousto-optic deflector 24 utilizes the acousto-optic effect to form an acousto-optic grating inside the crystal through an RF drive signal, causing the laser beam to deflect. By controlling the RF frequency, rapid scanning of the laser beam can be achieved, thereby equivalently forming light spots of different shapes.

[0111] The electro-optic deflector 25 utilizes the electro-optic effect to change the refractive index of the crystal through voltage drive, thereby achieving sub-microsecond modulation of the beam phase and optimizing the energy distribution inside the beam spot.

[0112] The diffractive optical element group 26 may contain multiple DOE (optical element) lenses, which can shape the Gaussian distributed laser beam into a flat-top distribution or a ring distribution to adapt to different cladding requirements.

[0113] The focusing lens group 27 can be a biconvex lens group with a focal length range of 100-200mm. The size of the focused spot can be continuously adjusted by adjusting the lens spacing.

[0114] The protective output window 28 can be made of high-transmittance quartz glass with an anti-reflection coating on the surface to reduce laser reflection loss.

[0115] The laser cladding head 20 is provided with a powder channel 211 for spraying alloy powder. The powder channel 211 surrounds the outer side of the protective output window 28 and is in the shape of a rectangular ring. The inner wall of the powder channel 211 on the outer diameter side is made of a flexible metal sheet 212. The flexible metal sheet 212 can be beryllium bronze or stainless steel foil, with a thickness of 0.1~0.2mm, and has good elasticity and fatigue life. A micro pressure actuator 213 is integrated on the back of the flexible metal sheet 212. The micro pressure actuator 213 is electrically connected to the control system. The micro pressure actuator 213 can generate radial displacement according to the voltage to drive the flexible metal sheet 212 to change the opening size of the powder channel 211 outlet.

[0116] When the acousto-optic deflector 24 adjusts the spot size, the control system synchronously applies a corresponding driving voltage to the micro-pressure actuator 213, causing the rectangular outlet size of the powder channel 211 to change accordingly. For example, when the acousto-optic deflector 24 adjusts the spot to a larger size, the micro-pressure actuator 213 drives the flexible metal sheet 212 to expand outward, widening the outlet of the powder channel 211 and widening the ejected powder beam to match the spot size. When the spot size is adjusted to a smaller size, the outlet of the powder channel 211 contracts, and the powder beam narrows. This ensures that the powder beam can always accurately cover the spot area, improving powder utilization efficiency and reducing powder waste.

[0117] The laser cladding head 20 is also provided with a gas delivery channel 214 for spraying protective gas. The gas delivery channel 214 surrounds the outside of the powder channel 211 and is in the shape of a rectangular ring, forming a concentric nested structure with the powder channel 211. After the protective gas is sprayed out from the gas delivery channel 214, it can form a uniform air curtain around the powder bundle, effectively isolating the outside air, while not interfering with the convergence characteristics of the powder flow.

[0118] The gas supply system may include a second gas source, a gas pipeline, a flow controller, and a gas delivery channel 214. During the cladding process, the second gas source supplies inert protective gas, which can be argon or helium, to the gas delivery channel 214 via the gas pipeline. The flow controller, which can be a solenoid valve and is located on the gas pipeline, regulates the gas flow rate in real time. This regulates the opening of the gas pipeline, ensuring that the outlet gas velocity of the gas delivery channel 214 is controlled within the range of 5-20 L / min. If the flow rate is too low, it will not effectively isolate air; if the flow rate is too high, it may disturb the molten pool or cause powder to scatter.

[0119] The attitude adjustment assembly includes a first base 41, a second base 42, a first drive motor 43, a second drive motor 44, a mounting platform 45, and a clamp.

[0120] The first drive motor 43 is mounted on the first base 41 and is used to drive the second base 42 to rotate around the Y-axis; the second drive motor 44 is mounted on the second base 42 and is used to drive the mounting platform 45 to rotate around the X-axis; the clamp is mounted on the mounting platform 45 and is used to clamp the blade 10, so that the long axis of the blade 10 is parallel to the plane XOZ.

