A method of scanning an upward facing surface region in a support-free additive manufacturing of an inclined workpiece using an electron beam

Abstract

The application provides a scanning method for an upward surface area in an unsupported inclined workpiece in electron beam additive manufacturing, and the scanning method comprises: dividing a forming area of the inclined workpiece into a downward surface area, a filling area and an upward surface area; optimizing scanning parameters and a melt pool parameter of the upward surface area, and the scanning parameters and the melt pool parameter of a profile area and a compensation area in the upward surface area are independent of each other. By dividing the upward surface area into the profile area and the compensation area, and optimizing the parameters and the melt pool morphology according to the characteristics of the profile area and the compensation area, the same layer scanning different energy inputs are realized by using the characteristics of high-speed jumping and fast response of the electron beam, and then the step effect in the scanning process of the upward surface area is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology and relates to a scanning method for the upward surface region of an unsupported tilted workpiece in electron beam additive manufacturing. Background Technology

[0002] Additive manufacturing offers the capability to fabricate highly complex geometries. In the field of electron beam powder bed melting (EB-PBF), electron beams provide high-temperature forming, reduced stress, high vacuum, and reduced contamination. Current manufacturing systems typically require support structures to increase heat dissipation and reduce thermal stress. However, these support structures limit design freedom and negatively impact surface quality, part cost, and production efficiency. The complex internal or external geometries of additive manufacturing distinguish it from conventional manufacturing methods. Through topology-optimized components, complex freeform surfaces can achieve lightweight structures. Depending on the target shape, internal cooling channels can improve heat transfer efficiency, thereby increasing productivity and tool life during processing.

[0003] Currently, the forming process for the upper and lower surfaces of inclined workpieces does not clearly distinguish between them. However, in actual forming, the forming environments for the upper and lower surfaces are completely different. For the lower surface, unsupported forming requires overcoming issues such as slag adhesion caused by excessive penetration of the molten pool and thermal stress deformation due to low heat transfer. For the upper surface, the problem arises from the "step effect" caused by the combined effects of layer thickness and the projected angle during the layer-by-layer deposition process.

[0004] Currently, no research has been found on unsupported forming in EB-PBF. When the tilt angle is greater than 45°, an offset scanning method from the outside to the inside is usually used, balancing gravity through the surface tension of the melt during solidification. The energy density typically decreases from the outside to the inside. A similar optimization method for surface quality is proposed in CN116833428A. However, when the tilt angle is less than 45°, current methods typically involve adding supports to increase heat dissipation and prevent stress deformation. No research has been reported on optimizing the quality of the upward-facing surface.

[0005] In traditional powder bed manufacturing methods, existing optimization techniques for unsupported forming using powder bed melting technology involve: using pulsed lasers for forming on the powder bed, performing multi-layer sintering on the powder bed, and then using a flat-top laser for laser remelting scanning. The energy of continuous scanning meets the energy requirements for thin-layer remelting in the second sintered state and semi-melting in the first sintered state. Related research reports that lasers use secondary remelting to achieve surface smoothing. Compared to laser powder bed melting technology, electron beam powder bed melting technology has advantages such as high vacuum, high forming chamber temperature, and high heat source energy absorption rate. However, for complex suspended structures, the high energy absorption rate also means stronger electron beam penetration. Scanning the upper layer can affect the integrity of the lower suspended structure. Furthermore, because the suspended structure is in direct contact with the powder bed, the relatively poor thermal conductivity of the high-temperature powder bed will lead to difficulty in heat dissipation for the suspended structure. Large heat accumulation will cause component deformation, making unsupported forming of suspended structures difficult. In a high-vacuum forming environment, the modification of equipment is more difficult, and the laser is more susceptible to the effects of the vapor deposition of lightweight elements during the forming process, leading to phenomena such as the laser beam failing to focus. The loose accumulation of powder bed also limits the application of multi-axis rotational unsupported forming technology for the formed substrate.

[0006] Therefore, developing a scanning strategy suitable for electron beam powder bed melting of multi-angle unsupported parts is of great practical significance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a scanning method for the upward surface region in unsupported inclined workpieces using electron beam additive manufacturing. By dividing the upward surface region into a contour region and a compensation region, and optimizing parameters and melt channel morphology based on the characteristics of the contour region and the compensation region, the method utilizes the high-speed hopping and rapid response characteristics of the electron beam to achieve the forming of different energy inputs in the same layer, thereby eliminating the step effect in the scanning process of the upward surface region.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a scanning method for the upward surface region of an unsupported tilted workpiece in electron beam additive manufacturing, the scanning method comprising:

[0010] The forming area of ​​the inclined workpiece is divided into a downward surface area, a filling area, and an upward surface area;

[0011] The scanning parameters and melt flow parameters of the upward surface region are optimized, and the scanning parameters and melt flow parameters of the contour region and the compensation region in the upward surface region are independent of each other.

