Method for producing a tailored surface coating with real-time adjustable laser deposition profile

Abstract

The application provides a laser deposition contour real-time adjustable follow-up surface coating preparation method, comprising the following steps: determining two side boundary lines of a coating preparation area and a center curve equidistant to the two side boundary lines; taking the center curve as a spatial motion track of a laser spot center point; fitting the two side boundary lines to obtain a curve equation, and making a difference to obtain a distance equation between the two boundary curves; taking the distance equation as a laser spot adjustment basis, adjusting the size of a square laser spot in real time according to the distance between two points on the two side boundary lines in a laser cladding process, so that the laser spot size is consistent with the coating contour, and the powder feeding width is synchronously adjusted to be consistent with the size of the laser spot, and the laser deposition contour real-time adjustable follow-up preparation is realized. Through the application, the laser beam coverage size can be changed in real time for the gradual change boundary contour shape of a workpiece, and the dynamic adjustment of the powder feeding width is combined, so that the problem that the laser deposition area of the workpiece is a gradual change contour and needs to be deposited and formed at one time is solved.

Description

Technical Field

[0001] This invention relates to the field of laser cladding technology, and more specifically to a method for preparing conformal surface coatings with real-time adjustable laser deposition profiles. Background Technology

[0002] Laser cladding additive manufacturing technology is an advanced manufacturing technology that enables rapid, short-process manufacturing and performance and microstructure control. The laser cladding layer prepared by this technology has the advantages of low dilution rate and metallurgical bonding with the substrate. It can significantly improve the wear resistance, corrosion resistance, heat resistance, oxidation resistance or electrical properties of the substrate material surface, thereby achieving the purpose of surface modification or repair. While meeting the specific performance requirements of the material surface, it can save a lot of material costs.

[0003] There are two common powder feeding methods for laser cladding: pre-feeding and synchronous feeding. Pre-feeding involves pre-covering the substrate surface with alloy powder material, then scanning the pre-coated surface with a laser beam. The pre-coated surface absorbs laser energy, causing its temperature to rise and melt. Simultaneously, heat is transferred from the surface to the interior through thermal conduction. After the laser beam leaves, the molten metal quickly solidifies on the substrate surface, forming a metallurgically bonded alloy cladding layer. Synchronous feeding uses a specialized conveyor to directly feed the alloy material into the laser action zone. Before reaching the melting zone, the powder passes through the beam, is heated to a red-hot state, and melts immediately upon entering the melting zone, forming the alloy cladding layer along with the substrate.

[0004] Synchronous powder feeding is further divided into synchronous lateral powder feeding and coaxial powder feeding. Synchronous lateral powder feeding has a simple structure and lower price, but its powder utilization rate is low and the cladding quality is relatively poor. It is suitable for laser cladding of planar and axial surfaces. Coaxial powder feeding, on the other hand, has a complex structure, preheated powder, good cladding quality, and strong versatility. However, pre-feeding laser cladding requires a high degree of precision in the workpiece structure shape, making it difficult to prepare coatings for inclined, arc-shaped, and irregularly shaped curved workpieces. Synchronous powder feeding laser cladding improves adaptability to different workpiece structures; however, the size of the powder convergence point is often not adjustable in real time.

[0005] For workpieces with gradually changing contours, it is almost impossible to achieve the above process by simultaneously adjusting the powder size and the spot size in real time. Summary of the Invention

[0006] The purpose of this invention is to address the technical problem of preparing coatings in gradient contour areas by proposing a conformal surface coating preparation method with real-time adjustable laser deposition contour. This method enables real-time changes in the laser beam coverage size based on the gradient boundary contour shape of the workpiece, and solves the problem of the workpiece laser deposition area having a gradient contour and requiring one-time deposition by dynamically adjusting the powder delivery width.

[0007] According to a first aspect of the present invention, a method for preparing conformal surface coatings with real-time adjustable laser deposition profiles is provided, comprising the following steps:

[0008] Based on the coating preparation area on the surface of the workpiece to be processed, determine the two side boundary lines of the coating preparation area, and the center curve equidistant from the two side boundary lines;

[0009] Configure the spatial motion trajectory of the square laser spot for laser cladding with the central curve as the center point, and control the movement of the laser cladding head.

[0010] Based on the two boundary lines of the coating preparation area, the curve equations of the two boundary lines are respectively fitted, and the difference between the two curve equations is used to obtain the equation of the distance between the two boundary curves.

