Preparation method of random surface coating with real-time adjustable laser deposition contour

Abstract

The invention provides a preparation method of a random surface coating with a real-time adjustable laser deposition contour. The preparation method comprises the following steps: determining boundary lines on two sides of a coating preparation area and a central curve equidistant from the boundary lines on the two sides; taking the center curve as a space movement track of a laser spot center point; fitting boundary lines on the two sides to obtain a curvilinear equation, and performing subtraction to obtain a distance equation of two boundary curves; a distance equation is used as a laser spot adjusting basis, the size of a square laser spot is adjusted in real time according to the distance between two points on boundary lines on the two sides in the laser cladding process, so that the size of the laser spot is consistent with the coating outline, and the powder feeding width is synchronously adjusted to be consistent with the size of the laser spot; and real-time adjustable conformal preparation of the laser deposition contour is realized. Real-time change of the laser beam covering size of the workpiece gradient boundary contour shape can be achieved, dynamic adjustment of the powder conveying width is combined, and the problem that a workpiece laser deposition area is of a gradient contour and needs one-time deposition forming is solved.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding, and in particular to a method for preparing a conformal surface coating with a real-time adjustable laser deposition profile. Background Art

[0002] Laser cladding additive manufacturing technology is an advanced manufacturing technology that achieves rapid, short-process manufacturing and performance organization regulation. 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, meeting the specific performance requirements of the material surface while saving a lot of material costs.

[0003] There are two common powder feeding methods for laser cladding: pre-set powder feeding and synchronous powder feeding. Pre-set powder feeding is to pre-cover the alloy powder material to be clad on the surface of the substrate, and then use the laser beam to scan the surface of the alloy pre-cladding layer. The surface of the pre-cladding layer absorbs the laser energy to increase the temperature and melt, and at the same time transfers the surface heat to the inside through heat conduction. After the laser beam leaves, the molten metal quickly solidifies on the surface of the substrate to form a metallurgically bonded alloy cladding layer; synchronous powder feeding is to use a special conveyor to directly feed the alloy material into the laser action area. Before the powder reaches the melting zone, it passes through the beam and is heated to a red-hot state. After falling into the melting zone, it melts immediately and is fed into the alloy cladding layer along with the substrate and powder.

[0004] Among them, the synchronous powder feeding method is divided into synchronous lateral powder feeding and coaxial powder feeding. The synchronous lateral powder feeding has a simple structure and a low price, but the powder utilization rate is not high and the cladding quality is relatively poor. It can be applied to laser cladding of planes and shafts. The coaxial powder feeding structure is complex, the powder is preheated, the cladding quality is good, and it has strong versatility. However, the preset powder feeding laser cladding process has high requirements for the structural shape of the workpiece, and it is difficult to prepare coatings for inclined surfaces, arc surfaces, and special-shaped curved surfaces. The synchronous powder feeding laser cladding process has improved adaptability to the workpiece structure type, but the size of the powder convergence point in this method is often not adjustable in real time.

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

[0006] The purpose of the present invention is to address the technical problem of preparing coatings in gradient contour areas, and to propose a method for preparing conformal surface coatings with real-time adjustable laser deposition contours, thereby realizing real-time changes in the laser beam coverage size based on the gradient boundary contour shape of the workpiece, and dynamically adjusting the powder delivery width, thereby solving the problem that the laser deposition area of ​​the workpiece has a gradient contour and requires a one-time deposition forming requirement.

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

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

[0009] The center curve is configured as the spatial motion trajectory of the center point of the square laser spot for laser cladding, and the laser cladding head is controlled and driven to move;

[0010] Based on the boundary lines on both sides of the coating preparation area, curve equations of the boundary lines on both sides are obtained by fitting respectively, and the two obtained curve equations are subtracted to obtain the equation of the distance between the two boundary curves;

[0011] 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 square laser spot is adjusted in real time according to the distance between two points on the boundary lines on both sides 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 synchronously adjusted to be consistent with the size of the square laser spot, thereby realizing the form-fitting preparation with real-time adjustable laser deposition contour.