[0121] The attitude adjustment component adopts a dual-axis orthogonal rotation structure, which can realize the attitude adjustment of the blade 10 in two degrees of freedom in space, ensuring that the surface of the blade 10 to be repaired always maintains a perpendicular relationship with the laser cladding head 20.

[0122] The first drive motor 43 is mounted on the first base 41, and its output shaft is connected to the second base 42 for driving the second base 42 to rotate around the Y-axis. The Y-axis rotation is used to adjust the swing angle of the blade 10 in the horizontal plane to accommodate the curved geometry of the blade 10. The second drive motor 44 is mounted on the second base 42, and its output shaft is connected to the mounting platform 45 for driving the mounting platform 45 to rotate around the X-axis. The X-axis rotation is used to adjust the pitch angle of the blade 10 in the vertical plane to ensure that the surface to be repaired is horizontal. The first drive motor 43 and the second drive motor 44 can be servo motors or stepper motors, working in conjunction with a high-precision encoder to achieve closed-loop angle control, with a rotation accuracy of ±0.01°.

[0123] A clamp is mounted on a mounting platform 45 and is used to clamp the blade 10. The clamp may include a connecting seat 461, a clamping motor 462, a lead screw 463, and two clamping blocks 464. The connecting seat 461 is fixed to the mounting platform 45, one clamping block 464 is fixed to the connecting seat 461, and the other clamping block 464 is slidably mounted on the connecting seat 461 and threadedly connected to the lead screw 463. The clamping motor 462 is fixed to the connecting seat 461 and is used to drive the lead screw 463 to rotate. When the clamping motor 462 rotates, it causes one of the clamping blocks 464 to slide relative to the connecting seat 461, changing the distance between the two clamping blocks 464, thereby achieving the function of clamping or releasing the blade 10.

[0124] The clamping block 464 may be equipped with a rubber pad 465 with teeth for contacting the base of the blade 10 to avoid damaging the blade 10.

[0125] During the attitude adjustment process, the control system first determines the normal direction of the surface to be repaired based on the thickness distribution model of the blade 10, and then calculates the rotation angles of the Y-axis and X-axis that need to be adjusted. The first drive motor 43 and the second drive motor 44 act according to the instructions of the control system, driving the blade 10 to rotate to the target attitude. During the cladding process, the blade 10 moves along the processing path with the laser cladding head 20. The control system can also fine-tune the attitude in real time according to the changes in the curvature of the blade 10 to achieve dynamic pose compensation.

[0126] The attitude adjustment component may also include a position sensor, which is mounted on the mounting platform 45 and electrically connected to the control system. The position sensor monitors the actual spatial position of the blade 10 in real time and feeds back the detected value to the control system, which then adjusts the attitude adjustment component in real time based on the detected value.

[0127] The attitude adjustment assembly also includes a first heat-conducting element 47, a second heat-conducting element 48, a cooling water circulation unit (not shown in the figure), a mounting base 49, and a universal bracket 410. The first heat-conducting element 47 and the second heat-conducting element 48 are both mounted on the mounting base 49. The first heat-conducting element 47 is used to abut against the air intake edge 11 of the blade 10, and the second heat-conducting element 48 is used to abut against the exhaust edge 12 of the blade 10. A heat-insulating gasket 411 is provided between the first heat-conducting element 47 and the blade 10. The second heat-conducting element 48 is made of a high thermal conductivity metal material and is connected to the cooling water circulation unit. The mounting base 49 is mounted on the universal bracket 410.

[0128] One end of the first heat-conducting element 47 is provided with a first mounting groove for engaging the air inlet end of the blade 10. The other end of the first heat-conducting element 47 slides through the mounting base 49. A compression spring 412 is sleeved on the outside of the first heat-conducting element 47, with both ends of the compression spring 412 abutting against the first heat-conducting element 47 and the mounting base 49, respectively. A first limiting block 471 is also provided at the end of the first heat-conducting element 47 away from the first mounting groove. The mounting base 49 is provided with a first mounting hole adapted to the first heat-conducting element 47. The cross-sectional area of ​​the first limiting block 471 is larger than the area of ​​the first mounting hole. The first limiting block 471 is used to prevent the first heat-conducting element 47 from detaching from the mounting base 49.