[0012] Electron beam additive manufacturing technology uses a computer-generated three-dimensional CAD solid model of the part to convert the three-dimensional contour information of the part into two-dimensional contour information using layering software and generate a scanning path. The high-energy electron beam emitted by the electron gun melts and deposits thin layers of pre-alloyed metal powder laid by a powder scraper according to the established scanning path, and the three-dimensional alloy parts are obtained by layering. Electron beam additive manufacturing technology is particularly suitable for the preparation of complex-shaped components of difficult-to-machine, high-performance refractory alloys. The electron beam selective melting process generally includes (1) substrate preheating; (2) powder laying; (3) powder bed preheating; (4) forming of the forming area; (5) heat compensation; (6) lowering of the forming substrate. The additive manufacturing of the part is achieved by repeating steps (2)-(6).

[0013] In this invention, the longitudinal section of the inclined workpiece can be divided into a downward surface region, a filling region, and an upward surface region. If the inclined workpiece is extremely thin (thickness < 1 mm), there is no filling region, and it is only divided into a downward surface region and an upward surface region. If the upward surface region and the downward surface region overlap simultaneously in the middle area from the first layer to the last m layers of the workpiece, the overlapping area will preferentially implement the relevant strategies and parameters of the downward surface region.

[0014] The scanning method provided by this invention mainly improves step (4) to solve the problem of optimizing the surface quality of multi-angle forming. The forming method of the filling area is described in CN116833428A. The parameters and scanning paths of the downward surface area, the filling area, and the upward surface area are independent of each other.

[0015] The scanning method provided by this invention first divides the suspended structure of the inclined workpiece into a downward surface area, a filling area, and an upward surface area. Then, the upward surface area is divided into a contour area and a compensation area. Based on the characteristics of the contour area and the compensation area, the parameters and melt channel morphology are optimized. By utilizing the characteristics of high-speed jumping and rapid response of the electron beam, the forming of different energy inputs in the same layer can be achieved, thereby eliminating the step effect in the scanning process of the upward surface area.

[0016] Preferably, the angle between the inclined workpiece and the base plate is 15°-90°, for example, it can be 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or 85°, etc.

[0017] In this invention, the scanning method can eliminate the step effect on the upward surface area of ​​the workpiece with an inclination angle of 15°-90°, and the roughness Ra of the upward surface area of ​​the workpiece with an inclination angle of 45° is less than 5μm, while the roughness of the upward surface area of ​​the workpiece with other inclination angles is lower than that of the upward surface area of ​​the workpiece with an inclination angle of 45°.

[0018] Preferably, the downward surface area includes a first layer of the inclined workpiece on the base plate and a suspended area along the forming direction, as well as a transition area within a certain width range.

[0019] In this invention, the first layer of the inclined workpiece refers to the first layer of the inclined workpiece closest to the base plate.

[0020] Preferably, the upward surface area includes the last m layers of the inclined workpiece on the base plate, the step area of ​​the upward surface of the inclined workpiece, and a compensation area of ​​several width ranges, wherein m is 0-15, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, etc.

[0021] Preferably, the width of the compensation zone is calculated according to the following formula:

[0022]

[0023] in, The width of the compensation zone, The width of the upward surface area. The width of the outline area.

[0024] Preferably, the width of the upward surface area is calculated according to the following formula:

[0025]

[0026] in, The width (mm) of the upward surface area. The thickness of the molten pool penetration in the filled region (μm). The thickness of the powder bed (μm) is the powder bed thickness. The angle (°) between the inclined workpiece and the base plate; The powder bed thickness is 1 to 15 times the powder bed thickness (μm); the powder bed thickness is 30μm to 200μm, for example, it can be 50μm, 60μm, 80μm, 100μm, 120μm, 140μm, 150μm, 160μm or 180μm, etc.

[0027] In this invention, during the forming process, the appearance of the upward surface area can be detected 1-3 layers in advance, and independent parameter design can be performed for the upward surface area.

[0028] Preferably, the width of the contour area is calculated according to the following formula:

[0029]

[0030] in, The width of the outline area (mm). This represents the amount of inward offset from the outer contour. The offset distance (mm) from the outer contour inward. The radius of the molten pool in the contour region is (mm).