[0012] As an optional embodiment, based on a three-dimensional model or a two-dimensional drawing of the workpiece to be processed, two side boundary lines of the coating preparation area and a 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 boundary lines on both sides.

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

[0015] According to 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, and the intersection of the line connecting the two points and the center curve is used as a reference, and the symmetry axes on both sides 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.

[0016] As an optional embodiment, the real-time adjustment of the length of the square laser spot is achieved by controlling the movement of the mirror adjustment motor inside the laser cladding processing 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 at the same time.

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

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

[0020] As an optional embodiment, circular powder feeding tubes arranged in a line are used at the laser cladding processing head end, 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 regulation of the size of the square laser spot and the spatial motion trajectory of the center of the square laser spot, the real-time adjustment of the square laser spot coverage size based on the shape of the workpiece gradient boundary contour is realized, and the powder delivery width is dynamically adjusted in combination with the square laser spot size, so as to realize the one-time deposition preparation forming of the laser deposition area with a gradient contour

[0022] Based on the above technical solution of the present invention, a method for preparing a conformal surface coating with real-time adjustable laser deposition profile is proposed to address the technical problem of preparing coatings in gradient contour areas, thereby realizing real-time changes in the laser beam coverage size based on the gradient boundary contour shape of the workpiece and dynamically adjusting the powder delivery width, thereby solving the difficult problem that the laser deposition area of ​​the workpiece has a gradient contour and requires one-time deposition and forming requirements.

[0023] Compared with the prior art, the method for preparing a conformal surface coating with real-time adjustable laser deposition profile proposed in the present invention has significant advantages in adaptability and process control for preparing a coating with a gradual profile, as follows:

[0024] (1) The method for preparing a conformal surface coating based on laser cladding of the present invention first determines the boundary lines and the center curve of the coating preparation area on both sides, and obtains the spacing equation by fitting the boundary line equation and performing the difference, and uses this as the basis for adjusting the laser spot size, so as to adjust the size of the square laser spot 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 a gradient contour workpiece with a complex curved shape, whether it is a convex or concave boundary change, the laser spot can be accurately fitted to the boundary to achieve accurate contour matching, thereby ensuring that laser deposition can be performed uniformly in the entire gradient contour area, effectively solving the problem that the laser deposition area of ​​the workpiece is a gradient contour; and the present invention can complete the deposition forming at one time when processing a gradient contour workpiece by adjusting the laser spot size in real time and synchronously adjusting the powder feeding width. Different from the traditional method that requires multiple processing or subsequent additional processing of the gradient area, the conformal surface coating preparation proposed by the present invention reduces the processing steps and improves the processing efficiency. At the same time, it can also better ensure the quality and overall performance of the coating, and avoid the problems of uneven coating and loose bonding that may be caused by multiple processing;

[0025] (2) When adjusting the size of the long side of the square laser spot (i.e., the length between the points on the boundary lines on both sides), the intersection of the line connecting the two points on the boundary lines on both sides and the center curve is used as the reference, and the symmetry axes on both sides are adjusted in both directions equally. The symmetrical adjustment method can ensure the relative stability of the spot shape and can adapt to the gradient contour more accurately. By controlling the movement of the mirror group adjustment motor inside the laser cladding processing head, it can be adjusted 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 motion trajectory control of the center point of the square laser spot are started and closed at the same time (and synchronized with the powder width adjustment), ensuring the synchronization of the motion trajectory and size adjustment of the spot in time, avoiding the mismatch between the spot and the coating area due to time difference, and making the entire laser deposition process more coordinated and efficient.

[0026] (3) Combined with the broadband powder delivery method using a multi-tube unidirectional array arrangement, the powder delivery system is synchronously controlled to adjust the on and off of the powder delivery tubes of different pipelines in real time according to the real-time adjustment of the square laser spot to adjust the powder delivery width. At the same time, a set of on and off switches are set at the powder feeder end and the laser cladding processing head end to control the output and shutdown of the powder, so that the change in the powder delivery width is consistent with the speed of the square laser spot change. The synchronous control mechanism obtained by the present invention can ensure that during the laser deposition process, the powder supply and the size of the laser spot are always matched, ensuring the stability of the coating quality and improving the quality and accuracy of the form-based preparation.