[0129] One end of the second heat-conducting element 48 is provided with a second mounting groove for engaging the air inlet end of the blade 10. The other end of the second heat-conducting element 48 slides through the mounting base 49. A compression spring 412 is sleeved on the outside of the second heat-conducting element 48, with both ends of the compression spring 412 abutting against the second heat-conducting element 48 and the mounting base 49, respectively. A second limiting block 481 is also provided at the end of the second heat-conducting element 48 away from the second mounting groove. The mounting base 49 is provided with a second mounting hole adapted to the second heat-conducting element 48. The cross-sectional area of ​​the second limiting block 481 is larger than the area of ​​the second mounting hole. The second limiting block 481 is used to prevent the second heat-conducting element 48 from detaching from the mounting base 49.

[0130] When installing the blade 10 with the first heat-conducting element 47 and the second heat-conducting element 48, simply pull the first heat-conducting element 47 and the second heat-conducting element 48 away from each other, and then place the first heat-conducting element 47 and the second heat-conducting element 48 on both sides of the blade 10 respectively. At this time, release the first heat-conducting element 47 and the second heat-conducting element 48, and the compression spring 412 can drive the first heat-conducting element 47 and the second heat-conducting element 48 to clamp the blade 10. The operation is simple.

[0131] In this embodiment, the heat insulation pad 411 can be made of ceramic fiber or aerogel material to block heat loss from the air intake edge 11 of the blade 10, keeping the air intake edge 11 area at a higher temperature; the second heat-conducting element 48 is made of a high thermal conductivity metal material, such as copper or molybdenum alloy, and has water-cooled microchannels inside, which are connected to the cooling water circulation unit. The cooling water circulates in the water-cooled microchannels at a flow rate of 0.1-0.5 m / s, quickly removing heat from the exhaust edge 12 area.

[0132] The first heat-conducting element 47, the heat-insulating pad 411, the second heat-conducting element 48, and the cooling water circulation unit (not shown in the figure) constitute an asymmetric heat-conducting structure, resulting in a temperature gradient inside the blade 10: the inlet edge 11 has a higher temperature and slower heat dissipation; the exhaust edge 12 has a lower temperature and faster heat dissipation. During laser cladding, when the molten pool solidifies, the grains tend to grow along the direction of the largest temperature gradient, that is, from the low-temperature exhaust edge 12 to the high-temperature inlet edge 11, forming a directional columnar crystal structure. By controlling the cooling water flow rate and the thickness of the heat-insulating pad 411, the magnitude of the temperature gradient can be precisely adjusted, thereby controlling the size and orientation of the columnar crystals.

[0133] Mounting base 49 is mounted on universal bracket 410. The two ends of universal bracket 410 are connected to mounting base 49 and worktable 51 respectively through ball joints, so that when the spatial position of blade 10 changes, the first heat conduction element 47 and the second heat conduction element 48 can always maintain good contact with the surface of blade 10 and are not affected by the twisted shape of blade 10.

[0134] The first heat-conducting element 47 and the second heat-conducting element 48 may also be equipped with pressure sensors electrically connected to the control system to monitor the contact pressure between the heat-conducting element and the blade 10, so as to prevent excessive pressure from causing deformation of the blade 10 or insufficient pressure from causing poor contact.

[0135] The laser cladding head 20 is equipped with a monitoring system (not shown in the figure) electrically connected to the control system. The monitoring system includes:

[0136] Infrared thermometers are used to collect instantaneous temperature signals on the surface of the molten pool in real time. When the temperature exceeds the set threshold, the control system adjusts the laser power in time to prevent overheating from causing burn-through or element loss.