[0031] Preferably, during the single-layer forming process, the energy density of the total heat input in the plane increases from the filling area and the compensation area to the contour area, and the increase difference is 6J / mm. 3 -20J / mm 3 For example, it could be 8J / mm 3 10J / mm 3 12J / mm 3 14J / mm 3 15J / mm 3 16J / mm 3 Or 18J / mm 3 wait.

[0032] It should be noted that by adjusting the energy density of the contour area and compensation area decreasing towards the filling area during the scanning process of the upward surface area, the generation of the interface can be eliminated. Moreover, the gradually increasing heat input method from the inside to the outside is also beneficial to the flattening and densification of the upper surface of the inclined workpiece.

[0033] Preferably, the angle between the fill area scan line and the compensation area scan line is 30°-90°, for example, it can be 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or 85°, etc.

[0034] It should be noted that by adjusting the angle between the scan lines of the filling area and the scan lines of the compensation area, a uniform transition between the filling area and the upward surface area can be achieved, suppressing the formation of interfaces between different areas.

[0035] Preferably, the contour area has at least two contours.

[0036] Furthermore, the contour area is provided with 2-5 inner contours. By controlling the number of inner contours within the above range, a smooth transition from the contour area to the filling area can be achieved, while avoiding the problem of a significant decrease in efficiency caused by an excessive number of inner contours.

[0037] Preferably, the energy density of the outer contour in the contour region is greater than the energy density of the inner contour.

[0038] It should be noted that during the scanning process of the upward surface area, it is only necessary to control the energy density of the outer contour to be greater than that of the inner contour. The melting parameters of the inner contour can be determined according to actual production needs, or by referring to the melting parameters of the outer contour.

[0039] Preferably, the height of the melt channel of the outer contour in the contour area is 2 to 15 times the thickness of the powder bed, for example, it can be 3, 4, 5, 6, 8, 10, 12 or 14 times, etc.

[0040] Preferably, the width of the weld line of the outer contour in the contour area is 0.3mm-1.5mm, for example, it can be 0.4mm, 0.5mm, 0.6mm, 0.8mm, 0.7mm, 1mm, 1.1mm, 1.3mm or 1.4mm, etc.

[0041] Preferably, the difference between the wetting angle of the outer contour melt channel in the contour area and the tilt angle of the inclined workpiece is ≤5°, for example, it can be 4.5°, 4°, 3.5°, 3°, 2.5°, 2°, 1.5°, 1° or 0°.

[0042] In this invention, the lower bounding point of the outer contour in the contour area is obtained by offsetting the actual contour boundary of the model inward by 1 melt pool radius, which is 1 / 2 of the actual melt channel width of the outer contour.

[0043] Preferably, the height of the melt channel in the compensation zone is greater than 1.5 times the thickness of the powder bed, and more preferably greater than 2.5 times the thickness of the powder bed.

[0044] Preferably, the width of the melt channel in the compensation zone is 0.4mm-1.5mm, for example, it can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm or 1.4mm, etc.

[0045] Preferably, the line spacing between the melt channels in the compensation zone is 0.1mm-0.3mm, for example, it can be 0.12mm, 0.15mm, 0.16mm, 0.18mm, 0.2mm, 0.22mm, 0.25mm, 0.26mm or 0.28mm, etc.

[0046] Preferably, the angle between the scan line of the compensation area and the contour line of the upward surface area is 5°-175°, for example, it can be 10°, 20°, 40°, 50°, 60°, 80°, 100°, 120°, 140°, 150° or 160°, etc.

[0047] It should be noted that by optimizing the scanning parameters and melt flow parameters of the contour area and compensation area in the upward surface area, the influence of powder bed thickness and step length on the quality of the upward surface in the step effect is eliminated, and the planarization and densification of the upward surface area are achieved.

[0048] Preferably, after optimizing the scanning parameters and melt flow parameters of the upward surface region, the method further includes:

[0049] The first step is to scan the downward surface region;

[0050] The second step involves scanning the filled region;

[0051] The third step is to scan the upward surface region, which does not include the last m layers;

[0052] The fourth step is to perform a scan of the last m layers in the upward surface region;

[0053] The scanning parameters for the first execution, the second execution, the third execution, and the fourth execution are each independent.

[0054] In this invention, by planning independent scanning paths for each region, the scanning of the lower surface region is performed first during the forming process to form a loose layer on the lower surface, and then the scanning of the filling region and the upper surface region are performed in sequence.

[0055] In this invention, the preferred scanning order for the third execution is to first scan the contour area and then scan the compensation area.

[0056] Preferably, after the third execution and before the fourth execution, a remelting process is also included.