[0011] Using the equation for the distance between the two boundary curves as the basis for adjusting the square laser spot during the laser cladding process, the size of the square laser spot is adjusted in real time according to the distance between two points on the two boundary lines during the laser cladding process, so that the size of the square laser spot is consistent with the coating contour, and the powder feeding width is adjusted simultaneously to be consistent with the size of the square laser spot, thereby realizing the conformal preparation with real-time adjustable laser deposition contour.

[0012] As an optional embodiment, based on the three-dimensional model or two-dimensional drawing of the workpiece to be processed, the two side boundary lines of the coating preparation area and the center curve equidistant from the two side boundary lines are determined.

[0013] As an optional embodiment, polynomial fitting is used to obtain the curve equations of the two boundary lines.

[0014] As an optional embodiment, the step of adjusting the size of the square laser spot in real time according to the distance between two points on the two boundary lines during the laser cladding process includes:

[0015] Based on the distance between two points on the boundary lines on both sides during the laser cladding process, the size of the long side of the square laser spot is adjusted in real time. Taking the intersection of the line connecting the two points and the center curve as a reference, the size of the long side of the square laser spot is adjusted in both directions with equal amount to ensure that the size of the long side of the square laser spot is consistent with the distance between the two points.

[0016] As an optional embodiment, the length of the square laser spot can be adjusted in real time by controlling the movement of the motor adjusted by the mirror assembly inside the laser cladding head.

[0017] As an optional embodiment, the size adjustment control signal of the square laser spot and the motion trajectory control signal of the center point of the square laser spot are started and stopped simultaneously.

[0018] As an optional embodiment, a broadband powder delivery method with a multi-tube unidirectional array arrangement is adopted. The powder delivery system is synchronously controlled to adjust the on / off state of different powder delivery tubes in real time according to the real-time adjustment of the square laser spot, so as to adjust the powder delivery width and make the adjusted powder width consistent with the long side dimension of the square laser spot, thereby realizing conformal preparation.

[0019] As an optional embodiment, a set of on / off switches is provided at both the powder feeder end and the laser cladding head end to control the output and shut-off of powder, so as to keep the speed of powder conveying width change consistent with the speed of square laser spot change.

[0020] As an optional embodiment, circular powder feeding tubes arranged in a straight line are used at the laser cladding head. The powder convergence point size of a single powder feeding tube is controlled at 0.5 mm, and the overlap area between the powder convergence points of two adjacent powder feeding tubes is set at 0.2 mm.

[0021] As an optional embodiment, based on the synchronous control of the size of the square laser spot and the spatial motion trajectory of the center of the square laser spot, the coverage size of the square laser spot based on the gradient boundary contour shape of the workpiece can be adjusted in real time. Combined with the dynamic adjustment of the powder delivery width by the size of the square laser spot, a one-time deposition preparation of the laser deposition area with a gradient contour can be achieved.

[0022] Based on the above technical solutions of the present invention, a conformal surface coating preparation method with real-time adjustable laser deposition profile is proposed to address the technical problem of preparing coatings in gradient contour regions. This method enables real-time changes in the laser beam coverage size based on the gradient boundary contour shape of the workpiece, and solves the problem of the workpiece laser deposition area having a gradient contour and requiring one-time deposition by dynamically adjusting the powder delivery width.

[0023] Compared with existing technologies, the laser deposition contour-adjustable conformal surface coating preparation method proposed in this invention has significant advantages in adaptability and process control for coating preparation with gradient contours, as detailed below:

[0024] (1) The conformal surface coating preparation method based on laser cladding of the present invention first determines the two side boundary lines and the center curve of the coating preparation area. By fitting the boundary line equation and subtracting it, the spacing equation is obtained, which is used as the basis for adjusting the size of the laser spot. The size of the square laser spot is adjusted in real time according to the gradient boundary contour of the workpiece, so that the spot size is consistent with the coating contour. Especially for workpieces with complex curve shapes and gradient contours, whether the boundary changes are convex or concave, the laser spot can be accurately fitted to the boundary to achieve precise contour matching, thereby ensuring that laser deposition can be uniformly carried out in the entire gradient contour area, effectively solving the problem of the laser deposition area of ​​the workpiece being a gradient contour. Furthermore, the present invention adjusts the laser spot size in real time and adjusts the powder feeding width synchronously, so that the deposition can be completed in one go when processing workpieces with gradient contours. Unlike the traditional method that requires multiple processing or subsequent additional processing of the gradient area, the conformal surface coating preparation method proposed in the present invention reduces the processing steps, improves the processing efficiency, and can better guarantee the quality and overall performance of the coating, avoiding problems such as uneven coating and weak bonding that may be caused by multiple processing.