[0137] An industrial camera is used to capture images of the geometric shape of the molten pool. Image recognition algorithms are used to extract the width and aspect ratio data of the molten pool. The size and shape of the molten pool reflect the magnitude and distribution of heat input. When the rate of increase in the width of the molten pool exceeds a threshold, it indicates that the heat input is too large, and the power of the laser cladding head 20 needs to be reduced or the scanning speed increased. When the length of the molten pool is too long, it indicates that the heat dissipation conditions are poor, and cooling needs to be strengthened.

[0138] A laser displacement sensor is used to monitor the real-time accumulation height of the cladding layer along the length of the blade 10. During the cladding process, the displacement sensor scans the surface contour of the cladding layer and compares it with the target model stored in the control system to calculate the current height deviation of the cladding layer. When the height deviation exceeds ±0.03mm, the control system adjusts the powder feeding amount or path offset during the next layer cladding to compensate, so that the repair size meets the requirements.

[0139] The target model is the data model of the undamaged blade 10.

[0140] In this embodiment, the translation mechanism is used to drive the laser cladding head 20 to move along the X, Y, and Z axes. The translation mechanism includes a worktable 51, a frame 52, a slide 53, a first lead screw mechanism 54, a second lead screw mechanism 55, and a third lead screw mechanism 56; the first lead screw mechanism 54 is used to drive the worktable 51 to move along the X-axis; the attitude adjustment component is disposed on the worktable 51; the second lead screw mechanism 55 is disposed on the frame 52 and is used to drive the slide 53 to move along the Y-axis; the third lead screw mechanism 56 is disposed on the slide 53 and is used to drive the laser cladding head 20 to move along the Z-axis.

[0141] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0142] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Additionally, the term "connection" as used herein, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

Claims

1. A method for laser cladding repair of APU turbine blade tips, characterized in that, Includes the following steps: S10. Perform cleaning pretreatment on the defective areas of the blade to make the surface roughness of the blade less than the threshold. S20. The blade is scanned using a scanning device to obtain a thickness distribution model of the blade; the control system generates the processing path of the laser cladding head based on the thickness distribution model. In step S20, the processing path is constructed through the following steps: S210. Establish a polar coordinate system with the geometric center or centroid of the blade section as the origin, and set the initial radius according to the maximum radial dimension of the blade profile. The initial circular trajectory constructed by the initial radius can completely cover the area to be repaired. S220, Set the polar angle that increases with the processing progress. Establish information regarding the number of cladding layers. l and the polar angle polar radius function ;in, = ； in, k The preset attenuation rate; It is the spiral expansion factor; S230, according to the polar angle and through the polar radius function Calculated polar diameter Generate the planar coordinates of the processing path points ,in, , ; S30. Install the blade onto the attitude adjustment assembly; based on the thickness distribution model, use the control system to adjust the cladding process parameters of the laser cladding head in real time, so that the power of the laser cladding head is proportional to the cross-sectional thickness of the blade, and the scanning speed of the laser cladding head is inversely proportional to the cross-sectional thickness of the blade. S40. The alloy powder is first mixed using a powder feeding system, and then the mixed alloy powder is conveyed to the laser cladding head. At the same time, an inert protective gas is delivered to the output end of the laser cladding head using a gas path system to form a local protective atmosphere above the molten pool. S50. The laser cladding head is driven by a translation mechanism to clad the blade layer by layer according to the processing path; wherein, the laser cladding head is equipped with an acousto-optic deflector and an electro-optic deflector; the control system controls the acousto-optic deflector to adjust the geometric size of the light spot in real time according to the thickness distribution model, and controls the electro-optic deflector to adjust the energy density distribution inside the light spot. S60. After the blade cladding is completed, the blade is subjected to cooling treatment, stress relief and quality inspection.

2. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, In step S30, the attitude adjustment assembly includes a first base, a second base, a first drive motor, a second drive motor, a mounting platform, and a clamp. The first drive motor is mounted on the first base and is used to drive the second base to rotate around the Y-axis; the second drive motor is mounted on the second base and is used to drive the mounting platform to rotate around the X-axis; the clamp is mounted on the mounting platform and is used to clamp the blade so that the long axis of the blade is parallel to the plane XOZ.

3. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, The power of the laser cladding head Satisfy the following formula: ； The scanning speed of the laser cladding head Satisfy the following formula: ； in, x This represents the displacement distance from the starting point of the blade's air intake edge to the current machining position. L This is the total path length from the intake side to the exhaust side; The preset power of the laser cladding head at the air inlet edge of the blade; The preset power of the laser cladding head at the blade exhaust edge; The scanning speed of the laser cladding head at the air inlet edge of the blade; The scanning speed of the laser cladding head at the exhaust edge of the blade; wherein, > ; < .

4. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, In step S40, the powder feeding system can deliver at least two types of alloy powders to the laser cladding head. The powder feeding system adjusts the proportion of alloy powders in different components in real time through a flow controller, and delivers the corresponding alloy powders to the laser cladding head according to the real-time position of the laser cladding head.

5. The method for laser cladding repair of APU turbine blade tips according to claim 4, characterized in that, The alloy powder conveyed by the powder feeding system includes at least a first powder and a second powder. The first powder contains components for improving the blade's erosion resistance, and the second powder contains components for improving the blade's oxidation resistance. The ratio of the first powder to the second powder... Satisfy the following formula: = ； in, x This represents the displacement distance from the starting point of the blade's air intake edge to the current machining position. L This is the total path length from the intake side to the exhaust side; The proportion of the first powder at the air inlet edge of the blade when the laser cladding head is used; The proportion of the first powder when the laser cladding head is at the blade exhaust edge.

6. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, The laser cladding head includes the following components arranged sequentially along the laser transmission optical axis: Laser input interface for introducing high-power laser beams; Collimating lenses are used to convert an introduced laser beam into parallel light; The beam shaping module, including the acousto-optic deflector and the electro-optic deflector, is used to geometrically stretch and modulate the energy distribution of parallel light to obtain a first laser beam; A diffractive optical element group is used to perform preliminary auxiliary modification of the first laser beam with a preset contour to obtain a second laser beam; A focusing lens group is used to focus the second laser beam onto the processing area on the blade surface, and the focusing lens group has an adjustable focal length structure; A protective output window is provided to allow the second laser beam to pass through while physically isolating processing spatter.

7. The method for laser cladding repair of APU turbine blade tips according to claim 6, characterized in that, The laser cladding head is provided with a powder channel for spraying alloy powder. The powder channel surrounds the outside of the protective output window and is in the shape of a rectangular ring. The inner wall of the powder channel on the outer diameter side is made of a flexible metal sheet. A micro pressure actuator is integrated on the back of the flexible metal sheet. The micro pressure actuator is electrically connected to the control system. The micro pressure actuator can generate radial displacement according to the voltage to drive the flexible metal sheet to change the opening size of the powder channel outlet.

8. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, In step S30, the attitude adjustment assembly further includes a first heat-conducting element, a second heat-conducting element, a cooling water circulation unit, a mounting base, and a universal bracket; both the first heat-conducting element and the second heat-conducting element are disposed on the mounting base, the first heat-conducting element is used to abut against the air inlet side of the blade, and the second heat-conducting element is used to abut against the air outlet side of the blade; a heat-insulating gasket is provided between the first heat-conducting element and the blade; the second heat-conducting element is made of a high thermal conductivity metal material, and the second heat-conducting element is connected to the cooling water circulation unit; the mounting base is disposed on the universal bracket.

9. The method for laser cladding repair of APU turbine blade tips according to claim 1, characterized in that, The laser cladding head is equipped with a monitoring system electrically connected to the control system, the monitoring system comprising: Infrared thermometers are used to collect instantaneous temperature signals on the surface of the molten pool in real time. Industrial cameras are used to capture images of the geometric shape of the molten pool and extract the width and aspect ratio data of the molten pool through image recognition algorithms; A laser displacement sensor is used to monitor the real-time stacking height of the cladding layer along the blade length.

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