[0057] Preferably, the remelting process includes: a fifth step of performing a simultaneous scan of the filling region and the upward surface region; and a sixth step of performing a scan of the upward surface region.

[0058] It should be noted that after the third execution, remelting can be selected according to actual production needs. The entire cross section is melted once by the synchronous scanning of the filling area and the upward surface area in the fifth execution. Then, the upward surface area is scanned in the sixth execution, and the upward surface area is remelted once.

[0059] The fourth execution specifically includes scanning the last m layers in the upward surface region:

[0060] All cross sections of the last m layers are identified as upward surface regions. Except for the contour parameters, which are executed according to the downward surface region, all other parameters are executed according to the parameters of the upward surface region.

[0061] It should be noted that by using the above parameters for scanning, the problem of looseness at the top of the downward surface area can be eliminated, and a densification effect can be achieved on both the upward and downward surface areas.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] (1) The scanning method provided by the present invention first divides the suspended structure of the inclined workpiece into a downward surface area, a filling area and an upward surface area. Then, the upward surface area is divided into a contour area and a compensation area. Based on the characteristics of the contour area and the compensation area, the parameters and melt channel morphology are optimized. By utilizing the characteristics of high-speed jumping and fast response of the electron beam, the forming of different energy inputs in the same layer is realized, thereby eliminating the step effect in the scanning process of the upward surface area. Among them, the roughness Ra of the upward surface area is <5μm.

[0065] (2) The scanning method provided by the present invention can eliminate the generation of interfaces by adjusting the energy density of the contour area and the compensation area to the filling area during the scanning process. The heat input method that gradually increases from the inside to the outside is beneficial to the flattening and densification of the upper surface of the inclined workpiece. By adjusting the angle between the scanning line of the filling area and the scanning line of the upper surface area, a uniform transition between the filling area and the upper surface area can be achieved, and the generation of interfaces between different areas can be suppressed.

[0066] (3) The scanning method provided by the present invention identifies the cross sections of the last m layers as the upward surface area. Except for the contour parameters which are executed according to the downward surface area, all other parameters are executed according to the parameters of the upward surface area. This can eliminate the problem of looseness at the top position of the downward surface area and achieve a densification effect on the upward and downward surface areas. The density of the upper surface of the inclined workpiece is >99.97%, and the density of the lower surface is ≥99.9%. Attached Figure Description

[0067] Figure 1 This is a schematic diagram of the inclined workpiece provided in Example 1;

[0068] Figure 2 This is a schematic diagram of the scanning path planning for the lower surface area, filling area, and upper surface area of ​​the inclined workpiece provided in Example 1;

[0069] Figure 3 This is the state diagram after the third execution of step S3 in Example 1;

[0070] Figure 4 This is the state diagram after the fourth execution of step S3 in Example 1;

[0071] Among them, 1-base plate, 2-downward surface area, 3-filling area, 4-upward surface area, 5-forming cylinder, 6-metal powder bed, 7-sintered porous thin layer, 8-compensation area, 9-last m layer, 10-densification sintered layer of the last m layer on the downward surface.

[0072] Figure 5 This is a SEM image of the upward surface area of ​​the inclined workpiece obtained in Example 2.

[0073] Figure 6This is a SEM image of the upward surface region of the inclined workpiece obtained in Example 3.

[0074] Figure 7 This is a SEM image of the upward surface region of the inclined workpiece obtained in Example 4.

[0075] Figure 8 This is a SEM image of the upward surface region of the inclined workpiece obtained in Example 6.

[0076] Figure 9 This is a SEM image of the upward surface region of the inclined workpiece obtained in Example 7. Detailed Implementation

[0077] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0078] It should be understood that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0079] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0080] Example 1

[0081] This embodiment provides a scanning method for the upward surface region of an unsupported inclined workpiece in electron beam additive manufacturing. The scanning method includes the following steps:

[0082] S1. Divide the forming area of ​​the inclined workpiece into three parts: downward surface area 2, filling area 3, and upward surface area 4 (e.g., ...). Figure 1 (as shown)

[0083] In step S1, the angle between the inclined workpiece and the base plate 1 is 15°-90°.

[0084] In step S1, the downward surface area 2 includes the first layer of the inclined workpiece on the base plate 1 and the suspended area along the forming direction and the transition area within a certain width range.

[0085] In step S1, the upward surface area 4 includes the last m layers of the inclined workpiece on the base plate 1, the step area of ​​the upward surface of the inclined workpiece, and a compensation area of ​​several width ranges, where m is 0-15.

[0086] Furthermore, the width of the compensation zone is calculated according to the following formula:

[0087]

[0088] in, The width of the compensation zone, The width of the upward surface area. The width of the outline area.