[0025] (2) When adjusting the long side dimension of the square laser spot (i.e. the length between the points on the two boundary lines), the intersection of the line connecting the two points on the two boundary lines and the center curve is used as the reference. The two sides of the axis of symmetry are adjusted in both directions with equal amount. The symmetrical adjustment can ensure the relative stability of the spot shape and can more accurately adapt to the gradient contour. By controlling the movement of the mirror group adjustment motor inside the laser cladding head, the adjustment can be made quickly and accurately according to the change of the boundary spacing. At the same time, the size adjustment control of the square laser spot and the movement trajectory control of the center point of the square laser spot are started and stopped at the same time (and synchronized with the powder width adjustment). This ensures the synchronization of the movement trajectory and size adjustment of the spot in time, avoids the mismatch between the spot and the coating area due to the time difference, and makes the whole laser deposition process more coordinated and efficient.

[0026] (3) Combining a broadband powder delivery method using a multi-tube unidirectional array arrangement, the powder delivery system is synchronously controlled to adjust the on / off state of different powder delivery pipes in real time according to the real-time adjustment of the square laser spot, thereby adjusting the powder delivery width. Simultaneously, by setting a set of on / off switches at both the powder feeder end and the laser cladding head end, the powder output and shutdown are controlled, ensuring that the change in powder delivery width matches the speed of change in the square laser spot. The synchronous control mechanism of this invention ensures that the powder supply and the size of the laser spot remain matched throughout the laser deposition process, guaranteeing the stability of the coating quality and improving the quality and precision of conformal molding.

[0027] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below may be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Furthermore, all combinations of the claimed subject matter are considered part of the inventive subject matter of this disclosure.

[0028] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0029] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of the boundary lines on both sides of the gradient contour area and the equidistant center line in an exemplary embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram illustrating the adjustment of the long side dimension of a square laser beam according to an exemplary embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of a powder width control method according to an exemplary embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram illustrating the positional relationship between the powder convergence point and the square laser beam in an exemplary embodiment of the present invention.

[0034] The meanings of the various markings in the attached diagram are as follows:

[0035] A: The starting point of the centerline equidistant from the two boundary lines;

[0036] B: The endpoint of the centerline equidistant from the two boundary lines;

[0037] l: Half the length of the laser spot;

[0038] L1: Length of the square laser spot;

[0039] L2: Width of powder aggregation point. Detailed Implementation

[0040] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0041] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0042] {Example 1}

[0043] Combination Figures 1-4 As shown, the method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to an embodiment of the present invention includes the following steps:

[0044] Based on the coating preparation area on the surface of the workpiece to be processed, determine the two side boundary lines of the coating preparation area, and the center curve equidistant from the two side boundary lines;

[0045] Configure the spatial motion trajectory of the square laser spot for laser cladding with the central curve as the center point, and control the movement of the laser cladding head.

[0046] Based on the two boundary lines of the coating preparation area, the curve equations of the two boundary lines are obtained by fitting, as follows: Figure 1 As shown, the difference between the two curve equations is then used to obtain the equation for the distance between the two boundary curves;

[0047] Using the equation for the distance between the two boundary curves as the basis for adjusting the square laser spot during the laser cladding process, the size of the square laser spot is adjusted in real time according to the distance between two points on the two boundary lines during the laser cladding process, so that the size of the square laser spot is consistent with the coating contour, and the powder feeding width is adjusted simultaneously to be consistent with the size of the square laser spot, thereby realizing the conformal preparation with real-time adjustable laser deposition contour.

[0048] As an optional embodiment, based on a three-dimensional model or two-dimensional drawing of the workpiece to be processed, the two side boundary lines of the coating preparation area and the center curve equidistant from the two side boundary lines are determined. Figure 1 As shown, bell-shaped curves are extracted in the three-dimensional model. Based on the two boundary lines of the coating preparation area, the center point of the 1 / 2 position corresponding to each point on the two boundary lines can be determined, thereby obtaining the center curve equidistant from the two boundary lines.

[0049] In embodiments of the present invention, this center curve is used as the spatial motion trajectory of the center point of the square laser spot used for laser cladding, controlling the movement of the laser cladding head. For example, precise control is achieved through offline programming software RobotMaster, which outputs the corresponding trajectory program and imports it into the robot to drive the laser cladding head to move along the trajectory of the center curve.