[0027] It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below can be considered as part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent. In addition, all combinations of the claimed subject matter are considered as part of the inventive subject matter of the present disclosure.

[0028] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0031] Figure 2 Schematic diagram of adjusting the size of the long side of a square laser beam according to an exemplary embodiment of the present invention.

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

[0033] Figure 4 Schematic diagram of the positional relationship between the powder convergence point and the square laser beam according to an exemplary embodiment of the present invention.

[0034] The meanings of the various symbols in the accompanying drawings are as follows:

[0035] A: The starting point of the center line equidistant from the boundary lines on both sides;

[0036] B: The end point of the center line equidistant from the boundary lines on both sides;

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

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

[0039] L2: Width of powder convergence point. DETAILED DESCRIPTION

[0040] In order 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 present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed by the present invention are not limited to any implementation. In addition, some aspects disclosed by the present invention can be used alone or in any appropriate combination with other aspects disclosed by the present invention.

[0042] {Example 1}

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

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

[0045] The center curve is configured as the spatial motion trajectory of the center point of the square laser spot for laser cladding, and the laser cladding head is controlled and driven to move;

[0046] Based on the boundary lines on both sides of the coating preparation area, the curve equations of the boundary lines on both sides are respectively fitted, such as Figure 1 As shown, the two curve equations are then subtracted to obtain the distance equation between the two boundary curves;

[0047] 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 square laser spot is adjusted in real time according to the distance between two points on the boundary lines on both sides 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 synchronously adjusted to be consistent with the size of the square laser spot, thereby realizing the form-fitting preparation with real-time adjustable laser deposition contour.

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

[0049] In an embodiment of the present invention, the center curve is used as the spatial motion trajectory of the center point of the square laser spot for laser cladding to control and drive the laser cladding head to move. For example, precise control is performed through the offline programming software RobotMaster, and the corresponding trajectory program is output through the offline programming software RobotMaster and imported into the robot to drive the laser cladding processing head to move according to the trajectory of the center curve.

[0050] Combination Figure 1 , Figure 2 As shown, in an embodiment of the present invention, on the basis of obtaining the boundary lines on both sides of the coating preparation area, the boundary lines on both sides can be fitted by numerical simulation software, and this can be used as the basic condition for real-time adjustment of the size of the square laser beam. For example, based on the boundary lines on both sides of the area where the workpiece needs to be coated, two curve equations are fitted by Matlab numerical simulation software, and the two curve equations are subtracted to obtain the spacing equation of the two boundary curves. The spacing equation of the two boundary curves is used as the basis for adjusting the size of the long side of the square laser beam, and the spacing equation expression is converted into a digital control signal to drive the mirror group adjustment motor inside the laser processing head to achieve real-time changes in 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 as an example to fit the curve equations of the boundary lines on both sides. As shown in the figure, the curve equations of the boundary lines on both sides are respectively expressed as fitting equations:

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

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

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

[0055] In the embodiment of the present invention, numerical simulation may also be performed by other curve simulation methods to obtain a fitting equation of the curve.

[0056] On this basis, combined with Figure 2 As shown, the difference between the two curve equations is used to obtain the equation of the distance between the two boundary curves, that is, the long side size of the square laser spot is adjusted in real time according to the following method:

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

[0058] Wherein, l represents half of the length of the square laser spot, and 2l represents 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 boundary lines on both sides during the laser cladding process, including:

[0060] According to 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, and the intersection of the line connecting the two points and the center curve is used as a reference, and the symmetry axes on both sides 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.

[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 started and stopped at the same time.

[0062] In an embodiment of the present invention, a broadband powder delivery method with a multi-tube unidirectional array arrangement is adopted. The powder delivery system is synchronously controlled according to the real-time adjustment of the square laser spot to adjust the on-off of the powder delivery tubes of different pipelines in real time to achieve the adjustment of the powder delivery width, so that the adjusted powder width is consistent with the long side size of the square laser spot, thereby realizing conformal coating preparation.