[0089] In step S1, the width of the upward surface area is calculated according to the following formula:

[0090]

[0091] in, The width of the upward surface area. The penetration thickness of the molten pool in the filling region. For powder bed thickness, The angle between the inclined workpiece and the base plate; The powder bed thickness is 1 to 15 times; the powder bed thickness is 30 μm to 200 μm.

[0092] S2. Optimize the scanning parameters and melt flow parameters of the upward surface region, and the scanning parameters and melt flow parameters of the contour region and the compensation region in the upward surface region are independent of each other;

[0093] In step S2, the width of the contour area is calculated according to the following formula:

[0094]

[0095] in, The width of the outline area. This represents the amount of inward offset from the outer contour. The offset distance from the outer contour inward. The radius of the molten pool in the contour region.

[0096] In step S2, during the single-layer forming process, the energy density of the total heat input in the plane increases from the filling area and the compensation area to the contour area, and the increase difference is 6J / mm. 3 -20J / mm 3The angle between the fill area scan line and the compensation area scan line is 30°-90°.

[0097] Furthermore, the contour region is provided with at least two contours; the energy density of the outer contour in the contour region is greater than the energy density of the inner contour.

[0098] In step S2, the height of the melt channel of the outer contour in the contour area is 2 to 15 times the powder bed thickness; the width of the melt channel of the outer contour in the contour area is 0.3 mm to 1.5 mm; and the difference between the wetting angle of the melt channel of the outer contour in the contour area and the tilt angle of the inclined workpiece is ≤5°.

[0099] In step S2, the height of the melt channel in the compensation zone is greater than 1.5 times the thickness of the powder bed; the width of the melt channel in the compensation zone is 0.4mm-1.5mm; the spacing between the melt channels in the compensation zone is 0.1mm-0.3mm; and the angle between the scan line of the compensation zone and the outline of the upward surface area is 5°-175°.

[0100] In step S2, by adjusting the decreasing energy density from the contour area and compensation area to the filling area during the scanning process, the generation of interfaces can be eliminated. Moreover, the gradually increasing heat input from the inside to the outside is also beneficial to the flattening and densification of the upper surface of the inclined workpiece. By optimizing the scanning parameters and melt channel parameters of the contour area and compensation area in the upward surface area, the influence of powder bed thickness and step length on the quality of the upward surface in the step effect is eliminated, and the planarization and densification of the upward surface area are achieved. Furthermore, by adjusting the angle between the scanning lines of the filling area and the scanning lines of the upward surface area, a uniform transition between the filling area and the upward surface area can be achieved, suppressing the generation of interfaces between different areas.

[0101] S3. First, perform a scan of the downward surface region; second, perform a scan of the filled region; third, perform a scan of the upward surface region, excluding the last m layers (scan path diagram as shown). Figure 2 As shown, the state diagram after the third execution is as follows: Figure 3 As shown); the fourth execution scans the last m layers in the upward surface region (the state diagram after the fourth execution is shown in the figure). Figure 4 (as shown); wherein the scanning parameters of the first execution, the second execution, the third execution, and the fourth execution are each independent.

[0102] Furthermore, in step S3, remelting can be performed after the third execution and before the fourth execution, depending on actual production needs; the remelting process includes: the fifth execution of synchronous scanning of the filling area and the upward surface area; and the sixth execution of scanning of the upward surface area.

[0103] In step S3, the fourth execution of scanning the last m layers in the upward surface region specifically includes:

[0104] All cross sections of the last m layers are identified as upward surface regions. Except for the contour parameters, which are executed according to the downward surface region, all other parameters are executed according to the parameters of the upward surface region.

[0105] In step S3, by using the above-mentioned parameter scanning, the problem of looseness at the top position of the downward surface area can be eliminated, and the densification effect of the upward and downward surface areas can be achieved.

[0106] The scanning method provided in this embodiment first divides the suspended structure of the inclined workpiece into a downward surface region, a filling region, and an upward surface region. Then, the upward surface region is further divided into a contour region and a compensation region. Based on the characteristics of the contour region and the compensation region, parameters and melt channel morphology are optimized. Utilizing the high-speed hopping and rapid response characteristics of the electron beam, the forming of different energy inputs in the same layer is achieved, thereby eliminating the step effect in the upward surface region scanning process. Combined with the control of the energy density decreasing from the contour region and the compensation region to the filling region during the scanning process, the generation of interfaces can be eliminated. Furthermore, the gradually increasing heat input from the inside to the outside is beneficial for the flattening and densification of the upper surface of the inclined workpiece. Finally, the cross-sections of the last m layers are all identified as upward surface regions. Except for the contour parameters, which are executed according to the downward surface region, all other parameters are executed according to the parameters of the upward surface region. This can eliminate the problem of looseness at the top position of the downward surface region and achieve a densification effect on both the upward and downward surface regions.