[0050] Combination Figure 1 , Figure 2 As shown, in an embodiment of the present invention, based on obtaining the boundary lines on both sides of the coating preparation area, the boundary lines can be fitted using numerical simulation software, which serves as the basis for real-time adjustment of the square laser beam size. For example, based on the boundary lines on both sides of the area of ​​the workpiece requiring coating preparation, two curve equations are fitted using Matlab numerical simulation software, and the difference between the two curve equations is used to obtain the equation for the distance between the two boundary curves. The equation for the distance between the two boundary curves is used as the basis for adjusting the long side size of the square laser beam. The expression of the distance equation is converted into a digital control signal to drive the mirror adjustment motor inside the laser processing head, thereby realizing the real-time change of the spot size (i.e., the length of the square laser spot).

[0051] Combination Figure 1 , Figure 2 In the example shown, polynomial fitting is used to obtain the curve equations of the two boundary lines respectively. As shown in the figure, the curve equations of the two boundary lines are expressed by the fitted equations as follows:

[0052] y i =k1x 2 +k2x+k3;

[0053] y s =j1x 2 +j2x+j3;

[0054] Where k1, k2, and k3 are the coefficients of the curve equation on one side, and j1, j2, and j3 are the coefficients of the curve equation on the other side.

[0055] In embodiments of the present invention, numerical simulation can also be performed using other curve simulation methods to obtain the fitting equation of the curve.

[0056] Based on this, combined Figure 2 As shown, the equation for the distance between the two boundary curves is obtained by subtracting the equations of the two curves. That is, the long side dimension of the square laser spot is adjusted in real time according to the following method:

[0057] l=(y i -y s ) / 2;

[0058] Where l represents half the length of the square laser spot, and 2l is the length of the entire square laser spot.

[0059] Combination Figure 2 As shown, the size of the square laser spot is adjusted in real time according to the distance between two points on the two boundary lines during the laser cladding process, including:

[0060] Based on the distance between two points on the boundary lines on both sides during the laser cladding process, the size of the long side of the square laser spot is adjusted in real time. Taking the intersection of the line connecting the two points and the center curve as a reference, the size of the long side of the square laser spot is adjusted in both directions with equal amount to ensure that the size of the long side of the square laser spot is consistent with the distance between the two points.

[0061] In an embodiment of the present invention, the size adjustment control signal of the square laser spot and the motion trajectory control signal of the center point of the square laser spot are activated and deactivated simultaneously.

[0062] In the embodiments of the present invention, a broadband powder conveying method with a multi-tube unidirectional array arrangement is adopted. The powder conveying system is synchronously controlled to adjust the on / off state of the powder feeding tubes of different pipelines in real time according to the real-time adjustment of the square laser spot, so as to adjust the powder conveying width and make the adjusted powder width consistent with the long side dimension of the square laser spot, thereby realizing the preparation of conformal coating.

[0063] Therefore, based on the powder conveying selection of a multi-tube unidirectional array arrangement, the powder conveying width is adjusted by real-time adjustment of different pipe on / off combinations in the powder conveying system. The adjusted width is consistent with the change in the long side dimension of the square laser beam, and the powder convergence point falls on the symmetrical axis of the long side of the square spot.

[0064] In an optional embodiment, to improve the dimensional accuracy of powder width control, a set of on / off switches can be set at both the powder feeder end and the laser cladding head end to control the output and shut-off of powder, keeping the speed of powder conveying width change consistent with the speed of square laser spot change, thereby improving the response speed of powder width control.

[0065] In an optional embodiment, to improve the dimensional accuracy of powder width control, circular powder feeding tubes arranged in a straight line can be used at the end of the laser cladding head. The powder convergence point size of a single powder feeding tube is controlled at 0.5 mm, and the overlap area between the powder convergence points of two adjacent powder feeding tubes is set at 0.2 mm.

[0066] In embodiments of the present invention, the powder may be selected as spherical powder with a particle size of 25-53 μm.

[0067] In an embodiment of the present invention, during the process of preparing a gradient contour region metal coating by laser cladding, three signals—laser spot size adjustment signal, laser beam center point motion trajectory control signal, and multi-powder channel control system signal—are simultaneously activated and deactivated, and can be integrated and controlled by the central control unit of the whole system.