[0063] Therefore, based on the powder delivery, a multi-tube unidirectional array arrangement is selected, and the powder delivery width is adjusted by the powder delivery system in real time to adjust the on-off combination of different pipelines. The adjusted width is consistent with the change in the long side size of the square laser beam, and the powder convergence point falls on the symmetry axis of the long side of the square spot.

[0064] In an optional embodiment, in order to improve the dimensional accuracy of powder width control, a set of on-off switches can be set at the powder feeder end and the laser cladding processing head end to control the output and shutdown of the powder, keep the change of the powder delivery width consistent with the speed of the square laser spot change, and improve the response speed of the powder width control.

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

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

[0067] In an embodiment of the present invention, in the process of preparing a metal coating in a gradient contour area by laser cladding, the laser spot size adjustment signal, the motion trajectory control signal of the laser beam center point and the multi-powder path control system signal are started and shut down at the same time, and can be integrated and controlled by the central control unit of the whole system.

[0068] Therefore, 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 real-time adjustment of the coverage size of the square laser spot based on the gradient boundary contour shape of the workpiece is realized, and the powder delivery width is dynamically adjusted in combination with the square laser spot size, so as to realize one-time deposition preparation and forming with a gradient contour in the laser deposition area. It has obvious advantages in high-precision deposition forming and rapid coating preparation in the gradient area of ​​the workpiece, which can solve the laser strengthening needs of the surface of parts in engineering applications and realize rapid prototyping or surface performance enhancement of parts.

[0069] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for preparing a conformal surface coating with real-time adjustable laser deposition profile, characterized in that: The following steps are involved: Based on the coating preparation area on the surface of the workpiece to be processed, determining two side boundary lines of the coating preparation area and a center curve equidistant from the two side boundary lines; The center curve is configured as the spatial motion trajectory of the center point of the square laser spot for laser cladding, and the laser cladding head is controlled and driven to move; Based on the boundary lines on both sides of the coating preparation area, curve equations of the boundary lines on both sides are obtained by fitting respectively, and the two obtained curve equations are subtracted 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 square laser spot is adjusted in real time according to the distance between two points on the boundary lines on both sides 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 synchronously adjusted to be consistent with the size of the square laser spot, thereby realizing the form-fitting preparation with real-time adjustable laser deposition contour.

2. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 1, characterized in that: Based on the three-dimensional model or two-dimensional drawing of the workpiece to be processed, the boundary lines on both sides of the coating preparation area and the center curve equidistant from the boundary lines on both sides are determined.

3. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 1, characterized in that: Use polynomial fitting to obtain the curve equations of the boundary lines on both sides.

4. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 1, characterized in that: The method of adjusting the size of the square laser spot in real time according to the distance between two points on the boundary lines on both sides during the laser cladding process includes: According to 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, and the intersection of the line connecting the two points and the center curve is used as a reference, and the symmetry axes on both sides 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.

5. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 4, characterized in that: By controlling the movement of the mirror adjustment motor inside the laser cladding processing head, the length of the square laser spot can be adjusted in real time.

6. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to any one of claims 1 to 5, 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 started and stopped at the same time.

7. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to any one of claims 1 to 5, characterized in that: A broadband powder delivery method with a multi-tube unidirectional array arrangement is adopted. The powder delivery system is synchronously controlled according to the real-time adjustment of the square laser spot to adjust the on-off of the powder delivery tubes of different pipelines in real time to adjust the powder delivery width. The adjusted powder width is kept consistent with the long side size of the square laser spot, thus realizing shape-conforming preparation.

8. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 7, characterized in that: By setting a set of on-off switches at the powder feeder end and the laser cladding processing head end, the output and shutdown of the powder can be controlled to keep the change of the powder delivery width consistent with the speed of the square laser spot change.

9. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 7, characterized in that: Circular powder feeding tubes arranged in a line are used at the laser cladding processing head end. The size of the powder convergence point 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.

10. The method for preparing a conformal surface coating with real-time adjustable laser deposition profile according to claim 1, characterized in that: 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, real-time adjustment of the coverage size of the square laser spot based on the gradient boundary contour shape of the workpiece is realized, and the powder delivery width is dynamically adjusted in combination with the square laser spot size to achieve a one-time deposition preparation with a gradient contour in the laser deposition area.

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