[0107] Example 2

[0108] This embodiment provides a scanning method for the upward surface region of an unsupported inclined workpiece in electron beam additive manufacturing. The scanning method includes the following steps:

[0109] First, based on S1, the thickness of the inclined workpiece is 15mm, and the angle between it and the base plate is 45°. The downward surface area includes the first layer of the inclined workpiece on the base plate and the suspended area along the forming direction and the transition area within a certain width range. The upward surface area includes the last 3 layers of the inclined workpiece on the base plate, the step area of ​​the upward surface of the inclined workpiece, and the compensation area within a certain width range.

[0110] The thickness of each powder layer is 100μm, the number of inward offsets of the outer contour is 2, the inward offset distance of the outer contour is 0.15mm, the radius of the molten pool in the contour region is 0.3mm, the penetration thickness of the molten pool in the filling region is 11 times the layer thickness, the width of the transition region is 0.2mm, the width of the compensation region is 0.11mm, and the width of the contour region is 0.9mm.

[0111] Secondly, based on step S2, the scanning parameters and melt flow parameters of the contour area and the compensation area in the upward surface area are independent; during the single-layer forming process, the energy density of the overall heat input in the plane increases from the filling area and the compensation area to the contour area, and the increase difference is 10J / mm. 3The angle between the scan line of the filled area and the scan line of the compensation area is 50°.

[0112] The contour region has three contours, and the energy density difference between the outer contour and the first inner contour in the contour region is 10 J / mm². 3 The energy density difference between the first and second inner contours in the contour region is 8 J / mm². 3 The height of the melt channel in the outer contour of the contour area is 2.5 times the thickness of the powder bed, the width of the melt channel is 0.6 mm, and the difference between the wetting angle and the tilt angle of the inclined workpiece is 2°.

[0113] The height of the melt channel in the compensation zone is 2.5 times the thickness of the powder bed, the width of the melt channel is 0.4 mm, and the spacing between melt channels is 0.2 mm; the angle between the scan line of the compensation zone and the outline of the upward surface area is 60°.

[0114] Then, based on step S3, the following steps are performed: first, a scan of the downward surface region is performed; second, a scan of the filled region is performed; third, a scan of the upward surface region is performed, excluding the last three layers; fourth, a scan of the last three layers in the upward surface region is performed, identifying all cross-sections of the last m layers as upward surface regions. Except for the contour parameters, which are performed according to the downward surface region, all other parameters are performed according to the parameters of the upward surface region. The scanning parameters of the first, second, third, and fourth executions are independent of each other.

[0115] The first execution profile parameters are beam current I = 6 mA and velocity V = 0.17 m / s; the second execution scanning parameters are those provided in Example 1 of CN116833428A.

[0116] Example 3

[0117] This embodiment provides a scanning method for the upward surface region of an unsupported inclined workpiece in electron beam additive manufacturing. Besides the fact that during the single-layer forming process, the energy density of the overall in-plane heat input decreases from the filling region and compensation region to the contour region, with a decrease difference of 10 J / mm, this method is particularly useful. 3 Except for the above, all other conditions are the same as in Example 2.

[0118] Example 4

[0119] This embodiment provides a scanning method for the upward surface region in an unsupported inclined workpiece in electron beam additive manufacturing. Except that the angle between the scanning line of the filling region and the scanning line of the compensation region is 20°, all other conditions are the same as in Embodiment 2.

[0120] Example 5

[0121] This embodiment provides a scanning method for the upward surface region in an unsupported inclined workpiece in electron beam additive manufacturing. Except that the angle between the scanning line of the filling region and the scanning line of the compensation region is 110°, all other conditions are the same as in embodiment 2.

[0122] Example 6

[0123] This embodiment provides a scanning method for the upward surface region of an unsupported inclined workpiece in electron beam additive manufacturing. Except that the melt channel height of the outer contour in the contour region is 1 times the powder bed thickness, all other conditions are the same as in Embodiment 2.

[0124] Example 7

[0125] This embodiment provides a scanning method for the upward surface region of an unsupported inclined workpiece in electron beam additive manufacturing. Except that the melt channel height of the outer contour in the contour region is 20 times the powder bed thickness, all other conditions are the same as in Embodiment 2.