[0068] Therefore, by synchronously controlling the size of the square laser spot and the spatial motion trajectory of the center of the square laser spot, the coverage size of the square laser spot based on the gradient boundary contour shape of the workpiece can be adjusted in real time. Combined with the dynamic adjustment of the powder delivery width by the size of the square laser spot, the laser deposition area with a gradient contour can be formed in one-time deposition. It has obvious advantages in high-precision deposition forming and rapid coating preparation in the gradient area of ​​the workpiece. It can solve the laser strengthening needs of the surface of parts in engineering applications and realize the rapid prototyping or surface performance enhancement of components.

[0069] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for producing a tailored surface coating with real-time adjustable laser deposition profile, characterized in that, Includes the following steps: Based on the coating preparation area on the surface of the workpiece to be processed, determine the two side boundary lines of the coating preparation area, and the center curve equidistant from the two side boundary lines; Configure the spatial motion trajectory of the square laser spot for laser cladding with the central curve as the center point, and control the movement of the laser cladding head. Based on the two boundary lines of the coating preparation area, the curve equations of the two boundary lines are respectively fitted, and the difference between the two curve equations is used to obtain the equation of the distance between the two boundary curves. The equation for the distance between the two boundary curves is used as the basis for adjusting the square laser spot during the laser cladding process. The size of the long side of the square laser spot is adjusted in real time according to the distance between two points on the two boundary lines during the laser cladding process. The intersection of the line connecting the two points and the center curve is used as the reference, and the two sides of the axis of symmetry are adjusted in both directions equally so that the size of the long side of the square laser spot is consistent with the distance between the two points. The powder feeding width is synchronously adjusted to match the size of the square laser spot. Specifically, a broadband powder feeding method with a multi-tube unidirectional array arrangement is adopted. The powder feeding system is synchronously controlled to adjust the on / off state of different pipelines in real time according to the real-time adjustment of the square laser spot, so as to adjust the powder feeding width and make the adjusted powder width consistent with the long side dimension of the square laser spot, thus realizing conformal fabrication.

2. The method for preparing conformal surface coatings with real-time adjustable laser deposition profiles according to claim 1, characterized in that, Based on the three-dimensional model or two-dimensional drawing of the workpiece to be processed, determine the two side boundary lines of the coating preparation area, as well as the center curve equidistant from the two side boundary lines.

3. The method for preparing conformal surface coatings with real-time adjustable laser deposition profiles according to claim 1, characterized in that, The curve equations of the two boundary lines are obtained by polynomial fitting, and are expressed as follows: y i = k 1 x 2 + k 2 x + k 3 ； y s = j 1 x 2 + j 2 x + j 3 ； in, k 1 、k 2 、k 3 These are the coefficients of the curve equation on one side; j 1 、j 2 、j 3 These are the coefficients of the curve equation on the other side; Then, by subtracting the equations of the two curves, we obtain the equation for the distance between the two boundary curves, which is expressed as: l =( y i - y s ) / 2； in, l This represents half the length of a square laser spot. l That is, the length of the entire square laser spot; Therefore, the long side dimension of the square laser spot is based on l =( y i - y s Adjust the constraint of ) / 2.

4. The method for preparing conformal surface coatings with real-time adjustable laser deposition profiles according to claim 1, characterized in that, The length of the square laser spot can be adjusted in real time by controlling the movement of the motor adjusted by the mirror assembly inside the laser cladding head.

5. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to any one of claims 1 to 4, characterized in that, The size adjustment control signal of the square laser spot and the motion trajectory control signal of the center point of the square laser spot are activated and deactivated simultaneously.

6. The method for preparing conformal surface coating with real-time adjustable laser deposition profile according to any one of claims 1 to 4, wherein a set of on / off switches is provided at both the powder feeder end and the laser cladding head end to control the output and shutdown of powder, thereby maintaining the speed of powder conveying width change consistent with the speed of square laser spot change.

7. The method for preparing conformal surface coatings with real-time adjustable laser deposition profiles according to claim 6, characterized in that, The laser cladding head uses circular powder feeding tubes arranged in a straight line. The powder gathering point size of a single powder feeding tube is controlled at 0.5mm, and the overlap area between the powder gathering points of two adjacent powder feeding tubes is set at 0.2mm.

8. The method for preparing conformal surface coatings with real-time adjustable laser deposition profiles according to claim 1, characterized in that, By synchronously controlling the size of the square laser spot and the spatial motion trajectory of the center of the square laser spot, the coverage size of the square laser spot based on the gradient boundary contour shape of the workpiece can be adjusted in real time. Combined with the dynamic adjustment of the powder delivery width by the size of the square laser spot, the laser deposition area can be formed by one-time deposition with a gradient contour.

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