[0126] Example 8

[0127] This embodiment provides a scanning method for the upward surface region in an unsupported inclined workpiece in electron beam additive manufacturing. Except that the scanning parameters and contour parameters in the fourth execution are both the parameters for the upward surface region, all other conditions are the same as in embodiment 2.

[0128] Comparative Example 1

[0129] This comparative example provides a scanning method for the upward surface region in an unsupported inclined workpiece in electron beam additive manufacturing. Except that the parameters of the contour region are applied to the upward surface region, all other conditions are the same as in Example 2.

[0130] Comparative Example 2

[0131] This comparative example provides a scanning method for the upward surface region in an unsupported inclined workpiece in electron beam additive manufacturing. Except for the parameters of the compensation region being applied to the upward surface region, all other conditions are the same as in Example 2.

[0132] The inclined workpieces obtained in Examples 2-4 and 6-7 above were characterized by SEM on their upward surface region. The characterization results are as follows: Figure 5-9 As shown. The scanning method provided by this invention can achieve a densification effect on the upward surface region without a step effect (such as...). Figure 5As shown); if the energy density of the overall heat input in the plane decreases from the filling area and compensation area to the contour area, the low energy density of the contour parameters causes significant interlayer differences in the morphology of the workpiece's upper surface area. This is because the contour heat input is small, and the upper contour melt channel cannot smooth the step differences caused by the layer thickness. The rapid solidification of the outer contour melt results in extremely poor smoothing. In addition, the decrease in heat input from the inside to the outside leads to a smaller accumulation of scanning heat in the contour area, and a faster melt solidification rate, which weakens its smoothing effect (e.g. Figure 6 (As shown); if the angle between the scan lines of the filling area and the scan lines of the compensation area is too small, there is an interface problem between the filling area scan and the compensation area, causing the morphology of the workpiece's upward surface area to exhibit abnormal protrusions and depressions at the interface region between the filling and transition areas (e.g. Figure 7 As shown); if the weld bead height of the outer contour is set too low, the step effect caused by the layer thickness and step length cannot be eliminated, resulting in obvious interlayer depressions in the morphology of the workpiece's upper surface area, leading to increased roughness (e.g. Figure 8 As shown); if the weld bead height of the outer contour is set too high, the wetting angle will be too large, the melt stability will decrease, and melt will overflow between the interlayer weld beads on the upper surface area of ​​the workpiece, forming obvious droplets. These abnormal droplets will adhere to the loose powder nearby, resulting in a poor smoothing effect in the subsequent forming process (such as...). Figure 9 (As shown).

[0133] The inclined workpieces prepared in the above embodiments and comparative examples were subjected to performance tests. Roughness was measured using a probe-type roughness meter, and density was measured using an optical microscope and the Archimedes method. The test results are shown in Table 1.

[0134] Table 1

[0135]

[0136] As shown in Table 1:

[0137] The scanning method provided by this invention divides the upward surface region into a contour region and a compensation region, and optimizes the parameters and melt channel morphology according to the characteristics of the contour region and the compensation region. This eliminates the influence of layer thickness and step size on the quality of the upward surface in the step effect. Combined with the scanning optimization of the last m layers of the upward surface region, a densification effect is achieved on the upward and downward surface regions. The resulting inclined workpiece has an upper surface roughness Ra < 5 μm and a lower surface density ≥ 99.9%.

[0138] A comparison of Examples 2 and 3 shows that if the energy density of the overall heat input in the plane decreases from the filling area and the compensation area to the contour area, the upper surface area is formed directly on the lower deposited body, and the heat dissipation capacity is faster. The preheating effect of the pre-scanning in the same layer on the subsequent scan is poor, and the energy density of the contour parameters is low, which cannot achieve the effect of smoothing the steps. This results in a more obvious step effect on the upper surface of the workpiece and a larger roughness value. However, the lower surface area has a weaker heat dissipation capacity of the powder bed, which will cause powder adhesion and thus make the lower surface area loose.

[0139] A comparison of Examples 2 and 4-5 reveals that if the angle between the scan lines of the filling area and the compensation area is not within the preferred range, interface problems will exist between the filling area and the compensation area, and some scan lines will overlap. All of these will lead to significant interface problems on the upper surface of the workpiece, resulting in abnormal protrusions or depressions and a decrease in surface quality. Simultaneously, unsupported forming on a relatively fragile, loose powder bed can lead to localized overheating, severely reducing the support effect of the powder bed and ultimately causing forming failure.

[0140] A comparison of Examples 2 and 6-7 shows that if the height of the melt channel on the outer contour is set too low, the wetting angle of the melt channel during the staggered remelting process is small, which cannot eliminate the step effect caused by the layer thickness and step length, and cannot meet the smoothing requirements, resulting in an increase in the roughness of the workpiece surface. If the height of the melt channel on the outer contour is set too high, the wetting angle is too large, the stability of the melt decreases, and the melt overflows, resulting in more melt droplets on the workpiece surface, which in turn leads to an increase in the roughness of the workpiece surface.

[0141] A comparison of Examples 2 and 8 shows that if the scanning parameters of the last m layers are all implemented according to the parameters of the upper surface region, the problem of looseness at the top position of the lower surface region cannot be eliminated, resulting in a decrease in the density of the lower surface of the workpiece.

[0142] A comparison of Example 2 and Comparative Examples 1-2 shows that if the same parameters are applied to the upward surface region, it is impossible to achieve the forming of different energy inputs in the same layer, and thus the influence of layer thickness and step length on the quality of the upward surface in the step effect cannot be eliminated.

[0143] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A scanning method for the upward surface region in an unsupported inclined workpiece during electron beam additive manufacturing, characterized in that, The scanning method includes: The forming area of ​​the inclined workpiece is divided into a downward surface area, a filling area, and an upward surface area; The downward surface area includes the first layer of the inclined workpiece on the base plate and the suspended area along the forming direction and the transition area within a certain width range. The upward surface area includes the last m layers of the inclined workpiece on the base plate, the stepped area of ​​the upward surface of the inclined workpiece, and a compensation area of ​​several width ranges, where m is 0-15. The width of the compensation zone is calculated according to the following formula: in, The width of the compensation zone, The width of the upward surface area. The width of the outline area; The width of the upward surface area is calculated according to the following formula: in, The width of the upward surface area. The penetration thickness of the molten pool in the filling region. For powder bed thickness, The angle between the inclined workpiece and the base plate; The powder bed thickness is 1 to 15 times; the powder bed thickness is 30 μm to 200 μm. The width of the contour area is calculated according to the following formula: in, The width of the outline area. This represents the amount of inward offset from the outer contour. The offset distance from the outer contour inward. The radius of the molten pool in the contour region; The scanning parameters and melt flow parameters of the upward surface region are optimized, and the scanning parameters and melt flow parameters of the contour region and the compensation region in the upward surface region are independent of each other.

2. The scanning method according to claim 1, characterized in that, The angle between the inclined workpiece and the base plate is 15°-90°.

3. The scanning method according to claim 1, characterized in that, During the single-layer forming process, the energy density of the overall heat input in the plane increases from the filling area and the compensation area to the contour area, and the increase difference is 6J / mm. 3 -20J / mm 3 ; And / or, the angle between the fill area scan line and the compensation area scan line is 30°-90°.

4. The scanning method according to claim 1, characterized in that, The contour area is provided with at least two contours; And / or, the energy density of the outer contour in the contour region is greater than the energy density of the inner contour; And / or, the melt channel height of the outer contour in the contour area is 2 to 15 times the powder bed thickness; And / or, the width of the weld line of the outer contour in the contour area is 0.3mm-1.5mm; And / or, the difference between the wetting angle of the outer contour melt channel in the contour area and the tilt angle of the tilted workpiece is ≤5°.

5. The scanning method according to claim 1, characterized in that, The height of the melt channel in the compensation zone is greater than 1.5 times the thickness of the powder bed; And / or, the width of the melt channel in the compensation zone is 0.4mm-1.5mm; And / or, the inter-line spacing between the melt channels in the compensation zone is 0.1mm-0.3mm; And / or, the angle between the scan line of the compensation area and the contour line of the upward surface area is 5°-175°.

6. The scanning method according to claim 1, characterized in that, The optimization of the scanning parameters and melt flow parameters for the upward surface region also includes: The first step is to scan the downward surface region; The second step involves scanning the filled region; The third step is to scan the upward surface region, which does not include the last m layers; The fourth step is to perform a scan of the last m layers in the upward surface region; The scanning parameters for the first execution, the second execution, the third execution, and the fourth execution are each independent.

7. The scanning method according to claim 6, characterized in that, The process includes a remelting process after the third execution and before the fourth execution. The remelting process includes: fifth, performing simultaneous scanning of the filling region and the upward surface region; and sixth, performing scanning of the upward surface region.

8. The scanning method according to claim 6, characterized in that, The fourth execution specifically includes scanning the last m layers in the upward surface region: All cross sections of the last m layers are identified as upward surface regions. Except for the contour parameters, which are executed according to the downward surface region, all other parameters are executed according to the parameters of the upward surface region.

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